Redundant control device and method of HVDC system

A redundant control device of a high voltage direct current (HVDC) transmission system, the redundant control device comprising:

• a first system and a second system that performs a function corresponding to that of the first system;
• and
• a first change over logic (COL) and a second COL that determine whether to switch between the first system and the second system,
• wherein there are optical communication modules between the first system and the first COL, between the first COL and the second COL, and between the second system and the second COL to transmit and receive data,
• wherein the first COL and the second COL comprise a monitoring control unit that checks a connection or wiring state of the optical communication modules and validity of transmission data, and
• wherein the first COL controls the first control module, the second COL controls the second control module, and according to states of the first system and the second system, the first COL controls the first control module and the second control module or the second COL controls the first control module and the second control module.