Research On The Control Optimization Of Doubly Salient Electro-Magnetic Motor Starting System

Doubly salient electro magnetic motor has the advantages of simple and reliable structure, convenient manufacture, flexible adjustment of the air gap flux etc. And it can realize the integration of starting and power generation, so it has a broad application prospect in the field of aviation power supply. But it has the problem of large torque ripple when running as a starter. Position sensors are required to provide accurate location information for commutation. These reduce the performance of the starting system, but also limit its application. This project is devoted to the study on the control optimization of DSEM starting system, which includes control strategy optimization and sensorless control technology of low speed starting.In this paper, a 18 KW 12/8-pole DSEM is proposed. The mathematical model of the motor is developed, and the mechanism of the torque is expounded. The basic electromagnetic characteristics are analyzed by the finite element software, which lays the foundation for the research of the control strategy in starting procedure. The three common control strategies of DSEM are analyzed in detail from aspects of the commutation, the circulation of inactive phase, and the torque characteristics. The analysis shows that :the windings will feedback energy to the power supply because of the flowing current when commutating under the three-states control strategy; the inactive phase’s circulation problem is relatively serious under three-states advanced angle control strategy; the six-states control strategy solves the circulation problem and makes the motor get optimal torque characteristics.In this paper, the sensorless starting technique of DSEM is also studied. Four initial position detection methods are proposed based on the basic principle of pulse injection. 1) The whole period of the series inductance is re partitioned, and the judgment logic is optimized to avoid the initial location failure caused by the low accuracy of current detection; 2) Accurate rotor position can be obtained by fitting the function relationship between the peak current and the position of the rotor. 3) A phase inductance comparison method and its improved algorithm is proposed based on the terminal voltage of the inactive phase, which can be used as the backup of the current response method. 4) A kind of accurate position initialization algorithm base on the phase inductance linear partition model is proposed, which is not affected by the variation of bus voltage.In this paper, a low speed sensorless control method based on voltage pulse injection is put forward, which realizes the start in the position closed loop. The effect of armature reaction on the ideal commutation point is also analyzed. And it is pointed out that the armature reaction is caused by the distortion of the inductance waveform, but it does not make the ideal commutation point shift. At the same time, the error analysis of the method is also carried out, which shows that the maximum error is the width of a combined pulse. Finally, the hardware system and the flow chart of software program are introduced, and the experimental verification is carried out.