Study On Direct-Driven Permanent Magnet Generator And Brushless Doubly-Fed Generator For Variable Speed Constant Frequency Wind Power Generation Systems

Variable speed constant frequency (VSCF) has been becoming the main operation mode of large wind power generation systems due to its high utilization ratio of wind energy, there are basically two kinds of VSCF wind generators: the low speed direct-driven permanent magnetic synchronous generator (PMSG) and the high speed doubly-fed generator with multi-stage gearbox.The different structures for VSCF wind power generators are theoretically analyzed and experimentally studied, the contents of this are following:1. The doctoral dissertation presents a comparative study on the performance and key technology of the VSCF low-speed direct-driven, mid-speed half-direct-driven and high-speed wind power generators with the same rated power and different structures acoording to their structures, performance, control technique, reliability as well as cost.2. The effect of pole-slot number combination and phase numbers on the performance of DPMG is analyzed, the choice method of pole-slot number combination, pole-arc coefficient to reduce cogging torque and enhance output power is discussed. How to solve the problems of the transportation limit of railway and highway and the large size of the high-power, low-speed direct-driven PMSG, the structure of direct-driven PMSG with inner rotor and outer rotor combination is proposed, the interior of multi-poles, large-size machine is sufficiently ultilized. The beavior of the 5MW PMSG with inner rotor and outer rotor combination is studied.3. Based on field-circuit coupled analysis, the direct-driven PM generators of 1.5MW and 3MW are designed, the operation characteristic is therotically analyzed and experimentally studied. The prototype of 1.5MW direct-driven PM generator has operated for two years, the operation results show that the design of 1.5MW direct-driven PM wind generator is feasible and practical. 4. In order to solve the problem of brush, slip ring and periodical maintenance of doubly-fed machine, the performance of brushless doubly-fed machine for VSCF wind generation system is basically studied to enhance the operation relibibity of wind generator, the principal of magnetic field modulation and the performance of brushless doubly-fed machine for different rotor structures are analyzed. The barrier rotor structure of brushless doubly-fed generator with low cost and high reliability is presented.5. The prototype with barrier rotor of brushless doubly-fed generator is designed. The performance of simulation and experiment for the variable speed constant frequency brushless doubly-fed generator is studied, these results show that the brushless doubly-fed machine with barrier rotor is suitable for the VSCF wind power generation. On these basis, the high power brushless doubly-fed generator is designed, the operation characteristic is analyzed based on field-circuit coupled method, the new hybrid rotor structure with barrier rotor and cage combination of brushless doubly-fed machine is proposed, the output power of the generator is greatly increased under the same condition of the volume and operation.