| Compared with the three-phase drive system,the multi-phase permanent magnet synchronous motor has the advantages of low torque ripple,more freedom of control,and easy to achieve high-power driving under low-voltage power supply in terms of ship electric propulsion.At the same time,due to the large inertia of the ship's propulsion system,the reliability of the control system is relatively high,making its open-loop control possible.This article takes the marine large-capacity nine-phase permanent magnet synchronous motor as the target motor,and uses a small prototype as the specific research object.The structure is basically the same as the actual large-capacity motor except that the capacity is greatly reduced in proportion.Aiming at the problem of insufficient rotor damping when the studied motor adopts open-loop control,causing the motor to start and run with load,the rotation speed oscillation problem is caused by the use of the motor's active power change to provide frequency feedback to increase the rotor damping and improve the nine-phase permanent magnet open-loop control performance of synchronous motors.The effectiveness of the damping modulation link used when the nine-phase permanent magnet synchronous motor adopts the two open-loop control strategies of V/F and I/F is verified.First,according to the winding distribution of the nine-phase permanent magnet synchronous motor,this paper derives the expansion transformation matrix of the motor winding in the case of semi-symmetrical distribution,and then establishes the mathematical model of the studied motor in the natural coordinate system and t he rotating coordinate system.The basic composition and control function of each harmonic plane of the motor are analyzed,and the voltage,flux linkage and torque equations of the nine-phase permanent magnet synchronous motor based on the rotating coordinate system are listed as the next step to analyz e the stability of the open-loop control system.basis.Secondly,the basic control principles of the two open-loop control strategies of the nine-phase permanent magnet synchronous motor in V/F control and I/F control are respectively described.The rotor small under the open-loop control state of the motor is established in the fundamental wave coordinate plane of the motor.Disturbance model.Under the two open-loop control methods,the instability problem of the motor due to insufficient damping of the rotor system is analyzed,and the system state equation under the open-loop V/F control method is derived.The system characteristic root method is adopted and the real part variation curve is analyzed.Motor stability characteristics.Subsequently,in order to improve the operating stability of the nine-phase permanent magnet synchronous motor in the open-loop control state,based on the traditional open-loop control,according to the proportional relationship between the frequency feedback amount and the instantaneous active power disturbance amount of the motor input,an anti-oscillation feedback is added The modulation link enhances the rotor damping and eliminates the speed fluctuation of the motor during the starting process and when the load is impacted,so as to realize the open loop stable operation of the motor in a wide frequency range.Finally,in order to verify the actual control effect of the open-loop control scheme,the experimental platform of the existing nine-phase permanent magnet synchronous motor prototype was used to compile the control algorithm experimental program required in this article,and the open-loop control system of the motor was debugged and tested.experiment.The experimental results show that the open-loop control scheme of the nine-phase permanent magnet synchronous motor based on frequency feedback used in this paper can effectively eliminate the speed fluctuation of the motor starting process,optimize the starting performance of the motor,improve the running capacity of the motor with load,and improve the system The stability of open loop operation. |
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