Directional interlocking overcurrent protection of microgrids powered by inverters injected with characteristic currents

摘要

A microgrid powered by inverters has become a typical approach to efficient use of renewable energy source. However, the behavior of constantcurrent of the inverters will make it difficult to protect the network. To solve this problem, this paper offers the directional interlocking overcurrent protection for the microgrid powered by the inverters injected with characteristic current. When a fault occurs, the inverter switches to the constantcurrent mode. Then, the N multiple frequency and small amplitude current are output as a characteristic signal to decide the direction of fault current in outputting the fundamental frequency current. The digital relay protection device is used to protect the network. Finally, with the microgrid powered by four inverters as an example, the proposed protection strategy is verified by means of the PSCAD/EMTDC software.