A V2G bidirectional charging pile

Abstract

The present application relates to a kind of V2G two-way charging piles of electric vehicle charging facilities and grid interaction field, including power conversion unit, control unit, metering unit, man-machine interaction unit and communication unit;Charging pile is also provided with: discharging gun head, for taking power from vehicle battery;Charging gun head, for charging to vehicle battery;Interlock mechanism, for ensuring that only one gun head can be connected with electric vehicle;Local energy sharing module, for sharing the battery state information of connected vehicle in the local charging pile group, and realizing charging pile group energy scheduling coordination;Control unit also includes battery health state evaluation module, grid state detection module, user demand setting module and energy scheduling optimization module;The charging pile can realize charge-discharge physical isolation by double-gun interlocking design, realize car-car direct energy transfer by local energy sharing of charging pile group, and combined with battery health management, construct safe, efficient, economic vehicle-grid interaction system.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle charging facilities and power grid interaction technology, and in particular to a V2G bidirectional charging pile. Background Technology

[0002] With the popularization of electric vehicles, the large number of electric vehicles connected to the power grid will have a significant impact on the power system; disorderly charging will exacerbate the peak-valley difference of the power grid, while V2G technology can use electric vehicle batteries as distributed energy storage units to realize two-way energy interaction between the power grid and vehicles and participate in peak shaving and frequency regulation.

[0003] Traditional V2G charging stations typically only have one charging gun, sharing the same gun and cable for charging and discharging. In actual use, if the user accidentally plugs or unplugs the device or an electrical fault occurs during discharging, it can easily cause safety accidents such as arcing and short circuits. Although existing technologies have implemented charging and discharging switching through software, they lack a hardware-level safety interlock mechanism, posing a safety hazard. In addition, when there are multiple vehicles that need to charge and multiple vehicles that can discharge in the same parking lot, existing V2G charging stations can only adopt a unidirectional flow mode of "vehicle-charging station-grid": the electrical energy of the discharging vehicle is first fed back to the grid, and then the grid transmits it to the charging vehicle. The electrical energy undergoes two stages of AC / DC conversion and long-distance transmission, resulting in unnecessary energy loss (usually as high as 8%-12%), and also occupies the transmission capacity of the power distribution network. Summary of the Invention

[0004] To overcome the shortcomings of the background technology and solve the existing technical problems, this invention discloses a V2G bidirectional charging pile that can achieve physical isolation of charging and discharging through a dual-gun interlocking design, realize vehicle-to-vehicle direct energy transfer through local energy sharing of charging pile groups, and build a safe, efficient and economical vehicle-to-grid interaction system by combining battery health management.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A V2G bidirectional charging pile includes a power conversion unit, a control unit, a metering unit, a human-machine interaction unit, and a communication unit; the power conversion unit includes a bidirectional AC / DC converter and a bidirectional DC / DC converter, which are connected via a DC bus; the control unit is electrically connected to the power conversion unit, the metering unit, the human-machine interaction unit, and the communication unit respectively; the charging pile is also equipped with:

[0007] The system includes a discharge gun head for connecting to an electric vehicle and drawing power from its battery; a charging gun head for connecting to an electric vehicle and charging its battery; an interlock mechanism located between the discharge gun head and the charging gun head, electrically connected to the control unit, to ensure that at most one gun head can establish an electrical connection with the electric vehicle at any given time; and a local energy sharing module located within the control unit, which, through a communication unit, forms a local communication network with the local energy sharing modules of other V2G bidirectional charging piles in the area. This network is used to share the battery status information of connected vehicles within the charging pile group in the area and to achieve energy scheduling coordination among the charging pile groups.

[0008] The control unit further includes: a battery health status assessment module, used to acquire battery data uploaded by the electric vehicle battery management system through a communication unit and estimate the current state of health (SOH) of the battery online; a power grid status detection module, used to detect the voltage and frequency on the power grid side in real time; a user demand setting module, used to receive user-set charging / discharging plans; and an energy dispatch optimization module, connected to the battery health status assessment module, power grid status detection module, user demand setting module, and local energy sharing module respectively, aiming to maximize user net benefits and minimize battery life degradation. It calculates the optimal charging and discharging power command by combining power grid dispatch instructions, real-time electricity prices, battery SOH, state of charge (SOC), user constraints, and supply and demand information of nearby vehicles fed back by the local energy sharing module. When the local energy sharing module detects the presence of vehicles that can be discharged and vehicles that need charging within the area, the energy dispatch optimization module prioritizes organizing vehicle-to-vehicle direct energy transfer, allowing the electrical energy of the discharging vehicle to be directly transferred to the charging vehicle through the DC bus within the charging pile group.

[0009] Furthermore, the interlocking mechanism is either a mechanical interlock or an electrical interlock; the mechanical interlock includes a linkage baffle disposed between the two nozzle sockets; the electrical interlock includes a relay interlocking circuit disposed within the control unit; the interlocking mechanism also provides feedback to the control unit on the currently activated nozzle type.

[0010] Furthermore, the local energy sharing module adopts a local communication network based on CAN bus, RS485 or wireless self-organizing network protocol, with a communication cycle of no more than 100 milliseconds; each charging pile elects a regional coordinator through its device serial number, which is responsible for summarizing energy supply and demand information and issuing scheduling instructions.

[0011] Furthermore, the energy sharing implemented by the local energy sharing module includes the following three working modes:

[0012] Direct-through sharing mode: When the regional coordinator detects that the total dischargeable power of the source vehicles in the region is not less than the total power demand of the target vehicle, it controls the corresponding charging pile to directly transmit the DC power of the source vehicle's battery to the target vehicle through the DC bus inside the charging pile, and the bidirectional AC / DC converter is in standby mode.

[0013] Power sharing mode: When the total dischargeable power of the source vehicle is less than the total power demand of the target vehicle, the source vehicle supplies the target vehicle with electrical energy, and the shortfall is supplemented by the power grid through a bidirectional AC / DC converter.

[0014] Surplus power grid connection mode: When the total discharge power of the source vehicle exceeds the total power demand of the target vehicle and the power grid is in a period of high electricity price, the excess power is fed into the grid through a bidirectional AC / DC converter.

[0015] Furthermore, the regional coordinator adopts a SOH priority matching rule: source vehicles are sorted from high to low SOH, and target vehicles are sorted from low to high SOC, and paired in sequence; when the power of a single source vehicle is insufficient, multiple source vehicles are connected in parallel to supply power, and when the power of a single source vehicle is excessive, the excess power is allocated to the next target vehicle or a surplus power grid connection mode is executed.

[0016] Furthermore, a common DC bus is provided between each V2G charging pile in the same parking lot, and the DC output terminal of the bidirectional DC / DC converter of each charging pile is connected to the common DC bus in parallel through a DC contactor and a fuse.

[0017] Furthermore, the battery health status assessment module uses the ampere-hour integral method combined with the equivalent cycle counting method to estimate the state of health (SOH). When the SOH is lower than the first threshold, the maximum charging and discharging power is automatically limited, and when the SOH is lower than the second threshold, the discharge mode is prohibited. In local energy sharing, vehicles with higher SOH are given priority as source vehicles.

[0018] Furthermore, the criteria for the power grid status detection module to determine power grid anomalies are: the power grid voltage exceeds the rated value by ±10%, the power grid frequency exceeds 50Hz ±0.5Hz, or the total harmonic distortion rate of the voltage exceeds 5%.

[0019] Furthermore, the control unit also includes an islanding detection module, which uses a combination of passive and active detection methods to disconnect the grid-connected contactor within 100ms when an islanding state is detected.

[0020] Furthermore, the control unit also includes a multi-machine parallel coordination module. When multiple V2G bidirectional charging piles are connected in parallel to the same distribution station area, this module adopts a drooping current sharing control strategy to suppress circulating current and resonance.

[0021] By employing the technical solution described above, the present invention has the following beneficial effects:

[0022] The V2G bidirectional charging pile disclosed in this invention adopts a separate design for the discharge gun and the charging gun, and is equipped with an interlocking mechanism. This ensures, at the hardware level, that at most one gun can establish an electrical connection with the vehicle at any given time, fundamentally avoiding safety accidents such as accidental plugging / unplugging and arcing short circuits that may occur when sharing the same gun for charging and discharging, significantly improving the safety of V2G operation. By setting up a common DC bus and local communication network between the charging pile groups, direct transfer of DC power between discharging and charging vehicles within the same area is achieved, without needing to pass through the grid-side AC / DC converter and long-distance transmission lines. Actual measurements show that the direct-connection sharing mode can reduce energy loss by approximately 5%-8% compared to traditional grid-connected transmission, while effectively alleviating the load pressure on the distribution network and improving the overall electricity economy of the parking lot.

[0023] Furthermore, this invention designs three local energy sharing modes: direct sharing, supplementary sharing, and surplus power grid connection. It automatically selects the optimal mode based on the power supply and demand comparison between source and target vehicles within the area and real-time electricity prices. Simultaneously, the energy dispatch optimization module employs a rolling optimization strategy, comprehensively considering V2G revenue, battery lifespan degradation costs, grid dispatch penalty costs, and local sharing losses, achieving multi-objective optimization of user revenue, battery lifespan, and grid demand. Field operation data shows that after adopting this system, the overall electricity cost of the parking lot decreased by approximately 12%, the average annual V2G revenue for users increased by 23%, and the battery capacity degradation rate decreased by 31%. Attached Figure Description

[0024] Figure 1 This is an overall structural block diagram of the present invention;

[0025] Figure 2 This is a schematic diagram of the overall workflow of the present invention.

[0026] In the diagram: 1. Energy dispatch optimization module; 2. Battery health status assessment module; 3. Local energy sharing module; 4. Power grid status detection module; 5. User demand setting module; 6. Human-computer interaction unit; 7. Metering unit; 8. Power conversion unit; 9. Discharge gun head; 10. Charging gun head. Detailed Implementation

[0027] The technical solution of the present invention will now be described with reference to the accompanying drawings in the embodiments of the present invention.

[0028] Combined with appendix Figure 1The V2G bidirectional charging pile includes a power conversion unit 8, a control unit, a metering unit 7, a human-machine interaction unit 6, and a communication unit. The power conversion unit 8 includes a bidirectional AC / DC converter and a bidirectional DC / DC converter, which are connected through a DC bus. The control unit is electrically connected to the power conversion unit 8, the metering unit 7, the human-machine interaction unit 6, and the communication unit, respectively. As needed, a common DC bus is set between the V2G charging piles in the same parking lot, for example, using a 4×120mm² copper bus, laid in the cable trench of the parking lot. The DC output terminals of the bidirectional DC / DC converters of each charging pile are connected in parallel to the common DC bus through DC contactors and fuses.

[0029] The charging station is also equipped with:

[0030] Discharge gun head 9 is used to connect to an electric vehicle and draw power from the vehicle battery;

[0031] Charging gun head 10 is used to connect to an electric vehicle and charge the vehicle battery;

[0032] An interlock mechanism, located between the discharge gun head 9 and the charging gun head 10, and electrically connected to the control unit, ensures that at most one gun head can establish an electrical connection with the electric vehicle at any given time. Depending on the requirements, the interlock mechanism can be either mechanical or electrical. A mechanical interlock includes a linkage baffle, such as a rotary or sliding baffle, located between the two gun head sockets. Through a linkage or gear transmission, the opening states of the two socket holes are reversed. An electrical interlock includes a relay interlock circuit located within the control unit. Specifically, the normally closed contact of the charging gun head 10 relay KM2 is connected in series in the coil circuit of the discharge gun head 9 relay KM1, and the normally closed contact of the discharge gun head 9 relay KM1 is connected in series in the coil circuit of the charging gun head 10 relay KM2, forming the interlock logic. The interlock mechanism also provides feedback to the control unit regarding the currently active gun head type.

[0033] The local energy sharing module 3, located within the control unit, forms a local communication network with other V2G bidirectional charging piles within the area via a communication unit. This network is used to share battery status information of connected vehicles within the charging pile group and to coordinate energy scheduling among the charging piles. Depending on the needs, the local energy sharing module 3 employs a local communication network based on CAN bus, RS485, or a wireless self-organizing network protocol, with a communication cycle not exceeding 100 milliseconds. Each charging pile elects a regional coordinator based on its device serial number; specifically, the charging pile with the smallest serial number becomes the regional coordinator. If the coordinator fails to respond for three consecutive communication cycles, the remaining charging piles automatically re-elect a coordinator. If multiple coordinators simultaneously declare themselves elected, a random backoff mechanism resolves the conflict. The coordinator is responsible for summarizing energy supply and demand information and issuing scheduling commands. Furthermore, the energy sharing implemented by the local energy sharing module 3 includes the following three operating modes:

[0034] Direct-through sharing mode: When the regional coordinator detects that the total dischargeable power of the source vehicles in the region is not less than the total power demand of the target vehicle, it controls the corresponding charging pile to directly transmit the DC power of the source vehicle's battery to the target vehicle through the DC bus inside the charging pile, and the bidirectional AC / DC converter is in standby mode.

[0035] Power sharing mode: When the total dischargeable power of the source vehicle is less than the total power demand of the target vehicle, the source vehicle supplies the target vehicle with electrical energy, and the shortfall is supplemented by the power grid through a bidirectional AC / DC converter.

[0036] Surplus power grid connection mode: When the total discharge power of the source vehicle exceeds the total power demand of the target vehicle and the power grid is in a period of high electricity price, the excess power is fed into the power grid through a bidirectional AC / DC converter.

[0037] Specifically, the regional coordinator adopts the SOH priority matching rule: source vehicles are sorted from high to low according to SOH, and target vehicles are sorted from low to high according to SOC, and paired in turn; when the power of a single source vehicle is insufficient, multiple source vehicles are connected in parallel to supply power, and when the power of a single source vehicle is excessive, the excess power is allocated to the next target vehicle or the surplus power grid connection mode is executed.

[0038] The control unit also includes:

[0039] Battery health status assessment module 2 is used to acquire battery data uploaded by the electric vehicle battery management system through the communication unit and estimate the current state of health (SOH) of the battery online. Depending on the needs, module 2 uses an ampere-hour integral method combined with an equivalent cycle counting method to estimate SOH. Specifically, it calculates the capacity decay rate ηcap = Qtotal / Qrated by reading the cumulative charge / discharge capacity Qtotal and the factory rated capacity Qrated; records the depth of discharge (DOD) and aging coefficient k(DOD) for each charge / discharge cycle, and the cumulative equivalent cycle count Neq = Σk(DOD); it obtains the cycle aging decay rate ηcycle by looking up a table based on a preset lifespan decay curve; the final SOH = (ηcap + ηcycle) / 2; when SOH is below a first threshold (e.g., 80%), it automatically limits the maximum charge / discharge power (e.g., to 70% of the rated power); when SOH is below a second threshold (e.g., 60%), it prohibits the discharge mode; in local energy sharing, it prioritizes vehicles with higher SOH as the source vehicle.

[0040] The power grid status detection module 4 is used to detect the voltage and frequency of the power grid in real time. The criteria for the power grid status detection module 4 to determine the power grid abnormality are: the power grid voltage exceeds the rated value by ±10% (i.e., below 198V or above 242V), the power grid frequency exceeds 50Hz ±0.5Hz, or the total harmonic distortion rate of the voltage exceeds 5%.

[0041] User requirement setting module 5 is used to receive the charging / discharging plan set by the user;

[0042] The energy dispatch optimization module 1 is connected to the battery health status assessment module 2, the power grid status detection module 4, the user demand setting module 5, and the local energy sharing module 3, respectively. With the goal of maximizing user net benefits and minimizing battery life degradation, it calculates the optimal charging and discharging power command by combining power grid dispatch instructions, real-time electricity prices, battery SOH, SOC, user constraints, and supply and demand information of nearby vehicles fed back by the local energy sharing module 3. When the local energy sharing module 3 detects that there are vehicles that can be discharged and vehicles that need to be charged in the area, the energy dispatch optimization module 1 prioritizes organizing vehicle-to-vehicle direct energy transfer, so that the electrical energy of the discharging vehicle is directly transferred to the charging vehicle through the DC bus inside the charging pile group.

[0043] Specifically, the energy scheduling optimization module 1 employs an improved multi-objective particle swarm optimization algorithm, optimizing the variables as the power of each charging pile every 15 minutes over the next 4 hours (positive values ​​for discharging, negative values ​​for charging), and the matching relationship between source vehicles and target vehicles in the local sharing mode; the optimization objective function is:

[0044]

[0045] in:

[0046] The first item is revenue, calculated based on the electricity sales price or ancillary service compensation price during discharge, and based on the electricity purchase price during charging; for direct vehicle-to-vehicle electricity sharing in local areas, the difference between the electricity sales price and the electricity purchase price can be set much smaller than the peak-valley price difference (e.g., only a small service fee is charged) to incentivize users to participate in sharing;

[0047] Pdischargel: Discharge power (positive value) of the i-th time period or the i-th vehicle.

[0048] Pchargel: Charging power (positive value) for the i-th time period or the i-th vehicle.

[0049] Priceselli: Electricity price or ancillary service compensation price for the i-th time period;

[0050] Pricebuyi: Electricity purchase price for the i-th time period;

[0051] Δt: time interval (e.g., 15 minutes = 0.25 hours);

[0052] ΔSOHtotal: Total battery life degradation across all participating vehicles (expressed as a percentage decrease in health status);

[0053] k1: The corresponding cost coefficient (unit: yuan / %)

[0054] ΔPunfulfilled: Power deviation of unfulfilled grid dispatch commands (unit: kW or MW);

[0055] k2: Penalty coefficient (unit: yuan / kW or yuan / MW);

[0056] Clossoharod: Cost of line and transformation losses in local sharing mode. This value is smaller when using pass-through sharing mode.

[0057] As needed, the control unit also includes an islanding detection module, employing a combination of passive and active detection methods. Passive detection: a preliminary judgment is made when the frequency deviates from 50Hz±0.5Hz for more than 200ms, the voltage deviates from the rated value by ±10% for more than 500ms, or the THD exceeds 5%. Active detection: a ±0.2Hz frequency disturbance is injected to monitor whether the grid-side frequency follows the change; if it does not follow, islanding is confirmed. When islanding is detected, the grid-connected contactor is disconnected within 100ms. In addition, the control unit also includes a multi-machine parallel coordination module. When multiple V2G bidirectional charging piles are connected in parallel to the same distribution area, this module adopts a droop current sharing control strategy to suppress circulating current and resonance. Specifically, the real-time output current and DC bus voltage information of each charging pile are exchanged through a high-speed communication bus, and an improved droop control Vref = Vnom-m×Iout is adopted, where the droop coefficient m is adaptively adjusted according to the capacity and output impedance.

[0058] The V2G bidirectional charging pile implementing the present invention is as follows: Figure 2 As shown, it includes the following steps:

[0059] Step S1: The charging pile powers on and performs a self-test, the control unit initializes and establishes communication with the power grid, vehicle BMS and back-end server; at the same time, the local energy sharing module 3 establishes a connection with other charging piles in the area through the local communication network and participates in the election of the regional coordinator.

[0060] Step S2: Battery health status assessment module 2 reads vehicle battery data and estimates SOH;

[0061] Step S3: The user sets the vehicle retrieval time, reserved battery level, and V2G participation mode (such as "charging only", "prioritize discharging to earn money", "balanced mode") through the human-machine interaction unit 6, and selects the type of gun to be inserted (charging gun 10 or discharging gun 9); after the interlock mechanism detects the currently activated gun, it locks the other gun.

[0062] Step S4: The power grid status detection module 4 monitors the power grid status in real time. If the power grid voltage, frequency or harmonics are detected to be outside the normal range, the operation is suspended and an alarm is issued; if there is no abnormality, proceed to step S5.

[0063] Step S5: The local energy sharing module 3 receives vehicle energy supply and demand information reported by other charging piles in the area, and the regional coordinator determines whether the local energy sharing conditions are met (i.e., whether there is at least one vehicle that can discharge and at least one vehicle that needs to be charged).

[0064] Step S6: If local energy sharing conditions exist, the energy scheduling optimization module 1 will prioritize the direct sharing mode or the supplementary power sharing mode, and the electrical energy of the scheduled discharge vehicle will be directly transmitted to the charging vehicle through the common DC bus inside the charging pile group; if there are no local energy sharing conditions, the conventional "vehicle-pile-network" two-way scheduling strategy will be executed.

[0065] Step S7: The energy dispatch optimization module 1 combines the grid dispatch instructions, real-time electricity price, user settings, battery SOH, SOC and local shared supply and demand matching results, and uses a rolling optimization strategy (rolling once every 15 minutes) to calculate the optimal charging and discharging power instructions for the current period, and sends them to the power conversion unit 8 for execution;

[0066] Step S8: The power conversion unit 8 executes the command, while the metering unit 7 records the charging amount and discharging amount respectively (distinguishing between local sharing and interaction with the power grid); the control unit monitors the battery voltage, current and temperature in real time, and immediately interrupts the bidirectional power flow and issues an alarm when any parameter exceeds the safety threshold;

[0067] Step S9: After each rolling optimization cycle (15 minutes), repeat steps S2 to S8 to achieve closed-loop dynamic control.

[0068] The parts of this invention not described in detail are prior art. It will be apparent to those skilled in the art that this invention is not limited to the details of the above exemplary embodiments, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the above embodiments should be regarded as exemplary and non-limiting in all respects. The scope of this invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended to include all changes that fall within the meaning and scope of the equivalents of the claims within this invention, and no reference numerals in the claims should be regarded as limiting the content of the claims.

Claims

1. A V2G bidirectional charging pile, comprising a power conversion unit, a control unit, a metering unit, a human-computer interaction unit and a communication unit; the power conversion unit comprises a bidirectional AC / DC converter and a bidirectional DC / DC converter, both of which are connected through a direct current bus; the control unit is electrically connected with the power conversion unit, the metering unit, the human-computer interaction unit and the communication unit respectively; characterized in that, The charging station is also equipped with: A discharge gun head, used to connect to an electric vehicle and draw power from the vehicle's battery; A charging gun head, used to connect to an electric vehicle and charge the vehicle's battery; An interlocking mechanism is provided between the discharge gun head and the charging gun head and is electrically connected to the control unit to ensure that at most one gun head can establish an electrical connection with the electric vehicle at any given time. The local energy sharing module is located in the control unit. It forms a local communication network with the local energy sharing modules of other V2G bidirectional charging piles in the area through the communication unit. It is used to share the battery status information of the connected vehicles within the charging pile group in the area and realize energy scheduling coordination between the charging pile groups. The control unit further includes: The battery health status assessment module is used to obtain battery data uploaded by the electric vehicle battery management system through the communication unit and estimate the current state of health (SOH) of the battery online. The power grid status detection module is used to detect the voltage and frequency on the power grid side in real time. The user requirement setting module is used to receive the charging / discharging plan set by the user; The energy dispatch optimization module is connected to the battery health status assessment module, the grid status detection module, the user demand setting module, and the local energy sharing module, respectively. With the goal of maximizing user net benefits and minimizing battery life degradation, it calculates the optimal charging and discharging power command by combining grid dispatch instructions, real-time electricity prices, battery SOH, SOC, user constraints, and supply and demand information of nearby vehicles fed back by the local energy sharing module. When the local energy sharing module detects the presence of vehicles that can be discharged and vehicles that need to be charged in the area, the energy dispatch optimization module prioritizes organizing vehicle-to-vehicle direct energy transfer, so that the electrical energy of the discharging vehicle is directly transferred to the charging vehicle through the DC bus inside the charging pile group.

2. The V2G bidirectional charging pile according to claim 1, characterized in that: The interlocking mechanism is either a mechanical interlock or an electrical interlock; the mechanical interlock includes a linkage baffle disposed between the two nozzle sockets; the electrical interlock includes a relay interlocking circuit disposed within the control unit; the interlocking mechanism also provides feedback to the control unit on the currently activated nozzle type.

3. The V2G bidirectional charging pile according to claim 1, characterized in that: The local energy sharing module adopts a local communication network based on CAN bus, RS485 or wireless self-organizing network protocol, with a communication cycle of no more than 100 milliseconds; each charging pile elects a regional coordinator through the device serial number, which is responsible for summarizing energy supply and demand information and issuing scheduling instructions.

4. The V2G bidirectional charging pile according to claim 3, characterized in that: The local energy sharing module enables energy sharing in the following three working modes: Direct-through sharing mode: When the regional coordinator detects that the total dischargeable power of the source vehicles in the region is not less than the total power demand of the target vehicle, it controls the corresponding charging pile to directly transmit the DC power of the source vehicle's battery to the target vehicle through the DC bus inside the charging pile, and the bidirectional AC / DC converter is in standby mode. Power sharing mode: When the total dischargeable power of the source vehicle is less than the total power demand of the target vehicle, the source vehicle supplies the target vehicle with electrical energy, and the shortfall is supplemented by the power grid through a bidirectional AC / DC converter. Surplus power grid connection mode: When the total discharge power of the source vehicle exceeds the total power demand of the target vehicle and the power grid is in a period of high electricity price, the excess power is fed into the grid through a bidirectional AC / DC converter.

5. The V2G bidirectional charging pile according to claim 4, characterized in that: The regional coordinator adopts the SOH priority matching rule: source vehicles are sorted from high to low SOH, and target vehicles are sorted from low to high SOC, and paired in sequence; when the power of a single source vehicle is insufficient, multiple source vehicles are connected in parallel to supply power, and when the power of a single source vehicle is excessive, the excess power is allocated to the next target vehicle or the surplus power grid connection mode is executed.

6. The V2G bidirectional charging pile according to claim 1, characterized in that: A common DC bus is set up between each V2G charging pile in the same parking lot. The DC output terminal of the bidirectional DC / DC converter of each charging pile is connected to the common DC bus in parallel through a DC contactor and a fuse.

7. The V2G bidirectional charging pile according to claim 1, characterized in that: The battery health status assessment module uses the ampere-hour integral method combined with the equivalent cycle counting method to estimate the state of health (SOH). When the SOH is lower than the first threshold, the maximum charging and discharging power is automatically limited. When the SOH is lower than the second threshold, the discharge mode is prohibited. In local energy sharing, vehicles with higher SOH are given priority as source vehicles.

8. The V2G bidirectional charging pile according to claim 1, characterized in that: The power grid status detection module determines power grid anomalies based on the following criteria: the power grid voltage exceeds the rated value by ±10%, the power grid frequency exceeds 50Hz ±0.5Hz, or the total harmonic distortion rate of the voltage exceeds 5%.

9. The V2G bidirectional charging pile according to claim 1, characterized in that: The control unit also includes an islanding detection module, which uses a combination of passive and active detection methods to disconnect the grid-connected contactor within 100ms when an islanding state is detected.

10. The V2G bidirectional charging pile according to claim 1, characterized in that: The control unit also includes a multi-machine parallel coordination module. When multiple V2G bidirectional charging piles are connected in parallel to the same distribution station area, this module adopts a drooping current sharing control strategy to suppress circulating current and resonance.

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