Three-phase adaptive reclosing method for wind farm transmission line based on network-forming pcs signal injection

Abstract

This application relates to the field of power system relay protection technology, and in particular to a three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection. By injecting signals into the transmission lines through a grid-type energy storage PCS, the nature of phase-to-phase faults in the power system is identified, enabling rapid determination of whether a phase-to-phase fault is permanent or transient. The aim is to address the problem of how to avoid the interference of unreasonable reclosing strategies on the operational stability of wind farms.

Description

Technical Field

[0001] This application relates to the field of power system relay protection technology, and in particular to a three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection. Background Technology

[0002] Against the backdrop of continuous development of renewable energy grid-connection technologies, the crucial role of electrochemical energy storage devices in smart grids is gradually becoming apparent. Efficient and reliable power conversion between electrochemical energy storage devices and the power system relies on power conversion systems (PCS). Grid-based PCS, due to their unique active anti-interference and dynamic support characteristics, have become a key research focus.

[0003] In current wind farm grid connection configurations, 110kV or 220kV overhead transmission lines are typically used for power transmission. For 220kV wind power transmission lines, a common reclosing strategy is to not perform a reclosing operation after a three-phase trip, in order to prevent serious consequences that may be caused by reclosing on a permanent phase-to-phase fault.

[0004] However, when the three-phase power transmission line trips, the power output of the wind farm cannot be transmitted outward, which may lead to an imbalance in its active power, a large number of wind turbines disconnecting from the grid, and at this time the wind farm is difficult to reconnect to the grid quickly. If reclosing is not performed for a long time, the power generation efficiency of the wind farm will be greatly reduced.

[0005] Therefore, it is necessary to determine the nature of the fault before the circuit breaker operates again, and to execute a specific reclosing strategy based on the determination result, so as to avoid unreasonable reclosing strategies from interfering with the operational stability of the wind farm. Summary of the Invention

[0006] The main objective of this application is to provide a three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection, aiming to solve the problem of how to avoid unreasonable reclosing strategies from interfering with the operational stability of wind farms.

[0007] To achieve the above objectives, this application provides a three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection. This method is applied to a power system with a grid-type PCS, a three-phase circuit, and a transmission line. The power system includes a first circuit breaker at the wind farm outlet, a second circuit breaker at the grid-type PCS outlet, a third circuit breaker on the transmission line near the wind farm side, and a fourth circuit breaker on the transmission line far from the wind farm side. The method includes the following steps:

[0008] When a two-phase or three-phase fault is detected in the transmission line, the third and second circuit breakers are reclosed after a preset delay. Current is injected into the transmission line of the wind farm through the grid-type PCS, and the current energy generated by the transmission line based on the injected current within a preset time window is calculated.

[0009] When the current energy exceeds a preset threshold, the second circuit breaker and the third circuit breaker trip.

[0010] Otherwise, control the first circuit breaker and the fourth circuit breaker to reclose.

[0011] Optionally, the expression for calculating the current energy is:

[0012]

[0013] In the formula, t z The initial injection time of the network-type PCS is given by Δt, where Δt is the duration of the injected current, and i A i B and i C These are the injection currents of phase A, phase B, and phase C in a three-phase circuit, respectively.

[0014] Optionally, the preset delay is calculated based on the arc deionization time at the fault point and / or the arc insulation recovery time.

[0015] Optionally, the detection methods for the two-phase or three-phase faults include:

[0016] When a phase voltage value less than a preset voltage threshold is collected in any two phase circuits within the second preset time window, and / or a phase current value greater than a preset current threshold is collected in any two phase circuits, it is determined that a two-phase fault has occurred in the sending line.

[0017] When the second preset time window collects a phase voltage value less than a preset voltage threshold for each phase of the three-phase circuit, and / or collects a phase current value greater than a preset current threshold for each phase of the three-phase circuit, it is determined that a three-phase fault has occurred in the sending line.

[0018] Furthermore, to achieve the above objectives, this application also provides a three-phase adaptive reclosing system for wind farm transmission lines based on grid-type PCS signal injection, including a first circuit breaker installed at the wind farm outlet, a second circuit breaker installed at the grid-type PCS outlet, a third circuit breaker installed on the near-wind farm side of the transmission line, and a fourth circuit breaker installed on the far-wind farm side of the transmission line. The three-phase adaptive reclosing system for wind farm transmission lines based on grid-type PCS signal injection includes:

[0019] The data acquisition module is used to collect voltage and current signals in the wind farm.

[0020] The protection processing module is used to reclose the third circuit breaker and the second circuit breaker after a preset delay when a fault signal indicating a two-phase or three-phase fault occurs in the transmitting line is received.

[0021] The current injection and calculation module is used to inject current into the wind farm's transmission line through the grid-type PCS, and to calculate the current energy generated by the transmission line based on the injected current within a preset time window.

[0022] The judgment module is used to determine the numerical relationship between the current energy and the preset threshold.

[0023] The execution module is used to trip the second circuit breaker and the third circuit breaker when the current energy is greater than a preset threshold; otherwise, it controls the first circuit breaker and the fourth circuit breaker to reclose.

[0024] Optionally, the data acquisition module includes:

[0025] The acquisition unit is used to acquire analog signals of three-phase current and / or three-phase voltage on the transmission line;

[0026] An analog-to-digital converter is used to convert the analog signals of the three-phase current and / or the three-phase voltage into digital signals.

[0027] Optionally, the current injection and calculation module includes:

[0028] A current injection unit is used to control the injection of current from the grid-type PCS into the wind farm's power transmission line;

[0029] An energy calculation unit is used to calculate the current energy generated by the output line based on the injected current within a preset time window.

[0030] Optionally, the execution module includes:

[0031] A trip unit is used to trip the second circuit breaker and the third circuit breaker;

[0032] The reclosing unit is used to control the first circuit breaker and the fourth circuit breaker to reclose.

[0033] In addition, to achieve the above objectives, this application also provides a computer system, the computer system comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the computer program is executed by the processor, it implements the steps of the three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection as described in any of the preceding claims.

[0034] In addition, to achieve the above objectives, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the steps of the three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection as described in any of the preceding claims.

[0035] This application has at least the following beneficial effects:

[0036] 1. By injecting signals into the transmission line through a grid-type energy storage PCS, the nature of phase-to-phase faults in the power system can be identified, enabling a rapid judgment on whether a phase-to-phase fault is permanent or transient.

[0037] 2. Different countermeasures are taken according to different types of faults. Compared with the existing reclosing technology, which uses three-phase reclosing that fails and then disconnects and does not reclose, this application uses the method of injecting signals to perform a second reclosing, so as to avoid the reduction of wind farm power generation efficiency due to long-term non-reclosing.

[0038] 3. It only utilizes the control capabilities of the network-type PCS itself, without the need to install additional signal injection equipment or modify the physical architecture of the original equipment;

[0039] 4. It has low requirements for sampling rate, small error, and is easy to implement; it also does not require changes to the equipment structure of existing projects, has low cost, and high universality. Attached Figure Description

[0040] Figure 1 This is a topology diagram of the simulation system involved in the embodiments of this application;

[0041] Figure 2 This is a flowchart illustrating the first embodiment of the three-phase adaptive reclosing method for wind farm transmission lines based on network-type PCS signal injection in this application.

[0042] Figure 3 This is a waveform diagram of the PCS injected current signal when a transient ABC three-phase short-circuit fault occurs in the transmission line involved in the embodiments of this application;

[0043] Figure 4 This is a waveform diagram of the PCS injected current signal when a permanent ABC three-phase short-circuit fault occurs in the transmission line involved in the embodiments of this application.

[0044] Figure 5 This is a waveform diagram of the PCS injected current signal when a permanent two-phase ground fault (AB phase) occurs on the transmission line involved in this application embodiment;

[0045] Figure 6This is a schematic diagram of the architecture of the three-phase adaptive reclosing system for wind farm transmission lines based on grid-type PCS signal injection in this application.

[0046] Figure 7 This is a schematic diagram of the hardware operating environment of the computer system involved in the embodiments of this application.

[0047] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0048] To better understand the above technical solutions, exemplary embodiments of this disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of this disclosure are shown in the drawings, it should be understood that this disclosure can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0049] First Embodiment

[0050] This embodiment provides a three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection, referring to... Figure 1 The power system simulation topology diagram shown is applied to a power system with a grid-type PCS (i.e., energy storage in the diagram), a wind farm containing three-phase circuits, and a transmission line. The power system includes a first circuit breaker QF1 located at the wind farm outlet, a second circuit breaker QF2 located at the grid-type PCS outlet, a third circuit breaker QF3 located on the transmission line near the wind farm side, and a fourth circuit breaker QF4 located on the transmission line far from the wind farm side.

[0051] Reference Figure 2 The method includes the following steps:

[0052] Step S10: When a two-phase or three-phase fault is detected in the transmission line, the third circuit breaker and the second circuit breaker are reclosed after a preset delay, and current is injected into the transmission line of the wind farm through the grid-type PCS, and the current energy generated by the transmission line based on the injected current within a preset time window is calculated.

[0053] In this embodiment, a three-phase adaptive reclosing method is provided, which is used to determine phase-to-phase faults in transmission lines where two-phase or three-phase faults occur. For single-phase faults, the faulty phase can be disconnected directly.

[0054] It should be noted that the purpose of the preset interval delay is because after a line fault occurs, a period of time is needed for the circuit breaker to disconnect. That is, the circuit breaker can only be closed after a certain period of time. Therefore, in this embodiment, the third circuit breaker QF3 and the second circuit breaker QF2 are reclosed only after the preset interval delay in order to isolate the fault.

[0055] Further, and optionally, the preset delay is calculated based on the arc deionization time and / or arc insulation recovery time at the fault point. The reason is that after the sending line completes the tripping operation, the recovery time of the insulation medium at the fault point is closely related to the arc extinguishing process. The arc extinguishing time is influenced by a combination of factors, including ambient wind speed, air humidity, arc geometry, and transmission line parameters. The characteristic time constant of the arc deionization process is typically distributed between 150-250 ms. In some optional implementations, considering a certain margin, the delay T is fixed. d It can be set to 200ms.

[0056] Also in this step, current is injected into the wind farm's transmission line through a grid-type PCS, and the current energy generated by the transmission line based on the injected current within a preset time window is calculated.

[0057] It is worth noting that the amplitude of the injected current in a grid-type energy storage PCS is much greater than the current amplitude during transient faults and after the fault disappears.

[0058] It should be noted that this step does not limit the overlap between the third circuit breaker and the second circuit breaker, and the execution order between the current injection and current energy calculation operations can be performed simultaneously or sequentially based on certain rules. It is only emphasized that the above operations are triggered when a two-phase or three-phase fault is detected in the sending line.

[0059] Furthermore, and optionally, the expression for calculating current energy is:

[0060]

[0061] In the formula, t z The initial injection time of the network-type PCS is given by Δt, where Δt is the duration of the injected current, and i A i B and i C These are the injection currents of phase A, phase B, and phase C in a three-phase circuit, respectively.

[0062] Step S20: When the current energy is greater than a preset threshold, trip the second circuit breaker and the third circuit breaker;

[0063] Step S30: Otherwise, control the first circuit breaker and the fourth circuit breaker to reclose.

[0064] In this embodiment, the current energy S calculated in S10 is compared with the preset threshold S. set Comparisons are used to identify the nature of the fault.

[0065] The principle behind this criterion is as follows: In the case of a transient fault, the transmission line is open after the fault disappears, and the integral of the current actively injected by the grid-type PCS approaches zero; while in the case of a permanent single-phase fault, the fault point always exists, and the injected current on the transmission line will change significantly.

[0066] Therefore, when the current energy is greater than the preset threshold, the fault is considered to have not disappeared and is judged as a "permanent fault" with a serious impact. A blocking closing signal is output to trip the second circuit breaker QF2 and the third circuit breaker QF3. If not (i.e., the current energy is less than or equal to the preset threshold), it is judged as a transient fault with a minor impact. A closing signal is output to control the first circuit breaker QF1 and the fourth circuit breaker QF4 to reclose.

[0067] The preset threshold is an empirical value that has been verified through extensive testing and takes into account a certain margin. In some optional implementations, the preset threshold can be 0.005.

[0068] In the technical solution provided in this embodiment, a signal is injected into the transmission line by a grid-type energy storage PCS to identify the nature of the phase-to-phase fault in the power system. This enables a rapid judgment on whether the phase-to-phase fault is permanent or transient, and different countermeasures are taken according to different types of faults. Compared with the existing reclosing technology, which uses a three-phase reclosing method that fails and then disconnects and does not reclose, this embodiment uses a signal injection method to perform a second reclosing, avoiding the reduction in power generation efficiency of the wind farm due to prolonged non-reclosing.

[0069] Second Embodiment

[0070] Based on the first embodiment, this embodiment provides a method for detecting two-phase or three-phase faults in a transmission line:

[0071] For two-phase or three-phase faults occurring in wind power transmission lines, protection devices can detect them using at least one of voltage and current:

[0072] Step S101: When a phase voltage value less than a preset voltage threshold is collected in any two phase circuits within the second preset time window, and / or a phase current value greater than a preset current threshold is collected in any two phase circuits, it is determined that a two-phase fault has occurred in the sending line.

[0073] Step S102: When the second preset time window collects a phase voltage value less than a preset voltage threshold for each phase of the three-phase circuit, and / or collects a phase current value greater than a preset current threshold for each phase of the three-phase circuit, it is determined that a three-phase fault has occurred in the sending line.

[0074] If current is chosen as the sole criterion for phase-to-phase faults, the principle of Current Differential Protection is applied. This is based on Kirchhoff's Current Law, where current transformers (CTs) are installed at both ends of the line (the wind farm substation end and the grid end) to measure and transmit current data in real time. Under normal operation, the current flowing into and out of the line is equal in magnitude and phase, and the differential current is theoretically zero. However, when a fault occurs, a large short-circuit current is generated at the fault point (i.e., when the phase current value exceeds the preset current threshold). This current is supplied simultaneously by the power sources on both sides of the line (the grid and the wind farm). At this time, the sum of the currents flowing into the line is no longer equal to zero, but equal to this short-circuit current.

[0075] If only voltage is chosen as the criterion for phase-to-phase faults, it is done under the condition that the impedance is known. Since the impedance per unit length of the line is basically fixed, the calculated impedance value Z can directly reflect the distance of the fault point. When a fault point appears in the line, the impedance of the fault point is much smaller than the load impedance. For two-phase or three-phase faults, the voltage will drop significantly and the current will rise sharply, causing the calculated impedance Z to become very small. In some cases, it can be simplified to choose voltage as the criterion for phase-to-phase faults.

[0076] If voltage and current are chosen together as the criteria for phase-to-phase faults, the basis is distance protection and overcurrent / directional overcurrent protection. Since simple overcurrent protection cannot distinguish between a fault at the end of the line and a serious fault in the next section of the line, in order to improve selectivity, it is combined with low-voltage elements or directional elements to form low-voltage blocked overcurrent protection or directional overcurrent protection. When the current is too large and the voltage is too low, it is judged as a fault, thereby preventing false tripping caused by normal load overcurrent (normal voltage).

[0077] Third Embodiment

[0078] Based on any of the above embodiments, this embodiment provides a verification embodiment for the aforementioned three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection, as detailed below:

[0079] Similarly, refer to Figure 1The power system simulation topology shown has 100 doubly-fed induction generator (DFIG) wind turbines with a rated capacity of 2MW each, a PCS (Power Concentration System) rated capacity of 1.75MW, and an energy storage system consisting of 10 PCS units. The overhead transmission line is 100km long with a voltage level of 220kV. No parallel reactors are installed on either side of the line, and the sampling frequency is 20kHz. Line parameters: R1=0.0103Ω / km, R0=0.3156Ω / km; L1=0.9694mH / km, L0=3.156mH / km; C1=0.0122μF / km, C0=0.00834μF / km. At t=1.49s, a three-phase ABC short-circuit fault occurs 50km from side M on the wind power transmission line. 100ms later, the circuit breakers on both sides of the transmission line and the main circuit breaker of the wind farm are opened successively. The fault is a transient fault (transition resistance is 50Ω, fault duration is 250ms). At t=1.8s, the transmission line circuit breaker QF3 and the PCS main circuit breaker QF2 are closed respectively.

[0080] Assume a three-phase (ABC) short-circuit fault occurs on the transmission line at t=1.49s. 100ms later, the circuit breakers installed on both sides of the transmission line and the main circuit breaker of the wind farm successively trip in three phases, isolating the fault. After a fixed delay T... d At 200ms, or t=1.8s, the circuit breaker QF3 on the side of the transmission line closest to the wind farm and the main circuit breaker QF2 of the grid-type PCS are re-closed.

[0081] In this embodiment, power is injected into the wind farm's transmission line via a grid-type energy storage PCS. When a transient ABC three-phase short-circuit fault occurs in the transmission line, the waveform of the PCS injected current signal is as follows: Figure 3 As shown, Figure 3 In the figure, the horizontal axis represents time, in seconds (s), and the vertical axis represents the injected current, in kiloamperes (kA).

[0082] In this embodiment, the integral S of the absolute value of the current is calculated to be 8.5047e-4, which is less than the preset threshold S. set =0.005, that is, S set The fault was deemed to have disappeared and was classified as a transient fault.

[0083] Fourth embodiment

[0084] Based on any of the above embodiments, this embodiment provides another verification embodiment of the aforementioned three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection, as detailed below:

[0085] Similarly, refer to Figure 1 ​The power system simulation topology diagram shown in this embodiment assumes that the rated capacity of the doubly-fed induction generator (DFIG) wind turbines is 2MW, the number of DFIG wind turbines is 100, the rated capacity of the power storage system (PCS) is 1.75MW, the energy storage system consists of 10 PCS units, the length of the overhead transmission line is 100km, its voltage level is 220kV, no parallel reactors are installed on either side of the line, and the sampling frequency is 20kHz. Line parameters: R1=0.0103Ω / km, R0=0.3156Ω / km; L1=0.9694mH / km, L0=3.156mH / km; C1=0.0122μF / km, C0=0.00834μF / km. At t=1.49s, a three-phase ABC short-circuit fault occurs 50km from side M on the wind power transmission line. 100ms later, the circuit breakers on both sides of the transmission line and the main circuit breaker of the wind farm are opened successively. The fault is a permanent fault (transition resistance is 50Ω). At t=1.8s, the transmission line circuit breaker QF3 and the PCS main circuit breaker QF2 are closed respectively.

[0086] Assume a three-phase (ABC) short-circuit fault occurs on the transmission line at t=1.49s. 100ms later, the circuit breakers installed on both sides of the transmission line and the main circuit breaker of the wind farm successively trip in three phases, isolating the fault. After a fixed delay T... d The reclosing occurs at 200ms, or t=1.8s, at the circuit breaker QF3 on the wind farm side of the transmission line and the main circuit breaker QF2 of the grid-type PCS. In this embodiment, the duration Δt of the injected signal is set to 50ms.

[0087] Power is injected into the wind farm's transmission line via a grid-type energy storage PCS. In this embodiment, the waveform of the PCS-injected current signal when a permanent three-phase (A, B, C) short-circuit fault occurs in the transmission line is as follows: Figure 4 As shown. Figure 4 In the figure, the horizontal axis represents time, in seconds (s), and the vertical axis represents the injected current, in kiloamperes (kA).

[0088] In this embodiment, the integral S of the absolute value of the current is calculated to be 0.316, which is greater than the preset threshold S. set =0.005, that is, S>S set This means that the fault is considered to have not disappeared and is judged as a permanent fault.

[0089] Fifth Embodiment

[0090] Based on any of the above embodiments, this embodiment provides another verification embodiment of the aforementioned three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection, as detailed below:

[0091] Similarly, refer to Figure 1The power system simulation topology diagram shown in this embodiment has a rated capacity of 2MW for the doubly-fed induction generator (DFIG) wind turbines, a quantity of 100 DFIG wind turbines, a rated capacity of 1.75MW for the power generation system (PCS), and an energy storage system consisting of 10 PCS units. The overhead transmission line is 100km long with a voltage level of 220kV. No parallel reactors are installed on either side of the line, and the sampling frequency is 20kHz. Line parameters: R1=0.0103Ω / km, R0=0.3156Ω / km; L1=0.9694mH / km, L0=3.156mH / km; C1=0.0122μF / km, C0=0.00834μF / km. At t=1.49s, a two-phase ground fault (AB phase) occurs 50km from side M on the wind power transmission line. 100ms later, the circuit breakers on both sides of the transmission line and the main circuit breaker of the wind farm are opened successively. The fault is a permanent fault (transition resistance is 50Ω). At t=1.8s, the transmission line circuit breaker QF3 and the PCS main circuit breaker QF2 are closed respectively.

[0092] Assume a three-phase (ABC) short-circuit fault occurs on the transmission line at t=1.49s. 100ms later, the circuit breakers installed on both sides of the transmission line and the main circuit breaker of the wind farm successively trip in three phases, isolating the fault. After a fixed delay T... d The reclosing occurs at 200ms, or t=1.8s, at the circuit breaker QF3 on the wind farm side of the transmission line and the main circuit breaker QF2 of the grid-type PCS. In this embodiment, the duration Δt of the injected signal is set to 50ms.

[0093] Power is injected into the wind farm's transmission line via a grid-type energy storage PCS. In this embodiment, the waveform of the PCS-injected current signal when a permanent three-phase (A, B, C) short-circuit fault occurs in the transmission line is as follows: Figure 5 As shown. Figure 5 In the figure, the horizontal axis represents time, in seconds (s), and the vertical axis represents the injected current, in kiloamperes (kA).

[0094] In this embodiment, the integral S of the absolute value of the current is calculated to be 0.205, which is greater than the preset threshold S. set =0.005, that is, S>S set This means that the fault is considered to have not disappeared and is judged as a permanent fault.

[0095] In addition, refer to Figure 6 This embodiment also proposes a three-phase adaptive reclosing system for wind farm transmission lines based on grid-type PCS signal injection, including a first circuit breaker installed at the wind farm outlet, a second circuit breaker installed at the grid-type PCS outlet, a third circuit breaker installed on the near-wind farm side of the transmission line, and a fourth circuit breaker installed on the far-wind farm side of the transmission line. The three-phase adaptive reclosing system for wind farm transmission lines based on grid-type PCS signal injection includes:

[0096] Data acquisition module 100 is used to acquire voltage and current signals in the wind farm;

[0097] The protection processing module 200 is used to reclose the third circuit breaker and the second circuit breaker after a preset delay when it receives a fault signal indicating that a two-phase fault or a three-phase fault has occurred in the transmitting line.

[0098] The current injection and calculation module 300 is used to inject current into the wind farm's transmission line through the grid-type PCS, and to calculate the current energy generated by the transmission line based on the injected current within a preset time window.

[0099] The judgment module 400 is used to determine the numerical relationship between the current energy and the preset threshold.

[0100] The execution module 500 is used to trip the second circuit breaker and the third circuit breaker when the current energy is greater than a preset threshold; otherwise, it controls the first circuit breaker and the fourth circuit breaker to reclose.

[0101] Further and optionally, the data acquisition module includes:

[0102] The acquisition unit is used to acquire analog signals of three-phase current and / or three-phase voltage on the transmission line;

[0103] An analog-to-digital converter is used to convert the analog signals of the three-phase current and / or the three-phase voltage into digital signals.

[0104] Further and optionally, the current injection and calculation module includes:

[0105] A current injection unit is used to control the injection of current from the grid-type PCS into the wind farm's power transmission line;

[0106] An energy calculation unit is used to calculate the current energy generated by the output line based on the injected current within a preset time window.

[0107] Further and optionally, the execution module includes:

[0108] A trip unit is used to trip the second circuit breaker and the third circuit breaker;

[0109] The reclosing unit is used to control the first circuit breaker and the fourth circuit breaker to reclose.

[0110] Furthermore, as an implementation scheme, Figure 7 This is a schematic diagram of the hardware operating environment of the computer system involved in the embodiments of this application.

[0111] like Figure 7As shown, the computer system may include: a processor 1001, such as a CPU; a memory 1005; a user interface 1003; a network interface 1004; and a communication bus 1002. The communication bus 1002 is used to enable communication between these components. The user interface 1003 may include a display screen or an input unit such as a keyboard; optionally, the user interface 1003 may also include a standard wired interface or a wireless interface. The network interface 1004 may optionally include a standard wired interface or a wireless interface (such as a Wi-Fi interface). The memory 1005 may be high-speed RAM or non-volatile memory, such as a disk drive. Optionally, the memory 1005 may also be a storage device independent of the aforementioned processor 1001.

[0112] Those skilled in the art will understand that Figure 7 The computer system architecture shown does not constitute a limitation on the computer system and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0113] like Figure 7 As shown, the memory 1005, as a storage medium, may include an operating system, a network communication module, a user interface module, and computer programs. The operating system is a program that manages and controls the hardware and software resources of the computer system, as well as the operation of the computer programs and other software or programs.

[0114] exist Figure 7 In the computer system shown, the user interface 1003 is mainly used to connect to the terminal and communicate with the terminal; the network interface 1004 is mainly used to communicate with the backend server; and the processor 1001 can be used to call the computer program stored in the memory 1005.

[0115] In this embodiment, the computer system includes: a memory 1005, a processor 1001, and a computer program stored in the memory and executable on the processor, wherein:

[0116] When processor 1001 calls a computer program stored in memory 1005, it performs the following operations:

[0117] When a two-phase or three-phase fault is detected in the transmission line, the third and second circuit breakers are reclosed after a preset delay. Current is injected into the transmission line of the wind farm through the grid-type PCS, and the current energy generated by the transmission line based on the injected current within a preset time window is calculated.

[0118] When the current energy exceeds a preset threshold, the second circuit breaker and the third circuit breaker trip.

[0119] Otherwise, control the first circuit breaker and the fourth circuit breaker to reclose.

[0120] When processor 1001 calls a computer program stored in memory 1005, it performs the following operations:

[0121] The formula for calculating the current energy is:

[0122]

[0123] In the formula, t z The initial injection time of the network-type PCS is given by Δt, where Δt is the duration of the injected current, and i A i B and i C These are the injection currents of phase A, phase B, and phase C in a three-phase circuit, respectively.

[0124] When processor 1001 calls a computer program stored in memory 1005, it performs the following operations:

[0125] The preset delay is calculated based on the arc deionization time at the fault point and / or the arc insulation recovery time.

[0126] When processor 1001 calls a computer program stored in memory 1005, it performs the following operations:

[0127] When a phase voltage value less than a preset voltage threshold is collected in any two phase circuits within the second preset time window, and / or a phase current value greater than a preset current threshold is collected in any two phase circuits, it is determined that a two-phase fault has occurred in the sending line.

[0128] When the second preset time window collects a phase voltage value less than a preset voltage threshold for each phase of the three-phase circuit, and / or collects a phase current value greater than a preset current threshold for each phase of the three-phase circuit, it is determined that a three-phase fault has occurred in the sending line.

[0129] Furthermore, those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program includes program instructions and can be stored in a storage medium, which is a computer-readable storage medium. The program instructions are executed by at least one processor in a computer system to implement the process steps of the embodiments of the above methods.

[0130] Therefore, this application also provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the various steps of the three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection as described in the above embodiments.

[0131] The computer-readable storage medium can be any computer-readable storage medium capable of storing program code, such as a USB flash drive, portable hard drive, read-only memory (ROM), magnetic disk, or optical disk.

[0132] It should be noted that, since the storage medium provided in the embodiments of this application is the storage medium used to implement the methods of the embodiments of this application, those skilled in the art can understand the specific structure and variations of the storage medium based on the methods described in the embodiments of this application, and therefore will not be repeated here. All storage media used in the methods of the embodiments of this application fall within the scope of protection of this application.

[0133] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0134] This application is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of this application. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart... Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0135] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0136] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0137] It should be noted that any reference signs placed between parentheses in the claims should not be construed as limiting the claims. The word "comprising" does not exclude the presence of components or steps not listed in the claims. The word "a" or "an" preceding a component does not exclude the presence of a plurality of such components. This application can be implemented by means of hardware comprising several different components and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names.

[0138] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0139] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection, characterized in that, The method is applied to a power system with a grid-type PCS, a wind farm containing three-phase circuits, and a transmission line. The power system includes a first circuit breaker at the wind farm outlet, a second circuit breaker at the grid-type PCS outlet, a third circuit breaker on the transmission line near the wind farm side, and a fourth circuit breaker on the transmission line far from the wind farm side. The method includes the following steps: When a two-phase or three-phase fault is detected in the transmission line, the third and second circuit breakers are reclosed after a preset delay. Current is injected into the transmission line of the wind farm through the grid-type PCS, and the current energy generated by the transmission line based on the injected current within a preset time window is calculated. When the current energy exceeds a preset threshold, the second circuit breaker and the third circuit breaker trip. Otherwise, control the first circuit breaker and the fourth circuit breaker to reclose; The formula for calculating the current energy is: ； In the formula, t z The initial injection time of the network-type PCS is given by Δt, where Δt is the duration of the injected current, and i A i B and i C These are the injection currents of phase A, phase B, and phase C in a three-phase circuit, respectively. The preset delay is calculated based on the arc deionization time at the fault point and / or the arc insulation recovery time; The detection methods for two-phase or three-phase faults include: When a phase voltage value less than a preset voltage threshold is collected in any two phase circuits within the second preset time window, and / or a phase current value greater than a preset current threshold is collected in any two phase circuits, it is determined that a two-phase fault has occurred in the sending line. When the second preset time window collects a phase voltage value less than a preset voltage threshold for each phase of the three-phase circuit, and / or collects a phase current value greater than a preset current threshold for each phase of the three-phase circuit, it is determined that a three-phase fault has occurred in the sending line.

2. A system for implementing the three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection as described in claim 1, characterized in that, The system includes a first circuit breaker located at the wind farm outlet, a second circuit breaker located at the grid-type PCS outlet, a third circuit breaker located on the near-wind farm side of the transmission line, and a fourth circuit breaker located on the far-wind farm side of the transmission line. The three-phase adaptive reclosing system for the wind farm transmission line based on grid-type PCS signal injection includes: The data acquisition module is used to collect voltage and current signals in the wind farm. The protection processing module is used to reclose the third circuit breaker and the second circuit breaker after a preset delay when a fault signal indicating a two-phase or three-phase fault occurs in the transmitting line is received. The current injection and calculation module is used to inject current into the wind farm's transmission line through the grid-type PCS, and to calculate the current energy generated by the transmission line based on the injected current within a preset time window. The judgment module is used to determine the numerical relationship between the current energy and the preset threshold. The execution module is used to trip the second circuit breaker and the third circuit breaker when the current energy is greater than a preset threshold; otherwise, it controls the first circuit breaker and the fourth circuit breaker to reclose.

3. The system as described in claim 2, characterized in that, The data acquisition module includes: The acquisition unit is used to acquire analog signals of three-phase current and / or three-phase voltage on the transmission line; An analog-to-digital converter is used to convert the analog signals of the three-phase current and / or the three-phase voltage into digital signals.

4. The system as described in claim 2, characterized in that, The current injection and calculation module includes: A current injection unit is used to control the injection of current from the grid-type PCS into the wind farm's power transmission line; An energy calculation unit is used to calculate the current energy generated by the output line based on the injected current within a preset time window.

5. The system as described in claim 2, characterized in that, The execution module includes: A trip unit is used to trip the second circuit breaker and the third circuit breaker; The reclosing unit is used to control the first circuit breaker and the fourth circuit breaker to reclose.

6. A computer system, characterized in that, The computer system includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is executed by the processor, it implements the steps of the three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection as described in claim 1.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program that, when executed by a processor, implements the steps of the three-phase adaptive reclosing method for wind farm transmission lines based on grid-type PCS signal injection as described in claim 1.

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