Study On Electrically Excitation System Of A Novel Brushless Synchronous Machine

Electrically excited brushless synchronous machine is a new kind of motor proposed inrecent years. It not only has the advantages of a conventional electrically excited synchronousmachine, but also has some other advantages such as brushless structure, low maintenance feeand high reliability. It can be used in a variety of occassion, especially for wind power,inflammable and explosive occasions.There are two sets of windings on the stator which havedifferent pole numbers, one is a2p-pole three-phase armature winding which is directlyconnected to grid; the other set of winding is a2q-pole single-phase field winding which needan excitation current. The rotor of this machine is a magnetic barrier rotor. However, there isno suitable excitation control system can cope with this kind of machine, therefore, anelectrical excitation control system was designed and manufactured in this thesis for the bestperformance of this machine.Firstly, working mechanism of electrically excited brushless synchronous machine wasstudied in this thesis. The special stator and rotor structure was introduced and compared withtraditional brushless electrically excited synchronous motors, to clarify the purpose of thisstudy.Secondly, a finite element analysis model of electrically excited brushless synchronousmachine was established by using the finite element simulation software Ansoft Maxwell, asimulation model of excitation control system was established with multi-domain simulationsoftware Simplorer, and then finite element model was imported into Simplorer for aco-simulation. Multiple operating condition was simulated and the circuit structure of theexcitation control system has been optimized to improve the performance of the controller.Thirdly, a method of controlling the excitation current was proposed in this thesis. Inmotor condition, the excitation control system can automatically pull in synchronizationduring startup and then the excitation current is maintained at a given current value. Ingenerator condition, the dual-loop algorithm can make the generator terminal voltage kept neara given value, when the generator load is mutated, excitation control system can quickly adjustthe excitation current in response to this change, to ensure a stable output voltage of thegenerator.Finally, a prototype of excitation control system was designed and manufactured to meetthe needs of the electrically excited brushless synchronous machine. Hardware PWM moduleand a digital PI algorithm was applied to achieve precise control of the excitation current. Theeffectiveness of proposed control method was verified through experiment.