STATIC COMPENSATOR AND METHOD FOR CONTROLLING THEREOF

• US 20110074367A1
• Filed: 09/28/2010
• Published: 03/31/2011
• Est. Priority Date: 09/30/2009
• Status: Active Grant

• Current Assignee: Korea Electric Power Corporation (Government of South Korea)
• Original Assignee: Korea Electric Power Corporation (Government of South Korea)
• Inventors: Yoon, Jong-Su, Kim, Yong-Hak
• Granted Patent: US 8,508,197 B2
• Time in Patent Office: Days
• US Class Current: 323/210
• CPC Class Codes: H02J 3/1842 wherein at least one reactive element is actively controlled by a bridge converter, e.g. active filters
• CPC Class Codes: Y02E 40/20 Active power filtering [APF]

Abstract

The present invention relates to a static compensator and a method for controlling thereof, more particularly, to a static compensator including a transformer connected with a bus of a power system; an inverter operating according to a control signal and connected to the transformer in series; a tap changer changing turn ratio of the transformer; and a controller generating the control signal to operate the inverter and generating a tap up or a tap down signal to provide to the tap changer and a method for controlling thereof.

Claims

1. A static compensator comprising:

a transformer connected with a bus of a power system;

an inverter operating according to a control signal and connected to the transformer in series;

a tap changer changing turn ratio of the transformer; and

a controller generating the control signal to operate the inverter and generating a tap up or a tap down signal to provide to the tap changer.

2. The static compensator of claim 1, wherein the controller comprises

an reactive current controller and a voltage controller generating a control signal to operate the inverter;

a tap changer controller generating the tap up signal or the tap down signal,

wherein the tap changer controller extracts an integrated value of a bus voltage when the bus voltage inputted from the bus is higher or smaller than a predetermined reference and outputs the tap up signal or the tap down signal after comparing the extracted integrated value with a predetermined excessive integration threshold value.

3. The static compensator of claim 2, wherein the tap changer controller comprises:

a first comparing unit comparing the bus voltage and the predetermined reference and generating an on or off signal;

an integrator extracting an integrated value of the bus voltage;

a timer positioned between the integrator and the first comparing unit and transmitting a time delay signal to the integrator when a signal is inputted from the comparing unit; and

a second comparing unit comparing the integrated value with a excessive integration threshold value and outputting a tap up signal or a tap down signal.

4. The static compensator of claim 3, wherein the predetermined reference is an upper limit or a lower limit of an operating voltage of the power system.

5. The static compensator of claim 2, wherein the voltage controller calculates reactive power using a difference between the bus voltage and the predetermined voltage and provides the calculated first reactive current to the reactive current controller, and

the reactive current controller calculates a voltage phase angle using a difference between the first reactive current and a predetermined reactive current and provides a phase angle of an output voltage of the inverter using the calculated voltage phase angle and a bus voltage phase angle.

6. A method for controlling a static compensator comprising:

(a) inputting a bus voltage of a power system;

(b) comparing the bus voltage with a predetermined reference;

(c) extracting an integrated value by integrating the bus voltage when the bus voltage is higher than the reference;

(d) comparing the extracted integrated value with a predetermined excessive integration threshold value; and

(e) providing a tap up signal to a tap changer of a transformer when the integrated value is equal to or higher than the excessive integration threshold value to change a turn ratio of the transformer.

7. The method of claim 6, wherein in the step (c), the reference is an operating voltage upper limit of the power system.

8. A method for controlling a static compensator comprising:

(a) inputting a bus voltage of a power system;

(b) comparing the bus voltage with a predetermined reference;

(c) extracting an integrated value by integrating the bus voltage when the bus voltage is smaller than the reference;

(d) comparing the extracted integrated value with a predetermined excessive integration threshold value; and

(e) providing a tap down signal to a tap changer of a transformer when the integrated value is equal to or higher than the excessive integration threshold value to change a turn ratio of the transformer.

9. The method of claim 8, wherein in the step (c), the reference is an operating voltage lower limit of the power system.