Research On Fault-Tolerant Operation And Efficiency Optimization Control Strategy For Dual Three-Phase Pmsm With Open Phases Fault

The multiphase motor variable frequency speed regulation system,compared to conventional three-phase motors,can effectively reduce the motor’s output torque ripple,provide a more stable and reliable power output,and exhibit superior fault tolerance.Consequently,it has found extensive applications in areas such as warships,aerospace power systems,electric vehicles,and other domains with constrained power supply voltages and demanding reliability requirements.This paper focuses on the dual three-phase permanent magnet synchronous motor(DT-PMSM)as the research subject and conducts a comprehensive investigation into the optimal control strategy for enhancing its fault-tolerant operational efficiency.Firstly,the mathematical models of DT-PMSM in these two coordinate systems are derived from the six-phase natural coordinate system model of DT-PMSM using double d-q transformation and vector space decomposition(VSD)transformation.Additionally,the vector control strategy based on the VSD model is analyzed.The VSD transformation matrix is selected based on the neutral point connection mode of the chosen DT-PMSM and its corresponding current constraints in the event of open-phase fault.The mathematical model of DT-PMSM based on VSD is established for both single open-phase fault and orthogonal two open-phase fault scenarios.Furthermore,the vector control strategy for DT-PMSM under single open-phase fault is analyzed.Secondly,The study focuses on investigating fault-tolerant control strategies for DT-PMSM based on the principle of total magnetic potential invariance.Specifically,it explores the minimum losses(ML)and maximum torque(MT)strategies.To address the limitation of the previous fault-tolerant control strategies in simultaneously considering copper consumption and torque range,this study further investigates the full-range minimum losses(FRML)fault-tolerant control strategy,aiming to enhance the shortcomings identified in the earlier strategies.This strategy minimizes stator copper consumption within the entire torque operating range following an open-phase fault.However,it requires offline lookup of the control coefficient of the harmonic subplane,making the implementation more complex.Subsequently,a hybrid fault-tolerant control strategy is proposed,which involves a linear combination of the ML and MT strategies.This approach yields an analytical solution for the harmonic subplane current reference,resulting in effective reduction of stator copper consumption throughout the torque range after a fault,while simplifying the process.The four fault-tolerant control strategies mentioned earlier are extended to address the scenario of two open-phase fault.Furthermore,each of these strategies is applicable to the two open-phase fault situation.The effectiveness of each fault-tolerant control strategy is verified by simulation.Thirdly,the study focuses on two current nonsinusoidal fault-tolerant control strategies specifically designed for single open-ophase fault.The first strategy,grounded on the principle of constant power,aims to maintain the consistency of active power generated by the remaining phases of the motor before and after single open-phase fault.It deduces a current nonsinusoidal fault-tolerant control strategy by applying the principle of constant power.The second strategy deduces a current nonsinusoidal fault-tolerant control strategy that minimizes copper consumption,taking into account theoretical minimum values,and without imposing unnecessary constraints.Both current nonsinusoidal fault-tolerant control strategies are simulated and analyzed using hysteresis control and vector control methods.A comparative analysis is performed between these strategies and the previous fault-tolerant control strategies.Lastly,the experimental platform for the DT-PMSM drive system is constructed based on the overall system design.The experimental results provide effective verification of the accuracy and feasibility of the fault-tolerant control strategies investigated in this study.