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 low-distortion, high-power factor AC current. For low-power applications, like photovoltaic panels and fuel cells, a single-phase 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.