Research On Phase Current Reconstruction And Fault Diagnosis Method Of AC Drive System

AC drive systems are widely used in industrial production,transportation,industrial transmission and other fields.In an AC drive system,more than two current sensors are usually required to realize accurate acquisition of phase current and complete vector control.Multiple sensors not only increase the system cost,but also affect the motor control performance due to the inconsistency among the sensors,which limits the performance in high-performance applications.Therefore,reducing the size and cost of the control system and improving the reliability of the operation are very important for the electric drive system.In this paper,the research on single-sensor current reconstruction,error correction and fault diagnosis of the DC link is carried out for the three-phase two-level inverter.The principle of DC link sampling technology is analyzed,and the voltage space modulation area using SVPWM method is accurately divided by defining the minimum sampling time.In order to eliminate the current unobservable area,a single-sensor phase current reconstruction method based on Complementary Non-zero Space Vector Pulse Width Modulation(CNSVPWM)is proposed.Based on the principle of volt-second balance,the modulation method introduces a pair of complementary effective vectors and non-zero compensation vectors to extend the current sampling window,realizes the reconstruction of the three-phase current,and analyzes the loss under different modulation degrees,different speeds and switching frequencies.The simulation and experimental results show that the proposed CNSVPWM method can achieve accurate current reconstruction in the voltage space plane,the reconstruct current THD is less than 6.15%,and the current error is lower than 2.72%.In order to reduce the influence of zero drift on the reconstructed current accuracy in the single sensor motor control system,the cause of the zero drift error and the mechanism of the error amplification effect were analyzed,and an error self-correction pulse width modulation method was proposed based on the CNSVPWM strategy.By inserting measurement vector and compensation vector in the PWM carrier period instead of zero voltage vector,dynamic double sampling is performed on the DC link side current,and the detection and self-correction of current zero drift are realized.The experimental results show that the reconstruction error is less than 1.26%,which effectively eliminates the influence of zero drift on the reconstruction accuracy.Aiming at the open-circuit fault problem of the power tube of the three-phase two-level voltage source inverter,the fault type of the power tube of the inverter and the conduction state of the fault operation are analyzed,and the three-phase current reconstructed by the CNSVPWM method under the power tube fault state The information is transformed by Clark,and the converted reference current vector is normalized,and a normalized power tube fault diagnosis method based on single sensor complementary vector pulse width modulation is proposed,which realizes the detection of inverter power tube open circuit fault,the simulation results verify the effectiveness of the proposed fault diagnosis strategy.