Method and controller for operating a propulsion system of a railway or heavy haul vehicle, and propulsion system

A method for operating a propulsion system of a railway or heavy haul vehicle in a catenary mode, the propulsion system comprising a first DC link electrically coupling the propulsion system to a catenary (12), a second DC link electrically coupled to a traction battery system of the railway vehicle, a first half-bridge electrically coupled to the first DC link, a second half-bridge electrically coupled to the second DC link, and an inductance electrically coupling the first half-bridge to the second half-bridge, the method comprising:

• receiving a first voltage signal which is representative of a first voltage provided by the catenary;
• receiving a second voltage signal which is representative of a second voltage provided by the traction battery system;
• comparing the first voltage with the second voltage;
• using the first half-bridge as a step-down converter to reduce the first voltage to the second voltage, when the first voltage is higher than the second voltage;
• and
• using the second half-bridge as a step-up converter to increase the first voltage to the second voltage, when the first voltage is lower than the second voltage.