A microgrid distance protection method and device considering access of distributed power supply

Abstract

This invention relates to the field of power system relay protection technology, and discloses a microgrid distance protection method and device considering distributed generation access. The invention establishes an AC transmission system model containing distributed generation, comprehensively utilizes locally measured voltage and current information, point-of-combination voltage, and the amplitude and phase angle of the distributed generation output current, combined with the known R / X ratio of the transmission line, to construct a voltage-current phasor diagram. Geometric theorems are then applied to accurately calculate the impedance from the relay to the fault point. This invention can equivalently transform a system containing distributed generation into a traditional unidirectional power flow system, thereby simplifying protection criteria, significantly improving protection sensitivity and selectivity, effectively compensating for impedance deviations caused by transition impedance and distributed generation access, and enhancing the accuracy and adaptability of distance protection. This invention is not only applicable to purely impedance-type transition impedances, but also to inductive and capacitive transition impedance situations, possessing high engineering practical value and promising prospects for widespread application.

Description

Technical Field

[0001] This application relates to power system relay protection technology, and in particular to a distance protection method applicable to AC transmission systems with distributed generation access, which can effectively address the problems of fault transition impedance and impedance measurement errors caused by distributed power source access. Background Technology

[0002] In power systems, line faults are common operational safety hazards, seriously threatening grid stability and reliable power supply. Effective protection measures must be taken to ensure system safety. Distance protection, a relay protection method that operates based on fault distance, has been widely used in power systems due to its advantages such as accurate location and rapid action. Its basic principle is to determine whether the fault is located within the protection zone by measuring the impedance between the protection installation point and the fault point. In uniform transmission lines, impedance is proportional to distance, so fault location can be indirectly achieved through impedance measurement. Traditional distance protection algorithms are usually based on short-circuit models, calculating the fault loop impedance (i.e., U / I) by measuring local voltage and current. While this method is simple to implement, it relies on a fundamental assumption: the fault transition resistance is zero, meaning the fault point voltage is considered zero during a metallic short circuit.

[0003] However, in real-world systems, especially ground faults via transition resistance, the transition resistance is not zero. This resistance is composed of various factors, including the resistance of the fault arc, the grounding resistance of the tower, and the resistance of trees or other dielectric materials. The presence of transition resistance, particularly its resistive component, significantly increases the amplitude of the measured impedance, resulting in a measured impedance greater than the actual line impedance. This narrows the protection range and may cause protection failure, hindering rapid fault isolation. To address the impact of transition resistance, scholars both domestically and internationally have proposed several improvement schemes, such as using adaptive methods based on virtual measured voltage, dynamically adjusting setpoints using voltage drop equations, or employing distributed parameter models to accurately account for line distributed capacitance and mutual inductance effects. These methods improve the ability to withstand transition resistance to some extent, but still suffer from problems such as computational complexity, limited adaptability, or dependence on specific network parameters.

[0004] Meanwhile, with the rapid development of renewable energy, distributed generation (DG) has been massively integrated into the grid, profoundly changing the traditional power system structure and operation. Distributed sources typically connect to the transmission and distribution network via power electronic converters, which not only alters the unidirectional nature of power flow, leading to bidirectional power flow in the lines, but also challenges the traditional distance protection principle based on single-source systems. During faults, distributed sources provide additional short-circuit currents to the fault point. This current flows through the protection installation location, significantly affecting voltage and current measurements, causing serious errors in impedance calculations, potentially leading to over-range or under-range protection operation, or even false tripping or failure to trip. Although existing research has attempted to suppress the impact of distributed sources by controlling converter output or using artificial intelligence algorithms for adaptive adjustment, these methods either rely on specific control of the power source (difficult to coordinate in practical multi-source systems) or suffer from insufficient real-time performance and reliability.

[0005] In summary, traditional distance protection algorithms exhibit significant performance degradation when simultaneously facing non-negligible fault transition impedance and bidirectional currents introduced by distributed generation (DG) connections, making it difficult to meet the requirements of modern complex power grids for protection selectivity, speed, and reliability. Therefore, a novel distance protection method is urgently needed that comprehensively considers the effects of fault transition resistance and DG connection. This method should not rely on specific control of DG connections and should possess strong versatility and robustness. Summary of the Invention

[0006] This invention provides a method and apparatus for distance protection of microgrids considering distributed power source access, in order to solve the problems existing in the prior art.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a microgrid distance protection method considering distributed power source access, the method comprising: After establishing a fault model of a system with distributed power supply access, the voltage phasors and current phasors at the relays, as well as the voltage phasors and load current phasors at the common connection point, are obtained to construct a voltage-current phasor diagram. Based on the voltage-current phasor diagram, the fault impedance value from the relay to the fault point is calculated using geometric theorems. The fault impedance value is compared with a preset impedance threshold. If the fault impedance value is less than the preset impedance threshold, the fault is determined to be located within the protection zone and a protection action command is generated.

[0008] Furthermore, the establishment of a fault model for a system with distributed power supply access includes: The fault model of the system with distributed power supply access is a short-circuit model that considers fault transition impedance and distributed power supply access; wherein, the fault point voltage is not zero, and the fault transition impedance includes resistive, inductive and capacitive impedances.

[0009] Furthermore, after establishing the fault model of the distributed power supply access system, the voltage phasors and current phasors at the relays, and the voltage phasors and load current phasors at the point of common coupling, are obtained to construct a voltage-current phasor diagram, including: The first voltage phasor and the first current phasor after the fault occurs are collected at the relay installation point, and the first phase angle between the first voltage phasor and the first current phasor is obtained. The second voltage phasor and the load current phasor are acquired at the point of common coupling of the distributed power source, and the second phase angle between the second voltage phasor and the load current phasor is obtained. Determine the line impedance angle based on the line's preset nominal ratio; Based on the first phase angle, the second phase angle, and the line impedance angle, voltage-current phasor diagrams are constructed for fault transition impedances of different types.

[0010] Furthermore, based on the first phase angle, the second phase angle, and the line impedance angle, voltage-current phasor diagrams are constructed for fault transition impedances of different characteristics, including: When the fault transition impedance is a pure resistance, the first voltage phasor is constructed to be in phase with the load current phasor, and a voltage-current phasor diagram is obtained. When the fault transition impedance is inductive or capacitive, the voltage phasor at the fault point is collected, and the third phase angle between the load current phasor and the voltage phasor is obtained. The voltage-current phasor diagram is determined based on the third phase angle and the second phase angle.

[0011] Furthermore, the calculation of the fault impedance value from the relay to the fault point using geometric theorems based on the voltage-current phasor diagram includes: When the fault transition impedance is purely resistive, the fault impedance value includes a simplified criterion: ; in, The fault impedance value from the point of common coupling to the fault point. The second phase angle is the relationship between the second voltage phasor and the load current phasor. Acquire the second voltage phasor for the distributed power source's point of common coupling. The line impedance angle. This is the load current phasor.

[0012] Furthermore, the step of calculating the fault impedance value from the relay to the fault point using geometric theorems based on the voltage-current phasor diagram also includes: When the fault transition impedance is inductive or capacitive, the fault impedance value includes a general criterion: when The specific fault impedance value is as follows: ; when The specific fault impedance value is as follows: ; when When the impedance is capacitive, the specific fault impedance value is as follows: ; in, The fault impedance value, Load current phasor and voltage phasor The third phase angle between them, The second phase angle is the relationship between the second voltage phasor and the load current phasor. Acquire the second voltage phasor for the distributed power source's point of common coupling. The line impedance angle. This is the load current phasor.

[0013] Furthermore, the method for obtaining the load current phasor is as follows: The load current phasor is the sum of the first current phasor and the distributed source injection current phasor; ; in, For load current phasor, This is the first current phasor. Inject current phasors into distributed power sources.

[0014] Furthermore, the total impedance from the relay to the fault point is the sum of the impedance from the relay to the point of common coupling and the impedance from the point of common coupling to the fault point; The total impedance from the relay to the fault point is: ; in, The impedance value from the relay to the point of common connection. This represents the fault impedance value from the point of common coupling to the fault point.

[0015] Thirdly, the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the steps of the microgrid distance protection method considering distributed power source access as described above.

[0016] Fourthly, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the microgrid distance protection method considering distributed power source access as described above.

[0017] The microgrid distance protection method and device considering distributed power source access provided by this invention have the following advantages compared with the prior art: This invention provides a distance protection method for microgrids considering distributed generation (DG) integration. By transforming the complex system fault impedance calculation problem involving DG into a geometric analytical problem based on voltage-current phasor diagrams, and utilizing known line R / X ratios and local electrical quantity measurement information, a mapping relationship with clear geometric constraints is constructed in the complex plane, significantly improving the accuracy and adaptability of impedance measurement. This invention extracts the amplitude and phase angle of the point of common coupling voltage and the DG output current, and combines geometric methods such as the sine and cosine theorems to derive analytical expressions applicable to various transition impedance types, including resistive, inductive, and capacitive impedances, establishing a universal distance protection criterion independent of power source control strategies. Compared with traditional solutions, this invention effectively overcomes impedance measurement errors caused by transition resistance and DG backflow current, significantly improving the selectivity and reliability of protection. It has significant engineering practical value for enhancing the fault protection level of grids with a high proportion of distributed energy and preventing protection maloperation and failure to operate. Attached Figure Description

[0018] Figure 1 This is a flowchart illustrating an optional microgrid distance protection method considering distributed power source access provided by the present invention. Figure 2 is an optional system model with distributed power source access provided by the present invention, including a) a distributed generation and transmission system model and b) a distributed generation and transmission system short-circuit model.

[0019] Figure 3 This invention provides a voltage-current phasor diagram when the optional fault transition resistor is a pure resistor.

[0020] Figure 4 This is an optional method provided by the present invention. Voltage-current phasor diagram.

[0021] Figure 5 This is an optional method provided by the present invention. Time-corresponding phasor diagram.

[0022] Figure 6 This is an optional method provided by the present invention. Time-corresponding phasor diagram.

[0023] Figure 7 This is an optional dual distributed generation system architecture diagram provided by the present invention.

[0024] Figure 8 This is a comparison diagram of different distance protection schemes under different transition resistors for an optional dual distributed power supply system provided by the present invention. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "an" or "a" and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "connected" or "linked" and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up," "down," "left," "right," etc., are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship also changes accordingly.

[0027] This invention provides a distance protection method for microgrids considering distributed power source integration, applicable to the field of power system relay protection. Its key feature is that it transforms the problem of accurately calculating fault impedance involving distributed power sources into a geometric constraint solution problem in a voltage-current phasor diagram. Based on the known R / X ratio of the line and local measurability, a mapping function is constructed using geometric relationships such as the sine theorem and cosine theorem to derive an explicit analytical expression for the fault impedance. This leads to the establishment of a universal criterion applicable to different transition impedance properties and distributed power source integration scenarios.

[0028] Figure 1 This is a flowchart illustrating the distance protection method for microgrids considering distributed power source access provided by the present invention, as shown below. Figure 1 As shown, including but not limited to the following steps: Step S102: After constructing the fault model of the system with distributed power supply access, obtain the voltage phasor and current phasor at the relay, and the voltage phasor and load current phasor at the common connection point, and construct the voltage-current phasor diagram. Step S104: Based on the voltage-current phasor diagram, calculate the fault impedance value from the relay to the fault point using geometric theorems; Step S106: Compare the fault impedance value with a preset impedance threshold. If the fault impedance value is less than the preset impedance threshold, determine that the fault is located within the protection zone and generate a protection action command.

[0029] The aforementioned microgrid distance protection method considering distributed power source access addresses the problem of large impedance measurement errors and malfunctions in traditional distance protection due to transition resistance and backfeed current from distributed power sources in complex power grid environments. It proposes a systematic solution based on voltage-current phasor geometric analysis.

[0030] By establishing a fault model for a power transmission system with distributed power source access, and by comprehensively utilizing local electrical quantity measurement information from relay installation points and points of common coupling (PCC), combined with the known preset nominal ratio R / X of the line, a geometric relationship diagram of voltage and current phasors is constructed in the complex plane.

[0031] Based on this, and using geometric laws such as the sine and cosine laws, the problem of fault impedance calculation is transformed into an analytical problem under geometric constraints. Through rigorous mathematical derivation, a general explicit expression applicable to resistive, inductive, and capacitive transition impedances is obtained. Applying this criterion to distance protection can accurately quantify the intrinsic relationship between the type of transition resistance, the current injected by distributed generation, and the measured impedance. High-precision fault location can be achieved without relying on specific control of distributed generation. This has significant guiding significance for improving the protection reliability of power grids with a high proportion of distributed energy, preventing protection maloperation and failure to operate, and providing an effective technical means for fault protection and safe and stable operation of modern power grids.

[0032] The following is a detailed description of the above-mentioned microgrid distance protection method considering distributed power source access, using a complete example: Figure 2 shows a system model with distributed power source access, including a distributed generation and transmission system model and a distributed generation and transmission system short-circuit model.

[0033] In this embodiment, the distributed power sources in the distributed power source access system are connected to the grid via high-voltage DC or AC. The system structure can be a single distributed power source or a multi-distributed power source access structure. The fault model of the distributed power source access system is a short-circuit model considering fault transition impedance and distributed power source access, wherein the fault point voltage is not zero, and the fault transition impedance includes resistive, inductive, and capacitive impedances.

[0034] Optionally, the total impedance from the relay to the fault point is the sum of the impedance from the relay to the point of common coupling and the impedance from the point of common coupling to the fault point; The total impedance from the relay to the fault point is:

[0035] in, It is the impedance value from the relay to the point of common connection. It is the fault impedance value from the point of common coupling to the fault point.

[0036] Based on the above embodiments, as an optional embodiment, in the microgrid distance protection method considering distributed power source access provided by the present invention, after constructing a fault model of the system with distributed power source access, the voltage phasors and current phasors at the relay, and the voltage phasors and load current phasors at the point of common coupling, are obtained to construct a voltage-current phasor diagram, including: The first voltage phasor after the fault occurred was collected at the relay installation point. With the first current phasor and obtain the first voltage phasor With the first current phasor The first phase angle between ; Second voltage phasor is acquired at the point of common coupling of the distributed power source. and load current phasor and obtain the second voltage phasor and load current phasor The second phase angle between ; Determine the line impedance angle based on the line's preset nominal ratio. ; Based on the first phase angle Second phase angle and line impedance angle Voltage-current phasor diagrams are constructed for fault transition impedances of different types.

[0037] Furthermore, the statement based on the first phase angle Second phase angle and line impedance angle For fault transition impedances of different types, voltage-current phasor diagrams are constructed respectively, including: When the fault transition impedance is purely resistive, construct the first voltage phasor. With the load current phasor In phase, a voltage-current phasor diagram is obtained; When the fault transition impedance is inductive or capacitive, the voltage phasor at the fault point is collected. and obtain the load current phasor and voltage phasor The third phase angle between ; According to the third phase angle Second phase angle Determine the voltage-current phasor diagram.

[0038] Based on the above embodiments, as an optional embodiment, the microgrid distance protection method considering distributed power source access provided by the present invention, wherein calculating the fault impedance value from the relay to the fault point using geometric theorems based on the voltage-current phasor diagram, includes: When the fault transition impedance is purely resistive, the fault impedance value includes a simplified criterion: ; in, The fault impedance value from the point of common coupling to the fault point. The second phase angle is the relationship between the second voltage phasor and the load current phasor. Acquire the second voltage phasor for the distributed power source's point of common coupling. The line impedance angle. This is the load current phasor.

[0039] Furthermore, the step of calculating the fault impedance value from the relay to the fault point using geometric theorems based on the voltage-current phasor diagram also includes: When the fault transition impedance is inductive or capacitive, the fault impedance value includes a general criterion: when The specific fault impedance value is as follows: ; when The specific fault impedance value is as follows: ; when When the impedance is capacitive, the specific fault impedance value is as follows: ; in, The fault impedance value, Load current phasor and voltage phasor The third phase angle between them, The second phase angle is the relationship between the second voltage phasor and the load current phasor. Acquire the second voltage phasor for the distributed power source's point of common coupling. The line impedance angle. This is the load current phasor.

[0040] The method for obtaining the load current phasor is as follows: It is the sum of the first current phasor and the distributed source injection current phasor.

[0041]

[0042] in, For load current phasor, This is the first current phasor. Inject current phasors into distributed power sources.

[0043] Specifically, when the fault transition impedance is purely resistive, the following expression is defined. , and Phasor relationships between them:

[0044] in, This is the first voltage phasor at the relay mounting point after the fault occurs. This is the first current phasor at the relay mounting point after the fault occurs. The impedance value from the relay to the point of common connection. Acquire the second voltage phasor for the distributed power source's point of common coupling. Voltage phasor at the fault point For distributed power source current, The voltage at the point of common coupling is given, and point F is the short-circuit point. This is the fault transition impedance.

[0045] Figure 3 This shows the voltage-current phasor diagram when the fault transition resistance is a pure resistance. Because... The existence of [the current] is based solely on locally measured current and impedance. , and It cannot be directly determined. To achieve localized impedance measurement between the relay and the fault point, the following assumptions can be made: (1) Impedance from the relay to the point of common coupling (PCC) Known; (2) and The R / X ratios are the same; (3) Assume that there is no load at point PCC and all loads are connected to the system bus P.

[0046] In practice, the distance between the relay and the PCC point is fixed, and their impedance can be measured in advance. Furthermore, if the cable types are the same, then... and The R / X ratios must be equal. Therefore, the above assumption is considered reasonable.

[0047] Therefore, according to geometric theorems, we can obtain :

[0048] in, This is the voltage phasor at the relay. For the voltage phasor at point PCC, Let F be the voltage phasor at fault point F. The current phasor at the relay. Injecting current phasors into distributed power sources , It is the impedance from the relay to the point of common connection (PCC). It is the impedance from the point of common coupling to the point of fault. The phase angle is the line impedance. for and The angle between them for and The angle between them for and The angle between them.

[0049] when When a short-circuit fault is identified and the protection action is triggered. The set operating impedance.

[0050] Given the voltage, current, and angle after the connection point of the distributed power source. A simpler calculation method is obtained by not considering its angle:

[0051] in, For the voltage phasor at point PCC, The current phasor at the relay. Injecting current phasors into distributed power sources , The phase angle is the line impedance. for and The angle between them.

[0052] As can be seen, if the voltage amplitude at the point of common coupling of the distributed power sources and the current amplitude and angle after grid connection are known, the expression is the same as when no distributed power sources are connected. Therefore, as long as the voltage amplitude at the point of common coupling of the distributed power sources and the current amplitude and angle after grid connection are known, regardless of how many distributed power source systems are connected or where they are connected, the problem can be transformed into the case where no distributed power sources are connected.

[0053] In the above discussion, the transition resistance has been considered a pure resistor. However, short-circuit faults occurring in real-world problems are not necessarily metallic short circuits. Therefore, this invention considers transition impedances as either inductance or capacitance, and the transition impedance is... In this case, we get the expression:

[0054] express and The angle between them, its value is located in ( Within the range of ).

[0055] I. hour, Figure 3 Show the corresponding phasor diagram, impedance It can be represented as:

[0056] II. hour, Figure 4 Show the corresponding phasor diagram, impedance It can be represented as:

[0057] III. hour, Figure 5 Show the corresponding phasor diagram, impedance It can be represented as:

[0058] when When a short-circuit fault is identified and the protection action is triggered. Set the impedance for distance protection.

[0059] in, For the voltage phasor at point PCC, Let F be the voltage phasor at fault point F. The current phasor at the relay. Injecting current phasors into distributed power sources , The phase angle is the line impedance. for and The angle between them for and The angle between them.

[0060] Figure 6 This diagram illustrates the architecture of a dual distributed generation system. The system inputs consist only of: the voltage at the PCC, the primary-side current after grid connection, and the phase angle between these two quantities. Figure 7 This diagram compares different distance protection schemes under varying transition resistances in a dual distributed power supply system. The comparison is made by setting three different transition resistances: 50Ω, 100Ω, and 150Ω. The quadrilaterals represent the setting boundaries of the distance protection relays. Red asterisks indicate the measured values ​​of the protection algorithm proposed in this invention, while yellow asterisks indicate the measured values ​​of conventional distance protection algorithms. Under dual-source conditions, traditional methods exhibit significant deviations. The distance protection algorithm proposed in this paper ensures that all protected measured values ​​fall within the operating area of ​​the dual distributed power supply system, thereby enabling the distance protection to function properly.

[0061] On the other hand, the present invention also provides a computer program product, the computer program product including a computer program stored on a non-transitory computer-readable storage medium, the computer program including program instructions, when the program instructions are executed by the computer, the computer is able to execute the microgrid distance protection method considering distributed power source access provided in the above embodiments, the method including: after constructing a fault model of a system with distributed power source access, obtaining voltage phasors and current phasors at the relay, and voltage phasors and load current phasors at the point of common coupling, constructing a voltage-current phasor diagram; based on the voltage-current phasor diagram, calculating the fault impedance value from the relay to the fault point using geometric theorems; comparing the fault impedance value with a preset impedance threshold, and if the fault impedance value is less than the preset impedance threshold, determining that the fault is located within the protection zone and generating a protection action command.

[0062] In another aspect, the present invention also provides a non-transitory computer-readable storage medium storing a computer program thereon. When executed by a processor, the computer program is implemented to perform the microgrid distance protection method considering distributed power source access provided in the above embodiments. The method includes: constructing a fault model of a system with distributed power source access; obtaining voltage phasors and current phasors at relays, and voltage phasors and load current phasors at the point of common coupling, and constructing a voltage-current phasor diagram; calculating the fault impedance value from the relay to the fault point using geometric theorems based on the voltage-current phasor diagram; comparing the fault impedance value with a preset impedance threshold; and determining that the fault is located within the protection zone and generating a protection action command when the fault impedance value is less than the preset impedance threshold.

[0063] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0064] Through the above description of the embodiments, those skilled in the art can clearly understand that each embodiment can be implemented by means of software plus necessary general-purpose hardware platforms, and of course, it can also be implemented by hardware. Based on this understanding, the above technical solutions, in essence or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in the various embodiments or some parts of the embodiments.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A distance protection method for microgrids considering distributed power source integration, applied to AC transmission systems, characterized in that, The method includes: After establishing a fault model for a system with distributed power supply access, the voltage and current phasors at the relays, and the voltage and load current phasors at the point of common coupling, are obtained to construct a voltage-current phasor diagram. The establishment of the fault model for the system with distributed power supply access includes: The fault model for the system with distributed power supply access is a short-circuit model considering fault transition impedance and distributed power supply access; wherein, the fault point voltage is not zero, and the fault transition impedance includes resistive, inductive, and capacitive impedances; after establishing the fault model for the system with distributed power supply access, the voltage phasor and current phasor at the relay, and the voltage phasor and load current phasor at the point of common coupling are obtained to construct a voltage-current phasor diagram, including: The first voltage phasor and the first current phasor after the fault occurs are collected at the relay installation point, and the first phase angle between the first voltage phasor and the first current phasor is obtained. The second voltage phasor and the load current phasor are acquired at the point of common coupling of the distributed power source, and the second phase angle between the second voltage phasor and the load current phasor is obtained. Determine the line impedance angle based on the line's preset nominal ratio; Based on the first phase angle, the second phase angle, and the line impedance angle, voltage-current phasor diagrams are constructed for different types of fault transition impedances; the construction of voltage-current phasor diagrams based on the first phase angle, the second phase angle, and the line impedance angle for different types of fault transition impedances includes: When the fault transition impedance is a pure resistance, the first voltage phasor is constructed to be in phase with the load current phasor, and a voltage-current phasor diagram is obtained. When the fault transition impedance is inductive or capacitive, the voltage phasor at the fault point is collected, and the third phase angle between the load current phasor and the voltage phasor is obtained. The voltage-current phasor diagram is determined based on the third phase angle and the second phase angle. Based on the voltage-current phasor diagram, the fault impedance value from the relay to the fault point is calculated using geometric theorems. The fault impedance value is compared with a preset impedance threshold. If the fault impedance value is less than the preset impedance threshold, the fault is determined to be located within the protection zone and a protection action command is generated.

2. The microgrid distance protection method considering distributed power source access according to claim 1, characterized in that, The calculation of the fault impedance value from the relay to the fault point based on the voltage-current phasor diagram and using geometric theorems includes: When the fault transition impedance is purely resistive, the fault impedance value includes a simplified criterion: ； in, The fault impedance value from the point of common coupling to the fault point. The second phase angle is the relationship between the second voltage phasor and the load current phasor. Acquire the second voltage phasor for the distributed power source's point of common coupling. The line impedance angle. This is the load current phasor.

3. A microgrid distance protection method considering distributed power source access according to claim 1, characterized in that, The calculation of the fault impedance value from the relay to the fault point based on the voltage-current phasor diagram and using geometric theorems also includes: When the fault transition impedance is inductive or capacitive, the fault impedance value includes a general criterion: when The specific fault impedance value is as follows: ； when The specific fault impedance value is as follows: ； when When the impedance is capacitive, the specific fault impedance value is as follows: ； in, The fault impedance value, Load current phasor and voltage phasor The third phase angle between them, The second phase angle is the relationship between the second voltage phasor and the load current phasor. Acquire the second voltage phasor for the distributed power source's point of common coupling. The line impedance angle. This is the load current phasor.

4. A microgrid distance protection method considering distributed power source access according to claim 1, characterized in that, The method for obtaining the load current phasor is as follows: The load current phasor is the sum of the first current phasor and the distributed source injection current phasor; ； in, For load current phasor, This is the first current phasor. Inject current phasors into distributed power sources.

5. A microgrid distance protection method considering distributed power source access according to claim 1, characterized in that, The total impedance from the relay to the fault point is the sum of the impedance from the relay to the point of common coupling and the impedance from the point of common coupling to the fault point. The total impedance from the relay to the fault point is: ； in, The impedance value from the relay to the point of common connection. This represents the fault impedance value from the point of common coupling to the fault point.

6. 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 computer program, it implements the steps of the microgrid distance protection method considering distributed power source access as described in any one of claims 1 to 5.

7. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the microgrid distance protection method considering distributed power source access as described in any one of claims 1 to 5.

Images