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

Abstract

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.