New Analysis Framework for Transient Stability Evaluation of Power Electronics Dominated Power System: Coupling Factors Based Nonlinear Decoupling Method

Being different from the conventional synchronous generators dominated power system, the power electronics dominated power system (PEPS) has much lower inertia. Hence, system state variables are easily changed acutely after being disturbed, which makes the system meet the serious transient stability issues. However, for a long time, there has been no effective analysis method to process the transient stability of the PEPS. Focusing on this problem, this paper proposed a coupling factors based nonlinear decoupling (CFND) method. Based on the decoupling thought, the proposed CFND method approximately transforms the original high-order nonlinear system into a series of first-order quadratic or second-order quadratic subsystems. In the decoupled state, some mature tools can be adopted to analyze these low-order quadratic subsystems. Then, the transient stability of the original system can be reflected in an indirect way. To provide the better guidance for the nonlinear decoupling, the concept about the coupling factor was proposed, which can evaluate the coupling degree among different state variables and can help determine the final form of the decoupled system. The CFND method has universality and has no special requirement for the studied PEPS, thus it can be viewed as a new analysis framework for transient stability studies. At last, through a case of a DC microgrid, the accuracy of the proposed CFND method was verified. © 2020 Chin. Soc. for Elec. Eng.