A Comparative Analysis of Transformer-less Inverter Topologies for Grid-Connected PV Systems: Minimizing Leakage Current and THD

TL;DR

This paper compares transformer-less inverter topologies for grid-connected PV systems, focusing on leakage current and THD, and finds the H5 topology offers a good balance of performance and efficiency.

Contribution

It provides a comparative analysis of three inverter topologies, highlighting the advantages of H5 in reducing leakage current and THD while maintaining efficiency.

Findings

H5 topology achieves low leakage current and THD.

Simulation results validate H5's balanced performance.

H5 is suitable for practical grid-connected PV applications.

Abstract

The integration of distributed energy resources (DERs), particularly photovoltaic (PV) systems, into power grids has gained major attention due to their environmental and economic benefits. Although traditional transformer-based grid-connected PV inverters provide galvanic isolation for leakage current, they suffer from major drawbacks of high cost, lower efficiency, and increased size. Transformer-less grid-connected PV inverters (TLGI) have emerged as a prominent alternative, as they achieve higher efficiency, compact design, and lower cost. However, due to a lack of galvanic isolation, TLGIs are highly affected by leakage current caused by the fluctuation of common-mode voltage (CMV). This paper investigates three topologies H4, H5, and HERIC with comparisons between their CMV, differential-mode voltage (DMV), total harmonic distortion (THD), and leakage current. A simulation was conducted for each topology in MATLAB/Simulink R2023a, and the results demonstrate that the H5 topology achieves a balance between low leakage current, reduced THD, and optimal operational efficiency, making it suitable for practical application.