针对两台三相PWM 整流器在并联时的环流问题，在分析其等效的平均模型基础上，建立了并联系统在两相同步旋转坐标系下的零序环流数学模型． 分析了环流抑制的原理，详细分析了调零矢量占空比的对称空间矢量脉宽调制( SVPWM) 控制策略，在此基础上，设计了“重复控制+ PI”的电流环组合控制策略，基于无差拍算法提出了一种可调零矢量的七段对称式SVPWM 调制策略，该控制方法能有效抑制零序环流且不需要增加额外的硬件，而且具有动态响应快等优点． 实验结果验证了理论分析的正确性，解决了波形畸变、不均流、电感参数不对称等问题，提高了系统的可靠性．

In order to solve the zero-sequence circulating current problem existing in two parallel three-phase PWM rectifiers,by analyzing their equivalent average models,a mathematical model of the zero-sequence circulating current of the parallel system is constructed in a two-phase synchronous rotating coordinate system.Then,the control principle of the circulating current is discussed,and the symmetrical SVPWM ( Space Vector Pulse Width Modulation) control strategy with a variable zero vector duty cycle is explored.On this basis,a control strategy of the circulating current,which combines the repetitive control with the PI control,is designed,and a novel deadbeat control strategy is then proposed to suppress the circulating current by adjusting the voltage zero vector of SVPWM.The proposed strategy can effectively suppress the circulating current without additional hardware,and it has a fast dynamic response.Experimental results demonstrate that the model analysis is correct,and the proposed strategy can solve such problems as waveform distortion,current discrepancy and inductors unbalance.Thus,the system reliability is greatly improved.