Balancing Voltage in the DC Bus with Split Capacitors in Three-Phase Four-Wire PWM Boost Rectifier

Abstract

This paper presents a balancer circuit to be used in a four wire three phase boost rectifier with split capacitor topology. The goal is to discuss the problems related to the injection of DC current on the grid when the rectifier feeds unbalanced loads. Since the converter uses four wires, it is suitable for use in UPS where the fourth wire is needed to keep fixed the neutral point. This work will analyze the converter's behavior when unbalanced loads are applied to the DC bus and how they impact on the AC line currents. A balancer circuit will be modeled and a control strategy is applied to overcome the problem.