An Optimized H5 Hysteresis Current Control with Clamped Diodes in Transformer-less Grid-PV Inverter

TL;DR

This paper introduces a novel H5 inverter topology with clamped diodes that reduces leakage current and voltage spikes in transformer-less grid-connected PV systems, improving efficiency and safety.

Contribution

The paper proposes the HCH5-D2 inverter topology, which decouples AC and DC parts to stabilize CMV and reduce leakage current, with validation through MATLAB simulations.

Findings

Reduced leakage current compared to traditional H4 inverter.

Improved voltage spike mitigation during freewheeling.

Enhanced overall efficiency and safety in PV inverter operation.

Abstract

With the rise of renewable energy penetration in the grid, photovoltaic (PV) panels are connected to the grid via inverters to supply solar energy. Transformer-less grid-tied PV inverters are gaining popularity because of their improved efficiency, reduced size, and lower costs. However, they can induce a path for leakage currents between the PV and the grid part due to the absence of galvanic isolation between them. This leads to serious electromagnetic interference, loss in efficiency and safety concerns. The leakage current is primarily influenced by the nature of the common mode voltage (CMV), which is determined by the switching techniques of the inverter. In this paper, a novel inverter topology of Hysteresis Controlled H5 with Two Clamping Diodes (HCH5-D2) has been derived. The HCH5-D2 topology helps to decouple the AC part (Grid) and DC part (PV) during the freewheeling to make the CMV constant and in turn, reduces the leakage current. Also, the additional diodes help to reduce the voltage spikes generated during the freewheeling period and maintain the CMV at a constant value. Finally, a 2.2kW grid-connected single-phase HCH5-D2 PV inverter system's MATLAB simulation has been presented with better results when compared with a traditional H4 inverter.