Permanent Magnet Synchronous Motor Drive Technology Research

In electrical drive applications, three-phase drives are widely used for theirconvenience. However, with the advent of modern power electronics, computertechniques and control theories, the inverter-fed motor drives remove the limitation onthe number of power supplies and machines phases. Especially in the applications ofhigh power, high reliability, and low dc bus voltage, multiphase drives show severaladvantages over three-phase drives. Therefore, multiphase drives are very suitable forship propulsion, electrical/hybrid vehicles, aerospace applications and high powerapplications. Multiphase drives expand the research field of electrical drives andfascinate researchers all over the world.This study analyzes motors with any number of phases firstly, and focuses on thedevelopment and application of five-phase PMSM drives. The organization of thisstudy is as follows:By using Winding Function theory, the MMF time-space harmonics distribution ofsymmetrical multiphase windings with any number of phases is analyzedquantitatively, which demonstrate that the low order time-space harmonics play a veryimportant role in multiphase motors. Generalized Park's Transformation is provedbased on Symmetrical Component Transformation for the first time, and modeling ofn-m winding induction machines is developed. It is clearly indicated that multiphasemachine drives are multi-dimensional. All of above are very useful and lay thetheoretical foundation for the following researches.Park's Equations of five-phase PMSM are obtained, and research is carried out oncoupling between d-q subspace and generalized zero-sequence subspaces based on themodel. In addition, multi-dimensional vector control and decoupling control aredevelpoed according to the different characteristics of model of the motors withdifferent structures.By the analysis of the multiphase motors model and the traditional SVPWM, anovel SVPWM strategy, which is based on the idea of multi-dimensional orthogonalvector space, is developed. It not only provides the foundation for themulti-dimensional vector control but solves the stator current harmonics problem;otherwise the harmonics would be uncontrollable if traditional SVPWM were applied.Modeling of five-phase PMSM with one phase open is developed from the point ofview of symmetrical winding structure for the first time. Current commands fordisturbance-free operation are presented. Also, fault-tolerance control methods offive-phase PMSM are discussed, one of which is implemented by extending carrierPWM based on effective time.Experiments have been conducted on a 5kW five-phase PMSM by using TMS320LF2407A DSP to systematically test and compare current harmonics and torque usingtraditional SVPWM and the novel SVPWM. The experimental results are consistentwith theoretical studies and simulation analysises, and further demonstrate thefeasibility and practical significance of the five-phase PMSM drives developed.