A Simulation Analysis of 300 kV DC Power Supply for Neutral Beam Injector Accelerator Grid

The acceleration grid power supply (AGPS) is an integral part of the neutral beam injector (NBI) system. With the advent of negative-ion based NBIs, output voltage of AGPS is becoming higher and higher, even reaching to 1000 kV as in the case of the International Thermonuclear Experimental Reactor (ITER). The key features that characterizes the AGPS are the low output voltage ripple and fast dynamic response. A rectifier-inverter type system is most suited for the AGPS, as the output voltage can be easily regulated from the inverters which are located at the low voltage side. This also facilitates rapid cutoff of the high voltage output during grid breakdown phenomenon. This paper describes a simulation study of 300 kV, 2.0 A AGPS for powering the prototype NBI being developed at IPR. The power supply comprises of three stages, where each stage has an inverter-coupled step-up transformer-rectifier system having an output voltage of 100 kV. Firstly, design of major components of the power converters were investigated. Next, simulation of the entire power supply was carried out in PSIM software. In the simulation model the thyristorized rectifier and the inverters are controlled by a PI master controller, which ensures the desired performance of the system. The simulation results presents the steady state and dynamic response of the controller to meet the technical requirements of the power supply. Apart from the controller performance, voltage stresses in the transformer winding were also estimated.