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Research On Regenerating Energy Utilization Technique In Urban Rail System

Posted on:2010-01-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:A G XuFull Text:PDF
GTID:1102360302490003Subject:Power electronics and electric drive
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With the rapid economical development and China's accelerating urbanization process, urban railway transit system grows flourish. On the urban rail trains, regenerative brake is usually used. It can save energy and meets the trends of energy saving and emission reducing. But now, the regenerating energy is of a low utilization rate, and the extra energy is wasted in heat. The wasted energy can even cause increasing aerator load of the tunnel. So, to improve the utilization rate of the regenerating energy and to save more energy, it's important and valuable to have a research on regenerating energy feeding to utility and buffering method. And this also goes with the direction of the urban railway transit's development.Firstly, the simulation model of the urban railway transit system for the analysis of regenerating energy is set up, and simulation study was carried out based on the data of the Nanjing Metro Line 1. The characteristic of the regenerating energy of the train set is discovered, which can be represented as high amplitude, shortly lasting time and highly power strike. The simulation model and results are helpful tools to the whole study for analysis and validation.Sencondly, as the problem of regenerating energy handling is caused by the unidirectional rectifier of the traction power supply, a new type of regenerating traction power supply with the ability of feeding the regenerating energy back to the utility is carried out, which adopts bidirectional rectifier. A new type bidirectional converter based on staircase-synthesize converter structure, which is also called mulitypulse converter and is characterized with low switching frequency, low switching losses, low EMI, low hamonics and low filter volume, is proposed in the paper. Thus, it's more suitable for high power conversion of the tranction power supply. To improve the regulation performance, a new sequential SVM technique is also proposed, which make the number of converter's adjustable switching events improving from 6 to 24 during a fundamental periode. It enlarges the bandwidth and reduces the time delay of the modulation link, and this gives an important foundation to improve the converter's dynamic regulation performance. With the analysis of the converter's transfer function model, a time-delay compensation method is brought out, which can reduce the system coupling made by the time delay of SVM link and can help the close loop controller to realize the decoupling current control and independent regulation of active power and reactive power. An instantaneous-value feedback control algorithm of the converter is introduced and the optimization of the controller parameters'selection is also described in detail to improve the dynamic performance, which makes the converter suitable for the urban rail transit with high regulation performance of the DC supply voltage. A 3kW protytype is also built up. The experimental results validate the fesibility of the bidirectional converter and control algorithm and prove that the converter is characterized with not only low switching frequency and sine current waveform but also fast dynamic regulation.Thirdly, a new hybrid traction power supply system is proposed based on the analysis of the merits and demerits of both regenerative power supply and storage method to handle the whole regenerating energy, which is composed with a regenerative power converter and an energy storage device. The most energy of the regenerating energy is feed back to the utility and this can reduce the energy storage capacity, device volume and costs. The energy storage device provides a peak power buffer and limits the peak power feeding back to the utility to a lower level to reduce the power shock, and this can also reduce the converter's capability of the power supply and improve the utilization rate of the converter's power capability. Three types of capacity configuration are proposed and two types of realization of the control algorithm are also provided in detail. Simulation is carried out based on the urban rail transit model. The regenerative energy's flow is studied and the DC supply voltage's deviation is also observed.Lastly, to cooperating with the regenerative power supply and reduce the energy's strike on the utility, a new scheme of energy storage system based on ultracapacitor is proposed. A modular energy storage topology is brought out, which can make the energy storage system adaptive to different supply voltage system and also reduce the number of the ultracapacitor connected in series and then improve the reliability of the energy storage system. The control algorithm of the bidirection DC/DC converter in the energy storage system, with the ability of input voltage balance when the converters are connected with inputs in series, is analyzed in detail. It makes the series-input power conversion topology applicable in the bidirectional power conversion. The voltage equallization is a key technology to improve the ultracapacitor stack's capacity and reliability. On the analysis of the existing equalization methods, a new type voltage equalization circuit is also proposed, which can be open-loop controlled or close-loop controlled according to needs of equalization speed. The circuit is simple and can realized automatic voltage equalization with no needs of voltage sensing network and voltage comparising circuits. Simulation and experiment studies are carried out to validate the fesibility of the key technology of the energy storage system.
Keywords/Search Tags:Urban rail transit, traction power supply, regenerative brake, regenerating energy, reversible rectification, staricase waveforme synthesization, energy storage system, ESS, ultracapacitor, voltage equalizer
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