Speed Sensorless Control Of Induction Motor Based On Phase Current Reconstruction

With the development of power electronics technology,microprocessing technology and the proposed of vector control,it completely breaks the monopoly position of DC speed regulation in the variable speed system and makes the AC speed control develop rapidly.As the asynchronous motor has the advantages of simple structure,low cost and reliable operation,it is widely used in the field of industrial control.The vector control system of asynchronous motor needs acquire real-time current and rotor position information.In order to get the information of current and rotor position,the current sensor and position sensor is usually adopted.But the price and maintenance costs of the sensors are high.And it greatly affected the expansion of the application range of asynchronous motor vector control system.Therefore,this thesis analyzes the speed sensorless vector control system of asynchronous motor based on single resistance sampling,which can eliminate the current sensor and position sensor.Firstly,the principle of reconstructing the phase current of the asynchronous motor based on the sampling of inverter bus current through single-resistor under the control of Space Vector Pulse Width Modulation(SVPWM)is analyzed in detail.Due to the influence of irrational factors in the actual control system,there is a blind spot of current reconstruction.For convenience,it is divided into three regions:low modulation non-observable area,medium modulation observable area and high modulation non-observable area.In the low modulation non-observable and medium-modulation observable region,the method of inserting the effective vector is used,and the voltage vector approximation is adopted in the high modulation non-observable region to extend the range of the current reconstruction algorithm.Secondly,in order to further reduce the cost of asynchronous motor vector control system,a speed sensorless control method called model reference adaptive system(MRAS)which based on asynchronous motor rotor flux observation is introduced.The combination of current reconstruction strategy to obtain the phase current,and through the combination model of the voltage and current model is used to estimate the rotor flux.This method deal with the difference of the flux between voltage model and current model through a PI regulation,then the results of its operation is used to compensate the flux of the voltage model so that the voltage model plays a major role at high speed,and the current model plays a major role at low speeds,thus avoiding the respective drawbacks of voltage model and current model.Finally,taking the voltage and current combination model as the reference model,the current model is the adjustable model.Then,the MRAS is used to estimate the speed of the motor.Finally,a simulation model of asynchronous motor speed sensorless system based on phase current reconstruction is built on MATLAB/SIMULINK platform,and the simulation results are analyzed.Then the hardware and software design of experiment platform based on STM320F103ZC chip is introduced.Experiments were carried out on a 4KW squirrel cage induction motor,and the experimental results show that the proposed algorithm is effective and feasible.