A Practical Structure and Control for Reactive Power Sharing in Microgrid

Due to the uncertainty of feeder impedance, conventional droop control-based power sharing scheme presents poor reactive power sharing accuracy in microgrid. As microgrid configuration becomes more and more complicated, reactive power sharing between various distributed generation (DG) equipment is very challenging. To achieve proper power sharing with a simple control method in microgrid, a new structure and power sharing method is proposed in this paper. Instead of using complicated reactive power sharing scheme, this paper proposes separated energy server (ES) units to provide reactive power. Then, active power supplying and reactive power supplying can be achieved separately by energy routers (ERs) and ESs, respectively. With the introduction of ES, the power sharing between DG units can be easily achieved without any supplementary communications or control algorithms. In addition, to reduce costs,a hybrid reactive power compensation configuration with capacitor banks and ESs is provided. Operation principle and power control strategy for DG units and ESs are explained and analyzed in this paper. In order to properly select the coefficients of the power controllers, sensitivity and stability of the system are investigated. Simulation and experimental results are presented to prove the validity of the proposed power sharing method, showing that ERs can effectively share the active power and ESs can effectively share the reactive power according to their capacity.