Instability Mitigation of Constant Power Load in Microgrid

This paper proposes a novel stabilizing control method aimed at overcoming the instability challenges posed by the negative incremental resistance characteristics of a constant power load (CPL) within an autonomous microgrid (MG). The proposed stabilization technique integrates a power derivative-integral term with conventional droop control, strategically applied to enhance the MG's dynamic stability in the presence of CPL. The considered MG model, encompassing three inverter-based distributed generations (DGs), a constant impedance load (CIL), and CPL, is meticulously developed and simulated using MATLAB environment. Phase Locked Loop (PLL) is employed to synchronize the CPL with MG. The proposed controller is a key highlight, featuring optimally designed and tuned controller parameters for all DGs, CPL, and PLL. Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) are employed to address the challenges linked to the laborious tuning process of controllers. The simulation results, which include scenarios involving three-phase faults and step changes, provide compelling evidence of the proposed controller's superior performance compared to conventional droop scheme. Furthermore, a comparative analysis is conducted to affirm and quantify the enhancements achieved through the proposed modified droop PSO-based MG controller concerning transient response. The results obtained emphasize the effectiveness of the proposed approach in simultaneously minimizing both overshoot and settling time. In comparison with the conventional controller, the proposed controller demonstrates a substantial decrease in percentage overshoot for the active power of DG3 and DC voltage of the CPL, with values of 93.89 and 99.9