A capacity equivalent current protection method and device suitable for a high-proportion new energy power grid

Abstract

The application discloses a capacity equivalent current protection method and device suitable for a high-proportion new energy power grid. The method can effectively solve the problem that traditional current protection cannot accurately act due to the fact that the fault characteristics are not obvious after the power line short-circuit caused by the large-scale grid connection of new energy power sources. The new energy power source after the line short-circuit fault is converted into a traditional generator with the same capacity, which is further equivalent to the original traditional generator, and the equivalent internal impedance on the power source side is calculated. The impedance on the short-circuit point side is calculated through the voltage / current measured at the protection installation after the line short-circuit fault. Then, the equivalent short-circuit current is calculated by using the original internal potential of the traditional generator and the series relationship between the equivalent internal impedance on the power source side and the impedance on the short-circuit point side. Finally, the fault interval can be determined by referring to the conventional sectional current protection method setting operation, and the fault can be selectively removed. The equivalent short-circuit current fault characteristics are obvious enough to solve the problem that the fault interval is not enough due to the large-scale grid connection of new energy, and the performance of the existing current protection is improved.

Description

Technical Field

[0001] This invention relates to a capacity equivalent current protection method and device suitable for high-proportion renewable energy power grids, belonging to the field of power system relay protection. Background Technology

[0002] The proportion of new energy power generation in the power system is increasing, and the power system power supply side is showing a hybrid power supply form with both traditional generators and new energy power sources. The significant increase in the proportion of new energy on the power generation side has also become an important feature of the new power system.

[0003] Thanks to the materials and structure of traditional generators, after a short circuit fault occurs in a power line, it can still continue to operate for a short period of time when the short circuit current reaches tens of times its rated value. Traditional power systems with only the original traditional generators on the power supply side have sufficiently obvious fault characteristics after a line fault, which can distinguish the location of the fault.

[0004] Unlike traditional generators, new energy power sources use power electronic methods for grid connection. To prevent excessive short-circuit current from damaging the internal power electronic devices, its internal control strategy determines that it limits the output after a line short-circuit fault. The fault current is only 1.0-2.0 times the rated current, and it exhibits a strong nonlinear relationship with the terminal voltage.

[0005] The integration of numerous renewable energy sources into the grid has significantly reduced the short-circuit current level of the power grid, weakening fault characteristics. The reduced amplitude of the short-circuit current makes it difficult to distinguish fault locations, leading to maloperation and failure to operate of traditional current protection systems. This substantial decrease in protection performance seriously affects the safe and stable operation of the power system. Currently, engineering practices often employ only modifying the current protection setting values ​​to achieve coordination between the measured short-circuit current and the current protection setting values. However, this method is only suitable for situations with a low proportion of renewable energy. Even with a high proportion of renewable energy, it remains difficult to distinguish fault locations, and maloperation and failure to operate of current protection systems will still occur.

[0006] Against this backdrop, how to utilize the measurement information from existing protection devices to recover weakened fault characteristics, and to achieve selective fault isolation by combining appropriate protection setting methods, has become a technical challenge that relevant power researchers urgently need to solve. Summary of the Invention

[0007] The purpose of this invention is to provide a capacity equivalent current protection method and device suitable for high-proportion renewable energy power grids, which is beneficial to improving the performance of existing current protection and ensuring the safe and stable operation of the power system.

[0008] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0009] In a first aspect, the present invention provides a capacity equivalent current protection method suitable for high-proportion renewable energy power grids, comprising the following steps:

[0010] Obtain circuit information; the circuit information includes: pre-fault voltage signal U1, pre-fault current signal I1, existing conventional generator internal potential E, and existing conventional generator internal impedance Z. rM Post-fault voltage signal U k and the short-circuit current I flowing through the short-circuit point after the fault k ;

[0011] Based on the circuit information, the equivalent internal impedance of the power supply side is calculated by converting the new energy power supply after the line short circuit fault into a traditional generator of the same capacity, and further equivaling it to the original traditional generator as a single traditional generator.

[0012] According to the voltage signal U after the fault k and the short-circuit current I flowing through the short-circuit point after the fault k Calculate the impedance on the short-circuit point side;

[0013] The equivalent short-circuit current is calculated based on the original internal potential of the traditional generator, the equivalent internal impedance of the power supply side, and the impedance of the short-circuit point side.

[0014] The fault location can be determined based on the equivalent short-circuit current.

[0015] Furthermore, the pre-fault voltage signal U1 and the pre-fault current signal I1 are obtained by measuring at the protection installation point before the fault.

[0016] The post-fault voltage signal U k and the short-circuit current I flowing through the short-circuit point after the fault k Obtained by measurement at the protection installation point after a fault;

[0017] The original traditional generator internal impedance Z rM The output current I of the new energy power supply before the short circuit fault DG1 Obtained through identification;

[0018] The internal electromotive force E of the original traditional generator is obtained from the nameplate parameters of the original traditional generator equipment or from experience.

[0019] Furthermore, the internal impedance Z of the original traditional generator rM The identification methods include:

[0020] This indicates the original internal impedance Z of the conventional generator. rM and the output current I of the new energy power supply before the fault DG1Two parameters are set to be determined. Using the measured pre-fault voltage signal U1, pre-fault current signal I1, and the original internal electromotive force E obtained through experience or equipment nameplate parameters, the normal current on the line can be expressed as: The objective function is established to minimize the absolute value of the difference between the calculated normal current and the measured normal current. The measured parameters are then constrained by upper and lower limits. The formula is as follows:

[0021]

[0022] In the formula, I DG1min I DG1max These 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 original traditional generator internal impedance are respectively. rM The minimum and maximum values, i.e., the upper and lower limit constraints;

[0023] The above problem is solved using methods such as the interior point method to solve optimization problems, and the original internal impedance Z of the traditional generator is obtained. rM .

[0024] Furthermore, methods for calculating the equivalent internal impedance on the power supply side after a short-circuit fault include:

[0025] Calculate the power generation capacity S of the original traditional generator. M :

[0026] In the formula, E is the internal electromotive force of the original conventional generator; Z rM U1 is the internal impedance of the original traditional generator; U2 is the voltage value measured at the protection installation point before the short-circuit fault.

[0027] Calculate the output current I of the new energy power supply after a short-circuit fault. DGk :

[0028] In the formula, U k The voltage signal after the fault, I k This refers to the short-circuit current flowing through the short-circuit point after a fault.

[0029] The output capacity S of new energy power source after power line short circuit DGk The capacity should be calculated based on the grid connection voltage before the fault (because after a fault, the renewable energy power supply directly controls the output current based on its internal control strategy and voltage drop, therefore the capacity should be calculated based on the grid connection voltage before the fault, not the grid connection voltage after the fault): S DGk =I DGk ×U1;

[0030] Based on the principle of constant capacity, the internal impedance Z of the new energy power source is converted into a traditional generator of the same capacity. rDG :

[0031] The converted traditional generator from the renewable energy source is connected in parallel with the original traditional generator. These two generators are treated as a single traditional generator, and the equivalent impedance Z on the power supply side after a short-circuit fault is calculated. r Z r =Z rM ||Z rDG .

[0032] Furthermore, based on the voltage signal after the fault and the short-circuit current flowing through the short-circuit point after the fault, the impedance on the short-circuit point side is calculated, including:

[0033] Obtain the short-circuit voltage U 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 ;

[0034] Calculate the impedance Z on the short-circuit point side. k :

[0035] Furthermore, based on the original traditional generator internal potential, the equivalent internal impedance on the power supply side, and the impedance on the short-circuit point side, the equivalent short-circuit current is calculated, including:

[0036] Equivalent impedance Z on the power supply side and impedance Z on the short-circuit point side k They are connected in series, utilizing the existing traditional generator's internal r

[0037] Electric potential, calculate the equivalent short-circuit current I k ′:

[0038] Furthermore, based on the equivalent short-circuit current, the fault location area is determined, including:

[0039] Based on the equivalent short-circuit current I k The circuit is set and operated in accordance with the conventional segmented current protection method, the fault location is determined, and the corresponding circuit breaker is controlled to operate and clear the fault.

[0040] Secondly, the present invention provides a capacity-equivalent current protection device suitable for high-proportion renewable energy power grids, comprising:

[0041] Monitoring module: used to acquire circuit information; the circuit information includes: pre-fault voltage signal U1, pre-fault current signal I1, existing traditional generator internal potential E, and existing traditional generator internal impedance Z. rM Post-fault voltage signal U kand the short-circuit current I flowing through the short-circuit point after the fault k ;

[0042] Power supply side internal impedance module: Based on the circuit information, it is used to calculate the equivalent internal impedance of the power supply side by converting the new energy power supply after the line short circuit fault into a traditional generator of the same capacity, and equating the original traditional generator with a traditional generator.

[0043] Short-circuit impedance module: used to determine the voltage signal U after a fault. k and the short-circuit current I flowing through the short-circuit point after the fault k Calculate the impedance on the short-circuit point side;

[0044] Current calculation module: used to calculate the equivalent short-circuit current based on the circuit information, the series relationship between the equivalent internal impedance of the power supply side and the impedance of the short-circuit point side;

[0045] Judgment module: Used to determine the fault location based on the equivalent short-circuit current.

[0046] Thirdly, the present invention provides a capacity equivalent current protection device suitable for high-proportion new energy power grids, including a processor and a storage medium;

[0047] The storage medium is used to store instructions;

[0048] The processor is configured to operate according to the instructions to perform the steps of the method described in the first aspect.

[0049] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0050] 1. The present invention proposes a capacity equivalent current protection method applicable to high-proportion new energy power grids, which can calculate the equivalent short-circuit current using the measurement information of existing protection devices. The equivalent short-circuit current has a sufficiently large amplitude and sufficiently obvious fault characteristics, which can distinguish the fault location and improve the operating performance of existing current protection.

[0051] 2. This invention proposes a capacity equivalent current protection method for new power systems containing a large number of new energy sources. This method can cope with the continuous changes in the proportion of new energy sources caused by fluctuations in new energy sources (such as photovoltaic and wind power). It can restore fault characteristics under different proportions of new energy sources and has a certain degree of adaptability.

[0052] 3. The capacity equivalent current protection method proposed in this invention can be set and operated with reference to the conventional segmented current protection method. The setting method is simple and has a certain degree of universality.

[0053] 4. It can utilize the measurement information (measured voltage and measured current) of distance protection to achieve integrated operation of protection.

[0054] 5. The capacity equivalent current protection method proposed in this invention, applicable to high-proportion renewable energy power grids, can make full use of existing power line relay protection devices, without the need for additional hardware installation, and only requires functional expansion at the software level, thus significantly reducing the construction and operating costs of the power system. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of a new type of power system structure;

[0056] Figure 2 This is a schematic diagram illustrating the conversion of new energy power sources after a fault.

[0057] Figure 3 A schematic diagram of a power system structure suitable for capacity-equivalent grid current protection;

[0058] Figure 4 This is a diagram illustrating the setting calculations for a conventional segmented current protection system.

[0059] Figure 5 This is a schematic diagram of a capacity equivalent current protection method suitable for high-proportion renewable energy power grids. Detailed Implementation

[0060] The present invention will be further explained in detail below with reference to the accompanying drawings and specific embodiments, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0061] Example 1:

[0062] like Figure 1 The diagram shows a schematic of a new type of power system. A key characteristic of this new power system is the presence of a large number of renewable energy sources on the power supply side. Due to the limiting effect caused by the nonlinear self-control characteristics of these renewable energy sources, the short-circuit current flowing through the power lines in a new power system with a large number of renewable energy sources is significantly less than that in a traditional power system with only conventional generators of equal capacity on the power supply side under the same fault scenario. This weakens the fault characteristics considerably, leading to false tripping or failure to trip by traditional current protection systems, making them unsuitable for the increasingly diverse and ever-changing proportion of renewable energy sources in this new power system. Furthermore, viewed from the protection installation point towards the power supply side, all existing conventional generators on the power supply side of the new power system can be considered as a single aggregated conventional generator, and all renewable energy sources can be considered as a single aggregated renewable energy source.

[0063] like Figure 2The diagram illustrates the conversion of renewable energy sources after a power system fault. During normal power system operation, renewable energy sources are often not operating at full load. After a short-circuit fault in the power line, the renewable energy source enters a low-voltage ride-through state, and depending on the grid connection voltage, it outputs a short-circuit current at a certain proportion of its full load capacity. Following the principle of maintaining the same capacity before and after conversion, the renewable energy source after the fault is converted into a traditional generator of the same capacity. The converted traditional generator has the same internal potential as the original traditional generator, and its internal impedance can be calculated proportionally from the capacity of the renewable energy source after the fault, the capacity of the original traditional generator, and the internal impedance of the original traditional generator.

[0064] like Figure 3 The diagram shows a power system structure suitable for capacity-equivalent grid current protection. Figure 2 After a line fault, the internal potential of the converted traditional generator from the new energy source is equal to that of the original traditional generator, and their internal impedances are in parallel. Therefore, it can be further equivalent to a traditional generator. Introducing the internal potential of the original traditional generator, the equivalent internal impedance on the power supply side and the impedance on the short-circuit point side are in series. Therefore, the equivalent short-circuit current can be calculated, and the fault characteristics of this equivalent short-circuit current are sufficiently obvious.

[0065] This invention provides a capacity equivalent current protection method suitable for high-proportion renewable energy power grids. Its key features include: converting the renewable energy source after a line short-circuit fault into a conventional generator of the same capacity, further equipping it with the original conventional generator as a single conventional generator, and calculating the equivalent internal impedance on the power source side; calculating the impedance on the short-circuit point side using the voltage / current measured at the protection installation location after the line short-circuit fault; calculating the equivalent short-circuit current using the internal potential of the original conventional generator and the series relationship between the equivalent internal impedance on the power source side and the impedance on the short-circuit point side; and finally, setting the operation with reference to conventional segmented current protection methods to determine the fault occurrence interval and selectively disconnect the fault.

[0066] Specifically, all existing traditional generators on the power supply side of a new power system containing a high proportion of volatile new energy power sources are considered as a single aggregated traditional generator, and all new energy power sources on the power supply side are considered as a single aggregated new energy power source.

[0067] Specifically, the internal impedance Z of the original traditional generator is obtained through identification. rM The identification methods include:

[0068] This indicates the original internal impedance Z of the conventional generator. r and the output current I of the new energy power supply before the fault DG1 Two parameters are set to be determined. Using the measured pre-fault voltage signal U1, pre-fault current signal I1, and the original internal electromotive force E obtained through experience or equipment nameplate parameters, the normal current on the line can be expressed as: The objective function is established to minimize the absolute value of the difference between the calculated normal current and the measured normal current. The measured parameters are then constrained by upper and lower limits. The formula is as follows:

[0069]

[0070] In the formula, I DG1min I DG1max These 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 original traditional generator internal impedance are respectively. r The minimum and maximum values, i.e., the upper and lower limit constraints;

[0071] The above problem is solved using methods such as the interior point method to solve optimization problems, and the original internal impedance Z of the traditional generator is obtained. r and the output current I of the new energy power supply before the fault DG1 .

[0072] Specifically, the process essentially involves obtaining the parameters of the original traditional generator and new energy power source on the power supply side before the fault, and, following the principle of maintaining the same capacity before and after conversion, converting the new energy power source after the fault into a traditional generator of the same capacity, thus equating it with the original traditional generator to a single traditional generator, and calculating the equivalent impedance on the power supply side; using the short-circuit voltage and short-circuit current measured at the protection installation point after the fault, calculating the impedance on the short-circuit point side; using the internal potential of the original traditional generator, and the series relationship between the equivalent internal impedance on the power supply side and the impedance on the short-circuit point side, calculating the equivalent short-circuit current; and selectively isolating the faulty portion by referring to the conventional segmented current protection settings.

[0073] This embodiment of a distance-based current protection method applicable to high-proportion renewable energy power grids specifically includes the following steps:

[0074] Step 1: Using the existing 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;

[0075] Step 2: Calculate the power generation capacity S of the existing traditional generator. M :

[0076] In the formula, E is the internal electromotive force of the original conventional generator; Z rM The original traditional generator's internal impedance is Z; U1 is the voltage value measured at the protection installation point before the short-circuit fault; the original traditional generator's internal impedance Z... rM The electromotive force E inside the original traditional generator was obtained from the nameplate parameters of the original traditional generator equipment or from experience.

[0077] Step 3: Using existing measurement information at the protection installation point, obtain the short-circuit voltage U 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 ;

[0078] Calculate the impedance Z on the short-circuit point side. k :

[0079] Step 4: Calculate the output current I of the new energy power supply after the short-circuit fault. DGk :

[0080] The output capacity S of new energy power source after power line short circuit DGk The voltage at the grid connection point before the fault should be used for calculation: S DGk =I DGk ×U1;

[0081] Based on the principle of constant capacity, the internal impedance Z of the new energy power source is converted into a traditional generator of the same capacity. rDG :

[0082] The converted traditional generator from the renewable energy source is connected in parallel with the original traditional generator. These two generators are treated as a single traditional generator, and the equivalent impedance Z on the power supply side after a short-circuit fault is calculated. r Z r =Z rM ||Z rDG ;

[0083] Step 5: The equivalent impedance on the power supply side and the impedance on the short-circuit point side are in series. Using the existing internal potential of the traditional generator, calculate the equivalent short-circuit current I. k ′:

[0084] Step 6: Refer to the conventional segmented current protection settings and operation to determine the faulty section, and the corresponding circuit breaker will operate to selectively disconnect the faulty part.

[0085] Specifically, the conventional segmented current protection setting method, i.e., the protection action includes the following process:

[0086] If the equivalent 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.

[0087] If the equivalent short-circuit current I kIf the current is greater than the setting value of the second stage of the current protection for this line, the second stage of the current protection for this line will start timing; if the equivalent short-circuit current I is greater than the setting value of the second stage of the current protection for this line before the timing time arrives, the equivalent 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 equivalent short-circuit current I... k If the current protection level remains higher than the set value of the second stage of the current protection for this line, it indicates that the fault occurred on this line or the protection of the next line failed to operate. Therefore, the fault is cleared by the second stage of the current protection for this line, realizing full line protection for this line and backup protection for the outlet of the next line.

[0088] The current protection stages I and II of all the aforementioned lines constitute a complete protection range. Additionally, a current protection stage III needs to be installed, with an operating setting value approximately 1.5 to 2 times the rated current. If the equivalent short-circuit current I... k If the current exceeds the set value of current protection stage III, timing begins; if the current still exceeds the limit after the timing time, it indicates that a fault or overload still exists, therefore tripping occurs; if the equivalent short-circuit current I before the timing time is reached... k If the value is less than the setting value of current protection stage III, it indicates that the fault or overload has disappeared, and the operation should return to normal. Due to the strong nonlinearity of the power supply, the operating settings of current protection stage III for each line are not significantly different. In this case, different delay times can be used, i.e., the delay time of the next line is less than the delay time Δt of the previous line, so as to achieve the sequential operation of current protection stage III for different lines.

[0089] like Figure 4 As shown, taking protection 3 as an example, the operating current of the current protection stage I (i.e., instantaneous overcurrent protection) of protection 3 must be greater than the short-circuit current when a three-phase short circuit occurs on bus B under the maximum operating mode. Therefore, the operating setting value of the current protection stage I of protection 3 is... for:

[0090]

[0091] In the formula, E represents the internal electromotive force of the generator; Z r Z represents the equivalent impedance on the power supply side before the fault; A-B The impedance of the line between busbars A and B is the total length of the line. The reliability coefficient is typically 1.1-1.2.

[0092] If the current protection stage II (i.e., time-limited instantaneous overcurrent protection) of protection 3 is coordinated with the current protection stage I of the next line, then the operating setting value of the current protection stage II of protection 3 is... for:

[0093]

[0094] In the formula, The reliability matching factor is typically 1.1-1.2. This is the current protection stage I setting value for the next line protection 2.

[0095] The overload setting for the current stage III protection of protection 3 (i.e., definite-time overcurrent protection) must be greater than the maximum load current occurring on the line. Therefore, the operating setting value for the current stage III protection of protection 3 is... for:

[0096]

[0097] In the formula, The reliability factor is typically 1.15-1.25; K ss K is the self-starting coefficient, generally greater than 1; re This is the return coefficient for the current relay, typically between 0.85 and 0.95.

[0098] It should be noted that the power system fault in this embodiment is a three-phase symmetrical short-circuit fault, and the power transmission line model is considered to be "straight line", that is, the distance L between the fault point and the protection installation point and the impedance Z per unit length of the power line. l The product of these two values ​​is the line impedance between the short-circuit point and the protection installation point.

[0099] Example 2:

[0100] This embodiment provides a capacity-equivalent current protection device suitable for high-proportion renewable energy power grids, including:

[0101] Monitoring module: used to acquire circuit information; the circuit information includes: pre-fault voltage signal U1, pre-fault current signal I1, existing traditional generator internal potential E, and existing traditional generator internal impedance Z. rM Post-fault voltage signal U k and the short-circuit current I flowing through the short-circuit point after the fault k ;

[0102] Power supply side internal impedance module: Based on the circuit information, it is used to calculate the equivalent internal impedance of the power supply side by converting the new energy power supply after the line short circuit fault into a traditional generator of the same capacity, and further equivalence it to the original traditional generator as a traditional generator.

[0103] Short-circuit impedance module: used to determine the voltage signal U after a fault. k and the short-circuit current I flowing through the short-circuit point after the fault k Calculate the impedance on the short-circuit point side;

[0104] Current calculation module: used to calculate the equivalent short-circuit current based on the circuit information, the series relationship between the equivalent internal impedance of the power supply side and the impedance of the short-circuit point side;

[0105] Judgment module: Used to determine the fault location based on the equivalent short-circuit current.

[0106] The apparatus in this embodiment can be used to implement the method described in Embodiment 1.

[0107] Example 3:

[0108] This embodiment provides a capacity equivalent current protection device suitable for high-proportion renewable energy power grids, including a processor and a storage medium;

[0109] The storage medium is used to store instructions;

[0110] The processor is configured to operate according to the instructions to execute the steps of the method described in Embodiment 1.

[0111] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to facilitate the description of this embodiment and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the protection content of this embodiment.

[0112] Those skilled in the art will understand that embodiments of this application can be provided as methods, systems, or computer program products. Therefore, this application can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, this application can take the form of a computer program product embodied 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.

[0113] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0114] The above description is only a preferred embodiment of this embodiment. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this embodiment, and these improvements and modifications should also be considered within the protection scope of this embodiment.

Claims

1. A capacity-equivalent current protection method suitable for high-proportion renewable energy power grids, characterized in that, Includes the following steps: Obtain circuit information; the circuit information includes: pre-fault voltage signal. Pre-fault current signal The internal electromotive force of the original traditional generator The internal impedance of the original traditional generator Voltage signal after fault and the short-circuit current flowing through the short-circuit point after the fault ; Based on the circuit information, the equivalent internal impedance of the power supply side is calculated by converting the new energy power supply after the line short circuit fault into a traditional generator of the same capacity, and further equivaling it to the original traditional generator as a single traditional generator. Based on the voltage signal after the fault and the short-circuit current flowing through the short-circuit point after the fault Calculate the impedance on the short-circuit point side; The equivalent short-circuit current is calculated based on the original internal potential of the traditional generator, the equivalent internal impedance of the power supply side, and the impedance of the short-circuit point side. The fault location can be determined based on the equivalent short-circuit current; Voltage signal before the fault Pre-fault current signal Obtained by measurement at the protection installation point prior to the fault; The voltage signal after the fault and the short-circuit current flowing through the short-circuit point after the fault Obtained by measurement at the protection installation point after a fault; The original traditional generator internal impedance Output current of new energy power supply before short circuit fault Obtained through identification; The internal electromotive force of the original traditional generator Obtained from the nameplate parameters or experience of traditional generator equipment; The original traditional generator internal impedance The identification methods include: Indicates the internal impedance of the original traditional generator and the output current of the new energy power supply before the fault Both parameters are set to be determined, and the measured pre-fault voltage signal is used. Pre-fault current signal And the internal potential of the original conventional generator obtained through experience or equipment nameplate parameters The normal current on the line can be expressed as The objective function is established to minimize the absolute value of the difference between the calculated normal current and the measured normal current. The measured parameters are then constrained by upper and lower limits. The formula is as follows: ； In the formula, , These represent the magnitudes of the current sources that would otherwise cause the new energy power supply to output current before the fault. The minimum and maximum values, i.e., the upper and lower limit constraints; , These are the impedance values ​​of the original traditional generator's internal impedance. The minimum and maximum values, i.e., the upper and lower limit constraints; The above problem is solved by using the interior-point method to solve the optimization problem, and the original internal impedance of the traditional generator is obtained. ; Methods for calculating the equivalent internal impedance on the power supply side after a short-circuit fault include: Calculate the power generation capacity of the original traditional generator. : ; In the formula, This refers to the internal electromotive force of a traditional generator. This refers to the internal impedance of a traditional generator. The voltage value measured at the protection installation point before the short-circuit fault; Calculate the output current of the new energy power source after a short-circuit fault. : ; In the formula, This is the voltage signal after the fault. This refers to the short-circuit current flowing through the short-circuit point after a fault. Output capacity of new energy power sources after power line short circuit Calculated based on the grid connection point voltage before the fault: ; Based on the principle of constant capacity, the internal impedance of the new energy power source is converted into a traditional generator of the same capacity. : ; The converted traditional generator from the renewable energy source is connected in parallel with the original traditional generator. The converted traditional generator and the original traditional generator are treated as a single traditional generator, and the equivalent impedance on the power supply side after a short-circuit fault is calculated. : .

2. The capacity equivalent current protection method for high-proportion renewable energy power grids according to claim 1, characterized in that, Based on the voltage signal after the fault and the short-circuit current flowing through the short-circuit point after the fault, the impedance on the short-circuit point side is calculated, including: Based on the short-circuit voltage at the protection installation point after a short-circuit fault occurs in the power system and the short-circuit current flowing through the short-circuit point Calculate the impedance at the short-circuit point. : .

3. The capacity equivalent current protection method for high-proportion renewable energy power grids according to claim 1, characterized in that, Based on the original internal potential of the traditional generator, the equivalent internal impedance on the power supply side, and the impedance on the short-circuit point side, the equivalent short-circuit current is calculated, including: Equivalent impedance of power supply side and short-circuit point impedance The generators are connected in series. The equivalent short-circuit current is calculated using the internal potential of the existing traditional generator. : .

4. The capacity equivalent current protection method for high-proportion renewable energy power grids according to claim 1, characterized in that, Based on the equivalent short-circuit current, the fault location area is determined, including: Based on equivalent short-circuit current The circuit is set and operated in accordance with the segmented current protection method to determine the fault location and control the corresponding circuit breaker to clear the fault.

5. A capacity-equivalent current protection device suitable for high-proportion renewable energy power grids for performing the method according to any one of claims 1-4, characterized in that, include: Monitoring module: used to acquire circuit information; The circuit information includes: pre-fault voltage signal. Pre-fault current signal The internal electromotive force of the original traditional generator The internal impedance of the original traditional generator Voltage signal after fault and the short-circuit current flowing through the short-circuit point after the fault ; Power supply side internal impedance module: Based on the circuit information, it is used to calculate the equivalent internal impedance of the power supply side by converting the new energy power supply after the line short circuit fault into a traditional generator of the same capacity, and equating the original traditional generator with a traditional generator. Short-circuit impedance module: used to determine the voltage signal after a fault. and the short-circuit current flowing through the short-circuit point after the fault Calculate the impedance on the short-circuit point side; Current calculation module: used to calculate the equivalent short-circuit current based on the circuit information, the series relationship between the equivalent internal impedance of the power supply side and the impedance of the short-circuit point side; Judgment module: Used to determine the fault location based on the equivalent short-circuit current.

6. A capacity-equivalent current protection device suitable for high-proportion renewable energy power grids, characterized in that, Including processor and storage media; The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to any one of claims 1-4.

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