A novel grid interface for photovoltaic, wind-electric, and fuel-cell systems with a controllable power factor of operation

This paper presents a novel control for a grid interface, for interconnection of renewable energy sources with a three-phase utility, with a controllable power factor of operation. The total harmonic distortion in the line currents meets the 5% limit recommended by the IEEE 519-1992. The novel control strategy for operating the interface at unity or even slightly leading power factor is described and the simulation results are presented. The grid interface described is based on a novel topology for transferring power from the DC side to the three-phase AC system. It consists of a thyristor inverter where the firing angle can be kept at a constant value. The power flow from the DC source to the utility is controlled by two stepdown DC-DC converters