A Modified Three and Five Level Cascaded NPC Inverter Topology for Grid Connected PV System

Abstract

An efficient three phase modified three and five level neutral point clamped (NPC) inverter for grid connected photovoltaic (PV) systems is proposed in this paper. In order to achieve desired output voltage levels with less harmonic distortion, a carrier based modulation technique is used. In the proposed NPC inverter design, less number of switches are required in compared to the traditional NPC topology which reduces the cost, size as well as the complexity of control circuit. Additionally, the conduction loss of the device is reduced. The proposed topology is compared with the existing NPC topology and conventional H-bridge inverter in terms of number of switches, total harmonic distortion (THD), and overall efficiency. The effectiveness of the proposed inverter topology in carried out extensively in MATLAB/Simulink software and sample results are presented. It is found that, the THD profile of the proposed topology is lower than the existing NPC and other inverter topologies. Additionally, higher efficiency is achieved, and common voltage is kept constant in the design stage to reduce the leakage current.