Design Of Measurement Device Of Impedance-frequency Characteristic For Traction Power Supply Network Of Electric Railway

Since the railway transportation plays a key role in guaranteeing people's life and promoting the national economy,it is very important to ensure the safety and reliability of the railway.With the exuberantly development of Chinese railway,it has made remarkable achievements in the world.However,with the wide operation of AC-DC-AC electric multiple units(EMUs),the problem of high frequency harmonic resonance,caused by the electrical parameter mismatch between supply networks and vehicles,usually occurs.To solve this problem,it is significant to investigate the impedance-frequency characteristics of the networks.Therefore,this work engages to the developing of an impedance-frequency characterises measurement device using a converter as a harmonic source.Connected with the supply network through a transformer,an H-bridge converter abosorbs active power at fundamental frequency.The fundamental active power is converted to harmonic power through associate converter control such that harmonic current with adjustable frequency and amplitude can be injected into the network.Based on measured data of primary voltage and current,impedamce values of the network can be calculated by using interharmonic interpolation method.According to the calculated impedance values at different frequencies,an impedamce-frequency curve can be plotted.Consequently,the resonant frequency for a real supply network will be found.First,the function of the device is introduced and the production plan is discussed.Then,the characteristics and measurement methods of the harmonic impedance of the traction network are studied,including the influence of the background harmonic and the interharmonic interpolation method.A system model is developed through Matlab/Simulink,and simulation results validates the feasibility of the device.The topology of the main circuit of the device is studied,and the purity of the harmonic is analyzed by the formula of the converter output voltage.The types of the power swiches,capacitors and inductors are selected according to the analysis of the electrical parameter constraints of the device.The relevant equipments of the device,such as sensor,power source,etc.,are selected.In addition,necessary protection devices are configured to ensure the safety.The technical scheme and the layout of the measurement device are studied.The CAD drawing of the engineering application is drawn,and the FPGA program of the main control system is completed.The result of the theoretical analysis is validated on a scale-down experimental platform,which verified the reliability of the equipment,the function of the control system and the rationality of the overall design.The production of the actual device is completed,and the experiment of the power unit and the transformer is carried out.Finally,the whole system is tested.