A Quasi-Z-Source-Based Five-Level PV Inverter With Leakage Current Reduction

Impedance-source based solar PV systems are capable of achieving both voltage boosting and inversion in a single stage, resulting in a simple design thereby enhancing reliability. One of the major concerns of PV systems is their leakage current, as it can cause hazardous operational insecurity and reliability. This paper introduces a quasi Z-source based five-level inverter, which displays the following advantages: (i) reactive power handling capability, (ii) single-stage boosting, (iii) shoot-through immunity, and (iv) reduced leakage current based on VDE 0126-1-1. The proposed single-stage power converter is constituted by the fusion of a boosting stage, consisting of two back-to-back connected quasi-Z-sources, with a 5-level inverter produced by the combination of T-type and neutral point clamped (NPC) arms. The problem of the leakage current is addressed by a modified modulation technique and a passive filter structure, which filters high frequency variations in the common mode voltage (CMV). The working principle of the proposed power converter and the effectiveness of the modulation scheme to reduce the leakage current are assessed with the aid of simulation studies in both stand-alone and the grid-connected modes. The simulation results are experimentally validated with the aid of a laboratory prototype of 500 W rating.