Analysis and Design of H5 Topology in Grid-Connected Single-Phase Transformerless Photovoltaic Inverter System

Abstract

Objectives: The transformerless inverters are more efficient, less bulky and cost-effective. But the system faces the problem of leakage current on account of the elimination of isolation transformers. Thus, the problem needs to be mitigated through the inverter topology itself. The objective of this paper is to study and analyze a topology designed for reducing the leakage current. The H5 inverter significantly reduces the leakage current by checking the variation of common mode voltages. The topology uses only one extra switch apart from the conventional full bridge and is simple to design. Method: To reduce the leakage current H5 inverter topology has been designed which works on the basis of decoupling. This work is to be implemented in MATLAB/SIMULINK. The main parameters for analysis are efficiency, leakage current, common mode voltage and their variation with load. H4 and H5 topology will be simulated and results will be compared. Findings: The H5 topology has been found to be effective in suppressing the leakage current to a fairly acceptable magnitude. It has been observed that the H5 topology has a lower leakage current than the conventional H4 topology, i.e. 23mA as opposed to 402mA in H4 topology. But the leakage current increases to up to 5 times if the system is used at load less than the full load. Novelty: The study presents the H5 inverter topology and its SPWM modulation strategy. In order to verify the topology, simulation results are provided. The performance has been tested for different loads connected to grid. The leakage current has been found to be reduced to 23.37 mA but it rises to about 100mA if used at 10% of the full load. Keywords: PV Inverters; H5 Inverters; Leakage Current (Common Mode Current); Common-Mode Voltages; Transformerless Power Converters