Research On Key Techniques Of Drive And Control System For Five-phase Permanent Magnet Synchronous Motors In Series

Multiphase permanent magnet synchronous motor has the characteristics of low torque ripple,high power density and high reliability.Double and multi machine systems have been widely used in automation systems The multi-phase multi-motors in series drive structure has apparent benefits in lowering drive volume,enhancing output torque,and strengthening fault-tolerance,particularly in applications with limited volume and high dependability.Based on the application context of the autonomous underwater vehicle(AUV)towed automated cable retraction and discharge electric drive system,this topic examines in depth the essential technologies of the dual machines in series system for five phase permanent magnet synchronous motor(FPMSM).Firstly,in order to tackle the harmonic current problem caused by the employment of over modulation technology to increase the usage rate of bus voltage,a technique of over modulation with the lowest harmonic voltage is proposed.By establishing the mathematical relationship between the associated harmonic voltage vector and the synthetic basic vector and employing the extreme value solution method,the harmonic voltage in the non-sinusoidal over-modulation region is minimized,and the method is extended to the sinusoidal modulation region to realize the voltage minimum modulation method in full harmonic space.The harmonic superiority of minimum harmonic voltage(MHA)modulation is simulated and experimentally validated,as is the harmonic current effect of two-dimensional current control based on MHA-SVPWM.Second,in order to resolve the torque fluctuation caused by current harmonics,as well as the issues of difficult synthesis,asymmetric waveform,and low modulation ratio of biplane space vector modulation,the biplane SVPWM and four-dimensional current control technologies are investigated.An EV-DVSVPWM is proposed in this paper,and on this basis,two modulation ratio improved strategies are also proposed.To overcome the issue of eight vector’s low fundamental modulation ratio,a six vector modulation method with the highest fundamental modulation ratio is proposed.By means of the associated voltage compensation for harmonics,the modulation range of the fundamental is expanded using this technique.The DVSVPWM-based four-dimensional current control can suppress harmonic current disturbances caused by uncontrolled harmonic current,inverter dead time,and motor nonlinearity.Simulation and experiment validate the benefits of the modulation method and four-dimensional current control strategy.Thirdly,in order to solve frequent SPD problem which is highly depend ent on mechanical synchronization under coaxial structure and independent operation problem with different functional requirements under non-coaxial structure,a cross-series structure based on DFV-DVSVPWM and the associated series control control strategy are proposed.The biplane subspace decoupling model of dual THI-FPMSMs in cross series is established,and the voltage-current relationship of FPMSM in series is revealed.The influence of 3th flux-linkage on the torque ripple of motors in series is analyzed.A decoupling control strategy with harmonic torque ripple compensation based on DFV-DVSVPWM is proposed for FPMSMs in cross series to minimize the torque disturbance induced by harmonic flux-linkage.The control effect of the proposed cross-series decoupling control strategy in coaxial system and non-coaxial system are verified by simulation and experiment.Finally,aiming at reliability problems of mechanical SPD and electrical open-fault in FPMSM series-connected system,and improving torque output efficiency and operation stability,SPD and open-phase fault-tolerant control techniques are deeply studied.An optimal efficiency compensation approach is proposed to enhance output torque under SPD operation and solve the problem of uneven torque.Furthermore,the harmonic torque influence on full-order decoupling unified fault-tolerant control is analyzed.A minimum torque ripple(MTR)fault-tolerant control strategy used for all open-faults based on OF-SVPWM is proposed.The fault-tolerant torque ripple is minimized through full compensation optimization of fundamental q-axis current,which furher improve the stability of fault-tolerant operation.Combining SPD compensation with MTR fault-tolerant control approach enables the research and validation work to be performed.