On The Interaction Between The Maglev Power Convertor And The Magnetic Levitation Control System Of Maglev Train

The power supply for maglev levitaion systems (called as maglev power convertor, MPC) is an important power convertor equipment on the vehicle. Installed capability and transient performance are the key features of MPC, which greatly affect the performance of the maglev control systems (MLS). In the experiments, the output voltage and current of MPC changes greatly and even becomes unstable under the condition of over loading. This phenomenon will lead to the over-current protection of the MPC, the failure of the MPS and then affect the running of maglev trains. To solve these problems, the interaction influence between MLCS and MPCs,the regulation control technology of the output voltage, and the design method of the performance parameters of MPC are researched in this paper.Firstly, the whole system consisting of the MPC and MLCS is modeled. On the basis of this model, the influence of the MLCS to the output voltage and current of MPCs and the stability of the maglev power control system (MPCS) are analyzed under various working-conditions, which points out that the main reason why MPCS becomes unstable is that the impedance of the MLCS is negative. It can be solved by increasing the capacitance or decreasing the equivalent series resistance of the output capacitor of MPC. Finally, the methods of suppressing the interaction between MPC and MLCS, and minimizing the ripple of the output voltage are proposed, which include optimizing the control law and improving the output stage circuit of the MLPS, optimizing the switching mode and increasing the input capacitance of the maglev chopper, and so on. The experimental results show that the fluctuation of the output voltage and the current can be decreased by 10% using these methods.Secondly, the methods of designing and optimizing the performance parameters of MPCs, including installed capacity, output voltage and slew rate of output current, are studied. First of all, the relationship between the steady/dynamic output power and the levitation power loss are investigated. On the basis of this, the design criterion of the installed capacity is proposed: the nominal installed capacity can be chosen as the sum of the rated steady power and the maximum dynamic power, and the maximum installed capacity should equale to the sum of the maximum steady power and maximum dynamic power. This requirement can be reduced by 40% with the strategy of restricting the range of the dynamic output power and improving the levitation-up algorithm. Secondly, the relationship betweent the slew rate of output current and the electromagnet current is studied. The results show that the design criterion of slew rate of output current that the nominal slew rate of output current should equal to the slew rate of the electromagnet current, which can descend 50% by modifying the format of the connectin between the electromagnet and the maglev amplifier, and by saving the dynamic powe loss of MLCS. Finally, the practical design criterion of the output voltage according to the instant ouput power and the maximum dynamic power of MPC is proposed, and the application to the low-speed maglev train shows that this method is available. Finally, the implementation and experiments of the MPCs are performed. A 60kW engineering demo convertor is designed and developed according to the proposed design criteria. Its steady and transient performance is separately tested in the system of a single maglev bogy and a whole train. The results show that the required performance is fully satisfied. Considering that auxiliary power supplyment is widely equipped on the vehicles, the output performance of the designed MPC parallel with Ni-H or Ni-Cd battery is tested. The experimental results illustrate that the response speed of Ni-H battery is faster, and it can be used as the auxiliary power supplyment for the maglev trains.