A Modified Droop Control Technique for Accurate Power-Sharing of a Resilient Stand-Alone Micro-grid

This paper proposes a modified droop control technique for accurate power-sharing of a resilient stand-alone microgrid. Two cases were presented in this study; In case 1, a stand-alone microgrid system with a single inverter operating as a voltage source and a local load is presented. A conventional droop-based control strategy was used to modify the voltage magnitude and frequency in relation to reactive and active power signals in order to employ an inner current loop and an outer voltage loop. Although the control scheme accomplishes high flexibility and reliability, the only drawback is that the sharing is realized via frequency and voltage variations in the system, which has motivated the case-2 study to solve these problems. The islanded micro-grid system considered in case 2 consists of two inverters operating as voltage sources (also known as network-forming converters) and a shared load. The load is shared between the first and second converter after a specified period. Therefore, since case- 2 aims to solve the problems of frequency and voltage variations induced by the primary control in case-L, centralized secondary control (modified droop control technique) is implemented in the micro-grid in case-2 to reinstate the nominal frequency and voltage amplitude value in the micro-grid. Additionally, case 2 considered the integration of virtual impedance in the converter's output using an additional closed-loop control to attenuate distortion, minimize the influence of circulating current, and ensure the sharing of harmonic current under unbalanced and non-linear loads. The system model was simulated using the MATLAB/Simulink environment.