Research on Restart Strategy and Scheme of Flexible Medium Voltage DC Distribution Network without DC Circuit Breaker after Faults

In the system without DC circuit breaker, the equivalent capacitor voltage and the fault current of hybrid converter before and after blocking based on full bridge sub-module and double active bridge under the bipolar short circuit fault are deduced, and the analytical formulas are obtained. The transient characteristics of the system before and after locking are analyzed, and the system restart process after fault clearance is analyzed. In order to accelerate the restart process after fault clearing, a fast restart strategy for hybrid converter is proposed. The strategy points out that during the blocking period of the hybrid converter, while energy storage provides power support for essential loads such as data center, the capacitor voltages of sub-modules during the blocking period are adjusted to shorten the restart time and ensure that the system can restart safely and reliably. A simulation model is built on the PSCAD/EMTDC simulation platform to verify the correctness of the strategy.