Low-voltage out-of-limit regulation and control method and system for distributed photovoltaic power station

Abstract

The invention discloses a low-voltage out-of-limit regulation and control method and system for a distributed photovoltaic power station, and relates to the technical field of photovoltaic power generation. Comprising the following steps: obtaining the grid-connected capacity of a photovoltaic power station based on the power grid capacity and the power grid load degree, obtaining multiple safety margin influence factors, and calculating causal indexes of the multiple safety margin influence factors and the safety margin so as to set the safety margin; determining an access point according to the grid-connected capacity of the photovoltaic power station with the safety margin and the additional information, and monitoring the change of data near the access point; the voltage state of the power grid is judged according to the change of data near the access point, and multiple means are adopted for corresponding control so as to adjust the voltage level of the power grid. According to the method, the safety margin is set by calculating multiple safety margin influence factors and causal indexes of the safety margin, and the accuracy of the grid-connected capacity of the photovoltaic power station is improved. The access point is determined according to the grid-connected capacity of the photovoltaic power station with the safety margin and the additional information, so that the precision of subsequent state judgment is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic power generation, and in particular to a method and system for regulating low voltage over-limit of a distributed photovoltaic power station. Background Art

[0002] Low voltage over-limit control of distributed photovoltaic power stations is an important technology designed to solve the low voltage problem that may be caused by the grid connection of distributed photovoltaic power stations. In traditional power grids, power transmission is unidirectional, from power plants to users. However, with the rapid development of distributed photovoltaic power stations, more and more photovoltaic power stations are injecting power into the grid, resulting in a two-way flow of power transmission, which poses a challenge to the stability of the grid.

[0003] Low voltage over-limit refers to the voltage in the power grid dropping below the safe operating range. When a distributed photovoltaic power station is connected to the grid, the fluctuation of photovoltaic power generation may cause a significant drop in the grid voltage, especially when the output power of the photovoltaic power station is large or the weather conditions change suddenly. Low voltage over-limit will not only affect the normal operation of the power grid, but may also cause a decline in the quality of electricity used by users and even damage the power grid equipment.

[0004] In the prior art, before low voltage over-limit regulation, it is necessary to first determine the voltage status of the power grid. Voltage data alone cannot reliably describe the voltage status, resulting in inaccurate subsequent regulation and poor regulation effect.

[0005] Therefore, how to improve the accuracy of judging the voltage status of the power grid is a technical problem that needs to be solved. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention is proposed.

[0007] Therefore, the problem to be solved by the present invention is how to solve the technical problem of low accuracy in judging the voltage state of the power grid in the prior art.

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

[0009] In a first aspect, an embodiment of the present invention provides a method for controlling low voltage over-limit of a distributed photovoltaic power station, which includes obtaining relevant capacity information of a power grid and determining the capacity of the power grid, obtaining load data of the power grid and determining the load degree of the power grid;

[0010] Based on the grid capacity and grid load level, the grid-connected capacity of the photovoltaic power station is obtained, multiple safety margin influencing factors are obtained, and the causal indicators of multiple safety margin influencing factors and safety margin are calculated to set the safety margin;

[0011] Determine the access point based on the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, and monitor the data changes near the access point;

[0012] The grid voltage status is determined based on data changes near the access point, and multiple control methods are used to adjust the grid voltage level.

[0013] As a preferred solution of the low voltage over-limit control method of the distributed photovoltaic power station of the present invention, the obtaining of grid load data and determining the grid load degree includes:

[0014] The grid load data includes daily load curve and peak load. The daily load curve is split into multiple sub-load curves according to different time periods within a day.

[0015] Calculate the slope change of each sub-load curve and the peak load of each sub-load curve;

[0016] The difference between the peak load of each sub-load curve and the grid capacity is calculated according to the time impact weight corresponding to different time periods;

[0017] A correction coefficient is determined based on the slope change, thereby correcting each difference to obtain a comprehensive difference;

[0018] The grid load level is determined based on the combined difference.

[0019] As a preferred solution of the low voltage over-limit control method of the distributed photovoltaic power station of the present invention, wherein: the causal index of multiple safety margin influencing factors and safety margin is calculated to set the safety margin, including:

[0020] The safety margin influencing factors whose causal indicators exceed the threshold of the first indicator are regarded as the main influencing factors;

[0021] The safety margin influencing factors whose causal indicators exceed the second indicator threshold and do not exceed the first indicator threshold are taken as the influencing factors to be studied;

[0022] Calculate the causal index between the influencing factor to be investigated and the main influencing factor, and take the influencing factor to be investigated whose causal index exceeds the third indicator threshold as the auxiliary influencing factor;

[0023] The corresponding influence weights are assigned to the main influencing factors and the auxiliary influencing factors respectively, so as to set the safety margin.

[0024] As a preferred solution of the low voltage over-limit control method of the distributed photovoltaic power station of the present invention, wherein: the access point is determined according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, including:

[0025] According to the grid-connected capacity of the photovoltaic power station with a safety margin, multiple voltages matching its capacity are determined, thereby determining multiple access points to be selected;

[0026] Additional information includes the distance from the access point to the substation, grid load conditions, and grid stability;

[0027] The priorities of the distance to the substation, the grid load and the grid stability are determined respectively, and an optimal access point is selected from multiple candidate access points according to the priority comparison.

[0028] As a preferred solution of the low voltage over-limit control method of the distributed photovoltaic power station of the present invention, wherein: the voltage state of the power grid is judged according to the data change near the access point, and multiple means are used for corresponding control to adjust the voltage level of the power grid, including:

[0029] The data near the access point include grid voltage, grid frequency, grid load and grid power factor;

[0030] If the grid voltage is not within the preset reasonable range, the grid voltage state is judged to be high or low;

[0031] Otherwise, the grid voltage state is determined according to the degree of matching between the grid frequency, grid load and grid power factor and their respective preset change relationships;

[0032] If the comprehensive matching degree exceeds the preset matching degree, it is judged that the grid voltage state is higher or lower;

[0033] Otherwise, it is judged that the grid voltage state is normal;

[0034] When the grid voltage is high or low, active power control, reactive power control and energy storage system control are performed.

[0035] As a preferred solution of the low voltage over-limit control method of the distributed photovoltaic power station described in the present invention, the active power control includes:

[0036] Acquiring voltage information through a voltage monitoring device;

[0037] When the grid voltage is too low, the active power output of the photovoltaic power station is reduced, reducing the power injected into the grid.

[0038] As a preferred solution of the low voltage over-limit control method of the distributed photovoltaic power station of the present invention, the energy storage system control includes:

[0039] In low-voltage situations, the energy storage system injects stored electricity into the grid, increasing the grid voltage;

[0040] Under high voltage conditions, the energy storage system absorbs electricity from the grid and reduces the grid voltage.

[0041] In a second aspect, an embodiment of the present invention provides a low voltage over-limit control system for a distributed photovoltaic power station, which includes a capacity acquisition module, a safety margin setting module, an access point determination module, and a voltage control module;

[0042] The capacity acquisition module is used to acquire the capacity information related to the power grid and determine the power grid capacity, acquire the power grid load data and determine the power grid load degree;

[0043] The safety margin setting module is used to obtain the grid-connected capacity of the photovoltaic power station based on the grid capacity and the grid load degree, obtain multiple safety margin influencing factors, and calculate the causal indicators of the multiple safety margin influencing factors and the safety margin, so as to set the safety margin;

[0044] The access point determination module is used to determine the access point according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, and monitor the data changes near the access point;

[0045] The voltage control module is used to determine the voltage status of the power grid according to the data changes near the access point, and adopt multiple means to control accordingly to adjust the voltage level of the power grid.

[0046] In a third aspect, an embodiment of the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, the steps of the low-voltage over-limit control method of the distributed photovoltaic power station as described in the first aspect of the present invention are implemented.

[0047] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, the steps of the low-voltage over-limit control method for a distributed photovoltaic power station as described in the first aspect of the present invention are implemented.

[0048] The beneficial effects of the present invention are as follows: the present invention proposes a low voltage over-limit control method and system for a distributed photovoltaic power station, obtains grid-related capacity information and determines the grid capacity, obtains grid load data and determines the grid load degree; obtains the grid-connected capacity of the photovoltaic power station based on the grid capacity and the grid load degree, obtains multiple safety margin influencing factors, and calculates the causal index of multiple safety margin influencing factors and the safety margin, thereby setting the safety margin; determines the access point according to the grid-connected capacity of the photovoltaic power station with safety margin and additional information, and monitors the data changes near the access point; judges the grid voltage state according to the data changes near the access point, and adopts multiple means to control accordingly to adjust the voltage level of the grid. The present invention judges and controls the voltage state of the grid through comprehensive analysis of multiple data, which greatly improves the accuracy and effect of the control. Specifically, the present invention sets the safety margin by calculating the causal index of multiple safety margin influencing factors and the safety margin, so as to improve the accuracy of the grid-connected capacity of the photovoltaic power station and facilitate the subsequent state judgment. At the same time, by determining the access point according to the grid-connected capacity of the photovoltaic power station with safety margin and additional information, the accuracy of the subsequent state judgment is improved. By judging the grid voltage status based on data changes near the access point and adopting multiple means of corresponding control, the accuracy of grid voltage status judgment, regulation precision and regulation effect are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of 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 work.

[0050] Figure 1 It is a flow chart of the low voltage over-limit control method of the distributed photovoltaic power station;

[0051] Figure 2 It is a structural diagram of the low voltage over-limit control system of the distributed photovoltaic power station; DETAILED DESCRIPTION

[0052] In order to make the above-mentioned objects, 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 accompanying drawings.

[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] Example 1

[0056] Reference Figure 1 , which is the first embodiment of the present invention, and provides a method for regulating low voltage over-limit of a distributed photovoltaic power station, comprising:

[0057] S1, obtaining grid-related capacity information and determining grid capacity, obtaining grid load data and determining grid load degree;

[0058] In the embodiment of the present application, obtaining grid load data and determining the grid load degree include:

[0059] The grid load data includes daily load curve and peak load. The daily load curve is split into multiple sub-load curves according to different time periods within a day.

[0060] Calculate the slope change of each sub-load curve and the peak load of each sub-load curve;

[0061] The difference between the peak load of each sub-load curve and the grid capacity is calculated according to the time impact weight corresponding to different time periods;

[0062] A correction coefficient is determined based on the slope change, thereby correcting each difference to obtain a comprehensive difference;

[0063] The grid load level is determined based on the combined difference.

[0064] It should be noted that the capacity information related to the power grid includes the substation capacity, transmission line capacity and distribution transformer capacity of the power grid, so as to understand the power supply capacity of the power grid; a correction coefficient is determined based on the slope change, so as to correct each difference and obtain a comprehensive difference. Each slope change corresponds to a correction coefficient, and the correction of each difference = correction coefficient * difference.

[0065] S2, based on the grid capacity and grid load level, the grid-connected capacity of the photovoltaic power station is obtained, multiple safety margin influencing factors are obtained, and the causal indicators of multiple safety margin influencing factors and the safety margin are calculated, so as to set the safety margin;

[0066] In the embodiment of the present application, multiple safety margin influencing factors and causal indicators of the safety margin are calculated to set the safety margin, including:

[0067] The safety margin influencing factors whose causal indicators exceed the threshold of the first indicator are regarded as the main influencing factors;

[0068] The safety margin influencing factors whose causal indicators exceed the second indicator threshold and do not exceed the first indicator threshold are taken as the influencing factors to be studied;

[0069] Calculate the causal index between the influencing factor to be investigated and the main influencing factor, and take the influencing factor to be investigated whose causal index exceeds the third indicator threshold as the auxiliary influencing factor;

[0070] The corresponding influence weights are assigned to the main influencing factors and the auxiliary influencing factors respectively, so as to set the safety margin.

[0071] It should be noted that when determining the grid-connected capacity of a photovoltaic power station, it is usually necessary to set a certain safety margin. The safety margin is to ensure the stable operation of the power grid and the safe operation of the photovoltaic power station, and to make appropriate conservative settings for the grid-connected capacity in consideration of unforeseen factors and changes. Multiple safety margin influencing factors include weather and climate, sunshine intensity, inverter capacity, etc.

[0072] It should also be noted that the causal index here is a nonlinear interdependence index, which is based on the state space reconstruction and neighbor distance method to determine the direction and size of the causal relationship. For two independent systems or factors X and Y, the state space of the two systems is established according to the state space reconstruction theory.

[0073] For a sample point X in the state space X n , x rn,1 ,...,Xrn,ko represents X n k nearest neighbor points in the state space X, calculate X n The average Euclidean distance to k nearest neighbors:

[0074]

[0075] For a sample point y in the state space Y n ,y sn，1 , ..., y sn，k Represents y n The k nearest points in the state space Y are mapped to the state space X and X is calculated. n and k nearest neighbor points x sn，1 , ..., x sn，k The average Euclidean distance of :

[0076] In order to simplify the calculation, we can use X n The average distance to all N sample points:

[0077]

[0078] The nonlinear interdependence indicator is the state space method, which determines the causal relationship between systems based on the mapping relationship of the state space and is defined as:

[0079] According to the definition, 0 X→Y ≤1, when S X→Y When S approaches 0, systems X and Y are independent of each other. X→Y When it is significantly greater than 0, there is a causal relationship from system X to Y, and the closer it is to 1, the stronger the causality.

[0080] S3, determining the access point according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, and monitoring the data changes near the access point;

[0081] In the embodiment of the present application, the access point is determined according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, including:

[0082] According to the grid-connected capacity of the photovoltaic power station with a safety margin, multiple voltages matching its capacity are determined, thereby determining multiple access points to be selected;

[0083] Additional information includes the distance from the access point to the substation, grid load conditions, and grid stability;

[0084] The priorities of the distance to the substation, the grid load and the grid stability are determined respectively, and an optimal access point is selected from multiple candidate access points according to the priority comparison.

[0085] It should be noted that nearby data include voltage, frequency, load, etc. Just looking at the voltage cannot accurately indicate the voltage status of the power grid, and it needs to be judged in combination with other relevant parameters.

[0086] When the power grid is in a low voltage or high voltage state, the following parameters may change:

[0087] Grid voltage: In the low voltage state, the grid voltage will decrease and be lower than the rated voltage range; in the high voltage state, the grid voltage will increase and exceed the rated voltage range.

[0088] Grid frequency: Grid frequency is usually stable, but it may be affected under low or high voltage conditions. For example, when the grid voltage is low, the grid frequency may decrease; when the grid voltage is high, the grid frequency may increase.

[0089] Grid load: In a low-voltage state, the grid load may be large because the grid voltage drops and more electricity is needed to meet the load demand; in a high-voltage state, the grid load may be small because the grid voltage rises and less electricity is needed to meet the load demand.

[0090] ​Grid power factor: Under low voltage conditions, due to voltage drop, the power factor may be low, resulting in a mismatch between active power and reactive power; under high voltage conditions, the power factor may be high, resulting in a mismatch between active power and reactive power.

[0091] S4, judging the voltage status of the power grid according to the data changes near the access point, and adopting multiple means of corresponding control to adjust the voltage level of the power grid;

[0092] In the embodiment of the present application, the voltage state of the power grid is determined according to the data changes near the access point, and multiple means are used for corresponding control to adjust the voltage level of the power grid, including:

[0093] The data near the access point include grid voltage, grid frequency, grid load and grid power factor;

[0094] If the grid voltage is not within the preset reasonable range, the grid voltage state is judged to be high or low;

[0095] Otherwise, the grid voltage state is determined according to the degree of matching between the grid frequency, grid load and grid power factor and their respective preset change relationships;

[0096] If the comprehensive matching degree exceeds the preset matching degree, it is judged that the grid voltage state is higher or lower;

[0097] Otherwise, it is judged that the grid voltage state is normal;

[0098] When the grid voltage is high or low, active power control, reactive power control and energy storage system control are performed.

[0099] Furthermore, active power control includes:

[0100] Acquiring voltage information through a voltage monitoring device;

[0101] When the grid voltage is too low, the active power output of the photovoltaic power station is reduced, reducing the power injected into the grid.

[0102] Furthermore, the energy storage system control includes:

[0103] In low-voltage situations, the energy storage system injects stored electricity into the grid, increasing the grid voltage;

[0104] Under high voltage conditions, the energy storage system absorbs electricity from the grid and reduces the grid voltage.

[0105] It should be noted that active power control: the control system of the distributed photovoltaic power station adjusts the active power of the photovoltaic power station according to the information provided by the voltage monitoring device. When the grid voltage is too low, the active power output of the photovoltaic power station is reduced to reduce the power injected into the grid. Reactive power control: In addition to active power control, the voltage level of the grid can also be affected by adjusting the reactive power output of the photovoltaic power station. Increase or decrease the reactive power output of the photovoltaic power station to adjust the voltage to an appropriate range. Energy storage system assists in regulation: If the distributed photovoltaic power station is equipped with an energy storage system, the energy storage system can be used to adjust the voltage. In low-voltage conditions, the energy storage system can inject stored power into the grid to increase the grid voltage.

[0106] This embodiment also provides a computer device, which is suitable for the low-voltage over-limit control method of a distributed photovoltaic power station, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute computer-executable instructions to implement the low-voltage over-limit control method of a distributed photovoltaic power station proposed in the above embodiment.

[0107] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0108] This embodiment further provides a storage medium on which a computer program is stored. When the program is executed by a processor, the method for implementing low-voltage over-limit control of a distributed photovoltaic power station as proposed in the above embodiment is implemented.

[0109] In summary, the present invention proposes a low-voltage over-limit control method and system for a distributed photovoltaic power station, which obtains grid-related capacity information and determines the grid capacity, obtains grid load data and determines the grid load degree; obtains the grid-connected capacity of the photovoltaic power station based on the grid capacity and the grid load degree, obtains multiple safety margin influencing factors, and calculates the causal index of multiple safety margin influencing factors and the safety margin, thereby setting the safety margin; determines the access point according to the grid-connected capacity of the photovoltaic power station with safety margin and additional information, and monitors the data changes near the access point; judges the grid voltage state according to the data changes near the access point, and adopts multiple means to control accordingly to adjust the voltage level of the grid. The present invention judges and regulates the voltage state of the grid through comprehensive analysis of multiple data, which greatly improves the accuracy and effect of regulation. Specifically, the present invention sets the safety margin by calculating the causal index of multiple safety margin influencing factors and the safety margin, so as to improve the accuracy of the grid-connected capacity of the photovoltaic power station and facilitate subsequent state judgment. At the same time, by determining the access point according to the grid-connected capacity of the photovoltaic power station with safety margin and additional information, the accuracy of subsequent state judgment is improved. By judging the grid voltage status based on data changes near the access point and adopting multiple means of corresponding control, the accuracy of grid voltage status judgment, regulation precision and regulation effect are improved.

[0110] Example 2

[0111] This is the second embodiment of the present invention. This embodiment provides a low-voltage over-limit control method for a distributed photovoltaic power station. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0112] This experiment selected a newly built distributed photovoltaic power station in the suburbs of City A in a certain province as the test object. The installed capacity of the photovoltaic power station is 5MW. In order to verify the effectiveness of the present invention, March 15, 2024 to March 21, 2024 was selected as the test period, during which the photovoltaic power station was subjected to a low voltage over-limit regulation experiment.

[0113] First, the grid capacity information of the area is obtained through the grid monitoring system. The rated capacity of the substation is 20MVA, the maximum transmission capacity of the transmission line is 15MW, and the capacity of the distribution transformer is 10MVA. The load data of the area within a week is collected through the load monitoring system, and the 24 hours a day are divided into 4 time periods (0:00-6:00, 6:00-12:00, 12:00-18:00, 18:00-24:00), and 28 sub-load curves are obtained. The slope change is calculated for each sub-load curve, with a value range of 0.15 to 0.85, and the peak load is recorded. At the same time, according to historical statistical data, the time impact weights of 0.6, 1.0, 0.9, and 0.8 are assigned to the four time periods respectively.

[0114] In terms of safety margin setting, five influencing factors are considered, including weather and climate (X1), sunshine intensity (X2), inverter capacity (X3), grid fluctuation (X4) and load change (X5). The causal index of each factor and the safety margin is calculated by the nonlinear interdependence index calculation method. The threshold of the first index is set to 0.8, the threshold of the second index is set to 0.6, and the threshold of the third index is set to 0.7. After calculation, X1 and X2 are determined to be the main influencing factors, and X3 is determined to be the auxiliary influencing factor, and the influence weights are assigned to 0.4, 0.4, and 0.2 respectively.

[0115] In terms of access point selection, four candidate access points A1-A4 with matching voltage levels were determined based on the 5MW grid-connected capacity of the photovoltaic power station. Taking into account three factors, namely, the distance to the substation (weight 0.3), the grid load (weight 0.4), and the grid stability (weight 0.3), a scoring system was established for priority sorting.

[0116] During operation, the grid voltage, grid frequency, grid load and grid power factor data near the access point are collected every 5 minutes. The voltage reasonable range is set to ±5% of the rated voltage, the frequency change relationship matching threshold is 0.85, the load change relationship matching threshold is 0.80, and the power factor change relationship matching threshold is 0.75. When voltage anomalies are detected, multiple control measures are activated, including active power regulation, reactive power compensation and energy storage system coordinated control.

[0117] Testing Site A1 A2 A3 A4 Traditional methods Access point distance (km) 2.1 3.5 1.8 4.2 2.8 Voltage stability (%) 98.5 97.2 98.8 96.5 95.1 Voltage regulation time(s) 1.2 1.5 1.1 1.8 3.5 Power factor improvement rate (%) 6.8 5.9 7.2 5.5 3.2 System reliability (%) 99.2 98.5 99.5 97.8 96.4 Power quality indicators 0.95 0.92 0.96 0.89 0.85 Load balance (%) 95.8 94.2 96.5 93.5 91.2 Control success rate (%) 98.5 97.2 98.9 96.8 94.3

[0118] By comparing the experimental data, the following important conclusions can be drawn:

[0119] Voltage regulation performance: The voltage regulation time achieved by the method of the present invention at the A3 access point is only 1.1 seconds, which is 68.6% shorter than the 3.5 seconds of the traditional method, and the voltage stability reaches 98.8%, which is 3.7 percentage points higher than the traditional method. This significant improvement is mainly due to the synergy of multi-dimensional data analysis and multiple control methods adopted by the present invention.

[0120] System reliability: Through the precise setting of the safety margin and the optimal selection of access points, the system reliability achieved by the present invention at the A3 access point reached 99.5%, which is 3.1 percentage points higher than the 96.4% of the traditional method. This shows that the causal indicator analysis method proposed by the present invention can more accurately evaluate the role of each influencing factor, thereby improving the overall stability of the system.

[0121] Load balancing: Experimental data show that the load balancing degree of the method of the present invention at the A3 access point reaches 96.5%, which is 5.3 percentage points higher than that of the traditional method. This improvement is due to the refined processing of the power grid load data by the present invention, which better adapts to the load change characteristics through time division and weight allocation.

[0122] Control effect: The control success rate of the method of the present invention at the A3 access point reached 98.9%, which is 4.6 percentage points higher than that of the traditional method. At the same time, the power factor improvement rate reached 7.2%, which is 2.25 times that of the traditional method. This fully proves the superiority of the multi-means corresponding control strategy proposed by the present invention.

[0123] Comprehensive performance: From the perspective of power quality indicators, the method of the present invention reaches 0.96 at the A3 access point, which is 12.9% higher than the traditional method. This shows that the present invention can not only effectively deal with the low voltage limit problem, but also comprehensively improve the power quality level.

[0124] Through this set of experimental data, it can be clearly seen that the method of the present invention has achieved significant advantages in key indicators such as voltage regulation time, system reliability, and load balance. In particular, the comprehensive performance of the A3 access point is the most outstanding, which verifies the effectiveness of the access point selection method proposed in the present invention. At the same time, the experimental data also shows that the safety margin setting method and multiple control strategies proposed in the present invention can better adapt to the actual operating environment and achieve better control effects.

[0125] Example 3

[0126] Reference Figure 2 , which is the third embodiment of the present invention, and which provides a low voltage over-limit control system for a distributed photovoltaic power station, comprising:

[0127] Capacity acquisition module 201, safety margin setting module 202, access point determination module 203, voltage regulation module 204;

[0128] The capacity acquisition module 201 is used to acquire the capacity information related to the power grid and determine the capacity of the power grid, acquire the load data of the power grid and determine the load degree of the power grid;

[0129] A safety margin setting module 202 is used to obtain the grid-connected capacity of the photovoltaic power station based on the grid capacity and the grid load degree, obtain multiple safety margin influencing factors, and calculate the causal indicators of the multiple safety margin influencing factors and the safety margin, so as to set the safety margin;

[0130] An access point determination module 203 is used to determine an access point according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, and monitor data changes near the access point;

[0131] The voltage control module 204 is used to determine the voltage status of the power grid according to the data changes near the access point, and adopt multiple means to control accordingly to adjust the voltage level of the power grid.

[0132] Furthermore, the capacity acquisition module 201 is used to:

[0133] Grid load data includes daily load curve and peak load;

[0134] Split the daily load curve into multiple sub-load curves according to different time periods within a day;

[0135] Calculate the slope change of each sub-load curve and the peak load of each sub-load curve;

[0136] The difference between the peak load of each sub-load curve and the grid capacity is calculated according to the time impact weight corresponding to different time periods;

[0137] A correction coefficient is determined based on the slope change, thereby correcting each difference to obtain a comprehensive difference;

[0138] The grid load level is determined based on the combined difference.

[0139] Furthermore, the safety margin setting module 202 is used to:

[0140] The safety margin influencing factors whose causal indicators exceed the threshold of the first indicator are regarded as the main influencing factors;

[0141] The safety margin influencing factors whose causal indicators exceed the second indicator threshold and do not exceed the first indicator threshold are taken as the influencing factors to be studied;

[0142] Calculate the causal index between the influencing factor to be investigated and the main influencing factor, and take the influencing factor to be investigated whose causal index exceeds the third indicator threshold as the auxiliary influencing factor;

[0143] The corresponding influence weights are assigned to the main influencing factors and the auxiliary influencing factors respectively, so as to set the safety margin.

[0144] Furthermore, the access point determination module 203 is configured to:

[0145] According to the grid-connected capacity of the photovoltaic power station with a safety margin, multiple voltages matching its capacity are determined, thereby determining multiple access points to be selected;

[0146] Additional information includes the distance from the access point to the substation, grid load conditions, and grid stability;

[0147] The priorities of the distance to the substation, the grid load and the grid stability are determined respectively, and an optimal access point is selected from multiple candidate access points according to the priority comparison.

[0148] Furthermore, the voltage control module 204 is used to:

[0149] The data near the access point include grid voltage, grid frequency, grid load and grid power factor;

[0150] If the grid voltage is not within the preset reasonable range, the grid voltage state is judged to be high or low;

[0151] Otherwise, the grid voltage state is determined according to the degree of matching between the grid frequency, grid load and grid power factor and their respective preset change relationships;

[0152] If the comprehensive matching degree exceeds the preset matching degree, it is judged that the grid voltage state is higher or lower;

[0153] Otherwise, it is judged that the grid voltage state is normal;

[0154] When the grid voltage is high or low, active power control, reactive power control and energy storage system control are performed.

[0155] 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 may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A low voltage over-limit control method for a distributed photovoltaic power station, characterized in that: include, Obtain relevant capacity information of the power grid and determine the capacity of the power grid, obtain power grid load data and determine the degree of power grid load; Based on the grid capacity and grid load level, the grid-connected capacity of the photovoltaic power station is obtained, multiple safety margin influencing factors are obtained, and the causal indicators of multiple safety margin influencing factors and safety margin are calculated to set the safety margin; Determine the access point based on the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, and monitor the data changes near the access point; The grid voltage status is determined based on data changes near the access point, and multiple control methods are used to adjust the grid voltage level.

2. The low voltage over-limit control method of a distributed photovoltaic power station according to claim 1, characterized in that: The obtaining of grid load data and determining the grid load degree includes: The grid load data includes daily load curve and peak load. The daily load curve is split into multiple sub-load curves according to different time periods within a day. Calculate the slope change of each sub-load curve and the peak load of each sub-load curve; The difference between the peak load of each sub-load curve and the grid capacity is calculated according to the time impact weight corresponding to different time periods; A correction coefficient is determined based on the slope change, thereby correcting each difference to obtain a comprehensive difference; The grid load level is determined based on the combined difference.

3. The low voltage over-limit control method of a distributed photovoltaic power station as claimed in claim 2, characterized in that: Describe and calculate multiple safety margin influencing factors and safety margin causal indicators to set the safety margin, including: The safety margin influencing factors whose causal indicators exceed the threshold of the first indicator are regarded as the main influencing factors; The safety margin influencing factors whose causal indicators exceed the second indicator threshold and do not exceed the first indicator threshold are taken as the influencing factors to be studied; Calculate the causal index between the influencing factor to be investigated and the main influencing factor, and take the influencing factor to be investigated whose causal index exceeds the third indicator threshold as the auxiliary influencing factor; The corresponding influence weights are assigned to the main influencing factors and the auxiliary influencing factors respectively, so as to set the safety margin.

4. The low voltage over-limit control method of a distributed photovoltaic power station as claimed in claim 3, characterized in that: The step of determining the access point according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information includes: According to the grid-connected capacity of the photovoltaic power station with a safety margin, multiple voltages matching its capacity are determined, thereby determining multiple access points to be selected; Additional information includes the distance from the access point to the substation, grid load conditions, and grid stability; The priorities of the distance to the substation, the grid load and the grid stability are determined respectively, and an optimal access point is selected from multiple candidate access points according to the priority comparison.

5. The low voltage over-limit control method of a distributed photovoltaic power station as claimed in claim 4, characterized in that: The method of judging the voltage state of the power grid according to the data changes near the access point and adopting multiple means of corresponding control to adjust the voltage level of the power grid includes: Data near the access point include grid voltage, grid frequency, grid load and grid power factor; If the grid voltage is not within the preset reasonable range, the grid voltage state is judged to be high or low; Otherwise, the grid voltage state is determined according to the degree of matching between the grid frequency, grid load and grid power factor and their respective preset change relationships; If the comprehensive matching degree exceeds the preset matching degree, it is judged that the grid voltage state is higher or lower; Otherwise, it is judged that the grid voltage state is normal; When the grid voltage is high or low, active power control, reactive power control and energy storage system control are performed.

6. The low voltage over-limit control method of a distributed photovoltaic power station as claimed in claim 5, characterized in that: The active power control comprises: Acquiring voltage information through a voltage monitoring device; When the grid voltage is too low, the active power output of the photovoltaic power station is reduced, reducing the power injected into the grid.

7. The low voltage over-limit control method of a distributed photovoltaic power station according to claim 6, characterized in that: The energy storage system control includes: In low-voltage situations, the energy storage system injects stored electricity into the grid, increasing the grid voltage; Under high voltage conditions, the energy storage system absorbs electricity from the grid and reduces the grid voltage.

8. A low voltage over-limit control system for a distributed photovoltaic power station, based on the low voltage over-limit control method for a distributed photovoltaic power station according to any one of claims 1 to 7, characterized in that: It also includes a capacity acquisition module, a safety margin setting module, an access point determination module, and a voltage control module; The capacity acquisition module is used to acquire the capacity information related to the power grid and determine the power grid capacity, acquire the power grid load data and determine the power grid load degree; The safety margin setting module is used to obtain the grid-connected capacity of the photovoltaic power station based on the grid capacity and the grid load degree, obtain multiple safety margin influencing factors, and calculate the causal indicators of the multiple safety margin influencing factors and the safety margin, so as to set the safety margin; The access point determination module is used to determine the access point according to the grid-connected capacity of the photovoltaic power station with a safety margin and additional information, and monitor the data changes near the access point; The voltage control module is used to determine the voltage status of the power grid according to the data changes near the access point, and adopt multiple means to control accordingly to adjust the voltage level of the power grid.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the low-voltage over-limit control method for a distributed photovoltaic power station according to any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the low-voltage over-limit control method for a distributed photovoltaic power station according to any one of claims 1 to 7 are implemented.

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