A power supply system for an electrical equipment comprises a first power supply module for supplying power to the electrical equipment, wherein the first power supply module is connectable to a first electrical network and is adapted for converting a first input current from the first electrical network to an output current suppliable to the electrical equipment; a second power supply module for supplying electrical power to the electrical equipment, wherein the second power supply module is connectable to a second electrical network of different frequency and/or different voltage as the first electrical network and is adapted for converting a second input current from the second electrical network to the output current, when the first power supply module is not able to converting the first input current; and an electrical energy storage for supplying electrical power to the electrical equipment, wherein the electrical energy storage is adapted for providing the output current, when the first and/or second power supply module is not able to convert the first and/or second input current.