A superimposed power grid distance protection method and device for a high proportion of new energy power sources

Abstract

The application discloses a kind of superimposed power grid distance protection method and device for high proportion new energy power supply, method includes two specific schemes of "current amount superposition" method and "voltage amount superposition" method.This method is based on the equivalent of the power supply component of the power system containing high proportion new energy power supply, respectively using short-circuit current and short-circuit voltage measured by existing relay protection device, using superposition method, the distance between fault point and protection installation is calculated, and then the original distance protection principle is used to selectively remove the fault part, protect the normal operation of non-fault part of power grid.At the same time, the distance protection method can use the existing distance protection device without additional installation of equipment, only software extension.This method can effectively reduce the construction cost and operation cost of power system while effectively ensuring the safe operation of power system.

Description

TECHNICAL FIELD

[0001] The present application relates to a superimposed power grid distance protection method and device for a high proportion of new energy power sources, belonging to the field of power system relay protection. BACKGROUND

[0002] At present, the proportion of electricity in the terminal energy consumption of human society is becoming higher and higher, and the demand for electric energy is growing rapidly worldwide. At the same time, under the background of energy depletion and environmental pollution caused by large-scale consumption of fossil energy, new energy power generation has become an important development direction of global energy strategy transformation.

[0003] With the large-scale grid connection of new energy power sources, the existing power grid power side tends to present a mixed power supply form of traditional generators and new energy power sources coexisting, and the proportion of new energy power sources is continuously increasing.

[0004] After a line fault occurs in a power grid containing a large number of new energy power sources, the fault output current of the new energy power source is subject to its internal control strategy, and has a strong nonlinear relationship with the grid connection point voltage. And due to the line fault, the new energy power source usually limits or locks its output, resulting in a decrease in the line short-circuit current after the power system line fault, further reducing the grid connection point fault voltage, and as the proportion of new energy power sources in the power grid power supply increases, the line fault current value and the grid connection point fault voltage value also decrease. Under extreme conditions, new energy power sources constitute all power grid power sources and maintain low voltage ride-through, the fault current in the line and the grid voltage are no longer related.

[0005] In addition, there are a large number of power electronic devices in new energy power sources, such as grid-connected inverters in photovoltaic power sources and AC-DC-DC converters in wind turbine generators. And affected by the volatility and uncertainty of new energy, the output of new energy power sources changes frequently, even switching between grid-connected and off-grid states. This power conversion is achieved through the opening and closing of power electronic devices, during which the new energy power source generates a large amount of harmonics.

[0006] Traditional distance protection usually calculates the measured impedance by dividing the measured voltage and current at the protection installation site, and then calculates the fault distance to act. But as the proportion of new energy power sources increases, the measured current and voltage at the protection installation site decrease significantly after the power system line fault, and the traditional distance protection faces the mathematical problem of small value division and cannot accurately calculate.

[0007] In addition, due to the existence of a large number of harmonics caused by the control characteristics and internal power electronic devices of new energy power sources and the measurement error of the relay protection measuring device itself, the error of the fault distance measured by the traditional distance protection is further increased, which makes it difficult for the traditional distance protection to continue to be applicable, further threatening the normal and safe operation of the power grid. Summary of the Invention

[0008] The purpose of this invention is to provide a superimposed grid distance protection method and device for high proportion of new energy power sources, which is beneficial for calculating the distance from the fault point to the protection installation point, so that the improved distance protection can operate accurately.

[0009] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0010] In a first aspect, the present invention provides a superimposed grid distance protection method for high-proportion renewable energy power sources, comprising the following steps:

[0011] When a fault occurs, acquire circuit information;

[0012] Based on the circuit information, the distance from the corresponding fault point to the generator bus is calculated and obtained;

[0013] Based on the distance from the corresponding fault point to the generator bus, the distance protection of the corresponding circuit breaker will trip the fault.

[0014] Furthermore, the circuit information includes the fault current I flowing through the short-circuit point after a short-circuit fault occurs in the power system. k The voltage source value E of the equivalent conventional generator's internal potential, and the impedance value Z of the equivalent conventional generator's internal impedance. r The magnitude of the current source I represents the equivalent output current of the new energy power source after the fault.

[0015] Based on the circuit information, the method for calculating the distance from the corresponding fault point to the generator bus includes the "current superposition" method. This method is equivalent to traditional generators and new energy power sources on the power supply side of the power system. Based on the obtained parameters, the method relies solely on the magnitude of the fault current measured at the protection installation point after the power grid line fault to calculate the magnitude of the line impedance between the short-circuit point and the protection installation point, and further calculates the distance from the short-circuit point to the protection installation point.

[0016] Furthermore, the "current superposition" method includes the following steps:

[0017] Step 1: Measure the fault current I flowing through the short-circuit point after a short-circuit fault occurs in the power system. k ;

[0018] Step 2: According to the sub-power system where the current source exists alone, the following conditions must be met: (II) k1 )×Z r =I k1 ×Z, further calculated, yields the sub-current response I of the current source across the line impedance. k1 for:

[0019] Step three, according to the voltage source alone in the sub-power system to meet: E = I k2 × (Z r + Z), further obtained, the current source on the line impedance sub-current response I k2 :

[0020] Step four, according to the sum of the sub-current response is equal to the measured fault current after the line fault: I k = I k1 + I k2 Further obtained, the line impedance value between the protection installation and the fault point after the grid line fault:

[0021] Step five, the distance L from the fault point to the generator bus is calculated,

[0022]

[0023] Wherein, E is the value of the equivalent voltage source of the traditional generator; Z r is the internal impedance of the equivalent traditional generator; Z l is the impedance value per unit length of the power line;

[0024] Further, the fault current I k flowing through the short-circuit point can be directly measured by the existing relay protection measuring device, the value E of the equivalent voltage source of the internal potential of the traditional generator can be obtained from the traditional generator equipment nameplate parameters or experience, the impedance value Z r of the equivalent traditional generator internal impedance and the size I of the equivalent new energy power source output current after the fault can be obtained by a certain identification program.

[0025] Further, the circuit information includes the fault voltage U k at the protection installation, the value E of the equivalent voltage source of the internal potential of the equivalent traditional generator, the impedance value Z r of the equivalent traditional generator internal impedance and the size I of the equivalent new energy power source output current after the fault;

[0026] According to the circuit information, the method for calculating the distance from the corresponding fault point to the generator bus includes the "voltage superposition" method, on the basis of equivalent of the traditional generator and new energy power source on the power system power source side and obtaining the corresponding parameters, only relying on the size of the fault voltage measured at the protection installation after the line fault, the size of the line impedance between the short-circuit point and the protection installation is calculated, and the distance between the short-circuit point and the protection installation is further calculated.

[0027] Further, the "voltage superposition" method includes the following steps:

[0028] Step one, measure the fault voltage U at the protection installation after the short-circuit fault of the power system k ;

[0029] Step two, in the sub-power system where the current source exists alone, it satisfies: (I-I k1 )×Z r =I k1 ×Z, further, the sub-current response I k1 of the current source on the line impedance is: Then the sub-voltage response U k1 of the voltage source on the line impedance is:

[0030] Step three, in the sub-power system where the voltage source exists alone, it satisfies: E=I k2 ×(Z r +Z), further, the sub-current response I k2 of the current source on the line impedance is: Then the sub-voltage response U k2 of the voltage source on the line impedance is:

[0031] Step four, according to the sum of the sub-voltage responses being equal to the measured fault voltage after the line fault: U k =U k1 +U k2 , further, the line impedance value between the protection installation and the fault point after the power grid fault is obtained:

[0032] Step five, the distance L from the fault point to the generator bus is calculated

[0033]

[0034] In the formula, E is the value of the equivalent voltage source of the traditional generator; Z r is the equivalent internal impedance of the traditional generator; and Z l is the impedance value per unit length of the power line.

[0035] Further, the fault voltage U k at the protection installation can be directly measured by the existing relay protection measuring device, the value E of the voltage source representing the equivalent internal potential of the traditional generator can be obtained from the traditional generator equipment nameplate parameters or experience, and the impedance value Z r representing the equivalent internal impedance of the traditional generator and the size I of the current source representing the output current of the equivalent new energy power source after the fault can be obtained by a certain identification program.

[0036] Further, the impedance value Z r of the equivalent internal impedance of the traditional generator obtained by identificationThe method for determining the size I of the current source representing the output current of the equivalent new energy power source after the fault comprises:

[0037] The impedance value Z representing the equivalent internal impedance of the traditional generator after the fault r The two parameters of the size I of the current source representing the output current of the equivalent new energy power source after the fault and the value E of the voltage source representing the equivalent internal potential of the traditional generator after the fault are set as undetermined, and the measured fault voltage signal U is used k The fault current on the line can be represented as The difference between the represented fault current and the measured fault current is minimized, so that a target function is established, and the undetermined parameters are given lower and upper value constraints, and the formula is:

[0038]

[0039] In the formula, I min , I max are the minimum value and the maximum value of the size I of the current source representing the output current of the equivalent new energy power source after the fault, that is, the upper and lower limit constraints; Z rmin , Z rmax are the minimum value and the maximum value of the impedance value Z representing the equivalent internal impedance of the traditional generator after the fault, that is, the upper and lower limit constraints; r

[0040] The above problem is solved by an interior point method or other method for solving an optimal problem, and the impedance value Z representing the equivalent internal impedance of the traditional generator after the fault and the size I of the current source representing the output current of the equivalent new energy power source after the fault are obtained. r

[0041] In a second aspect, the application provides a superimposed power grid distance protection device for a high-proportion new energy power source, comprising:

[0042] A monitoring module: when a fault occurs, circuit information is obtained;

[0043] A distance calculation module: used for calculating the distance from the corresponding fault point to the generator bus according to the circuit information;

[0044] A protection action module: used for starting a protection interrupt service, that is, acting on the corresponding circuit breaker to remove the fault, and jumping to a recognition module.

[0045] In a third aspect, the application provides a superimposed power grid distance protection device for a high-proportion new energy power source, comprising a processor and a storage medium;

[0046] The storage medium is used for storing instructions;

[0047] The processor is used for operating according to the instructions to perform the steps of the method of the first aspect. ​​

[0048] Compared with the prior art, the present application has the following beneficial effects:

[0049] 1. The superimposed power grid distance protection method for high-proportion new energy power sources provided by the present application is applicable to a power system containing a large amount of new energy power generation, can equivalently process the existing power system, establish a simple circuit structure, calculate the distance from the fault point to the protection installation site according to the equivalent power system structure and the measured current or voltage information, and enable the improved distance protection to accurately act.

[0050] 2. The superimposed power grid distance protection method for high-proportion new energy power sources provided by the present application is applicable to a power system containing a large amount of new energy power generation, can effectively solve the problem that the short-circuit current flowing through the short-circuit point and the short-circuit voltage measured at the protection installation site are too small due to the large amount of new energy power source grid connection, and a large amount of harmonics caused by frequent opening of the internal power electronic device of the new energy power source, thereby leading to inaccurate calculation of the traditional distance protection and further difficulty in accurate action. The distance protection provided by the present application is applicable to a power system containing a large amount of new energy power generation, can accurately calculate the distance from the short-circuit point to the protection installation site on the basis of equivalently processing the power system, and provide a basis for the action of the distance protection.

[0051] 3. The superimposed power grid distance protection method for high-proportion new energy power sources provided by the present application can fully utilize the existing traditional relay protection device, does not need to install an additional hardware device, can reduce the construction and operation cost of the power system while ensuring the accurate action of the relay protection. BRIEF DESCRIPTION OF DRAWINGS

[0052] Figure 1 It is a schematic diagram of a traditional power system structure;

[0053] Figure 2 It is a schematic diagram of a new type of power system structure;

[0054] Figure 3 It is a schematic diagram of the power source side equivalent power system structure;

[0055] Figure 4 It is a schematic diagram of a superimposed power grid distance protection method for high-proportion new energy power sources. DETAILED DESCRIPTION

[0056] The present application will be further explained and described in detail below in combination with the drawings and specific embodiments, but it should be understood that the protection scope of the present application is not limited by the specific embodiments.

[0057] Embodiment one:

[0058] The present embodiment provides a superimposed power grid distance protection method for high-proportion new energy power sources, comprising the following steps:

[0059] When a fault occurs, acquire circuit information;

[0060] Based on the circuit information, the distance from the corresponding fault point to the generator bus is calculated and obtained;

[0061] Based on the distance from the corresponding fault point to the generator bus, the distance protection of the corresponding circuit breaker will trip the fault.

[0062] like Figure 1 As shown in the diagram, the traditional power system consists only of traditional generators on the power supply side (the impact of a very small number of new energy power sources on distance protection calculations can be ignored). When viewed from the protection installation point towards the power supply side, all traditional generators on the power supply side can be considered as a single traditional generator. After a short-circuit fault occurs in the power grid line, the short-circuit current flowing through the short-circuit point is entirely provided by the traditional generator.

[0063] like Figure 2 As shown in the schematic diagram of the new power system structure, a large number of new energy power sources are connected to the grid in the new power system. The power source side of the grid presents a mixed form of traditional generators and new energy power sources. From the perspective of the protection installation point, all traditional generators on the power source side can be equivalent to one traditional generator, and all new energy power sources on the power source side can be equivalent to one new energy power source. After a short circuit fault occurs in the grid line, the short circuit current flowing through the short circuit point is jointly provided by traditional generators and new energy power sources.

[0064] In power systems with a large proportion of renewable energy sources, after a line short-circuit fault, the renewable energy source typically limits its output to protect internal power electronic devices from damage. This results in a significantly lower fault output current for the renewable energy source compared to a traditional generator of equivalent capacity. As the proportion of renewable energy sources in the power system increases, the fault current flowing through the short-circuit point also decreases, leading to a smaller fault voltage measured at the protection installation point. Traditional distance protection methods, which calculate the fault distance by dividing the fault voltage and current measured at the protection installation point, face the challenge of mathematically minimizing the calculation and resulting in significant errors. Furthermore, the output of renewable energy sources fluctuates with the renewable energy supply. Because its output is controlled by internal power electronic converters, the power electronic devices frequently switch on and off, introducing numerous harmonics. Combined with the measurement errors inherent in the protection measurement devices themselves, the calculation error of traditional distance protection methods further increases, making them unsuitable for new power systems with a large number of renewable energy sources.

[0065] like Figure 3As shown in the equivalent power system structure diagram of the power supply side, after a short-circuit fault occurs in the power grid line, the traditional generator undergoes a short transient state and a transient state process, and then enters a steady state process. In the analysis and calculation of the power system, the traditional generator mainly provides a voltage quantity. Therefore, the traditional generator on the power supply side can be equivalent to a voltage source in series with an impedance, wherein the size of the voltage source represents the internal potential of the traditional generator, and the size of the impedance in series represents the internal impedance of the traditional generator. After a short-circuit fault occurs in the power grid line, the new energy power supply undergoes a very short time and then outputs stably. In the analysis and calculation of the power system, the new energy power supply mainly provides a current quantity. Therefore, the new energy power supply on the power supply side can be equivalent to a current source, and the size of the current source represents the output current size of the new energy power supply.

[0066] Specifically, the superimposed power grid distance protection method for high-proportion new energy power supply is characterized in that, based on a certain identification procedure, the value of the impedance in series with the voltage source in the equivalent circuit of the power system (the impedance value represents the internal impedance of the equivalent traditional generator on the power supply side of the power system) and the current value of the current source (the impedance value represents the output current size of the equivalent new energy power supply on the power supply side of the power system) can be identified, and the size of the voltage source can be obtained from the nameplate parameters of the traditional generator equipment or experience (the size of the voltage source represents the internal potential of the equivalent traditional generator on the power supply side of the power system).

[0067] Specifically, the superimposed power grid distance protection method for high-proportion new energy power supply is characterized in that: according to the superposition theorem, the equivalent power system is divided into two sub-equivalent power systems of a current source existing alone and a voltage source existing alone by setting the voltage source and the current source to zero respectively, and the response of the original system is equal to the sum of the responses of the two sub-equivalent power systems.

[0068] Specifically, the superimposed power grid distance protection method for high-proportion new energy power supply is characterized in that the "current superposition" method specifically calculates the size of the line impedance between the short-circuit point and the protection installation, and further calculates the distance from the short-circuit point to the protection installation, only by relying on the size of the fault current measured at the protection installation after the fault of the power grid line, on the basis of the equivalent of the traditional generator and the new energy power supply on the power supply side of the power system and the acquisition of the corresponding parameters.

[0069] The "current superposition" method is characterized in that the mathematical calculation steps are as follows:

[0070] Step one, measure the fault current I flowing through the short-circuit point after a short-circuit fault occurs in the power system k ;

[0071] Step two, according to the sub-power system in which the current source exists alone, satisfy: (I-I k1 )×Zr = I k1 × Z, further obtain the sub-current response I of the current source on the line impedance k1 = I

[0072] Step three, according to the sub-power system where the voltage source exists alone, meet: E = I k2 × (Z r + Z), further obtain the sub-current response I of the current source on the line impedance k2 = I

[0073] Step four, according to the sum of the sub-current responses equal to the measured fault current after the line fault: I k = I k1 + I k2 Further obtain the line impedance value between the protection installation and the fault point after the grid line fault:

[0074] Step five, calculate the distance L from the fault point to the generator bus, and (E is the value of the equivalent voltage source of the traditional generator; Z r is the equivalent internal impedance of the traditional generator; Z l is the impedance value per unit length of the power line);

[0075] Step six, according to the distance L from the corresponding fault point to the generator bus, the distance protection of the corresponding circuit breaker is removed;

[0076] The "current superposition" method has the characteristics that the fault current I k flowing through the short-circuit point can be directly measured by the existing relay protection measuring device, the value E of the equivalent voltage source representing the internal potential of the equivalent traditional generator can be obtained from the traditional generator equipment nameplate parameters or experience, the impedance value Z r representing the equivalent internal impedance of the traditional generator and the size I of the current source representing the output current of the equivalent new energy power source after the fault can be obtained by a certain identification program.

[0077] Specifically, the method for identifying the impedance value Z r representing the equivalent internal impedance of the traditional generator and the size I of the current source representing the output current of the equivalent new energy power source after the fault includes:

[0078] The impedance value Z r representing the equivalent internal impedance of the traditional generator and the size I of the current source representing the output current of the equivalent new energy power source after the fault are set as undetermined, and the measured fault voltage signal U kAnd the value E of the voltage source representing the equivalent post-conventional generator internal potential obtained via experience or equipment nameplate parameters, the fault current on the line can be represented as So that the difference between the represented fault current and the measured fault current is minimized, thus establishing the objective function, and the to-be-measured parameters are constrained by upper and lower values, and the formula is:

[0079]

[0080] In the formula, I min , I max are the minimum and maximum values of the size I of the current source of the equivalent post-conventional generator output current, i.e., the upper and lower limit constraints; Z rmin , Z rmax are the minimum and maximum values of the impedance value Z r of the equivalent post-conventional generator internal impedance, i.e., the upper and lower limit constraints.

[0081] The above problem is solved by an interior point method or other optimal problem solving method to obtain the impedance value Z r of the equivalent post-conventional generator internal impedance and the size I of the current source of the equivalent post-conventional generator output current.

[0082] Specifically, the superimposed power grid distance protection method for high-proportion new energy power sources, characterized in that the "voltage quantity superposition" method specifically scheme is essentially equivalent to the traditional generator and the new energy power source on the power system power source side, and the corresponding parameters are obtained, and only the size of the fault voltage measured at the protection installation after the line fault is relied on to calculate the size of the line impedance between the short-circuit point and the protection installation, and further calculate the distance from the short-circuit point to the protection installation.

[0083] The "voltage quantity superposition" method specifically scheme, characterized in that the mathematical calculation steps are:

[0084] Step one, measure the fault voltage U k at the protection installation after the short-circuit fault of the power system occurs;

[0085] Step two, according to the sub-power system in which the current source exists alone, it satisfies: (I-I k1 )×Z r =I k1 ×Z, further obtained, the sub-current response I k1 of the current source on the line impedance is: Then the sub-voltage response U k1 on the line impedance is:

[0086] Step three, according to the sub-power system in which the voltage source exists alone, it satisfies: E=I k2 ×(Zr +Z), further obtain the sub-current response I k2 is: then the sub-voltage response U k2 of the voltage source on the line impedance is:

[0087] Step four, according to the sum of the sub-voltage response equal to the measured fault voltage after the line fault: U k =U k1 +U k2 Further obtain the line impedance value between the protection installation and the fault point after the grid line fault:

[0088] Step five, calculate the distance L from the fault point to the generator bus, and (wherein E is the value of the equivalent voltage source of the traditional generator; Z r is the equivalent internal impedance of the traditional generator; Z l is the impedance value per unit length of the power line);

[0089] Step six, according to the distance L from the corresponding fault point to the generator bus, the distance protection action of the corresponding circuit breaker is removed;

[0090] The specific scheme of the "voltage superposition" method is characterized in that the fault voltage U k at the protection installation can be directly measured by the existing relay protection measuring device, the value E of the voltage source representing the internal potential of the equivalent traditional generator can be obtained from the traditional generator equipment nameplate parameters or experience, the impedance value Z r representing the equivalent internal impedance of the traditional generator and the size I of the current source representing the output current of the equivalent new energy power source after the fault can be obtained by a certain identification program.

[0091] It should be noted that the power system fault of the embodiment is a three-phase symmetrical short circuit fault, and the power transmission line model is regarded as "a type", that is, the product of the distance L between the fault point and the protection installation and the impedance Z l per unit length of the power line is the line impedance between the short circuit point and the protection installation.

[0092] Embodiment two:

[0093] The embodiment provides a superimposed grid distance protection device for a high proportion of new energy power sources, comprising:

[0094] The monitoring module acquires circuit information when a fault occurs;

[0095] The distance calculation module is used to calculate the distance from the corresponding fault point to the generator bus according to the circuit information;

[0096] Protection action module: for starting protection interruption service, i.e. action on corresponding circuit breaker action to remove fault, and jump to identification module.

[0097] The device of the embodiment can be applied to implement the method described in embodiment one.

[0098] Embodiment three:

[0099] The embodiment provides a superimposed power grid distance protection device for a high-proportion new energy power source, including a processor and a storage medium.

[0100] The storage medium is used for storing instructions.

[0101] The processor is used for operating according to the instructions to perform the steps of the method described in embodiment one.

[0102] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the protection scope of the present application.

[0103] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer usable program code.

[0104] These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are performed on the computer or other programmable device to generate a computer implemented process, and the instructions executed on the computer or other programmable device provide a process for implementing the functions specified in one or more flows Figure 1 one flow or multiple flows and / or the functions specified in one or more blocks Figure 1 one block or multiple blocks.

[0105] The above only describes the preferred embodiments of the present application, and it should be noted that for those skilled in the art, without departing from the technical principles of the present application, a number of improvements and modifications can be made, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A superimposed power grid distance protection method for a high proportion of new energy power sources, characterized in that, Comprising the following steps: When a fault occurs, obtain circuit information; According to the circuit information, calculate the distance from the corresponding fault point to the generator bus; According to the distance from the corresponding fault point to the generator bus, the distance protection of the corresponding circuit breaker is actuated to remove the fault; The circuit information includes a fault current flowing through a short-circuit point after a short-circuit fault occurs in the power system a value of a voltage source equivalent to an internal potential of a conventional generator an impedance value of an impedance equivalent to an internal impedance of a conventional generator and a size of a current source representing an output current of an equivalent new energy power source after a fault ​ The method for calculating the distance from the corresponding fault point to the generator bus according to the circuit information includes the "current superposition" method, which is equivalent to the traditional generator and new energy power source on the power supply side of the power system, and only relies on the size of the fault current measured at the protection installation after the grid line fault to calculate the size of the line impedance between the short-circuit point and the protection installation, and further calculates the distance from the short-circuit point to the protection installation; The "current superposition" method comprises the following steps: Measuring the fault current flowing through a short circuit point after a short circuit fault in a power system ; According to the current source existing alone in the sub-power system, it is satisfied that: Further, the sub-current response of the current source on the line impedance is obtained as: ;​ According to the voltage source existing alone in the sub-power system, it is satisfied that: Further, the sub-current response of the current source on the line impedance is obtained as: ;​ According to the sum of the sub-current responses being equal to the measured fault current after the line fault: Further, the line impedance value between the protection installation and the fault point after the grid line fault is obtained: ; Step five, calculate the distance from the fault point to the generator bus , ; wherein Z is the impedance value per length of the power line; Fault current flowing through the short circuit point The value of the voltage source representing the equivalent post-fault internal voltage of the conventional generator The value of the impedance representing the equivalent post-fault internal impedance of the conventional generator And the size of the current source representing the output current of the equivalent post-fault new energy source Obtained by identification.

2. A superimposed power grid distance protection method for a high proportion of new energy power sources, characterized in that, Comprising the following steps: When a fault occurs, obtain circuit information; According to the circuit information, calculate the distance from the corresponding fault point to the generator bus; According to the distance from the corresponding fault point to the generator bus, the distance protection of the corresponding circuit breaker is actuated to remove the fault; said circuit information comprises a fault voltage at the point of installation a value of a voltage source equivalent to the internal voltage of the conventional generator an impedance value of an impedance equivalent to the internal impedance of the conventional generator and a size of a current source equivalent to the output current of the new energy power source after the fault ; The method for calculating the distance from the corresponding fault point to the generator bus according to the circuit information includes the "voltage superposition" method, which is equivalent to the traditional generator and new energy power source on the power supply side of the power system, and only relies on the size of the fault voltage measured at the protection installation after the grid line fault to calculate the size of the line impedance between the short-circuit point and the protection installation, and further calculates the distance from the short-circuit point to the protection installation; The "voltage superposition" method comprises the following steps: Measuring the fault voltage at the installation of a protection after a short circuit fault in a power system ; According to the current source existing alone in the sub-power system, it is satisfied that: Further, the sub-current response of the current source on the line impedance is obtained as : The sub-voltage response on the line impedance is : ; According to the sub-power system where the voltage source exists alone, it is satisfied that: Further, the sub-current response of the current source on the line impedance is obtained as: The sub-voltage response of the voltage source on the line impedance is: ;​​ According to the sum of the sub-voltage responses being equal to the measured fault voltage after the line fault: , it is further obtained that the line impedance value between the protection installation and the fault point after the grid line fault: ; Step five, calculate the distance from the fault point to the generator bus : ; wherein is the value of the voltage source equivalent to the internal voltage of the conventional generator after the equivalence; is the value of the impedance equivalent to the internal impedance of the conventional generator after the equivalence; is the value of the impedance per unit length of the power line.

3. The power grid distance protection method of claim 2, characterized in that, Fault voltage at the point of protection The value of the voltage source representing the equivalent post-fault internal voltage of the conventional generator The value of the impedance representing the equivalent post-fault internal impedance of the conventional generator And the size of the current source representing the post-fault output current of the equivalent new energy source Obtained by identification.

4. The power grid distance protection method of claim 3, characterized in that, identifying an impedance value that is equivalent to an impedance of a conventional generator after a fault and a size of a current source of an output current of a new energy power source after a fault the method comprises: impedance value representing the equivalent post-fault generator internal impedance and the size of a current source representing the equivalent post-fault new energy source output current two parameters are set as undetermined, and the measured fault voltage signal is used and the value of a voltage source representing the equivalent post-fault generator internal voltage obtained via experience or equipment nameplate parameters the fault current on the line is represented as so that the difference between the represented fault current and the measured fault current is minimized, thereby establishing an objective function and giving the undetermined parameters an upper and lower value constraint, which is ; In the formula, , are the minimum and maximum values of the impedance value of the equivalent post-fault conventional generator impedance , i.e. the upper and lower limit constraints; , are the minimum and maximum values of the size of the current source of the equivalent post-fault new energy power output current , i.e. the upper and lower limit constraints; The above problem is solved by a method of solving an optimal problem by an interior point method to obtain an impedance value representing the impedance of the equivalent post-conventional generator and a size of a current source representing the output current of the equivalent post-new energy power source .

5. A superimposed power grid distance protection device for high proportion of new energy power sources for performing the method of any one of claims 1-4, characterized in that, Comprising: A monitoring module: when a fault occurs, obtain circuit information; A distance calculation module: for calculating the distance from the corresponding fault point to the generator bus according to the circuit information; A protection action module: for starting protection interrupt service, i.e. acting on the corresponding circuit breaker to remove the fault, and jumping to the identification module.

6. A superimposed power grid distance protection device for a high proportion of new energy power sources, characterized in that, Comprising a processor and a storage medium; The storage medium is used to store instructions; The processor is used to operate according to the instructions to perform the steps of the method of any one of claims 1-4.

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