A new energy power grid transmission line virtual voltage differential protection method and system

Abstract

The application discloses a new energy power grid transmission line virtual voltage differential protection method and system, belongs to the technical field of power system relay protection, and solves the problem of low sensitivity of traditional current differential protection caused by small short-circuit current amplitude of a new energy power grid transmission line; the technical scheme of the application is characterized in that: a two-end concentrated resistance segmented lossless line parameter model of the new energy power grid transmission line is established; three-phase voltages and three-phase currents at left and right ends of the new energy power grid transmission line are collected respectively; positive and negative zero sequence transformation matrices are used to calculate positive sequence voltages and positive sequence currents at left and right ends of the transmission line respectively; voltages at concentrated resistance points at left and right ends are calculated respectively; virtual voltages at the middle point of the transmission line are calculated according to the voltages at the concentrated resistance points at left and right ends; the two calculated virtual voltages are subtracted, and when the difference is greater than a pre-set differential voltage threshold value, it is determined that a fault occurs in the transmission line; the application can adapt to the rapid identification of the new energy power grid transmission line fault.

Description

Technical Field

[0001] This invention belongs to the field of power system relay protection technology, and relates to a virtual voltage differential protection method and system for new energy power grid transmission lines. Background Technology

[0002] In high-proportion renewable energy power systems, renewable energy generation, represented by wind and solar power, differs significantly from traditional synchronous power generation in terms of power generation principles, control methods, grid-connected equipment, and external characteristics. The dynamic characteristics of high-proportion renewable energy power systems exhibit entirely new and more complex dynamic features. Compared to traditional power systems dominated by synchronous generators, significant differences emerge in primary energy characteristics, the number and types of components, and time scales, leading to profound changes in system dynamic characteristics. The frequency stability characteristics of the entire system will undergo a qualitative transformation, stemming from the low inertia and weak frequency regulation capabilities of the generating units. As the proportion of conventional power sources decreases, the synchronous inertia level of the entire system will continuously decline. Inertia determines the rate of change of electrical quantities after a disturbance; a decrease in inertia will directly affect the frequency change rate and minimum frequency during system faults, thus impacting system stability.

[0003] The short-circuit current characteristics of new energy power grid transmission lines differ significantly from those of traditional power grids. New energy sources are connected to the grid directly or indirectly through power electronic converters. The short-circuit current of new energy power grid transmission lines is subject to converter current control, resulting in a short-term rise followed by a significant drop. At the initial moment of different faults, the rise is slow due to the influence of low-frequency periodic components, and the short-circuit current amplitude is small, possibly even lower than the rated current. Traditional current differential protection suffers from reduced sensitivity due to the small short-circuit current. When differential protection is applied to high-proportion new energy grid-connected systems, its operating performance deteriorates, and there is a risk of failure to operate. Therefore, there is an urgent need to develop new protection systems to quickly isolate faults in new energy power grid transmission lines. Summary of the Invention

[0004] The purpose of this invention is to design a virtual voltage differential protection method and system for new energy power grid transmission lines, so as to solve the problem of reduced sensitivity of traditional current differential protection caused by the small short-circuit current amplitude of new energy power grid transmission lines.

[0005] The present invention solves the above-mentioned technical problems through the following technical solutions: A method for virtual voltage differential protection of new energy power grid transmission lines includes the following steps: S1. Establish a segmented lossless line parameter model for the two ends of the new energy power grid transmission line with concentrated resistors; S2. Collect the three-phase voltage and three-phase current at the left and right ends of the new energy power grid transmission line respectively, and calculate the positive sequence voltage and positive sequence current at the left and right ends of the transmission line respectively using the positive and negative zero sequence transformation matrix. S3. Calculate the voltage at the concentrated resistor points on the left and right ends respectively; S4. Calculate the virtual voltage at the midpoint of the transmission line based on the voltage at the concentrated resistance points at the left and right ends respectively; S5. Calculate the difference between the two virtual voltages. When the difference is greater than the preset differential voltage threshold, determine that the transmission line has a fault.

[0006] Further, the method for establishing the segmented lossless line parameter model of the concentrated resistance at both ends of the new energy power grid transmission line in step S1 is as follows: The protected new energy power grid transmission line is divided into four segments. The positive sequence resistance per unit length of the transmission line is measured as R, the positive sequence inductance as L, the positive sequence capacitance as C, and the length of the transmission line is d. Then, the total resistance of the transmission line is... If the total resistance of the transmission line is concentrated and equally distributed across the left and right ends of the lossless line, then the concentrated resistance at the left end is... The right-end lumped resistor is The remaining lossless line is divided into two equal segments, and the midpoint X of the transmission line is taken as the virtual voltage calculation point.

[0007] Furthermore, the method for calculating the positive-sequence voltage and positive-sequence current at the left and right ends of the transmission line using the positive and negative zero-sequence transformation matrix in step S2 is as follows: (1) Collect the three-phase voltage and three-phase current at the left end of the transmission line, and calculate the positive sequence voltage U at the left end of the transmission line using the positive-negative-zero sequence transformation matrix. L+ and positive sequence current I L+ The calculation formula is as follows:

[0008]

[0009] in, , , These are the three-phase voltages (A, B, and C) at the left end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the left end of the transmission line, measured by current transformers. (2) Collect the three-phase voltage and three-phase current at the right end of the transmission line, and calculate the positive sequence voltage U at the right end of the transmission line using the positive-negative-zero sequence transformation matrix. R+ and positive sequence current I R+ The calculation formula is as follows:

[0010]

[0011] in, , , These are the three-phase voltages (A, B, and C) at the right end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the right end of the transmission line, measured by current transformers.

[0012] Furthermore, the method for calculating the voltage at the condensed resistance points at the left and right ends in step S3 is as follows: The formula for calculating the voltage at the condensed resistance point at the left end is: The formula for calculating the voltage at the right-hand condenser resistor point is: .

[0013] Furthermore, the method for calculating the virtual voltage at the midpoint of the transmission line based on the voltages at the concentrated resistance points at the left and right ends, as described in step S4, is as follows: (1) Using the voltage at the point of the concentrated resistor on the left end Calculated virtual voltage at the midpoint of the transmission line as follows:

[0014] (2) Utilize the voltage at the right-hand condenser resistor point Calculated virtual voltage at the midpoint of the transmission line as follows:

[0015] Where i is a mathematical imaginary number.

[0016] A virtual voltage differential protection system for transmission lines in a new energy power grid includes: a transmission line parameter model module, a positive sequence voltage and current calculation module, a concentrated resistance point voltage calculation module, a virtual voltage calculation module, and a differential judgment module; The aforementioned transmission line parameter model module is used to establish a segmented lossless line parameter model of the two ends of the transmission line of the new energy power grid with concentrated resistors. The positive sequence voltage and current calculation module is used to collect the three-phase voltage and three-phase current at the left and right ends of the new energy power grid transmission line, and calculate the positive sequence voltage and positive sequence current at the left and right ends of the transmission line using the positive and negative zero sequence transformation matrix. The lumped resistance point voltage calculation module is used to calculate the voltage at the lumped resistance points at the left and right ends, respectively. The virtual voltage calculation module is used to calculate the virtual voltage at the midpoint of the transmission line based on the voltage at the concentrated resistance points at the left and right ends, respectively. The differential judgment module is used to calculate the difference between the two virtual voltages calculated by the virtual voltage calculation module. When the difference is greater than the preset differential voltage threshold value, the transmission line is judged to have a fault.

[0017] Furthermore, the method for establishing the segmented lossless line parameter model of the new energy power grid transmission line with concentrated resistance at both ends, as described in the transmission line parameter model module, is as follows: The protected new energy power grid transmission line is divided into four segments. The positive sequence resistance per unit length of the transmission line is measured as R, the positive sequence inductance as L, the positive sequence capacitance as C, and the length of the transmission line as d. Then, the total resistance of the transmission line is... If the total resistance of the transmission line is concentrated and equally distributed across the left and right ends of the lossless line, then the concentrated resistance at the left end is... The right-end lumped resistor is The remaining lossless line is divided into two equal segments, and the midpoint X of the transmission line is taken as the virtual voltage calculation point.

[0018] Furthermore, the method described in the positive sequence voltage and current calculation module for calculating the positive sequence voltage and positive sequence current at the left and right ends of the transmission line using positive, negative, and zero sequence transformation matrices is as follows: (1) Collect the three-phase voltage and three-phase current at the left end of the transmission line, and calculate the positive sequence voltage U at the left end of the transmission line using the positive-negative-zero sequence transformation matrix. L+ and positive sequence current I L+ The calculation formula is as follows:

[0019]

[0020] in, , , These are the three-phase voltages (A, B, and C) at the left end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the left end of the transmission line, measured by current transformers. (2) Collect the three-phase voltage and three-phase current at the right end of the transmission line, and calculate the positive sequence voltage U at the right end of the transmission line using the positive-negative-zero sequence transformation matrix. R+ and positive sequence current I R+ The calculation formula is as follows:

[0021]

[0022] in, , , These are the three-phase voltages (A, B, and C) at the right end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the right end of the transmission line, measured by current transformers.

[0023] Furthermore, the method for calculating the voltage at the left and right ends of the concentrated resistance point, as described in the concentrated resistance point voltage calculation module, is as follows: The formula for calculating the voltage at the left end of the concentrated resistance point is: The formula for calculating the voltage at the right-hand condenser resistor point is: .

[0024] Furthermore, the method described in the virtual voltage calculation module for calculating the virtual voltage at the midpoint of the transmission line based on the voltages at the concentrated resistance points at the left and right ends is as follows: (1) Using the voltage at the point of the concentrated resistor on the left end Calculated virtual voltage at the midpoint of the transmission line as follows:

[0025] (2) Utilize the voltage at the right-hand condenser resistor point Calculated virtual voltage at the midpoint of the transmission line as follows:

[0026] Where i is a mathematical imaginary number.

[0027] The advantages of this invention are: The technical solution of this invention samples the voltage and current signals at both ends of a transmission line and uses a positive-negative-zero sequence transformation matrix to obtain the positive-sequence components of the line voltage and current. The equivalent resistance of the transmission line is centrally processed and divided into two parts, placed at both ends of the line. The remaining part is considered a lossless line and evenly divided into two parts. The midpoint of the transmission line is taken as the virtual voltage calculation point. The voltage and current at the left end of the lossless line are calculated using the voltage and current at the left end and the resistance at the left end. The virtual voltage at the midpoint of the lossless line is calculated using the steady-state equation of the lossless line. Similarly, the voltage and current at the right end of the lossless line are calculated using the voltage and current at the right end and the resistance at the left end. The virtual voltage at the midpoint of the lossless line is calculated using the steady-state equation of the lossless line. The virtual voltages calculated from both ends of the line to the midpoint are compared, and the difference between the virtual voltages is calculated. If the voltage difference is greater than a set threshold, a fault is considered to have occurred in the transmission line, and a trip command is issued to clear the fault. This technical solution of the invention quickly identifies faults by comparing the differences in the virtual voltages calculated at both ends, and can adapt to the rapid identification of faults in transmission lines of new energy power grids. Attached Figure Description

[0028] Figure 1 This is a flowchart of the virtual voltage differential protection method for new energy power grid transmission lines of the present invention; Figure 2 This is a structural diagram of the virtual voltage differential protection system for new energy power grid transmission lines of the present invention; Figure 3 This is a parameter model diagram of the new energy power grid transmission line of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments: Example 1 like Figure 1 As shown in the figure, a virtual voltage differential protection method for new energy power grid transmission lines in this embodiment includes the following steps: 1. Establish a segmented lossless line parameter model for the two ends of the new energy power grid transmission line with concentrated resistors. The specific method is as follows: like Figure 3 As shown, the protected new energy power grid transmission line is divided into four sections. The measured positive-sequence resistance per unit length of the transmission line is R, the positive-sequence inductance is L, the positive-sequence capacitance is C, and the length of the transmission line is d. Therefore, the total resistance of the transmission line is... If the total resistance of the transmission line is concentrated and equally distributed across the left and right ends of the lossless line, then the concentrated resistance at the left end is... The right-end lumped resistor is The remaining lossless line is divided into two equal segments, and the midpoint X of the transmission line is taken as the virtual voltage calculation point.

[0031] 2. Collect the three-phase voltage and three-phase current at the left and right ends of the new energy power grid transmission line, respectively. Calculate the positive-sequence voltage and positive-sequence current at the left and right ends of the transmission line using the positive-negative-zero sequence transformation matrix. The specific calculation formulas are as follows: (1) Collect the three-phase voltage and three-phase current at the left end of the transmission line, and calculate the positive sequence voltage U at the left end of the transmission line using the positive-negative-zero sequence transformation matrix. L+ and positive sequence current I L+ The calculation formula is as follows:

[0032]

[0033] in, , , These are the three-phase voltages (A, B, and C) at the left end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the left end of the transmission line, measured by current transformers. (2) Collect the three-phase voltage and three-phase current at the right end of the transmission line, and calculate the positive sequence voltage U at the right end of the transmission line using the positive-negative-zero sequence transformation matrix. R+ and positive sequence current I R+ The calculation formula is as follows:

[0034]

[0035] in, , , These are the three-phase voltages (A, B, and C) at the right end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the right end of the transmission line, measured by current transformers.

[0036] 3. Calculate the voltage at the condensed resistor points on both the left and right sides respectively; the formula for calculating the voltage at the condensed resistor point on the left side is: The formula for calculating the voltage at the right-hand condenser resistor point is: .

[0037] 4. Calculate the virtual voltage at the midpoint of the transmission line based on the voltages at the concentrated resistance points at the left and right ends. The specific calculation formula is as follows: (1) Using the voltage at the point of the concentrated resistor on the left end Calculated virtual voltage at the midpoint of the transmission line as follows:

[0038] (2) Utilize the voltage at the right-hand condenser resistor point Calculated virtual voltage at the midpoint of the transmission line as follows:

[0039] Where i is a mathematical imaginary number.

[0040] 5. Calculate the difference between the two virtual voltages obtained in step 4. When the difference is greater than the preset differential voltage threshold, the condition is met. When a fault is detected in the transmission line, the voltage threshold value is considered to be present. Preferred to , This refers to the rated voltage of the transmission line, such as a 110kV transmission line. If we take 110kV as the voltage threshold and apply it to the secondary side, then... Set it to 100V.

[0041] Example 2 like Figure 2 As shown in this embodiment, a virtual voltage differential protection system for a new energy power grid transmission line includes: a transmission line parameter model module, a positive sequence voltage and current calculation module, a concentrated resistance point voltage calculation module, a virtual voltage calculation module, and a differential judgment module. The aforementioned transmission line parameter model module is used to establish a segmented lossless transmission line parameter model with concentrated resistors at both ends of a new energy power grid transmission line. The specific method is as follows: like Figure 3 As shown, the protected new energy power grid transmission line is divided into four sections. The measured positive-sequence resistance per unit length of the transmission line is R, the positive-sequence inductance is L, the positive-sequence capacitance is C, and the length of the transmission line is d. Therefore, the total resistance of the transmission line is... If the total resistance of the transmission line is concentrated and equally distributed across the left and right ends of the lossless line, then the concentrated resistance at the left end is... The right-end lumped resistor is The remaining lossless line is divided into two equal segments, and the midpoint X of the transmission line is taken as the virtual voltage calculation point.

[0042] The positive sequence voltage and current calculation module is used to collect the three-phase voltage and three-phase current at the left and right ends of the new energy power grid transmission line, respectively, and calculate the positive sequence voltage and positive sequence current at the left and right ends of the transmission line using the positive and negative zero sequence transformation matrix. The specific calculation formula is as follows: (1) Collect the three-phase voltage and three-phase current at the left end of the transmission line, and calculate the positive sequence voltage U at the left end of the transmission line using the positive-negative-zero sequence transformation matrix. L+ and positive sequence current I L+ The calculation formula is as follows:

[0043]

[0044] in, , , These are the three-phase voltages (A, B, and C) at the left end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the left end of the transmission line, measured by current transformers. (2) Collect the three-phase voltage and three-phase current at the right end of the transmission line, and calculate the positive sequence voltage U at the right end of the transmission line using the positive-negative-zero sequence transformation matrix. R+ and positive sequence current I R+ The calculation formula is as follows:

[0045]

[0046] in, , , These are the three-phase voltages (A, B, and C) at the right end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the right end of the transmission line, measured by current transformers.

[0047] The lumped resistance point voltage calculation module is used to calculate the voltage at the lumped resistance points on the left and right sides respectively. The specific calculation formula is as follows: The calculation formula for the voltage at the lumped resistance point on the left side is: The formula for calculating the voltage at the right-hand condenser resistor point is: .

[0048] The virtual voltage calculation module is used to calculate the virtual voltage at the midpoint of the transmission line based on the voltages at the concentrated resistance points at the left and right ends. The specific calculation formula is as follows: (1) Using the voltage at the point of the concentrated resistor on the left end Calculated virtual voltage at the midpoint of the transmission line as follows:

[0049] (2) Utilize the voltage at the right-hand condenser resistor point Calculated virtual voltage at the midpoint of the transmission line as follows:

[0050] Where i is a mathematical imaginary number.

[0051] The differential determination module is used to calculate the difference between the two virtual voltages obtained by the virtual voltage calculation module. When the difference is greater than a preset differential voltage threshold, the condition is met. At that time, a fault is determined to have occurred in the transmission line. Voltage threshold value. Preferred to , This refers to the rated voltage of the transmission line, such as a 110kV transmission line. If we take 110kV as the voltage threshold and apply it to the secondary side, then... Set it to 100V.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A virtual voltage differential protection method for transmission lines in a new energy power grid, characterized in that, Includes the following steps: S1. Establish a parameter model for the segmented lossless line with concentrated resistors at both ends of the new energy power grid transmission line; S2. Collect the three-phase voltage and three-phase current at the left and right ends of the new energy power grid transmission line respectively, and calculate the positive sequence voltage and positive sequence current at the left and right ends of the transmission line respectively using the positive and negative zero sequence transformation matrix. S3. Calculate the voltage at the concentrated resistor points on the left and right ends respectively; S4. Calculate the virtual voltage at the midpoint of the transmission line based on the voltage at the concentrated resistance points at the left and right ends respectively; S5. Calculate the difference between the two virtual voltages. When the difference is greater than the preset differential voltage threshold, determine that the transmission line has a fault.

2. The virtual voltage differential protection method for new energy power grid transmission lines according to claim 1, characterized in that, The method for establishing the segmented lossless line parameter model of the concentrated resistance at both ends of the new energy power grid transmission line in step S1 is as follows: The protected new energy power grid transmission line is divided into four segments. The positive sequence resistance per unit length of the transmission line is measured as R, the positive sequence inductance as L, the positive sequence capacitance as C, and the length of the transmission line is d. Then, the total resistance of the transmission line is... If the total resistance of the transmission line is concentrated and equally distributed across the left and right ends of the lossless line, then the concentrated resistance at the left end is... The right-end lumped resistor is The remaining lossless line is divided into two equal segments, and the midpoint X of the transmission line is taken as the virtual voltage calculation point.

3. The virtual voltage differential protection method for new energy power grid transmission lines according to claim 2, characterized in that, The method for calculating the positive sequence voltage and positive sequence current at the left and right ends of the transmission line using the positive and negative zero sequence transformation matrix in step S2 is as follows: (1) Collect the three-phase voltage and three-phase current at the left end of the transmission line, and calculate the positive sequence voltage U at the left end of the transmission line using the positive-negative-zero sequence transformation matrix. L+ and positive sequence current I L+ The calculation formula is as follows: in, , , These are the three-phase voltages (A, B, and C) at the left end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the left end of the transmission line, measured by current transformers. (2) Collect the three-phase voltage and three-phase current at the right end of the transmission line, and calculate the positive sequence voltage U at the right end of the transmission line using the positive-negative-zero sequence transformation matrix. R+ and positive sequence current I R+ The calculation formula is as follows: in, , , These are the three-phase voltages (A, B, and C) at the right end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the right end of the transmission line, measured by current transformers.

4. The virtual voltage differential protection method for new energy power grid transmission lines according to claim 3, characterized in that, The method for calculating the voltage at the lumped resistance points on the left and right ends in step S3 is as follows: The formula for calculating the voltage at the lumped resistance point on the left end is: The formula for calculating the voltage at the right-hand condenser resistor point is: .

5. The virtual voltage differential protection method for new energy power grid transmission lines according to claim 4, characterized in that, The method for calculating the virtual voltage at the midpoint of the transmission line based on the voltages at the concentrated resistance points at the left and right ends, as described in step S4, is as follows: (1) Utilize the voltage at the point of the concentrated resistor on the left end Calculated virtual voltage at the midpoint of the transmission line as follows: (2) Utilize the voltage at the right-hand condenser resistor point Calculated virtual voltage at the midpoint of the transmission line as follows: in, The length of the transmission line, It is a positive sequence inductor. It is a positive sequence capacitor. This represents the positive sequence current at the left end of the transmission line. This represents the positive sequence current at the right end of the transmission line. The voltage at the point where the resistor is concentrated on the left is the voltage. Let be the voltage at the point where the resistor is concentrated on the right end, and i be a mathematical imaginary number.

6. A virtual voltage differential protection system for new energy power grid transmission lines, characterized in that, include: Transmission line parameter model module, positive sequence voltage and current calculation module, lumped resistance point voltage calculation module, virtual voltage calculation module, differential judgment module; The aforementioned transmission line parameter model module is used to establish a segmented lossless line parameter model of the two ends of the transmission line of the new energy power grid with concentrated resistors. The positive sequence voltage and current calculation module is used to collect the three-phase voltage and three-phase current at the left and right ends of the new energy power grid transmission line, and calculate the positive sequence voltage and positive sequence current at the left and right ends of the transmission line using the positive and negative zero sequence transformation matrix. The lumped resistance point voltage calculation module is used to calculate the voltage at the lumped resistance points at the left and right ends, respectively. The virtual voltage calculation module is used to calculate the virtual voltage at the midpoint of the transmission line based on the voltage at the concentrated resistance points at the left and right ends, respectively. The differential judgment module is used to calculate the difference between the two virtual voltages calculated by the virtual voltage calculation module. When the difference is greater than the preset differential voltage threshold value, the transmission line is judged to have a fault.

7. A virtual voltage differential protection system for new energy power grid transmission lines according to claim 6, characterized in that, The method for establishing the segmented lossless line parameter model of the new energy power grid transmission line with concentrated resistance at both ends, as described in the transmission line parameter model module, is as follows: The protected new energy power grid transmission line is divided into four segments. The positive sequence resistance per unit length of the transmission line is measured as R, the positive sequence inductance as L, the positive sequence capacitance as C, and the length of the transmission line is d. Then, the total resistance of the transmission line is... If the total resistance of the transmission line is concentrated and equally distributed across the left and right ends of the lossless line, then the concentrated resistance at the left end is... The right-end lumped resistor is The remaining lossless line is divided into two equal segments, and the midpoint X of the transmission line is taken as the virtual voltage calculation point.

8. A virtual voltage differential protection system for new energy power grid transmission lines according to claim 7, characterized in that, The method for calculating the positive sequence voltage and positive sequence current at the left and right ends of a transmission line using positive, negative, and zero sequence transformation matrices, as described in the positive sequence voltage and current calculation module, is as follows: (1) Collect the three-phase voltage and three-phase current at the left end of the transmission line, and calculate the positive sequence voltage U at the left end of the transmission line using the positive-negative-zero sequence transformation matrix. L+ and positive sequence current I L+ The calculation formula is as follows: in, , , These are the three-phase voltages (A, B, and C) at the left end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the left end of the transmission line, measured by current transformers. (2) Collect the three-phase voltage and three-phase current at the right end of the transmission line, and calculate the positive sequence voltage U at the right end of the transmission line using the positive-negative-zero sequence transformation matrix. R+ and positive sequence current I R+ The calculation formula is as follows: in, , , These are the three-phase voltages (A, B, and C) at the right end of the transmission line, measured by a voltage transformer. , , These are the three-phase currents A, B, and C at the right end of the transmission line, measured by current transformers.

9. A virtual voltage differential protection system for new energy power grid transmission lines according to claim 8, characterized in that, The method for calculating the voltage at the left and right ends of the concentrated resistance point, as described in the concentrated resistance point voltage calculation module, is as follows: The formula for calculating the voltage at the left end of the concentrated resistance point is: The formula for calculating the voltage at the right-hand condenser resistor point is: .

10. A virtual voltage differential protection system for new energy power grid transmission lines according to claim 9, characterized in that, The method described in the virtual voltage calculation module for calculating the virtual voltage at the midpoint of the transmission line based on the voltages at the concentrated resistance points at the left and right ends is as follows: (1) Utilize the voltage at the point of the concentrated resistor on the left end Calculated virtual voltage at the midpoint of the transmission line as follows: (2) Utilize the voltage at the right-hand condenser resistor point Calculated virtual voltage at the midpoint of the transmission line as follows: in, The length of the transmission line, It is a positive sequence inductor. It is a positive sequence capacitor. This represents the positive sequence current at the left end of the transmission line. This represents the positive sequence current at the right end of the transmission line. The voltage at the point where the resistor is concentrated on the left is the voltage. Let be the voltage at the point where the resistor is concentrated on the right end, and i be a mathematical imaginary number.

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