Some Technical Research Of Energy-saving Control Of Induction Motor Supplied By Converter

With the requirement of speed-regulated energy saving for fan and water pump, manufacturing technique and servo control, frequency control of induction motor has developed. The techniques for motor control in engineering have the advantages of simple algorithm and good dynamic performance. However, they are not considered high efficiency for light load. As the increasing prominence of global environmental protection and energy shortage, people have to pay more attention on energy saving. The induction motor is the main power consumption equipment. Thus, the research for its energy saving has great practical significance. In this case, the paper adheres to energy saving for induction motor supplied by converter to solve the low efficiency for the motor with light load.The main control techniques for speed regulation are coordinated control for voltage to frequency, slip frequency control, vector control and direct torque control. By analyzing these techniques and the mathematical model of induction motor, we find that the low efficiency for the motor with light load result from neglecting core loss and constant rated flux. On that basis, we present vector control considering core loss. It realizes decoupling control of torque and flux by controlling components of gap current, which indirectly command stator currents to achieve vector control. The research indicates the distinct improvement of the proposed control in dynamic performance.For the motor parameters used for speed control and energy-saving control have time variant and nonlinear characteristics, the paper investigates the offline technique and the online technique for parameter identification. It further proposes offline technique and online auto-tuning rotor resistance identification considering core loss.The paper has presented three items research for speed controller. The first is the improvement for PI speed controller. Its parameters adapt operating condition. Thus, the dynamic and static performances improve. The second is the improvement for sliding mode controller and neural network controller. A nonlinear smooth and continuous function takes the place of sign function on sliding surface and eliminates the high dither of sliding mode controller. The weight for neural network controller can be adjusted adaptively. The third is to present an novel zero-order disturbance observer and disturbance rejection control based on slip regulation. The disturbance observer uses tracking differentiator to observer all disturbance. Then, the disturbance torque is compensated based on slip control. It can overcome the disadvantages of poor dynamic response and lower control precision in slip regulation. The energy-saving control of induction motor fed by converter is the key research in the paper. By analyzing the losses and operating efficiency of the motor system, we find that the orientation of efficiency optimum is the energy saving of the motor self. And it stress on medium and small-sized motors. The optimum efficiency can be realized by adjusting stator voltage, frequency, ratio of voltage to frequency, or flux. From this, we get the following methods of energy saving control.(1) By the steady model, we propose a novel energy-saving realization of scale-controlled induction motor. The proposition adjusts the supply frequency by the speed, and adjusts supply voltage to meet the required load torque.(2) According to the different operating condition, we present fuzzy energy-saving control of induction motor by adjusting ratio of voltage to frequency. By the way, the motor runs at high efficiency and keeps good dynamic response.(3) We present vector-energy-saving control. We consider the core loss both in vector control and in energy-saving control. Also, we discuss the vector-energy-saving control for the motor operated below the rated speed and up the rated speed. The proposition gives consideration to better dynamic performance, large scope speed regulation, and energy saving.