Method and control system for voltage control at a converter station

• US 6,400,585 B2
• Filed: 06/04/2001
• Issued: 06/04/2002
• Est. Priority Date: 06/02/2000
• Status: Active Grant

• Current Assignee: ABB Power Grids Switzerland AG (ABB Limited)
• Original Assignee: ABB AB (ABB Limited)
• Inventors: Jiang-Hafner, Ying
• Primary Examiner(s): Riley, Shawn
• Application Number:
  US09/871,893
• Publication Number:
  US 20020008982A1
• Time in Patent Office: 365 Days
• Field of Search: 363/35, 323/207, 307/82
• US Class Current: 363/35
• CPC Class Codes: H02J 3/36 Arrangements for transfer of electric power between ac networks via a high-tension dc link
• CPC Class Codes: H02M 7/7575 for high voltage direct transmission link
• CPC Class Codes: Y02E 60/60 Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

Abstract

A converter station (STN1, STN2) having a voltage source converter (CON1, CON2) is coupled between a direct current link (W1, W2) and an alternating current network (N1, N2) in a high voltage direct current transmission system. A control system (CTRL1, CTRL2) for the converter station has means for control of active power flow (P) between the direct current link and the alternating current network by influencing the phase displacement (γ) between a bus voltage (UL1, UL2, UL) in the alternating current network and a bridge voltage (UV1, UV2, UV) of the voltage source converter. The control system comprises detection means (48) for generation of a phase change order signal (PCO) in response to an indication of an abnormal voltage condition at the direct current link, and means (49) for influencing the phase position of the bridge voltage in response to said phase change order signal, so as to ensure that the phase displacement between the bridge voltage and the bus voltage will result in an active power flow from the direct current link to the alternating current network.

Claims

1. A control system (CTRL1, CTRL2) for a converter station (STN1, STN2) having a voltage source converter (CON1, CON2) coupled between a direct current link (W1, W2) and an alternating current network (N1, N2) in a high voltage direct current transmission system, the control system having means for control of active power flow (P) between the direct current link and the alternating current network by influencing the phase displacement (γ

) between a bus voltage (UL1, UL2, UL) in the alternating current network and a bridge voltage (UV1, UV2, UV) of the voltage source converter, characterised in that the control system comprises

detection means (48) for generation of a phase change order signal (PCO) in response to an indication of an abnormal voltage condition at the direct current link, and

means (49) for influencing the phase position of the bridge voltage in response to said phase change order signal, so as to ensure that the phase displacement between the bridge voltage and the bus voltage will result in an active power flow from the direct current link to the alternating current network.

2. A control system as claimed in claim 1, characterised in that said means for influencing the phase position of the bridge voltage comprises means for adding a fixed phase contribution (Δ

δ

) to the phase position of the bridge voltage.

3. A control system as claimed in claim 1, characterised in that said detection means comprises means (481, 482, 483) for receiving a sensed value of the voltage (Ud) of the direct current link, and for generating said phase change order signal when the amplitude of said sensed value exceeds a first limit value and the rate of change with respect to time of said sensed value exceeds a second limit value.

4. A control system as claimed in claim 2, characterised in that said detection means comprises means (481, 482, 483) for receiving a sensed value of the voltage (Ud) of the direct current link, and for generating said phase change order signal when the amplitude of said sensed value exceeds a first limit value and the rate of change with respect to time of said sensed value exceeds a second limit value.

5. A control system as claimed in claim 1, characterised in that the control system further comprises:

detection means (485, 486) for generation of the phase change order signal in response to an indication that the bridge voltage has lost its synchronism with the bus voltage.

6. A control system as claimed in claim 4, characterised in that the control system further comprises:

detection means (485, 486) for generation of the phase change order signal in response to an indication that the bridge voltage has lost its synchronism with the bus voltage.

7. A control system as claimed in claim 5, wherein the control system generates a reference value (IV_R^d) for the active power component of the alternating current (IV1, IV2, IV) at the converter, characterised in that said detection means comprises means (485) for receiving that reference value and a sensed value (IV^d) representative of the active power component of the alternating current at the converter, and for generating said phase change order signal when a difference of said sensed value representative of the active power component of the alternating current at the converter and the reference value exceeds a third limit value.

8. A control system as claimed in claim 6, wherein the control system generates a reference value (IV_R^d) for the active power component of the alternating current (IV1, IV2, IV) at the converter, characterised in that said detection means comprises means (485) for receiving that reference value and a sensed value (IV^d) representative of the active power component of the alternating current at the converter, and for generating said phase change order signal when a difference of said sensed value representative of the active power component of the alternating current at the converter and the reference value exceeds a third limit value.

9. A control system as claimed in claim 1, having a current control system (IREG) that generates a reference value ( {overscore (UV)}_R^abc) for the bridge voltage in dependence on a synchronising signal (ξ

) indicative of the phase position of the bus voltage, characterised in that said means for influencing the phase position of the bridge voltage in dependence on said phase change order signal comprises means (47) for receiving the synchronising signal, and for adding thereto said fixed phase contribution in dependence on said phase change order signal.

10. A control system as claimed in claim 8, having a current control system (IREG) that generates a reference value ({overscore (UV)}_R^abc) for the bridge voltage in dependence on a synchronising signal (ξ

) indicative of the phase position of the bus voltage, characterised in that said means for influencing the phase position of the bridge voltage in dependence on said phase change order signal comprises means (47) for receiving the synchronising signal, and for adding thereto said fixed phase contribution in dependence on said phase change order signal.

11. A control system as claimed in claim 9, wherein the alternating current network is a three-phase system (abc-system) and the current control system is operating in a rotating two-axis reference plane (dq-reference plane), the current control system comprising transformation means (43, 44) for transformation of the reference value ({overscore (UV)}_R^dq) for the bridge voltage from the rotating two-axis reference plane to the three-phase system in dependence on a transformation angle (ξ

′

), characterised in that said means for influencing the phase position of the bridge voltage in dependence on said phase change order signal real comprises means (47) for receiving the synchronising signal and said fixed phase contribution, and forming the transformation angle in dependence on a sum thereof.

12. A control system as claimed in claim 10, wherein the alternating current network is a three-phase system (abc-system) and the current control system is operating in a rotating two-axis reference plane (dq-reference plane), the current control system comprising transformation means (43, 44) for transformation of the reference value ({overscore (UV)}_R^dq) for the bridge voltage from the rotating two-axis reference plane to the three-phase system in dependence on a transformation angle (ξ

′

), characterised in that said means for influencing the phase position of the bridge voltage in dependence on said phase change order signal comprises means (47) for receiving the synchronising signal and said fixed phase contribution, and forming the transformation angle in dependence on a sum thereof.

13. Method for control of a converter station (STN1, STN2), using a converter station having a voltage source converter (CON1, CON2) coupled between a direct current link (W1, W2) and an alternating current network (N1, N2) in a high voltage direct current transmission system, the control system having means for control of active power flow (P) between the direct current link and the alternating current network by influencing the phase displacement (γ

) between a bus voltage (UL1, UL2, UL) in the alternating current network and a bridge voltage (UV1, UV2, UV) of the voltage source converter, characterised in that the method comprises the steps of;

generating of a phase change order signal (PCO) in response to an indication of an abnormal voltage condition at the direct current link, and

influencing the phase position of the bridge voltage in response to said phase change order signal, so as to ensure that the phase displacement between the bridge voltage and the bus voltage will result in an active power flow from the direct current link to the alternating current network.

14. A method as claimed in claim 13, characterised in that said step of influencing the phase position of the bridge voltage comprises the step of adding a fixed phase contribution (Δ

δ

) to the phase position of the bridge voltage.

15. A method as claimed in claim 13, characterised in that said step of generating a phase change order signal comprises the step of receiving a sensed value of the voltage (Ud) of the direct current link, and generating said phase change order signal when the amplitude of said sensed value exceeds a first limit value and the rate of change with respect to time of said sensed value exceeds a second limit value.

16. A method as claimed in claim 14, characterised in that said step of generating a phase change order signal comprises the step of receiving a sensed value of the voltage (Ud) of the direct current link, and generating said phase change order signal when the amplitude of said sensed value exceeds a first limit value and the rate of change with respect to time of said sensed value exceeds a second limit value.

17. A method as claimed in claim 13, characterised in that said step of generating of a phase change order signal comprises the step of generating the phase change order signal in response to an indication that the bridge voltage has lost its synchronism with the bus voltage.

18. A method as claimed in claim 16, characterised in that said step of generating of a phase change order signal comprises the step of generating the phase change order signal in response to an indication that the bridge voltage has lost its synchronism with the bus voltage.

19. A method as claimed in claim 17, wherein the control system generates a reference value (IV_R^d) for the active power component of the alternating current (IV1, IV2, IV) at the converter, characterised in that said step of generating a phase change order signal comprises the steps of receiving that reference value and a sensed value (IV^d) representative of the active power component of the alternating current at the converter, and generating said phase change order signal when a difference of said sensed value representative of the active power component of the alternating current at the converter and the reference value exceeds a third limit value.

20. A method as claimed in claim 18, wherein the control system generates a reference value (IV_R^d) for the active power component of the alternating current (IV1, IV2, IV) at the converter, characterised in that said step of generating a phase change order signal comprises the steps of receiving that reference value and a sensed value (IV^d) representative of the active power component of the alternating current at the converter, and generating said phase change order signal when a difference of said sensed value representative of the active power component of the alternating current at the converter and the reference value exceeds a third limit value.

21. A method as claimed in claim 13, wherein the control system has a current control system (IREG) that generates a reference value ({overscore (UV)}_R^abc) for the bridge voltage in dependence on a synchronising signal (ξ

) indicative of the phase position of the bus voltage, characterised in that said step of influencing the phase position of the bridge voltage comprises the steps of receiving the synchronising signal, and adding thereto said fixed phase contribution in dependence on said phase change order.

22. A method as claimed in claim 20, wherein the control system has a current control system (IREG) that generates a reference value ({overscore (UV)}_R^abc) for the bridge voltage in dependence on a synchronising signal (ξ

) indicative of the phase position of the bus voltage, characterised in that said step of influencing the phase position of the bridge voltage comprises the steps of receiving the synchronising signal, and adding thereto said fixed phase contribution in dependence on said phase change order.

23. A method as claimed in claim 21, wherein the alternating current network is a three-phase system (abc-system) and the current control system is operating in a rotating two-axis reference plane (dq-reference plane), the current control system comprising transformation means (43, 44) for transformation of the reference value ({overscore (UV)}_R^dq) for the bridge voltage from the rotating two-axis reference plane to the three-phase system in dependence on a transformation angle (ξ

′

), characterised in that said step of influencing the phase position of the bridge voltage comprises the steps of receiving the synchronising signal and said fixed phase contribution, and forming the transformation angle in dependence on a sum thereof.

24. A method as claimed in claim 22, wherein the alternating current network is a three-phase system (abc-system) and the current control system is operating in a rotating two-axis reference plane (dq-reference plane), the current control system comprising transformation means (43, 44) for transformation of the reference value ({overscore (UV)}_R^dq) for the bridge voltage from the rotating two-axis reference plane to the three-phase system in dependence on a transformation angle (ξ

′

), characterised in that said step of influencing the phase position of the bridge voltage comprises the steps of receiving the synchronising signal and said fixed phase contribution, and forming the transformation angle in dependence on a sum thereof.