Switching Losses Reduction of Grid-tied Inverters With Variable Switching Frequency Discontinuous PWM

Three-phase two-level inverters are widely used in industry for dc-ac power conversion. Discontinuous pulse width modulation (DPWM) can reduce power losses but cause worse current quality. A same switching frequency is often applied for three phases in conventional modulation methods. This paper proposes a variable switching frequency discontinuous PWM method by increasing the switching frequency near the current zero-crossing point. Thus, better harmonic performance and negligible losses increase can be achieved. The discussion of the deadtime and narrow pulse effect is also presented and a simple carrier-based algorithm is proposed to implement this method. Simulation and experimental results are presented to verify the performance of the proposed method.