Study on the Current-Sharing Control System of the TF Power Supply for a Superconducting Tokamak

The superconducting toroidal field （TF） plays an important role in a superconducting tokamak, whose power supply was developed based on the feedback control principle. In this paper, superconducting tokamaks in different countries are described, and the TF power supply of the International Thermonuclear Experimental Reactor （ITER） is taken as an example to study the current-sharing characteristics in the current-stabilized stage. Firstly, the mathematical model of the TF power supply is established, and then the 3-loop control method is put forward for achieving the stability and reliability of current-stabilization and current-sharing. Furthermore, further studies indicate that the current-sharing controller has no influence on the current-stabilized control, and current-stabilizing and current-sharing can be realized at the same time. All the work done provides valuable references for the current-sharing design of the TF power supply for a superconducting tokamak, and all these studies lay a solid foundation for developing superconducting tokamaks.

A novel current-sharing scheme based on magamp

The magamp (magnetic amplifier) is widely used in power supplies due to its low cost, simplicity and other advan-tages. This paper discusses a novel application of the magamp in switching power supplies, where the magamp is used to regulate pulse width modulation (PWM) instead of power signal in the main circuit. This method extends the application of the magamp in power supplies, and makes it possible to further regulate control signal when PWMs have been generated. Based on this applica-tion, a new current-sharing (CS) scheme using the magamp is proposed, which uses a modified inner loop CS structure. In this scheme PWMs are generated by one main controller, and CS is achieved by regulating PWMs using a magamp in each module. Compared with traditional application of the magamp, the new CS scheme can be used in most topologies and only requires magamps of low power capacity. Then a test circuit of parallel power supply is developed, in which CS is achieved by a PWM regulator with the magamp. The proposed scheme is also used to upgrade an electroplate power to make it capable of paralleling supplies. Experimental results show that the proposed scheme has good CS performance.

Adaptive droop control for better current-sharing in VSC-based MVDC railway electrification system

The share of voltage source converter(VSC)technology is increasing in conventional power systems,and it is penetrating into specific transportation systems such as electric vehicles,railways,and ships.Researchers are identifying feasible methods to improve the performance of railway electrification systems(RESs)by utilizing VSC-based medium-voltage direct current(MVDC)railways.The continuous motion of electric trains makes the catenary resistance a variable quantity,as compared to the traction substation(TSS),and affects the currentsharing behavior of the system.A modified droop control technique is proposed in this paper for VSC-based MVDC RES to provide more effective current-sharing while maintaining catenary voltages above the minimum allowable limit.The droop coefficient is selected through an exponential function based on the ratio between the concerned TSS current and the system average current.This enables small adjustments of droop values in less concerning marginal current deviations,and provides higher droop adjustments for large current deviations.Meanwhile,the catenary voltages are regulated by considering the voltage data at the midpoint between two TSSs,which experiences the lowest voltages owing to the larger distance from the TSSs.The proposed techniques are validated via simulations and experiments.

Analysis and verification of electrodynamic force,thermal stress and current sharing for CRAFT converter structure design

In the design realm of fusion power supplies,structural components play a pivotal role in ensuring the safety of fusion devices.To verify the reliability of the converter structure design at the Comprehensive Research Facility for Fusion Technology(CRAFT),meticulous analysis of the converter's dynamic impact is carefully performed based on the worst fault current(400k A),firstly.Subsequently,the thermal stress analysis based on the maximum allowable steadystate temperature is finished,and the equivalent thermal stress,thermal deformation,maximum shear stress of a single bridge arm and the whole converter are studied.Furthermore,a simple research method involving the current-sharing characteristics of a bridge arm with multithyristor parallel connection is proposed using a combination of Simplorer with Q3D in ANSYS.The results show that the current-sharing characteristics are excellent.Finally,the structural design has been meticulously tailored to meet the established requirements.