Analysis and Control of a Novel Transformer-Less Microinverter for PV-Grid Interface

Abstract

In this paper, a novel single-phase, transformer-less microinverter configuration derived from the basic C¨uk topology is proposed for photovoltaic (PV)-grid interface applications. The topology has a direct connection between the grid neutral and the negative terminal of the PV array, which completely eliminates the ground leakage current. Further, the proposed topology has several appealing features such as high reliability due to the absence of shoot-through problems, symmetrical operation, low grid current distortion, capability of processing reactive power, low voltage ride through capability, and simple control for tracking the output current reference. Small-signal analysis has been employed to derive the topology's dynamic model using which a proportional resonant (PR) controller is designed and implemented. A step by step design procedure for obtaining the optimized proportional and integral gains of the PR controller, considering the effects of pulsewidth modulation transport and digital sampling delays, is presented. Theoretical claims and simulation results are corroborated by experimental studies carried out on a 200 W laboratory prototype controlled by using DSP TMS320F28335 controller.