Research On DC Microgrid Protection Strategy Based On Dual-Slope Current Differential Protection

Based on the advantages of its own, DC microgrids received extensive attention of researchers both at home and abroad. However, there are many differences between microgrid and the traditional grid, lead to the traditional methods of power system relay protection is not entirely suitable for microgrid. Relay protection is one of the important technology to maintain power grid safety and operation, this paper focuses on the dc microgrid protection strategy to carry out the ralated research work.First, this paper analyzes the operation characteristics of DC microgrid, and presents a fault detection method based on the dual-slope current differential protection. Considering the action sensitivity of internal faults and the reliability of external faults, the restraint coefficient of the traditional current differential protection can’t set too low, so the sensitivity for internal high impedance fault is low. Therefore, in order to solve the above problem, the dual-slope current differential protection method is put forward, without changing the original performance increases the sensitivity of the differential protection for internal high impedance fault, and improves the power supply capacity of the system.Then, the fault network restoration strategy based on reclosing is proposed. To avoid the secondary damage of microgrid caused by reclosing on permanent fault, this paper firstly distinguishes the fault type, instantaneous fault or permanent fault, before reclosing, opens reclosing function Selectively, increased the reclosing success rate and reliability of the system.Finally, in order to validate the proposed protection scheme, the simulation experiment based on PSCAD/EMTDC software was carried out, and set the low voltage DC microgird laboratory platform based on DSP control, the simulation and experimental results verify the feasibility and effectiveness of the proposed protection strategy.