Design And Research Of5MW Permanent Magnet Synchronous Generators For Wind Turbines

With the fossil energy slowly draining away, more and more attention has been paid to the wind energy, which is a kind of abundant, endless, widely distributed, clean, safe and renewable energy. In recent years, wind generator has a great development in the field of wind power generation and its tendency is Permanent Magnet Synchronous Generator (PMSG) and larger capacity. At the same time, there are more and more strict requirements on the operation performance of the wind generator. In this paper, according to the design requirements, a5MW PMSG is designed, the structure is optimized and the electromagnetic properties are analyzed and verified. Details are as follows:1. According to the design requirements, select the appropriate type of the PMSG and determine the basic magnetic circuit structure of the generator, which is designed to be a radial interior PMSG. By combining the design principle and requirements, the main dimensions are calculated, such as the inner and outer diameter of the stator, the axial length of the generator. Through analyzing some key design parameters such as stator slot, the armature winding, the air gap length, the permanent magnet and the flux barrier, the basic design program of the5MW PMSG is obtained.2. Due to the cogging torque which is caused by the interaction of permanent magnet and the slotted armature lamination, there are torque ripple, accompanied by vibration and noise when the permanent magnet machine operators. Cogging torque must be considered and reduced when a high performance is required. This paper obtains the expression of cogging torque through combining the energy method and Fourier decomposition by some equivalent and assumptions. By analyzing the coefficients of the Fourier decomposition which play an important role in the cogging torque, several methods for reducing cogging torque are obtained, such as changing the stator slot width, changing the pole arc-coefficient, changing the air gap ratio, etc. The effectiveness of the above methods is verified by the Finite Element Method (FEM). Based on this research, the structure of the5MW PMSG can be optimized.3. By designing and optimizing the structure of the5MW PMSG, the final design program is determined. By using the Ansoft Maxwell finite element analysis software, all kinds of operating conditions such as no load, rated load, and short circuit are analyzed. Through simulation and calculation, the cogging torque, rated torque ripple, voltage waveform distortion rate are all less than2%, complying with the design requirements. The rated power is5429kW,14kW more than expectation, also complying with the design requirement. Then through the analysis of three phase sudden short circuit, two phase grounded short circuit and two phase sudden short circuit respectively, short circuit current, electromagnetic torque, demagnetization situation of the permanent magnet are obtained. The result shows that only a very small area of the permanent magnet end appears demagnetization.