双馈调相机接入的风电并网系统小扰动稳定性分析OA

The interaction between a doubly-fed condenser(DFC),as a new type of power electronic equipment supporting system voltage and frequency stabilization,and the alternating current(AC)grid has the risk of inducing the system's small-signal instability.Therefore,it is urgent to research the small-signal stability of DFC connected to the AC grid.Firstly,in this paper,by analogy with the stability analysis method of a second-order typical system,the concept of equivalent damping coefficient is extended to the stability analysis of the oscillation mode of the phase-locked loop(PLL)involved in a wind turbine.Then,based on the equivalent damping coefficient,the damping coefficient sensitivity reflecting the influence of control parameters on system stability is proposed.Finally,based on a wind power grid-connected system with DFC,the validity of the equivalent damping coefficient and the damping coefficient sensitivity has been verified.The findings show that the oscillation mode,primarily controlled by the PLL involved in the wind turbine,poses a stability risk.As the proportional coefficient of the wind turbine PLL rises,the integral coefficient diminishes,and the proportional coefficients of the rotor-side power outer-loop and current inner-loop rise;the system stability is improved.