Design Study Of Third Harmonic Brushless Hybrid Excitation Synchronous Generator

The third harmonic excitation generator has adjustable excitation magnetic field and fast electromechanical transient characteristics,and is often used in power system power generation,all-electric aircraft and electrified rail transit.However,this kind of generator has some problems,such as insufficient excitation power,difficulty in starting excitation and the need for brush slip rings.Hybrid excitation synchronous generator includes the advantages of electric excitation synchronous generator and permanent magnet synchronous generator,with permanent magnet excitation as the main and electric excitation as the auxiliary.On the basis of a third harmonic electric excitation synchronous generator,a third harmonic brushless hybrid excitation synchronous generator is formed,and its design,system performance and prototype experiment are studied.The generation mechanism and working principle of harmonic electromotive force of traditional third harmonic brushless electric excitation synchronous generator are analyzed.Taking a third harmonic brushless electric excitation synchronous generator as an example,its no-load performance,load performance,external characteristics and sudden load are calculated,which lays the foundation for designing the third harmonic brushless hybrid excitation synchronous generator.The principle of third harmonic brushless excitation is analyzed.The idea is to use the electromagnetic coupling relationship between the stator side third harmonic winding and the rotor side third harmonic winding to directly transfer the harmonic excitation power from the stator side to the rotor side,thus realizing brushless motor.Three different rotor permanent magnet design schemes are put forward,and the distribution of air gap magnetic density of the motor under the three schemes is calculated respectively,and the arrangement mode of built-in hybrid permanent magnets with radial and tangential magnetization is determined.According to the generation mechanism of rotor harmonic electromotive force,the size parameters and arrangement of rotor permanent magnets,as well as the design of rotor third harmonic winding and excitation winding are completed.The field-circuit coupling model of the third harmonic brushless hybrid excitation synchronous generator system is established.The no-load characteristics,external characteristics,adjustment characteristics and dynamic performance of the hybrid excitation synchronous generator system are calculated and analyzed,and the operation performance of the third harmonic brushless excitation system is verified.In addition,the influence of stator third harmonic winding arrangement,load and air gap size on stator third harmonic winding voltage,and the influence of third harmonic winding turns on harmonic brushless excitation system performance are calculated and analyzed.A prototype of the third harmonic brushless hybrid excitation synchronous generator was developed,and an experimental test platform was built to test the generator’s no-load characteristics,brushless harmonic excitation system performance,external characteristics and adjustment characteristics,as well as the dynamic performance of the generator before and after the third harmonic brushless excitation system was connected.The experimental test results verified the correctness of the design of the third harmonic brushless hybrid excitation synchronous generator.