A new method for vector control of high power synchronous motors

SUMMARY Ph. D. Thesis A NEW METHOD FOR VECTOR CONTROL OF HIGH POWER SYNCHRONOUS MOTORS Ahmet ORHAN Firat University Graduate School of Natural and Applied Science Department of Electrical and electronics Engineering 1999 -Page: 101 In the control of an AC motor the aim is to obtain the performance of DC motor. To achieve this goal increases the cost. It is generally possible to classify the control methods as scalar and vector control methods. Although scalar control methods are cheaper, they cannot provide the performance of a DC motor. Therefore, it has become unavoidable to use the vector control method in a system where the performance of a DC motor is desired. The inverters to drive induction motor require a complex switching system to obtain a sine wave form. However in vector control it is necessary to do calculations which force the capacity of microprocessor. In vector control applications, synchronous motors can be more attractive than the combinations of motor inverter drives even though they are expensive, due to their economy in service. In this study, a comprehensive literature research has been done about synchronous motor control methods. As a result of this research, the problems on drive systems with synchronous motors by inverter fed are defined. Direct current motors, induction motors and synchronous motor drives were compared. The dampers and silency effects of rotor on motor were investigated in detail. The unity power factor control of the synchronous motor fed by self-commutaded current source inverter was investigated. During this investigation, the mathematical modelVI of synchronous motor in rotor reference frame was established. The simulation program of this model was also prepared. In this study, an alghoritm was presented. The alghoritm determines the magnitude of the compensation capacitor which shows large effects on the cost. The mathematical model of the synchronous motor and inverter system, which is also called compensated current source converter, was presented. The problems on the drive and solutions of these problems were presented. Finally, the unity power factor vector control of the synchronous motor fed by compensated current source inverter (CCSI) was studied. The effect of the control of the unity power factor on the capacitor size was determined. It is hoped that the results from this study provide a new point of view for synchronous motors with high performance and variable speed drive. KEY WORDS: Synchronous motor, vector control of synchronous motor, field oriented control of synchronous motor.