Study On Energy-saving And Anti-oscillation Strategy For Regenerative Braking Of Metro Trains

The braking of metro train is performed by mechanical braking and regenerative braking cooperatively. When regenerative braking happens, to restrain overvoltage, the current of motors is controlled by current-limiting curve. The key parameters of this curve can effect the energy consumption and voltage of traction power system. Meanwhile, the regenerative braking control strategy is strongly linked with the stability of train. The instability problem of the system when regenerative braking happens can be solved through analyzing the control strategy in different working modes, improving it and then restraining the oscillation of current and voltage.At first, in this paper, to study the effects of the current-limiting curve key parameters on the traction power system. The models of every part in the system are analyzed and established, simulation software is made. The correctness and accuracy of this software are verified by comparing the simulation results and the actual data collected in a real metro line. To quantify the effects, the voltage-limiting rate and the splitting rate of nearby substations are defined. With the software, the effects that the current-limiting parameters have on the voltage and energy consumption are analyzed respectively.Next, to research the stability of the system controlled by current-limiting curve, the model of a single power supply interval with a tracting train and a braking train is established, the working modes of this model are classified according to the research requirements. Four main working modes of this model are analyzed, the instability mode is confirmed. In the working mode which is not stable, the static characteristics of the tracting train and the braking train are studied, the balance point is found out. Through the analysis of the small signal model near the balance point, the corresponding transfer function is established. By observing the characteristics of the transfer function under the control of current-limiting curve, the reason for the oscillation under the curren limiting curve is analyzed. Based on above, the first anti-oscillation strategy with PI control is put forward, by simplifying the transfer function, the control parameters designing is finished. Effects of other parameters on the stability under PI control are discussed. The second anti-oscillation strategy is based on the Hamiltonian system, the energy-shaping theory is used to analyze the system. The interconnection and damping assignment passivity-based control (IDA-PBC) is applied to finish the designing of the controller. The traction power observer is also designed to calculate the current and voltage at the balance point.Finally, with the models built in Matlab, the oscillation phenomenon is proved in a single power interval, the two strategies are carried out and the validity and feasibility of the strategies are proved. The experiments are performed with motors platform based on DSP control system and a motor controlled by Myway system. The results of system debug prove the existence of the oscillation and the correctness of the oscillation reasons. Analyses of the experiments results show the validity and feasibility of the two anti-oscillation strategies too.