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JPE, Vol. 19, No. 2, March 2019
Performance Improvement Strategy for Parallel-operated Virtual Synchronous Generators in Microgrids
Hui Zhang, Ruixue Zhang, Kai Sun, and Wei Feng
Area Power Quality and Utility Application
Abstract The concept of virtual synchronous generators (VSGs) is a valuable means for improving the frequency stability of microgrids (MGs). However, a great virtual inertia in a VSG¡¯s controller may cause power oscillation, thereby deteriorating system stability. In this study, a small-signal model of an MG with two paralleled VSGs is established, and a control strategy for maintaining a constant inertial time with an increasing active-frequency droop coefficient (m) is proposed on the basis of a root locus analysis. The power oscillation is suppressed by adjusting virtual synchronous reactance, damping coefficient, and load frequency coefficient under the same inertial time constant. In addition, the dynamic load distribution is sensitive to the controller parameters, especially under the parallel operation of VSGs with different capacities. Therefore, an active power increment method is introduced to improve the precision of active power sharing in dynamic response. Simulation and experimental is used to verify the theoretical analysis findings.
Keyword Active-frequency droop coefficient,Power oscillation,Virtual synchronous generator (VSG),Virtual synchronous reactance
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