Photovoltaic power grid fault transient control method, device and equipment

Abstract

The invention discloses a photovoltaic power grid fault transient control method, device and equipment, and relates to the technical field of photovoltaic auxiliary equipment, and the method comprises the following steps: obtaining the operation data of a photovoltaic grid-connected point, constructing a three-phase coupling characteristic matrix, and generating a disturbance discrimination result according to the dynamic evolution of the three-phase coupling characteristic matrix; based on a disturbance judgment result, collecting three-phase output current of the photovoltaic inverter, calculating disturbance increment of each phase of current, extracting a stable current component during a fault period based on low-voltage ride-through control logic, and calculating equivalent support power of the stable current component at a fault point; the equivalent support power is compared with a preset arc extinguishing threshold value, and the dissociation condition of the fault point is dynamically evaluated; when the fault point is not free, the photovoltaic inverter is controlled to perform state conversion, so that the equivalent support power is lower than an arc extinguishing threshold value; and after detecting that the voltage of the fault point is recovered and the arc light is extinguished, dynamically adjusting the reclosing time sequence based on the voltage recovery rate. The problems that arc light is difficult to extinguish and the reclosing failure rate is high are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of photovoltaic auxiliary equipment, and more particularly to a photovoltaic power grid fault transient control method, device and equipment. BACKGROUND

[0002] With the large-scale access of distributed photovoltaic, the inverter has become the main power interface in the distribution network. The existing photovoltaic inverter generally has low voltage ride-through capability, which can maintain grid-connected operation during voltage sag or fault to support the stability of the power grid. However, this feature also brings new problems in fault handling. When a short-circuit fault occurs in the distribution network, the low voltage ride-through characteristic of the inverter will cause it to continue to provide support current to the fault point, even if the upper protection device has tripped, there may still be a residual current channel at the fault point, making it difficult to extinguish the arc and forming a "not completely ionized" state. In this case, the traditional reclosing action is often difficult to succeed, and even may cause secondary faults or lead to reclosing failure.

[0003] In addition, since the output current of the inverter is controlled by power electronic devices, its short-circuit current amplitude is much lower than that of traditional synchronous generators, usually only 1.2 to 2 times the rated current, which not only makes it difficult to provide reliable action criteria for relay protection, but also may maintain insufficient support power to clear the fault during low voltage ride-through. This feature not only weakens the efficiency of fault isolation and arc extinction, but also makes the traditional reclosing criterion based on current amplitude and phase angle invalid.

[0004] The above disclosed technical solutions have at least the following technical problems: the existing inverter generally has low voltage ride-through capability, which can maintain grid-connected operation during fault. However, in the case where the fault point is not completely ionized, this feature will cause the short-circuit current to persist, hinder the arc extinction, cause the fault point to be difficult to completely clear, and thus make the reclosing unsuccessful.

[0005] In view of the above problems, the present application provides a solution. SUMMARY

[0006] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a photovoltaic power grid fault transient control method, device and equipment, which solves the problem that the existing photovoltaic inverter still maintains low voltage ride-through operation in the case where the fault point is not completely ionized, resulting in the persistence of short-circuit current, the difficulty of arc extinction, and the high failure rate of reclosing, by means of transient disturbance discrimination based on three-phase coupling characteristic matrix, equivalent support power calculation and inverter state conversion control.

[0007] To achieve the above object, the present application provides the following technical solutions: In one aspect, a photovoltaic grid fault transient control method comprises the following steps: obtaining operation data of a photovoltaic grid point, constructing a three-phase coupling feature matrix by calculating the phase angle offset change rate of voltage and current, and generating a disturbance discrimination result according to the dynamic evolution of the three-phase coupling feature matrix; based on the disturbance discrimination result, collecting three-phase output currents of a photovoltaic inverter, taking the current amplitude and phase angle before the disturbance as the reference, calculating the disturbance increment of each phase current, extracting the stable current component during the fault based on the low-voltage ride-through control logic, and calculating the equivalent support power of the stable current component at the fault point; comparing the equivalent support power with a preset arc extinction critical power threshold, dynamically evaluating the ionization condition of the fault point, and generating a state evaluation result; when the state evaluation result determines that the fault point has not ionized, controlling the photovoltaic inverter to perform state conversion to reduce the energy fed into the fault point, so that the equivalent support power is lower than the arc extinction threshold, and the arc light is extinguished; after detecting that the voltage of the fault point is restored and the arc light is extinguished, dynamically adjusting the reclosing timing based on the voltage recovery rate.

[0008] In one preferred embodiment, the disturbance discrimination result is generated, specifically: real-time collection of three-phase voltage, current and phase angle dynamic quantities of the photovoltaic grid point; calculation of the change rate of the phase angle offset of the voltage and the inverter output current with time in a set short-time sliding window, and formation of a phase angle change dynamic sequence; integration of the phase angle change dynamic sequence into a three-phase coupling feature matrix, determination of the initial time of disturbance occurrence based on the dynamic evolution of the three-phase coupling feature matrix, and determination of the disturbance type according to the matrix pattern, including single-phase grounding, two-phase short circuit, three-phase short circuit or high-resistance grounding.

[0009] In one preferred embodiment, the initial time of disturbance occurrence is determined based on the dynamic evolution of the three-phase coupling feature matrix, specifically: in the short-time sliding window, the first-order difference of each element in the coupling feature matrix is calculated; a disturbance judgment threshold is set, when the first-order difference of any element in the matrix continuously exceeds the disturbance judgment threshold, the time point is recorded as the disturbance candidate time; the above judgment is repeated in multiple sliding windows, and the earliest time when the disturbance judgment threshold is continuously exceeded is selected as the initial time of disturbance occurrence.

[0010] In one preferred embodiment, the stable current component during the fault is extracted based on the low-voltage ride-through control logic, specifically: obtaining the disturbance discrimination result, including the initial time of disturbance, the disturbance type and the evolution result of the coupling feature matrix, and determining the time period of the fault occurrence and the affected phase angle change dynamic sequence; real-time collection of three-phase output current and phase angle of the photovoltaic inverter during the fault, and filtering processing of the collected current signal to remove high-frequency noise and interference; taking the current amplitude and phase angle before the disturbance as the reference, calculating the disturbance increment of each phase current; according to the disturbance type and the low-voltage ride-through control logic of the inverter, extracting the stable current component maintained by the inverter during the fault.

[0011] In a preferred embodiment, the calculation of the equivalent support power of the fault point by the stable current component specifically comprises: based on the extracted three-phase stable current component and the corresponding phase angle of the low-voltage ride-through maintenance, the transient equivalent support power of each phase to the fault point during the fault is calculated in combination with the fault point voltage and the fault point phase angle.

[0012] In a preferred embodiment, the comparison between the equivalent support power and the preset arc extinction critical power threshold value for dynamically evaluating the ionization condition of the fault point and generating the state evaluation result specifically comprises: based on the equivalent support power, the equivalent power residual is calculated in combination with the arc extinction critical power threshold value; the arc extinction critical power threshold value is calculated based on the equivalent impedance of the fault point, the fault type and the fault gap, and is used to quantify the minimum power condition required to maintain the arc during the fault; based on the equivalent power residual and the fault point voltage change rate, the fault point ionization probability is calculated by an adaptive decision function, and the state evaluation result is generated.

[0013] In a preferred embodiment, when the state evaluation result determines that the fault point is not ionized, the photovoltaic inverter is controlled to perform state conversion to reduce the energy fed into the fault point, so that the equivalent support power is lower than the arc extinction threshold value, and the arc light is extinguished, specifically: when the fault point ionization determination result is not ionized, a state conversion instruction is issued to the photovoltaic inverter; the state conversion instruction is used to trigger the inverter to adjust the output strategy in the low-voltage ride-through control mode, and the adjustment of the output strategy includes shifting the phase of the current output by the inverter by changing the active and reactive distribution relationship of the output current, reducing the active component injected into the fault point; a specific frequency disturbance component is superimposed in the inverter control loop to form an energy coupling effect opposite to the fault arc; through the combined action of phase shift and frequency disturbance, the maintenance energy of the fault point arc is gradually reduced, and when the energy level falls below the preset arc extinction threshold value, it is determined that the arc extinction condition is met.

[0014] In a preferred embodiment, after detecting the voltage recovery of the fault point and the extinction of the arc light, the reclosing timing is dynamically adjusted based on the voltage recovery rate, specifically: after confirming that the fault point has been ionized and detecting the extinction of the arc light, the voltage recovery sequence is obtained, and the voltage recovery rate is calculated; according to the comparison result of the voltage recovery rate and the preset reference rate, the delay of the reclosing is determined; during the delay, the voltage phase angle and frequency synchronization are checked, and when the synchronization is satisfied, the reclosing operation is performed after the delay arrives; if non-synchronous impact or voltage drop is detected after reclosing, re-opening is triggered and reclosing attempt is re-performed according to the incremental delay strategy; during the reclosing process, if island operation or non-synchronous risk is detected, the reclosing is delayed, and the inverter is controlled to maintain the de-rating operation until the grid synchronization condition is met.

[0015] In another aspect, a photovoltaic grid fault transient control device includes the following modules: a disturbance identification module for obtaining operation data of a photovoltaic grid-connected point, constructing a transient disturbance criterion, and generating a disturbance discrimination result; a current decomposition and support power calculation module for decomposing an output current of a photovoltaic inverter based on the disturbance discrimination result and calculating equivalent support power during a fault point maintenance process; a fault arc extinction evaluation module for comparing the equivalent support power with a preset arc extinction critical power threshold, dynamically evaluating an extinction condition of the fault point, and generating a state evaluation result; an inverter state transition control module for controlling the photovoltaic inverter to perform state transition to reduce energy fed into the fault point when the state evaluation result determines that the fault point is not extinguished, so as to make the equivalent support power lower than the arc extinction threshold and promote arc extinction; and a reclosing timing adjustment module for dynamically adjusting a reclosing timing based on a voltage recovery rate after detecting that the fault point voltage is restored and the arc is extinguished.

[0016] A computer device includes a memory and a processor, which are communicatively connected with each other, the memory stores computer instructions, and the processor executes the computer instructions to perform a photovoltaic grid fault transient control method.

[0017] The photovoltaic grid fault transient control method, device and equipment have the following technical effects and advantages: 1. The present application can accurately identify the fault occurrence time and disturbance type by constructing a transient disturbance criterion based on a three-phase coupling characteristic matrix in the initial stage of the fault, and extract the stable current component maintained by the inverter low-voltage ride-through control, thereby realizing accurate calculation of the equivalent support power of the fault point. Compared with the existing criterion which only relies on the current amplitude or voltage drop, the present application can more comprehensively represent the dynamic support characteristics of the photovoltaic inverter during the fault process, providing a reliable foundation for the subsequent evaluation of the extinction condition.

[0018] 2. The present application realizes dynamic weakening and extinction determination of the arc light energy of the fault point by coupling the equivalent support power with the arc extinction critical power threshold and introducing inverter state transition and specific frequency disturbance control; at the same time, based on the voltage recovery rate, the reclosing timing can be adaptively adjusted. Compared with the existing method which relies on fixed delay or single voltage recovery criterion, the present application significantly improves the success rate of reclosing and the safety of grid operation. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The flowchart of the photovoltaic grid fault transient control method of the present application; Figure 2 The structural diagram of the photovoltaic grid fault transient control device of the present application. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application.

[0021] Embodiment 1, Figure 1 A photovoltaic grid fault transient control method is given, comprising the following steps: S1, obtaining operation data of a photovoltaic grid connection point, constructing a three-phase coupling feature matrix by calculating the phase angle offset change rate of voltage and current, and generating a disturbance discrimination result according to the dynamic evolution of the three-phase coupling feature matrix; The operation data includes voltage, current and phase angle dynamic quantity; In this embodiment, the generation of the disturbance discrimination result is specifically: Real-time acquisition of three-phase voltage, current and phase angle dynamic quantity of the photovoltaic grid connection point; Calculate the phase angle offset change rate of voltage and inverter output current with time in a set short-time sliding window, and form a phase angle change dynamic sequence; the window length is pre-set according to the fault duration characteristic; Integrate the phase angle change dynamic sequence into a three-phase coupling feature matrix to represent the synchronism and asymmetry of disturbances among phases; Based on the dynamic evolution of the three-phase coupling feature matrix, determine the initial time of disturbance occurrence, and discriminate the disturbance type according to the matrix mode, including single-phase grounding, two-phase short circuit, three-phase short circuit or high-resistance grounding.

[0022] The determination of the initial time of disturbance occurrence based on the dynamic evolution of the three-phase coupling feature matrix is specifically: Calculate the first-order difference of each element in the coupling feature matrix in the short-time sliding window; Set a disturbance judgment threshold, when the first-order difference of any element in the matrix continuously exceeds the disturbance judgment threshold, record the time point as the disturbance candidate time; Repeat the above judgment in continuous multiple sliding windows, and select the earliest time point appearing continuously exceeding the disturbance judgment threshold as the initial occurrence time of disturbance.

[0023] The discrimination of the disturbance type according to the matrix mode is specifically: Single-phase grounding: the change amplitude of the corresponding single-phase element in the matrix is significantly greater than that of the other two phases, and the power flow direction is biased to the phase; Two-phase short circuit: the amplitude of the corresponding two-phase elements in the matrix changes significantly at the same time, and the three-phase total power drops moderately; Three-phase short circuit: The amplitude of the three-phase elements in the matrix changes significantly at the same time, and the power flow rate increases uniformly. High-resistance grounding: The amplitude changes in the matrix are small, but the phase angle shift is significant, and the power flow direction fluctuates randomly.

[0024] S2. Based on the disturbance discrimination results, the three-phase output current of the photovoltaic inverter is collected. The current amplitude and phase angle before the disturbance are used as a reference to calculate the current disturbance increment of each phase. Based on the low-voltage ride-through control logic, the stable current component during the fault period is extracted, and the equivalent supporting power of the stable current component at the fault point is calculated. In this embodiment, the extraction of the steady current component during the fault period based on the low-voltage ride-through control logic specifically includes: Obtain disturbance discrimination results, including the initial time of disturbance, disturbance type and the evolution results of coupling feature matrix, and determine the time period of fault occurrence and the dynamic sequence of affected phase angle changes accordingly, so as to clarify the time window and the affected phase for current acquisition and decomposition; The three-phase output current and phase angle of the photovoltaic inverter during a fault are collected in real time, and the collected current signal is filtered to remove high-frequency noise and interference. Using the current amplitude and phase angle of stable operation before the disturbance as a reference, the current disturbance increment of each phase is calculated. , ,in For fault current, The reference current; Based on the disturbance type and the inverter's low-voltage ride-through control logic, the steady current component maintained by the inverter during the fault period is extracted. .

[0025] The inverter low-voltage ride-through control logic refers to the process whereby, upon detecting a grid disturbance and determining that the grid connection point voltage is below a set threshold, the inverter enters a low-voltage ride-through control state. This state utilizes a current decomposition method to separate the three-phase current into an active component in phase with the voltage and a reactive component orthogonal to the voltage, prioritizing reactive power support according to the grid's low-voltage ride-through requirements. Under this control logic, the inverter dynamically adjusts the ratio of active to reactive components based on the disturbance type and voltage drop magnitude, and filters and limits the output current to eliminate short-term high-frequency disturbances and overshoot. Ultimately, it extracts the current component that can be stably maintained during the fault period. This stable current component characterizes the inverter's effective support capability for the fault point during low-voltage ride-through.

[0026] The step of extracting the stable current component maintained by the inverter during a fault, based on the disturbance type and the inverter's low-voltage ride-through control logic, specifically involves: According to the low-voltage ride-through control strategy of the inverter, a low-voltage ride-through component maintained by the low-voltage ride-through mechanism in the current is identified, the low-voltage ride-through component is separated from the total disturbance increment through time sequence filtering, and a stable current component is obtained.

[0027] The equivalent support power of the stable current component at the fault point is calculated, and specifically is: based on the extracted three-phase stable current component maintained by the low-voltage ride-through and the corresponding phase angle; combined with the voltage at the fault point and the phase angle at the fault point , the transient equivalent support power of each phase to the fault point during the fault is calculated.

[0028] The transient equivalent support power, specifically is:

[0029]

[0030] wherein, is the equivalent support active power, is the voltage amplitude at the fault point, is the stable current component maintained by the low-voltage ride-through, is the current phase angle, is the voltage phase angle at the fault point, is the equivalent support reactive power.

[0031] S3, based on the comparison between the equivalent support power and the preset arc extinction critical power threshold, the ionization condition of the fault point is dynamically evaluated, and a state evaluation result is generated; The ionization generally refers to that the arc current or arc channel at the fault point completely disappears, the fault electrical gap returns to an insulating state, and the circuit regains the ability to withstand voltage.

[0032] In the embodiment, the comparison between the equivalent support power and the preset arc extinction critical power threshold, the ionization condition of the fault point is dynamically evaluated, and a state evaluation result is generated, and specifically is: based on the equivalent support power, combined with the arc extinction critical power threshold, the equivalent power residual error is calculated; The arc extinction critical power threshold is calculated based on the equivalent impedance at the fault point, the fault type and the fault gap, and is used to quantify the minimum power condition required to maintain the arc during the fault; based on the equivalent power residual error and the voltage change rate at the fault point, the ionization probability of the fault point is calculated through an adaptive decision function, and a state evaluation result is generated.

[0033] The specific calculation formula of the arc extinction critical power threshold is:

[0034]

[0035] the equivalent power residual, the specific calculation formula is:

[0036] the fault point ionization probability, the specific calculation formula is:

[0037] wherein, the arc extinguishing critical power threshold, the preset safety margin coefficient, the fault point voltage amplitude, the equivalent impedance of the fault point, the fault type correction coefficient (different fault types are assigned different coefficients, which are set according to historical experience), the fault gap correction coefficient, the arc gap, the preset standard gap coefficient, the equivalent power residual, the equivalent influence coefficient of the reactive power on the arc light maintenance, the power residual threshold, the judgment sensitivity coefficient.

[0038] the generated state evaluation result, specifically: when the fault point ionization probability is greater than the preset safety threshold, it is determined that the arc light of the fault point has ionized; when the fault point ionization probability is less than or equal to the preset safety threshold, it is determined that the arc light of the fault point is still maintained.

[0039] S4, when the state evaluation result determines that the fault point has not ionized, the photovoltaic inverter is controlled to perform state conversion to reduce the energy fed into the fault point, so that the equivalent support power is lower than the arc extinguishing threshold, and the arc light is extinguished; In the embodiment, when the state evaluation result determines that the fault point has not ionized, the photovoltaic inverter is controlled to perform state conversion to reduce the energy fed into the fault point, so that the equivalent support power is lower than the arc extinguishing threshold, and the arc light is extinguished, specifically: when the fault point ionization determination result is not ionized, a state conversion instruction is issued to the photovoltaic inverter; the state conversion instruction is used to trigger the inverter to adjust the output strategy in the low-voltage ride-through control mode, and the adjustment of the output strategy includes shifting the phase of the current output by the inverter by changing the active and reactive distribution relationship of the output current, thereby reducing the active component injected into the fault point; Meanwhile, a specific frequency disturbance component is superimposed in the inverter control loop to form an energy coupling effect opposite to the arc; Through the combined effect of phase shift and frequency disturbance, the arc maintenance energy gradually decreases, and when the energy level falls below the preset arc extinction threshold, it is determined that the arc extinction condition is met.

[0040] The specific frequency disturbance component superimposed in the inverter control loop to form an energy coupling effect opposite to the arc is specifically: Based on the difference between the equivalent support power and the arc extinction critical power threshold, the dominant frequency characteristic of the arc maintenance is determined; In the inverter current loop modulation process, a disturbance component with controlled amplitude is generated according to the dominant frequency characteristic and superimposed in the inverter output reference current, so that the inverter output current at the fault point forms a phase opposite coupling effect with the arc maintenance current, thereby further weakening the arc maintenance energy while reducing the inverter output active power; When the arc energy is detected to decay below the arc extinction threshold, the superimposed disturbance component is removed, and the inverter returns to the normal low-voltage ride-through control mode.

[0041] S5, after detecting the voltage recovery of the fault point and the arc extinction, the reclosing timing is dynamically adjusted based on the voltage recovery rate.

[0042] After detecting the voltage recovery of the fault point and the arc extinction, the reclosing timing is dynamically adjusted based on the voltage recovery rate, specifically: After confirming that the fault point has been ionized and detecting that the arc has been extinguished, a reclosing preparation program is started, and a continuous sampling sequence of the fault point voltage amplitude over time is obtained in the preparation program; The voltage recovery rate of the sampling sequence is used as the voltage recovery criterion, and the voltage recovery rate is used as the primary input for dynamically adjusting the reclosing timing; According to the comparison result of the voltage recovery rate and the preset reference rate, the candidate delay of this reclosing is determined: when the voltage recovery rate is greater than the reference rate and the voltage waveform is stable, a shorter delay is selected to quickly attempt reclosing; when the voltage recovery rate is less than the reference rate or the voltage waveform has oscillation / distortion, a longer reclosing delay is selected to ensure safety; After determining the candidate delay, a synchronization check is performed, including but not limited to: detecting the voltage phase angle difference, frequency deviation, and frequency change rate of the fault point and the upstream power grid or bus; if the phase angle difference, frequency deviation, or frequency change rate exceeds the preset allowable range, the reclosing timing is extended or canceled and the comparison is performed again; If the synchronization check passes, a trial reclosing action is performed after the candidate delay arrives, while monitoring the current, voltage and frequency waveforms in real time in a short time after reclosing; if non-synchronous impact, overcurrent or voltage drop occurs after reclosing, immediate reclosing is performed again and the next reclosing attempt is adjusted according to the incremental delay strategy; The reclosing attempt adopts an incremental delay and number limit strategy, when the number of continuous reclosing attempts reaches the preset maximum attempt number and is still unsuccessful, reclosing is kept locked and the upper dispatching or manual treatment is triggered, while the inverter is restored to a safe reduced capacity or off-grid state; During the reclosing process, if island operation or non-synchronization risk is detected, the reclosing is delayed, and the inverter is controlled to maintain reduced capacity operation until the grid synchronization condition is met.

[0043] The grid synchronization condition includes: A voltage amplitude condition: the deviation of the grid point voltage amplitude from the main grid voltage amplitude is less than a set threshold; A frequency consistency condition: the deviation of the grid point frequency from the main grid frequency is less than a set threshold; A phase angle deviation condition: the difference between the grid point voltage phase angle and the main grid voltage phase angle is less than a set threshold; A voltage recovery rate condition: the fault point voltage recovery rate is within a preset stable range, indicating that the system has entered a stable recovery phase.

[0044] Embodiment 2, Figure 2 A photovoltaic grid fault transient control device is given, which includes the following modules: A disturbance identification module: used to obtain the operation data of the photovoltaic grid point, construct a three-phase coupling feature matrix by calculating the phase angle offset change rate of the voltage and current, and generate a disturbance discrimination result according to the dynamic evolution of the three-phase coupling feature matrix; A current decomposition and supporting power calculation module: used to collect the three-phase output current of the photovoltaic inverter based on the disturbance discrimination result, calculate the disturbance increment of each phase current based on the current amplitude and phase angle before the disturbance, extract the stable current component during the fault based on the low voltage ride through control logic, and calculate the equivalent supporting power of the stable current component at the fault point; A fault free evaluation module: used to compare the equivalent supporting power with a preset arc extinction critical power threshold, dynamically evaluate the free condition of the fault point, and generate a state evaluation result; An inverter state conversion control module: used to control the photovoltaic inverter to convert the state when the state evaluation result determines that the fault point is not free, so as to reduce the energy fed into the fault point, so that the equivalent supporting power is lower than the arc extinction threshold, and the arc light is extinguished; A reclosing timing adjustment module: used to dynamically adjust the reclosing timing based on the voltage recovery rate after detecting the voltage recovery of the fault point and the arc light extinction.

[0045] The above formulas are all dimensionless values calculated, and the formulas are obtained by collecting a large amount of data to simulate a formula of the most recent real situation, and the preset parameters in the formula are set by a person skilled in the art according to the actual situation.

[0046] The above embodiments can be realized wholly or partially by software, hardware, firmware or any other combination. When realized by software, the above embodiments can be realized wholly or partially in the form of a computer program product.

[0047] Those skilled in the art can realize that the modules and algorithm steps of the examples described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solutions. A person skilled in the art can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0048] In addition, each functional module in each embodiment of the present application can be integrated in one processing module, or each module can exist physically alone, or two or more modules can be integrated in one module.

[0049] The above is merely a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0050] Finally, the above is only the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for transient control of photovoltaic power grid faults, characterized in that, Includes the following steps: The system acquires the operating data of the photovoltaic grid-connected point, constructs a three-phase coupling feature matrix by calculating the phase angle shift rate of voltage and current, and generates disturbance discrimination results based on the dynamic evolution of the three-phase coupling feature matrix. Based on the disturbance discrimination results, the three-phase output current of the photovoltaic inverter is collected. The current amplitude and phase angle before the disturbance are used as the reference to calculate the current disturbance increment of each phase. Based on the low voltage ride-through control logic, the stable current component during the fault period is extracted, and the equivalent supporting power of the stable current component at the fault point is calculated. The system dynamically assesses the ionization conditions of the fault point by comparing the equivalent support power with the preset arc extinction critical power threshold, and generates a state assessment result. When the condition assessment results determine that the fault point is not ionized, the photovoltaic inverter is controlled to perform a state transition to reduce the energy fed into the fault point, so that the equivalent support power is lower than the arc extinguishing threshold, thereby causing the arc to be extinguished. After the voltage at the fault point is detected to have recovered and the arc has been extinguished, the reclosing timing is dynamically adjusted based on the voltage recovery rate.

2. The photovoltaic grid fault transient control method according to claim 1, characterized in that, The generated perturbation discrimination result is specifically as follows: Real-time acquisition of three-phase voltage, current, and phase angle dynamics at the photovoltaic grid connection point; Within a set short-time sliding window, the rate of change of the phase angle offset of voltage and inverter output current over time is calculated, and a dynamic sequence of phase angle changes is formed. The dynamic sequence of phase angle changes is integrated into a three-phase coupling characteristic matrix. Based on the dynamic evolution of the three-phase coupling characteristic matrix, the initial moment of the disturbance is determined, and the disturbance type is identified according to the matrix pattern, including single-phase grounding, two-phase short circuit, three-phase short circuit or high-resistance grounding.

3. The photovoltaic grid fault transient control method according to claim 2, characterized in that, The dynamic evolution based on the three-phase coupling characteristic matrix determines the initial moment of the disturbance, specifically as follows: Within a short-time sliding window, calculate the first-order difference of each element in the coupling feature matrix; Set a disturbance judgment threshold. When the first difference of any element in the matrix continuously exceeds the disturbance judgment threshold, the time point is recorded as a disturbance candidate time. Repeat the above judgment in multiple consecutive sliding windows, and select the earliest time when the disturbance judgment threshold is exceeded consecutively as the initial time of the disturbance.

4. The photovoltaic grid fault transient control method according to claim 3, characterized in that, The extraction of the steady current component during the fault period based on the low-voltage ride-through control logic is specifically as follows: Obtain the disturbance discrimination results, including the initial time of the disturbance, the type of disturbance, and the evolution results of the coupling feature matrix, and determine the time period of the fault occurrence and the dynamic sequence of the affected phase angle changes accordingly; The three-phase output current and phase angle of the photovoltaic inverter during a fault are collected in real time, and the collected current signal is filtered to remove high-frequency noise and interference. Using the current amplitude and phase angle of stable operation before the disturbance as a reference, the current disturbance increment of each phase is calculated; Based on the disturbance type and the inverter's low-voltage ride-through control logic, the stable current component maintained by the inverter during the fault is extracted.

5. The photovoltaic grid fault transient control method according to claim 4, characterized in that, The calculation of the equivalent supporting power of the steady current component at the fault point is specifically as follows: Based on the extracted three-phase steady current components and corresponding phase angles maintained by low-voltage ride-through; By combining the fault point voltage and the fault point phase angle, the transient equivalent support power of each phase to the fault point during the fault period is calculated.

6. The photovoltaic grid fault transient control method according to claim 5, characterized in that, The process involves comparing the equivalent support power with a preset arc extinction critical power threshold to dynamically assess the ionization conditions at the fault point and generate a state assessment result. Specifically: Based on the equivalent supporting power and combined with the critical power threshold for arc extinction, the equivalent power residual is calculated. The arc extinction critical power threshold is calculated based on the equivalent impedance of the fault point, the fault type, and the fault gap, and is used to quantify the minimum power condition required to maintain the arc during a fault. Based on the equivalent power residual and the fault point voltage change rate, the fault point ionization probability is calculated through an adaptive decision function, and the state assessment result is generated.

7. The photovoltaic grid fault transient control method according to claim 6, characterized in that, When the state assessment result determines that the fault point is not ionized, the photovoltaic inverter is controlled to perform a state transition to reduce the energy fed into the fault point, so that the equivalent supporting power is lower than the arc extinguishing threshold, thereby causing the arc to be extinguished. Specifically: When the fault point is determined to be non-ionized, a state transition command is sent to the photovoltaic inverter. The state transition command is used to trigger the inverter to adjust its output strategy in the low-voltage ride-through control mode. The adjusted output strategy includes changing the active and reactive power distribution relationship of the output current to shift the phase of the inverter output current and reduce the active component injected into the fault point. A specific frequency disturbance component is superimposed in the inverter control loop, forming an energy coupling effect opposite to the fault arc. Through the combined effect of phase shift and frequency disturbance, the sustaining energy of the arc at the fault point is gradually reduced. When the energy level drops below the preset arc extinguishing threshold, the arc extinguishing condition is determined to be met.

8. The photovoltaic grid fault transient control method according to claim 7, characterized in that, The step of dynamically adjusting the reclosing timing based on the voltage recovery rate after detecting that the fault point voltage has recovered and the arc has been extinguished is as follows: After confirming that the fault point has been detached and detecting that the arc has been extinguished, the voltage recovery sequence is acquired and the voltage recovery rate is calculated. The reclosing delay is determined based on the comparison between the voltage recovery rate and the preset reference rate. During the delay period, voltage phase angle and frequency synchronization are checked, and a reclosing operation is performed after the delay is reached when the synchronization is satisfied. If an asynchronous surge or voltage drop is detected after reclosing, the circuit breaker will be tripped again and reclosing will be attempted again according to the incremental delay strategy. If islanding or asynchronous risk is detected during the reclosing process, the reclosing is delayed and the inverter is controlled to maintain derating operation until the grid synchronization conditions are met.

9. An apparatus using the photovoltaic grid fault transient control method as described in any one of claims 1-8, characterized in that, Includes the following modules: Disturbance identification module: used to acquire the operating data of photovoltaic grid-connected points, construct a three-phase coupling feature matrix by calculating the phase angle shift rate of voltage and current, and generate disturbance discrimination results based on the dynamic evolution of the three-phase coupling feature matrix; Current decomposition and supporting power calculation module: Based on the disturbance discrimination results, it collects the three-phase output current of the photovoltaic inverter, calculates the current disturbance increment of each phase based on the current amplitude and phase angle before the disturbance, extracts the stable current component during the fault based on the low voltage ride-through control logic, and calculates the equivalent supporting power of the stable current component at the fault point. Fault Isolation Assessment Module: This module is used to dynamically assess the ionization conditions of a fault point by comparing the equivalent support power with a preset arc extinction critical power threshold, and to generate a status assessment result. Inverter state transition control module: When the state assessment result determines that the fault point is not ionized, it controls the photovoltaic inverter to perform state transition, so as to reduce the energy fed into the fault point, make the equivalent support power lower than the arc extinguishing threshold, and promote the arc to be extinguished; Reclosing timing adjustment module: used to dynamically adjust the reclosing timing based on the voltage recovery rate after the voltage at the fault point is detected to have recovered and the arc has been extinguished.

10. A computer device, characterized in that, include: The system includes a memory and a processor, which are interconnected. The memory stores computer instructions, and the processor executes the computer instructions to perform a photovoltaic grid fault transient control method according to any one of claims 1 to 8.

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