Design And Research Of Double-fed Speed Control System Of J-TEXT Pulse Generator Unit

J-TEXT device is a medium size tokamak device,reconstructed and reworked in HUST,formerly known as TEXT-U in USA.It's supplied by of a pulse generator.The rated speed of the unit is 713rpm and the rated stored energy is 185MJ in USA grid(12kV/60Hz),now the max speed is 598rpm as the State Gird is 10kV/50Hz.The shortage of the stored energy determines that the power supply systems of the J-TEXT device operate under the rated parameters.It's difficult to carry out physical experiments with high parameters.It's necessary to improve the speed of the pulse generator unit,which can ensure the J-TEXT device operates with the rated parameters.Double-fed speed control system can decrease the capacity of the converter obviously.This paper investigated vector control strategy of double-fed motor,AC-DC-AC converter and common mode current of speed control system.A double-fed speed control system is designed on the basis of previous research.Simulation and experiment results prove that the designed system meet design requirements.A vector control strategy oriented by stator flux is researched.A double closed-loop feedback control system is constructed to control the speed and rotor current.Current can be decomposed to torque component and flux component,the MT axis current can be controlled independently by forward compensation strategy.A stator flux observer is constructed.The active power flow of motor is analyzed under different conditions,the rated flux current of is calculated with zero rotor reactive power or minimal rotor current.The calculated maximum active power at rotor side is 100kW,the main circuit equipment parameters are designed on this account.The converter is a AC-DC-AC converter based on full control devices.The vector control strategy oriented by grid voltage of LCL rectifer is analyzed,decoupled dq axis current is controlled by feedforward compensation strategy.Parameters of LCL filter is designed.A double closed-loop feedback control system is constructed to control the DC bus voltage and rectifer legs current.The SVPWM algorithm is researched and achieved in digital signal processor.The issue of motor terminal voltage increase caused by transmission of PWM pulses in long cable is analyzed and the output reactor of inverter is designed.Experiments proves that the designed 100kW converter satisfies the demand.A control system based on monitor layer,real time layer and scene layer is designed.Monitor layer works in Windows platform to monitor and control the system status;real time layer works in QNX platform to undertake tasks of collection,calculation,control and communication and the keys tasks are the measurement of rotor angle,the measurement of rotor speed and the achievement of double loop control system;scene layer works in DSP28335 platform to maintain the DC bus voltage stable and output rated rotor voltage according to the orders of real time layer.Common mode voltage in the motor system powered by PWM power supply could generate common mode current.The model of motor shaft voltage is built with motor parasitic electric capacities,the relationship between shaft voltage and the common voltage of motor wound neutral point is analyzed.The grounded network of motor hall is described,the high frequency parameters of ground wires and the route of common mode current are analyzed.The shaft voltage and common mode current under different conditions are simulated,the means to decrease shaft voltage and common mode current are designed.Based on the previous study,a double-fed speed control system for J-TEXT pulse generator is designed,a series of experiments are implemented,which proves the feasibility and correctness of designed double-fed speed control system of J-TEXT pulse generator unit.The speed control system can improve motor speed to rated speed 713rpm,which proves that the design strategy is correct and operable.