Research On Load Modeling Of CRH2 EMU

High-speed railway can provide long-distance, mass-load transportation with environmentally friendly low emission. China has gained great progress in this field during recent years. As result, high-speed railway takes a growing proportion in the electrical power system. Equipped with the non-linear load, the high-speed railway has features such as mass capacity and high impact, which will influence the operational stability at some level. To cooperate with the current trend, researches of high-speed railway load pattern is extremely important to safe operation and reducing the stress on electricity system.Based on this ground, this thesis mainly focuses on the research of load modeling of CRH trains. A simulation model of CRH2 traction drive system has been built, so that the load modeling research can be conducted with different kinds of parameter identification algorithm.When building the model, the thesis focuses on the operation methods, control methods and control strategy of CRH2 traction rectifier and traction invertor, among which, the CRH2 traction rectifier circuit configurations, using single-phase three-level PWM rectifiers, provide a theoretical foundation for the following model simulation by analyzing the control method of transient direct current and SPWM pulse-width modulation principle. It also illustrates the reasons of neutral imbalance. Later, the thesis discusses how to reach neutral-point-potential balance control through the charge-discharge of the upper and lower capacitances. The thesis also elaborates the circuit configuration and operation model of CRH2 traction invertor, focusing on the analysis of the directional vector control of indirect rotor magnetic field, as well as the SVPWM pulse-width modulation principle. Based on the understanding and analysis of CRH2 construction and control strategy, a simulation model of CRH2 traction transmission mechanism is built with Simulink, and the validity of this model is examined through model verification, therefore can support the load modeling statistically.In the part of load modeling, the thesis briefly states the relevant information about the topic, including model category (TYPE SEL), recognition process, and recognition method, complaining with the characteristics of CRH2 units, describing the parallel index model of the used induction motor. Characterization is made to the engine torque of the trains by quadratic function of the speed, so that train models under different speed can be simulated. At the meantime, the parameter identification, and Generalization ability test can be conducted through genetic algorithm and particle swarm optimization on the dynamic load models of the trains. As a result, the identifications of both tests show an excellent ability of extrapolation and interpolation, which indicates the induction motor Parallel index model can describe the dynamic process of the train in an agreeable way.To sum up, this thesis uses induction motor in parallel index model, which shows an agreeable descriptive ability of the load characteristic of CRH2, and has great practical value to the research on high-speed train load characteristic as well as its impact on electricity system.