Distributed Reactive Power Control Scheme for Parallel Inverters Based on Virtual Impedance

Droop control is an important control strategy for microgrids with multiple inverters in parallel. Adding virtual impedance to droop control can effectively increase the voltage of the common coupling point and achieve equal sharing of reactive power. However, in practical engineering, due to line aging and environmental changing, line parameters will change, which will affect the traditional virtual impedance control performance, making it difficult to divide reactive power accurately. To address this issue, we propose a distributed optimization compensation control scheme based on dynamic virtual impedance. Using the reactive power output by an inverter as a communication signal, based on the multi-agent consensus, we optimize the virtual impedance, which effectively compensates the influence of line impedance mismatch, realizes the uniform sharing of load reactive power, and compensates the line voltage drop. When the line parameters change due to the factors such as aging and damage, the scheme can still realize the uniform share of reactive power and compensate the voltage drop on the line. The addition of secondary regulation to the droop control can significantly suppress the variations of the bus voltage and frequency when the load changes. The effectiveness of the scheme is verified by the MATLAB/Simulink simulation software and a RTDS-based hardware-in-the-loop simulation platform.