A line interfaced inverter with active control of the output current waveform

Abstract

A line interfaced inverter for photovoltaic systems is presented. This inverter employs a high frequency dc-chopper for shaping the output current, providing unity power factor operation and minimizing the size of the output filter. The isolation of the solar array from the utility is accomplished with a high frequency transformer, eliminating the need for large, 60 Hz magnetics. The dynamics of the power circuit are analyzed to determine proper compensation of the output current control loop. This analysis shows that a minor loop is required to stabilize the power circuit and that system response varies during the 60 Hz cycle. A Parity Simulation of the power circuit/control system is performed to verify this analysis. The results of this simulation are presented and compared to waveforms from a test inverter. The special considerations required for properly loading a photovoltaic array with a line interfaced inverter are discussed.