基于直流电流二倍频分量抑制的电流源型PWM整流器控制策略

A control strategy for current source PWM rectifier with suppressing double frequency component of DC current

电流源型脉宽调制整流器在电网电压不平衡工况下运行时,电网电压中负序分量的影响将导致直流侧引起低频脉动,网侧电流出现低次谐波。为了解决此问题,在含有源阻尼的传统双闭环控制基础上,利用直流侧电流内环谐振控制直接抑制直流侧输出低频脉动,同时使网侧电流正弦化;在网侧电流参考指令中加入滤波电容电流补偿项,实现系统网侧电流和电网电压同相位运行。为进一步提升系统在高不平衡度工况下运行性能,在调制环节中引入陷波器消除低次谐波分量,提高了网侧电流波形质量。最后利用MATLAB/Simulink进行仿真测试,并搭建了一台3 kW实验样机,仿真与实验结果表明在电网不平衡度为6.7%和20%时,文中所提出控制策略均能将直流侧电压波动限制在1.2 V以内,同时网侧电流总谐波畸变率小于4%。

When the current source PWM rectifier is at the operate condition that the grid voltage is unbalanced,the negative sequence component of grid voltage will cause low-frequency pulsation in DC side and low-order harmonics in grid side current.To solve this problem,the resonance control with the inner DC current loop based on the traditional double closed loop with active damping is applied in this article to directly suppress low-frequency pulsation existed in the DC side outputs,and the sinusoidal current at the grid side is formed.Besides,the current of the filter capacitor as the compensation term is added into the current reference value on the grid side.In this case,current and voltage with the same phase are realized on the grid side.Furthermore,to improve the operating performance of the system under extremely unbalance conditions,a notch filter is introduced in the modulation link to eliminate low-order harmonic components,which improves the current waveform on grid side.Finally,simulation test is studied by using MATLAB/Simulink and a 3 kW prototype is established.The simulation and experimental results indicate that when the unbalance degree of the grid reach 6.7%and 20%,the proposed control strategy can effectively suppress the voltage fluctuation on DC side within 1.2 V,and the total harmonic distortion rate on the grid side current is less than 4%.