Method and control system for voltage control at a converter station
First Claim
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 comprisesdetection 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.
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Accused Products
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.
24 Citations
24 Claims
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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.
- ) 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
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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.
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7. A control system as claimed in claim 5, wherein the control system generates a reference value (IVRd) 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 (IVd) 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.
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8. A control system as claimed in claim 6, wherein the control system generates a reference value (IVRd) 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 (IVd) 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.
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9. A control system as claimed in claim 1, having a current control system (IREG) that generates a reference value ( {overscore (UV)}Rabc) 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.
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10. A control system as claimed in claim 8, having a current control system (IREG) that generates a reference value ({overscore (UV)}Rabc) 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.
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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)}Rdq) 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.
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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)}Rdq) 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.
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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. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
- ) 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;
Specification