(19)
(11)EP 3 211 743 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
09.10.2019 Bulletin 2019/41

(21)Application number: 15871856.9

(22)Date of filing:  09.12.2015
(51)International Patent Classification (IPC): 
H02J 3/36(2006.01)
H02H 7/122(2006.01)
H02J 3/38(2006.01)
(86)International application number:
PCT/CN2015/096747
(87)International publication number:
WO 2016/101787 (30.06.2016 Gazette  2016/26)

(54)

ISLAND-TO-NETWORK SWITCHING METHOD

ISLAND-TO-NETWORK-SCHALTVERFAHREN

PROCÉDÉ DE COMMUTATION D'ÎLOT À RÉSEAU


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 23.12.2014 CN 201410812231

(43)Date of publication of application:
30.08.2017 Bulletin 2017/35

(73)Proprietors:
  • NR Electric Co., Ltd.
    Nanjing, Jiangsu 211102 (CN)
  • NR Engineering Co., Ltd
    Nanjing, Jiangsu 211102 (CN)

(72)Inventors:
  • DONG, Yunlong
    Nanjing Jiangsu 211102 (CN)
  • TIAN, Jie
    Nanjing Jiangsu 211102 (CN)
  • HU, Zhaoqing
    Nanjing Jiangsu 211102 (CN)
  • LI, Haiying
    Nanjing Jiangsu 211102 (CN)
  • CAO, Dongming
    Nanjing Jiangsu 211102 (CN)
  • LIU, Haibin
    Nanjing Jiangsu 211102 (CN)
  • LU, Yu
    Nanjing Jiangsu 211102 (CN)

(74)Representative: Hanna Moore + Curley 
Garryard House 25/26 Earlsfort Terrace
Dublin 2, D02 PX51
Dublin 2, D02 PX51 (IE)


(56)References cited: : 
CN-A- 102 255 329
CN-A- 102 510 124
CN-A- 103 904 676
US-A1- 2008 084 643
CN-A- 102 403 735
CN-A- 103 647 286
CN-A- 104 485 683
US-A1- 2014 103 727
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND


    Technical Field



    [0001] The present invention relates to the field of power electronics, and in particular, to an island-to-active network switching method for a VSC-HVDC transmission system.

    Related Art



    [0002] The voltage source type converter is used for high direct-current transmission, and active power and reactive power can be controlled independently and fast, so as to improve system stability, inhibit fluctuation of a system frequency and a system voltage, and improve stable performance of a grid-connection alternating-current system. Flexible direct-current transmission has great advantages in fields such as new energy grid connection, distributed power generation grid connection, island power supply, and urban distribution network power supply. Therefore, researches on technologies related to flexible direct-current transmission have important meanings.

    [0003] When a flexible direct-current transmission system is in an island operation state, a proximal-end in a converter station is closed to connect to an alternating-current grid or a remote-end switch is closed. A flexible direct-current converter station is connected in parallel to an active grid for operation. The flexible direct-current system needs to switch from a current island operation control mode to a grid-connected operation control mode, to maintain continuous operation of the direct-current transmission system.

    [0004] When a flexible direct-current transmission system is in an island operation state, if the flexible direct-current transmission system enters a grid-connected state because of a close operation on a switch, a moment at which the flexible direct-current transmission system enters the grid-connected state needs to be accurately detected, and the current island operation needs to be switch into active operation in time. Otherwise, relatively long duration will cause the grid to be out-of-synchronization, and consequently the VSC HVDC transmission system stops operation. Meanwhile, smooth switching to operation in an online manner is also required, so that the VSC HVDC transmission system is prevented from performing a protection action and being out of service that are caused by an overcurrent or overvoltage phenomenon aroused at a switching moment. Currently, there no report related to a detection manner for detecting a change of a grid operation manner by a flexible direct-current transmission system in an island operation state for entering an online state and smoothness control.

    [0005] The relevant state of the art is represented by CN 103647286 A and CN 103904676 A.

    SUMMARY



    [0006] The present teaching provides a method as detailed in claim 1. Also provided is a control system according to claim 5. Advantageous features are provided in dependent claims.

    [0007] An objective of the present invention is to provide a method for detecting a change of a grid operation manner by a flexible direct-current transmission system in an island operation state for entering a grid-connected state, so as to ensure accurate and smooth switching of the flexible direct-current transmission system from an island operation state to an online operation state.

    [0008] To achieve the foregoing objective, a technical solution is used in the present invention:
    A control system determines, by detecting whether an overcurrent phenomenon occurs in a converter bridge arm current and change statuses of network-side and valve-side voltages, whether a VSC HVDC transmission system enters a grid-connected state, including the following steps:
    1. (1) when a converter station of the VSC HVDC transmission system is in an island operation state, detecting whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current; and if the overcurrent phenomenon occurs and the overcurrent phenomenon lasts for a duration t1, performing step (2); and otherwise, performing step (1) again;
    2. (2) Blocking a converter, and detecting whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, deblocking the converter and performing step (1) again; and otherwise, performing step (3); and
    3. (3) controlling setting of a system phase-locked loop to track the current alternating-current side voltage phase, at the same time, starting to switch a control mode, switching from a current island control mode of the converter station of the flexible direct-current transmission system to an active control mode, and unlocking the converter.


    [0009] In the foregoing step (1), the overcurrent constant value setting is set to n times a converter rated valve-side current or a converter bridge arm current. A value range of n is 1 to 10, a value range of the duration t1 is 0 to 1s, and a value range of t2 is 0 to 1s.

    [0010] In the foregoing step (2), a value range of the threshold of the alternating-current side voltage is 0 to 0.99 pu, and a value range of a duration t is 0 to 1s.

    [0011] At a moment of switching the control mode in step (3), active power and reactive power instructions maintain current operation values of an active power and a reactive power. Alternatively, an active power and are active power may be 0, and may gradually increase, by means of a slope, to current operation values.

    [0012] The present invention further includes an island-to-online control apparatus, including a converter overcurrent detection unit, an alternating-current side voltage detection unit, and an island-to-online mode switching unit.

    [0013] When a converter station of a VSC HVDC transmission system is in island operation state, the converter overcurrent detection unit detects whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current; and if the overcurrent phenomenon occurs, and the overcurrent phenomenon lasts for a duration t1, the alternating-current side voltage detection unit works; and otherwise, the converter overcurrent detection unit works again.

    [0014] The alternating-current side voltage detection unit first locks a converter, and then detects whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, the converter is unlocked, and the converter overcurrent detection unit continues to perform detection; and otherwise, the island-to-online mode switching unit works.

    [0015] A function of the island-to-online mode switching unit is switching a control mode; at a moment of switching the control mode, active power and reactive power instructions maintain current operation values of an active power and a reactive power; or, after the switching, an active power and a reactive power are converted to 0, and gradually increase to operation values before the switching.

    [0016] The present invention further includes an island-to-online control system, including a converter, an upper layer controller, and a valve-controlled apparatus, where
    1. (1) when a converter station of a flexible direct-current transmission system is in an island operation state, the upper layer controller detects whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current;
      and if the overcurrent phenomenon occurs, and the overcurrent phenomenon lasts for a duration t1, step (2) is performed, otherwise, step (1) is performed again;
    2. (2) a converter is blocked, and it is detected whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, the converter is deblocked, and step (1) is performed again; and otherwise, step (3) is performed;
    3. (3) the upper layer controller sets a phase-locked loop to track the current alternating-current side voltage phase, at the same time, starts to switch a control mode, switches from a current island control mode of the converter station of the flexible direct-current transmission system to an active control mode, and unlocks the converter.


    [0017] After the foregoing solutions are adopted, the present invention has the following beneficial effects:
    In the method for detecting a change of a grid operation manner by a flexible direct-current transmission system in an island operation state for entering an online state provided in the present invention, detection on a grid connection moment is accurate, and an online operation manner may be smoothly switched to without causing an impact on a grid.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0018] 

    FIG. 1 is a schematic structural diagram of double stations of a VSC HVDC transmission system;

    FIG. 2 is a schematic diagram of a control mode of a grid connection detection converter station;

    FIG. 3 is a schematic diagram of a control mode of a constant direct-current voltage control station; and

    FIG. 4 is a flowchart of VSC HVDC grid connection detection in an island operation mode.


    DETAILED DESCRIPTION



    [0019] The technical solutions are described below in detail with reference to accompany drawings and specific embodiments

    [0020] As shown in FIG. 1, flexible direct-current transmission converter stations 201 and 202 are in an island operation state. A remote-end switch 102 is not closed, the VSC HVDC transmission systems 201 and 202 are not connected to an alternating-current grid 400, and the VSC HVDC transmission systems 201 and 202 are in the island operation state. 202 is a constant direct-current voltage control side. Refer to FIG. 3 for a control mode of 202. 201 uses a control mode in FIG. 2. FIG. 3 shows a constant direct-current voltage control mode, which remains unchanged before and after switching. An active control mode is switched to when an online state is detected in a grid connection detection section in FIG. 2. If the switch 102 is closed, whether to switch from island operation to online state operation is detected (refer to FIG. 4) according to the following steps:
    1. (1) When a converter station of the flexible direct-current transmission system is in an island operation state, detect whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current; and if the overcurrent phenomenon occurs and the overcurrent phenomenon lasts for a duration t1, perform step (2); and otherwise, perform step (1) again.
    2. (2) Block a converter, and detect whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, unlock the converter and perform step (1) again; and otherwise, perform step (3).
    3. (3) Control setting of a system phase-locked loop to track a current alternating-current side voltage phase, at the same time, start to switch a control mode, switch from a current island control mode of the converter station of the flexible direct-current transmission system to an active control mode, and unlock the converter.


    [0021] A value range of the duration t1 is 0 to 1s, and a value range of t2 is 0 to 1s.

    [0022] After the switch 102 is closed, if a network side 400 is in an active state, the converter 201 switches from an island control mode to an active control mode according to the foregoing steps. In a special case, the network side 400 is a passive system. After the switch 102 is closed, a bridge arm overcurrent phenomenon does not occur in a normal status. Therefore, the control mode is not switched. Alternatively, after the converter is locked, if it is detected that an alternating-current side voltage is lower than a threshold, an online detection condition is immediately barred for a period of time, it is forbidden to switch from island operation to online operation, and at the same time, the converter is immediately released to trigger a pulse. The online detection process ends, and the converter 201 still maintains an original island operation state.

    [0023] The present invention further provides a passive islanding-to-grid connected control apparatus, including a converter overcurrent detection unit, an alternating-current side voltage detection unit, and an island-to-online mode switching unit. When a converter station of a VSC HVDC transmission system is in an island operation state, the converter overcurrent detection unit detects whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current; and if the overcurrent phenomenon occurs, and the overcurrent phenomenon lasts for a duration t1, the alternating-current side voltage detection unit works; and otherwise, the converter overcurrent detection unit works again.

    [0024] The alternating-current side voltage detection unit first locks a converter, and then detects whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, the converter is deblocked, and the converter overcurrent detection unit continues to perform detection; and otherwise, the passive islanding to grid-connection mode switching unit works.

    [0025] A function of the passive islanding to grid-connection mode switching unit is switching a control mode; at a moment of switching the control mode, active power and reactive power instructions maintain current operation values of an active power and a reactive power; or, after switching, an active power and a reactive power are converted to 0, and gradually increase to operation values before the switching.

    [0026] The present invention further provides a passive islanding to grid-connection control system, including a converter, an upper layer controller, and a valve-controlled apparatus, where
    1. (1) when a converter station of a VSC HVDC transmission system is in an island operation state, the upper layer controller detects whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current; and if the overcurrent phenomenon occurs, and the overcurrent phenomenon lasts for a duration t1, step (2) is performed, otherwise, step (1) is performed again;
    2. (2) A converter is blocked, and it is detected whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, the converter is unlocked, and step (1) is performed again; and otherwise, step (3) is performed.
    3. (3) The upper layer controller sets a phase-locked loop to track a current alternating-current side voltage phase, at the same time, starts to switch a control mode, switches from a current island control mode of the converter station of the VSC HVDC transmission system to an active control mode, and deblocked the converter.


    [0027] The foregoing embodiments are merely used to describe technical ideas of the present invention and do not define the protection scope of the present invention.


    Claims

    1. A method for switching from a passive islanding control mode to a grid-connected control mode for a VSC, voltage Source Converter, HVDC transmission system, the method comprising the following steps:

    1) when a converter station (201, 202) of the VSC HVDC transmission system is in a passive islanding operation state, detecting whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current of said converter station, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current;
    if overcurrent phenomenon occurs, and the overcurrent phenomenon lasts for a duration t1, performing step 2); and otherwise, performing step 1) again;

    2) blocking said converter, and detecting whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, unlocking said converter and performing step 1) again; and otherwise, performing step 3); and

    3) setting a phase-locked loop to track a current alternating-current side voltage phase, and at the same time, starting to switch to the active grid-connected control mode, wherein starting to switch to the active grid-connected control mode comprises switching from a current passive islanding control mode of the converter station of the VSC HVDC transmission system to the active grid-connected control mode, and deblocking said converter.


     
    2. The method for switching from a passive islanding control mode to a grid-connected control mode for a VSC HVDC transmission system according to claim 1, wherein in step 1), the overcurrent constant value setting is set to n times a converter rated valve-side current or a rated bridge arm current; a value range of n is 1 to 10, a value range of the duration t1 is 0 to 1s, and a value range of t2 is 0 to 1s.
     
    3. The method for switching from a passive islanding control mode to a grid-connected control mode for a VSC HVDC transmission system according to claim 1, wherein in step 2), a value range of the threshold of the alternating-current side voltage is 0 to 0.99 pu, and a value range of a duration t is 0 to 1s.
     
    4. The method for switching from a passive islanding control mode to a grid-connected control mode for a VSC HVDC transmission system according to claim 1, wherein at a moment of switching the control mode in step 3), active power and reactive power instructions maintain current operation values of an active power and a reactive power; or, after the switching, the active power and the reactive power are converted to 0, and gradually increase to operation values before the switching.
     
    5. A control system for switching from a passive islanding control mode to a grid-connected control mode, comprising a converter, an upper layer controller, and a valve-controlled apparatus, wherein

    1) when a converter station (201, 202) of a VSC HVDC transmission system is in an island operation state, the upper layer controller detects whether an overcurrent phenomenon occurs in a converter valve-side three-phase alternating-current or a converter bridge arm current of said converter station, wherein an overcurrent constant value setting is taken as n times a converter rated valve-side current or a rated bridge arm current;
    if overcurrent phenomenon occurs, and the overcurrent phenomenon lasts for a duration t1, step 2) is performed, otherwise, step 1) is performed again;

    2) said converter is blocked, and it is detected whether an alternating-current side voltage is lower than a threshold; if the voltage is lower than the threshold and lasts for a duration t2, said converter is unlocked, and step 1) is performed again; and otherwise, step 3) is performed; and

    3) the upper layer controller sets a phase-locked loop to track a current alternating-current side voltage phase, and at the same time, starts to switch to the active grid-connected control mode, wherein upon starting to switch to the active grid-connected control mode the upper layer controller is configured to switch from the current passive islanding control mode of the converter station of the VSC HVDC transmission system to the active control mode, and unlocks said converter.


     


    Ansprüche

    1. Verfahren zum Schalten aus einem passiven Inselbildungssteuermodus in einen netzgekoppelten Steuermodus für eine HGÜ-Anlage mit selbstgeführtem Stromrichter, VSC, wobei das Verfahren die folgenden Schritte umfasst:

    1) wenn eine Stromrichterstation (201, 202) der VSC HGÜ-Anlage sich in einem passiven Inselbetriebszustand befindet, Erkennen, ob ein Überstromphänomen in einem stromrichterventilseitigen Dreiphasenwechselstrom oder Stromrichterbrückenzweigstrom der Stromrichterstation auftritt, wobei eine Einstellung eines konstanten Überstromwertes verwendet wird als das n-Fache eines stromrichterventilseitigen Stroms oder eines Brückenzweig-Nennstroms;
    wenn ein Überstromphänomen auftritt und das Überstromphänomen während einer Dauer t1 andauert, Durchführen von Schritt 2); und andernfalls erneutes Durchführen von Schritt 1);

    2) Blockieren des Stromrichters und Erkennen, ob eine wechselstromseitige Spannung niedriger ist als ein Schwellenwert; wenn die Spannung niedriger ist als der Schwellenwert und während einer Dauer t2 andauert, Entsperren des Stromrichters und erneutes Durchführen von Schritt 1); und andernfalls Durchführen von Schritt 3); und

    3) Einstellen eines Phasenregelkreises, um eine aktuelle wechselstromseitige Spannungsphase nachzuverfolgen und gleichzeitig Beginnen des Schaltens in den aktiven netzgekoppelten Steuermodus, wobei das Beginnen des Schaltens in den aktiven netzgekoppelten Steuermodus das Schalten aus einem aktuellen passiven Inselbildungssteuermodus der Stromrichterstation der VSC HGÜ-Anlage in den aktiven netzgekoppelten Steuermodus und das Entblockieren des Stromrichters umfasst.


     
    2. Verfahren zum Schalten aus einem passiven Inselbildungssteuermodus in einen netzgekoppelten Steuermodus für eine HSC HGÜ-Anlage nach Anspruch 1, wobei in Schritt 1) die Einstellung eines konstanten Überstromwertes auf das n-Fache eines stromrichterventilseitigen Stroms oder eines Brückenzweig-Nennstroms eingestellt wird; ein Wertebereich von n 1 bis 10 beträgt, ein Wertebereich der Dauer t1 0 bis 1 s beträgt und ein Wertebereich von t2 0 bis 1 s beträgt.
     
    3. Verfahren zum Schalten aus einem passiven Inselbildungssteuermodus in einen netzgekoppelten Steuermodus für eine HSC HGÜ-Anlage nach Anspruch 1, wobei in Schritt 2) ein Wertebereich des Schwellenwerts der wechselstromseitigen Spannung 0 bis 0,99 pu beträgt und ein Wertebereich einer Dauer t 0 bis 1 s beträgt.
     
    4. Verfahren zum Schalten aus einem passiven Inselbildungssteuermodus in einen netzgekoppelten Steuermodus für eine HSC HGÜ-Anlage nach Anspruch 1, wobei zu einem Zeitpunkt des Schaltens des Steuermodus in Schritt 3) Wirkleistungs- und Blindleistungsanweisungen aktuelle Betriebswerte einer Wirkleistung und einer Blindleistung aufrechterhalten; oder nach dem Schalten die Wirkleistung und die Blindleistung in 0 umgewandelt werden und allmählich auf Betriebswerte vor dem Schalten ansteigen.
     
    5. Steuersystem zum Schalten aus einem passiven Inselbildungssteuermodus in einen netzgekoppelten Steuermodus, umfassend einen Stromrichter, eine Steuerung der oberen Schicht und eine ventilgesteuerte Vorrichtung, wobei, wenn

    1) eine Stromrichterstation (201, 202) einer VSC HGÜ-Anlage sich in einem Inselbetriebszustand befindet, die Steuerung der oberen Schicht erkennt, ob ein Überstromphänomen in einem stromrichterventilseitigen Dreiphasenwechselstrom oder Stromrichterbrückenzweigstrom der Stromrichterstation auftritt, wobei eine Einstellung eines konstanten Überstromwertes erfolgt als das n-Fache eines stromrichterventilseitigen Stroms oder eines Brückenzweig-Nennstroms;
    wenn ein Überstromphänomen auftritt und das Überstromphänomen während einer Dauer t1 andauert, wird Schritt 2) durchgeführt, andernfalls wird Schritt 1) erneut durchgeführt;

    2) der Stromrichter blockiert wird und erkannt wird, ob eine wechselstromseitige Spannung niedriger ist als ein Schwellenwert; wenn die Spannung niedriger ist als der Schwellenwert und während einer Dauer t2 andauert, wird der Stromrichter entsperrt und Schritt 1) wird erneut durchgeführt; und andernfalls wird Schritt 3) durchgeführt; und

    3) die Steuerung der oberen Schicht eine Phasenregelkreis einstellt, um eine aktuelle wechselstromseitige Spannungsphase nachzuverfolgen und gleichzeitig beginnt, in den aktiven netzgekoppelten Steuermodus zu schalten, wobei nach dem Beginnen des Schaltens in den aktiven netzgekoppelten Steuermodus die Steuerung der oberen Schicht konfiguriert wird, um aus dem aktuellen passiven Inselbildungssteuermodus der Stromrichterstation der VSC HGÜ-Anlage in den aktiven Steuermodus zu schalten, und den Stromrichter entsperrt.


     


    Revendications

    1. Procédé de commutation d'un mode de commande d'îlotage passif à un mode de commande à connexion au réseau pour un système de transmission HVDC de convertisseur de source de tension, VSC, le procédé comprenant les étapes suivantes :

    1) lorsqu'une station de convertisseur (201, 202) du système de transmission HVDC de VSC est dans un état de fonctionnement d'îlotage passif, détecter si un phénomène de surintensité se produit ou non dans un courant alternatif triphasé côté soupape de convertisseur ou un courant de bras de pont de convertisseur de ladite station de convertisseur, un réglage de valeur constante de surintensité étant pris en tant que n fois un courant côté soupape nominal de convertisseur ou un courant de bras de pont nominal ;
    si un phénomène de surintensité se produit, et que le phénomène de surintensité dure pendant une durée t1, réaliser l'étape 2) ; et autrement, réaliser l'étape 1) à nouveau ;

    2) bloquer ledit convertisseur, et détecter si une tension côté courant alternatif est ou non inférieure à un seuil ; si la tension est inférieure au seuil et dure pendant une durée t2, déverrouiller ledit convertisseur et réaliser l'étape 1) à nouveau ; et autrement, réaliser l'étape 3) ; et

    3) régler une boucle à verrouillage de phase pour suivre une phase de tension côté courant alternatif de courante, et simultanément, démarrer la commutation vers le mode de commande à connexion au réseau actif, le démarrage de la commutation vers le mode de commande à connexion au réseau actif comprenant la commutation depuis un mode de commande d'îlotage passif courant de la station de convertisseur du système de transmission HVDC de VSC vers le mode de commande à connexion au réseau actif, et débloquer ledit convertisseur.


     
    2. Procédé de commutation d'un mode de commande d'îlotage passif à un mode de commande à connexion au réseau pour un système de transmission HVDC de VSC selon la revendication 1, dans lequel, à l'étape 1), le réglage de valeur constante de surintensité est réglé à n fois un courant côté soupape nominal de convertisseur ou un courant de bras de pont nominal ; une plage de valeurs de n allant de 1 à 10, une plage de valeurs de la durée t1 allant de 0 à 1s, et une plage de valeurs de t2 allant de 0 à 1s.
     
    3. Procédé de commutation d'un mode de commande d'îlotage passif à un mode de commande à connexion au réseau pour un système de transmission HVDC de VSC selon la revendication 1, dans lequel, à l'étape 2), une plage de valeurs du seuil de la tension côté courant alternatif va de 0 à 0,99 pu, et une plage de valeurs d'une durée t va de 0 à 1s.
     
    4. Procédé de commutation d'un mode de commande d'îlotage passif à un mode de commande à connexion au réseau pour un système de transmission HVDC de VSC selon la revendication 1, dans lequel, à un moment de commutation du mode de commande à l'étape 3), des instructions de puissance active et de puissance réactive maintiennent des valeurs de fonctionnement courantes d'une puissance active et d'une puissance réactive ; ou, après la commutation, la puissance active et la puissance réactive sont converties à 0, et augmentent progressivement vers des valeurs de fonctionnement avant la commutation.
     
    5. Système de commande pour une commutation d'un mode de commande d'îlotage passif à un mode de commande à connexion au réseau, comprenant un convertisseur, un dispositif de commande de couche supérieure, un appareil commandé par soupape, dans lequel

    1) lorsqu'une station de convertisseur (201, 202) d'un système de transmission HVDC de VSC est dans un état de fonctionnement d'îlotage, le dispositif de commande de couche supérieure détecte si un phénomène de surintensité se produit ou non dans un courant alternatif triphasé côté soupape de convertisseur ou un courant de bras de pont de convertisseur de ladite station de convertisseur, un réglage de valeur constante de surintensité étant pris en tant que n fois un courant côté soupape nominal de convertisseur ou un courant de bras de pont nominal ;
    si un phénomène de surintensité se produit, et que le phénomène de surintensité dure pendant une durée t1, l'étape 2) est réalisée, autrement, l'étape 1) est réalisée à nouveau ;

    2) ledit convertisseur est bloqué, et il est détecté si une tension côté courant alternatif est ou non inférieure à un seuil ; si la tension est inférieure au seuil et dure pendant une durée t2, ledit convertisseur est déverrouillé, et l'étape 1) est réalisée à nouveau ; et autrement, l'étape 3) est réalisée ; et

    3) le dispositif de commande de couche supérieure règle une boucle à verrouillage de phase pour suivre une phase de tension côté courant alternatif courante, et simultanément, démarre la commutation vers le mode de commande à connexion au réseau actif, dans lequel, lors du démarrage de la commutation vers le mode de commande à connexion au réseau actif, le dispositif de commande de couche supérieure est configuré pour commuter depuis le mode de commande d'îlotage passif courant de la station de convertisseur du système de transmission HVDC de VSC vers le mode de commande actif, et déverrouille ledit convertisseur.


     




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    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description