Energy Transmission Test Stand for Battery-Powered Railway Vehicles

For replacing diesel locomotives with battery-electric alternatives, a new system is introduced that relies on energy transmission via head-end power interface. The system consists of a battery storage unit, an inverter as well as filter components, and galvanic isolation. An important aspect is the reuse of main components for keeping the environmental impact as low as possible. In order to test its practicability, the concept is set up as a laboratory test stand. As the main parts of the equipment have been in use already, determination of their condition is necessary respectively modifications are required. The essential components of the laboratory set-up are an 800 V lithium-ion battery (LIB) storage unit, a gate turn-off (GTO) thyristor H-bridge, and passive filter inductors and capacitors. The LIB energy storage consists of 32 reuse modules. A second test environment is set up for determining whether a battery module is suitable for a second life cycle. For this purpose, a low-voltage high-current DC switch on basis of MOSFET semiconductors was designed and implemented. Furthermore, during testing and operation all LIB modules were monitored by a custom-made supervision circuit that reacts to any irregularity by shutting down the system. Two GTO inverters had to undergo modifications as in their original design they were used as a 3-level neutral point clamped (NPC) inverter leg. After surveying the state of the GTO inverters, they were formed into 2-level H bridges by applying minor changes. The original asymmetrical snubber circuit could be reused for the new topology. One of the inverters was used as solid-state switch for the battery while the other was used as an inverter for generating a 16.7 Hz AC voltage. It could be shown that a reuse of power electronics and lithium-ion batteries is possible as long as the components properties are taken into consideration. Also, the identification of a non-reusable LIB was shown and the properties of such a cell were measured.