Power transfer system, charging device and control method

Abstract

The present disclosure relates to an electric energy transmission system, a charging device and a control method. The electric energy transmission system comprises a coupling transformer, a first converter, a first end of the first converter being electrically connected with a power supply, a second end of the first converter being electrically connected with a primary side of the coupling transformer, a second converter, a first end of the second converter being electrically connected with a secondary side of the coupling transformer, a second end of the second converter being used for being electrically connected with a load, the second converter comprising at least two full-bridge converters, and a controller, the controller being electrically connected with the first converter and the second converter. The technical scheme makes the wide-range regulation of the system output voltage more smooth on the basis of simplifying the phase-shift control strategy, and realizes the effective optimization of the system transmission efficiency.

Description

Technical Field

[0001] This disclosure relates to the field of charging technology, specifically to an electrical energy transmission system, charging equipment, and control method. Background Technology

[0002] With the development of electric vehicle technology, wireless charging technology for electric vehicles has also evolved. Wireless charging is a contactless charging method based on the principle of electromagnetic induction, characterized by safety, flexibility, speed, and convenience. In this contactless charging method, bidirectional inductive transmission technology can be employed, further enabling contactless bidirectional energy flow based on unidirectional inductive transmission technology. Summary of the Invention

[0003] The purpose of this disclosure is to provide a power transmission system, charging device, and control method that can, based on a simplified phase-shift control strategy, make the wide-range adjustment of the system output voltage smoother and effectively optimize the system transmission efficiency.

[0004] To achieve the above objectives, in a first aspect, this disclosure provides an electrical power transmission system, comprising: a coupling transformer; a first converter, a first terminal of which is electrically connected to a power supply, and a second terminal of which is electrically connected to the primary side of the coupling transformer; a second converter, a first terminal of which is electrically connected to the secondary side of the coupling transformer, and a second terminal of which is used for electrical connection to a load, the second converter comprising at least two full-bridge converters; and a controller electrically connected to the first converter and the second converter; wherein the controller is used to perform phase-shift control on one of the at least two full-bridge converters, and, after one of the at least two full-bridge converters satisfies a bypass condition, to perform phase-shift control on the remaining full-bridge converters.

[0005] Optionally, the power transmission system further includes: a switch-controlled capacitor; the second terminal of the first converter is electrically connected to the first terminal of the switch-controlled capacitor, the second terminal of the switch-controlled capacitor is electrically connected to the primary side of the coupling transformer, and the controller is electrically connected to the switch-controlled capacitor; the controller is also used to adjust the equivalent capacitance value of the switch-controlled capacitor.

[0006] Optionally, the controller is further configured to: acquire the phase shift angle of the first converter and the phase shift angle of the second converter; determine the control information of the switch control capacitor based on the phase shift angle of the first converter and the phase shift angle of the second converter; and adjust the equivalent capacitance value of the switch control capacitor based on the control information.

[0007] Optionally, the controller is further configured to: acquire actual operating information and reference operating information of the power transmission system; determine the phase shift angle of the second converter based on the magnitude relationship between the actual operating information and the reference operating information; and perform phase shift control on the full-bridge converter in the second converter that requires phase shift control, at least based on the phase shift angle of the second converter.

[0008] Optionally, the bypass condition includes: the phase shift angle of one of the at least two full-bridge converters is greater than the target phase shift angle.

[0009] Optionally, the controller is further configured to: acquire the phase shift angle of the second converter; determine the phase shift angle of the first converter based at least on the phase shift angle of the second converter; and perform phase shift control on the first converter based on the phase shift angle of the first converter.

[0010] Optionally, the controller includes: a PI controller and a PWM signal generator; the PI controller is used to determine the phase shift angle of the second converter; the PWM signal generator is used to output a phase shift control signal to the full-bridge converter in the second converter that requires phase shift control according to the phase shift angle of the second converter.

[0011] Optionally, the PI controller includes: a first PI controller and / or a second PI controller; the first PI controller is used to determine the phase shift angle of the second converter based on the current information of the power transmission system; the second PI controller is used to determine the phase shift angle of the second converter based on the voltage information of the power transmission system.

[0012] In a second aspect, this disclosure provides a charging device, comprising: a device body; and a power transmission system as described in the first aspect of this disclosure disposed on the device body.

[0013] Thirdly, this disclosure provides a control method applied to a power transmission system as described in the first aspect of this disclosure, the control method comprising: performing phase-shift control on one of the at least two full-bridge converters; and performing phase-shift control on the remaining full-bridge converters in response to one of the at least two full-bridge converters satisfying a bypass condition.

[0014] Through the above technical solution, at least two full-bridge converters are configured on the secondary side of the transformer to form a cascaded H-bridge. Based on the system structure of the cascaded H-bridge, phase-shift modulation technology is introduced on the secondary side. Specifically, one of the full-bridge converters on the secondary side is first phase-shifted until it meets the bypass condition, and then the remaining full-bridge converters are phase-shifted. This phase-shift modulation method is relatively simple and can reduce the inductor current stress on the secondary side, making the wide-range adjustment of the output voltage of the power transmission system smoother and optimizing the system transmission efficiency.

[0015] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0016] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of an electrical power transmission system according to an exemplary embodiment.

[0017] Figure 2 This is a circuit diagram of a power transmission system of a related technology according to an exemplary embodiment.

[0018] Figure 3 This is a circuit diagram of an electrical power transmission system according to an exemplary embodiment.

[0019] Figure 4 This is a circuit diagram illustrating a switch-controlled capacitor according to an exemplary embodiment.

[0020] Figure 5 This is a waveform diagram of an electrical power transmission system according to an exemplary embodiment.

[0021] Figure 6 This is a schematic diagram of an equivalent model of an electrical power transmission system according to an exemplary embodiment.

[0022] Figure 7 This is a flowchart illustrating the determination of a phase shift angle according to an exemplary embodiment.

[0023] Figure 8 This is an equivalent control block diagram of a current inner loop according to an exemplary embodiment.

[0024] Figure 9 This is an equivalent control block diagram of a voltage outer loop according to an exemplary embodiment.

[0025] Figure 10 This is a schematic diagram of a control flow according to an exemplary embodiment.

[0026] Figure 11 This is a control block diagram illustrated according to an exemplary embodiment.

[0027] Figure 12 This is a flowchart illustrating a control method according to an exemplary embodiment.

[0028] Figure 13 This is a block diagram illustrating a control device according to an exemplary embodiment. Detailed Implementation

[0029] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0030] As mentioned in the background section, bidirectional inductive transmission technology can be used in wireless charging technology for electric vehicles. This technology establishes a bidirectional energy flow channel between the vehicle's battery and the power grid, providing a reliable and convenient charging method for electric vehicles and facilitating the feedback of energy from the battery to the grid, thus playing a role in peak shaving and valley filling of the power grid.

[0031] In bidirectional inductive transmission technology, attention needs to be paid to the transmission efficiency and anti-offset capability of the wireless power transmission system.

[0032] In related technologies, variable inductors are designed to enable soft switching of transformers over a wide load range. Combined with phase-shift control and dual closed-loop control, this allows the power transmission system to maintain a constant output even when the load or mutual inductance changes, thereby improving the system's efficiency. However, this method involves a complex control process and makes it difficult to guarantee optimal system transmission efficiency.

[0033] Based on this, the present disclosure provides a technical solution in which at least two full-bridge converters are configured on the secondary side of the transformer to form a cascaded H-bridge. Based on the system structure of the cascaded H-bridge, phase-shift modulation technology is introduced on the secondary side. Specifically, one of the full-bridge converters on the secondary side is first subjected to phase-shift control until it meets the bypass condition, and then the remaining full-bridge converters are subjected to phase-shift control. This phase-shift modulation method is relatively simple and can reduce the inductor current stress on the secondary side, making the wide-range adjustment of the output voltage of the power transmission system smoother, thereby optimizing the system transmission efficiency.

[0034] Therefore, this technical solution can simplify the phase-shift control strategy, make the wide-range adjustment of the system output voltage smoother, and effectively optimize the system transmission efficiency.

[0035] The technical solutions of the embodiments disclosed herein can be applied to wireless charging scenarios for electric vehicles, as well as wireless charging scenarios for other devices, and are not limited thereto.

[0036] Figure 1 This is a schematic diagram of a power transmission system 100 according to an exemplary embodiment, as shown below. Figure 1 As shown, the power transmission system 100 includes: a coupling transformer 101, a first converter 102, a second converter 103, and a controller 104.

[0037] Regarding the coupling transformer 101, it can be a loosely coupled transformer 101, or other types of coupling transformer 101.

[0038] The coupling transformer 101 consists of a transmitting (primary) coil and a receiving (secondary) coil. Figure 1 In the coupling transformer 101, the coil on the left side can be called the primary side (coil), and the coil on the right side can be called the secondary side (coil). Correspondingly, the part connected to the primary side of the coupling transformer 101 is called the primary side, and the part connected to the secondary side of the coupling transformer 101 is called the secondary side.

[0039] Regarding the first converter 102, its first terminal is electrically connected to the power supply, and its second terminal is electrically connected to the primary side of the coupling transformer 101. Therefore, the first converter 102 and the power supply can belong to the primary side.

[0040] In this embodiment of the disclosure, the first converter 102 may include a full-bridge converter.

[0041] A full-bridge converter can be understood as a converter that includes four switching transistors. As an example, the switching transistors can be MOSFETs, which stands for Metal Oxide Semiconductor Field Effect Transistor.

[0042] Regarding the second converter 103, its first terminal is electrically connected to the secondary side of the coupling transformer 101, and its second terminal is used for electrical connection to the load.

[0043] The load can vary depending on the application scenario. For example, in the scenario of wireless charging for electric vehicles, the load could be the electric vehicle's battery.

[0044] In this embodiment of the disclosure, the second converter 103 may include at least two full-bridge converters, for example, two full-bridge converters.

[0045] The controller 104 is electrically connected to the first converter 102 and the second converter 103. It can be understood that the controller 104 is used to implement power transmission control for the entire system.

[0046] Therefore, during the operation of the system, the controller 104 can perform phase-shift control on one of the at least two full-bridge converters, and after one of the at least two full-bridge converters meets the bypass condition, it can perform phase-shift control on the remaining full-bridge converters.

[0047] Taking the second converter 103, which includes two full-bridge converters, as an example, the controller 104 first performs phase-shift control on the first full-bridge converter, and after the first full-bridge converter meets the bypass condition, it performs phase-shift control on the second full-bridge converter.

[0048] Taking the second converter 103, which includes three full-bridge converters, as an example, the controller 104 first performs phase-shift control on the first full-bridge converter. After the first full-bridge converter meets the bypass condition, it performs phase-shift control on the second full-bridge converter. After the second full-bridge converter meets the bypass condition, it performs phase-shift control on the third full-bridge converter.

[0049] In some embodiments, the power transmission system 100 may further include a switch-controlled capacitor. The second terminal of the first converter 102 is electrically connected to the first terminal of the switch-controlled capacitor, the second terminal of the switch-controlled capacitor is electrically connected to the primary side of the coupling transformer 101, and the controller 104 is electrically connected to the switch-controlled capacitor.

[0050] In this implementation, a switch-controlled capacitor is also introduced into the primary-side circuit. The switch-controlled capacitor, also known as SCC, is a circuit structure that adjusts its capacitance value by actively controlling the switching state. It can be used to optimize power conversion efficiency and output voltage regulation.

[0051] By controlling the capacitor through switching, the capacitance value of the primary side can be compensated, achieving minimum reactive power ZVS (Zero Voltage Switching) operation and reducing current stress. Without changing the symmetrical structure of the primary and secondary sides, the system's anti-offset effect can be effectively improved.

[0052] Figure 2 This is a circuit diagram of a power transmission system 100 according to an exemplary embodiment of the related art. Figure 2 The controller 104 is not shown; only the power transmission part is shown.

[0053] like Figure 2 As shown, the primary-side circuit of the coupling transformer 101 includes a DC power supply Vp and a primary-side full-bridge converter, wherein the primary-side full-bridge converter includes four MOSFETs S1 to S4. Additionally, a capacitor Cp can be connected in series on the primary side.

[0054] The secondary-side circuit of the coupling transformer 101 includes: a load battery Vs and a secondary-side full-bridge converter, wherein the secondary-side full-bridge converter includes four MOSFETs Q1 to Q4. Additionally, a capacitor Cs can be connected in series on the secondary side.

[0055] The coupling transformer 101 may include a primary-side inductance Lp and a secondary-side inductance Ls. Furthermore, Cp, Lp, Cs, and Ls can form an SS resonant compensation network, where M is the mutual inductance.

[0056] In related technologies, Cp is a fixed capacitor whose capacitance value remains constant.

[0057] Figure 3 This is a circuit diagram illustrating a power transmission system 100 according to an exemplary embodiment, which employs the implementation methods provided in this disclosure. Figure 3 The controller 104 is not shown; only the power transmission part is shown.

[0058] like Figure 3 As shown, the primary-side circuit of the coupling transformer 101 includes a DC power supply Vp and a primary-side full-bridge converter, wherein the primary-side full-bridge converter includes four MOSFETs S1 to S4. Additionally, a capacitor Cp can be connected in series on the primary side.

[0059] The secondary-side circuit of the coupling transformer 101 includes: a load battery Vs, a secondary-side full-bridge converter one, and a secondary-side full-bridge converter two. The secondary-side full-bridge converter one includes four MOSFETs Q1 to Q4, and the secondary-side full-bridge converter two includes four MOSFETs Q5 to Q8. Additionally, a capacitor Cs can be connected in series on the secondary side.

[0060] Additionally, a capacitor can be provided for the secondary side circuit. The secondary side full-bridge converter can be connected in parallel with this capacitor, which is connected in parallel with the load battery Vs.

[0061] The coupling transformer 101 may include a primary-side inductance Lp and a secondary-side inductance Ls. Furthermore, Cp, Lp, Cs, and Ls can form an SS resonant compensation network, where M is the mutual inductance.

[0062] In addition, when two full-bridge converters are set, a 1:2 transformer can be set at the front end of each of the two full-bridge converters.

[0063] exist Figure 2 and Figure 3 In the middle, the excitation voltage of the primary coil is U p The excitation voltage of the secondary coil is U s The current in the primary coil can be I p The current in the secondary coil can be I s The internal resistance of the primary coil is R. p The internal resistance of the secondary coil is R. s .

[0064] In this embodiment of the disclosure, the capacitor Cp on the original side is a switch control capacitor, which is a capacitor with an adjustable capacitance value.

[0065] As can be seen, the technical solution of this disclosure, based on the power transmission system 100 of related technologies, improves the secondary-side circuit by increasing the number of full-bridge converters; and improves the capacitors in the primary-side circuit by setting them as switch-controlled capacitors. Therefore, it not only effectively optimizes the system transmission efficiency but also effectively improves the system's anti-offset performance.

[0066] Figure 4 This is a circuit diagram illustrating a switch-controlled capacitor according to an exemplary embodiment, such as... Figure 4 As shown, the switch control capacitor includes: a fixed capacitor Cx and two MOSFETs (Sa and Sb).

[0067] The operation of the switch-controlled capacitor (SCC) involves the following: when Cx is short-circuited, current flows through Sa and Sb, but not through the anti-parallel diodes of the two MOSFETs. Therefore, low conduction losses in the MOSFETs of the SCC can be achieved. Simultaneously, since Sa and Sb conduct at zero voltage, ZVS switching losses can be minimized.

[0068] In some embodiments, the equivalent capacitance value of the switch control capacitor can be adjusted by changing the control angle of the MOSFET.

[0069] As an example, without considering higher harmonics, the equivalent capacitance of a switch-controlled capacitor can be expressed as: , where C eq C represents the equivalent capacitance value. x Indicates a fixed capacitor C x The size of the capacitor, θ Indicates the control angle.

[0070] As can be seen from the representation of this equivalent capacitance value, the equivalent capacitance of the switch-controlled capacitor changes with the control angle, thus achieving adjustable capacitance value.

[0071] In some embodiments, the size of the control angle may be related to the phase shift angle of the first converter 102 and the phase shift angle of the second converter 103.

[0072] Therefore, as an optional implementation, the controller 104 is further configured to: acquire the phase shift angle of the first converter 102 and the phase shift angle of the second converter 103; determine the control information of the switch control capacitor based on the phase shift angle of the first converter 102 and the phase shift angle of the second converter 103; and adjust the equivalent capacitance value of the switch control capacitor based on the control information.

[0073] In this implementation, the control information for switching the capacitor can be understood as a control angle. The relationship between this control information, the phase shift angle of the first converter 102, and the phase shift angle of the second converter 103 will be described in subsequent embodiments.

[0074] In some embodiments, control signals for the control switches (i.e., MOSFETs) in the switch-controlled capacitor can be generated based on control information, thereby enabling the adjustment of the equivalent capacitance value of the switch-controlled capacitor.

[0075] To facilitate understanding of the technical solutions of the embodiments of this disclosure, the relationship between the various parameters in the power transmission system 100 will be introduced next.

[0076] Figure 5 This is a waveform diagram of a power transmission system 100 according to an exemplary embodiment. Figure 5 The diagrams involve the control waveforms of switches Q1, Q3, S1, and S3, as well as the primary coil voltage U. p Secondary coil voltage U s Primary coil current I p and secondary coil current I s The corresponding waveforms.

[0077] It can be seen that the primary coil voltage U p The phase angle of the primary-side switches S1 and S3 is α; the secondary-side coil voltage U s The phase angle of U, and the phase shift angles of the primary-side switches Q1 and Q3 are both β. Also, θ is the phase angle of U. p and U s The phase angle between them.

[0078] Figure 6 This is a schematic diagram of an equivalent model of a power transmission system 100 according to an exemplary embodiment, such as... Figure 6 As shown, U p and U s These are the excitation voltages of the primary and secondary coils, I, respectively. p and I sThese are the currents in the primary and secondary coils, R. p and R s The internal resistances of the primary and secondary coils are L and L, respectively. p and L s Let represent the inductances of the primary and secondary coils, respectively. Ignoring losses and resistance, and using Kirchhoff's voltage law, the relationship between the voltage and current of the primary and secondary coils can be obtained:

[0079] in, w This indicates the operating frequency of the full-bridge converter, which remains consistent on both the primary and secondary sides; Z p and Z s These represent the equivalent impedances of the primary and secondary coils, respectively.

[0080] The equivalent impedance of the primary and secondary coils can be expressed as:

[0081] Among them, X p and X s These represent the impedances in the primary and secondary circuits, respectively.

[0082] Combining the two expressions above, we can obtain the expression for the primary and secondary coil currents:

[0083] Furthermore, the active power P and reactive power Q of the primary and secondary coils can be obtained:

[0084] in, And, M represents the mutual inductance of coupling transformer 101, P p and P s Q represents the active power of the primary and secondary coils, respectively. p and Q s These represent the reactive power of the primary and secondary coils, respectively.

[0085] It can be seen that the direction of energy transmission in the system is determined by the phase difference θ between the voltages of the primary and secondary coils. By adjusting θ, soft switching of the full-bridge converter on the primary and secondary sides can be achieved. In order to analyze the ZVS condition, a time-domain model of the full-bridge output current can be established considering harmonics:

[0086] Where λ=L p / C p =L s / C s k represents the coupling coefficient of the system, which can be expressed as: k = M / ZIzvs This indicates the zero-voltage turn-on current.

[0087] All power switches on both the primary and secondary sides can achieve the optimal phase angle for ZVS. θ It can be represented as: .

[0088] In some embodiments, the control angle of the aforementioned switch-controlled capacitor can be calculated using the above formula, combined with the phase shift angle α of the first converter 102 and the β of the second converter 103.

[0089] Furthermore, the loss P of the resonant network loss_net Represented as: .

[0090] Furthermore, the system power factor It can be represented as: Among them, P o This indicates the system's output power.

[0091] The ratio of the primary and secondary coil voltages is defined as T. ac ,but: Among them, V s V represents the output voltage on the primary side. p This indicates the output voltage on the secondary side.

[0092] By solving Relative to T ac The derivative of can be used to obtain the excitation voltage ratio that maximizes system efficiency:

[0093] This equation shows that to achieve maximum system efficiency, equal primary and secondary excitation voltages are required. Therefore, the relationship between the phase shift angles of the primary and secondary sides is as follows:

[0094] For a given output power P o ,optimal α and β It can be represented as:

[0095] Where X = w C p = w C s .

[0096] However, the phase-shift control method can only achieve ZVS of the primary-side converter under minimum reactive power conditions, resulting in significant reactive power on the secondary side. Furthermore, the high current stress at the input of the secondary-side converter leads to increased turn-on and turn-off losses. These two factors limit further improvements in system efficiency. Therefore, in this embodiment, the aforementioned phase-shift angle calculation formula is not used to perform phase-shift control on the primary and secondary-side converters.

[0097] As an optional implementation, the phase-shift control process of the controller 104 includes: acquiring actual operating information and reference operating information of the power transmission system 100; determining the phase-shift angle of the second converter 103 based on the magnitude relationship between the actual operating information and the reference operating information; and performing phase-shift control on the full-bridge converter in the second converter 103 that requires phase-shift control, at least based on the phase-shift angle of the second converter 103.

[0098] In this implementation, the phase shift angle of the second converter 103 can be determined based on the relationship between the actual operating information and the reference operating information. Then, based on the phase shift angle of the second converter 103, phase shift control can be performed on the full-bridge converter in the second converter 103 that requires phase shift control.

[0099] In some embodiments, the actual operating information of the power transmission system 100 may be the actual output voltage and / or actual output current on the secondary side, and correspondingly, the reference operating information may be the reference output voltage and / or reference output current on the secondary side.

[0100] In some embodiments, phase-shift control can be performed on the full-bridge converter in the second converter 103 that requires phase-shift control by combining the phase-shift angle of the second converter 103 and the phase difference between the primary and secondary coil voltages.

[0101] In this embodiment of the disclosure, the bypass condition may be: the phase shift angle of one of the at least two full-bridge converters is greater than the target phase shift angle.

[0102] In some embodiments, the phase shift angle on the secondary side can be in the range of 0 to 2π, and the target phase shift angle can be π. Therefore, when the phase shift angle of the full-bridge converter on the secondary side is greater than π, it can be considered as satisfying the bypass condition, and phase shift control can be performed on the remaining full-bridge converters.

[0103] In some embodiments, taking the output voltage as an example, if the actual output voltage is less than the reference voltage, the current phase shift angle of the second converter 103 can be increased to improve the output voltage. If the actual output voltage is greater than the reference voltage, the current phase shift angle of the second converter 103 can be decreased to reduce the output voltage.

[0104] Figure 7This is a flowchart illustrating the determination of a phase shift angle according to an exemplary embodiment, such as... Figure 7 As shown, by referencing the output voltage V ref With the actual output voltage V o The comparison is performed, and based on the comparison results, different phase shift angle adjustment methods are adopted to obtain the corresponding phase shift angle. Here, n represents the number of phase shift control cycles, and Δβ represents the adjustment amount of the phase shift angle, which can be a preset value.

[0105] In this embodiment of the disclosure, in addition to controlling the phase shift angle of the converter on the secondary side, the control of the phase shift angle of the converter on the primary side may also be involved.

[0106] Therefore, as an optional implementation, the controller 104 is further configured to: acquire the phase shift angle of the second converter 103; determine the phase shift angle of the first converter 102 based at least on the phase shift angle of the second converter 103; and perform phase shift control on the first converter 102 based on the phase shift angle of the first converter 102.

[0107] In this implementation, the phase shift angle of the first converter 102 can be determined based on the phase shift angle of the second converter 103.

[0108] In some embodiments, based on the relationship between the primary and secondary phase shift angles in the foregoing embodiments, and having determined the phase shift angle of the second converter 103, the phase shift angle of the first converter 102 can be further determined.

[0109] In some embodiments, the phase shift angle of the first converter 102 can be determined by combining the output voltage on the primary side, the reference output power, the output voltage on the secondary side, and the phase shift angle on the secondary side.

[0110] As can be seen from the foregoing embodiments, the controller 104 can first determine the phase shift angle of the second converter 103, then determine the phase shift angle of the first converter 102 based on the phase shift angle of the second converter 103, and then determine the control angle of the switch control capacitor by combining the phase shift angles of the first converter 102 and the second converter 103 respectively. Furthermore, based on the phase shift angle of the first converter 102, phase shift control is performed on the first converter 102; based on the phase shift angle of the second converter 103, phase shift control is performed on the second converter 103; and based on the control angle of the switch control capacitor, the switch control capacitor is controlled. This control method effectively optimizes system efficiency and keeps the output voltage as constant as possible.

[0111] In some embodiments, the controller 104 may include a PI (proportional integral) controller 104 and a PWM (Pulse width modulation) signal generator.

[0112] In some embodiments, the PI controller can be used to determine the phase shift angle of the second converter 103, and then the PWM signal generator is used to output a phase shift control signal to the full-bridge converter in the second converter 103 that needs to be phase shift controlled, according to the phase shift angle of the second converter 103.

[0113] In some embodiments, the controller 104 may include multiple PWM signal generators, each used to output corresponding phase-shift control signals to different switching transistors or full-bridge converters. For example, a PWM signal generator corresponding to the first converter 102, a PWM signal generator corresponding to the switch control capacitor, a PWM signal generator corresponding to the second converter 103, etc.

[0114] In this embodiment of the disclosure, the PI controller may include: a first PI controller and / or a second PI controller.

[0115] The first PI controller is used to determine the phase shift angle of the second converter 103 based on the current information of the power transmission system 100; the second PI controller is used to determine the phase shift angle of the second converter 103 based on the voltage information of the power transmission system 100.

[0116] In this implementation, the two PI controllers determine the phase shift angle based on different system operating information. Therefore, the first PI controller can be called a current regulator, and the second PI controller can be called a voltage regulator. The two controllers 104, based on different control objectives, control the current and voltage respectively by controlling the phase shift angle.

[0117] In some embodiments, a current regulator can be used for inner-loop current control, and a voltage regulator can be used for outer-loop voltage control. In this dual-closed-loop PI control, the outer-loop voltage control can ensure the stability of the entire system by stabilizing the output voltage, thus enhancing the system's anti-interference performance. Using a PI regulator can achieve zero steady-state error in the output voltage. The inner-loop current control is used to quickly track the leakage inductance current setpoint, enhancing the system's dynamic performance.

[0118] Figure 8 This is an equivalent control block diagram of a current inner loop illustrated according to an exemplary embodiment. Figure 8 middle, I ref I represents the reference current. o This represents the actual current.

[0119] like Figure 8 As shown, the transfer function G from the current regulator control to the state is... sd The standard form is expressed as:

[0120] Where K1 is the DC gain, and T1 and T2 represent two time constants.

[0121] The transfer function G of the PI controller pli for:

[0122] Among them, K pi K is the proportional gain of the PI controller. li These are the coefficients of the integrator, from which the open-loop transfer function G of the current loop can be obtained. opi Represented as:

[0123] The function of the voltage outer loop controller 104 is to enhance the system's anti-interference performance. Unlike the target of the current inner loop controller 104, the response speed of the voltage outer loop can be taken as 1 / 20 to 1 / 5 of the response speed of the current inner loop. To simplify the design, it is approximated that the current inner loop remains unchanged as a component of the voltage outer loop when the voltage outer loop is working. Thus, when designing the voltage outer loop, the voltage outer loop and the current inner loop can be regarded as two independent closed-loop systems and designed separately.

[0124] Figure 9 This is an equivalent control block diagram of a voltage outer loop according to an exemplary embodiment. Figure 9 In the middle, V ref Indicates the reference voltage, V o This indicates the actual voltage.

[0125] like Figure 9 As shown, PI is a PI regulator for the outer voltage loop, and its transfer function G... plv Represented as:

[0126] K pv K is the proportional coefficient of the inner loop PI regulator. LV It is the coefficient of the integral element.

[0127] Therefore, the open-loop transfer function G of the outer voltage loop opv for:

[0128] Among them, G cli It is the closed-loop transfer function of the inner current loop (i.e., the aforementioned G). sdK2 is the DC gain.

[0129] Figure 10 This is a schematic diagram of a control flow according to an exemplary embodiment, such as... Figure 10 As shown, when the system starts working, the primary-side converter provides square wave excitation, while the lower (or upper) diode on the secondary side is turned on, and the output load side is short-circuited, preventing current from entering the load side. The current signal is obtained through a current transformer, and after passing through a second-order low-pass filter to remove the third and fifth harmonics, the fundamental signal is obtained. A comparator then generates a square wave signal in phase with the fundamental current. The phase of the fundamental current can be calculated using the edge-capturing function of the DSP (Digital Signal Processing) controller. Based on the current phase φ... o Phase φ with the target ref The difference is used to calculate the frequency increment Δf through a PI controller, and the carrier frequency f is adjusted to achieve synchronization between the primary and secondary sides. The coupling coefficient k is then calculated based on the current amplitude in the resonant cavity for subsequent efficiency optimization.

[0130] After achieving synchronization between the primary and secondary sides, the secondary side calculates the phase shift angle of the converter through the power loop. The phase shift angle of the secondary side ranges from 0 to 2π. When the phase shift angle of the secondary side is less than π, the first full-bridge converter on the secondary side operates. When the phase shift angle is greater than π, phase shift control is applied to the other full-bridge converter to adjust the output power.

[0131] Figure 11 This is a control block diagram illustrated according to an exemplary embodiment, such as Figure 11 As shown, in this system, the PI controller can be based on the reference current I. ref Reference voltage V ref Actual output voltage V o Actual output current I o Based on this information, the phase shift angle β of the secondary-side full bridge is determined. Then, based on the phase shift angle β of the secondary-side full bridge, and combined with the voltage V on the primary-side full bridge... p Information such as reference power can be used to determine the phase shift angle α of the primary side of the full bridge. Furthermore, based on the phase shift angles of the primary and secondary sides respectively, the switching control capacitor C can be calculated. p The control angle θ. Thus, PWM generators 1-3 respectively realize primary-side phase shift control, switching capacitor control, and secondary-side phase shift control based on the corresponding control information.

[0132] Figure 12 This is a flowchart illustrating a control method according to an exemplary embodiment, which can be applied to the controller 104 in the foregoing embodiments, such as... Figure 12 As shown, the control method includes: Step S1201: Perform phase shift control on one of the at least two full-bridge converters.

[0133] In step S1202, in response to one of the at least two full-bridge converters satisfying the bypass condition, phase-shift control is performed on the remaining full-bridge converters among the at least two full-bridge converters.

[0134] It is understood that this control method is applied to controller 104. Therefore, the specific implementation of each step can refer to the aforementioned implementation of controller 104, and will not be repeated here.

[0135] Figure 13 This is a block diagram illustrating a control device 1300 according to an exemplary embodiment. The control device 1300 can be applied to the controller 104 in the aforementioned embodiments, such as... Figure 13 As shown, the control device 1300 includes a phase shift control module 1301.

[0136] The phase-shift control module 1301 is used to perform phase-shift control on one of the at least two full-bridge converters.

[0137] Furthermore, the phase-shift control module 1301 is also configured to: perform phase-shift control on the remaining full-bridge converters among the at least two full-bridge converters in response to one of the at least two full-bridge converters satisfying the bypass condition.

[0138] It is understood that the control device 1300 is applied to the controller 104. Therefore, the specific implementation of each step can refer to the aforementioned implementation of the controller 104, and will not be repeated here.

[0139] In this embodiment of the present disclosure, a charging device is also provided, which includes: a device body and a power transmission system 100 disposed on the device body, wherein the power transmission system 100 adopts the implementation method described in the foregoing embodiments.

[0140] It is understood that this charging device can be used in wireless charging scenarios for electric vehicles, as well as in wireless charging scenarios for other electronic devices, without any limitation.

[0141] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0142] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0143] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A power transmission system, characterized in that, include: Coupling transformer; A first converter, wherein a first terminal of the first converter is electrically connected to a power supply, and a second terminal of the first converter is electrically connected to the primary side of the coupling transformer; The second converter has a first terminal electrically connected to the secondary side of the coupling transformer and a second terminal for electrical connection to the load. The second converter includes at least two full-bridge converters. A controller, electrically connected to the first converter and electrically connected to the second converter; wherein the controller is configured to perform phase-shift control on one of the at least two full-bridge converters, and after one of the at least two full-bridge converters satisfies the bypass condition, to perform phase-shift control on the remaining full-bridge converters.

2. The power transmission system according to claim 1, characterized in that, The power transmission system further includes: a switch-controlled capacitor; The second terminal of the first converter is electrically connected to the first terminal of the switch control capacitor, the second terminal of the switch control capacitor is electrically connected to the primary side of the coupling transformer, and the controller is electrically connected to the switch control capacitor; The controller is also used to adjust the equivalent capacitance value of the switch-controlled capacitor.

3. The power transmission system according to claim 2, characterized in that, The controller is also used for: Obtain the phase shift angle of the first converter and the phase shift angle of the second converter; The control information of the switch-controlled capacitor is determined based on the phase shift angle of the first converter and the phase shift angle of the second converter; Based on the control information, the equivalent capacitance value of the switch control capacitor is adjusted.

4. The power transmission system according to claim 1, characterized in that, The controller is also used for: To obtain actual and reference operating information of the power transmission system; The phase shift angle of the second converter is determined based on the relationship between the actual operating information and the reference operating information. At least based on the phase shift angle of the second converter, phase shift control is performed on the full-bridge converter in the second converter that requires phase shift control.

5. The power transmission system according to claim 1, characterized in that, The bypass condition includes: the phase shift angle of one of the at least two full-bridge converters is greater than the target phase shift angle.

6. The power transmission system according to any one of claims 1 to 5, characterized in that, The controller is also used for: Obtain the phase shift angle of the second converter; The phase shift angle of the first converter is determined at least based on the phase shift angle of the second converter; Phase shift control is performed on the first converter based on the phase shift angle of the first converter.

7. The power transmission system according to claim 1, characterized in that, The controller includes: a PI controller and a PWM signal generator; The PI controller is used to determine the phase shift angle of the second converter; The PWM signal generator is used to output a phase-shift control signal to the full-bridge converter in the second converter that requires phase-shift control, based on the phase-shift angle of the second converter.

8. The power transmission system according to claim 7, characterized in that, The PI controller includes: a first PI controller and / or a second PI controller; The first PI controller is used to determine the phase shift angle of the second converter based on the current information of the power transmission system; The second PI controller is used to determine the phase shift angle of the second converter based on the voltage information of the power transmission system.

9. A charging device, characterized in that, include: Equipment body; The power transmission system as described in any one of claims 1 to 8 is disposed on the main body of the device.

10. A control method, characterized in that, The control method, applied to the power transmission system as described in any one of claims 1 to 8, comprises: Phase-shift control is applied to one of the at least two full-bridge converters; In response to one of the at least two full-bridge converters satisfying the bypass condition, phase-shift control is performed on the remaining full-bridge converters among the at least two full-bridge converters.

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