Improved hyper-spherical search algorithm for voltage total harmonic distortion minimization in 27-level inverter

Multi-level inverters(MLIs)have become popular in different applications such as industrial power control systems and distributed generations.There are different forms of MLIs.The cascaded MLIs(CMLIs)have some special advantages among them such as more different output voltage levels using the same number of components and higher power quality.In this paper,a 27-level inverter switching algorithm considering total harmonic distortion(THD)minimization is investigated.Switching angles of the inverter switches are achieved by minimizing a THD-based objective function.In order to minimize the THD-based objective function,the hyper-spherical search(HSS)algorithm,as a novel optimization algorithm,is improved and the results of improved HSS(IHSS)are compared with HSS algorithm and other five evolutionary algorithms to show the advantages of IHSS algorithm.

Design and Analysis of Cascaded Hybrid-Bridge Multi-Cell Multilevel Inverter with Reduced Total Harmonic Distortion Profile

This multilevel inverter methodology is the center of focus among researchers in recent era.It has been focused due to its advantages over existing topologies,drawbacks and improvement of power quality,Multi-level inverter has the ability to generate nearly sinusoidal waves.This sinusoidal wave can be further improved by increasing the level of output voltage or with the help of filter design,and this manuscript presents single-phase Multi cell Multi-Level Inverter(MLI).It has been considered for reducing component count to get a higher number of output voltage levels and lower Total harmonics distortion profile.It comprises with four symmetric DC input voltage and 10 IGBT switches to produces stepped output of 9 level,and when deploy asymmetric Dc voltage source the same circuit will produce 31 level output with some changes in firing scheme,moreover this circuit is the family of cascaded hybrid bridge inverter so this circuit covered advantage of CHB MLI,This circuit uses lower no.of switch as compared to existing conventional MLIs such as FC-MLI,CHB-MLI,NPC-MLI,This paper also provides one of most pertinent controls and modulation mechanisms for a MLI using a hybrid reference/carrier-oriented sinusoidal PWM mechanism.At last,simulated outcomes are to validate the performance of both architectures in MLI structure as well as verify the concept.

HARMONIC ANALYSIS OF SINGLE-PHASE SPWM

Based on theoretical inference and computer simulation,the relationship between the harmonics and the parameters of SPWM was widely investigated.The rule of the total harmonic distortion and the harmonic spectrum distribution has been obtained.In order to decrease the harmonics,the selecting methods for optimal magnitude of the amplitude modularity and the frequency modularity are also given.

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.

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.

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.

Harmonics Extraction Scheme for Power Quality Improvement Using Chbmli-Dstatcom Module

In recent day’s power distribution system is distress from acute power quality issues.In this work,for compensating Power Quality(PQ)disturbances a seven level cascaded H-bridge inverter is implemented in distribution static com-pensator which protects power quality problems in currents.Distribution Static Compensator(DSTATCOM)aid to enhances power factor and removes total har-monic distortion which is drawn from non-linear load.The D–Q reference theory based hysteresis current controller is employed to generate reference current for compensation of harmonics and reactive power,additionally Probabilistic Neural Network(PNN)classifier is used which easily separates exact harmonics.In the meantime fuzzy logic controller is also used to maintain capacitor DC-link poten-tial.When comparing to PI controller it decreases steady state time and reduces maximum peak overshoot.Cascaded H-bridge multilevel inverter converts direct current to Alternating current,through inductor opposite harmonics are injected in Power Control Centre reduces source current harmonics and reactive power.The implementation of CHBMLI in distribution STATic COMpensator simulation model is simulated by means of MATLAB.

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.

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.

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。

Total Harmonics Distortion Prediction at the Point of Common Coupling of industrial load with the grid using Artificial Neural Network

Power quality challenges have generated a lot of disputes between utilities,customers,network operators,and equipment manufacturers around the world as regards the share of responsibility for power quality solutions,this results in different levels of financial and technical losses for both the network operators and the customers.One of the major consequences of the operation of heavy-duty factories globally is the corruption of power quality at the point of common coupling(PCC).In order to quantify the harmonics contribution at the PCC by industrial consumers,this paper presents three-phase total harmonics distortion of current(THDi)prediction model at the PCC.The proposed artificial neural network(ANN)models use a multilayer perceptron neural network(MLPN)to predict three-phase total harmonic distortion.The input parameter used in the models is easily measured with basic power meters.The model was trained with input parameters captured at 33 kV and 132 kV voltage levels using power quality meters at five(5)different steel manufacturing plants.Eight(8)different models were designed,trained,validated,and tested with different combinations of input parameters,number of hidden layers,and number of neurons in the hidden layer.The results show that the model with two hidden layers which uses four major power parameters(Current,apparent power,reactive and active power)as input parameters in the training model had the best performance with a 95.5%coefficient of correlation between the measured THDi and the predicted THDi.

光伏反激并网微型逆变器THD性能仿真研究

针对光伏反激并网微型逆变器的输出功率随着太阳能电池输出功率不断地变化,且在逆变器的输出功率比较低时并网输出电流的总谐波失真(THD)指标不能满足并网要求的问题,研究利用PI准谐振控制器对光伏反激并网逆变器进行了并网控制。通过运用状态空间平均法建立了光伏反激并网微型逆变器的数学模型,基于该数学模型建立了仿真模型,对传统的PI控制器与PI准谐振控制器的控制性能进行了仿真分析。研究结果表明,在不同输入电压、负载条件下,采用PI控制器的逆变器输出并网电流的THD较大,不能满足并网要求;而采用PI准谐振控制器时THD均小于5%,能满足并网要求,从而验证了新控制方法的有效性。

基于新过采样方法的APF电流THD测量

电流总谐波畸变率(THD)是有源电力滤波器(APF)的一项重要性能指标,工业现场一般要求APF补偿后电流THD<5%。实验发现A/D转换引入的噪声对THD测量影响极大,其误差可达200%,不能满足应用要求。针对大功率电力电子装置采样频率低和THD测量对采样信号信噪比要求高的特点,提出一种新的过采样方法,对其进行原理分析,进而结合THD测量的实际讨论了该方法应用的相关问题。最后,通过仿真和实验对传统采样方法和新过采样方法进行比较,验证了该方法的有效性。

三相光伏并网发电系统THD及DCI优化方法研究

电流总谐波畸变(THD)和直流电流注入(DCI)等电能质量问题限制了光伏并网发电系统的大规模应用。提出新的减小THD及抑制DCI的方法以提高逆变器输出电流波形的质量,即将基于多个矢量比例积分(VPI)控制器并联的多矢量比例积分(MVPI)控制器应用于电流控制中以减小入网电流THD;设计一种直流分量提取电路,通过基于预测算法的控制策略达到抑制DCI的目的,同时探讨了THD和DCI二者之间的关系。在一台10k W光伏并网逆变器样机上进行了实验验证,实验结果证明了所提方法的有效性和实用性。

小信号放大电路任意波形THD全自动测量系统研究

总谐波失真THD是衡量信道非线性程度的重要指标,应用于音频小信号放大电路的任意输出波形识别和总谐波失真的全自动测量系统成为检测信号放大性能的有效手段。为准确计算放大后的波形总谐波失真度,采用了快速傅里叶变换FFT技术。从提高系统效率角度,使用高频率采样并半数提取的技术方案。通过动态控制继电器、阻容元件及多级放大等手段,合理调整放大系统静态工作点的位置和输入波形大小,实现不同类型的失真波形输出。基于stm32f103c6单片机,联动开关一键式完成任意波形采集、识别、计算和显示,极大提升了小信号放大电路失真度测量的工作效率。Matlab运算仿真、Multisim电路仿真及实物测试表明,多级晶体管放大一致性调节电路和单片机FFT运算组成的小信号放大电路任意波形THD全自动测量系统,可准确、实时识别波形并计算出总谐波失真,一键式切换设计操作方便、节约成本,颇具实用价值。

DCM模式APFC电路寄生参数对THD的影响

有源功率因数校正(APFC)技术广泛应用于提高电网适应能力及减小谐波污染的场合,其性能与工作模式及参数设计密切相关。提出基于Boost电感电流数学模型,其分析方法弥补了传统周期平均电流模型不精确、分析范围小的不足,并利用该数学模型系统分析了在断续导通模式(DCM)下Boost PFC电路主要元器件寄生参数对输入电流畸变(THD)的影响。实验验证了理论分析的正确性。

Power-Sharing Enhancement Using Harmonized Membership Fuzzy Logic Droop Control Based Micro-Grid

The contribution of Renewable Energy Resources(RER)in the process of power generation is significantly high in the recent days since it paves the way for overcoming the issues like serious energy crisis and natural contamination.This paper deals with the renewable energy based micro-grid as it is regarded as the apt solution for integrating the RER with the electrical frameworks.As thefixed droop coefficients in conventional droop control approaches have caused various limitations like low power-sharing and sudden drops of grid voltage in the Direct Current(DC)side,the Harmonized Membership Fuzzy Logic(MFL)droop control is employed in this present study.This proposed droop control for the hybrid PV-wind-battery system with MFL assists in achieving proper power-sharing and minimizing Total Harmonic Distortion(THD)in the emer-gency micro-grid.It eradicates the deviations in voltage and frequency with itsflexible and robust operation.The THD is reduced and attains the value of 3.1%compared to the traditional droop control.The simulation results of harmo-nized MFL droop control are analogized with the conventional approaches to vali-date the performance of the proposed method.In addition,the experimental results provided by the Field Programmable Gate Array(FPGA)based laboratory setup built using a solar photovoltaic(PV)and wind Permanent Magnet Synchro-nous Generator(PMSG)reaffirms the design.

三相VIENNA整流器THD优化控制策略

三相VIENNA整流器具有高效率、高功率密度的特点,在充电桩和通信电源中得到了广泛的应用。但由于其驱动电路存在延时而引入的附加占空比易在网侧电流中引入6k±1(k≥1)次谐波。详细分析了驱动电路延时产生的原因及其作用机制,提出了在三相a,b,c静止坐标系下,分别对三相调制波叠加延时补偿分量的策略,并给出了补偿后三相调制波的计算方法。最后,搭建了 1台7.5 kW的三相VIENNA整流器样机,实验结果表明所提驱动延时补偿策略改善了网侧电流总谐波畸变率(THD)。

Applying MILP for 27-Level CMLIs to Obtain Low THD Values over Wide Voltage Range

The 27-level cascaded multilevel inverter (CMLI) is a popular CMLI, since it can produce an output voltage with nearly sinusoidal wave form and may be realized as a trinary asymmetric CMLI that consists of only three H-bridges. A new approach using a mixed integer linear programming (MILP) model is applied, that can determine the switching angles of this CMLI that minimize the values of any undesired harmonics. The model is applied first to determine the number of harmonics to be minimized to obtain least percentage total harmonic distortion (%THD) utilizing the 13 positive levels of the inverter. The obtained result is then included in the model and it is solved for different values of the output voltage. Single phase and three phase cases are investigated. The results show very low values of %THD and low order harmonics over wide voltage range till the 91st harmonic in both cases, which agree with the IEEE standards 519-1992 for voltage distortion limits till 161 kv.

宽输入范围高PF低THD的低系统成本LED驱动电源

昂宝电子(上海)有限公司最新推出的高PF低THD的LED驱动电源方案OB3619x,能够采用降压(Buck)架构实现高功率因数(PF)、低总谐波(THD)特性,具有极低的系统成本,能够在全电压范围(90~277 Vac)输入均能够满足总谐波(THD)小于15%的要求,获得了客户的认可和好评。从原理分析角度,介绍了降压(Buck)架构在实现低总谐波(THD)的挑战以及该芯片是如何解决架构困难从而实现其低THD特性的。通过内部专利算法实现,该芯片用Buck架构,采用精简的外围零件,可以实现比一般的高PF低THD方案节省15~30%的成本,非常适合在商用LED照明系统上使用。