Research on Current Limiting Method Used for Short Circuit Fault Current of Resonant DC Transformer Based on Inverted Displacement Phase Control

Abstract

Due to the characteristics of high efficiency and flexible transformation ratio, full-bridge CLLC resonant DC transformers have been increasingly used for DC grid in recent years. Based on the analysis of the working principle of CLLC resonant DC transformer circuit, this article analysis the current gain characteristics by using fundamental wave analysis method, the parameter influences of resonance network frequency and the transformer gain is also being concerned. On the basis of using soft switching method, this article will introduce a method of inverted displacement phase control. The working range will be further refined in the original circuit, and the linear control region will be expanded as well. In this way, the output current will have a precise control under the condition of short circuit, which will satisfy the low voltage ride-through requirements of DC transformers applied to the grid connection of renewable energy. Finally, the method proposed in this article is verified by simulation and hardware-in-the-loop experiment.

Keywords

• Resonance
• power electronics transformer
• short circuit current limit
• low voltage ride through
• phase shift control