Research On Open Circuit Fault Diagnosis Method Of Vector Control System Power Switching Device

As the new energy power equipment,motor has many advantages such as green environmental protection,small size,high energy efficiency,precise control and so on.Especially under the background of the increasingly serious energy and environment problems,it has been widely used in industry,agriculture,transportation,aerospace and national defense.According to research and statistics,power switching device is one of the devices with the highest fault frequency in motor control system.Its faults can be divided into open-circuit faults and short-circuit faults.The short-circuit faults have mature hardware protection measures,and in the case of open-circuit faults,the control system still operates sustainably.If not processed,it will cause secondary faults of the system until the system collapses under open-circuit faults.Fault detection and location is challenging and has become a hot topic for scholars.In this paper,the real-time open-circuit fault diagnosis method of two-level voltage source power converter in asynchronous motor vector control system is studied to improve its reliability.This paper introduces the working principle of motor vector control system and analyzes the fault mechanism of power converter.The current distortion of closed-loop control system under different faults is discussed in depth.Based on covariance theory,the current correlation under different faults is analyzed,and the mathematical model of covariance proportional coefficient is established.A fault diagnosis method of power converter bridge leg based on covariance theory is proposed,which can detect three kinds of open-circuit faults of bridge leg.The d-q axis current is preprocessed by wavelet transform,the approximate components and detail components of wavelet decomposition are extracted for fault feature analysis.A novel open-circuit fault diagnosis method based on wavelet transform and covariance analysis is proposed.The method extracts features based on wavelet transform,realizes fault detection and distinguishes open-circuit faults between single-leg and double-leg.At the same time,based on covariance theory,the faults of power switching devices are located,and the 21 kinds of open-circuit faults of power switching devices can be detected.In this paper,the MATLAB simulation experiment platform of asynchronous motor vector control system is built to simulate and verify the designed bridge leg fault diagnosis method and power switch device composite fault diagnosis method,the system deep test and verification work is carried out based on the physical experiment platform.The simulation and test results show that the bridge leg fault diagnosis method and power switch device composite fault diagnosis method designed in this paper have the advantages of fast fault detection speed,less dependence on system parameters and strong anti-interference ability of transient response such as variable speed and variable load of the system.The methods are applicable to different work environment with simple threshold setting,less CPU resources and strong engineering practicality.