Power distribution network feeder protection method and system suitable for access of optical storage system

Abstract

The invention discloses a power distribution network feeder protection method and system suitable for access of an optical storage system, and the method comprises the steps: collecting the output current of a photovoltaic power generation system, carrying out the first protection state criterion, and judging whether to start a protection system or not; if the protection system is started, performing single-cycle current integral calculation to obtain a current integral value; and performing a second protection state criterion based on the current integral value, distinguishing a fault state from a non-fault state, realizing rapid judgment of overcurrent and triggering a corresponding protection action. The method can realize rapid overcurrent judgment under various fault conditions such as illumination intensity sudden change caused by a photovoltaic feeder line fault and an extreme event, photovoltaic and load grid-connected and off-grid disturbance and the like. The low-voltage feeder line fault is accurately identified, and the influence of the fault on the low-voltage distribution network is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power distribution system protection, and in particular to a distribution network feeder protection method and system suitable for access to a photovoltaic storage system. Background Art

[0002] In the context of energy transformation, photovoltaic power generation technology, as an important means to promote low-carbon energy transformation, has made significant contributions to the energy field with its characteristics of distributed development, low-voltage access and local consumption. The DC distribution network has shown excellent compatibility in accessing renewable energy sources such as solar energy and wind power generation, greatly improving energy utilization efficiency. However, the periodicity and unpredictability of photovoltaic power generation have brought challenges to power supply reliability. With the intensification of the "abandonment of light and power rationing" phenomenon and the fluctuation of the output power of photovoltaic power generation systems, the utilization and promotion of renewable energy have encountered many restrictions. In response to this challenge, the integration of energy storage systems into grid-connected photovoltaic systems has become a new trend in large-scale energy storage research.

[0003] The main problems faced by photovoltaic power generation systems are sudden changes in light intensity and shadow effects, which limit their wider application. At the same time, factors such as distribution network reconstruction, natural disasters or feeder failures often lead to interruptions in power supply systems containing distributed energy. Compared with traditional power generation, distributed renewable energy generation is more susceptible to severe weather, and the design of protection methods under extreme and intermittent weather conditions is complex. Therefore, reducing the scope of impact of faults and extreme events is an urgent problem to be solved in new DC distribution networks.

[0004] Distributed generation plays a key role on the low-voltage load side of the DC distribution network, but the randomness of its output increases the difficulty of formulating distribution network protection strategies. In order to improve power supply reliability, it is crucial to monitor the operating status of low-voltage power feeders in real time and design protection measures. Distributed renewable energy power generation systems such as photovoltaics are susceptible to natural factors, such as light fluctuations and intermittency, which may cause sudden changes in feeder current and voltage, falsely trigger overcurrent protection, and cause unnecessary power outages. To this end, technicians in this field urgently need to develop a set of reliable anti-false operation feeder protection solutions and devices to enhance system operation stability and power supply efficiency. Summary of the invention

[0005] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0006] In view of the above existing problems, the present invention is proposed.

[0007] Therefore, the present invention provides a distribution network feeder protection method and system suitable for access to a photovoltaic storage system to solve the problems of poor system operation stability and power supply efficiency.

[0008] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0009] In a first aspect, the present invention provides a distribution network feeder protection method applicable to a photovoltaic storage system access, comprising:

[0010] Collect the output current of the photovoltaic power generation system, perform the first protection state judgment, and determine whether to start the protection system;

[0011] If the protection system is activated, a single-cycle current integral calculation is performed to obtain the current integral value;

[0012] Based on the current integral value, a second protection state judgment is performed to distinguish between a fault state and a non-fault state, thereby realizing a quick judgment of overcurrent and triggering a corresponding protection action.

[0013] As a preferred solution of the distribution network feeder protection method applicable to the access of the photovoltaic storage system described in the present invention, wherein:

[0014] The first protection status criterion comprises the following steps:

[0015] If the real-time measured output current meets the first state criterion, then return to re-collect data;

[0016] If the output current measured in real time does not meet the first state criterion, the protection system is activated.

[0017] As a preferred solution of the distribution network feeder protection method applicable to the access of the photovoltaic storage system described in the present invention, wherein:

[0018] The first state criterion is expressed as:

[0019] i≥1.2i n

[0020] Where i represents the current value measured in real time, i n Represents the output current of the photovoltaic system in steady state.

[0021] As a preferred solution of the distribution network feeder protection method applicable to the access of the photovoltaic storage system described in the present invention, wherein:

[0022] The second protection state criterion comprises the following steps:

[0023] After the protection system is started, the single-cycle current integral values ​​of three consecutive cycles are calculated respectively;

[0024] If the current integral values ​​of three consecutive cycles all meet the second state criterion, it is judged to be a fault state;

[0025] If the current integral value of three consecutive cycles does not meet the second state criterion, it is judged as a non-fault state;

[0026] As a preferred solution of the distribution network feeder protection method applicable to the access of the photovoltaic storage system described in the present invention, wherein:

[0027] The second state criterion is expressed as:

[0028] Q>1.2Q ref

[0029] Among them, Q represents the current integral value of the current cycle, Q ref Indicates the reference current integral value.

[0030] As a preferred solution of the distribution network feeder protection method applicable to the access of the photovoltaic storage system described in the present invention, wherein:

[0031] The fault state includes sending an action signal to the DC circuit breaker and the photovoltaic converter to perform a tripping operation if it is judged to be a fault state.

[0032] The non-fault state includes that if it is determined to be a non-fault state, the protection device does not operate.

[0033] As a preferred solution of the distribution network feeder protection method applicable to the access of the photovoltaic storage system described in the present invention, wherein:

[0034] The current integral value of the current cycle is expressed as:

[0035]

[0036] Among them, Δt is the interval time of the reset signal, i f (t) represents the instantaneous value of the fault current measured at time t, t represents the time when the current cycle starts, and t+Δt represents the time when the current cycle ends.

[0037] In a second aspect, the present invention provides a distribution network feeder protection system suitable for access to a photovoltaic storage system, comprising:

[0038] The current monitoring and start-up judgment module is used to collect the output current of the photovoltaic power generation system, perform the first protection state judgment, and determine whether to start the protection system;

[0039] A single-cycle current integral calculation module is used to perform single-cycle current integral calculation to obtain a current integral value if the protection system is started;

[0040] The fault identification and protection action module is used to perform a second protection state judgment based on the current integral value, distinguish between the fault state and the non-fault state, realize a rapid judgment of overcurrent and trigger a corresponding protection action.

[0041] In a third aspect, the present invention provides a computing device, comprising:

[0042] Memory, used to store programs;

[0043] A processor is used to execute the computer executable instructions, which, when executed by the processor, implement the steps of the distribution network feeder protection method applicable to the access of the photovoltaic storage system.

[0044] In a fourth aspect, the present invention provides a computer-readable storage medium, comprising: when the program is executed by a processor, the steps of implementing the distribution network feeder protection method applicable to the access of a photovoltaic storage system are implemented.

[0045] Beneficial effects of the present invention: The present invention constructs a single-cycle current integration criterion by monitoring the output current of the photovoltaic system in real time and calculating the integral value of the single-cycle current; based on the criterion, it effectively distinguishes between fault and non-fault states, thereby reducing protection malfunctions caused by non-fault overcurrent phenomena such as sudden changes in light intensity, thereby improving the reliability of the protection system. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0047] Figure 1 A basic flow chart of a distribution network feeder protection method applicable to a photovoltaic storage system accessed according to an embodiment of the present invention;

[0048] Figure 2 An equivalent circuit diagram of a photovoltaic system in the event of a bipolar short-circuit fault in a distribution network feeder protection method applicable to a photovoltaic storage system accessed according to an embodiment of the present invention;

[0049] Figure 3 A low-voltage photovoltaic storage system topology diagram of a distribution network feeder protection method applicable to photovoltaic storage system access provided by an embodiment of the present invention;

[0050] Figure 4 A signal processing circuit structure and a fault judgment control device diagram of a distribution network feeder protection method applicable to a photovoltaic storage system accessed according to an embodiment of the present invention;

[0051] Figure 5 A flow chart of a feeder protection method for a distribution network feeder protection method applicable to a photovoltaic storage system accessed according to an embodiment of the present invention. DETAILED DESCRIPTION

[0052] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0053] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0054] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0055] The present invention is described in detail with reference to schematic diagrams. When describing the embodiments of the present invention, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0056] At the same time, in the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "upper, lower, inner and outer" are based on the directions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first, second or third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0057] In the present invention, unless otherwise clearly specified and limited, the terms "install, connect, connect" should be understood in a broad sense, for example: it can be a fixed connection, a detachable connection or an integral connection; it can also be a mechanical connection, an electrical connection or a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0058] Example 1

[0059] Reference Figure 1-5 , is an embodiment of the present invention, and provides a distribution network feeder protection method suitable for access to a photovoltaic storage system, such as Figure 1 As shown, the following steps are included:

[0060] S1: Collect the output current of the photovoltaic power generation system, perform the first protection state judgment, and determine whether to start the protection system;

[0061] In the embodiments of the present application, Figure 2 As shown in the figure, it is the equivalent circuit of the photovoltaic system in the case of a bipolar short-circuit fault. The short-circuit fault of the DC line has a significant impact on the safety of the system, especially the bipolar short-circuit fault and the unipolar grounding fault. In a low-voltage distribution network that is not directly grounded, the grounding fault current of a unipolar grounding fault is much smaller than the corresponding current in a directly grounded system. Specifically, in an indirect grounding system consisting of a low-voltage feeder, a DC transformer, and a Boost converter in a photovoltaic system, if a grounding fault occurs, the fault current may be too weak to be detected. This is because the fault current lacks an effective return path and cannot generate enough current shock to affect the safety of the system and equipment.

[0062] In an embodiment of the present application, during the operation of a photovoltaic power station, a sudden change in light intensity or an instantaneous change in grid connection may cause a rapid response in output power, resulting in a sharp change in current or voltage, a phenomenon similar to the fault characteristics of a low-voltage feeder. Therefore, traditional feeder protection methods based on overcurrent or current differential may face the risk of misjudgment and malfunction. Photovoltaic power stations have certain limitations in their ability to withstand overcurrents. During a fault, the output current needs to be suppressed by a current limiter or control strategy to ensure that the system operates stably at no more than 1.2 times the rated current, thereby protecting the converter equipment.

[0063] In the embodiment of the present application, considering that the short-term surge current of millisecond level may meet the overcurrent standard, but the converter has a certain overcurrent tolerance, if this overcurrent persists for a short period of time, that is, the overcurrent accumulates over time, it can be used as an auxiliary basis for judging the fault. In traditional overcurrent protection, the increase in current caused by the sudden change of light intensity may be misjudged as a fault, resulting in unnecessary protection action, and further identification of transient current is required to avoid false protection action.

[0064] In the embodiment of the present application, by using the single-cycle current integration as a criterion for preventing misoperation, it is easier to distinguish between fault states and non-fault states. The discharge of capacitors and photovoltaic power sources causes the fault process to enter a stable phase, resulting in a high level of continuous overcurrent. However, for the rapid increase in current caused by changes in light intensity, the current will respond quickly once the transient process stops or changes. The integral of the current can be used as an auxiliary feature for state identification.

[0065] In the embodiment of the present application, the sampling can be completed within one cycle by using the integral reset function, and the frequency of the reset signal can be set according to the specific requirements of the protection system. The advantage of using single-cycle current integration is that the signals of each cycle will not affect each other, which means that the judgment of the state will not be interfered by the transient signal of the previous cycle, thereby improving the accuracy and reliability of the protection. The output power of photovoltaic cells is highly dependent on light intensity and temperature. Under standard conditions (G ref =1000W / m 2 , T ref =25℃) Output current i of photovoltaic cell pv It can be calculated as:

[0066]

[0067] In the formula, A1, A2, I m , I sc , U m and U oc They are maximum power point current, short circuit current, maximum power point voltage and open circuit voltage respectively.

[0068] In the embodiment of the present application, when the light intensity or temperature changes, a compensation coefficient needs to be introduced. The expression of maximum power point current, short circuit current, maximum power point voltage, and open circuit voltage changing with weather conditions is:

[0069]

[0070] Among them, G is the real-time light intensity, T is the real-time temperature, T = TT ref , α=0.0025℃,β=0.5W / m 2And γ = 0.00288°C.

[0071] In the embodiments of the present application, Figure 3 The figure shows the topology of a low-voltage photovoltaic energy storage system. Taking the typical photovoltaic energy storage system connected to the low-voltage side of the DC distribution network as an example, the distributed photovoltaic power station is connected to the low-voltage DC bus through the Boost converter, and then connected to the AC grid through the modular multilevel converter (MMC). The energy storage and DC load are connected to the low-voltage DC bus through the Buck / Boost bidirectional converter and the Buck converter respectively. The DC circuit breaker is installed between the low-voltage feeder and the DC solid-state transformer to protect the photovoltaic storage DC system and its feeder.

[0072] In the embodiments of the present application, Figure 4 As shown, the signal processing circuit structure and the fault judgment control device, including the application in the fault judgment control device, use the sensor to collect the current, and the controller actively extracts the accumulated current in one cycle by integration and reset. In order to calculate the single-cycle integral value of the current, a fast integrator with reset function is studied. The integrator reset signal is adjusted by a fixed-frequency clock pulse (f=200Hz) with a sampling frequency of 10kHz, so as to realize the rapid detection of the current integral mutation within each cycle (5ms).

[0073] Specifically, it includes the following key parts:

[0074] Sensor: used to monitor the current in the DC feeder and convert it into electrical signals for subsequent processing.

[0075] Comparator and integrator: These are the core components for calculating current integral. The comparator is used to compare the actual current with the set reference current, while the integrator accumulates the current change within a cycle (such as 5 milliseconds) to obtain the current integral value within a single cycle.

[0076] Reset mechanism: The integrator will automatically reset after completing a cycle of integral calculation to start a new cycle calculation. Reset is usually controlled by an external clock signal, which is a fixed frequency clock pulse with a frequency of 10kHz.

[0077] PV system and load: It can be the input source or load of the system, PV system generates electricity and load consumes this electricity.

[0078] DC transformer and circuit breaker: DC transformer is used to regulate voltage to ensure normal operation of the system; circuit breaker is used as a safety measure to prevent excessive current from damaging the system.

[0079] RS flip-flop: accepts signals from sensors, comparators, and integrators and decides whether to activate the circuit breaker based on these signals.

[0080] Single-cycle control: It has wide applicability and strong resistance to power supply disturbances. Single-cycle control provides good waveform quality and fast dynamic response, which can overcome some inherent defects in PWM control methods. Single-cycle control can eliminate most harmonic components and significantly reduce the output harmonic content. The delay between the reference signal and the output value of single-cycle control is less than that of PWM regulation. This means that single-cycle control can respond to system changes more quickly, thereby improving the real-time nature of control and the overall performance of the system.

[0081] S2: If the protection system is activated, a single-cycle current integral calculation is performed to obtain the current integral value;

[0082] In the embodiment of the present application, the current integral can be expressed as a charge Q, which is calculated by integrating the fault current over time and is defined as:

[0083]

[0084] Wherein, Δt is the interval time of the reset signal, which is set to be equal to a cycle interval.

[0085] Similarly, in the operation of photovoltaic power generation, due to weather-related factors that may cause certain output current fluctuations, the photovoltaic output current can be accumulated over time, expressed as:

[0086]

[0087] Among them, i pv (t) is the output current of the photovoltaic system obtained by equations (1.1) and (1.2).

[0088] In the embodiment of the present application, since the current value in the fault stabilization stage is much higher than the current value when the fault occurs, the current time integral value can construct a clear protection boundary. However, when the system only encounters a short surge current process or transient disturbance, the system state can be further judged by comparing the current integral with the current integral during a long-term fault. Due to its single-cycle and reset characteristics, the fault or non-fault characteristics within a single cycle are not affected by the previous cycle. The composition of this criterion only needs to collect and process the current on the photovoltaic outlet side, and can ensure rapid response capability without communication synchronization, which can reduce the cost of basic protection facilities.

[0089] S3: Based on the current integral value, a second protection state judgment is performed to distinguish between the fault state and the non-fault state, thereby realizing a quick judgment of the overcurrent and triggering a corresponding protection action.

[0090] In the embodiment of the present application, based on the above analysis, the output current and current integral of the photovoltaic system are combined to form the photovoltaic protection status judgment criteria, further distinguishing between fault and non-fault interference, and avoiding false operation of relays or circuit breakers due to protection.n Represents the output current of the photovoltaic system in steady state. Overcurrent as the starting criterion for protection is expressed as:

[0091] i≥1.2i n (1.5)

[0092] As an auxiliary fault criterion, the current integral is expressed as:

[0093]

[0094] In the formula, Q n is the current integral of the steady-state current.

[0095] In the embodiment of the present application, the protection should avoid the risk of misjudgment due to a single judgment when a surge current occurs in a large disturbance. Therefore, after the protection is started, the Q value of the second and third cycles is used to further distinguish the operating state of the system. This setting will ensure that overcurrent phenomena caused by faults or non-fault-related situations can be distinguished within an acceptable time delay.

[0096] In the embodiment of the present application, the fault is determined based on the rapid increase of the fault current and the ability to maintain a high current level. Once the protection is activated, if the Q value of the second and third cycles continues to meet the fault state criterion in formula (1.6), a trip command is issued. On the contrary, the instantaneous mutation of the current often does not have continuity, that is, it will not continuously reach the preset protection threshold after 3 judgments. If the Q of the second and third cycles meets the judgment condition of the fault-free state, the protection device will not operate.

[0097] It should be noted that if Figure 5 As shown in the figure, it is a flow chart of the feeder protection method. The innovation of the present invention lies in its fast response capability. Even after three consecutive cycles of judgment, the fault identification time can still be controlled within 15 milliseconds after the protection is started. This time is much shorter than the lower limit of the overcurrent tripping time of 0.03 seconds specified in the low-voltage DC circuit breaker triggering standard IEEE Std.C37.17-2012. This design ensures that within the acceptable time range after the protection system detects the overcurrent phenomenon, the cause of the overcurrent can be further subdivided, effectively avoiding the refusal or malfunction of the protection system.

[0098] It should be noted that the present invention improves the accuracy and efficiency of protection, reduces unnecessary power outages caused by misjudgment, and ensures the stable operation and power supply reliability of the power grid. At the same time, it also meets the needs of modern power grids for fast and accurate protection measures, especially in the context of the increasing popularity of distributed energy. This protection method is of great significance for maintaining the stability of the power grid and improving the operating efficiency of photovoltaic power stations.

[0099] In the embodiments of the present application, the present invention is divided into the following stages:

[0100] 1) Fault feature extraction

[0101] Current transformers (CTs) are used to monitor the output current of the PV system in real time, and the protection system continuously tracks the current waveform to capture any abnormal changes.

[0102] 2) Single cycle current integral calculation:

[0103] After the current anomaly is detected, the single-cycle current integral is calculated immediately. By recording and comparing the current integral values ​​in three consecutive cycles, the protection auxiliary judgment criteria are constructed. These current integral values ​​are analyzed to identify whether there is a continuous current increase trend.

[0104] 3) Fault detection

[0105] When the current exceeds the preset threshold (Equation (1.5)), the protection mechanism is triggered. After confirming the fault, the system further distinguishes the nature of the fault, that is, whether it is a transient or permanent fault. If the current integral value exceeds the set threshold for three consecutive cycles, the protection action of the circuit breaker and photovoltaic converter is executed. The time when the current exceeds the threshold and the corresponding current value are recorded for subsequent data analysis.

[0106] 4) Prevention of misoperation

[0107] For transient non-fault conditions caused by sudden changes in light intensity, by comparing the current integral values ​​of multiple cycles, if the current integral threshold is not continuously crossed, the protection will not be triggered erroneously, thereby ensuring the stable operation of the system.

[0108] It should be noted that the present invention is effective in distinguishing instantaneous and permanent faults of feeders, sudden changes in light intensity, and grid-connected and off-grid conditions of photovoltaic systems and loads. The proposed protection device can respond quickly to fault and non-fault conditions, which can further overcome the limitations of traditional measurement protection in intermittent weather.

[0109] This embodiment also provides a distribution network feeder protection system suitable for access to a photovoltaic storage system, including:

[0110] The current monitoring and start-up judgment module is used to collect the output current of the photovoltaic power generation system, perform the first protection state judgment, and determine whether to start the protection system;

[0111] A single-cycle current integral calculation module is used to perform single-cycle current integral calculation to obtain a current integral value if the protection system is started;

[0112] The fault identification and protection action module is used to perform a second protection state judgment based on the current integral value, distinguish between the fault state and the non-fault state, realize a rapid judgment of overcurrent and trigger a corresponding protection action.

[0113] Furthermore, it also includes:

[0114] Memory, used to store programs;

[0115] A processor is used to load the program to execute the distribution network feeder protection method applicable to the access of the photovoltaic storage system.

[0116] This embodiment also provides a computer-readable storage medium storing a program, and when the program is executed by a processor, the distribution network feeder protection method applicable to the access of a photovoltaic storage system is implemented.

[0117] The storage medium proposed in this embodiment and the distribution network feeder protection method suitable for access to the photovoltaic storage system proposed in the above embodiment belong to the same inventive concept. The technical details not described in detail in this embodiment can be referred to the above embodiment, and this embodiment has the same beneficial effects as the above embodiment.

[0118] Through the above description of the implementation methods, the technicians in the relevant field can clearly understand that the present invention can be implemented by means of software and necessary general hardware, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ReadOnly, Memory, ROM), random access memory (RandomAccess Memory, RAM), flash memory (FLASH), hard disk or optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform the methods of various embodiments of the present invention.

[0119] Example 2

[0120] This is an embodiment of the present invention, which provides a distribution network feeder protection system suitable for access to a photovoltaic storage system, including a current monitoring and start-up criterion module, a single-cycle current integral calculation module, and a fault identification and protection action module;

[0121] In the embodiment of the present application, the current monitoring and start-up criterion module includes collecting the output current of the photovoltaic power generation system, performing a first protection state criterion, and determining whether to start the protection system;

[0122] In the embodiment of the present application, the current monitoring and start-up criterion module also includes real-time acquisition of the output current of the photovoltaic power generation system, and according to a preset over-current threshold (such as i≥1.2i n ) Perform the first protection status judgment to determine whether to start the protection system.

[0123] In the embodiment of the present application, the current monitoring and start-up criterion module also includes inputting the real-time current measurement value i and the steady-state current i n , output protection start signal;

[0124] In the embodiment of the present application, the single-cycle current integral calculation module includes: if the protection system is started, performing a single-cycle current integral calculation to obtain a current integral value;

[0125] In an embodiment of the present application, the single-cycle current integral calculation module also includes performing a single-cycle current integral calculation immediately once the protection system is started to obtain the current integral value Q in the current cycle. This module ensures that the integral of each cycle is calculated independently to avoid mutual interference between different cycles.

[0126] In the embodiment of the present application, the single-cycle current integral calculation module also includes an input protection start signal and a fault current, and an output current integral value.

[0127] In an embodiment of the present application, the fault identification and protection action module includes performing a second protection state judgment criterion based on the current integral value, distinguishing between the fault state and the non-fault state, achieving rapid judgment of overcurrent and triggering corresponding protection actions.

[0128] In an embodiment of the present application, the fault identification and protection action module also includes performing a second protection state criterion based on the calculated current integral value Q, distinguishing between the fault state and the non-fault state, achieving rapid judgment of the overcurrent phenomenon, and triggering corresponding protection actions (such as tripping operations).

[0129] In the embodiment of the present application, the fault identification and protection action module also includes an input current integral value and a reference current integral value, and outputs a protection action signal (such as a tripping command).

[0130] Through the division of labor and cooperation among these three modules, the entire protection system can efficiently and accurately monitor the operating status of the photovoltaic system and quickly respond to and handle potential fault conditions. Each module has clear functions and input and output definitions, ensuring the reliability and maintainability of the system.

[0131] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A distribution network feeder protection method suitable for access to a photovoltaic storage system, characterized in that: include: Collect the output current of the photovoltaic power generation system, perform the first protection state judgment, and determine whether to start the protection system; If the protection system is activated, a single-cycle current integral calculation is performed to obtain the current integral value; Based on the current integral value, a second protection state judgment is performed to distinguish between a fault state and a non-fault state, thereby realizing a quick judgment of overcurrent and triggering a corresponding protection action.

2. The distribution network feeder protection method applicable to the access of the photovoltaic storage system as claimed in claim 1, characterized in that: The first protection status criterion comprises the following steps: If the real-time measured output current meets the first state criterion, then return to re-collect data; If the output current measured in real time does not meet the first state criterion, the protection system is activated.

3. The distribution network feeder protection method applicable to the access of the photovoltaic storage system as claimed in claim 1 or 2, characterized in that: The first state criterion is expressed as: <h2 style=";text-align:left;direction:ltr">i≥1.2i<h2 style=";text-align:left;direction:ltr"> n Where i represents the current value measured in real time, i n Represents the output current of the photovoltaic system in steady state.

4. The distribution network feeder protection method applicable to the access of the photovoltaic storage system as claimed in claim 3, characterized in that: The second protection state criterion comprises the following steps: After the protection system is started, the single-cycle current integral values ​​of three consecutive cycles are calculated respectively; If the current integral values ​​of three consecutive cycles all meet the second state criterion, it is judged to be a fault state; If the current integral value of three consecutive cycles does not meet the second state criterion, it is judged to be a non-fault state.

5. The distribution network feeder protection method applicable to the access of the photovoltaic storage system as claimed in claim 4, characterized in that: The second state criterion is expressed as: Q>1.2Q ref Among them, Q represents the current integral value of the current cycle, Q ref Indicates the reference current integral value.

6. The distribution network feeder protection method applicable to the access of the photovoltaic storage system as claimed in claim 5, characterized in that: The fault state includes sending an action signal to the DC circuit breaker and the photovoltaic converter to perform a tripping operation if it is judged to be a fault state. The non-fault state includes that if it is determined to be a non-fault state, the protection device does not operate.

7. The distribution network feeder protection method applicable to the access of the photovoltaic storage system as claimed in claim 6, characterized in that: The current integral value of the current cycle is expressed as: Among them, Δt is the interval time of the reset signal, i f (t) represents the instantaneous value of the fault current measured at time t, t represents the time when the current cycle starts, and t+Δt represents the time when the current cycle ends.

8. A system based on the distribution network feeder protection method applicable to the access of a photovoltaic storage system as claimed in claim 1, characterized in that: The current monitoring and start-up judgment module is used to collect the output current of the photovoltaic power generation system, perform the first protection state judgment, and determine whether to start the protection system; A single-cycle current integral calculation module is used to perform single-cycle current integral calculation to obtain a current integral value if the protection system is started; The fault identification and protection action module is used to perform a second protection state judgment based on the current integral value, distinguish between the fault state and the non-fault state, realize a rapid judgment of overcurrent and trigger a corresponding protection action.

9. A computing device, characterized in that include: Memory, used to store programs; A processor is used to load the program to execute the steps of the distribution network feeder protection method applicable to the access of the photovoltaic storage system as described in any one of claims 1 to 7.

10. A computer-readable storage medium storing a program, characterized in that: When the program is executed by the processor, the steps of the distribution network feeder protection method applicable to the access of the photovoltaic storage system as described in any one of claims 1 to 7 are implemented.

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