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.

Topology for current-source grid-connected inverter with improved effciency and pulse width modulation control strategy

A novel topology of the current-source grid-connected inverter is proposed based on the immittance converter theory. A control strategy of sine-sine pulse width modulation （PWM） is studied. Compared with the traditional current-source inverter, the power frequency inductors and power frequency transformer are replaced with high frequency inductors and a high frequency transformer. Thus, the proposed inverter has advantages of small volume, low cost, low total harmonic distortion （THD）, low power losses, high power factor （PF） and simple control. Furthermore, grid voltage cannot influence output current of the grid-connected inverter and the current-source inverter with a high PF that approaches one has been realized. Finally, validity of the theory analysis and feasibility of the control scheme are shown by simulation and experimental results.

Analysis of Symmetrical and Asymmetrical Current Source Multilevel Inverter

The paper proposes a Current Source Multilevel Inverter (CSMLI) with single rating inductor topology. Multilevel inverters are most familiar with power converter’s applications due to reduced dv/dt, di/dt stress, and very efficient for reducing harmonic distortion in the output voltage and output current. The proposed nine-level current source inverter has been tested under symmetrical and asymmetrical modes of operation, and their activities are compared using PI and Fuzzy PI (Proportional Integral) controllers with multicarrier PWM (Pulse Width Modulation) strategy. MATLAB/Simulink simulation has been made for the proposed converter to obtain its performance measures. Some experimental results are given to verify the presented Current Source Multilevel Inverter.

A Comparison of Control Methods for Z-Source Inverter

In recent years, Z-source inverters (ZSI) have been proposed as an replacement power conversion concept which it has both voltage buck and boost abilities. In addition, ZSI doesn’t require dead-time to protection short circuit at two switches any of the same phase leg in the inverter bridge and to achieve optimal harmonic of current, voltage. This paper presents two different control methods (CM) for ZSI. The aim of this study to compare between two modulation methods, there are modi?ed space vector pulse width modulation method (MSVM) and the simple boost control (SBC) about the unique harmonic performance features, the total average and peak switching device power of the inverter system. In addition, this paper also analyzes about the ability exceed modulation index in linear region of two CM using MATLAB/Simulink.

Power Transfer of PV Inverter from DC to AC Voltage Source

This paper presents a simple approach of a topology already known in the literature, applied in active power transfer from direct current source to any alternating current voltage source, whether the utility power or a voltage inverter that is forming an isolated AC grid. The photovoltaic inverter works as current controlled voltage source inverter that provides a sinusoidal current to the AC grid. The inverter is insulated from the grid by a transformer. The system is discussed and modeled. Simulation results of this application are presented and experimental results validate this topology.

多载波PWM技术在三相五电平CSI中的应用

多载波PWM技术大多应用在电压型多电平变流器中,而将其应用于电流型多电平变流器中也具有良好的消谐波性能。本文介绍一种多载波PWM技术——载波位置相反分布(Phase Opposition Disposition,POD)PWM在三相分相控制式五电平电流型逆变器(Current Source Inverter,CSI)中的应用原理,提出了PODPWM技术数字化实现方案。最后给出了该三相分相控制式五电平CSI系统的实验结果。

CSIM自适应控制系统的研究

本文提出了电流型逆变器－异步电动机（ＣＳＩＭ）传动系统的速度自适应控制方案，利用模型降阶技术，在不显著影响系统性能的前提下，将原来系统的高阶数学模型降为便于控制器设计的低阶模型。设计了自适应控制系统，并用两片８０３１实现了该系统。实验结果表明，系统具有良好的动态静态特性。

CSI and CSI7 Current Source Inverters for Modular Transformerless PV Inverters

Current source inverter(CSI)is a class of power electronic converters that,thanks to the inherent boost capability and ease of control,is investigated for grid-tied photovoltaic power conversion applications.Traditional CSI and CSI7 topologies are here analyzed and compared with two kind of space vector modulation strategies mainly in terms of ground leakage current both in simulations and experiments.Furthermore,THD of the injected grid current and the computation of conduction and switching semiconductor power losses are also carried out in numerical simulations.The topology comparison is carried out with the use of a different number of PV modules,to analyze the robustness of the topologies to different size of the PV strings.Simulation and experimental results show that the CSI7 topology,with respect to conventional CSI,allows to strongly reduce ground leakage current,phase current THD and semicondutor power losses,at the price of an additional power device.

计及采样扰动抑制的电压源逆变器三矢量无模型预测电流控制方法

针对传统电压源逆变器无模型预测电流控制(model-free predictive current control,MFPCC)方法存在电流纹波大、电流梯度更新停滞以及预测性能易受采样扰动影响的问题。该文提出一种计及采样扰动的三矢量MFPCC方法。在一个控制周期应用3个基本矢量,并根据价值函数计算矢量作用时间,降低了输出电流纹波;其次,通过建立不同矢量作用下的电流梯度方程组,实现电流梯度数据的实时更新,消除了停滞现象;再次,分析采样扰动对MFPCC的影响,采用扩张状态观测器估计采样扰动以补偿预测电流控制,抑制其对输出电流的影响。最后,通过仿真和实验,对所提方法的有效性进行了验证。

Three Phase Dual Input Direct Matrix Converter for Integration of Two AC Sources from Wind Turbines

This project proposes a novel dual-input matrix converter (DIMC) which is used to integrate the output of the wind energy to a power grid. The proposed matrix converter is developed based on the traditional indirect matrix converter under reverse power flow operation mode, but with its six-switch voltage source converter replaced by a nine-switch configuration followed by the current source inverter (CSI). Matrix electric power conversion topologies and their switch functions are flexible and are used for specific applications. With the additional three switches, the proposed DIMC can provide six input terminals, which make it possible to integrate two independent AC sources from two independent wind turbines into a single grid tied power electronics interface. Commanded currents can be extracted from the two input sources to the grid. The proposed PI control and modulation schemes guaranteed sinusoidal input and output waveforms as well as reduced THD. The simulation results are provided to validate the effectiveness of the proposed control and modulation schemes for the proposed converter.

改进滑模观测器的电流源逆变器驱动PMSM无位置传感器控制

由于电流源逆变器(CSI)的叠流效应以及前级DC-DC控制的母线电流脉动较大,使得扩展反电动势中含有大量谐波,造成较大的位置误差。针对此问题,该文提出一种改进滑模观测器的电流源逆变器驱动永磁同步电机无传感器控制方法。首先,基于传统滑模观测器,设计复系数滤波器代替传统低通滤波器,实现了对估计反电动势的准确提取,同时也抑制了估计反电动势中的高频抖动和高次谐波。其次,将二阶广义积分器内嵌于锁相环中,用于消除位置误差信号中的低次谐波,提高位置观测准确度。最后,将估算的速度信息反馈回复系数滤波器,实现复系数滤波器的自适应性。实验结果表明,所提方法在不同工况下,能够有效提高估算的转子位置精度,验证了方法的可行性与有效性。

Distorted Waveform Balancing Using an Artificial Bee Colony (ABC) Based Optimal Control for Mitigating Total Harmonics in Single Phase Inverter

The main objective of this paper is to reduce the total harmonics in a single phase voltage source inverter using Artificial Bee Colony (ABC) optimization technique for critical load applications. Single phase inverter is a non-linear load using power electronic components causing distortions in the load voltage and current wave patterns from the sinusoidal waveforms due to harmonics. The mapping state space model for a full bridge voltage source inverter was developed using output load resistance. An optimal ABC technique has been designed and optimized values are estimated using a full bridge voltage controlled inverter using Proportional Integral Algorithm. The MATLAB/SIMULINK tool and Experimental setup were implemented and their THD values were estimated. Also this ABC scheme is compared with the previous results such as PI Algorithm, Fuzzy logic controller and Neuro-fuzzy controllers. From the simulation and experimental results using ABC algorithm, it is observed that the total harmonics are mitigated considerably compared to previous results with respect to the power quality standards such as IEEE-519 and IEC 61000.

基于电流源型逆变器驱动的五相永磁同步电机控制策略研究

在现代电机驱动系统中,采用电流源型逆变器控制方案可有效提升系统可靠性,降低电机电流谐波含量,并提升电磁兼容性能。电流源型逆变器拓扑采用电感元件作为母线储能装置,对于功率回路中的短路故障具有较强的抵抗能力。同时,逆变器输出侧并联滤波电容网络,实现对高频谐波的旁路作用。该文对五相电流源型驱动系统控制策略进行研究,采用五相半桥型逆变器拓扑结构,电机绕组采用星型连接方式以限制零序电流,给出基波与谐波电流矢量空间分布特征,提出双平面矢量脉宽调制策略,有效抑制3次谐波电流。考虑到逆变器输出侧CL型负载可能引起的谐振问题,采用基于电机电流的有源阻尼策略,降低谐振电流分量,提升系统稳定性。最后,通过实验验证所提控制策略的有效性。

一种多模态组合型Y源逆变器

针对耦合电感型阻抗源逆变器升压能力不足和直通电流较大的问题,将多模态组合思想引入到Y源阻抗网络,提出一种多模态组合型Y源逆变器。对所提逆变器的所有模态组合方式、相应的调制策略和电压电流关系进行详细分析,推导出升压比和关键器件应力。与改进型Y源逆变器和高升压Y源逆变器进行对比,多模态组合方式使所提逆变器的升压比引入新的影响因子,能在相同绕组系数K和直通占空比d下令升压能力更高。同时具有更低的二极管电压应力,且抑制了直通电流的大小。最后通过搭建200 W的实验平台,验证所提逆变器的可行性和优越性。

电流源逆变器复矢量解耦与前馈解耦联合降阶控制策略研究

电流源逆变器输出侧需添加电容器对输出斩波电流进行滤波,导致电流源逆变器电机驱动系统控制模型具有系统阶次高、存在谐振点、旋转坐标系下模型耦合严重等问题。针对上述问题,以降阶控制为主要目的,提出了复矢量解耦与前馈解耦联合降阶控制策略。针对电流源逆变器的复矢量模型,引入电机电流前馈消除模型中电机电流耦合项,在此基础上,使用复矢量解耦策略,针对二阶串联模型设计带有耦合误差项的比例积分控制器,消除常规控制器中高阶模型导致的闭环系统谐振,简化闭环模型,实现系统的解耦与降阶。同时,该控制器具有结构与参数整定简单的优点,通过稳定性分析验证了所提闭环电流控制器的可行性。以一台3 kW永磁同步电机为对象进行仿真,并与传统控制策略、双闭环控制策略进行对比验证。结果表明,所提控制策略在降低模型阶次、简化控制器设计的同时,相较于传统控制策略解耦合能力更强,在阶跃响应与转速耦合作用下表现出更强稳定性,电流在阶跃信号作用下均没有发生振荡。

一种具有直通电流抑制能力的低电压尖峰Y源逆变器

针对传统耦合电感型阻抗源逆变器存在直流链电压尖峰和直通电流过大的问题,提出一种具有直通电流抑制能力的低电压尖峰Y源逆变器。分析了所提拓扑在直通状态和非直通状态下的工作原理,并给出了一个开关周期内的主要波形。采用安秒和伏秒平衡原理,分别推导出关键器件的电压、电流应力。与改进型Y源逆变器对比,当绕组系数相同时,所提拓扑在相同的升压比下具有更小的直通占空比,增大了调制比范围,提高了直流链电压利用率,并能够降低直流链电压尖峰。而且,所提拓扑能够抑制直通电流的增大,相同直流链电压下需要更小的直通时间使其直通状态下的开关管导通损耗更小。最后,搭建240 W实验装置充分验证所提拓扑的先进性。

准Z源逆变器的模型预测电流误差控制

为降低准Z源逆变器模型预测控制的控制误差,提出一种模型预测电流误差控制方法。首先,在充分分析电压矢量对被控量性能影响的基础上,合理地选择适合各被控量的电压矢量组合方式。然后,利用电流对称控制思想保证电感电流关于其参考指令对称。最后,采用电压矢量抵消原理使输出电流幅值逼近其目标值。实验结果表明,所提方法能够大幅降低电感电流脉动和输出电流谐波含量;证明了所提方法能有效提高准Z源逆变器的控制精度,简化了对权重系数的设计工作。

Inherently Sinusoidal Single-phase Voltage Source Inverter Based on Modified Cuk Cell

Renewable energy has become important for electricity generation because of the high air pollution associated with conventional fossil-based energy systems.Conventional fossil-based power plants are gradually transitioning by incorporating renewable energy sources,such as photovoltaic(PV)cells.In a PV system,an inverter converts DC power from solar panels to AC power required to serve common electrical loads.A conventional H-bridge inverter topology has several disadvantages,such as the voltage being not sinusoidal,switching the DC voltage and high common-mode voltage.The common-mode voltage can cause a large leaked capacitive current,which can result in undesirable operation in solar power applications.A common solution to this problem is the addition of a large filter to the input or output of an inverter.An inherent sinusoidal voltage source inverter based on a modified Cuk converter as its basic cell,which simultaneously generates a sinusoidal output voltage and a lower common-mode voltage,is proposed.The proposed topology does not require additional input or output filters.Analytical expressions are derived to confirm the operation of the proposed topology.Simulation results confirm the mathematical analysis.A laboratory-scale experiment is performed to verify the proposed inverter.

一种Z源光伏并网逆变器及其共模漏电流抑制

传统准Z源桥式并网逆变器(GCI)具有允许桥臂直通、直流电压利用率高等优点,但存在体积大、可靠性低和共模漏电流高的缺陷。针对传统准Z源桥式GCI的问题,首先提出一种具有更小体积的新型耦合电感线圈Z源光伏并网逆变器(ZPGCI)及其调制策略。然后,对ZPGCI的运行模态、共模漏电流与桥臂直通状态进行探究,理论研究表明新型ZPGCI不仅具有允许桥臂直通和可靠性高的优点,且可有效抑制传统准Z源桥式GCI的高频共模漏电流。最后,对传统准Z源桥式GCI和新型ZPGCI进行对比实验分析,验证ZPGCI电路设计及其理论推理的正确性。

计及锁相环和电流内环暂态过程的逆变型电源故障电流解析方法

为应对新型电力系统中高比例新能源接入对保护原理的挑战,亟需对新能源故障特性进行分析。新能源常以逆变型电源的形式并入电网,而锁相环(phase-locked loop,PLL)作为逆变型电源并网的关键控制环节,其暂态过程直接影响逆变型电源故障特性。该文提出一种计及锁相环和电流内环暂态过程的逆变型电源故障电流解析方法,从锁相环对Park变换的影响入手,明确锁相环对逆变型电源故障电流的影响路径,同时简化锁相环对电流内环暂态过程的影响,通过理论推导得到与锁相环和电流内环参数相关的故障电流解析式,定量分析了故障电流的影响因素,根据电流内环和锁相环暂态特性将故障电流划分了3个阶段并明确各阶段过渡时间,并与仿真波形进行对比验证了有效性。