Study And Design Of The Switching Power Supply For40T Hybrid Magnet Superconducting Outsert

The40T hybrid-magnet in High Magnetic Field Laboratory (HFML) of Chinese Academy of Sciences (CAS) consists of a resistive-insert magnet and a superconducting outsert magnet, and the latter requires a highly stabilized power supply whose maximum output parameter is8V/16KA. The existing power supply adopts the traditional dual reverse star-shaped SCR scheme. Its major shortcoming is bulkiness. At the same time, another alternative is based on switching power supply technology. In General, such power supply have much smaller volume and much higher efficiency. However, it is hard to depress the low frequency ripple, which is caused by three-phase uncontrolled rectifier and a normal switching power supply cannot output negative voltage which can be used to make the current down controllably.In the beginning of chapter2, different kinds of inverters and rectification circuits are introduced. Considering the actual requirements of the power supply, the main circuit topology is combined by a full bridge invertor on primary side and a full wave rectifier on secondary side. In order to reduce switching loss, the phase-shift control full-bridge soft switching technology, which is characterized by saturated inductor connected to transformer primary coils in series, and the secondary synchronous rectification technology are also applied in the main circuit. At the end of chapter2, the overall topology of the superconducting outsert magnet power supply is given and the proposed quench protection scheme is briefly described. Moreover, in chapter3the calculation of each parameters of the power supply is presented in detail.In order to restrain output ripple, an active filter is added to the output end of the switching converter. In the beginning of chapter4, all kinds of DC active power filter are briefly introduced, and the reasons why SSLAPF (Series Linear Active Power Filter) is chosen for the superconducting outsert magnet power supply is analyzed emphatically. One of the most important reasons is that the SSLAPF can be combine with the synchronous rectifier and the power supply can generate negative voltage with the help of proper controlling methods. The output adjustment capacity of MOSFET is specifically analyzed.The chapter5begins with the overall control scheme, which can make the controller of the SSLAPF and the controller of the switching converter work in cooperation. Based on the circuit modeling and analysis of bode graphs, the outer inner voltage-current dual closed loop control system is designed for the SSLAPF. The designing of controller of the switching converter takes the adjusting transistor’s on-resistance influence on open-loop transfer function into account. Based on the main topology modeling in the chapter2, a specific PID compensating network is given. Meanwhile, the switching converter can also adopt the peak-current controlling method, which is briefly introduced at the end of chapter5.In chapter6, a prototype is designed and the simulation results of the soft switching, SSLAPF and the overall control system is presented to validate the correctness of the design of the main circuit and the controlling strategy. At the same time, the experiment results are also provided in detail. The simulation and experiment results show that the two feedback control loops of the overall control system cooperate well.In the end, chapter7summarizes this thesis and presents tentative researches and perspectives on some other related issues.