Multi-terminal area protection method and system for digital-analog signal fusion comparison

Abstract

The invention relates to the technical field of power system relay protection, and provides a multi-terminal area protection method and system for digital-analog signal fusion comparison, and the method comprises the steps: collecting the current amplitude of each node in a protection area in real time; when any node in the protection area meets the following condition: Ii (t) is greater than IsetL + delta I * sin (2pif0t); if so, judging that the node is started, and adding 1 to the kqd value of the counter; continuously monitoring when no starting node exists, and executing criterion selection when kqd is greater than or equal to 1; selecting a criterion mode according to the kqd value, and when kqd is equal to 1, executing a switching value criterion; when kqd is greater than 1, executing a region amplitude comparison criterion; and according to the selected criterion, executing a region protection action, and resetting the kqd value of the counter. According to the method, the protection reliability of the distributed photovoltaic power distribution network is remarkably improved, and the problem that the traditional criterion based on switching value protection fails due to the additional short-circuit current provided by the distributed photovoltaic power distribution network is solved.

Description

Technical Field

[0001] This invention relates to the field of power system relay protection technology, and in particular to a multi-terminal area protection method and system for digital-analog signal fusion and comparison. Background Technology

[0002] Traditional current protection criteria based on switching quantities require that only one node in the area fails, while other nodes do not meet the fault conditions. This criterion relies on a significant increase in short-circuit current on one side exceeding a set value during a fault, while the other side exhibits weak deficiencies. In systems without distributed photovoltaic (PV) grid connection, the short-circuit current on the power supply side is larger than that on the load side during a fault, a fault characteristic consistent with switching quantity-based protection criteria. However, with the grid connection of distributed PV, the additional current generated by its connection affects the fault current detected at each protection installation point, thus impacting the accuracy of current protection operation. Furthermore, as the capacity and number of distributed PV installations increase, the impact of distributed PV grid connection becomes more significant. If traditional switching quantity protection criteria for distribution networks are still used, protection devices are prone to failure to operate or maloperation, which is detrimental to the stable operation of the distribution network. Summary of the Invention

[0003] The purpose of this invention is to solve at least one technical problem in the background art and to provide a multi-terminal area protection method and system for digital-analog signal fusion and comparison.

[0004] To achieve the above objectives, the present invention provides a multi-terminal region protection method for digital-analog signal fusion comparison, comprising:

[0005] Real-time acquisition of current amplitude at each node within the protected area;

[0006] When any node within the protected area satisfies: I i (t)>I setL +ΔI·sin(2πf0t), where I i (t) represents the real-time current sample value at time t, I setL The current threshold value set for overcurrent protection is low, ΔI is the anti-oscillation margin, and f0 = 50Hz; then the node is determined to start, and the counter k is set. qd Increment the value by 1; continuously monitor when there is no startup node, when k qd When ≥1, the criterion is selected.

[0007] According to k qd Value selection criterion mode, when k qd When k = 1, execute the switch quantity criterion; when k qd When the value is greater than 1, the regional amplitude comparison criterion is applied;

[0008] Based on the selected criterion, execute the area protection action and reset the counter k. qd The value is reset to zero.

[0009] According to one aspect of the invention, when k qd When = 1, execute the switch quantity criteria, including:

[0010] Phase current at this node > I setH Or zero-sequence current > I 0setH If the node fails, then the node is considered faulty; where I setH The high value of the current threshold set for overcurrent protection, I 0setH The high value of the current threshold set for zero-sequence current protection;

[0011] If there is no fault at this node and the line voltage is less than the weak feeder voltage setting, then the non-fault side permission signal is triggered.

[0012] If a single node in the protected area fails, and the remaining nodes trigger the non-faulty side permission signal, then the fault is determined to be within the protected area.

[0013] According to one aspect of the invention, the overcurrent protection setting current threshold high value I setH And the high value of the current threshold set by zero-sequence current protection I 0setH Calculated using the following formula:

[0014]

[0015] Among them, I setL The low current threshold value set for overcurrent protection, I 0setL The low current threshold value set for zero-sequence current protection.

[0016] According to one aspect of the invention, the weak feed voltage setting is 30V.

[0017] According to one aspect of the invention, when k qd When >1, the regional amplitude comparison criterion is applied, including:

[0018] Maximum current in the region I max Satisfy the following formula:

[0019] I max ≥(1+k margin )I setH ;

[0020] In the formula, k margin k is the marginal coefficient. margin ∈[0.05,0.15];

[0021] The current at all starting nodes is less than k1*I. maxIf all non-starting nodes send a weak-side permission signal, then a fault is determined in the area, where k1 is the reliability coefficient, which is taken as 0.4.

[0022] To achieve the above objectives, the present invention also provides a multi-terminal area protection system for digital-analog signal fusion and comparison, comprising:

[0023] The real-time current amplitude acquisition module acquires the current amplitude of each node within the protection area in real time.

[0024] The detection module is activated when any node within the protected area satisfies: I i (t)>I setL +ΔI·sin(2πf0t), where I i (t) represents the real-time current sample value at time t, I setL The current threshold value set for overcurrent protection is low, ΔI is the anti-oscillation margin, and f0 = 50Hz; then the node is determined to start, and the counter k is set. qd Increment the value by 1; continuously monitor when there is no startup node, when k qd When ≥1, the criterion is selected.

[0025] The criterion selection module, based on k qd Value selection criterion mode, when k qd When k = 1, execute the switch quantity criterion; when k qd When the value is greater than 1, the regional amplitude comparison criterion is applied;

[0026] The protection execution module executes the area protection action according to the selected criteria and sets the counter k. qd The value is reset to zero.

[0027] To achieve the above objectives, the present invention also provides an electronic device, including a processor, a memory, 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 multi-terminal region protection method for digital-analog signal fusion comparison as described above.

[0028] To achieve the above objectives, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the multi-terminal region protection method for digital-analog signal fusion comparison as described above.

[0029] According to the present invention, in view of the risks of non-operation and false operation of traditional switch quantity protection due to the influence of distributed photovoltaic grid connection, the present invention provides a multi-terminal area protection method and system for digital-analog signal fusion comparison. The present invention significantly improves the protection reliability of distribution networks containing distributed photovoltaics and solves the problem that the additional short-circuit current provided by distributed photovoltaics causes the criterion of traditional switch quantity-based protection to fail. Attached Figure Description

[0030] Figure 1 A flowchart illustrating a multi-terminal region protection method for digital-analog signal fusion comparison according to an embodiment of the present invention;

[0031] Figure 2 The diagram illustrates a system diagram containing a distributed photovoltaic power station according to Embodiment 1 of the present invention. Detailed Implementation

[0032] The invention will now be discussed with reference to exemplary embodiments. It should be understood that the described embodiments are merely intended to enable those skilled in the art to better understand and thus implement the invention, and are not intended to imply any limitation on the scope of the invention.

[0033] As used herein, the term "comprising" and its variations are to be interpreted as open-ended terms meaning "including but not limited to". The term "based on" is to be interpreted as "at least partially based on". The terms "one embodiment" and "an embodiment" are to be interpreted as "at least one embodiment".

[0034] Figure 1 A flowchart illustrating a multi-terminal region protection method for digital-analog signal fusion comparison according to an embodiment of the present invention is shown. Figure 1 As shown, in this embodiment, the multi-terminal region protection method for digital-analog signal fusion comparison includes:

[0035] Real-time acquisition of current amplitude at each node within the protected area;

[0036] When any node within the protected area satisfies: I i (t)>I setL +ΔI·sin(2πf0t), where I i (t) represents the real-time current sample value at time t, I setL The current threshold value set for overcurrent protection is low, ΔI is the anti-oscillation margin, and f0 = 50Hz; then the node is determined to start, and the counter k is set. qd Increment the value by 1; continuously monitor when there is no startup node, when k qd When ≥1, the criterion is selected.

[0037] According to k qd Value selection criterion mode, when k qd When k = 1, execute the switch quantity criterion; when k qd When the value is greater than 1, the regional amplitude comparison criterion is applied;

[0038] Based on the selected criterion, execute the area protection action and reset the counter k. qd The value is reset to zero.

[0039] Furthermore, according to one embodiment of the present invention, when k qd When = 1, execute the switch quantity criteria, including:

[0040] Phase current at this node > I setH Or zero-sequence current > I 0setH If the node fails, then the node is considered faulty; where I setH The high value of the current threshold set for overcurrent protection, I 0setH The high value of the current threshold set for zero-sequence current protection;

[0041] If there is no fault on this side and the line voltage is less than the weak feeder voltage setting, then the non-fault side permission signal is triggered.

[0042] If a single node in the protected area fails, and the remaining nodes trigger the non-faulty side permission signal, then the fault is determined to be within the protected area.

[0043] Furthermore, according to one embodiment of the present invention, the high value I of the overcurrent protection current threshold is set... setH And the high value of the current threshold set by zero-sequence current protection I 0setH Calculated using the following formula:

[0044]

[0045] Among them, I setL The low current threshold value set for overcurrent protection, I 0setL The low current threshold value set for zero-sequence current protection.

[0046] As can be seen from the above, in this embodiment, the protection setting adopts a dual threshold coordination mechanism, specifically, the overcurrent protection setting is the high value (I) of the above-mentioned overcurrent protection. setH ) and low value (I setL Zero current protection set high value (I) 0setH ) and low value (I 0setL Combining the above-mentioned dual-threshold collaborative mechanism, and through wired or wireless communication networks to synchronize the current amplitude and switching status of each node in real time, a full-area information fusion criterion is constructed.

[0047] Furthermore, according to one embodiment of the present invention, the weak feed voltage setting is 30V.

[0048] Furthermore, according to one embodiment of the present invention, when k qd When >1, the regional amplitude comparison criterion is applied, including:

[0049] Maximum current in the region I max Satisfy the following formula:

[0050] I max ≥(1+k margin )IsetH ;

[0051] In the formula, k margin k is the marginal coefficient. margin ∈[0.05,0.15];

[0052] The current at all starting nodes is less than k1*I. max ,Right now: In the formula I i Let be the current amplitude of the i-th node in the startup node, and k1 be the reliability coefficient, which is taken as 0.4; if all non-starting nodes issue a weak-side allow operation signal, then a fault is determined in the area.

[0053] According to the above-described solution of the present invention, the present invention addresses the risk of non-operation and false operation of traditional switch quantity protection due to the influence of distributed photovoltaic grid connection, and provides a multi-terminal area protection method of digital-analog signal fusion comparison. This method significantly improves the protection reliability of distribution networks containing distributed photovoltaics and solves the problem that the additional short-circuit current provided by distributed photovoltaics causes the criterion of traditional switch quantity-based protection to fail.

[0054] Furthermore, to achieve the above objectives, the present invention also provides a multi-terminal area protection system for digital-analog signal fusion and comparison, comprising:

[0055] The real-time current amplitude acquisition module acquires the current amplitude of each node within the protection area in real time.

[0056] The detection module is activated when any node within the protected area satisfies: I i (t)>I setL +ΔI·sin(2πf0t), where I i (t) represents the real-time current sample value at time t, I setL The current threshold value set for overcurrent protection is low, ΔI is the anti-oscillation margin, and f0 = 50Hz; then the node is determined to start, and the counter k is set. qd Increment the value by 1; continuously monitor when there is no startup node, when k qd When ≥1, the criterion is selected.

[0057] The criterion selection module, based on k qd Value selection criterion mode, when k qd When k = 1, execute the switch quantity criterion; when k qd When the value is greater than 1, the regional amplitude comparison criterion is applied;

[0058] The protection execution module executes the area protection action according to the selected criteria and sets the counter k. qd The value is reset to zero.

[0059] Furthermore, according to one embodiment of the present invention, when k qdWhen = 1, execute the switch quantity criteria, including:

[0060] Phase current at this node > I setH Or zero-sequence current > I 0setH If the node fails, then the node is considered faulty; where I setH The high value of the current threshold set for overcurrent protection, I 0setH The high value of the current threshold set for zero-sequence current protection;

[0061] If there is no fault on this side and the line voltage is less than the weak feeder voltage setting, then the non-fault side permission signal is triggered.

[0062] If a single node in the protected area fails, and the remaining nodes trigger the non-faulty side permission signal, then the fault is determined to be within the protected area.

[0063] Furthermore, according to one embodiment of the present invention, the high value I of the overcurrent protection current threshold is set... setH And the high value of the current threshold set by zero-sequence current protection I 0setH Calculated using the following formula:

[0064]

[0065] Among them, I setL The low current threshold value set for overcurrent protection, I 0setL The low current threshold value set for zero-sequence current protection.

[0066] As can be seen from the above, in this embodiment, the protection setting adopts a dual threshold coordination mechanism, specifically, the overcurrent protection setting is the high value (I) of the above-mentioned overcurrent protection. setH ) and low value (I setL Zero current protection set high value (I) 0setH ) and low value (I 0setL Combining the above-mentioned dual-threshold collaborative mechanism, and through wired or wireless communication networks to synchronize the current amplitude and switching status of each node in real time, a full-area information fusion criterion is constructed.

[0067] Furthermore, according to one embodiment of the present invention, the weak feed voltage setting is 30V.

[0068] Furthermore, according to one embodiment of the present invention, when k qd When >1, the regional amplitude comparison criterion is applied, including:

[0069] Maximum current in the region I max Satisfy the following formula:

[0070] I max ≥(1+k margin )I setH ;

[0071] In the formula, k margin k is the marginal coefficient. margin ∈[0.05,0.15];

[0072] The current at all starting nodes is less than k1*I. max ,Right now: In the formula I i Let be the current amplitude of the i-th node in the startup node, and k1 be the reliability coefficient, which is taken as 0.4; if all non-starting nodes issue a weak-side allow operation signal, then a fault is determined in the area.

[0073] According to the above-described solution of the present invention, the present invention addresses the risk of non-operation and false operation of traditional switch quantity protection due to the influence of distributed photovoltaic grid connection, and provides a multi-terminal area protection system that integrates analog and digital signals. This system significantly improves the protection reliability of distribution networks containing distributed photovoltaics and solves the problem that the additional short-circuit current provided by distributed photovoltaics causes the criteria of traditional switch quantity-based protection to fail.

[0074] Furthermore, to achieve the above objectives, the present invention also provides an electronic device, including a processor, a memory, 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 multi-terminal region protection method for digital-analog signal fusion comparison as described above.

[0075] Furthermore, to achieve the above objectives, the present invention also provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the multi-terminal region protection method for digital-analog signal fusion comparison as described above.

[0076] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely one preferred embodiment of the invention and are only used to explain the invention. They do not limit the scope of protection of the invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0077] Example 1

[0078] according to Figure 2 The topological relationships shown are simulated, with a photovoltaic capacity of 15MW. / 11=0.787kA, I setL Taking 1.2 times the rated photovoltaic current, we get: 0.944kA; taking k H =0.8, then *I setL=1.18kA. Taking the protection zone formed by switches 3, 4, and 32 as an example, switch 3 is defined as the system side, switch 32 as the photovoltaic side, and switch 4 as the load side.

[0079] When a metallic fault occurs at point F1 within the zone, the system-side current is 8.69 kA, and the photovoltaic-side current is 1.07 kA. qd =2, enter the regional amplitude comparison criterion. I max =8.69A, since the photovoltaic side current is less than k1*I max The criteria are met, and reliable protection is provided without rejection.

[0080] The reliability coefficient k1 in the criterion should be chosen to ensure reliable operation during faults outside the designated area. Considering extreme cases where photovoltaic power is concentrated within the area, when a fault occurs downstream outside the area via a transition resistor, the short-circuit current supplied by the system is essentially the same as the short-circuit current of the distributed power source. The difference in short-circuit current flowing through the two sectionalizing switches within the area is the largest, reaching twice the value. To ensure that faults outside the designated area do not cause false tripping, k1 is set to 0.4. Simulation results show that when a fault occurs via the transition resistor F2 outside the designated area, the system-side current is 1.12 kA, the photovoltaic-side current is 1.06 kA, and the load-side current is 2.02 kA. qd =3, I max = 2.02A. Since both the photovoltaic side current and the system side current are greater than k1*I... max It provides reliable protection and prevents accidental activation.

[0081] Those skilled in the art will recognize that the modules and algorithm steps described in conjunction with the embodiments disclosed herein can be implemented using electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0082] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the above-described apparatus and equipment can be referred to the corresponding process in the foregoing method implementation, and will not be repeated here.

[0083] In the embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0084] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical modules; that is, they may be located in one place or distributed across multiple network modules. Some or all of the modules can be selected to achieve the objectives of the embodiments of the present invention, depending on actual needs.

[0085] In addition, the functional modules in the embodiments of the present invention can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0086] If the aforementioned functions are implemented as software functional modules and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the sending / receiving methods of various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, ROM, RAM, magnetic disks, or optical disks.

[0087] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

[0088] It should be understood that the sequence number of each step in the invention and its embodiments does not absolutely imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

Claims

1. A multi-terminal region protection method for digital-analog signal fusion and comparison, characterized in that, include: Real-time acquisition of current amplitude at each node within the protected area; When any node within the protected area satisfies: I i (t)>I setL +ΔI·sin(2πf0t), where I i (t) represents the real-time current sample value at time t, I setL The current threshold value set for overcurrent protection is low, ΔI is the anti-oscillation margin, and f0 = 50Hz; then the node is determined to start, and the counter k is set. qd Increment the value by 1; continuously monitor when there is no startup node, when k qd When ≥1, the criterion is selected. According to k qd Value selection criterion mode, when k qd When k = 1, execute the switch quantity criterion; when k qd When the value is greater than 1, the regional amplitude comparison criterion is applied; Based on the selected criterion, execute the area protection action and reset the counter k. qd The value is reset to zero.

2. The multi-terminal region protection method for digital-analog signal fusion and comparison according to claim 1, characterized in that, When k qd When = 1, execute the switch quantity criteria, including: Phase current at this node > I setH Or zero-sequence current > I 0setH If the node is faulty, then the node is determined to be faulty; where I setH The high value of the current threshold set for overcurrent protection, I 0setH The high value of the current threshold set for zero-sequence current protection; If there is no fault at this node and the line voltage is less than the weak feeder voltage setting, then the non-fault side permission signal is triggered. If a single node in the protected area fails, and the remaining nodes trigger the non-faulty side permission signal, then the fault is determined to be within the protected area.

3. The multi-terminal region protection method for digital-analog signal fusion and comparison according to claim 2, characterized in that, The high value of the overcurrent protection current threshold I setH And the high value of the current threshold set by zero-sequence current protection I 0setH Calculated using the following formula: Among them, I setL The low current threshold value set for overcurrent protection, I 0setL The low current threshold value set for zero-sequence current protection.

4. The multi-terminal region protection method for digital-analog signal fusion and comparison according to claim 3, characterized in that, The weak feed voltage setting is 30V.

5. The multi-terminal region protection method for digital-analog signal fusion and comparison according to claim 4, characterized in that, When k qd When >1, the regional amplitude comparison criterion is applied, including: Maximum current in the region I max Satisfy the following formula: I max ≥(1+k margin )I setH ; In the formula, k margin k is the marginal coefficient. margin ∈[0.05,0.15]; The current at all starting nodes is less than k1*I. max If all non-starting nodes send a weak-side permission signal, then a fault is determined in the area, where k1 is the reliability coefficient, which is taken as 0.

4.

6. A multi-terminal area protection system for digital-analog signal fusion and comparison, characterized in that, include: The real-time current amplitude acquisition module acquires the current amplitude of each node within the protection area in real time. The detection module is activated when any node within the protected area satisfies: I i (t)>I setL +ΔI·sin(2πf0t), where I i (t) represents the real-time current sample value at time t, I setL The current threshold value set for overcurrent protection is low, ΔI is the anti-oscillation margin, and f0 = 50Hz; then the node is determined to start, and the counter k is set. qd Increment the value by 1; continuously monitor when there is no startup node, when k qd When ≥1, the criterion is selected. The criterion selection module, based on k qd Value selection criterion mode, when k qd When k = 1, execute the switch quantity criterion; when k qd When the value is greater than 1, the regional amplitude comparison criterion is applied; The protection execution module executes the area protection action according to the selected criteria and sets the counter k. qd The value is reset to zero.

7. An electronic device, characterized in that, It includes a processor, a memory, and a computer program stored in the memory and executable on the processor, wherein the computer program, when executed by the processor, implements the multi-terminal region protection method for digital-analog signal fusion comparison as described in any one of claims 1-5.

8. A computer-readable storage medium, characterized in that, A computer program is stored on the computer-readable storage medium, which, when executed by a processor, implements the multi-terminal region protection method for digital-analog signal fusion comparison as described in any one of claims 1-5.

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