It is well accepted that lower hybrid current drive （LHCD） is the most efficient method for non-inductive current drive in fusion devices and the effect of the current drive is dependent on not only microwave power ...It is well accepted that lower hybrid current drive （LHCD） is the most efficient method for non-inductive current drive in fusion devices and the effect of the current drive is dependent on not only microwave power but also its grill phase shift. This paper presents a new kind of feedback control system for antenna phase difference in LHCD experiments. In this highspeed control system, a lot of new technologies and methods are incorporated. The results of the experiments show a very good agreement with the system design.展开更多
When a modular multilevel converter based high voltage direct current(MMC-HVDC)system operates under grid faults,there will be a phase difference between the grid voltage and the converter output.It can be caused by g...When a modular multilevel converter based high voltage direct current(MMC-HVDC)system operates under grid faults,there will be a phase difference between the grid voltage and the converter output.It can be caused by grid voltage phase shifting and the integration effect of the phase-locked loop(PLL)in the converter.The system may exhibit an undesirable transient process with expanded current which is harmful for the converter devices.In this paper,a transient current estimation method is proposed for the scenario of converter-grid phase difference caused by the frequency shifting of the grid side.A piecewise phase calculation model is established to determine the transient phase difference of the system.Then,according to the maximum phase difference calculated by the model,the system stability is assessed and the maximum value of system transient current can be estimated after comparing the maximum phase difference with the critical phase difference and π,Finally,the current estimation results are verified by detailed circuit simulations of a 21-level MMC-HVDC system built in PSCAD.展开更多
This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage cir...This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.展开更多
基金Meg-science Engineering Project of the Chinese Academy of Sciences
文摘It is well accepted that lower hybrid current drive （LHCD） is the most efficient method for non-inductive current drive in fusion devices and the effect of the current drive is dependent on not only microwave power but also its grill phase shift. This paper presents a new kind of feedback control system for antenna phase difference in LHCD experiments. In this highspeed control system, a lot of new technologies and methods are incorporated. The results of the experiments show a very good agreement with the system design.
基金supported by the National Natural Science Foundation of China under Grants 51877159,51637007the Fundamental Research Funds for Central Universities Program 2042019kf0195。
文摘When a modular multilevel converter based high voltage direct current(MMC-HVDC)system operates under grid faults,there will be a phase difference between the grid voltage and the converter output.It can be caused by grid voltage phase shifting and the integration effect of the phase-locked loop(PLL)in the converter.The system may exhibit an undesirable transient process with expanded current which is harmful for the converter devices.In this paper,a transient current estimation method is proposed for the scenario of converter-grid phase difference caused by the frequency shifting of the grid side.A piecewise phase calculation model is established to determine the transient phase difference of the system.Then,according to the maximum phase difference calculated by the model,the system stability is assessed and the maximum value of system transient current can be estimated after comparing the maximum phase difference with the critical phase difference and π,Finally,the current estimation results are verified by detailed circuit simulations of a 21-level MMC-HVDC system built in PSCAD.
基金Project (No. 043804411) supported by the Tianjin Natural ScienceFoundation, China
文摘This paper outlines the significance of enhancing the instantaneous protection reliability of low voltage circuit breakers and describes their main failure modes. The instantaneous failure mechanism of low voltage circuit breakers was analyzed so that measures to improve instantaneous protection reliability can be determined. Furthermore, the theory of the instantaneous characteristics calibration device for low voltage circuit breakers and the method of eliminating the non-periodic component of test current are given in detail. Finally, the test results are presented.
