Design And Research Of Metro Auxiliary Converter

The auxiliary converter in mass-transit vehicles acts mainly as the energy converting device, which transforms DC power from pantograph into AC power, for the consumption of balanced loads, such as air-conditioners, air-compressors, and of un-balanced loads, such as heaters and contactors. The configurations and structures of auxiliary convertor are various in kind, which are analyzed and compared thoroughly in the thesis. After having obtained the advantages and disadvantages of each configuration, structure and control strategy, the thesis proposes an applicable topology.In the thesis, the hardware setup is analyzed, and circuit parameters are given, based on which the simulation and experimental prototype is built.In the view of former DC-DC, the high-frequency and modularized DC-DC circuit, as well as its switching scheme, to which is adopted the soft-switching scheme, are introduced and studied. Of the soft-switching scheme, the switching states in a switching period are analyzed thoroughly. To increase the voltage capacity of the device, DC-DC circuits are connected in series. The control strategy of this structure is studied, and power-equality strategy is proposed herein. The strategy is then testified with simulated results.In the view of latter inverter, for the solution of the problem of un-balanced loads, various applicable structures of the inverter are analyzed and compared, based on the conclusions from which a split-capacitor inverter is selected. What's more, three-dimension-space-vector modulation scheme is applied to latter inverter. Such scheme is capable of controlling zero-vector, making it perfect for the control of unbalanced loads. A novel control strategy based on symmetrical component method is proposed, and is proved to be capable of inhibiting unbalanced loads with the help of three-dimension-space-vector modulation scheme. The strategy stated above is also testified with simulated results.In the final part, experimental results from Line One in Guangzhou Metro System are given, which further proves the effectiveness and applicability of the hardware and control strategy of auxiliary converter, proposed in the thesis.