1. Feedback control of the LHW Power by HVPS Huang Yiyun Institute of Plasma Physics, Chinese Academy of Science, P.O.Box 1126, Hefei, Anhui, 230031, P.R.China (2003.9)

2. 1. Background 2. The 2.45GHz 1MW LHCD system and HVPS 3. The purposes of the feedback control 4. Mathematic model of the control system 5. Simulation result and analyse 6. Conclusion Content

3. 1. Background a. LHCD---to heat and drive the plasma current efficiently. b. HVPS---to control the output micro-wave power of the LHCD (LHW)through regulating high voltage of the HVPS. c. Traditionally---Voltage of the HVPS is feedback controlled to hold the power of LHW constant. d. Expectation ---Power of the LHW is feedback controlled to dissipate fluctuation of other disturbances.

4. 2. The 2.45GHz 1MW LHCD system and HVPS a.The 2.45GHz 1MW LHCD system Oscillator—PIN—Phase—Amplifier—Klystron—Circulator—cerimic windows —Antenna —Plasma

5. b. The -35KV/2.8MW HVPS E-Grid—transformer—switch—star-point controller—rectifier —RLC filter —Crowbar—klystron

6. 3. The purposes of the feedback control a.Keep the power of the microwave steadily from fluctuate Fluctuation from the HVPS. Fluctuation from the low power ratio frequency driver. Fluctuation from the other device such as magnet Protection of reflection power for cerimic windows b. Modulate the power of the microwave based of the HT-7 experiment Ram up or down the power of the microwave at any time

7. 4. Mathematic model of the control system object properties K=4300 Ts=23.6mS

8. HV of HVPS sometime fluctuate due to fluctuation of electrical grid 5. Simulation result a. The feedback controlled LHW when Fluctuation from the HVPS

9. HV of HVPS fluctuate sometime due to fluctuation of low power ratio frequency driver or other device b. The feedback controlled LHW when Fluctuation from the LHCD

10. c. The LHW feedback control when protection of reflection power HVPS is feedback controlledLHW is feedback controlled One klystron of LHCD system will be cut by sub-PINA when reflection power endanger cerimic windows

11. d. Confinement of condition The controller will result in saturation when the power of LHW decrease more than 50%,such as 3 or 4 klystron is cut by sub-PIN at the same time. The rebound of the power of LHW will endanger the klystron, such as arc inside etc. which will deduce the natural life of the klystron.

12. d. The modulated LHW feedback controlled by HVPS The LHW can be controlled by rated value and time stably by regulating HVPS with compatible PID law For HT-7 experimental require.

13. The power of LHW ramp up by HVPS control

14. 6. Conclusion To keep the steady plasma current on HT-7 and HT-7U, power of LHW is need to be feedback controlled against all kinds of disturbances. Setup the control system by analyzing objective properties by Mathematic model. Parameter PID must be adjusted through simulation. The LHW can be controlled at rated value and time to satisfied the requires of experiment.

15. thanks