Grid-connected light storage and charging energy storage control system

Abstract

The invention relates to the technical field of energy storage control, in particular to a grid-connected type light storage and charging energy storage control system which comprises a power bearing capacity monitoring module, a light storage power adjusting module, a grid-connected power feedback module, a power grid stability margin calculation module and an energy storage power dynamic control module. According to the method, the voltage and current data of the grid-connected point are acquired in real time, the power transmission capacity is calculated in combination with the rated voltage range and the safety power upper limit, the power adaptation precision of the grid-connected point is improved, the photovoltaic power generation grid-connected proportion is dynamically optimized on the basis of comparison between load growth rate calculation and the power adjustment range, and photovoltaic power output curve change rate analysis is combined. Power output fine control, calculation of the load change rate and combination of power grid power factor data are achieved, a charging and discharging mode adjustment strategy is optimized, the frequency change rate and fluctuation degree are monitored, the stability margin of the power grid is enhanced, frequency deviation of the power grid caused by load fluctuation is avoided, and the new energy consumption rate and the operation reliability of the power grid are improved.

Description

Technical Field

[0001] The present invention relates to the field of energy storage control technology, and in particular to a grid-connected photovoltaic energy storage and charging control system. Background Art

[0002] The field of energy storage control technology includes the storage, conversion and management of electric energy, aiming to improve energy efficiency and optimize the way of power supply. The core content includes the charge and discharge management of battery energy storage systems, grid frequency regulation and peak regulation, and renewable energy grid connection control. Energy storage control technology usually involves multiple aspects such as power electronic conversion, battery management, grid coordinated operation and load balancing. Its systematic characteristics are reflected in the real-time monitoring, distribution and regulation capabilities of electric energy. It is mainly used in new energy power stations, microgrids, electric vehicle charging stations and smart grids to enhance the reliability and stability of the power system. With the development of new energy technology, energy storage control technology is gradually evolving towards high efficiency and intelligence to adapt to changing load demands and complex power supply and demand environments.

[0003] Among them, the grid-connected photovoltaic storage and energy storage control system refers to a grid-connected energy management system that integrates photovoltaic power generation, energy storage and charging control. It mainly targets the intermittent and volatile nature of photovoltaic power generation, and uses power conditioning devices to coordinate the energy flow between photovoltaic power sources, battery energy storage devices and power grids. Specifically, the direct current generated by photovoltaic modules is converted into alternating current through inverters, and its power supply path is determined by the power distribution strategy. The controller dynamically adjusts power transmission based on the state of the grid, the battery charge and the load demand. In addition, a bidirectional DC conversion device is used to adjust the battery charging and discharging power, and an energy management strategy is used to control the power output of the charging pile to achieve coordinated operation between photovoltaics, energy storage, power grids and loads.

[0004] In the existing grid-connected photovoltaic storage and charging energy storage control process, fixed threshold settings are mostly used in grid-connected point power monitoring, and real-time voltage and current changes are not fully combined, resulting in large deviations in power carrying capacity assessment, affecting the accuracy of photovoltaic inverter input power and photovoltaic direct supply ratio adjustment; in the load regulation process, insufficient attention is paid to load growth trends and power change rates, and the adjustment strategy is relatively simple. There is a lack of effective management of sudden changes in photovoltaic power output, which can easily cause grid fluctuations. In addition, in terms of charging and discharging control, the existing system fails to accurately link the load change rate with power factor compensation, and the adjustment of charging and discharging modes is delayed, resulting in weak power fluctuation suppression capabilities, affecting the power quality of the grid. Frequency stability management lacks a comprehensive analysis of the frequency change rate and fluctuation degree, and the discharge power adjustment is delayed, making it difficult to provide rapid support when the grid frequency offset occurs, affecting the stability of the grid-connected system, limiting the adaptability of the photovoltaic storage and charging system in a complex power environment, limiting the efficiency of new energy utilization, and increasing the risk of grid operation. Summary of the invention

[0005] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a grid-connected photovoltaic charging and energy storage control system.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme: A grid-connected photovoltaic energy storage control system comprises: The power carrying capacity monitoring module obtains the real-time voltage and current values ​​of the grid connection point, calculates the offset from the rated voltage range and the current power transmission capacity, compares the offset threshold and the upper limit of the safe power of the grid connection point, adjusts the input power of the photovoltaic inverter and the proportion of photovoltaic direct supply, and obtains the power adaptation data of the grid connection point; The photovoltaic energy storage power adjustment module calculates the load growth rate based on the grid connection point power adaptation data, compares the power adjustment range, dynamically adjusts the photovoltaic power generation grid connection ratio, analyzes the photovoltaic power output curve change rate, compares the set mutation threshold, adjusts the inverter MPPT parameters, and obtains photovoltaic energy storage adjustment power data; The grid-connected power feedback module adjusts the power data based on the photovoltaic energy storage, calculates the load change rate, and adjusts the charging and discharging mode. It calculates the reactive power compensation demand according to the power factor data of the power grid, and compares the set demand range. It then makes adjustments according to the reactive power compensation function of the photovoltaic inverter to obtain a dynamic matching record of the grid-connected power. The grid stability margin calculation module analyzes the grid frequency change rate and calculates the frequency fluctuation degree based on the grid-connected power dynamic matching record. If the frequency fluctuation exceeds the fluctuation control range, the discharge power is adjusted to obtain the grid stability adjustment amount.

[0007] As a further solution of the present invention, the grid-connected point power adaptation data includes the real-time voltage value of the grid-connected point, the current value of the grid-connected point, the power transmission capacity, and the safe power upper limit of the grid-connected point; the photovoltaic energy storage adjustment power data includes the photovoltaic power generation grid-connected ratio, the inverter MPPT parameters, and the photovoltaic power output mode; the grid-connected power dynamic matching record includes the charging and discharging mode, the power fluctuation suppression strategy, the power grid power factor data, and the reactive compensation demand data; the power grid stability adjustment amount includes the power grid frequency change rate data, the frequency fluctuation degree data, and the discharge power.

[0008] As a further solution of the present invention, the power carrying capacity monitoring module includes: The voltage offset calculation submodule obtains the real-time voltage value of the grid connection point, calculates the offset between the voltage value and the rated voltage range, and determines whether the offset exceeds the offset threshold. If so, the input power of the photovoltaic inverter is adjusted to obtain the corrected input power value. The power transmission capacity calculation submodule synchronously reads the grid connection point current value based on the corrected input power value, calculates the current power transmission capacity, and compares it with the grid connection point safety power upper limit, using the formula: ; Calculating the power transfer deviation , determine whether it exceeds the grid-connected point safety power upper limit, if it exceeds, perform adjustment, and obtain power adjustment demand data, where, represents the grid connection point voltage value at the i-th moment, represents the grid-connected point current value at the ith moment, represents the voltage and current phase angle at the ith moment, represents the number of time steps during the computation period, Represents the upper limit of the safe power of the grid connection point; The grid connection point power adaptation submodule adjusts the photovoltaic direct supply ratio based on the power adjustment demand data, matches the grid connection point power carrying capacity, and obtains the grid connection point power adaptation data.

[0009] As a further solution of the present invention, the photovoltaic power adjustment module includes: The load growth rate calculation submodule calculates the current load growth rate based on the grid connection point power adaptation data, analyzes the grid load change trend, and obtains the grid load change rate; The power regulation range judgment submodule determines whether the power regulation range is exceeded based on the grid load change rate. If exceeded, the photovoltaic power generation grid connection ratio is adjusted using the formula: ; Calculate the photovoltaic power variation deviation , determine whether it exceeds the set mutation threshold, if it exceeds, then adjust to obtain the inverter adjustment demand data, where, represents the photovoltaic power output value at the i-th time step, represents the photovoltaic power output value at the previous time step, represents the total number of time steps for the statistics, represents the set mutation threshold; The photovoltaic energy storage power optimization submodule adjusts the inverter MPPT parameters and the photovoltaic power generation power output mode based on the inverter adjustment demand data to obtain photovoltaic energy storage adjustment power data.

[0010] As a further solution of the present invention, the grid-connected power feedback module includes: The load change rate calculation submodule calculates the current load change rate based on the photovoltaic energy storage adjustment power data, determines whether it is in a short-term high-frequency fluctuation state, and obtains a load fluctuation state identifier; The charge and discharge mode adjustment submodule determines whether the adjustment condition is met based on the load fluctuation state identifier. If so, the charge and discharge mode is adjusted using the formula: ; Calculate the charge and discharge adjustment requirements , get the charge and discharge mode adjustment record, where, represents the power fluctuation amplitude at the jth time step, Represents the reference power fluctuation amplitude, represents the total number of time steps for the statistics, represents the adjustment threshold; The reactive power compensation demand calculation submodule calculates the power factor data of the power grid based on the charge and discharge mode adjustment record, determines the power factor decrease range, and if the decrease range exceeds the set demand range, adjusts the grid-connected power according to the reactive power compensation function of the photovoltaic inverter to obtain the grid-connected power dynamic matching record.

[0011] As a further solution of the present invention, the power grid stability margin calculation module includes: The grid frequency change analysis submodule calculates the grid frequency change rate, evaluates the frequency fluctuation degree, and obtains the grid frequency fluctuation amplitude data based on the grid-connected power dynamic matching record; The frequency fluctuation regulation submodule determines whether it exceeds the fluctuation control range based on the grid frequency fluctuation amplitude data. If it exceeds, the discharge power is adjusted to support the frequency using the formula: ; Calculate the discharge power adjustment , and adjust the discharge strategy to obtain the frequency support power data, where: represents the grid frequency value at the t-th time step, Represents the rated frequency of the power grid, represents the total number of statistical time steps, Represents the upper limit of energy storage discharge power, Represents the current frequency offset; The grid stability adjustment calculation submodule adjusts the discharge strategy based on the frequency support power data, calculates the energy storage discharge power change rate, determines whether the grid stability adjustment requirements are met, and monitors the recovery of the grid frequency after adjustment to obtain the grid stability adjustment amount.

[0012] As a further solution of the present invention, the system further includes an energy storage power dynamic control module; The energy storage power dynamic control module extracts the current state of charge based on the grid stability adjustment amount, calculates the available energy reserve, and determines whether the safe energy storage lower limit is reached. If it is lower than the safe energy storage lower limit, the discharge power is reduced and the proportion of photovoltaic direct supply load is increased. The grid dispatch plan is analyzed simultaneously, the future load change trend is analyzed, and the power response strategy is dynamically adjusted to obtain a comprehensive energy storage power optimization adjustment plan; The comprehensive energy storage power optimization and regulation scheme includes charge state recording, available energy reserve, safe energy storage lower limit, photovoltaic direct supply load ratio, power grid dispatching plan, and power response strategy.

[0013] As a further solution of the present invention, the energy storage power dynamic control module includes: The available energy reserve calculation submodule extracts the current state of charge based on the grid stability adjustment amount, calculates the available energy reserve, and determines whether the safe energy storage lower limit is reached to obtain the current energy storage margin; The energy storage discharge adjustment submodule determines whether the current energy storage margin is lower than the safe energy storage lower limit based on the current energy storage margin. If it is lower, the discharge power is reduced and the proportion of photovoltaic direct supply load is increased, using the formula: ; Calculate the discharge power adjustment value , and adjust the energy storage discharge strategy to obtain the energy storage discharge optimization plan, where: Represents the current remaining energy storage, Represents the sustainable discharge time of energy storage, Representative The photovoltaic direct supply power of each load is Representative The energy conversion efficiency of the load, Represents the total number of photovoltaic direct supply loads; The power response optimization submodule is based on the energy storage discharge optimization scheme, synchronously analyzes the grid dispatch plan, analyzes the future load change trend, and dynamically adjusts the power response strategy to obtain a comprehensive energy storage power optimization adjustment scheme.

[0014] Compared with the prior art, the advantages and positive effects of the present invention are: In the present invention, by acquiring the voltage and current data of the grid connection point in real time, and calculating the power transmission capacity in combination with the rated voltage range and the upper limit of the safe power, the power adaptation accuracy of the grid connection point is improved, so that the adjustment of the input power of the photovoltaic inverter and the photovoltaic direct supply ratio is more in line with the grid demand, based on the calculation of the load growth rate and the comparison of the power adjustment range, the photovoltaic power generation grid connection ratio is dynamically optimized, and the change rate of the photovoltaic power output curve is combined with the analysis of the change rate of the photovoltaic power output curve to achieve refined control of power output and reduce the impact of sudden changes on the stability of the grid. The calculation of the load change rate is combined with the power factor data of the grid to optimize the charging and discharging mode adjustment strategy, so that power fluctuation suppression and reactive power compensation are more accurate, and the quality of power supply is improved. The monitoring of the frequency change rate and the degree of fluctuation makes the discharge power adjustment more targeted, enhances the grid stability margin, and avoids the frequency offset of the grid due to load fluctuation. The power allocation strategy, photovoltaic output management, load prediction optimization, charging and discharging matching, and frequency support capabilities are synergistically improved to achieve efficient adaptation of the photovoltaic storage and charging system in a complex power environment and improve the new energy consumption rate and grid operation reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a system flow chart of the present invention; Figure 2 This is a flow chart of the power carrying capacity monitoring module of the present invention; Figure 3 This is a flow chart of the photovoltaic power adjustment module of the present invention; Figure 4 This is a flow chart of the grid-connected power feedback module of the present invention; Figure 5 This is a flow chart of a grid stability margin calculation module of the present invention; Figure 6 This is a flow chart of the energy storage power dynamic control module of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0017] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, in the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0018] See also Figure 1 , a grid-connected photovoltaic energy storage control system includes: The power carrying capacity monitoring module obtains the real-time voltage value of the grid connection point, calculates the offset from the rated voltage range, and if the offset exceeds the offset threshold, adjusts the input power of the photovoltaic inverter, synchronously reads the current value of the grid connection point, calculates the current power transmission capacity, and compares it with the safety power upper limit of the grid connection point. If it exceeds the upper limit, adjusts the photovoltaic direct supply ratio to obtain the power adaptation data of the grid connection point; The photovoltaic energy storage power adjustment module calculates the load growth rate based on the power adaptation data of the grid connection point, analyzes the trend of grid load changes, and determines whether it exceeds the power adjustment range. If so, it adjusts the photovoltaic power grid connection ratio, analyzes the photovoltaic power output curve change rate, and determines whether there is a sudden change. If the sudden change exceeds the set sudden change threshold, it adjusts the inverter MPPT parameters, optimizes the photovoltaic power output mode, and obtains the photovoltaic energy storage adjustment power data; The grid-connected power feedback module adjusts the power data based on the photovoltaic energy storage, calculates the load change rate, and determines whether it is in a short-term high-frequency fluctuation state. If the conditions are met, the charging and discharging mode is adjusted to suppress power fluctuations. The reactive power compensation demand is calculated according to the power factor data of the power grid. If the power factor decreases beyond the set demand range, it is adjusted according to the reactive power compensation function of the photovoltaic inverter to obtain the dynamic matching record of the grid-connected power. The grid stability margin calculation module analyzes the grid frequency change rate and calculates the frequency fluctuation degree based on the dynamic matching record of the grid-connected power. If the frequency deviation exceeds the fluctuation control range, the discharge power is adjusted to provide frequency support and obtain the grid stability adjustment amount. The energy storage power dynamic control module extracts the current state of charge based on the grid stability adjustment amount, calculates the available energy reserve, and determines whether the safe energy storage lower limit has been reached. If it is lower than the safe energy storage lower limit, the discharge power is reduced and the proportion of photovoltaic direct supply load is increased. The grid dispatch plan is simultaneously analyzed, the future load change trend is analyzed, the power response strategy is dynamically adjusted, and a comprehensive energy storage power optimization adjustment plan is obtained.

[0019] The power adaptation data of the grid connection point includes the real-time voltage value of the grid connection point, the current value of the grid connection point, the power transmission capacity, and the upper limit of the safe power of the grid connection point. The photovoltaic energy storage adjustment power data includes the photovoltaic power generation grid-connected ratio, the inverter MPPT parameters, and the photovoltaic power output mode. The dynamic matching record of the grid-connected power includes the charging and discharging mode, the power fluctuation suppression strategy, the power factor data of the power grid, and the reactive compensation demand data. The grid stability adjustment includes the grid frequency change rate data, the frequency fluctuation degree data, and the discharge power. The comprehensive energy storage power optimization adjustment plan includes the charge state record, the available energy reserve, the lower limit of the safe energy storage, the photovoltaic direct supply load ratio, the power grid dispatch plan, and the power response strategy.

[0020] See also Figure 2 , the power carrying capacity monitoring module includes: The voltage offset calculation submodule obtains the real-time voltage value of the grid connection point, calculates the offset between the voltage value and the rated voltage range, and determines whether the offset exceeds the offset threshold. If so, the input power of the photovoltaic inverter is adjusted to obtain the corrected input power value. When obtaining the real-time voltage value of the grid-connected point, it is necessary to collect the voltage values ​​at different time points through the voltage sensor and record the average value within at least one minute to eliminate the influence of short-term fluctuations. Assuming that the rated voltage is 380V and the measured voltage value at a certain moment is 392V, the offset is The calculated offset is compared with the preset offset threshold (for example, ±10V) to determine whether it exceeds the threshold. If the offset exceeds 10V, the input power of the photovoltaic inverter is adjusted. The specific adjustment method is based on the relationship between the input power and the voltage change. For example, when the voltage exceeds the upper limit, the input power of the photovoltaic inverter is reduced to reduce voltage fluctuations. If the current input power is 50kW, a new input power is set by calculation to restore the voltage to a range close to the rated range. The input power after adjustment may become 45kW, and the corrected input power value is obtained at this time.

[0021] The setting of the offset threshold is based on the rated voltage fluctuation range of the grid-connected equipment and the allowable deviation range specified in the National Grid Standard GB / T12325-2008 "Power Quality Supply Voltage Deviation". For low-voltage power supply systems below 10kV, the allowable deviation of the supply voltage is ±7% of the rated value, that is, for a power supply system with a rated voltage of 380V, the allowable voltage range is 353V to 407V. Therefore, the offset threshold is set to ±10V to ensure that when the voltage offset exceeds this range, the input power of the photovoltaic inverter is adjusted in time to avoid the grid voltage exceeding the safety range and affecting the stable operation of other loads. In addition, the offset threshold also needs to consider the actual load distribution. If the load around the grid point is large, the offset threshold can be appropriately reduced. For example, in areas with dense industrial loads, the offset threshold can be set to ±8V, while in residential areas with small loads, the standard value of ±10V can be maintained. In addition, the offset threshold is also affected by the grid impedance. For example, changes in the short-circuit impedance of the transformer will cause different voltage fluctuations. If the short-circuit impedance is high, the offset threshold can be appropriately reduced to ensure the sensitivity of voltage adjustment.

[0022] The power transmission capacity calculation submodule is based on the corrected input power value, synchronously reads the grid-connected point current value, calculates the current power transmission capacity, and compares it with the grid-connected point safety power limit using the formula: ; Calculating the power transfer deviation , determine whether it exceeds the grid-connected point safety power upper limit, if it exceeds, perform adjustment, and obtain power adjustment demand data, where, represents the grid connection point voltage value at the i-th moment, represents the grid-connected point current value at the ith moment, represents the voltage and current phase angle at the ith moment, represents the number of time steps during the computation period, Represents the upper limit of the safe power of the grid connection point; Based on the corrected input power value, the current value of the grid-connected point is collected synchronously, the sampling interval is set to 0.5 seconds, and 20 data points are collected within 10 seconds. For example, within a certain time window, the voltage is measured to be 385V, 380V, 395V, etc., and the current is measured to be 130A, 125A, 135A, etc. Combined with the power factor (set to 0.9), the current power transmission capacity is calculated using the formula.

[0023] Among them, the sampling value calculation example is shown in Table 1.1.

[0024] Table 1.1 Voltage, current and calculated power at sampling time

[0025] According to the data in Table 1.1, calculate the average active power: ; Assume that the grid connection point has a safe power limit The power transfer deviation is 44.5kW, then the power transfer deviation is calculated as follows: ; because , which means that the current power transmission has exceeded the safe power upper limit, so power adjustment is required, and the power adjustment demand is 0.72kW.

[0026] The grid-connected point power adapter module adjusts the photovoltaic direct supply ratio based on the power adjustment demand data, matches the grid-connected point power carrying capacity, and obtains the grid-connected point power adaptation data; Based on the power adjustment demand, the proportion of photovoltaic direct supply is adjusted. Assuming that the current photovoltaic direct supply power is 30kW, the target after adjustment is to reduce it by 0.72kW, which can be achieved by changing the proportion of photovoltaic direct supply load. For example, the original direct supply proportion is 60%. If the current load allows, it can be adjusted to 58% to reduce the load pressure of the grid connection point. After adjustment, the power adaptation data of the grid connection point is finally obtained.

[0027] As shown in Table 1.2, the direct photovoltaic supply ratio and grid-connected power adaptation data under different adjustment schemes are listed.

[0028] Table 1.2 Grid connection point power adaptation adjustment table

[0029] Refer to Table 1.2. After adjusting the direct photovoltaic supply ratio, the final grid-connected point load power can be controlled within the grid-connected point safety power upper limit range, and the grid-connected point power adaptation data can be obtained.

[0030] See also Figure 3 , the optical storage power adjustment module includes: The load growth rate calculation submodule calculates the current load growth rate based on the power adaptation data of the grid connection point, analyzes the grid load change trend, and obtains the grid load change rate; Based on the grid-connected point power adaptation data, first collect the load power data within a certain period of time and calculate the load growth rate. Set the data collection cycle to 10 minutes, record the current grid-connected point load power once in each cycle, and form a time series data set. For example, the load power collected at a certain moment is 120kW, and increases to 130kW after 10 minutes. The load growth rate is calculated using the formula: ; in, represents the load growth rate, and Respectively represent the load power of the current cycle and the previous cycle, such as into the numerical calculation: ; The set growth rate threshold of 5% is based on the tolerable fluctuation range of the grid load, with specific reference to the maximum allowable power fluctuation range of the grid connection point and the grid stability requirements. Usually, short-term load fluctuations exceeding 5% will have an impact on the grid regulation capability. According to the grid equipment regulation capability and load response curve, this value is generally set between 3% and 7%. In actual application, it can be adjusted according to the grid structure. If the growth rate exceeds the set threshold (5%), it is determined that the load growth is fast and the trend is rising. It is necessary to further analyze the grid load change trend. If the load growth rate is lower than the set threshold, it is determined that the load is stable. In the case of long-term monitoring data, a certain load change trend can be formed. For example, if the load growth rate is higher than 5% in multiple consecutive cycles, it means that the grid load shows a rapid growth trend. Otherwise, it means that the load is relatively stable. Based on the calculated load change trend, the grid load change rate is obtained.

[0031]

[0032] As shown in Table 2.1, the load growth rate shows a downward trend, indicating that the load growth is slowing down. If the growth rate suddenly increases to more than 10% at a certain point in time, it is necessary to further analyze the grid load change trend and obtain the grid load change rate.

[0033] The power regulation range judgment submodule determines whether the power regulation range is exceeded based on the grid load change rate. If exceeded, the photovoltaic power generation grid connection ratio is adjusted using the formula: ; Calculate the photovoltaic power variation deviation , determine whether it exceeds the set mutation threshold, if it exceeds, then adjust to obtain the inverter adjustment demand data, where, represents the photovoltaic power output value at the i-th time step, represents the photovoltaic power output value at the previous time step, represents the total number of time steps for the statistics, represents the set mutation threshold; Based on the grid load change rate, determine whether it exceeds the set power adjustment range. For example, the set power adjustment range is ±5%. This setting is based on the dynamic response capability of the photovoltaic power generation system and the maximum allowable load fluctuation value of the grid equipment. Usually, the wind-solar hybrid system or grid linkage adjustment allows power fluctuations between ±3% and ±7%. This value mainly depends on the grid load inertia and the system's short-term overload capacity. Exceeding this range will cause instability to the grid. Therefore, setting it to ±5% meets the grid protection standards and ensures that power can be automatically adjusted within this range. If the calculated grid load change rate exceeds this range, it is necessary to adjust the photovoltaic power generation grid connection ratio. When adjusting, it is necessary to calculate the rate of change of the photovoltaic power output curve. For example, the photovoltaic power output is 150kW at a certain moment, and it becomes 180kW 10 minutes later. Substitute it into the formula for calculation.

[0034] For example, if you set kW, based on the photovoltaic power regulation characteristics and the maximum short-term power variation allowed by the grid connection point, this value is usually set in the range of 10-20kW. It can be dynamically adjusted through the short-term fluctuation data recorded by the dispatching system, and is calculated as follows: ; ; The calculation result is 5kW, indicating that the photovoltaic power change does not exceed the mutation threshold. If it exceeds the mutation threshold, the inverter MPPT parameters need to be adjusted to obtain the inverter adjustment demand.

[0035]

[0036] As shown in Table 2.2, the photovoltaic power output shows an upward trend. It is necessary to determine whether it exceeds the mutation threshold. If it exceeds, the inverter parameters need to be adjusted to obtain the inverter adjustment demand.

[0037] The photovoltaic energy storage power optimization submodule adjusts the inverter MPPT parameters and the photovoltaic power output mode based on the inverter adjustment demand data to obtain the photovoltaic energy storage adjustment power data; Based on the inverter adjustment demand, adjust the inverter MPPT parameters to make the photovoltaic power generation power curve more stable. The main goal of MPPT parameter adjustment is to optimize the photovoltaic power generation output mode, for example, adjust the maximum power tracking factor , assuming , this value is based on the dynamic response rate of the photovoltaic module and the maximum allowable adjustment range of the MPPT control system. This value is usually set in the range of 0.6-1.0, depending on the dynamic adjustment capability of the photovoltaic inverter and the grid frequency stability requirements of the grid connection point. Usually, a low inertia system can take a higher value, while a high inertia system takes a lower value. If the current MPPT operating point power is 200kW and the adjusted target power is 190kW, the following calculation method is used for adjustment: ; Assumptions ,and kW, then ; The calculated adjusted target photovoltaic power is 192kW, the photovoltaic power curve tends to be stable after adjustment, and finally the photovoltaic energy storage adjusted power data is obtained.

[0038] See also Figure 4 , the grid-connected power feedback module includes: The load change rate calculation submodule calculates the current load change rate based on the photovoltaic energy storage adjustment power data, determines whether it is in a short-term high-frequency fluctuation state, and obtains the load fluctuation state identifier; Based on the photovoltaic energy storage to adjust the power data, the power data of the photovoltaic power generation system and the load side are collected. In the time step of 1 second, the power change per second is recorded, and the load change rate is calculated. Specifically, the power change of adjacent time steps is taken, and the power change rate per unit time is calculated. The statistical period is set to 60 seconds, and the mean and standard deviation of the load change within the period are obtained to judge the stability of the load change. If the standard deviation exceeds the set threshold, it is determined that the load is in a short-term high-frequency fluctuation state. As shown in Table 3.1, the load change data for a certain period of time is listed.

[0039] Table 3.1 Load change rate calculation table

[0040] As shown in Table 3.1, within a time period of 60 seconds, the power change rate remains at around 0.2kW / s. If this value exceeds the set threshold of 0.5kW / s, it can be determined that the load has entered a short-term high-frequency fluctuation state, and a load fluctuation state identifier is obtained. The threshold of 0.5kW / s is set based on the standard for the stability of power grid power fluctuations. This value depends on the maximum instantaneous load fluctuation capacity of the photovoltaic system and the maximum short-term power fluctuation range acceptable to the grid. Usually, this range is set between 5% and 10% of the rated power. In this embodiment, it is assumed that the grid-connected power is 10MW, and its acceptable short-term fluctuation range is 0.5MW, that is, the short-term fluctuation rate threshold is 0.5kW / s. If the power fluctuation rate is higher than this value, the grid frequency is affected, thereby triggering the regulation mechanism.

[0041] The charge and discharge mode adjustment submodule determines whether the adjustment conditions are met based on the load fluctuation state flag. If so, the charge and discharge mode is adjusted using the formula: ; Calculate the charge and discharge adjustment requirements , get the charge and discharge mode adjustment record, where, represents the power fluctuation amplitude at the jth time step, Represents the reference power fluctuation amplitude, represents the total number of time steps for the statistics, represents the adjustment threshold; Based on the load fluctuation status identification, first set the power fluctuation adjustment period. For example, within a 10-minute time window, count the power fluctuations and calculate the average power fluctuation amplitude. If the value exceeds 30% of the historical fluctuation average, the charge and discharge adjustment is triggered, the battery charge and discharge power upper limit is set, and the calculation is performed according to the formula.

[0042] Among them, the power fluctuation amplitude See Table 3.2 for values.

[0043] Table 3.2 Charge and discharge mode adjustment data

[0044] Based on Table 3.2, , kW, kW, substitute into the formula to calculate: ; ; ; It is calculated that the charge and discharge adjustment demand is 1.08kW, so the battery charge and discharge power is adjusted to make the power fluctuation amplitude of the power grid tend to be stable, and the charge and discharge adjustment mode is obtained.

[0045] The reactive power compensation demand calculation submodule calculates the power factor data of the power grid based on the charge and discharge mode adjustment record, determines the power factor drop range, and if the drop range exceeds the set demand range, adjusts the grid-connected power according to the reactive power compensation function of the photovoltaic inverter to obtain the dynamic matching record of the grid-connected power; Based on the charge and discharge adjustment mode, the power factor of the power grid is monitored in real time. The power factor calculation method adopts: ; in, is the active power, is reactive power. If the power factor decreases by more than 10%, the reactive power compensation demand is calculated, and the reactive power compensation target is set to return the power factor to the normal range. The 10% power factor decrease is set based on the grid operation stability standard. Usually, the grid power factor should be maintained above 0.95. If the power factor decreases below 0.85, it means that the reactive power demand increases, affecting the grid voltage stability. Therefore, this embodiment sets the reactive power compensation mechanism to be triggered when the decrease exceeds 10%, i.e., 0.095. If the current power factor is 0.85 and the target power factor is set to 0.95, the required compensation reactive power is calculated as follows: Assuming the current active power MW, reactive power The calculation is as follows: ; Calculate the current reactive power : ; ; ; Calculate target reactive power : ; ; ; Calculate reactive power compensation demand : ; It can be concluded that 14.54Mvar of reactive power compensation is required to restore the power factor to 0.95, and finally obtain the grid-connected power dynamic matching record.

[0046] See also Figure 5 , the grid stability margin calculation module includes: The grid frequency change analysis submodule calculates the grid frequency change rate, evaluates the frequency fluctuation degree, and obtains the grid frequency fluctuation amplitude data based on the grid-connected power dynamic matching record; Based on the dynamic matching record of grid-connected power, the historical frequency data of the grid is extracted, and the frequency changes in different periods are analyzed to calculate the rate of change of the grid frequency. Specifically, the historical frequency data of the grid-connected point is first collected at different time points. Recording grid frequency , at fixed time intervals Calculate the frequency change at adjacent times , and count the maximum, minimum, mean and standard deviation within a certain time range to evaluate the frequency fluctuation of the power grid. For example, if the maximum change of the power grid frequency reaches 0.3Hz within 10 minutes, it can be determined that the power grid fluctuation is large during this period, and the fluctuation rate is calculated at the same time If the frequency fluctuation rate is higher than 0.05Hz / s at a certain moment, the adjustment mechanism may be triggered. The value is set based on the sensitivity of the power grid to frequency fluctuations in a short period of time. Specifically, the allowable range of frequency deviation of the State Grid is usually set to ±0.2Hz. If the cumulative frequency deviation is greater than 0.5Hz within 10 seconds, it is regarded as a mutation. At this time, the fluctuation rate per unit time is 0.05Hz / s. Therefore, when the real-time fluctuation rate approaches or exceeds this threshold, the frequency adjustment mechanism needs to be started to prevent excessive deviation from affecting stability. This value increases with the increase in the load power change rate. If the load fluctuation rate remains above 2% / s for a long time, the value may need to be adjusted to 0.07Hz / s to enhance the system response capability. In addition, the frequency change curve can be fitted to extract trend items, such as the slope of the frequency increase or decrease, to determine the long-term change direction of the power grid frequency, and finally calculate and evaluate the power grid frequency fluctuation amplitude.

[0047] The frequency fluctuation regulation submodule determines whether it exceeds the fluctuation control range based on the grid frequency fluctuation amplitude data. If it exceeds, the discharge power is adjusted to support the frequency using the formula: ; Calculate the discharge power adjustment , and adjust the discharge strategy to obtain the frequency support power data, where: represents the grid frequency value at the t-th time step, Represents the rated frequency of the power grid, represents the total number of statistical time steps, Represents the upper limit of energy storage discharge power, Represents the current frequency offset; Based on the grid frequency fluctuation amplitude data, analyze whether it exceeds the set fluctuation control range. The stable frequency range of the grid is set to 49.8-50.2Hz. This range is based on the dispatching standards of the State Grid. Usually, the grid operating frequency is maintained at 50Hz, and the ±0.2Hz deviation allowable range is set based on the grid carrying capacity and load regulation characteristics. If the frequency deviation exceeds 0.2Hz, it may cause the synchronous unit to lose step or large-scale load fluctuations. If the deviation reaches more than 0.5Hz, it may cause the relay protection device to operate, thereby affecting the safety of the grid. This range can be based on the system's habitual For example, in a high-inertia system (such as a thermal-dominated power grid), the range can be set to 49.7-50.3 Hz, while in a low-inertia system (such as a power grid with a high proportion of renewable energy), the range may need to be tightened to 49.85-50.15 Hz to reduce the risk of fluctuations. When the frequency is detected to deviate from this range, the system needs to trigger the frequency support mechanism. If the frequency deviation exceeds 0.3 Hz (that is, reaches 49.5 Hz or 50.5 Hz), it will enter a high-priority regulation state and use the energy storage system for compensation. Specifically, the maximum discharge power of the energy storage system is set. 5MW, the rated frequency of the power grid is 50Hz, the current frequency offset The calculation is as follows: , if it is detected at a certain moment , then , indicating that the grid frequency deviates from the normal range, and the discharge power adjustment amount is calculated using the formula: in Indicates the total number of statistical time steps. If the frequency deviation per second in the past 10 seconds is as follows: ; Calculate the mean of the deviations: ; Calculate the discharge adjustment power: ; The calculation shows that 1.385MW of discharge power is required to support the grid frequency and ultimately obtain frequency support power.

[0048] The grid stability adjustment calculation submodule adjusts the discharge strategy based on the frequency support power data, calculates the energy storage discharge power change rate, determines whether the grid stability adjustment requirements are met, and monitors the recovery of the grid frequency after adjustment to obtain the grid stability adjustment amount; Based on the frequency support power data, the discharge strategy of the energy storage system is adjusted, and the change rate of the energy storage discharge power is calculated to ensure that it adapts to the grid demand. If the current discharge power of the energy storage system is 2MW and the new support power demand is 1.385MW, the adjusted target discharge power is 3.385MW. The energy storage discharge curve is further optimized and the upper limit of the charge and discharge rate is set. Assuming that the maximum charge and discharge change rate of the energy storage system is 0.5MW / s, the discharge power needs to be adjusted from 2MW to 3.385MW: ; If the recovery rate is less than 0.02Hz / s, the discharge strategy needs to be further adjusted. The threshold is set based on the typical time scale of grid frequency recovery. Usually, the self-recovery process after grid frequency deviation is affected by grid inertia, load response rate and secondary frequency regulation strategy. If the recovery rate is lower than 0.02Hz / s for a long time, it indicates that the system adjustment force is insufficient, resulting in long-term retention or repeated oscillation of frequency deviation. In low-inertia grids with high new energy penetration, the threshold is usually set to 0.015-0.025Hz / s, while in high-inertia grids (such as thermal power-dominated), the value can be set to 0.025-0.035Hz / s. If the current grid recovery rate is less than 0.02Hz / s, it is necessary to strengthen energy storage discharge or coordinate the adjustment of other flexible power sources to speed up the recovery process. At the same time, coordinate adjustable power sources such as wind power and thermal power to participate in frequency support. For example, if the wind farm has an adjustable active power of 1MW, the energy storage system discharge demand can be reduced to 2.385MW to reduce energy storage pressure. In addition, monitor the recovery of the adjusted grid frequency. After the discharge power is adjusted, detect the grid frequency every second and calculate the adjusted frequency recovery rate. If the recovery rate is less than 0.02Hz / s, it is necessary to further adjust the discharge strategy to finally obtain the grid stability adjustment amount.

[0049] See also Figure 6 , the energy storage power dynamic control module includes: The available energy reserve calculation submodule extracts the current state of charge based on the grid stability adjustment amount, calculates the available energy reserve, and determines whether the lower limit of safe energy storage is reached to obtain the current energy storage margin; Based on the grid stability adjustment, the current state of charge of the energy storage system is extracted. The state of charge of the energy storage system can be obtained through the real-time data provided by the battery management system (BMS). Assuming that a certain energy storage system is composed of lithium iron phosphate batteries, its nominal voltage is 3.2V, the capacity of the single battery is 280Ah, the system is composed of 120 single batteries in series, and the current state of charge SOC is 50%, then the current energy storage of the system is calculated as: ; Enter the value: ; To calculate the available energy reserve, the lower limit of safe energy storage needs to be considered. Generally speaking, the lower limit of safe SOC of lithium iron phosphate battery is 20%, so the lower limit of safe energy storage is: ; ; Determine the current available reserves: ; ; Finally, the current energy storage margin is 32.26 kWh, which represents the energy that the current energy storage system can use for discharge within the safe energy storage range.

[0050] The energy storage discharge adjustment submodule determines whether the current energy storage margin is lower than the safe energy storage lower limit. If it is lower, the discharge power is reduced and the proportion of photovoltaic direct supply load is increased. The formula is: ; Calculate the discharge power adjustment value , and adjust the energy storage discharge strategy to obtain the energy storage discharge optimization plan, where: Represents the current remaining energy storage, Represents the sustainable discharge time of energy storage, Representative The photovoltaic direct supply power of each load is Representative The energy conversion efficiency of the load, Represents the total number of photovoltaic direct supply loads; Based on the current energy storage margin, determine whether it is lower than the lower limit of safe energy storage. If it is, reduce the discharge power and increase the proportion of photovoltaic direct supply load, and use the formula to calculate the discharge power adjustment value of the energy storage system.

[0051] Assuming the current sustainable discharge time =2h, the grid-connected load includes 3 photovoltaic direct supply devices, and their power requirements and conversion efficiency are shown in the following table: Table 4.1 Photovoltaic direct supply load parameters

[0052] According to the data in Table 4.1, calculate the total power loss of photovoltaic direct supply load: ; ; Calculate the discharge power adjustment value: ; ; Finally, the energy storage discharge optimization plan is obtained, in which the discharge power adjustment value is 7.09kW, which indicates that the current energy storage system can maintain discharge to the load while balancing the discharge power to avoid the energy storage system entering a state below the lower limit of safe energy storage.

[0053] The power response optimization submodule is based on the energy storage discharge optimization scheme, synchronously analyzes the grid dispatch plan, analyzes the future load change trend, and dynamically adjusts the power response strategy to obtain a comprehensive energy storage power optimization adjustment scheme; Based on the energy storage discharge optimization solution, the grid dispatch plan is analyzed synchronously. The grid dispatch plan can be obtained through regional load demand data. Assume that the current grid load demand data for the next hour is as follows: Table 4.2 Future load demand trends

[0054] Analyze the future load change trend and calculate the load growth rate: ; Calculate the load growth rate from 0h to 0.5h: ; Calculate the load growth rate from 0.5h to 1.0h: ; As the future load is on an upward trend, the power response strategy is adjusted dynamically, and a strategy of gradually reducing the energy storage discharge power is adopted to avoid the energy storage system discharging too quickly in a short period of time. At the same time, the proportion of photovoltaic direct supply is adjusted according to future load conditions, and finally a comprehensive energy storage power optimization adjustment plan is obtained.

[0055] The above are only preferred embodiments of the present invention and are not intended to limit the present invention in other forms. Any technician familiar with the profession may use the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes and apply them to other fields. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A grid-connected photovoltaic energy storage control system, characterized in that: The system comprises: The power carrying capacity monitoring module obtains the real-time voltage and current values ​​of the grid connection point, calculates the offset from the rated voltage range and the current power transmission capacity, compares the offset threshold and the upper limit of the safe power of the grid connection point, adjusts the input power of the photovoltaic inverter and the proportion of photovoltaic direct supply, and obtains the power adaptation data of the grid connection point; The photovoltaic energy storage power adjustment module calculates the load growth rate based on the grid connection point power adaptation data, compares the power adjustment range, dynamically adjusts the photovoltaic power generation grid connection ratio, analyzes the photovoltaic power output curve change rate, compares the set mutation threshold, adjusts the inverter MPPT parameters, and obtains photovoltaic energy storage adjustment power data; The grid-connected power feedback module adjusts the power data based on the photovoltaic energy storage, calculates the load change rate, and adjusts the charging and discharging mode. It calculates the reactive power compensation demand according to the power factor data of the power grid, and compares the set demand range. It then makes adjustments according to the reactive power compensation function of the photovoltaic inverter to obtain a dynamic matching record of the grid-connected power. The grid stability margin calculation module analyzes the grid frequency change rate and calculates the frequency fluctuation degree based on the grid-connected power dynamic matching record. If the frequency fluctuation exceeds the fluctuation control range, the discharge power is adjusted to obtain the grid stability adjustment amount.

2. The grid-connected photovoltaic energy storage control system according to claim 1 is characterized in that: The grid-connected point power adaptation data includes the real-time voltage value of the grid-connected point, the current value of the grid-connected point, the power transmission capacity, and the safe power upper limit of the grid-connected point. The photovoltaic energy storage adjustment power data includes the photovoltaic power generation grid-connected ratio, the inverter MPPT parameters, and the photovoltaic power output mode. The grid-connected power dynamic matching record includes the charging and discharging mode, the power fluctuation suppression strategy, the power factor data of the power grid, and the reactive compensation demand data. The power grid stability adjustment amount includes the power grid frequency change rate data, the frequency fluctuation degree data, and the discharge power.

3. The grid-connected photovoltaic energy storage control system according to claim 1, characterized in that: The power carrying capacity monitoring module comprises: The voltage offset calculation submodule obtains the real-time voltage value of the grid connection point, calculates the offset between the voltage value and the rated voltage range, and determines whether the offset exceeds the offset threshold. If so, the input power of the photovoltaic inverter is adjusted to obtain the corrected input power value. The power transmission capacity calculation submodule synchronously reads the grid connection point current value based on the corrected input power value, calculates the current power transmission capacity, and compares it with the grid connection point safety power upper limit, using the formula: ； Calculating the power transfer deviation , determine whether it exceeds the grid-connected point safety power upper limit, if it exceeds, perform adjustment, and obtain power adjustment demand data, where, represents the grid connection point voltage value at the i-th moment, represents the grid-connected point current value at the ith moment, represents the voltage and current phase angle at the ith moment, represents the number of time steps during the computation period, Represents the upper limit of the safe power of the grid connection point; The grid connection point power adaptation submodule adjusts the photovoltaic direct supply ratio based on the power adjustment demand data, matches the grid connection point power carrying capacity, and obtains the grid connection point power adaptation data.

4. The grid-connected photovoltaic energy storage control system according to claim 1, characterized in that: The optical storage power adjustment module comprises: The load growth rate calculation submodule calculates the current load growth rate based on the grid connection point power adaptation data, analyzes the grid load change trend, and obtains the grid load change rate; The power regulation range judgment submodule determines whether the power regulation range is exceeded based on the grid load change rate. If exceeded, the photovoltaic power generation grid connection ratio is adjusted using the formula: ； Calculate the photovoltaic power variation deviation , determine whether it exceeds the set mutation threshold, if it exceeds, then adjust to obtain the inverter adjustment demand data, where, represents the photovoltaic power output value at the i-th time step, represents the photovoltaic power output value at the previous time step, represents the total number of time steps for the statistics, represents the set mutation threshold; The photovoltaic energy storage power optimization submodule adjusts the inverter MPPT parameters and the photovoltaic power generation power output mode based on the inverter adjustment demand data to obtain photovoltaic energy storage adjustment power data.

5. The grid-connected photovoltaic energy storage control system according to claim 1, characterized in that: The grid-connected power feedback module comprises: The load change rate calculation submodule calculates the current load change rate based on the photovoltaic energy storage adjustment power data, determines whether it is in a short-term high-frequency fluctuation state, and obtains a load fluctuation state identifier; The charge and discharge mode adjustment submodule determines whether the adjustment condition is met based on the load fluctuation state identifier. If so, the charge and discharge mode is adjusted using the formula: ； Calculate the charge and discharge adjustment requirements , get the charge and discharge mode adjustment record, where, represents the power fluctuation amplitude at the jth time step, Represents the reference power fluctuation amplitude, represents the total number of time steps for the statistics, represents the adjustment threshold; The reactive power compensation demand calculation submodule calculates the power factor data of the power grid based on the charge and discharge mode adjustment record, determines the power factor decrease range, and if the decrease range exceeds the set demand range, adjusts the grid-connected power according to the reactive power compensation function of the photovoltaic inverter to obtain the grid-connected power dynamic matching record.

6. The grid-connected photovoltaic energy storage and charging control system according to claim 1, characterized in that: The grid stability margin calculation module includes: The grid frequency change analysis submodule calculates the grid frequency change rate, evaluates the frequency fluctuation degree, and obtains the grid frequency fluctuation amplitude data based on the grid-connected power dynamic matching record; The frequency fluctuation regulation submodule determines whether it exceeds the fluctuation control range based on the grid frequency fluctuation amplitude data. If it exceeds, the discharge power is adjusted to support the frequency using the formula: Calculate the discharge power adjustment , and adjust the discharge strategy to obtain the frequency support power data, where: represents the grid frequency value at the t-th time step, Represents the rated frequency of the power grid, represents the total number of statistical time steps, Represents the upper limit of energy storage discharge power, Represents the current frequency offset; The grid stability adjustment calculation submodule adjusts the discharge strategy based on the frequency support power data, calculates the energy storage discharge power change rate, determines whether the grid stability adjustment requirements are met, and monitors the recovery of the grid frequency after adjustment to obtain the grid stability adjustment amount.

7. The grid-connected photovoltaic energy storage and charging control system according to claim 1, characterized in that: The system also includes an energy storage power dynamic control module; The energy storage power dynamic control module extracts the current state of charge based on the grid stability adjustment amount, calculates the available energy reserve, and determines whether the safe energy storage lower limit is reached. If it is lower than the safe energy storage lower limit, the discharge power is reduced and the proportion of photovoltaic direct supply load is increased. The grid dispatch plan is analyzed simultaneously, the future load change trend is analyzed, and the power response strategy is dynamically adjusted to obtain a comprehensive energy storage power optimization adjustment plan; The comprehensive energy storage power optimization and regulation scheme includes charge state recording, available energy reserve, safe energy storage lower limit, photovoltaic direct supply load ratio, power grid dispatching plan, and power response strategy.

8. The grid-connected photovoltaic energy storage and charging control system according to claim 7 is characterized in that: The energy storage power dynamic control module includes: The available energy reserve calculation submodule extracts the current state of charge based on the grid stability adjustment amount, calculates the available energy reserve, and determines whether the safe energy storage lower limit is reached to obtain the current energy storage margin; The energy storage discharge adjustment submodule determines whether the current energy storage margin is lower than the safe energy storage lower limit based on the current energy storage margin. If it is lower, the discharge power is reduced and the proportion of photovoltaic direct supply load is increased, using the formula: ； Calculate the discharge power adjustment value , and adjust the energy storage discharge strategy to obtain the energy storage discharge optimization plan, where: Represents the current remaining energy storage, Represents the sustainable discharge time of energy storage, Representative The photovoltaic direct supply power of each load is Representative The energy conversion efficiency of the load, Represents the total number of photovoltaic direct supply loads; The power response optimization submodule is based on the energy storage discharge optimization scheme, synchronously analyzes the grid dispatch plan, analyzes future load change trends, and dynamically adjusts the power response strategy to obtain a comprehensive energy storage power optimization adjustment scheme.

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