A New Topology and Modulation Strategy to Suppress the Leakage Current in Transformerless Cascaded H-Bridge Inverters in PV Application
Milad Bahrami-Fard, Narges Moeini, Masoud Shahabadini, Hossein Iman‐Eini, Marco Liserre
Abstract
The use of transformerless inverters is common due to the lower cost, lighter weight, and higher efficiency. The lack of the transformer leads to the leakage current circulation through the parasitic capacitors, which increases the power losses, electromagnetic interferences, and safety issues. In this article, first, the proposed cascaded H-bridge (CHB) -based inverter’s equivalent common-mode (CM) model is determined. Then, a new multicarrier pulsewidth modulation strategy is proposed to suppress the leakage current. In the presented method, new redundancy states are provided due to the use of just one blocking switch. These extra redundancy states and the proposed modulation strategy help to keep the CM voltage (CMV) constant and suppress the leakage current. The validity of the proposed solution is verified by simulation in the MATLAB/Simulink environment. In addition, a universal prototype with a power rating of 600 W is built and tested, and the experimental results are presented to confirm the theoretical and simulation results. The experimental results show a maximum efficiency of 98.5% and a European efficiency of 98.3%. The proposed topology is also compared to the existing transformerless topologies to show its effectiveness.