Adaptive virtual impedance control strategy based on IWOA-fuzzy PID and its application to reactive power sharing in islanded microgrids

Accurate reactive power sharing in islanded microgrids is often compromised by resistive line impedances and parameter mismatches, causing power coupling and uneven distribution. This paper proposes an adaptive virtual impedance control strategy that integrates a fuzzy PID controller with the Improved Whale Optimization Algorithm (IWOA). The fuzzy PID ensures nonlinear adaptability, while IWOA globally optimizes fuzzy rules, membership functions, and PID gains for robust self-tuning. By dynamically adjusting virtual resistance and reactance, the strategy reshapes inverter output impedance, decouples active and reactive power, and enables proportional reactive power sharing under diverse network conditions. Simulation studies in MATLAB/Simulink with multiple DG units, varying loads, and unequal capacities verify its effectiveness. Results show improved sharing accuracy, faster response (<0.1 s), and reduced steady-state error compared with conventional droop control, fixed virtual impedance, and PSO-fuzzy-PID methods. The proposed IWOA-fuzzy-PID approach thus offers a practical and scalable solution to enhance stability and reliability in islanded microgrids.