Coupling Mechanism Analysis and Transient Stability Assessment for Multiparalleled Wind Farms During LVRT

Abstract

In this paper, the coupling mechanism of phase-locked loop (PLL)-synchronized multiparalleled wind farms under grid faults is analyzed in detail. First, the coupling effects of the currents and the equivalent power angles (EPAs) among wind farms are identified by analyzing the voltage characteristics during low voltage ride-through (LVRT). Subsequently, a transient stability assessment method is proposed for multiparalleled wind farms to evaluate the effect of output currents of multiple wind farms on the EPA distribution characteristics. This method can be applied to evaluate whether each wind farm in the system has equilibrium points as well as evaluate the transient instability risk of the system during LVRT. In addition, the dominant wind farms for the system transient instability can be identified. Due to the coupling effects, any inappropriate current in the wind farm may deteriorate the EPA distribution characteristics and even cause loss of synchronism. Consequently, the current distribution method to minimize transient instability risk can ensure that each wind farm in the system has equilibrium points and effectively improve the multiparalleled wind farms stability during LVRT. Finally, the simulations results validate the effectiveness of the theoretical analysis and proposed method.