非线性弹性耦合下双馈风电机组的暂态能量转移与振荡特性分析OA北大核心CSTPCD

After large-scale integration of renewable energy such as wind power and photovoltaics into the power grid,the dynamic stability of the system is affected,resulting in different types of power oscillations.The doubly-fed wind turbine is electrically decoupled from the grid frequency due to the grid-connected inverter connected to the grid.When the system frequency changes,it cannot provide effective power support.The virtual synchronous generator can provide frequency and power support for the system by simulating the operation characteristics of the synchronous generator.In order to further improve the grid-connected support performance of doubly-fed wind turbine,this paper introduces a cubic stiffness coupling link into the active power control system of the virtual synchronous generator.By establishing a two-degreee-of-freedom system dynamic model with wind power under nonlinear elastic coupling,a nonlinear elastic coupling control strategy for doubly-fed wind turbine is proposed. Firstly,the virtual shafting coupling relationship between synchronous generator and doubly-fed wind turbine in virtual synchronous operation is analyzed.Secondly,a two-degree-of-freedom system dynamic model with wind power under nonlinear elastic coupling is established by introducing cubic stiffness through nonlinear power coupling.Thirdly,based on the Hamiltonian principle,the transient energy transfer process of the wind power grid-connected system after introducing the cubic stiffness is analyzed,and the inertia setting condition between the units are derived.Finally,a nonlinear elastic coupling control strategy based on doubly-fed wind turbine is proposed.And the parameters of controller are optimized according to the inertia setting condition.The doubly-fed wind turbine is used to efficiently transfer transient energy and effectively suppress power oscillation. Simulation analysis of the proposed nonlinear elastic coupling control shows that under the nonlinear elastic coupling,when the power oscillation occurs in the system,the power support potential of the doubly-fed wind turbine is further released,and the transient energy of the synchronous generator is efficiently transferred to wind turbine,which effectively suppresses the system power oscillation.When the system frequency changes,the doubly-fed wind turbine reduces the drop amplitude of the system frequency by providing effective power support,and reduces the power fluctuation amplitude of the synchronous generator,which significantly improves the stability of the system. The following conclusions can be drawn from the simulation analysis:(1)The doubly-fed wind turbine can provide inertia and damping support for the system under virtual synchronous control,but the synchronous operation mode limits the power support potential of the wind turbine,and the virtual inertia delays the recovery of the system frequency.(2)After satisfying the inertia ratio and cubic stiffness optimization conditions,the doubly-fed wind turbine under nonlinear elastic coupling can efficiently transfer the transient energy of the synchronous generator,effectively suppress the power oscillation,and significantly reduce the risk of system resonance.(3)Under the proposed nonlinear elastic coupling control strategy,the grid-connected support performance of the doubly-fed wind turbine is significantly improved by efficiently transferring the system transient energy to the new energy side.By comparing the stability support effects of maximum power point tracking control,virtual synchronous control and nonlinear elastic coupling control through simulation,it is verified that the doubly-fed wind turbine can more effectively release its power oscillation suppression and frequency support potential under the proposed control.