Research On The Control Technologies Of Multiphase Induction Machine

Compared with three-phase motor drive system, multi-phase motor drive system has the advantages such as high power, high reliability and low dc power supply, however, as a new technology, the control of multi-phase machine has still some problems which are worth to be researched and probed in theory and practices. This paper has researched deeply on the theory of the multi-phase induction machine in detail and the control technology of SVPWM, direct torque control and operation in phase-fault conditions.The paper analyzed the winding structure of multi-phase machine firstly, using space vector decoupling, the multi-phase induction machine was decoupled from m dimension to some vertical harmonic sub-spaces, and the mathematic model under harmonic-base for the multi-phase induction machine was built. Then, the time and space harmonics and harmonic torque of the machine supplied by six-phase inverter were analyzed. The simulation studies of modeling six-phase induction machine and its characteristics were performed.The technology of space vector PWM for multi-phase machine was researched. Aimed to the shortage of the conventional SVPWM, a new SVPWM control method was presented based on zero-sequence balancing vector. This method simplified the algorithm of multi-phase SVPWM from multi dimensions to two dimensions, synthesized the vector in the d-q subspace based on zero-sequence voltage vector equaling to zero, it could satisfy the voltage-second balance at the d-q subspace and zero-sequence subspace at the same time, solved the uncontrolled current harmonic in zero-sequence subspace, the stator harmonic current was effectively restrained.According to the characteristics of multi-phase machine, an identification method was presented for the stator resistance of multi-phase machine which through observing harmonic current in zero-sequence subspace and by the recursive least squares estimator identification algorithm, the on-line identification of stator resistor and the leakage inductor was implemented.The effect on flux-linkage and torque of the voltage vector for the multi-phase induction machine was analyzed, a scheme of voltage vector selection for direct torque control of the multi-phase induction machine was given; a new direct torque control algorithm was described based on zero-sequence balancing vector; under this basement, a fuzzy direct torque control strategy was presented based on torque predicting. This strategy hardly used the parameters of machine in calculating and is well robust, it not only restrained the fluctuation of flux-linkage and torque, but also kept the advantage of conventional direct torque control.This paper analyzed and researched the operation of multi-phase machine with phase fault conditions systemically. The dynamic model with phase fault for the multi-phase machine was established. The performances variation and capability of loading under phase fault was analyzed in detail. By analyzing of torque pulsation under phase fault, a compensating control strategy was presented to restrain the torque fluctuation, the strategy not only removed the torque ripple at phase fault, but through the winding equivalent transforming, the asymmetric system was transformed into symmetric ones, the flux linkage orient decoupling control was achieved with phase fault condition.Taking the six-phase machine as object, the simulation and experiments researches were completed for the presented control strategy of SVPWM, direct torque control, and running with phase fault. The results verified the theoretical analyses and the validity of the control strategies.