A new, transformerless, photovoltaic array to utility grid interconnection

This paper describes a new interface between a photovoltaic (PV) array and a single-phase mains utility that avoids the bulky input (50 or 60 Hz) transformer on the AC side. The interface employs a PWM boost power converter on the DC side followed by a PWM current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly out of phase at all times. The circuit also has the advantage of requiring fewer switching devices than the circuits described in the existing literature. The controller for the boost rectifier in the DC side includes a discrete maximum power tracker (MPT) and the current-forced rectifier in the AC side autonomously feeds the maximum available PV energy into the mains. This paper describes a full dynamic model of the interconnection including the controllers, using which various control and power circuit parameters can be optimised and the performance of the interconnection studied. Experimental results on the performance of the connection are also presented