Control Of Doubly-Fed Wind Turbine Based On Virtual Synchronous Generator

In today's increasingly serious environmental problems,wind power has become the main form of new energy power generation.As the most commonly used model in the field of wind power generation,the doubly-fed wind power generators have an increasing proportion of power generation in the power system.The research on grid-connected control of doubly-fed wind turbines has an important impact on the development of wind power generation.Conventional doubly-fed wind turbine excitation converters are mostly dominated by power electronic devices,which makes the power system lack the inertia to maintain voltage frequency stability and the damping characteristics to cope with disturbances.Improving the moment of inertia and damping characteristics of the power system is of great significance to ensure the stable operation of the power system.This thesis focuses on the control strategy of doubly-fed wind turbines.Based on the network side and rotor side model and control structure of the doubly-fed wind turbine,the rotor-side vector control of the stator voltage oriented doubly-fed wind turbine system is adopted.By simulating the synchronous machine rotor mechanical equation and the stator electromagnetic equation.The virtual governor and virtual exciter model are obtained,and the control idea of synchronous generator is transplanted to the rotor-side converter of doubly-fed wind turbine.The virtual synchronous generator of rotor-side converter of doubly-fed wind turbine is given.Synchronous Generator(VSG)controls the system structure and determines the parameters of the virtual synchronous generator.For the VSG control strategy of the doubly-fed wind turbine under fault,Firstly,the operating characteristics of doubly-fed wind turbines under asymmetric faults are analyzed.According to the different control targets of wind turbines under faults,the positive sequence current compensation amount under VSG control strategy is given,and the current command value is generated.The structure of the VSG strategy of the doubly-fed wind turbine under symmetrical faults realizes the stability of the output current value,active power and reactive power of the doubly-fed wind turbine during faults.A current compensation value is introduced in the current loop to achieve a control target that meets the requirements of the grid connection with different output quantities.The simulation model was built in Matlab/Simulink software to verify the control effect.