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JPE, Vol. 17, No. 1, January 2017
An Enhanced Power Sharing Strategy for Islanded Microgrids Considering Impedance Matching for Both Real and Reactive Power
Liaoyuan Lin, Qian Guo, Zhihong Bai, and Hao Ma
Area Power Quality and Utility Application
Abstract There exists a strong coupling between real and reactive power owing to the complex impedances in droop based islanded microgrids (MGs). The existing virtual impedance methods consider improvements of the impedance matching for sharing of the voltage controlled power (VCP) (reactive power for Q-V droop, and real power for P-V droop), which yields a 1-DOF (degree of freedom) tunable virtual impedance. However, a weak impedance matching for sharing of the frequency controlled power (FCP) (real power for P-? droop, and reactive power for Q-? droop) may result in FCP overshoots and even oscillations during load transients. This in turn results in VCP oscillations due to the strong coupling. In this paper, a 2-DOF tunable adaptive virtual impedance method considering impedance matching for both real and reactive power (IM-PQ) is proposed to improve the power sharing performance of MGs. The dynamic response is promoted by suppressing the coupled power oscillations and power overshoots while realizing accurate power sharing. In addition, the proposed power sharing controller has a better parametric adaptability. The stability and dynamic performances are analyzed with a small-signal state-space model. Simulation and experimental results are presented to investigate the validity of the proposed scheme.
Keyword Microgrid,Droop control,Virtual impedance,Power sharing,Dynamic performance
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