A Measurement System Of Impedance-Frequency Characteristic For Traction Power Supply

Railway is a means of large freight volume. high economic efficiency, low pollution and convenient transport. And it becomes more important in the modern economic society. With the great development of our country’s railway, there are still exsit all kinds of problems. There are so many resonance overvoltage occurs because of traction power supply system do not match with the EMU parameters. In order to avoid parameter mismatch occurs resonance overvoltage, carry out research on the impedance-frequency characteristic for traction power supply is very essential. This thesis focuses on the impedance-frequency characteristic for traction power supply do the relevant research.In order to understand the impedance-frequency characteristic for traction power supply, we need to calculate traction network impedance parameters. Using J.R. Carson proposed method to calculate the impedance of different traction network. Using the above parameters gained from traction network impedance to simulate in Matlab/Simulink, the results shows that traction network occur resonance when traction network impedance versus frequency. Throughout power supply section will have a large impedance, it is the interaction result of the distributed capacitance of traction network, traction transformer leakage inductance and external power system impedance.Because of traction transformer leakage inductance and external power supply impedance is nonlinear, it is hard to estimate through simulation. So we can use the method of measurement to estimate the impedance. Measurement methods have non-invasive measurement and invasive measurement those two types. Non-invasive measurement method is divided into fluctuation method, linear regression analysis method and complex random variables covariance method. Invasive measurement method divided into switching branches method and harmonic current injection method. Use methods above to build mathematical models, and through examples in Matlab to verify the feasibility and conditions of use. Finally, we use the non-invasive measurement method to analysis partial A-phase HOkV power system harmonic impedance of Jixian south traction substation.After discussing methods of the impedance-frequency characteristic for traction power supply, in order to achieve the goal, we use C# programming language, HS4 data acquisition card, various voltage sensors, current sensors and other hardware equipment developed a measurement system of impedance-frequency characteristic for traction supply. Through acquire the data of voltage and current. using the relevant measurement and mathematical method get the impedance-frequency characteristic for traction power supply.