Abstract: DC active power filter（DC-APF）can effectively suppress the bus voltage ripple of DC microgrid. In

order to solve the problem that DC-APF can not work normally due to the failure of switching devices，a fault-tolerant DC-APF topology based on H-bridge converter was proposed，which could ensure the power quality management function of DC-APF after the device failure by using the topology reconstruction of non fault devices. Aiming at the problem that the topological structure is changed before and after the fault which causes the control parameters to be uncertain，a variable universe adaptive fuzzy PI control was proposed to track and control the compensation current effectively in DC-APF fault-tolerant mode. A DC microgrid system model with fault-tolerant DC-APF was built in Matlab/Simulink simulation environment. The simulation results show that the proposed DC-APF has good compensation performance for DC bus voltage ripple before and after the device failure，and the proposed variable universe adaptive fuzzy PI control has a good characteristic of real-time tuning controller parameters.

      Key words: DC active power filter（DC-APF）；fault tolerance；ripple；adaptive fuzzy PI with variable universe；DC microgrid