Microgrid is a small-scale power system in which distributed generations (DGs) such as wind turbines and photovoltaic arrays combined with energy-storage systems are integrated to energize local loads and to deliver electricity to utility grid.
Microgrids now play a more crucial role than ever before concerning the system stability and power quality requirement, thanks to power electronic converters, information and communication technologies and distributed generators. The existence of nonlinear loads such as power electronic devices, electric arc furnaces, variable frequency motor drives, etc. may affect the voltage of the point of common coupling (PCC) due to the current harmonics.
To compensate voltage distortion, nonlinear load current should be shared among the DGs in islanded microgrids. However, harmonic power cannot be accurately shared among the DGs by droop control due to mismatched line impedances.
In order to cope with this problem, Kim Sung Hyok, a researcher at the Faculty of Electrical Engineering, has proposed a distributed harmonic sharing control using adaptive regulation of virtual harmonic impedance, when large amount of nonlinear loads are connected to the PCC.
According to his method, DGs make proportional distribution of harmonic power by using a consensus algorithm. The virtual harmonic impedance is obtained according to discovered harmonic power sharing error and the harmonic power sharing error is removed through interaction between the harmonic power re-sharing and the virtual harmonic impedance regulation in steady state.
The validity of the proposed method has been proved by MATLAB/Simulink simulation.
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