Effect of harmonic distortion on electric energy meters of different metrological principles

This paper deals with the errors of electric energy metering devices as a result of distortions in the shape of the curves of voltage and current load. It is shown and proved that the errors in energy measurements depend on the design and the algorithms used in electricity meters. There are three main types of metering devises having different principles: inductive (electro-mechanical), elec-tronic static, and digital electronic (microprocessor). Each of these types has its measuring features. Some devices take into account all the harmonic distortions and the constant component which occur in the network while others measure the power and energy values of the fundamental harmonic only. Such traits lead to the discrepancies in the readings of commercial electric energy meters of different types. Hence, the violations in the measurement system unity occur, and a significant error can be observed in the balance of transmitted/consumed electric energy.

Power Quality Consideration for Off-Grid Renewable Energy Systems

Necessity of electricity access in remote area is the main reason for expanding decentralized energy system such as stand-alone power systems. The best electrical power supply must provide a constant magnitude and frequency voltage. Therefore, good power quality is an important factor for the reliable operation of electrical loads in a power system. However, the current drawn by most of electronic devices and non-linear loads are non-sinusoidal, which can result in a poor power quality, especially in off-grid power systems. Poor power quality is characterized by electrical disturbances such as transients, sags, swells, harmonics and even interruptions in the power supply. Off-grid power systems worldwide often struggle with system failures and equipment damage due to poor power quality. In this paper, MAT- LAB/Simulink is used to model and analyses power quality in an off-grid renewable energy system. The results show high voltage transient when the inductive loads were switched OFF. The voltage and current harmonics are also determined and compared for various types of loads.

Electrical Energy Quality Analysis in Hospital Centres

Today, energy is a vital component in the functioning of a hospital. Hospital technical facilities have several types of technologies, these include appliances for use;examination apparatus. So, for Quality Health Care in a hospital, there is a need to ensure the proper functioning of hospital equipment. In addition to the required maintenance as specified by the device manufacturer, the quality of the electrical energy across the device must be ensured. This article is an analysis of the quality of electric energy at the substation of National Hospital of Niamey. Thereby, the data collection, followed by the data processing and analysis revealed the parameters characterizing the quality of electrical energy across the substation. Our studies have shown that the substation is underutilized as the maximum inrush current is less than half the available current. The current was consumed by the three phases has resulted in a strong current unbalance (230 A). However, the current unbalance and the voltage amplitude, are admissible accordingly base on EN50160 standard. Furthermore, the harmonics voltages present in this medium are in the accepted range (1.8%) according to IEEE 519 standard. However, the fundamental frequency does not meet the standard, but the difference obtained has no adverse effect.

Wind Energy Conversion System from Electrical Perspective—A Survey

This paper focuses on the wind energy conversion system (WECS) with the three main electrical aspects: 1) wind turbine generators (WTGs), 2) power electronics converters (PECs) and 3) grid-connection issues. The current state of wind turbine generators are discussed and compared in some criteria along with the trends in the current WECS market, which are ‘Variable Speed’, ‘Multi-MW’ and ‘Offshore’. In addition, the other crucial component in the WECS, PECs will be discussed with its topologies available in the current WECS market along with their modulation strategies. Moreover, three main issues of the WECS associating with the grid-connection, fault-ride through (FRT) capability, harmonics/interharmonics emission and flicker, which are the power quality issues, will be discussed due to the increasing responsibility of WECS as utility power station. Some key findings from the review such as the attractiveness of BDFRG are presented in the conclusion of this paper.

Study on Negative Impact of Harmonic Components on Sensitive Electric Equipment

Distribution systems operators are often confronted with declined power quality, which can cause substantial economical losses. The problem analyzed in paper concerns thyristor controlled direct current motor used for ski-lift in ski resort as a source of disturbances with negative impact on sensitive electric equipment, which is then unable to operate correctly. To solve mentioned problems, series of measurements of voltage quality parameters were carried out according to the respective valid standards. Crucial power quality parameters necessary for parallel power active filter design were then analyzed. Power active filter compensates power factor and filters characteristic current harmonics. After power active filter was put into operation, power quality problems were eliminated. Payback period is estimated up to four years.

Global Harmonic Rate Assessment in the Electricity Distribution Network in Niamey City:Case Studies of Domestic,Industrial and Hospital Substations

Like others countries of the world, in Niger also, we are witnessing an increasing use of non-linear electric loads in the domestic, hospital and industrial sectors. However, these loads degrade the shape of the electrical signal and cause disastrous effects to the equipment of the distribution system and the devices which are connected to the network. This article highlights the presence of electric harmonics in the distribution network in Niamey city. In order to do this, measurements were taken at the secondary level of the substations using an energy quality analyze r (FLUKE 1735). By using this measuring instrument, we quantified the voltage and current Total Harmonic Distortion (THD) in the three substations. The results obtained show that, although the statutable rates set by the standards are not exceeded for phase conductors, the neutral contains a very critical percentage of distortion on the residential and hospital substations. Moreover, this assessment made it possible to observe the variation of harmonics in the presence of voltage drops.

Harmonic Measurement and Analysis during Electric Vehicle Charging

This paper presentsand describes harmonic measurement and analysis of studying harmonic propagation during electric vehicle (EV) charging. The measurement study is performed on a golf cart and two modern type of EVs. Harmonics from a single EV charging and a group of EV charging was measured. The voltage and current waveform during the charging was captured and analyzed to investigate the harmonic components that exist in the electrical system. Total current harmonic distortion (THDi) and total voltage harmonic distortion (THDi) were both calculated. Modern electric vehicles are found to release low THDi but higher THDv compared to a golf cart. On the measurement study during charging of? a group of EV, it is found that the summation of THD is not linear with a number of vehicles. The finding of the study reveals that harmonic contamination from EV charging on electrical grid is not as critical as thought by most of power system researchers and engineers.

Power Quality Analysis in Microgrid: An Experimental Approach

Microgrid (MG) integrated with Distributed Generation (DG) provides several benefits like reliable, secure, and high efficient of energy supply, while minimizing power loss, deferring expansion of power distribution infrastructures, and reduced carbon emission of energy supply etc. to the communities. Despite of the several benefits, there are several challenges existing due to the integration of different characteristics and technology of DG sources in MG network. Power Quality (PQ) issue is one of the main technical challenges in MG power system. In order to provide improved PQ of energy supply, it is necessary to analyse and quantify the PQ level in MG network. This paper investigates the detail of PQ impacts in a real MG network carried out through an experimental analysis. Voltage and frequency variations/deviations are analysed in both on-grid and off-grid mode of MG operation at varying generation and varying load conditions. Similarly unbalance voltage and current level in neutral are estimated at unbalanced PV generation and uneven load distribution in MG network. Also current and voltage THD are estimated at different PV power level. Finally the results obtained from the analysis are compared to that of Australian network standard level.

Power Quality Improvement and Signal Conditioning of PV Array and Grid Interfaced Off-board Charger for Electric Vehicles with V2G and G2V Capabilities

In this work,we present a photovoltaic(PV)-based off-board charging system integrated with the grid using a voltage source converter(VSC).The control of the grid-tied off-board charger is derived from the joint logarithmic hyperbolic cosine robust sparse adaptive filter(JLHCAF)algorithm.This algorithm effectively tracks the fundamental component of the load current in a short duration,providing a good dynamic response.Due to its robustness against impulsive interference,the JLHCAF outperforms other sparsity-aware robust algorithms The cascaded proportional-integral(PI)controller is used to control the bidirectional buck-boost converter for electric vehicle(EV)charging/discharging,which acts in buck operation if the EV is being charged and in boost operation if it is discharged.The reference DC link voltage for the controller is derived by using adaptive MPPT technique.The bidirectional properties of the system enable various functions,including grid-to-vehicle(G2V),vehicle-to-grid(V2G),PV source-to-grid(PV2G),vehicle-to-home(V2H),and PV source-to-vehicle(PV2V)operations.Additionally,the system can supply power to critical nonlinear loads.The control strategy ensures compliance with the power quality requirements set by the IEEE standard,as demonstrated in the results.To validate the effectiveness of the proposed system,we conducted tests under dynamic conditions by disconnecting and reconnecting household loads.Furthermore,the off-board charging system was subjected to actual conditions,such as variations in solar PV insolation,and its steady-state performance was evaluated through simulation and laboratory experimental prototypes.The results,including total harmonic distortion(THD),support the validation of the developed charging system.

配电电能质量导致电气火灾的要素分析

配电侧电气设备、线路及电气老化引发的电气火灾比例呈现高位态势,供网引入配网侧的电气火灾情况亦呈明显增长趋势。由于配电侧谐波污染程度是用电过程中极易被忽视的环节,而电能质量污染导致的配电侧用电不平衡、谐波以及电压闪变恰是造成负载用电侧失控的根源之一。因此,本文针对不同类型建筑电气用电性质,分析研究配电侧电能质量运行是电气火灾防范的重点。

对高速公路供配电系统电能质量的探析

为契合高速公路、特别是智慧高速公路的快速发展,对高速公路供配电系统的电能质量进行探析是很有必要的。针对谐波、电压偏差、电压三相不平衡、频率偏差等高速公路的典型电能质量问题,从来源、影响及危害对谐波问题进行着重分析,并对其他电能质量问题也进行了阐述和分析,之后分析了电能质量问题的监测措施和方案,最后分析了高速公路电能质量问题的治理措施。分析结果对于保证高速公路供配电系统的安全稳定可靠运行具有一定的参考价值。

电能质量的分析与测量

电力系统电网中逐渐增多的“污染性”负荷 (如非线性负荷、时变负荷等 )正在使电网中的电流、电压出现越来越多的、显著的畸变。本文主要阐述了有关电能质量、电能质量的标准及其相关检测的方法等基本内容。

用于电能质量研究的新型交流电弧炉混沌模型

提出一种用于电能质量研究的新型交流电弧炉混沌模型。首先,基于电弧炉负载U-i特性曲线的分段线性化,依据负载实际消耗的有功功率,得到能精确反映电弧炉稳态特性的静态模型,该模型适用于电弧炉引起的谐波问题研究。然后,用基于不对称非线性电阻蔡氏电路产生的低频混沌信号对静态电弧电压进行调制,模拟电弧炉运行的动态过程,得到电弧炉负载的动态模型,该模型特别适用于研究电弧炉引起的电压波动与闪变问题。在Matlab下,对电弧炉静态、动态模型进行仿真研究。仿真结果与实际测量数据相比较,显示该模型能够精确描述电弧炉引起的谐波和电压波动等电能质量问题。模型有效且易于使用,它的提出为电能质量治理措施研究奠定了基础。

同步参考坐标法和正、负序基波提取器在电流检测中的比较

简述正、负序基波提取器基本原理,提出无功、谐波和负序电流检测的2种方法,即改进同步参考坐标法和基于正、负序基波提取器的检测方法。改进同步参考坐标法通过对电网正序基波电压矢量的同步旋转跟踪,可以省去锁相环及三角函数的计算;基于正、负序基波提取器的检测方法则可以进一步省去α-β坐标系变换到d-q坐标系及其反变换的计算。仿真与实验结果表明:采用这2种检测算法都能准确地检测电网中的无功、谐波和负序电流;基于正序基波提取器的检测算法比改进同步参考坐标法的实时性更高。

城轨车辆牵引过程对配电网电能质量的影响分析

针对以谐波电流95%概率值和电压短时闪变值为指标的城轨电能质量传统评估方法时间粒度大的问题,提出基于小波包变换预处理的改进Hilbert-Huang变换(WPT-HHT)方法分析车辆牵引过程谐波电流时变特性。利用小波包变换的分频特性对检测信号进行预处理,避免了经验模态分解出现模态混叠的问题;分析了检测信号频率波动对瞬时电压d-q分解法计算精度的影响,推导了频率波动情况下的误差公式。采用瞬时电压d-q分解法提取车辆牵引过程网侧电压闪变包络线。对北京地铁一号线某牵引变电站24 h实测录波数据进行了算例分析,结果表明了所提方法的有效性。

电网谐波电能损耗的计量方法

非线性负荷的日益增多使得非线性负荷用户在电网中引起的谐波电能损耗的计量成为供用电双方共同关心的问题。本文建立了配电网的谐波分析模型 ,讨论了谐波电能的产生和消耗途径 ,提出了非线性负荷用户在配电网中引起的谐波电能损耗的计量方法。理论分析表明 ,电网中的谐波电能损耗为用户的基波电能与实际所耗电能之差。

谐波滤波、电压、无功综合控制装置的研制

针对目前谐波污染严重及部分无功补偿电容器因谐波电流放大而不能正常投运等问题 ,研制了一种微机型谐波滤波及电压无功综合控制装置。该装置由多 CPU单片机系统构成 ,集谐波实时测量、滤波器及电容器组投切控制、滤波器及电容器组保护、变压器分接头调整等功能于一体 ,在快速傅立叶变换 ( FFT)计算、微机保护算法及综合控制方案的设计中采用了一些独特而有效的方法。文中阐述了该装置的软。

风电并网引起的电压闪变及应对策略

介绍了风电并网所引起的电压闪变及其产生机理,指出了风速、塔影效应等因素对电压闪变的影响,风电并网点选择需考虑SCR和R/X对电压闪变的影响。依靠补偿、储能设备可以抑制电压闪变,总结了6种抑制电压闪变的储能补偿设备的工作特性、性价比、优缺点及使用状况。

电网中三相电压不对称谐波及负序电流检测方法的研究

大功率电力电子器件的应用，使得电网电流或电压波形产生畸变，进而使系统的电能质量下降。准确检测这些电流分量，正确评价用户电能质量的好坏，已经是非常迫切的问题。为此，本文提出了一种在三相电压不对称情况下，实时检测电网谐波、负序电流分量以及基波无功电流分量的方法，并对该检测方法进行了理论分析。实验和仿真证明了所提方法的正确性。

建立电能质量市场的合理性和可行性

建立电能质量市场的目的之一,是促进企业经济效益和社会公正的有机结合。电能质量作为重要的电力市场辅助服务内容,必须在电力市场环境中才能得到完善的解决。通过几类典型110kV负荷的投入、退出、调整等活动,对电能质量市场条件下如何实现社会公正、资源的优化配置和提高社会生产效率进行分析,分析表明电能质量市场的建立是合理和可行的。