Dual controller system

A dual controller system comprising:

• a plurality of lower-layer circuits for performing respective functions;
• a clock signal-generating circuit for generating a clock signal according to a preset period,
• a first and a second controllers for transmitting identical control signals to control each of the plurality of lower-layer circuits according to the clock signal generated by the clock signal-generating circuit;
• and
• a relay circuit for relaying and blocking information between the first and second controllers and the plurality of lower-layer circuits,
• wherein both of the first and second controllers simultaneously operate in an active state and transmit the control signals to the relay circuit in the active state,
• wherein the first and second controllers transmit the control signals including identification information about the first and second controllers in each control signal,
• wherein each of the plurality of lower-layer circuits receives two control signals at a same clock signal through the relay circuit from both of the first and second controllers, inspects whether data included in the two control signals received from the first and second controllers is within or out of a preset reference range to check whether an error occurs in the two control signals, compares the two control signals to determine whether an error occurs in any one of the two control signals, and transmits a message indicating an occurrence of the error in one of the two control signals to the relay circuit when the error occurs in any one of the two control signals received from the relay circuit,
• wherein the relay circuit checks the message transmitted from each of the plurality of lower-layer circuits and checks the number of the lower-layer circuits each of which transmitted the message indicating that the error occurred in one of the two control signals, and then, when the number of the lower-layer circuits is equal to or greater than a preset reference number, the relay circuit determines that the error occurred in the first or second controller and blocks the control signal transmitted from the controller in which the error occurred, and
• wherein the lower-layer circuits are a plurality of sub-modules used in a High Voltage Direct Current (HVDC) system and the first and second controllers are sub-module controllers of the HVDC system.