Research on the Control Strategy of AC/DC Interlinking Converters in Islanded Hybrid Microgrid

As the hub of the alternating current (AC) sub-microgrid and direct current (DC) sub-microgrid connection, the interlinking converter is responsible for the important tasks of power transmission within the AC and DC sub-microgrids. The quality of its control strategy is directly related to the AC/DC hybrid microgrid stable operation. In this paper, the droop control equations adopted by the distributed sources connected to the AC sub-microgrid and the DC sub-microgrid is analyzed in detail. Furthermore, a bidirectional droop control strategy for interlinking converters based on PI control is proposed to realize the power balance of isolated hybrid microgrids. This strategy considers the characteristics of interlinking converters that need to maintain AC bus frequency and DC bus voltage stability and power bidirectional transmission. Mutual power support between AC and DC subsystems can reduce the impact of the deviation of the individual subsystem from the rated operating conditions on the remaining subsystems. Finally, a simulation model of the AC/DC hybrid microgrid is built in MATLAB/Simulink to verify the feasibility and effectiveness of the proposed control strategy.