| The reliability of the motor drive system is crucial to the stable and continuous flight of the PV UAV,and the common three-phase motor drive,which is difficult to continue working in case of failure,is therefore studied in this paper.A dual-winding permanent magnet synchronous motor(PMSM)drive system with redundant structure is used,which not only can improve the reliability of the system,but also can distribute power and torque according to the difference of PV power generation,and improve energy utilization.Considering the complexity of UAV operation environment,we focus on the vector control,sensorless control and fault-tolerant control of dual-winding PMSM for the reliability and stability of the drive system.For the vector control of the dual-winding PMSM,this thesis adopts a vector control strategy based on the dual dq coordinate transformation,which treats the dual-winding PMSM as a combination of two sets of three-phase sub-winding and establishes a mathematical model under the dual dq coordinate system.The two windings are independent of each other in terms of control,but share the load torque and power,and each set of windings is equipped with its own inverter and controller,which together form a dual redundant control system.By adopting vector control of the three-phase motor for each of the two sets of windings,the control of the speed and torque of the dual-winding PMSM is realized.Simulations and experiments show that vector control can achieve stable operation of the motor.In order to realize the dual-winding PMSM without position sensor control in the full speed range,a composite control strategy combining the model reference adaptive(MRAS)algorithm and IF control algorithm is investigated in this thesis.In the zero-low speed range,the IF control algorithm is used to complete the start-up of the motor and achieve stable operation with load on the motor.In the medium and high speed range,the MRAS algorithm is used to identify the motor speed and rotor position angle,and to achieve stable operation of the motor in the medium and high speed range.In order to make the two algorithms switch smoothly,the switching strategies of the two algorithms are studied to ensure that the operating state of the motor does not change abruptly before and after the switching.Simulations and experiments show that the composite positionfree control algorithm can achieve stable control of the motor in the full speed range.In order to improve the fault operation capability of the dual-winding PMSM,a twophase four-switch fault-tolerant control strategy is focused on.When a phase loss occurs in the motor,the neutral point of the fault set winding is connected to the midpoint of the DC-side capacitor,while a four-switch modulation strategy is used to achieve faulttolerant operation of the single winding.To address the problem of large increase in residual phase current amplitude arising from single winding fault operation,the dual redundancy structure of two windings is fully utilized to redistribute the torque between the fault winding and normal winding,effectively reducing the current of the fault winding and finally equalizing the residual phase current amplitude.Simulation of the fault-tolerant control algorithm shows that the proposed fault-tolerant control strategy can achieve stable operation of the dual-winding PMSM in the event of a phase-breaking fault and complete the control of speed and torque under the fault condition. |
