Operation Analysis And Upgrade Scheme Design Of High Power Test Platform

The high power test center of Institute of Plasma Physics Chinese Academy of Sciences is the largest DC test platform in China, which is invested by the Ministry of Science and Technology to meet the related tests of ITER power supply equipments.In order to further improve and expand its test capability and scope, this dissertation mainly studies the operating characteristics, harmonic distribution,over-current and over-voltage faults and other issues for three platforms: the high power DC test, ITER poloidal field converter integration test, reactive power compensation and filtering system test. The main contents and innovations are as follows:1)、Based on the theory of high power converter system, the converter equivalent model for impulse output current is established. On this basis, the parallel output characteristics and the influence of commutative coupling of multi-converter are analyzed. The feasibility study of the short-circuit test supplied by the converter system with the reactive power compensation system is carried out. The reactive power forecast control strategy combined open-loop with closed-loop is proposed to increase the response speed, and the impact of reactive load and grid voltage sag is improved. For the short-circuit test in series mode, considering the abnormal commutation state of equivalent three-phase short circuit, the load characteristic curve under abnormal commutation for high output current is given. The accurate establishment of the equivalent transient model ensures the safe and reliable operation of the short-circuit impact test, and the perfect test flow design. Joint operation analysis and control system improvement to maximize the use of existing resource to optimize system test.2)、A piecewise method is proposed to convert harmonic problems of complex functions into algebraic solutions of simple functions. The harmonic analysis of the three operating modes is calculated, and the simulation and experimental analysis and comparison are carried out. The harmonic characteristics of the ITER PF series power supply system under sequential control and symmetrical control strategy are compared and analyzed. The sequential control not only improves the reactive power consumption of the system, but also greatly reduces the THD content of the system.The harmonic calculation of PF power supply system can not only evaluate its influence on power grid and other equipments,but also provide reference for the selection and design of the filtering system. The direction of the control optimization of harmonic suppression for future series systems is pointed out.3)、The theoretical analysis and simulation comparison are carried out for the common over-current and over-voltage faults of the DC test platform, especially the the impact values of several over-current faults are calculated. According to the above analysis of various faults, the corresponding protection measures are put forward, and various protection action flows are designed. Finally, the system interlock protection mechanism is given. It provides a series of security guarantees for the safe and reliable operation of the system test.4)、According to the upgrade requirements of the DC test platform, the basic parameters of the transformer are preliminarily determined. The selection of the thyristor is studied, and the selection result is confirmed by the calculation of the junction temperature and the thermal effect. The steady-state and short-circuit output current capability of the new scheme in series and parallel mode is verified. The feasibility study of the upgraded DC test platform is completed, which provides the support for the future upgrade.