Zero-sequence Component Injection ZVS-PWM for Three-phase Grid Inverter with Arbitrary Power Factor Angle

In this paper, a generalized zero-voltageswitching pulse-width-modulation (ZVS-PWM) method for three-phase inverter with arbitrary power factor is proposed. By introducing an appropriate zero-sequence component to the three-phase sinusoidal modulation waves, there always exists one leg among the three legs whose switches do not commutate in every 60
⁰
of the fundamental cycle. Then the turn-on instants of the remaining two legs in each switching cycle can be synchronized according to equivalent-pulse-area theory so that zero-voltage-turn-on can be realized with the help of auxiliary circuit in the DC side. All switches can realize Zero-Voltage-Switching (ZVS) including the auxiliary switch. Furthermore, only one switching operation of the auxiliary switch is needed in a switching period. It is natural that this modulation scheme keeps the advantage of conventional third-harmonic injected SPWM method with higher DC voltage utilization. Stage analysis of the ZVS-PWM inverter and ZVS condition will be given. Finally the proposed modulation scheme is verified by experiment.