| In the occasion of strict reliability requirements such as ship propulsion,aerospace and electric vehicles,multiphase motors are widely used due to their high power output,small torque ripple and high reliability.Thanks to the vector space decomposition(VSD)theory,the control of the multi-phase motor drive system can be simplified as the speed and flux control in the torque subspace of the VSD model,which is no different from the three-phase motor drive model.Most of the control methods of multiphase motor drives can therefore be extended from that of three-phase motor.However,its additional subspace for the improvement of motor drive performance still need to be explored.The in-depth research on multiphase drive system is conducive to its application and performance improvement in aforementioned occasion,which is of great theoretical and engineering significance.Compared with other multiphase motors,dual three-phase permanent-magnet synchronous motor(PMSM)have attracted much attention by the merits of good threephase compatibility,high power factor and power/torque density.In this thesis,relying on field oriented vector control based on VSD model,aiming at fully exploiting the cooperation advantages of additional subspaces,the system modeling,multi-parameter identification,deadbeat model predictive control,sensorless control and fault-tolerant control methods are deeply investigated for the dual three-phase PMSM drive system.The main contents are summarized as follows:Firstly,the VSD model,the double dq model and their relationship are summarized for dual three-phase PMSM with arbitrary phase shift angle.For dual three-phase PMSM with 30 degree phase shift angle,the rotation transformation matrix is proposed for the harmonic subspace in VSD model,and the relationship of physical quantities such as voltage,current and flux linkage between the two models in different reference frames are clarified.Then,based on the aforementioned transformation relationship between two models,the VSD model and its transformation matrix of dual three-phase PMSM with any phase shift angle are derived from the perspective of double dq model.The two models and their relationship lay a solid foundation for the subsequent design and elaboration of motor control methods.Secondly,a multi-parameter identification method based on position offset and high-frequency square wave voltage is proposed to solve rank-deficient problem and parameter accuracy coupling in parameter identification.Combined with the additional subspace,an online identification method based on harmonic subspace current injection is proposed for voltage amplitude of inverter nonlinearity.The voltage equations of dual three-phase PMSM considering position-offset error is established.The permanent-magnet flux linkage term is introduced into the harmonic subspace by injecting opposite position-offset into two sets of three-phase windings.The influence of resistance,inductance and other parameters can be eliminated by setting zero current in harmonic subspace to realize independent identification of rotor flux linkage.Based on the high-frequency model,a simple method for extracting the amplitude of high-frequency positive-and negative-sequence current under square-wave voltage injection is described,and the inductance identification based on high-frequency square-wave voltage injection is proposed.The expression of harmonic subspace current injection is derived for symmetrical current amplitude.Combined with the identified inductance parameters,the stator resistance is finally identified using the voltage equation in harmonic subspace.Thirdly,aiming at the deterioration and instability of the system control performance under parameters mismatch,a cascaded deadbeat predictive control system based on composite disturbance observer is proposed for dual three-phase PMSM.The parameter sensitivity of steady-state current error under the conventional deadbeat current predictive control(DPCC)method is analyzed.According to the characteristics of the higher-order derivative of the disturbance in the time domain,a composite disturbance observer based on generalized proportional integral observer(GPIO)and sliding mode observer(SMO)is proposed,which improves the parameter robustness of DPCC.The speed loop predictive model including speed filter,current loop is studied.Combined with the composite disturbance observer,the problems of parameter mismatch and unknown load torque in the deadbeat speed predictive control method are solved.A cascaded speed deadbeat predictive control scheme is proposed.Furthermore,the deadbeat predictive control method with disturbance observer is modeled in discrete domain,and the variation range of system parameters under different disturbance observer coefficients is explored.Fourthly,to solve the limitations of filter phase delay and torque ripple in the conventional method,an improved position sensorless control method is proposed for dual three-phase interior PMSM(IPMSM)from the two perspectives of injection frequency and injection subspace.On the one hand,the position model under high-frequency voltage injection is established in the complex vector for IPMSM,the limitations of the filter phase delay in the signal processing of conventional method are analyzed,and a general signal separation method under orthogonal square-wave voltage injection with adjustable frequency is proposed.Finally,a position signal extraction method without phase delay is obtained.On the other hand,the saliency of dual three-phase IPMSM in harmonic subspace is studied,and the position model of harmonic subspace is modified.Finally,the sensorless control based on high-frequency square wave injection in harmonic subspace is proposed for dual three-phase IPMSM with reduced toque ripples.Finally,a natural fault-tolerant control method for single-phase open-circuit fault without prior fault diagnosis and reconfiguration is proposed for dual three-phase PMSM.The sequence components of two sets of three-phase winding currents under single-phase fault condition are analyzed,the objective compatibility of current control in torque space(CCTS)and current control in harmonic space(CCHS)is investigated,the voltage disturbance of CCTS under fault condition is analyzed,the generation mechanism of torque ripple under open-circuit fault condition of conventional control scheme is clarified.In summary,a natural faulttolerance control method based on notch filter and disturbance observer is proposed.The corresponding relationship between different post-fault operation modes and the positive-sequence current in harmonic subspace under the natural fault-tolerant control method is explored,and the setting method of positivesequence current in harmonic subspace with amplitude ratio and phase shift as intermediate variables under different post-fault operation modes is deduced.The advantages of the minimum copper loss(ML)strategy and the maximum torque(MT)strategy are compared in terms of the torque operation range and copper loss,and an online calculation strategy of the minimum copper loss in the full torque range is proposed for the natural fault-tolerant control.The proposed natural fault-tolerance control method,as a general control method,is suitable to the normal condition and the fault condition,and reduces the priority of fault diagnosis in the fault-tolerance operation process. |
