The Research On Control Method Of Variable Speed System Of Multi-phase Permanent Magnetic Synchronous Motor

Multi-phase Permanent Magnetic Synchronous Motor (PMSM) variable frequency variable speed system is becoming one of the emphasis in electric drive fields for it's high reliability. Multi-phase PMSM is usually used in situation of high reliability, military and high power transformation, such as circulation water motor in nuclear power station and warship propulsion system etc.. This kind of Variable Frequency Variable Speed (VFVS) system is tested successfully in electrical propulsion system of foreign submarine, however, there are still many problems about it's controlling method in theory and in practice, especially they are lack of systemic research on controlling strategy when one or more phase of multi-phase PMSM is opened.Multi-phase PMSM VFVS system is deeply studied in this paper, and controlling strategy on multi-phase PMSM when faults occurred is emphasized, technique mentioned in this paper and the conclusion of this paper have very important meaning for improving performance of multi-phase PMSM after its' broken faults. This paper include the following contents:(1) The mathematical model of multi-phase PMSM is established and the analysis method of harmonic wave are given out under the supply of inverter. In the second chapter of the paper, making use of voltage vector space, multi-phase PMSM model is decoupled to some planes plumb each other via conversion of canonical base to harmonic wave base which provided theoretical basis for deeply and systemic understand of multi-phase PMSM. Mathematical formulae of harmonic wave and potential of a random 'm' phases PMSM are given out and quantitative analysis on harmonic wave torque of PMSM impressed by different space-time harmonic wave, which offered theoretical foundation for choosing a right phase of PMSM.(2) Field-oriented decoupling control of multi-phase PMSM is realized in this paper. AC machine is an electric-magnetic system of multi-variable, nonlinear and tighten coupled. Comparing with general three phases synchronous motor, multi-phase PMSM is a system of more variable, nonlinear and tighten coupled. Precision torque control can't obtained in traditional stationary coordinate system, and in the third chapter it is described that the mathematical model of multi-phase PMSM on multi-phase stationary coordinate to based on synchronous reference frame system that permanent flux linkage ψf is in d axis. A calculation method of transformation matrix based on invariable power and invariable magnet-motive forceis put forward. In new coordinate, multi-phase PMSM's decoupling control is realized by setting the multi-phase PMSM stator d axis component /, = 0, and then multi-phase PMSM could keep the same torque control performance, similar to separately DC excited motor. Aim it at the shortage of the traditional PI modulator, a Fuzzy-PI double module modulator combined nonlinear fuzzy control with traditional linear PI modulator is put forward and which is used to modulate speed of multi-phase PMSM to improve dynamic performance of variable speed system and to overcome the influence of parameter variety to the system. It is verified by simulation results.lt is showed that dynamic performance of the new double module controller is better than traditional PI modulator.The position angle of rotor flux linkage must be known in field-oriented decoupling control of multi-phase PMSM, and its usually by encoder which connect the axis of the motor or by rotating transformer to get information of position angle 8, however this method increases the cost of the system and reduces its' reliability. In this paper an method is obtained which estimate rotor position via each phase's voltage and current, The method don't need to change structure of multi-phase permanent motor and it also fits to salient pole and non-salient pole permanent synchronous machine and has good position precision in very wide speed scope inside.(3) Control strategy of multi-phase PMSM's asymmetrical running is systemic studied. Compared with traditional three phase PMSM, the most important advantage of multi-phase PMSM is its' strong reliability. By changing controlling strategy propriety multi-phase PMSM can keep nice performance of speed modulating when faults are happened such as one or more phases are opened. The state of Multi-phase PMSM asymmetrical running is that one or more phases of stator winding or invert is opened, and then the magnetic potential distribution produced by winding is asymmetrical in space. In this paper, it is described firstly that decomposition control of torque by general field-oriented control isn't obtained when one or more phases of multi-phase PMSM are opened. Because the impulsive motion component changed with position angle 9 in torque equation, the performance of speed variable is dropped greatly. Aimed at multi-phase PMSM asymmetrical running, two kinds of compensating control strategies are obtained in chapter 4 and chapter 5 respectively, i.e. compensating control strategy based on invariable stator magnetic potential and field-oriented decoupling control. The former is based on invariable stator magnetic potential by adjusting current amplitude and phase angle of surplus normal phases to compensating magnet potential losses of open phases, and different compensating...