Current Following Control Study Of Soft-Switching Maglev Chopper

Maglev chopper is an important part of the maglev train, and its stability and comfort is decided by the performance of current following control. Based on the hybrid EMS system, a four-quadrant soft-switching chopper using on maglev train is designed and verified in this thesis.The traditional H type hard-switching chopper is frequently used on maglev train because of its simple structure, reliable performance and convenient control. However, it costs a large switching losses and has large EMI, so it needs an extra buffer circuits and a big heat sink which is not good for making chopper smaller and lighter. Therefore, it is necessary to study the soft-switching chopper which can not only increase efficiency and reduce the EMI, but also cut down the switching losses, decrease the heat sink and make the chopper smaller and lighter.Firstly the topology of the four-quadrant soft-switching chopper is introduced in the paper, and the ZVT principle of the resonant component, the IGBT control sequence and how the load current influence the ZVT are analyzed in details. Besides, a multi-step digital PID current-following control scheme is designed in this thesis. After that, the losses principle of IGBT and fly-wheel diode(FWD) are analyzed respectively, and the losses is compared between soft-switching chopper and hard-switching chopper. Meanwhile, the four-quadrant soft-switching chopper model and four-quadrant hard-switching chopper model are made in software PLECS which is known as losses simulation. According to the analysis and compare of the IGBT losses, the FWD losses and the total losses of two topology, it was concluded that the soft-switching chopper’s losses is lesser when it achieve ZVT. But to achieve ZVT, the current of soft-switching chopper must be big enough to a certain value.Finally, a low power experiment of four-quadrant soft-switching chopper based on TMS320F28335 is designed, and the ZVT and its control feasibility based on multi-step digital PID control scheme are verified. It come to the conclusion that the multi-step digital PID control scheme has a good performance when it tracks step signal, single-phase sine signal below 427Hz and AC sine signal below 285Hz.