Basic Research On New Hybrid Excitation Brushless Synchronous Generator

Hybrid excitation is an combination of current excitation and permanent magnet excitation.It has the characteristics of high efficiency and high power density of permanent magnet machine and flexible magnetic field adjustment ability of electric excitation machine,which can be applied in wide fields and has excellent performance.However,some hybrid excitation machines have shortcomings in structure design,such as the series connection of permanent magnets and excitation windings,which has lower excitation efficiency and easily leads to irreversible demagnetization of permanent magnets.Even though some structures are parallel connection,the stability of operation and the convenience of maintenance are reduced obviously due to the existence of brush and slip ring.In order to solve the problem and improve the performance of hybrid excitation machine,we study a new hybrid excitation brushless synchronous generator.This generator adopts induction excitation,and its excitation winding is installed on the stator,and its induction winding is installed on the rotor.The design avoids the installation of brush and slip ring and it can adjust air gap magnetic field by changing induced current in rotor inductive winding.At the same time,it could make the excitation of electric windings and permanent magnets into parallel excitation through the reasonable structural design,and so the generator has a good magnetic field adjustment capability.The main works of the thesis are as follows:1)Structure design and principle analysis of the hybrid excitation generator.This part introduces the structure of the new hybrid excitation generator,the operating principle of induced-excitation and the design of the parallel excitation structure,besides,it points out the advantages of the generator compared with other hybrid excitation machines.After that,the operating principle of the generator is explained.At the same time,this part gives a detail introduction of the design parameters and the specific structural parameters of the machine:Finally,we give the winding methods of the three-phase armature winding,the excitation winding and the rotor induction winding,and the number of turns and the wire diameters are also described in detail.2)The equivalent magnetic circuit analysis of the hybrid excitation synchronous generator.Based on the operating principle of the generator,this part establishes an equivalent magnetic circuit model for the generator.The calculation method of the magnetomotive forces are introduced in detail,and the relationship between the stator excitation current and the magnetomotive force of the induction winding is analyzed detailedly.The calculation method of the magnetic reluctance in each part of permanent magnet magnetic circuit and induction winding magnetic circuit are described as much as possible.At last,the results of equivalent magnetic circuit method are compared with the results of two-dimensional finite element simulation to verify the effectiveness of magnetic circuit method in the design of hybrid excitation machine.3)Finite element simulation and analysis of the hybrid excitation synchronous generator.According to the structure design and parameters of the generator,a two-dimensional finite element model is constructed at first,and then the magnetic field of the machine is analyzed through it.After that,the no-load operation characteristics,load characteristics and regulation characteristics are simulated and compared with the operating characteristics of the permanent magnet synchronous generator and the induction-excitation synchronous generator at the same size,which demonstrates the superiority in power output and magnetic field regulation of the hybrid excitation machine.Besides,the effect of rotor groove size on magnetic properties and effect of polar arc coefficient on generator performance are studied.Finally,we find the design of unequal air gap could not only make the machine has a good magnetic field regulation capability,but also make the torque fluctuation at a low level.4)Experimental research of prototype.We first make a prototype of the new hybrid excitation synchronous generator and then set up an experimental platform for it.The no-load operation characteristics,load characteristics and regulation characteristics of the prototype are studied experimentally on the experimental platform,and the experimental results are compared with the results of two-dimensional finite element simulation.The two simulation results are compared and analyzed carefully to verify the rationality of the hybrid excitation generator designed in this thesis.