A layered control method for an electric vehicle charging station and related devices

Abstract

The application provides a layered control method for an electric vehicle charging station and related equipment, acquires the state of charge of a battery, the output power of a charger and the nominal voltage of a direct-current micro-grid when all electric vehicles work in a vehicle-grid interaction operation mode, obtains the output reference voltage of each electric vehicle charger, and uses the output reference voltage to realize the state of charge balance among the electric vehicles through droop control; introduces a state factor including the output power and the output voltage for each electric vehicle charger, and obtains the average value of the state factor based on all the state factors; generates the voltage compensation item of each electric vehicle charger according to the average value of the state factor, compensates the output reference voltage of each electric vehicle charger, obtains a compensation result, and performs power distribution on the electric vehicle charging station through the compensation result; and solves the problem of bus voltage fluctuation caused by the deep charging and discharging damage of the battery and the power change of the direct-current micro-grid when the vehicle-grid interaction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of charging station control, in particular to a layered control method for electric vehicle charging stations and related equipment. BACKGROUND

[0002] With the growth of energy demand and the decarbonization of global energy systems, sustainable green clean energy becomes more important. By replacing traditional fuels with new green energy such as solar energy, carbon emissions can be reduced.

[0003] DC microgrids have no frequency and phase problems compared to AC microgrids, and the control complexity is relatively low. In the case of distributed power supply and load in DC, DC microgrids have incomparable advantages. With the increasing popularity of electric vehicles, electric vehicle charging stations in islanded DC microgrids not only reduce energy costs, but also provide environmentally friendly power. In islanded DC microgrids with electric vehicle charging stations, on the one hand, considering the large current fluctuations caused by fast charging of electric vehicles, on the other hand, considering the volatility and randomness of distributed power generation, therefore, a reasonable control strategy is needed to control the DC microgrid to handle power imbalance and maintain the stability of the microgrid.

[0004] There is an improved control method for electric vehicle charging stations in an islanded DC microgrid, which intelligently manages charging power through power controllers and parallel voltage controllers to achieve fast charging of electric vehicles. There is also a microgrid electric vehicle charging method based on a semi-empirical battery degradation model and a particle swarm optimization framework, which has advantages in regulating bus voltage. There is also an electric vehicle charging station design combined with light storage, which can effectively reduce carbon emissions and improve energy utilization. There is also an islanded DC microgrid integrated control framework with an electric vehicle charging station, an energy storage unit and an AC / DC load, which coordinates the management of power generation and power consumption through a central control system to achieve stable operation of the microgrid under different working conditions and has fault ride-through capability. There is also a centralized power flow control scheme for electric vehicle DC microgrids, which can effectively regulate the DC bus voltage, reduce voltage transients, and improve the flexibility and robustness of the microgrid. However, the above research only allocates electric vehicle power according to the energy difference between the power generation end and the power consumption end and the rated capacity of the electric vehicle when interacting with the network, which can easily cause the electric vehicle to deep charge and discharge due to the state of charge, damaging the battery. SUMMARY

[0005] The present application provides a layered control method for electric vehicle charging stations and related equipment, which aims to solve the problem of battery damage caused by deep charging and discharging of electric vehicles due to the state of charge and bus voltage fluctuations caused by changes in DC microgrid power when interacting with the network.

[0006] In order to achieve the above object, the present invention provides a hierarchical control method for electric vehicle charging stations, comprising:

[0007] Step 1: Obtain the battery state of charge, charger output power, and DC microgrid nominal voltage of all electric vehicles when they are operating in the vehicle-grid interaction mode;

[0008] Step 2: Based on the state of charge of each electric vehicle battery, the output power of the charger, and the nominal voltage of the DC microgrid, an output reference voltage of each electric vehicle charger is obtained, which is used to achieve charge balance between electric vehicles through droop control;

[0009] Step 3: introducing a state factor including output power and output voltage for each electric vehicle charger, and obtaining an average value of the state factor based on all state factors;

[0010] Step 4, generating a voltage compensation term for each electric vehicle charger according to the average value of the state factor;

[0011] Step 5: Compensate the output reference voltage of each electric vehicle charger based on the voltage compensation term to obtain a compensation result, and distribute power to the electric vehicle charging station according to the compensation result.

[0012] To further explain, the output reference voltage of each electric vehicle charger is calculated as:

[0013]

[0014] in, represents the output reference voltage of the i-th electric vehicle charger, U nom represents the nominal voltage of the DC microgrid, It represents the charge balance equivalent droop coefficient of the i-th electric vehicle charger, P i represents the output power of the charger of the i-th electric vehicle.

[0015] Furthermore, the calculation expression of the charge balance equivalent droop coefficient is:

[0016]

[0017] Where Δd i Indicates the adjustment item of the charge balance equivalent droop coefficient, K P_SOC Indicates the proportional coefficient for adjusting charge balance, K I_SOC Indicates the integral coefficient for adjusting the charge balance, Represents the average state of charge of n electric vehicle chargers, SOC i represents the state of charge of the i-th electric vehicle charger, DOD represents the average depth of discharge of n electric vehicles, DODi represents the discharge depth of the i-th electric vehicle.

[0018] Furthermore, droop control is used to achieve charge balance between electric vehicles, including:

[0019] When the output power P of the electric vehicle charger i When >0, the electric vehicle works in the vehicle-grid interactive discharge mode. If the state of charge of the electric vehicle charger is higher than the average state of charge, the charge balance equivalent droop coefficient decreases and the output power of the electric vehicle charger increases. If the state of charge of the electric vehicle charger is lower than the average state of charge, the charge balance equivalent droop coefficient increases and the output power of the electric vehicle charger decreases to balance the charge between the electric vehicles.

[0020] When the output power P of the electric vehicle charger i <0, the electric vehicle works in charging mode. If the state of charge of the electric vehicle charger is lower than the average state of charge, the charge balance equivalent droop coefficient increases, and the absorbed power of the electric vehicle charger increases. If the state of charge of the electric vehicle charger is higher than the average state of charge, the charge balance equivalent droop coefficient decreases, and the absorbed power of the electric vehicle charger decreases, so as to balance the charge between the electric vehicles.

[0021] Furthermore, the calculation expression of the state factor including output power and output voltage is:

[0022]

[0023] Among them, λ i represents the state factor of the i-th electric vehicle, U evi represents the output voltage of the i-th electric vehicle, P evi represents the output power of the i-th electric vehicle, P imax represents the rated power of the i-th electric vehicle.

[0024] Furthermore, the voltage compensation term is calculated as:

[0025]

[0026] Among them, δ ui represents the voltage compensation term of the i-th electric vehicle charger, Indicates the nominal voltage of the DC bus, λ avg represents the average value of all state factors, and n represents the number of electric vehicles connected to the charging station.

[0027] Furthermore, the output reference voltage of each electric vehicle charger is compensated based on the voltage compensation term, and the calculation expression is:

[0028]

[0029] wherein, represents the output reference voltage of the i-th electric vehicle charger after compensation.

[0030] The application further provides an electric vehicle charging station hierarchical control device, comprising:

[0031] an acquisition module, configured to acquire the state of charge of the battery, the output power of the charger and the nominal voltage of the DC micro-grid when all the electric vehicles work in the operation mode of vehicle-grid interaction;

[0032] a primary control module, configured to obtain the output reference voltage of each electric vehicle charger based on the state of charge of the battery, the output power of the charger and the nominal voltage of the DC micro-grid, so as to realize the state of charge balance among the electric vehicles through droop control;

[0033] an introduction module, configured to introduce a state factor containing the output power and the output voltage for each electric vehicle charger, and obtain the average value of the state factor based on all the state factors;

[0034] a generation module, configured to generate the voltage compensation item of each electric vehicle charger according to the average value of the state factor;

[0035] a secondary control module, configured to compensate the output reference voltage of each electric vehicle charger based on the voltage compensation item, obtain the compensation result, and perform power distribution on the electric vehicle charging station through the compensation result.

[0036] The application further provides a terminal device, comprising a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor realizes the electric vehicle charging station hierarchical control method when executing the computer program.

[0037] The application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the electric vehicle charging station hierarchical control method.

[0038] The above-mentioned scheme of the application has the following advantages:

[0039] The application obtains the state of charge of the battery, the output power of the charger and the nominal voltage of the direct-current micro-grid when all electric vehicles work in the operation mode of vehicle-grid interaction, obtains the output reference voltage of each electric vehicle charger, and uses the droop control to realize the charge balance among the electric vehicles; the state factor containing the output power and the output voltage is introduced for each electric vehicle charger, and the average value of the state factor is obtained based on all the state factors; the voltage compensation term of each electric vehicle charger is generated according to the average value of the state factor, so as to compensate the output reference voltage of each electric vehicle charger, obtain the compensation result, and distribute the power of the electric vehicle charging station through the compensation result; compared with the prior art, the state of charge among the electric vehicles is controlled by the droop control, so as to realize the charge balance among the electric vehicles, the output reference voltage of each electric vehicle charger is compensated by the voltage compensation term generated by introducing the state factor, so as to realize the accurate power distribution and bus voltage balance, and the problem of bus voltage fluctuation caused by the deep charge and discharge of the state of charge of the electric vehicle and the power change of the direct-current micro-grid during the vehicle-grid interaction is solved.

[0040] Other benefits of the application will be described in detail in the subsequent specific embodiment part. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 The flowchart of the embodiment of the application is shown in the figure;

[0042] Figure 2 The equivalent model diagram of two electric vehicles in parallel in the embodiment of the application is shown in the figure;

[0043] Figure 3 The control block diagram of the embodiment of the application is shown in the figure;

[0044] Figure 4 The state of charge change curve diagram of two groups of electric vehicles under different working conditions is shown in the figure;

[0045] Figure 5 The regulation effect diagram of only the droop control and the added voltage compensation term when the electric vehicle participates in the bus voltage regulation in the direct-current micro-grid when the power of the electric vehicle jumps is shown in the figure;

[0046] Figure 6 The schematic diagram of the hierarchical control device of the electric vehicle charging station in the embodiment of the application is shown in the figure;

[0047] Figure 7 The schematic diagram of the terminal device in the embodiment of the application is shown in the figure. DETAILED DESCRIPTION

[0048] To make the technical problems, technical solutions, and advantages to be solved by the present invention more clear, the following is a detailed description with reference to the accompanying drawings and specific embodiments. It is obvious that the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0049] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0050] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to a locking connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0051] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0052] In view of the existing problems, the present invention provides a hierarchical control method for an electric vehicle charging station and related equipment.

[0053] like Figure 1 As shown, an embodiment of the present invention provides a hierarchical control method for an electric vehicle charging station, comprising:

[0054] Step 1: Obtain the battery state of charge, charger output power, and DC microgrid nominal voltage of all electric vehicles when they are operating in the vehicle-grid interaction mode;

[0055] Step 2: Based on the state of charge of each electric vehicle battery, the output power of the charger, and the nominal voltage of the DC microgrid, an output reference voltage of each electric vehicle charger is obtained, which is used to achieve charge balance between electric vehicles through droop control;

[0056] Step 3, introduce state factors including output power and output voltage for each electric vehicle charger, and obtain an average value of the state factors based on all the state factors;

[0057] Step 4, generate a voltage compensation term for each electric vehicle charger according to the average value of the state factors;

[0058] Step 5, compensate the output reference voltage of each electric vehicle charger based on the voltage compensation term, obtain a compensation result, and perform power distribution on the electric vehicle charging station through the compensation result.

[0059] In the embodiment of the application, the electric vehicle is connected to the DC bus through the charger as a mobile energy storage device in the DC micro-grid, and the charger adopts a bidirectional DC-DC converter to realize bidirectional flow of energy. When the DC micro-grid is normally operated, the distributed photovoltaic power source can be regarded as a current source in the system, and the electric vehicle can be regarded as a voltage source, which functions to adjust the bus voltage through charging and discharging and maintain the power balance of the system. When the output power of the distributed photovoltaic power source is less than the consumed power of the load, the electric vehicle works in a discharging mode of vehicle-to-grid (V2G) to provide energy to the system to stabilize the operation of the DC micro-grid, and at this time, the charger works in a step-up mode. When the output power of the distributed photovoltaic power source is greater than the consumed power of the DC load end, the electric vehicle works in a charging mode to absorb the excess energy in the system, and the charger works in a step-down mode, and the working principle is similar to the above-mentioned step-up mode.

[0060] In order to obtain the output reference voltage of each electric vehicle charger, the U-P droop control similar to the U-I droop control is adopted in the embodiment of the application, which can better realize power sharing of multiple electric vehicles in parallel and balance of the DC bus voltage. The U-P droop control expression of the electric vehicle is constructed based on the state of charge of each electric vehicle battery, the output power of the charger and the nominal voltage of the DC micro-grid as follows:

[0061]

[0062] wherein, U represents the output reference voltage of the i th electric vehicle charger, U nom U represents the nominal voltage of the DC micro-grid, d i K represents the droop coefficient of the i th electric vehicle charger, P i P represents the output power of the i th electric vehicle charger.

[0063] The droop coefficient is determined according to the rated power capacity and the maximum voltage change allowed by the bus as follows:

[0064]

[0065] wherein P ratei represents the rated power capacity, ΔV max represents the maximum voltage variation allowed by the bus;

[0066] In the above droop control expression, the electric vehicles only proportionally distribute power according to the rated power, without considering the state of charge level, and the state of charge among the electric vehicles will have a large deviation, causing overcharging or over-discharging of the electric vehicles, damaging the batteries of the electric vehicles in extreme cases, and affecting the normal operation of the electric vehicles.

[0067] Therefore, in order to maintain the state of charge balance among the electric vehicles, an improved droop control expression is proposed in the embodiments of the present application to calculate the output reference voltage of each electric vehicle charger, and the calculation expression is:

[0068]

[0069] wherein, represents the state of charge balance equivalent droop coefficient of the i-th electric vehicle charger, and the calculation expression of the state of charge balance equivalent droop coefficient is:

[0070]

[0071] wherein, Δd i represents the adjustment term of the state of charge balance equivalent droop coefficient, K P_SOC represents the proportional coefficient for adjusting the state of charge balance, K I_SOC represents the integral coefficient for adjusting the state of charge balance, represents the average value of the state of charge of the n electric vehicle chargers, SOC i represents the state of charge of the i-th electric vehicle charger, represents the average value of the depth of discharge of the n electric vehicles, DOD i represents the depth of discharge of the i-th electric vehicle, DOD i = 1 - SOC i .

[0072] As can be seen from the improved droop control expression and the calculation expression of the state of charge balance equivalent droop coefficient, the equivalent droop coefficient of the electric vehicle changes adaptively according to the values of the state of charge and the depth of discharge, and the output power of the electric vehicle decreases as the droop coefficient increases.

[0073] Specifically, the state of charge balance among the electric vehicles is achieved through droop control, including:

[0074] When the output power P iWhen SOC > 0, the electric vehicle works in the discharging mode, the electric vehicle discharges the DC micro-grid, if the state of charge of the electric vehicle charger is higher than the average state of charge, the equivalent droop coefficient of the charge balance decreases, the output power of the electric vehicle charger increases, if the state of charge of the electric vehicle charger is lower than the average state of charge, the equivalent droop coefficient of the charge balance increases, the output power of the electric vehicle charger decreases, so as to balance the state of charge among the electric vehicles;

[0075] When the output power P i <0, the electric vehicle works in the charging mode, if the state of charge of the electric vehicle charger is lower than the average state of charge, the equivalent droop coefficient of the charge balance increases, the absorption power of the electric vehicle charger increases, if the state of charge of the electric vehicle charger is higher than the average state of charge, the equivalent droop coefficient of the charge balance decreases, the absorption power of the electric vehicle charger decreases, so as to balance the state of charge among the electric vehicles.

[0076] In summary, the discharging rate of the electric vehicle is proportional to the state of charge, the charging rate of the electric vehicle is inversely proportional to the state of charge; when the electric vehicle works in different modes, that is, part of the vehicles are charging and part of the vehicles are discharging, the equivalent droop coefficient of the electric vehicle will change with the change of the state of charge, the electric vehicle with high state of charge releases more energy when working in V2G mode, and absorbs less energy when charging, the electric vehicle with low state of charge releases less energy when working in V2G mode, and absorbs more energy when charging, until the state of charge of the electric vehicle is at the average value. At this time, the adjustment term of the droop coefficient is 0; therefore, the improved droop control can balance the state of charge of the electric vehicle under different working conditions.

[0077] Since the performance of the above-mentioned state of charge balancing strategy may be reduced due to the difference of the line resistance outside each charger, in order to analyze the influence of the line resistance outside the charger in detail, the embodiment of the present application takes a simple micro-grid model composed of two associated electric vehicles as an example, as shown in Figure 2 , in the figure, U ev1 represents the output voltage of the first electric vehicle, U ev2 represents the output voltage of the second electric vehicle, I ev1 represents the output current of the first electric vehicle, I ev2 represents the output current of the second electric vehicle, R1 represents the equivalent resistance of the external circuit of the charger of the first electric vehicle, R2 represents the equivalent resistance of the external circuit of the charger of the second electric vehicle, and R load represents the equivalent DC load.

[0078] It is assumed that the output voltage of the electric vehicle completely follows the output reference voltage, from Figure 2 combined with Kirchhoff's law, the output voltage at the load end is:

[0079]

[0080] From the above formula, the output power ratio of two electric vehicles can be obtained:

[0081]

[0082] In order to ensure accurate power distribution between electric vehicles, the following constraints need to be met:

[0083]

[0084] From the expression of the output power ratio and the constraint expression, to meet the accurate power distribution, the influence of the external line resistance of the charger needs to be considered, although increasing the droop coefficient can effectively improve this problem, but will cause the bus voltage to deviate from the nominal value of the microgrid voltage, and the value of the line resistance is difficult to determine, so it is difficult to meet the requirements.

[0085] In order to realize accurate power distribution and bus voltage balance, a voltage compensation term is introduced in the process of secondary control, and the voltage compensation term of a single electric vehicle is calculated according to the output voltage and output power of the electric vehicle connected to the charging station to realize accurate power distribution and bus voltage balance; The voltage compensation term introduced by the embodiment of the application introduces a state factor as an information state.

[0086] Specifically, the calculation expression of the state factor containing the output power and the output voltage is:

[0087]

[0088] Where λ i represents the state factor of the i-th electric vehicle, U evi represents the output voltage of the i-th electric vehicle, P evi represents the output power of the i-th electric vehicle, P imax represents the rated power of the i-th electric vehicle.

[0089] Specifically, in a control cycle, the charger obtains the voltage compensation term by calculating the state factor of a single electric vehicle, and the calculation expression is:

[0090]

[0091] Where δ ui represents the voltage compensation term of the i-th electric vehicle charger, represents the nominal voltage of the DC bus, λ avg represents the average value of all state factors, and n represents the number of electric vehicles connected to the charging station.

[0092] Specifically, the output reference voltage of each electric vehicle charger is compensated based on a voltage compensation term, and the calculation expression is:

[0093]

[0094] wherein, represents the compensated output reference voltage of the i-th electric vehicle charger.

[0095] The control block diagram corresponding to the above formula is shown as Figure 3 The charger obtains the output reference voltage of a single electric vehicle through the control block diagram shown as Figure 3 and realizes power distribution of multiple electric vehicles.

[0096] The embodiment of the present application builds an island direct-current micro-grid model with an electric vehicle charging station based on MATLAB / Simulink to verify the feasibility and effectiveness of the proposed hierarchical control method. A simulation model is established by using a photovoltaic power generation unit, two groups of electric vehicle charging and discharging units and a direct-current load, and the specific simulation parameters are shown in Table 1:

[0097] Table 1

[0098] Parameter Value Rated voltage U nom / V]]> 400 Electric vehicle rated power P imax / W]] 500 Line resistance R line / Ω 0.1 Load 1, 2, 3R load / Ω]] 600、150、80 Illumination intensity / Lux 1000 Temperature / °C 25 Voltage loop proportional coefficient K p_u ]]> 2.5 <![CDATA[Voltage loop integral coefficient K i_u > 100 Current loop proportional coefficient K p_i ]] 0.05 Current loop integral coefficient K i_i ]]> 10 [CAT] SOC ring proportionality coefficient K p_soc ]]> 0.5 [CAT] SOC ring integration coefficient K i_soc ]]> 5 Busbar allowable maximum voltage variation Δv max / V]] 5

[0099] The simulation conditions are set as follows: the distributed photovoltaic power supply always works in the maximum power point tracking (MPPT) control mode to provide a rated output power of 1000W to the system. In order to make the electric vehicles work in different operating conditions, the consumption power of the direct-current load is 260W, 1060W and 2100W respectively. When the consumption of the direct-current load is 260W, the two electric vehicles work in the charging mode at the same time; when the consumption of the direct-current load is 1060W, the two electric vehicles work in the V2G and charging modes respectively; when the consumption of the direct-current load is 2100W, the two electric vehicles work in the V2G mode at the same time, and the state of charge variation curves of the two electric vehicles under different operating conditions are shown as Figure 4 .

[0100] In order to better verify the effect of the state of charge balancing control, the initial values of the state of charge of the first electric vehicle and the second electric vehicle are set to 80% and 79% respectively.

[0101] In Figure 4 (a), the state of charge of the two electric vehicles continuously increases within 0-15s, which indicates that the two electric vehicles absorb the excess energy in the system by operating in the charging mode, thereby reducing the system redundancy.

[0102] From Figure 4(b)It can be seen that two electric vehicles work in V2G and charging mode respectively, the state of charge of the first electric vehicle with high state of charge level continuously decreases in 0-15s, and the state of charge of the second electric vehicle with low state of charge level continuously increases in 0-15s;

[0103] From Figure 4 (c)It can be seen that the state of charge of the two electric vehicles continuously decreases in 0-15s, which indicates that the two electric vehicles provide energy to the system through V2G mode operation, make up for the power shortage of the system, and enhance the stability of the microgrid.

[0104] In summary, from Figure 4 It can be seen that the state of charge deviation between the two electric vehicles in the three working conditions becomes smaller and finally reaches the same level with the change of time; the results show that the improved droop control can quickly realize the state of charge balance of the electric vehicles in different working conditions.

[0105] In order to verify the effectiveness of the proposed control strategy when the system power jumps, the distributed photovoltaic power is controlled by MPPT to always work in the maximum power to provide the rated output power of 1000W to the system, and the consumption power of the DC load is 2100W during 0-3s, reduced to 260W at 3s, and increased to 2100W at 6s. The comparison chart of the adjustment effect of the electric vehicle participating in the bus voltage regulation only once and adding voltage compensation term when the DC microgrid system power jumps is shown in Figure 5 .

[0106] As shown in Figure 5 (a), the DC bus voltage gradually increases to 450V in 0-3s, gradually increases to 1100V in 3-6s, and decreases to 450V in 6-15s, and the electric vehicle with only one control cannot quickly balance the voltage when the system power jumps. By increasing the voltage compensation term in the process of secondary control, the adjustment effect of the DC bus voltage is shown in 5(b), and the bus voltage is always stable at 400V when the system power jumps, which fully verifies the effectiveness of the proposed control strategy and enhances the stability of the islanded DC microgrid.

[0107] The embodiment of the present application obtains the state of charge of the battery, the output power of the charger and the nominal voltage of the DC micro-grid when all electric vehicles work in the operation mode of vehicle-grid interaction, obtains the output reference voltage of each electric vehicle charger, and realizes the state of charge balance between the electric vehicles through droop control; the state factor including the output power and the output voltage is introduced for each electric vehicle charger, and the average value of the state factor is obtained based on all the state factors; the voltage compensation term of each electric vehicle charger is generated according to the average value of the state factor, the output reference voltage of each electric vehicle charger is compensated, the compensation result is obtained, and the power distribution of the electric vehicle charging station is realized through the compensation result; compared with the prior art, the state of charge between the electric vehicles is controlled through droop control to realize the state of charge balance between the electric vehicles, the output reference voltage of each electric vehicle charger is compensated through the voltage compensation term generated by introducing the state factor, the accurate power distribution and bus voltage balance are realized, and the problem of bus voltage fluctuation caused by the deep charge and discharge of the state of charge of the electric vehicle and the power change of the DC micro-grid during the vehicle-grid interaction is solved.

[0108] The embodiment of the present application also provides an electric vehicle charging station hierarchical control device, as shown in the figure, the electric vehicle charging station hierarchical control device 100 comprises: Figure 6

[0109] The acquisition module 101 is used for acquiring the state of charge of the battery, the output power of the charger and the nominal voltage of the DC micro-grid when all electric vehicles work in the operation mode of vehicle-grid interaction;

[0110] The primary control module 102 is used for obtaining the output reference voltage of each electric vehicle charger based on the state of charge of the battery, the output power of the charger and the nominal voltage of the DC micro-grid of each electric vehicle, and realizing the state of charge balance between the electric vehicles through droop control;

[0111] The introduction module 103 is used for introducing the state factor including the output power and the output voltage for each electric vehicle charger, and obtaining the average value of the state factor based on all the state factors;

[0112] The generation module 104 is used for generating the voltage compensation term of each electric vehicle charger according to the average value of the state factor;

[0113] The secondary control module 105 is used for compensating the output reference voltage of each electric vehicle charger based on the voltage compensation term, obtaining the compensation result, and realizing the power distribution of the electric vehicle charging station through the compensation result.

[0114] ​Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is taken as an example, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to complete all or part of the above described functions. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can be physically present separately, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or software. In addition, the specific names of each functional unit and module are only for easy distinction, and do not limit the protection scope of the embodiments of the present application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be repeated here.

[0115] As shown in Figure 7 The embodiments of the present application also provide a terminal device. The terminal device D10 includes at least one processor D100 (only one processor is shown in the figure), a memory D101, and a computer program D102 stored in the memory D101 and executable on the at least one processor D100. When the processor D100 executes the computer program D102, the steps in any of the above method embodiments are implemented. Alternatively, when the processor D100 executes the computer program D102, the functions of each module / unit in the above apparatus embodiments are implemented. Figure 7

[0116] The processor can be a central processing unit (CPU), and can also be other general-purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs) or other programmable logic devices, discrete gates or transistor logic components, discrete hardware components, etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor.

[0117] ​The memory can be an internal storage unit of the terminal device, such as a hard disk or a memory of the terminal device, in some embodiments. The memory can also be an external storage device of the terminal device, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc. equipped on the terminal device, in other embodiments. Further, the memory can include both the internal storage unit and the external storage device of the terminal device. The memory is used to store an operating system, an application program, a boot loader, data, and other programs, such as program codes of the computer program, etc. The memory can also be used to temporarily store data that has been output or will be output.

[0118] It should be noted that the information interaction and execution process between the above apparatuses / units are based on the same concept as the method embodiments of the embodiments of the present application, and the specific functions and technical effects brought by the above apparatuses / units can be referred to the method embodiments part, which will not be described herein.

[0119] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is taken as an example for illustration, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the apparatus is divided into different functional units or modules to complete all or part of the above described functions. Each functional unit and module in the embodiments can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit, and the integrated unit can be realized in the form of hardware or in the form of software functional unit. In addition, the specific names of each functional unit and module are only for convenient distinction, and do not limit the protection scope of the embodiments of the present application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be described herein.

[0120] The embodiment of the present application further provides a computer readable storage medium, the computer readable storage medium stores a computer program, and the computer program is executed by a processor to realize the layered control method of the electric vehicle charging station.

[0121] The integrated module, if implemented in the form of a software function unit and sold or used as an independent product, can be stored in a computer readable storage medium. Based on such understanding, all or part of the processes in the above method embodiments can be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of the above various method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or some intermediate forms. The computer readable medium at least includes any entity or device capable of carrying the computer program code to the construction device / terminal equipment, recording medium, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signal, telecommunication signal, and software distribution medium. For example, U disk, mobile hard disk, magnetic disk or optical disk, etc. In some jurisdictions, according to legislation and patent practice, the computer readable medium cannot be an electrical carrier signal and a telecommunication signal.

[0122] The above is the preferred embodiment of the present application, it should be pointed out that, for those skilled in the art, without departing from the principles of the present application, can make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A hierarchical control method for an electric vehicle charging station, characterized by, The method comprises the following steps: Step 1, obtaining the state of charge of the battery of each electric vehicle, the output power of the charger and the nominal voltage of the DC micro-grid when the electric vehicle works in the operation mode of vehicle-grid interaction; Step 2, obtaining the output reference voltage of each electric vehicle charger based on the state of charge of the battery of each electric vehicle, the output power of the charger and the nominal voltage of the DC micro-grid, so as to realize the state of charge balancing among the electric vehicles through droop control; Step 3, introducing a state factor containing the output power and the output voltage for each electric vehicle charger, and obtaining the average value of the state factor based on all the state factors; Step 4, generating a voltage compensation term for each electric vehicle charger according to the average value of the state factor; Step 5, compensating the output reference voltage of each electric vehicle charger based on the voltage compensation term, obtaining a compensation result, and distributing the power of the electric vehicle charging station through the compensation result; The calculation expression of the output reference voltage of each electric vehicle charger is: ； in, Indicates the The output reference voltage of an electric vehicle charger, represents the nominal voltage of the DC microgrid, Indicates the The charge balance equivalent droop coefficient of an electric vehicle charger, Indicates the Output power of electric vehicle charger; The calculation expression of the equivalent droop coefficient of the state of charge balancing is: ； ； in, Indicates the adjustment item of the charge balance equivalent droop coefficient, Indicates the proportional coefficient for adjusting the charge balance, Indicates the integral coefficient for adjusting the charge balance, express The average state of charge of electric vehicle chargers, Indicates the The state of charge of the electric vehicle charger, express The average depth of discharge of electric vehicles, Indicates the The depth of discharge of electric vehicles; The droop control of the state of charge balancing among the electric vehicles comprises: When the output power of the electric vehicle charger is greater than the average output power of the electric vehicle chargers, the electric vehicle works in the discharging mode of vehicle-to-grid interaction, if the state of charge of the electric vehicle charger is higher than the average state of charge, the equivalent droop coefficient of the charge balance is reduced, the output power of the electric vehicle charger is increased, if the state of charge of the electric vehicle charger is lower than the average state of charge, the equivalent droop coefficient of the charge balance is increased, the output power of the electric vehicle charger is reduced, so that the charge balance between the electric vehicles is achieved. When the output power of the electric vehicle charger is less than the average output power, the electric vehicle works in the charging mode, if the state of charge of the electric vehicle charger is lower than the average state of charge, the equivalent droop coefficient of the charge balance is increased, the absorption power of the electric vehicle charger is increased, if the state of charge of the electric vehicle charger is higher than the average state of charge, the equivalent droop coefficient of the charge balance is decreased, the absorption power of the electric vehicle charger is decreased, so as to balance the charge between the electric vehicles.

2. The hierarchical control method of an electric vehicle charging station according to claim 1, wherein, The calculation expression of the state factor containing the output power and the output voltage is: ； ； wherein, represents the state factor of the first electric vehicle, represents the output voltage of the first electric vehicle, represents the output power of the first electric vehicle, represents the rated power of the first electric vehicle.

3. The hierarchical control method of an electric vehicle charging station according to claim 2, characterized in that, The calculation expression of the voltage compensation term is: ； ； wherein represents the voltage compensation term of the i-th electric vehicle charger, represents the nominal voltage of the DC bus, represents the average value of all state factors, represents the number of electric vehicles connected to the charging station.

4. The hierarchical control method of an electric vehicle charging station according to claim 3, characterized in that, The calculation expression of the compensation of the output reference voltage of each electric vehicle charger based on the voltage compensation term is: ； wherein, represents the output reference voltage of the first electric vehicle charger after compensation.

5. An electric vehicle charging station hierarchical control apparatus, characterized by, The method comprises the following steps: An obtaining module is configured to obtain the state of charge of the battery of each electric vehicle, the output power of the charger and the nominal voltage of the DC micro-grid when the electric vehicle works in the operation mode of vehicle-grid interaction; A primary control module is configured to obtain the output reference voltage of each electric vehicle charger based on the state of charge of the battery of each electric vehicle, the output power of the charger and the nominal voltage of the DC micro-grid, so as to realize the state of charge balancing among the electric vehicles through droop control; An introducing module is configured to introduce a state factor containing the output power and the output voltage for each electric vehicle charger, and obtain the average value of the state factor based on all the state factors; A generating module is configured to generate a voltage compensation term for each electric vehicle charger according to the average value of the state factor; A secondary control module is configured to compensate the output reference voltage of each electric vehicle charger based on the voltage compensation term, obtain a compensation result, and distribute the power of the electric vehicle charging station through the compensation result; The calculation expression of the output reference voltage of each electric vehicle charger is: ； wherein, represents the output reference voltage of the first electric vehicle charger, represents the output reference voltage of the first electric vehicle charger, represents the nominal voltage of the direct current microgrid, represents the output reference voltage of the first electric vehicle charger, represents the charge balancing equivalent droop coefficient of the first electric vehicle charger, represents the output power of the first electric vehicle charger, represents the output power of the first electric vehicle charger, The calculation expression of the equivalent droop coefficient of the state of charge balancing is: ； ； wherein represents an adjustment term for the charge balance equivalent droop coefficient, represents a proportional coefficient for regulating the charge balance, represents an integral coefficient for regulating the charge balance, represents represents an average value of the state of charge of the electric vehicle charger, represents the state of charge of the electric vehicle charger, represents represents represents an average value of the depth of discharge of the electric vehicle, represents the depth of discharge of the electric vehicle, represents the depth of discharge of the electric vehicle. The droop control of the state of charge balancing among the electric vehicles comprises: When the output power of the electric vehicle charger is greater than the average output power of the electric vehicle chargers, the electric vehicle works in the discharging mode of vehicle-to-grid interaction, if the state of charge of the electric vehicle charger is higher than the average state of charge, the equivalent droop coefficient of the charge balance is reduced, the output power of the electric vehicle charger is increased, if the state of charge of the electric vehicle charger is lower than the average state of charge, the equivalent droop coefficient of the charge balance is increased, the output power of the electric vehicle charger is reduced, so that the charge balance between the electric vehicles is achieved. When the output power of the electric vehicle charger is less than the average output power, the equivalent droop coefficient of the charge balance is increased, the absorption power of the electric vehicle charger is increased, if the state of charge of the electric vehicle charger is higher than the average state of charge, the equivalent droop coefficient of the charge balance is decreased, the absorption power of the electric vehicle charger is decreased, so as to balance the charge between the electric vehicles.

6. A terminal device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the hierarchical control method of the electric vehicle charging station according to any one of claims 1 to 4.

7. A computer-readable storage medium storing a computer program, wherein the computer program comprises the following steps of: The computer program is executed by the processor to realize the hierarchical control method of the electric vehicle charging station according to any one of claims 1 to 4.

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