Analysis of Bifurcation Behaviors in MMC Connected to a Weak Grid
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Conventional small-signal approaches present obvious advantages applied in analyzing closed-loop stability in power electronics systems. However, linearized models fall short of predicting any nonlinear behavior which means not able to acquire the accurate stability margin. This paper mainly analyzes bifurcation behaviors of the Modular Multilevel Converter (MMC) connected to a weak grid and calculates the parameters' precise stability margin. The nonlinear continuous-time averaging model of the MMC is established to study two common bifurcation phenomena, i.e. Saddle-Node bifurcation (SNB) and Hopf bifurcation (HB). Characteristics of limit cycles caused by HB are analyzed by changing the value of a certain parameter. The theoretical analysis has been validated by the time domain simulation results.