Bibliography
This section provides a listing of publications we find relevant to the Open Power Quality project. The next section provides citations to publications and technical reports produced by members of the OPQ project. The following section presents citations to related literature.
If you are aware of relevant literature not included here, we would appreciate it if you contact Professor Philip Johnson (johnson@hawaii.edu) and provide this information to us. Thanks for your support!
OPQ Publications
This section contains citations to publications produced by members of the OPQ project.
Anthony Christe, Sergey Negrashov, and Philip M. Johnson. OpenPowerQuality: An Open Source Framework for Power Quality Collection, Analysis, Visualization, and Privacy. In Proceedings of the Seventh Conference on Innovative Smart Grid Technologies (ISGT2016), Minneapolis, MN, USA, 2016. [ .pdf ]
As power grids transition from a centralized distribution model to a distributed model, maintaining grid stability requires real-time power quality (PQ) monitoring and visualization. As part of the Open Power Quality (OPQ) project, we designed and deployed a set of open source power quality monitors and an open source cloud-based aggregation and visualization system built with the utility customer in mind. Our aim is to leverage a flexible privacy model combined with inexpensive and easy to use PQ meters in order to deploy a high density power quality monitoring network across the Hawaiian islands. In this paper we describe OPHub, a privacy focused open source PQ visualization along with results of a small scale deployment of our prototype PQ meter across the island of Oahu. Our results demonstrate that OPQ can provide useful power quality data at an order of magnitude less cost than prior approaches.
Anthony Christe, Sergey Negrashov, Philip M. Johnson, Dylan Nakahodo, David Badke, and David Aghalarpour. OPQ Version 2: An Architecture for Distributed, Real-Time, High Performance Power Data Acquisition, Analysis, and Visualization. In Proceedings of the Seventh Annual IEEE International Conference on CYBER Technology in Automation, Control, and Intelligent Systems, Honolulu, HI, USA, July 2017. [ .pdf ]
OpenPowerQuality (OPQ) is a framework that supports end-to-end capture, analysis, and visualizations of distributed real-time power quality (PQ) data. Version 2 of OPQ builds on version 1 by providing higher sampling rates, optional battery backup, end-to-end security, GPS synchronization, pluggable analysis, and a real-time visualization framework. OPQ provides real-time distributed power measurements which allows users to see both local PQ events and grid-wide PQ events. The OPQ project has three principal components: back-end hardware for making power measurements, middleware for data acquisition and analysis, and a front-end providing visualizations. OPQBox2 is a hardware platform that takes PQ measurements, provides onboard analysis, and securely transfers data to our middleware. The OPQ middleware performs filtering on the OPQBox2 sensor data and performs high-level PQ analysis. The results of our PQ analysis and real-time state of the sensor network are displayed using OPQView. We’ve collected distributed PQ datafrom locations across Oahu, Hawaii and have demonstrated our ability to detect both local and grid-wide power quality events.
Sergey Negrashov. Compression and compressed sensing in bandwidth constrained sensor networks. Technical Report CSDL-17-02, University of Hawaii, Honolulu, HI, March 2017. [ .pdf ]
Improvements in sensor and radio technologies allow for creation of cheap sensors interconnected via radio links and the Internet. These advancements opened the door for creation of large area autonomous monitoring networks referred to as sensor networks. Bandwidth requirements of a wireless sensor network has a direct effect on its performance. This paper describes three bandwidth reduction methods: lossless compression, lossy compression, and compressed sensing.
Anthony Christe. Data management for distributed sensor networks: A literature review. Technical Report CSDL-17-01, University of Hawaii, Honolulu, HI, March 2017. [ .pdf ]
Sensor networks are spatially distributed autonomous sensors that monitor the physical world around them and often communicate those reading over a network to a server or servers. Sensor networks can benefit from the generally “unlimited resources” of the cloud, namely processing, storage, and network resources. This literature review surveys the major components of distributed data management, namely, cloud computing, distributed persistence models, and distributed analytics.
Sergey Negrashov. Design, Implementation, and Initial Evaluation of OPQBox: A low-cost device for crowdsourced power quality monitoring. Technical Report CSDL-14-11, University of Hawaii, Honolulu, HI, November 2014. [ .pdf ]
The face of power distribution has changed rapidly over the last several decades. Modern grids are evolving to accommodate distributed power generation, and highly variable loads. Furthermore as the devices we use every day become more electronically complex, they become increasingly more sensitive to power quality problems. Distributed power quality monitoring systems have been shown to provide real-time insight on the status of the power grid and even pinpoint the origin of power disturbances. [6] Oahu’s isolated power grid combined with high penetration of distributed renewable energy generators create perfect conditions to assess the feasibility and utility of such a network. Over the last three months we have been collecting power quality data from several locations on Oahu as a pilot study for a larger monitoring system. This papers describes our methodology, hardware and software design and presents a preliminary analysis of the data we collected so far. Lastly this paper presents a design for an improved power quality monitor based upon the pilot study experiences.
Anthony J. Christe. OPQ Cloud: A scalable software framework for the aggregation of distributed power quality data. Technical Report CSDL-14-04, University of Hawaii, Honolulu, HI, April 2014. [ .pdf ]
Power quality issues can be caused in a variety of situations. Voltage fluctuations, frequency fluctuations, and harmonics are all power quality issues which can be caused by weather, high penetration of renewables, man-made issues, or other natural phenomena. We designed a software framework which can aggregate crowdsourced distributed power quality measurements in order to study power quality issues over a dense geographic area.
Philip M. Johnson. Enabling active participation in the Smart Grid through crowdsourced power quality data. Technical Report CSDL-14-01, University of Hawaii, Honolulu, HI, April 2014. [ .pdf ]
This technical report presents a research project designed to gain insight into the following questions: Can crowdsourced power quality data enable active participation in the Smart Grid? What are the technical, social, behavioral, and economic requirements for crowdsourced data that make it effective for detection, monitoring, prediction and diagnosis of selected Smart Grid power quality issues? And finally, how can these project outcomes improve “citizen science” in general and the kinds of intrinsic and extrinsic motivators needed for successful outcomes?
Related work
The following sections contain citations to publications related to the project.
General
This section contains citations to general introductions and overviews of power quality.
R Vedam and Mulukutla Sarma. Power Quality- VAR compensation in Power Systems. January 2009. [ http ]
This book is organized into 11 chapters. Chapter 1 deals with general terminology used in power quality, reliability, and the ITI (CBEMA) curve. Chapter 2 discusses SVCs used in main transmission systems, as well as those used to correct unbalances due to traction loads. Chapter 3 deals with the control of the SVCs both for main transmission systems and those used to compensate unsymmetric traction single-phase loads. Chapter 4 considers harmonics and their sources. Chapter 5 describes the utility harmonic regulations and standards. Chapter 6 focuses on the undesirable effects of harmonics and mitigation techniques. Chapter 7 presents the computation tools that are available for the design and analysis of SVCs and harmonic filters. Chapter 8 is devoted to the different aspects of monitoring power quality. Chapter 9 presents the constructional details of HV reactors and the considerations involved in the choice of their location at the end of EHV lines, tertiary windings of transformers, etc. Chapter 10 describes the use of shunt capacitors for reactive compensation and power factor correction. Chapter 11 presents fast Fourier transforms (FFT).
Mark Stephens. Power Factor Correction and Harmonics, 2007.
Two parts. First part explains what power factor is, how harmonics impact on power factor, and how to correct power factor. Second part explains what harmonics are, what causes them (switch mode power supplies, adjustable speed drives, DC drives, and electronic ballasts); impacts of harmonics (not much on heating, most impact on data processing/communications equipment), and how to deal with them (filtering).
Mark Stephens. Embedded Solution Approaches Through Equipment Design Strategies, 2007. [ .pdf ]
How to protect against problems due to voltage sags by appropriate design. Approaches: Use DC power instead of AC, Utilize sag-tolerant components that satisfy SEMI F47, apply custom programming techniques such as delay filters, state machine programming, phase voltage sensing relay, specify configuration settings appropriately, use appropriate trip curves for circuit breakers.
Mark Stephens. Chiller PQ Issues. [ .pdf ]
A powerpoint presentation overviewing power quality problems that can result from HVAC systems. Overviews the components of an HVAC system and how these components can be affected by power quality events. Describes a study that determines what levels of voltage sags appear to result in component problems.
Mark Stephens. Effects of Voltage Sags on Industrial Equipment, 2007. [ .pdf ]
Presents examples of using "Porto-Sag" to assess the impact of voltage sags on equipment. Voltage sags are "the most important pq variation affecting sensitive equipment". Voltage sags are defined in terms of magnitude (i.e. 50% of nominal) and duration (i.e. 4 cycles). Results on various computers (Dell, HP netserver, Compaq) show actual values for voltage sags that induce equipment failure. Also looked at PLCs, relays, adjustable speed drives.
Jonathan Rodriguez and Gavin Saldanha. No Harmony in Harmonics. January 2013. [ .pdf ]
Harmonic currents generated by non-linear electronic loads increase power system heat losses and power bills for end users. These harmonic-related losses reduce system efficiency, cause apparatus overheating, and increase power and air conditioning costs. As the number of harmonics-producing loads has increased over the years, it has become increasingly necessary to address their influence when making any additions or changes to an installation. Harmonic currents can have a significant impact on electrical distribution systems and the facilities they feed. It is important to consider their impact when planning additions or changes to a system. In addition, identifying the size and location of non-linear loads should be an important part of any maintenance, troubleshooting and repair program.
Ahmed Zobaa. Power Quality Monitoring. In Power Quality: Monitoring, Analysis, and Enhancement. InTechOpen, October 2010. [ http ]
An introductory chapter on power quality monitoring, discussing voltage sag measurement, balanced and unbalanced voltage sag, line to line faults, double line to ground faults, prediction of voltage sags, and optimal placement of voltage sag monitors.
Troubleshooting Industrial Power Quality Problems, July 1998. [ http ]
This article provides basic rules of thumb and practical test procedures for diagnosing power quality problems, including EMI/RFI sources, electrostatic discharge, harmonics, transverse mode noise, and conductor terminations.
Phiilp Keebler. Ranking Electrical Disturbances ― Part 2 of 7, May 2018. [ http ]
LED driver response to short-duration RMS voltage variations. This article is Part 2 of a new seven-part series on the effects of power quality disturbances on a five-stage electronic LED driver. In Part 1, which ran in the April 2018 issue, we listed seven categories of electrical disturbances as defined in Table 2 per IEEE 1159-2009, Recommended Practice for Monitoring Electric Power Quality. Our discussion focused on long-duration RMS variations. We now turn our attention to short-duration RMS variations.
Philip Keebler. Ranking Electrical Disturbances — Part 1 of 7, April 2018. [ http ]
Which power quality interruptions are most likely to disturb your LED lighting system? This article starts a seven-part series on the effects of power quality disturbances on a five-stage electronic LED driver. As electrical designers, we know each circuit has a characteristic frequency response, meaning that signals of some frequency can get through a circuit, and others cannot. The same is true when you talk about the effects of power quality (PQ) disturbances on electronic ballasts. Each disturbance category has its own frequency characteristics as well.
Standards
This section contains citations to standards documents and publications.
Mark Stephens. The Electrical Environment: Common Levels of Power Quality in the United States and Abroad, 2007.
Presents reported costs of power quality problems, power quality definitions and terms, frequency of occurrence of power quality problems, causes of PQ not insufficent utility capacity, but rather distribution faults and short circuits.Conclusions: voltage sag is most common problem for industrial customers, majory of events are less than 200ms and from 10% to 50%, SEMI F47 compliance is helpful.
Mark Stephens. Power Quality Standards: CBEMA, ITIC, SEMI F47, IEC 61000-4-11/34, 2009. [ .pdf ]
Describes existing standards for power quality (CBEMA, ITIC, SEMI F47, IEC 61000). Problems with existing standards are that they advocate different test methods , do not require 3 phase sags, do not provide testing methodology, and only result in pass/fail. References a new standard, IEEE P1668 to address these problems.
International Electrotechnical Commission. Electromagnetic compatibility (EMC) – Part 4-30: Testing and measurement techniques – Power quality measurement methods. International Electrotechnical Commission, March 2015. OCLC: 935175130. [ http ]
This part of IEC 61000-4 defines the methods for measurement and interpretation of results for power quality parameters in a.c. power supply systems with a declared fundamental frequency of 50 Hz or 60 Hz. Measurement methods are described for each relevant parameter in terms that give reliable and repeatable results, regardless of the method’s implementation. This standard addresses measurement methods for in-situ measurements. Measurement of parameters covered by this standard is limited to conducted phenomena in power systems. The power quality parameters considered in this standard are power frequency, magnitude of the supply voltage, flicker, supply voltage dips and swells, voltage interruptions, transient voltages, supply voltage unbalance, voltage harmonics and interharmonics, mains signalling on the supply voltage, rapid voltage changes, and current measurements. Emissions in the 2 kHz to 150 kHz range are considered in Annex C (informative), and over- and underdeviations are considered in Annex D (informative). Depending on the purpose of the measurement, all or a subset of the phenomena on this list may be measured.
Douglas Dorr. IEEE P1668: Approved Draft Recommended Practice for Voltage Sag and Short Interruption Ride-Through Testing for End-Use Electrical Equipment Rated Less than 1000 V. IEEE, January 2016. [ http ]
IEEE P1668 is a non-industry-specific trial use recommended practice for voltage sag and short interruption ride-through performance and compliance testing for all electrical and electronic equipment connected to low-voltage power systems that can experience malfunction or shutdown as a result of reductions in supply voltage lasting less than one minute. Testing procedures and requirements for test equipment are clearly defined within this document to reflect this electrical environment, including single-phase, two-phase, and three-phase balanced and unbalanced voltage sags. The recommended practice also defines requirements for certification and test reporting, including characterization of voltage-sag ride-through equipment. Current Status: Active
Alexander McEachern. Voltage Sags (Dips) and Swells, 2004. [ http ]
Great high level overview of voltages sags and swells as well as some breadcrumbs to other standards.
John Kyei. Analysis and design of power acceptability curves for industrial loads. Master's thesis, Arizona State University, 2001. [ http ]
There has been a concern in recent years for electric power utilities to satisfy the increasingly expectations of not only the industrial and commercial, but also the residential users with respect to the quality of the supplied energy. This concern calls for the redesigning of the existing power quality indices to capture all the industrial, commercial and household loads, which hitherto has not been considered. Several electric power indices have evolved over the years as tools to represent, quantify and measure a complex issue at hand. The use of these indices is widespread in the field of electric power generation, transmission and distribution. Another way of quantifying power quality issues is the use of power acceptability curves. These curves are plots of bus voltage deviation versus time duration. And they separate the bus voltage deviation - time duration plane into two regions: an "acceptable" and "unacceptable". Various power acceptability curves exist but the most widely publicized one, which could stand the test of time and could be relied on, is the Computer Business Equipment Manufacturers Association or CBEMA curve. The CBEMA curve has been in existence since 1970’s. Its primarily intent was to give a measure of the vulnerability of mainframe computer to the disturbance in the electric power supply. But the curve has been used as a measure of power quality indices for electric drives and solid-state loads. In this report, the concept of 'standards' is introduced for the design of power acceptability curves. The power acceptability curves are aides in the determination of whether the supply voltage to a load is acceptable for the maintenance of a load process. The construction of the well known CBEMA power acceptability curve is discussed, and issues of three phase and rotating loads are discussed. iiiThe main conclusion of this work is that power acceptability curves can be designed to detect compliance or noncompliance of the distribution supply to effect a standard. If the load is a rectifier load, the standard is generally the permissible low threshold of DC voltage at the rectifier output. Other standards are possible including a speed standard for rotating loads. The general process of the design of a power acceptability curve entails the solution of a dynamic model for the load. The dynamic solution then gives a standard parameter versus time, and this is compared with the ultimate standard (e.g., Vdc = 0.87 per unit). This gives a permissible duration of a voltage sag event. The method is easily extended to the unbalanced three phase case. It is shown in the report that the CBEMA curve is effectively based on a single phase rectifier load with DC threshold voltage of 0.87 per unit in the undervoltage region. A double exponential equation describing the curve is developed. This provides a useful method to consider the effect of unbalanced voltage sags and to develop CBEMA-like curves for other types of loads. A scalar index of compliance with a power acceptability curve has been illustrated in this report as well.
Daniel Sabin and William Dabbs. IEEE STD 1159.3: The Power Quality Data Interchange Format (PQDIF). In 23rd International Conference on Electricity Distribution, page 5, June 2015. [ .pdf ]
IEEE Std 1159.3-2003 specifies the Power Quality Data Interchange Format, which is better known as PQDIF. This binary file format is used for the transfer of power quality data between software and hardware systems. This includes raw, processed, simulated, proposed, specified, and calculated data. The transfer file format includes the power quality measurements as well as appropriate characterization parameters, such as sampling rate, resolution, calibration status, instrument identification, location, and other related data or characteristics. The recommended practice also provides guidelines for transferring power quality data. Although it was reaffirmed in 2008, the field of power quality monitoring has evolved in the past decade, and the changes in this domain are not reflected in the current version of 1159.3. The paper will present the changes planned for the revision that will take place in 2015 and 2016.
Timothy Unruh. IEEE P1159/D3: Draft Recommended Practice for Monitoring Electric Power Quality, February 2018. [ http ]
This recommended practice encompasses the monitoring of electrical characteristics of single-phase and polyphase ac power systems. It includes consistent descriptions of conducted electromagnetic phenomena occurring on power systems. This recommended practice describes nominal conditions and deviations from these nominal conditions that may originate within the source of supply or load equipment or may originate from interactions between the source and the load. Also, this recommended practice discusses power quality monitoring devices, application techniques, and the interpretation of monitoring results.
Case Studies
This section contains citations to case studies involving power quality measurement.
Amit Kumar Shukla. Studies on Power Quality and, an LSE & PSOPC based Harmonic Estimation to Real Time Data. PhD Thesis, National Institute of Technology, Roukela, Odisha, India, May 2009. [ http ]
Electric power as a commodity is very different from other products – it is generated far from the point of use, is fed to the grid together with the output of many other generators and arrives at the point of use via several transformers and many kilometers of overhead and possibly underground cabling. Quality check of power is very important. But it has constantly been polluted by both consumers (non-linear loads) and utility companies (due to increased use of semi conductor based power processors). Assuring the quality of delivered power to be good enough for the application at hand calls for measurement and study of power quality at the point of common coupling.There are various categories of Power Quality issues. Issues related to voltage amplitude variations will include voltage sags/dips and voltage swells. Issue related to frequency is harmonics in the power system. Short term problems include transients and momentary interruptions. We have carried out a brief study of all these PQ issues, and problems caused by them.
Developments in the field of power electronics has brought tremendous power processing capability to engineers but it has also polluted the power system with harmonics. Then there are non linear loads that inject harmonics in the power system. Measurement and estimation of harmonics in power system has become one of the most important tasks in the hands of power system engineers for increasing reliability and quality of supplied power. For harmonic analysis FFT based schemes are unable to give enough information for PQ mitigation. So researchers have been attempting other methods to estimate harmonics in sampled voltage and current signals. Among these; least square estimation, for estimating amplitudes and particle swarm optimization with passive congregation, for estimating phase and frequency used together has most attractive features of compactness and fastness. We have developed a harmonic estimator based on LSE and PSOPC to estimate amplitude, phase and frequency of the sampled signal. We have used the estimator on real time data acquired using a digital storage oscilloscope in Electrical Machines Laboratory of Department of Electrical Engineering at NIT Rourkela. The results for estimating integral harmonics are attractive and encourage researchers to modify the estimator code to make it able to estimate inter-harmonics and sub-harmonics also.
Dilek Kucuk and Ozgul Salor. Assessment of extensive countrywide electrical power quality measurements through a database architecture. Electrical Engineering, 95, March 2013. [ http ]
This paper describes countrywide electrical power quality (PQ) assessments of the Turkish Electricity Transmission System through a genuine PQ database. The database stores the output of mobile PQ measurement systems which are established at 172 transformer substations of the transmission system. At 601 measurement points in these substations, which are potentially critical in terms of PQ, measurements are carried out by the mobile systems for a period of 1 week. PQ parameters defined in the IEC-61000- 4-30 standard in addition to power values are calculated from acquired raw data by the mobile-monitoring system and the resulting data are transferred to the PQ database. The database, based on a novel PQ data model, enables its users to take PQ snapshots of the transmission system countrywide and can be accessed through several interfaces including a visual query interface, a natural language interface, and a map interface. The overall PQ status of the measured points, representing the characteristics of the transmission system, is assessed through these interfaces and problematic points are determined while deriving important conclusions about the transmission system’s PQ behavior. Moreover, several novel PQ assessment methods are proposed and their applications on the PQ data are demonstrated especially through the map interface.
E. Gasch, M. Domagk, J. Meyer, S. Abdelrahman, H. Liao, and J. V. Milanović. Assessment of Power quality performance in distribution networks part I - Measurement campaign and initial analysis. In 2016 17th International Conference on Harmonics and Quality of Power (ICHQP), pages 164-169, October 2016. [ DOI | http ]
Power quality (PQ) is a raising concern in distribution grids of modern industrialized countries. The PQ monitoring activities of distribution system operators (DSO) and consequently the amount of PQ measurement data increases continuously. To keep the routine assessment of PQ levels efficient, new and automated tools for validating, analysing and visualizing these data are required. The paper illustrates the challenges of processing long-term PQ monitoring campaigns by using measurement data at 8 different sites in public low voltage (LV) networks for more than one year (64 weeks). The paper is divided into two parts. The first part describes the measurement campaign, the pre-processing of the data and an easy and flexible way for routine compliance assessment. The second part is dedicated to the comparison of two different global PQ indices for assessing an average site performance as basis for e.g. benchmarking purposes.
Classification
This section contains citations to publications regarding classification of power quality events.
Math H.J. Bollen, Irene Y.H. Gu, Peter G.V. Axelberg, and Emmanouil Styvaktakis. Classification of Underlying Causes of Power Quality Disturbances: Deterministic versus Statistical Methods. EURASIP Journal on Advances in Signal Processing, 2007(1), December 2007. [ DOI | http ]
This paper presents the two main types of classification methods for power quality disturbances based on underlying causes: deterministic classification, giving an expert system as an example, and statistical classification, with support vector machines (a novel method) as an example. An expert system is suitable when one has limited amount of data and sufficient power system expert knowledge; however, its application requires a set of threshold values. Statistical methods are suitable when large amount of data is available for training. Two important issues to guarantee the effectiveness of a classifier, data segmentation, and feature extraction are discussed. Segmentation of a sequence of data recording is preprocessing to partition the data into segments each representing a duration containing either an event or a transition between two events. Extraction of features is applied to each segment individually. Some useful features and their effectiveness are then discussed. Some experimental results are included for demonstrating the effectiveness of both systems. Finally, conclusions are given together with the discussion of some future research directions.
Mikael Wämundsson. Calculating voltage dips in power systems using probability distributions of dip durations and implementation of the Moving Fault Node method. PhD thesis, Chalmers University of Technology, Sweden, 2007. [ .pdf ]
This report is based on a master thesis work aimed at improving the Simpow Dips program, by implementing new features. Simpow Dips, in its existing version, simulates faults in all nodes in a given network and creates a result-file containing the during-fault voltages at each node for every fault. Improvements have been made in three aspects: the ability to also calculate the dip duration, an improved method for calculating the magnitude of the dip and a graphical presentation of the calculation results.
Sami Ekici. Classification of power system disturbances using support vector machines. Expert Systems with Applications, 36, August 2009. [ http ]
This paper presents an effective method based on support vector machines (SVM) for identification of power system disturbances. Because of its advantages in signal processing applications, the wavelet transform (WT) is used to extract the distinctive features of the voltage signals. After the wavelet decomposition, the characteristic features of each disturbance waveforms are obtained. The wavelet energy criterion is also applied to wavelet detail coefficients to reduce the sizes of data set. After feature extraction stage SVM is used to classify the power system disturbance waveforms and the performance of SVM is compared with the artificial neural networks (ANN).
Giovanni Pozzebon, Ricardo Machado, Natanael Gomes, Luciane Canha, and Alexandre Barin. Wavelet and PCA to Power Quality Disturbance Classification Applying a RBF Network. In Power Quality: Monitoring, Analysis, and Enhancement. InTechOpen, October 2010. [ http ]
This chapter proposes the application of a different method of power quality disturbance classification by combining discrete wavelet transform (DWT), principal component analysis (PCA) and an artificial neural network in order to classify power quality disturbances. The method proposes to analyze seven classes of signals, namely Sinusoidal Waveform, Capacitor Switching Transient, Flicker, Harmonics, Interruption, Notching and Sag, which is composed by four main stages: (1) signal analysis using the DWT; (2) feature extraction; (3) data reduction using PCA; (4) classification using a radial basis function network (RBF). The MRA technique of DWT is employed to extract the discriminating features of distorted signals at different resolution levels. Subsequently, the PCA is used to condense information of a correlated set of variables into a few variables, and a RBF network is employed to classify the disturbance types.
Economic Impact
This section contains citations to studies of the economic impact of power quality.
David Chapman. The cost of poor power quality. October 2001. [ .pdf ]
Electrical power is an important raw material for all commercial operations and, like any other raw material, the quality of supply is very important. The nature and causes of power quality defects have been outlined in Section 1 and are discussed in detail in later sections; this section concentrates on the effects of defects on production and the costs that can be expected to occur. As discussed in Section 1 there are five basic types of defect, each with different causes and effects and, of course, different cost implications.
Sean Elphick, Phil Ciufo, Vic Smith, and Sarath Parera. Summary of the economic impacts of power quality on consumers. In 2015 Australasian Universities Power Engineering Conference, September 2015. [ http ]
The quality of the electrical supply has a direct impact on the correct function and operation of equipment connected to the public electricity supply network. There is an expectation that devices will operate as designed and that equipment lifetime should, statistically, be close to the designed value. The reliability of the network is generally assumed to be high enough so as to not cause unacceptable issues with regard to loss of production or loss of functionality. Quantifying the cost to the consumer when the supply power quality or reliability are not as expected is an important metric and can be used as business case to justify expenditure in order to improve the supply network. This paper explores the research associated with quantifying the cost of reliability and power quality. Several power quality disturbances are investigated and possible methods of quantifying both the effect and cost are presented. Due to the complex nature of equipment performance with regard to power quality, there is a need for extensive research in order to develop a generalised approach to lifetime and cost evaluation.
N. Edomah. Effects of voltage sags, swell and other disturbances on electrical equipment and their economic implications. In Proceedings of the 20th International Conference and Exhibition on Electricity Distribution, pages 1-4, May 2009. [ DOI | http ]
Poor power quality has come to stay in most parts of the world. In most part of Africa, especially in Nigeria, it is almost normal not to have good clean power free from disturbances. If power equipment and loads could talk or express feelings, I am sure they would have made a big protest against the great injustice imposed on them. A survey was carried out amongst 15 multi-national companies in southwest Nigeria to ascertain the cause(s) and effects of poor power quality on electrical equipment and its economic implications. The survey revealed that 9 out of 15 of those companies loose an average of 5 variable speed (AC) drives every year owing to poor power quality. It also revealed that the most common disturbances faced are voltage sag and swell. This paper is aimed at stating some of the predominant power disturbance parameters, their sources and causes, the effect they have on electrical equipment, and their cost/economic implications. It also identifies some practical solutions and methods of addressing poor power quality issues
Hawaii
This section contains citations to publications regarding issues of renewable energy and power quality in Hawaii.
Christian Roselund. HECO grid plan could enable 3x as much rooftop solar in Hawaii. PV Magazine USA, July 2017. [ http ]
The draft grid modernization plan which HECO released late last week can be seen in light of these contradictions, as well as the requirement by state regulators that such grid modernization be done cost-effectively. After the state’s Public Utilities Commission rejected a 340 million grid modernization plan six months ago, HECO has come back with a plan whose first phase involves outlays of 205 million through 2023.
Hawaiian Electric Company. Modernizing Hawaii's Grid for our customers. Technical report, Hawaiian Electric Company, Inc., August 2017. [ .pdf ]
Modernizing Hawai‘i’s Grid For Our Customers is a grid modernization strategy that describes the scope, purpose, and estimated cost of the work required to update the Hawaiian Electric Companies’ energy network in the next six years, and how it will help the five islands served by the Companies to achieve a renewable portfolio standard of 48 percent by 2020 and ultimately 100 percent by 2045. Achieving the renewable portfolio standard goals will require a combination of both customer-owned distributed resources as well as larger grid-scale resources
Hawaiian Electric Company. Hawaiian Electric Company Tariff Rule No. 16 Interruption of Service. [ .pdf ]
Specifies ruies for interruption of electrical service.
Hawaiian Electric Company. Hawaiian Electric Tariff Rule No. 2 Character of Service. [ .pdf ]
Specifies the "character of service" to be provided to customers, including: "voltage variation will normally be no more than 5 percent above or below the nominal voltage", along with a list of seven situations in which voltage can vary outside the 5 percent threshold. In particular, fluctuations outside this threshold can last up to five minutes.Customers must provide power factor corrective equipment if they have equipment that reduces PF below 85%.
Monitoring
This section contains citations to publications regarding monitoring devices and systems.
Shahedul Haque Laskar. Power quality issues and need of intelligent PQ monitoring in the smart grid environment. In Universities Power Engineering Conference (UPEC), 2012 47th International, pages 1-6. IEEE, September 2012. [ http ]
PQ issues are very much important for utilities, customers and end users and it is essential to be known by the concerned authorities and users for reduction of economic losses due to the poor PQ. The cost of poor PQ is high and rising. The paper gives insights on global economical losses due to poor PQ. The business risk posed by PQ problems is a real one with even ‘low tech’ industries exposed to serious financial losses. The global economic meltdown is not the only factor that is pulling down the revenues of Asian countries. A study released said Indian industries lost more than $ 9.6 billion in 2008-09 due to power outages. According to 2008 reports, poor power quality costs European business more than 150 billion dollars a year.In this paper, a comprehensive survey on different power quality related problems as experienced by customers in different countries are highlighted. Summary of PQ costs are given. As the consequence of poor PQ might have large financial impacts on a country’s economy, more initiatives are expected from the concerned parties and regulating bodies to take corrective measures for maintaining better power quality from utility and at end users. Smart grid requires intelligent PQ monitoring to solve different PQ related problems. Authors proposed an intelligent power quality monitoring system that will help to detect different PQ disturbances and consequently assist in employing or implementing appropriate mitigation techniques.
Richard Bingham. Measurement instruments for power quality monitoring. In Transmission and Distribution Conference and Exposition, April 2008. [ http ]
IEEE 1159 is a recommended practice for monitoring electric power quality. Among the clauses within this standard is a section describing the measurement instruments for power quality monitoring. Depending on the situation being addressed, or the survey being made, a variety of different measuring instruments could be used. For simple situations, a handheld multimeter or oscilloscope could suffice. For more involved situations, a dedicate power quality monitor might be required. No matter how sophisticated, each measuring instrument has limitations that should be considered. Often these limitations are imposed by the response of the voltage and/or current probes and transducers, external to the measurement device. This paper outlines these various issues that should be considered when selecting a measuring instrument for use to measure power quality and its influence in an electrical power system.
L. Ferrigno, C. Landi, and M. Laracca. FPGA-based Measurement Instrument for Power Quality Monitoring according to IEC Standards. In 2008 Instrumentation and Measurement Technology Conference Proceedings, May 2008. [ http ]
Nowadays, large scale monitoring of Power Quality (PQ) in electrical power plants is a pressing need in many countries due to the liberalization of the electrical market and the deeper interconnections of electrical networks. Many instruments are available on the market but their cost make them not suited for the purpose. To overcome this problem the paper proposes a prototypal measurement instrument for PQ monitoring based on field programmable gate arrays, in compliance with IEC 61000-4-30 and IEC 61000-4-7 standards. Features of the proposing instrument are the good accuracy and the cost effectiveness. The realized instrument applies a novel digital filter approach to harmonic and interharmonic estimation. After a detailed description of the proposed instrument, an experimental performance characterization in emulated environment is presented. Results are also compared with those furnished by a FFT approach suggested by IEC61000-4-7 standard confirming the goodness of the proposal.
Marcos Xavier and Mayra Noronha. High performance power quality monitoring system. In 17th International Conference on Harmonics and Quality of Power, October 2016. [ http ]
Monitoring systems related to power quality were built in order to verify that a system or machine is functioning properly in accordance to standards. This paper aims to present a system that was developed on the CompactRIO controller from National Instruments. As a programming tool, LabVIEW software was used to elaborate the platform in order to monitor and to detect disturbances that can occur in any power system. Methods such as Fast Fourier transform (FFT) and the Wavelet transform were used to monitor harmonics on the system and to detect short time voltage variations. When a short duration voltage fluctuation or an exceeding in the harmonic limits is noticed, the implemented system records the event time for further analysis. The platform also records all the signal in the time domain continuously without any blank window. The postprocessing is performed using the samples of the recorded signal. The analyzer can choose the amount of pre- and/or post event time, in 60 Hz cycles, to rebuild the event waveform. To validate the platform, it was subjected to tests such as the system voltage variation, momentary interruption, voltage sag and violations in harmonic distortion rates.
K. Suslov, N. Solonina, and A. Smirnov. Distributed power quality monitoring. In IEEE 16th International Conference on Harmonics and Quality of Power, January 2014. [ http ]
One of the most important characteristics of the electric power system is its observability. The observability is essential not only for the power flows and power supply reliability indices, but also for the power quality indicators, particularly for the nonsinusoidality of supply voltage waveform. The wide use of power electronics components in intelligent electric power systems, which will increase in the future, leads to the occurrence of harmonic voltage and currents. Moreover, the electric power system facilities can be represented by both the sources and the consumers of high harmonics []. In this connection the assessment of impact of individual facilities on the power quality is a topical problem. The observability of electric power systems can be provided with the use of phasor measurement units (PMUs). The paper proposes a distributed power quality monitoring system based on the available PMU infrastructure to continuously control the level of high harmonics in different cutsets of the electric power system.
Wangfang Xu, Gang Xu, Zhijiang Xi, and Chuanyong Zhang. Distributed power quality monitoring system based on EtherCAT. In 2012 China International Conference on Electricity Distribution, September 2012. [ http ]
To resolve multi-point power quality monitor of smart grid and voltage fluctuation of industrial and mining enterprises,the distributed power quality monitoring system is developed. The system includes three parts:monitoring terminal, communication network and monitoring center. Monitoring terminal can be installed on any node for Monitoring, collect the high speed data of grid, and show the power quality message real-timely. Communication network can exchange mass data between monitoring terminal and monitoring center by using EtherCAT. EtherCAT is very excellent at transmission speed and reliability. Monitoring center collects and stores the power quality data of all monitoring terminals. Through analyzing the data, monitoring center can recognize power quality disturbance, find the disturbance source, evaluate power quality and publish information.
Wangfang Xu, Gang Xu, and Haitao Yuan. High performance distributed power quality monitoring IED used in smart grid. In 2014 China International Conference on Electricity Distribution, September 2014. [ http ]
With the development of Chinese smart grid, power quality problem becomes more and more serious, and it is most urgent to establish a large-scale management system which can real-time monitor multi-node power quality of power generation, transmission and distribution aspects. Power quality monitoring IED based on the design of IEC61850 standard for substation automation system can unify device external port, effectively solve interoperability problem of different devices, and greatly simplify the architecture design and communication network of large-scale power quality management system. This article develops a high-performance distributed power quality monitoring IED based on I EC6 1850 standard. The IED is composed by three cores high-performance PowerPC, D S P and FPGA. So it can realize high-speed acquisition, real-time processing and analysis of huge amounts of data. It supports both high-speed analog sampling and digital sampling that means the IED can receive IEC61850-9-2 packets through SV module. The SV and CPU modules exchange real-time data via high-speed LVDS bus on the backplane. The monitoring IED can be installed on any monitoring node as its distributed architecture design. Through MMS service the remote monitoring center collects power quality data of all monitoring nodes, according to the data analysis, completes the funtions of power quality disturbance identification, power quality disturbance source localization, power quality assessment, etc.
Maxim Chernyshov, Maxim Nadymov, Paul Buyankin, and Valery Dovgun. A distributed measurement system for power quality monitoring. MATEC Web of Conferences, 37(01015), 2015. [ .pdf ]
A good power quality (PQ) is an important factor for the reliable operation of electrical loads. High penetration of nonlinear loads, such as compact fluorescent lamps, light-emitting diode (LED) lamps, switching mode power suppliers give rise to serious challenges in power quality for distribution systems. Harmonic distortion produced by nonlinear loads causes several problems, ranging from increased power losses in customer equipment, power transformers and power lines, shorter life of organic insulation to malfunction of electronic devices and telecommunication systems. Last decade power quality issues have become serious concern for commercial and office customers. According to Electric Power Research Institute (EPRI) estimates, more than 70% of all loads are nonlinear. The IEEE and international standards [1, 2] set the limits for harmonic distortions. However they do not offer any strategy for the detection of distorting sources in the grid. Information on the location of the distorted sources can be obtained by distributed measurement system abled to perform simultaneous measurements in different nodes of the considered grid. This paper describes a distributed measurement system for power quality monitoring. The results of PQ measurements are reported.
Petr Bilik, Ludvik Koval, and Jiri Hula. Modular system for distributed power quality monitoring. In 9th International Conference on Electrical Power Quality and Utilization, October 2007. [ http ]
BK-ELCOM is a modular HW & SW platform for power quality monitoring and analysis based on virtual instrumentation technology. The analyzer of BK-ELCOM product line is based on PC hardware equipped by 16-bit NI data acquisition board running the instrument firmware fully written in LabVIEWtrade 8.2. Implemented algorithms follow the requirements of the latest power quality standards like IEC61000-4-30, IEC61000-4-15, IEC61000-4-7, EN 50160. Newly developed data storage format EDF (Extended Data Format) brings open platform for storing any type data for power quality analyzer. EDF brings also new possibilities for the postprocessing software package.
Juan Rosa and Antonio Moreno-Munoz. A web-based distributed measurement system for electrical Power Quality monitoring. In 2010 Sensor Applications Symposium, February 2010. [ http ]
Industries' systems are shifting toward almost entirely sophisticated electronic devices. Power Quality (PQ) analysis is getting importance for the economy because this equipment is highly sensitive to PQ events. Control and supervision of an industrial process has mainly been focused on the electrical protection, and little attention has been paid to the quality of the electrical supplies. Nowadays, measurement and communications systems have advanced to enable the installation of web-based sensors within a PQ assessment scenario. In this sense, this paper presents an innovative low-cost measurement system, as well as investigates the challenges and trends in the development of distributed PQ measurement systems using smart sensors.
M. Di Manno, P. Varalone, P. Verde, M. De Santis, C. Di Perna, and M. Salemme. User friendly smart distributed measurement system for monitoring and assessing the electrical power quality. In Proceedings of the 2015 AEIT International Annual Conference, 2015. [ http ]
This paper presents an innovative smart measurement system, as well as investigates the challenges and trends in the development of distributed Power Quality (PQ) smart measurement systems. PQ monitoring is getting importance for the customers even for the more sensitive modern equipment. Up today, the control and supervision of an industrial process has mainly been focused on the electrical protection, and little attention has been paid to the quality of the electrical supplies. Nowadays, measurement and communication systems have advanced to enable the installation of web-based sensors within a PQ assessment scenario. In this perspective, we propose a measurement instrument easy to use, chip, flexible, and with advanced world wide web capability. This paper also shows the first releases of prototypes already realised.
P. Daponte, M. Di Penta, and G. Mercurio. TRANSIENTMETER: a distributed measurement system for power quality monitoring. In Ninth International Conference on Harmonics and Quality of Power, October 2000. [ http ]
The paper deals with the design and implementation of TRANSIENTMETER, a monitoring system for the detection, classification and measurement of disturbances on electrical power systems. TRANSIENTMETER uses a CORBA architecture as communication interface, wavelet-based methods for automatic signal classification and characterization, and a smart trigger circuit for the detection of disturbances.
Andres Legarreta, Javier Figueroa, and Julio Bortolin. An IEC 61000-4-30 Class A Power quality monitor: Development and performance analysis. In 11th International Conference on Electrical Power Quality and Utilisation, September 2011. [ http ]
Power Quality assessment is today one of the main ways to improve energy efficiency. International standards tend to restrict the way this assessment is done, by defining the measurements methods that should be adopted by an instrument. This work describes some of the constrictions and requirements assumed for the design of the high performance Power Quality data logger PQ1000, taking into account the international standards IEC 61000-4-30 Class A and the IEC 61000-4-15 published in August 2010. Trough it, the most important demands of the IEC 61000-4-30 class A instruments are exposed. Details of the hardware components are also shown, and the most important points of the signal processing path are explained. The performance in the RMS values determination is given, also the frequency response for harmonics measurement are shown, and a detailed analysis of fulfillment of the tests given in the IEC 61000-4-15 ed. 08-2010 are given in the final section. Before the publication of this ed.08-2010 the Cigre C4.1.01/CIRED 2 CC02/UIE WG2 - 2004 protocol was the reference document that in addition with the IEC standard was used for the evaluation of digital flicker meters. This protocol aim is to guarantee a higher degree of compatibility between instruments of different manufacturers and models. The tests here presented intend to submit the equipments to a more real situation, and try to show possible hardware or firmware defects. The results given by the PQ1000 widely surpasses the standards exigencies.
Omar Sayied, James Spaulding, and Basier Akbary. Power quality metrics calculations for the smart grid. May 2013. [ .pdf ]
The main goal of this project was to create a software system that analyzed data collected from smart meters and alerted the user of power quality issues. Power quality, for the purposes of this project, will be defined as IEEE Std 1159 states, “a wide variety of electromagnetic phenomena that characterize the voltage and current at a given time and at a given location on the power system.” Power quality metrics are defined by a percentage variance from the nominal value over a period of time. The metrics focused on in this report were limited by the resolution of data collected from the smart meters, which was 16.67 ms. This resolution allowed us to analyze disturbances including voltage sags, voltage swells, and harmonics (these disturbances will be further discussed in the body of the report). Along with these disturbances, we also found intervals in the data where low power factor (PF) was of concern.During phase one; we researched definitions, causes, and effects of the aforementioned disturbances. From this, we determined that the best approach to classify these issues would be to use the per-unit system and classify them according to parameters set for power quality issues described in IEEE Std 1159. Once enough data was collected, algorithms were written to extract the data from a comma separated value (.csv) file and uploaded into MatLab. Once the data was uploaded into MatLab, techniques such as the fast Fourier transform (FFT) and averaging sliding window were carried out to locate disturbances. The FFT gave us a means to traverse between the time domain and the frequency domain. The averaging sliding window acted as a low pass filter and got rid of noise that would otherwise flag the beginning of a disturbance haphazardly, ultimately slowing down our algorithms. The algorithms were written as functions, tested and compared with known results from other sources, and then added to a graphical user interface (GUI). The GUI was designed to logically allow any user to plot and textually output any power quality issues, found within our resolution limits, for their own inspection.
Dilek Kucuk, Tolga Inan, Ozgul Salor, Turan Demirci, Yener Akkaya, Serkan Buhan, Burak Boyrazoglu, Osgur Unsar, Erinc Altintas, Burhan Haliloglu, Isik Cadirci, and Muammer Ermis. An extensible database architecture for nationwide power quality monitoring. Electrical Power and Energy Systems, 32, 2010. [ http ]
Electrical power quality (PQ) data is one of the prevalent types of engineering data. Its measurement at relevant sampling rates leads to large volumes of PQ data to be managed and analyzed. In this paper, an extensible database architecture is presented based on a novel generic data model for PQ data. The proposed architecture is operated on the nationwide PQ data of the Turkish Electricity Transmission System measured in the field by mobile PQ monitoring systems. The architecture is extensible in the sense that it can be used to store and manage PQ data collected by any means with little or no customization. The architecture has three modules: a PQ database corresponding to the implementation of the generic data model, a visual user query interface to enable its users to specify queries to the PQ database and a query processor acting as a bridge between the query interface and the database. The operation of the architecture is illustrated on the field PQ data with several query examples through the visual query interface. The execution of the architecture on this data of considerable volume supports its applicability and convenience for PQ data.
Y. Liu, S. You, W. Yao, Y. Cui, L. Wu, D. Zhou, J. Zhao, H. Liu, and Y. Liu. A Distribution Level Wide Area Monitoring System for the Electric Power Grid: FNET/GridEye. IEEE Access, 5:2329-2338, February 2017. [ DOI | http ]
The wide area monitoring system (WAMS) is considered a pivotal component of future electric power grids. As a pilot WAMS that has been operated for more than a decade, the frequency monitoring network FNET/GridEye makes use of hundreds of global positioning system-synchronized phasor measurement sensors to capture the increasingly complicated grid behaviors across the interconnected power systems. In this paper, the FNET/GridEye system is overviewed and its operation experiences in electric power grid wide area monitoring are presented. Particularly, the implementation of a number of data analytics applications will be discussed in details. FNET/GridEye lays a firm foundation for the later WAMS operation in the electric power industry.
J. Guo, Y. Zhang, M. A. Young, M. J. Till, A. Dimitrovski, Y. Liu, P. Williging, and Y. Liu. Design and Implementation of a Real-Time Off-Grid Operation Detection Tool from a Wide-Area Measurements Perspective. IEEE Transactions on Smart Grid, 6(4):2080-2087, July 2015. [ DOI | http ]
Real-time situational awareness tools are of critical importance to power system operators, especially during emergencies. The availability of electric power has become a linchpin of most post-disaster response efforts, because public and private sector services depend upon it. Knowledge of the scope and extent of facilities impacted, as well as the duration of their dependence on backup power, enables emergency response officials to plan for contingencies and provide a better overall response. Based on the measurement data acquired by the frequency disturbance recorders deployed in the North American power grids, an off-grid detection method is proposed and implemented. This method monitors the critical electrical loads and detects the transition of these loads from an on-grid operation to an off-grid operation, during which the loads are fed by an uninterrupted power supply or a backup generation system. The details of the detection algorithm are presented, and some case studies and off-grid detection scenarios are also provided to verify the effectiveness and robustness. This paper also presents the real-time implementation of this method and several effectively detected off-grid situations. Moreover, two visualization tools are developed to display the real-time system operation condition in an intuitive manor.
Impact of Renewable Energy
This section contains citations to case studies involving the impact of renewable energy on power quality.
R. Bayindir, S. Demirbas, E. Irmak, U. Cetinkaya, A. Ova, and M. Yesil. Effects of renewable energy sources on the power system. In 2016 IEEE International Power Electronics and Motion Control Conference (PEMC), pages 388-393, September 2016. [ DOI | http ]
Recently, growing electrical energy market and increasing integration of renewable energy sources (RES) in power systems have lead to new challenges on network planning step and operation, thus it is required to investigate and analyze properly the impacts of integrated RES on the power system. In this paper, the electricity transmission network with wind farms (WF) is modeled. For the grid model, a part of Izmir region is chosen due to the amount of installed generation plants based RES especially wind energy in this region. The comparison between unexpected variations to voltage profile of the power system before and after RES integration to the power system is demonstrated. In the modeling of the electricity transmission network with RES, Digsilent/Power Factory is used as software. The different case studies in integration of different amounts of RES are implemented on the developed grid model. As a result of the conducted case studies, effects of RES on existing power system are evaluated and graphics obtained from the simulation are presented. Especially, the voltage profile of power system is examined.
Gopa Ranjan Mohapatra. Voltage and stability analysis of distribution networks with non-conventional energy sources / Gopa Ranjan Mohapatra. PhD thesis, 1997. [ http ]
The impact of renewable energy installations connected to the utility grid is an important issue concerning the technical and economic viability of harnessing these emerging energy sources. Distribution networks must be carefully controlled in order to maintain an acceptable power supply quality. The major sources of non-conventional energy are small scale generation and storage from mini hydro, photovoltaic, wind power, fuel cells, battery, flywheel, pump storage and biomass. The aim of this thesis is to analyse the variation in voltage of the distribution network when renewable energy sources are interconnected to the distribution network, in terms of it's stability. In particular this study analyses the impact of interconnection of small synchronous generators to the utility power grid. Dynamic stability analysis is mainly concerned with analysing the response of electrical power system to small perturbation about a given operating point. These studies are particularly important due to the growing interest in interconnecting small renewable energy sources to large and complex power systems. Simulation studies were carried out in order to find out the transient stability and voltage stability of the non-conventional energy sources under different operating conditions. A 5-second simulation was conducted using explicit numerical integration (Euler method) and an integration time step of 0.002 second. Power System Toolbox was used for analysis.The multimachine power system models used in this thesis are generated in MATLAB code. The load flow is performed on the multimachine power system correponding to the loading condition to be investigated. The machines are represented by the two-axis models, the exciters by IEEE Type-1 models and the loads are modelled as constant impedances. To save programming time, it has become common to limit the machine and exciter representations to some specified models. The network admittance matrix is reduced by retaining only the internal buses of the generators. The reduced network, machine and exciter data are then combined to form a linearised state-space model representing the entire system. The simulation studies are applied to a four machine ten bus system. It is clear from the analysis that much care should be taken based on the stability point of view while interconnecting the small renewable energy sources to the utility. The renewable energy sources should be interconnected at a point which provides higher stability margin.The renewable energy sources is a viable option if it is connected to the distribution network with necessary methods of improving transient stability and voltage stability.
Titiksha Vjay Joshi, Gerald T. Heydt, Raja Ayyanar, Vijay Vittal, and Arizona State University. Impact of Distributed Photovoltaic Generation and Customer Loads on Power Quality of a Distribution System. PhD thesis, 2014. [ http ]
abstract: There has been a considerable growth in distributed photovoltaic (PV) genera-tion and its integration in electric power distribution systems. This has led to a change in the distribution system infrastructure. Properly planned distributed gen-eration can offer a variety of benefits for system operations and enhance opera-tional performance of the distribution system. However, high penetration of PV resources can give rise to operating conditions which do not arise in traditional systems and one of the potential issues that needs to be addressed involves impact on power quality of the system with respect to the spectral distortion in voltages and currents. The test bed feeder model representing a real operational distribution feeder is developed in OpenDSS and the feeder modeling takes into consideration the ob-jective of analysis and frequency of interest. Extensive metering infrastructure and measurements are utilized for validation of the model at harmonic frequencies. The harmonic study performed is divided into two sections: study of impact of non-linear loads on total harmonic voltage and current distortions and study of impact of PV resources on high frequency spectral distortion in voltages and cur-rents. The research work incorporates different harmonic study methodologies such as harmonic and high frequency power flow, and frequency scan study. The general conclusions are presented based on the simulation results and in addition, scope for future work is discussed. Dissertation/Thesis Masters Thesis Electrical Engineering 2014
Bryan G. Salvatierra, Diego H. Dominguez, Diego Chacon-Troya, and Walter H. Orozco. Power quality analysis of a low-voltage grid with a solar photovoltaic system. In Electrical and Computer Engineering (CCECE), 2017 IEEE 30th Canadian Conference on, pages 1-6. IEEE, 2017. [ DOI | http ]
The generation of electricity through renewable sources has exponentially increased in recent years in response to environmental pollution caused by fossil fuels. When we talk about renewable energy is difficult not to refer to solar photovoltaic technology due to its high rate of growth compared to their peers and potential. This is associated with the fact that the Ecuadorian government is implementing a process of changing the production and country's energy matrix where one of the fundamental pillars is to eliminate dependence on fossil resources and promote the use of renewable energy. Therefore, this makes clear that it is important and needed to study the effects and possible problems that entails the use of photovoltaic systems connected to the network. In this context, this work focuses on power quality by connecting photovoltaic plants to low-power electrical distribution networks. The evaluated system is composed of a group of panels of different technologies connected to a communication unit that forms the connection point of the photovoltaic system and the electric network. Measurement and data acquisition in real time of the implemented system and the respective analysis was made by considering the existing regulations. Finally, a mathematical analysis was performed in order to analyze the impact of the most important variables on power quality.
G. M. Shafiullah, Amanullah M. T. Oo, A. B. M. Shawkat Ali, Peter Wolfs, and Alex Stojcevski. Experimental and simulation study of the impact of increased photovoltaic integration with the grid. Journal of Renewable and Sustainable Energy, 6(3), 2014. [ DOI | http ]
The abundance, availability, and climate-friendly characteristics of solar photovoltaic (PV) energy encourage nations around the globe to adopt it to assist in overcoming global warming as well as build a sustainable society for the future. The intermittent nature of solar energy generation and the associated power electronic inverters with connected consumer loads creates a number of potential challenges in integrating large-scale PV into the grid that affects power quality of the distribution networks. This paper investigates the impacts of varying PV integration into the grid through experimental and simulation studies. Initially, several experiments were conducted with varying PV penetration and load conditions using the Renewable Energy Integration Facility at CSIRO, Newcastle, Australia. Later, a simulation model was developed that mimics the experimental facility used at CSIRO to investigate the adverse impacts on integrating large-scale PV into the grid using the power system simulation software PSS Sincal. Experimental and simulation analyses clearly indicate that integration of PV into the grid causes power quality issues such as voltage instability, harmonic injection, and low power factor into the networks and the level of these impacts increases with the increase of PV penetration.
Elson N. M. Silva, Anselmo B. Rodrigues, and Maria Da Guia Da Silva. Stochastic assessment of the impact of photovoltaic distributed generation on the power quality indices of distribution networks. Electric Power Systems Research, 135:59-67, 2016. [ DOI | http ]
•Power quality indices based on the cumulative duration are evaluated.•DG may degrade the voltage conformity indices in feeders with voltage regulators.•The connection of DG increases the lifespan of the voltage regulators.•DG causes large variations in the voltage unbalance indices.•Power quality is less affected by the photovoltaic DG than the fossil DG. This paper aims to assess the impact of photovoltaic distributed generation (PVDG) connection on the power quality indices (PQI) of distribution networks, such as: long term voltage variations (voltage conformity issues) and voltage unbalance. The stochastic nature of PVDG and loads were considered in the study using probabilistic techniques. The impact of PVDG on the number of tap changes of the voltage regulators was investigated. The tests results in a real life large scale distribution network demonstrated that the PVDG can cause around 31% of improvements in the voltage conformity indices. This impact is less beneficial than the one associated with the connection of conventional distributed generation due to the variability in the primary energy resource. Furthermore, it was demonstrated that the connection of PVDG increases the lifespan of the voltage regulators as a result of a reduction about 20% in the number of tap changes.
Myat Mon Yee and Chatchai Sirisamphanwong. Analysis of the Impact of Distributed Grid-Connected PV System on Power Quality of the Electrical Distribution Network. Applied Mechanics and Materials, 839-839(World Future Alternatives):124-129, July 2016. [ DOI | http ]
Electricity generation from solar energy by using PV cells is drastically increased due to global warming concern, greenhouse effect, and quality of living standards. However, PV generation may offer variable and unpredictable energy output due to intermittent nature of solar irradiance and hence, integration of PV into grid may provide some drawback effect to the power system. The aim of this paper is to investigate the impact of grid connected PV system on the power quality of distribution network. The power quality analysis is based on real measurements of 10 kWp, Energy Park SERT, School of Renewable Energy, Naresuan University, Thailand. Parameters such as active and reactive power, voltage, current, power factor, THDv, THDi, individual harmonic voltage and harmonic current are observed for the investigation of the interaction between SERT PV system and distribution network’s power quality. According to the measured data, PV system operation is negligible in terms of voltage distortion, voltage magnitude and frequency variation. Therefore, it can be noticed that 10 kWp SERT PV system does not effect on the distribution system power quality due to low PV penetration level.
Sebastijan Seme, Niko Lukač, Bojan Štumberger, and Miralem Hadžiselimović. Power quality experimental analysis of grid-connected photovoltaic systems in urban distribution networks. Energy, 2017. [ DOI | http ]
This paper presents the analysis of the impact of dispersed source production on the electric distribution network. The focus is on the production of electric energy by photovoltaic systems in public distribution networks. Photovoltaic systems may in certain cases influence voltage quality in public distribution networks, which is determined by the EN 50160 standard. Photovoltaic systems affect the voltage profile and harmonic distortion of current and voltage. Ensuring the appropriate voltage profile is especially important in radial networks because of eventual huge voltage drops. Many photovoltaic systems on a radial network with relatively high short-circuit impedance and relatively low short-circuit power can be problematic with regard to the permitted level of harmonic distortion, particularly at lower power. The analysis of power quality is based on real measurements of total harmonic distortion (THD) on four existing photovoltaic systems and two transformer stations in the urban electric distribution networks. •The production of electric energy by photovoltaic systems.•Voltage quality and harmonic distortion of current and voltage (EN 50160).•The power quality of PV systems connected to an urban distribution network.•PV systems use inverter, which enable synchronous operation with the dist. network.
Rita Pinto, Sílvio Mariano, Maria Do Rosário Calado, and José Felippe de Souza. Impact of Rural Grid-Connected Photovoltaic Generation Systems on Power Quality. Energies, 9(9):739, September 2016. [ DOI | http ]
Photovoltaic (PV) generation systems have been increasingly used to generate electricity from renewable sources, attracting a growing interest. Recently, grid connected PV micro-generation facilities in individual homes have increased due to governmental policies as well as greater attention by industry. As low voltage (LV) distribution systems were built to make energy flow in one direction, the power feed-in of PV generation in rural low-voltage grids can influence power quality (PQ) as well as facility operation and reliability. This paper presents results on PQ analysis of a real PV generation facility connected to a rural low-voltage grid. Voltage fluctuations and voltage harmonic contents were observed. Statistical analysis shows a negative impact on PQ produced by this PV facility and also that only a small fraction of the energy available during a sunny day is converted, provoking losses of revenue and forcing the converter to work in an undesirable operating mode. We discuss the disturbances imposed upon the grid and their outcome regarding technical and economic viability of the PV system, as well as possible solutions. A low-voltage grid strengthening has been suggested and implemented. After that a new PQ analysis shows an improvement in the impact upon PQ, making this facility economically viable.
R. O. Anurangi, Asanka S. Rodrigo, and Upuli Jayatunga. Effects of high levels of harmonic penetration in distribution networks with photovoltaic inverters. In Industrial and Information Systems (ICIIS), 2017 IEEE International Conference on, pages 1-6. IEEE, 2017. [ DOI | http ]
The rapid increase of the grid-connected solar photovoltaic (PV) has been reported to make a considerable impact on the power quality (PQ) in the grid. This paper discusses the generation and propagation of significant current/voltage harmonics which are caused by PV inverters in distribution networks. The impact made by high switching frequencies and different operating scenarios are studied by detailed modelling of PV inverters in a typical low voltage (LV) distribution network using PSCAD/EMTDC simulation platform. It was found that the PV inverter systems inject high frequency current harmonics at the switching frequency or associated side bands. Low order current harmonics are also significant due to the inability of switching control system of PV inverter to produce perfectly sinusoidal output. It is found that the amount of harmonics depend on the inverter control strategy, background distortion present at the point of connection (POC) and the percentage of inverter loading. Further, harmonic voltage distortion is found to be mainly dependent on the impedance of the distribution network where weak networks lead to give rise to higher voltage distortions. Moreover, harmonic resonances are significant due to the interaction of the inverter output impedance and the grid inductance. The current harmonics injected by single phase inverters have been found substantial and influential with regard to the energy transmission and increase losses.
Rahmat Heidari, Julio H. Braslavsky, and Maria M. Seron. Analysis of voltage bounds in grid-connected inverters with automatic reactive power control under persistent load variations. In Decision and Control (CDC), 2017 IEEE 56th Annual Conference on, pages 2047-2052. IEEE, 2017. [ DOI | http ]
The rapid growth of variable electricity generation in low-voltage electricity grids poses new challenges to the operation of power systems. Distributed non-dispatchable electricity from renewable sources, such as photovoltaic solar energy, can potentially impact power quality, particularly voltage regulation. In response, inverter manufacturers and recent standards have introduced automatic inverter response functions, such as the commonly known as Volt-Watt and Volt-VAR functions. These functions aim to mitigate under- and over-voltage events by gracefully curtailing injected active power, or injecting/absorbing reactive power when the voltage at the point of coupling exceeds the predefined regulation limits. While the utility of these new inverter functionalities has been established in various studies, the analysis of their stability properties, particularly in the context of persistent changes in load, remains scarce. This paper contributes a framework for nonlinear analysis of voltage stability and boundedness in distribution networks with variable loads. The framework is applied to the case of a single grid-connected inverter to derive sufficient conditions for steady-state voltage boundedness as a function of the load variation levels in the inverter bus. Simulation results illustrate the accuracy of these bounds for varying load conditions.
M. Farhoodnea, A. Mohamed, H. Shareef, and H. Zayandehroodi. Power quality impact of grid-connected photovoltaic generation system in distribution networks. In 2012 IEEE Student Conference on Research and Development (SCOReD), pages 1-6, December 2012. [ DOI | http ]
In recent decades, the presence of photovoltaic (PV) systems is increased to provide power for local or remote loads. However, when a large PV system connects to the distribution network under variable weather conditions, it may cause severe problems for power system components. This paper presents a dynamic power quality analysis on a grid-connected PV system in a distribution system subjected to different weather conditions. A 1.8 MW grid-connected PV system in a radial 16 bus test system is modelled and simulated under varying solar irradiations using the Matlab/Simulink software. The simulation results proved that the presence of high penetrated grid-connected PV systems can cause power quality problems such as voltage rise, voltage flicker and power factor reduction.