A Two-level Pulse Width Modulation to Balance Neutral Point Voltage in Three-level NPC Inverter

Abstract

The paper presents a novel offset based two-level pulse width modulations to balance neutral point voltage in
three-phase three-level neutral point clamped inverters. The proposed method uses local offset voltages to
calculate the value and identify the direction of neutral point current between two capacitors through the
feedback signals of load current and two capacitor voltages. With the pulse width modulation method and
flexible offset voltages, the proposed method can control and maintain the balance voltages between two
capacitors. Simulation and experimental results are provided in order to validate the proposed method.