A ZVZCS Full-Bridge Converter Suitable for Renewable Energy-Based MVDC Collection System

Abstract

A zero-voltage zero-current-switching (ZVZCS) full-bridge DC-DC converter, based on a dual transformer with two output filter capacitors, is proposed in this paper. The proposed topology is suitable for application in renewable energy at medium voltage, integrated with a DC collection system. To realize voltage and power regulation for the converter, pulse width modulation (PWM) is employed with a fixed duty cycle for the main switches. Through careful design of the turns ratio of the main transformer, most of the power under full load range is delivered by the main full-bridge circuit, which also achieves zero-voltage switching (ZVS). This significantly reduces the switching losses. A small portion of the total power is delivered by the auxiliary circuit that realizes ZVZCS. Therefore, the turns ratio of the auxiliary transformer can be optimized such that the efficiency of the proposed converter can be improved. The optimzation is discussed in detail, along with the design parameters of the proposed converter. A prototype of 200V-2kV/3kW has been developed to verify the simulation results and validate the working of the proposed scheme.

Keywords

• Full-bridge converter
• medium voltage direct current (MVDC)
• zero voltage zero current switching (ZVZCS)
• high power DC-DC converter
• energy efficient