Research On The Drive Strategy Of Permanent Magent Motor Used In Deep-sea Propulsions

Permanent magnet motor is widely used in the field of deep-sea explorationbecause of its high efficiency and high power density. It requires different controlstrategies to meet the different requirements of deep sea applications. Brushless DCmotors with square wave drive are applied for the occasion where control accuracyis not critical, while when the control accuracy is very critical, permanent magnetsynchronous motors with vector control are needed. For two drive ways, this paperinvestigates how to limit the starting current, simple sine wave drive based on Hallsensor and vector control based on the single bus current.Firstly, the switch fully shutdown method is studied to solve the problem thatthe start-up current of deep-sea propulsion motor is large in the full voltage startingconditions. After introducing the operation principles of switch fully shutdownmethod in detail, the improve methods are proposed to solve related problems. Thispaper gives a detailed analysis of the influence of the filter capacitor values on thebridge arm to the capacitor voltage and the influence of the switch resistance valuesto the reverse current absorption.Secondly, simple sine wave drive was studied in order to reduce torque rippleand noise of brushless DC motor. Based on the analysis of conventional positionestimation method, an improved acceleration method to estimate the rotor positionwas proposed. Moreover, for square wave and sine wave drive, effect of differentdrive modes to the entire loss of motor drive system was studied based on invertertransient model built by Saber and motor finite element model built by Ansoft. Thesimulation results show that the two drive modes have same loss when the switchingfrequency is9kHz.Thirdly, in order to achieve the low-cost and high-performance operation ofpermanent magnet motor used in deep-sea propulsion, voltage space vector controlbased on bus current sensor was studied. This paper gives a detailed analysis of twokinds of three-phase current reconstruction method, sampling method within theSVPWM cycle and sampling method outside the SVPWM cycle, based on thedc-link current sensor. The effect of two control methods towards vector controlperformance is also analyzed. The simulation results of Simulink model shows thatsampling method outside the SVPWM cycle has better performance.Finally, a brushless DC motor control system experimental platform based onthe dsPIC30F4011is designed and constructed. The hardware includes the PICmicrocontroller and its peripheral circuits, fault detection and protection circuitbased on the CPLD, signal conditioning circuit and IPM drive circuit. Through the relevant software design, starting current limiter，simple sine wave drive and speedloop are studied experimentally, the experimental results verify the correctness oftheoretical analysis.