Photovoltaic energy storage charging station and control method thereof

Abstract

The invention discloses a photovoltaic energy storage charging station and a control method thereof, and belongs to the field of photovoltaic energy storage, the photovoltaic energy storage charging station comprises a charging module and a control module connected with the charging module, and the photovoltaic energy storage charging station is characterized in that the charging module comprises a power grid charging branch, a photovoltaic charging branch and a contactor switch matrix; the power grid charging branch comprises a bidirectional charging pile unit and a bidirectional rectification unit which are sequentially connected to the contactor switch matrix and the power grid; the photovoltaic charging branch comprises a photovoltaic power generation unit connected with the contactor switch matrix; the contactor switch matrix is further electrically connected with the battery energy storage unit and the charging pile. According to the photovoltaic energy storage charging station and the control method thereof, photovoltaic, energy storage and charging stations are combined, and the principle of peak load shifting is utilized, so that the load fluctuation of the charging station is effectively balanced, and the operation cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of photovoltaic energy storage, and in particular to a photovoltaic energy storage charging station and a control method thereof. Background Art

[0002] As renewable energy generation technology continues to mature, microgrid power supply systems that use solar energy, wind energy and other renewable energy sources as their main energy sources have gradually attracted widespread attention and have been fully utilized in practical applications. However, due to the lack of microgrid's own regulation capabilities, its stability is relatively low, and the uncertainty of renewable energy generation and volatility when connected to the grid have become key factors restricting its utilization and development prospects.

[0003] To solve the above problems, existing technologies deploy energy storage equipment in the power grid to absorb and release electricity, thereby balancing the supply and demand relationship and reducing the fluctuation of the power grid, which has significant advantages in improving the stability of the power grid and smoothing the output of renewable energy. However, energy storage technology has not yet made a major breakthrough, and the cost of energy storage equipment is still relatively high. Large-scale use will not only increase the initial investment of the system, but may also reduce the overall economic benefits of the power grid system.

[0004] Electric vehicles (EVs) have attracted much attention due to their dual characteristics of load and energy storage. Without affecting the normal travel needs of EV users, by arranging the charging and discharging process of EVs in an orderly and reasonable manner, they can fully play their role as energy storage devices and further improve the stability of the power grid.

[0005] With the rapid development of the electric vehicle industry, the construction of related infrastructure, especially the construction and layout of charging stations, has become a key area of ​​research. At present, most electric vehicle charging stations mainly rely on power distribution networks, with a single power supply form and a fixed charging direction. However, with the rapid growth in the number of electric vehicles and the continuous expansion of battery capacity, the demand for charging power is also increasing. When a large number of electric vehicles are charged at high power at the same time, it will inevitably bring a huge impact on the power grid, affect the stable operation of the power grid, and bring greater safety risks. Summary of the invention

[0006] The purpose of the present invention is to provide a photovoltaic energy storage charging station and a control method thereof to solve the above technical problems.

[0007] To achieve the above-mentioned object, the present invention provides a photovoltaic energy storage charging station, comprising a charging module and a control module connected to the charging module, the charging module comprising a power grid charging branch, a photovoltaic charging branch and a contactor switch matrix, the power grid charging branch comprising a bidirectional charging pile unit and a bidirectional rectifier unit connected to the contactor switch matrix and the power grid in sequence, wherein the bidirectional rectifier unit is used to realize the bidirectional transmission of the 10KV AC output of the power grid and the 1KV DC in the charging station, and the bidirectional charging pile unit is used to establish a bidirectional charging and discharging channel;

[0008] The photovoltaic charging branch includes a photovoltaic power generation unit connected to a contactor switch matrix;

[0009] The contactor switch matrix is ​​also electrically connected to the battery energy storage unit and the charging stack respectively, wherein the battery energy storage unit is used to release electric energy when the electric energy is lower than a set value, and the charging stack is used to charge multiple electric vehicles at the same time.

[0010] Preferably, the bidirectional rectifier controller includes multiple AC / DC converters connected in parallel, the bidirectional charging pile unit includes multiple DC / DC converters connected in parallel, the charging pile includes multiple charging piles connected in parallel, and the battery energy storage unit includes multiple lithium iron phosphate batteries connected in series;

[0011] The control module includes a control center and a bidirectional rectifier controller, a photovoltaic power generation controller, a bidirectional charging pile controller and a switch controller which are respectively connected to the control center via a station-level CAN bus, wherein the bidirectional rectifier controller is respectively connected to a plurality of AC / DC converters via the rectifier CAN bus; the photovoltaic power generation controller is electrically connected to the photovoltaic power generation unit; the bidirectional charging pile controller is respectively electrically connected to a plurality of DC / DC converters via the charging pile CAN bus, and the switch controller is electrically connected to the contactor switch matrix.

[0012] The control method of a photovoltaic energy storage charging station comprises the following steps:

[0013] S1. Parameter collection: In the photovoltaic power generation state, the collected parameters include the total charging power of the electric vehicle, photovoltaic power generation and energy storage state;

[0014] S2. Determine the operating state of the battery energy storage unit based on the energy storage state, and execute the corresponding charging and discharging strategy in combination with the total charging power of the electric vehicle and the photovoltaic power generation;

[0015] S3, establishing a multi-objective energy optimization model, and using the multi-objective energy optimization model to optimize the charge and discharge strategy described in step S2;

[0016] S4. Simulation verification.

[0017] Preferably, step S2 specifically includes the following steps:

[0018] S21, determine the operating status of the battery energy storage unit: set SOC CN min Indicates the maximum state of charge allowed by the battery energy storage unit; SOC CN Indicates the current state of charge of the battery energy storage unit; SOC CN min Indicates the minimum state of charge allowed by the battery energy storage unit; P V Represents photovoltaic power generation; P CAR The total charging power of the electric vehicle; P CN Indicates the charging and discharging power of the battery energy storage unit; |P in max | represents the maximum charging power of the battery energy storage unit; |P out max | represents the maximum discharge power of the battery energy storage unit; P G out represents the electricity purchased by the grid;

[0019] When SOC CN min <SOC CN <SOC CN max When the battery energy storage unit is in a normal charging and discharging state;

[0020] When SOC CN =SOC CN min When the battery energy storage unit is at the maximum discharge depth;

[0021] When SOC CN =SOC CN max When , it is determined that the battery energy storage unit is in the maximum charging state;

[0022] S22, determining a charging and discharging strategy based on the operating status of the battery energy storage unit, the total charging power of the electric vehicle and the photovoltaic power generation;

[0023] When the battery energy storage unit is in a normal charging and discharging state, if P V >P CAR Then the first charging and discharging strategy is executed, otherwise the second charging and discharging strategy is executed;

[0024] When the battery energy storage unit is at the maximum discharge depth, if P V >P CAR Then the first charging and discharging strategy is executed, otherwise the third charging and discharging strategy is executed;

[0025] When the battery energy storage unit is in the maximum charging state, if P V >P CAR Then the fourth charge-discharge strategy is executed, otherwise the second charge-discharge strategy is executed;

[0026] The first charge-discharge strategy is: if P V >|P in max |+P CAR, then it is determined that the battery energy storage unit is in the state of charging at maximum power: P CN =|P in max |; At the same time, the remaining electric energy is transmitted to the grid, and the transmission power P G in The calculation formula is as follows:

[0027] P G in =P V -|P in max |-P CAR ;

[0028] Otherwise, adjust the charging power of the battery energy storage unit according to the following formula:

[0029] P V =P CN +P CAR ;

[0030] P G out =0;

[0031] The second charge and discharge strategy is: if P V +|P out max |<P CAR When the battery energy storage unit discharges at the maximum discharge power: P CN =|P out max |; Meanwhile, purchase electricity from the grid P G out The calculation formula is as follows:

[0032] P G out =P CAR -P V -|P out max |;

[0033] Otherwise, adjust the charging power of the battery energy storage unit according to the following formula:

[0034] P V =P CN +P CAR ;

[0035] P G out =0;

[0036] The third charging and discharging strategy is to purchase electricity from the grid according to the following formula:

[0037] P G out =P CAR -P V ;

[0038] P CN =0;

[0039] The fourth charging and discharging strategy is: the electricity generated by the photovoltaic power generation unit is output to the power grid:

[0040] PG in =P V -P CAR ;

[0041] P CN =0.

[0042] Preferably, step S3 specifically includes the following steps:

[0043] S31. Determine the objective function of the multi-objective energy optimization model: the objective function is to minimize the operating cost of the charging station throughout the day and minimize the load fluctuation caused by the charging station to the power grid;

[0044] S32, determining the constraint conditions of the multi-objective energy optimization model, wherein the constraint conditions include: power balance constraint, photovoltaic power generation constraint, battery energy storage operation constraint and power grid operation constraint;

[0045] S33. Optimize the charging and discharging strategy based on a multi-objective energy optimization model.

[0046] Preferably, in step S31, the objective function F1 for minimizing the full-day operating cost of the charging station is expressed as follows:

[0047]

[0048] Where fi represents the electricity price that the charging station purchases from the power grid during the sampling period Δt; P Gi represents the average electricity purchased during the sampling period Δt; T represents the number of sampling points; i represents the sampling point;

[0049] in,

[0050] P Gi =P CARi +P CNi -P Vi ;

[0051] Where P CARi Represents the total charging power of the electric vehicle; P CNi Represents the average charge and discharge power of the battery energy storage unit; P Vi Represents the average power of photovoltaic power generation.

[0052] Preferably, in step S31, the objective function F2 for minimizing the load fluctuation caused by the charging station to the power grid is expressed as follows:

[0053]

[0054] Where P av Indicates the average amount of electricity purchased throughout the day.

[0055] Preferably, the power balance constraint in step S32 is that the power between the charging station and the power grid is balanced, and its expression is as follows:

[0056] P CARi +P CNi =P Gi +P Vi ;

[0057] The photovoltaic power generation power constraint expression described in step S32 is as follows:

[0058] P Vi min ≤P Vi ≤P Vi max ;

[0059] Where P Vi min Indicates the lower limit of photovoltaic power generation; P Vi max Indicates the upper limit of photovoltaic power generation;

[0060] The battery energy storage operation constraints described in step S32 include battery energy storage charge and discharge power constraints and discharge depth constraints;

[0061] The battery energy storage charging and discharging power constraint expression is as follows:

[0062] 0≤|P CNi |≤η CN ×P CNi max ;

[0063] Where η CN Indicates the charging and discharging efficiency of the battery energy storage unit; P CNi max Indicates the upper limit of charge and discharge of the battery energy storage unit;

[0064] The discharge depth constraint expression is as follows:

[0065] 1-D≤SOC CNi ≤1;

[0066] Where D represents the maximum discharge depth of the battery energy storage unit;

[0067] The grid operation constraint described in step S32 is that the power provided by the grid to the charging pile is subject to the rated capacity constraints of the bidirectional rectifier unit and the distribution transformer:

[0068] P Gi ≤min(P ACDC , P T );

[0069] Where P ACDC Indicates the rated capacity of the bidirectional rectifier unit; P T Indicates the rated capacity of the distribution transformer.

[0070] Preferably, the maximum discharge depth D of the battery energy storage unit is 70%.

[0071] Therefore, the present invention adopts the above-mentioned photovoltaic energy storage charging station and control method thereof, which has the following beneficial effects:

[0072] By combining photovoltaics, energy storage and charging stations and utilizing the principle of peak shaving and valley filling, the load fluctuations of charging stations can be effectively balanced and operating costs can be reduced.

[0073] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Figure 1 This is a structural block diagram of a photovoltaic energy storage charging station of the present invention;

[0075] Figure 2 This is a control block diagram of a photovoltaic energy storage charging station of the present invention;

[0076] Figure 3 A flowchart of a control method for a photovoltaic energy storage charging station according to the present invention;

[0077] Figure 4 The photovoltaic power output power diagram described in the simulation verification example;

[0078] Figure 5 The required charging power diagram of the electric vehicle described in the simulation verification example;

[0079] Figure 6 This is a comparison chart of the electricity purchase amount before and after the optimization described in the simulation verification example. DETAILED DESCRIPTION

[0080] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invented product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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 a limitation on the present invention. In the description of the present invention, it should also be noted that, unless otherwise clearly specified and limited, the terms "setting", "installation", and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0081] The embodiments of the present invention are described in detail below in conjunction with the accompanying drawings.

[0082] like Figure 1 and Figure 2 As shown, a photovoltaic energy storage charging station includes a charging module and a control module connected to the charging module, the charging module includes a power grid charging branch, a photovoltaic charging branch and a contactor switch matrix, the power grid charging branch includes a bidirectional charging pile unit and a bidirectional rectifier unit connected to the contactor switch matrix and the power grid in sequence, wherein the bidirectional rectifier unit is used to realize the bidirectional transmission of 10KV AC output from the power grid and 1KV DC in the charging station, and the bidirectional charging pile unit is used to establish a bidirectional charging and discharging channel, such as converting 1kV DC into 300V-750V DC for charging electric vehicles in constant current mode, or converting 300V-750V DC output from electric vehicles into 1kV DC;

[0083] The photovoltaic charging branch includes a photovoltaic power generation unit connected to a contactor switch matrix;

[0084] The contactor switch matrix is ​​also electrically connected to the battery energy storage unit and the charging stack respectively, wherein the battery energy storage unit is used to release electric energy when the electric energy is lower than a set value, and the charging stack is used to charge multiple electric vehicles at the same time.

[0085] The bidirectional rectifier controller includes multiple parallel AC / DC converters, the bidirectional charging pile unit includes multiple parallel DC / DC converters, the charging stack includes multiple parallel charging piles, and the battery energy storage unit includes multiple lithium iron phosphate batteries connected in series; the control module includes a control center and a bidirectional rectifier controller, a photovoltaic power generation controller, a bidirectional charging pile controller and a switch controller respectively connected to the control center via a station-level CAN bus, wherein the bidirectional rectifier controller is respectively connected to the multiple AC / DC converters via the rectifier CAN bus; the photovoltaic power generation controller is electrically connected to the photovoltaic power generation unit; the bidirectional charging pile controller is respectively electrically connected to the multiple DC / DC converters via the charging pile CAN bus, and the switch controller is electrically connected to the contactor switch matrix.

[0086] like Figure 3 As shown, the control method of a photovoltaic energy storage charging station comprises the following steps:

[0087] S1. Parameter collection: In the photovoltaic power generation state, the collected parameters include the total charging power of the electric vehicle, photovoltaic power generation and energy storage state;

[0088] S2. Determine the operating state of the battery energy storage unit based on the energy storage state, and execute the corresponding charging and discharging strategy in combination with the total charging power of the electric vehicle and the photovoltaic power generation;

[0089] Step S2 specifically includes the following steps:

[0090] S21, determine the operating status of the battery energy storage unit: set SOC CN min Indicates the maximum state of charge allowed by the battery energy storage unit; SOC CN Indicates the current state of charge of the battery energy storage unit; SOC CN min Indicates the minimum state of charge allowed by the battery energy storage unit; P V Represents photovoltaic power generation; P CAR The total charging power of the electric vehicle; P CN Represents the charging and discharging power of the battery energy storage unit. In this embodiment, when P CN When it is a negative value, it means that the battery energy storage unit is in a discharging state. CN When it is a positive value, it means that the battery energy storage unit is in a charging state; |P in max | represents the maximum charging power of the battery energy storage unit; |P out max | represents the maximum discharge power of the battery energy storage unit; P G out represents the electricity purchased by the grid;

[0091] When SOC CN min <SOC CN <SOC CN max When the battery energy storage unit is in a normal charging and discharging state;

[0092] When SOC CN =SOC CN min When the battery energy storage unit is at the maximum discharge depth;

[0093] When SOC CN =SOC CN max When , it is determined that the battery energy storage unit is in the maximum charging state;

[0094] S22, determining a charging and discharging strategy based on the operating status of the battery energy storage unit, the total charging power of the electric vehicle and the photovoltaic power generation;

[0095] When the battery energy storage unit is in a normal charging and discharging state, if P V >P CAR Then the first charging and discharging strategy is executed, otherwise the second charging and discharging strategy is executed;

[0096] When the battery energy storage unit is at the maximum discharge depth, if P V >P CAR Then the first charging and discharging strategy is executed, otherwise the third charging and discharging strategy is executed;

[0097] When the battery energy storage unit is in the maximum charging state, if P V >P CAR Then the fourth charge-discharge strategy is executed, otherwise the second charge-discharge strategy is executed;

[0098] The first charge-discharge strategy is: if P V >|P in max |+P CAR , then it is determined that the battery energy storage unit is in the state of charging at maximum power: P CN =|P in max |; At the same time, the remaining electric energy is transmitted to the grid, and the transmission power P G in The calculation formula is as follows:

[0099] P G in =P V -|P in max |-P CAR ;

[0100] Otherwise, adjust the charging power of the battery energy storage unit according to the following formula:

[0101] P V =P CN +P CAR ;

[0102] P G out =0;

[0103] The second charge and discharge strategy is: if P V +|P out max |<P CAR When the battery energy storage unit discharges at the maximum discharge power: P CN =|P out max |; Meanwhile, purchase electricity from the grid P G out The calculation formula is as follows:

[0104] P G out =P CAR -P V -|P out max |;

[0105] Otherwise, adjust the charging power of the battery energy storage unit according to the following formula:

[0106] P V =P CN +P CAR ;

[0107] P G out =0;

[0108] The third charging and discharging strategy is to purchase electricity from the grid according to the following formula:

[0109] P G out =P CAR -P V ;

[0110] P CN =0;

[0111] The fourth charging and discharging strategy is: the electricity generated by the photovoltaic power generation unit is output to the power grid:

[0112] P G in =P V -P CAR ;

[0113] P CN =0.

[0114] S3, establishing a multi-objective energy optimization model, and using the multi-objective energy optimization model to optimize the charge and discharge strategy described in step S2;

[0115] Step S3 specifically includes the following steps:

[0116] S31. Determine the objective function of the multi-objective energy optimization model: the objective function is to minimize the operating cost of the charging station throughout the day and minimize the load fluctuation caused by the charging station to the power grid;

[0117] In step S31, the objective function F1 for minimizing the full-day operating cost of the charging station is expressed as follows:

[0118]

[0119] In the formula, f i P represents the price of electricity purchased by the charging station from the power grid during the sampling period Δt; Gi represents the average power purchased within the sampling period Δt; T represents the number of sampling points; i represents the sampling point; in this embodiment, 1h is used as a sampling period, and the whole day is divided into 24 sampling points.

[0120] in,

[0121] P Gi =P CARi +P CNi -P Vi ;

[0122] Where P CARi Represents the total charging power of the electric vehicle; P CNi Represents the average charge and discharge power of the battery energy storage unit; P Vi Represents the average power of photovoltaic power generation.

[0123] In step S31, the objective function F2 for minimizing the load fluctuation caused by the charging station on the power grid is expressed as follows:

[0124]

[0125] Where P aν Indicates the average amount of electricity purchased throughout the day.

[0126] S32, determining the constraint conditions of the multi-objective energy optimization model, wherein the constraint conditions include: power balance constraint, photovoltaic power generation constraint, battery energy storage operation constraint and power grid operation constraint;

[0127] The power balance constraint in step S32 is to maintain power balance between the charging station and the power grid, and its expression is as follows:

[0128] P CARi +P CNi =P Gi +P Vi ;

[0129] The photovoltaic power generation power constraint expression described in step S32 is as follows:

[0130] P Vi mmin ≤P Vi ≤P Vi max ;

[0131] Where P Vi min Indicates the lower limit of photovoltaic power generation; P Vi max Indicates the upper limit of photovoltaic power generation;

[0132] The battery energy storage operation constraints described in step S32 include battery energy storage charge and discharge power constraints and discharge depth constraints;

[0133] The battery energy storage charging and discharging power constraint expression is as follows:

[0134] 0≤|P CNi |≤η CN ×PC Ni max ;

[0135] Where η CN Indicates the charging and discharging efficiency of the battery energy storage unit; P CNi max Indicates the upper limit of charge and discharge of the battery energy storage unit;

[0136] The discharge depth constraint expression is as follows:

[0137] 1-D≤SOC CNi ≤1;

[0138] Wherein, D represents the maximum discharge depth of the battery energy storage unit; the maximum discharge depth D of the battery energy storage unit is 70%.

[0139] The grid operation constraint described in step S32 is that the power provided by the grid to the charging pile is subject to the rated capacity constraints of the bidirectional rectifier unit and the distribution transformer:

[0140] P Gi ≤min(P ACDC , P T );

[0141] Where P ACDC Indicates the rated capacity of the bidirectional rectifier unit; P T Indicates the rated capacity of the distribution transformer.

[0142] S33. Optimize the charging and discharging strategy based on a multi-objective energy optimization model.

[0143] S4. Simulation verification.

[0144] Verification Example

[0145] In this verification example, the rated capacity of photovoltaic power generation is 240KW; the rated capacity of the battery energy storage unit is 1000KW·h, the maximum discharge depth does not exceed 70%, the maximum charge and discharge power is 150KW, and the charge and discharge efficiency is 90%; the rated capacity of the distribution transformer is 1MV·A; the rated power of the bidirectional rectifier unit is 560KW.

[0146] Table 1 Distribution of electricity prices in different time periods

[0147]

[0148]

[0149] Combined with Figure 4 The photovoltaic power output shown in Figure 5 The electric vehicle charging load demand shown in the figure is simulated and verified by MATLAB software on the above charging station, and the optimization results are as follows Figure 6 As shown, it can be seen that after achieving optimal scheduling using the multi-objective optimization model described in the present invention, the power curve of the electricity purchased by the charging station from the power grid in each period of the day is significantly smoother than the power curve of the electricity purchased before the optimal scheduling, that is, the load fluctuation is significantly reduced.

[0150] Table 2 Comparison of total electricity purchase price of charging station in one day before and after optimization

[0151] Total cost (yuan) Load fluctuation mean square error Before optimization scheduling 1391.7 86.5 After optimizing scheduling 1108.6 40.5

[0152] It can be seen from Table 2 that after the optimized scheduling of the present invention, the electricity purchase cost is saved by 283.1 and the mean square error of load fluctuation is reduced, which proves that the present invention not only reduces the operating cost, but also reduces the load fluctuation, thus proving the effectiveness of the present invention.

[0153] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A photovoltaic energy storage charging station, comprising a charging module and a control module connected to the charging module, characterized in that: The charging module includes a power grid charging branch, a photovoltaic charging branch and a contactor switch matrix. The power grid charging branch includes a bidirectional charging pile unit and a bidirectional rectifier unit which are sequentially connected to the contactor switch matrix and the power grid. The bidirectional rectifier unit is used to realize the bidirectional transmission of the 10KV AC output of the power grid and the 1KV DC in the charging station. The bidirectional charging pile unit is used to establish a bidirectional charging and discharging channel. The photovoltaic charging branch includes a photovoltaic power generation unit connected to a contactor switch matrix; The contactor switch matrix is ​​also electrically connected to the battery energy storage unit and the charging stack respectively, wherein the battery energy storage unit is used to release electric energy when the electric energy is lower than a set value, and the charging stack is used to charge multiple electric vehicles at the same time.

2. A photovoltaic energy storage charging station according to claim 1, characterized in that: The bidirectional rectifier controller includes multiple AC / DC converters connected in parallel, the bidirectional charging pile unit includes multiple DC / DC converters connected in parallel, the charging pile includes multiple charging piles connected in parallel, and the battery energy storage unit includes multiple lithium iron phosphate batteries connected in series; The control module includes a control center and a bidirectional rectifier controller, a photovoltaic power generation controller, a bidirectional charging pile controller and a switch controller which are respectively connected to the control center via a station-level CAN bus, wherein the bidirectional rectifier controller is respectively connected to a plurality of AC / DC converters via the rectifier CAN bus; the photovoltaic power generation controller is electrically connected to the photovoltaic power generation unit; the bidirectional charging pile controller is respectively electrically connected to a plurality of DC / DC converters via the charging pile CAN bus, and the switch controller is electrically connected to the contactor switch matrix.

3. A control method for a photovoltaic energy storage charging station as claimed in claim 2, characterized in that: The following steps are involved: S1. Parameter collection: In the photovoltaic power generation state, the collected parameters include the total charging power of the electric vehicle, photovoltaic power generation and energy storage state; S2. Determine the operating state of the battery energy storage unit based on the energy storage state, and execute the corresponding charging and discharging strategy in combination with the total charging power of the electric vehicle and the photovoltaic power generation; S3, establishing a multi-objective energy optimization model, and using the multi-objective energy optimization model to optimize the charge and discharge strategy described in step S2; S4. Simulation verification.

4. A control method for a photovoltaic energy storage charging station according to claim 3, characterized in that: Step S2 specifically includes the following steps: S21, determine the operating status of the battery energy storage unit: set SOC CNmin Indicates the maximum state of charge allowed by the battery energy storage unit; SOC CN Indicates the current state of charge of the battery energy storage unit; SOC CNmin Indicates the minimum state of charge allowed by the battery energy storage unit; P V Represents photovoltaic power generation; P CAR The total charging power of the electric vehicle; P CN Indicates the charging and discharging power of the battery energy storage unit; |P inmax | represents the maximum charging power of the battery energy storage unit; P outmax | represents the maximum discharge power of the battery energy storage unit; P Gout represents the electricity purchased by the grid; When SOC CNmin <SOC CN <SOC CNmax When the battery energy storage unit is in a normal charging and discharging state; When SOC CN =SOC CNmin When the battery energy storage unit is at the maximum discharge depth; When SOC CN =SOC CNmax When , it is determined that the battery energy storage unit is in the maximum charging state; S22, determining a charging and discharging strategy based on the operating status of the battery energy storage unit, the total charging power of the electric vehicle and the photovoltaic power generation; When the battery energy storage unit is in a normal charging and discharging state, if P V >P CAR Then the first charging and discharging strategy is executed, otherwise the second charging and discharging strategy is executed; When the battery energy storage unit is at the maximum discharge depth, if P V >P CAR Then the first charging and discharging strategy is executed, otherwise the third charging and discharging strategy is executed; When the battery energy storage unit is in the maximum charging state, if P V >P CAR Then the fourth charge-discharge strategy is executed, otherwise the second charge-discharge strategy is executed; The first charge-discharge strategy is: if P V >|P inmax |+P CAR , then it is determined that the battery energy storage unit is in the state of charging at maximum power: P CN =|P in max |; At the same time, the remaining electric energy is transmitted to the grid, and the transmission power P Gin The calculation formula is as follows: P Gin =P V -|P inmax |-P CAR ; Otherwise, adjust the charging power of the battery energy storage unit according to the following formula: P V =P CN +P CAR ; P Gout ＝0； The second charge and discharge strategy is: if P V +|P out max | <P CAR When the battery energy storage unit discharges at the maximum discharge power: P CN =|P out max |; Meanwhile, purchase electricity from the grid P Gout The calculation formula is as follows: P Gout =P CAR -P V -|P outmax |; Otherwise, adjust the charging power of the battery energy storage unit according to the following formula: P V =P CN +P CAR ; P Gout ＝0； The third charging and discharging strategy is to purchase electricity from the grid according to the following formula: P Gout =P CAR -P V ; P CN ＝0； The fourth charging and discharging strategy is: the electricity generated by the photovoltaic power generation unit is output to the power grid: P Gin =P V -P CAR ; P CN ＝0。 5. A control method for a photovoltaic energy storage charging station according to claim 4, characterized in that: Step S3 specifically includes the following steps: S31. Determine the objective function of the multi-objective energy optimization model: the objective function is to minimize the operating cost of the charging station throughout the day and minimize the load fluctuation caused by the charging station to the power grid; S32, determining the constraint conditions of the multi-objective energy optimization model, wherein the constraint conditions include: power balance constraint, photovoltaic power generation constraint, battery energy storage operation constraint and power grid operation constraint; S33. Optimize the charging and discharging strategy based on a multi-objective energy optimization model.

6. A control method for a photovoltaic energy storage charging station according to claim 5, characterized in that: In step S31, the objective function F1 for minimizing the full-day operating cost of the charging station is expressed as follows: In the formula, f i P represents the price of electricity purchased by the charging station from the power grid during the sampling period Δt; Gi represents the average electricity purchased during the sampling period Δt; T represents the number of sampling points; i represents the sampling point; in, P Gi =P CARi +P CNi -P Vi ; Where P CARi Represents the total charging power of the electric vehicle; P CNi Represents the average charge and discharge power of the battery energy storage unit; P Vi Represents the average power of photovoltaic power generation.

7. A control method for a photovoltaic energy storage charging station according to claim 6, characterized in that: In step S31, the objective function F2 for minimizing the load fluctuation caused by the charging station to the power grid is expressed as follows: Where P av Indicates the average amount of electricity purchased throughout the day.

8. A control method for a photovoltaic energy storage charging station according to claim 7, characterized in that: The power balance constraint in step S32 is to maintain power balance between the charging station and the power grid, and its expression is as follows: P CARi +P CNi =P Gi +P Vi ; The photovoltaic power generation power constraint expression described in step S32 is as follows: P Vi min ≤P Vi ≤P Vi max ; Where P Vi min Indicates the lower limit of photovoltaic power generation; P Vi max Indicates the upper limit of photovoltaic power generation; The battery energy storage operation constraints described in step S32 include battery energy storage charge and discharge power constraints and discharge depth constraints; The battery energy storage charging and discharging power constraint expression is as follows: 0≤|P CNi |≤η CN ×P CNi max ; Where η CN Indicates the charging and discharging efficiency of the battery energy storage unit; P CNi max Indicates the upper limit of charge and discharge of the battery energy storage unit; The discharge depth constraint expression is as follows: 1-D≤SOC CNi ≤1; Where D represents the maximum discharge depth of the battery energy storage unit; The grid operation constraint described in step S32 is that the power provided by the grid to the charging pile is subject to the rated capacity constraints of the bidirectional rectifier unit and the distribution transformer: P Gi ≤min(P ACDC ,P T ); Where P ACDC Indicates the rated capacity of the bidirectional rectifier unit; P T Indicates the rated capacity of the distribution transformer.

9. A control method for a photovoltaic energy storage charging station according to claim 8, characterized in that: The maximum discharge depth D of the battery storage unit is 70%.

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