Research On The Internal Composite-rotor Controllable-flux Permanent Magnet Synchronous Motor And Control Method

The operation range of Permanent Magnet Synchronous Machines (PMSMs) is limited because the flux of the rotor cannot be changed. The problems of many studies are the capability of flux weakening is too small, the structures are too complex, and the loss of the motor is too high. This paper analyzed a new type PMSM-the internal composite-rotor controllable-flux PMSM which get rid of the disadvantage of the controllable-flux motor given by Vlado Ostovic. The motor can memorize the level of the flux after the flux of the rotor is changed, so it can also be called Memory Motor.In Memory Motor's magnetic circuit, the flux can be strengthened when the AlNiCo magnet is positively magnetized or be weakened when the AlNiCo magnet is reverse magnetized. On magnetic hysteresis cycles, it can be find that the NdFeB has litter effect and the AlNiCo in properly size can be change the operating point by the magnetic motive force from the stator. The result of the finite element analysis of the two prototypes is shown that the magnetic density in the air gap between the two extreme statuses is changed more than four times without load. The test of the prototype gave a magnetic density and magnetic motive force curve, which is similar to its hysteresis cycle, which prove that the memory motor is a feasible design. According to the model and control strategy of the normal PMSM, the mathematic model of the memory motor is analyzed and the control method is designed. When the motor need not change the flux of the rotor, the id=0 strategy is adopted. The stator current iq is controlled by speed regulator. And then the dq variables are transformed to three phases current to control the motor by the current relay regulator. When the flux of the rotor need be changed, an impulse of the id will be created. The magnet in the rotor will move their operating point to new position. The status of the magnetic field in the rotor will be changed. And then the motor come back to the steady status which also uses the id=0 control strategy. The normal PI regulator can not adapt the process quicly because the current and the magnetic field will change tempestuously. So a Fuzzy-PI switch regulator is designed. After the fluctuating process fade away, the simply PI regulator will replace it to get better steady effect. At last a DSP based speed control system is present, which considered both the hardware and software.