Improved Voltage-Current Double Closed-Loop Control of an Interlinking Converter Based on Fractional-Order PID Controller

To solve the problem that the traditional droop control of interlinking converter (ILC) in the low voltage grade AC-DC microgrid is not applicable, a double closed-loop control strategy of ILC based on fractional-order PID controller is proposed. Firstly, the mathematical model is established according to the topological structure of the ILC. Then analyzes the disadvantages of the traditional droop control in the low voltage level microgrid, make up for the deficiency of droop control by introducing virtual impedance. And then using the power law convergence characteristic of fractional-order system, switching between fractional-order PID controller and conventional PID controller is adopted to improve the voltage - current double closed-loop control and improve the power quality of the ILC. Finally, simulation experiments are carried out in Simulink. The experimental results show that the proposed strategy is reliable and effective, which improves the transient performance of the system and reduces the regulation time.