A Single-Phase Low-Frequency Commutation Inverter for Renewables

Co-generation systems integrating distributed low power sources with the utility generally ask for an electronic power converter for conditioning the locally generated power and inject current into the grid. If the source provides a DC voltage, the converter should be able to produce a lowdistortion, high-power factor AC current. For low-power applications, like photovoltaic panels and fuel cells, a singlephase inverter (DC-AC converter) can be used for connecting the source with the grid. The paper describes a single-phase DC-AC topology for interfacing DC sources with the utility. The commutation of the power switches is at the line frequency. The main advantages of the proposed converter are: (1) negligible switching losses – high efficiency; (2) negligible EMI; (3) the current injected into the grid presents low harmonic distortion and high power factor; (4) higher reliability compared to PWM inverters (due to the simpler control circuitry). The power flux can be controlled either by varying the DC voltage or controlling the switches command.