Trams as electric means of transport were brought into worldwide operation in the 19th century, and after significant reduction of the systems being used at the end of the 20th century, the 21st century witnesses their return into towns in Europe. Introduction of modern rolling stock with regenerative braking, especially into old infrastructure systems, requires significant modernization of power supply infrastructure in order to deliver energy to more powerful wagons and to use recuperated energy effectively. The process of improvement of the re-use of energy returned by braking trams is to be analysed globally, both taking into account rolling stock and power supply infrastructure. Sending regeneration energy from a braking tram to the power supply network, requires a tram taking energy (the network is receptive); otherwise braking energy will be dissipated at a braking resistor. There are certain methods for modernization of the existing power supply schemes, which could increase receptiveness of the power supply network. In case there is not enough energy storage devices (ultracapacitors or battery) on-board of vehicles or in a power supply system (in traction substations or just connected to a catenary) could be installed. It is also possible to equip traction substations with inverters to transfer energy from a DC to AC network.
The paper presents a review of parameters of power supply infrastructure of trams systems in Poland and a study case of their modernization in order to fit with new requirements and improve energy efficiency. Some results of application of such solutions with presentation of their effectiveness based on simulation analysis as well as data from measurements in real systems are enclosed

tram, power supply infrastructure, energy efficiency, recuperation