High voltage converter system

A high voltage down-converter system comprising:

• a plurality of stations interconnected between a high voltage power line at a first voltage level and a common voltage lower than said first voltage level, each said station including:
• a step-down device connected to said common voltage;
• a high voltage switch module including a plurality of controllable switch elements in which the voltage is limited across each said controllable switch element to a predetermined voltage when each said voltage limiting controllable switch circuit is in an open state and to a zero voltage when each said voltage limiting controllable switch element is in a closed state, said voltage limited controllable switch elements being connected in series between said power line and said step-down device;
• and
• a control system to selectively set said open state and said closed state of said voltage limiting controllable switch elements to control the passage of current through said step-down device.

A high voltage converter system for undersea cable repeater stations comprising:

• a plurality of stations interconnected between a high voltage undersea power line at a first high voltage level and a common ground, each said station including:
• a step-down device connected to said common ground;
• a high voltage switching module including a plurality of controllable switch elements in which the voltage across each said controllable switch element is limited to a predetermined voltage when each said voltage limiting controllable switch element is in an open state and to a zero voltage when each said voltage limiting controllable switch element is in a closed state, said voltage limiting controllable switch elements being connected in series between said power line and said step-down device, and
• a control system to selectively set said open state and said closed state of each said voltage limiting controllable switch elements to control the current flowing through said step-down device in response to the potential difference between the first and second voltage levels;
• a conditioning circuit connected to said step-down device configured to output low voltage DC;
• and
• a repeater station connected to said conditioning device.