Research On Portable Electric Power Quality Comprehensive Test And Analysis Equipment Based On VMD

With the rapid development of electrified railways in China,high-speed railways and heavy-duty railways have played an increasingly important role,and at the same time brought some problems.Due to the large number of non-linear new power electronic devices used in electrified railways,the problems of harmonics,negative sequence and voltage sags in the traction power supply system become more complicated,which will not only affect the safety of the traction power supply system,but also cause pollution to the large power grid,affect the reliable and stable operation of the power grid,and even lead to the occurrence of safety hazards in the abnormal noise of the traction transformer.Using power quality comprehensive testing and analysis equipment to detect problems in time will not only help the traction power supply system to operate safely and reliably,improve its transportation efficiency,but also enable the related equipment to fully play its role and reduce maintenance costs.In addition,the general traction substations are remote,and the transportation is inconvenient.There is an urgent need for portable test and analysis equipment with small size,light weight and full functions.Therefore,this paper designs and develops a set of portable electric railway power quality comprehensive test and analysis equipment,and uses this equipment to collect and analyze the current,voltage,and vibration signals of the traction power supply system,as follows:First,a data acquisition system was designed.The hardware was selected for the current clamp,voltage signal line and acceleration sensor.The conditioning circuit of the data acquisition part was designed and manufactured to collect the current signal,voltage signal,and traction transformer vibration signal;On the software side,Lab VIEW-based data acquisition programming was performed to acquire the sensor signals to the computer.The designed data acquisition system was applied to the field test.The test results show that the data acquisition system can run normally,and the data collection work is realized.Secondly,according to the harmonic characteristics of traction power supply system,a harmonic detection method based on Matching Pursuit algorithm and Variational Modal Decomposition algorithm is proposed,and this method is used with common harmonics such as fast Fourier transform and wavelet transform.The detection and analysis methods are simulated and compared,and the results prove that the method can effectively detect the harmonic content of the electrified railway traction power supply system.Then,the related voltage sag detection algorithms are studied,and simulations and comparisons are performed to illustrate the applicable occasions and advantages and disadvantages of their respective algorithms.Finally,a voltage sag detection analysis method based on Variational Modal Decomposition and Hilbert transform is proposed for voltage sags of high-speed and heavy-load railways.and the effectiveness of the method for voltage sag detection is proved by simulation.Finally,a data comprehensive analysis system based on Lab VIEW was designed,and the harmonic analysis and voltage sag detection methods mentioned in this paper were applied to the system.Finally,a set of portable electric railway power quality synthesis from data collection to data analysis was developed.The test and analysis equipment realizes the test and analysis of the traction power supply capability,including power quality analysis such as harmonics and voltage sags,and related vibration frequency analysis.Field tests have been performed using the device to verify that the device is of applicable value.