The Study On Several Key Techniques Of High Voltage Power Supply For Auxiliary Heating System In Tokamaks

Auxiliary heating is a necessary method to igniting in tokamaks. As a key component of auxiliary heating systems, high voltage power supply (HVPS) has the following characteristics: high voltage, high power, high precision, low ripple, quick response and so on. To improve the performance of the HVPS, some further researches are important. This paper focuses on the pulse step modulation (PSM) power supply and inverter type high voltage power supply, which are main solutions for the auxiliary heating system power supply technology in modern time. The main contents of this paper are introduced as following.The circuit topology and system insulation is studied for a100kV PSM HVPS in J-TEXT (Joint Texas Experimental Tokamak) device. A topology of four multi-secondary transformers is proposed in this paper, the HVPS system is powered and insulated by these transformers at the same time as single transformer stage. The transformer winding connection is discussed and the primary side winding is designed as extended delta connection to reduce the voltage ripple, while all the secondary windings are designed as wye connection to reduce the phase voltage of each windings. The power capacity and insulation voltage of the transformers are calculated in this paper. The high voltage insulation structure of HVPS system including all transformers and power supply modules is designed and has been tested.The soft start of PSM HVPS is studied. An equivalent circuit, which is a series RLC circuit, is proposed to analyze the characteristics of inrush current. The series-resistor soft start procedure along with the voltage regulation soft start procedure are all discussed in this paper. The criterion to select the soft start resistor and voltage ramp is proposed. A1.2kV power supply, contains12converters, with soft-start has been built up in laboratory. Simulation and experiment results are shown to verify the theoretical analysis. The soft start strategy of100kV high voltage power supply system is designed and tested.The topology of inverter type HVPS is investigated focusing on topology and operation procedure of the insulated DC-DC converter. An insulated DC-DC converter based on three level three phase inverter and D-Y connection transformer is proposed here to decrease the output ripple. The operation mode is analyzed in detail as the duty cycle changes from0to1, while the output current is continuous.The output characteristics of the invert type HVPS is studied, based on it’s operation procedure. The equations on the output voltage, voltage ripple, circuit inductance, dc-link voltage, load current, and duty cycle at all six operation modes are provided. The relationship between the output voltage and dc-link voltage to get the output ripple minimum is revealed, and a control strategy is proposed based on this condition. A control system is designed for the HVPS of ITER neutral beam system, simulation result is showed. Finally, a400V,6A power supply prototype is set up, experimental results demonstrate the analysis of operation procedure is proper and the design of control strategy is reliable.