Research Of Energy-saving Control Of Induction Motor

As a main equipment of power machinery, induction motor is widelyused in industry, agriculture, national defense and other fields. It convertselectrical energy to mechanical energy. The energy conversion efficiency ishigh when induction motor runs at rated conditions，however, it decreasedsignificantly when induction runs at low speed and light load. It haspractical significance to take appropriate measures to reduce the loss ofinduction motor and improve its operating efficiency. The energy-savingoperation of induction motor is favorable for energy conservation,environmental protection and sustainable development.Based on the vector control system, this paper studies on theminimum loss control strategy of the induction motor, which include lossmodel control and on-line search control. The dynamic mathematicalmodel of induction motor considering the iron loss is studied under thetwo-phase stationary coordinate system, the mathematical expression thatfacilitate the modeling is derived and the simulation mode considering theiron loss is constructed using the basic modules. The simulation resultsshow that the simulation model considering iron loss is closer to the actualmotor and it lays a foundation for the further study of efficiencyoptimization control.The loss model considering iron loss is established based onequivalent circuit of induction motor under two-phase rotating coordinatesystem. Then the induction motor and inverter loss characteristics areanalyzed and the formulas of minimum loss and optimal flux are derived.The relationship between the rotor flux and motor loss under theconditions of different torque and speed is studied. The simulation resultsshow that this motor loss and improve motor efficiency with differentdegrees. The impact on parameter changes of the minimum loss of control has also studied, the research results indicate that the change wouldadversely affect the minimum loss of control, the rotor flux correspondingthe minimum loss running will deviates from the optimal value.Search algorithms do not rely on motor parameters and the optimalvalue is global optimum. Two controllers are designed based on the goldensearch method and fuzzy search method. Golden method is simple andshow fast convergence rate but the initial step lengths are too large thatwould cause torque fluctuations and bring adverse impact to the system.Fuzzy control method adjusts the step lengths adaptively and theconvergence rate performing well, while the drawback is fuzzy rules,membership functions and scale factors are dependent on the humanexperience.