| The tearing mode(TM)is a common MHD instability in tokamaks.Applying a dynamic resonant magnetic perturbation(DRMP)can effectively suppress the TM.It is difficult to unlock locked mode using DRMP after initiative mode locking.In order to input DRMP before mode locking,power supplies need to input DRMP within 3~5 ms before mode locked.However,it takes 15~25 ms to input the DRMP using the current AC PS.So it is necessary to upgrade the topology of current AC PS and their corresponding control system.The AC power supply topology has been improved by adding a transitional load branch to form a parallel structure with the inverter and the perturbation coils.The stable DC bus voltage is established by the transitional load,and then switch to the inverter and the coils,so that the perturbation field can be quickly put into operation.More importantly,the power supply's control system needs to be upgraded to achieve this function,and the power supply protection system is designed to ensure that the power supply can operate stably under different conditions.This paper mainly focuses on the idea and process of upgrading the control system.To achieve accurate control of power supply,software support is indispensable.QNX operating system is quite suitable,which has excellent timeliness and stability.And program organization structure under this operating system is single-process multithreading organization structure is determined.Each thread in this structure shares data space,adopts modular design,and has strong program portability,fast running speed and good real-time performance.Finally,the functions undertaken by each thread are determined,such as processing parameters,communication,monitoring power supply status,data transmission,etc.These threads work together to control the power supply.After determining the operating system and program organization,the power supply should be controlled according to the power supply timing logic.The most important thing is that the timing logic of the power supply can determine the different power supply states corresponding to the power supply in different operation periods.Due to transitional load,the operation state of the power supply increases,and the conversion paths between the various states of the power supply also increase.Therefore,in order to ensure the safe and stable operation of the power supply,it is necessary to specify the various paths of the power supply state conversion,so as to ensure that the power supply can quickly return to the safe state no matter in what state a fault is detected.Then it introduces the switching of the power supply state under normal and abnormal working conditions at different times,which is the basis for the subsequent design of the power protection program.At last,how the designed power protection system works is explained.The working principle of the power protection system is elaborated in detail by using the program block diagram and text description,and combining the functions of each thread in the program at different times,the judgment conditions in the running process,signal transmission,hardware cooperation and the conversion of the power running state.The power supply is simulated,tested and finally put into physical experiments.Experimental results show that the amplitude of AC power supply current waveform with transitional load increases rapidly without obvious overshoot.This shows that the application of transitional load can indeed improve the dynamic response result of AC power supply.The control effect of AC power supply with transitional load on plasma was also observed in the physical experiment,that is,the rotating perturbation field can be rapidly input,the tearing mode can be locked at a specific frequency,the rotating frequency is increased,and the disruption can be effectively delayed.This shows that the application of transitional load can indeed have a better control effect on plasma and delay disruption.The above experimental results are completely consistent with the theoretical analysis. |
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