Dc Motor Vector Control

As a typical electromechanical integration product,permanent magnet brushless DC motor has many advantages such as high power density,high output peak torque and average torque,simple control strategy,etc.It is widely used in the field of electric drive.Shipboard electric thrusters have high requirements on the power density of the device,so the choice of a brushless DC motor as its power source would be very suitable.However,the particularity of the drive system and technical indicators will introduce new issues worthy of study for the control of brushless DC motors.This paper studies the following aspects of the brushless DC motor control system for ship electric propulsion:The ship’s propulsion motor control system has specific design indicators.At the same time,the motor load is the fluid load characteristic.The power model of the twin-screw propellers is coupled to each other.Therefore,the load characteristics and operating conditions of the brushless DC motor are first analyzed,and the load model is obtained.Fully analyze the design requir ements of the plan and use this as a starting point for designing a motor control system.The mathematical model of the brushless DC motor was established.The control strategy of square wave drive,two-two conduction and six-step commutation was adopted.The simulation model of the electric propulsion system was built on the Simulink simulation platform based on the load characteristics of the actual system.The model verifies the control effect of the traditional double loop control method of speed loop and current loop PI.In order to reduce the noise and torque ripple of brushless DC motors,the effects of PWM modulation and switching frequency on torque ripple are analyzed