Active distribution network line protection method and medium based on additional harmonic current signal

Abstract

This invention discloses an active distribution network line protection method and medium based on additional harmonic current signals. The method includes: acquiring the positive-sequence and negative-sequence voltage components at the IIDG grid connection point and determining whether the IIDG has activated variable amplitude limiting control; if the IIDG has activated variable amplitude limiting control, injecting variable amplitude harmonic current into the system, and then acquiring the three-phase positive-sequence measured voltage to determine whether active protection has been activated; determining the relative phase relationship between the variable amplitude harmonic current and the three-phase positive-sequence measured voltage, determining the fault direction based on the relative phase relationship, and sending corresponding logic judgment signals to the protection equipment at the opposite end of the same level line; determining the amplitude relationship between the variable amplitude harmonic current and the three-phase positive-sequence measured voltage, and combining the logic judgment signals to determine the additional protection measurement values ​​to determine whether the fault is located within the protection zone, and controlling the execution of corresponding protection actions. This invention can improve protection sensitivity and avoid the problem of fault characteristics being unclear due to the influence of the injected signal strength.

Description

Technical Field

[0001] This invention relates to the field of power system technology, and in particular to an active distribution network line protection method and medium based on additional harmonic current signals. Background Technology

[0002] Active distribution networks (ADNs) are multi-source systems capable of controlling various high-proportion distributed power sources. As an effective solution for large-scale distributed renewable energy integration, they represent a major form of future distribution network development. However, with the increasing penetration of distributed power sources such as photovoltaics and wind power in active distribution networks, primarily in the form of full-power inverter-interfaced distributed generation (IIDGs), the fault characteristics of active distribution networks have fundamentally changed compared to traditional distribution networks.

[0003] The changing characteristics of faults bring new technical problems and challenges to the direct application of traditional protection schemes in active distribution networks. Currently, protection schemes for ADN can be broadly categorized into passive and active protection approaches. Passive protection often improves protection criteria to adapt to the fault characteristics of ADN. However, considering the ADN scenario, the core problem facing protection is that with the increasing penetration rate of IIDG (Integrated Intrusion Detection and Control) networks, the continuous weakening of the system's own fault characteristics and the enhancement of uncertainty mean that the performance of the aforementioned protection schemes is always constrained by the IIDG penetration rate.

[0004] Active protection schemes can compensate for the shortcomings of passive protection schemes due to the limited penetration rate of IIDG, but existing active protection schemes still have the following problems: low protection sensitivity, insufficient consideration of the attenuation of harmonic signals by the system, resulting in the influence of the injected signal strength; no consideration of the impact of the response of harmonic current on the grid side on IIDG control; high requirements for the synchronization of communication between protection systems, resulting in weak engineering practicality in distribution networks. Summary of the Invention

[0005] The present invention aims to at least partially solve one of the technical problems in the related art. Therefore, the first objective of the present invention is to provide an active distribution network line protection method based on an additional harmonic current signal, which can improve protection sensitivity and avoid the problem of fault characteristics being unclear due to the influence of the injected signal strength.

[0006] A second objective of this invention is to provide a computer-readable storage medium.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution:

[0008] An active distribution network line protection method based on additional harmonic current signals includes:

[0009] Obtain the positive-sequence voltage component and negative-sequence voltage component at the IIDG grid connection point, and determine whether the IIDG should start variable amplitude control based on the positive-sequence voltage component and negative-sequence voltage component.

[0010] If IIDG initiates variable amplitude control, it injects variable amplitude harmonic current into the distribution network system, and after injecting the variable amplitude harmonic current, it acquires the three-phase positive sequence measurement voltage of the distribution network system so as to determine whether active protection should be activated based on the three-phase positive sequence measurement voltage.

[0011] After the active protection is activated, the relative phase relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage is determined, the fault direction is determined based on the relative phase relationship, and a logic judgment signal corresponding to the fault direction is sent to the protection equipment at the other end of the line.

[0012] The amplitude relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage is determined, and the additional protection measurement value is determined based on the amplitude relationship and the logic judgment signal, so as to determine whether the fault is located in the protection zone based on the additional protection measurement value, and control the execution of the corresponding protection action.

[0013] Preferably, when the amplitude of either the positive-sequence voltage component or the negative-sequence voltage component is greater than the set value, it is determined that the IIDG starts variable amplitude control.

[0014] Preferably, when determining that the IIDG starts variable amplitude control, the method further includes: obtaining the voltage drop depth at the IIDG grid connection point, so as to inject second harmonic current and fourth harmonic current of corresponding intensity into the distribution network system according to the voltage drop depth at the IIDG grid connection point.

[0015] Preferably, if the amplitude of any one of the three-phase positive sequence measured voltages is less than a set value, then active protection is activated.

[0016] Preferably, the variable-amplitude harmonic current used to determine the relative phase relationship and the amplitude relationship is a second harmonic current.

[0017] Preferably, the method further includes: when injecting the variable amplitude harmonic current into the distribution network system, adjusting the amplitude of the injected variable amplitude harmonic current.

[0018] Preferably, when injecting the variable amplitude harmonic current into the power distribution network system, the injected variable amplitude harmonic current is also filtered.

[0019] Preferably, the additional protective measurement value is expressed by the following formula:

[0020] H = Darctan(I) h / U + )

[0021] Where H represents the additional protection measurement value, D represents the logic judgment signal value, and I represents the additional protection measurement value. h U represents the amplitude of the second harmonic current. + This represents the amplitude of the three-phase positive sequence measured voltage, h represents the harmonic component, and + represents the positive sequence measured voltage component.

[0022] Preferably, when the fault is determined to be located within the protected area, the protection device is controlled to trip; when the fault is determined to be located outside the protected area, the protection device is controlled not to operate.

[0023] To achieve the above objectives, a second aspect of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, it implements the above-described active distribution network line protection method based on additional harmonic current signals.

[0024] This invention has at least the following technical effects:

[0025] This invention injects variable-amplitude harmonic current into the distribution network system after the IIDG starts variable-amplitude control, thereby preventing the injected harmonic current intensity from being too low and attenuated by the system, resulting in indistinct fault characteristics. Furthermore, this invention can inject second and fourth harmonic currents of appropriate intensity into the distribution network system according to the voltage drop depth at the IIDG grid connection point, thus preventing the injected harmonic current intensity from being too low and resulting in indistinct fault characteristics. When injecting variable-amplitude harmonic current into the distribution network system, this invention also adjusts the amplitude of the injected variable-amplitude harmonic current, thereby improving protection sensitivity. This invention also adjusts the amplitude of the injected variable-amplitude harmonic current when injecting it into the distribution network system. The variable-amplitude harmonic current is filtered, and by adding a filtering stage, the response of the harmonic current on the grid side can be prevented from affecting the IIDG control. In addition, the present invention also determines the fault direction based on the relative phase relationship between the variable-amplitude harmonic current and the three-phase positive sequence measured voltage, and obtains the corresponding logic judgment signal. Then, based on the amplitude relationship between the variable-amplitude harmonic current and the three-phase positive sequence measured voltage and the logic judgment signal, the additional protection measurement value is determined, and a new protection criterion is constructed based on the additional protection measurement value, thereby providing a new active distribution network line protection method. In addition, the present invention does not require synchronization between protections, so it also has the characteristic of low dependence on communication.

[0026] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0027] Figure 1 This is a flowchart of an active distribution network line protection method based on additional harmonic current signals, according to an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of a 10KV active distribution network topology according to an embodiment of the present invention.

[0029] Figure 3 This is a schematic diagram of the harmonic current amplitude setting injected into the IIDG according to an embodiment of the present invention.

[0030] Figure 4 This is a schematic diagram illustrating the relative phase relationship between the second harmonic current and the three-phase positive sequence measured voltage in an embodiment of the present invention. Detailed Implementation

[0031] The following describes this embodiment in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0032] The following description, with reference to the accompanying drawings, illustrates an active distribution network line protection method and medium based on an additional harmonic current signal, according to an embodiment of this invention.

[0033] Figure 1 This is a flowchart of an active distribution network line protection method based on additional harmonic current signals, according to an embodiment of the present invention. Figure 2 This is a schematic diagram of a 10kV active distribution network topology according to an embodiment of the present invention. Wherein, A, B, and C are busbar numbers, A1~A5, B1~B4, C1, C2, D1, and D2 are protection device numbers, and E... S Zs is the voltage source, f1 to f3 are the simulated fault locations, and all three are located at the midpoint of their respective lines. The method described can be applied to… Figure 2 The topology shown is as follows. Figure 1 As shown, the method includes:

[0034] Step S1: Obtain the positive sequence voltage component and negative sequence voltage component at the IIDG grid connection point, and determine whether the IIDG should start variable amplitude control based on the positive sequence voltage component and negative sequence voltage component.

[0035] Specifically, after the IIDG collects the grid connection point voltage from the grid side, it can obtain the positive and negative sequence components of the grid connection point voltage, namely the positive sequence voltage component and the negative sequence voltage component, in the sequence component separation stage. If the amplitude of either the positive sequence voltage component or the negative sequence voltage component exceeds the set value, it is determined that the IIDG starts variable amplitude limiting control.

[0036] The specific criteria for initiating IIDG variable amplitude control are as follows:

[0037]

[0038] In the formula, E N The enable signal for controlling the switching is ∪, which represents a logical OR; S neg S pos These are positive and negative sequence discrimination signals, respectively; These represent the amplitudes of the positive-sequence and negative-sequence voltage components at the IIDG grid connection point, respectively, with ε being the tuning parameter. Considering that the negative-sequence voltage component only occurs when an asymmetrical fault occurs in the system, the value of ε can be relatively small; to ensure sensitivity, ε = 0.1 can be taken. All the above variables are per-unit normalized with the system rated voltage as the reference value.

[0039] In this embodiment, if the amplitude of either the positive-sequence voltage component or the negative-sequence voltage component exceeds the set value, then E N If the output is 1, then the variable amplitude control is enabled by switching the start of the control.

[0040] Step S2: If IIDG starts variable amplitude control, then variable amplitude harmonic current is injected into the distribution network system. After injecting the variable amplitude harmonic current, the three-phase positive sequence measurement voltage of the distribution network system is obtained so as to determine whether the active protection should be started based on the three-phase positive sequence measurement voltage.

[0041] Specifically, when determining whether IIDG (Integrated Distributed Generation) starts variable amplitude control, the method further includes obtaining the voltage drop depth at the IIDG grid connection point so as to inject second and fourth harmonic currents of corresponding strength into the distribution network system based on the voltage drop depth. Furthermore, when injecting variable amplitude harmonic current into the distribution network system, the amplitude of the injected variable amplitude harmonic current is also adjusted.

[0042] Specifically, to ensure that the inverter in the distribution network system does not disconnect from the grid for a certain period of time while simultaneously providing voltage support to the system, the inverter initiates low-voltage ride-through when the voltage drop at the IIDG grid connection point exceeds the dead zone specified in the national standard. At this time, the power outer loop in the distribution network system is disconnected, and the command value of the current inner loop is given by the low-voltage ride-through strategy based on the voltage drop at the grid connection point. Meanwhile, to protect power electronic equipment, the IIDG control generally includes a limiting circuit. This limits the output current amplitude of the IIDG by setting a corresponding maximum value at the input of the command value. Specifically:

[0043]

[0044] In the formula, i d i q These are the dq-axis currents in a power frequency synchronous rotating coordinate system, respectively. I is the initial phase angle that the IIDG will inject into the system, and also the initial phase angle of the actual output current phasor of the IIDG.IIDG i represents the magnitude of the actual output current phasor of the IIDG. IIDG ω is the actual output current phasor of the IIDG. P This is the angular velocity output by the phase-locked loop.

[0045] To achieve harmonic current injection and prevent insignificant fault characteristics due to excessively low injected harmonic current intensity, the fixed limiting value can be changed to a variable limiting value. The modified limiting value is shown below:

[0046]

[0047] Among them, i I ′ IDG To modify the actual output current phasor of the IIDG, I I ′ IDG To modify the amplitude of the actual output current phasor of the IIDG, ω ex The parameters to be tuned are related to the frequency of the injected harmonics. M and h are the amplitudes of the fundamental current and harmonic current, respectively.

[0048] Furthermore, i in equation (3) can be... I ′ IDG Expanding, the current phasor form of the IIDG output is as follows:

[0049]

[0050] Among them, i m1 For the fundamental component, i h1 The first harmonic component, i.e., harmonic component 1, is... h2 This is the second harmonic component, i.e., harmonic component 2. From equation (4), it can be seen that by adjusting the harmonic currents M, h, and ω... ex The value of IIDG will inject an initial phase angle of 0. angular frequency is ω ex +ω P The frequency is f ex +f p The initial phase angle is - angular frequency is ω ex -ω P The frequency is f ex -f p The two harmonic currents have time-varying angular frequencies.

[0051] The intensity or amplitude of the harmonic current injected by IIDG is set according to the following formula:

[0052]

[0053] Where k1, k2, b1, and b2 are undetermined coefficients, j is the IIDG number, and U PCC.j Let U be the voltage amplitude at the grid connection point of the j-th IIDG, and U1 and U2 be the upper and lower limits of the setting, respectively. In this embodiment, considering both the power output capability of the IIDG under fault conditions and the sensitivity requirements of the protection, U1 can be set to 0.8.

[0054] After a fault occurs, all IIDGs that meet the switching conditions for variable amplitude control will act as harmonic sources, injecting harmonic current into the system. However, considering factors such as the fault point potentially being close to the upstream power grid or having a large transition resistance, resulting in a shallow voltage drop at the IIDG grid connection point, insufficient injected harmonic current intensity, and unclear fault characteristics, the amplitude of the injected harmonic current needs to be adjusted. Specifically, based on the voltage drop at the IIDG grid connection point, it can be divided into a constant value region, a low value region, and a high value region, as detailed below. Figure 3 As shown, Figure 3 In the diagram, h1 and h2 are the amplitudes of the first and second harmonic components, respectively, and U PCC This indicates the voltage amplitude at the grid connection point of the IIDG.

[0055] It should be noted that when injecting variable amplitude harmonic current into the distribution network system, the injected variable amplitude harmonic current can also be filtered. In this embodiment, the response of the harmonic current on the grid side can be prevented from affecting the IIDG control by adding a filtering stage.

[0056] Furthermore, after injecting variable amplitude harmonic current, the three-phase positive sequence measurement voltage of the distribution network system can be obtained, so as to determine whether the active protection should be activated based on the three-phase positive sequence measurement voltage.

[0057] Specifically, if the amplitude of any phase positive sequence measured voltage in the three-phase positive sequence is less than the set value, the active protection is activated; otherwise, the protection process ends.

[0058] Specifically, considering that the line protection method is applied to an active distribution network scenario under a new power system, the short-circuit current that the system side can provide is relatively small, which may prevent the protection from starting. Therefore, the change in the voltage amplitude measured in three-phase positive sequence can be used as the starting criterion. For example, when the voltage amplitude of any phase decreases by more than 10% of the rated value, the protection will start and enter the fault judgment process.

[0059] Step S3: After the active protection is started, determine the relative phase relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage, determine the fault direction based on the relative phase relationship, and send a logic judgment signal corresponding to the fault direction to the protection equipment at the opposite end of the line.

[0060] Among them, the variable-amplitude harmonic current used to determine the relative phase relationship and amplitude relationship is the second harmonic current.

[0061] In this embodiment, the relative phase relationship between the second harmonic current and the three-phase positive sequence measured voltage is used to determine whether the fault is in the positive direction. If the fault is in the positive direction, a "1" signal is sent to the protection device at the opposite end of the same line; if the fault is in the reverse direction, a "-1" signal is sent.

[0062] Specifically, the positive direction of the current is defined as the direction from the busbar to the line. In this embodiment, the relative phase difference between the second harmonic current and the three-phase positive sequence measured voltage is a power frequency variation. Considering the negative sequence nature of the injected second harmonic, with the power frequency voltage phasor as the horizontal axis, the second harmonic current is a quantity rotating clockwise at the power frequency angular velocity. The relative phase relationship between the two is as follows: When the fault is in the positive direction, dΦ1 / dt>0; otherwise... dΦ1 / dt<0. Wherein, Let I be the initial phase angle. h U is the amplitude of the second harmonic current. + The amplitude of the three-phase positive sequence measured voltage is given by Φ1 and Φ2, where h represents the harmonic component, + represents the positive sequence measured voltage component, and Φ1 and Φ2 are the relative phase relationships between the second harmonic current and the positive sequence measured voltage.

[0063] Using this property, a direction criterion can be defined, and the direction judgment result sent, i.e., the logical judgment signal D, is shown in equation (6):

[0064]

[0065] In the formula, Φ i Φ represents the relative phase relationship between the second harmonic current measured at terminal i and the positive sequence measured voltage. j This indicates the relative phase relationship between the second harmonic current measured at terminal j and the positive sequence measured voltage, where i and j should be the two ends of the same circuit. For example, comparing the positive and negative directions... Figure 4 As shown, Figure 4 middle, These represent the second harmonic currents flowing through protection devices A4, A2, B4, and B2, respectively. These represent the positive sequence measured voltages at busbars A, B, and C, respectively. When the protection system determines the fault direction to be positive, it sends the direction determination result, i.e., the logic determination signal D=1, to the protection equipment at the opposite end of the same line; otherwise, it sends D=-1.

[0066] Step S4: Determine the amplitude relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage, and determine the additional protection measurement value based on the amplitude relationship and logic judgment signal, so as to determine whether the fault is located in the protection zone based on the additional protection measurement value, and control the execution of the corresponding protection action.

[0067] Specifically, when facing a non-high-impedance fault, harmonic currents converge towards the fault point, resulting in the largest harmonic current flowing through the protection device closest to the fault point. Combined with the voltage distribution characteristics within the system after the fault point, it can be concluded that the protection device closest to the fault point measures both the lowest voltage and the largest harmonic current. Therefore, an additional protection measurement value is proposed. In this embodiment, the additional protection measurement value can be determined based on the amplitude relationship between the second harmonic current and the three-phase positive-sequence measured voltage, and the logic judgment signal.

[0068] H = Darctan(I) h / U + (7)

[0069] Where H represents the additional protection measurement value, and D represents the logic judgment signal value.

[0070] Furthermore, new protection criteria can be proposed based on additional protection measurement values:

[0071]

[0072] in, To protect the action setting value.

[0073] When the above protection criteria are met, it can be determined whether the fault is located within the protection zone, and the protection equipment can be controlled to trip. When the additional protection measurement value does not meet the above criteria, it is determined that the fault is not located within the protection zone, and the protection equipment is controlled not to operate.

[0074] Furthermore, the present invention also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, can implement the above-described active distribution network line protection method based on additional harmonic current signals.

[0075] In summary, this invention injects variable-amplitude harmonic current into the distribution network system after the IIDG starts variable-amplitude control, thereby preventing the injected harmonic current intensity from being too low and attenuated by the system, resulting in indistinct fault characteristics. Furthermore, this invention can inject second and fourth harmonic currents of appropriate intensity into the distribution network system according to the voltage drop depth at the IIDG grid connection point, thus preventing the injected harmonic current intensity from being too low and resulting in indistinct fault characteristics. When injecting variable-amplitude harmonic current into the distribution network system, this invention also adjusts the amplitude of the injected variable-amplitude harmonic current, thereby improving protection sensitivity. This invention also... The injected variable amplitude harmonic current is filtered, and by adding a filtering stage, the response of the harmonic current on the grid side can be prevented from affecting the IIDG control. In addition, the present invention also determines the fault direction based on the relative phase relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage, and obtains the corresponding logic judgment signal. Then, based on the amplitude relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage and the logic judgment signal, the additional protection measurement value is determined, and a new protection criterion is constructed based on the additional protection measurement value, thereby providing a new active distribution network line protection method. In addition, the present invention does not require synchronization between protections, so it also has the characteristic of low dependence on communication.

[0076] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0077] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for active distribution network line protection based on additional harmonic current signals, characterized in that, include: Obtain the positive-sequence voltage component and negative-sequence voltage component at the IIDG grid connection point, and determine whether the IIDG should start variable amplitude control based on the positive-sequence voltage component and negative-sequence voltage component. If IIDG initiates variable amplitude control, it injects variable amplitude harmonic current into the distribution network system, and after injecting the variable amplitude harmonic current, it acquires the three-phase positive sequence measurement voltage of the distribution network system so as to determine whether active protection should be activated based on the three-phase positive sequence measurement voltage. After the active protection is activated, the relative phase relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage is determined, the fault direction is determined based on the relative phase relationship, and a logic judgment signal corresponding to the fault direction is sent to the protection equipment at the other end of the line. The amplitude relationship between the variable amplitude harmonic current and the three-phase positive sequence measured voltage is determined, and the additional protection measurement value is determined based on the amplitude relationship and the logic judgment signal, so as to determine whether the fault is located in the protection zone based on the additional protection measurement value, and control the execution of the corresponding protection action.

2. The active distribution network line protection method based on additional harmonic current signals as described in claim 1, characterized in that, When the amplitude of either the positive-sequence voltage component or the negative-sequence voltage component is greater than the set value, it is determined that the IIDG starts variable amplitude limiting control.

3. The active distribution network line protection method based on additional harmonic current signals as described in claim 1, characterized in that, When determining whether IIDG initiates variable amplitude limiting control, the method further includes: The voltage drop depth at the IIDG grid connection point is obtained so that the second and fourth harmonic currents of corresponding strength can be injected into the distribution network system according to the voltage drop depth at the IIDG grid connection point.

4. The active distribution network line protection method based on additional harmonic current signals as described in claim 1, characterized in that, If the amplitude of any one of the three-phase positive sequence measured voltages is less than the set value, then active protection is activated.

5. The active distribution network line protection method based on additional harmonic current signals as described in claim 3, characterized in that, The variable-amplitude harmonic current used to determine the relative phase relationship and the amplitude relationship is the second harmonic current.

6. The active distribution network line protection method based on additional harmonic current signals as described in claim 1, characterized in that, The method further includes: When injecting the variable amplitude harmonic current into the power distribution network system, the amplitude of the injected variable amplitude harmonic current is also adjusted.

7. The active distribution network line protection method based on additional harmonic current signals as described in claim 1, characterized in that, When injecting the variable amplitude harmonic current into the power distribution network system, the injected variable amplitude harmonic current is also filtered.

8. The active distribution network line protection method based on additional harmonic current signals as described in claim 5, characterized in that, The additional protective measurement value is expressed by the following formula: H=Darctan(I h / U + ) Where H represents the additional protection measurement value, D represents the logic judgment signal value, and I represents the additional protection measurement value. h U represents the amplitude of the second harmonic current. + This represents the amplitude of the three-phase positive sequence measured voltage, h represents the harmonic component, and + represents the positive sequence measured voltage component.

9. The active distribution network line protection method based on additional harmonic current signals as described in any one of claims 1-8, characterized in that, When the fault is determined to be within the protected area, the protection device will trip; when the fault is determined to be outside the protected area, the protection device will not operate.

10. A 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 active distribution network line protection method based on additional harmonic current signals as described in any one of claims 1-9.

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