Magnetothermal Performance Analysis Of Large Doubly-fed Hydro-generators

In recent years,hydropower technology has attracted more and more attention as green and renewable energy.As the core of the hydropower system,the electrical performance and the quality of the output power directly affect the stability of the entire power system.Compared with traditional hydro-generators,doubly-fed hydro-generators have good speed adaptability,can realize two-way energy flow,and can adjust the speed of the generator.At the same time,the demand for electric energy in various fields continues to grow,and the capacity of the generator is gradually increased,resulting in a significant increase in losses during the operation of the generator,and the temperature rise problem of each component has become more severe,which seriously reduces the reliability of the generator operation.Therefore,improving the cooling performance of the generator and using the least cooling flow to achieve the best cooling effect is an inevitable trend in the development of the generator industry.This paper takes a 6.5MW doubly-fed hydro-generator as an example,firstly establishes a finite element two-dimensional electromagnetic field physical model based on electromagnetics,and analyzes the magnetic flux density,magnetic field lines,and air gap of the doubly-fed hydro-generator under rated conditions.The basic electromagnetic properties such as magnetic density and Fourier decomposition,and the loss of the stator and rotor strands and core of the motor are obtained according to the Bertotti core loss calculation model to prepare for the solution of the temperature field.Then,according to the theory of numerical heat transfer and the actual ventilation structure of the generator,a three-dimensional flow-heat coupling physical model is established.First,take 1/2 of the axial direction and 1/24 of the circumference as the solution domain,and attach the corresponding heat density to the metal component area.And analyze in detail the temperature rise of the stator and rotor strands and the stator and rotor cores of the generator under rated conditions.Further,in order to study the influence of channel steel on the generator,a single radial air duct in the axial direction is selected as the solution domain,and four schemes are proposed,and the temperature rise of each scheme is analyzed separately.By comparing the difference of the calculation results,an optimal solution is obtained.At the same time,the temperature field changes before and after the use of magnetic slot wedges are compared,and the influence of insulation aging on the generator is finally analyzed.The research results of this paper lay a theoretical foundation for the analysis of the magnetic field and temperature field of the large-scale doubly-fed hydro-generator,and at the same time provide a reference for the structural design of the radial ventilation channel steel of the generator and the optimization of the ventilation performance.