Variable-Frequency Pulse-Width Modulation for an Improved Grid-Connected Converter Efficiency

This paper presents a high-efficient three-phase DC- AC grid-connected converter rated at 150 W. Two fundamental aspects led to the high efficiency, e.g. 96.2% at nominal power which corresponds to only 5.9 W losses. First, over the whole operation range, the converter operates as a resonant pole inverter (RPI), thus zero voltage switching at turn on is achieved. Second, the variable-frequency pulse-width modulation is optimized to a minimum rms-current in the filter inductor, leading to minimized conduction and inductor losses. Different experiments qualify the losses of the circuit components. A comparison between the conventional RPI and the PWM converter is given.