The requirements regarding modern light traction vehicles, such as trolleybuses and trams, gradually increase. Special focus is set to operation without trolley power supplytemporarily while remaining free of emissions. Efficiency, power density, volume and weight of the system become more important. At the same time, low acoustic noise and restrictive EMI-standards have to be met.
These particular requirements can be met using energy storage systems based on Lithium-Ion traction batteries or supercapacitors. To fully utilize the capabilities of the storage systems, it is necessary to employ suitable power converters to manage the flow of energy in both, charging and consuming. This correlates to DC-DC converters which have to handle substantial cyclic loads at potentially high operating temperatures.
The ability to temporarily operate without the trolley power supply is a feature found more often among the requirements regarding light traction vehicles. This mode of operation is utilized within the urban areas lacking the catenary infrastructure such as historical centers. It also applies for connections between separated lines and is needed for emergency vehicle operation during power blackout as well. In addition, low-noise, high-comfort, zero-emission operation is demanded, ruling out the diesel-electric drive train as it was commonly used inthe past.
The sum of requirements can be met installing an electric/electric hybrid approach.
In this, traction batteries or super-capacitors are installed as energy storage systems, providing intermediate power to the electric drive
train.