Space-vector analysis and modulation issues of passively clamped quasi-resonant inverters

The passively clamped quasi-resonant DC-link (PCQRL) inverter basic topology and other quasi-resonant inverters have been shown to be only partially compatible with pulsewidth modulation (PWM), due to a minimum dwell time created by the clamping mode in the inverter operation. This paper addresses this kind of modulation nonlinearity, employing the space-vector approach as a modeling tool. Closed-form expressions are obtained, defining the inverter linear modulation range in terms of the dwell time and other inverter and load parameters and characteristics. An alternative implementation of the resonant snubber that eliminates the low-order harmonics in the output voltages is presented. Experimental and simulation results are presented to support the theoretical analysis.