Study and Design of a DC/AC Energy Converter for PV System Connected to the Grid Using Harmonic Selected Eliminated (HSE) Approach

Nowadays, distributing network-connected photovoltaic (PV) systems are expanded by merging a PV system and a Direct Current (DC)/Alternating Current (AC) energy converter. DC/AC conversion of PV energy is in great demand for AC applications. The supply of electrical machines and transfer energy to the distribution network is a typical case. In this work, we study and design a DC/AC energy converter using harmonic selective eliminated (HSE) method. To this end, we have combined two power stages connected in derivation. Each power stage is constituted of transistors and transformers. The connection by switching of the two rectangular waves, delivered by each of the stages, makes it possible to create a quasi-sinusoidal output voltage of the inverter. Mathematical equations based on the current-voltage characteristics of the inverter have been developed. The simulation model was validated using experimental data from a 25.2 kWp grid-coupled (PV) system, connected to Gridfit type inverters. The data were exported and implemented in programming software. A good agreement was observed and this shows all the robustness and the technical performances of the energy converter device. It emerges from this analysis that the inverter output voltage and the phase angle thus simulated are very important to control in order to orientate the transfer of the power flow from the continuous cell to cell to the alternating part. Simulated and field-testing results also show that increases in the value of the modulation factor (m) for low power output are highly significant. This study is an important tool for DC/AC inverter designers during initial planning stages. A short presentation of the design model of the inverter has been proposed in this article.

Selective harmonic elimination method for wide range of modulation indexes in multilevel inverters using ICA

Selective harmonic elimination(SHE) in multilevel inverters is an intricate optimization problem that involves a set of nonlinear transcendental equations which have multiple local minima. A new advanced objective function with proper weighting is proposed and also its efficiency is compared with the objective function which is more similar to the proposed one. To enhance the ability of the SHE in eliminating high number of selected harmonics, at each level of the output voltage, one slot is created. The SHE problem is solved by imperialist competitive algorithm(ICA). The conventional SHE methods cannot eliminate the selected harmonics and satisfy the fundamental component in some ranges of modulation indexes. So, to surmount the SHE defect, a DC-DC converter is applied. Theoretical results are substantiated by simulations and experimental results for a 9-level multilevel inverter. The obtained results illustrate that the proposed method successfully minimizes a large number of identified harmonics which consequences very low total harmonic distortion of output voltage.

Harmonic Minimization in Seven Level Cascaded Multilevel Inverter Using Selective Harmonic Elimination PWM Techniques

This paper concentrates on enhancing the productivity of the multilevel inverter and nature of yield voltage waveform. Seven level lessened switches topology has been actualized with just seven switches. Essential Switching plan and Selective Harmonics Elimination were executed to diminish the Total Harmonics Distortion (THD) esteem. Selective Harmonics Elimination Stepped Waveform (SHESW) strategy is executed to dispense with the lower order harmonics. Fundamental switching plan is utilized to control the switches in the inverter. The proposed topology is reasonable for any number of levels. The harmonic lessening is accomplished by selecting fitting switching angles. It indicates would like to decrease starting expense and unpredictability consequently it is able for modern applications. In this paper, third and fifth level harmonics have been disposed of. Simulation work is done utilizing the MATLAB/Simulink programming results have been displayed to accept the hypothesis.

The General Technique of Selected Harmonics Elimination for Multilevel Converters

Forhigh power applications,multilevel converters have many advantages in comparison with other circuit topologies with output transformers. Cascaded inverters are one type of multilevel converters,they are easy to implement,very suitable for modularized layout and packaging.Their manufacturing cost is low.A multilevel PWM technique,called as General Technique of Selected Harmonics Elimination (GTSHE) ,is proposed in the paper. A general harmonic elimination equation for N cells,M pulses per half cycle,nth harmonic is derived,and verified by simulation results.

Genetic Algorithm Based 7-Level Step-Up Inverter with Reduced Harmonics and Switching Devices

This paper presents a unique voltage-raising topology for a single-phase seven-level inverter with triple output voltage gain using single input source and two switched capacitors.The output voltage has been boosted up to three times the value of input voltage by configuring the switched capacitors in series and parallel combinations which eliminates the use of additional step-up converters and transformers.The selective harmonic elimination(SHE)approach is used to remove the lower-order harmonics.The optimal switching angles for SHE is determined using the genetic algorithm.These switching angles are com-bined with a level-shifted pulse width modulation(PWM)technique for pulse generation,resulting in reduced total harmonic distortion(THD).A detailed com-parison has been made against other relevant seven-level inverter topologies in terms of the number of switches,drivers,diodes,capacitors,and boosting facil-ities to emphasize the benefits of the proposed model.The proposed topology is simulated using MATLAB/SIMULINK and an experimental prototype has been developed to validate the results.The Digital Signal Processing(DSP)TMS320F2812 board is used to generate the switching pulses for the proposed technique and the experimental results concur with the simulated model outputs.

Harmonic Minimization in Seven-Level Cascaded Multilevel Inverter Using Evolutionary Algorithm

Inverters are power electronic devices that change over DC to sinusoidal AC quantity. Be that as it may, in down to earth, these devices produce non-sinusoidal yield which contains harmonics, so as to blend a close sinusoidal component and to lessen the harmonic distortion multilevel inverters developed. Mathematical methods, which were developed, are derivative based and need initial considerations. To overcome this, evolutionary algorithms, which are derivative free and accurate, were developed for obtaining multi levels of output voltage. The proposed work uses two evolutionary algorithms, namely, Genetic Algorithm (GA) and Particle Swarm Optimization (PSO) algorithm. These algorithms are used to generate the switching angles by satisfying the non linear transcendental equations that govern the low order harmonic components. A seven level cascaded full bridge inverter is designed using MATLAB/Simulink and the results validate the results for switching angles. The Total Harmonic Distortion (THD) value obtained for GA and PSO is 11.81% and 10.84% respectively. The solution obtained from GA algorithm was implemented in hardware using dsPIC controller to validate the simulation results. The THD value obtained for cascaded seven-level multilevel inverter in the hardware prototype is 25.9%.

混合级联H桥逆变器的新型SHEPWM功率均衡控制策略

对于直流侧电压比为1∶1∶2的混合级联H桥逆变器,传统的指定谐波消除脉宽调制法(SHEPWM)存在各单元间输出功率不均衡问题,因此,提出一种双层功率均衡调制策略。首先,通过对消谐方程组中的基波幅值方程表达式进行等效拆分,使2个低压H桥单元的输出电压基波幅值之和与高压H桥单元的输出电压基波幅值相等,实现了高低压H桥单元间的功率均衡,即外层功率均衡。其次,利用逻辑运算的方法对低压单元的初始驱动信号进行逻辑重组,实现2个低压单元间的功率均衡,即内层功率均衡;然后使用改进的实数型遗传算法(IRCGA-2)求出消谐方程组的解,消除指定的谐波,得到高质量的输出电压。最后,通过仿真和实验证明了调制策略的正确性与有效性。

改进蛇算法的七电平逆变器SHEPWM研究

多电平逆变器控制策略中的特定谐波消除脉宽调制(SHEPWM)能够以较低的开关频率得到较好的电压输出波形,重点在于开关角的求取。在多电平逆变器SHEPWM调制的开关角求解算法上提出改进蛇优化算法,对传统蛇优化算法采用Tend混沌映射初始种群,使初始种群分布更加均匀;引入Levy飞行策略增强算法的全局搜素能力,能够更加精准快速得到全局开关角的最优解。仿真结果表明,改进蛇优化算法所求的开关角相较于传统算法更好地消除低次谐波,并降低了输出线电压的畸变率,充分验证了该方法的可行性。

NPC逆变器SHE-PWM开关角度的计算方法研究

以应用于高压变频调速装置中的三电平中点嵌位(Neutral Point Clamped)逆变器为研究对象,对特定消谐技术(Selected Harmonic Elimination PWM)的应用进行了分析与研究;针对用数值方法求解SHE-PWM开关角度时非线性方程组计算初值选择困难的情况,给出了采用解轨迹微分预估初值的计算方法,并总结了调制比m 0时的开关角度解初值公式;实际计算结果表明:该文提出的方法在数值计算中可以得到快速收敛和准确的结果,并通过计算结果分析了SHE-PWM技术应用于NPC逆变器时所能达到的最大调制比,且其计算结果得到实验验证。

基于3次谐波控制及脉冲波动分析的三电平SHE-PWM调制优化策略

提出一种改进的特定谐波消除调制(SHE-PWM)策略,该策略能够抑制NPC型三电平逆变器中点电压波动,消除线电压低次谐波。传统特定谐波消除策略下的脉宽调制电压幅值始终默认为恒定值,即1/2直流侧电压。但实际工况下中点电压波动会导致脉宽调制电压变化不等。因此传统调制求出的开关角在脉冲电压波动的情况下并不能彻底完成指定次谐波消除,输出电压中仍含有少量低次谐波。针对该问题,深入分析了相电压中基波与3次谐波对中点电压波动的影响,对传统SHE-PWM策略进行了改进,通过引入3次谐波控制方程和脉冲电压波动权值系数重构傅里叶方程组。通过实验与传统SHE-PWM策略进行对比,结果表明利用重构的傅里叶方程组求得的开关角能更好地抑制中点电压波动,降低低次谐波含量,进而验证了改进SHE-PWM策略的有效性。

电流源型逆变器SHE-PWM开关角度的计算方法研究

该文以电流源型逆变器(CSI)为研究对象,对特定消谐技术(SHE)的应用进行了分析和研究;针对用数值方法求解SHE-PWM开关角度时,非线性超越方程组计算初值选择困难的问题,提出了以梯形调制法(TPWM)生成方程组初值的方法,使求解速度明显加快;根据非线性方程组的数值解进行了仿真和实验,其结果证明了计算结果的正确性。

NPC三电平逆变器SHE-PWM开关模式

文章以中点钳位型三电平逆变器为模型,在介绍SHE-PWM原理的基础上,采用同伦算法对非线性方程组求解,求取SHE-PWM的开关角度,进行NPC逆变器消谐模型的求解,具有收敛范围宽、收敛速度快等优点;用MatLab/Simulink仿真研究了谐波消除的效果,并用IGBT搭建了三电平逆变器实验电路模型,对SHE-PWM的谐波消除效果进行了验证;实验结果证明了基于同伦模型的NPC三电平逆变器SHE-PWM方法的有效性。

三电平SHE-PWM调制方法的DSP实现

有选择性的消谐波脉宽调制Selective H arm onic Elim inated-PW M ,简称SH E-PW M )方法具有开关频率小、输出波形质量好和调制比高的特点,是一种频率最优化的PW M 调制方法。本文在介绍三电平SH E-PW M 方法原理的基础上,讨论了如何采用DSP LF2407A 实现三电平SH E-PW M 调制的问题。实验结果验证了SH E-PW M 方法的特点。

单桥电流源型整流器SHE-PWM控制技术研究

介绍了一种单桥电流源型整流器,运用特定谐波消除技术消除其5次和7次谐波。对SHE-PWM调制时器件的开关角度进行了具体的分析,并得出了各种情况下全部开关角度的数据。实验研究结果证明,这种拓扑结构及调制方案具有很高的实用价值。

一种新颖的SHE-PWM双波段整流器研究

介绍一种采用移相变压器的双桥整流器,对这种拓扑结构进行了阐述和分析,并对相移变压器的消谐原理进行了推导,得出了系统可以四象限运行,并且具有很高的功率因数的结论。运用SHE-PWM的调制思想,提出了双波段SHE-PWM调制方案,得出了具体的计算数据。实验结果证明,该拓扑结构及调制方案对电网的污染很小,具有一定的实用价值。

有源中点钳位5电平变流器SHE-PWM控制方法

考虑到传统二极管钳位型和电容钳位型拓扑应用于6 k V/10 k V高压变频领域时存在的诸多问题,提出了一种有源中点钳位式(ANPC)5电平变流器选择谐波消除脉宽调制(SHE-PWM)控制方法。在分析了ANPC 5电平拓扑各桥臂的基本结构的基础上,建立了ANPC拓扑相关数学模型;分析了5电平SHE-PWM的基本原理,构建了以消除低次谐波为目标的非线性方程组,并基于牛顿迭代法给出N=7时的SHE-PWM相关解域;针对ANPC拓扑存在的飞跨电容稳压问题,分析了飞跨电容的稳压原理,进而给出了冗余电压矢量调度方式。样机实验结果表明,所提ANPC 5电平拓扑SHE-PWM控制方法实现了低开关频率下变流系统的高效控制,在消除系统低次谐波的基础上,保证了直流电容和飞跨电容的稳压效果。

基于双波段SHE-PWM开关方案的双桥整流器研究

介绍了一种采用相移变压器的双桥整流器,对这种拓扑结构进行阐述和分析,并且通过对相移变压器的消谐原理进行的推导,得出系统可以四象限运行,并且还具有很高的功率因数的结论。运用SHE-PWM的调制思想,提出了双波段的SHE-PWM的调制方案,得出了具体的计算数据。通过实验研究证明这种拓扑结构以及调制方案对电网的污染很小,具有实用价值。

基于MPSO算法的特定谐波消除技术研究

目的对于级联H桥逆变器的调制,特定谐波消除技术具有开关损耗小,能够消除特定次谐波,变换效率高等优点,但传统粒子群优化算法(Particle Swarm Optimization,PSO)在求解消谐方程组时收敛性差,容易局部最优,提出一种改进的粒子群优化算法(Modified Particle Swarm Optimization,MPSO)。方法该算法用非线性惯性权重取代线性变化的惯性权重,并在非线性惯性权重引入混沌映射以产生随机性更好的随机量,新的惯性权重可权衡粒子的全局搜索和局部搜索能力,使粒子具有后期跳出局部最优的能力;另外,该算法优化了速度和位置的更新机制,以增强算法的收敛速度,并保证粒子在后期仍具有一定种群多样性优势。结果根据级联H桥型逆变器的非线性消谐方程组,在保证输出电压基波的前提下最大化降低目标次谐波,建立适应度函数,将MPSO算法应用于级联H桥型逆变器的SHEPWM,能够在1~1.2的调制度范围内得到优化的开关角,提高收敛精度和求解成功率。通过七电平CHB逆变器仿真平台验证了MPSO算法所求的优化开关角能够有效地消除5次、7次谐波。结论通过使用非线性惯性权重和优化粒子的速度和位置更新机制,可以增加开关角求解成功率,所得解可以有效地消除目标次谐波。

基于SHE-PWM逆变器在变电站自动化中的研究

介绍了特定消谐技术的基本思想。通过对SHE-PWM原理的分析,推导出SHE-PWM的数学模型。在所提出的用于直流控制系统的逆变器拓扑结构的基础上,应用所提出的SHE-PWM技术,在MATLAB/SIMULINK下进行了仿真研究,结果表明该逆变器系统具有优良的性能,谐波畸变率完全符合国际谐波限制标准。

Modulation Index Effect on the 5-Level SHE-PWM Voltage Source Inverter

Harmonic content of the voltage source inverters is important and must be in the allowed ranges. Different method are proposed to decrease the Total Harmonic Distortion (THD) and caused to be sinusoidal the output voltage of inverters. One of these methods is using multilevel structure. In this structure many important parameters which are effective on voltage source inverter operation that among them we can mention to modulation index (MI). Variation of modulation index can change the THD. One of the harmonic reduction methods is using multilevel structure. In this paper, a sample 5-level SHE-PWM voltage source inverter is presented and all equation and choosing switching angles for elimination desired harmonics from different order. To investigate the effective parameters on the inverter operation, a typical 5-level inverter is simulated in PSPICE software. The simulation has been done for different values of modulation and its effect on the inverter operation is evaluated.