Improving the performance of an isolated photovoltaic grid-connected inverter using a high-frequency-link resonant capacitor

In the common photovoltaic grid-connected inverter topology, composed of a full-bridge converter, a high-frequency isolation transformer, a diode rectifier, a shaping inductor, and an unfolding circuit, the equivalent series inductance introduced by the high-frequency transformer has adverse effects on the input and output waveform qualities. In this paper, a high-frequency-link resonant capacitor is proposed to nullify the equivalent series inductive reactance at the switching frequency. As a result, the unwanted negative current pulses at the full-bridge converter input are eliminated and successful output current waveshaping in a wide range of loading conditions is guaranteed, irrespective of the value of the series equivalent inductance. The theoretical expectations are verified using simulation results.