Rotor Parameter Estimation And Efficiency Optimization Control Of Asynchronous Motor When The Load Is Unknown

Vector control is widely used in induction motor control because of its excellent control performance.However,the parameters of the induction motor,especially the rotor resistance,will change during operation,which will result in the terrible dynamic and steady performance because of the wrong flux orientation.The induction motor based on vector control has large energy loss and low efficiency under low speed and light-load conditions.Aiming at the above problems,a novel vector control scheme for induction motors based on rotor resistance on-line identification is proposed.Firstly,a vector control system oriented by the rotor magnetic field is constructed by building the mathematical model of the asynchronous motor in each coordinate system,which explains why rotor resistance affects vector control.Secondly,instead of the traditional PI controller,backstepping control is used to design the speed controller to obtain faster dynamic response and better steady-state performance.Load torque observer is designed to enhance the anti-interference ability of the vector control system.According to the pole placement theory,the full-order flux observer is designed to estimate the rotor flux linkage amplitude in real-time.Then,the model reference adaptive system(MRAS)is built by taking the asynchronous motor itself as the reference model and the full-order flux observer as the adjustable model.The rotor resistance adaptive law is designed according to Popov's superstability theory to identify the rotor resistance on-line.The loss model of the induction motor is established by analyzing the loss composition of the induction motor during steady-state operation.The mathematical method is used to obtain the optimal efficiency rotor flux to reduce the motor loss.Because the motor parameter changes can affect the efficiency optimization scheme,the rotor resistance identification algorithm is added to the efficiency optimization control to improve the efficiency optimization accuracy.Simulation experiments show,the proposed novel vector control system has faster dynamic response speed and better anti-load disturbance ability.The identification scheme can identify the rotor resistance quickly and accurately,and enhance the robustness of the novel vector control.The efficiency optimization control can effectively reduce the loss of the motor at steady state and increase the efficiency of the motor.When the rotor resistance identification is added into the efficiency optimization scheme,the motor loss is lower,the optimization accuracy of the efficiency optimization control is higher.Estimating the rotor resistance on-line can enhance the robustness of system to the parameter changes.In summary,the proposed novel vector control system has a good dynamic performance than the traditional one.The proposed vector control strategy has a better practical application value.