Power Quality Measurements Research Articles

Assessing the Performance of a Static Var Compensator for an Electric Arc Furnace

The advantages of a static var compensator (SVC) for electric arc furnace (EAF) and ladle melt furnace (LMF) applications are well known. The SVC minimizes the impact of the EAF and LMF on the utility and improves the efficiency of both furnaces. In this application, it was desirable to quantify the performance of the SVC. This paper describes power quality measurements that were taken on the electrical distribution system to evaluate the performance of the SVC. The purpose of the power quality measurements was to monitor the voltage regulation, harmonics, flicker, and other power quality quantities at the 138-kV utility point of common coupling (PCC), as well as the 34.5-kV system serving the SVC, EAF, and LMF. The measurements and subsequent analysis established a baseline for the SVC performance and identified areas of concern. This paper describes the analysis of the measurements and evaluation of the SVC performance.

Measurement of Power Quality on the COTEK S1500-124 Inverter’S Terminals in Case of Linear Load Supplying

This paper describes the approach and results of power quality measurement at the outputs of DC/AC inverter COTEK S1500-124 supplying a linear load. There were used load examples as a classic light bulb of 150 W nominal power and an air heater with adjustable power chosen as linear load. The measurement was realized for purposes of verification of power quality indexes at the outputs of DC/AC inverter COTEK S1500-124 declared by its manufacturer.

IEC 국제표준에 따른 계통연계형 풍력터빈 발전기계통의 전력품질 측정방법에 관한 심화연구

As more and more renewable energy resources are connected into the existing power system and their generation capacities are increasing, the need for regulations to minimize their impacts on the power grid is increasingly growing. And minimizing the irregular impacts made by grid-connected wind generators is important, since the output power generated by renewable energy resources can be changed easily by the weather condition and surrounding environment. In South Korea, an operational technical standard for distributed generation is used as a regulation, in which renewable energy sources including wind power are considered as a kind of distributed generation. In this paper, an international standard, IEC 61400-21, for the grid-connected wind turbine generating system(WTGS) will be introduced and a comprehensive and detailed review on the measuring methods of power quality characteristic parameters for WTGS based on the related IEC standards will be presented. Additionally, some prerequisites for applying the international standards to KEPCO system will be proposed.

Optimization of Voltage Dip Suppression Effect by Resistor Insertion in Startup of Low-frequency Induction Furnace

Recently, in the distribution network, the rated capacities of the special loads that have the large starting currents are becoming bigger. So, the technical pre-studies for power quality are very important to suppress voltage troubles. In this study, as a special load, we consider the case that a large low-frequency induction furnace is connected to near the end of distribution network. The rated output is 800kW, and the rated capacity of the electric furnace transformer is 1000kVA. The inrush current generates during startup of the low-frequency induction furnace. By measurement of power quality, it is revealed that the inrush currents consist of the “magnetizing inrush current due to magnetic saturation of the electric furnace transformer” and the “inrush current due to the power factor correction capacitors”. We clarify the influence of the inrush currents on the voltage dip. And the effective measure (resistor insertion method) to reduce the inrush currents is proposed. We performed the EMTP simulation for the optimization of proposed method. As a result, it was verified that the analysis value and the measured value are in good agreement.

Development of the Low Cost Harmonic and Power Instrument by Using Fourier Series Method with Microcontroller

The objective of this paper is to present the application of microcontroller dsPIC30F6012A to measure the harmonics current and electrical power by using the Fourier series method to calculate the electrical parameters. This design is to develop the low cost harmonics instrument and to focus on working with the single phase AC system. The prototype was then developed to measure the harmonics current and power factor, and the result was compared with the standard instrument. The result is that most electrical parameters have the measurement errors of less than 4.0%. However, this idea could be developed so that it applies in the related work with the power quality measurement.

Assessing power quality of power system using FICA algorithm

The new developments in power system such as restructuring and competitive electricity market make power quality (PQ) an important factor in competition. However, finding a measure for PQ evaluation is very difficult due to many indices involved in PQ measurement. For this reason, obtaining a single quantitative index based on the standard measurements has been a new challenge in recent researches. In this paper, a data mining method is proposed to determine global indices for PQ. The continuous and discrete indices of PQ are considered and a Unified Power Quality Index (UPQI) is presented for each PQ index, based on the method of incorporation and normalization. The indices are normalized and classified. Then, the global PQ index of each distribution site is determined by the Fast Independent Component Analysis (FICA) algorithm. In this approach, the PQ measurements of 313 real distribution sites are used to assess and classify the indices for different type of loads in the real distribution system. The results show the capability of this method to obtain an accurate measure for PQ evaluation. In this method, the convergence rate is very fast. Also for evaluating the accuracy of the proposed algorithm, an intelligent method based on artificial neural network (ANN) and fuzzy logic to obtain a global index for PQ assessment are implemented that the comparing between this two method show that the proposed method is stronger and proper than the intelligent method. This method can be extended for many distribution sites.

On the Effects of Unbalances, Harmonics and Interharmonics on PLL Systems

The effects of unbalances, harmonics, and interharmonics on PLL systems are analyzed. After a brief review of some typical schemes for three-phase and single-phase PLLs, an analytical assessment of the phase angle and frequency errors for PLLs in the presence of disturbances is performed to obtain simple analytical formulas. Numerous case studies for the significant conditions and a possible application to the design of PLLs or to the compliance tests for PLL standards are discussed. Finally, the results of laboratory experiments on a power quality measurement instrument are presented.

A Low-Cost Power-Quality Meter With Series Arc-Fault Detection Capability for Smart Grid

This paper presents a low-cost digital single-phase power-quality measurement device for consumer use with a wide range of features, including series arc-fault detection, load trip on failure, and phase/neutral line wiring mix up indication. A wavelet multiresolution analysis technique was utilized for the voltage transient event detection and the current drop pattern recognition, specifically to arc fault. The last feature also involved the use of adaptive thresholding, peak detection, and repetition frequency calculation. A computationally efficient and accurate Goertzel filter was used for total harmonic distortion calculation. In addition, this meter can measure phase fundamental frequency (using the zero-crossing technique), rms values, and power. MATLAB and MathCAD packages were used to build and simulate arc-fault model and phase voltage distortion, to design and test part of the developed algorithms, which were further implemented in Embedded C and Assembler programming languages. A prototype circuit board with the required sensors and relay, analog isolation, indication, user controls, communication link, and a low-cost microchip microcontroller (MCU) dsPIC33 was designed and built to validate implemented algorithms and conduct experiments.

Design of Measurement System Based on Signal Reconstruction for Analysis and Protection of Distributed Generations

Maintenance of power quality is an important issue in the interconnection and protection between distributed generations and a power system. With the development of measuring techniques and digital signal processors, multifunction monitoring devices are introduced. However, the installation of numerous terminal units usually would increase the cost for the wide-area measurement. In order to promote the deployment of distributed measurement, low-cost acquisition units with low operational burden are applied in this paper. By combining the proposed reconstruction technique for power signals, a simple remote power-quality measurement system is developed.

LED 기반 그린에너지 조명시스템을 위한 전력품질 측정

LED 기반 그린에너지 조명 시스템의 성공적인 연구 개발과 원만한 설치 운영을 위해서는 펄스 파, 스파이크 파를 비롯한 비선형신호와 고조파, sag, swell 등을 포함한 불요신호에 대한 실시간 전력품질측정이 요구된다. 본 논문에서는 그린에너지 조명시스템 응용을 타깃으로 기존 저주파수 대 (60Hz～수KHz)는 물론 수십 KHz 이상의 고주파수 대에 발생하는 각종 전원 신호 분석이 가능한 저가형 전력품질측정 (power quality measurement: PQM) 방안을 제안하고, 이를 TI 320F28335 MCU(micro-controller unit) 기반 PQM 테스트 베드로 구현한다. 제안된 알고리즘은 CCS (Code Composer Studio) 3.3 환경에서 C언어로 작성하였으며, 임의 신호 발생기(NF-WF1974)로부터 발생된 모의 신호를 활용하여 구현된 알고리즘을 검증한다. 테스트 베드를 이용하여 LED SMPS로부터 발생되는 각종 비선형 전류 신호 측정, FFT를 이용한 고조파 신호의 분석이 가능할 뿐 아니라 이산 웨이블렛 변환을 이용한 sag, swell, interruption 등의 고품질 전력신호 측정도 가능하다.

Overview of Important State-of-the-Art Technologies in Offshore Wind Energy Systems

Modern wind plants in offshore wind farms have grown in capacity into facilities that can no longer be ignored in transmission planning studies. Additionally, a large penetration of wind generation in an offshore wind farm into the power system will bring a number of challenges on system planning, operation, and impact analyses. This paper will provide an overview of the important state-of-the-art technologies in offshore wind energy systems, including the designs on internal electric system of an offshore wind farm, transmission system to shore, generator type, system frequency, transmission cable, communications medium and SCADA system, offshore substation and transformer. Additionally, the development on reactive power compensation, collection grid topologies, redundancy design for improving system reliability, power quality standard and measurement, and protection scheme on switching transient will also illustrated in this paper.

Power Quality Improvement in Faulty Conditions using Tuned Harmonic Filters

The Electrical power quality has become an important topic of discussion and research these days. As per IEEE 519 std. parameters of power quality measurement, are four in number, of which Total Harmonic Distortion is most widely used. This paper proposes the optimal planning of passive tuned harmonic filters for improvement of power quality in faulty conditions of electrical power system. The Total Harmonic Distortion analysis of power quality disturbances is carried out in the faulty conditions and in the presence of single tuned and double tuned harmonic filters. The four bus system having two load and two generator buses is modeled in MATLAB/Simulink environment. A fault is created near the load bus and power quality disturbances are detected near the generator bus and improved using single tuned and double tuned filters near the generator bus under study. The Matlab results show the performance of double tuned filter in improvement of power quality disturbances during faulty conditions. Keywords - power quality disturbances, total harmonic distortion, power system fault, single tuned harmonic filter, double tuned harmonic filter. I. INTRODUCTION

Measurement and assessment of power quality characteristics for photovoltaic systems: Harmonics, flicker, unbalance, and slow voltage variations

This paper provides guidelines for the measurement and assessment of power quality (PQ) characteristics for photovoltaic (PV) systems at a site. These include harmonics, flicker, unbalance, and slow voltage variations. A description is given of the PQ indices and objectives. Such indices and objectives help distribution network operators (DNOs) to report on PQ performance to third parties when collecting and presenting PQ data.The indices are obtained with the measurement procedure described in this paper. Previous work explained how to specify the objectives, which were initially based on the planning level proposed in IEC technical reports.The field measurements taken in a currently operating MV PV power plant were characterized in terms of PQ indices and compared to the objectives for this PV power plant. Results showed that within the context of the current state of PV technology, the disturbance objectives for the PV power plant monitored were not always met.

Microgrid Generation Capacity Design With Renewables and Energy Storage Addressing Power Quality and Surety

Microgrids are receiving attention due to the increasing need to integrate distributed generations and to insure power quality and to provide energy surety to critical loads. Since renewables need to be in the mix for energy surety, a high renewable-energy penetrated microgrid is analyzed in this paper. The standard IEEE 34 bus distribution feeder is adapted and managed as a microgrid by adding distributed generation and load profiles. The 25 kV system parameters are scaled down to 12 kV and renewable sources including solar PV and wind turbines, an energy storage system, and a diesel generator for islanded mode have been added to the 34-bus system. The distribution generations (DG) and renewables are modeled in detail using PSCAD software and practical constraints of the components are considered. The monitoring of the microgrid for measuring power quality and control requirements for these DGs and storage are modeled to maintain the power quality of the system when loads are varied. Renewable sources are modeled with seasonal variation at different locations. The microgrid is monitored at number of buses and the power quality issues are measured and indexes are calculated. This paper proposes a generalized approach to design (determine the capacity requirements) and demonstrates the management of microgrids with metrics to meet the power quality indexes.

Random Generation of Arbitrary Waveforms for Emulating Three-Phase Systems

This paper describes an apparatus for generating a signal representative of steady-state and transient disturbances in three-phase waveforms of an ac electrical system as described in IEEE Std 1159-09. It can be configured as a synthesizer of randomly distorted signals for different applications: for testing the effects of disturbed grid on equipment and to generate patterns of electrical disturbances for the training of artificial neural networks, which are used for measuring power quality tasks. For the first purpose, voltage and current amplifiers are added in the output stage, which allows the generation of disturbed signals at grid level.

전력 품질 및 전력 고조파 측정 장치에 관한 연구

전력 계통에서 발생하는 고조파는 전동기 등 기기 오동작 및 고장, 불필요한 전력 소모 등을 야기시킨다. 고조파 발생에 대한 근본적인 대책은 고조파 발생 원인을 찾아 제거하는 것이며 본 논문에서는 아날로그 디바이스사의 ADE7880을 이용하여 고조파 발생 원인을 실시간으로 파악할 수 있는 전력품질 측정장치를 제작하고 동작을 검증하여 다양한 전력 품질 측정 분야에 활용할 수 있도록 하였다. 전력은 일반적으로 45Hz에서 66Hz까지의 라인 주파수를 가지고 있는데, 본 연구에서 사용한 ADE7880 필터대역인 2.8kHz 밴드 내에서 분석될 수 있는 고조파의 수는 2800/f로 최대 2800/45 = 63차 고조파까지 가능하며, 라인주파수가 60Hz인 한국에서의 최대 고조파차수는 2800/60 = 46차까지 측정할 수 있었다. 또한 전압, 전류, 전력 측정의 정확도는 0.1%이내의 오차를 가져 매우 정밀한 수준임을 확인하였다.

SIGNAL PROCESSING TECHNIQUES FOR ESTIMATING POWER SYSTEM MODAL PARAMETERS

Smart Grid is expected to provide a reliable power supply with fewer and briefer outages, cleaner power, and self-healing power systems through advanced Power Quality (PQ) monitoring, analysis and diagnosis of the PQ measurements and identification of the root cause, and timely automated controls. It is important to understand that signal processing has been an integral part of advancing and expanding the horizons of this PQ research significantly and the capabilities and applications of signal processing for PQ are continually evolving. This paper thus presents a survey on the proven and emerging signal applications for enhancing PQ, focusing on algorithms for estimating system modal parameters because resonant frequencies and their damping information are critical signatures in evaluating the PQ. In particular, we discuss the need for investigating time-varying and nonlinear characteristics of the modal parameters due to dynamic changes in system operating conditions and introduce promising signal processing techniques for this purpose.

Luminous and power quality analysis of office building light sources

Important efforts are being made to increase electric energy savings in the field of lighting. Of all the different approaches possible, two are used more frequently than others: The use of lighting control systems and the replacement of old light sources with better ones. One direct effect of the employment of new light sources and light dimming controls is a decrease of the power quality of the electrical network. This paper addresses luminous and power quality measurements of different light sources that are suitable for office buildings. The measurements were performed with and without dimming. In this way, the luminous and the power quality characteristics of the light sources, at different light levels, were established.

Power Quality Considerations for Microgrids Integrating Pairs of Mechanically Coupled Electrical Machines Driven by Power Converters

Microgrids integrating distributed motor-generator units are commonplace in locomotive and industrial applications. The behavior of these systems is dependent upon various design-operating parameters. However there is a distinct relation between power quality and power flow within these units. This paper presents an analysis of power quality measurements, depicting this interdependence. Respective results can be taken under consideration during power flow programming, enabling enhanced system operation.

A Novel Ultra High Fidelity Power Quality and Energy Management Software Using NI LabVIEW

This paper presents a novel concept of power quality and energy management software using NI LabVIEW. The investigator has developed highly powerful real time power quality and energy management software by using NI LabVIEW, which is capable of doing very complex calculations in fraction of seconds, giving the real time data immediately, hence giving an excellent solution to power quality development. Now a days power quality problems are serious apprehension for electrical power users in view of its negative influence on the electrical equipment and the utility bill. This leads to a greater demand for the power quality measurement tools and especially for the low-cost high fidelity instruments. That is why high fidelity, high precision, high speed real time solutions are required for measuring the power quality parameters. This paper presents an ultimate high fidelity approach based on NI ELVIS Instruments and NI LabVIEW for constant measurement and monitoring of specific power quality parameters.