Winding Design Of Wound-Rotor Brushless Doubly Fed Machine And Study Of Magnetic Field Characteristics Under Faults

As a new type of induction machine,brushless doubly-fed machine,compared with conventional brushed doubly-fed machine,not only eliminates brushes and slip rings,but also has two sets of windings with different pole pairs embedded in the stator.Because the rotating magnetic fields generated by two sets of windings with different pole pairs are orthogonal.There is no direct energy transfer between the two sets of windings,and the magnetic field of two different pole numbers is modulated by its special rotor structure.This requires that the rotor of a brushless doubly-fed machine can simultaneously modulate two rotating magnetic fields with different pole numbers,which has high requirements on the performance of the rotor and also limits the development of the brushless doubly-fed machine.Therefore,it is of practical significance to study the design of the rotor winding of the brushless doubly-fed machine and the law of the magnetic field of the machine.This dissertation uses a 4/8 pole 45 k W brushless doubly-fed machine as the research object.Based on the theory of AC motor windings,the magnetic potential of unequal-toothed harmonic windings meeting the pole-change requirements was derived,and the characteristics and content of rotor winding harmonics were analyzed.Finally,based on the theory of double sinusoidal winding and the principle of tooth harmonics,a set of rotor winding design methods for low-harmonic multi-span brushless doubly-fed machines is given.The output power and harmonic content of the whole machine are analyzed.The analytical calculations and simulation results show that the design method is correct.At the same time,considering that the windings of brushless doubly-fed machine are prone to inter-turn faults,this dissertation analyzes the characteristics of electromagnetic torque in thecase of interturn faults in brushless doubly-fed machine.At the same time,based on the time-step finite element method,a solution model for brushless doubly-fed machine for analyzing inter-turn faults.Discrete spectrum analysis of electromagnetic torque waveforms before and after machine failure.The electromagnetic torque components in the transient and steady state after the fault are studied,and the influence of the short-circuit fault location on the three-phase current and its components is also analyzed.This dissertation provides a reference for the further study of the design of the rotor winding of the brushless doubly-fed machine and the magnetic field characteristics under the fault.