Electric vehicle bidirectional wireless charging device based on reconfigurable compensation network and control method

Abstract

The application discloses a kind of based on reconfigurable compensation network electric vehicle bidirectional wireless charging device and control method, the device includes control unit, primary side power conversion unit, secondary side power conversion unit, primary side transmitting coil, secondary side receiving coil, primary side compensation network, secondary side compensation network, mode switching unit and communication unit;The control method includes collecting power battery end voltage, power battery state of charge SOC, power grid state information and system operation request information;According to the acquisition result, judge the current target operation mode, control mode switching unit changes the access state of the switchable compensation branch in primary side compensation network and / or secondary side compensation network, to build the equivalent compensation topology corresponding to target operation mode.The present application is conducive to taking into account charging efficiency and battery service life;It can effectively inhibit the coil current mutation, battery end voltage overshoot and bus power fluctuation in switching transient, improve the stability and security in system switching process.

Description

Technical Field

[0001] This invention relates to the field of wireless power transmission technology, and in particular to a bidirectional wireless charging device and control method for electric vehicles based on a reconfigurable compensation network, applicable to forward charging, reverse power feeding, and vehicle-to-vehicle charging scenarios. Background Technology

[0002] Currently, wired charging remains the primary method for replenishing electric vehicles, mainly including DC fast charging and AC slow charging. DC fast charging can replenish a large amount of energy to the battery in a short time, but its control system is usually located at an external charging station, resulting in high construction, installation, and maintenance costs. Furthermore, the high-power charging process can easily cause battery temperature rise, which is detrimental to battery life management. While AC slow charging is more battery-friendly, its charging time is longer due to limitations in the power and heat dissipation of the onboard charger, making it difficult to meet the needs of emergency replenishment and high-frequency usage scenarios.

[0003] Meanwhile, wired charging also suffers from problems such as interface mechanical wear, inconvenience in plugging and unplugging charging guns, increased risks of insulation and leakage in severe weather, and constraints on site layout imposed by cables. Although battery swapping, which has emerged in recent years, has improved the speed of energy replenishment to some extent, it still faces practical difficulties such as large infrastructure investment, inconsistent battery standards for different vehicle models, and complex operating systems, making it difficult to fully promote in all application scenarios.

[0004] Wireless power transfer technology boasts advantages such as contactless operation, high security, high automation, and strong environmental adaptability, and is considered one of the important development directions for future electric vehicle (EV) charging. However, most existing EV wireless charging systems focus on a single forward charging scenario, making it difficult to address the differentiated requirements of the power battery for constant current and constant voltage output at different charging stages. Furthermore, for scenarios such as bidirectional energy interaction between vehicles and the grid, reverse feeding, and emergency charging between vehicles under grid-free conditions, existing solutions generally suffer from complex compensation network switching, high hardware redundancy, significant impact from mode switching, and fragmented control strategies. Therefore, there is an urgent need to propose a bidirectional wireless charging technology solution that can achieve integrated operation of constant current, constant voltage, reverse feeding, and vehicle-to-vehicle charging on a single platform. Summary of the Invention

[0005] Purpose of the invention: The purpose of this invention is to provide a bidirectional wireless charging device and control method for electric vehicles based on a reconfigurable compensation network, applicable to forward charging, reverse power feeding, and vehicle-to-vehicle charging scenarios.

[0006] Technical Solution: The bidirectional wireless charging device for electric vehicles based on a reconfigurable compensation network described in this invention includes a control unit, a primary-side power conversion unit, a secondary-side power conversion unit, a primary-side transmitting coil, a secondary-side receiving coil, a primary-side compensation network, a secondary-side compensation network, a mode switching unit, and a communication unit. The primary-side power conversion unit is located on the wireless charging transmitting side and connected to the external power grid. It is used to convert the power frequency AC power input from the external power grid into high-frequency AC power after rectification and inversion, and then wirelessly transmit it to the secondary side through the primary-side transmitting coil. The secondary-side power conversion unit is located on the vehicle's energy storage side and connected to the power battery. It is used to rectify and regulate the high-frequency power received by the secondary-side receiving coil to charge the power battery. In the reverse feed-in mode, the secondary-side power conversion unit can also operate in an inverter state, converting the DC power in the power battery into high-frequency AC power, transmitting it to the primary side through a coupling mechanism, and then feeding it back to the external power grid.

[0007] Furthermore, the primary-side transmitting coil and the secondary-side receiving coil form a magnetic coupling mechanism, and wireless power transmission is achieved between them through an alternating magnetic field. The primary-side compensation network is set between the primary-side power conversion unit and the primary-side transmitting coil, and the secondary-side compensation network is set between the secondary-side receiving coil and the secondary-side power conversion unit. The primary-side compensation network and / or the secondary-side compensation network are provided with switchable compensation branches. The mode switching unit controls the access, removal or bypass of the switchable compensation branches to enable the system to form different equivalent compensation topologies in different operating modes.

[0008] Furthermore, the control unit adopts a control method that combines hierarchical mode judgment and execution control; the control unit first collects the power battery state of charge (SOC), grid status information and vehicle mutual charging request information, and determines the target operating mode of the system based on the collected parameters.

[0009] Furthermore, the control unit sets three SOC determination thresholds. When the SOC is lower than the first threshold, the control unit controls the system to preferentially enter the vehicle-to-grid power supply forward charging mode. When the SOC is higher than the first threshold but lower than the second threshold, the control unit controls the system to maintain the charging hold state and prohibits the system from entering the reverse power supply mode. When the SOC is higher than the second threshold and a power support demand is detected from the external power grid, the control unit controls the system to enter the vehicle-to-grid reverse power supply mode. When the SOC is higher than the third threshold and a vehicle mutual charging request is received, the control unit controls the system to enter the vehicle mutual charging mode.

[0010] The bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network according to the present invention includes the following steps:

[0011] S1. Collect power battery terminal voltage, power battery state of charge (SOC), grid status information, and system operation request information;

[0012] S2. Based on the collected results, determine whether the current target operating mode is constant current forward charging mode, constant voltage forward charging mode, reverse power feeding mode, or vehicle mutual charging mode.

[0013] S3. The control mode switching unit changes the access status of switchable compensation branches in the primary side compensation network and / or secondary side compensation network to construct an equivalent compensation topology corresponding to the target operating mode.

[0014] S4. Control the primary-side power conversion unit and the secondary-side power conversion unit to output drive signals corresponding to the target operating mode, so that the system enters the target operating mode;

[0015] S5. Perform transition control during the operation mode switching process to suppress current surges and voltage fluctuations;

[0016] S6. In the target operating mode, closed-loop regulation is performed based on the output current feedback value and / or output voltage feedback value to maintain constant current output or constant voltage output.

[0017] Furthermore, in step S2, under constant current forward charging mode, the control system forms an LCC-LCC equivalent compensation topology and charges the power battery with constant current using the output current as the control target; under constant voltage forward charging mode, the control system forms an LCC-S equivalent compensation topology and charges the power battery with constant voltage using the output voltage as the control target; under reverse power supply mode, the system transmits the electrical energy in the power battery to the grid in reverse; under vehicle mutual charging mode, the system completes wireless power replenishment between vehicles.

[0018] Furthermore, in step S2, when the target operating mode is determined to be the vehicle-to-grid power forward charging mode, the control unit determines the power battery terminal voltage U. b The charging stage is determined, and the determination relationship is as follows:

[0019] (1)

[0020] (2)

[0021] Among them, M c Indicates charging phase mode; M CC Indicates constant current charging mode; M CV Indicates constant voltage charging mode; U th This indicates the threshold voltage for switching between constant current and constant voltage.

[0022] When the system needs to participate in vehicle-to-grid interaction, the control unit determines whether to participate based on the grid power support requirements and whether the power battery's state of charge has entered reverse feed-in mode. The determination relationship is as follows:

[0023] (3)

[0024] Among them, SOC fb This indicates the reverse power feed-in threshold. When the state of charge of the power battery exceeds this threshold, the system is capable of transmitting electrical energy back to the grid; M represents the operating mode; M V2G Indicates vehicle-to-grid mode;

[0025] In this mode, the power direction of the system satisfies:

[0026] (4)

[0027] Or equivalent to:

[0028] (5)

[0029] Among them, P grid This represents the system's active power relative to the grid side; it takes a negative value when the system supplies power to the grid. P bat→grid This indicates the power transmitted from the battery to the power grid;

[0030] When the external power grid is unavailable or a vehicle cross-charging request exists, the control unit determines the vehicle cross-charging mode:

[0031] (6)

[0032] (7)

[0033] Among them, M V2V Indicates vehicle charging mode, SOC v2v This indicates the allowed threshold for vehicle-to-vehicle charging mode.

[0034] Furthermore, in step S3, before mode switching, the control unit first determines whether the system meets the safety conditions required for compensation network switching. The safe switching window can be defined as:

[0035] (8)

[0036] (9)

[0037] (10)

[0038] Where P represents the instantaneous transmission power of the system; P sw Indicates the power threshold that allows mode switching; I coil Indicates the amplitude of the coil current; I sw Indicates the coil current threshold that allows mode switching; U ref Indicates the reference voltage before switching; ε u Indicates the allowable voltage deviation threshold;

[0039] When the current operating mode needs to be switched to the target operating mode, the control unit first pre-adjusts the phase shift angle of the inverter and / or active rectifier, so that the system gradually transitions from the current high-power transmission state to the safe switching state.

[0040] The phase shift angle pre-adjustment law can be expressed as:

[0041] (11)

[0042] Where φ(k) represents the actual phase shift angle in the k-th control cycle; φ ref Indicates the target safety phase angle; △φ max This represents the maximum allowable rate of change of phase angle within a single control cycle; sat(·) represents the limiting function;

[0043] When the system switches between forward charging modes, the target safe phase angle corresponds to a low-power transmission state; when the system switches between forward charging and reverse feeding modes, the target safe phase angle corresponds to a zero-power transmission state or a near-zero-power transmission state, provided that the system transmission power can be expressed as a function of the phase shift angle:

[0044] (12)

[0045] The control unit adjusts Φ to achieve the following:

[0046] (13)

[0047] This allows the system to enter a safe switching window. After the phase shift angle is pre-adjusted to bring the system into the safe switching window, the control unit further gradually adjusts the duty cycle of the bridge inverter to reduce the energy injection rate on the bus side before and after the compensation network switching. The duty cycle adjustment law can be expressed as:

[0048] (14)

[0049] Where d(k) represents the actual duty cycle in the k-th control cycle; d ref Indicates the buffer duty cycle; △d max This indicates the maximum allowable change in duty cycle within a single control cycle;

[0050] To limit voltage and current overshoot, the duty cycle change rate must satisfy:

[0051] (15)

[0052] (16)

[0053] Where, γ uIndicates the allowable rate of change threshold of battery terminal voltage; γ i This indicates the threshold for the allowable rate of change of coil current;

[0054] Once the phase shift angle and duty cycle both enter the safe switching window, the control unit activates the mode switching unit to change the access status of switchable compensation branches in the primary and / or secondary compensation networks, thereby constructing an equivalent compensation topology corresponding to the target operating mode.

[0055] Furthermore, step S4 includes, after the compensation network handover is completed, the control unit maintains a safe phase angle and / or a buffer duty cycle minus a preset hold time T. h Then, the control input is restored to the steady-state operating point corresponding to the target operating mode. The restoration law is expressed as follows:

[0056] (17)

[0057] (18)

[0058] Where, φ tar and d tar These represent the target phase shift angle and target duty cycle corresponding to the target operating mode, respectively; △φ rec and △d rec These represent the step size of the phase shift angle change and the step size of the duty cycle change during the recovery phase, respectively.

[0059] When the system operates in constant current charging mode, the control objective is to make the output current I0 track the constant current setpoint I. ref Its current error is defined as:

[0060] (19)

[0061] The control unit can perform closed-loop adjustment of the phase shift angle and / or duty cycle based on the error, and the control law is expressed as:

[0062] (20)

[0063] Among them, u i (k) represents the control quantity in constant current mode; K pi and K ii The proportional and integral coefficients of the current loop, respectively;

[0064] The control quantity u i (k) Mappable phase shift angle command φ * Or duty cycle instruction d * ,Right now:

[0065] (twenty one)

[0066] or

[0067] (twenty two)

[0068] When the system operates in constant voltage charging mode, the control objective is to reduce the terminal voltage U of the power battery. b Tracking constant pressure setpoint U ref Its voltage error is defined as:

[0069] (twenty three)

[0070] The corresponding closed-loop control law is:

[0071] (twenty four)

[0072] Among them, u u (k) represents the control quantity under constant pressure mode; K pu and K iu These represent the proportional and integral coefficients of the voltage loop, respectively.

[0073] The control quantity u u (k) can be further converted into a phase shift angle reference value or a duty cycle reference value, that is:

[0074] (25)

[0075] or

[0076] (26)

[0077] When the system operates in vehicle-to-grid reverse power supply mode, the control objective is to maximize the feedback power P. fb Tracking reference power P ref Its power error is defined as:

[0078] (27)

[0079] The control law can be expressed as:

[0080] (28)

[0081] Among them, K pp and K ip These represent the proportional gain and integral gain of the power loop, respectively.

[0082] The control unit also satisfies the following constraints:

[0083] (29)

[0084] When SOC is detected <SOC min When this occurs, the control unit commands to reduce the feedback power or exit the reverse feed mode.

[0085] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0086] (1) Based on the same set of bidirectional wireless power transmission main circuit, the present invention achieves the integration of multiple operating modes such as constant current forward charging, constant voltage forward charging, vehicle-to-grid reverse power feeding and vehicle-to-vehicle wireless power replenishment through the synergistic effect of reconfigurable compensation network and mode switching unit, thus avoiding the structural redundancy and increased control complexity caused by setting up independent hardware platforms for different working conditions.

[0087] (2) By constructing different equivalent compensation topologies at different operating stages, the present invention enables the system to charge stably in a constant current mode in the early stage of power battery charging and to smoothly switch to constant voltage charging mode when it is close to being fully charged. This is more in line with the charging law of power battery and is conducive to balancing charging efficiency and battery life.

[0088] (3) By setting up a bidirectional power conversion unit and a hierarchical mode determination strategy, the present invention enables the electric energy in the power battery to not only be transmitted from the power grid to the vehicle, but also to be fed back to the power grid by the vehicle when there is a demand from the power grid, or to provide external power supply and emergency energy replenishment when there is a demand from external loads and other vehicles, thereby improving the ability of electric vehicles to participate in energy scheduling in multiple scenarios.

[0089] (4) By introducing a transition control strategy during mode switching, this invention coordinates and adjusts parameters such as phase shift angle, duty cycle and compensation branch access status, which can effectively suppress sudden changes in coil current, overshoot of battery terminal voltage and fluctuations in bus power during switching, thereby improving the stability and safety of the system during switching.

[0090] (5) The present invention further expands the application scenarios of wireless charging system. When the external power grid is unavailable, a vehicle-to-vehicle wireless energy transmission link can be established through the vehicle-to-vehicle wireless emergency power replenishment interface, so that vehicles with remaining power can provide emergency power replenishment to vehicles with insufficient power. It has high engineering application value. Attached Figure Description

[0091] Figure 1 This is a schematic diagram of the overall structure of the bidirectional wireless charging device for electric vehicles according to the present invention;

[0092] Figure 2 This is a flowchart of the bidirectional wireless charging control method for electric vehicles according to the present invention;

[0093] Figure 3 This is a circuit schematic diagram of the primary-side power conversion unit, the secondary-side power conversion unit, and the reconfigurable compensation network of the present invention.

[0094] Figure 4This is a schematic diagram of the equivalent circuit in the constant current forward charging mode of the present invention.

[0095] Figure 5 (a) is the equivalent circuit schematic diagram of the constant voltage forward charging mode of the present invention; Figure 5 (b) is the equivalent circuit schematic diagram of the reverse-feed mode of the present invention;

[0096] Figure 6 This is a diagram of the wireless emergency power replenishment interface between vehicles and its charging topology according to the present invention.

[0097] Figure 7 This is a schematic diagram of the equivalent resonance principle of the vehicle mutual charging mode of the present invention. Detailed Implementation

[0098] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0099] like Figure 1 As shown, this embodiment provides a bidirectional wireless charging device for electric vehicles based on a reconfigurable compensation network, including a control unit, a primary-side power conversion unit, a secondary-side power conversion unit, a primary-side transmitting coil, a secondary-side receiving coil, a primary-side compensation network, a secondary-side compensation network, a mode switching unit, and a communication unit. The primary-side power conversion unit is located on the wireless charging transmitting side and connected to the external power grid. It is used to rectify and invert the power frequency AC power input from the external power grid into high-frequency AC power, and then wirelessly transmit it to the secondary side through the primary-side transmitting coil. The secondary-side power conversion unit is located on the vehicle's energy storage side and connected to the power battery. It is used to rectify and regulate the high-frequency electrical energy received by the secondary-side receiving coil to charge the power battery. In reverse feed-in mode, the secondary-side power conversion unit can also operate in an inverter state, converting the DC power in the power battery into high-frequency AC power, transmitting it to the primary side via a coupling mechanism, and then feeding it back to the external power grid.

[0100] The primary-side transmitting coil and the secondary-side receiving coil form a magnetic coupling mechanism, and wireless power transmission between them is achieved through an alternating magnetic field. A primary-side compensation network is located between the primary-side power conversion unit and the primary-side transmitting coil, while a secondary-side compensation network is located between the secondary-side receiving coil and the secondary-side power conversion unit. Switchable compensation branches are provided in the primary-side and / or secondary-side compensation networks. The mode switching unit controls the access, disconnection, or bypassing of these switchable compensation branches, enabling the system to form different equivalent compensation topologies under different operating modes.

[0101] The control unit, as the core of the system, is connected to the primary-side power conversion unit, secondary-side power conversion unit, mode switching unit, and communication unit. It receives user operation requests, collects information such as battery terminal voltage, battery current, state of charge (SOC), bus voltage, coil current, and grid status, and determines the target operating mode the system needs to enter based on the collected data. The switchable compensation branch includes a compensation inductor branch, a compensation capacitor branch, and connected switching devices. These switching devices are used to change the series, parallel, or bypass relationships in the primary-side and / or secondary-side compensation networks under different operating modes, thereby altering the system's equivalent resonance parameters.

[0102] like Figure 3 As shown, the primary-side power conversion unit in this embodiment includes inverter bridges S1-S4, compensation inductor L1, compensation capacitors C1 and C2, and primary-side transmitting coil L. p The secondary power conversion unit includes inverter bridges S5-S8, compensation inductors L2, compensation capacitors C3-C5, relays, a load-side interface, and a secondary receiving coil L. s On the primary side, inverter bridges S1-S4 form a bidirectional voltage source converter, with compensation inductor L1, compensation capacitors C1 and C2, and primary-side transmitting coil L... p This forms the primary-side compensation network. On the secondary side, inverter bridges S5-S8 form a bidirectional voltage source converter, along with compensation inductor L2, compensation capacitors C3-C5, controllable relays, and the secondary-side receiving coil L. s It forms a secondary side compensation network and switchable compensation branches. Figure 3 The left side consists of the primary-side power electronic converter and the transmitting coil L. p The primary-side power electronic converter includes S1-S4, compensation inductor L1, and compensation capacitors C1 and C2. S1 and S2 are connected in series, and S3 and S4 are connected in series, respectively, and are connected to the power grid. L1, L2, and C... p After being connected in series, the two ends are connected to the circuit nodes between S1 and S2, and S3 and S4 respectively. One end of C1 is connected to C2, and the other end is connected to L. p connect. Figure 3 The right side consists of the secondary power electronic converter and the receiving coil L. s The secondary-side power electronic converter includes S5-S8, compensation capacitors C3-C5, compensation inductor L2, relays, and load R. L S5 and S6 are connected in series, S7 and S8 are connected in series, and then connected to C5 and R respectively. L After parallel connection, relay, L2, and C4 are connected in series, their two ends are connected to the circuit nodes between S5 and S6, and S7 and S8, respectively. C3, L... S After being connected in series, terminal C3 is connected to the circuit node between L2 and C4, L S The terminal is connected to the source of S6. Figure 3 M represents mutual inductance. The mode switching unit changes the connection relationship of the compensation branch in the secondary compensation network by controlling the on and off states of relays or other switching devices, thereby enabling the system to form different equivalent resonant topologies under different operating modes. In this embodiment, the switchable compensation branch can be implemented using relays, MOSFET arrays, IGBT arrays, solid-state relays, or contactors.

[0103] like Figure 4 As shown, in constant current forward charging mode, the mode switching unit controls the switchable compensation branch to work, so that the system forms an LCC-LCC equivalent compensation topology suitable for constant current output. Figure 4 In the diagram, R1 is the equivalent resistance of inverters S1 and S4, R2 is the equivalent resistance of inverters S2 and S3, R3 is the equivalent resistance of inverters S7 and S8, R4 is the equivalent resistance of inverters S5 and S6, and R... ac For C5, R L The equivalent resistance, R ac L1, R1, C2, L P R1 and R2 are connected in series. One end of C1 is connected to the circuit node between R1 and C2, and the other end is connected to R2. S In this mode, L2, R4, and R3 are connected in series. The primary-side power converter converts the electrical energy input from the external power grid into high-frequency alternating current, which is then output through the primary-side compensation network and the primary-side transmitting coil. The secondary-side receiving coil receives the energy transferred by magnetic coupling, which is then rectified by the secondary-side compensation network and the secondary-side power converter before being supplied to the power battery. Because the system forms an LCC-LCC topology at this time, the output side exhibits good constant current characteristics within a certain parameter range, making it suitable for the high-current stable charging stage during the initial charging phase of the power battery. The control unit monitors the power battery terminal voltage U in real time. b , when U b When the current is below the preset switching threshold, the system will prioritize constant current charging mode to improve charging efficiency and shorten the initial charging time.

[0104] When the control unit detects the power battery terminal voltage U b When a preset switching threshold is reached or exceeded, the system switches from the constant current charging stage to the constant voltage charging stage. At this time, as follows... Figure 5As shown in (a), the mode switching unit controls the switchable compensation branch to change its connection state, enabling the system to form an LCC-S equivalent compensation topology. In this mode, the system output characteristic changes from constant current to constant voltage. The secondary power conversion unit maintains the battery terminal voltage within the target range and gradually reduces the charging current as the battery charge level increases to meet the constant voltage control requirements of the later stages of battery charging. When the battery reaches the preset full charge condition, the control unit issues a stop charging command, ending the current forward charging process. The transition between the constant current stage and the constant voltage stage is not an instantaneous hard switch, but rather a transitional control performed by the control unit in conjunction with the mode switching unit. Specifically, this can be achieved by pre-adjusting the inverter phase shift angle, gradually adjusting the duty cycle, short-term bypassing of the compensation branch, and closed-loop recovery control after switching, thereby suppressing the current surge and voltage fluctuation at the moment of switching and improving the system's stability and reliability.

[0105] like Figure 5 As shown in (b), in the vehicle-to-grid reverse feed-back mode, the system still adopts the LCC-S equivalent compensation topology, but the energy flow direction is reversed compared to the forward charging mode. When the control unit detects insufficient external grid power supply and the state of charge (SOC) of the power battery is higher than the preset feedback threshold, the control unit controls the secondary power conversion unit to switch from rectification to inverter operation, converting the DC power in the power battery into high-frequency AC power. This AC power is then transmitted to the primary side via the magnetic coupling between the secondary receiving coil and the primary transmitting coil, and finally output to the external grid after conversion by the primary power conversion unit. Through this mode, the electric vehicle can not only receive power from the grid as a power receiving terminal, but also feed back energy to the grid as a mobile energy storage unit when needed, realizing bidirectional energy interaction between the vehicle and the grid.

[0106] like Figure 6 and Figure 7 As shown, this embodiment also provides a wireless emergency power replenishment method between vehicles. Figure 6 In the diagram, VSC-A and VSC-B represent the bidirectional boost voltage source inverters for electric vehicles A and B, respectively. Each inverter consists of four inverters connected in series and then in parallel. In the diagram, V... a V b L represents the power supply of the batteries in electric vehicles A and B, respectively. fa L fb C1 represents the compensation inductance at the transmitting and receiving ends, respectively. ’ and C2 ’ L1 represents the compensation capacitors at the transmitting and receiving ends, respectively. ’ and L2 ’ C represents the coil inductance at the transmitting and receiving ends, respectively. fa C fbThese represent the filter capacitors at the transmitting and receiving ends, respectively. The following description uses VSC-A as an example to illustrate the topology connections. C fa ,L fa After VSC-A is connected in series, it is connected with V a Parallel connection, C1 ’ After being connected in series with L1, both ends are connected to the circuit nodes of VSC-A respectively. Figure 7 for Figure 6 The equivalent resonance principle diagram, where R c1 R L1 R is the internal resistance of the transmitter. C2 R L2 R is the internal resistance of the receiving end. b L b These represent the resistance and inductance on the load side, respectively. I1 and I2 are equivalent to the DC input / output currents of VSC-A and VSC-B, respectively. V1 and V2 are equivalent to the fundamental AC output voltages of the primary and secondary full-bridge circuits, respectively. L1 ’ and L2 ’ The primary and secondary inductances are respectively, M is the mutual inductance, and C1 is the self-inductance. ’ and C2 ’ For resonant compensation capacitor, V b This is the voltage of the DC voltage source. In the circuit, V1 and resistor R... c1 C1', R L1 L1 and L2 are connected in series to form a circuit. Capacitor C2' and R... c2 R b L b V b L2, R L2 The circuits are connected in series and closed. The primary and secondary sides are magnetically coupled via mutual inductance M. When the external power grid is unavailable or the vehicle is in an environment without fixed charging facilities, a first electric vehicle with remaining power can wirelessly provide emergency power to a second electric vehicle that is out of power. The power supply vehicle and the receiving vehicle are each equipped with a bidirectional voltage source converter (VSC-A) and a VSC-B, respectively. The two vehicles establish a wireless energy transmission link through their respective coupling mechanisms. The bidirectional voltage source converter on the power supply vehicle side operates in inverter mode, while the bidirectional voltage source converter on the receiving vehicle side operates in rectification mode. The control unit controls the system to operate in constant current charging mode or constant voltage charging mode based on the battery voltage state of the receiving vehicle and the current coupling state.

[0107] To improve safety and operability during vehicle-to-vehicle charging, this embodiment preferably uses a wireless emergency charging interface between vehicles. This interface includes a docking and positioning structure, a communication handshake unit, and a safety detection unit. The docking and positioning structure guides and limits the coupling position of the two vehicles, ensuring the coupling mechanism is in a power-transferable position. The communication handshake unit performs vehicle identification, charging authorization, mode negotiation, and parameter matching. The safety detection unit detects foreign objects, temperature rise, insulation status, and alignment status. If any safety condition is not met, the control unit prohibits energy transmission or actively terminates the charging process. In the specific control process, the control unit monitors the battery status of both the power supply and receiving vehicles in real time. When the receiving vehicle is in a low-charge state, the system first enters a constant-current charging mode; when the battery voltage of the receiving vehicle reaches a preset threshold, the system switches to a constant-voltage charging mode until a preset termination condition is met, at which point charging stops.

[0108] like Figure 2 As shown, this embodiment also provides a bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network, including the following steps: S1, collecting the power battery terminal voltage, power battery state of charge (SOC), grid status information, and system operation request information; S2, determining the current target operating mode as constant current forward charging mode, constant voltage forward charging mode, reverse feed-in mode, or vehicle mutual charging mode based on the collected results; S3, controlling the mode switching unit to change the access state of the switchable compensation branches in the primary-side compensation network and / or secondary-side compensation network to construct an equivalent compensation topology corresponding to the target operating mode; S4, controlling the primary-side power conversion unit and secondary-side power conversion unit to output drive signals corresponding to the target operating mode, so that the system enters the target operating mode; S5, performing transition control during the operating mode switching process to suppress current surges and voltage fluctuations; S6, in the target operating mode, performing closed-loop regulation based on the output current feedback value and / or output voltage feedback value to maintain constant current output or constant voltage output. In the constant current forward charging mode, the control system forms an LCC-LCC equivalent compensation topology and charges the power battery with constant current using the output current as the control target; in the constant voltage forward charging mode, the control system forms an LCC-S equivalent compensation topology and charges the power battery with constant voltage using the output voltage as the control target; in the reverse power supply mode, the system transmits the electrical energy in the power battery to the grid in reverse; in the vehicle mutual charging mode, the system completes wireless power replenishment between vehicles.

[0109] In one specific implementation, the control unit employs a control method combining hierarchical mode determination and execution control. The control unit first collects the battery's State of Charge (SOC), grid status information, and vehicle inter-charging request information, and then determines the system's target operating mode based on the collected parameters. In this embodiment, the control unit sets three SOC determination thresholds: a first threshold of 40%, a second threshold of 60%, and a third threshold of 80%. When the SOC is below the first threshold, the control unit prioritizes entering the vehicle-to-grid forward charging mode; when the SOC is above the first threshold but below the second threshold, the control unit maintains the charging hold state and prohibits the system from entering the reverse power supply mode; when the SOC is above the second threshold and an external grid power support demand is detected, the control unit enters the vehicle-to-grid reverse power supply mode; when the SOC is above the third threshold and a vehicle inter-charging request is received, the control unit enters the vehicle inter-charging mode.

[0110] After determining the target operating mode, the control unit further controls the mode switching unit to adjust the access status of the switchable compensation branches in the compensation network to form an equivalent compensation topology corresponding to the target operating mode, and controls the primary power conversion unit and / or the secondary power conversion unit to output the corresponding drive signal so that the system can complete forward charging, reverse power feeding or vehicle mutual charging energy transmission in the corresponding mode.

[0111] When the target operating mode is determined to be the vehicle-to-grid positive charging mode, the control unit further determines the power battery terminal voltage U. b The charging phase is determined to decide whether the system should operate in constant current charging mode or constant voltage charging mode.

[0112] The relationship is determined as follows:

[0113] (1)

[0114] (2)

[0115] Among them, M c Indicates charging phase mode; M CC Indicates constant current charging mode; M CV Indicates constant voltage charging mode; U th This indicates the threshold voltage for switching between constant current and constant voltage.

[0116] When the system needs to participate in vehicle-to-grid interaction, the control unit makes a determination based on the grid power support requirements and whether the power battery's state of charge has entered reverse feed-in mode.

[0117] The determination relationship is:

[0118] (3)

[0119] Among them, SOC fb This indicates the reverse power feed-in threshold. When the state of charge of the power battery exceeds this threshold, the system is capable of transmitting electrical energy back to the grid; M represents the operating mode; M V2G This indicates the vehicle-to-grid mode.

[0120] In this mode, the power direction of the system satisfies:

[0121] (4)

[0122] Or equivalent to:

[0123] (5)

[0124] Among them, P grid This represents the system's active power relative to the grid side; it takes a negative value when the system supplies power to the grid. P bat→grid This indicates the power transmitted from the battery to the power grid.

[0125] When the external power grid is unavailable or there is a vehicle mutual charging request, the control unit determines the vehicle mutual charging mode.

[0126] (6)

[0127] Among them, M V2V Indicates vehicle charging mode, SOC v2v This indicates the permissible threshold for vehicle cross-charging mode, which must satisfy:

[0128] (7)

[0129] This ensures that the vehicles providing energy still have sufficient remaining charge after the mutual charging is completed.

[0130] Before mode switching, the control unit first determines whether the system meets the safety conditions required for compensation network handover. The safe handover window can be defined as:

[0131] (8)

[0132] (9)

[0133] (10)

[0134] Where P represents the instantaneous transmission power of the system; P sw Indicates the power threshold that allows mode switching; I coil Indicates the amplitude of the coil current; I sw Indicates the coil current threshold that allows mode switching; U ref Indicates the reference voltage before switching; εu This indicates the permissible voltage deviation threshold.

[0135] When the current operating mode needs to be switched to the target operating mode, the control unit first pre-adjusts the phase shift angle of the inverter and / or active rectifier, so that the system gradually transitions from the current high-power transmission state to a safe switching state. The phase shift angle pre-adjustment law can be expressed as:

[0136] (11)

[0137] Where φ(k) represents the actual phase shift angle in the k-th control cycle; φ ref Indicates the target safety phase angle; △φ max This represents the maximum allowable rate of change of phase angle within a single control cycle; sat(·) represents the amplitude limiting function.

[0138] The phase shift angle does not abruptly reach the target value, but rather gradually approaches the target safe phase angle according to a preset slope to limit the rate of power change and the rate of coil current change. Preferably, when the system switches between forward charging modes, the target safe phase angle corresponds to a low-power transmission state; when the system switches between forward charging mode and reverse feeding mode, the target safe phase angle corresponds to a zero-power transmission state or a near-zero-power transmission state.

[0139] If the system's transmission power can be expressed as a function of the phase shift angle:

[0140] (12)

[0141] The control unit adjusts Φ to achieve the following:

[0142] (13)

[0143] This will cause the system to enter the safe switching window.

[0144] After the phase shift angle is pre-adjusted to bring the system into the safe switching window, the control unit further gradually adjusts the duty cycle of the bridge inverter to reduce the energy injection rate on the bus side before and after the compensation network switching. The duty cycle adjustment law can be expressed as:

[0145] (14)

[0146] Where d(k) represents the actual duty cycle in the k-th control cycle; d ref Indicates the buffer duty cycle; △d max This indicates the maximum allowable change in duty cycle within a single control cycle.

[0147] To limit voltage and current overshoot, the duty cycle change rate must satisfy:

[0148] (15)

[0149] (16)

[0150] Where, γ u Indicates the allowable rate of change threshold of battery terminal voltage; γ i This indicates the allowable rate of change threshold of the coil current.

[0151] Once the phase shift angle and duty cycle both enter the safe switching window, the control unit activates the mode switching unit to change the access status of switchable compensation branches in the primary and / or secondary compensation networks, thereby constructing an equivalent compensation topology corresponding to the target operating mode.

[0152] After the compensation network switch is completed, the control unit maintains a safe phase angle and / or a buffer duty cycle minus a preset hold time T. h Then, the control input is restored to the steady-state operating point corresponding to the target operating mode. The restoration law can be expressed as follows:

[0153] (17)

[0154] (18)

[0155] Where, φ tar and d tar These represent the target phase shift angle and target duty cycle corresponding to the target operating mode, respectively; △φ rec and △d rec These represent the step size of the phase shift angle and the step size of the duty cycle during the recovery phase.

[0156] When the system operates in constant current charging mode, the control objective is to make the output current I0 track the constant current setpoint I. ref Its current error is defined as:

[0157] (19)

[0158] The control unit can perform closed-loop adjustment of the phase shift angle and / or duty cycle based on the error, and the control law is expressed as:

[0159] (20)

[0160] Among them, u i (k) represents the control quantity in constant current mode; K pi and K ii The proportional and integral coefficients of the current loop are respectively.

[0161] The control quantity u i (k) Mappable phase shift angle command φ* Or duty cycle instruction d * ,Right now:

[0162] (twenty one)

[0163] or

[0164] (twenty two)

[0165] When the system operates in constant voltage charging mode, the control objective is to reduce the terminal voltage U of the power battery. b Tracking constant pressure setpoint U ref Its voltage error is defined as:

[0166] (twenty three)

[0167] The corresponding closed-loop control law is:

[0168] (twenty four)

[0169] Among them, u u (k) represents the control quantity under constant pressure mode; K pu and K iu These represent the proportional coefficient and integral coefficient of the voltage loop, respectively.

[0170] The control quantity u u (k) can be further converted into a phase shift angle reference value or a duty cycle reference value, that is:

[0171] (25)

[0172] or

[0173] (26)

[0174] When the system operates in vehicle-to-grid reverse power supply mode, the control objective is to maximize the feedback power P. fb Tracking reference power P ref Its power error is defined as:

[0175] (27)

[0176] The control law can be expressed as:

[0177] (28)

[0178] Among them, K pp and K ip These represent the proportional and integral coefficients of the power loop, respectively.

[0179] To ensure the power battery does not over-discharge, the control unit also meets the following constraints:

[0180] (29)

[0181] When SOC is detected <SOC min When this occurs, the control unit commands to reduce the feedback power or exit the reverse feed mode.

Claims

1. A bidirectional wireless charging device for electric vehicles based on a reconfigurable compensation network, characterized in that, It includes a control unit, a primary-side power conversion unit, a secondary-side power conversion unit, a primary-side transmitting coil, a secondary-side receiving coil, a primary-side compensation network, a secondary-side compensation network, a mode switching unit, and a communication unit. The primary-side power conversion unit is located on the wireless charging transmitting side and connected to the external power grid. It is used to convert the power frequency AC power input from the external power grid into high-frequency AC power after rectification and inversion, and then wirelessly transmit it to the secondary side through the primary-side transmitting coil. The secondary-side power conversion unit is located on the vehicle-mounted energy storage side and connected to the power battery. It is used to rectify and regulate the high-frequency power received by the secondary-side receiving coil to charge the power battery. In reverse feed-in mode, the secondary-side power conversion unit can also operate in inverter mode, converting the DC power in the power battery into high-frequency AC power, which is then transmitted to the primary side through a coupling mechanism and then fed back to the external power grid.

2. The bidirectional wireless charging device for electric vehicles based on a reconfigurable compensation network according to claim 1, characterized in that, The primary-side transmitting coil and the secondary-side receiving coil form a magnetic coupling mechanism, and wireless power transmission between them is achieved through an alternating magnetic field. The primary-side compensation network is set between the primary-side power conversion unit and the primary-side transmitting coil, and the secondary-side compensation network is set between the secondary-side receiving coil and the secondary-side power conversion unit. The primary-side compensation network and / or the secondary-side compensation network are provided with switchable compensation branches. The mode switching unit controls the access, removal or bypass of the switchable compensation branches to enable the system to form different equivalent compensation topologies in different operating modes.

3. The bidirectional wireless charging device for electric vehicles based on a reconfigurable compensation network according to claim 1, characterized in that, The control unit adopts a control method that combines hierarchical mode judgment and execution control. The control unit first collects the power battery state of charge (SOC), grid status information and vehicle mutual charging request information, and then determines the target operating mode of the system based on the collected parameters.

4. The bidirectional wireless charging device for electric vehicles based on a reconfigurable compensation network according to claim 1, characterized in that, The control unit sets three SOC (State of Charge) thresholds. When the SOC is below the first threshold, the control unit prioritizes entering the vehicle-to-grid (V2G) forward charging mode. When the SOC is above the first threshold but below the second threshold, the control unit maintains the charging hold state and prohibits the system from entering the reverse power supply mode. When the SOC is above the second threshold and a power support requirement is detected from the external power grid, the control unit enters the V2G reverse power supply mode. When the SOC is above the third threshold and a vehicle-to-grid (V2G) mutual charging request is received, the control unit enters the vehicle-to-grid mutual charging mode.

5. A bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network, characterized in that, Includes the following steps: S1. Collect power battery terminal voltage, power battery state of charge (SOC), grid status information, and system operation request information; S2. Based on the collected results, determine whether the current target operating mode is constant current forward charging mode, constant voltage forward charging mode, reverse power feeding mode, or vehicle mutual charging mode. S3. The control mode switching unit changes the access status of switchable compensation branches in the primary side compensation network and / or secondary side compensation network to construct an equivalent compensation topology corresponding to the target operating mode. S4. Control the primary-side power conversion unit and the secondary-side power conversion unit to output drive signals corresponding to the target operating mode, so that the system enters the target operating mode; S5. Perform transition control during the operation mode switching process to suppress current surges and voltage fluctuations; S6. In the target operating mode, closed-loop regulation is performed based on the output current feedback value and / or output voltage feedback value to maintain constant current output or constant voltage output.

6. The bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network according to claim 5, characterized in that, In step S2, under constant current forward charging mode, the control system forms an LCC-LCC equivalent compensation topology and charges the power battery with constant current using the output current as the control target; under constant voltage forward charging mode, the control system forms an LCC-S equivalent compensation topology and charges the power battery with constant voltage using the output voltage as the control target; under reverse power supply mode, the system transmits the electrical energy in the power battery to the grid in reverse; under vehicle mutual charging mode, the system completes wireless power replenishment between vehicles.

7. The bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network according to claim 5, characterized in that, In step S2, when the target operating mode is determined to be the vehicle-to-grid power forward charging mode, the control unit determines the power battery terminal voltage U. b The charging stage is determined, and the determination relationship is as follows: (1) (2) Among them, M c Indicates charging phase mode; M CC Indicates constant current charging mode; M CV Indicates constant voltage charging mode; U th This indicates the threshold voltage for switching between constant current and constant voltage. When the system needs to participate in vehicle-to-grid interaction, the control unit determines whether to participate based on the grid power support requirements and whether the power battery's state of charge has entered reverse feed-in mode. The determination relationship is as follows: (3) Among them, SOC fb This indicates the reverse power feed-in threshold. When the state of charge of the power battery exceeds this threshold, the system is capable of transmitting electrical energy back to the grid; M represents the operating mode; M V2G Indicates vehicle-to-grid mode; In this mode, the power direction of the system satisfies: (4) Or equivalent to: (5) Among them, P grid This represents the system's active power relative to the grid side; it takes a negative value when the system supplies power to the grid. P bat→grid This indicates the power transmitted from the battery to the power grid; When the external power grid is unavailable or a vehicle cross-charging request exists, the control unit determines the vehicle cross-charging mode: (6) (7) Among them, M V2V Indicates vehicle charging mode, SOC v2v This indicates the allowed threshold for vehicle-to-vehicle charging mode.

8. The bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network according to claim 5, characterized in that, Before mode switching in step S3, the control unit first determines whether the system meets the safety conditions required for compensation network switching. The safe switching window can be defined as follows: (8) (9) (10) Where P represents the instantaneous transmission power of the system; P sw Indicates the power threshold that allows mode switching; I coil Indicates the amplitude of the coil current; I sw Indicates the coil current threshold that allows mode switching; U ref Indicates the reference voltage before switching; ε u Indicates the allowable voltage deviation threshold; When the current operating mode needs to be switched to the target operating mode, the control unit first pre-adjusts the phase shift angle of the inverter and / or active rectifier, so that the system gradually transitions from the current high-power transmission state to the safe switching state. The phase shift angle pre-adjustment law can be expressed as: (11) Where φ(k) represents the actual phase shift angle in the k-th control cycle; φ ref Indicates the target safety phase angle; △φ max This represents the maximum allowable rate of change of phase angle within a single control cycle; sat(·) represents the limiting function; When the system switches between forward charging modes, the target safe phase angle corresponds to a low-power transmission state; when the system switches between forward charging and reverse feeding modes, the target safe phase angle corresponds to a zero-power transmission state or a near-zero-power transmission state, provided that the system transmission power can be expressed as a function of the phase shift angle: (12) The control unit adjusts Φ to achieve the following: (13) This allows the system to enter a safe switching window; After the phase shift angle is pre-adjusted to bring the system into the safe switching window, the control unit further gradually adjusts the duty cycle of the bridge inverter to reduce the energy injection rate on the bus side before and after the compensation network switching. The duty cycle adjustment law can be expressed as: (14) Where d(k) represents the actual duty cycle in the k-th control cycle; d ref Indicates the buffer duty cycle; △d max This indicates the maximum allowable change in duty cycle within a single control cycle; To limit voltage and current overshoot, the duty cycle change rate must satisfy: (15) (16) Where, γ u Indicates the allowable rate of change threshold of battery terminal voltage; γ i This indicates the threshold for the allowable rate of change of coil current; Once the phase shift angle and duty cycle both enter the safe switching window, the control unit activates the mode switching unit to change the access status of switchable compensation branches in the primary and / or secondary compensation networks, thereby constructing an equivalent compensation topology corresponding to the target operating mode.

9. The bidirectional wireless charging control method for electric vehicles based on a reconfigurable compensation network according to claim 5, characterized in that, Step S4 includes, after the compensation network handover is completed, the control unit maintains a safe phase angle and / or a buffer duty cycle minus a preset hold time T. h Then, the control input is restored to the steady-state operating point corresponding to the target operating mode. The restoration law is expressed as follows: (17) (18) Where, φ tar and d tar These represent the target phase shift angle and target duty cycle corresponding to the target operating mode, respectively; △φ rec and △d rec These represent the step size of the phase shift angle change and the step size of the duty cycle change during the recovery phase, respectively. When the system operates in constant current charging mode, the control objective is to make the output current I0 track the constant current setpoint I. ref Its current error is defined as: (19) The control unit can perform closed-loop adjustment of the phase shift angle and / or duty cycle based on the error, and the control law is expressed as: (20) Among them, u i (k) represents the control quantity in constant current mode; K pi and K ii The proportional and integral coefficients of the current loop, respectively; The control quantity u i (k) Mappable phase shift angle command φ * Or duty cycle instruction d * ,Right now: (21) or (22) When the system operates in constant voltage charging mode, the control objective is to reduce the terminal voltage U of the power battery. b Tracking constant pressure setpoint U ref Its voltage error is defined as: (23) The corresponding closed-loop control law is: (24) Among them, u u (k) represents the control quantity under constant pressure mode; K pu and K iu These represent the proportional and integral coefficients of the voltage loop, respectively. The control quantity u u (k) can be further converted into a phase shift angle reference value or a duty cycle reference value, that is: (25) or (26) When the system operates in vehicle-to-grid reverse power supply mode, the control objective is to maximize the feedback power P. fb Tracking reference power P ref Its power error is defined as: (27) The control law can be expressed as: (28) Among them, K pp and K ip These represent the proportional gain and integral gain of the power loop, respectively. The control unit also satisfies the following constraints: (29) When SOC is detected <SOC min When this occurs, the control unit commands to reduce the feedback power or exit the reverse feed mode.

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