Three-port cooperative bidirectional wireless power transmission system and control method thereof

Abstract

The application relates to the technical field of electric energy transmission, and particularly discloses a three-port cooperative bidirectional wireless electric energy transmission system and a control method thereof. The system comprises a power grid side, an airborne side energy storage and a load side port. An FSBB converter is arranged in the airborne side port, which is connected with an airborne front side converter, an airborne battery load and the load side port, so that three-port integration is realized. The control method collects key physical quantities of the system in real time, calculates voltage gain and critical gain determined by mutual inductance and compensation inductance; according to the connection state of the grid side, the gain comparison result and the direction of the inductance current in the rear stage, the system is decided to enter a forward power supply mode, an energy feedback mode or an independent power supply mode; the front stage phase shift angle locking, the rear stage duty cycle and phase shift ratio joint regulation and disturbance observation efficiency optimization are respectively executed corresponding to each mode, so that port constant voltage output and efficiency online optimization are realized. The application reduces the number of switching devices and the system volume, and significantly improves the system integration, switching stability and anti-deviation constant voltage output capacity.

Description

Technical Field

[0001] This invention relates to the field of power transmission technology, and in particular to a three-port cooperative bidirectional wireless power transmission system and its control method. Background Technology

[0002] With the large-scale application of new energy mobile equipment (such as electric vehicles, drones, and mobile robots), higher demands are being placed on flexible and efficient energy supply methods. Wireless Power Transfer (WPT) technology, with its advantages of electrical isolation, plug-and-play functionality, and strong environmental adaptability, has gradually become an important technical path for static charging and dynamic power supply of various mobile equipment. In typical application scenarios, mobile equipment energy interaction systems usually involve three key energy ports: the grid-side port, serving as a fixed energy source or feedback target; the onboard port, serving as the mobile equipment's own energy storage unit; and the load-side port, serving as an independent power supply target for external or accompanying electrical equipment. There are multiple energy interaction needs among these three: when mobile equipment docks at a refueling point, the grid can simultaneously supply power to the onboard energy storage and external electrical equipment; mobile equipment can also feed stored energy back to the grid; and after leaving a fixed refueling point, the onboard energy storage can also independently provide emergency power to external electrical equipment. This presents new challenges to the port integration and energy dispatch flexibility of the energy supply system.

[0003] Existing wireless power transfer technologies have the following main shortcomings in three-port applications:

[0004] First, the port integration method lacks efficient multiplexing design. To simultaneously achieve power distribution among the three ports—grid side, onboard energy storage, and load side—existing systems typically use multiple independent converters connected to each port, or configure a separate compensation network for each port. This non-multiplexed topology results in a large number of switching devices, a large system size, and high cost. Furthermore, the multi-stage power conversion introduces additional losses, reducing overall transmission efficiency and hindering equipment integration and miniaturization.

[0005] Secondly, the stability of the multi-mode switching process is poor. When the existing system switches between modes such as equipment docking for charging, energy feedback to the grid, and power supply to the load side after disconnection from the supply point, the control variables (such as phase shift angle and duty cycle) need to be adjusted significantly by step, which can easily cause voltage and current overshoot and power transmission oscillation. The switching process is not smooth enough, which affects the system reliability and the safety of the load equipment.

[0006] Third, multi-port efficiency optimization is limited. Existing research lacks systematic mathematical modeling of the power coupling characteristics between ports, and efficiency optimization is mostly limited to a single transmission path, failing to establish a unified efficiency model covering multiple operating modes. Under multi-mode operation, it is difficult to coordinate the parameters of each port to the global efficiency optimum, resulting in low transmission efficiency of the system under certain operating conditions.

[0007] Fourth, the output constant voltage characteristic and anti-offset capability are insufficient. When the relative offset between the transmitting coil and the receiving coil causes a change in mutual inductance, the port output voltage of the existing system fluctuates significantly. Especially in the context of multi-port coupling, the cross-coupling effect between the coils further exacerbates the parameter detuning. The traditional single compensation network is unable to simultaneously meet the constant voltage output requirements of multiple ports, weakening the power supply quality of the system under dynamic operating conditions. Summary of the Invention

[0008] This invention provides a three-port cooperative bidirectional wireless power transfer system and its control method. The technical problem it solves is: how to achieve flexible power allocation and bidirectional flow between ports based on a clear understanding of the energy interaction requirements of the three ports, while improving system integration, switching stability, multi-mode efficiency coordination, and anti-offset constant voltage output capability.

[0009] To address the above technical problems, this invention provides a three-port cooperative bidirectional wireless power transmission system, including a grid-side port, an airborne-side port, a load-side port, and a commutation control circuit.

[0010] The grid-side port includes a DC power supply, a grid-side converter, a grid-side compensation network, and a grid-side coil connected in sequence. ;

[0011] The airborne side port includes airborne front-side coils connected in sequence. The system includes an airborne front-side compensation network, an airborne front-side converter, an airborne rear-side converter, and an airborne battery load. It also includes an airborne rear-side compensation network and an airborne rear-side coil connected to the airborne rear-side converter. ;

[0012] The airborne rear-side converter is a four-switch Buck-Boost converter, or FSBB converter, comprising a first switching transistor. Second switching transistor The left half-bridge, and the third switch tube and the fourth switching transistor The right half-bridge is formed, with the midpoint of the left half-bridge being point A and the midpoint of the right half-bridge being point B; the left half-bridge is connected to the airborne front-side converter, the right half-bridge is connected to the airborne battery load, and the midpoints A of the left half-bridge and B of the right half-bridge are connected to the airborne rear-side compensation network.

[0013] The load-side port includes load coils connected in sequence. , load compensation network, load-side converter and battery load;

[0014] The wire-side coil and the airborne front coil The mutual inductance of the first magnetic circuit mechanism that constitutes mutual coupling is expressed as follows: The airborne rear coil and the load coil The mutual inductance of the second magnetic circuit mechanism that forms a mutual coupling is expressed as follows: ;

[0015] The commutation control circuit is connected to the grid-side converter, the airborne front-side converter, and the FSBB converter. It is used to control the switching state of each switch in the grid-side converter, the airborne front-side converter, and the FSBB converter, so as to control the system to switch between different operating modes.

[0016] Preferably, the operating mode includes:

[0017] In the first mode, the grid-side port supplies power to both the airborne-side port and the load-side port simultaneously;

[0018] In the second mode, the airborne side port supplies power to the grid side port;

[0019] In the third mode, the airborne side port supplies power to the load side port.

[0020] Preferably, the grid-side compensation network is an LCC compensation network, comprising grid-side compensation inductors connected in series. Parallel compensation capacitors on the grid side and the wire-side coil Series-connected grid-side series compensation capacitors ;

[0021] The airborne front compensation network is an S-compensation network, including the airborne front coil. Series-connected airborne front-side series compensation capacitor ;

[0022] The airborne rear-side compensation network is an LC compensation network, including the airborne rear-side coil. Series-connected airborne rear-side compensation inductors and the airborne rear coil Parallel-connected airborne rear-side compensation capacitors ;

[0023] The load compensation network is an S-compensation network, including the load coil. Series-connected load series compensation capacitor .

[0024] This invention also provides a control method for a three-port cooperative bidirectional wireless power transfer system, the key of which includes the following steps:

[0025] S1. Real-time acquisition of grid-side inverter AC output voltage Airborne preamplifier AC input voltage Airborne rear-side compensation inductor current Mutual induction ;

[0026] S2. Based on the vehicle's entry and exit status at the charging station and the parameters collected in step S1, identify the current operating mode of the system.

[0027] S3. Implement differentiated closed-loop voltage regulation control for different identified operating modes and optimize system transmission efficiency online.

[0028] Further, step S2 specifically includes:

[0029] S21. Detect the physical connection status of the grid-side port. If the vehicle leaves the charging station and the grid-side port is disconnected, the system will directly enter the third mode. If the vehicle enters the charging station, proceed to the next step.

[0030] S22, Calculate voltage gain Critical voltage gain and current RMS value of fundamental current Average value within a preset time period , , Voltage and The effective value of the fundamental voltage, if and If the system is determined to be in the second mode, then it is in the first mode; otherwise, it is in the first mode.

[0031] Furthermore, step S3 specifically includes:

[0032] S31. When the first mode is determined, the voltage is fixed. fundamental component of Leading voltage fundamental component of Outward phase angle The duty cycle of the FSBB converter is adjusted in a closed loop to achieve a constant voltage output from the onboard battery load and maximize efficiency while maintaining a constant voltage output. Compared to moving ;

[0033] S32. When the system is determined to be in the second mode, the voltage is fixed. fundamental component of Leading voltage fundamental component of Outward phase angle The duty cycle of the FSBB converter is adjusted in a closed loop to achieve constant voltage feedback output at the grid-side port, with the goal of zeroing out the current. ;

[0034] S33. When the system determines that it is in the third mode, shut down the airborne front-side converter and, with the goal of achieving constant voltage output from the battery load, adjust the duty cycle of the FSBB converter in a closed loop. Compared to moving At the same time, the perturbation observation method is used to match the optimal load operating point to achieve maximum efficiency.

[0035] Furthermore, step S31 specifically includes:

[0036] S311, Fixed Outward Phase Angle The value is zero, thus determining the desired voltage of the airborne battery load. Desired voltage of battery load The expected voltage between points A and B ;

[0037] S312, Based on the voltage of the onboard battery load Battery load voltage and the voltage between points A and B Duty cycle of the FSBB converter Compared to moving The relationship between the two, and the determination of expectations , and The corresponding duty cycle Compared to moving ;

[0038] S313, Detect current duty cycle Compared to moving voltage under , If the fluctuation is within the allowable range, then fine-tune the duty cycle using the preset step size. Proceed to the next step; otherwise, return to step S311 to redetermine the desired voltage. ;

[0039] S314. Detect the duty cycle for fine-tuning in the current mode. If the system efficiency is improved, return to step S313; otherwise, end the process.

[0040] Furthermore, the voltage of the onboard battery load Battery load voltage and the voltage between points A and B Duty cycle of the FSBB converter Compared to moving The relationship between them is:

[0041] , ,

[0042] in, This represents the fundamental RMS value of the input voltage to the airborne rear-side converter.

[0043] Further, step S32 specifically includes:

[0044] S321, Fixed outward phase angle The value is zero, which determines the desired voltage at the grid-side port. ;

[0045] S322, Desired voltage based on grid-side port and the voltage of the current onboard battery load Determine the duty cycle ;

[0046] S323, S323, Detect current duty cycle Voltage at the downstream grid port If the fluctuation is within the allowable range, then fine-tune the duty cycle using the preset step size. Proceed to the next step; otherwise, return to the previous step to re-detect the voltage of the onboard battery load. Then determine the duty cycle ;

[0047] S324. Detect the duty cycle for fine-tuning in the current mode. Check if the system efficiency has improved. If so, return to step S323; otherwise, end.

[0048] Furthermore, step S33 specifically includes:

[0049] S331. Turn off the grid-side converter and determine the desired voltage of the battery load. The expected voltage between points A and B ;

[0050] S332, Based on the desired voltage between points A and B and the voltage of the current onboard battery load Determine the duty cycle Compared to moving The relationship between them is used to determine a set of duty cycles. Compared to moving ;

[0051] S333, Detect current duty cycle Compared to moving voltage under , If the fluctuation is within the allowable range, then the battery load is perturbed and the process proceeds to the next step; otherwise, return to the previous step and redetermine a new duty cycle. Compared to moving ;

[0052] S334. Detect whether the system efficiency has improved after load disturbance in the current mode. If yes, return to step S333; otherwise, end.

[0053] This invention provides a three-port cooperative bidirectional wireless power transfer system and its control method. By introducing a four-switch Buck-Boost converter as a key multiplexing unit, it simultaneously integrates DC bidirectional power transfer and wireless power transfer functions within a single power converter. This significantly reduces the number of switching devices, lowers system size and multi-stage conversion losses, and substantially improves the integration and power density of the three-port system from a hardware architecture perspective. Based on a systematic modeling of the front-stage and rear-stage resonant networks, the optimal setting of the front-stage phase shift angle is clarified, simplifying the judgment criteria for power flow direction and providing precise mathematical constraints for mode switching. This ensures smooth voltage and current transitions during switching, avoiding overshoot and oscillation. Differentiated closed-loop control strategies are designed for three operating modes: when the grid is involved, the front-stage phase shift angle is fixed and the duty cycle and phase shift ratio are adjusted in coordination, while taking into account the constant voltage output of each port and the overall system efficiency; when the grid is disconnected, the front-stage converter is blocked, and only the rear-stage parameters are adjusted to maintain constant load voltage, and an online optimization mechanism is introduced to automatically track the optimal efficiency point. This hierarchical control architecture maps theoretical criteria to execution actions one by one, achieving seamless switching between multiple modes and global efficiency coordination. At the same time, it effectively suppresses voltage drops caused by coil offset through closed-loop dynamic compensation, significantly enhancing the system's anti-offset capability and power supply reliability. It can be widely used in scenarios requiring multi-port energy interaction, such as wireless charging of electric vehicles, collaborative power supply for drones, and flexible power replenishment for mobile robots. Attached Figure Description

[0054] Figure 1 This is a circuit diagram of a three-port cooperative bidirectional wireless power transmission system provided in an embodiment of the present invention;

[0055] Figure 2 This is a power flow diagram of the three operating modes provided in the embodiments of the present invention;

[0056] Figure 3 This is an equivalent circuit model diagram of the network-side port-vehicle-side front-end port system provided in an embodiment of the present invention;

[0057] Figure 4This is an equivalent circuit model diagram of the vehicle-side rear-stage port-UAV-side port system provided in an embodiment of the present invention;

[0058] Figure 5 This is a flowchart of the system control method provided in an embodiment of the present invention;

[0059] Figure 6 The output voltage in Mode 1 provided by the embodiment of the present invention With inductor current Waveform diagram;

[0060] Figure 7 The output voltage in mode 2 provided in this embodiment of the invention. With inductor current Waveform diagram;

[0061] Figure 8 The transmission efficiency of the high-voltage battery system between the grid side and the vehicle side under Mode 1 provided in this embodiment of the invention is... picture;

[0062] Figure 9 The transmission efficiency between the vehicle-side high-voltage battery system and the grid side in Mode 2 provided by the embodiments of the present invention is... picture;

[0063] Figure 10 The transmission efficiency between the vehicle-side high-voltage battery port and the UAV-side battery system in Mode 3 provided by the embodiments of the present invention is... picture. Detailed Implementation

[0064] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0065] I. System Structure Description

[0066] This invention first provides a three-port cooperative bidirectional wireless power transfer system, the circuit structure of which is as follows: Figure 1 As shown, it includes the grid-side port, the airborne-side port, the load-side port, and the commutation control circuit. Figure 1 (Not shown in the image). The grid-side port includes, in sequence, a DC power supply 1, a grid-side converter 2, a grid-side compensation network 3, and a grid-side coil. The airborne side port includes airborne front-side coils connected in sequence. The system includes an airborne front compensation network 5, an airborne front converter 6, an airborne rear converter 7, an airborne battery load 8, and also includes an airborne rear compensation network 9 connected to the airborne rear converter 7, and an airborne rear coil. The load-side port includes load coils connected in sequence. 11. Load compensation network, 12. Load-side converter, 13. Commutation control circuit connected to grid-side converter 2, airborne front converter 6, and airborne rear converter 7 is used to control the switching transistors therein, so that the system can operate in the first mode (mode 1), the second mode (mode 2), or the third mode (mode 3).

[0067] wire side coil and the airborne front coil The mutual inductance of the first magnetic circuit mechanism 4, which constitutes mutual coupling, is expressed as follows: Airborne rear coil and load coil The mutual inductance of the second magnetic circuit mechanism 10, which constitutes mutual coupling, is expressed as follows: The equivalent series resistance of each coil is expressed as follows: , , and The output voltage of DC power supply 1 is expressed as: This is typically provided by a front-end power factor correction (PFC) converter. The grid-side converter 2 uses MOSFETs... The full-bridge converter constructed has an output current of Output voltage is The grid-side compensation network 3 uses grid-side compensation inductors. (Its current is) The equivalent series resistance is ), grid-side parallel compensation capacitor Grid-side series compensation capacitor The LCC compensation network is formed, in which The current is , and The current is The airborne front-side compensation network 5 adopts the same... Series-connected airborne front-side series compensation capacitor Together with the network-side compensation network 3, it forms an LCC-S type compensation topology. and The current is The airborne front-side converter 6 uses MOSFETs. The input voltage of the constructed full-bridge converter is .

[0068] Airborne rear-side converter 7 includes filter capacitors. and by MOSFET The four-switch Buck-Boost converter (FSBB converter for short) is constructed. , Forming the left half of the bridge, , This forms the right half of the bridge. Point A is the midpoint of the left half of the bridge, and point B is the midpoint of the right half of the bridge. This is the voltage between points A and B. This voltage is an asymmetrical PWM wave with DC bias, serving as the bridge connecting the FSBB converter to the subsequent LCL resonant network. The onboard battery load 8 is connected to the right half-bridge, including the filter capacitor. (Voltage (i.e., the input voltage of the FSBB converter) and the onboard battery pack (voltage) The airborne rear-side compensation network 9 includes... Series compensating inductor (current) internal resistance ) and with (current) Parallel compensation capacitors These three elements constitute an LCL resonant network. The load compensation network 11 uses the same components as the load coil. (current) series capacitors This constitutes S-compensation. The load-side converter 12 uses a diode rectifier, and the battery load 13 includes a filter capacitor. and load battery pack (voltage) The equivalent load of the battery pack is .

[0069] The aforementioned network-side compensation network 3 constitutes an LCC compensation network, the airborne front-side compensation network 5 constitutes an S compensation network, the airborne rear-side compensation network 9 constitutes an LC compensation network, and the load compensation network 11 constitutes an S compensation network.

[0070] The power flow of the system in its three operating modes is as follows: Figure 2 As shown, Mode 1 involves the grid-side port simultaneously supplying power to both the airborne and load-side ports (e.g., when an electric vehicle is parked and charging); Mode 2 involves the airborne-side port feeding energy back to the grid-side port; and Mode 3 involves the airborne-side port supplying power solely to the load-side port (e.g., when an electric vehicle is driving and supplying power to a drone). The commutation control circuit achieves mode switching and power flow control by controlling the state of each converter switch.

[0071] II. System Theoretical Analysis

[0072] (I) Reactive power analysis and determination of external phase angle of the front-end LCC-S system

[0073] Figure 3 The fundamental equivalent circuit of the transmission stage at both the grid side and the vehicle side is presented, employing an LCC-S compensation topology. The system operating angular frequency is assumed to be... The reactance parameters are defined as follows: To compensate for inductance resistance, Parallel capacitor Capacitive resistance, For mutual induction resistance, The total reactance of the parallel branch on the grid side, For the airborne front coil resistance, Series capacitor The capacitive reactance. Based on the AC output voltage of grid-side converter 2. fundamental component of As the reference phasor, it is represented as ( for If the effective value is 6, then the AC input voltage of the airborne front converter 6 is 6. fundamental component of ( for (effective value), where for Advanced The outward phase shift angle. Through Fourier series expansion, the fundamental expressions for the AC terminal voltages of the grid-side and vehicle-side converters are:

[0074] (1)

[0075] To achieve resonance between the network-side and vehicle-side front-end systems, the angular frequency of its full-bridge converter... The parameters of the resonant network should satisfy:

[0076] (2)

[0077] Based on Kirchhoff's voltage and current laws, write the circuit equation matrix for the grid-side and vehicle-side front-end systems:

[0078] (3)

[0079] in, For compensating inductance flowing through the grid side The current phasor, Parallel compensation capacitors flowing through the grid side The current phasor, For the flow through the wire side coil The current phasor, For flow through the airborne front coil The current phasor, Compensating inductor for grid side The equivalent series resistance. For wire side coil The equivalent series resistance. For the airborne front coil The equivalent series resistance. Solving the above matrix equation, we can obtain the expressions for the phasors of the currents in each branch as follows:

[0080] (4)

[0081] Among them, custom parameters .

[0082] From the above current expression, the reactive power at the AC terminal of the grid-side full-bridge converter can be derived. :

[0083] (5)

[0084] In this context, the asterisk (*) in the upper right corner of the phasor indicates complex conjugate (the same applies in subsequent formulas). This indicates taking the imaginary part.

[0085] Similarly, the reactive power at the AC terminal of the front-stage full-bridge converter on the vehicle side is:

[0086] (6)

[0087] Observe equations (5) and (6), both of which contain Factor. When the system is in a fully resonant state, take... Can make At this point, reactive power reaches its minimum value, and active power reaches its maximum value. Therefore, this invention fixes the external phase shift angle to [value missing]. This serves as a fundamental constraint for the upstream control, ensuring that the upstream always operates in a state of low reactive power loss.

[0088] (II) Expression of active power of upstream stage and criterion for mode switching

[0089] Further derivation of the upstream active power. The active power at the AC terminal of the grid-side full-bridge converter is:

[0090] (7)

[0091] in, This indicates taking the real part.

[0092] The active power of the AC terminal of the front-stage full-bridge converter on the vehicle side is:

[0093] (8)

[0094] Active power The sign determines the direction of energy flow: when At this time, energy flows from the mesh side to the vehicle side (Mode 1); when At this time, energy flows back from the vehicle side to the grid side (Mode 2). Define voltage gain. Substituting equation (8) into the critical condition The critical gain can be solved to satisfy:

[0095] (9)

[0096] Since the coil's internal resistance is much smaller than its reactance, it can be ignored. After that, the critical gain simplifies to:

[0097] (10)

[0098] Equation (10) is one of the core criteria for front-end mode switching: when the actual voltage gain hour, The system is in mode 1; when hour, The system is in mode 2.

[0099] (III) Voltage transformation relationship and constant voltage control of the subsequent FSBB converter

[0100] The subsequent FSBB converter employs a strategy combining pulse width modulation (PWM) and phase-shift control. Switching transistors... , The driving signals are complementary. , Complementary, and and Simultaneous conduction with the same conduction time. Let the duty cycle be... (Right now , (conduction duty cycle), shift ratio is (correspond , Phase shift angle between ,satisfy According to the inductor volt-second balance principle, the DC voltage across the FSBB converter satisfies:

[0101] (11)

[0102] Equation (11) shows that by adjusting the duty cycle The vehicle battery voltage can be adjusted. This achieves constant voltage output.

[0103] Regarding the voltage between points A and B of the FSBB converter (Point A is the midpoint of the left half-bridge, and point B is the midpoint of the right half-bridge). Its waveform is an asymmetrical PWM wave with DC bias. The expression for its fundamental effective value, obtained through Fourier decomposition, is as follows:

[0104] (12)

[0105] Equation (12) shows Simultaneously affected by duty cycle Compared to moving Control, the two constitute two independent degrees of freedom for subsequent control: Mainly adjusts the DC voltage amplitude. It is mainly used to adjust the effective value of AC voltage.

[0106] (iv) Voltage characteristic analysis of the subsequent LCL-S system

[0107] Figure 4 The fundamental equivalent circuit for the vehicle-side rear stage and the UAV-side system adopts an LCL-S compensation topology. The voltage between points A and B at the output terminals of the FSBB converter is... The vehicle-side rear-stage compensation network 9 includes the airborne rear-side coil. Series compensating inductor (current) ) and the rear-side coil (current) Parallel compensation capacitors These three elements constitute an LCL resonant network. The load compensation network 11 uses the same components as the load coil. (current) Series-connected compensation capacitors This forms an S-compensation network. The angular frequency of the FSBB converter... The parameters of the resonant network should satisfy the resonance condition at both ends of the circuit:

[0108] (13)

[0109] This condition ensures that both the vehicle-side rear-stage LCL network and the load-side S network operate in a fully resonant state.

[0110] Based on Kirchhoff's voltage and current laws, write the circuit equations:

[0111] (14)

[0112] in, Inductor resistance, For mutual induction resistance, For load coil resistance, Inductor The equivalent series resistance. For load coil The equivalent series resistance. The fundamental voltage component between points A and B. This refers to the fundamental component of the AC terminal voltage of the load-side converter. For flow through the inductor The current phasor, For flow through the load coil The current phasor.

[0113] Solving the above equations, we can obtain the expressions for the currents in each branch as follows:

[0114] (15)

[0115] Among them, custom parameters ,in The equivalent AC resistance on the load side. Airborne rear coil The equivalent series resistance. This is the equivalent load resistance of the drone battery.

[0116] In equation (15), the values ​​of each equivalent series internal resistance are very small, so this term can be ignored. Further considering the equivalent relationship of the rectifier bridge on the load side, the AC voltage at the load side port can be obtained. and The relationship is:

[0117] (16)

[0118] Equation (16) shows that the output voltage at the load port Mutual intuition with variables and Regarding static charging, the spacing between systems does not change during this time, and the mutual inductance... Unchanged. When mutual inductance When the coil is constant (i.e., there is no relative offset), it is controlled by It can precisely control the load voltage. This achieves constant voltage output.

[0119] As analyzed above, the voltage between points A and B is an asymmetrical PWM wave with DC bias. The effective values ​​of the voltages at points A and B are analyzed by Fourier decomposition, and the effective values ​​of the voltages at points A and B are obtained as shown in equation (12).

[0120] (v) System efficiency model

[0121] To guide the optimization of control parameters, efficiency expressions are established for three modes. In Mode 1, the transmission efficiency from the network side to the vehicle side is... for:

[0122] (17)

[0123] Taking into account the parasitic resistance of the compensating inductor, transmitting coil, and receiving coil, the transmission efficiency of the vehicle-side rear-stage to UAV-side system. for:

[0124] (18)

[0125] in, The AC equivalent load resistance is the load-side port.

[0126] Therefore, in modes 1 and 3, the transmission efficiency of the vehicle-side rear-stage to UAV-side system is... for:

[0127] (19)

[0128] In Mode 2, the efficiency of the transmission stage of the network-vehicle front-end system is:

[0129] (20)

[0130] It can be seen from equations (18) to (21) that the efficiency , With mutual induction It decreases as the duty cycle decreases. Impact; efficiency With equivalent load It exhibits a trend of first increasing and then decreasing, and there exists an optimal load matching point to maximize efficiency.

[0131] Based on the electric vehicle's driving status, the transmission efficiency expressions for the three modes are as follows:

[0132] .(twenty one)

[0133] When an electric vehicle is parked on the grid side for vehicle-to-grid energy interaction, the entire system operates in Mode 1 or Mode 2, supplying and feeding energy to the grid side. Once the electric vehicle is in operation and disconnected from the grid side, the entire system operates in Mode 3. The switching between modes can be determined by the vehicle's operating status.

[0134] (vi) Efficiency Analysis

[0135] In addition to the voltage gain criterion, the average inductor current in the FSBB converter This also reflects the direction of power flow. When When energy flows from the input to the output of the FSBB converter (corresponding to mode 1, in which case forward power is supplied); when At this time, energy flows in the reverse direction (corresponding to mode 2 feeding back to the grid or mode 3 supplying the load). Therefore, by detecting... The average value allows switching between the three modes. Assuming a network connection is already established, when... and If the system enters mode 2, it will enter mode 2; otherwise, it will enter mode 1.

[0136] According to equations (17) and (20), regarding and ,make:

[0137] .(twenty two)

[0138] For efficiency and efficiency Seeking information about Partial derivative.

[0139] .(twenty three)

[0140] From equation (23), we can see that the efficiency extremum satisfies The optimal duty cycle can be solved by setting the numerator to 0. The efficiency extreme point satisfies The optimal duty cycle can be solved by setting the numerator to 0. Therefore, in modes 1 and 2, while keeping the output voltage within the allowable fluctuation range, the duty cycle can be further adjusted. Improve system efficiency.

[0141] III. System Control Methods

[0142] Based on the mathematical model and criteria established by the above theoretical analysis, the control method of a three-port cooperative bidirectional wireless power transfer system is systematically described below. (Refer to...) Figure 5 The control flow diagram shown illustrates the steps of this method:

[0143] S1. Real-time acquisition of grid-side inverter AC output voltage Airborne preamplifier AC input voltage Airborne rear-side compensation inductor current Mutual induction ;

[0144] S2. Based on the vehicle's entry and exit status at the charging station and the parameters collected in step S1, identify the current operating mode of the system.

[0145] S3. Implement differentiated closed-loop voltage regulation control for different identified operating modes and optimize system transmission efficiency online.

[0146] Specifically, step S2 includes:

[0147] S21. Detect the physical connection status of the grid-side port. If the vehicle leaves the charging station and the grid-side port is disconnected, the system will directly enter the third mode. If the vehicle enters the charging station, proceed to the next step.

[0148] S22, Calculate voltage gain Critical voltage gain and current RMS value of fundamental current Average value within a preset time period , , Voltage and The effective value of the fundamental voltage, if and If the system is determined to be in the second mode, then it is in the first mode; otherwise, it is in the first mode.

[0149] Specifically, step S3 includes:

[0150] S31. When the first mode is determined, the voltage is fixed. fundamental component of Leading voltage fundamental component of Outward phase angle The duty cycle of the FSBB converter is adjusted in a closed loop to achieve constant voltage output for onboard battery load 8 and constant voltage output for battery load 13, while maximizing efficiency while achieving constant voltage output. Compared to moving ;

[0151] S32. When the system is determined to be in the second mode, the voltage is fixed. fundamental component of Leading voltage fundamental component of Outward phase angle The duty cycle of the FSBB converter is adjusted in a closed loop to achieve constant voltage feedback output at the grid-side port, with the goal of zeroing the duty cycle. ;

[0152] S33. When the system is determined to be in the third mode, shut down the airborne front converter 6, and adjust the duty cycle of the FSBB converter in a closed loop to achieve constant voltage output from the battery load 13. Compared to moving At the same time, the perturbation observation method is used to match the optimal load operating point to achieve maximum efficiency.

[0153] Specifically, step S31 includes:

[0154] S311, Fixed Outward Phase Angle The value is zero, thus determining the desired voltage of the onboard battery load 8. 1. Desired voltage of battery load 13 The expected voltage between points A and B ;

[0155] S312, based on the voltage of the onboard battery load 8 Voltage of battery load 13 and the voltage between points A and B Duty cycle of FSBB converter Compared to moving The relationship between the two, and the determination of expectations , and The corresponding duty cycle Compared to moving ;

[0156] S313, Detect current duty cycle Compared to moving voltage under , If the fluctuation is within the allowable range, then fine-tune the duty cycle using the preset step size. Proceed to the next step; otherwise, return to step S311 to redetermine the desired voltage. ;

[0157] S314. Detect the duty cycle for fine-tuning in the current mode. If the system efficiency is improved, return to step S313; otherwise, end the process.

[0158] In step S312, the voltage of the airborne battery load 8 Voltage of battery load 13 and the voltage between points A and B Duty cycle of FSBB converter Compared to moving The relationship between them is:

[0159] , ,

[0160] in, This represents the fundamental RMS value of the input voltage to the airborne rear-side converter 7. (At the outer phase shift angle...) When it is zero, Given, corresponding Given, , , Replace with the corresponding expected voltage , and Then a unique set of duty cycles can be determined. Compared to moving value.

[0161] Specifically, step S32 includes:

[0162] S321, Fixed outward phase angle The value is zero, which determines the desired voltage at the grid-side port. ;

[0163] S322, Desired voltage based on grid-side port and the voltage of the current onboard battery load 8 Determine the duty cycle ;

[0164] S323, Detect current duty cycle Voltage at the downstream grid port If the fluctuation is within the allowable range, then fine-tune the duty cycle using the preset step size. Proceed to the next step; otherwise, return to the previous step to re-detect the voltage of the onboard battery load 8. Then determine the duty cycle ;

[0165] S324. Detect the duty cycle for fine-tuning in the current mode. Check if the system efficiency has improved. If so, return to step S323; otherwise, end.

[0166] In step S312, at the outer phase angle When it is zero, Given (at this point, the expected value), the corresponding Given that, according to A relationship can determine a unique The value can realize the voltage at the grid-side port. Is it within the allowable fluctuation range? If not, then the detection... There is a large error; retesting is required. And recalculate value.

[0167] Specifically, step S33 includes:

[0168] S331. Turn off grid-side converter 2 and determine the desired voltage of battery load 13. The expected voltage between points A and B ;

[0169] S332, Based on the desired voltage between points A and B and the voltage of the current onboard battery load 8 Determine the duty cycle Compared to moving The relationship between them is used to determine a set of duty cycles. Compared to moving ;

[0170] S333, Detect current duty cycle Compared to moving voltage under , If the fluctuation is within the allowable range, then perturb the battery load 13 and proceed to the next step; otherwise, return to the previous step and redetermine a new duty cycle. Compared to moving ;

[0171] S334. Detect whether the system efficiency has improved after load disturbance in the current mode. If yes, return to step S333; otherwise, end.

[0172] In step S332, the corresponding expected value and detected value can only be substituted according to... Determine the duty cycle Compared to moving The relationship is satisfied, therefore in voltage , If the fluctuation is outside the allowed range, directly determine a new set of duty cycles. Compared to moving .

[0173] IV. Experimental Verification and Waveform Analysis

[0174] Figure 6 The output voltage is given under mode 1, assuming no relative offset between the grid-side transmitting coil and the vehicle-side front-stage receiving coil. With inductor current The experimental waveform, corresponding to the duty cycle , compared to . It is approximately an AC square wave with DC bias, because The rate of change is high at the zero-crossing point, and the stray inductance of the system causes certain voltage spikes; due to the nonlinearity of the FSBB converter... It contains certain harmonic components, which causes a certain degree of distortion in the waveform.

[0175] Figure 7 The FSBB converter in mode 2 is given. Voltage and inductor current The steady-state waveform is selected from the vehicle-side DC power supply. To achieve constant voltage output and grid-connected operation, the grid-side DC power supply Since both the vehicle-side DC voltage and the grid-side DC voltage are constant, when considering the impact of the offset between the vehicle-side front-stage transmitting coil and the grid-side receiving coil on power transfer, only the FSBB converter needs to be changed. and duty cycle The value is 0.3061, at which point the shift ratio is... .

[0176] Figure 8 The transmission efficiency of the high-voltage battery system between the grid side and the vehicle side under Mode 1 is given. The figure shows the duty cycle of the FSBB converter. Mutual induction For system efficiency The impact mechanism. During wireless power transmission from the grid side to the vehicle side front stage, the relative offset between the grid-side transmitting coil and the vehicle-side front stage receiving coil will lead to mutual inductance. Dynamic attenuation occurs. The input voltage on the grid side... Under constant constraints, based on the voltage gain relationship It can be seen that mutual induction The reduction will directly affect the output voltage of the front stage on the vehicle side. The voltage drop. To maintain the rated output voltage at the electric vehicle terminals, the duty cycle of the FSBB converter needs to be increased. To compensate for voltage loss, and duty cycle The increase in power loss will further increase the system power loss, leading to a decrease in the efficiency of the network-to-vehicle front-end transmission. decline.

[0177] Figure 9 The transmission efficiency of the high-voltage battery system between the grid side and the vehicle side under Mode 2 is given. The figure shows the duty cycle of the FSBB converter. Mutual induction For system efficiency The mechanism of influence. During the wireless power feedback process from the vehicle-side front stage to the grid side, the relative offset between the vehicle-side front stage transmitting coil and the grid-side receiving coil will lead to mutual inductance. Dynamic degradation occurs. This is observed at the input voltage of the vehicle-side rear-stage on-board battery. Under constant constraints, based on the voltage gain relationship It can be seen that mutual induction The reduction will directly affect the front-stage input voltage on the vehicle side. Too small, unable to meet the requirements of the network side Output voltage rating. To maintain the rated output voltage on the grid side, the duty cycle of the FSBB converter needs to be increased. To reduce the front-stage input voltage on the vehicle side Duty cycle The increase will further increase system power loss, ultimately leading to a decrease in the reverse transmission efficiency between the network side and the vehicle side. decline.

[0178] Figure 10 The transmission efficiency between the vehicle-side high-voltage battery port and the UAV-side battery system in Mode 3 is given. Figure. Wireless power transfer efficiency from the vehicle-side rear stage to the UAV side. With equivalent load resistance The system exhibits a pattern of rapid initial increase followed by a decrease, indicating the existence of an optimal load matching condition under which system efficiency can be achieved. This property verifies the necessity and effectiveness of the perturbation-observation method for online optimization.

[0179] In summary, this invention achieves flexible power allocation and bidirectional power flow between three ports through a composite compensation topology of LCC-S and LCL-S and a multiplexed design of the FSBB converter. It simultaneously integrates bidirectional DC power transmission and wireless power transmission within a single power conversion unit. Furthermore, it establishes a front-stage reactive / active power model and a critical gain criterion based on Kirchhoff's laws. The constant voltage transmission relationship of the subsequent stage provides a precise mathematical basis for mode switching and parameter optimization, and determines the optimal solution for the outward phase shift angle of the preceding stage as follows: The efficiency expressions for three modes were derived, and the optimal matching law of the subsequent stage efficiency first increasing and then decreasing with the equivalent load was revealed. In terms of control, the system collects voltage, current, and grid-side connection status in real time, calculates voltage gain and inductor current average values, and then... and The system employs a dual-criteria decision-making mode 2, while in other cases it operates in mode 1. When the network side is not connected, it directly enters mode 3. Subsequently, based on the target mode, it performs pre-stage external phase angle locking, FSBB converter duty cycle and phase angle adjustment, and optimal load matching. In each mode, cyclic sampling and deviation judgment ensure that the output accuracy meets requirements, thereby achieving smooth mode switching and efficient and stable system operation. This invention effectively improves system integration, switching stability, and anti-offset constant voltage output capability, and can be widely applied to scenarios requiring multi-port energy interaction, such as wireless charging of electric vehicles and collaborative power supply for drones.

[0180] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A three-port cooperative bidirectional wireless power transfer system, characterized in that, This includes grid-side ports, airborne ports, load-side ports, and commutation control circuitry; The grid-side port includes a DC power supply (1), a grid-side converter (2), a grid-side compensation network (3), and a grid-side coil connected in sequence. ; The airborne side port includes airborne front-side coils connected in sequence. The system includes an airborne front compensation network (5), an airborne front converter (6), an airborne rear converter (7), and an airborne battery load (8), as well as an airborne rear compensation network (9) and an airborne rear coil connected to the airborne rear converter (7). ; The airborne rear-side converter (7) is a four-switch Buck-Boost converter, i.e., an FSBB converter, comprising a first switch transistor... Second switching transistor The left half-bridge, and the third switch transistor and the fourth switching transistor The right half-bridge is formed, the midpoint of the left half-bridge is point A, and the midpoint of the right half-bridge is point B; the left half-bridge is connected to the airborne front converter (6), the right half-bridge is connected to the airborne battery load (8), and the midpoints A of the left half-bridge and B of the right half-bridge are connected to the airborne rear compensation network (9). The load-side port includes load coils connected in sequence. , load compensation network (11), load-side converter (12) and battery load (13). The wire-side coil and the airborne front coil The first magnetic circuit mechanism (4) that forms mutual coupling is represented as follows: The airborne rear coil and the load coil The mutual inductance of the second magnetic circuit mechanism (10) that forms a mutual coupling is expressed as follows: ; The commutation control circuit is connected to the grid-side converter (2), the airborne front-side converter (6), and the FSBB converter (7) to control the switching state of each switch in the grid-side converter (2), the airborne front-side converter (6), and the FSBB converter (7) so as to control the system to switch between different working modes.

2. The three-port cooperative bidirectional wireless power transmission system according to claim 1, characterized in that, The working modes include: In the first mode, the grid-side port supplies power to both the airborne-side port and the load-side port simultaneously; In the second mode, the airborne side port supplies power to the grid side port; In the third mode, the airborne side port supplies power to the load side port.

3. The three-port cooperative bidirectional wireless power transmission system according to claim 2, characterized in that, The grid-side compensation network (3) is an LCC compensation network, including grid-side compensation inductors connected in series. Parallel compensation capacitors on the grid side and the wire-side coil Series-connected grid-side series compensation capacitors ; The airborne front compensation network (5) is an S-compensation network, including the airborne front coil. Series-connected airborne front-side series compensation capacitor ; The airborne rear-side compensation network (9) is an LC compensation network, including the airborne rear-side coil. Series-connected airborne rear-side compensation inductors and the airborne rear coil Parallel-connected airborne rear-side compensation capacitors ; The load compensation network (11) is an S-compensation network, including the load coil. Series-connected load series compensation capacitor .

4. The control method for a three-port cooperative bidirectional wireless power transfer system according to any one of claims 1 to 3, characterized in that, Including the following steps: S1. Real-time acquisition of grid-side inverter AC output voltage Airborne preamplifier AC input voltage Airborne rear-side compensation inductor current Mutual induction ; S2. Based on the vehicle's entry and exit status at the charging station and the parameters collected in step S1, identify the current operating mode of the system. S3. Implement differentiated closed-loop voltage regulation control for different identified operating modes and optimize system transmission efficiency online.

5. The control method for a three-port cooperative bidirectional wireless power transfer system according to claim 4, characterized in that, Step S2 specifically includes: S21. Detect the physical connection status of the grid-side port. If the vehicle leaves the charging station and the grid-side port is disconnected, the system will directly enter the third mode. If the vehicle enters the charging station, proceed to the next step. S22, Calculate voltage gain Critical voltage gain and current RMS value of fundamental current Average value within a preset time period , , Voltage and The effective value of the fundamental voltage, if and If the system is determined to be in the second mode, then it is in the first mode; otherwise, it is in the first mode.

6. The control method for a three-port cooperative bidirectional wireless power transfer system according to claim 5, characterized in that, Step S3 specifically includes: S31. When the first mode is determined, the voltage is fixed. fundamental component of Leading voltage fundamental component of Outward phase angle The duty cycle of the FSBB converter is adjusted in a closed loop to achieve constant voltage output of the onboard battery load (8) and constant voltage output of the battery load (13), and to maximize efficiency while achieving constant voltage output. Compared to moving ; S32. When the system is determined to be in the second mode, the voltage is fixed. fundamental component of Leading voltage fundamental component of Outward phase angle The duty cycle of the FSBB converter is adjusted in a closed loop to achieve constant voltage feedback output at the grid-side port, with the goal of zeroing out the current. ; S33. When the system determines that it is in the third mode, shut down the airborne front converter (6) and adjust the duty cycle of the FSBB converter in a closed loop to achieve constant voltage output of the battery load (13). Compared to moving At the same time, the perturbation observation method is used to match the optimal load operating point to achieve maximum efficiency.

7. The control method for a three-port cooperative bidirectional wireless power transfer system according to claim 6, characterized in that, Step S31 specifically includes: S311, Fixed Outward Phase Angle The value is zero, thus determining the desired voltage of the airborne battery load (8). , Desired voltage of battery load (13) The expected voltage between points A and B ; S312, based on the voltage of the onboard battery load (8) Voltage of battery load (13) and the voltage between points A and B Duty cycle of the FSBB converter Compared to moving The relationship between the two, and the determination of expectations , and The corresponding duty cycle Compared to moving ; S313, Detect current duty cycle Compared to moving voltage under , If the fluctuation is within the allowable range, then fine-tune the duty cycle using the preset step size. Proceed to the next step; otherwise, return to step S311 to redetermine the desired voltage. ; S314. Detect the duty cycle for fine-tuning in the current mode. If the system efficiency is improved, return to step S313; otherwise, end the process.

8. The control method for a three-port cooperative bidirectional wireless power transfer system according to claim 7, characterized in that, Voltage of airborne battery load (8) Voltage of battery load (13) and the voltage between points A and B Duty cycle of the FSBB converter Compared to moving The relationship between them is: ， ， in, The fundamental effective value of the input voltage of the airborne rear-side converter (7).

9. The control method for a three-port cooperative bidirectional wireless power transfer system according to claim 8, characterized in that, Step S32 specifically includes: S321, Fixed outward phase angle The value is zero, which determines the desired voltage at the grid-side port. ; S322, Desired voltage based on grid-side port and the voltage of the current airborne battery load (8) Determine the duty cycle ; S323, S323, Detect current duty cycle Voltage at the downstream grid port If the fluctuation is within the allowable range, then fine-tune the duty cycle using the preset step size. Proceed to the next step, or return to the previous step to re-detect the voltage of the onboard battery load (8). Then determine the duty cycle ; S324. Detect the duty cycle for fine-tuning in the current mode. Check if the system efficiency has improved. If so, return to step S323; otherwise, end.

10. The control method for a three-port cooperative bidirectional wireless power transfer system according to claim 9, characterized in that, Step S33 specifically includes: S331. Turn off the grid-side converter (2) and determine the desired voltage of the battery load (13). The expected voltage between points A and B ; S332, Based on the desired voltage between points A and B and the voltage of the current airborne battery load (8) Determine the duty cycle Compared to moving The relationship between them is used to determine a set of duty cycles. Compared to moving ; S333, Detect current duty cycle Compared to moving voltage under , If the fluctuation is within the allowable range, then the battery load (13) is perturbed and the process proceeds to the next step; otherwise, the process returns to the previous step to redetermine a new duty cycle. Compared to moving ; S334. Detect whether the system efficiency has improved after load disturbance in the current mode. If yes, return to step S333; otherwise, end.

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