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Selected papers from the 4th International Conference and Exhibition on Ecological Vehicles and Renewable Energies (EVER'09)
Edited by Professor Ahmed Masmoudi
1 Introduction
Electric traction is one of the major present-day solutions for environmental problems. Electric traction is safe, economical, reliable and with a minimum environmental impact. The latest demands for energy efficient, reliable and safe rolling stock require new technologies for the design of power electronic converters in the railway applications. The auxiliary power supply converter (APS) is one of the basic systems used in rolling stock. It provides low-voltage power to every onboard electrical system and equipment on a rail vehicle, including those that are critical to its safety and operability (like brakes or lighting systems). In brief, APS represents a step-down DC/DC converter, transforming high voltage from the traction catenary (3.0 kV DC in the case of a high-voltage DC catenary) to a lower voltage (350 V DC) for the onboard electric facilities. It is obvious that a failure within this system would render the whole vehicle non-operational, resulting in a financial loss, operational problems to the rolling stock owner and discomfort to passengers.
The development of APS converters began in the middle of the 1980s with the replacement of rotational converters (motor-generators) with new fully electronic concepts (static converters). Obvious achievements, like reduced weight and size, more flexible control and protection algorithms, have sufficiently improved the quality and reliability of the light rail vehicles. At the end of the 1990s, the thyristorized static converters began to be replaced by the transistorized ones. As a result, the efficiency, flexibility and reliability were further improved. In 2000, with the introduction of 6.5 kV insulated gate bibolar transistor (IGBTs), further optimization possibilities became available. Such transistors offer an attractive possibility to avoid series connection of IGBTs (for proper blocking voltage), providing higher efficiency, power density and reliability than the combined HV switch designs. Thus, the concept of 50 kW rolling stock APS was developed and implemented at the Department of Electrical Drives and Power Electronics of Tallinn University of Technology in 2007 ([5] Jalakas et al. , 2007). Based on simple two-level half-bridge topology, the APS (Figure 1 [Figure omitted. See Article Image.]) has shown an outstanding performance (Table I [Figure omitted. See...