The Study For Design Of A7MW Direct-Drive Interior Permanent Magnet Wind Generator

The development of new sources of energy is promoted by the energy crisis and the environmental problems. As a kind of green and renewable energy, wind energy has become the third major electric source besides coal-fire power and hydroelectric power. The wind power generation has great potential of large scale production and commercial prospect among all kinds of renewable energy. As the generator is the core component in the wind power generation system, wind generators design is one of the key technologies which boost the wind power industry. To increase the power density, efficiency and reliability, large-scale direct-drive generators are preferred for wind power generation. Interior permanent magnet (IPM) machines, characterized by high torque density, light weight, compact size and high reliability, could be strong candidates for large-scale direct-drive wind generators. This thesis conducts an in-depth research into the key technologies of large-scale IPM generators by designing a7MW direct-drive IPM generator.Firstly, the analytical model and performances of large-scale IPM generators are studied. An improved analytical model to calculate the inductances of the interior permanent magnet (IPM) machine is presented, equipped with either fractional slot concentrated windings or distributed windings. Subsequently, research on the FSCW and the machine topology is carried out to find the best winding configuration for large-scale direct-drive IPM generators. The demagnetization characteristic of IPM generator and the influencing factors are analyzed, and a method is proposed to improve the anti-demagnetization ability. The electromagnetic forces and the vibration characteristics are also studied, considering the influences of the air gap permeance harmonics due to slot opening, the IPM rotor topology, the slot-pole combinations and the rotor eccentricity.An integrated design method is developed for large-scale direct-drive IPM generators. Taking the optimal weight and cost as design object, the key design parameters are optimized, including the aspect ratio, the pole number, the tooth width, and the size and grade of the permanent magnets. After the preliminary design, the detailed design and parameter modification are conducted to achieve a complete design which meets the processing and assembly requirements.An approach to check the electromagnetic performance of large-scale direct-drive IPM generators is presented based on the aforementioned generator design. Above all, the torque ripple, voltage quality and power factor are checked at rated condition. Furthermore, the losses and the efficiency are accurately calculated, and the temperature rise is also reviewed to ensure the safety of the insulation and the permanent magnets. Finally, the output performance of the generator is analyzed in view of the changing wind condition.The worst fault condition of a large-scale direct-drive wind generator is considered in the output performance analysis and the strength check of the supporting structure. It reveals reliable power output performance is guaranteed even at serious fault conditions.