Bidirectional Droop Control of Interlinking Converter in AC/DC Hybrid Micro-Grid

Abstract

The interlinking converter in an AC/DC hybrid micro-grid plays a crucial role in the stable operation and power allocation of power system. A bidirectional droop control method for the converter is proposed, which measures the power demand degree of AC sub-grid and DC sub-grid according to AC bus frequency and DC bus voltage respectively, and determines the direction and magnitude of the converter transmission power. Two droop control modules, DC voltage-active power and AC frequency-active power, are included in the control structure. The power reference value of the converter is achieved from the output subtraction of two modules. Meanwhile to reduce the deviation of voltage and frequency caused by droop control, a recovery control is designed to improve the power quality and the reliability of the hybrid micro-grid. The bidirectional droop control can accurately coordinate the transmission power between AC subgrid and DC sub-grid and make full use of the distributed energy. The feasibility of the control method is verified by a simulation system built with DigSILENT.