Design And Analysis Of A Twelve-Phase Flux-Switching Permanent Magnet Wind Generator

Multiphase flux-switching(FS)permanent magnet(PM)(FSPM)machines have broad application prospect in wind power generation which requires high power,high reliability and strong fault-tolerant capability,due to the inherited advantages of both multiphase windings and FS machines.Based on the solid research accumulation of the research group on novel stator-PM machines and wind power generation technologies,a twelve-phase FSPM generator is proposed in this dissertation.This generator has both structural merits of robust rotor,easy thermal management and modular design,and excellent performances of high power,strong fault tolerance,low torque ripple and high overload capability,which becomes one of the development directions of the MW-rating wind power generator.This dissertation focuses on the design and analysis of the twelve-phase FSPM generator,including the general design rules of multiphase windings,the optimization process of dimensional parameters,the mathematical modeling and the analysis of electromagnetic performances.This work has laid a good foundation for the development of high quality wind power generation system,with following achievements obtained:1.The general design rules of multiphase winding configurations are investigated through deriving the mathematical relationships between torque/rectified voltage and the phase shift of the multi-star windings.The optimal phase shifts for the lowest torque ripple and/or the lowest DC voltage oscillation are analytically obtained and the influence of phase number on torque/DC voltage characteristics is concluded.The analytical results are verified by finite-element(FE)analysis and experimental tests on a twelve-phase FSPM prototype machine with different multiphase winding topologies.2.The differences between generator design and motor design are concluded in terms of design considerations and methods,which provides some instructions for the design of the multiphase FSPM wind generator.The design considerations for wind generators are given explicitly,such as the output power,the cogging torque and the voltage regulation factor.The importance of the FE co-simulation method connecting the generator with the external circuits is emphasized for the generator design.3.The design procedure of the multiphase FSPM generator is presented,including the selection of the phase number,the combination of stator-/rotor-pole numbers,the determination of rated specifications and design considerations,and the optimization of key design parameters,according to the features of FSPM machines and the requirements of the direct-drive wind power generation system.Finally,the optimal twelve-phase FSPM generator topology is obtained by comparing the electromagnetic performances of the candidate generators with four stator/rotor-pole combinations.4.The co-simulation system of the twelve-phase FSPM generator connected with resistive-load circuit is set up based on ANSYS/Maxwell to predict the open-circuit and on-load generating performances at different loads and rotor speeds.The main characteristics including cogging torque,output power,electromagnetic torque,voltage regulation factor,efficiency and overload capability meet the demands of the wind power system.5.The mathematical model of the twelve-phase FSPM generator is established based on the idealized model of the twelve-phase inductance matrix and a novel transformation from the stator reference frame to the rotor reference frame.During the transformation process,the twelve-phase winding is considered as four three-phase subsystems which are transformed separately by four three-phase transformation matrixes and then integrated in rotor reference frame.The output voltage,flux-linkage,torque and output power equations in d-q reference frame are provided for the analysis and control of the twelve-phase generator.6.The static characteristics and generating performances of the twelve-phase FSPM generator and twelve-phase PM synchronous generator(PMSG)are comparatively analysed based on FE prediction.The differences between the two generators' performances are explained through voltage phasor diagram,showing that the winding inductance has great influence on the voltage regulation factor and hence the generating capability.7.The 10 kW prototype of the twelve-phase FSPM generator is manufactured and the experimental platform is set up for the measurement of the generator's performances,including the output power,mechanical torque,efficiency,voltage regulation factor,overload capability and winding temperature rise at different operating conditions.The test results meet the rated specification,verify the effectiveness of the generator design and accuracy of the FE analysis and mathematical derivation.