A New Modulation Technique for H6 Transformerless Inverter to Minimize Leakage Current with Reduced Power Loss

Abstract

Solar energy has a significant role to play in supplying the world's growing energy needs, while transformerless inverters (TLIs) are effectively used in photovoltaic (PV) applications due to their high efficiency, small size, and lower cost. Though transformer-based inverter is frequently employed to offer galvanic isolation and voltage ratio conversions between input and output, they're getting less popular due to high iron and copper loss. Among various types of single-phase transformerless inverters, most of their switching techniques are based on the unipolar pulse width modulation (UPPWM) or bipolar pulse width modulation (BPPWM) method. Due to some unbalanced gate pulses in both UPPWM and BPPWM techniques, total harmonic distortion (THD) of output voltage (without filter) increases significantly. The leakage current also increases due to high harmonics content in the output power of TLI systems. The asymmetrical switching of the power semiconductor switches leads to a substantial increase in power loss due to unbalanced gate pulses. In this paper, a new modulation technique is proposed to reduce the output voltage THD, leakage current, as well as the total power losses compared to mostly used UPPWM and BPPWM techniques employing in PV fed TLI system. The mostly used H6 transformerless inverter topology is chosen here for performance evaluation. The simulation is carried out in MATLAB/Simulink and PLECS simulation environments to validate the proposed claim. By using the H6 transformerless inverter topology, 12.2 mA of common mode current is achieved by maintaining a steady common mode voltage via the proposed modulation technique. The output voltage (without filter) THD is found to be 37.5% with the proposed modulation technique, while BPPWM and UPPWM show 98.7% and 53.8% THD, respectively. A reduced-scaled laboratory prototype is built and tested to verify the simulated claim.