Abstract: Multi-energy complementary microgrid has obvious advantages in energy comprehensive utilization， power supply reliability and operational economy due to the multiple complementary power sources connected to the grid. However， compared with conventional distribution network， the incorporation of various types of distributed power sources has made the microgrid topology and operation mode more complicated， and there are some differences in fault characteristics corresponding to grid-connected/islanded operation. Conventional relay protection scheme is difficult to meet the protection requirements of microgrid. Aiming at this problem， this paper firstly discusses the shortcomings of conventional relay protection schemes， analyzes the fault characteristics in microgrid， and proposes an improved fault identification algorithm to achieve fast and accurate fault identification in microgrid. Considering the requirements of relay protection of microgrid， combined with improved fault identification algorithm， an integrated relay protection algorithm is proposed on the basis of an improved current differential protection and adaptive current quick-break protection on the feeder upstream and downstream. The relay protection algorithm not only reduces the scope of fault， but also improves the protection response speed and reduces the probability of protection rejection. Finally， in the RT-LAB real-time simulation system， a multi-energy complementary microgrid model including distributed power sources such as wind turbine， photovoltaic panel， energy storage battery， and micro gas turbine is established， and the simulations are conducted under different fault conditions. The simulation results verify the correctness and effectiveness of the proposed relay protection algorithm.

Key words: microgrid, relay protection, current differential protection, current quick break protection, fault identification