An impedance identification type power grid current protection method and device for a high proportion of new energy power sources

Abstract

The application discloses an impedance identification type power grid current protection method and device for high-proportion new energy power sources, and the method is suitable for a new power system containing high-proportion new energy power sources with fluctuation. Firstly, the voltage / current measured by a measuring loop at the installation position of a relay protection before a short-circuit fault is used to perform power source side equivalence on the new power system containing high-proportion new energy power sources with fluctuation, and to calculate the equivalent impedance of the power source side before the short-circuit fault; then, the voltage / current measured by the protection installation position after the short-circuit fault is used to calculate the impedance of the short-circuit point side after the short-circuit fault; and finally, the traditional generator internal potential is used to calculate a virtual short-circuit current, which is equivalent to the short-circuit current flowing through the line of a traditional power system containing only the same capacity traditional generator on the power source side when the same short-circuit fault occurs at the same position, and then, the existing conventional sectional current protection method is referred to to selectively remove the fault, so that the normal operation of the non-fault part is ensured.

Description

TECHNICAL FIELD

[0001] The application relates to an impedance identification type power grid current protection method and device for a high proportion of new energy power sources and belongs to the field of power system relay protection. BACKGROUND

[0002] Under the background of global energy exhaustion, new energy power generation technology has been valued by governments and researchers all over the world. The proportion of new energy power sources in power systems is continuously increasing, which has become an important feature of new power systems.

[0003] In traditional power grids, the proportion of new energy power sources is low, and the influence on the power grid is small, so the related calculation and analysis can be ignored. However, with the increase of the proportion of new energy power sources in the power grid, the power supply side of the power grid begins to present a mixed power supply form of traditional generators and new energy power sources coexisting, and its influence on the power grid begins to increase. At this time, the related calculation and analysis of the power system begin to take into account the influence of new energy power sources.

[0004] After a line fault occurs in a power grid containing new energy power sources, the fault output current of the new energy power source is subject to its internal control strategy and has a strong nonlinear relationship with the grid-connected point voltage. After a line short-circuit fault occurs in the power grid, the new energy power source usually limits or locks its output, resulting in a significant reduction in the short-circuit current flowing through the line after a line fault in the power system, and the fault characteristics are no longer obvious.

[0005] With the continuous increase of the proportion of new energy power sources in the power grid, the short-circuit current flowing through the line after a line short-circuit fault in the power system is also continuously reduced. Only by relying on the short-circuit current measured at the installation of the protection and referring to the conventional segmented current protection setting value, the traditional current protection is difficult to accurately act to remove the fault part, and thus it is difficult to continue to be applied in the new power system with continuously increasing new energy power sources, which seriously threatens the normal safe and stable operation of the power grid. SUMMARY

[0006] The purpose of the present application is to provide an impedance identification type power grid current protection method and device for a high proportion of new energy power sources, which is beneficial to improve the performance of the existing current protection and ensure the safe and stable operation of the power system.

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0008] In a first aspect, the present application provides an impedance identification type power grid current protection method for a high proportion of new energy power sources, comprising the following steps:

[0009] Obtaining circuit information;

[0010] According to the circuit information, a virtual short-circuit current equivalent to a short-circuit current flowing through the line when a same short-circuit fault occurs at a same position in a traditional power system with only same-capacity traditional generators on the power supply side is calculated;

[0011] According to the virtual current, a fault occurrence interval is determined.

[0012] Further, the circuit information comprises a pre-fault voltage signal U1, a pre-fault current signal I1, an internal potential of the traditional generator E, an internal impedance of the traditional generator Z rM , a new energy power supply output current I DG1 before a short-circuit fault, a post-fault voltage signal U k , and a post-fault short-circuit current I k flowing through the short-circuit point.

[0013] Further, the pre-fault voltage signal U1 and the pre-fault current signal I1 are obtained by measurement at a protection installation before the fault;

[0014] The post-fault voltage signal U k and the post-fault short-circuit current I k flowing through the short-circuit point are obtained by measurement at the protection installation after the fault;

[0015] The internal impedance of the traditional generator Z rM and the new energy power supply output current I DG1 before the short-circuit fault are identified;

[0016] The internal potential of the traditional generator E is obtained from a device nameplate parameter or experience.

[0017] Further, the internal impedance of the traditional generator Z rM and the new energy power supply output current I DG1 before the fault are identified by a method comprising:

[0018] The internal impedance of the traditional generator Z rM and the new energy power supply output current I DG1 before the fault are set as undetermined parameters, and the normal current on the line can be expressed as by using the measured pre-fault voltage signal U1, the measured pre-fault current signal I1, and the internal potential of the traditional generator E obtained from experience or a device nameplate parameter.

[0019]

[0020] In the formula, I DG1min , I DG1maxThese are the magnitudes I of the current source of the new energy power supply's output current before the fault. DG1 The minimum and maximum values, i.e., the upper and lower limits constraints; Z rMmin Z rMmax The impedance values ​​Z of the internal impedance of a conventional generator are respectively. rM The minimum and maximum values, i.e., the upper and lower limit constraints;

[0021] The above problem is solved using methods such as the interior point method to solve optimization problems, and the internal impedance Z of the traditional generator is obtained. rM and the output current I of the new energy power supply before the fault DG1 .

[0022] Furthermore, based on the circuit information, the virtual short-circuit current is calculated, including the following steps:

[0023] Calculate the capacity ratio P of new energy power sources before the fault. DG : Calculate the capacity percentage P of the traditional generator before the fault. M :

[0024] In the formula, E is the internal electromotive force of a conventional generator; Z rM The internal impedance of a traditional generator; I DG1 U1 represents the output current of the new energy power source before the short-circuit fault; U1 and I1 represent the voltage and current values ​​measured at the protection installation point before the short-circuit fault; Z represents the internal impedance of the traditional generator. rM The output current I of the new energy power supply before the short circuit fault DG1 The internal electromotive force E of a conventional generator is obtained from the parameters on the nameplate of the conventional generator equipment or from experience.

[0025] Convert the pre-fault renewable energy source into a conventional generator of the same capacity and calculate the internal impedance Z of the converted conventional generator. rDG : The converted traditional generator from the renewable energy source is connected in parallel with the existing traditional generator. The converted traditional generator and the original traditional generator are treated as a single traditional generator, and the equivalent impedance Z on the power supply side before the short-circuit fault is calculated. r Z r =Z rM ||Z rDG ;

[0026] The short-circuit voltage U measured at the protection installation point after a short-circuit fault occurs in the power system. k and the short-circuit current I flowing through the short-circuit point k Calculate the impedance at the short-circuit point after the short-circuit fault, that is, the line impedance value Z between the protection installation point and the short-circuit point. k :

[0027] The power supply side equivalent impedance and the short-circuit point side impedance are in series, and a virtual short-circuit current I equivalent to a short-circuit current of a traditional power system with only a traditional generator with the same capacity on a line under the same fault scenario is calculated k

[0028] Further, according to the virtual current, a fault occurrence interval is judged, including:

[0029] According to comparison of the virtual short-circuit current I k ′ and a setting value obtained by a segmented current protection setting method, a fault occurrence section is judged, and a corresponding circuit breaker is operated to remove the fault.

[0030] In a second aspect, the application provides an impedance identification type power grid current protection device for a high-proportion new energy power supply, including:

[0031] A monitoring module is used to acquire circuit information;

[0032] A current calculation module is used to calculate a virtual short-circuit current according to the circuit information, the virtual short-circuit current being equivalent to a short-circuit current of a traditional power system with only a traditional generator with the same capacity on a line under the same fault scenario;

[0033] A protection operation module is used to judge a fault occurrence interval according to the virtual current.

[0034] In a third aspect, the application provides an impedance identification type power grid current protection device for a high-proportion new energy power supply, including a processor and a storage medium;

[0035] The storage medium is used to store instructions;

[0036] The processor is used to operate according to the instructions to perform steps of the method in the first aspect.

[0037] Compared with the prior art, the application has the following beneficial effects:

[0038] 1. The impedance identification type power grid current protection method for a high-proportion new energy power supply is proposed, the virtual short-circuit current equivalent to the short-circuit current of the traditional power system with only the traditional generator with the same capacity on the line under the same fault scenario is calculated by using the measurement information at the protection installation position, and thus the current protection performance is improved, and the safe and stable operation of the power system is ensured.

[0039] 2. The existing power system can be equivalently calculated, the equivalent power system structure is simple enough, and the key information amount required by the relay protection calculation after the power system is short-circuited can be reflected. ​

[0040] 3. The impedance identification type power grid current protection method is proposed for a new power system containing a large number of new energy power sources, and the calculated virtual short-circuit current is equivalent to the short-circuit current flowing through the line when the same short-circuit fault occurs at the same position in a traditional power system containing only the same capacity of traditional generators on the power source side, effectively solving the problem that the short-circuit current flowing through the line is continuously reduced due to the increasing proportion of new energy power sources, and the traditional current protection cannot accurately act.

[0041] 4. The impedance identification type power grid current protection method proposed in the application can completely use the setting value obtained by the segmented current protection setting method after calculating and obtaining the equivalent short-circuit current, without changing the existing conventional segmented current protection setting value. In addition, the virtual short-circuit current under different new energy power source proportions can be obtained, which has a certain adaptability and is suitable for new power systems with increasing proportion of new energy power sources in the future.

[0042] 5. The impedance identification type power grid current protection method proposed in the application can fully utilize the existing power line relay protection device, without the need for additional installation of hardware equipment, and effectively reduces the construction cost and operation cost of the power system while ensuring the accurate action of the relay protection. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 is a schematic diagram of a new power system structure;

[0044] Figure 2 is a schematic diagram of a new power system structure before fault;

[0045] Figure 3 is a schematic diagram of a power system structure suitable for impedance identification type power grid current protection;

[0046] Figure 4 is a conventional segmented current protection setting calculation diagram;

[0047] Figure 5 is a schematic diagram of a new power system structure before fault; DETAILED DESCRIPTION

[0048] The application will be further explained and described in detail below in combination with the drawings and specific embodiments, but it should be understood that the protection scope of the application is not limited by the specific embodiments.

[0049] Example 1:

[0050] As Figure 1The diagram shows a schematic of the new power system structure. In this new power system, a large number of new energy sources are integrated into the grid. The power supply side of the grid exhibits a mixed structure of traditional generators and new energy sources. From the perspective of the protection installation, all traditional generators on the power supply side can be considered equivalent to a single aggregated traditional generator, and all new energy sources on the power supply side can be considered equivalent to a single aggregated new energy source. After a short-circuit fault occurs in the grid line, the short-circuit current flowing through the short-circuit point is jointly provided by the traditional generators and the new energy sources.

[0051] like Figure 2 The diagram shows the power system structure after conversion from renewable energy sources before and after the fault. Based on the principle that the capacity of renewable energy sources remains unchanged before and after conversion, the following can be considered: Figure 1 When the renewable energy power source is converted into a traditional generator of equivalent capacity, the converted traditional generator has the same internal potential as the existing traditional generator, and its internal impedance is determined by the proportion of renewable energy power source in the total power capacity.

[0052] like Figure 3 The diagram shows a power system structure suitable for impedance-based grid current protection. Figure 2 The traditional generators obtained by China New Energy Power after being converted according to the same capacity can be further equivalent to a single traditional generator. This can be used to calculate the virtual short-circuit current, which is equivalent to the short-circuit current flowing through the line when the same short-circuit fault occurs in the same location in a traditional power system with only traditional generators of the same capacity on the power supply side.

[0053] In power systems with a large proportion of renewable energy sources, after a line short-circuit fault occurs, the renewable energy source typically limits its output to protect internal power electronic devices from damage. This results in a fault output current from the renewable energy source being much smaller than that of a traditional generator of the same capacity. As the proportion of renewable energy sources in the power system increases, the fault current flowing through the line short-circuit point also decreases, and the fault characteristics become less obvious. Referring to the setting values ​​of conventional segmented current protection, traditional current protection cannot operate accurately, making it difficult to continue to be applicable to new power systems with a large proportion of renewable energy sources.

[0054] The embodiment provides an impedance identification type power grid current protection method for a high-proportion new energy power source.

[0055] Specifically, the impedance identification type power grid current protection method for the high-proportion new energy power source is characterized in that all traditional generators on the power source side of the new type power system containing the fluctuation high-proportion new energy power source are equivalent to an aggregated traditional generator, and all new energy power sources on the power source side are equivalent to an aggregated new energy power source.

[0056] Specifically, the impedance identification type power grid current protection method for the high-proportion new energy power source is characterized in that all traditional generators on the power source side of the new type power system containing the fluctuation high-proportion new energy power source are equivalent to an aggregated traditional generator, and all new energy power sources on the power source side are equivalent to an aggregated new energy power source. rM And the pre-fault new energy power source output current I DG1 The identification method comprises the following steps.

[0057] The traditional generator internal impedance Z rM And the pre-fault new energy power source output current I DG1 Two parameters are set as undetermined, the measured pre-fault voltage signal U1, the pre-fault current signal I1 and the traditional generator internal potential E obtained through experience or device nameplate parameters are used, and the normal current on the line can be represented as So that the absolute value of the difference between the calculated normal current and the measured normal current is minimized, thereby establishing an objective function, and the to-be-measured parameters are constrained by upper and lower values, and the formula is as follows:

[0058]

[0059] In the formula, I DG1min , I DG1max are the minimum value and the maximum value of the current source size I DG1 of the pre-fault new energy power source output current, that is, the upper and lower limit constraints; Z rMmin , Z rMmax are the minimum value and the maximum value of the impedance value Z rM of the traditional generator internal impedance, that is, the upper and lower limit constraints.

[0060] The above problem is solved using methods such as the interior point method to solve optimization problems, resulting in the representation of the internal impedance Z of a traditional generator. rM and the output current I of the new energy power supply before the fault DG1 .

[0061] Specifically, the impedance identification-based grid current protection method for high-proportion renewable energy power sources essentially involves, based on the equivalent conversion of traditional generators and renewable energy power sources on the power source side of the new power system before a short-circuit fault and the acquisition of corresponding parameters, and adhering to the principle that the total power capacity remains unchanged before and after the conversion, converting the renewable energy power source on the power source side before the fault into a traditional generator of the same capacity, and calculating the equivalent impedance on the power source side before the short-circuit fault; calculating the line impedance on the short-circuit point side after the short-circuit fault based on the short-circuit voltage and short-circuit current obtained from the measuring device at the protection installation location; and further utilizing the internal potential of the traditional generator to calculate the virtual short-circuit current, which is equivalent to the short-circuit current flowing through the line in the same fault scenario in a traditional power system with only traditional generators of the same capacity on the power source side.

[0062] Specifically, the impedance identification-based grid current protection method for high-proportion renewable energy power sources, as described above, is... Figure 5 As shown, it includes the following steps:

[0063] Step 1: Using the measurement information at the protection installation point, obtain the voltage U1 measured at the protection installation point and the current I1 flowing through the line before the short-circuit fault;

[0064] Step 2: After all traditional generators on the power supply side are equivalent to a single traditional generator and all new energy power sources are equivalent to a single new energy power source, since the grid connection point voltage is the same, the capacity ratio of new energy power sources and traditional generators is equal to the ratio of their respective output current in the total line current.

[0065] Calculate the capacity percentage P of new energy power sources before the fault. DG : Calculate the capacity percentage P of the traditional generator before the fault. M :

[0066] In the formula, E is the internal electromotive force of a conventional generator; Z rM The internal impedance of a traditional generator; I DG1 U1 represents the output current of the new energy power source before the short-circuit fault; U1 and I1 represent the voltage and current values ​​measured at the protection installation point before the short-circuit fault; Z represents the internal impedance of the traditional generator. rM The output current I of the new energy power supply before the short circuit fault DG1 The internal electromotive force E of a conventional generator is obtained from the parameters on the nameplate of the conventional generator equipment or from experience.

[0067] Step 3: Convert the pre-fault renewable energy source into a conventional generator of the same capacity, and calculate the internal impedance Z of the converted conventional generator. rDG : (Since the converted traditional generator and the existing traditional generator have the same internal potential, only the internal impedance of the converted traditional generator needs to be calculated); the converted traditional generator of the new energy power source and the existing traditional generator are connected in parallel. The converted traditional generator of the new energy power source and the original traditional generator are equivalent to a single traditional generator. Calculate the equivalent impedance Z on the power supply side before the short-circuit fault. r Z r =Z rM ||Z rDG ;

[0068] Step 4: Measure the short-circuit voltage U measured at the protection installation point after a short-circuit fault occurs in the power system. k and the short-circuit current I flowing through the short-circuit point k Calculate the impedance at the short-circuit point after the short-circuit fault, that is, the line impedance value Z between the protection installation point and the short-circuit point. k :

[0069] Step 5: The equivalent impedance on the power supply side and the impedance on the short-circuit point side are in series. The virtual short-circuit current I is calculated, which is equivalent to the short-circuit current flowing through the line in a conventional power system with only a conventional generator of the same capacity on the power supply side under the same fault scenario. k ′:

[0070] Step 6: Based on the virtual short-circuit current I k By comparing the setting values ​​obtained from the segmented current protection setting method with those obtained from the segmented current protection setting method, the fault location is determined, and the corresponding circuit breaker operates to clear the fault.

[0071] Specifically, the conventional segmented current protection setting method, i.e., the protection action includes the following process:

[0072] If the virtual short-circuit current I k If the value is greater than the setting value of the current protection stage I of this line, then the short-circuit fault is within the protection range of the current protection stage I of this line, and the corresponding protection will operate; otherwise (i.e., less than the setting value of the current protection stage I of this line), the current protection stage I of this line will not operate.

[0073] If the virtual short-circuit current I k If the current is greater than the setting value of the second stage of the line current protection, the second stage of the line current protection will start timing; if the virtual short-circuit current I is greater than the setting value of the second stage of the line current protection before the timing time arrives, the virtual short-circuit current I will start timing. k If the current drops sufficiently, it indicates that the fault occurred on the next line and has been cleared by the current protection stage I of that next line; if the timing indicator arrives, the virtual short-circuit current I...k Still maintaining greater than the current protection II section setting value of the line, it is explained that the fault occurs in the line or the next line protection refusal, so the fault is removed by the current protection II section of the line, and the full line protection of the line and the backup protection of the next line outlet are realized.

[0074] All the current protection I sections and current protection II sections of the above lines constitute a complete protection range in turn. In addition, a current protection III section needs to be set, and the action setting value thereof is about 1.5 times to 2 times of the general rated current. If the virtual short-circuit current I k is greater than the setting value of the current protection III section, timing is started; if the current still exceeds the standard after the timing time is reached, it is explained that the fault or overload still exists, so tripping is performed; if the virtual short-circuit current I k is less than the setting value of the current protection III section, it is explained that the fault or overload has disappeared, so returning is performed. Due to the strong nonlinearity of the power supply, the action setting values of the current protection III sections of the lines are not much different, at this time, different time delays can be adopted, that is, the time delay of the next line is less than that of the previous line by a time delay Δt, so that the current protection III sections of different lines are sequentially operated.

[0075] As shown in Figure 4 , taking protection 3 as an example, the action current of the current protection I section (that is, the current instantaneous trip protection) of protection 3 must be greater than the short-circuit current when a three-phase short circuit occurs on bus B in the maximum operating mode, so the action setting value of the current protection I section of protection 3 is :

[0076]

[0077] In the formula, E represents the internal potential of the generator; Z r represents the equivalent impedance on the power supply side before the fault; Z A-B is the full-length impedance of the line between bus A and bus B; is a reliability coefficient, generally 1.1-1.2.

[0078] The current protection II section (that is, the time-limited current instantaneous trip protection) of protection 3 cooperates with the current protection I section of the next line, so the action setting value of the current protection II section of protection 3 is :

[0079]

[0080] In the formula, is a reliability cooperation coefficient, generally 1.1-1.2; is the action setting value of the current protection I section of the next line protection 2.

[0081] The current III section protection of protection 3 (i.e. the time limit overcurrent protection) is set for overload and must be greater than the maximum load current appearing on the line, then the current III section protection action setting value of protection 3 is:

[0082]

[0083] In the formula, is a reliability coefficient, generally 1.15-1.25; K ss is a self-starting coefficient, generally greater than 1; K re is a current relay return coefficient, generally 0.85-0.95.

[0084] It should be noted that the power system fault of the embodiment is a three-phase symmetrical short circuit fault, and the power transmission line model is regarded as "a word type", that is, the product of the distance L between the fault point and the protection installation and the unit length impedance Z of the power line is the line impedance between the short circuit point and the protection installation. l

[0085] Embodiment two:

[0086] The embodiment provides an impedance identification type power grid current protection device for a high proportion of new energy power sources, comprising:

[0087] A monitoring module is configured to acquire circuit information;

[0088] A current calculation module is configured to calculate a virtual short circuit current according to the circuit information, the virtual short circuit current being equivalent to a short circuit current flowing through a line in a traditional power system with only a same capacity conventional generator on the power source side when a same short circuit fault occurs at a same position;

[0089] A protection action module is configured to determine a fault occurrence interval according to the virtual current.

[0090] The device of the embodiment can be applied to the method of the embodiment one.

[0091] Embodiment three:

[0092] The embodiment provides an impedance identification type power grid current protection device for a high proportion of new energy power sources, comprising a processor and a storage medium;

[0093] The storage medium is configured to store instructions;

[0094] The processor is configured to operate according to the instructions to perform the steps of the method of the embodiment one.

[0095] ​In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for convenience of describing the present embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the protection scope of the present embodiment.

[0096] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0097] These computer program instructions can also be loaded onto a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide the function implemented in the flow Figure 1 one or more flows and / or blocks Figure 1 one or more blocks or steps of the function specified in the flow

[0098] The above description is only the preferred embodiment of the present application, and it should be pointed out that for those skilled in the art, without departing from the technical principles of the present embodiment, a number of improvements and modifications can be made, and these improvements and modifications should be considered as the protection scope of the present embodiment.

Claims

1. An impedance identification type power grid current protection method for a high proportion of new energy power sources, characterized in that, The method comprises the following steps: obtaining circuit information; calculating a virtual short-circuit current according to the circuit information, the virtual short-circuit current being equivalent to a short-circuit current flowing through a line when a traditional power system with only traditional generators of the same capacity on the power supply side has the same short-circuit fault at the same location; judging a fault occurrence interval according to the virtual short-circuit current; The circuit information includes: pre-fault voltage signal , pre-fault current signal , internal potential of the conventional generator , internal impedance of the conventional generator , output current of the new energy power supply before short-circuit fault , post-fault voltage signal , and post-fault short-circuit current flowing through the short-circuit point ; said pre-fault voltage signal , a pre-fault current signal obtained by measuring at the protection installation before the fault; the post-fault voltage signal and the short circuit current flowing through the short circuit point after the fault obtained by measuring at the protection installation after the fault Conventional generator internal impedance And short-circuit fault before new energy power supply output current Derived from identification; Conventional generator internal potential Obtained from conventional generator equipment nameplate parameters or experience; calculating a virtual short-circuit current according to the circuit information, comprising the following steps: The capacity proportion of the new energy power supply before the fault is calculated : The capacity proportion of the traditional generator before the fault is calculated : : ; The new energy power supply before the fault is converted into a traditional generator of the same capacity, and the converted traditional generator impedance is calculated : ; The converted traditional generator of the new energy power supply and the existing traditional generator are in parallel connection, the converted traditional generator of the new energy power supply and the original traditional generator are equivalent to a single traditional generator, and the equivalent impedance of the power supply side before the short circuit fault is calculated : ; measured at the installation of the protection after a short circuit fault in the power system and the short circuit current flowing through the short circuit point , calculating the impedance at the short circuit point after the short circuit fault, the line impedance value between the installation of the protection and the short circuit point : ; The power supply side equivalent impedance and the short circuit point side impedance are in series, and a virtual short circuit current equivalent to a short circuit current of a traditional power system containing only a traditional generator with the same capacity on a line under the same fault scenario is calculated : .

2. The impedance identification type power grid current protection method for a high proportion of new energy power sources according to claim 1, characterized in that, Impedance within a conventional generator and the output current of the new energy power supply before the fault The identification method comprises: The internal impedance of the conventional generator is represented as and the pre-fault output current of the new energy power supply is represented as Two parameters are set as undetermined, the pre-fault voltage signal , the pre-fault current signal and the internal potential of the conventional generator obtained via experience or equipment nameplate parameters are used to represent the internal potential of the conventional generator , the normal current on the line is represented as , so that the absolute value of the difference between the calculated normal current and the measured normal current is minimized, thereby establishing an objective function, and the undetermined parameters are given lower and upper value constraints, and the formula is: ； In the formula, , are the minimum and maximum values of the impedance value of the internal impedance of the conventional generator, i.e. the upper and lower limit constraints, respectively. , , are the minimum and maximum values of the impedance value of the internal impedance of the conventional generator, i.e. the upper and lower limit constraints, respectively. , The above problem is solved by a method of solving an optimal problem by an interior point method to obtain a conventional generator internal impedance and the pre-fault new energy source output current .

3. The impedance identification type power grid current protection method for high proportion of new energy power source according to claim 1, characterized in that, judging a fault occurrence interval according to the virtual short-circuit current, comprising: According to virtual short-circuit current And the comparison of the setting values obtained by the segmented current protection setting method, the fault occurring section is judged, and the corresponding circuit breaker is controlled to act to remove the fault.

4. An impedance recognition type power grid current protection device for high proportion of new energy power source for performing the method of any one of claims 1-3, characterized in that, comprising: a monitoring module for obtaining circuit information; a current calculation module for calculating a virtual short-circuit current according to the circuit information, the virtual short-circuit current being equivalent to a short-circuit current flowing through a line when a traditional power system with only traditional generators of the same capacity on the power supply side has the same short-circuit fault at the same location; a protection action module for judging a fault occurrence interval according to the virtual short-circuit current.

5. An impedance identification type power grid current protection device for a high proportion of new energy power sources, characterized in that, comprise a processor and a storage medium; the storage medium is used for storing instructions; the processor is used for operating according to the instructions to perform the steps of the method in any one of claims 1-3.

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