Study On Parameter Analysis And Characteristic Of Brushless Doubly-Fed Machine

The brushless doubly-fed machine(BDFM)cancels the brush and the slip ring,and the system configuration has a small capacity,which provides higher reliability and lower design cost,and has broad application prospects in the fields of AC drive and variable-speed constant-frequency power generation.This paper mainly introduces the structure and basic working principle of the brushless doubly-fed electric machine,and derives the steady-state equivalent circuit from the mathematical model on the three-phase stationary coordinate system,and studies the brushless doubly-fed rotor with unequal winding.The parameter calculation of the brushless doubly-fed machine with unequal winding is studied,and the accuracy of the leakage inductance calculation method is verified by stall test.This paper mainly deduces the calculation method of the equivalent circuit inductance parameters.The calculation formula of the excitation impedance is introduced.According to the different characteristics of the leakage magnetic field established by the winding current at different positions in the machine,the calculation formula of the leakage inductance,the end leakage inductance and the harmonic leakage inductance are derived.Referring to the Rogowski method,according to whether the current density is zero or not,the space in the slot is partitioned.When the slot leakage inductance is solved,the single-slot leakage magnetic field energy model is established,and the leakage magnetic field energy of the slot is calculated in layers.The superposition theorem is used to find the slot.For the leakage inductance of the conductor,refer to the network diagram to write the correlation matrix to find the leakage inductance of each phase slot.When solving the leakage inductance at the endwinding,the air gap current and the mirror current are introduced,and the leakage inductance calculation model of the coil end is established in the uniform medium.The discrete Bio-Savart's law is used to solve the leakage flux linkage between the two coils.Write the correlation matrix to find the leakage inductance at the end of each phase.When solving the harmonic leakage inductance,the length of the air gap is equal,so that the magnetic potential waveform and the magnetic dense waveform have similarities.For the magnetic fields with two kind of pole pairs match,the harmonic inductance between the two coils is calculated by using the total inductance minus the fundamental inductance.Write the correlation matrix to find the harmonic leakage inductance of each phase;ignore the difference between the resistance of the winding through DC or AC,and calculate the winding resistance according to the DC resistance formula under a certain operating temperature.In this paper,a unequal concentric winding rotor brushless doubly-fed machine is studied,and its leakage inductance parameters are calculated.The results of the stall test are compared with the calculation results of this paper and the traditional method to test the accuracy of parameter calculation.Through the no-load variable speed simulation and constant load speed mutation simulation and constant speed load abrupt test,the simulation of the operation of the power generation system caused by wind waves at sea is simulated,and the good prospect of brushless doubly-fed machine in the field of ship power generation is verified.