Research On Direct Torque Control On Electrically Excited Synchronous Motors

Direct torque control (DTC) which has been developed after vector control in recent years, is a new technology in domain of variable frequency adjustable speed AC -drivers. It has many merits, its structure is very simple and the principle is clear, and the response of torque is rapid and little dependence on the interior parameters of the motors, and easy digitization. Recently, many scholars and experts focus on it in domain of AC-drivers.Electrically excited synchronous motor (ESM) has been widely applied in high voltage and high power of motor speed control system because of its advantages of adjustable power factor and high efficiency. Under the process and energy saving consideration, variable frequency speed regulation is the most economical and reasonable way to high power of AC-motors. Therefore, research and development of high-performance direct torque control system of electrically excited synchronous motor is of great economic value. This paper gives a preliminary study about theory and practice on direct torque control system on electrically excited synchronous motor. The main work of this thesis as follows:Firstly, it is analyzed the basis of theoretical of direct torque control system on electrically excited synchronous motor. The mathematic model of salient-pole synchronous under the natural axis and d-q axis has been given. It is discussed the relation between space voltage vector and stator flux. Some control strategies about stator flux and torque and rotor excitation current have been analyzed about direct torque control system on electrically excited synchronous motor in details.Under the theoretical research of direct torque control system on electrically excited synchronous motor, simulations have been done. Because there isn't simulation model about electrically excited synchronous motor in Matlab/Simulink, Per-unit value of simulation model has been build by S-function. And also some units of direct torque control system have been build and also the overall system simulation model have been presented. It is detailed analyzed the waveforms under the load disturbance, speed of mutation and high power factor.Under briefly introduced two structure of real-time recurrent neural network, this paper attempts to apply real-time recurrent neural network on stator flux. Learning algorithm of real-time recurrent neural networks has been given. Stator flux observation based on real-time recurrent neural networks has been presented. Simulations show that the stator flux based on recurrent neural network on direct torque control system has better static and dynamic performance. Improved the torque ripple and current distortion and non-ideal of low speed about direct torque control.Finally, a preliminary validation on direct torque control system on electrically excited synchronous motor has been carried out. Some mainly hardware units of direct torque control system has been built. And the software flow charts of the system have been given.