Because of the low inertia of dc microgrids, systemstate variables are easily changed acutely after being disturbed.Hence, dc microgrids meet the serious transient stability issuesespecially for some stressed states. But the transient stabilityanalysis is a very challenging problem since the dc microgridsystem is high-order and nonlinear. To offer a new and moreeffective analysis framework, this paper proposes a nonlineardecoupling method to evaluate the transient stability of dcmicrogrids. The proposed nonlinear decoupling method takes fullconsideration of the nonlinearity of the dc microgrid system andapproximately transforms the original nonlinear system into aseries of decoupled first-order quadratic or second-orderquadratic systems. For these decoupled low-order quadraticsystems, their dynamics and stability can be analyzed easily, thenthe transient stability of the original system can be reflectedindirectly. Also, the nonlinear decoupling based analysisframework can be extended to other power electronics dominatedpower systems to evaluate their transient stability. The accuracyof the proposed analysis method has been validated throughrelated case studies.
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