Method for evaluating dispatchable capacity of integrated light storage and charging fast charging station considering V2G technology

Abstract

A method for evaluating the dispatchable capacity of a photovoltaic-storage-charging integrated fast charging station that takes into account V2G technology includes the following steps: (1) collecting charging parameters, user demand parameters, power dispatch parameters, and charging station configuration parameters of electric vehicles; (2) establishing charging and discharging constraints for electric vehicles; (3) solving the thresholds for the adjustable capacity and adjustable capacity of a single electric vehicle, and then establishing a solution model for the dispatchable capacity of the electric vehicle cluster of the fast charging station; (4) determining the working mode and energy constraints of centralized energy storage, analyzing the energy relationship between the dispatchable capacity of electric vehicles, the dispatchable capacity of centralized energy storage, and photovoltaic power generation, and establishing a calculation model for the adjustable capacity and adjustable capacity of the photovoltaic-storage-charging integrated fast charging station; (5) combining the calculation model for the dispatchable capacity of the photovoltaic-storage-charging station, establishing a solution strategy for the daily dispatchable capacity of the charging station, and analyzing the impact of illumination conditions, load scenarios, dispatch time scale, and centralized energy storage configuration on the model solution.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle charging and discharging technology, and in particular to a method for assessing the dispatchable capacity of an integrated photovoltaic, energy storage and charging fast charging station that takes into account V2G technology. Background Technology

[0002] Given the current energy shortage, the widespread deployment of electric vehicles and their supporting infrastructure is a crucial measure to accelerate the construction of a new generation of power systems and promote green, safe, efficient, and sustainable energy development. With the increasing use of electric vehicles, major power grid companies have emphasized the importance of developing electric vehicles in their development plans, providing corresponding support in areas such as charging and discharging characteristics and modeling methods, charging pile planning, and coordinated dispatching. In recent years, scholars from various countries have actively explored the development model of "new energy + energy storage + electric vehicles," and integrated photovoltaic-storage-charging facilities will play a vital role in the future. However, the large-scale grid connection of electric vehicles will have a significant impact on the operation and planning of the power system. Vehicle-to-grid (V2G) technology is a new type of grid technology. The basic principle of V2G technology is to control the charging and discharging process of electric vehicles. During periods of low load, the grid dispatches electric vehicles to charge in order to store excess power generated by the grid; during periods of high load, electric vehicles feed power back to the grid. As a distributed energy storage system, electric vehicles, combined with the effective utilization of V2G technology, can provide peak shaving, valley filling, and frequency regulation services to the grid, bringing benefits to the grid, users, and society. Rapidly and accurately predicting the dispatchable capacity (SC) of electric vehicles is the first step in realizing the participation of electric vehicles in grid interaction.

[0003] Currently, research on the dispatchable capacity of electric vehicles (EVs) is relatively comprehensive, but most studies focus only on the dispatchable capacity of large-scale EV clusters. Few studies explore the dispatchable capacity by considering new energy storage charging stations and EVs as a microgrid. This is significant because EVs charging at stations exhibit clustering; the centralized energy storage at the charging station and the onboard batteries can both be objects of grid dispatch and influence each other, resulting in dispatchable capacity characteristics different from those of individual EVs or large-scale EV clusters. Charging stations often participate in grid dispatch as a whole; understanding the distribution trend of their dispatchable capacity is more conducive to the grid's rational dispatch strategy formulation. Therefore, considering a dispatchable capacity assessment method for integrated photovoltaic-storage-charging fast-charging stations using V2G technology is particularly important. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for evaluating the dispatchable capacity of an integrated photovoltaic-storage-charging fast charging station that takes into account V2G technology, so as to accurately calculate the dispatchable capacity of distributed mobile energy storage participating in vehicle-to-grid interaction.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast-charging station that takes into account V2G technology, characterized by the following steps:

[0007] Step S1. Based on the electrical structure of the integrated photovoltaic-storage-charging fast charging station and the calculation requirements for the dispatchable capacity of electric vehicles under different scheduling time scales, collect real-time operating data of electric vehicles and configuration parameters of the charging station.

[0008] Step S2. Establish charging and discharging constraints for electric vehicles, including:

[0009] ① Battery capacity constraint, which refers to the constraint on the battery capacity of the vehicle while considering the travel needs of electric vehicles:

[0010]

[0011] ② Battery life constraints, which are constraints on the lifespan of the vehicle battery considering the lifespan degradation of the energy storage battery:

[0012]

[0013] In the formula, SOC EV (j,t) represents the energy storage value of the j-th vehicle at the left endpoint of the t-th dispatch interval. Let SOC be the charging and discharging power of the j-th vehicle in the t-th dispatch interval after dispatching. EV,min (j) and SOC EV,max (j) represents the lower and upper limits of on-board battery energy storage, S ba (j) represents the battery capacity of the j-th vehicle, and η is the charging and discharging efficiency;

[0014] ③ Maximum battery charge / discharge power constraint, which refers to the constraint condition that the maximum charge / discharge power of the battery needs to be limited within a specified range, considering the charging and discharging power of the charging pile and the vehicle battery:

[0015]

[0016] In the formula, Let represent the charging and discharging power of the j-th electric vehicle after being dispatched in the t-th dispatch interval. and Let represent the maximum charging and discharging power of the j-th electric vehicle, respectively;

[0017] ④ Time and object constraints, which are the time and object constraints on the charging behavior of electric vehicles, considering the time when electric vehicles enter and exit the power grid:

[0018] t arrive ≤t≤t sche ≤tleave

[0019] Step S3. Considering the choice of scheduling time, solve for the threshold of the schedulable capacity of a single electric vehicle, and calculate the schedulable capacity of the electric vehicle cluster of the photovoltaic-storage-charging integrated fast charging station.

[0020] Step S4. Determine the working mode and energy constraints of centralized energy storage, analyze the energy relationship between the dispatchable capacity of electric vehicles, the dispatchable capacity of centralized energy storage, and photovoltaic power generation, and calculate the adjustable capacity and adjustable capacity of the photovoltaic-storage-charging integrated fast charging station.

[0021] Step S5. Based on the adjustable capacity and adjustable capacity of the photovoltaic-storage-charging integrated fast charging station, calculate the daily dispatchable capacity of the charging station, and analyze the impact of lighting conditions, load scenarios, dispatch time scale, and centralized energy storage configuration on the dispatchable capacity.

[0022] Furthermore, the electrical structure of the photovoltaic-storage-charging integrated fast charging station described in step S1 is divided into a power distribution system, a charging system, a monitoring system, an energy storage system, and a photovoltaic power generation system; the photovoltaic power generation system transfers solar energy to the energy storage system, and when needed, supplies electricity to the charging system.

[0023] Furthermore, the real-time operating data of the electric vehicle in step S1 includes: charging parameters, user demand parameters, and power dispatch parameters; the configuration parameters of the charging station include photovoltaic power generation, number of charging piles, charging power, and centralized energy storage capacity.

[0024] Furthermore, in step S3, the schedulable capacity of electric vehicles is divided into adjustable capacity and adjustable capacity; step S3 solves for the threshold of the schedulable capacity of a single electric vehicle, including calculating the threshold of adjustable capacity. The formula is as follows:

[0025]

[0026]

[0027] In the formula, This represents the un-scheduled charging power of the j-th electric vehicle in the t-th scheduling interval.

[0028] Let represent the charging and discharging power of the j-th electric vehicle after being dispatched in the t-th dispatch interval.

[0029] Charging and discharging power considering battery capacity constraints The threshold; and

[0030] Calculate the threshold for adjustable capacity The formula is as follows:

[0031]

[0032]

[0033] In the formula, Charge and discharge power considering battery capacity constraints The threshold.

[0034] Furthermore, step S3 calculates the dispatchable capacity of the electric vehicle cluster of the integrated photovoltaic-storage-charging fast charging station, including: calculating the V2G upscalable capacity of the electric vehicle cluster within the dispatching interval. and adjustable capacity The formula is as follows:

[0035]

[0036]

[0037] Furthermore, in step S4, the adjustable capacity of the integrated photovoltaic-storage-charging fast charging station is calculated. The formula is as follows:

[0038]

[0039] In the formula, For the adjustable capacity of centralized energy storage, P pv (t) represents the photovoltaic power generation in the t-th scheduling interval;

[0040] In step S4, the adjustable capacity of the photovoltaic-storage-charging integrated fast charging station is calculated. The formula is as follows:

[0041]

[0042] In the formula, This represents the maximum charging power of centralized energy storage in the t-th scheduling interval. This represents the maximum discharge power of the centralized energy storage in the t-th scheduling interval.

[0043] Furthermore, in step S5, based on the adjustable and de-adjustable capacities of the integrated photovoltaic-storage-charging fast charging station, the daily dispatchable capacity of the charging station is calculated, and the impact of lighting conditions, load scenarios, dispatch time scales, and centralized energy storage configuration on the dispatchable capacity is analyzed. It should be noted that step S5 is based on the design described above and specifically includes:

[0044] Step S51: Calculate the daily dispatchable capacity of the charging station.

[0045] Step S511, Preparation: Determine the length t of the scheduling interval.dispatch Determine the current scheduling interval t. If t < 24h, then obtain the photovoltaic power generation P for the current time period. pv (t), begin calculating the schedulable capacity;

[0046] Step S512: If there is an available charging pile, accept the electric vehicle for charging and generate the charging scenario of the electric vehicle load according to step S12, including the charging parameters of the electric vehicle, user demand parameters and power dispatch parameters.

[0047] Step S513: Generate a state matrix based on the charging scenario of the electric vehicle load, record information such as the electric vehicle's grid connection, off-grid status, and whether it is fully charged, and calculate the SOC curve of the on-board battery and the load power within the scheduling interval.

[0048] Step S514: Determine the number of electric vehicles that can be dispatched by the charging stations within the current dispatch interval, and calculate the dispatchable capacity of electric vehicles according to step S3. and

[0049] Step S515: Based on the load power of the electric vehicle and photovoltaic power generation P pv (t), and combined with the energy relationship in step S42, obtain the SOC curve of centralized energy storage;

[0050] Step S516: Obtain the dispatchable capacity of centralized energy storage based on energy storage boundary constraints and power constraints, and then determine the dispatchable capacity of the t-th dispatch interval from steps S43 and S44. and The calculation method is used to generate the daily dispatchable capacity curve of the photovoltaic-storage-charging integrated fast charging station;

[0051] Step S52 analyzes the impact of lighting conditions, load scenarios, scheduling timescales, and centralized energy storage configuration on dispatchable capacity: Changing lighting conditions does affect the upscalable capacity; under favorable lighting conditions... The value will increase accordingly, while changing the lighting conditions has little impact on the adjustable capacity; different electric vehicle load scenarios will exhibit different dispatchable capacity characteristics; the smaller the dispatch interval length, the larger the average dispatchable capacity will be; the smaller the dispatch interval, the more vehicles can be dispatched, and the larger the corresponding dispatchable capacity will be; centralized energy storage capacity configuration must meet certain emergency backup power time requirements:

[0052]

[0053]

[0054] In the formula, Indicates the emergency power supply capacity of photovoltaic power. This represents the average daily photovoltaic power generation; n pile P represents the number of charging stations. sdc For low DC charging power, based on the design of the smallest power unit in most current DC charging piles, P sdc =15kW,t reserve For emergency backup power time, energy storage capacity needs to be configured reasonably. If the energy storage capacity is too small, it is easy to reach the upper or lower limit of its SOC, reducing the dispatchable capacity of the charging station; if the energy storage capacity is too large, it will cause a waste of capacity resources.

[0055] Compared with the prior art, the beneficial effects of the present invention are:

[0056] Current research on the dispatchable capacity assessment of electric vehicles (EVs) is relatively comprehensive, but most studies focus only on the dispatchable capacity of EV clusters or parking lots. Few studies explore the dispatchable capacity of new energy storage charging stations and EVs as a local microgrid. This invention considers the charging station as a whole in grid dispatch, which is significant. EVs charging at charging stations exhibit clustering; both the centralized energy storage of the charging station and the onboard batteries of the EVs can be objects of grid dispatch and influence each other, resulting in dispatchable capacity characteristics different from those of a single EV or a large-scale EV cluster. This invention focuses on integrated photovoltaic-storage-charging fast-charging stations, exploring the energy relationships within the charging station during grid dispatch response. It accurately quantifies the distribution trend of its dispatchable capacity throughout the day, providing a basis for V2G technology to participate in grid ancillary services and facilitating the grid's rational formulation of dispatch strategies. Attached Figure Description

[0057] Figure 1 A flowchart for assessing the dispatchable capacity of integrated photovoltaic, energy storage, and charging fast charging stations that take V2G technology into account.

[0058] Figure 2 A schematic diagram illustrating the principle of dispatchable capacity formation for electric vehicles.

[0059] Figure 3 The diagram illustrates the energy relationship of an integrated photovoltaic, energy storage, and charging fast charging station. Figure (a) shows the energy relationship during the process of generating adjustable capacity, and Figure (b) shows the energy relationship during the process of generating adjustable capacity.

[0060] Figure 4 The following are the calculation results of the dispatchable capacity of an integrated photovoltaic, energy storage and charging fast charging station under different scheduling time scales in a specific example. Detailed Implementation

[0061] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Note that the following description of the embodiments is merely illustrative and is not intended to limit the applicability or use of the invention, nor is the invention limited to the following embodiments.

[0062] A method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast charging station that takes V2G technology into account includes the following steps:

[0063] Step S1: Considering the electrical structure and operation mode of the integrated photovoltaic-storage-charging fast charging station, collect the charging parameters of electric vehicles, user demand parameters, power dispatch parameters, and charging station configuration parameters; the specific implementation method is as follows:

[0064] Step S11: Analyze the electrical structure of the integrated photovoltaic-storage-charging fast charging station. It is divided into five parts: power distribution system, charging system, monitoring system, energy storage system, and photovoltaic power generation system. Its core consists of three parts: photovoltaic power generation, energy storage batteries, and charging piles. These three parts form a microgrid. Photovoltaic power generation stores electricity in energy storage batteries. When needed, the energy storage batteries supply electricity to the charging piles. Through the photovoltaic-storage-charging system, clean solar energy is transferred to the vehicle's power battery for vehicle operation.

[0065] Step S12: To meet the calculation needs of dispatchable capacity of electric vehicles under different scheduling time scales, and considering both user demand and power dispatching requirements, the real-time operation data of electric vehicles consists of three parts: electric vehicle charging parameters, user demand parameters, and power dispatching parameters. Electric vehicle charging parameters are defined as follows: j is the vehicle sequence number, t is the current scheduling interval sequence number, and t... arrive For the grid connection time of electric vehicles, S ba For vehicle battery capacity, Initial SOC before charging the vehicle battery EV For the current SOC of the vehicle battery, t full The time it takes for the vehicle to fully charge, t sche The schedulable time for electric vehicles; User requirement parameter: t leave This refers to the off-grid time of electric vehicles. The expected SOC value for vehicle battery charging by the owner; power dispatch parameter: t dispatch This refers to the length of the scheduling interval. In addition, configuration parameters for the charging station are needed to calculate the total scheduling capacity of the entire charging station, including photovoltaic power generation, number of charging piles, charging power, and centralized energy storage capacity, which will be discussed in detail later.

[0066] Step S2: Based on the formation principle of V2G schedulable capacity of electric vehicles, establish charging and discharging constraints for electric vehicles; the specific implementation method is as follows:

[0067] The primary function of electric vehicles is to meet people's travel needs as a means of transportation; fulfilling users' travel goals is the top priority under any scheduling conditions. Furthermore, excessively frequent or over-charging and discharging can damage the onboard battery, which is also a factor that V2G must consider. Therefore, whether an electric vehicle can continue to reduce its charging power or reverse discharge, or whether it can increase its charging power, is mainly limited by the electric vehicle user's travel electricity demand, battery life, and the battery's maximum charging and discharging power. Calculating the dispatchable capacity requires satisfying the constraints in step S2:

[0068] Step S21, Mobility Constraints: Ensure that the onboard battery reaches the owner's expected SOC target before the electric vehicle leaves the grid.

[0069]

[0070] Equation (1) is the constraint condition for the battery power of the vehicle under the consideration of the travel needs of electric vehicles.

[0071] Step S22, Battery Life Constraint: After scheduling, the SOC of the EV battery must vary within a reasonable range.

[0072]

[0073] Equation (2) represents the on-board battery life constraint considering the life loss of the energy storage battery. SOC EV (j,t) represents the energy storage value of the j-th vehicle at the left endpoint of the t-th dispatch interval. Let SOC be the charging and discharging power of the j-th vehicle in the t-th dispatch interval after dispatching. EV,min (j) and SOC EV,max (j) represents the lower and upper limits of on-board battery energy storage. The depth of discharge of lithium batteries is negatively correlated with their lifespan. According to relevant data, when the depth of discharge of a lithium battery is 80%, its cycle life is 3000 cycles, which meets the standards for lithium battery use. S ba (j) represents the battery capacity of the j-th vehicle, and η is the charging and discharging efficiency.

[0074] Step S23, Maximum charge / discharge power constraint of the battery: The charge / discharge power of the vehicle battery needs to be limited within the specified range:

[0075]

[0076] Equation (3) is the maximum charging and discharging power constraint of the vehicle battery. Let represent the charging and discharging power of the j-th electric vehicle after being dispatched in the t-th dispatch interval. and These represent the maximum charging and discharging power of the j-th electric vehicle, respectively. The maximum charging and discharging power depends on the parameters of the charging station.

[0077] Step S24, Time and Object Constraints: The time for electric vehicles to enter and exit the power grid is determined by the user, and scheduling is only possible within the time frame of electric vehicle grid connection.

[0078] t arrive ≤t≤t sche ≤t leave (4)

[0079] Equation (4) represents the time and object constraints for the electric vehicle charging behavior. The meanings of the relevant variables have been described in step S12.

[0080] Step S3: Considering the formation principle of the schedulable capacity of electric vehicles, solve for the thresholds of the adjustable capacity and the adjustable capacity of a single electric vehicle, and then establish a solution model for the schedulable capacity of the electric vehicle cluster of the fast charging station; the specific implementation method is as follows:

[0081] Step S31: Based on the charging and discharging process, analyze the formation principle of the dispatchable capacity of electric vehicles. The dispatchable capacity of electric vehicles is divided into adjustable capacity and adjustable capacity. For vehicles charging at fast charging stations, the charging pile calculates the estimated charging time based on the initial energy storage of the electric vehicle and the target energy storage set by the user. We define this time period as the dispatchable time t of the electric vehicle. sche This means that the vehicle's battery is available for dispatch within this timeframe. If the dispatchable time is exceeded, the user may pick up the vehicle at any time, and the electric vehicle's battery level needs to reach the user's set level at the time of pickup, therefore it cannot respond to grid dispatch. The charging station sets a reference charging power, which is the promised charging power for the electric vehicle, and the dispatchable time is calculated based on this. However, the actual charging power of the charging station can fluctuate, and charging may exceed the reference charging power during the charging process. For example, a 60-150kW DC charging station promises a charging power of 60kW, but its actual maximum achievable charging power is approximately 90-100kW. Therefore, electric vehicles can be equated to distributed power sources. Within their dispatchable range, during peak grid periods, fast charging stations can temporarily reduce the charging power supplied to electric vehicles in response to grid demand. This reduced charging load power is equivalent to the increased generation power of the distributed power source, forming the adjustable capacity of electric vehicles within that dispatchable range. After the dispatchable range ends, charging power is increased to reach the user's target charge level before the dispatchable time for electric vehicles ends. Conversely, during off-peak periods, charging power can be temporarily increased to absorb excess grid energy, allowing electric vehicles to be fully charged earlier (which is perfectly acceptable to users). This increased charging load power is equivalent to the reduced generation power of the distributed power source, forming the adjustable capacity of electric vehicles within that dispatchable range. (Appendix) Figure 2A schematic diagram illustrating the formation principle of the dispatchable capacity of electric vehicles is provided. In this embodiment, dispatchable capacity is represented in the form of power.

[0082] Step S32: Solve for the adjustable capacity threshold of a single electric vehicle. To meet travel constraints, the adjustable capacity of an electric vehicle must satisfy the following equation:

[0083]

[0084] In formula (4) Let SOC represent the target battery level of the j-th vehicle. EV (j,t) represents the initial battery level of the j-th vehicle in the t-th dispatch interval. When the above equation holds true, the charging and discharging power can be obtained. threshold This leads to the calculation method for the threshold of adjustable capacity:

[0085]

[0086]

[0087]

[0088] In formula (6) Let represent the unscheduled charging power of the j-th electric vehicle in the t-th scheduling interval. Since the arrival and departure times of electric vehicles are discrete, they often do not start charging at the beginning of the scheduling interval. However, in order to be consistent with other variables, it is equivalent to the entire scheduling interval.

[0089] Equation (7) is the power constraint for charging and discharging of electric vehicles. This represents the charging and discharging power of the electric vehicle of vehicle j after being dispatched in the t-th dispatch interval.

[0090] Equation (8) is the formula for calculating the adjustable capacity of electric vehicles within the scheduling interval. The assessment of schedulable capacity explores the maximum potential capacity of electric vehicles that can be scheduled under actual charging and discharging conditions. Therefore, based on the actual SOC change curve of the on-board battery, the potential schedulable capacity of electric vehicles is calculated for certain time periods that meet the scheduling requirements. Thus, the power changes caused by the simulated charging and discharging scheduling of electric vehicles during the calculation process do not affect the actual SOC changes of the on-board battery and centralized energy storage; only the actual SOC conditions and other constraints need to be met.

[0091] Step S33: Solve for the adjustable capacity threshold for a single electric vehicle. The calculation of the adjustable capacity first considers the battery capacity constraint:

[0092]

[0093] When equation (9) is taken as equal, we can obtain threshold The method for calculating the threshold for adjusting capacity can then be described as follows:

[0094]

[0095]

[0096] Equation (10) is the power constraint for charging and discharging of electric vehicles. This represents the charging and discharging power of the electric vehicle of vehicle j after being dispatched in the t-th dispatch interval.

[0097] Equation (11) is the formula for calculating the adjustable capacity of electric vehicles within the scheduling interval. This represents the adjustable capacity of the j-th electric vehicle in the t-th scheduling interval.

[0098] Step S34: Calculate the dispatchable capacity of the electric vehicle cluster of the integrated photovoltaic-storage-charging fast charging station. The dispatchable capacity of a charging station should be the sum of the dispatchable capacities of all dispatchable electric vehicles within the dispatch interval. Based on the calculation method for a single electric vehicle described above, the V2G adjustable capacity of the electric vehicle cluster within this dispatch interval can be obtained. and adjustable capacity Calculation method:

[0099]

[0100]

[0101] Equations (12-13) are the calculation method for the dispatchable capacity of an electric vehicle fleet connected to the grid via a photovoltaic-storage-charging integrated fast charging station. If the j-th vehicle is not dispatchable in the t-th dispatch interval, then:

[0102]

[0103] The charging load characteristics of integrated photovoltaic-storage-charging fast charging stations vary due to user behavior and can be categorized based on actual conditions. For example, the first type of load is mostly during the day, with electric vehicles utilizing the high power of fast charging piles for quick charging and short dwell times. The second type of load is mostly during the night, with vehicles being picked up the following morning, resulting in longer dwell times. When modeling the charging load and calculating the dispatchable capacity of fast charging stations, attention should be paid to these differences in charging load behavior, primarily reflected in the difference in dispatchable time.

[0104] Step S4: Determine the working mode and energy constraints of centralized energy storage, analyze the energy relationship between the dispatchable capacity of electric vehicles, the dispatchable capacity of centralized energy storage, and photovoltaic power generation, and establish a calculation model for the adjustable and de-adjustable capacity of the photovoltaic-storage-charging integrated fast charging station.

[0105] In one embodiment of the present invention, step S4 is specifically implemented as follows:

[0106] Step S41: Definition of photovoltaic power generation. The photovoltaic power generation of the charging station can be obtained based on the principles and related knowledge of photovoltaic power generation, but this will not be the focus of this study. Define photovoltaic power generation P. pv (t) represents the photovoltaic power generation in the t-th scheduling interval.

[0107] Step S42: Determine the operating mode and energy constraints of centralized energy storage. Due to the strong volatility of new energy power generation, an energy storage system is needed as a buffer. Energy storage batteries can store energy at night, and during peak charging periods, the energy storage station and the grid work together to supply power to the charging station, achieving peak shaving and valley filling, saving on distribution capacity expansion costs, and effectively solving the volatility and instability of new energy power generation. A centralized energy storage system typically consists of several energy storage batteries and is equipped with a control unit. Currently, photovoltaic-energy storage charging stations adopt a valley-charge-peak-discharge and flat-charge-peak-discharge operating mode, which can reduce overall energy costs. Energy storage stations typically implement a "two-charge, two-discharge" operation strategy. Considering the peak output of photovoltaic power generation at midday, the charging periods for energy storage stations are 03:30–05:30 and 13:30–16:30. Based on this, we obtain the changes and constraints of the energy storage capacity of the photovoltaic-energy storage charging station:

[0108]

[0109]

[0110] SOC cent,min ≤SOC cent (t)≤SOC cent,max (17)

[0111]

[0112]

[0113]

[0114] Equation (15-19) represents the constraints for centralized energy storage. This indicates the charging power of centralized energy storage under the "two-charge, two-discharge" operation strategy. SOC cent (t) represents the amount of energy stored in the centralized energy storage of the t-th dispatch interval. cent This indicates the capacity of centralized energy storage. This represents the total load power of EVs in the t-th scheduling interval. SOC cent,min and SOC cent,max This indicates the upper and lower bounds of the centralized energy storage system (SOC). This represents the charging power of the centralized energy storage in the t-th scheduling interval. This represents the discharge power of the centralized energy storage in the t-th scheduling interval. This represents the maximum charging power of centralized energy storage in the t-th scheduling interval. This represents the maximum discharge power of the centralized energy storage in the t-th scheduling interval.

[0115] Equation (20) represents the change in the amount of electricity stored in centralized energy storage. The amount of electricity stored in centralized energy storage is affected by the photovoltaic power generation, the charging power of electric vehicle loads, and the operating strategy.

[0116] Step S43: Analyze the energy relationship between the dispatchable capacity of electric vehicles, the dispatchable capacity of centralized energy storage, and photovoltaic power generation, and calculate the adjustable capacity of the photovoltaic-energy storage-charging integrated fast charging station. The dispatchable capacity of electric vehicles is calculated according to the method in step S3, and the dispatchable capacity of centralized energy storage is determined based on meeting the current electric vehicle load. And considering the boundaries of the energy storage system, the maximum power output of a centralized energy storage battery:

[0117]

[0118]

[0119] In equation (21) The adjustable capacity of centralized energy storage. Equation (22) is the calculation formula for the adjustable capacity of the final photovoltaic-storage-charging integrated fast charging station. The adjustable capacity of the charging station consists of three parts: the adjustable capacity of electric vehicles, the adjustable capacity of centralized energy storage, and photovoltaic power generation.

[0120] Step S44: Calculate the adjustable capacity of the photovoltaic-storage-charging integrated fast charging station. The adjustable capacity of the photovoltaic-storage-charging integrated fast charging station consists of two parts: the adjustable capacity of electric vehicles and the adjustable capacity of centralized energy storage. Since this is in response to the remaining power of the grid, all photovoltaic power is discarded. The adjustable capacity of electric vehicles is calculated according to the method in step S3, and the adjustable capacity of energy storage is the maximum charging power of the centralized energy storage (constrained by the upper limit of energy storage capacity and the existing power of the stored energy).

[0121]

[0122] Equation (23) is the formula for calculating the adjustable capacity of the final photovoltaic-storage-charging integrated fast charging station. The adjustable capacity of a charging station consists of two parts: the adjustable capacity of electric vehicles and the adjustable capacity of centralized energy storage. Thus, we have obtained the calculation method for the adjustable and de-adjustable capacity of an integrated photovoltaic-energy storage-charging fast charging station. (Appendix) Figure 3 A schematic diagram of the energy relationship structure of an integrated photovoltaic, energy storage, and charging fast charging station is provided.

[0123] Step S5: Based on the calculation model of the dispatchable capacity of the photovoltaic-storage charging station, establish a solution strategy for the daily dispatchable capacity of the charging station, and analyze the impact of illumination conditions, load scenarios, dispatch time scale, and centralized energy storage configuration on the model solution.

[0124] In one embodiment of the present invention, step S5 is specifically implemented as follows:

[0125] Step S51: Based on the dispatchable capacity solution model of steps S1-S4, establish a solution strategy for the daily dispatchable capacity of integrated photovoltaic-storage-charging fast charging stations. This strategy serves as a reference for grid dispatch, allowing different response strategies to be formulated according to the different dispatchable capacities of the photovoltaic-storage-charging stations throughout the day. The 24-hour period is divided according to the size of the dispatch interval; for example, if the dispatch interval length is 15 minutes, then the day will be divided into 96 points.

[0126] Step S511, Preparation. Determine the length t of the scheduling interval. dispatch Determine the current scheduling interval t. If t < 24h, then obtain the photovoltaic power generation P for the current time period. pv (t), start calculating the schedulable capacity.

[0127] Step S512: If there is an available charging pile, accept the electric vehicle for charging. Generate the charging scenario of the electric vehicle load according to step S12, including the charging parameters of the electric vehicle, user demand parameters, and power dispatch parameters, etc.

[0128] Step S513: Generate a state matrix based on the charging scenario of the electric vehicle load, record information such as the electric vehicle's grid connection, off-grid status, and whether it is fully charged, and calculate the SOC curve of the on-board battery and the load power within the scheduling interval.

[0129] Step S514: Determine the number of electric vehicles that can be dispatched by the charging stations within the current dispatch interval, and calculate the dispatchable capacity of electric vehicles according to the method in step S3. and

[0130] Step S515: Based on the load power of the electric vehicle and photovoltaic power generation P pv (t), and combined with the energy relationship in step S42, the SOC curve of centralized energy storage is obtained.

[0131] Step S516: Obtain the dispatchable capacity of centralized energy storage based on energy storage boundary constraints and power constraints, and then determine the dispatchable capacity of the t-th dispatch interval from steps S43 and S44. and The calculation method is used to generate the daily dispatchable capacity curve of the integrated photovoltaic, energy storage and charging fast charging station.

[0132] Step S52: Analyze the impact of lighting conditions, load scenarios, scheduling time scales, and centralized energy storage configuration on the solution of the schedulable capacity calculation model. Changing lighting conditions does affect the adjustable capacity; under favorable lighting conditions... The value will increase accordingly, while changing the lighting conditions has little impact on the adjustable capacity; different electric vehicle load scenarios will exhibit different dispatchable capacity characteristics; the smaller the dispatch interval length, the larger the dispatchable capacity on average, because due to the limitation of vehicle dispatchable time, the smaller the dispatch interval, the more vehicles can be dispatched, and the larger the corresponding dispatchable capacity will be; centralized energy storage capacity configuration must meet certain emergency backup power time requirements:

[0133]

[0134]

[0135] In equations (24-25), Indicates the emergency power supply capacity of photovoltaic power. This represents the average daily photovoltaic power generation. pile P represents the number of charging stations. sdc For low DC charging power, based on the design of the smallest power unit in most current DC charging piles, P sdc =15kW,t reserve For emergency backup power time, energy storage capacity needs to be configured reasonably. If the energy storage capacity is too small, it will easily reach the upper or lower limit of its SOC, which will greatly reduce the dispatchable capacity of the charging station; if the energy storage capacity is too large, it will cause a large amount of waste of resources.

Claims

1. A method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast-charging station considering V2G technology, characterized in that, Includes the following steps: Step S1. Based on the electrical structure of the integrated photovoltaic-storage-charging fast charging station and the calculation requirements for the dispatchable capacity of electric vehicles under different scheduling time scales, collect real-time operating data of electric vehicles and configuration parameters of the charging station. Step S2. Establish charging and discharging constraints for electric vehicles, including: ① Battery capacity constraint, which refers to the constraint on the battery capacity of the vehicle while considering the travel needs of electric vehicles: ② Battery life constraints, which are constraints on the lifespan of the vehicle battery considering the lifespan degradation of the energy storage battery: In the formula, Represents the target battery level of the j-th vehicle, SOC EV (j,t) represents the energy storage value of the j-th vehicle at the left endpoint of the t-th dispatch interval. Let t be the charging and discharging power of the j-th vehicle in the t-th dispatch interval after dispatching. dispatch Let SOC be the interval length. EV,min (j) and SOC EV,max (j) represents the lower and upper limits of on-board battery energy storage, S ba (j) represents the battery capacity of the j-th vehicle, and η is the charging and discharging efficiency; ③ Maximum battery charge / discharge power constraint, which refers to the constraint condition that the maximum charge / discharge power of the battery needs to be limited within a specified range, considering the charging and discharging power of the charging pile and the vehicle battery: In the formula, Let represent the charging and discharging power of the j-th electric vehicle after being dispatched in the t-th dispatch interval. and Let represent the maximum charging and discharging power of the j-th electric vehicle, respectively; ④ Time and object constraints, which are the time and object constraints on the charging behavior of electric vehicles, considering the time when electric vehicles enter and exit the power grid: t arrive ≤t≤t sche ≤t leave Step S3. Considering the choice of scheduling time, solve for the threshold of the schedulable capacity of a single electric vehicle, and calculate the schedulable capacity of the electric vehicle cluster of the photovoltaic-storage-charging integrated fast charging station. Step S4. Determine the working mode and energy constraints of centralized energy storage, analyze the energy relationship between the dispatchable capacity of electric vehicles, the dispatchable capacity of centralized energy storage, and photovoltaic power generation, and calculate the adjustable capacity and adjustable capacity of the photovoltaic-storage-charging integrated fast charging station. Step S5. Based on the adjustable capacity and adjustable capacity of the photovoltaic-storage-charging integrated fast charging station, calculate the daily dispatchable capacity of the charging station, and analyze the impact of lighting conditions, load scenarios, dispatch time scale, and centralized energy storage configuration on the dispatchable capacity.

2. The method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast-charging station considering V2G technology as described in claim 1, characterized in that, The electrical structure of the photovoltaic-storage-charging integrated fast charging station described in step S1 is divided into a power distribution system, a charging system, a monitoring system, an energy storage system, and a photovoltaic power generation system. The photovoltaic power generation system transfers solar energy to the energy storage system, and when needed, supplies electricity to the charging system.

3. The method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast-charging station considering V2G technology as described in claim 1, characterized in that... The real-time operating data of the electric vehicle mentioned in step S1 includes: charging parameters, user demand parameters, and power dispatch parameters; the configuration parameters of the charging station include photovoltaic power generation, number of charging piles, charging power, and centralized energy storage capacity.

4. The method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast-charging station considering V2G technology as described in claim 1, characterized in that, In step S3, the schedulable capacity of electric vehicles is divided into adjustable capacity and adjustable capacity; step S3 solves for the threshold of the schedulable capacity of a single electric vehicle, including calculating the threshold of adjustable capacity. The formula is as follows: In the formula, This represents the un-scheduled charging power of the j-th electric vehicle in the t-th scheduling interval. Let represent the charging and discharging power of the j-th electric vehicle after being dispatched in the t-th dispatch interval. Charging and discharging power considering battery capacity constraints The threshold; and Calculate the threshold for adjustable capacity The formula is as follows: In the formula, Charge and discharge power considering battery capacity constraints The threshold.

5. The method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast charging station considering V2G technology according to claim 4, characterized in that, Step S3 calculates the dispatchable capacity of the electric vehicle cluster of the integrated photovoltaic-storage-charging fast charging station, including: calculating the V2G upscalable capacity of the electric vehicle cluster within the dispatching interval. and adjustable capacity The formula is as follows:

6. The method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast-charging station considering V2G technology as described in claim 5, characterized in that... In step S4, the adjustable capacity of the photovoltaic-storage-charging integrated fast charging station is calculated. The formula is as follows: In the formula, For the adjustable capacity of centralized energy storage, P pv (t) represents the photovoltaic power generation in the t-th scheduling interval; In step S4, the adjustable capacity of the photovoltaic-storage-charging integrated fast charging station is calculated. The formula is as follows: In the formula, This represents the maximum charging power of centralized energy storage in the t-th scheduling interval. This represents the maximum discharge power of the centralized energy storage in the t-th scheduling interval.

7. The method for assessing the dispatchable capacity of an integrated photovoltaic-storage-charging fast charging station considering V2G technology as described in claim 5, characterized in that, Step S5. Calculate the daily dispatchable capacity of the charging station based on the adjustable capacity and adjustable capacity of the integrated photovoltaic-storage-charging fast charging station, and analyze the impact of lighting conditions, load scenarios, dispatch time scale, and centralized energy storage configuration on the dispatchable capacity. It should be noted that step S5 is based on the design described above, and specifically includes: Step S51: Calculate the daily dispatchable capacity of the charging station. Step S511, Preparation: Determine the length t of the scheduling interval. dispatch Determine the current scheduling interval t. If t < 24h, then obtain the photovoltaic power generation P for the current time period. pv (t), begin calculating the schedulable capacity; Step S512: If there is an available charging pile, accept the electric vehicle for charging and generate the charging scenario of the electric vehicle load according to step S12, including the charging parameters of the electric vehicle, user demand parameters and power dispatch parameters. Step S513: Generate a state matrix based on the charging scenario of the electric vehicle load, record the grid connection, off-grid status, and whether the electric vehicle is fully charged, and calculate the SOC curve of the on-board battery and the load power within the scheduling interval. Step S514: Determine the number of electric vehicles that can be dispatched by the charging stations within the current dispatch interval, and calculate the dispatchable capacity of electric vehicles according to step S3. and Step S515: Based on the load power of the electric vehicle and photovoltaic power generation P pv (t), and combined with the energy relationship in step S42, obtain the SOC curve of centralized energy storage; Step S516: Obtain the dispatchable capacity of centralized energy storage based on energy storage boundary constraints and power constraints, and then determine the dispatchable capacity of the t-th dispatch interval in step S4. and The calculation method is used to generate the daily dispatchable capacity curve of the photovoltaic-storage-charging integrated fast charging station; Step S52 analyzes the impact of lighting conditions, load scenarios, scheduling timescales, and centralized energy storage configuration on dispatchable capacity: Changing lighting conditions does affect the upscalable capacity; under favorable lighting conditions... The value will increase accordingly, while changing the lighting conditions has little impact on the adjustable capacity; different electric vehicle load scenarios will exhibit different dispatchable capacity characteristics; the smaller the dispatch interval length, the larger the average dispatchable capacity will be; the smaller the dispatch interval, the more vehicles can be dispatched, and the larger the corresponding dispatchable capacity will be; centralized energy storage capacity configuration must meet certain emergency backup power time requirements: In the formula, Indicates the emergency power supply capacity of photovoltaic power. This represents the average daily photovoltaic power generation; n pile P represents the number of charging stations. sdc For low DC charging power, based on the design of the smallest power unit in most current DC charging piles, P sdc =15kW,t reserve For emergency backup power time, energy storage capacity needs to be configured reasonably. If the energy storage capacity is too small, it is easy to reach the upper or lower limit of its SOC, reducing the dispatchable capacity of the charging station; if the energy storage capacity is too large, it will cause a waste of capacity resources.

Images