Method for coordinated voltage control of distributed photovoltaic agricultural park access to power grid

Abstract

A method for coordinated voltage control of distributed photovoltaic agricultural parks connected to the grid, belonging to the field of control and regulation technology, employs fuzzy control to optimize the state of charge (SOC) of energy storage devices. This method maintains the SOC of both batteries and supercapacitors within a reasonable range, with reduced fluctuations, avoiding operation in overcharge and over-discharge zones and thus extending the life of the energy storage components. Maintaining the battery SOC between 0.2 and 0.8 effectively reduces grid transmission congestion. This method effectively avoids the drawback of existing methods for coordinated voltage control of distributed photovoltaic agricultural parks connected to the grid, which often fail to achieve comprehensive coordinated control of low-voltage grid voltage fluctuations and non-blocking transmission.

Description

Technical Field

[0001] The present invention belongs to the technical field of control and regulation, and in particular relates to a method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid. Background Art

[0002] To address the coordinated control of grid voltage in agricultural parks with a high proportion of distributed photovoltaics, dynamic regulation must be achieved through a combination of grid structure optimization, multi-level resource coordination, and intelligent control technologies. Current methods for coordinated grid voltage control in agricultural parks connected to distributed photovoltaics require comprehensive coordinated control of low-voltage grid voltage fluctuations and non-blocking transmission.

[0003] However, the current method of coordinated control of voltage in agricultural parks connected to distributed photovoltaic grids cannot achieve the functions of comprehensive coordinated control of voltage fluctuations in low-voltage grids and non-blocking transmission. Summary of the Invention

[0004] In order to solve the defects in the existing technology, the present invention proposes a method for coordinated control of voltage of agricultural parks connected to distributed photovoltaic grids, which effectively avoids the defects of the existing technology in that the method for coordinated control of voltage of agricultural parks connected to distributed photovoltaic grids cannot achieve the functions of comprehensive coordinated control of low-voltage grid voltage fluctuations and non-blocking transmission.

[0005] The present invention utilizes the following technical solutions.

[0006] A method for coordinated voltage control of an agricultural park connected to a distributed photovoltaic grid, comprising:

[0007] Step 1: Analyze and identify voltage fluctuations in the grid connected to the agricultural park connected to distributed photovoltaics;

[0008] Step 2: Configure the distributed energy storage capacity connected to the grid voltage coordinated control;

[0009] Step 3: Energy storage control enables non-blocking transmission of low-voltage grid fluctuations and system optimization.

[0010] Preferably, step 1 specifically includes:

[0011] Step 1-1: First, deploy intelligent monitoring equipment and data acquisition systems to monitor grid voltage fluctuations in real time;

[0012] Step 1-2: The intelligent monitoring equipment collects the voltage signal, frequency, amplitude, and duration of voltage fluctuations in real time and transmits them to the data center for further processing and analysis.

[0013] Preferably, in step 1-1, the data center, the intelligent monitoring device and the data acquisition system are communicatively connected in sequence; the data acquisition system transmits the voltage signal of the power grid collected in real time to the intelligent monitoring device to obtain the frequency, amplitude and duration parameters of the voltage fluctuation.

[0014] Preferably, in step 1-1, the method for the intelligent monitoring device to obtain the frequency, amplitude and duration parameters of the voltage fluctuation includes:

[0015] (1) Use the Fast Fourier Transform (FFT) algorithm to perform frequency domain analysis on the collected voltage signal and extract the frequency components of the voltage fluctuation;

[0016] (2) Amplitude calculation: Calculate the amplitude of the voltage fluctuation based on the analysis results obtained by the Fast Fourier Transform (FFT) algorithm. The amplitude calculation method is as follows: Count the amplitudes of the corresponding frequency components in the FFT results to obtain the maximum amplitude of the voltage fluctuation, which is used as the amplitude of the voltage fluctuation.

[0017] (3) Duration calculation: The duration of voltage fluctuation is detected by the time window sliding method.

[0018] Preferably, in step 1-1, the amplitude value The calculation method corresponding to the formula is:

[0019]

[0020] in, Indicates the amplitude at each frequency point in the FFT result.

[0021] Preferably, in steps 1-2, the method for further processing and analysis by the data center includes: establishing a data model of voltage fluctuations, the data model including voltage signals, the frequency, amplitude and duration of voltage fluctuations, spectrum analysis results and waveform diagrams, to help analysts fully understand the characteristics of grid voltage fluctuations. Through data analysis and processing, voltage fluctuation problems in the grid can be identified and the causes of the fluctuations can be determined.

[0022] Preferably, in step 1-2, the method for determining the cause of the fluctuation includes:

[0023] Analyze the cause based on the frequency, amplitude and duration of the extracted voltage fluctuations:

[0024] Frequency analysis: The main frequency component is 50 Hz, which is related to power failure;

[0025] Amplitude analysis: If the amplitude value is below 0.5, the severity of the fluctuation is judged to be low, otherwise it is judged to be high;

[0026] Duration analysis: If the fluctuation duration is less than 50ms, the instantaneous nature of the fault is good; otherwise, the instantaneous nature of the fault is poor.

[0027] Preferably, in step 1-2, a wave recording meter is installed in the park to perform grid voltage waveform analysis.

[0028] Preferably, step 2 specifically includes:

[0029] Step 2-1: Consider cost, efficiency, and applicability factors and select a suitable energy storage method;

[0030] Step 2-2: Determine the optimal energy storage location, which is between the grid load and the photovoltaic power generation system;

[0031] Step 2-3: Determine the most economical energy storage capacity based on the load demand of the substation and the output characteristics of the photovoltaic system to meet the compensation needs for voltage fluctuations and reduce costs.

[0032] Preferably, in step 2-1, a method for selecting a suitable energy storage method taking into account factors such as cost, efficiency, and applicability includes:

[0033] Step 2-1-1: Construction of evaluation index system, which specifically includes:

[0034] Cost indicators:

[0035] Initial investment cost: the initial purchase and installation cost of the energy storage method;

[0036] Operation and maintenance costs: maintenance and management costs of energy storage during operation;

[0037] Total life cycle cost: The total cost of the energy storage method over its entire life cycle, including initial investment cost, operation and maintenance costs, and decommissioning costs;

[0038] Efficiency indicators:

[0039] Energy storage efficiency: the efficiency of energy conversion during charging and discharging of energy storage methods;

[0040] Charge and discharge rate: The charge and discharge rate of the energy storage method, reflecting its response speed;

[0041] Energy conversion efficiency: the energy conversion efficiency of the energy storage method during the charging and discharging process;

[0042] Applicability indicators:

[0043] Cycle life: The number of charge and discharge cycles of an energy storage method reflects its service life.

[0044] Environmental adaptability: the ability of energy storage methods to adapt to different environmental conditions;

[0045] Installation convenience: The installation complexity and convenience of the energy storage method;

[0046] Maintenance ease: How easy and difficult it is to maintain the energy storage method;

[0047] Step 2-1-2: Weight determination, which specifically includes:

[0048] Data preparation: Collect historical data, including performance data of various energy storage methods in actual applications;

[0049] Model building: Build a performance data-driven weight determination model;

[0050] Weight calculation: Use the weight determination model to calculate the weight of each evaluation indicator.

[0051] Step 2-1-3: Score calculation:

[0052] Data standardization: standardize the data of different evaluation indicators to make them comparable;

[0053] Weighted average: Calculate the comprehensive score of each energy storage method based on the weights and standardized data. The calculation formula is as follows:

[0054]

[0055] in, For the Comprehensive rating of energy storage methods, For the The weight of the evaluation index, For the Energy storage method Standardized values ​​on the evaluation indicators;

[0056] The energy storage method with the highest value is regarded as the appropriate energy storage method.

[0057] Preferably, in step 2-3, the following steps are performed:

[0058] (1) Collect the load demand data of the substation and the output characteristic data of the photovoltaic system, including but not limited to the following aspects:

[0059] Load demand data: load curve, load peak, load fluctuation;

[0060] Photovoltaic output characteristic data: photovoltaic power output curve, photovoltaic power peak, photovoltaic power fluctuation;

[0061] Voltage fluctuation data: historical data of voltage fluctuation;

[0062] (2) Load demand analysis:

[0063] Analyze the load demand of the substation. The specific steps are as follows:

[0064] Load curve analysis: draw the load curve of the substation and analyze the peak and fluctuation of the load;

[0065] Load peak determination: determine the peak value of the load, that is, the maximum load value;

[0066] Load fluctuation: Analyze load fluctuations, including the frequency and amplitude of load changes;

[0067] (3) Photovoltaic output characteristics analysis:

[0068] Analyze the output characteristics of the photovoltaic system. The specific steps are as follows:

[0069] Photovoltaic power output curve analysis: draw the power output curve of the photovoltaic system and analyze the peak and fluctuation of photovoltaic power;

[0070] Determination of photovoltaic power peak value: Determine the peak value of photovoltaic power, that is, the maximum output power of the photovoltaic system;

[0071] Photovoltaic power fluctuations: Analyze the fluctuations of photovoltaic power, including the frequency and amplitude of power changes;

[0072] (4) Voltage fluctuation analysis:

[0073] Combined with the load demand and photovoltaic output characteristics, analyze the voltage fluctuation in the substation area. The specific steps are as follows:

[0074] Voltage fluctuation frequency analysis: determine the frequency distribution of voltage fluctuations and analyze the periodicity and regularity of voltage fluctuations;

[0075] Voltage fluctuation amplitude analysis: determine the amplitude of voltage fluctuation, that is, the maximum amplitude of voltage fluctuation;

[0076] Voltage fluctuation duration analysis: determine the duration of voltage fluctuations, analyze the persistence and impact range of voltage fluctuations;

[0077] (5) Calculation of energy storage requirements:

[0078] Based on the analysis results of voltage fluctuations, calculate the required energy storage capacity to meet the voltage fluctuation compensation requirements. The specific steps are as follows:

[0079] Load compensation requirements: Calculate the energy storage capacity required for load compensation based on the peak and fluctuation conditions of load demand;

[0080] Photovoltaic fluctuation compensation requirements: Calculate the energy storage capacity required for photovoltaic fluctuation compensation based on the fluctuation of photovoltaic output characteristics.

[0081] Comprehensive energy storage demand: Determine the total energy storage demand by comprehensively considering the load compensation demand and the photovoltaic fluctuation compensation demand;

[0082] (6) Economic analysis:

[0083] Cost analysis: Analyze the initial investment cost and operation and maintenance costs of the energy storage system, including battery costs, installation costs, and maintenance costs;

[0084] Benefit analysis: Analyze the compensation effect of the energy storage system, including the degree of smoothing of voltage fluctuations and the degree of optimization of load balance;

[0085] Economic evaluation: Comprehensively consider costs and benefits, evaluate the economic feasibility of different energy storage capacities, and determine the most economical energy storage capacity;

[0086] (7) Optimize configuration:

[0087] Based on the economic analysis results, optimize the configuration of the energy storage system. The specific steps are as follows:

[0088] Capacity configuration: Determine the capacity configuration of the energy storage system based on the most economical energy storage capacity;

[0089] System design: Design the structure and layout of the energy storage system, including battery type, control system, and installation location;

[0090] Operation strategy: Develop an operation strategy for the energy storage system, including charge and discharge control, fault handling, and maintenance plans.

[0091] Preferably, in step 3, in the process of achieving non-blocking transmission, the discharging and charging power of the energy storage system are dynamically adjusted by a fuzzy algorithm.

[0092] The beneficial effects of the present invention are that, compared with the prior art, the technical effects of the present invention include:

[0093] The present invention converts voltage signals into the frequency domain for analysis, thereby understanding the frequency components and spectral characteristics of fluctuations, which helps identify fluctuation components within different frequency ranges. Subsequently, cause identification and analysis are performed. Combining the results of feature analysis and spectral analysis, the possible causes of voltage fluctuations in the power grid, such as fluctuations in the photovoltaic power generation system, grid load fluctuations, and equipment failures, are analyzed to determine the root cause of the fluctuations. Finally, an impact assessment and control strategy are conducted to evaluate the impact of voltage fluctuations on grid stability and equipment operation, determine the severity and impact range of the fluctuations, and formulate corresponding control strategies and optimization plans to ensure the stability and reliability of grid operation. The comprehensive analysis of these steps will help to fully understand the voltage fluctuations in the power grid, provide a scientific basis for further control and optimization, and ensure the safe and stable operation of the power grid. When fuzzy control is used to optimize the state of charge of energy storage devices, the state of charge of both batteries and supercapacitors can be maintained within a reasonable range, and the fluctuation amplitude is reduced, avoiding operation in the overcharge and overdischarge range, thereby extending the life of the energy storage components. Maintaining the battery state of charge between 0.2 and 0.8 effectively reduces grid transmission congestion. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 It is a flow chart of the method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid as described in the present invention. DETAILED DESCRIPTION

[0095] To make the objectives, technical solutions, and advantages of the present invention more clear, the following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely express the technical solutions of the present invention. The embodiments expressed in this application are only some embodiments of the present invention, not all embodiments. Based on the spirit of the present invention, other embodiments obtained by those skilled in the art without making creative efforts shall fall within the scope of protection of the present invention.

[0096] like Figure 1 As shown, the method of coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to the present invention includes:

[0097] Step 1: Analyze and identify voltage fluctuations in the grid connected to the agricultural park connected to distributed photovoltaics;

[0098] In a preferred but non-limiting embodiment of the present invention, step 1 specifically includes: Voltage fluctuation analysis in the power grid to which the agricultural park is connected is a key step in ensuring effective control of voltage fluctuations. Step 1-1: First, it is necessary to deploy intelligent monitoring equipment and data acquisition systems to monitor the voltage fluctuations of the power grid in real time;

[0099] In a preferred but non-limiting embodiment of the present invention, in step 1-1, a data center, an intelligent monitoring device, and a data acquisition system are sequentially communicatively connected. The data center can be a server, the intelligent monitoring device can be a PLC, and the data acquisition system can be a voltage sensor. The data acquisition system transmits real-time grid voltage signals to the intelligent monitoring device, thereby obtaining parameters such as the frequency, amplitude, and duration of voltage fluctuations.

[0100] In a preferred but non-limiting embodiment of the present invention, in step 1-1, the method for the intelligent monitoring device to obtain parameters such as the frequency, amplitude, and duration of voltage fluctuations includes:

[0101] (1) Use the Fast Fourier Transform (FFT) algorithm to perform frequency domain analysis on the collected voltage signal and extract the frequency components of the voltage fluctuation;

[0102] (2) Amplitude calculation: Calculate the amplitude of the voltage fluctuation based on the analysis results obtained by the Fast Fourier Transform (FFT) algorithm. The amplitude calculation method is as follows: Count the amplitudes of the corresponding frequency components in the FFT results to obtain the maximum amplitude of the voltage fluctuation, which is used as the amplitude of the voltage fluctuation.

[0103] (3) Duration calculation: The duration of voltage fluctuation is detected by the time window sliding method. The specific method is as follows: in the voltage signal, a time window is set, the time window is moved one by one, the fluctuation of the voltage signal within the time window is detected, and the start and end time points of the voltage fluctuation are recorded to calculate its duration. The time interval between the start and end time points of the voltage fluctuation is its duration. The duration of voltage fluctuation is detected by the time window sliding method. For example: in the voltage signal, a time window (such as 100 ms) is set, the time window is moved one by one, and the fluctuation of the voltage signal within the time window is detected. When the voltage signal exceeds the preset threshold within the time window, the start and end time points of the time window are recorded to calculate its duration. The size of the time window can be adjusted according to the actual application requirements to obtain more accurate detection results.

[0104] In a preferred but non-limiting embodiment of the present invention, in step 1-1, the amplitude value The calculation method corresponding to the formula is:

[0105]

[0106] in, Indicates the amplitude at each frequency point in the FFT result.

[0107] Step 1-2: At the same time, the intelligent monitoring equipment will collect the voltage signal, frequency, amplitude and duration of voltage fluctuations in real time and transmit it to the data center for further processing and analysis.

[0108] In a preferred but non-limiting embodiment of the present invention, in steps 1-2, the data center performs further processing and analysis, including establishing a data model of voltage fluctuations to better understand voltage fluctuations in the power grid. The data model may include information such as voltage signals, the frequency, amplitude, and duration of voltage fluctuations, spectrum analysis results, and waveform diagrams, helping analysts fully understand the characteristics of grid voltage fluctuations. Through data analysis and processing, voltage fluctuations in the power grid can be identified and the cause and impact of the fluctuations determined. Possible causes include fluctuating output from photovoltaic power generation systems, sudden changes or imbalances in grid load, and other factors. This process requires the use of data analysis tools and algorithms to process large amounts of monitoring data, identify abnormal fluctuations, and conduct trend analysis. Furthermore, by comparing the data with actual field conditions, the source and impact of voltage fluctuations can be determined, providing accurate basic data for subsequent energy storage system deployment and optimized design. Detailed voltage fluctuation analysis provides important reference for subsequent energy storage system deployment and control strategy development, achieving the goal of comprehensive coordinated control and unblocked transmission of low-voltage grid voltage fluctuations.

[0109] In a preferred but non-limiting embodiment of the present invention, in step 1-2, the method for determining the cause of the fluctuation includes:

[0110] Analyze the cause based on the extracted frequency, amplitude and duration of voltage fluctuations:

[0111] Frequency analysis: The main frequency component is 50 Hz, which is related to power failure;

[0112] Amplitude analysis: If the amplitude value is below 0.5, the severity of the fluctuation is judged to be low, otherwise it is judged to be high;

[0113] Duration analysis: If the fluctuation duration is less than 50ms, the instantaneous nature of the fault is good; otherwise, the instantaneous nature of the fault is poor.

[0114] Methods for determining the scope of impact of fluctuations include:

[0115] Assess the scope of impact based on the causes and characteristics of voltage fluctuations:

[0116] Spatial distribution analysis: Based on the grid GIS and topology data, it was found that voltage fluctuations mainly affect the city center;

[0117] Equipment Impact Assessment: This evaluates potential damage to substations, transformers, and user equipment, taking into account equipment sensitivity and operating conditions. The method for determining the impact of fluctuations can be tailored to specific requirements.

[0118] In a preferred but non-limiting embodiment of the present invention, in step 1-2, the present invention installs a wave recording meter in the park to perform grid voltage waveform analysis to better analyze and identify grid voltage fluctuations.

[0119] In summary, analyzing grid voltage fluctuations requires data acquisition and monitoring. By deploying monitoring equipment and data acquisition systems, grid voltage fluctuations are monitored in real time, including real-time voltage values, frequency, waveforms, and other information. Waveform recording meters can generate waveform files, providing data support and waveform images for subsequent analysis. The collected data is then processed and cleaned, including denoising, filtering, and normalization to ensure data quality and accuracy. Feature extraction and analysis are then performed, using data analysis methods to extract characteristic parameters of voltage fluctuations, such as frequency content, amplitude, and waveform shape, to understand the characteristics and patterns of the fluctuations. Spectral analysis is then performed, converting the voltage signal into the frequency domain for analysis. This analysis reveals the frequency components and spectral characteristics of the fluctuations, helping to identify fluctuation components within different frequency ranges. Cause identification and analysis is then performed, combining the results of feature and spectrum analysis to identify possible causes of grid voltage fluctuations, such as fluctuations in the photovoltaic power generation system, grid load fluctuations, and equipment failure, to determine the root cause of the fluctuations. Finally, impact assessment and control strategies are conducted to evaluate the impact of voltage fluctuations on grid stability and equipment operation, determine the severity and scope of the fluctuations, and develop corresponding control strategies and optimization plans to ensure grid stability and reliability. The comprehensive analysis of these steps will help us fully understand the voltage fluctuations in the grid, provide a scientific basis for further control and optimization, and ensure the safe and stable operation of the grid.

[0120] Step 2: Configure the distributed energy storage capacity connected to the grid voltage coordinated control;

[0121] Existing technical research indicates that integrating energy storage systems into agricultural parks can help reduce voltage fluctuations in the low-voltage grid. First, energy storage systems offer rapid response capabilities, enabling them to quickly release or absorb energy when grid voltage fluctuates, smoothly regulating grid voltage and effectively mitigating voltage fluctuations. Second, energy storage systems can achieve power balancing, absorbing fluctuating power output from renewable energy sources like photovoltaics and releasing stored energy to address grid load fluctuations, maintaining grid power balance and reducing voltage fluctuations. Furthermore, energy storage systems offer flexibility and controllability, enabling flexible dispatch and control based on grid demand, effectively addressing grid voltage fluctuations. Most importantly, deploying energy storage systems within agricultural parks can achieve localized voltage regulation. By placing energy storage devices in key locations, they can effectively address large voltage fluctuations and improve grid stability and reliability. Therefore, integrating energy storage systems can effectively reduce voltage fluctuations in the low-voltage grid, improve grid operational efficiency and stability, and provide reliable support for integrating a high proportion of distributed photovoltaic systems into agricultural parks.

[0122] To reduce voltage fluctuations in agricultural park substations, it is necessary to select a suitable energy storage solution. In a preferred but non-limiting embodiment of the present invention, step 2 specifically includes: first, determining the problem by analyzing the voltage fluctuations of the power grid in detail, including parameters such as frequency, amplitude, and duration. Then, step 2-1: considering factors such as cost, efficiency, and applicability, select a suitable energy storage method, such as battery energy storage and large capacitor energy storage;

[0123] In a preferred but non-limiting embodiment of the present invention, in step 2-1, a method for selecting a suitable energy storage method taking into account factors such as cost, efficiency, and applicability specifically includes:

[0124] Step 2-1-1: Construction of evaluation index system, which specifically includes:

[0125] Cost indicators:

[0126] Initial investment cost: the initial purchase and installation cost of the energy storage method;

[0127] Operation and maintenance costs: maintenance and management costs of energy storage during operation;

[0128] Total life cycle cost: The total cost of the energy storage method over its entire life cycle, including initial investment cost, operation and maintenance costs, and decommissioning costs;

[0129] Efficiency indicators:

[0130] Energy storage efficiency: the efficiency of energy conversion during charging and discharging of energy storage methods;

[0131] Charge and discharge rate: The charge and discharge rate of the energy storage method, reflecting its response speed;

[0132] Energy conversion efficiency: the energy conversion efficiency of the energy storage method during the charging and discharging process;

[0133] Applicability indicators:

[0134] Cycle life: The number of charge and discharge cycles of an energy storage method reflects its service life.

[0135] Environmental adaptability: The ability of the energy storage method to adapt to different environmental conditions, such as temperature, humidity, etc.; can be set according to specific requirements.

[0136] Installation convenience: The installation complexity and convenience of the energy storage method; can be set according to specific requirements.

[0137] Maintenance ease: The maintenance difficulty and ease of the energy storage method; can be set according to specific requirements.

[0138] Step 2-1-2: Weight determination, which specifically includes:

[0139] Using a data-driven approach, combined with historical data and actual application results, the weights of each evaluation indicator are determined. The specific steps are as follows:

[0140] Data preparation: Collect historical data, including performance data of various energy storage methods in actual applications; this performance data can be used as evaluation indicators.

[0141] Model building: Building performance data-driven weight determination models, such as machine learning-based regression models or decision tree models;

[0142] Weight calculation: Use the weight determination model to calculate the weight of each evaluation indicator to ensure the objectivity and scientific nature of the weight.

[0143] Step 2-1-3: Score calculation:

[0144] Based on the collected evaluation indicators and determined weights, various energy storage methods are scored. The specific steps are as follows:

[0145] Data standardization: standardize the data of different evaluation indicators to make them comparable;

[0146] Weighted average: Calculate the comprehensive score of each energy storage method based on the weights and standardized data. The calculation formula is as follows:

[0147]

[0148] in, For the Comprehensive rating of energy storage methods, For the The weight of the evaluation index, For the Energy storage method Standardized values ​​on the evaluation indicators;

[0149] The energy storage method with the highest value is regarded as the appropriate energy storage method.

[0150] Step 2-2: Determine the optimal energy storage location, which is between the grid load and the photovoltaic power generation system to balance power fluctuations;

[0151] Step 2-3: Determine the most economical energy storage capacity based on the load demand of the substation and the output characteristics of the photovoltaic system to meet the compensation needs for voltage fluctuations and reduce costs.

[0152] In a preferred but non-limiting embodiment of the present invention, in step 2-3, the following steps are performed:

[0153] (1) Collect the load demand data of the substation and the output characteristic data of the photovoltaic system, including but not limited to the following aspects:

[0154] Load demand data: load curve, load peak, load fluctuation;

[0155] Photovoltaic output characteristic data: photovoltaic power output curve, photovoltaic power peak, photovoltaic power fluctuation;

[0156] Voltage fluctuation data: historical data of voltage fluctuations, including frequency, amplitude, and duration;

[0157] Data collection can be carried out through historical data recording, real-time monitoring and simulation to ensure the accuracy and completeness of the data.

[0158] (2) Load demand analysis:

[0159] Analyze the load demand of the substation. The specific steps are as follows:

[0160] Load curve analysis: draw the load curve of the substation and analyze the peak and fluctuation of the load;

[0161] Load peak determination: determine the peak value of the load, that is, the maximum load value;

[0162] Load fluctuation: Analyze load fluctuations, including the frequency and amplitude of load changes;

[0163] Through the above steps, we can fully understand the load demand of the substation and provide basic data for subsequent energy storage demand calculations.

[0164] (3) Photovoltaic output characteristics analysis:

[0165] Analyze the output characteristics of the photovoltaic system. The specific steps are as follows:

[0166] Photovoltaic power output curve analysis: draw the power output curve of the photovoltaic system and analyze the peak and fluctuation of photovoltaic power;

[0167] Determination of photovoltaic power peak value: Determine the peak value of photovoltaic power, that is, the maximum output power of the photovoltaic system;

[0168] Photovoltaic power fluctuations: Analyze the fluctuations of photovoltaic power, including the frequency and amplitude of power changes;

[0169] By conducting a detailed analysis of the output characteristics of the photovoltaic system, we can better understand the output capacity of the photovoltaic system at different times and provide data support for subsequent energy storage demand calculations.

[0170] (4) Voltage fluctuation analysis:

[0171] Combined with the load demand and photovoltaic output characteristics, analyze the voltage fluctuation in the substation area. The specific steps are as follows:

[0172] Voltage fluctuation frequency analysis: determine the frequency distribution of voltage fluctuations and analyze the periodicity and regularity of voltage fluctuations;

[0173] Voltage fluctuation amplitude analysis: determine the amplitude of voltage fluctuation, that is, the maximum amplitude of voltage fluctuation;

[0174] Voltage fluctuation duration analysis: determine the duration of voltage fluctuations, analyze the persistence and impact range of voltage fluctuations;

[0175] By analyzing the frequency, amplitude, and duration of voltage fluctuations, we can fully understand the characteristics and impact of voltage fluctuations, providing a scientific basis for subsequent energy storage demand calculations.

[0176] (5) Calculation of energy storage requirements:

[0177] Based on the analysis results of voltage fluctuations, calculate the required energy storage capacity to meet the voltage fluctuation compensation requirements. The specific steps are as follows:

[0178] Load compensation requirements: Calculate the energy storage capacity required for load compensation based on the peak and fluctuation conditions of load demand;

[0179] Photovoltaic fluctuation compensation requirements: Calculate the energy storage capacity required for photovoltaic fluctuation compensation based on the fluctuation of photovoltaic output characteristics.

[0180] Comprehensive energy storage demand: Determine the total energy storage demand by comprehensively considering the load compensation demand and the photovoltaic fluctuation compensation demand;

[0181] Through the above steps, the energy storage capacity that meets the voltage fluctuation compensation requirements can be accurately calculated, providing basic data for subsequent economic analysis.

[0182] (6) Economic analysis:

[0183] Taking into account the initial investment cost, operation and maintenance costs, and compensation effect of the energy storage system, the most economical energy storage capacity is determined. The specific steps are as follows:

[0184] Cost analysis: Analyze the initial investment cost and operation and maintenance costs of the energy storage system, including battery costs, installation costs, maintenance costs, etc.

[0185] Benefit analysis: Analyze the compensation effect of the energy storage system, including the degree of smoothing of voltage fluctuations and the degree of optimization of load balance;

[0186] Economic evaluation: Comprehensively consider costs and benefits, evaluate the economic feasibility of different energy storage capacities, and determine the most economical energy storage capacity;

[0187] Through economic analysis, it can be ensured that the selected energy storage capacity meets the voltage fluctuation compensation requirements while minimizing costs and improving the economy of the system.

[0188] (7) Optimize configuration:

[0189] Based on the economic analysis results, optimize the configuration of the energy storage system. The specific steps are as follows:

[0190] Capacity configuration: Determine the capacity configuration of the energy storage system based on the most economical energy storage capacity;

[0191] System design: Design the structure and layout of the energy storage system, including battery type, control system, and installation location;

[0192] Operation strategy: Develop an operation strategy for the energy storage system, including charge and discharge control, fault handling, and maintenance plans.

[0193] Through the above steps, it can be ensured that the energy storage system can meet the voltage fluctuation compensation requirements and have high economy and reliability during configuration and operation.

[0194] Through the above steps, the present invention can achieve a comprehensive analysis of the load demand and photovoltaic output characteristics of the substation, determine the most economical energy storage capacity, meet the compensation needs for voltage fluctuations, and reduce costs, providing effective support for the optimized operation and economic management of the power grid.

[0195] Reference Examples

[0196] Data Collection:

[0197] Assume there is a substation that needs to collect PV and load data to support subsequent analysis and energy storage demand calculation. The collected data includes the following:

[0198] Load demand data:

[0199] Load curve: Daily load demand, assuming a maximum of 200 kW and a minimum of 80 kW per day.

[0200] Peak load: occurs at 4 p.m. with a peak of 200 kW.

[0201] Load fluctuation: The load is higher in the morning and afternoon, and lower at noon and late at night.

[0202] Photovoltaic output characteristic data:

[0203] Photovoltaic power output curve: 80 kW from 7:00 to 9:00 a.m., 150 kW from 11:00 a.m. to 3:00 p.m., and 0 output during the rest of the time.

[0204] Photovoltaic power peak: 12 noon, peak 150 kW.

[0205] Photovoltaic power fluctuations: gradually increase in the morning, reach a peak at noon, and gradually decrease in the afternoon.

[0206] Voltage fluctuation data:

[0207] Historical data contains information such as the frequency, amplitude and duration of voltage fluctuations.

[0208] Load demand analysis:

[0209] Load curve analysis: The load curve of the substation was drawn and confirmed that the load was low at 6:00 in the morning, and the load was higher in the afternoon and evening, reaching a maximum of 200 kW.

[0210] Load peak determination: The maximum load is 200 kW, which occurs at 4 pm.

[0211] Load fluctuation: The load changes roughly within the range of 120 kW, with the highest frequency of changes occurring in the morning and afternoon.

[0212] Photovoltaic output characteristics analysis:

[0213] Analysis of photovoltaic power output curve: Photovoltaic output has a daily cycle, with an upward trend from morning to noon and a downward trend thereafter.

[0214] The peak PV power is determined as 150 kW at 12 noon.

[0215] Photovoltaic power fluctuations: From noon to afternoon, the photovoltaic power changes the most, with a fluctuation range of about 70 kW.

[0216] Voltage fluctuation analysis:

[0217] Through historical data:

[0218] Voltage fluctuation frequency analysis: The fluctuation frequency is approximately once per hour, 24 times a day.

[0219] Voltage fluctuation amplitude analysis: The main fluctuation range is ±5V, and the most significant fluctuation is from ±10V.

[0220] Analysis of voltage fluctuation duration: The duration is generally 20-30 minutes, and the peak duration is 1 hour.

[0221] Energy storage demand calculation:

[0222] Load compensation needs: Load compensation is primarily needed in the evening, when load demand increases and PV output decreases. Assuming the energy storage system needs to provide a maximum load compensation capacity of 200 kW, at least 100 kW of energy storage is required.

[0223] Photovoltaic fluctuation compensation needs: The maximum fluctuation range of photovoltaic output is 70 kW, and the energy storage system needs to support compensation needs within this range.

[0224] Comprehensive energy storage demand: Taking both aspects into consideration, the energy storage demand is highest from 6 pm to 8 pm. Based on the maximum fluctuation calculation, the energy storage system needs to provide a compensation capacity of up to 150 kW.

[0225] Economic analysis:

[0226] Cost analysis: Assume that the initial investment cost per kW of energy storage is 5,000 yuan and the annual maintenance cost is 1,000 yuan.

[0227] Benefit analysis: By smoothing voltage fluctuations and reducing system losses and maintenance costs caused by voltage fluctuations, it is expected that system operating costs can be reduced by 10%.

[0228] Economic Assessment: Calculations show that the total cost of a 150 kW energy storage system is 750,000 yuan, with annual operation and maintenance costs of 150,000 yuan. The payback period is expected to be reached in the fifth year.

[0229] Optimized configuration:

[0230] Capacity configuration: Based on the most economical energy storage capacity, a 150 kW energy storage system was constructed.

[0231] System design: Lithium-ion batteries are used to simplify the control system design and are placed inside the substation for easy maintenance.

[0232] Operation strategy: The energy storage system optimizes the scheduling strategy, giving priority to charging during off-peak periods and discharging during peak periods, and sets up fault alarms and automatic emergency response strategies.

[0233] Through the above analysis and verification, this solution can provide effective load balancing, reduce voltage fluctuations, and significantly improve the power supply stability and economy of the substation.

[0234] Finally, system optimization can be performed based on actual needs, taking into account factors such as energy storage capacity, location, and control strategy to ensure that the deployment of energy storage systems in substations effectively reduces voltage fluctuations and improves grid stability and reliability. Regular monitoring and adjustments should be made to the energy storage system to maintain optimal performance. These measures can effectively address the problem of large voltage fluctuations in agricultural park substations and improve grid efficiency and stability.

[0235] To reduce voltage fluctuations, the optimal energy storage location is selected within the substation to address the aforementioned large voltage fluctuations with the most economical capacity. For example, based on the above, the energy storage configuration target is configured, ultimately installing energy storage at the designated nodes with installed capacities of 19.156 kWh and 134.9 kWh, respectively. The maximum storage output does not exceed 50 kW, and the optimized initial storage capacity is 0 kWh and 61.1793 kWh. The energy storage status at the end of the day is the same as at the beginning.

[0236] Step 3: Energy storage control enables non-blocking transmission of low-voltage grid fluctuations and system optimization.

[0237] In a preferred but non-limiting embodiment of the present invention, in step 3, the deployment and control of the energy storage system are of great significance for achieving non-blocking transmission and system optimization of power grid fluctuations. In terms of deployment, factors such as power grid load distribution, transmission line capacity and voltage stability should be considered, and a suitable deployment location should be selected to minimize transmission losses and improve system efficiency. In terms of control, flexible scheduling and optimal distribution of electric energy are achieved through intelligent algorithms and energy management systems to ensure that the energy storage system can flexibly adjust the discharge and charging power according to factors such as power grid load conditions and energy prices, maintain the balance of power grid supply and demand, smooth load fluctuations, improve power grid stability, and reduce transmission congestion. In addition, the deployment and control of the energy storage system can also optimize power grid operation, reduce operating costs, and improve energy utilization efficiency. At the same time, it plays a role in frequency regulation, voltage support, peak-valley balance, etc., and optimizes the quality and stability of power grid operation. Therefore, the deployment and control of the energy storage system has important academic and practical significance for the optimization and improvement of power grid operation.

[0238] Non-blocking transmission refers to the deployment and control of energy storage systems in power systems to achieve flexible scheduling and optimized distribution of electric energy, thereby reducing grid transmission congestion and improving grid stability and reliability. In the process of achieving non-blocking transmission, factors such as grid load distribution, transmission line capacity, and voltage stability need to be considered, and fuzzy algorithms are used to dynamically adjust the discharge and charging power of the energy storage system to achieve grid supply and demand balance, smooth load fluctuations, and eliminate grid transmission bottlenecks. By optimizing the deployment location and capacity scale of the energy storage system, transmission losses can be effectively reduced and grid efficiency can be improved. At the same time, flexible scheduling and distribution of energy can be achieved during grid operation to ensure that the grid operates in the best state. The implementation of non-blocking transmission can not only optimize grid operation, reduce operating costs, and improve energy utilization efficiency, but also enhance the anti-interference ability of the grid, enhance the stability and resilience of the grid, and provide strong support for the sustainable development of future power systems. Therefore, achieving non-blocking transmission through the deployment and control of energy storage systems is an important direction for the intelligent and efficient development of power systems, and is also one of the important contents of this invention.

[0239] As the capacity of photovoltaic power generation connected to the grid continues to increase, the impact of uncertainty on the power grid also increases. In order to cope with and solve the system voltage fluctuation and achieve non-blocking transmission, it is necessary to control the energy storage action to a certain extent.

[0240] The simulation selected the time period of 8:00~9:00 and compared the state of charge of the energy storage equipment under fuzzy control and without fuzzy control. The results showed that when the state of charge of the energy storage equipment was optimized without fuzzy control, the battery was overcharged and over-discharged, and the supercapacitor was overcharged, which would seriously affect the service life of the battery and supercapacitor; when fuzzy control was used to optimize the state of charge of the energy storage equipment, the state of charge of the battery and supercapacitor were both kept within a reasonable range, and the fluctuation amplitude decreased, avoiding operation in the overcharge and over-discharge area, thereby extending the life of the energy storage element. At the same time, maintaining the battery state of charge in the range of 0.2 to 0.8 can effectively reduce grid transmission congestion.

[0241] The beneficial effects of the present invention are that, compared with the prior art, the technical effects of the present invention include:

[0242] The present invention converts voltage signals into the frequency domain for analysis, thereby understanding the frequency components and spectral characteristics of fluctuations, which helps identify fluctuation components within different frequency ranges. Subsequently, cause identification and analysis are performed. Combining the results of feature analysis and spectral analysis, the possible causes of voltage fluctuations in the power grid, such as fluctuations in the photovoltaic power generation system, grid load fluctuations, and equipment failures, are analyzed to determine the root cause of the fluctuations. Finally, an impact assessment and control strategy are conducted to evaluate the impact of voltage fluctuations on grid stability and equipment operation, determine the severity and impact range of the fluctuations, and formulate corresponding control strategies and optimization plans to ensure the stability and reliability of grid operation. The comprehensive analysis of these steps will help to fully understand the voltage fluctuations in the power grid, provide a scientific basis for further control and optimization, and ensure the safe and stable operation of the power grid. When fuzzy control is used to optimize the state of charge of energy storage devices, the state of charge of both batteries and supercapacitors can be maintained within a reasonable range, and the fluctuation amplitude is reduced, avoiding operation in the overcharge and overdischarge range, thereby extending the life of the energy storage components. Maintaining the battery state of charge between 0.2 and 0.8 effectively reduces grid transmission congestion.

[0243] Finally, 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 above embodiments, those skilled in the art should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents, and any modifications or equivalent replacements that do not deviate from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid, characterized in that: include: Step 1: Analyze and identify voltage fluctuations in the grid connected to the agricultural park connected to distributed photovoltaics; Step 2: Configure the distributed energy storage capacity connected to the grid voltage coordinated control; Step 3: Energy storage control enables non-blocking transmission of low-voltage grid fluctuations and system optimization; Step 1 specifically includes: Step 1-1: First, deploy intelligent monitoring equipment and data acquisition systems to monitor grid voltage fluctuations in real time; Step 1-2: The intelligent monitoring equipment collects the voltage signal in real time, including the frequency, amplitude, and duration of voltage fluctuations, and transmits it to the data center for further processing and analysis. In step 1-1, the method for the intelligent monitoring device to obtain the frequency, amplitude, and duration parameters of the voltage fluctuation includes: (1) Use the Fast Fourier Transform (FFT) algorithm to perform frequency domain analysis on the collected voltage signal and extract the frequency components of the voltage fluctuation; (2) Amplitude calculation: Calculate the amplitude of the voltage fluctuation based on the analysis results obtained by the Fast Fourier Transform (FFT) algorithm. The amplitude calculation method is as follows: Count the amplitudes of the corresponding frequency components in the FFT results to obtain the maximum amplitude of the voltage fluctuation, which is used as the amplitude of the voltage fluctuation. (3) Duration calculation: Detect the duration of voltage fluctuations through the time window sliding method; In step 1-1, the amplitude value The calculation method corresponding to the formula is: in, Indicates the amplitude at each frequency point in the FFT result; Step 2 specifically includes: Step 2-1: Consider cost, efficiency, and applicability factors and select a suitable energy storage method; Step 2-2: Determine the optimal energy storage location, which is between the grid load and the photovoltaic power generation system; Step 2-3: Determine the most economical energy storage capacity based on the load demand of the substation and the output characteristics of the photovoltaic system to meet the compensation needs of voltage fluctuations and minimize costs.

2. The method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to claim 1, characterized in that: In step 1-1, the data center, intelligent monitoring equipment and data acquisition system are connected in communication in sequence; the data acquisition system transmits the real-time collected voltage signal of the power grid to the intelligent monitoring equipment to obtain the frequency, amplitude and duration parameters of the voltage fluctuation.

3. The method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to claim 2, characterized in that: In steps 1-2, the data center performs further processing and analysis, including: establishing a data model of voltage fluctuations. The data model includes voltage signals, the frequency, amplitude, and duration of voltage fluctuations, spectrum analysis results, and waveform diagrams, helping analysts fully understand the characteristics of power grid voltage fluctuations. Through data analysis and processing, voltage fluctuation problems in the power grid can be identified and the causes of the fluctuations can be determined. In steps 1-2, methods for determining the cause of the fluctuation include: Analyze the cause based on the frequency, amplitude and duration of the extracted voltage fluctuations: Frequency analysis: The main frequency component is 50 Hz, which is related to power failure; Amplitude analysis: If the amplitude value is below 0.5, the severity of the fluctuation is judged to be low, otherwise it is judged to be low-high; Duration analysis: If the fluctuation duration is less than 50ms, the instantaneous nature of the fault is good; otherwise, the instantaneous nature of the fault is poor.

4. The method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to claim 3, characterized in that: In step 1-2, a wave recording meter is installed in the park to analyze the grid voltage waveform.

5. The method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to claim 4, characterized in that: In step 2-1, consider cost, efficiency, and applicability factors to select a suitable energy storage method, including: Step 2-1-1: Construction of evaluation index system, which specifically includes: Cost indicators: Initial investment cost: the initial purchase and installation cost of the energy storage method; Operation and maintenance costs: maintenance and management costs of energy storage during operation; Total life cycle cost: The total cost of the energy storage method over its entire life cycle, including initial investment cost, operation and maintenance costs, and decommissioning costs; Efficiency indicators: Energy storage efficiency: the efficiency of energy conversion during charging and discharging of energy storage methods; Charge and discharge rate: The charge and discharge rate of the energy storage method, reflecting its response speed; Energy conversion efficiency: the energy conversion efficiency of the energy storage method during the charging and discharging process; Applicability indicators: Cycle life: The number of charge and discharge cycles of an energy storage method reflects its service life. Environmental adaptability: the ability of energy storage methods to adapt to different environmental conditions; Installation convenience: The installation complexity and convenience of the energy storage method; Maintenance ease: How easy and difficult it is to maintain the energy storage method; Step 2-1-2: Weight determination, which specifically includes: Data preparation: Collect historical data, including performance data of various energy storage methods in actual applications; Model building: Build a performance data-driven weight determination model; Weight calculation: Use the weight determination model to calculate the weight of each evaluation indicator; Step 2-1-3: Score calculation: Data standardization: standardize the data of different evaluation indicators to make them comparable; Weighted average: Calculate the comprehensive score of each energy storage method based on the weights and standardized data. The calculation formula is as follows: in, For the Comprehensive rating of energy storage methods, For the The weight of the evaluation index, For the Energy storage method Standardized values ​​on the evaluation indicators; The energy storage method with the highest value is regarded as the appropriate energy storage method.

6. The method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to claim 5, characterized in that: In steps 2-3, perform the following steps: (1) Collect the load demand data of the substation and the output characteristic data of the photovoltaic system, including but not limited to the following aspects: Load demand data: load curve, load peak, load fluctuation; Photovoltaic output characteristic data: photovoltaic power output curve, photovoltaic power peak, photovoltaic power fluctuation; Voltage fluctuation data: historical data of voltage fluctuation; (2) Load demand analysis: Analyze the load demand of the substation. The specific steps are as follows: Load curve analysis: draw the load curve of the substation and analyze the peak and fluctuation of the load; Load peak determination: determine the peak value of the load, that is, the maximum load value; Load fluctuation: Analyze load fluctuations, including the frequency and amplitude of load changes; (3) Photovoltaic output characteristics analysis: Analyze the output characteristics of the photovoltaic system. The specific steps are as follows: Photovoltaic power output curve analysis: draw the power output curve of the photovoltaic system and analyze the peak and fluctuation of photovoltaic power; Determination of photovoltaic power peak value: Determine the peak value of photovoltaic power, that is, the maximum output power of the photovoltaic system; Photovoltaic power fluctuations: Analyze the fluctuations of photovoltaic power, including the frequency and amplitude of power changes; (4) Voltage fluctuation analysis: Combined with the load demand and photovoltaic output characteristics, analyze the voltage fluctuation in the substation area. The specific steps are as follows: Voltage fluctuation frequency analysis: determine the frequency distribution of voltage fluctuations and analyze the periodicity and regularity of voltage fluctuations; Voltage fluctuation amplitude analysis: determine the amplitude of voltage fluctuation, that is, the maximum amplitude of voltage fluctuation; Voltage fluctuation duration analysis: determine the duration of voltage fluctuations, analyze the persistence and impact range of voltage fluctuations; (5) Calculation of energy storage requirements: Based on the analysis results of voltage fluctuations, calculate the required energy storage capacity to meet the voltage fluctuation compensation requirements. The specific steps are as follows: Load compensation requirements: Calculate the energy storage capacity required for load compensation based on the peak and fluctuation conditions of load demand; Photovoltaic fluctuation compensation requirements: Calculate the energy storage capacity required for photovoltaic fluctuation compensation based on the fluctuation of photovoltaic output characteristics; Comprehensive energy storage demand: Determine the total energy storage demand by comprehensively considering the load compensation demand and the photovoltaic fluctuation compensation demand; (6) Economic analysis: Cost analysis: Analyze the initial investment cost and operation and maintenance costs of the energy storage system, including battery costs, installation costs, and maintenance costs; Benefit analysis: Analyze the compensation effect of the energy storage system, including the degree of smoothing of voltage fluctuations and the degree of optimization of load balance; Economic evaluation: Comprehensively consider costs and benefits, evaluate the economic feasibility of different energy storage capacities, and determine the most economical energy storage capacity; (7) Optimize configuration: Based on the economic analysis results, optimize the configuration of the energy storage system. The specific steps are as follows: Capacity configuration: Determine the capacity configuration of the energy storage system based on the most economical energy storage capacity; System design: Design the structure and layout of the energy storage system, including battery type, control system, and installation location; Operation strategy: Develop an operation strategy for the energy storage system, including charge and discharge control, fault handling, and maintenance plans.

7. The method for coordinated control of voltage of an agricultural park connected to a distributed photovoltaic grid according to claim 6, characterized in that: In step 3, in the process of achieving non-blocking transmission, the discharging and charging power of the energy storage system are dynamically adjusted through a fuzzy algorithm.

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