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.

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.

Online Learning Control for Harmonics Reduction Based on Current Controlled Voltage Source Power Inverters

Nonlinear loads in the power distribution system cause non-sinusoidal currents and voltages with harmonic components.Shunt active filters(SAF) with current controlled voltage source inverters(CCVSI) are usually used to obtain balanced and sinusoidal source currents by injecting compensation currents.However,CCVSI with traditional controllers have a limited transient and steady state performance.In this paper,we propose an adaptive dynamic programming(ADP) controller with online learning capability to improve transient response and harmonics.The proposed controller works alongside existing proportional integral(PI) controllers to efficiently track the reference currents in the d-q domain.It can generate adaptive control actions to compensate the PI controller.The proposed system was simulated under different nonlinear(three-phase full wave rectifier) load conditions.The performance of the proposed approach was compared with the traditional approach.We have also included the simulation results without connecting the traditional PI control based power inverter for reference comparison.The online learning based ADP controller not only reduced average total harmonic distortion by 18.41%,but also outperformed traditional PI controllers during transients.

Randomized Integral Gain of Pi Current Controller for A Single Pv Inverter System

This paper is concerned with the problem of network power quality when grid connected systems are used to feed the grid. These systems use power electronic components such as inverters that produce harmonics which adversely affect the power quality of the distribution network. Instead of using a conventional PI current controller with a fixed proportional and integral gain, development of new control method is considered to overcome the total harmonic emissions in PV inverters. It considers a modification to the controller where a random integral gain is used in the system. Experimental hardware is developed and result shows a reduced total harmonic distortion (THD) of the output current when tested with a resistive load.

Analysis on Harmonics of Distribution Network with Distributed Generators

In this paper, the authors analyze the influence that connection of many distributed generators （DGs） has on the harmonics of the distribution network from the viewpoints of harmonic current, harmonic voltage, and voltage total harmonic distortion （THD）, when it is assumed that the harmonic voltages or the harmonic currents in a distribution network increases by connection of many DGs through the inverters. The analysis on the influence of DGs is carried out by using a standard analytical model of distribution network with DGs based on the practical data. The authors evaluate quantitatively the influence which harmonics generated from DGs has on the harmonics of the distribution network, and analyze visually about propagation of harmonics within the distribution network. In addition, the authors also verify about the restraint effect of the harmonics in the network scale by the active filters installation.

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.

Investigation of Current Control Techniques of AC-DC Interleaved Boost PFC Converter

This paper presents the comparison of various current control strategies employed for an interleaved power factor correction (PFC) boost converter for improving the power quality. The major control strategies discussed in this paper are: peak current control, average current control, hysteresis control, borderline current control and non-linear control. These strategies are implemented in MATLAB/SIMULINK and the performance of the proposed converter is compared under open loop and closed loop operation. From the results, the input current waveform was close to input voltage waveform implying improved power factor and reduced total harmonic distortion for nonlinear current control technique. Experimental results validate the proposed method.

Impact of welding equipment on power quality

In an industrial facility,many electrical consumers can affect the quality of electricity.Therefore,the freedom from interference sources of these devices and equipment can be crucial for quality and uninterrupted electricity supply.Electric welding equipment is also a possible source of interference.The electrical harmonic injections created by welding equipment into the electrical network can affect the operation of other consumers connected to the given distribution points and cause unjustified overheating and shutdowns of some network components.The aim of the research is to analyse the current harmonic injection of welding equipment of different types and modes of operation connected to the internal distribution network of the industrial facility.The effectiveness of the active harmonic filter built into the welding equipment was also examined in the paper.The results showed that the built-in active harmonic filter of the DC045 laser welding equipment was ineffective because the total harmonic distortion(THD)was about three times the 8%allowed by IEEE 519−2022 standard.The current harmonic injection of MIG 320 and MM403 type welding equipment was more than five times the permissible value of 5%.The current harmonic distortion of the PLAS140 type plasma-jet cutter equipment was below the 5% value allowed in the standard,thus it complied with it.Based on the measurement results,it can be concluded that the use of protection against harmonics is also necessary for welding equipment.Finally,proposals were made in the paper to reduce the effect of harmonics.

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.

Eco-Friendly Selection of Diesel Generator Based on Genset-Synchro Technology for Off-Grid Remote Area Application in the North of Quebec

For most of their energy requirements, greater part of remote communities and small islands around the world rely on imported fossil fuels. The economical cost of energy is therefore very high not only due to inherent cost of fuel, but also due to transportation and due to maintenance costs. One solution for saving fuel in a diesel generator is to allow the engine to operate directly in relation to the request for electrical load at variable speeds. Genset-Synchro Technology has developed an innovative variable speed?generator technology (patent pending) that allows applications where power demand varies widely to benefit from the new technology that maintains constant voltage and frequency while adjusting the generator stator speed to power demand. This paper will present an innovative approach for optimizing the energy production based from the fact that the structure that contains the stator windings of the generator is mounted on roller bearings, which allows its free rotation around the axis of the rotor, consequently stopping the stator structure from being static and aims to minimize the unit cost of electricity. Case study on application in remote area in the north of Quebec is described. A saving of 7%?-?9% on fuel consumption and greenhouse gas (GHG) under low winter ambient temperatures has been registered.

Microcontroller-Based Sinusoidal Voltage Generation for Electrical Bio-Impedance Spectroscopy Applications

A sinusoidal voltage wave generator is proposed based on the use of micro-processor digital signals with programmable duty-cycles, with application to real-time Electrical Cell-substrate Impedance Spectroscopy (ECIS) assays in cell cultures. The working principle relies on the time convolution of the programmed microcontroller (μC) digital signals. The expected frequency is easily tuned on the bio-impedance spectroscopy range [100 Hz, 1 MHz] thanks to the μC clock frequency selection. This system has been simulated and tested on the 8 bits μC ArduinoTM Uno with ATmega328 version. Results obtained prove that only three digital signals are required to fit the general specification in ECIS experiments, below 1% THD accuracy, and show the appropriateness of the system for the real-time monitoring of this type of biological experiments.

A NOVEL CONTROL STRATEGY FOR SINUSIODAL WAVE INVERTER WITH PI REGULATORS AND CAPACITOR CURRENT FEEDBACK

Objective For the inverters used in UPS, it is important to maintain the pure sinusoidal AC output voltage waveform over all loading conditions and transients. Methods A novel sinusoidal output voltage control strategy is pregented in this paper. The output voltage is controlled by introducing filtering eapacitor current feedback. Two simple PI regulators are used for the current and voltage control loops. Results With the new control strategy, the inverter achieves very low output voltage distortion, good output voltage regulation and strong perturbation rejection, fast dynamic response, and good performance under nonlinear loads. The THD under capacitance rectifying load is better than 0.2%, the output voltage regulation within 0 to full load is less than 0.1%. The resting time under load transient is within 200?μ s . Conclusion The merits of the new control strategy include rapid response and good steady state stiffness.

适用于三电平逆变器的电流谐波最小脉宽调制策略

受限于散热条件,大功率牵引传动系统中逆变器开关频率通常很低,三电平逆变器由于在低开关频率下具有较小的输出谐波、较低的dv/dt等特点在中高压大功率领域中被广泛应用。以三电平中点钳位型逆变器为研究对象,提出一种电流谐波最小脉宽调制策略(CHMPWM),基于加权总谐波畸变最小的优化目标求解不同开关角个数下的开关角曲线,与目前应用较为广泛的特定次谐波消除脉宽调制进行谐波性能对比。该方法不会完全消除特定次数的谐波成分,但是总体电流谐波可以达到最小。针对电流谐波最小脉宽调制策略在实现过程中存在的困难,设计全速度范围基于电流谐波最小脉宽调制的多模式调制策略。仿真和实验结果表明,提出的调制策略具有良好的谐波性能,与理论分析结果一致。

一种抑制高速电机低次电流谐波的调制方法

针对高速永磁同步电机低载波比、数字控制延时所引起的电流谐波较大的问题,提出一种抑制低次电流谐波的改进型特定次谐波消除调制方法。首先,对该调制方法的调制波形原理和数字实现特点进行分析,建立新的电压谐波方程和开关角求解方程;其次,以电流总谐波失真为目标优化函数,研究了调制比和载波比对开关角分布、电流谐波含量的影响;最后,以三相高速永磁同步电机为研究对象,搭建系统仿真模型对所提调制方法进行验证。验证结果表明,通过与特定次谐波消除调制方式相比,所提调制方法计算量更少,可以提高输出脉宽调制波形的对称性,具有更优的低次电流谐波抑制能力。

基于主轴电机电流信号的表面粗糙度检测

针对表面粗糙度不能及时检测造成的工件浪费问题,首次提出根据主轴电机电流信号进行表面粗糙度检测分类。通过实验采集不同表面粗糙度加工时的主轴电机电流信号,采用小波包分解将电流信号分解成不同频段,借助能量特征和裕度因子对不同频段电流信号进行评估,过滤低相关性频段,再通过随机森林筛选特征,降低特征的冗余性。总谐波失真特征实现了积屑瘤检测,仅依赖构建的电流信号特征工程表面粗糙度检测准确率高达95%以上,并且检测时间在2 s以内,基本实现了工件表面粗糙度的快速准确检测。

2021—2023年济宁市场流通领域中LED照明产品电磁骚扰抽检结果的分析

为了更好地了解济宁地区LED照明产品的整体质量情况及动态变化情况,本文通过对济宁县市区照明灯具市场及大型商超进行随机抽样检测的方法,对2021—2023年济宁流通领域中LED照明产品进行抽样检测,并对抽检结果进行了分析研究。通过对抽检数据进行统计和分析,发现济宁地区流通领域LED照明产品的电磁骚扰水平整体较好,存在的问题主要集中在骚扰电压和谐波电流发射项目上,总谐波电流畸变率(I-THD)普遍偏高。

基于多种群遗传算法的多电平逆变器输出电压THD最小化调制策略

多电平逆变器具有低谐波含量,电磁干扰小,高压大容量,输出波形质量好等特点,被广泛用于中高压大功率系统当中。特定谐波消除技术SHEPWM是在多电平逆变器中的一种常用开关策略,相比于高频调制,SHEPWM技术能够消除某特定次谐波,而且具有更低的开关频率和开关损耗等优点。针对传统SHEPWM技术中THD不能达到最优的问题,推导出了输出电压谐波总含量的解析表达式,并采用多种群遗传算法对解析表达式进行求解,在得到最优开关角度的同时求出全调制度下输出电压的最小THD值。文中以三单元7电平级联H桥为例,给出了THD解析式模型及其开关角度轨迹图,和传统多波段SHE进行了对比,发现谐波总含量THD得到很大程度上的降低,同时也解决了其存在电流倒灌的问题。仿真分析和实验结果验证了方法的可行性和优势。

具有直流故障清除能力的双端口半桥MMC子模块

半桥型模块化多电平换流器无法通过自身来清除直流侧故障,通过改进子模块拓扑,可以实现故障电流的自清除功能。在半桥的基础上,提出了一种具有直流故障阻断能力的双端口半桥子模块,具有负电平输出能力,使用相同规模开关器件的情况下,可以输出全桥两倍的电平数。基于MATLAB/Simulink搭建仿真模型进行验证。结果表明,所提出的子模块具有良好的故障电流阻断能力,输出电平多,能够显著改善电压输出质量。

模块化多电平换流器子模块电容电压波动与内部环流分析

为了分析模块化多电平换流器(modular multilevel converter,MMC)子模块电容电压波动和内部环流的基本成分,以开关函数为出发点,对电容电压波动和环流进行了数学分析。分析结果表明:基频波动和2倍频波动是电容电压波动的基本成分,并得出其解析表达式;内部环流仅包含偶次谐波成分,且以2次谐波环流为主,并给出其幅值的解析表达式。针对环流对MMC运行的影响,分析了MMC交流侧相电压中的谐波成分,结果表明环流导致MMC输出相电压中的奇次谐波含量增大,尤以3次谐波最为明显,且给出了3次谐波幅值的计算表达式。仿真结果表明上述理论分析是准确的,为子模块电容值和桥臂电感的选取提供了理论基础。

污秽绝缘子泄漏电流频率和相位特征的试验研究

污闪是电力系统安全运行的严重威胁,提取污秽绝缘子泄漏电流特征量是有效实现污闪预警的前提之一,目前污闪预警并不十分理想的原因之一是表征污闪与泄漏电流关系的特征量尚未达成共识。以人工污秽试验为基础,结合交流下污秽绝缘子表面电弧放电机制,分析了盐密和湿度(relative humidity,RH)对绝缘子表面泄漏电流相位(θ)的影响,泄漏电流的总谐波畸变率(total harmonic distortion,THD)、高次谐波和低次谐波与泄漏电流波形畸变之间的内在联系。结果表明:θ随RH的增加而减小;泄漏电流波形畸变的主要原因是电弧放电产生的3次谐波,轻污时THD随RH的增加而缓慢增加,污秽较重时THD随RH的增加呈先减小后增加的趋势,存在极小值,在THD极小值处,污秽绝缘子开始产生局部放电现象。根据理论分析和试验验证,提出可利用θ和THD的变化趋势在空气湿度较低时进行污闪预警。