Research On Four-Quadrant Maglev Chopper

Maglev chopper is an important part of the maglev control system, providing excitation current for the suspension magnet to produce levitation force. Hybrid suspension system which is one of the suspended maglev train technology's research directions can reduce the solenoid coil current. In hybrid suspension system, the load current can flow in both directions by using four-quadrant chopper. The traditional maglev chopper using hard-switching mode, the IGBT's voltage and current stress is high.switching losses are serious,efficiency is low,heat is large,electromagnetic radiation is serious.In order to improve the working state of the switcher, soft-switching method is applied to the traditional maglev chopper to overcome the problems in the hard-switching mode. the goal is to solve the hard switching problems.Firstly this paper introduces the topology of the traditional four-quadrant maglev chopper;makes the theoretical study on two level and three-level control method; builds simulation models on the basis of theoretical analysis of the two control methods. Simulation results show that under the three-level control mode the load voltage stress is smaller.To improve the traditional suspension chopper this paper introduces the zero-voltage-switching (ZVS) and zero-voltage-transform (ZVT) topology, analyzes the working principle of the two programs. This paper focuses on and analyzes the ZVT soft-switching technology, the corresponding simulation model has been built, and studies have shown that the technology can achieve the soft-switching function on the main switchers;improve the switcher's working environment.The design method of experimental hardware platform is introduced; This thesis explains the suspension chopper device selection method for each module. Design requirements and precautions for IGBT's driver have been studied, discussed the characteristics of integrated drive module 2SD315A.The various components' characteristics of FPGA-based control board are described.Finally, experimental analysis is made for various types of maglev chopper. Experiments show that the three-level control reduces the load current's ripple, but it is not the best strategy. Under the soft-switching mode, the main switchers can achieve soft-switching function and the input current's RMS of DC side decreases, while the IGBT's temperature rise is significantly less than that of the hard switching mode. All in all ZVT soft-switching is a very promising technology.