Current differential protection refusing identification method for new energy station and related equipment

Abstract

The embodiment of the invention discloses a current differential protection refusing identification method and related equipment for a new energy station, and the method comprises the steps: obtaining a current phasor ratio of the two sides of a protected line according to the instantaneous current of the two sides of the protected line; a corresponding critical ratio braking coefficient on the current differential protection critical action curve is obtained according to the coordinate value of the ratio of the current phasors on the two sides of the line, and the critical ratio braking coefficient can effectively reflect the boundary of current differential protection; therefore, the judgment accuracy can be effectively improved by judging whether the operation refusal condition occurs or not according to the critical ratio braking coefficient.

Description

[Technical field]

[0001] The present invention relates to the field of protection technology for power grids connected to new energy stations, and in particular to a current differential protection refusal identification method and related equipment for new energy stations. [Background technology]

[0002] The dedicated access lines of new energy power sources usually need to be equipped with current differential protection as the main protection. However, due to the characteristics of limited amplitude and capacitively controlled phase angle of the short-circuit current provided by photovoltaic and other new energy power sources under grid faults, this will make the differential current smaller than the braking current when an intra-regional fault occurs on photovoltaic and other new energy dedicated lines, which will lead to the risk of refusal to operate of the widely used ratio-braked current differential protection. Existing studies have added amplitude compensation and phase angle compensation to the current differential protection criterion based on the current change characteristics on both sides of the lines connected to photovoltaic and other new energy power sources, and realized the adaptive adjustment of the ratio-braked current differential protection criterion, thereby ensuring that the protection can operate correctly under intra-regional faults. However, these studies have not systematically analyzed the adaptability boundary of the traditional ratio-braked current differential protection in the scenario of new energy power access, making it impossible to accurately judge whether the current differential protection will refuse to operate. [Summary of the invention]

[0003] In view of this, the present invention provides a current differential protection refusal identification method and related equipment for a new energy station.

[0004] The specific technical solution of the first embodiment of the present invention is: a method for identifying refusal to operate of current differential protection of a new energy station, the method comprising: obtaining the current phasor ratio on both sides of the protected line according to the instantaneous current on both sides of the protected line; obtaining the critical ratio braking coefficient corresponding to the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line; judging whether the current differential protection of the protected line will refuse to operate according to the critical ratio braking coefficient and a preset ratio braking coefficient.

[0005] Preferably, the method of obtaining the current phasor ratio on both sides of the protected line according to the instantaneous currents on both sides of the protected line includes: obtaining a first instantaneous current on one side of the protected line, and obtaining a second instantaneous current on the other side of the protected line; comparing the current amplitudes of the first instantaneous current and the second instantaneous current; taking the instantaneous current with a large current amplitude as the first target instantaneous current, and taking the instantaneous current with a small current amplitude as the second target instantaneous current; obtaining a first amplitude and a first phase angle of the first target instantaneous current, and obtaining a second amplitude and a second phase angle of the second target instantaneous current; and obtaining the current phasor ratio on both sides of the line according to the first amplitude, the first phase angle, the second amplitude and the second phase angle.

[0006] Preferably, the current phase ratio on both sides of the line is obtained using the following formula:

[0007]

[0008] in, is the current phasor ratio on both sides of the line, is the second target instantaneous current, is the first target instantaneous current, is the second amplitude, is the first amplitude, θ1 is the second phase angle, θ2 is the first phase angle, and A is and The ratio of θ d is the phase angle difference between θ2 and θ1.

[0009] Preferably, the critical ratio braking coefficient is obtained using the following formula:

[0010]

[0011] Among them, K c is the critical ratio braking coefficient, x is the abscissa of the current phasor ratio on both sides of the line, and y is the ordinate of the current phasor ratio on both sides of the line.

[0012] Preferably, judging whether the current differential protection of the protected line will fail to operate based on the critical ratio braking coefficient and the preset ratio braking coefficient includes: comparing the critical ratio braking coefficient and the preset ratio braking coefficient; if the critical ratio braking coefficient is less than or equal to the preset ratio braking coefficient, the current differential protection of the protected line will fail to operate, otherwise it will not fail to operate.

[0013] Preferably, the method also includes: performing phase angle compensation on the current phasor ratio on both sides of the line according to a preset target control function; judging whether the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection condition; if the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection condition, the protected line performs differential protection action, otherwise the protected line does not perform differential protection action.

[0014] Preferably, the preset differential protection condition is obtained using the following formula:

[0015]

[0016] in, is the current phasor ratio on both sides of the line, j is an imaginary unit, f(K c) is the preset target control function, K0 is the preset ratio braking coefficient, and is the instantaneous current on both sides of the protected line, I op is the starting current value.

[0017] The specific technical solution of the second embodiment of the present invention is: a current differential protection refusal identification system for a new energy station, the system comprising: a current phasor ratio acquisition module, a critical ratio braking coefficient acquisition module and a judgment module; the current phasor ratio acquisition module is used to obtain the current phasor ratio on both sides of the protected line according to the instantaneous current on both sides of the protected line; the critical ratio braking coefficient acquisition module is used to obtain the corresponding critical ratio braking coefficient on the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line; the judgment module is used to judge whether the current differential protection of the protected line will refuse to operate based on the critical ratio braking coefficient and the preset ratio braking coefficient.

[0018] The specific technical solution of the third embodiment of the present invention is: a current differential protection refusal to operate identification device for a new energy station, comprising a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method described in any one of the first embodiments of the present application.

[0019] The specific technical solution of the fourth embodiment of the present invention is: a computer-readable storage medium storing a computer program, which, when executed by a processor, enables the processor to perform the steps of the method described in any one of the first embodiments of the present application.

[0020] Implementing the embodiments of the present invention will have the following beneficial effects:

[0021] The present invention obtains the current phasor ratio of both sides of the protected line according to the instantaneous current on both sides of the protected line, and obtains the critical ratio braking coefficient corresponding to the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line. The critical ratio braking coefficient can effectively reflect the boundary of the current differential protection. Therefore, judging whether a refusal to operate will occur according to the critical ratio braking coefficient can effectively improve the accuracy of the judgment.

Brief Description of the Drawings

[0022] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a flow chart of the steps of the method for identifying the refusal of current differential protection in a new energy station;

[0024] Figure 2 This is a schematic diagram of the topological structure of photovoltaic power station connected to the power grid;

[0025] Figure 3 It is the differential protection action area corresponding to the amplitude-phase plane analysis method;

[0026] Figure 4a It is a comparison diagram of the action characteristic curve of the traditional differential protection when there is a three-phase short-circuit fault in the area;

[0027] Figure 4b It is a comparative diagram of the action characteristic curves of the improved differential protection when there is a three-phase short-circuit fault in the area;

[0028] Figure 5a It is a schematic diagram for comparing the characteristic curves of the traditional differential protection when there is a two-phase short-circuit fault in the area;

[0029] Figure 5b It is a schematic diagram for comparing the action characteristic curves of the improved differential protection when there is a two-phase short-circuit fault in the area;

[0030] Figure 6 This is a structural diagram of the current differential protection refusal identification system for new energy stations;

[0031] Figure 7 It is a diagram of the internal structure of a computer device;

[0032] Among them, 201 is a current phase ratio acquisition module; 202 is a critical ratio braking coefficient acquisition module; 203 is a judgment module. [Specific implementation method]

[0033] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0034] The terms "first", "second", etc. in the specification, claims and drawings of this application are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or modules is not limited to the listed steps or modules, but optionally includes steps or modules that are not listed, or optionally includes other steps or modules that are inherent to these processes, methods, products or devices.

[0035] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0036] See also Figure 1 , is a flow chart of the steps of a method for identifying refusal to operate of current differential protection of a new energy station in the first embodiment of the present application, which effectively improves the accuracy of judging refusal to operate, and the method includes:

[0037] Step 101, obtaining a current phasor ratio between two sides of the protected line according to instantaneous currents on two sides of the protected line;

[0038] Specifically, a first instantaneous current on one side of the protected line is obtained, and a second instantaneous current on the other side of the protected line is obtained; the current amplitudes of the first instantaneous current and the second instantaneous current are compared; the instantaneous current with the larger current amplitude is used as the first target instantaneous current, and the instantaneous current with the smaller current amplitude is used as the second target instantaneous current; the first amplitude and the first phase angle of the first target instantaneous current are obtained, and the second amplitude and the second phase angle of the second target instantaneous current are obtained; and the current phasor ratio on both sides of the line is obtained according to the first amplitude, the first phase angle, the second amplitude and the second phase angle.

[0039] Specifically, the current phasor ratio on both sides of the line is obtained using the following formula:

[0040]

[0041] in, is the current phasor ratio on both sides of the line, is the second target instantaneous current, is the first target instantaneous current, is the second amplitude, is the first amplitude, θ1 is the second phase angle, θ2 is the first phase angle, and A is and The ratio of θ d is the phase angle difference between θ2 and θ1.

[0042] Step 102, obtaining a critical ratio braking coefficient corresponding to a current differential protection critical action curve according to the coordinate value of the current phasor ratio on both sides of the line;

[0043] Obtain the current phasor ratio on both sides of the protected line based on the instantaneous current on both sides of the protected line The action criterion expression of the ratio-restrained current differential protection widely used at present is as follows:

[0044]

[0045] Where: is the differential current, i.e. the vector sum of the currents flowing through the protection devices on both sides; is the braking current, i.e. the current vector difference of the protection devices on both sides; I op is the starting current value, which is set according to the maximum unbalanced current of the current transformer; K0 is the ratio braking coefficient, which is generally 0.5 to 0.8. m with I n The schematic diagram of the photovoltaic power station connected to the grid topology is as follows Figure 2 shown.

[0046] Substituting formula (2) into the traditional current differential protection action criterion equation, after simplification, we can obtain the current phasor ratio on both sides of the line: The current differential protection action criterion represented is:

[0047]

[0048] In the above formula, the phase The corresponding coordinates in the rectangular coordinate system are (x, y), and the criterion of formula (3) can be further expressed as:

[0049]

[0050] From the knowledge of analytical mathematics, we know that the critical action curve of the protection criterion is a circle with the center at The radius is The critical action curve corresponding to formula (4) is as follows: Figure 3 shown. Figure 3 The solid curve circle in the middle is the critical action curve of the current differential protection when the ratio braking coefficient is 0.5 to 0.8. The area inside the dotted circle and outside the solid circle is the correct action area of ​​the protection, and the area inside the dotted circle and inside the solid circle is the protection refusal area under the fault in the area. Figure 3It was found that when the phase angle θa of the current ratio phasor on both sides of the dedicated line connected to new energy sources such as photovoltaic power generation is greater than 90°, the traditional current differential protection is prone to refusal to operate. In addition, it can be found that the smaller the ratio braking coefficient, the smaller the refusal to operate area will be, and the larger the protection action area will be. This means that the size of the ratio braking coefficient can reflect the action characteristics of the current differential protection. In fact, when the current on both sides of the protected line can be measured, the critical ratio braking coefficient K that can be obtained from the critical action curve is c .

[0051] Step 103: Determine whether the current differential protection of the protected line will fail to operate according to the critical ratio braking coefficient and the preset ratio braking coefficient.

[0052] Specifically, under normal operation of the power system, the ratio of the current phasors on both sides of the protected line usually presents a balanced state. Since the current phasor reflects not only the magnitude of the current but also the direction of the current, the sum of the current phasors on both sides of the line (i.e., the vector sum of the current phasors on both sides) is usually equal to zero during normal operation. This means that the currents on both sides of the line are equal in magnitude and opposite in direction, so their ratio (taking the direction into account) should theoretically be -1 (i.e., equal in magnitude but opposite in direction). However, in actual applications, this ratio may deviate due to factors such as line parameters, load distribution, and measurement errors, but it usually still fluctuates within an acceptable range.

[0053] When a fault occurs in the protected line, the current phasor ratio on both sides of the line will change significantly. These changes can vary depending on the type of fault:

[0054] Internal fault: When a fault occurs inside the line (such as a phase-to-phase short circuit or a ground short circuit), a short-circuit current will flow out of the fault point. At this time, if the positive direction of the current is specified as flowing from the busbar to the line, the sum of the current phasors on both sides of the line will be equal to the current phasor flowing into the fault point. Since the current directions on both sides of the fault point are the same (both flow to the fault point), the current phasor ratio on both sides of the line will be greater than 1 (that is, the currents on both sides are in phase and unequal in magnitude). In addition, due to the presence of the fault current, the measured impedance on both sides of the line will also change, usually manifested as a decrease in short-circuit impedance.

[0055] External fault: When a fault occurs outside the line (such as an adjacent line fault), although the fault point is not on the protected line, the fault current may flow in or out through the protected line's transformer and other equipment, so it may still affect the current phasor ratio on both sides of the line. However, unlike internal faults, the current phases on both sides of the line are usually opposite during external faults (that is, the phase difference is 180°), so the current phasor ratio on both sides of the line will be less than 1 (but not necessarily -1, because the magnitude and direction of the fault current may be affected by many factors). In addition, during external faults, the measured impedance on one side of the line may appear as a short-circuit impedance (the side where the fault current flows in), while the other side may still be a load impedance (the side where the fault current does not flow in).

[0056] In the longitudinal protection of transmission lines, the electrical quantity information (including current phasors) on both sides of the line is transmitted to the opposite side for comparison and judgment. By comparing the current phasor ratios on both sides of the line and other related electrical quantities (such as power direction, measurement impedance, etc.), it is possible to accurately determine whether the line has a fault and the type and location of the fault. This protection method is highly selective and sensitive, and can quickly remove the fault and protect the stable operation of the power system. Therefore, the current phasor ratio characteristics on both sides of the protected line are significantly different in normal operation and when a fault occurs. By monitoring and analyzing these characteristic changes, effective protection and fault location of the transmission line can be achieved.

[0057] The method in this embodiment obtains the current phasor ratio on both sides of the protected line according to the instantaneous current on both sides of the protected line, and obtains the critical ratio braking coefficient corresponding to the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line. The critical ratio braking coefficient can effectively reflect the boundary of the current differential protection. Therefore, judging whether a refusal to operate will occur based on the critical ratio braking coefficient can effectively improve the accuracy of the judgment.

[0058] In a specific embodiment, according to formula (4), the critical ratio braking coefficient is obtained by the following formula:

[0059] Among them, K c is the critical ratio braking coefficient, x is the abscissa of the current phasor ratio on both sides of the line, and y is the ordinate of the current phasor ratio on both sides of the line.

[0060] In a specific embodiment, judging whether the current differential protection of the protected line will fail to operate based on the critical ratio braking coefficient and the preset ratio braking coefficient includes: comparing the critical ratio braking coefficient and the preset ratio braking coefficient; if the critical ratio braking coefficient is less than or equal to the preset ratio braking coefficient, the current differential protection of the protected line will fail to operate, otherwise it will not fail to operate.

[0061] Specifically, the ratio braking coefficient determines the action characteristics of the differential protection. When the braking current increases, the differential current constant also increases at a certain ratio, thereby ensuring that the braking effect is enhanced in the case of external faults and the braking effect is minimal in the case of internal faults. The critical ratio braking coefficient refers to the ratio braking coefficient value when the differential protection starts to operate or loses the braking effect under specific conditions (such as CT saturation, large external fault current, etc.). It is a critical point used to distinguish the action behavior of the differential protection under different fault conditions. The critical ratio braking coefficient and the ratio braking coefficient are of great significance for the correct configuration and optimization of differential protection. Therefore, combined with the above formula (5), the judgment method for the existence of refusal to operate of the traditional current differential protection under intra-zone faults can be further obtained:

[0062] K c ≤K0 (6)

[0063] From the above formula, we can see that if the critical ratio braking coefficient K c If it is less than the ratio braking coefficient K0, the current differential protection will refuse to operate, otherwise the protection can operate correctly.

[0064] In a specific embodiment, in view of the situation where the conventional current differential protection refuses to operate, a protection improvement criterion is proposed, and the protection improvement criterion (preset differential protection condition) is obtained by the following formula:

[0065]

[0066] in, is the current phasor ratio on both sides of the line, j is an imaginary unit, f(K c ) is the preset target control function, K0 is the preset ratio braking coefficient, and is the instantaneous current on both sides of the protected line, I op The improved criterion in this embodiment can realize reliable and correct identification of faults inside and outside the zone when a high proportion of new energy stations are connected; in addition, combined with the existing traditional differential protection principle, it has good adaptability in various fault conditions.

[0067] In a specific embodiment, the method also includes: performing phase angle compensation on the current phasor ratio on both sides of the line according to a preset target control function; judging whether the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection condition; if the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection condition, the protected line performs differential protection action, otherwise the protected line does not perform differential protection action.

[0068] Specifically, when K c When the ratio braking coefficient K0 is less than or equal to the ratio braking coefficient K0, the traditional current differential protection will refuse to operate. From formula (7), it can be seen that in this case f(K c ) is less than 1. In the protection criterion proposed by the present invention, the current phasor ratio term on both sides of the line is compensated for the phase angle of -π / 2*f(K c ), thereby ensuring that the differential current is always greater than the braking current under intra-area faults, and solving the problem that the differential current is less than the braking current due to the current phase angle difference on both sides of the dedicated line connected to photovoltaic and other new energy power sources under intra-area faults is greater than π / 2. The proposed protection improvement criterion can reliably identify faults, avoid the problem of false operation of traditional current differential protection due to the large current phase angle difference on both sides of the line under intra-area faults after a high proportion of new energy stations are connected, and thus ensure that the protection can operate correctly and reliably when an intra-area fault occurs on the line after a high proportion of new energy stations are connected.

[0069] For the comparison diagram of the traditional differential protection action characteristic curve when the three-phase short-circuit fault occurs in this example area, please refer to Figure 4a For a comparison diagram of the action characteristic curves of improved differential protection, please refer to Figure 4b ,analyze Figure 4a It can be seen that when the photovoltaic power access capacity ratio is 3 / 5, when the ABC three-phase fault occurs in the area, the differential current I of the fault phase A of the traditional current differential protection is d Both are less than 0.6 times the braking current I r , does not meet the operating conditions of traditional current differential protection, and the protection refuses to operate; Figure 4b It can be seen that the improved current differential protection criterion is that the differential current of the fault phase A is greater than the product of 0.6 times the braking current, and the protection can operate normally.

[0070] For a comparison diagram of the characteristic curve of the traditional differential protection when the two-phase short-circuit fault occurs in the zone in this embodiment, please refer to Figure 5a For a comparison of the action characteristic curves of the improved differential protection, please refer to Figure 5b shown by Figure 5a and Figure 5bIt can be seen that when the photovoltaic power access capacity ratio is 3 / 5, when a two-phase short-circuit fault occurs in the area, the differential current of the traditional current differential protection is less than the product of the braking current and the ratio braking coefficient 0.6, and the protection refuses to operate; while the differential current of the improved protection is greater than 0.6 times the braking current, and the protection operates normally.

[0071] In the specific embodiments, see Figure 6 , is a structural schematic diagram of a current differential protection refusal identification system for a new energy station in the second embodiment of the present application, the system comprising: a current phasor ratio acquisition module 201, a critical ratio braking coefficient acquisition module 202 and a judgment module 203; the current phasor ratio acquisition module 201 is used to obtain the current phasor ratio on both sides of the protected line according to the instantaneous current on both sides of the protected line; the critical ratio braking coefficient acquisition module 202 is used to obtain the corresponding critical ratio braking coefficient on the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line; the judgment module 203 is used to judge whether the current differential protection of the protected line will refuse to operate according to the critical ratio braking coefficient and the preset ratio braking coefficient.

[0072] The system in this embodiment obtains the current phasor ratio on both sides of the protected line based on the instantaneous current on both sides of the protected line, and obtains the corresponding critical ratio braking coefficient on the critical action curve of the current differential protection based on the coordinate value of the current phasor ratio on both sides of the line. The critical ratio braking coefficient can effectively reflect the boundary of the current differential protection. Therefore, judging whether a refusal to operate will occur based on the critical ratio braking coefficient can effectively improve the accuracy of the judgment.

[0073] The system in this embodiment can also perform phase angle compensation on the current phasor ratio on both sides of the line according to a preset target control function; determine whether the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection condition; if the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection condition, the protected line performs differential protection action, otherwise the protected line does not perform differential protection action.

[0074] In a specific embodiment, the third embodiment of the present application provides a current differential protection refusal identification device for a new energy station, including a memory and a processor, characterized in that the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the method as described in any one of the first embodiments of the present application. The device in this embodiment obtains the current phasor ratio on both sides of the protected line according to the instantaneous current on both sides of the protected line, and obtains the corresponding critical ratio braking coefficient on the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line. The critical ratio braking coefficient can effectively reflect the boundary of the current differential protection, so judging whether a refusal to operate will occur according to the critical ratio braking coefficient can effectively improve the accuracy of the judgment.

[0075] In a specific embodiment, the fourth embodiment of the present application provides a computer-readable storage medium storing a computer program, and when the computer program is executed by a processor, the processor executes the steps of the method described in any one of the first embodiments of the present application. The storage medium in this embodiment obtains the current phasor ratio of the two sides of the protected line according to the instantaneous current on both sides of the protected line, and obtains the corresponding critical ratio braking coefficient on the critical action curve of the current differential protection according to the coordinate value of the current phasor ratio on both sides of the line. The critical ratio braking coefficient can effectively reflect the boundary of the current differential protection, so judging whether a refusal to operate will occur according to the critical ratio braking coefficient can effectively improve the accuracy of the judgment.

[0076] Figure 7 The internal structure of a computer device in one embodiment is shown. The computer device can be a terminal or a server. Figure 7 The computer device includes a processor, a memory, etc. connected via a system bus. The memory includes a non-volatile storage medium and an internal memory. The non-volatile storage medium of the computer device stores an operating system and may also store a computer program. When the computer program is executed by the processor, the processor can implement the method in this embodiment. The internal memory may also store a computer program. When the computer program is executed by the processor, the processor can implement the method in this embodiment. Those skilled in the art can understand that Figure 7 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0077] The above embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

[0078] The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for identifying refusal of current differential protection in a new energy station, characterized in that: The method comprises: Obtaining a current phasor ratio of two sides of the protected line according to instantaneous currents on two sides of the protected line; Obtaining a corresponding critical ratio braking coefficient on a current differential protection critical action curve according to the coordinate value of the current phasor ratio on both sides of the line; Whether the current differential protection of the protected line will fail to operate is determined based on the critical ratio braking coefficient and the preset ratio braking coefficient.

2. The method for identifying refusal of current differential protection of a new energy station according to claim 1, characterized in that: The step of obtaining the current phasor ratio of both sides of the protected line according to the instantaneous currents of both sides of the protected line includes: Acquire a first instantaneous current on one side of the protected line, and acquire a second instantaneous current on the other side of the protected line; comparing the current amplitudes of the first instantaneous current and the second instantaneous current; Taking the instantaneous current with a large current amplitude as the first target instantaneous current, and taking the instantaneous current with a small current amplitude as the second target instantaneous current; Acquire a first amplitude and a first phase angle of the first target instantaneous current, and acquire a second amplitude and a second phase angle of the second target instantaneous current; A phasor ratio of currents on both sides of the line is obtained according to the first amplitude, the first phase angle, the second amplitude and the second phase angle.

3. The method for identifying refusal of current differential protection of a new energy station according to claim 2, characterized in that: The current phasor ratio on both sides of the line is obtained by the following formula: in, is the current phasor ratio on both sides of the line, is the second target instantaneous current, is the first target instantaneous current, is the second amplitude, is the first amplitude, θ1 is the second phase angle, θ2 is the first phase angle, and A is and The ratio of θ d is the phase angle difference between θ2 and θ1.

4. The method for identifying refusal of current differential protection of a new energy station according to claim 1, characterized in that: The critical ratio braking coefficient is obtained by the following formula: Among them, K c is the critical ratio braking coefficient, x is the abscissa of the current phasor ratio on both sides of the line, and y is the ordinate of the current phasor ratio on both sides of the line.

5. The method for identifying refusal of current differential protection of a new energy station according to claim 1, characterized in that: The determining whether the current differential protection of the protected line will fail to operate according to the critical ratio braking coefficient and the preset ratio braking coefficient includes: Comparing the critical ratio braking coefficient with the preset ratio braking coefficient; If the critical ratio braking coefficient is less than or equal to the preset ratio braking coefficient, the current differential protection of the protected line will fail to operate, otherwise it will not fail to operate.

6. The method for identifying refusal of current differential protection of a new energy station according to claim 1, characterized in that: The method further comprises: Performing phase angle compensation on the current phasor ratio on both sides of the line according to a preset target control function; Determine whether the current phasor ratio on both sides of the line after phase angle compensation meets the preset differential protection conditions; If the current phasor ratio on both sides of the line after the phase angle compensation meets the preset differential protection condition, the protected line performs differential protection action, otherwise the protected line does not perform differential protection action.

7. The method for identifying refusal of current differential protection of a new energy station according to claim 1, characterized in that: The preset differential protection condition is obtained by using the following formula: in, is the current phasor ratio on both sides of the line, j is an imaginary unit, f(K c ) is the preset target control function, K0 is the preset ratio braking coefficient, and is the instantaneous current on both sides of the protected line, I op is the starting current value.

8. A current differential protection refusal identification system for a new energy station, characterized in that: The system comprises: a current phasor ratio acquisition module, a critical ratio braking coefficient acquisition module and a judgment module; The current phasor ratio acquisition module is used to acquire the current phasor ratio of both sides of the protected line according to the instantaneous currents on both sides of the protected line; The critical ratio braking coefficient acquisition module is used to acquire the corresponding critical ratio braking coefficient on the current differential protection critical action curve according to the coordinate value of the current phasor ratio on both sides of the line; The judgment module is used to judge whether the current differential protection of the protected line will fail to operate according to the critical ratio braking coefficient and the preset ratio braking coefficient.

9. A current differential protection refusal identification device for a new energy station, comprising a memory and a processor, characterized in that: The memory stores a computer program, and when the computer program is executed by the processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the processor is caused to perform the steps of the method according to any one of claims 1 to 7.

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