Polyphase Motor Control System For Motor Pump Based On Pure Electric-driven Construction Machinery

With the continuous consumption of energy and the deterioration of ecological environment,green development has become the theme of the world.Due to the characteristics of zero emission,low noise and high efficiency,pure electric-driven construction machinery has become the hot development direction of construction machinery industry.The power part of the hydraulic system of pure electric-driven construction machinery is the motor pump,which has a high demand for the torque response speed and pulsation of the driving motor under the time-varying load.At present,the driving motor of motor pump is usually three-phase motor,which has the disadvantages of slow torque response and large torque ripple.The polyphase motor has the advantages of rich modulation resources,fast dynamic response,small torque ripple and high reliability.At present,there are few researches on the application of polyphase motor in hydraulic system in China,so it is of great significance to study the polyphase motor control system based on motor pump.According to the flow continuity equation and torque equation of the hydraulic pump,this paper establishes the mathematical model of the hydraulic pump,and analyzes the control requirements of the hydraulic system for the motor speed control system.Based on the analysis of four common motor characteristics,the type of AC asynchronous motor as the driving motor of motor pump is determined.Through the Ansoft modeling and simulation,it is determined that the number of phases of polyphase motor is half twelve,so the polyphase motor studied in this paper is also called six-phase induction motor.The mathematical model of six-phase induction motor is decoupled by using the space decoupling theory,and the mathematical model of the motor in twophase static coordinate system is established.Through the analysis of common motor control strategies,the direct torque control technology is determined as the control strategy of six-phase induction motor.In order to improve the dynamic response of the motor pump and reduce the torque ripple,a pulse width modulation(SVPWM)algorithm based on the space decoupling transformation theory is introduced.By synthesizing the intermediate voltage vector,the stator harmonic current is reduced and the torque ripple is reduced.The simulation results show that the six-phase motor direct torque control system based on motor pump has good robustness,fast dynamic response and small torque ripple.In order to meet the control needs of polyphase motor,this paper presents the overall hardware design scheme of six-phase induction motor control system.Taking TMS320F28335 of Texas Instruments Company as the control core,the design and test of related hardware circuits are completed.According to the principle of the control system,the relevant software program is completed.At the same time,a test platform is built to complete the no-load test of six-phase induction motor.Under the condition of time-varying load,the six-phase motor and three-phase motor are tested respectively.The test results show that the six-phase motor is more suitable for motor pump than the three-phase motor,with better dynamic performance and less torque ripple.