双馈风力发电机转子网侧PWM整流器的设计和仿真

采用了一种新的三相电压型PWM整流器控制方案,建立了整流器输入电流控制的d-q模型,该模型对电网波动和负载扰动具有较强的抗干扰能力。仿真表明,该整流器能获得单位功率因数的正弦输入电流、稳定的直流输出电压和快速的动态相应,能够实现能量的双向流动,是满足双馈风力发电机交流励磁要求的理想整流电源。     

改进的PWM整流技术控制策略研究

针对不可控或半控整流引起电网大量谐波和无功日益严重问题,采用改进的前馈解耦控制策略对三相电压型PWM整流器设计,分析了三相电压型PWM整流器的数学模型及改进的前馈控制策略,在Matlab/Simulink平台下搭建了系统的仿真模型,与传统PWM整流器对比,并对三相电压型PWM整流器进行了系统试验。仿真与试验结果表明,该整流器能快速获得稳定的直流母线输出电压,鲁棒性良好。     

PWM整流器在变速恒频风力发电系统中的应用

变速恒频风力发电系统要求励磁电源有良好的输入、输出特性和能量双向流动的能力.交-直-交双PWM变频器是理想的励磁电源,而PWM整流器是其中一项关键技术.文章从三相电压型PWM整流器主电路拓扑结构出发,建立了基于三相静止坐标系和两相同步旋转坐标系的数学模型.阐述了电压、电流双闭环控制的基本原理和空间矢量脉宽调制技术在三相PWM整流器中的应用.在Matlab/Simulink环境下,对其进行了单位功率因数整流和逆变的仿真研究.结果证明,该整流器是满足交流励磁需要的理想整流电源.     

基于双采样的LCL型并网逆变器并网电流间接控制研究北大核心CSCD

在并网逆变器滤波方面,LCL型滤波器比LC型滤波器具有更加优良的高频谐波滤除能力,但是LCL型滤波器的谐振效应也给并网系统的稳定性带来一定的挑战。实际的并网逆变器通常采用逆变器侧电流和电容电压作为反馈进行控制,在分析LCL型并网逆变器结构的基础上,文章提出一种逆变器侧电流反馈控制并网电流和电容电压反馈抑制谐振的并网逆变器控制方案,无需逆变器外部增加电流传感器,给出了精确的并网电流参考值计算方法。实验验证了文章所提控制方案的有效性。     

非正弦输入电压下三相四线PWM整流器控制策略研究

在dq0坐标系下建立了三相四线PWM整流器的状态空间平均模型,分析了非正弦输入电压对PWM整流器输入电流控制的影响,指出k次输入电压谐波将在输入电流中产生k次相应谐波。为抑制非正弦输入电压的影响,提出了基于SRF的dq0轴控制策略,实验结果表明,分析及采用的控制策略正确、有效。     

电网畸变条件下基于LCL型滤波的STATCOM电流控制策略研究

在节约总电感用量的前提下,为了提高系统的滤波性能,选择LCL型滤波器作为配电网STATCOM(D-STATCOM)的输出滤波器。LCL型滤波器是一个三阶系统,采用直接入网电流控制时谐振峰的存在会影响系统的稳定性。为此,提出一种基于状态反馈的虚拟阻抗法用于抑制LCL型滤波器的谐振峰,从而避免无源阻尼法增大系统的损耗。由于电网电压中含有谐波含量会造成补偿电流畸变,从而不能准确跟踪其指令值,针对这一问题,提出一种多谐振比例谐振(PR)控制器,用于增大特定频率处电网电压对入网电流的输入阻抗,从而抑制电网谐波电压的扰动,优化补偿电流波形,提高电流追踪性能。仿真和实验结果证实了控制策略的有效性。     

LCL型滤波器在并联APF中的应用研究

针对L型滤波器应用于并联有源电力滤波器(APF)中的不足,建立了LCL型输出滤波器的数学模型,分析了APF系统采用LCL型滤波器的优越性;设计了基于LCL型输出滤波器的并联APF三环控制系统,在APF输出电流环的基础上引入电容电流内环,增大系统阻尼,保证系统的稳定性。通过MATLAB/simulink仿真验证了采用三环控制策略的LCL型APF系统能够对电网中的谐波电流实现精确跟踪和补偿,证明了控制策略的正确性和有效性。     

带LCL滤波器的单相并网逆变器

针对相同滤波效果下采用L型滤波器的单相光伏并网逆变器的PI控制需要较大的电感值以及存在高损耗、电流内环响应速度降低和成本较高的不足,提出了采用基于LCL滤波的电容电流反馈和电网电压前馈的准PR控制策略,以增加系统阻尼、抑制振荡、提高系统稳定性能,并通过Matalab/Simulink软件搭建仿真模型进行了验证。结果表明,经LCL滤波后,在准PR控制策略下,加入电容电流反馈和电网电压前馈后,获得的入网电流畸变率更小,实现了入网电流的无静差跟踪,抑制了电网电压的扰动,且系统输出的波形满足入网要求。     

储能双向变流器主电路参数设计及控制策略研究

设计了一种适用于电化学储能系统的双向变流器,采用一级变换主电路拓扑结构,交流侧采用LCL滤波器,减少注入电网的谐波,直流侧采用CL滤波器,降低电池侧纹波;介绍了储能双向变流器的工作原理,给出了交流侧LCL滤波器与直流侧CL滤波器设计原则,推导出基于LCL滤波器主电路数学模型,并设计了闭环控制系统。通过仿真和试验表明,该双向变流器主电路参数设计合理,电流谐波小,直流侧纹波小,可满足大容量储能系统的工作要求。     

面向电流源型PWM整流器的双矢量模型预测直接功率控制

电流源型脉宽调制(Pulse width modulation,PWM)整流器因其网侧存在LC滤波器,系统的控制难度增加。传统直接功率控制策略下的整流器功率波形存在脉动,因模型预测控制具有卓越的动态特性以及直观的控制规律,采用模型预测直接功率控制(Model predictive direct power control,MPDPC)对传统控制策略进行改进。首先建立了三相PWM整流器的数学模型,给出了每个采样周期内的功率变化率,并推导出相邻采样周期之间的功率关系,然后给出基于单矢量的模型预测直接功率控制策略,提出了基于双矢量的模型预测直接功率控制策略,并优选出两个电流矢量,计算在一个采样周期内的作用时间,并对其进行修正。最后,在Matlab/Simulink仿真软件验证了所提控制策略的可行性和有效性。     

光伏模拟器用死区消除PWM整流器运行方式

针对光伏模拟器用单相脉宽调制（PWM）整流器提出电压平方外环电流内环的控制策略,同时揭示直流侧存在2倍基波频率的纹波电压以及此纹波电压对网侧电流的影响。PWM整流器采用的基于H桥死区消除SPWM,在网侧电流非过零区域,各桥臂上下两开关管中,必定存在其中一个开关管驱动信号为低电平,而在电流过零处推导出存在的天然死区时间。由微控制器（MCU）与现场可编程门阵列（FPGA）相结合的控制系统可实现提出的运行方式。实验结果验证了理论推导的正确性以及提出运行方式的有效性。     

Design and implementation of Type-2 fuzzy neural system controller for PWM rectifiers

It is necessary to convert AC to DC for the systems that do not work with AC sources. For this reason, diode and thyristor rectifiers were developed and designed. However, these rectifiers are not well suited for industrial applications requiring high performance. With the advances in power electronics and semiconductor technology, Pulse width modulation (PWM) rectifiers have been successfully employed in various industrial applications including variable-speed drives and uninterruptible power supplies. PWM rectifiers have the advantages of being low input current harmonic, adjustable input power factor, and controllable DC voltage and bidirectional energy flow. Because of all these features of the PWM rectifiers, the control and design of these rectifiers are very important topic. The aim of this paper is to control DC-link voltage of PWM rectifier with type-2 fuzzy neural system (T2FNS) instead of PI controller. For this aim, three-phase PWM rectifier with proposed controller is designed and simulated for four scenarios in this paper. A simulation model of the PWM rectifier is designed in MATLAB/Simulink and the performance of PWM rectifier with proposed controller is analyzed.     

电压不对称情形下基于DSP软件锁相环的设计

准确的相位信息对大部分现代电能变换装置的稳定运行至关重要,比如高频PWM整流。软件锁相环(SPLL)具有设计自由、适应性强等优点可快速准确获得电网电压的相位和频率信息。本文针对电网电压不对称的情形,分析SPLL原理,获得SPLL线性化模型,设计SPLL控制器,讨论实际情况对控制器参数的要求,并用DSP实现所设计SPLL。仿真表明所设计SPLL良好运行于高频PWM整流,并对其他电能变换装置中的SPLL设计具有指导意义。     

一种谐振型混合调制的电流型高增益双向变换器

为减小双向变换器低压侧电流纹波,改善变换器硬开关现象,降低其闭环系统设计的复杂程度,提出一种谐振型混合调制的电流型高增益双向变换器。该变换器在低压侧全桥桥臂中点加入2个交错并联的Boost电感,在增加变换器增益的同时可减小变换器低压侧电流纹波,高压侧为倍压整流电路,进一步增加了变换器增益,同时利用变压器漏感与谐振电容谐振创造了高压侧开关管ZCS的条件。该变换器正反向均采用PWM+PFM混合调制控制,通过改变占空比调节输出电压,调节开关频率实现高压侧开关管的ZCS,采用该控制方案降低了变换器闭环系统设计的复杂程度,并可减小高压侧开关管的关断损耗。搭建一台600 W试验样机,进行正反向实验,验证所提方案的有效性。     

Effectiveness of active noise and vibration cancellation for switched reluctance machines operating under alternative control strategies

The effectiveness of active vibration cancellation by inducing antiphase vibration of the stator to reduce the acoustic noise emitted from a switched reluctance machine is evaluated under typical operating modes, viz., single pulse excitation, pulsewidth modulation (PWM) voltage control, and PWM current control. Measurements in both the frequency and time domains are complemented by sound pressure level measurements. It is shown that active vibration cancellation is most effective in reducing a single mode of vibration when a switched reluctance (SR) machine is operated under single-pulse excitation, and becomes less effective when more than one dominant vibration mode exists within the audible frequency range. In general, it also works relatively well when the machine is operated under fixed frequency PWM voltage control, although less effectively than for single pulse control. Further, it is shown that the technique is ineffective when the machine is operated under PWM current control since the duration of the zero voltage period varies significantly from the optimal value due to the random nature of the PWM.     

AC/DC power conversion interface for self-excited induction generator

A new AC/DC power conversion interface for the self-excited induction generator (SEIG) is proposed here. The proposed AC/DC conversion interface includes an excitation systemand a diode rectifier connected in parallel.The variable frequency AC power generated by the SEIG is converted into DC power by the diode rectifier.The DC power of the diode rectifier can charge a battery set and supply DC loads or be further converted into fixed-frequency AC power by an inverter for AC loads.The DC voltage is expected to be regulated in the above applications.The excitation system supplies an exciting reactive current to maintain the amplitude of the SEIG output voltage to be a constant value. Moreover, it can also serve as an active power filter to suppress the harmonic current generated by the diode rectifier. The excitation system is composed of an AC power capacitor and a power converter connected in series. The AC power capacitor is adapted to provide a basic reactive power, and it can also reduce the voltage rating and the capacity of the power converter. The salient point of the proposed AC/DC power conversion interface is that the capacity of the power converter in the AC/DC power conversion interface can be minimised, and the power loss of the AC/DC power conversion interface can also be reduced. A prototype is developed and tested to verify the performance of the proposed AC/DC power conversion interface.     

Comprehensive control strategy for a variable speed cage machine wind generation unit

A comprehensive control strategy, that addresses all three control objectives in a wind generation system, i.e. control of the local bus voltage to avoid voltage rise, capture of the maximum power in the wind and minimization of the power loss in the induction generator is proposed. The control signals are the desired current wave shapes (instantaneous three-phase currents) of the rectifier and the inverter in a double-sided PWM converter system connected between the wind generating unit and the grid. Studies performed on a complete model for a variable speed cage machine wind generation unit, including wind profile, wind turbine, induction generator, PWM converter, local load and transmission line, show that even as the wind speed changes randomly, the proposed control strategy leads the system to the optimum operating conditions.     

Modelling of a 5-kW wind energy conversion system with induction generator and comparison with experimental results

A 5-kW wind energy conversion system (WECS) having induction generator is designed and implemented. The induction machine is connected to the power system through PWM inverter and PWM rectifier. Two digital PI controllers are used, one of them is for regulating dc link voltage and the other is for speed control of induction machine. The whole system is governed by a single fixed point digital signal processing unit (DSP). A detailed simulation program is prepared by using Matlab facilities in order to predict the performance of the controllers before implementation.     

Power quality improvement using fuzzy logic controller for five-level shunt active power filter under distorted voltage conditions

In this paper, a five-level inverter is used as a shunt active power filter (APF), taking advantages of the multilevel inverter such as low harmonic distortion and reduced switching losses. It is used to compensate reactive power and eliminate harmonics drawn from a thyristor rectifier feeding an inductive load (RL) under distorted voltage conditions. The APF control strategy is based on the use of self-tuning filters (STF) for reference current generation and a fuzzy logic current controller. The use of STF instead of classical extraction filters allows extracting directly the voltage and current fundamental components in the α-β axis without phase locked loop (PLL). The MATLAB fuzzy logic toolbox is used for implementing the fuzzy logic control algorithm. The obtained results show that the proposed shunt APF controller has produced a sinusoidal supply current with low harmonic distortion and in phase with the line voltage.