A method, device and equipment for transient control of photovoltaic power grid faults

Abstract

This invention discloses a method, device, and equipment for transient control of photovoltaic grid faults, relating to the field of photovoltaic auxiliary equipment technology. The method includes the following steps: acquiring operational data from the photovoltaic grid-connected point, constructing a three-phase coupling characteristic matrix, and generating disturbance discrimination results based on its dynamic evolution; based on the disturbance discrimination results, collecting the three-phase output current of the photovoltaic inverter, calculating the current disturbance increment of each phase, extracting the stable current component during the fault period based on low-voltage ride-through control logic, and calculating its equivalent supporting power at the fault point; dynamically evaluating the ionization condition of the fault point by comparing the equivalent supporting power with a preset arc extinguishing threshold; when the fault point is not ionized, controlling the photovoltaic inverter to perform a state transition so that the equivalent supporting power is lower than the arc extinguishing threshold; and dynamically adjusting the reclosing sequence based on the voltage recovery rate after detecting that the voltage at the fault point has recovered and the arc has been extinguished. This invention solves the problems of difficult arc extinguishing and high reclosing failure rate.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic auxiliary equipment technology, and more specifically, to a method, apparatus, and equipment for transient control of photovoltaic power grid faults. Background Technology

[0002] With the large-scale integration of distributed photovoltaic (PV) power, inverters have become the main power interface in distribution networks. Existing PV inverters generally possess low-voltage ride-through capability, enabling them to maintain grid-connected operation during voltage dips or faults to support grid stability. However, this characteristic also introduces new challenges during fault handling. When a short-circuit fault occurs in the distribution network, the inverter's low-voltage ride-through characteristic causes it to continuously supply supporting current to the fault point. Even if the upstream protection device has tripped, a residual current path may still exist at the fault point, making it difficult to extinguish the arc and creating an "incompletely deionized" state. In this situation, traditional reclosing operations often fail, and may even trigger secondary faults or cause reclosing failure.

[0003] Furthermore, because the inverter output current is controlled by power electronic devices, its short-circuit current amplitude is much lower than that of traditional synchronous generators, typically only 1.2 to 2 times the rated current. This makes it difficult to provide reliable operating criteria for relay protection and may also result in insufficient supporting power to clear faults during low-voltage ride-throughs. This characteristic not only weakens the efficiency of fault isolation and arc extinguishing but also renders traditional reclosing criteria based on current amplitude and phase angle ineffective.

[0004] The aforementioned disclosed technical solutions have at least the following technical problems: Existing inverters generally have low-voltage ride-through capability, enabling them to maintain grid-connected operation during faults. However, if the fault point is not completely deionized, this characteristic will cause the short-circuit current to persist, hindering arc extinguishing and making it difficult to completely isolate the fault point, thus preventing successful reclosing.

[0005] To address the above problems, this invention proposes a solution. Summary of the Invention

[0006] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a photovoltaic grid fault transient control method, apparatus, and equipment. By using transient disturbance discrimination based on the three-phase coupling characteristic matrix, equivalent supporting power calculation, and inverter state transition control, the present invention addresses the problem that existing photovoltaic inverters continue to operate at low voltage ride-through when the fault point is not completely deionized, resulting in persistent short-circuit current, difficulty in extinguishing arcing, and high reclosing failure rate.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] On the one hand, a transient control method for photovoltaic grid faults includes the following steps: acquiring the operating data of the photovoltaic grid-connected point, constructing a three-phase coupling feature matrix by calculating the phase angle shift rate of voltage and current, and generating a disturbance discrimination result based on the dynamic evolution of the three-phase coupling feature matrix; based on the disturbance discrimination result, collecting the three-phase output current of the photovoltaic inverter, calculating the current disturbance increment of each phase based on the current amplitude and phase angle before the disturbance, extracting the stable current component during the fault period based on low-voltage ride-through control logic, and calculating the equivalent supporting power of the stable current component at the fault point; comparing the equivalent supporting power with a preset arc extinguishing 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 is not ionized, controlling the photovoltaic inverter 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 extinguish; after detecting that the voltage at the fault point has recovered and the arc has extinguished, dynamically adjusting the reclosing sequence based on the voltage recovery rate.

[0009] In a preferred embodiment, generating the disturbance discrimination result specifically involves: real-time acquisition of the three-phase voltage, current, and phase angle dynamics of the photovoltaic grid-connected point; calculating the rate of change of the phase angle offset of the voltage and inverter output current over time within a set short-time sliding window, and forming a phase angle change dynamic sequence; integrating the phase angle change dynamic sequence into a three-phase coupling feature matrix; determining the initial moment of disturbance occurrence based on the dynamic evolution of the three-phase coupling feature matrix; and discriminating the disturbance type according to the matrix pattern, including single-phase grounding, two-phase short circuit, three-phase short circuit, or high-resistance grounding.

[0010] In a preferred embodiment, determining the initial time of disturbance occurrence based on the dynamic evolution of the three-phase coupling feature matrix specifically involves: calculating the first-order difference of each element in the coupling feature matrix within a short-time sliding window; setting a disturbance determination threshold, and recording the time point as a disturbance candidate time when the first-order difference of any element in the matrix continuously exceeds the disturbance determination threshold; repeating the above judgment in multiple consecutive sliding windows, and selecting the earliest time when the disturbance determination threshold is continuously exceeded as the initial time of disturbance occurrence.

[0011] In a preferred embodiment, the step of extracting the stable current component during the fault based on the low-voltage ride-through control logic specifically involves: obtaining disturbance discrimination results, including the initial time of the disturbance, the disturbance type, and the evolution result of the coupling feature matrix, and determining the time period of the fault and the dynamic sequence of the affected phase angle changes accordingly; real-time acquisition of the three-phase output current and phase angle of the photovoltaic inverter during the fault, and filtering the acquired current signal to remove high-frequency noise and interference; using the current amplitude and phase angle of stable operation before the disturbance as a reference, calculating the current disturbance increment of each phase; and extracting the stable current component maintained by the inverter during the fault according to the disturbance type and the inverter's low-voltage ride-through control logic.

[0012] In a preferred embodiment, the calculation of the equivalent support power of the steady current component at the fault point specifically involves: based on the extracted three-phase steady current components maintained by low-voltage ride-through and the corresponding phase angles; and combining the fault point voltage and the fault point phase angle, calculating the transient equivalent support power of each phase to the fault point during the fault period.

[0013] In a preferred embodiment, the dynamic assessment of the ionization condition of the fault point and the generation of a state assessment result based on the comparison between the equivalent support power and a preset arc extinction critical power threshold are specifically as follows: Based on the equivalent support power and the arc extinction critical power threshold, 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 the fault; based on the equivalent power residual and the fault point voltage change rate, the ionization probability of the fault point is calculated through an adaptive decision function, and a state assessment result is generated.

[0014] In a preferred embodiment, 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 extinguish. Specifically, when the fault point ionization determination result is that it is not ionized, a state transition command is issued 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; superimposing a specific frequency disturbance component in the inverter control loop to form an energy coupling effect opposite to the fault arc; through the combined effect of phase shift and frequency disturbance, the maintenance 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.

[0015] In a preferred embodiment, after detecting that the fault point voltage has recovered and the arc has extinguished, the reclosing timing is dynamically adjusted based on the voltage recovery rate. Specifically, after confirming that the fault point has been detached and detecting that the arc has extinguished, the voltage recovery sequence is obtained and the voltage recovery rate is calculated. Based on the comparison result between the voltage recovery rate and the preset reference rate, the reclosing delay is determined. During the delay period, the voltage phase angle and frequency synchronization are checked, and the reclosing operation is performed after the delay is reached when the synchronization is satisfied. If an asynchronous impact or voltage drop is detected after reclosing, the circuit breaker is triggered to trip again and reclosing is attempted again according to the incremental delay strategy. During the reclosing process, if islanding operation or asynchronous risk is detected, the reclosing is delayed and the inverter is controlled to maintain derating operation until the grid synchronization condition is met.

[0016] On the other hand, a photovoltaic grid fault transient control device includes the following modules: a disturbance identification module, used to acquire the operating data of the photovoltaic grid connection point, construct transient disturbance criteria, and generate disturbance discrimination results; a current decomposition and supporting power calculation module, used to decompose the output current of the photovoltaic inverter based on the disturbance discrimination results and calculate the equivalent supporting power during the fault point maintenance process; a fault ionization assessment module, used to compare the equivalent supporting power with a preset arc extinguishing critical power threshold, dynamically assess the ionization condition of the fault point, and generate a state assessment result; an inverter state transition control module, used to control the photovoltaic inverter to perform state transition when the state assessment result determines that the fault point is not ionized, so as to reduce the energy fed into the fault point, make the equivalent supporting power lower than the arc extinguishing threshold, and promote the arc extinguishing; and a reclosing timing adjustment module, used to dynamically adjust the reclosing timing based on the voltage recovery rate after detecting that the fault point voltage has recovered and the arc has extinguished.

[0017] A computer device includes a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform a photovoltaic grid fault transient control method.

[0018] The technical effects and advantages of the photovoltaic power grid fault transient control method, device and equipment of the present invention are as follows:

[0019] 1. This invention constructs a transient disturbance criterion based on a three-phase coupling characteristic matrix in the initial stage of a fault, enabling precise identification of the fault occurrence time and disturbance type. Based on this, it extracts the stable current component maintained by the inverter's low-voltage ride-through control, thereby achieving accurate calculation of the equivalent support power at the fault point. Compared to existing criteria that rely solely on current amplitude or voltage drop, this invention can more comprehensively characterize the dynamic support characteristics of the photovoltaic inverter during a fault process, providing a reliable foundation for subsequent assessment of ionization conditions.

[0020] 2. This invention couples the equivalent supporting power with the critical power threshold for arc extinction and introduces inverter state transition and specific frequency disturbance control to achieve dynamic attenuation and extinction determination of arc energy at fault points; simultaneously, based on the voltage recovery rate, it can adaptively adjust the reclosing sequence. Compared with existing methods that rely on fixed delays or a single voltage recovery criterion, this invention significantly improves the success rate of reclosing and the safety of power grid operation. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating a photovoltaic grid fault transient control method according to the present invention;

[0022] Figure 2This is a schematic diagram of the structure of a photovoltaic grid fault transient control device according to the present invention. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1, Figure 1 This invention provides a transient control method for photovoltaic power grid faults, comprising the following steps:

[0025] S1. Obtain the operating data of the photovoltaic grid-connected point, construct the three-phase coupling feature matrix by calculating the phase angle shift rate of voltage and current, and generate the disturbance discrimination result based on the dynamic evolution of the three-phase coupling feature matrix.

[0026] The operating data includes voltage, current, and phase angle dynamics.

[0027] In this embodiment, the generation of the perturbation discrimination result specifically refers to:

[0028] Real-time acquisition of three-phase voltage, current, and phase angle dynamics at the photovoltaic grid connection point;

[0029] Within a set short-time sliding window, the rate of change of the phase angle offset of the voltage and the inverter output current over time is calculated, and a dynamic sequence of phase angle changes is formed; the window length is preset according to the characteristics of the fault duration.

[0030] The dynamic sequence of phase angle changes is integrated into a three-phase coupled characteristic matrix to characterize the synchronicity and asymmetry of the disturbances between phases.

[0031] Based on the dynamic evolution of the three-phase coupling characteristic matrix, the initial moment of disturbance occurrence 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.

[0032] The dynamic evolution based on the three-phase coupling characteristic matrix determines the initial moment of the disturbance, specifically as follows:

[0033] Within a short-time sliding window, calculate the first-order difference of each element in the coupling feature matrix;

[0034] 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.

[0035] 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.

[0036] The method of determining the disturbance type based on the matrix pattern is as follows:

[0037] 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 towards that phase;

[0038] Two-phase short circuit: The amplitudes of the corresponding two-phase elements in the matrix change significantly at the same time, and the total three-phase power decreases moderately.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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:

[0043] 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;

[0044] 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.

[0045] 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;

[0046] 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. .

[0047] 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.

[0048] 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:

[0049] Based on the inverter's low-voltage ride-through control strategy, the 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 then separated from the total disturbance increment through timing filtering to obtain the stable current component.

[0050] The calculation of the equivalent supporting power of the steady current component at the fault point is specifically as follows:

[0051] Based on the extracted three-phase steady current components and corresponding phase angles maintained by low-voltage ride-through;

[0052] Combined with the voltage at the fault point and the phase angle of the fault point Calculate the transient equivalent support power of each phase to the fault point during the fault period.

[0053] The transient equivalent support power is specifically:

[0054]

[0055]

[0056] in, To provide equivalent support for active power, The voltage amplitude at the fault point. The stable current component maintained during low-voltage ride-through. The phase angle of the current. The voltage phase angle at the fault point. This is to provide equivalent support for reactive power.

[0057] S3, based on the comparison between the equivalent support power and the preset arc extinction critical power threshold, dynamically evaluate the ionization conditions of the fault point and generate the state evaluation results;

[0058] The term "ionization" typically refers to the complete disappearance of the arc current or arc channel at the fault point, the restoration of the fault electrical clearance to an insulating state, and the regaining of the circuit's ability to withstand voltage.

[0059] In this embodiment, the dynamic assessment of the ionization conditions at the fault point based on the comparison between the equivalent support power and the preset arc extinction critical power threshold, and the generation of a state assessment result, specifically involves:

[0060] Based on the equivalent supporting power and combined with the critical power threshold for arc extinction, the equivalent power residual is calculated.

[0061] 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.

[0062] 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.

[0063] The specific calculation formula for the arc extinction critical power threshold is as follows:

[0064]

[0065]

[0066] The equivalent power residual is specifically calculated using the following formula:

[0067]

[0068] The specific formula for calculating the detachment probability of the fault point is as follows:

[0069]

[0070] in, The critical power threshold for arc extinction. The preset safety margin coefficient, The voltage amplitude at the fault point. The equivalent impedance at the fault point. Adjust the fault type coefficient (different coefficients are assigned to different fault types, and the settings are based on historical experience). This is the fault gap correction factor. For the arc gap, The preset standard gap coefficient, For equivalent power residual, This represents the equivalent influence coefficient of reactive power on arc maintenance. The power residual threshold, To determine the sensitivity coefficient.

[0071] The generated state evaluation result is specifically as follows:

[0072] When the probability of the fault point becoming detached is greater than the preset safety threshold, it is determined that the arc light at the fault point has become detached.

[0073] When the probability of the fault point being free is less than or equal to the preset safety threshold, it is determined that the fault point still maintains the arc.

[0074] S4. When the state assessment result determines that the fault point is not ionized, control the photovoltaic inverter to perform a state transition in order to reduce the energy fed into the fault point, so that the equivalent support power is lower than the arc extinguishing threshold, and promote the arc to be extinguished.

[0075] In this embodiment, 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:

[0076] When the fault point is determined to be non-ionized, a state transition command is sent to the photovoltaic inverter.

[0077] 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.

[0078] At the same time, a specific frequency disturbance component is superimposed in the inverter control circuit to form an energy coupling effect opposite to the fault arc;

[0079] 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.

[0080] The simultaneous superposition of a specific frequency disturbance component in the inverter control circuit to form an energy coupling effect opposite to that of the fault arc is specifically as follows:

[0081] Based on the difference between the equivalent supporting power and the critical power threshold for arc extinction, the dominant frequency characteristics of fault arc maintenance are determined.

[0082] During the inverter current loop modulation process, a disturbance component with controlled amplitude is generated according to the dominant frequency characteristics and superimposed on the inverter output reference current, so that the inverter output current and the arc sustaining current form a coupling effect with opposite phase at the fault point, thereby reducing the active power output of the inverter and further weakening the arc sustaining energy.

[0083] When the arc energy is detected to have decayed to below the arc extinguishing threshold, the superposition of the disturbance components is removed, and the inverter returns to the normal low-voltage ride-through control mode.

[0084] S5, after detecting that the voltage at the fault point has recovered and the arc has been extinguished, dynamically adjusts the reclosing sequence based on the voltage recovery rate.

[0085] 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:

[0086] After confirming that the fault point has been detached and detecting that the arc has been extinguished, the reclosing preparation program is started, and the continuous sampling sequence of the fault point voltage amplitude over time is obtained in the preparation program;

[0087] 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.

[0088] Based on the comparison between the voltage recovery rate and the preset reference rate, the candidate delay for 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 oscillations / distortions, an extended reclosing delay is selected to ensure safety.

[0089] 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 between 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 current re-closing sequence is extended or canceled and re-compared.

[0090] If the synchronization check passes, a reclosing attempt will be performed after the candidate delay is reached, while the current, voltage and frequency waveforms will be monitored in real time for a short period after reclosing; if an asynchronous surge, overcurrent or voltage drop occurs after reclosing, the circuit breaker will be immediately re-opened and the next reclosing attempt will be adjusted according to the incremental delay strategy.

[0091] An incremental delay and number limit strategy is adopted for the overlap attempt. When the number of consecutive overlap attempts reaches the preset maximum number of attempts and still fails, the overlap is locked and the upper-level scheduling or manual handling is triggered. At the same time, the inverter is restored to a safe derating or grid disconnection state.

[0092] 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.

[0093] The power grid synchronization conditions include:

[0094] Voltage amplitude condition: The deviation between the voltage amplitude at the grid connection point and the voltage amplitude of the main grid is less than a set threshold;

[0095] Frequency consistency condition: The deviation between the grid connection frequency and the main grid frequency is less than a set threshold.

[0096] Phase angle deviation condition: The difference between the phase angle of the grid connection voltage and the phase angle of the main grid voltage is less than a set threshold.

[0097] Voltage recovery rate condition: When the voltage recovery rate at the fault point is within a preset stable range, it indicates that the system has entered a stable recovery phase.

[0098] Example 2, Figure 2 The present invention discloses a photovoltaic grid fault transient control device, comprising the following modules:

[0099] 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;

[0100] 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.

[0101] 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.

[0102] 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;

[0103] 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.

[0104] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0105] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0106] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0107] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0108] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0109] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A photovoltaic grid fault transient control method, characterized by, The method comprises the following steps: acquiring operation data of a photovoltaic grid-connected point, constructing a three-phase coupling feature matrix by calculating a phase angle offset change rate of voltage and current, and generating a disturbance discrimination result according to dynamic evolution of the three-phase coupling feature matrix; based on the disturbance discrimination result, collecting three-phase output currents of the photovoltaic inverter, taking the current amplitude and phase angle before the disturbance as a reference, calculating current disturbance increments of each phase, and extracting stable current components during the fault based on a low-voltage ride-through control logic, specifically: acquiring the disturbance discrimination result, including a disturbance initial time, a disturbance type and evolution results of the coupling feature matrix, and determining a time period of the fault occurrence and a dynamic sequence of the affected phase angle variation; real-time collection of three-phase output currents and phase angles of the photovoltaic inverter during the fault, and filtering processing of the collected current signals to remove high-frequency noise and interference; taking the stable operation current amplitude and phase angle before the disturbance as a reference, calculating the current disturbance increments of each phase; according to the low-voltage ride-through control strategy of the inverter, identifying the low-voltage ride-through components maintained by the low-voltage ride-through mechanism in the current, separating the low-voltage ride-through components from the current disturbance increments through time sequence filtering to obtain the stable current components, and calculating the equivalent support power of the stable current components at the fault point, specifically: based on the extracted three-phase stable current components maintained by the low-voltage ride-through and the corresponding phase angles; combining the fault point voltage and the fault point phase angle, calculating the transient equivalent support power of each phase to the fault point during the fault; comparing the equivalent support power with a preset arc extinction critical power threshold to dynamically evaluate the ionization condition of the fault point and generate a state evaluation result; when the state evaluation result determines that the fault point is 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 fault point voltage is restored and the arc light is extinguished, dynamically adjusting the reclosing timing based on the voltage recovery rate.

2. The photovoltaic grid fault transient control method of claim 1, wherein, The generation of the disturbance discrimination result is specifically: real-time collection of three-phase voltage, current and phase angle dynamic quantities of the photovoltaic grid-connected point; calculating the rate of change of the phase angle offset of the voltage and the inverter output current with time in a set short-time sliding window, and forming a dynamic sequence of the phase angle change; integrating the dynamic sequence of the phase angle change into a three-phase coupling feature matrix, determining the initial time of the disturbance occurrence based on the dynamic evolution of the three-phase coupling feature matrix, and identifying the disturbance type according to the matrix mode, including single-phase grounding, two-phase short circuit, three-phase short circuit or high-resistance grounding.

3. The photovoltaic grid fault transient control method of claim 2, wherein, The determination of the initial time of the disturbance occurrence based on the dynamic evolution of the three-phase coupling feature matrix is specifically: calculating the first-order difference of each element in the coupling feature matrix in the short-time sliding window; setting a disturbance judgment threshold, when the first-order difference of any element in the matrix continuously exceeds the disturbance judgment threshold, recording the time point as a disturbance candidate time; repeating the above judgment in multiple sliding windows, and selecting the earliest time when the continuous disturbance judgment threshold is exceeded as the initial disturbance occurrence time.

4. The photovoltaic grid fault transient control method of claim 3, wherein, The comparison of the equivalent support power with the preset arc extinction critical power threshold to dynamically evaluate the ionization condition of the fault point and generate the state evaluation result is specifically: An equivalent power residual is calculated based on the equivalent support power in combination with an arc extinction critical power threshold; 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 the fault; Based on the equivalent power residual and the voltage change rate of the fault point, the ionization probability of the fault point is calculated by an adaptive decision function, and a state evaluation result is generated.

5. The photovoltaic grid fault transient control method of claim 4, wherein, 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, and the arc 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, which includes changing the active and reactive distribution relationship of the output current to cause the phase of the inverter output current to deviate and reduce 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 deviation 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, it is determined that the arc extinction condition is met.

6. The photovoltaic grid fault transient control method of claim 5, wherein, After detecting that the voltage of the fault point is restored and the arc is extinguished, 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 is extinguished, 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 length of the reclosing delay is determined; During the delay period, the voltage phase angle and frequency synchronization are checked, and when the synchronization is satisfied, the reclosing operation is performed after the delay period arrives; If a non-synchronous impact or voltage drop is detected after reclosing, a re-opening is triggered and a reclosing attempt is re-performed with an 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.

7. An apparatus for using a photovoltaic grid fault transient control method as claimed in any one of claims 1 to 6, characterized by The following modules are included: A disturbance identification module is used to obtain the operating data of the photovoltaic grid-connected point, construct a three-phase coupling feature matrix by calculating the phase angle deviation 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 support power calculation module is used to acquire the three-phase output current of the photovoltaic inverter based on the disturbance discrimination result, calculate the current disturbance increment 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 support power of the stable current component at the fault point; A fault ionization evaluation module is used to compare the equivalent support power with the preset arc extinction critical power threshold, dynamically evaluate the ionization condition of the fault point, and generate a state evaluation result; The inverter state transition control module is configured to control the photovoltaic inverter to perform state transition when the state evaluation result determines that the fault point is not isolated, so as to reduce the energy fed into the fault point, make the equivalent support power lower than the arc extinction threshold, and promote the arc to be extinguished. The reclosing timing adjustment module is configured to dynamically adjust the reclosing timing based on the voltage recovery rate after detecting that the voltage of the fault point is recovered and the arc is extinguished.

8. A computer device, comprising: The photovoltaic power grid fault transient control method comprises the following steps: A memory and a processor are connected in communication with each other, the memory stores computer instructions, and the processor executes the computer instructions to perform the photovoltaic power grid fault transient control method according to any one of claims 1 to 6.

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