An auxiliary converter adapted to provide power to auxiliary loads of an auxiliary electrical network of a railway vehicle , the auxiliary loads including a main air compressor , the auxiliary converter comprising: - a main inverter stage with a main inverter input and a main inverter output , the main inverter stage being configured for generating an AC voltage at its main inverter output from DC voltage received at its main inverter input from a live catenary; - a transformer stage connected to the main inverter output and adapted to convert, in a catenary operating mode, the AC voltage from the main inverter stage , the transformer stage having a supply output for supplying a supply voltage to the auxiliary loads and a separate charging output for supplying a reversible battery charger ; and - the reversible battery charger being connected to said charging output and adapted to charge, in said catenary operating mode, an electrical battery of said railway vehicle , wherein the reversible battery charger is adapted to, in a battery operating mode, deliver a supply voltage from the battery to said transformer stage for powering auxiliary loads, characterised by a high power rectifying and inverting stage connected to said supply output and adapted to provide power to said auxiliary loads of said auxiliary electrical network , wherein said high power rectifying and inverting stage comprises in series from input to output a single phase rectifier , a set of buffer capacitors and a three phase inverter . - a main inverter stage with a main inverter input and a main inverter output , the main inverter stage being configured for generating an AC voltage at its main inverter output from DC voltage received at its main inverter input from a live catenary; - a transformer stage connected to the main inverter output and adapted to convert, in a catenary operating mode, the AC voltage from the main inverter stage , the transformer stage having a supply output for supplying a supply voltage to the auxiliary loads and a separate charging output for supplying a reversible battery charger ; and - the reversible battery charger being connected to said charging output and adapted to charge, in said catenary operating mode, an electrical battery of said railway vehicle , wherein the reversible battery charger is adapted to, in a battery operating mode, deliver a supply voltage from the battery to said transformer stage for powering auxiliary loads, characterised by a high power rectifying and inverting stage connected to said supply output and adapted to provide power to said auxiliary loads of said auxiliary electrical network , wherein said high power rectifying and inverting stage comprises in series from input to output a single phase rectifier , a set of buffer capacitors and a three phase inverter . wherein the reversible battery charger is adapted to, in a battery operating mode, deliver a supply voltage from the battery to said transformer stage for powering auxiliary loads, characterised by a high power rectifying and inverting stage connected to said supply output and adapted to provide power to said auxiliary loads of said auxiliary electrical network , wherein said high power rectifying and inverting stage comprises in series from input to output a single phase rectifier , a set of buffer capacitors and a three phase inverter . <EOS>