| The micro-turbine power generator system is one of the important study regions in the distributed power system. The rotational speed of high speed generator directly driven by micro-turbine is usually from several ten thousands to some hundred thousands rpm. Active magnetic bearing (AMB) attracts great attentions because of the advantage of without mechanical touch, no failure and free lubrication compared with the traditional bearing. In this thesis, the control system of magnetic bearing is studied in-depth. The main works have been done as follows:1. The mathematical model based electromagnetic force analysis of the magnetic bearing is established. The magnetic bearing uses a PID closed-loop control because of open-loop instability. The transfer functions of magnetic bearing system with differential forward PID and conventional PID are deduced respectively.2. Compared with the conventional two-level PWM power amplifier, the three-level main circuit of PWM power amplifier system for half-bridge main circuit is proposed. The current ripple and fluctuation of electromagnetic force can be reduced, which has been proved by experiment.3. Based on MATLAB/SIMULINK, the dynamic characteristics of magnetic bearing control system with differential PID controller and three-level PWM amplifier is simulated and compared to the conventional PID controller with two-level PWM power amplifier. The simulation result shows that the precision of rotor position can be improved with this method.4. The analog control system of magnetic bearing is studied. Each part of hardware circuit has been tested. The whole experiment has been done. The stable suspension rotor of high speed machine has been received in the experiment.
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