Analysis Of Electromagnetic Coupling Phenomenon And Fast Algorithm Of Saturated Inductance Of Brushless Doubly-fed Machine

Brushless Doubly-Fed Machine(BDFM)has many advantages such as no brush,low maintenance cost,small converter capacity and so on.It has wide applicable potentials in the fields of variable frequency drive as well as variable speed constant frequency power generation.Nevertheless,the magnetic field modulation mechanism of BDFM and the electromagnetic coupling relationship among the different windings stator and rotor are very complex,which lead to the difficulties to calculate the self-inductances of each winding and the mutual-inductances between the windings quickly and accurately.Therefore,the electromagnetic coupling phenomena among different windings of BDFM with cage rotor,as well as a fast and general algorithm for calculation of saturated inductances are studied by theoretical analysis,Matlab programming,finite element simulation and prototype test in this thesis.Firstly,the basic structure and the magnetic field modulation principle of BDFM are introduced,and the mathematical model of BDFM in three-phase static coordinate system is given.Secondly,considering the harmonic magnetomotive force but neglecting the core saturation,the direct coupling phenomenon between the stator power winding and the control winding of BDFM is studied by the winding function method,and the analytical expressions of direct coupling inductances between two sets of stator windings are deduced.And then,the influences of direct coupling inductances to the operation of a 3/1-pair-pole prototype with cage rotor are analyzed.Thirdly,a magnetic network iterative algorithm for general,fast and accurate calculation of saturated inductance of BDFM with cage rotor is proposed by considering the factors such as different structures of stator and rotor windings,different core saturation and different cogging effect.Finally,the comparison results of the proposed algorithm,the finite element energy perturbation method and the static AC experiment method shows that the proposed algorithm has a much higher solving efficiency on the premise of ensuring the accuracy of the inductance calculation.At the same time,the results of three different inductance calculation methods verify the theoretical analysis of direct coupling inductance.The research results of this thesis provide a theoretical foundation for analysis of the direct coupling inductances between the two sets of stator windings of BDFM with cage rotor,and a new idea for the fast calculation of winding inductances of AC rotating machine.