Direction pilot protection method and system based on control and protection cooperation, medium and equipment

Abstract

The invention belongs to the field of active power distribution network relay protection, and provides a direction pilot protection method and system based on control and protection cooperation, a medium and equipment in order to solve the problems that an existing direction pilot protection method cannot detect characteristic high-frequency signals, is limited in application scene and cannot effectively protect a power distribution line containing a T-connection IIDG and a load. The direction pilot protection method based on control and protection cooperation comprises the following steps: acquiring a positive sequence voltage drop degree and a phase current break variable of an IIDG grid-connected point; according to the IIDG grid-connected point positive sequence voltage drop degree and the phase current break variable, whether a control algorithm and a protection algorithm are started or not is judged, the method can be suitable for a distribution line containing a T-connection IIDG and a load, and the performance of directional protection is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of active power distribution network relay protection, and particularly relates to a direction pilot protection method and system based on control-protection coordination, a medium and equipment. BACKGROUND

[0002] The statements in this section merely provide background information related to the present application and do not necessarily constitute the prior art.

[0003] A large number of inverter-interfaced distributed generators (IIDGs) are connected to the distribution network, and the boost, sink and reverse effects of the IIDGs lead to the failure of traditional overcurrent protection. There are usually T-branch connections in the medium-voltage distribution lines, which leads to the fact that the traditional differential protection principle cannot be applied to the T-branch connection lines containing IIDGs and loads. The prior art analyzes the positive sequence current amplitude and fault component phase angle characteristics of the T-branch connection line, and constructs a double-proportion braking coefficient adaptive differential protection, which improves the adaptability of the differential protection in the T-branch connection line containing IIDGs and loads. However, the protection criterion based on the phase difference is sensitive to data synchronization errors.

[0004] Directional pilot protection has the advantages of less data transmission flow and lower data synchronization requirements, but the traditional power direction element and the positive sequence fault component direction element (PSFCDR) have adaptability problems when a high penetration rate of IIDGs is connected. Since the equivalent impedance angle of the IIDG under different fault types, fault locations and transition resistances may change between (0, 360°), it is difficult to solve the adaptability problem of the direction element by optimizing the direction criterion only. According to the different implementation modes of the IIDG control link, the protection scheme based on control-protection coordination can be divided into two categories: the first category is the active injection type. For example, the prior art proposes an active detection type distance protection, which injects a positive sequence double-frequency signal with a frequency of 950Hz and 1000Hz after a fault, and solves the fault distance equation by using the double-frequency signal. Although the boost and sink effects of the power supply at the other end are eliminated, when the IIDG is out of operation, the active injection type protection cannot detect the characteristic high-frequency signal. The second category of protection scheme based on control-protection coordination modifies the control strategy of the inverter to provide fault characteristics that are conducive to protection discrimination during fault ride-through. For example, the prior art adjusts the negative sequence current to meet the needs of calculating the additional impedance angle, and proposes a distance protection scheme based on negative sequence impedance reconstruction, which solves the problem of distance protection I section misoperation in new energy transmission lines, but is only applicable to asymmetric fault situations, and the application scenario is limited.

[0005] In summary, the existing directional pilot protection method cannot detect the characteristic high-frequency signal and is limited in application scenarios, and cannot effectively protect the distribution line containing T-connected IIDG and load. SUMMARY

[0006] To solve the above technical problems, the application provides a directional pilot protection method based on control and protection collaboration, which can be applied to distribution lines containing T-connected IIDG and load, and improve the performance of directional protection.

[0007] To achieve the above purpose, the application adopts the following technical solutions: The first aspect of the application provides a directional pilot protection method based on control and protection collaboration.

[0008] In one or more embodiments, a directional pilot protection method based on control and protection collaboration is provided, comprising: Obtaining the positive sequence voltage drop degree and phase current mutation of the IIDG grid connection point; According to the positive sequence voltage drop degree and phase current mutation of the IIDG grid connection point, it is judged whether to start the control algorithm and the protection algorithm; The control algorithm is: according to the positive sequence voltage and positive sequence current at the IIDG grid connection point, the dq axis current command value is calculated; The protection algorithm is: According to the positive sequence fault component voltage and positive sequence fault component current of the second cycle after fault obtained by each protection device, the local fault direction is calculated, and the fault direction is sent to the opposite end protection device; After obtaining the fault direction of the opposite end protection device, it is judged whether it is an internal fault; If both ends are positive direction faults, it is judged that an internal short circuit fault occurs, and a trip command is sent; Otherwise, it is judged as normal operation or an external short circuit fault occurs, and the protection device is controlled to return to normal.

[0009] As an embodiment, when the positive sequence voltage is less than 90% of the rated voltage, the control algorithm is started.

[0010] As an embodiment, when the mutation of any phase current exceeds 0.1 times of the load current, the protection algorithm is started.

[0011] As an embodiment, the process of calculating the local fault direction is:

[0012] Among them, And are the positive sequence fault component voltage and positive sequence fault component current of the second cycle after fault at the installation position of each protection device; when when the sign of the product of the positive sequence voltage and the positive sequence current is positive, it is determined that the fault is a forward fault; and when the sign of the product of the positive sequence voltage and the positive sequence current is negative, it is determined that the fault is a reverse fault.

[0013] As an embodiment, the dq-axis current command value is calculated as follows:

[0014] wherein, and is the command value of the dq-axis current; is the positive sequence current at the point of common coupling after the fault, is the phase jump angle of the positive sequence current; is the phase jump angle of the positive sequence voltage.

[0015] As an embodiment, the phase jump angle of the positive sequence voltage is: ; the phase jump angle of the positive sequence current is: ; wherein, is the phase angle of the positive sequence fault component voltage, ; is the positive sequence voltage at the point of common coupling before the fault, is the positive sequence voltage at the point of common coupling after the fault, is the positive sequence current before the fault, is the positive sequence current after the fault, and arg(·) is a phase taking operation.

[0016] A second aspect of the present application provides a direction pilot protection system based on control and protection collaboration.

[0017] In one or more embodiments, a direction pilot protection system based on control and protection collaboration comprises: an information acquisition module for acquiring the positive sequence voltage drop degree and the phase current mutation at the point of common coupling of an IIDG; an algorithm start judgment module for judging whether to start a control algorithm and a protection algorithm according to the positive sequence voltage drop degree and the phase current mutation at the point of common coupling of an IIDG; wherein the control algorithm is to calculate a dq-axis current command value according to the positive sequence voltage and the positive sequence current at the point of common coupling of an IIDG; the protection algorithm is: to calculate the fault direction locally according to the positive sequence fault component voltage and the positive sequence fault component current of the second cycle after the fault at the installation site of each protection device, and to send the fault direction to the opposite end protection device; after obtaining the fault direction of the opposite end protection device, it is judged whether it is an intra-zone fault; if both ends are forward faults, it is determined that an intra-zone short circuit fault occurs, and a trip command is sent. Otherwise, it is judged as normal operation or out-of-zone short-circuit fault, and the protection device is controlled to return to normal.

[0018] A third aspect of the present application provides a computer program product.

[0019] A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the control and protection collaborative directional pilot protection method as described above.

[0020] A fourth aspect of the present application provides a computer program product.

[0021] A computer program product comprising a computer program / instructions which, when executed by a processor, implements the steps of the control and protection collaborative directional pilot protection method as described above.

[0022] A fifth aspect of the present application provides an electronic device.

[0023] An electronic device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor, when executing the program, implements the steps of the control and protection collaborative directional pilot protection method as described above.

[0024] Compared with the prior art, the present application has the following beneficial effects: The present application judges whether to start the control algorithm and the protection algorithm according to the positive sequence voltage drop degree and the phase current mutation of the IIDG grid-connected point, calculates the dq axis current instruction value by the control algorithm to actively regulate the distributed power inverter, calculates the local fault direction by the protection algorithm and sends the fault direction to the opposite end protection device, and then judges whether it is an in-zone fault, thereby improving the performance of the directional protection and being suitable for the line containing the unmeasurable T-connected IIDG and the load branch. BRIEF DESCRIPTION OF DRAWINGS

[0025] The drawings accompanying the specification constitute part of this application and illustrate exemplary embodiments of the application and together with the description, serve to explain the application. The drawings described are intended to be illustrative only and not restrictive of the application.

[0026] Figure 1 The line schematic diagram of the embodiment of the present application containing the branch IIDG and the branch load; Figure 2 The positive sequence fault additional network when the F1 point of the embodiment of the present application occurs the reverse direction fault; Figure 3 The positive sequence fault additional network when the F2 point of the embodiment of the present application occurs the positive direction fault; Figure 4 The IIDG voltage and current phasor diagram of the embodiment of the present application; Figure 5 This is a simulation model of an active distribution network containing branch IIDGs and branch loads, as described in an embodiment of the present invention. Figure 6 This is the IIDG2 waveform when a metallic BC phase-to-phase short circuit occurs at point F2 in an embodiment of the present invention. Figure 7 This is the IIDG2 waveform when a metallic three-phase short circuit occurs at point F1 in an embodiment of the present invention; Figure 8 This is the simulation result of a metallic two-phase BC short circuit occurring at point F5 in an embodiment of the present invention; Figure 9 This is a simulation result of a metallic two-phase AB short circuit occurring at point F1 in an embodiment of the present invention; Figure 10 This is a flowchart of a directional longitudinal protection scheme based on control and protection collaboration according to an embodiment of the present invention. Detailed Implementation

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0029] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0030] Figure 10 This is a flowchart illustrating a directional longitudinal protection method based on control and protection coordination in an embodiment of the present invention, as shown below. Figure 10 The directional longitudinal protection method based on control and protection coordination shown in this embodiment may include the following steps: Step 1: Obtain the positive sequence voltage drop and phase current mutation at the IIDG grid connection point.

[0031] Step 2: Based on the degree of voltage drop in the positive sequence at the IIDG grid connection point and the sudden change in phase current, determine whether to activate the control algorithm and protection algorithm.

[0032] Figure 1The figure is a schematic diagram of a line with branch IIDG and load, J, K, M, and N are bus numbers, R1-R6 represent protection devices at different positions, and F1-F3 are fault points on different sections of the line.

[0033] To reflect the correlation between the output current of the IIDG and the voltage drop at the point of common coupling, the IIDG is usually equivalent to a voltage-controlled current source in parallel with a current-limiting impedance in the past. This equivalent model can accurately reflect the output characteristics of the IIDG during fault ride-through, but it is not convenient for fault feature analysis. Since the influence of the IIDG on the PSFCDR depends only on the amplitude and phase angle of its equivalent impedance to the outside, the IIDG is equivalent to a positive-sequence equivalent impedance model in this paper, and the positive-sequence equivalent impedance of the IIDG in the positive-sequence fault additional network is defined as

[0034] In the formula, is the positive-sequence equivalent impedance of the IIDG, is the positive-sequence fault component voltage at the point of common coupling of the IIDG, is the positive-sequence fault component current output by the IIDG. It should be noted that the positive direction of the IIDG output current is defined as the IIDG pointing to the power grid, and the negative sign in the above formula indicates the positive-sequence fault component current injected into the IIDG from the power grid, at this time and are the associated reference directions.

[0035] Taking protection R3 as an example, when Figure 1 a short-circuit fault in the opposite direction occurs at point F1 in the middle, the positive-sequence fault additional network of the system is as shown in Figure 2 .

[0036] In the figure, is the positive-sequence fault additional power, is the positive-sequence equivalent impedance of the system power, is the positive-sequence impedance of the line, is the positive-sequence impedance of the load, is the positive-sequence equivalent impedance of each IIDG, and are the positive-sequence fault component voltage and current at protection R3, respectively.

[0037] When the IIDG is out of operation, the positive-sequence fault component voltage and current at protection R3 satisfy

[0038] In the formula, This represents the external equivalent impedance of the network to the right of R3, which is the series and parallel combination of the positive-sequence impedances of each line and the positive-sequence impedance of the load. When the voltage and current of a circuit element are taken in the associated reference direction, if the element absorbs active and reactive power, the impedance angle variation range of its external equivalent impedance is (0, 90°). Since both the line elements and load elements in the network to the right of R3 absorb active and reactive power, therefore... Absorbing active and reactive power, i.e.

[0039] When the IIDG is operating normally, the ratio of the positive sequence fault component voltage and current at protection R3 should include the external equivalent impedance of the IIDG. Become

[0040] in,

[0041] In the above formula, This refers to the series and parallel connections of the positive-sequence impedances of each line, the positive-sequence impedance of the load, and the equivalent positive-sequence impedance of the IIDG. The impedance angle of the equivalent positive-sequence impedance of the IIDG during LVRT. It may vary between (0, 360°) for different distribution networks with different topologies and parameters. The range of phase angle variation may no longer strictly satisfy the equation. However, when When the variation range is controlled within (0, 90°), since the positive sequence fault component voltage and current are taken in the associated reference direction, each line element, load element, and IIDG in the above formula absorbs active and reactive power in the fault component network. Therefore, in the positive sequence fault component network, the network to the right of protection R3 absorbs active and reactive power. It still stands.

[0042] when Figure 1 When a positive-direction short-circuit fault occurs at point F2, the system's positive-sequence fault supplementary network is as follows: Figure 3 As shown, This represents the line impedance.

[0043] The positive sequence fault component voltage and current at protection R3 satisfy:

[0044] If the impedance angle of the positive sequence equivalent impedance of IIDG If the range of variation is also (0, 90°), then each impedance element in the above formula absorbs both active and reactive power in the positive-sequence fault supplementary network. The positive-sequence fault component voltage and current at R3 satisfy...

[0045] In summary, if the impedance angle of the equivalent impedance of the IIDG during LVRT is controlled in the range of (0, 90°), the measured impedance of the PSFCDR is located in the first and third quadrants respectively when the fault is in the opposite direction and positive direction, and the longitudinal directional protection in the direction of the positive sequence fault component can realize reliable protection of the branch IIDG and load feeder.

[0046] When the positive sequence voltage is less than 90% of the rated voltage, a control algorithm is started, and the expression is as follows:

[0047] wherein, is the positive sequence voltage at the IIDG grid connection point, is the rated voltage.

[0048] The control algorithm is: according to the positive sequence voltage and the positive sequence current at the IIDG grid connection point, the dq-axis current command value is calculated.

[0049] When the abrupt change of the current of any phase exceeds 0.1 times of the load current, a protection algorithm is started, and the expression is as follows:

[0050] wherein, represents the value of the current of a certain phase at the N-th sampling point; N is the total number of sampling points in one cycle; n is the sensitivity coefficient, which is usually taken as 0.1-0.3; is the amplitude of the load current in normal operation. wherein, the dq-axis current command value is calculated as:

[0051] wherein,

[0052] and are the command values of the dq-axis current; is the positive sequence current at the grid connection point after the fault, is the phase jump angle of the positive sequence current; is the phase jump angle of the positive sequence voltage. The phase jump angle of the positive sequence voltage is:

[0053] ; The phase jump angle of the positive sequence current is: ; wherein: is the phase angle of the positive sequence fault component voltage, ; is the positive sequence voltage at the grid connection point before the fault, is the positive sequence voltage at the grid connection point after the fault, ​​is the pre-fault positive sequence current, is the post-fault positive sequence current, and arg(·) is a phase operation.

[0054] In the embodiment of the present application, the protection algorithm is: According to the positive sequence fault component voltage and the positive sequence fault component current of the second cycle after the fault obtained by each protection device at the installation position of the protection device, the local fault direction is calculated, and the fault direction is sent to the opposite end protection device; After obtaining the fault direction of the opposite end protection device, it is judged whether it is an internal fault; If both ends are positive direction faults, it is judged that an internal short circuit fault occurs, and a trip command is sent; Otherwise, it is judged as normal operation or an external short circuit fault occurs, and the protection device is controlled to reset.

[0055] Specifically, the process of calculating the local fault direction is:

[0056] wherein, and are the positive sequence fault component voltage and the positive sequence fault component current of the second cycle after the fault at the installation position of each protection device; when , it is judged as a reverse direction fault; when , it is judged as a positive direction fault.

[0057] The principle of the control algorithm is: The voltage and current phasor diagrams of the IIDG before and after the fault are shown in Figure 4 . Wherein are the pre-fault and post-fault positive sequence voltages at the grid connection point, is the positive sequence voltage fault component at the grid connection point, are the pre-fault and post-fault IIDG output positive sequence currents, is the IIDG output positive sequence current fault component, is the maximum allowable output current of the IIDG, is the rated current of the IIDG, are the d-axis and q-axis positive sequence current reference values. is the phase jump angle of the positive sequence voltage at the grid connection point, is the phase jump angle of the positive sequence current, is the phase angle difference between the post-fault positive sequence voltage and the positive sequence current. are respectively:

[0058] is the angle lagging by Figure 4the voltage triangle in the

[0059] is the angle of lag , according to Figure 4 the current triangle in the

[0060] the angle of lag is , the impedance angle of the IIDG positive sequence equivalent impedance is the angle of lag , that is

[0061] After the short-circuit fault occurs in the distribution network, the voltage drop degree and the positive sequence voltage phase jump angle are both determined, and in the above formula the angle of lag is a constant value. The control target of the IIDG during the LVRT is In order to make the impedance angle of the IIDG positive sequence equivalent impedance during the LVRT satisfy the constraint condition

[0062] , the angle of lag may be adjusted to achieve it, and the impedance angle constraint of the IIDG positive sequence equivalent impedance can be converted into the IIDG positive sequence current phase jump angle constraint

[0063] During the LVRT, the IIDG outputs the positive sequence short-circuit current according to the maximum allowed value, and in the above formula, the IIDG fault current is

[0064] Since the IIDG adopts the grid voltage oriented vector control, the d-axis is oriented to the grid voltage vector, and during the LVRT, the IIDG outputs the positive sequence fault current lagging behind the d-axis reference current by an angle, which is the phase angle difference between the positive sequence voltage and the positive sequence current after the fault , that is

[0065] The above formula shows that the positive sequence d-axis and q-axis current reference values ​​​The magnitude of the value can change the phase jump angle of the positive sequence current. Scope, thereby further enabling Belongs to (0, 90°). The reference values ​​for the positive-sequence d-axis and q-axis currents that satisfy the constraints are...

[0066] It should be noted that the phase jump angle of the IIDG positive sequence current When the constraints are met, the longitudinal protection for the positive sequence fault component will operate correctly. The specific values ​​only change the magnitude of the active and reactive current output by the IIDG during LVRT.

[0067] The electromagnetic transient simulation software PSCAD was used to build such a system. Figure 5 The simulation model of the active distribution network shown is used to verify the directional longitudinal protection method for active distribution networks that considers inverter collaborative control proposed in this embodiment: 1) Establishing a model An active distribution network simulation model including branch IIDGs and branch loads, such as... Figure 5 As shown in the figure. The system frequency is 50Hz, and the sampling frequency is 10kHz. IIDG1 and load 1 are located 0.5km and 1km from bus J, respectively; IIDG2 and load 2 are located 1km and 2km from bus K, respectively; and IIDG3 and load 3 are located 0.3km and 0.6km from bus K, respectively. IIDG1-IIDG4 each have a capacity of 2MW. Before the line fault, they operated at unity power factor, only generating active power. After the fault, the LVRT control strategy proposed in this paper is adopted to control... Fault points F1, F2, and F3 are located at the midpoint between branch IIDG and the branch load, respectively. Fault point F4 is 0.5 km from bus K, and fault point F5 is 2.5 km from bus K. Line and load parameters are shown in Table 1.

[0068] Table 1 Line and Load Parameters

[0069] 2) Protection scheme verification a) LVRT control strategy verification At 0.5 seconds, a metallic two-phase short-circuit fault between phases BC is set at point F2. Taking IIDG2 as an example, the relevant waveform is as follows: Figure 6 As shown. Figure 6 In the diagram, (a) represents the three-phase voltage at the grid connection point of IIDG2. Figure 6 (b) IIDG2 outputs three-phase short-circuit current. Due to the adoption of negative sequence elimination control strategy, IIDG2 still outputs symmetrical three-phase current under asymmetrical fault. Figure 6 (c) in the figure represents the positive sequence fault component voltage at the grid connection point of IIDG2.Figure 6 In the figure, (d) represents the positive-sequence fault component current flowing into IIDG2; Figure 6 In the figure, (e) represents the positive sequence dq-axis current output by IIDG2. , and its instruction value ; Figure 6 In this context, (f) represents the impedance angle of the positive-sequence equivalent impedance of IIDG2. Given that the speed requirement for distribution network line protection is relatively low, this invention divides the first cycle after a fault into a fault transient stage and the second cycle after a fault into a protection discrimination stage. Figure 6 As shown in (f), the transient phase Variation between (-180°, 180°) during the protection discrimination stage. Then, within the range of (0, 90°), the longitudinal protection of the positive sequence fault component direction can accurately determine the faults inside and outside the zone, including branch IIDG and load feeders.

[0070] A metallic three-phase short-circuit fault is set at point F1 at 0.5 seconds. The relevant waveform of IIDG2 is as follows. Figure 7 As shown. Figure 7 (a) Figure 7 (b) shows the three-phase voltage and three-phase current waveforms of IIDG2 under symmetrical fault conditions. Figure 7 (c) Figure 7 In the figure, (d) represents the positive sequence fault component voltage and current of IIDG2 under symmetrical fault conditions, and the direction of the positive sequence fault component current is from the power grid to IIDG. Figure 7 In the figure, (e) represents the dq axis current and its command value. Since the command value of the dq axis current is calculated from the fault component, it reaches a stable value about one cycle after the fault. Figure 7 In the diagram, (f) represents the impedance angle of the positive sequence equivalent impedance of IIDG2, occurring in the second cycle after the fault, i.e., the protection discrimination stage. Between (0, 90°).

[0071] b) Protection principle verification In respectively Figure 5 The discrimination results of the proposed positive-sequence fault component directional longitudinal protection scheme were examined at points F1-F5. The measured impedance angles at protection points R1-R6 are shown in Table 2. The fault types in the table include metallic three-phase short circuits, metallic two-phase phase-to-phase short circuits, and two-phase-to-ground short circuits with a 100Ω transition resistor. Since the protection discrimination stage in the scheme uses the second cycle data after the fault, i.e., the data window of 0.52-0.54 seconds, to calculate the positive-sequence fault component voltage and current, the impedance angles are the calculation results at 0.54 seconds during PSCAD simulation.

[0072] Table 2 Simulation results for different fault types

[0073] In the table, "+" and "-" represent positive and reverse direction faults respectively. According to Table 2, when a positive direction fault occurs, the protection at the two ends of the section is in the range of (-225°, -45°), and when a reverse direction fault occurs, the protection at the two ends of the section is in the range of (-45°, 135°), which correctly satisfies the direction criterion. Only when an intra-zone fault occurs, the protection at the two ends of the section discriminates the fault direction as positive, that is, the protection scheme can correctly judge intra-zone and extra-zone faults under different fault positions, fault types and transition resistances.

[0074] 3) Simulation of the influence of IIDG penetration rate In order to investigate the influence of IIDG penetration rate on the protection scheme, two scenarios are selected for simulation: High penetration rate IIDG access: the capacity of IIDG1-IIDG4 is changed from 2MW to 4MW, and at this time the IIDG penetration rate is 100%.

[0075] IIDG exit operation: in the simulation, IIDG1-IIDG4 are disconnected to simulate the night exit operation scenario of photovoltaic. Short circuit faults are set at F1-F5 points, and the simulation results under the two scenarios are shown in Table 3 and Table 4 respectively.

[0076] Table 3 Simulation results when high penetration rate IIDG is accessed

[0077] Table 4 Simulation results when IIDG exits operation

[0078] From Table 3 and Table 4, it can be seen that when an intra-zone fault occurs, the measured impedance angle at the two ends of the line is in the range of (-225°, -45°), and both sides are judged as positive direction; when an extra-zone fault occurs, the measured impedance angle at the two ends of the line is in the range of (-225°, -45°) and (-45°, 135°) respectively, and the direction discrimination results are one positive and one reverse. The protection scheme can correctly judge intra-zone and extra-zone faults under the two scenarios of high penetration rate IIDG access and IIDG exit operation.

[0079] 4) Comparison of protection principles Select the KM section in Figure 5 , set a metallic BC two-phase short circuit fault at F5 point, and compare the action of the protection scheme in this embodiment with that of a kind of energy direction pilot protection in prior art under intra-zone fault, and the simulation results of protection R3, R4 are shown in Figure 8 .

[0080] According to Figure 8In (a), at 0.54 seconds, the measured angles at protection points R3 and R4 both fall within the angle range of the positive direction fault, and the protection scheme proposed in this invention correctly identifies the fault within the area. Figure 8 In (b), the solid and dashed lines represent the energy integrals at protection points R3 and R4, respectively. A negative energy integral indicates a fault in the forward direction, while a positive energy integral indicates a fault in the reverse direction. Figure 8 In (b), when a fault occurs within the zone, the energy integral at protection R4 is positive, and protection R4 is mistakenly identified as a fault in the opposite direction. The existing technology proposes an energy direction longitudinal protection that fails to operate.

[0081] Furthermore, in Figure 5 A metallic two-phase (AB) short-circuit fault was set at point F1. A traditional power-direction longitudinal protection system was selected as a comparison to examine the operation of both protection systems under fault conditions outside the fault zone. Simulation results for the two protection systems are as follows: Figure 9 As shown.

[0082] according to Figure 9 In (a), when an external short-circuit fault occurs at point F1, protection R3 correctly judges it as a reverse fault and protection R4 correctly judges it as a forward fault. That is, the protection scheme proposed in this paper does not malfunction when an external fault occurs.

[0083] For traditional power directional longitudinal protection, the line impedance angle in the model is 62°, and the operating equation for power directional longitudinal protection is set as follows:

[0084] In the formula, respectively protect R i If the fault phase current and the voltage between non-corresponding phases satisfy the above formula, then it is a positive direction fault.

[0085] Figure 9 (b) These represent the phase difference between the BC line voltage and the A-phase current at protection points R3 and R4, respectively. All satisfy the above formula, and the protection at R3 is misjudged as a positive direction fault, that is, the traditional power direction longitudinal protection malfunctions when an external fault occurs.

[0086] Compared with energy direction longitudinal protection and traditional power direction longitudinal protection, the protection scheme proposed in this embodiment of the invention can operate correctly in load distribution lines containing T-connection IIDG, and will not fail to operate during faults within the zone or malfunction during faults outside the zone.

[0087] The directional longitudinal protection system based on control and protection coordination provided in this embodiment of the invention can be implemented in software. The directional longitudinal protection system based on control and protection coordination includes the following software modules: The information acquisition module is used to acquire the degree of positive sequence voltage drop and the sudden change in phase current at the IIDG grid connection point; an algorithm starting judgment module configured to judge whether to start a control algorithm and a protection algorithm according to the positive sequence voltage drop degree of the IIDG grid connection point and the phase current abruptness; The control algorithm is to calculate a dq axis current instruction value according to the positive sequence voltage and the positive sequence current at the IIDG grid connection point. The protection algorithm is to: calculate a local fault direction according to the positive sequence fault component voltage and the positive sequence fault component current of the second cycle after the fault obtained by each protection device, and send the fault direction to the opposite end protection device. After obtaining the fault direction of the opposite end protection device, judge whether it is an internal fault. If both ends are positive direction faults, it is judged that an internal short circuit fault occurs, and a trip command is sent. Otherwise, it is judged as normal operation or an external short circuit fault occurs, and the protection device is controlled to return to normal.

[0088] It should be noted that each module in the direction pilot protection system based on the control and protection collaboration corresponds to each step in the direction pilot protection method based on the control and protection collaboration, and the specific implementation process is the same, which will not be repeated here.

[0089] In some embodiments, the direction pilot protection system based on the control and protection collaboration provided by the embodiments of the present application can be realized in a combination of software and hardware. For example, the direction pilot protection system based on the control and protection collaboration provided by the embodiments of the present application can be a processor in the form of a hardware decoding processor programmed to execute the direction pilot protection method based on the control and protection collaboration provided by the embodiments of the present application. For example, the processor in the form of a hardware decoding processor can use one or more application specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), or other electronic components.

[0090] For example, the processor 301 can be an integrated circuit chip with signal processing capability, such as a general purpose processor, a digital signal processor (DSP), or other programmable logic device, discrete gate or transistor logic device, discrete hardware component, etc., wherein the general purpose processor can be a microprocessor or any conventional processor.

[0091] As an example of the hardware implementation of the direction pilot protection system based on the coordination of control and protection provided by the embodiments of the present application, the apparatus provided by the embodiments of the present application can be directly implemented by a processor in the form of a hardware decoding processor, for example, by one or more application specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), complex programmable logic devices (CPLDs), field programmable gate arrays (FPGAs), or other electronic elements to implement the direction pilot protection method based on the coordination of control and protection provided by the embodiments of the present application.

[0092] The memory in the embodiments of the present application is used to store various types of data to support the operation of the direction pilot protection system based on the coordination of control and protection, or to store program codes for executing the method shown in the embodiments of the present application. Figure 10 Examples of these data include any executable instructions for operating on the direction pilot protection system based on the coordination of control and protection, such as executable instructions, and the program for implementing the direction pilot protection method based on the coordination of control and protection provided by the embodiments of the present application can be included in the executable instructions.

[0093] In particular, according to the embodiments of the present application, the processes described above with reference to the flowcharts can be implemented as a computer software program. For example, the embodiments of the present application include a computer program product comprising a computer program carrying the computer program on a computer readable medium, the computer program containing program codes for executing the method shown in the embodiments of the present application. Figure 10 In such embodiments, the computer program can be downloaded and installed from a network by a communication part, and / or installed from a detachable medium. When the computer program is executed by a central processing unit, various functions defined in the apparatus of the present application are performed.

[0094] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems) and computer program products of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts 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, a special purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate a means for implementing the functions described in the flowcharts and / or block diagrams. Figure 1 The flow or the combination of the flows and / or blocks Figure 1means for performing the function specified in the block or blocks.

[0095] The above descriptions are only the preferred embodiment of the application, not intended to limit the application. The application can be variously changed and modified by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall fall within the protection scope of the application.

Claims

1. A directional longitudinal protection method based on control and protection coordination, characterized in that, include: Obtain the positive sequence voltage drop and phase current abrupt change at the IIDG grid connection point; Based on the degree of positive sequence voltage drop and the sudden change in phase current at the IIDG grid connection point, determine whether to activate the control algorithm and protection algorithm; The control algorithm is as follows: calculate the dq axis current command value based on the positive sequence voltage and positive sequence current at the IIDG grid connection point; The protection algorithm is as follows: Based on the positive sequence fault component voltage and positive sequence fault component current of the second cycle after the fault at the protection installation location obtained by each protection device, the local fault direction is calculated and sent to the protection device at the other end. After obtaining the fault direction of the protection device at the other end, determine whether it is an intra-zone fault; If both ends are positive faults, it is determined that an intra-zone short circuit fault has occurred, and a trip command is sent. Otherwise, if the system is judged to be operating normally or experiencing an external short-circuit fault, the control and protection device will reset.

2. The directional longitudinal protection method based on control and protection coordination as described in claim 1, characterized in that, The control algorithm is activated when the positive sequence voltage is less than 90% of the rated voltage.

3. The directional longitudinal protection method based on control and protection coordination as described in claim 1, characterized in that, When the sudden change in the current of any phase exceeds 0.1 times the load current, the protection algorithm is activated.

4. The directional longitudinal protection method based on control and protection coordination as described in claim 1, characterized in that, The process of calculating the local fault direction is as follows: in, and These are the positive-sequence fault component voltage and positive-sequence fault component current of the second cycle after a fault at each protection device installation location; when When, it is judged as a reverse direction fault; when When the fault occurs, it is determined to be a positive direction fault.

5. The directional longitudinal protection method based on control and protection coordination as described in claim 1, characterized in that, Calculate the dq axis current command value: in, and This is the commanded value for the dq axis current; This is the positive sequence current at the grid connection point after the fault. This represents the phase jump angle of the positive sequence current. This is the phase jump angle of the positive sequence voltage.

6. The directional longitudinal protection method based on control and protection coordination as described in claim 5, characterized in that, The phase jump angle of the positive sequence voltage is ; The phase jump angle of the positive sequence current is: ; in: The phase angle of the positive-sequence fault component voltage. ; This is the positive sequence voltage at the grid connection point before the fault. This is the positive sequence voltage at the grid connection point after the fault. This is the positive sequence current before the fault. is the positive sequence current after the fault, and arg(·) is the phase taking operation.

7. A directional longitudinal protection system based on control and protection coordination, characterized in that, include: The information acquisition module is used to acquire the degree of positive sequence voltage drop and the sudden change in phase current at the IIDG grid connection point; The algorithm start-up judgment module is used to determine whether to start the control algorithm and protection algorithm based on the degree of voltage drop in the positive sequence at the IIDG grid connection point and the sudden change in phase current. The control algorithm is as follows: calculate the dq axis current command value based on the positive sequence voltage and positive sequence current at the IIDG grid connection point; The protection algorithm is as follows: Based on the positive sequence fault component voltage and positive sequence fault component current of the second cycle after the fault at the protection installation location obtained by each protection device, the local fault direction is calculated and sent to the protection device at the other end. After obtaining the fault direction of the protection device at the other end, determine whether it is an intra-zone fault; If both ends are positive faults, it is determined that an intra-zone short circuit fault has occurred, and a trip command is sent. Otherwise, if the system is judged to be operating normally or experiencing an external short-circuit fault, the control and protection device will reset.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the steps in the directional longitudinal protection method based on control and protection coordination as described in any one of claims 1-6.

9. A computer program product comprising a computer program / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the steps in the directional longitudinal protection method based on control and protection coordination as described in any one of claims 1-6.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the program, it implements the steps in the directional longitudinal protection method based on control and protection coordination as described in any one of claims 1-6.

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