Adaptive Time Constant Control Strategy for Micro-Grid Based on Improved Droop Control

For inverter control, droop control is an effective control scheme, but this scheme does not have the inertia and damping of the synchronous generator, resulting in insufficient frequency stability. In response to this problem, some scholars have proposed a virtual synchronous generator (VSG) control method to simulate the operating characteristics of traditional synchronous generators. In order to analyze the advantages and disadvantages of the two control strategies, this paper first established a small signal model of the inverter based on droop control and VSG control. The dynamic response of the time is compared. We can conclude that the droop control and the VSG control have their own advantages and disadvantages, and cannot meet the strict dynamic characteristics of the GC and SA states. Then, based on the comparison between the virtual synchronous generator and the droop control, the traditional droop control is improved. On this basis, an adaptive control is proposed to improve the response characteristics of the output frequency and active power when the power command changes in the grid-connected mode. In the GC state, the IDC-based adaptive control method can improve the output tracking of the input active power, reduce frequency fluctuations, and ensure frequency stability when the power reference value changes. In the SA state, the IDC-based adaptive control method can provide sufficient inertial characteristics. Finally, the simulation results verify the effectiveness of the proposed control strategy.