Electric vehicle charging station hierarchical control method and related equipment

Abstract

The invention provides an electric vehicle charging station hierarchical control method and related equipment, and the method comprises the steps: obtaining the charge state of a battery, the output power of a charger and the nominal voltage of a DC micro-grid when all electric vehicles work in a vehicle-network interaction operation mode, and obtaining the output reference voltage of each electric vehicle charger; the charge balance module is used for realizing charge balance between electric automobiles through droop control; introducing state factors including output power and output voltage for each electric vehicle charger, and obtaining an average value of the state factors based on all the state factors; generating a voltage compensation item of each electric vehicle charger according to the average value of the state factors so as to compensate the output reference voltage of each electric vehicle charger to obtain a compensation result, and performing power distribution on the electric vehicle charging station according to the compensation result; the problems that batteries are damaged due to deep charge and discharge of the state of charge of the electric vehicle during vehicle-network interaction and the bus voltage fluctuates due to power change of the direct-current micro-grid are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of charging station control, and in particular to a hierarchical control method for an electric vehicle charging station and related equipment. Background Art

[0002] As energy demand grows and the global energy system decarbonizes, sustainable green and clean energy becomes more important. Replacing traditional fuels with new green energy sources such as solar energy can reduce carbon emissions.

[0003] Compared with AC microgrids, DC microgrids have no frequency and phase problems and relatively low control complexity. When both distributed power sources and loads are in DC, DC microgrids have incomparable advantages. With the increasing popularity of electric vehicles, electric vehicle charging stations in isolated DC microgrids can not only reduce energy costs but also provide environmentally friendly electricity. In an isolated DC microgrid with an electric vehicle charging station, on the one hand, considering the large current fluctuations caused by the rapid charging of electric vehicles, on the other hand, considering the volatility and randomness of distributed power generation, 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 isolated DC microgrid, which intelligently manages the charging power through a power controller and a parallel voltage controller to achieve rapid charging of electric vehicles; there is also a microgrid electric vehicle charging method based on a physical semi-empirical battery degradation model and a particle swarm optimization framework, which has advantages in regulating bus voltage; there is also a design of electric vehicle charging stations combined with photovoltaic storage, which can effectively reduce carbon emissions and improve energy utilization; there is also an isolated DC microgrid integrated control framework with electric vehicle charging stations, energy storage units and AC and DC loads, which coordinates the management of power generation and power consumption through a central control system, realizes the stable operation of the microgrid under different working conditions and has fault ride-through capability, and there is also an electric vehicle DC microgrid centralized power flow control scheme, which can effectively regulate the DC bus voltage, reduce voltage transients, and improve the flexibility and robustness of the microgrid; but the above-mentioned studies only allocate the power of the electric vehicle according to the energy difference between the power generation end and the power consumption end and the rated capacity of the electric vehicle when conducting vehicle-grid interaction, which is easy to cause the electric vehicle to damage the battery due to deep charging and discharging of the charge state. Summary of the invention

[0005] The present invention provides a hierarchical control method and related equipment for electric vehicle charging stations, the purpose of which is to solve the problem of bus voltage fluctuation caused by deep charging and discharging of electric vehicles due to battery damage and power changes of DC microgrids during vehicle-grid interaction.

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

[0007] Step 1, obtaining the battery state of charge, charger output power and nominal voltage of the DC microgrid when all electric vehicles are operating in the vehicle-grid interaction operation 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 item to obtain a compensation result, and distribute power to the electric vehicle charging station according to the compensation result.

[0012] To go further, the calculation expression for the output reference voltage of each electric vehicle charger is:

[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, 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 charger of the i-th electric vehicle, DOD represents the average value of the depth of discharge of n electric vehicles, and DODi represents the discharge depth of the i-th electric vehicle.

[0018] Furthermore, the charge balance between electric vehicles is achieved through droop control, including:

[0019] When the output power P of the electric vehicle charger i >0, the electric vehicle works in the discharge mode of vehicle-grid interaction. 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, so as 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] Specifically, 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 ith 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 car.

[0024] Further, the calculation expression of the voltage compensation term is:

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

[0028]

[0029] in, represents the output reference voltage of the ith electric vehicle charger after compensation.

[0030] The present invention also provides a hierarchical control device for an electric vehicle charging station, comprising:

[0031] An acquisition module is used to obtain the battery state of charge, the charger output power and the nominal voltage of the DC microgrid when all electric vehicles are operating in the vehicle-grid interaction mode;

[0032] A primary control module, for obtaining an output reference voltage of each electric vehicle charger 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, for achieving charge balance between electric vehicles through droop control;

[0033] An introduction module is used for 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 the state factors;

[0034] A generating module, for generating a voltage compensation item of each electric vehicle charger according to an average value of the state factor;

[0035] The secondary control module is used to compensate the output reference voltage of each electric vehicle charger based on the voltage compensation item, obtain the compensation result, and distribute the power of the electric vehicle charging station according to the compensation result.

[0036] The present invention also provides a terminal device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, a hierarchical control method for an electric vehicle charging station is implemented.

[0037] The present invention also provides a computer-readable storage medium, which stores a computer program, and is characterized in that when the computer program is executed by a processor, a hierarchical control method for an electric vehicle charging station is implemented.

[0038] The above scheme of the present invention has the following beneficial effects:

[0039] The present invention obtains the charge state of the battery, the output power of the charger and the nominal voltage of the DC microgrid when all electric vehicles work in the vehicle-grid interaction operation mode, obtains the output reference voltage of each electric vehicle charger, and is used to control the droop control to achieve charge balance between electric vehicles; introduces a state factor including output power and output voltage for each electric vehicle charger, and obtains the average value of the state factor based on all state factors; generates a voltage compensation item for each electric vehicle charger according to the average value of the state factor to compensate for the output reference voltage of each electric vehicle charger, obtains a compensation result, and distributes power to the electric vehicle charging station according to the compensation result; compared with the prior art, the present invention performs droop control on the charge state between electric vehicles to achieve charge balance between electric vehicles, and generates a voltage compensation item by introducing the state factor to compensate the output reference voltage of each electric vehicle charger to achieve accurate power distribution and bus voltage balance, thereby solving the problem of bus voltage fluctuation caused by deep charging and discharging of the charge state of electric vehicles and power changes of the DC microgrid during vehicle-grid interaction.

[0040] Other beneficial effects of the present invention will be described in detail in the subsequent specific implementation section. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of a flow chart of an embodiment of the present invention;

[0042] Figure 2 An equivalent model diagram of two electric vehicles connected in parallel in an embodiment of the present invention;

[0043] Figure 3 is a control block diagram of an embodiment of the present invention;

[0044] Figure 4 The charge state change curves of two groups of electric vehicles under different working conditions;

[0045] Figure 5 This is a diagram showing the regulation effect of only the droop control and the addition of voltage compensation items when the electric vehicle participates in bus voltage regulation when the power jumps in the DC microgrid;

[0046] Figure 6 This is a schematic diagram of a hierarchical control device for an electric vehicle charging station according to an embodiment of the present invention;

[0047] Figure 7 Schematic diagram of a terminal device in an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work 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", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0050] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a locking 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 an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to 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, obtaining the battery state of charge, charger output power and nominal voltage of the DC microgrid when all electric vehicles are operating in the vehicle-grid interaction operation 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, 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;

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

[0058] Step 5: Compensate the output reference voltage of each electric vehicle charger based on the voltage compensation item to obtain a compensation result, and distribute power to the electric vehicle charging station according to the compensation result.

[0059] In an embodiment of the present invention, an electric vehicle is connected to a DC bus as a mobile energy storage device in a DC microgrid through a charger, and the charger uses a bidirectional DC-DC converter to achieve a bidirectional flow of energy. When the DC microgrid is operating normally, the distributed photovoltaic power source can be used as a current source in the system, and the electric vehicle is used as a voltage source to adjust the bus voltage through charging and discharging to maintain the power balance of the system. When the output power of the distributed photovoltaic power source is less than the power consumption of the load, the electric vehicle works in the discharge mode of vehicle-to-grid (V2G) interaction, providing energy to the system to stabilize the operation of the DC microgrid. At this time, the charger works in the boost mode; when the output power of the distributed photovoltaic power source is greater than the power consumption of the DC load end, the electric vehicle works in the charging mode to absorb excess energy in the system, and the charger works in the buck mode, and the working principle is similar to the above-mentioned boost mode.

[0060] In order to obtain the output reference voltage of each electric vehicle charger, the embodiment of the present invention first adopts UP droop control similar to UI droop control, which can better achieve power sharing and DC bus voltage balance of multiple electric vehicles in parallel. The UP droop control expression of the electric vehicle is constructed based on the charge state of each electric vehicle battery, the output power of the charger and the nominal voltage of the DC microgrid:

[0061]

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

[0063] The droop factor is determined based on the rated power capacity and the maximum allowable bus voltage change:

[0064]

[0065] Among them, P ratei Indicates rated power capacity, ΔV max Indicates the maximum voltage change allowed for the busbar;

[0066] In the above droop control expression, electric vehicles only distribute power in proportion to the rated power without considering the state of charge level. The state of charge between electric vehicles will have a large deviation, causing overcharging or over-discharging of the electric vehicle. In extreme cases, the battery of the electric vehicle is damaged, affecting the normal operation of the electric vehicle.

[0067] Therefore, in order to maintain the charge balance between electric vehicles, the embodiment of the present invention proposes an improved droop control expression to calculate the output reference voltage of each electric vehicle charger, and the calculation expression is:

[0068]

[0069] in, It represents the charge balance equivalent droop coefficient of the i-th electric vehicle charger. The calculation expression of the charge balance equivalent droop coefficient is:

[0070]

[0071] 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 charger of the i-th electric vehicle, represents the average discharge depth of n electric vehicles, DOD i represents the discharge depth of the i-th electric vehicle, DOD i =1-SOC i .

[0072] From the improved droop control expression and the calculation expression of the charge balance equivalent droop coefficient, it can be seen that the equivalent droop coefficient of the electric vehicle changes adaptively according to the value of the state of charge and the depth of discharge, and the output power of the electric vehicle decreases with the increase of the droop coefficient.

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

[0074] When the output power P of the electric vehicle charger i>0, the electric vehicle works in the discharge mode, and the electric vehicle discharges to the DC microgrid. 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, so as to balance the charge between the electric vehicles.

[0075] 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.

[0076] In summary, the discharge rate of electric vehicles is proportional to the state of charge, and the charging rate of electric vehicles is inversely proportional to the state of charge; when electric vehicles work in different modes, that is, some vehicles are charged and some vehicles are discharged, the equivalent droop coefficient of electric vehicles will change with the change of their state of charge. Electric vehicles with high charge levels release more energy when V2G is running and absorb less energy when charging. Electric vehicles with low charge levels release less energy when V2G is running and absorb more energy when charging, until the charge level 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 achieve the balance of the state of charge of electric vehicles under different working conditions.

[0077] Since the performance of the above-mentioned state of charge balancing strategy may be reduced due to the difference in 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 invention takes a simple microgrid model composed of two associated electric vehicles as an example, such as Figure 2 As shown in the figure, U ev1 represents the output voltage of the first electric car, U ev2 represents the output voltage of the second electric vehicle, I ev1 represents the output current of the first electric car, I ev2 represents the output current of the second electric vehicle, R1 represents the equivalent resistance of the external circuit of the first electric vehicle charger, R2 represents the equivalent resistance of the external circuit of the second electric vehicle charger, R load Indicates the equivalent DC load.

[0078] Assuming that the output voltage of the electric vehicle completely follows the output reference voltage, Figure 2 Combining Kirchhoff's law, the output voltage at the load end can be obtained as:

[0079]

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

[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, it can be seen that in order to meet the precise power distribution, it is necessary to consider the influence of the external line resistance of the charger. Although increasing the droop coefficient can effectively improve this problem, it 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 achieve accurate power distribution and bus voltage balance, a voltage compensation term is introduced in the secondary control process. 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 achieve accurate power distribution and bus voltage balance. The voltage compensation term proposed in the embodiment of the present invention introduces a state factor as an information state.

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

[0087]

[0088] Among them, λ i represents the state factor of the i-th electric vehicle, U evi represents the output voltage of the ith 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 car.

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

[0090]

[0091] 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.

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

[0093]

[0094] in, represents the output reference voltage of the ith electric vehicle charger after compensation.

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

[0096] The embodiment of the present invention builds an island DC microgrid 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 using a photovoltaic power generation unit, two groups of electric vehicle charging and discharging units, and a DC load. The specific simulation parameters are shown in Table 1:

[0097] Table 1

[0098] parameter Value <![CDATA[Rated voltage U nom / V]]> 400 <![CDATA[Rated power P of the tram imax / W]]> 500 <![CDATA[Line resistance R line / Ω]]> 0.1 <![CDATA[Loads 1, 2, 3R load / Ω]]> 600、150、80 Light intensity / Lux 1000 Temperature / ℃ 25 <![CDATA[Voltage loop proportionality coefficient K p_u > 2.5 <![CDATA[Voltage loop integral coefficient K i_u > 100 <![CDATA[Current loop proportionality coefficient K p_i > 0.05 <![CDATA[Current loop integral coefficient K i_i > 10 <![CDATA[SOC loop proportionality coefficient K p_soc > 0.5 <![CDATA[SOC loop integral coefficient K i_soc > 5 <![CDATA[Maximum allowable voltage change of the busbar Δv max / V]]> 5

[0099] The simulation conditions are set as follows: the distributed photovoltaic power source always works at maximum power through MPPT control to provide the system with a rated output power of 1000W. In order to make the electric vehicles work under different working conditions, the power consumption of the DC load is 260W, 1060W, and 2100W respectively. When the DC load consumption is 260W, the two electric vehicles work in charging mode at the same time; when the DC load consumption is 1060W, the two electric vehicles work in V2G and charging mode respectively; when the DC load consumption is 2100W, the two electric vehicles work in V2G mode at the same time. The charge state change curves of the two electric vehicles under different working conditions are shown as follows: Figure 4 shown.

[0100] In order to better verify the effect of SOC balancing control, the initial SOC values ​​of the first electric vehicle and the second electric vehicle were set to 80% and 79%, respectively;

[0101] exist Figure 4 In (a), the state of charge of the two electric vehicles continued to increase from 0 to 15 seconds, indicating that the two electric vehicles absorbed the excess energy in the system by operating in charging mode, reducing system redundancy;

[0102] from Figure 4(b) It can be seen that the two electric vehicles are working in V2G and charging modes respectively. The state of charge of the first electric vehicle with a higher state of charge level continues to decrease during the period of 0-15s, and the state of charge of the second electric vehicle with a lower state of charge level continues to increase during the period of 0-15s;

[0103] from Figure 4 (c) It can be seen that the state of charge of the two electric vehicles continued to decrease within 0-15s, indicating 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 with the change of time, the charge state deviation between the two electric vehicles under the three working conditions becomes smaller and smaller and finally reaches the same level; the results show that the improved droop control can quickly achieve the charge state balance of electric vehicles under different working conditions.

[0105] In order to verify the effectiveness of the proposed control strategy when the system power jumps, the distributed photovoltaic power source is always operated at maximum power through MPPT control to provide the system with a rated output power of 1000W. During the period of 0-3s, the power consumption of the DC load is 2100W, which decreases to 260W at 3s and increases to 2100W at 6s. The comparison chart of the regulation effect of the electric vehicle participating in the bus voltage regulation only once and after adding the voltage compensation term when the power of the DC microgrid system jumps is shown in the figure below. Figure 5 shown.

[0106] like Figure 5 As shown in (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. The electric vehicle with only one control cannot quickly balance the voltage when the system power jumps. By adding the voltage compensation term in the secondary control process, the DC bus voltage regulation effect is shown in 5(b). When the system power jumps, the bus voltage is always stable at 400V, which fully verifies the effectiveness of the proposed control strategy and enhances the stability of the island DC microgrid.

[0107] The embodiment of the present invention obtains the charge state of the battery, the output power of the charger and the nominal voltage of the DC microgrid when all electric vehicles work in the vehicle-grid interaction operation mode, obtains the output reference voltage of each electric vehicle charger, and is used to achieve charge balance between electric vehicles through droop control; introduces a state factor including output power and output voltage for each electric vehicle charger, and obtains the average value of the state factor based on all state factors; generates a voltage compensation item for each electric vehicle charger according to the average value of the state factor to compensate for the output reference voltage of each electric vehicle charger, obtains a compensation result, and distributes power to the electric vehicle charging station according to the compensation result; compared with the prior art, the embodiment of the present invention performs droop control on the charge state between electric vehicles to achieve charge balance between electric vehicles, and generates a voltage compensation item by introducing the state factor to compensate for the output reference voltage of each electric vehicle charger, so as to achieve accurate power distribution and bus voltage balance, thereby solving the problem of bus voltage fluctuation caused by deep charging and discharging of the charge state of electric vehicles and power changes of the DC microgrid during vehicle-grid interaction.

[0108] The embodiment of the present invention also provides a hierarchical control device for an electric vehicle charging station, such as Figure 6 As shown, the electric vehicle charging station hierarchical control device 100 includes:

[0109] The acquisition module 101 is used to obtain the state of charge of the battery, the output power of the charger and the nominal voltage of the DC microgrid when all electric vehicles are working in the vehicle-grid interaction operation mode;

[0110] A primary control module 102, for obtaining an output reference voltage of each electric vehicle charger 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, for achieving charge balance between electric vehicles through droop control;

[0111] An introduction module 103 is used to introduce a state factor including output power and output voltage for each electric vehicle charger, and obtain an average value of the state factor based on all the state factors;

[0112] A generating module 104, for generating a voltage compensation item for each electric vehicle charger according to an average value of the state factor;

[0113] The secondary control module 105 is used to compensate the output reference voltage of each electric vehicle charger based on the voltage compensation item to obtain a compensation result, and to distribute power to the electric vehicle charging station according to the compensation result.

[0114] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the protection scope of the embodiments of the present application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0115] like Figure 7 As shown, the embodiment of the present invention further provides a terminal device, the terminal device D10 includes: at least one processor D100 ( Figure 7 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, wherein the processor D100 implements the steps in any of the above-mentioned method embodiments when executing the computer program D102. Alternatively, the processor D100 implements the functions of each module / unit in the above-mentioned device embodiments when executing the computer program D102.

[0116] The processor may be a central processing unit (CPU), or other general-purpose processors, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor or any conventional processor, etc.

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

[0118] It should be noted that the information interaction, execution process, etc. between the above-mentioned devices / units are based on the same concept as the method embodiment of the embodiment of the present application. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0119] The technicians in the relevant field can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example for illustration. In practical applications, the above-mentioned function allocation can be completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiment can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units and modules are only for the convenience of distinguishing each other, and are not used to limit the protection scope of the embodiments of the present application. The specific working process of the units and modules in the above-mentioned system can refer to the corresponding process in the aforementioned method embodiment, which will not be repeated here.

[0120] An embodiment of the present invention further provides a computer-readable storage medium, which stores a computer program. When the computer program is executed by a processor, a hierarchical control method for an electric vehicle charging station is implemented.

[0121] If the integrated module is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present application implements all or part of the process in the above method embodiment, which can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned various method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may at least include: any entity or device that can carry the computer program code to the construction device / terminal device, recording medium, computer memory, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), electric carrier signal, telecommunication signal and software distribution medium. For example, U disk, mobile hard disk, disk or optical disk, etc. In some jurisdictions, according to legislation and patent practice, computer-readable media cannot be electric carrier signals and telecommunication signals.

[0122] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A hierarchical control method for electric vehicle charging stations, characterized in that: include: Step 1, obtaining the battery state of charge, charger output power and nominal voltage of the DC microgrid when all electric vehicles are operating in the vehicle-grid interaction operation mode; 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, obtaining an output reference voltage of each electric vehicle charger, for achieving charge balance between electric vehicles through droop control; 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; Step 4, generating a voltage compensation item for each of the electric vehicle chargers according to the average value of the state factor; Step 5: Compensate the output reference voltage of each electric vehicle charger based on the voltage compensation item to obtain a compensation result, and distribute power to the electric vehicle charging station according to the compensation result.

2. The hierarchical control method for electric vehicle charging stations according to claim 1, characterized in that: The calculation expression of the output reference voltage of each electric vehicle charger is: in, represents the output reference voltage of the i-th electric vehicle charger, U nom represents the nominal voltage of the DC microgrid, 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.

3. The hierarchical control method for electric vehicle charging stations according to claim 2, characterized in that: The calculation expression of the charge balance equivalent droop coefficient is: 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 charger of the i-th electric vehicle, Denotes the average discharge depth of n electric vehicles, DOD i represents the discharge depth of the i-th electric vehicle.

4. The hierarchical control method for electric vehicle charging stations according to claim 3, characterized in that: Droop control balances the charge between electric vehicles, including: When the output power P of the electric vehicle charger i >0, the electric vehicle operates in a 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, so as to balance the charge between the electric vehicles. When the output power P of the electric vehicle charger i <0, the electric vehicle operates in a 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 charges between the electric vehicles.

5. The hierarchical control method for electric vehicle charging stations according to claim 4, characterized in that: The calculation expression of the state factor including output power and output voltage is: 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 car.

6. The hierarchical control method for electric vehicle charging stations according to claim 5, characterized in that: The calculation expression of the voltage compensation term is: 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.

7. The hierarchical control method for electric vehicle charging stations according to claim 6, characterized in that: The output reference voltage of each electric vehicle charger is compensated based on the voltage compensation term, and the calculation expression is: in, represents the output reference voltage of the ith electric vehicle charger after compensation.

8. A hierarchical control device for an electric vehicle charging station, characterized in that: include: An acquisition module is used to obtain the battery state of charge, the charger output power and the nominal voltage of the DC microgrid when all electric vehicles are operating in the vehicle-grid interaction mode; A primary control module, for obtaining an output reference voltage of each electric vehicle charger 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, for achieving charge balance between electric vehicles through droop control; An introduction module, used for 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 the state factors; A generating module, used for generating a voltage compensation item of each electric vehicle charger according to an average value of the state factor; The secondary control module is used to compensate the output reference voltage of each electric vehicle charger based on the voltage compensation item to obtain a compensation result, and distribute power to the electric vehicle charging station according to the compensation result.

9. A terminal device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the hierarchical control method for an electric vehicle charging station as described in any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the hierarchical control method for an electric vehicle charging station as claimed in any one of claims 1 to 7 is implemented.

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