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 (v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CPV</sub> ). Half-bridge (HB) 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 article, a novel 1-φ, 5-level inverter is proposed, which employs a HB structure to eliminate voltage oscillations from v <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">CPV</sub> without compromising with the dc-bus utilization or symmetric operation. This is achieved by integrating a switched capacitor network with the HB 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 HB type configuration and 1-φ) to prove its superiority.