A line accelerated protection scheme of flexible MVDC distribution system based on transient current derivative

•A novel acceleration line scheme of MVDC distribution system is proposed that can realize fast fault removal and reduce the fault time.•This acceleration protection has a strong adaptability that can be used alone or in conjunction with other primary and backup protections. As the interest in DC-based power system increases, the medium voltage direct current (MVDC) distribution system is gaining attention. Its fault current has some characteristics such as high amplitude and fast rising rate. It is crucial to identify and remove faults quickly and accurately in order to ensure safe and reliable operation of the MVDC distribution system. This paper presents a new acceleration protection scheme for cable line. In the transient process of cable line, if a fault occurs over the cable line, the safety of power electronics will be destroyed. This paper analyzes the feasibility of combining the principle of acceleration protection and the second-order derivative of capacitor discharge current after fault. The protection scheme is designed and tested, accelerating devices send a trip command to the acceleration circuit breaker, which realizes fast fault removal. The proposed acceleration protection scheme is simple, reliable and practical. At the same time, various faults are simulated by using the ±10 kV DC distribution system of double terminal based on RT-LAB. The simulation results and hardware system simulation tests show that the proposed acceleration protection idea and its protection scheme can identify and remove faults accurately, quickly and effectively.