Modeling And Unbalance Control Of Dual Three- Phase Permanent Magnet Synchronous Machines

Dual three-phase permanent magnet synchronous motors?PMSM?have the advantages of high power density and reliability,and have been widely used in wind power generation,ship power,modern transportation and other fields in recent years.The dual three-phase PMSM has two sets of three-phase windings,and can be driven by two three-phase converters in parallel,which can reduce the power rating of each converter in a high-power system.Since the dual three-phase PMSM has two sets of windings,the machine can be continuous running with one set of windings failure.Dual three-phase PMSMs have various structures.According to the phase shift between the two sets of windings,there can be classifications such as 30°shifted dual three-phase motors,and no shifted angle dual three-phase motors.According to whether the neutral point of the two sets of windings is connected,it can be divided into neutral connection and neutral isolation.There are also various motor structures with different windings configurations.Due to the electromagnetic coupling between the two sets of windings,the dual three-phase PMSM has the characteristics of high order,nonlinearity and strong coupling problems.Modeling of dual three-phase PMSM is very important for subsequent research.This paper studies the dual three-phase PMSM with neutral isolated and no shifted angle between two windings.The structure of the dual three-phase PMSM studied in this paper appears a problem that the mutual-inductance values are different.Therefore,the fault-tolerant operation mode?only one set of three-phase windings are in operation?is unbalanced.The machine model is established by considering the mutual-inductance asymmetry and magnetic coupling between windings.These unbalances can result in the negative sequence currents appearing as the second harmonic currents in the dq-axis,which reach their maximum when only one set of winding is active during fault-tolerant operation.In order to suppress the 2^nd harmonic current,the quasi-resonant controller and the harmonic voltage feedforward controller based on the motor model are studied in this paper.The results show that the quasi-resonant controller has a better steady-state performance,and the harmonic voltage feedforward controller has a better dynamic performance.In order to achieve a better suppression effect,a hybrid controller is proposed in this paper combining the advantages of the quasi-resonant controller and the harmonic voltage feedforward controller.Finally,three harmonic current suppression strategies are tested on a 1.1kW dual three-phase PMSM experimental platform.The effectiveness of three harmonic current suppression strategies is verified by the results.Among them,the hybrid controller has the best performance.Compared with the traditional quasi-resonant controller and the harmonic voltage feedforward controller,it has better dynamic and steady-state performances.