Distributed feedback optimization in fully inverter based islanded microgrids for accurate reactive power sharing and fast response in P - f Droop

Abstract

A novel distributed feedback optimization (FO) based control method is proposed to replace the existing reactive power- voltage (Q-V) droop control and the related distributed secondary voltage control of grid-forming inverters (GFoIs) in fully inverter based islanded microgrids (MGs). The aims of the proposed controller are to accurately share active and reactive power among GFoIs, regulate bus voltages of the MGs, and improve the transient frequency response of the conventional active power-frequency (P - f) droop control. The design problem is formulated as an optimization problem and FO with gradient descent method is used to optimize the output voltage of GFoIs based on the real-time measurements in the MGs. The proposed method is implemented in a distributed way, eliminating the need of a central controller with a complex communication infrastructure. Comparing with the existing Q - V droop control with its distributed secondary control, simulation results show that the proposed method improves the reactive power sharing accuracy in GFoIs and accelerates the transient frequency response. Moreover, it drives the MGs to their optimal operating points.