A system and method for determining AC section power failure in a high-voltage flexible DC converter station

Abstract

The present invention discloses a system and method for distinguishing AC section power failure of a high-voltage flexible direct current converter station. The system includes a substation, which is an AC power failure distinguishing device configured in the converter station; a main station, which is an AC power failure distinguishing device configured in the AC station on the opposite side of the AC outgoing line of the converter station; the substation and the main station are connected in communication to form an AC section power failure distinguishing system; the main station is used to access the protection tripping signal and the switch position signal corresponding to the interval where the AC line of the converter station is located, and the main station uses the corresponding protection tripping signal and the switch position signal to form the AC section power failure distinguishing logic to realize the AC section power failure distinguishing system action logic. When the AC section power failure distinguishing system is actuated, a DC blocking command is sent to the substation, and the substation is forwarded to the DC control and protection system of the DC converter station to achieve DC blocking. The present invention solves the overvoltage risk when the flexible direct current converter station is not fully connected to the AC system.

Description

Technical Field

[0001] The present invention relates to the field of electric power technology, and in particular to a system and method for distinguishing power failure of an AC section in a high-voltage flexible DC converter station. Background Art

[0002] Different from the current source converter type HVDC transmission based on phase-controlled commutation technology, the converter in flexible DC transmission is a voltage source converter (VSC), whose biggest feature is the use of turn-off devices (usually IGBT) and high-frequency modulation technology. Compared with traditional methods, flexible DC transmission has strong technical advantages in island power supply, capacity expansion and transformation of urban distribution networks, AC system interconnection, and large-scale wind farm grid connection.

[0003] However, compared with conventional DC, when the flexible DC converter station is not fully connected to the AC system, the overvoltage generated is more serious than when it is lost. Therefore, if the DC system is not locked and shut down in time, a high overvoltage may be formed in the AC and DC systems in the station or the arrester energy may exceed the limit, seriously affecting the safety of the equipment. The AC section power failure identification system is an important protection to prevent the DC converter station from being fully connected or lost to the AC system. When it determines that the DC converter station is not fully connected or lost to the AC system, it sends a blocking command to the DC system to quickly block the DC and prevent overvoltage risks.

[0004] The existing AC section power failure judgment system generally only considers the loss of connection between the DC converter station and the three phases of the AC system. In addition, the specific logic of each project is not unified. Most of them are customized and have poor adaptability. In addition, there are hidden dangers of refusal to operate under certain operating modes, which are mainly reflected in the following aspects: (1) In some projects, only the access protection tripping signal is considered, and the access protection signal is not considered comprehensively; (2) In some projects, the access protection tripping signal is not considered, and only the switch position signal is used for logical judgment; (3) In some projects, only the line switch of the AC station on the opposite side of the AC outgoing line of the DC converter station (using 3 / 2 wiring) is considered, and the operating status of the same series components is not considered. There are situations that cannot be adapted under certain modes. Therefore, how to design a relatively standardized and comprehensive AC section power failure judgment system that is suitable for both flexible DC switching stations and conventional converter stations is of great significance to ensure the safe and stable operation of DC converter station equipment and systems. Summary of the invention

[0005] In order to solve at least one technical problem existing in the above-mentioned background technology, the present invention provides a system and method for determining AC section power failure in a high-voltage flexible DC converter station.

[0006] To achieve the above object, the technical solution of the present invention is:

[0007] In a first aspect, the present invention provides a system for determining AC section power failure in a high-voltage flexible DC converter station, comprising:

[0008] Substation, the substation is an AC section power failure determination device configured in a converter station;

[0009] A master station, wherein the master station is an AC section power failure determination device configured at an AC station on the opposite side of the AC outgoing line of the converter station;

[0010] The substation and the main station are connected in communication to form an AC section power failure identification system;

[0011] The master station is used to access the protection tripping signal and switch position signal corresponding to the interval where the AC line of the converter station is located. The master station uses the corresponding protection tripping signal and switch position signal to form the AC section power failure judgment logic to realize the AC section power failure judgment system action logic. When the AC section power failure judgment system is actuated, the DC blocking command is sent to the substation, and the substation forwards it to the DC control and protection system of the DC converter station to achieve DC blocking.

[0012] Furthermore, the master station comprises:

[0013] The binary input receiving module is used to receive the switch position status quantity and the protection trip signal binary input quantity;

[0014] A circuit breaker state determination module is used to determine whether the switch is in the closed position or the open position before tripping according to the circuit breaker position state quantity;

[0015] Action logic judgment module, used to determine whether to operate the output according to the circuit breaker position status and trip signal;

[0016] The main station action logic module sets four types of AC section power failure judgment logic and controls the activation and deactivation of the logic by control words respectively: protection tripping judges AC section power failure, switch position judges AC section power failure, protection tripping judges same-name phase failure, and switch position judges same-name phase failure.

[0017] In a second aspect, the present invention provides a method for determining power failure of an AC section of a high-voltage flexible DC converter station, comprising:

[0018] Step 1: If the number of AC outgoing lines of the converter station is no more than two, an AC power failure identification device is configured at the converter station as a substation, and an AC power failure identification device is configured at the AC station on the opposite side of the AC outgoing line of the converter station as a master station. The master station and the substation are connected in communication to form an AC section power failure identification system; the substation is also used for communication connection with the converter station control and protection system;

[0019] Step 2: The master station receives the position signals and trip signals of all associated circuit breakers;

[0020] Step 3: The master station determines the position status of the associated circuit breaker according to the circuit breaker position information;

[0021] Step 4: The master station determines that the circuit breaker trips according to the protection signal or switch position;

[0022] Step 5: AC section power failure identification system action identification and export;

[0023] Step 6: Send the DC blocking command to the substation, which then forwards it to the DC control and protection system of the DC converter station to block the DC.

[0024] Furthermore, in step 2, the access signal of each circuit breaker includes a protection signal for tripping the circuit breaker through a phase-splitting command and a protection signal for tripping the circuit breaker through a three-trip command. If a protection trip signal or a switch position change signal is input, the AC section power failure judgment system is started.

[0025] Further, in step 3, the position state of the circuit breaker includes a three-phase switch operation state and a single-phase switch operation state;

[0026] The three-phase operation state judgment logic of the switch is: when the circuit breaker maintenance pressure plate is not put into operation, when any two-phase HWJ of the circuit breaker is 1, and any two-phase TWJ is 0, it is judged that the circuit breaker is in the closed operation state;

[0027] The single-phase operation state judgment logic of the switch is: when the circuit breaker maintenance pressure plate is not put into operation, the HWJ of the circuit breaker phase is 1, and the TWJ of the phase is 0, it is judged that the circuit breaker phase is in the closed operation state.

[0028] Further, in step 4, four kinds of judgment logics are set for circuit breaker tripping judgment and are respectively controlled by control words, and the control words are: "protection tripping judgment AC section power failure", "switch position judgment AC section power failure", "protection tripping judgment same-name phase fault", "switch position judgment same-name phase fault";

[0029] The protection tripping judgment AC section power failure logic is: "Protection tripping judgment AC section power failure" control word is set to 1, and at the same time the circuit breaker is in operation, any two different phase protection signals or any three tripping protection signals are turned on, then the circuit breaker is judged to be tripped;

[0030] The switch position judgment AC section power failure logic is: when the "switch position judgment AC section power failure" control word is set to 1, and the circuit breaker is in operation, any phase switch HWJ or TWJ is changed and opened, and any two phases of the circuit breaker TWJ are 1, and any two phases of HWJ are 0, the circuit breaker is judged to be tripped;

[0031] The protection trip judgment same-phase fault logic is: when the "protection trip judgment same-phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, any one of the phase protection signals or any three trip protection signals are turned on, it is judged that the circuit breaker trips on the phase;

[0032] The logic of judging the same-name phase fault by switch position is: when the "switch position judging the same-name phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, and the switch HWJ or TWJ of the phase is changed and opened, and the TWJ of the phase of the circuit breaker is 1 and the HWJ of the phase is 0, it is judged that the circuit breaker is tripped by the phase.

[0033] Furthermore, in step 5, the AC section power failure identification system includes section power failure action and section same-name phase power failure action logic;

[0034] The section power failure action logic is: when any operating switch is judged to be tripped, the section power failure action logic is started. When the logic is started, if it is detected that all the circuit breakers in the operating state involved in the AC line are judged to be tripped, the AC section power failure logic action exit is performed;

[0035] The section same-phase power-off action logic is as follows: when any phase of any operating switch is judged to be tripped, the section same-phase power-off action logic is started; when the logic is started, if it is detected that all the same-phase circuit breakers in operation involved in the AC line are tripped, the AC section same-phase power-off logic action exit is performed.

[0036] Furthermore, the section power failure action logic also includes:

[0037] A pressure plate of "Line XX same-string side switch participates in logic input" is set on each AC line to the converter station. When the pressure plate is turned on, the same-string side switch participates in the logic. When the same-string side switch is judged to be tripped, it is equivalent to the same-string middle switch being judged to be tripped.

[0038] Furthermore, the section same-name phase power failure action logic also includes:

[0039] Each AC line to the converter station is equipped with a "Line XX Same-string Side Switch Participates in Logic Input" pressure plate. When the pressure plate is turned on, the same-string side switch participates in the logic. When one phase of the same-string side switch trips, it is equivalent to the corresponding phase of the switch in the same string tripping.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The present invention designs a system and method for distinguishing power failure of AC section in a converter station, which can solve the overvoltage risk when the flexible DC converter station is not fully connected to the AC system; the system and method clarify all switch quantity signals that need to be connected, and realize the standardization of system switch quantity access, function and logic by setting four independently switchable logics and "line same-string side switches participate in logic input" control words, etc., which are suitable for both flexible DC converter stations and conventional converter stations, improve the applicability and reliability of the system and logic, and improve the system construction efficiency; the system and method include protection signals and switch position criteria, and the switch position criteria can be used as a backup for the protection signal criteria, which greatly improves the reliability of the logic criteria and effectively avoids the DC overvoltage risk after a single criterion fails to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1a This is the connection diagram between the DC converter station side and the AC system;

[0043] Figure 1b This is a schematic diagram of the wiring in the AC station (other series wiring is not drawn);

[0044] Figure 2 This is the structure and communication diagram of the AC section power failure identification system;

[0045] Figure 3a It is the three-phase operation logic diagram of the switch;

[0046] Figure 3b For single-phase switch operation logic: A / B / C phase logic is the same, take A phase as an example;

[0047] Figure 4a To protect the three-phase tripping logic diagram of the signal edge detection switch;

[0048] Figure 4b It is the three-phase tripping logic diagram of the switch position judgment switch;

[0049] Figure 4c To protect the single-phase tripping logic diagram of the signal edge detection switch (taking phase A as an example);

[0050] Figure 4d This is the single-phase tripping logic diagram of the switch position judgment switch (taking phase A as an example);

[0051] Figure 5a To protect the signal / switch position (two out of three) to determine the AC section power failure logic diagram;

[0052] Figure 5b It is a logic diagram for determining the loss of power to the same phase of the AC section for protection signal / switch position. DETAILED DESCRIPTION

[0053] Example:

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a signal connection; it can be directly connected, or indirectly connected through an intermediate medium, which can be said to be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. The technical solution of the present invention is further explained below in conjunction with the accompanying drawings and embodiments.

[0055] The present invention discloses a system and method for distinguishing AC section power failure of a high-voltage flexible DC converter station. The method configures an AC power failure distinguishing device as a substation in the converter station, and configures an AC power failure distinguishing device as a master station in the AC station on the opposite side of the AC outgoing line of the converter station. The master and substations communicate through 2M multiplexed optical fiber connection to form an AC power failure distinguishing system, and the substation and the control and protection system of the converter station also use 2M multiplexed optical fiber connection communication. The master station accesses the protection tripping signal and switch position signal corresponding to the interval where the AC line of the converter station is located. The master station uses the corresponding protection tripping signal and the switch position signal to form the AC section power failure distinguishing logic, and realizes the action logic of the AC section power failure distinguishing system. When the AC section power failure distinguishing system is activated, the DC blocking command is sent to the substation through optical fiber communication, and the substation then forwards it to the DC control and protection system of the DC converter station through optical fiber communication to achieve DC blocking. The master station includes main functional modules such as a binary input receiving module, a circuit breaker state distinguishing module, an action logic distinguishing module, and a communication module. The input receiving module is used to receive the switch position status (HWJ, TWJ input) to protect the trip signal input. The circuit breaker status judgment module judges whether the switch is in the closed position or the open position before tripping according to the circuit breaker position status. The action logic judgment module determines whether to operate the output in combination with the circuit breaker position status and the trip signal. The main station action logic module sets four types of AC section power failure judgment logic and controls the input and output by control words respectively: protection tripping judges AC section power failure, switch position judges AC section power failure, protection tripping judges same-name phase failure, and switch position judges same-name phase failure. The entire AC section power failure judgment is implemented by the device software. The communication module sends the DC blocking command to the substation through optical fiber communication, and the substation forwards it to the DC commutation control and protection system. The specific steps are as follows:

[0056] Step 1: For converter stations with no more than two AC outgoing lines, configure an AC power failure identification device as a substation at the converter station, and configure an AC power failure identification device as a master station at the AC station on the opposite side of the AC outgoing line of the converter station. The master and substations are connected and communicated through 2M multiplexed optical fiber to form an AC power failure identification system. The substation and the converter station control and protection system also use 2M multiplexed optical fiber to connect and communicate. Figure 2 shown.

[0057] Step 2: The master station receives position signals and trip signals of all associated circuit breakers. The access signals of each circuit breaker include protection signals (such as line protection, circuit breaker protection, etc.) that trip the circuit breaker through phase-splitting commands and protection signals that trip the circuit breaker through three-trip commands, as shown in Table 1. If a protection trip signal or switch position change signal is input, the AC section power failure discrimination system is started.

[0058] Table 1 Input quantity of the AC section power failure device access line interval

[0059]

[0060]

[0061] Step 3: Determine the position status of the associated circuit breaker according to the circuit breaker position information, including the three-phase switch operation status and the single-phase switch operation status.

[0062] (1) The switch three-phase operation status judgment logic is as follows Figure 3a As shown, the circuit breaker position determination adopts the logic of "three out of two" and HWJ and TWJ double confirmation, that is, when the circuit breaker maintenance pressure plate is not put into use, when any two phases of the circuit breaker HWJ is 1, and any two phases of TWJ is 0, it is determined that the circuit breaker is in the closed operation state;

[0063] (2) The switch single-phase operation state judgment logic is as follows Figure 3b As shown, the circuit breaker position determination adopts the logic of HWJ and TWJ double confirmation, that is, when the circuit breaker maintenance pressure plate is not put into operation, the HWJ of the circuit breaker phase is 1, and the TWJ of the phase is 0, it is determined that the circuit breaker phase is in the closed operation state.

[0064] Step 4: Determine the tripping of the circuit breaker based on the protection signal or switch position. Four types of judgment logic are set for the circuit breaker tripping judgment and are controlled by control words. The control words are: "Protection tripping determines AC section power failure", "Switch position determines AC section power failure", "Protection tripping determines same-name phase failure", and "Switch position determines same-name phase failure".

[0065] (1) Protection signal (two out of three) tripping judgment (protection tripping judges AC section power failure) logic is as follows Figure 4a As shown, when the "protection trip judged AC section power failure" control word is set to 1, and the circuit breaker is in operation, any two different phase protection signals or any three trip protection signals are input, the circuit breaker is judged to be tripped;

[0066] (2) Switch position (two out of three) determines tripping (switch position determines AC section power failure) logic is as follows Figure 4bAs shown, when the "switch position determines AC section power failure" control word is set to 1, and the circuit breaker is in operation, any phase switch HWJ or TWJ is changed and opened, and any two phases of TWJ of the circuit breaker are 1, and any two phases of HWJ are 0, the circuit breaker is judged to be tripped;

[0067] (3) The protection tripping logic for judging the same-phase fault is as follows: Figure 4c As shown, when the "protection trip judged same-name phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, any one of the phase protection signals or any three trip protection signals are turned on, the circuit breaker is judged to trip on the phase;

[0068] (4) The tripping logic for judging the same phase fault by switch position is as follows: Figure 4d As shown, when the "switch position determines the same-name phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, and the phase switch HWJ or TWJ is changed and opened, and the circuit breaker TWJ of the phase is 1 and HWJ of the phase is 0, it is judged that the circuit breaker is tripped.

[0069] Step 5: AC section power failure discrimination system action discrimination and exit. The AC section power failure discrimination system includes section power failure action (two out of three) and section same-name phase power failure action logic.

[0070] (1) Section power failure action (two out of three) logic. Figure 5a As shown, when any operating switch is judged to be tripped, the section power-off action (three out of two) logic is started. After the logic is started, when the device program detects that all the circuit breakers in operation involved in the AC line are judged to be tripped, the AC section power-off (three out of two) logic action exits. In order to consider the versatility of the program and be compatible with the situation where the same-string elements are not connected to the system, a "Line XX Same-string Side Switch Participates in Logic Input" pressure plate is set for each AC line to the converter station. When the pressure plate is put into use, the same-string side switch participates in the logic. When the same-string side switch is judged to be tripped, it is equivalent to the same-string middle switch being judged to be tripped.

[0071] (2) The logic of the power failure action of the same phase in the section. Figure 5b As shown, when any phase of any operating switch is judged to be tripped, the same-name phase power loss action logic of the section is started. After the logic is started, when the device program detects that all the same-phase circuit breakers in operation involved in the AC line are judged to be tripped, the same-name phase power loss logic action exit of the AC section is activated. In order to consider the versatility of the program and be compatible with the situation where the same-string elements are not connected to the system, a "Line XX Same-string Side Switch Participates in Logic Input" pressure plate is set for each AC line in the converter station. When the pressure plate is put into use, the same-string side switch participates in the logic. When one phase of the same-string side switch is judged to be tripped, it is equivalent to the corresponding phase of the switch in the same string tripping.

[0072] Step 6: Send a DC blocking command. When the section power failure action (two out of three) logic or the section same-name phase power failure action logic in the AC section power failure discrimination device of the AC station is exited, the blocking DC command is sent to the AC section power failure discrimination device of the converter station through the 2M optical fiber channel, and then the device forwards the command to the DC control and protection system through optical fiber communication, which blocks the DC.

[0073] The technical solution implemented by the present invention is further described below in conjunction with an application scenario example.

[0074] As shown in Figure 1, it is a schematic diagram of an AC substation on the opposite side of the AC outgoing line of a converter station (inverter station). The wiring in the station is a 3 / 2 wiring method, in which lines 1 and 2 are connected to the converter station, and lines 3 and 4 are connected to other AC stations. Except for the two strings of lines connected to the converter station, the intervals where the other lines connected to the system are located are not drawn. The station is equipped with an AC section power failure discrimination device. After the protection action exits, it sends a command to the AC section power failure device of the opposite converter station through the 2M communication channel, and then forwards the locking command to the converter station to control the protection to lock the DC.

[0075] The method for determining power failure of an AC section of a high-voltage flexible DC converter station provided by an embodiment of the present invention comprises the following steps:

[0076] Step 1: For converter stations with no more than two AC outgoing lines, configure an AC power failure identification device as a substation at the converter station, and configure an AC power failure identification device as a master station at the AC station on the opposite side of the AC outgoing line of the converter station. The master and substations are connected and communicated through 2M multiplexed optical fiber to form an AC power failure identification system. The substation and the converter station control and protection system also use 2M multiplexed optical fiber to connect and communicate. Figure 2 shown.

[0077] In one example, a converter station (inverter side) is connected to the system only through two AC lines. Therefore, according to the principle of duplication, an AC section power failure detection device is configured at the converter station and the AC station on the opposite side of the AC outgoing line. The AC power failure detection device is configured at the converter station as a substation, and the AC station on the opposite side of the AC outgoing line of the converter station is configured as a main station. The main substation is connected through a 2M optical fiber channel, and the device of the converter station is also connected to the DC control and protection system through optical fiber communication. Figure 2 shown.

[0078] Step 2: The master station receives the position signals and trip signals of all associated circuit breakers. The access signals of each circuit breaker include the protection signals (such as line protection, circuit breaker protection, etc.) of the circuit breaker tripping through the phase command and the protection signals of the circuit breaker tripping through the three-trip command. If a protection trip signal or switch position change signal is input, the AC section power failure judgment system is started.

[0079] In one example, the master station receives position signals of all associated circuit breakers and protection trip signals, totaling 84 inputs, as shown in the following table.

[0080] Table 1 The number of inputs in the interval where the main station access line is located

[0081]

[0082]

[0083] Step 3: Determine the position status of the associated circuit breaker according to the circuit breaker position information, including the three-phase switch operation status and the single-phase switch operation status.

[0084] (1) The switch three-phase operation status judgment logic is as follows Figure 3a As shown, the circuit breaker position determination adopts the logic of "three out of two" and HWJ and TWJ double confirmation, that is, when the circuit breaker maintenance pressure plate is not put into use, when any two phases of the circuit breaker HWJ is 1, and any two phases of TWJ is 0, it is determined that the circuit breaker is in the closed operation state;

[0085] (2) The switch single-phase operation state judgment logic is as follows Figure 3b As shown, the circuit breaker position determination adopts the logic of HWJ and TWJ double confirmation, that is, when the circuit breaker maintenance pressure plate is not put into operation, the HWJ of the circuit breaker phase is 1, and the TWJ of the phase is 0, it is determined that the circuit breaker phase is in the closed operation state.

[0086] In one example, the three phases A, B, and C of switch 5013 are all in the open position, that is, the HWJA, HWJB, and HWJC inputs of switch 5013 are all 0, and the TWJA, TWJB, and TWJC inputs are all 1; the three phases A, B, and C of the remaining switches 5012, 5011, 5023, 5022, and 5021 are all in the closed position, that is, the HWJA, HWJB, and HWJC inputs of the above switches are all 1, and the TWJA, TWJB, and TWJC inputs are all 0; the circuit breaker maintenance pressure plate is not put into operation. According to the circuit breaker position state judgment logic, the operation output of switch 5013 is 0, that is, it is in the shutdown state, and the operation output of the remaining switches is 1, that is, it is in the operation state. The operation outputs of phases A, B, and C of switch 5013 are all 0, that is, phases A, B, and C are in the shutdown state; the operation outputs of phases A, B, and C of the remaining switches are 1, that is, phases A, B, and C are in the operation state.

[0087] Step 4: Determine the tripping of the circuit breaker based on the protection signal or switch position. Four types of judgment logic are set for the circuit breaker tripping judgment and are controlled by control words. The control words are: "Protection tripping determines AC section power failure", "Switch position determines AC section power failure", "Protection tripping determines same-name phase failure", and "Switch position determines same-name phase failure".

[0088] (1) Protection signal (two out of three) tripping logic Figure 4a As shown, when the "protection trip judged AC section power failure" control word is set to 1, and the circuit breaker is in operation, any two different phase protection signals or any three trip protection signals are input, the circuit breaker is judged to be tripped;

[0089] (2) Switch position (two out of three) tripping logic is as follows Figure 4b As shown, when the "switch position determines AC section power failure" control word is set to 1, and the circuit breaker is in operation, any phase switch HWJ or TWJ is changed and opened, and any two phases of TWJ of the circuit breaker are 1, and any two phases of HWJ are 0, the circuit breaker is judged to be tripped;

[0090] (3) The protection tripping logic for judging the same-phase fault is as follows: Figure 4c As shown, when the "protection trip judged same-name phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, any one of the phase protection signals or any three trip protection signals are turned on, the circuit breaker is judged to trip on the phase;

[0091] (4) The tripping logic for judging the same phase fault by switch position is as follows: Figure 4d As shown, when the "switch position determines the same-name phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, and the phase switch HWJ or TWJ is changed and opened, and the circuit breaker TWJ of the phase is 1 and HWJ of the phase is 0, it is judged that the circuit breaker is tripped.

[0092] In one example, the control words of "protection tripping to determine AC section power failure", "switch position to determine AC section power failure", "protection tripping to determine same-name phase fault", and "switch position to determine same-name phase fault" are all set to 1. Assume that the 1M bus differential protection is activated, that is, the TJR input of switches 5011 and 5021 is 1, and the corresponding circuit breaker is tripped after 50ms, that is, the HWJA, HWJB, and HWJC inputs of 5011 and 5021 are 0, and the TWJA, TWJB, and TWJC inputs are all 1. At the same time, the line 2 protection is activated to trip phase A, that is, the line 2 protection TA input is 1, and the corresponding circuit breaker is tripped after 50ms, that is, the HWJA input of 5023 and 5022 is 0, the HWJB and HWJC inputs are 1, TWJA is 1, and the TWJB and TWJC inputs are 0.

[0093] According to the above input signals, the circuit breaker tripping logic is determined according to the protection signal or switch position. The results are as follows:

[0094] (1) Based on Figure 4aIn the protection signal (two out of three) tripping logic, "protection tripping judged AC section power failure" is set to 1, and the TJR input of switches 5011 and 5021 is 1 and in operation, so it is judged that switches 5011 and 5012 are tripped on three phases, that is, "protection signal judged 5011 switch tripped" and "protection signal judged 5021 switch tripped" are output 1. Line 2 protection tripped phase A, so 5023 and 5022 do not meet the protection signal judgment switch tripping criteria.

[0095] (2) Based on Figure 4b The switch position (two out of three) tripping logic, "switch position judgment of AC section power failure" is set to 1. After 50ms, the HWJA, HWJB, HWJC inputs of 5011 and 5021 change from 1 to 0, and the TWJA, TWJB, TWJC inputs change from 0 to 1. Therefore, according to the switch position, the three-phase tripping of switches 5011 and 5012 is judged, that is, "switch position judgment 5011 switch tripped", "switch position judgment 5012 switch tripped" output is 1. For switches 5023 and 5022, only phase A tripped, which does not meet the switch position judgment tripping criteria.

[0096] (3) Based on Figure 4c The protection tripping judgment logic for the same-phase fault is "protection tripping judgment for the same-phase fault" is set to 1, the TJR input of switches 5011 and 5021 is 1 and they are in operation, so it is judged that the A, B, and C phases of switches 5011 and 5012 are tripped, that is, the outputs of "5011 switch A phase protection signal tripped", "5011 switch B phase protection signal tripped", and "5011 switch C phase protection signal tripped" are all 1, and the outputs of "5021 switch A phase protection signal tripped", "5021 switch B phase protection signal tripped", and "5021 switch C phase protection signal tripped" are all 1. The line 2 protection action trips the A phase, that is, the line 2 protection TA input is 1, and at the same time, the A phase of switches 5023 and 5022 are in operation, so it is judged that the A phase of switches 5023 and 5022 is tripped, that is, the output of "5023 switch A phase protection signal tripped" is 1, and the output of "5022 switch A phase protection signal tripped" is 1.

[0097] (4) Based on Figure 4d The switch position judgment same-phase fault tripping logic, the "switch position judgment same-phase fault" control word is set to 1. After 50ms, the HWJA, HWJB, HWJC inputs of 5011 and 5021 change from 1 to 0, and the TWJA, TWJB, TWJC inputs change from 0 to 1. Therefore, the outputs of "5011 switch A phase switch position tripped", "5011 switch B phase switch position tripped", and "5011 switch C phase switch position tripped" are all 1. For switches 5023 and 5022, only phase A trips. Therefore, the output of "5023 switch A phase switch position tripped" is 1, and the output of "5022 switch A phase switch position tripped" is 1.

[0098] Step 5: AC section power failure discrimination system action discrimination and exit. The AC section power failure discrimination system includes section power failure action (two out of three) and section same-name phase power failure action logic.

[0099] (1) Section power failure action (two out of three) logic. Figure 5a As shown, when any operating switch is judged to be tripped, the section power-off action (three out of two) logic is started. After the logic is started, when the device program detects that all the circuit breakers in operation involved in the AC line are judged to be tripped, the AC section power-off (three out of two) logic action exits. In order to consider the versatility of the program and be compatible with the situation where the same-string elements are not connected to the system, a "Line XX Same-string Side Switch Participates in Logic Input" pressure plate is set for each AC line to the converter station. When the pressure plate is put into use, the same-string side switch participates in the logic. When the same-string side switch is judged to be tripped, it is equivalent to the same-string middle switch being judged to be tripped.

[0100] (2) The same phase power failure action logic of the section. Figure 5b As shown, when any phase of any operating switch is judged to be tripped, the same-name phase power loss action logic of the section is started. After the logic is started, when the device program detects that all the same-phase circuit breakers in operation involved in the AC line are judged to be tripped, the same-name phase power loss logic action exit of the AC section is activated. In order to consider the versatility of the program and be compatible with the situation where the same-string elements are not connected to the system, a "Line XX Same-string Side Switch Participates in Logic Input" pressure plate is set for each AC line in the converter station. When the pressure plate is put into use, the same-string side switch participates in the logic. When one phase of the same-string side switch is judged to be tripped, it is equivalent to the corresponding phase of the switch in the same string tripping.

[0101] In an example, assuming that the control word of "line 1 same string side switch participates in logic input" is set to 1, and the control word of "line 2 same string side switch participates in logic input" is set to 0, according to the result of step 4, the AC section power failure judgment system action judgment and export logic, the results are as follows:

[0102] (1) Section power failure action (two out of three) logical action result. Figure 5a According to the logic shown, switches 5011 and 5021 are judged to be tripped, and the logic is started. However, since switches 5021 and 5022 at the sides of line 2 do not meet the criteria for tripping, the output of "section power failure action" is 0, i.e., no action is taken.

[0103] (2)” The logical result of the power failure action of the same phase of the section. Figure 5bThe logic shown is that the 5013 switch is in the shutdown state. At 0ms, the A-phase protection signals of the 5011, 5021, 5023, and 5022 switches are all judged to be tripped, so the "section A-phase power loss action" output is 1, that is, the action output; 50ms later, the A-phase switch positions of the 5011, 5021, 5023, and 5022 switches are all judged to be tripped, and the "section A-phase power loss action" output is 1 again, that is, the action output is again. Since the 5023 and 5022 switches of the B and C phases do not meet the judgment of tripping, the "section B-phase power loss action" and "section C-phase power loss action" outputs are both 0, that is, no action.

[0104] Step 6: Send a DC blocking command. When the section power failure action (two out of three) logic or the section same-name phase power failure action logic in the AC section power failure discrimination device of the AC station is exited, the blocking DC command is sent to the AC section power failure discrimination device of the converter station through the 2M optical fiber channel, and then the device forwards the command to the DC control and protection system through optical fiber communication, which blocks the DC.

[0105] In one example, according to the action and output results of step 5, at 0ms and 50ms, the main station twice determined that section A phase had lost power, and sent DC blocking commands to the substation twice. After receiving the command, the substation forwarded the blocking command to the DC control and protection system to block the DC.

[0106] In summary, the present invention designs a system and method for determining power failure of AC section in a converter station, which can solve the overvoltage risk when the flexible DC converter station is not fully connected to the AC system; the system and method clarify all switch signals that need to be connected, and achieve standardization of system switch access, functions and logic by setting four independent logics that can be put in and out, as well as control words such as "line same-string switches participate in logic input", which is suitable for both flexible DC converter stations and conventional converter stations, improves the applicability and reliability of the system and logic, and improves the efficiency of system construction; the system and method include protection signals and switch position criteria, and the switch position criteria can be used as a backup for the protection signal criteria, which greatly improves the reliability of the logic criteria and effectively avoids the risk of DC overvoltage after a single criterion fails to operate.

[0107] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable ordinary technicians in the field to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made based on the essence of the content of the present invention should be included in the protection scope of the present invention.

Claims

1. A high-voltage flexible DC converter station AC section power failure identification system, characterized in that: include: Substation, the substation is an AC section power failure determination device configured in a converter station; A master station, wherein the master station is an AC section power failure determination device configured at an AC station on the opposite side of the AC outgoing line of the converter station; The substation and the main station are connected in communication to form an AC section power failure identification system; The master station is used to access the protection trip signal and switch position signal corresponding to the interval where the AC line of the converter station is located. The master station uses the corresponding protection trip signal and switch position signal to form the AC section power failure judgment logic to realize the AC section power failure judgment system action logic. When the AC section power failure judgment system is actuated, the DC blocking command is sent to the substation, and the substation forwards it to the DC control and protection system of the DC converter station to realize DC blocking; The master station comprises: The binary input receiving module is used to receive the switch position status quantity and the protection trip signal binary input quantity; A circuit breaker state determination module is used to determine whether the switch is in the closed position or the open position before tripping according to the circuit breaker position state quantity; Action logic judgment module, used to determine whether to operate the output according to the circuit breaker position status and trip signal; The main station action logic module sets four types of AC section power failure judgment logic and controls the input and output by control words respectively: protection tripping judges AC section power failure, switch position judges AC section power failure, protection tripping judges same-name phase failure, and switch position judges same-name phase failure; The protection tripping judgment AC section power failure logic is: the "protection tripping judgment AC section power failure" control word is set to 1, and the circuit breaker is in operation. If any two different phase protection signals or any three tripping protection signals are input, the circuit breaker is judged to be tripped; The switch position judgment AC section power failure logic is: when the "switch position judgment AC section power failure" control word is set to 1, and the circuit breaker is in operation, any phase switch HWJ or TWJ is changed and opened, and any two phases of the circuit breaker TWJ are 1, and any two phases of HWJ are 0, the circuit breaker is judged to be tripped; The protection tripping judgment same-phase fault logic is: when the "protection tripping judgment same-phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, any one of the phase protection signals or any three tripping protection signals are turned on, it is judged that the circuit breaker trips on the phase; The switch position judgment same-phase fault logic is: when the "switch position judgment same-phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, and the phase switch HWJ or TWJ is changed and opened, and the circuit breaker TWJ of the phase is 1 and HWJ of the phase is 0, it is judged that the circuit breaker is tripped.

2. A method for determining AC section power failure in a high-voltage flexible DC converter station, characterized in that: include: Step 1: If the number of AC outgoing lines of the converter station is no more than two, an AC power failure identification device is configured at the converter station as a substation, and an AC power failure identification device is configured at the AC station on the opposite side of the AC outgoing line of the converter station as a master station. The master station and the substation are connected in communication to form an AC section power failure identification system; the substation is also used for communication connection with the converter station control and protection system; Step 2: The master station receives the position signals and trip signals of all associated circuit breakers; Step 3: The master station determines the position status of the associated circuit breaker according to the circuit breaker position information; Step 4: The master station determines that the circuit breaker trips according to the protection signal or switch position; Step 5: AC section power failure identification system action identification and export; Step 6: Send the DC blocking command to the substation, which then forwards it to the DC control and protection system of the DC converter station to achieve DC blocking; In step 4, four types of judgment logics are set for circuit breaker tripping judgment and are respectively controlled by control words, and the control words are: "protection tripping judgment AC section power failure", "switch position judgment AC section power failure", "protection tripping judgment same-name phase fault", "switch position judgment same-name phase fault"; The protection tripping judgment AC section power failure logic is: the "protection tripping judgment AC section power failure" control word is set to 1, and the circuit breaker is in operation. If any two different phase protection signals or any three tripping protection signals are input, the circuit breaker is judged to be tripped; The switch position judgment AC section power failure logic is: when the "switch position judgment AC section power failure" control word is set to 1, and the circuit breaker is in operation, any phase switch HWJ or TWJ is changed and opened, and any two phases of the circuit breaker TWJ are 1, and any two phases of HWJ are 0, the circuit breaker is judged to be tripped; The protection tripping judgment same-phase fault logic is: when the "protection tripping judgment same-phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, any one of the phase protection signals or any three tripping protection signals are turned on, it is judged that the circuit breaker trips on the phase; The switch position judgment same-phase fault logic is: when the "switch position judgment same-phase fault" control word is set to 1, and the phase of the circuit breaker is in operation, and the phase switch HWJ or TWJ is changed and opened, and the circuit breaker TWJ of the phase is 1 and HWJ of the phase is 0, it is judged that the circuit breaker is tripped.

3. The method for determining AC section power failure in a high-voltage flexible DC converter station according to claim 2, characterized in that: In step 2, the access signal of each circuit breaker includes a protection signal for tripping the circuit breaker through a phase-splitting command and a protection signal for tripping the circuit breaker through a three-trip command. If a protection trip signal or a switch position change signal is input, the AC section power failure judgment system is started.

4. The method for determining AC section power failure in a high-voltage flexible DC converter station according to claim 2, characterized in that: In step 3, the position state of the circuit breaker includes a three-phase switch operation state and a single-phase switch operation state; The three-phase operation state judgment logic of the switch is: when the circuit breaker maintenance pressure plate is not put into operation, when any two-phase HWJ of the circuit breaker is 1, and any two-phase TWJ is 0, it is judged that the circuit breaker is in the closed operation state; The single-phase operation state judgment logic of the switch is: when the circuit breaker maintenance pressure plate is not put into operation, the HWJ of the circuit breaker phase is 1, and the TWJ of the phase is 0, it is judged that the circuit breaker phase is in the closed operation state.

5. The method for determining AC section power failure in a high-voltage flexible DC converter station according to claim 2, characterized in that: In step 5, the AC section power failure identification system includes section power failure action and section same-name phase power failure action logic; The section power failure action logic is: when any operating switch is judged to be tripped, the section power failure action logic is started. When the logic is started, if it is detected that all the circuit breakers in the operating state involved in the AC line are judged to be tripped, the AC section power failure logic action exit is performed; The section same-phase power-off action logic is as follows: when any phase of any operating switch is judged to be tripped, the section same-phase power-off action logic is started; when the logic is started, if it is detected that all the same-phase circuit breakers in operation involved in the AC line are tripped, the AC section same-phase power-off logic action exit is performed.

6. The method for determining AC section power failure in a high-voltage flexible DC converter station according to claim 5, characterized in that: The section power failure action logic also includes: A "Line XX Same-string Side Switch Participates in Logic" pressure plate is set on each AC line to the converter station. When the pressure plate is turned on, the same-string side switch participates in the logic. When the same-string side switch is judged to be tripped, it is equivalent to the same-string middle switch being judged to be tripped.

7. The method for determining AC section power failure in a high-voltage flexible DC converter station according to claim 5, characterized in that: The section same-name phase power-off action logic also includes: A "Line XX same-string side switch participates in logic input" pressure plate is set on each AC line to the converter station. When the pressure plate is turned on, the same-string side switch participates in the logic. When one phase of the same-string side switch trips, it is equivalent to the corresponding phase of the switch in the same string tripping.

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