不平衡电网中三相脉冲调宽整流器的控制

Control scheme for three-phase pulse-width-modulation rectifier under unbalanced grid conditions

在常规的三相整流器控制器设计中，一般均假设三相电网电压平衡，然而当实际电网不平衡时，传统双闭环控制策略将使直流侧出现严重的二次谐波功率从而严重影响整流器输出品质．鉴于此，本文在分析PWM整流器数学模型和电网不平衡条件的基础上，圮压外环采用模糊PI控制，提高直流侧电压动态响应速度，电流内环采用无需进行正负序分解的正、负序电流独立控制策略，实现了不平衡电网下对三相PWM整流器的双闭环控制．仿真结果表明：所设计的控制方法保证了在不平衡条件下直流侧电压快速地稳定，有效抑制了直流侧二次谐波，提高了整流器的运行性能．

By the mathematical model of the pulse-width-modulation（PWM） rectifier and the characteristics of the unbalanced grid, we propose a new dual close-loop controller for the three-phase rectifier to reduce the second-harmonic power content on the DC side when the grid voltages are unbalanced. A fuzzy PI control is used in the voltage outer-loop to improve the speed of the dynamic response. Separate controls for the positive and negative sequence currents are employed in the current inter-loop with no decomposition of the current. The simulation results show that the proposed controller adjusts the DC voltage rapidly, reduces the harmonic power content and improves the dynamic performance of rectification under the unbalanced grid voltage condition.