Dual control apparatus and control method for HVDC system

1. A dual control apparatus for a HVDC system, the apparatus comprising:

a first controller and a second controller operated in a dual manner, the first controller and the second controller each including:

a deviation calculation unit calculating a deviation between a target value and a control value;

a PI controller performing proportional control and integral control on the deviation;

a first buffer storing an error value for the integral control performed by the PI controller of a relevant one of the first and second controllers; and

a second buffer storing an error value for the integral control performed by the PI controller of a remaining one of the first and second controllers,

wherein the PI controller of the first controller performs, using the error value stored in the first buffer of the first controller, the proportional control and the integral control on the deviation, and the PI controller of the second controller performs, using the error value stored in the second buffer of the second controller, the proportional control and the integral control on the deviation.

2. The dual control apparatus of claim 1 , wherein each of the first controller and the second controller stores the error value for the integral control performed by the PI controller of the relevant one of the first and second controllers in the first buffer of the relevant one, and provides the error value to the remaining one of the first and second controllers, and

the remaining one stores the received error value in the second buffer thereof.

3. The dual control apparatus of claim 2 , wherein when switching from the first controller to the second controller is performed, the PI controller of the second controller performs, using the error value stored in the first buffer of the second controller, the proportional control and the integral control on the deviation, and the PI controller of the first controller performs, using the error value stored in the second buffer of the first controller, the proportional control and the integral control on the deviation.

4. The dual control apparatus of claim 1 , further comprising:

a switching unit performing switching to select one of an output value of the PI controller of the first controller and an output value of the PI controller of the second controller,

wherein one of the output values of the PI controllers of the first controller and the second controller is provided to the HVDC system according to the switching of the switching unit.

5. A dual control method for a HVDC system, the method comprising:

a step a) of calculating, by a deviation calculation unit of a first controller, a deviation between a target value and a control value;

a step b) of performing, by a PI controller of the first controller, first proportional control and first integral control on the deviation;

a step c) of storing, by the first controller, an error value for the first integral control performed by the PI controller in a first buffer of the first controller;

a step d) of providing, by the first controller, the error value to a second controller;

a step e) of storing, by the second controller, the received error value in a second buffer of the second controller;

a step f) of performing, by the PI controller of the first controller, second proportional control and second integral control on the deviation using the error value stored in the first buffer of the first controller; and

a step g) of performing, by a PI controller of the second controller, third proportional control and third integral control on the deviation using the error value stored in the second buffer of the second controller.

6. The dual control method of claim 5 , further comprising: after the step g),

a step g1) of storing, by the second controller, an error value for the third integral control performed by the PI controller of the second controller in a first buffer of the second controller;

a step g2) of providing, by the second controller, the error value stored in the first buffer of the second controller to the first controller; and

a step g3) of storing, by the first controller, the received error value in a second buffer of the first controller.

7. The dual control method of claim 6 , further comprising: after the step g3), when switching from the first controller to the second controller is performed,

a step g4) of performing, by the PI controller of the second controller, fourth proportional control and fourth integral control on the deviation using the error value stored in the first buffer of the second controller; and

a step g5) of performing, by the PI controller of the first controller, fifth proportional control and fifth integral control on the deviation using the error value stored in the second buffer of the first controller.

8. The dual control method of claim 7 , further comprising: after the step g4),

storing, by the PI controller of the second controller, an error value for the fourth integral control in the first buffer of the second controller.

9. The dual control method of claim 7 , further comprising: after the step g5),

storing, by the PI controller of the first controller, an error value for the fifth integral control in the first buffer of the first controller; and

providing the error value stored in the first buffer of the first controller to the second controller.