Research On Fault Tolerant Control Of Current Sensors For Induction Motors Based On Dual Torque Model

At present,the new energy vehicle industry is developing rapidly,and induction motors(IM)are widely used in the field of new energy vehicles due to their advantages of good durability,stable structure,and high energy conversion efficiency.Direct torque control(DTC)is a partially decoupled control system using a hysteresis controller,which does not require complex rotational coordinate transformations and can achieve fast torque control in a short time.It has the advantages of good dynamic performance,simple structure,and high robustness,and is a high-performance control method for induction motors.However,DTC has large torque ripple and poor low-speed steady-state performance.The reliability and accuracy of current signals are crucial for the stability and control accuracy of DTC closed-loop control systems,while current sensors are prone to signal misalignment or even loss due to faults caused by high temperature,vibration,and complex electromagnetic interference.This article mainly conducts research on the shortcomings of the above DTC.Firstly,in response to the problem of large DTC ripple and insufficient low-speed steady-state performance,a dual torque model composed of electromagnetic torque and virtual torque is derived using the vector product and scalar product of stator flux and stator current vector as new state variables.Based on the dual torque model,a new DTC control method,Direct Dual Torque Control(DDTC),is designed.The proposed method can directly calculate electromagnetic torque and virtual torque,and add flux closed-loop negative feedback control to achieve independent control of variables at multiple time scales.It has good ripple suppression ability and torque response speed.By analyzing the sensitivity of electromagnetic torque and virtual torque to changes in motor parameters,it is theoretically demonstrated that the DDTC method has strong robustness to stator resistance and rotor resistance parameters.After simulation verification,the DDTC method has fast speed response and strong robustness,and can effectively suppress torque ripple and flux ripple.Then,in response to the strong dependence of the closed-loop control system on current signals and the problem of current sensor faults causing current signal misalignment or even loss,a current sensor fault-tolerant control scheme suitable for DDTC is proposed.By designing the feedback matrix,the stator current reconstructed by the full order state observer is used to replace the stator current measured by the current sensor,so that the induction motor can achieve fault tolerant operation under the fault condition of the current sensor.By analyzing the stability and parameter robustness of the observation system,it is theoretically proven that the observer system has low sensitivity to changes in stator resistance and rotor resistance parameters.The simulation results show that the full order state observer can accurately estimate the stator current,enable the DDTC control system to achieve fault tolerant operation without current sensors,reduce the dependence of the control system on current sensors,and improve the safety of the control system.Finally,on the basis of theoretical demonstration and simulation analysis,with the dSPACE DS1104 controller as the core,a hardware in the loop experimental platform of induction motor control system is built to test the conventional DTC method,DDTC method and DDTC method based on full order state observer.The experimental waveform results show that the proposed method can reduce torque ripple and flux ripple,achieve current sensorless control of induction motors,and have good dynamic and steady-state performance.