Comparison of hysteresis controlled three-wire and split-link four-wire grid connected inverters

Voltage-source six-switch three-phase inverters are widely used in distributed generation (DG) systems. The input of the inverter can be supplied from a normal DC bus or a split-link DC bus composed from two series capacitors. In case of split-link DC bus, neutral point of three phases is connected to the middle point of the series capacitors, and each phase current is controlled independently. When the DC bus is not split-link, phase current is determined by three phase switching states. In this paper, analysis of hysteresis current controlled three-wire and four-wire grid connected inverters are given. L filter is connected between the inverter and the grid to filter current. Two different topologies are analyzed in terms of DC-link voltage utilization, output current total harmonic distortion (THD) and switching frequency. Simulation results are given comparatively for 10 kW output power.