A Transformerless 1-, 5-level Half-Bridge PV Inverter Configuration based on Switched-Capacitor Technique

Abstract

Leakage current is a serious problem in the transformerless solar PV inverter configurations. The flow of leakage current is mainly due to the high-frequency oscillations in the voltage across PV parasitic capacitance (vCPV). Half-bridge and common ground type inverter topologies are highly suitable for eliminating these oscillations as these configurations allow direct electrical connection between the source and the load/grid ground. However, they suffer from either poor dc-bus utilization or asymmetric operation leading to dc-offset in the output voltage. In this paper, a novel 1-ϕ, 5-level inverter is proposed which employs a half-bridge structure to eliminate voltage oscillations from vCPV without compromising with the dc-bus utilization or symmetric operation. This is achieved by integrating a switched capacitor network with the half-bridge structure. All the necessary analysis and design procedures are included to support the various claims. The claims are further validated using MATLAB simulations and experiments on a laboratory prototype. The proposed topology is compared with the various existing topologies of similar nature (like 5-level output voltage, common ground or half-bridge type configuration and 1-ϕ) to prove its superiority.