Modeling And Low Voltage Ride-Through Analysis Of Direct Drive Permanent Magnet Synchronous Wind Generator With Stator Winding Inter-Turn Short Circuit

With the development of wind power generation market,wind power units with larger and larger installed capacity and wind power generation with increasing penetration in the power system,large-scale wind power Grid-connected has brought more and more challenges to the stability and security of the grid.On the one hand,the phenomenon of low voltage crossing in wind power generation can easily lead to the off-grid of the unit,which seriously affects the stable operation of the power system.On the other hand,motor internal faults are not easily detected.For example,stator turn-to-turn short circuit usually presents gradual degradation of winding insulation capability.Based on this,this paper takes the permanent magnet synchronous wind generator with a certain low voltage crossing ability as the research object,conducts modeling and simulation based on the permanent magnet synchronous wind power generation system,proposes the over-voltage protection scheme based on the super-capacitor energy storage,and verifies its role in improving the low voltage crossing ability.The stator inter-turn short-circuit fault of permanent magnet motor is modeled and simulated,and the effect of it on low voltage traversing ability of permanent magnet synchronous wind power generation system is studied.The main work of this paper is as follows:Firstly,the mathematical model of permanent magnet synchronous motor in normal state in ABC and dq coordinate systems is established.Then,based on the multi-loop theory,the mathematical model of the permanent magnet synchronous motor in the case of stator turn-to-turn short-circuit fault was established respectively in the two coordinate systems,and the simulation modeling and analysis were carried out on the MATLAB/Simulink platform.Furthermore,the correctness of the permanent magnet synchronousmotor model under the fault state was verified based on the simple three-phase permanent magnet synchronous motor vector control.Then,the topological structure of the machine side converter and the network side converter is proposed.Based on the three-phase non-equilibrium system under inter-turn short circuit,the basic principle of sliding mode speed control is introduced,and the PMSG vector control strategy based on sliding mode speed controller is proposed to meet the change of internal parameters of the motor,so as to realize the power control of the machine side.At the same time,based on phase-locking technology,a netside control strategy of directional vector control bus voltage is constructed.According to the above control strategies,the simulation models of the machine side control power and the network side control bus voltage of the direct drive permanent magnet wind power generation system are built respectively.Through the simulation analysis,the advantages of the control strategy are verified.Finally,the paper mainly introduces the mechanism of voltage sag in the power grid,proposes the dc side over-voltage protection strategy based on the super capacitor energy storage,and constructs a complete permanent magnet wind power generation system by combining the network side and machine side models.Three-phase symmetrical short-circuit caused voltage sags in power grid,on whether to join the super capacitor energy storage system and the stator winding interturn short circuit fault happens or not carried out simulation on the dynamic response of the permanent magnet wind turbine research,analyzes the interturn short circuit fault severity of permanent magnet wind turbine low voltage through the ability to influence.