Electromagnetic Analysis And Design Of ITER Poloidal Field High Power Non-Same-Phase Anti-Parallel Converter

ITER Poloidal Field (PF) converter is a main part of ITER magnet power supply system. It is mainly used to supply continuous and adjustable current to PF superconducting coil to drive and control the plasma. For the requirement of ITER "Advanced Tokamak Operation Mode" on the drive and control of plasma, the ITER PF converter is designed with a parameter as high as 1.42kV/55kA and in 4-quadrant circulating operation mode. Its parameter is far beyond the ones of the PF converters in all the exsiting tokamaks. Due to the high operation voltage and the requirement on the system stability, the non-same-phase anti-parallel connection structure is adopted in ITER PF converter, which is seldom used in other high power converters. However, the non-same-phase anti-parallel connection structure will increase the fault suppression capacity on one hand, but give rise to a series of severe electromagnetic interference (EMI) problems. It is never met in the design of all the other PF converters and needs detailed analyses. What's more, the stable operation of ITER PF converter is of great importance for the normal operation of ITER Tokamak and plasma physical experiment, so it's necessary to conduct a systematic, all-sided and intensive analysis of the electromagnetic interference problems existing in it.At first, the isolated-phase-bus is introduced to the rectifier system for the first time, and an analysis and design method for an isolated-phase-bus with a non-sinusoidal current is proposed. It greatly decreases the alternating magnetic field generated by the a.c. busbar and mitigates the EMI problem. It also verifies the feasibility of isolated-phase-bus to be used in a rectifier system.Secondly, an analysis and design method, namely current sharing equation method, is proposed for the design of the bridge arm structure of a high power convter for good current sharing purpose based on Partial Element Equivalent Circuit (PEEC) method. By decomposing and discretizing the bridge arm model, and abstracting the inductance matrics, this mothed builds a coupling equation to analyze the current distribution among the parallel thyristors. Fully considering the influence of the coupling betweem different arms on the current sharing as well as the influence of eddy current effect and the nonlinear U-I characteristic, it provides a systematic analysis and design method for the bridge arm structure design of high power converters. It has successfully been used in the design of ITER PF converter bridge and greatly increases the current sharing coefficient, which is far beyond the required value.Thirdly, an analysis method of the stray magnetic field surrounding the converter bridges is proposed. It is used to analyze the electromagnetic environment of the instrument and control (I&C) system, especially the detailed distributions of d.c. magnetic component and power frequency magnetic component. It verifies the necessity of the electromagnetic compatibility (EMC) on the I&C system of ITER PF converter and provides the necessary input for the EMC design and test.At last, EMC test against static magnetic field is required for all the electrical and electronic devices at ITER site by ITER Organization (IO).IO has defined the test level and the requirement on the magnetic field generator. So an analysis of the magnetic field uniformity for a two-coil system is conducted and a new two-coil construction better than conventional Helmholtz coils is proposed. A series of forlumae for the coil's design are obtained. Based on the analysis results, the premililary design of the field generator is performed according to the IO's definition.The electromagnetic analysis and design is a main part of the research and development (R&D) of ITER PF converter. This thesis presents the detailed analysis of several electromagnetic problems existing in ITER PF converter, and provides the corresponding solutions. It is of great value for the stability operation of ITER PF converter. By now, the R&D of ITER PF converter has complished the design, processing, manufacturing and test of all its components. The integrating installation and test of the first prototype is also completed. It has passed the 72-hour continuous operation test and accepted by IO. For the larger tokamaks in the future, their magnet power supply systems will be of higher parameters and much harder to be developed. The research presented in this thesis will provide valuable references for their research and development.