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 paper 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 paper 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 ridethrough requirements of DC transformers applied to the grid connection of renewable energy. Finally, the method proposed in this paper is verified by simulation and hardware-in-the-loop experiment.

Research on fault current limitation and active control for power electronic transformer in direct current grid

“…The input series mode can withstand high input voltage, and the output in parallel can output large current. Of course, the output voltage at this time is low, which is the voltage of a DAB module [35][36][37]. It can be seen from the DC transformer structure composed of DAB modules that the DAB module topology circuit has a large-capacity supporting capacitor at both ends, and the transformer formed by series and parallel connection also has the same output and input capacitance characteristics.…”

“…The input series mode can withstand high input voltage, and the output in parallel can output large current. Of course, the output voltage at this time is low, which is the voltage of a DAB module [35][36][37].…”