Research On Harmonics Detection And Compensation Method Of Electric Railway Traction Load

Electric locomotive with its energy-saving, environmental protection, efficient advantage has replaced traditional diesel locomotive, to become the main force of China’s railway transportation industry. At the same time, due to the electric locomotives converter circuit contains a large number of non-linear power electronic devices, as well as the operational status of the complex electric locomotive makes the running electric locomotive will generate a lot of harmonics. When these harmonics injected into the public grid, it will produce great harm, so we must do the work of electric railway harmonic control. The harmonic control study mainly focused on two aspects, harmonic analysis and harmonic compensation.In the field of harmonic analysis, the following analysis methods are being adopted.fast Fourier transform method, based on expansion Prony algorithm, artificial neural power line and wavelet transform. In recent years, wavelet transform has gradually become the hot spot of research in the field of signal analysis with its unique advantages, one of the focus of this study is the wavelet transform theory applied to the electric railway harmonic analysis. First, through the theoretical analysis verify the importance of selecting the appropriate wavelet function, and then based on the guidelines for the minimum length description of wavelet db10wavelet function select harmonic signal treatment and further select a reasonable decomposition level. Finally, simulate the analysis of harmonic current electric locomotive through using two methods of Fourier analysis and wavelet analysis respectively. By a comparative analysis of the two sets of simulation results we can know that wavelet analysis not only make the fundamental component of the harmonic currents and harmonic components of the electric locomotive effectively separated, and then get the relevant parameters such as the effective value of the harmonic, and have higher accuracy and real-time compared with Fourier analysis method.To solve the problem of active power filter application in the high power applications of electrified railways harmonic compensation, In this paper, a cascade active power filter based on a new hanging capacity of harmonic compensation package is being proposed. First, the main circuit topology works of the cascade active power filter were introduced. Then, the main circuit switching devices for the system overall are designed, the valve block unit as the cascade cascade APF core H-bridge and illustrate the start-up mode and redundant safety protection are designed. Finally, the number of cascaded H-bridge structure, switching frequency, the DC side capacitance values and other parameters and with the switching harmonics for cascade APF output compensation current I design the LCR output filter are designed.In order to achieve effective control of the cascade APF filter to achieve the desired effect, this paper designed a controller assisted of the master chassis and expansion chassis. In the controller, the main chassis mainly completes the function of the data processing and the commendation of task, the expansion chassis mainly completes the function of the data acquisition and the commendation of performing the task and exchange various kinds of information through the optical. The control method for single-phase power supply of electric railway traction power supply system, this paper based on the instantaneous reactive power theory of single-phase circuit harmonic detection method. Against the cascade APF DC side voltage instability as well as the various manifolds unit DC voltage imbalance, this paper presents a DC voltage balance control method, a very effective way to solve this problem. Finally, the simulation results show that the control system cascade APF has good harmonic compensation.The test Shenshuo traction substations linked power line running test results analysis shows that the cascade Active Power Filter can effectively compensate the electrified railway harmonics, harmonic content in the system is greatly reduced compared with with compensation, meet harmonic regard national standards. This shows that the program has a good filtering performance, fully able to meet the the harmonic compensation requirements of electric railway, and has good application prospects.