Voltage-Vector Optimal Redistribution-Based Hybrid PWM Strategy for Current Ripple Reduction in Three-Phase Two-Level Inverter

This paper aims to reduce the current ripple for three-phase two-level inverter in wide operation range. Based on the thought of voltage-vector optimal redistribution, a hybrid pulse-width modulation (PWM) strategy is proposed. Differing from conventional space-vector PWM scheme that the duration of zero-voltage and active-voltage vectors are always equally divided, the proposed hybrid PWM strategy redistributes the dwelling time of zero-voltage vectors and active-voltage vectors according to the minimum current ripple peak value. With the proposed strategy, the optimal PWM switching sequence-I based on zero-voltage vector redistribution is firstly obtained by establishing and analyzing the mathematical relationship of the current ripple peak value and the redistribution coefficient of two zero-voltage vectors' duration. And then, by splitting the dwelling time of maximum active-voltage vector based on the minimum current ripple peak value meanwhile merging zero voltage vectors according to the centrosymmetric modulation, the optimal PWM switching sequence-II and sequence-III are generated effectively and conveniently. With the comprehensive integration of three optimal PWM switching sequences, the proposed strategy not only reduces three-phase current ripples co-operatively and effectively, but also not increases the total switching power loss. Finally, experimental results are provided to validate the effectiveness and feasibility of the proposed hybrid strategy.