A photovoltaic power supply power distribution network protection method and device based on corrected short-circuit current, a terminal device and a storage medium

Abstract

The application discloses a photovoltaic power supply distribution network protection method and device based on a corrected short-circuit current, a terminal device and a storage medium, and belongs to the technical field of power systems. The method comprises the following steps: recording a short-circuit fault time and photovoltaic power supply inverter parameters in the case that a short-circuit fault occurs in a photovoltaic power supply distribution network; collecting meteorological data and load data of each node in the distribution network before and after the short-circuit fault time; calculating the inverter voltage after the short-circuit fault based on the meteorological data and the load data of each node before and after the short-circuit fault time; taking the inverter voltage after the short-circuit fault as an independent variable, and calculating the inverter short-circuit current through a current function corresponding to a voltage segmented interval; performing current limiting correction on the inverter short-circuit current to obtain the inverter corrected short-circuit current; and performing corresponding protection actions based on the inverter corrected short-circuit current. Therefore, through implementation of the application, the problem of low accuracy of power grid protection actions existing in the prior art can be solved.

Description

Technical Field

[0001] This invention relates to the field of power distribution network technology, and in particular to a photovoltaic power distribution network protection method, device, terminal equipment, and storage medium based on corrected short-circuit current. Background Technology

[0002] In modern power systems, with the development of photovoltaic (PV) power generation technology, the participation of PV power sources in distribution networks has increased. Because the nature of PV power differs from that of traditional power sources, the nature of the distribution networks in which PV power sources participate also differs. Distribution network protection requires calculating the short-circuit current of the inverter, selecting protection action strategies based on this current, and then implementing these strategies to protect the distribution network. However, the fixed power source model used in traditional calculation methods is not applicable to the voltage support, reactive power priority, and current limiting control characteristics of PV inverters during the low-voltage ride-through (LVRT) process. Therefore, it is impossible to calculate the accurate short-circuit current of the PV inverter, and thus impossible to select and execute the correct protection action, resulting in low accuracy of grid protection actions. Summary of the Invention

[0003] This invention provides a photovoltaic power distribution network protection method, device, terminal equipment, and storage medium based on corrected short-circuit current, which can solve the problem of low accuracy of grid protection actions in the prior art.

[0004] The present invention provides a photovoltaic power distribution network protection method based on modified short-circuit current, comprising: recording the time of the short-circuit fault and the parameters of the photovoltaic power inverter when a short-circuit fault occurs in the photovoltaic power distribution network; wherein, the photovoltaic power inverter parameters include: current saturation threshold voltage and reactive power compensation coefficient; Collect meteorological data of photovoltaic power sources in the distribution network before and after the short-circuit fault, as well as load data of each node; The inverter voltage after the photovoltaic power supply short circuit fault is calculated based on the meteorological data of the photovoltaic power supply in the distribution network before and after the short circuit fault and the load data of each node. Voltage segmentation intervals are set based on the current saturation threshold voltage; the current function corresponding to each segment interval is set based on the reactive power compensation coefficient and the inverter voltage after a photovoltaic power supply short circuit fault. Using the inverter voltage after a photovoltaic power supply short-circuit fault as the independent variable, the short-circuit current of the photovoltaic power supply inverter is calculated through the current function of the corresponding voltage segment interval. The short-circuit current of the photovoltaic power inverter is corrected by current limiting correction to obtain the corrected short-circuit current of the photovoltaic power inverter. The photovoltaic power inverter corrects the short-circuit current and executes corresponding protection actions.

[0005] Furthermore, the calculation of the inverter voltage after the photovoltaic power supply short-circuit fault based on meteorological data of the photovoltaic power supply in the distribution network before and after the short-circuit fault and load data of each node includes: The active and reactive power of the photovoltaic power source before and after the short circuit fault are calculated based on the meteorological data of the photovoltaic power source in the distribution network before and after the short circuit fault. Initialize the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before and after the short circuit fault. Based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initial voltage amplitude of each node, the initial voltage phase of each node, the initial active power injection of each node, and the initial reactive power injection of each node, the voltage amplitude and voltage phase of each node after the short-circuit fault are solved by the fast decoupling power flow method. Calculate the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault. The inverter voltage after a short-circuit fault in a photovoltaic power source is calculated based on the voltage phasors of each node after the short-circuit fault.

[0006] Furthermore, the calculation of the inverter voltage after the photovoltaic power supply short-circuit fault based on the voltage phasors of each node after the short-circuit fault includes: Extract the voltage phasor of the fault node from the voltage phasors of each node after the short-circuit fault. A composite sequence network is constructed based on the voltage phasors of the fault node using the symmetrical component method; the three-phase voltage increment of the fault node is calculated based on the composite sequence network. Calculate the three-phase voltage increment of the inverter after a short-circuit fault in a photovoltaic power source based on the three-phase voltage increment at the fault node. Calculate the three-phase voltage of the inverter after a photovoltaic power supply short-circuit fault based on the three-phase voltage increment of the inverter after the photovoltaic power supply short-circuit fault. The inverter voltage after a photovoltaic power supply short circuit fault is obtained by inverse transformation of the three-phase voltage of the inverter through symmetrical component transformation.

[0007] Furthermore, the short-circuit current of the photovoltaic power inverter is calculated using the following formula: ; In the formula, I IIDG U is the short-circuit current of the photovoltaic power inverter. IIDG U is the inverter voltage after a short-circuit fault in the photovoltaic power supply. IIDG(0) The inverter voltage before the photovoltaic power supply short-circuit fault; I max U is the maximum allowable current of the inverter. t1 I is the current saturation threshold voltage; MP0 represents the active current of the photovoltaic power source before the fault; K is the reactive power compensation coefficient; and P0 is the active power of the photovoltaic power source before the short-circuit fault.

[0008] Furthermore, the corrected short-circuit current of the photovoltaic power inverter is obtained by current limiting correction using the following formula: ; In the formula, I corr Correcting short-circuit current in photovoltaic power inverters; I lim This is the current limiting value; S N Rated capacity of photovoltaic power supply; U N This is the rated voltage of the power distribution network.

[0009] Furthermore, the step of performing corresponding protection actions based on the correction of short-circuit current by the photovoltaic power inverter includes: The total short-circuit current of the photovoltaic power inverter is obtained by superimposing the corrected short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault with the short-circuit current of other power sources. When the total short-circuit current of the photovoltaic power distribution network exceeds the preset first current safety threshold at the time of the short-circuit fault, the upstream switch of the photovoltaic power source is disconnected; otherwise, the inverter step-down control is activated.

[0010] Another embodiment of the present invention provides a photovoltaic power distribution network protection device based on corrected short-circuit current, including: a fault identification module, a data acquisition module, a voltage calculation module, a function setting module, a current calculation module, a current correction module, and a power grid protection module; The fault identification module is used to record the time of the short circuit fault and the parameters of the photovoltaic power inverter when a short circuit fault occurs in the photovoltaic power distribution network; wherein, the photovoltaic power inverter parameters include: current saturation threshold voltage and reactive power compensation coefficient. The data acquisition module is used to collect meteorological data of photovoltaic power sources and load data of each node in the distribution network before and after the short-circuit fault. The voltage calculation module is used to calculate the inverter voltage of the photovoltaic power source after the short circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before the short circuit fault and the load data of each node. The function setting module is used to set the voltage segmentation interval based on the current saturation threshold voltage; and to set the current function corresponding to each segmentation interval based on the reactive power compensation coefficient and the inverter voltage after a short circuit fault of the photovoltaic power supply. The current calculation module is used to calculate the short-circuit current of the photovoltaic power inverter by using the inverter voltage after a short-circuit fault of the photovoltaic power supply as the independent variable and the current function of the corresponding voltage segment interval. The current correction module is used to perform current limiting correction on the short-circuit current of the photovoltaic power inverter to obtain the corrected short-circuit current of the photovoltaic power inverter. The power grid protection module is used to perform corresponding protection actions based on the short-circuit current corrected by the photovoltaic power inverter.

[0011] Furthermore, it also includes a node voltage calculation module: The node voltage calculation module is used to calculate the active power and reactive power of the photovoltaic power source before and after the short-circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before and after the short-circuit fault. Initialize the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before and after the short circuit fault. Based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initial voltage amplitude of each node, the initial voltage phase of each node, the initial active power injection of each node, and the initial reactive power injection of each node, the voltage amplitude and voltage phase of each node after the short-circuit fault are solved by the fast decoupling power flow method. Calculate the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault. The inverter voltage after a short-circuit fault in a photovoltaic power source is calculated based on the voltage phasors of each node after the short-circuit fault.

[0012] Another embodiment of the present invention provides a terminal device, including: a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the steps of the photovoltaic power distribution network protection method based on modified short-circuit current provided by the present invention.

[0013] Another embodiment of the present invention provides a computer-readable storage medium item, including: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform the steps of the photovoltaic power distribution network protection method based on modified short-circuit current provided by the present invention.

[0014] The following benefits can be obtained by implementing the present invention: This invention discloses a photovoltaic power distribution network protection method based on corrected short-circuit current. The method calculates the voltage of the photovoltaic power inverter before and after the short-circuit fault based on the photovoltaic power distribution network data before and after the fault. It then sets a current function for a corresponding voltage segmentation interval based on the inverter parameters and the inverter voltage before and after the short-circuit fault. The inverter short-circuit current is then substituted into this segmentation function as an independent variable to calculate the corresponding inverter short-circuit current. Subsequently, the corrected short-circuit current of the inverter is calculated according to the current limiting correction formula. Finally, the corresponding protection action strategy is determined based on the corrected short-circuit current, and the protection action strategy is executed. Compared to traditional methods, this method embodies the voltage support control strategy of the low-voltage ride-through control logic by setting a voltage-current piecewise function, which selects different current outputs based on the inverter's voltage condition after a fault to support the main grid voltage; it also embodies the reactive power priority strategy of the low-voltage ride-through control logic by controlling the output current based on the reactive power compensation coefficient; and then adjusts the output result through the current limiting correction formula of the low-voltage ride-through control logic. By introducing the low-voltage ride-through control logic into the calculation process of the inverter's short-circuit current, results that conform to the characteristics of low-voltage ride-through control can be obtained; and precise protection action decisions are made based on the accurate correction of the photovoltaic power inverter's short-circuit current, thereby improving the accuracy of grid protection actions. Attached Figure Description

[0015] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a flowchart illustrating a photovoltaic power distribution network protection method based on modified short-circuit current provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the structure of a photovoltaic power distribution network protection device based on corrected short-circuit current according to an embodiment of the present invention; Figure 3 This is a simulation diagram of the two-phase short-circuit voltage at a fault node provided in an embodiment of the present invention; Figure 4 This is a simulation diagram of the two-phase short-circuit current at a fault node provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the phasor of a fault node provided in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0019] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0020] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0021] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0022] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0023] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0024] See Figure 1 To address the problem of low accuracy in existing power grid protection systems, an embodiment of the present invention provides a photovoltaic power distribution network protection method based on corrected short-circuit current, comprising: 101. In the event of a short-circuit fault in the photovoltaic power distribution network, record the time of the short-circuit fault and the parameters of the photovoltaic power inverter; wherein, the photovoltaic power inverter parameters include: current saturation threshold voltage and reactive power compensation coefficient.

[0025] Specifically, when a short-circuit fault is confirmed in the photovoltaic power distribution network, the time and fault node of the short-circuit fault are recorded; the photovoltaic power inverter of the branch to which the fault node belongs is queried according to the ledger records of the photovoltaic power distribution network; and relevant parameters, including current saturation threshold voltage, reactive power compensation coefficient, and maximum allowable current of the inverter, are queried according to the model of the photovoltaic power inverter.

[0026] By following the steps described above, when a short-circuit fault is determined to have occurred in the photovoltaic power distribution network, the grid protection strategy is activated, the fault node is located, and the basic parameters required for subsequent steps are obtained through the ledger records of the photovoltaic power distribution network.

[0027] 102. Collect meteorological data of photovoltaic power sources and load data of each node in the distribution network before and after the short-circuit fault.

[0028] Meteorological data is collected in real time through irradiance and temperature sensors pre-installed at the photovoltaic power station, with a sampling interval of 1 minute, including the on-site irradiance and temperature of the photovoltaic power station; load data of each node is collected in real time through the distribution automation terminal with a sampling interval of 10 milliseconds for the load parameters of each node.

[0029] Specifically, the irradiance and temperature of the photovoltaic power source before and after the fault are extracted from the data collected by the irradiance and temperature sensors pre-installed in the photovoltaic power station; and the load parameters of each node before and after the fault are extracted from the data collected by the distribution automation terminal.

[0030] The above data acquisition steps are used to obtain the basic data required by the subsequent short-circuit current meter based on the pre-configured facilities of the distribution network; setting an appropriate sampling interval can ensure data continuity and real-time data, providing a reliable data foundation for subsequent calculations.

[0031] 103. Calculate the inverter voltage of the photovoltaic power source after the short circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before and after the short circuit fault and the load data of each node.

[0032] In a preferred embodiment, the calculation of the inverter voltage after the photovoltaic power supply short-circuit fault based on meteorological data of the photovoltaic power supply in the distribution network before and after the short-circuit fault and load data of each node includes: The active and reactive power of the photovoltaic power source before and after the short circuit fault are calculated based on the meteorological data of the photovoltaic power source in the distribution network before and after the short circuit fault. Initialize the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before and after the short circuit fault. Based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initial voltage amplitude of each node, the initial voltage phase of each node, the initial active power injection of each node, and the initial reactive power injection of each node, the voltage amplitude and voltage phase of each node after the short-circuit fault are solved by the fast decoupling power flow method. Calculate the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault. The inverter voltage after a short-circuit fault in a photovoltaic power source is calculated based on the voltage phasors of each node after the short-circuit fault.

[0033] Specifically, the active and reactive power of the photovoltaic power source before the short-circuit fault are calculated based on the collected irradiance and temperature of the photovoltaic power source before the fault; the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node are initialized based on the collected load parameters of each node before the fault. Based on the above data, the voltage phasors of each node after the short-circuit fault are obtained using the fast decoupling power flow method, as shown below: (1) (2) (3) (4) In the formula, For a certain node i The active power deviation is addressed through active power injection prior to the fault at this node. Active power injection after subtracting the fault of this node Calculated; For a certain node i The reactive power deviation is determined by the reactive power injection prior to the fault at this node. Reactive power injection after subtracting the fault of this node Calculated; The active iteration matrix, The reactive power iteration matrix is ​​used, and both matrices are simplified admittance matrices for the distribution network. The active power deviation matrix is ​​composed of the active power deviation of each node. The node reactive power deviation matrix is ​​composed of the reactive power deviation of each node. This is the node rated voltage amplitude matrix, which consists of the rated voltage amplitude of each node. The rated voltage amplitude of each node is usually taken as 1.0 pu for normalization calculation. The node voltage magnitude deviation matrix is ​​obtained by solving the modified equation set (3) of the fast decoupling power flow method; The node voltage phase deviation matrix is ​​obtained by solving the modified equations of the fast decoupling power flow method. For a certain node i The voltage phasor after the fault, through a certain node i voltage amplitude after the fault Phase with voltage Calculated; a certain node i voltage amplitude after the fault The pre-fault voltage amplitude initialized by this node Deviation matrix of voltage magnitude from slave node Extracted node amplitude deviation Calculated; a certain node i voltage phase after fault The pre-fault voltage phase initialized by this node Phase deviation matrix of slave node voltage The extracted node phase deviation Calculated; Subsequently, the inverter voltage after a short-circuit fault in the photovoltaic power supply is calculated based on the voltage phasor of each node.

[0034] The above-mentioned steps for calculating the post-fault voltage phasors of each node employ a fast decoupled power flow method. By substituting the collected data into the equations of the simplified admittance matrix of the distribution network, the post-fault voltage phasors of each node can be quickly solved. This method enables rapid and convenient calculation of the post-fault voltage phasors of each node for subsequent calculations, which is beneficial for the rapid response of the power grid protection action after a fault.

[0035] In another preferred embodiment, the calculation of the inverter voltage after the photovoltaic power supply short-circuit fault based on the voltage phasors of each node after the short-circuit fault includes: Extract the voltage phasor of the fault node from the voltage phasors of each node after the short-circuit fault. A composite sequence network is constructed based on the voltage phasors of the fault node using the symmetrical component method; the three-phase voltage increment of the fault node is calculated based on the composite sequence network. Calculate the three-phase voltage increment of the inverter after a short-circuit fault in a photovoltaic power source based on the three-phase voltage increment at the fault node. Calculate the three-phase voltage of the inverter after a photovoltaic power supply short-circuit fault based on the three-phase voltage increment of the inverter after the photovoltaic power supply short-circuit fault. The inverter voltage after a photovoltaic power supply short circuit fault is obtained by inverse transformation of the three-phase voltage of the inverter through symmetrical component transformation.

[0036] Specifically, taking a two-phase short circuit between phases B and C at a fault node as an example, the voltage and current changes at the fault node are as follows: Figure 3 Simulation diagram of two-phase short-circuit voltage at fault node and Figure 4 The simulation diagram of the two-phase short-circuit current at the fault node is shown below; Figure 5 The symmetrical component method is used to construct a composite sequence network as shown in the phasor diagram of the fault node: Taking phase A as the reference phase, the fault point voltage is decomposed into positive sequence, negative sequence, and zero sequence components. The positive sequence components are A→B→C, with equal magnitude and a phase difference of 120°; the negative sequence components are A→C→B, with equal magnitude and a phase difference of 120°; the zero sequence components are all equal in magnitude and phase, and the zero sequence network does not participate in two-phase short circuits; the voltage phasor of phase A is... It can be decomposed into the positive sequence component of phase A. A-phase negative sequence component The voltage phasor of phase B is It can be decomposed into B-phase positive sequence components. B-phase negative sequence component The C-phase voltage phasor is It can be decomposed into C-phase positive sequence components. C-phase negative sequence component Phase A voltage phasor two components and Same direction, equal amplitude; components of the B and C phase voltage phasors , , as well as They are symmetrically distributed and, after synthesis, can be obtained as follows: ; Based on this composite sequence network, the following relationship can be obtained: (5) In the formula, The A-phase voltage phasor of the faulty node; The A-phase voltage phasor before the fault node; This refers to the short-circuit current output by the photovoltaic power source. This is the equivalent impedance of the system busbar; The line impedance between the photovoltaic power supply access point and the busbar; Phase A voltage phasor of the fault node The voltage phasor of the fault node can be extracted from the voltage phasors of each node after the short-circuit fault. The A-phase voltage phasor before the fault node was obtained through conversion. The voltage amplitude and phase initialized by the node are obtained through a three-phase symmetry relationship; the short-circuit current output by the photovoltaic power source is solved using the above relationship (5). ; Further, calculate the three-phase voltage increment at the fault node: (6) The three-phase voltage increment of the inverter after the fault is obtained by multiplying the three-phase voltage increment of the fault node by the voltage distribution coefficient; then the three-phase voltage of the inverter after the fault is obtained by superimposing the three-phase voltage of the inverter before the fault and the three-phase voltage increment of the inverter after the fault; finally, the inverter voltage after the photovoltaic power short circuit fault is obtained by inverse transformation of the symmetrical components of the three-phase voltage of the inverter after the fault.

[0037] In the above inverter voltage calculation steps, the fault composite sequence network is constructed by the symmetrical component method. This decomposes the asymmetrical three-phase fault system into three independent symmetrical networks: positive sequence, negative sequence, and zero sequence. Then, according to the specific fault type (such as two-phase short circuit), these sequence networks are connected at the fault point according to specific rules to form an equivalent composite calculation model. This clearly depicts the flow path and interrelationship of each sequence current in the system under fault conditions. As a result, the current at the fault point can be directly solved, and the sequence voltage components of any node in the system can be deduced using the network impedance relationship. Finally, the actual three-phase voltage of each node after the fault can be obtained by the inverse transformation of the symmetrical components.

[0038] 104. Set voltage segment intervals based on current saturation threshold voltage; set the current function corresponding to each segment interval based on reactive power compensation coefficient and inverter voltage after photovoltaic power supply short circuit fault.

[0039] In a preferred embodiment, the short-circuit current of the photovoltaic power inverter is calculated using the following formula: (7) In the formula, I IIDG U is the short-circuit current of the photovoltaic power inverter. IIDGU is the inverter voltage after a short-circuit fault in the photovoltaic power supply. IIDG(0) The inverter voltage before the photovoltaic power supply short-circuit fault; Imax = 1.2pu, which is the maximum allowable current of the inverter; U t1 I is the current saturation threshold voltage; M P0 represents the active current of the photovoltaic power source before the fault; K=1.5 is the reactive power compensation coefficient; P0 is the active power of the photovoltaic power source before the short-circuit fault.

[0040] Among them, the current saturation threshold voltage is the voltage threshold for the inverter to enter the constant current limiting mode; when the voltage drop exceeds this threshold, the inverter no longer follows the voltage support curve ( Instead of increasing the current, it forces the output current to be limited to the inverter's maximum allowable current. This is to prevent damage from overcurrent.

[0041] Specifically, the independent variable range of the voltage-power function is set based on the current saturation threshold voltage data collected in the preceding steps and the preset endpoint values; the current function corresponding to each segment interval is set based on the active power and active current of the photovoltaic power source before the short-circuit fault time calculated in the preceding steps, the inverter voltage before and after the photovoltaic power source short-circuit fault, and the maximum allowable inverter current and reactive power compensation coefficient collected in the preceding steps.

[0042] In the current functions corresponding to the above segmented intervals, setting the voltage-supply function as a piecewise function reflects the voltage support control strategy of the low-voltage ride-through control logic, which selects different current outputs to support the main grid voltage based on the inverter's voltage condition after a fault, and the lower the inverter voltage after a fault, the greater the current limiting degree; In the interval, introducing a reactive power compensation coefficient greater than 1 can amplify the proportion of reactive power in the corresponding current calculation function, reflecting the reactive power priority strategy of the low voltage ride-through control logic; the constraints in the low voltage control logic are integrated into analytical relationships and quickly constructed by looking up tables.

[0043] 105. Using the inverter voltage after a photovoltaic power supply short-circuit fault as the independent variable, calculate the short-circuit current of the photovoltaic power supply inverter through the current function of the corresponding voltage segment interval.

[0044] Specifically, the inverter voltage after a short-circuit fault in the photovoltaic power supply is directly substituted into the voltage-power function constructed in the above steps to directly calculate the short-circuit current of the photovoltaic power inverter.

[0045] Compared to the traditional fixed power supply model, the calculation steps for the short-circuit current of the photovoltaic power inverter in this invention can calculate a short-circuit current that is more closely aligned with the low-voltage ride-through control characteristics of the photovoltaic power inverter. Compared to the electromagnetic transient (EMT) simulation method, this invention integrates the constraints in the low-voltage control logic into piecewise functions, which can quickly calculate the current value through an approximate table lookup method, eliminating the need for complex configuration modeling in the early stage, saving calculation time and reducing computational complexity.

[0046] 106. Perform current limiting correction on the short-circuit current of the photovoltaic power inverter to obtain the corrected short-circuit current of the photovoltaic power inverter.

[0047] In a preferred embodiment, the short-circuit current of the photovoltaic power inverter is corrected by current limiting using the following formula to obtain the corrected short-circuit current of the photovoltaic power inverter: ; In the formula, Correcting short-circuit current in photovoltaic power inverters; I lim This is the current limiting value; S N Rated capacity of photovoltaic power supply; U N This is the rated voltage of the power distribution network.

[0048] Specifically, the corrected short-circuit current of the photovoltaic power inverter is the smaller of the short-circuit current of the photovoltaic power inverter calculated in the above steps and the fixed correction value; wherein, the fixed correction value is obtained by adjusting the current limiting value of the inverter after adjusting the rated capacity of the photovoltaic power supply and the rated voltage of the distribution network.

[0049] The aforementioned short-circuit current correction formula directly reflects the current amplitude limiting strategy in the low-voltage ride-through control logic. For example, when photovoltaic, wind power, and other new energy power generation systems are connected to the grid, if a grid fault causes a voltage drop, the power generation equipment cannot immediately disconnect from the grid but must remain connected and support grid recovery. During this process, an imbalance will occur between the power input from the photovoltaic panels on the DC side of the inverter and the power output to the grid on the AC side. Excess energy will cause the DC bus voltage to rise. At the same time, in order to support the grid voltage, the inverter needs to inject reactive current into the grid, which will also increase the amplitude of the total output current. The essence of the current amplitude limiting strategy is to dynamically coordinate and trade off between the output of active and reactive currents to ensure that the synthesized total output current is always within the maximum allowable current range of the inverter.

[0050] 107. Based on the photovoltaic power inverter, correct the short-circuit current and execute the corresponding protection action.

[0051] In a preferred embodiment, the step of performing corresponding protection actions based on the correction of short-circuit current by the photovoltaic power inverter includes: The total short-circuit current of the photovoltaic power inverter is obtained by superimposing the corrected short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault with the short-circuit current of other power sources. If the total short-circuit current of the photovoltaic power distribution network exceeds the preset first current safety threshold at the time of the short-circuit fault, the upstream switch of the photovoltaic power supply will be disconnected; otherwise, the inverter step-down control will be activated.

[0052] The first current safety threshold is the current judgment threshold for the protection action classification decision. When the total short-circuit current is greater than the first current safety threshold, it can be proven that the total short-circuit current is significantly higher than the safe current of the distribution network, and a high-time-efficiency protection action must be taken. When the total short-circuit current is not greater than the first current safety threshold, it can be proven that the total short-circuit current is not higher than the safe current of the distribution network, and a low-time-efficiency protection action can be taken.

[0053] Specifically, the photovoltaic power inverter corrected short-circuit current obtained through the above current correction steps is superimposed with other short-circuit currents in the power grid to which the photovoltaic power source belongs at the time of the fault, and finally the total short-circuit current of the distribution network to which the photovoltaic power source belongs at the time of the fault is obtained. The system compares the total short-circuit current of the distribution network to which the photovoltaic power source belongs at the time of the fault with a preset current judgment threshold, matches the protection strategy, and then executes the corresponding protection action. When the total short-circuit current is greater than the first current safety threshold, it can be proven that the total short-circuit current is significantly higher than the safe current of the distribution network. The highest risk level protection strategy is matched, and the upstream switch of the photovoltaic power source is immediately disconnected to ensure the safety of the photovoltaic power generation equipment to the greatest extent. When the total short-circuit current is not greater than the first current safety threshold, it can be proven that the total short-circuit current is not higher than the safe current of the distribution network. The low risk level protection strategy is matched, a warning signal is sent to the operation and maintenance personnel, and the inverter step-down control is automatically started to prevent the fault current from rising further.

[0054] In an optional embodiment, the total short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault is compared with preset safety thresholds for each current. If the total short-circuit current of the photovoltaic power distribution network exceeds the first current safety threshold at the time of the short-circuit fault, the instantaneous protection action strategy is executed to disconnect the upstream switch of the photovoltaic power source. If the total short-circuit current of the photovoltaic power distribution network is not greater than the first current safety threshold and not less than the second current safety threshold at the time of the short-circuit fault, the time-delay protection action strategy is executed, and the upstream and downstream protection actions are waited for. If the total short-circuit current of the photovoltaic power distribution network is less than the second current safety threshold at the time of the short-circuit fault, the step-down protection action strategy is executed, and the inverter step-down control is started.

[0055] Specifically, the system compares the total short-circuit current of the distribution network to which the photovoltaic power source belongs at the time of the fault with each preset current judgment threshold, matches the protection strategy, and then executes the corresponding protection action. When the total short-circuit current is greater than the first current safety threshold, it can be proven that the total short-circuit current is above the overcurrent range of the distribution network. The instantaneous protection action strategy is matched, and the upstream switch of the photovoltaic power source is immediately cut off to ensure the safety of the photovoltaic power generation equipment to the greatest extent. When the total short-circuit current is not greater than the first current safety threshold and not less than the second current safety threshold, it can be proven that the total short-circuit current is within the overcurrent range of the distribution network. The delayed protection action strategy is matched, and the system waits for the upstream and downstream protection action instructions. When the total short-circuit current is not greater than the first current safety threshold, it can be proven that the total short-circuit current is below the overcurrent range of the distribution network. The step-down protection action strategy is matched, and the inverter step-down control is automatically started to prevent the fault current from rising further.

[0056] The above-mentioned photovoltaic power distribution network protection steps calculate the total short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault, then make a judgment on the graded protection actions based on the total current, and finally execute the protection actions to realize the protection of the photovoltaic power distribution network. Based on the accurate correction of the short-circuit current of the photovoltaic power inverter, the precise protection action decision can improve the accuracy of the grid protection action.

[0057] By implementing the above embodiments, the total short-circuit current of the photovoltaic power distribution network that meets the low voltage ride-through control characteristics can be obtained; in addition, accurate protection action decisions can be made based on the accurate total short-circuit current flow of the photovoltaic power distribution network, thereby improving the accuracy of grid protection actions.

[0058] like Figure 2 As shown, based on the above method embodiments, corresponding apparatus embodiments are provided; An embodiment of the present invention provides a photovoltaic power distribution network protection device based on corrected short-circuit current, including: a fault identification module, a data acquisition module, a voltage calculation module, a function setting module, a current calculation module, a current correction module, and a power grid protection module; The fault identification module is used to record the time of the short circuit fault and the parameters of the photovoltaic power inverter when a short circuit fault occurs in the photovoltaic power distribution network; wherein, the photovoltaic power inverter parameters include: current saturation threshold voltage and reactive power compensation coefficient. Specifically, when a short-circuit fault is confirmed in the photovoltaic power distribution network, the time and fault node of the short-circuit fault are recorded; the photovoltaic power inverter of the branch to which the fault node belongs is queried according to the ledger records of the photovoltaic power distribution network; and relevant parameters, including current saturation threshold voltage, reactive power compensation coefficient, and maximum allowable current of the inverter, are queried according to the model of the photovoltaic power inverter.

[0059] By following the steps described above, when a short-circuit fault is determined to have occurred in the photovoltaic power distribution network, the grid protection strategy is activated, the fault node is located, and the basic parameters required for subsequent steps are obtained through the ledger records of the photovoltaic power distribution network.

[0060] The data acquisition module is used to collect meteorological data of photovoltaic power sources and load data of each node in the distribution network before and after the short-circuit fault. Meteorological data is collected in real time through irradiance and temperature sensors pre-installed at the photovoltaic power station, with a sampling interval of 1 minute, including the on-site irradiance and temperature of the photovoltaic power station; load data of each node is collected in real time through the distribution automation terminal with a sampling interval of 10 milliseconds for the load parameters of each node.

[0061] Specifically, the irradiance and temperature of the photovoltaic power source before and after the fault are extracted from the data collected by the irradiance and temperature sensors pre-installed in the photovoltaic power station; and the load parameters of each node before and after the fault are extracted from the data collected by the distribution automation terminal.

[0062] The aforementioned data acquisition module is used to obtain the basic data required for subsequent short-circuit current calculations based on the pre-configured facilities of the distribution network. Setting an appropriate sampling interval can ensure data continuity while maintaining data real-time performance, providing a reliable data foundation for subsequent calculations.

[0063] The voltage calculation module is used to calculate the inverter voltage of the photovoltaic power supply after the short circuit fault based on the meteorological data of the photovoltaic power supply in the distribution network before and after the short circuit fault and the load data of each node. In a preferred embodiment, the voltage calculation module is used to calculate the inverter voltage of the photovoltaic power source after the short-circuit fault based on meteorological data of the photovoltaic power source in the distribution network before and after the short-circuit fault and load data of each node. This includes: calculating the active and reactive power of the photovoltaic power source before and after the short-circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before and after the short-circuit fault; initializing the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before the short-circuit fault; solving for the voltage amplitude and voltage phase of each node after the short-circuit fault using the fast decoupling power flow method based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initialized voltage amplitude of each node, the initialized voltage phase of each node, the initialized active power injection of each node, and the initialized reactive power injection of each node; calculating the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault; and calculating the inverter voltage of the photovoltaic power source after the short-circuit fault based on the voltage phasor of each node after the short-circuit fault.

[0064] Specifically, the active and reactive power of the photovoltaic power source before the short-circuit fault are calculated based on the collected irradiance and temperature of the photovoltaic power source before the fault; the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node are initialized based on the collected load parameters of each node before the fault; and the voltage phasors of each node after the short-circuit fault are obtained using the fast decoupling power flow method based on the above data.

[0065] The voltage calculation module described above uses a fast decoupled power flow method to quickly solve the equations of the simplified admittance matrix of the distribution network by substituting the collected data into the equations. It can quickly and conveniently calculate the voltage phasors of each node after the fault for subsequent calculations, which is beneficial to the rapid response of the power grid protection action after the fault.

[0066] In another preferred embodiment, the voltage calculation module is used to calculate the inverter voltage after a photovoltaic power supply short-circuit fault based on the voltage phasors of each node after the short-circuit fault moment, including: extracting the voltage phasor of the fault node from the voltage phasors of each node after the short-circuit fault moment; constructing a composite sequence network based on the voltage phasors of the fault node using the symmetrical component method; calculating the three-phase voltage increment of the fault node based on the composite sequence network; calculating the three-phase voltage increment of the inverter after the photovoltaic power supply short-circuit fault based on the three-phase voltage increment of the fault node; calculating the three-phase voltage of the inverter after the photovoltaic power supply short-circuit fault based on the three-phase voltage increment of the inverter after the photovoltaic power supply short-circuit fault; and obtaining the inverter voltage after the photovoltaic power supply short-circuit fault by inverse symmetrical component transformation based on the three-phase voltage of the inverter after the photovoltaic power supply short-circuit fault.

[0067] The voltage calculation module can construct a fault composite sequence network using the symmetrical component method. It can decompose an asymmetrical three-phase fault system into three independent symmetrical networks: positive sequence, negative sequence, and zero sequence. Then, according to the specific fault type (such as two-phase short circuit), these sequence networks are connected at the fault point according to specific rules to form an equivalent composite calculation model. It clearly depicts the flow path and interrelationship of each sequence current in the system under fault conditions. Thus, the current at the fault point can be directly solved, and the sequence voltage components of any node in the system can be calculated using the network impedance relationship. Finally, the actual three-phase voltage of each node after the fault can be obtained through the inverse transformation of the symmetrical components.

[0068] The function setting module is used to set the voltage segmentation interval based on the current saturation threshold voltage; and to set the current function corresponding to each segmentation interval based on the reactive power compensation coefficient and the inverter voltage after a short circuit fault of the photovoltaic power supply. In a preferred embodiment, the function setting module sets the independent variable range of the voltage-power supply function based on the current saturation threshold voltage data collected in the pre-module and the preset endpoint value; and sets the current function corresponding to each segment interval based on the active power and active current of the photovoltaic power supply before the short-circuit fault time calculated by the pre-module, the inverter voltage before and after the photovoltaic power supply short-circuit fault, and the inverter maximum allowable current and reactive power compensation coefficient collected in the pre-step.

[0069] In the current functions corresponding to the above segmented intervals, setting the voltage-supply function as a piecewise function reflects the voltage support control strategy of the low-voltage ride-through control logic, which selects different current outputs to support the main grid voltage based on the inverter's voltage condition after a fault, and the lower the inverter voltage after a fault, the greater the current limiting degree; In the interval, introducing a reactive power compensation coefficient greater than 1 can amplify the proportion of reactive power in the corresponding current calculation function, reflecting the reactive power priority strategy of the low voltage ride-through control logic; the constraints in the low voltage control logic are integrated into analytical relationships and quickly constructed by looking up tables.

[0070] The current calculation module is used to calculate the short-circuit current of the photovoltaic power inverter by using the inverter voltage after a short-circuit fault of the photovoltaic power supply as the independent variable and the current function of the corresponding voltage segment interval. Specifically, the current calculation module directly substitutes the inverter voltage after a photovoltaic power supply short-circuit fault into the voltage-power function constructed by the above module to directly calculate the short-circuit current of the photovoltaic power supply inverter.

[0071] The current correction module is used to perform current limiting correction on the short-circuit current of the photovoltaic power inverter to obtain the corrected short-circuit current of the photovoltaic power inverter. In a preferred embodiment, the short-circuit current corrected by the current correction module for the photovoltaic power inverter is the smaller of the short-circuit current of the photovoltaic power inverter calculated by the above module and the fixed correction value; wherein, the fixed correction value is obtained by adjusting the current limiting value of the inverter after adjusting the rated capacity of the photovoltaic power supply and the rated voltage of the distribution network.

[0072] The aforementioned current correction module directly embodies the current amplitude limiting strategy in the low-voltage ride-through control logic. For example, when photovoltaic, wind power, and other new energy power generation systems are connected to the grid, if a grid fault causes a voltage drop, the power generation equipment cannot immediately disconnect from the grid but must remain connected and support grid recovery. During this process, an imbalance will occur between the power input from the photovoltaic panels on the DC side of the inverter and the power output to the grid on the AC side. Excess energy will cause the DC bus voltage to rise. At the same time, in order to support the grid voltage, the inverter needs to inject reactive current into the grid, which will also increase the amplitude of the total output current. The essence of the current amplitude limiting strategy is to dynamically coordinate and trade off between the output of active and reactive current to ensure that the synthesized total output current is always within the maximum allowable current range of the inverter.

[0073] The power grid protection module is used to perform corresponding protection actions based on the short-circuit current corrected by the photovoltaic power inverter. In a preferred embodiment, the grid protection module superimposes the corrected short-circuit current of the photovoltaic power inverter with the short-circuit current of other power sources at the time of the short-circuit fault to obtain the total short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault. If the total short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault is greater than a preset first current safety threshold, the upstream switch of the photovoltaic power source is disconnected; otherwise, the inverter step-down control is activated. The first current safety threshold is a current judgment threshold for the graded decision-making of protection actions. When the total short-circuit current is greater than the first current safety threshold, it can be proven that the total short-circuit current is significantly higher than the safe current of the distribution network, and a high-time-efficiency protection action must be taken. When the total short-circuit current is not greater than the first current safety threshold, it can be proven that the total short-circuit current is not higher than the safe current of the distribution network, and a low-time-efficiency protection action can be taken.

[0074] The grid protection module superimposes the corrected short-circuit current of the photovoltaic power inverter calculated by the current correction module with other short-circuit currents in the power grid to which the photovoltaic power source belongs at the time of the fault, and finally obtains the total short-circuit current of the distribution network to which the photovoltaic power source belongs at the time of the fault. It then compares the total short-circuit current of the distribution network to which the photovoltaic power source belongs at the time of the fault with a preset current judgment threshold, matches the protection strategy, and then executes the corresponding protection action. When the total short-circuit current is greater than the first current safety threshold, it can be proven that the total short-circuit current is significantly higher than the safe current of the distribution network, and the highest risk level protection strategy is matched, immediately disconnecting the upstream switch of the photovoltaic power source to ensure the safety of the photovoltaic power generation equipment to the greatest extent. When the total short-circuit current is not greater than the first current safety threshold, it can be proven that the total short-circuit current is not higher than the safe current of the distribution network, and the low risk level protection strategy is matched, issuing a warning signal to the operation and maintenance personnel and automatically starting the inverter's step-down control to prevent the fault current from rising further.

[0075] In a preferred embodiment, the photovoltaic power distribution network protection device based on corrected short-circuit current further includes a node voltage calculation module: The node voltage calculation module is used to calculate the active power and reactive power of the photovoltaic power source before and after the short-circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before and after the short-circuit fault. Initialize the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before and after the short circuit fault. Based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initial voltage amplitude of each node, the initial voltage phase of each node, the initial active power injection of each node, and the initial reactive power injection of each node, the voltage amplitude and voltage phase of each node after the short-circuit fault are solved by the fast decoupling power flow method. Calculate the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault. The inverter voltage after a short-circuit fault in a photovoltaic power source is calculated based on the voltage phasors of each node after the short-circuit fault.

[0076] Specifically, the active and reactive power of the photovoltaic power source before the short-circuit fault are calculated based on the collected irradiance and temperature of the photovoltaic power source before the fault. The voltage amplitude, voltage phase, active power injection, and reactive power injection of each node are initialized based on the collected load parameters of each node before the fault. The voltage phasor of each node after the short-circuit fault is obtained using the fast decoupling power flow method based on the above data. Subsequently, the inverter voltage after the photovoltaic power source short-circuit fault is calculated based on the voltage phasor of each node after the fault.

[0077] The node voltage calculation module uses a fast decoupled power flow method to quickly solve the equations of the simplified admittance matrix of the distribution network by substituting the collected data into the equations to obtain the post-fault voltage phasors of each node. It can quickly and conveniently calculate the post-fault voltage phasors of each node for subsequent calculations, which is beneficial to the rapid response of the power grid protection action after a fault.

[0078] It is understood that the above-described device embodiments correspond to the method embodiments of the present invention, and can realize the photovoltaic power distribution network protection method based on modified short-circuit current provided by any of the above-described method embodiments of the present invention.

[0079] It should be noted that the device embodiments described above are merely illustrative, and some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can specifically be implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0080] Based on the above embodiments of the photovoltaic power distribution network protection method based on corrected short-circuit current, another embodiment of the present invention provides a terminal device, which includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the photovoltaic power distribution network protection method based on corrected short-circuit current of any embodiment of the present invention.

[0081] For example, in this embodiment, the computer program can be divided into one or more modules, which are stored in the memory and executed by the processor to complete the present invention. The one or more modules may be a series of computer program instruction segments capable of performing a specific function, which describe the execution process of the computer program in the terminal device.

[0082] The terminal device may be a desktop computer, laptop, handheld computer, or cloud server, etc. The terminal device may include, but is not limited to, a processor and a memory.

[0083] The processor can be a Central Processing Unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor can be a microprocessor or any conventional processor. The processor is the control center of the terminal device, connecting all parts of the terminal device via various interfaces and lines.

[0084] Based on the above-described method embodiments, another embodiment of the present invention provides a computer-readable storage medium including a stored computer program, wherein, when the computer program is executed, it controls the device where the computer-readable storage medium is located to execute the photovoltaic power distribution network protection method based on modified short-circuit current as described in any of the above-described method embodiments of the present invention.

[0085] The modules / units integrated in the device / terminal equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, a recording medium, a USB flash drive, a portable hard drive, a magnetic disk, an optical disk, a computer memory, a read-only memory (ROM), a random access memory (RAM), an electrical carrier signal, a telecommunication signal, and a software distribution medium, etc.

[0086] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A photovoltaic power distribution network protection method based on modified short-circuit current, characterized in that, include: In the event of a short-circuit fault in the photovoltaic power distribution network, the time of the short-circuit fault and the parameters of the photovoltaic power inverter are recorded; wherein, the photovoltaic power inverter parameters include: current saturation threshold voltage and reactive power compensation coefficient. Collect meteorological data of photovoltaic power sources in the distribution network before and after the short-circuit fault, as well as load data of each node; The inverter voltage after the photovoltaic power supply short circuit fault is calculated based on the meteorological data of the photovoltaic power supply in the distribution network before and after the short circuit fault and the load data of each node. Voltage segmentation intervals are set based on the current saturation threshold voltage; the current function corresponding to each segment interval is set based on the reactive power compensation coefficient and the inverter voltage after a photovoltaic power supply short circuit fault. Using the inverter voltage after a photovoltaic power supply short-circuit fault as the independent variable, the short-circuit current of the photovoltaic power supply inverter is calculated through the current function of the corresponding voltage segment interval. The short-circuit current of the photovoltaic power inverter is corrected by current limiting correction to obtain the corrected short-circuit current of the photovoltaic power inverter. The photovoltaic power inverter corrects the short-circuit current and executes corresponding protection actions.

2. The photovoltaic power distribution network protection method based on modified short-circuit current as described in claim 1, characterized in that, The calculation of the inverter voltage after the photovoltaic power supply short-circuit fault based on meteorological data of the photovoltaic power supply in the distribution network before and after the short-circuit fault and load data of each node includes: The active and reactive power of the photovoltaic power source before and after the short circuit fault are calculated based on the meteorological data of the photovoltaic power source in the distribution network before and after the short circuit fault. Initialize the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before and after the short circuit fault. Based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initial voltage amplitude of each node, the initial voltage phase of each node, the initial active power injection of each node, and the initial reactive power injection of each node, the voltage amplitude and voltage phase of each node after the short-circuit fault are solved by the fast decoupling power flow method. Calculate the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault. The inverter voltage after a short-circuit fault in a photovoltaic power source is calculated based on the voltage phasors of each node after the short-circuit fault.

3. The photovoltaic power distribution network protection method based on modified short-circuit current as described in claim 2, characterized in that, The calculation of the inverter voltage after a short-circuit fault in the photovoltaic power supply based on the voltage phasors of each node after the short-circuit fault includes: Extract the voltage phasor of the fault node from the voltage phasors of each node after the short-circuit fault. A composite sequence network is constructed based on the voltage phasors of the fault node using the symmetrical component method; the three-phase voltage increment of the fault node is calculated based on the composite sequence network. Calculate the three-phase voltage increment of the inverter after a short-circuit fault in a photovoltaic power source based on the three-phase voltage increment at the fault node. Calculate the three-phase voltage of the inverter after a photovoltaic power supply short-circuit fault based on the three-phase voltage increment of the inverter after the photovoltaic power supply short-circuit fault. The inverter voltage after a photovoltaic power supply short circuit fault is obtained by inverse transformation of the three-phase voltage of the inverter through symmetrical component transformation.

4. The photovoltaic power distribution network protection method based on modified short-circuit current as described in claim 3, characterized in that, The short-circuit current of a photovoltaic power inverter can be calculated using the following formula: ； In the formula, I IIDG U is the short-circuit current of the photovoltaic power inverter. IIDG U is the inverter voltage after a short-circuit fault in the photovoltaic power supply. IIDG(0) The inverter voltage before the photovoltaic power supply short-circuit fault; I max U is the maximum allowable current of the inverter. t1 I is the current saturation threshold voltage; M P0 represents the active current of the photovoltaic power source before the fault; K is the reactive power compensation coefficient; and P0 is the active power of the photovoltaic power source before the short-circuit fault.

5. The photovoltaic power distribution network protection method based on modified short-circuit current as described in claim 4, characterized in that, The corrected short-circuit current of the photovoltaic power inverter is obtained by applying the following formula to correct the current limiting of the short-circuit current: ; In the formula, I corr Correcting short-circuit current in photovoltaic power inverters; I lim This is the current limiting value; S N Rated capacity of photovoltaic power supply; U N This is the rated voltage of the power distribution network.

6. The photovoltaic power distribution network protection method based on modified short-circuit current as described in claim 5, characterized in that, The protection action based on the correction of short-circuit current by the photovoltaic power inverter includes: The total short-circuit current of the photovoltaic power inverter is obtained by superimposing the corrected short-circuit current of the photovoltaic power distribution network at the time of the short-circuit fault with the short-circuit current of other power sources. When the total short-circuit current of the photovoltaic power distribution network exceeds the preset first current safety threshold at the time of the short-circuit fault, the upstream switch of the photovoltaic power source is disconnected; otherwise, the inverter step-down control is activated.

7. A photovoltaic power distribution network protection device based on corrected short-circuit current, characterized in that, include: Fault identification module, data acquisition module, voltage calculation module, function setting module, current calculation module, current correction module, and power grid protection module; The fault identification module is used to record the time of the short circuit fault and the parameters of the photovoltaic power inverter when a short circuit fault occurs in the photovoltaic power distribution network; wherein, the photovoltaic power inverter parameters include: current saturation threshold voltage and reactive power compensation coefficient. The data acquisition module is used to collect meteorological data of photovoltaic power sources and load data of each node in the distribution network before and after the short-circuit fault. The voltage calculation module is used to calculate the inverter voltage of the photovoltaic power source after the short circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before the short circuit fault and the load data of each node. The function setting module is used to set the voltage segmentation interval based on the current saturation threshold voltage; and to set the current function corresponding to each segmentation interval based on the reactive power compensation coefficient and the inverter voltage after a short circuit fault of the photovoltaic power supply. The current calculation module is used to calculate the short-circuit current of the photovoltaic power inverter by using the inverter voltage after a short-circuit fault of the photovoltaic power supply as the independent variable and the current function of the corresponding voltage segment interval. The current correction module is used to perform current limiting correction on the short-circuit current of the photovoltaic power inverter to obtain the corrected short-circuit current of the photovoltaic power inverter. The power grid protection module is used to perform corresponding protection actions based on the short-circuit current corrected by the photovoltaic power inverter.

8. A photovoltaic power distribution network protection device based on corrected short-circuit current, further comprising a node voltage calculation module; The node voltage calculation module is used to calculate the active power and reactive power of the photovoltaic power source before and after the short-circuit fault based on the meteorological data of the photovoltaic power source in the distribution network before and after the short-circuit fault. Initialize the voltage amplitude, voltage phase, active power injection, and reactive power injection of each node based on the load data of each node before and after the short circuit fault. Based on the active power of the photovoltaic power source before and after the short-circuit fault, the reactive power of the photovoltaic power source before and after the short-circuit fault, the initial voltage amplitude of each node, the initial voltage phase of each node, the initial active power injection of each node, and the initial reactive power injection of each node, the voltage amplitude and voltage phase of each node after the short-circuit fault are solved by the fast decoupling power flow method. Calculate the voltage phasor of each node after the short-circuit fault based on the voltage amplitude and voltage phase of each node after the short-circuit fault. The inverter voltage after a short-circuit fault in a photovoltaic power source is calculated based on the voltage phasors of each node after the short-circuit fault.

9. A terminal device, characterized in that, The method includes a processor, a memory, and a computer program stored in the memory and configured to be executed by the processor. When the processor executes the computer program, it implements the photovoltaic power distribution network protection method based on modified short-circuit current as described in any one of claims 1-6.

10. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform the photovoltaic power distribution network protection method based on modified short-circuit current as described in any one of claims 1-6.

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