A Novel Multi-Loop Base Carrier Mark PWM Strategy for Leakage Current Reduction in Grid-Connected Transformerless Inverters

This paper presents a novel multi-loop Base Carrier Mark (BCM) pulse-width modulation strategy to address leakage current challenges in grid connected transformer-less photovoltaic inverters. The proposed approach introduces a combination of sequential level shift, single-loop, two-loop, and three-loop carrier rotation techniques in BCM generation, specifically designed to minimize common-mode voltage variations and suppress leakage current. The method’s effectiveness was validated through comprehensive simulation studies using Matlab/Simulink, evaluating eight distinct BCM configurations. Results demonstrate that the proposed multi-loop BCM strategy, particularly in STATE-V configuration, achieves superior leakage current suppression while maintaining high system performance. This configuration reduces leakage current significantly below the standard 300mA limit without compromising other performance metrics. The strategy also demonstrates favorable outcomes in Total Harmonic Distortion (THD < 2% in STATE-VI), common mode voltage stability (optimal in STATE-III), and system efficiency (peak performance in STATE-IV).These findings present a significant advancement in transformer-less inverter technology, offering a practical solution to the critical challenge of leakage current in grid-connected PV systems.