| The power supply system is the key element which should be integrated to a tokamak facility. The major task of power supply system is to produce currents precisely for these magnetic coils in the proper way. Herein the generated magnitics fields can produce, confine and heat plasma, and drive and maintain plasma current as well.So the design and development of power supply system is important for reliable and flexible tokamak operation.The Joint TEXT (formly TEXT-U in University of Texas in USA) tokamak is a medium-sized tokamak facitity operated by Huazhong University of Science and Technology. The J-TEXT construction was started in 2005, And the installation of the machine and its periphery were completed in 2006. In 2007, the J-TEXT tokamak was successfully commissioned and obtained the first plasma discharge. In the first experimental campaign, a discharge with the plasma current up to 150kA and the pulse length up to 200ms can be achievable. The pulsed power supply of J-TEXT tokamak is set up and functioned. The achievement of this work is listed as follows:(1)The power distribution system and the pulsed power supplies used to produce the magnetic fields, including toroidal field, ohmic heating field, vertical field, and horizontal field, are re-designed and updated on base of the previous TEXT-U scheme; especially their monitor systems and control systems are totally replaced.(2)The timing of the current waveform for the power supply and the control option were examined by various experiments set up and finally fixed. At present, the pulsed power supply system is running for the J-TEXT tokamak was operating for the J-TEXT discharge and the performance is excellent.(3)The power distribution, controller, protection, excitation circuit for the J-TEXT 100MW motor-generator is redesigned and manufactured. The scheme takes the difference between USA grid and PRC grid into account, and can run above the rating parameter, and it would benefits for the J-TEXT operation on the rating parameters. The stator magnetic flux linkage vector oriented control method is defined for motor double-feed varying speed system, thereafter the ac converter scheme of 100MW motor-generator double-fed varying speed system is proposed. (4)As to toroidal field power supply, the unbalance current between two 12-pulse–converters connected in parallel is simulated and analyzed, hence an effective control model comes out. The tests show that the proposed model can solve the problem in a promissing way.(5)The coupling between ohmic heating field coil (primary) and plasma (secondrary) is analyzed using equivalent transformer model. Plasma current feedback control model is therefore established to conduct the transmission function.(6)Based on Shafranov equation, and the relation matrix between the vertical field and plasma position is calculated and constructed, consequently the transmission function is deduced.(7)Taking the control system and the PID control method into account, the simulation of power supply is done. The results are in a very good agreement with those practical processing in the J-TEXT operation. The comparison comes to a conclusion that the simulation would take great contribution to the operation of pulsed power supply and lead to a safe and reliable running of the machine.The completion of pulsed power supply system is sufficient to enable us to obtain the first plasma in the J-TEXT tokamak, and will lead to successful operation and fruitful experimental results.
|
PDF Full Text Request