电网不平衡下基于滑模变结构的三相电压型PWM整流器恒频控制

Constant frequency control for three-phase voltage PWM rectifier under unbalanced grid voltage conditions based on sliding mode control

基于滑模变结构的控制算法只需在αβ坐标系下完成控制目标无需进行复杂的d-q坐标系变化,且实现了恒频控制。当电网电压不平衡时,通过设置三个控制目标来对系统进行控制,即消除负序电流、消除有功功率波动、消除无功功率波动。为了提高控制精度,通过采用T/4延时法只提取正序电流分量和负序电压分量,无需提取负序电流分量,针对设置的三个控制目标进行不同的功率项补偿,进而达到控制目标的要求。理论推导和仿真实验结果证明了该控制策略的正确性和有效性。

Direct power control based on sliding mode control （SMC-PDC） can achieve its control purpose and constant switching frequency control simply under a - β coordinate system without the complex d-q transformation. When the grid voltage is unbalanced, this paper sets three control objectives to control system, namely eliminating negative sequence current, eliminating active power fluctuation and eliminating reactive power fluctuation. In order to improve control accuracy, T/4-shift method is adopted to extract only positive sequence current component and negative sequence voltage component and there is no need to extract negative sequence current component. So different control commands can be achieved through corresponding power component compensation of three control objectives set before. The simulation and experimental results verify the strategy＇s correctness and effectiveness.