Research On Virtual Synchronous Generator Control Strategy For Doubly-fed Wind Power Generation System

With the rapidly development of economic,dependence on energy of human is also increasing,the traditional fossil fuels bring about a series of pollution problems.Wind power as a clean energy,has been rapidly development.With the increasing capacity of new energy,the new energy penetration rate represented by wind power and photovoltaic in the grid power system is increasing.The wind farm behaved as low inertia,low short circuit capacity ratio,high impedance and weak damping,the supporting function of AC power system on wind farms will be weaker and weaker,which will adversely affect the steady-state characteristics and transient characteristics of the system.As the proportion of wind power increases,the inertia of the power system becomes smaller,and problems such as insufficient frequency support and power failure will occur,making the wind turbine output characteristics as synchronous generators in traditional power systems may provide a new idea.In this paper,a mathematical model of doubly-fed wind turbine(DFIG)is established.Based on the above,the relevant control strategy of DFIG rotor-side converter in synchronous rotating coordinate system is established.Taking the doubly-fed generator stator voltage as control target,control strategy of stator voltage is established.Based on the model analysis of traditional synchronous generator,the equations of rotor motion and electromagnetic equation of synchronous generator are used to establish the virtual rotor motion equation of DFIG,and a complete DFIG virtual synchronization(DFIG-VSG)control model is established.The virtual shaft system and actual mechanical shaft system model of fan are established.The energy coordination relationship of doubly-fed generator set and the virtual synchronous control of doubly fed generator are analyzed.The inertia kinetic energy of rotor is used as the energy storage link.For multi-mode operation characteristics of DFIG-VSG,the switching methods between different modes were analyzed,including three modes of operation:islanding operation?grid connection operation and parallel operation.The influences of power characteristics,frequency characteristics and control parameters of DFIG on the dynamic performance of the system are analyzed.Simulation and experimental proved the effectiveness of DFIG-VSG control strategies mentioned above.