In the high-power superconducting fusion converter, the single-phase neutral point clamped (NPC) three-level converter is applied to replace the traditional thyristor converter using an integrated gate-commutated thyristor (IGCT) as a power device. The operating frequency of IGCT is usually lower, only a few hundred Hz. An optimized hybrid space vector pulsewidth modulation (SVPWM)-8H is proposed to solve the problems of discontinuous output average voltage, low dc bus voltage utilization rate, dead time compensation, and neutral point potential balance. The new sectors are inserted to make the range of output average voltage of adjacent sectors intersect, which improves the continuity of output average voltage. Furthermore, some sectors are composed of four vectors to reduce the minimum working time of redundant small vectors, improving the dc bus voltage utilization ratio and the converter’s performance. Moreover, by analyzing the influence of dead time on redundant small vectors, redundant vectors are rearranged to make redundant small vectors’ working time synchronously in sector and sector switching, which reduces the influence of dead time on neutral point potential balance. Finally, by analyzing the influence of dead time on the output average voltage, dead time compensation is applied, which reduces the difficulty of compensation implementation. Simulations and experiments verify the rationality of the optimized hybrid SVPWM-8H.

Integrated gate commutated thyristor (IGCT) is the core device of a new fusion power supply for Comprehensive Research Facility for Fusion Technology (CRAFT), which is very important to establish an accurate, suitable, and effective device model. To establish a unified simulation model (USM) suitable, this article analyzes the process of carrier motion in the process of IGCT turning on and off. The structure of the electrical model and the calculation method of related parameters are obtained by fitting the mathematical equations. Using standard passive components, such as resistance, capacitance, inductance, and an accurate bipolar junction transistor (BJT) model, converting the physical model into the electrical model can be realized. At the same time, because the physical model contains temperature parameters, compared with the traditional IGCT model, this model combines the thermal model with the electrical model, which makes the model unified. In this article, the 4000-A/4500-V IGCT power device in ABB is taken as an example to verify the rationality of the electric-thermal model under different currents and temperatures through MATLAB/SIMULINK simulation and experimental test.

This paper presents a systematic structure and a control strategy for the electric vehicle charging station. The system uses a three-phase three-level neutral point clamped (NPC) rectifier to drive multiple three-phase three-level NPC converters to provide electric energy for electric vehicles. This topology can realize the single-phase AC mode, three-phase AC mode, and DC mode by adding some switches to meet different charging requirements. In the case of multiple electric vehicles charging simultaneously, a system optimization control algorithm is adopted to minimize DC-bus current fluctuation by analyzing and reconstructing the DC-bus current in various charging modes. This algorithm uses the genetic algorithm (ga) as the core of computing and reduces the number of change parameter variables within a limited range. The DC-bus current fluctuation is still minimal. The charging station system structure and the proposed system-level optimization control algorithm can improve the DC-side current stability through model calculation and simulation verification.

To improve the performance and dynamic response ability of poloidal field power supply (PFPS), the three-phase PWM converter-cascaded H-bridge inverter structure is adopted in the new generation PFPS. However, the load power of PFPS changes violently since the load characteristic is superconducting large inductance, which has a serious impact on the stability of the three-phase PWM converter control system. In this article, an improved dual closed-loop control strategy based on linear active disturbance rejection control (ADRC) is proposed to suppress the influence of load power disturbance, which is combined with the load power feedforward method and adding a decoupling link. Compared with the traditional control strategy based on PI controller, the simulation results show that the proposed control strategy has strong robustness to the change of load power, reduces the bus voltage fluctuation on the dc side, and improves the anti-interference ability and dynamic performance of the system.