Space-Vector-Based Hybrid PWM Strategy for Reduced DC-Link Capacitor Current Stress in the Postfault Grid-Connected Three-Phase Rectifier

A hybrid pulse width modulation (PWM) strategy for the postfault grid-connected three-phase rectifier is proposed in this paper to achieve a reduced current stress on the dc-link capacitors. The capacitor current per sampling period is investigated, which consists of the effective duty ratio-based currents and the ineffective duty ratio-based currents. The currents introduced by the ineffective duty ratio are highly dependent on the allocation of the ineffective duty ratio. Therefore, this degree of freedom of the ineffective duty ratio allocation can be utilized to minimize the capacitor current. Then, the effect of the ineffective duty ratio allocation on the amplitudes of the capacitor current is analyzed. Based on this analysis, the optimized ineffective duty ratio allocations are proposed, where the ineffective duty ratios are flexibly allocated with respect to the vector angle of the ac current. Furthermore, a novel distribution of the vector plane is developed for the proposed hybrid space vector modulation (HBSVM) strategy. Moreover, the root-mean-square (RMS) values of the capacitor current are used to evaluate the performance of the proposed hybrid PWM strategy. The analytical results demonstrate that the proposed HBSVM strategy results in the reduced capacitor current RMS, which avoids a failure of the dc-link capacitors. Finally, the experimental results validate the effectiveness of the proposed HBSVM strategy.