Research On Noise Reduction Strategy Of Six Phase PMSM For Underwater Propulsion Based On Random Modulation

Multi-phase motor control system has significant advantages in autonomous underwater vehicle propulsion.The supply voltage of multi-phase motor is low when the power is fixed.The output power of the driving system can be increased by the multi-phase motor when it is powered by its own battery.Multi phase motor has small output torque fluctuation and less noise vibration.Compared with the traditional three-phase motor,the multi-phase motor has good steady-state and dynamic performance.When autonomous underwater vehicle works underwater,the switching power electronic devices used inside the motor driver will generate high-order harmonics.These high-order harmonics will gather at the switching frequency and multiple of switching frequency,thus generating high-frequency noise.The high-frequency noise has small attenuation rate in the sea water,which is easy to be detected during task execution.In view of the stealth and low detection requirements of autonomous underwater vehicle,it is necessary to suppress the high-frequency noise.This paper is devoted to the optimization of higher harmonic spectrum.Aiming at suppressing the high frequency noise of six phase motor drive system,this paper presents a pseudo-random SVPWM modulation technique based on switch frequency and zero vector assignment randomization.This paper builds the random modulation model of six phase PMSM and the simulation results are compared and analyzed.The main contents of this paper are as follows:Firstly,the application and development of PWM technology in motor drive is summed.The research situation of random modulation technology at home and abroad is sumaried.A pseudo random modulation technique based on random switching frequency and zero vector assignment is proposed,which uses the sequence of pseudo-random numbers to realize switching frequency randomization and zero vector assignment randomization.The mathematical model of six phase permanent magnet synchronous motor in double d-q coordinate system is introduced and the vector control strategy based on double d-q model is given.This paper introduces the advantages and disadvantages of several modulation techniques,and analyzes the power spectrum of fixed frequency modulation and random modulation.Power spectrum analysis proves that random modulation can effectively suppress high frequency harmonics.Secondly,a six phase PMSM control model is built in MATLAB.The conventional fixed frequency modulation,general random switching frequency modulation and random switching frequency zero vector random modulation technology based on pseudo-random number are simulated.The simulation results of three modulation technologies are compared and analyzed.The simulation results show that the pseudo-random SVPWM modulation technique based on switch frequency and zero vector assignment randomization can effectively disperse the high-order harmonic spectrum.In addition,the low order harmonics of the stator current is suppressed.In this paper,the control algorithm based on proportional resonance is proposed to suppress the current low harmonic.The harmonic current is tracked using the proportional resonant regulator.Finally,in order to verify the low order harmonic current suppression effect,the six phase permanent magnet motor models introducing control algorithm based on proportional resonance is simulated in MATLAB.The simulation results show that the control algorithm based on proportional resonance can suppress the low harmonic current of the motor stator effectively.