High Performance Three Level ANPC Inverter with Thermal Balancing PWM Strategy for Grid Connected PV System

Abstract

This paper proposes a high performance grid connected Photovoltaic (PV) system based on a three-phase transformerless three level Active Neutral Point Clamped (3L-ANPC) inverter. The ANPC is one of the derived topologies from the Neutral Point Clamped (NPC) one, which is widely used for transformerless grid connected PV applications thanks to its inherent advantages such as: reduced voltage stress on its power switches, reduced output current THD, low , high efficiency, and loss and heat balancing capability. The 3L ANPC topology has mainly been proposed to overcome the NPC major issue of unbalanced loss and temperature distribution among its power devices. Furthermore, the modulation strategy is a key issue for loss and temperature balancing inside the ANPC topology. In this paper, the 3L-ANPC PV inverter is controlled by a Thermal Balancing PWM (ThB-PWM) strategy. This strategy allows an efficient balance of the loss and temperature distribution inside the inverter and a reduced total dissipated losses when compared with the conventional PWM strategies. The effectiveness of the proposed grid connected PV system based on a 6.37 kW 3L-ANPC inverter controlled by the ThB-PWM strategy is proven through simulation tests performed on PSIM simulator.