A photovoltaic array transformer-less inverter with film capacitors and silicon carbide transistors

A new photovoltaic (PV) array power converter circuit is presented. This inverter is a transformer-less topology with grounded PV array and only film capacitors. The motivations are to reduce circuit complexity, eliminate leakage ground currents, and improve reliability. The use of silicon carbide (SiC) transistors is the key enabling technology for this particular circuit to attain reasonable (>97%) efficiency. Some background about the challenges of ground currents and power decoupling to be addressed is first discussed. The proposed solution of a bidirectional buck boost converter, dynamically varying dc link, and half-bridge inverters is then presented along with details on the basic functionality. Some aspects of selecting passive components for the circuit are discussed. The average dynamic model and control system are then presented. Finally, simulation and experiment results are shown demonstrating that the proposed topology is a viable solution.