Research On Phase-loss Fault-tolerant Operation Control Of Nine-phase Permanent Magnet Synchronous Moto

The reliability of the propulsion subsystem as the power guarantee in the ship’s integrated power system will directly affect the ship’s speed and maneuverability.Therefore,due to the consideration of ship maneuverability and equipment safety,the propulsion motor often adopts a multi-phase winding structure,which can achieve low voltage and high power while having strong fault-tolerance.When the motor has an open-circuited fault of winding or inverter power device,the system needs to accurately identify the fault location online,and actively switch to the corresponding fault-tolerant operation mode to ensure the continuous and stable operation of the ship.This paper takes a nine-phase permanent magnet synchronous motor as the research object,and analyzes the stator magnetomotive force and torque of the motor during normal and open-circuited fault operation.The mathematical models of the motor are established in different coordinate systems.Aiming at the open-circuited fault of motor winding or power device,an improved diagnosis method based on the ratios of fundamental waves to harmonic currents is proposed to realize real time online detection.On this basis,the calculation method of motor fault-tolerant currents is studied and extended,and the fault-tolerant control strategy of the faulty motor in the full torque range is optimized to realize the online switching fault-tolerant operation of the motor.Firstly,the magnetomotive force of the stator winding of the nine-phase motor in normal and open-circuited operation is analyzed,and the torque of the nine-phase motor in normal and open-circuited fault operation is deduced.The space decoupling transformation and rotation transformation of the nine-phase vector are listed,and the mathematical models of the nine-phase motor in different coordinate system are deduced.Secondly,the current characteristics of the motor winding and power device open-circuited fault are analyzed.On this basis,in view of the problems of high no-load bias and large load disturbance in the traditional phase current average values diagnosis method,an improved diagnosis method based on the ratios of fundamental waves to harmonic currents is proposed to reduce the probability of misdiagnosis.And the two methods are compared experimentally.Thirdly,when the motor is faulty,the non-reduced fault-tolerant control is adopted,and the maximum output torque during fault operation is used as the objective function to solve the open-circuited fault-tolerant currents of the nine-phase motor.Considering the influence of phase number parity and winding structure difference on the fault-tolerant current calculation of multiple sets of three-phase motors,the calculation method of the open-circuited fault-tolerant currents is extended to multiple sets of three-phase motors,and taking six-phase fully symmetrical and nine-phase semi-symmetrical permanent magnet motor as examples,simulation and experimental verification are carried out respectively.Finally,in view of the problem of stator copper loss is the smallest and the torque is the largest when the motor is in open-circuited fault-tolerant operation,an optimization strategy for copper loss within the maximum torque range during fault-tolerant operation is proposed,so that the faulty motor can take into account the minimum stator copper loss and at the same time achieve the maximum output torque.The effectiveness of the optimized fault-tolerant control strategy is verified by experiments,and the stable operation of the multi-phase permanent magnet synchronous motor under open-circuited fault is guaranteed.