An Improved Droop-Based Adaptive Virtual Impedance for Accurate Power Sharing Among Multiple DGs in Islanded Microgrid

Accurate power sharing in islanded microgrids (MGs) is essential to preserve the system stability and deliver the required load power. However, the distinct ratings of feeders result in disparate voltage drops and, therefore, varying output voltages from distributed generators (DGs). So, this work proposes a distributed adaptive virtual complex impedance to achieve accurate power sharing of loads between DG units with minimum control loops. The controller dynamically adjusts its parameters based on the system parameters, allowing it to adapt to various conditions. Unlike previous controllers, the proposed controller can work effectively with multiple connected DGs in the system. The designed approach accounts for complex components of the feeders’ impedances, with actual ratios between the complex components to enhance the system performance and the point of common coupling voltage. Based on that, the decoupling between the active and reactive power is achieved. The proposed controller’s effectiveness, including two and multiple DGs, is verified and compared to conventional control methods. For two DGs, the proposed controller proved its superiority over previous methods and proved its scalability in the DG system. The proposed controller is capable of achieving accurate reactive power sharing, reducing active power oscillations, enhancing the point of common coupling (PCC) voltage, synchronizing system currents, and minimizing circulating currents within the system. This is demonstrated through different scenarios. The first scenario is through a 2-DG system and comparing the results with conventional droop control and conventional virtual impedance. The second scenario involves statistically comparing the proposed controller with those in the literature, focusing on the controller percentage overshoot, response time, and PCC voltage level. The third scenario is conducted to prove the ability of the proposed controller to be extended for multiple connected DGs in the MG system.