(A) study on high performance drive system of PM synchronous motor

Abstract

The drive and control techniques of the PM synchronous motor for applying the high performance drive system are presented. There exist some problems and limitations in the PM synchronous motor drive system. One of the most serious problems is related to the hardware of the PWM inverter and the other is disturbance problem caused by the harmonics in the linkage flux and the load variations. Therefore, in this dissertation, main topics are solutions of the problems above mentioned for high performance drive system of the PM synchronous motor. In a PWM voltage source inverter, since a switching device has finite switching times, a dead time should be inserted in a PWM switching signal in order to prevent the simultaneous conduction of two switching devices in each leg of the inverter. Since both switching devices in each leg are off during the dead time, the output voltage is dependent on the direction of an output current. These cause a distortion of the inverter output voltage, which is called as `dead-time effect`. The distortion of the inverter output voltage affects machine currents, which results in a phase current distortion, torque pulsations, and degradations of control performance. Moreover, the dead-time effect including effect of switching time is varied with operating conditions such as DC link voltage and currents. In order to compensate the dead-time effect, three on-line dead-time compensation methods using simple disturbance observer or time delay control are proposed. The dead-time effect can be considered as voltage disturbance of the inverter and the voltage disturbance is estimated by using proposed methods and fed to voltage commands. The second problem is about the disturbance torque which is generated from internal and external sources. The internal disturbance torque is due to the non-ideal characteristics of the flux density distribution of a PM rotor. The external disturbance torque is caused by the load torque and load parameter variati...