Analysis for the Minimization of Leakage and Common Mode Currents in Cascaded Half-Bridge PV Fed Multilevel Inverter

Abstract

This paper gives the detailed study and analysis of the terminal voltage and the common mode voltage (CMV) for the photovoltaic fed cascaded half-bridge (CHB) multilevel inverter (MLI). The expression for the terminal voltage and CMV are also derived using switching function. The analytical waveforms obtained using the expression of the terminal voltage and CMV clearly indicate that the terminal voltage and CMV are not constant simultaneously. Thus, two pulsewidth modulation (PWM) schemes are proposed using redundant states concept for CHB nine-level MLI without the addition of any extra circuit element. The first PWM scheme reduces the high-frequency transitions in the terminal voltage and, thus, minimizes the leakage current. The other PWM scheme is designed to reduce the common mode current by maintaining CMV constant. Furthermore, the proposed PWM schemes are compared with the conventional PWM schemes. The effect of each PWM schemes on the terminal voltage and CMV is analyzed using the given switching function analysis. The given switching function analysis is also supported with the help of simulation and experimental results. The simulation and experimental results of the proposed PWM schemes are further compared with the conventional SPWM technique.