A Novel Microgrid Power Sharing Scheme Enhanced by a Non-Intrusive Feeder Impedance Estimation Method

To address the issue that traditional droop control cannot realize reactive power, imbalance power and harmonic power sharing for an islanded microgrid, this paper proposes a novel load power sharing scheme based on hierarchical control structure. The hierarchical control consists of two levels: 1) the primary control, located at each distributed generation unit local controller, is composed of droop control and virtual impedance control; 2) the secondary level, located at microgrid central controller, estimates each feeder impedance and generates a virtual impedance command signal for primary control to eliminate the power sharing error. The proposed method has two distinguished features: 1) the reactive power, imbalance power and harmonic power can be equally shared since the equivalent impedance of each DG is compensated to a common value; 2) feeder impedance can be precisely estimated through a non-intrusive method, which can also be used to solve other issues in microgrid caused by feeder impedance mismatch. Simulation results are provided to validate the proposed method.