A modified control topology to improve stability margins in micro-grids with droop controlled IBDG

Droop control techniques of Inverter Based Distributed Generation (IBDG) are generally the most common approach for controlling micro-grids especially in the islanded mode of operation. An improved transient response as well as better load sharing can be achieved using higher droop gains. However, large droop gains drive the system into the unstable region. In this paper, a new control topology is proposed to facilitate the use of higher droop gains. The advantages of the proposed control topology are proven through small-signal stability analysis. The controller gains are optimally determined using Particle Swarm Optimization (PSO), where the main objective is to maximize the droop gain while maintaining micro-grid stability and adequate dynamic performance. The proposed control topology with its optimal parameters is verified through tests on a micro-grid with three IBDG units and validated using real time hardware in loop implementation. The results show that the proposed P-PID-PD controller facilitates the use of much higher droop gain values at higher stability margins compared to the PI-PI-P control topology.