Theoretical And Experimental Research On Low Voltage Ride Through Of The Main Transmission System Of The Turbine With Hydraulic Transmission

The reaserch object of the thesis is the wind turbine with hydraulic transmission.As anew type of the wind turbine, compared with gearbox wind turbine and direct drive windturbine, the wind turbine with hydraulic transmission is more safe,reliable and more easierto connect to the grid, the electricity quality is higher.The thesis focuses on the powercontrol method in the main transmission of the hydraulic drive wind turbine based on itsworking principle and structure.The hydraulic drive wind turbine uses fixed displacement pump-variabledisplacement motor closed hydraulic system and self-excitation synchronous generatorconnecting to the grid directly,its control variables and control method is different with thegearbox wind turbine’s and the direct drive wind turbine’s.The thesis gives a powercontrol strategy based on the swash plate control of the variable displacement motor, thekey components Mathematical models of the fixed displacement pump-variabledisplacement motor system are built by using the mechanism modeling technology,whenthe fixed displacement pump-variable displacement motor system is running on theconstant current source,the different motor swashplate initial position and the differentload pressure affect the characteristics of the power control.AMESim software is employed to construct the hydraulic system model,thesynchronous generator model and the control model of the generator steadyspeed,connecting to the grid and the power control system are modeled by the simulationsoftware MATLAB/Simulink.The two softwares co-simulation is completed with theinterface technology and the simulation analysis of the main factors affecting hydraulicdrive wind turbine power control is achieved,we propose a variable gain improvedoptimization PID control method and it improve the response of the generating powerobviously.Based on both theoretical and simulation analysis,a30kVA hydraulic drive windturbine experimental platform is built,dSPACE is used as the main controller and it cancomplete real-time debugging and data acquisition.We complete the generator steady speed,connecting to the grid and controlling the generator active power. We analyze thefactors affecting power control verify that the improved controller can make the powergeneration better transient and steady state response.The successful experimental platformverifies the hydraulic drive wind turbine is feasible in principle and controllablepractically in the generating power and it lays the foundation for carrying out the researchof the maximum power point tracking of the wind turbine with hydraulic transmission.