Hybrid Carrier-Based Pulse Width Modulation Techniques for ‎Leakage Current Suppression in Five Level Cascaded H-Bridge ‎Solar Inverter: A comparative Study

Abstract

Multilevel inverters have gained increasing popularity in the field of medium voltage and high-power applications. Among the three most favored configurations of multilevel inverters, cascaded H-bridge multilevel inverter has been considered as the most suitable topology to integrate photovoltaic system with the utility grid. However, transformer-less PV system suffers from leakage current problem. This paper investigates the adoption of hybrid switching frequency approaches in carrier based PWM for leakage current suppression.  To evaluate the effectiveness of using this strategy in minimization of this current, a comparative study between all standard and proposed hybrid carrier-based pulse width modulation methods is carried out using MATLAB/ Simulink environment for single-phase five-level cascaded H-bridge multilevel inverter. Both standard and hybrid level shifted and phase shifted are compared. The results demonstrate the ability of the proposed hybrid CB-PWM to minimize the leakage current and comply effectively with the VDE-0126-1-1 (German standard) in term of both rms and peak values of leakage current. The results are also show that the best leakage current rms value of (3.129 mA) is achieved when applying the hybrid phase and level shifted pulse width modulation (HPALS-PWM) approach, while the best leakage current peak value of (4.952 mA) is obtained when using hybrid phase shift pulse width modulation (HPS-PWM) approach. Therefore, the hybrid approach can be considered an appropriate PWM strategy for grid connection of transformer-less multilevel inverters for PV applications.