Research On Frequency Stability Control Strategy And Oscillation Analysis Method Of Wind Turbine

Large-scale new energy has led to more complex stability and protection issues,posing more serious challenges to the power system,and the control flexibility of the new energy grid-connected converter provides the possibility to meet this challenge..Therefore,how to realize the friendly access of centralized wind power through the control of grid-connected inverters has become a key issue to be solved urgently.On the other hand,the access of a large number of wind turbines changes the dynamic characteristics of the power grid,making the power electronic characteristics of the power system increasingly obvious.Explain the oscillation mechanism of the wind turbine grid-connected system,and deeply study the oscillation analysis method of the wind turbine grid-connected system.It is of great significance to the safe and stable operation of China's future power system.In this paper,the frequency adjustment control strategy and oscillation mechanism analysis method based on the wind turbine grid-connected system are studied.The main work is as follows:1)A virtual inertia coordinated control strategy for permanent magnet direct-drive wind turbines for weak networks is proposed.This strategy introduces virtual inertia control in the machine-side converter control of wind turbines,which uses the rotational kinetic energy in the rotor of the fan to provide the energy required for inertia simulation,providing additional power support for the system;in the grid-side converter Virtual synchronization control is introduced in the control.This control method can realize the grid-connected self-synchronization of direct-drive wind turbines by using DC capacitor dynamics instead of phase-locked loops.2)The oscillation analysis method of the doubly-fed wind turbine system based on complex circuit for studying the oscillation problem of the grid-connected system of the doubly-fed wind turbine is proposed,and the generalized impedance criterion and equivalent which can be used to analyze the stability of the grid-connected system of the doubly-fed wind turbine are established.The original-dual complex circuit.The port characteristics of the doubly-fed wind turbine and the AC grid side are derived and simplified in the global polar coordinates.Then,the generalized impedance model of the grid-connected system is given,and the generalized impedance criterion of the doubly-fed wind turbine system is derived.The proposed original-dual complex circuit of the doubly-fed wind turbine system is equivalent to the original grid-connected system.