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The ITER magnet system will operate in extremely severe conditions, which impose high requirements for mechanical and dielectric strength of the electrical insulation of the superconductive coils. Only monolithic structure obtained during the VPI procedure is capable to provide the required mechanical and dielectric strength for electrical insulation. To provide the qualitative insulation, a temperature non-uniformity of the electrical insulation should be kept within the range of [−5, +5 °C] and [−0, +20 °C] during filling with epoxy compound and its curing, respectively. The PF1 coil is about 150 t in weight and consists of materials with different thermal conductivity. Besides, a complicated geometry of the coil adds complexity to VPI. Since the VPI is usually a long-term and irreversible process (within pot life of compound), the whole process should be controllable. The paper describes the developed calculation model of the ITER PF1 coil and presents the results of numerical simulation of this model at VPI of electrical insulation. The completed VPI of the ITER PF1 coil has verified the proposed method for coil heating and proved an acceptable agreement between the calculated and measured temperature distributions throughout the VPI procedure. [ABSTRACT FROM AUTHOR]

The electromagnetic repulsion model of 400 V/630 A/12.5 kA fast vacuum transfer switch (FVTS) is established using finite element method. The speed and characteristics of the contact bounce of the FVTS are taken as constraints, and the objective is to keep the reliable opening of the mechanism with allowable bounce. The deceleration of the fast operating mechanism in the process of opening and closing is realized by applying the reverse electromagnetic repulsion force. Moreover, the simulation results demonstrate that the electromagnetic buffer effect is available, and the allowable bounce opening of the operating mechanism has been obtained. Furthermore, this paper compares the buffering effects of three kinds of conditions, such as no electromagnetic buffering, 110 V electromagnetic buffering and 220 V electromagnetic buffering. It can be found that the electromagnetic buffering is a necessary part of the 400 V FVTS, and the dynamic characteristics are the optimal scheme when the 220 V electromagnetic buffering is applied. Based on the results of simulation, a FVTS experimental prototype is developed to prove the effectiveness of the design scheme. [ABSTRACT FROM AUTHOR]

Microgrids with multiple converters suffer from excessive pressure on the communication network during traditional voltage and frequency regulation control. This paper proposed an event-triggered control strategy based superconducting magnetic energy storage (SMES) scheme to improve AC microgrids stability under successive disconnection of sources or step change of loads. By designing an event-triggered mechanism, each converter in the microgrid sends its own information to SMES in a non-periodic way. Then the control method of bus voltage and frequency regulation using SMES is constructed, which enables SMES to update its control mode. The microgrid model is established in PSCAD/EMTDC, and two cases of extreme conditions are conducted to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

To operate a converter at cryogenic temperatures, understanding the characteristics of power semiconductor devices is critical. This paper investigates the temperature and current dependence of the dynamic performance of five types of SiC power MOSFETs at 77 K. The turn-on and turn-off lasting time and the corresponding switching energy loss are extracted from a series of double-pulse tests. The transient peak voltage of cryogenic MOSFETs is lower, but the switching time is higher than the room-temperature ones. Moreover, power-exponential functional relations with the operating currents are found in the experiments. These results obtained lay some technical bases for exploring superconducting power electronics. [ABSTRACT FROM AUTHOR]