Research On APF Control Strategy And Fault-Tolerant In Fault Diagnosis Based On Model Prediction

As a clean energy,electric energy is easy to use.In the study of power quality,harmonics are an important part.The active filter can detect and compensate the harmonics of the power grid in real time,and the compensation effect is greatly affected by its topology,control strategy and power device tube fault.Based on the active power filter(APF)with T-type three-level topology,this thesis has carried out the following research on control strategy and fault diagnosis:(1)The traditional model predictive control(MPC)control strategy needs to traverse 27 output vectors in each optimization period,and the calculation time is long and the step duty cycle is large.In addition,the traditional voltage vector used by the traditional MPC may deviate from the reference output vector,resulting in poor harmonic compensation.On the basis of this research,a MPC control strategy based on virtual vector is proposed.The virtual voltage vector is synthesized by the basic voltage vector output by the three-level inverter,which improves the number and accuracy of the original candidate vector set predicted by the traditional model,and then improves the compensation accuracy of APF for harmonics.At the same time,in order to solve the problem of long calculation cycle,an improved sector judgment and vector allocation is proposed.After positioning the sector,the value function only needs to calculate the vectors in the specified small sector,and only 7-8 output vectors are calculated in one optimization cycle,which significantly improves the calculation speed of each cycle.(2)After the IGBT open-circuit fault occurs in the T-type three-level inverter,the DC-side capacitor voltage residual increases,and the output voltage of the inverter deviates from the command voltage.According to the fault characteristics,a T-type three-level fault diagnosis method based on voltage residual is proposed.The fault is judged and the odd and even power devices are located by the DC-side capacitor voltage residual value,and then the residual value of the inverter command voltage and output voltage is located to the phase power device and the upper and lower bridge arm power device,and the position of the IGBT open circuit fault of the power device is accurately found.(3)When the APF power device fails during operation,and the voltage vector corresponding to the fault power tube cannot be output normally after the fault,the harmonic compensation effect will be greatly reduced,and even further cause the decline of power quality and the damage of APF system power device.A fault-tolerant operation control strategy based on residual vector is proposed,which makes APF still have certain harmonic compensation ability after fault.When the longitudinal power device fails,the hardware reconfiguration is used to transform the T-type three-level inverter into a two-level inverter;when the lateral power device fails,only the large vector and zero vector of the normal output are used to realize the fault-tolerant operation of APF.(4)The simulation model of the proposed method is built on the Matlab / Simulink platform,and the experimental model based on the RT-LAB semi-physical platform is built to verify the effectiveness of the research content in this thesis.This thesis has 68 figures,9 tables and 85 references.