Research on Active Protection Method for Microgrids Based on Harmonic Injection

With the increasing penetration of inverter interfaced distributed generators (IIDGs) in microgrids, traditional protection schemes are difficult to cope with the complexities of microgrids. Harmonic-injected protection schemes based on power electronic devices can simplify the harmonic component equivalent network of the microgrid into a single-source radial structure. However, the performance of these schemes is degraded by the shunt effect of the non-harmonic injection source IIDGs and the utility grid. This paper focuses on the active protection method for microgrids based on harmonic injection. A fault control strategy based on harmonic current control and principles for PCC filter parameter design are proposed to address the shunt effect. With the proposed strategy, harmonic currents of varying frequencies are injected into the microgrid by the IIDGs, and the major portion of the injected harmonic currents can flow to the fault point. By analyzing the fault characteristics, a fault location method based on harmonic injection is proposed. Finally, simulation analysis is carried out on MATLAB/Simulink platform, and the effectiveness of the proposed active protection scheme is verified by the results.