Wireless electric energy transmission system and method, power system and vehicle

Abstract

The invention relates to a wireless electric energy transmission system and method, a power system and a vehicle. The wireless electric energy transmission system comprises a transformer module, a primary side capacitor module connected with a primary side winding of the transformer module in series and a secondary side capacitor module connected with a secondary side winding of the transformer module in series. The capacitance value of the secondary capacitor module is adjusted based on the difference phase angle so as to reduce the output current of the secondary capacitor module. According to the wireless electric energy transmission system provided by the embodiment of the invention, the secondary side capacitor module with the adjustable capacitance value can be adopted for the secondary side, so that the capacitance value of the secondary side capacitor module can be adjusted according to the determined difference phase angle, and the purpose of compensating the output characteristic of the wireless electric energy transmission system is achieved; therefore, the output current of the secondary capacitor module, namely the input current of the corresponding secondary converter, can be reduced, and the current stress and switching loss of the secondary side are finally reduced.

Description

Technical Field

[0001] The present application relates to the field of new energy technologies, and in particular to a wireless power transmission system, method, power system and vehicle. Background Art

[0002] Wireless charging technology for electric vehicles is a contactless charging method based on electromagnetic induction and centered around a transformer module. It's safe, flexible, fast, and convenient. Bidirectional inductive transmission technology builds on unidirectional inductive transmission technology by further enabling contactless, two-way energy flow. By establishing a bidirectional energy flow channel between the power battery and the power grid, the wireless power transmission system (BD-IPT) not only provides a reliable and convenient charging method for electric vehicles, but also facilitates the return of power from the power battery to the grid, effectively reducing peak loads and valley filling for the grid's electricity.

[0003] Existing technologies typically employ a symmetrical structure consisting of a transformer module, dual capacitors, and dual converters. Based on a phase-shift control strategy, these strategies determine the corresponding primary and secondary phase angles, as well as the difference between the two. Ultimately, these phase angles are used for control. However, existing technologies fail to account for the high current stress and switching losses on the secondary side, resulting in poor performance of the overall wireless power transmission system. Summary of the Invention

[0004] The embodiments of the present application provide a wireless power transmission system, method, power system and vehicle, which can adopt a secondary capacitor module with adjustable capacitance value for the secondary side, so that the capacitance value of the secondary capacitor module can be adjusted according to the determined differential phase angle to reduce the output current of the secondary capacitor module, so as to at least partially solve the above-mentioned technical problems.

[0005] To achieve the above-mentioned objectives, according to a first aspect of the present application, a wireless power transmission system is provided, comprising a transformer module, a primary capacitor module connected in series with a primary winding of the transformer module, and a secondary capacitor module connected in series with a secondary winding of the transformer module;

[0006] The capacitance value of the secondary capacitor module is adjusted based on the differential phase angle to reduce the output current of the secondary capacitor module;

[0007] The difference phase angle is the difference between the primary phase angle of the primary voltage corresponding to the primary capacitor module and the secondary phase angle of the secondary voltage corresponding to the secondary capacitor module.

[0008] Optionally, the secondary capacitor module includes a switch-controlled capacitor;

[0009] The switch-controlled capacitor includes a first access terminal and a second access terminal connected in series with the secondary winding, and a controlled terminal for receiving a control signal and for adjusting the capacitance value connected in series to the secondary winding according to the control signal.

[0010] Optionally, the switch-controlled capacitor includes a secondary capacitor and a control switch;

[0011] The first access terminal of the control switch and the first terminal of the secondary capacitor are electrically connected to the first common terminal, and the first common terminal serves as the first access terminal of the switch control capacitor;

[0012] The second access terminal of the control switch and the second end of the secondary capacitor are electrically connected to the second common terminal, and the second common terminal serves as the second access terminal of the switch control capacitor;

[0013] The controlled end of the control switch serves as the controlled end of the switch-controlled capacitor.

[0014] Optionally, the control switch includes a first MOS transistor.

[0015] Optionally, the control switch further includes a second MOS tube;

[0016] The drain of the first MOS transistor and the first end of the secondary capacitor are electrically connected to the first common terminal, the source of the first MOS transistor is electrically connected to the source of the second MOS transistor, and the drain of the second MOS transistor and the second end of the secondary capacitor are electrically connected to the second common terminal;

[0017] The gate of the first MOS transistor serves as a first controlled terminal of the switch-controlled capacitor and is used to receive a first control signal;

[0018] The gate of the second MOS transistor serves as the second controlled end of the switch-controlled capacitor and is used to receive the second control signal.

[0019] Optionally, the wireless power transmission system further includes a primary-side converter and a secondary-side converter;

[0020] The primary converter is electrically connected to the primary capacitor module to achieve energy transmission between the primary power supply and the primary capacitor module;

[0021] The secondary converter is electrically connected to the secondary capacitor module to achieve energy transmission between the secondary power supply and the secondary capacitor module.

[0022] Optionally, the primary-side converter includes a third MOS transistor, a fourth MOS transistor, a fifth MOS transistor, and a sixth MOS transistor;

[0023] The drain of the third MOS transistor and the drain of the fourth MOS transistor are respectively used to be electrically connected to the positive electrode of the primary power supply, the source of the third MOS transistor is respectively electrically connected to the drain of the fifth MOS transistor and the first end of the primary capacitor module, the second end of the primary capacitor module is electrically connected to the first end of the primary winding, the source of the fourth MOS transistor is respectively electrically connected to the drain of the sixth MOS transistor and the second end of the primary winding, and the source of the fifth MOS transistor and the source of the sixth MOS transistor are respectively used to be electrically connected to the negative electrode of the primary power supply.

[0024] Optionally, the secondary-side converter includes a seventh MOS transistor, an eighth MOS transistor, a ninth MOS transistor, and a tenth MOS transistor;

[0025] The drain of the seventh MOS transistor and the drain of the eighth MOS transistor are respectively used to be electrically connected to the positive electrode of the secondary power supply, the source of the seventh MOS transistor is respectively electrically connected to the drain of the ninth MOS transistor and the first end of the secondary capacitor module, the second end of the secondary capacitor module is electrically connected to the first end of the secondary winding, the source of the eighth MOS transistor is respectively electrically connected to the drain of the tenth MOS transistor and the second end of the secondary winding, and the source of the ninth MOS transistor and the source of the tenth MOS transistor are respectively used to be electrically connected to the negative electrode of the secondary power supply.

[0026] According to a second aspect of the present application, a wireless power transmission method is provided, which is applied to the wireless power transmission system in any of the above embodiments. The wireless power transmission method includes:

[0027] Get the difference phase angle;

[0028] Determine the target capacitance value of the secondary capacitor module according to the difference phase angle;

[0029] According to the target capacitance value, the capacitance value of the secondary capacitor module is adjusted to reduce the output current of the secondary capacitor module.

[0030] Optionally, before obtaining the difference phase angle, the wireless power transmission method further includes:

[0031] Obtaining the voltage of a primary power supply located on the primary side and the voltage of a secondary power supply located on the secondary side;

[0032] Perform proportional-integral control on the voltage of the secondary power supply to obtain the secondary phase angle of the secondary voltage;

[0033] Performing phase shift control on the voltage of the primary power supply, the voltage of the secondary power supply and the secondary phase angle to obtain the primary phase angle of the primary voltage;

[0034] The difference phase angle is obtained based on the difference between the primary phase angle and the secondary phase angle.

[0035] Optionally, proportional-integral control is performed on the voltage of the secondary power supply to obtain a secondary phase angle of the secondary voltage, including:

[0036] Compare the voltage of the secondary power supply with the reference voltage to obtain a voltage comparison result;

[0037] The voltage comparison result is subjected to proportional-integral control to obtain the secondary side phase angle.

[0038] Optionally, proportional-integral control is performed on the comparison result to obtain the secondary side phase angle, including:

[0039] Obtain the secondary current corresponding to the voltage of the secondary power supply;

[0040] Compare the secondary current with the reference current to obtain a current comparison result;

[0041] Proportional-integral control is performed on the current comparison result and the voltage comparison result to obtain the secondary side phase angle.

[0042] Optionally, performing phase shift control on the voltage of the primary power supply, the voltage of the secondary power supply, and the secondary phase angle to obtain the primary phase angle of the primary voltage includes:

[0043] The voltage of the primary power supply, the voltage of the secondary power supply and the secondary phase angle are triple phase-shifted to achieve zero voltage switching of the wireless power transmission system and obtain the primary phase angle.

[0044] Optionally, the secondary capacitor module includes a switch-controlled capacitor; and adjusting the capacitance value of the secondary capacitor module according to the target capacitance value includes:

[0045] Determining switching parameters of the switch-controlled capacitor according to a target capacitance value;

[0046] According to the switch parameter, a control signal is sent to the switch-controlled capacitor, so that the switch-controlled capacitor adjusts its capacitance value connected in series to the secondary winding based on the control signal.

[0047] According to a third aspect of the present application, a power system is provided, comprising the wireless power transmission system in any one of the above embodiments.

[0048] According to a fourth aspect of the present application, a vehicle is provided, comprising a power system according to any one of the above embodiments.

[0049] The wireless power transmission system of the embodiment of the present application can adopt a secondary side capacitor module with adjustable capacitance value for the secondary side, so that the capacitance value of the secondary side capacitor module can be adjusted according to the determined differential phase angle to achieve the purpose of compensating for the output characteristics of the wireless power transmission system, thereby reducing the output current of the secondary side capacitor module, that is, the input current of the corresponding secondary side converter, and ultimately reducing the current stress and switching loss on the secondary side.

[0050] Other features and advantages of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0052] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings, wherein the same drawing numbers represent the same parts in the following description.

[0053] Figure 1 is a schematic structural diagram of a wireless power transmission system provided in an exemplary embodiment of the present application;

[0054] Figure 2 is a schematic diagram of a specific circuit implementation of a switch-controlled capacitor provided in an exemplary embodiment of the present application;

[0055] Figure 3 Schematic diagram of various waveforms of a wireless power transmission system provided in an exemplary embodiment of the present application under a triple phase shift strategy;

[0056] Figure 4 is a schematic diagram of an equivalent model of a wireless power transmission system provided in an exemplary embodiment of the present application;

[0057] Figure 5 is a schematic diagram of a control strategy of a wireless power transmission system provided in an exemplary embodiment of the present application;

[0058] Figure 6 is a schematic diagram of a single-loop PI control provided in an exemplary embodiment of the present application;

[0059] Figure 7 is a schematic diagram of PI control of the current inner loop provided in an exemplary embodiment of the present application;

[0060] Figure 8 Schematic diagram of PI control of the voltage outer loop provided in an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0061] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0062] According to a first aspect of the present application, a wireless power transmission system is provided, comprising a transformer module, a primary capacitor module, a primary converter electrically connected to the primary winding of the transformer module through the primary capacitor module, a secondary capacitor module, and a secondary converter electrically connected to the secondary winding of the transformer module through the secondary capacitor module.

[0063] Among them, Figure 1 As shown, the transformer module includes a transformer M, which includes a primary winding L P and the secondary winding L S The primary capacitor module includes a fixed capacitor C P The secondary capacitor module includes an adjustable switch controlled capacitor (SCC, Switch Controlled Capacitor) C S The primary side converter includes MOS transistors S1, S2, S3 and S4, and the secondary side converter includes MOS transistors Q1, Q2, Q3 and Q4.

[0064] The drain of MOS transistor S1 and the drain of MOS transistor S2 are respectively used to be electrically connected to the positive electrode of the primary power supply (such as the power grid), and the source of MOS transistor S1 is respectively connected to the drain of MOS transistor S3 and the fixed capacitor C P The first end is electrically connected to the fixed capacitor C P The second end of the primary winding L P The first end of the MOS tube S2 is electrically connected to the drain of the MOS tube S4 and the primary winding L. P The source of the MOS transistor Q3 and the source of the MOS transistor Q4 are respectively used to be electrically connected to the negative electrode of the primary power supply.

[0065] The drain of MOS tube Q1 and the drain of MOS tube Q2 are respectively used to be electrically connected to the positive electrode of the secondary power supply (such as a power battery), and the source of MOS tube Q1 is respectively connected to the drain of MOS tube Q3 and the switch control capacitor C S The first end of the switch is electrically connected to the capacitor C S The second end of the secondary winding L S The first end of the MOS tube Q2 is electrically connected to the drain of the MOS tube Q4 and the secondary winding L SThe source of the MOS transistor Q3 and the source of the MOS transistor Q4 are respectively used to be electrically connected to the negative electrode of the secondary power supply.

[0066] In other embodiments, the primary converter may also be composed of power devices other than MOS tubes, and the secondary converter may also be composed of power devices other than MOS tubes.

[0067] Among them, in other embodiments, the secondary side capacitor module can also adopt other methods besides switch-controlled capacitors to achieve the purpose of adjustable capacitance, such as adjusting the capacitance value through hardware. Specifically, the distance between the capacitor plates can be controlled by a certain driving device to achieve the adjustment of the capacitance value.

[0068] Transformer M can be a loosely coupled transformer. A loosely coupled transformer is a transformer design whose main feature is a relatively low degree of magnetic field coupling during energy transfer. Traditional transformers typically use a tightly coupled design, in which the magnetic field coupling between the primary and secondary windings is very tight. In contrast, a loosely coupled transformer reduces the degree of magnetic field coupling by increasing the gap between the primary and secondary windings or using a special magnetic circuit design. This design can reduce magnetic field leakage and mutual inductance effects, thereby reducing energy loss and electromagnetic interference during energy transmission.

[0069] Among them, the primary side converter composed of MOS transistors S1, MOS transistors S2, MOS transistors S3 and MOS transistors S4 realizes full-bridge conversion on the primary side, and the secondary side converter composed of MOS transistors Q1, MOS transistors Q2, MOS transistors Q3 and MOS transistors Q4 realizes full-bridge conversion on the secondary side.

[0070] Among them, the switch controls the capacitor C S The capacitance value of the switch control capacitor C is adjusted based on the difference phase angle to reduce S The output current of the secondary converter is also the input current of the secondary converter.

[0071] Wherein, the difference phase angle is the fixed capacitor C P The corresponding primary voltage u p The primary phase angle and switch control capacitor C S The corresponding secondary voltage u s The primary voltage is determined by the primary power supply V P and the primary converter, the secondary voltage is determined by the secondary power supply V S The primary voltage u is determined by the secondary converter. p With the primary current i p Correspondingly, the secondary voltage u s and the secondary current is Correspondingly, the secondary side also includes output current I0.

[0072] Among them, the switch controls the capacitor C S The capacitance value of the wireless power transmission system will affect the output characteristics, so based on this relationship, the capacitor C can be controlled by adjusting the switch. S For example, in this embodiment, after determining the primary phase angle, the secondary phase angle, and the difference phase angle, the switch control capacitor C can be further adjusted according to the difference phase angle based on the idea of compensating the output characteristics of the wireless power transmission system. S The capacitance value is adjusted to achieve the purpose of minimum circulating reactive power between the primary side and the secondary side. In this process, even if the primary power supply V P and the secondary power supply V S The difference is large, and it can also reduce the switch control capacitor C S output current (i.e., the input current of the secondary converter), thereby reducing the current stress and switching loss on the secondary side.

[0073] The wireless power transmission system of the embodiment of the present application can adopt a secondary side capacitor module with adjustable capacitance value for the secondary side, so that the capacitance value of the secondary side capacitor module can be adjusted according to the determined differential phase angle to achieve the purpose of compensating for the output characteristics of the wireless power transmission system, thereby reducing the output current of the secondary side capacitor module, that is, the input current of the corresponding secondary side converter, and ultimately reducing the current stress and switching loss on the secondary side.

[0074] Optionally, the switch-controlled capacitor includes a secondary capacitor and a control switch.

[0075] The first access terminal of the control switch and the first end of the secondary capacitor are electrically connected to the first common terminal, and the first common terminal serves as the first access terminal of the switch-controlled capacitor; the second access terminal of the control switch and the second end of the secondary capacitor are electrically connected to the second common terminal, and the second common terminal serves as the second access terminal of the switch-controlled capacitor; and the controlled end of the control switch serves as the controlled end of the switch-controlled capacitor.

[0076] In this embodiment, the switch controls the capacitor by controlling the ratio of the short-circuited and non-short-circuited secondary capacitors by controlling the switch, thereby achieving an equivalent capacitance value of the secondary capacitor connected in series in the secondary winding.

[0077] Among them, when the control signal connected to the controlled end of the control switch indicates conduction, the control switch is turned on, and the secondary capacitor cannot work due to short circuit; conversely, when the control signal connected to the controlled end of the control switch indicates disconnection, the control switch is disconnected, the secondary capacitor is not short-circuited, and can work normally.

[0078] The control switch can be any typical power tube.

[0079] like Figure 1 and Figure 2 As shown, optionally, the control switch includes a MOS tube S a and MOS tube S b .

[0080] Among them, MOS tube S a The drain and secondary capacitor C X The first end of the MOS tube S is electrically connected to the first common end. a The source and MOS tube S b The source of the MOS tube is electrically connected to b The drain and secondary capacitor C X The second end of the MOS tube S is electrically connected to the second common end; a The gate of the MOS tube S is used as the first controlled terminal of the switch control capacitor for receiving the first control signal; b The gate of the switch serves as the second controlled end of the switch-controlled capacitor, and is used to receive the second control signal.

[0081] Among them, when the MOS tube S a The first control signal connected to the gate of the MOS tube S b When the gate of the MOS tube is connected to the second control signal, the MOS tube S a The MOS tube S is turned on b is turned on, at this time the secondary capacitor C X is short-circuited, and the current mainly flows through the MOS tube S a and MOS tube S b , but does not flow through the MOS tube S a and MOS tube S b The anti-parallel diode. Therefore, the switch control capacitor C S Low on-state power consumption.

[0082] In other embodiments, only MOS tube S may be provided. a and MOS tube S b one of the.

[0083] According to a second aspect of the present application, a wireless power transmission method is provided, which is applied to the wireless power transmission system in any of the above embodiments. The wireless power transmission method includes:

[0084] Get the difference phase angle.

[0085] The target capacitance value of the secondary capacitor module is determined according to the difference phase angle.

[0086] Among them, after obtaining the difference phase angle, the system can determine the appropriate target capacitance value according to the corresponding compensation requirements, so that after the secondary side capacitor module is connected to the circuit with the target capacitance value, the secondary side current can be reduced.

[0087] According to the target capacitance value, the capacitance value of the secondary capacitor module is adjusted to reduce the output current of the secondary capacitor module.

[0088] After the target capacitance value is determined, the corresponding adjustment degree can be determined according to the target capacitance value and the current real-time capacitance value of the secondary capacitor module, thereby achieving capacitance adjustment of the secondary capacitor module.

[0089] The wireless power transmission method of the embodiment of the present application can adopt a secondary side capacitor module with adjustable capacitance value for the secondary side, so that the capacitance value of the secondary side capacitor module can be adjusted according to the determined differential phase angle to achieve the purpose of compensating for the output characteristics of the wireless power transmission system, thereby reducing the output current of the secondary side capacitor module, that is, the input current of the corresponding secondary side converter, and ultimately reducing the current stress and switching loss on the secondary side.

[0090] Optionally, before obtaining the difference phase angle, the wireless power transmission method further includes:

[0091] Get the voltage of the primary power supply and the voltage of the secondary power supply;

[0092] Perform proportional-integral control on the voltage of the secondary power supply to obtain the secondary phase angle of the secondary voltage;

[0093] Performing phase shift control on the voltage of the primary power supply, the voltage of the secondary power supply and the secondary phase angle to obtain the primary phase angle of the primary voltage;

[0094] The difference phase angle is obtained based on the difference between the primary phase angle and the secondary phase angle.

[0095] It should be noted that the primary voltage refers to the voltage between the primary capacitor module and the primary converter, and the primary power supply voltage refers to the voltage of the primary power supply itself; similarly, the secondary voltage refers to the voltage between the secondary capacitor module and the secondary converter, and the secondary power supply voltage refers to the voltage of the secondary power supply itself.

[0096] After obtaining the voltage of the primary power supply, the voltage of the secondary power supply, and the secondary phase angle, a triple phase shift (TPS) strategy can be used to perform phase shift control, thereby obtaining the corresponding primary phase angle and differential phase angle. In other embodiments, a single phase shift (SPS) strategy and a dual phase shift (DPS) strategy can also be used. Under the control of the triple phase shift strategy, the main waveforms of the wireless power transmission system are as follows: Figure 3 As shown, α is the primary voltage u p The primary phase angle, β is the secondary voltage u s The secondary phase angle is θ, the difference phase angle is θ, and the operating frequency of the primary converter and the secondary converter is ω. The equivalent model of the wireless power transmission system is as follows: Figure 4 As shown, U P is the equivalent primary winding L P The primary excitation voltage, U S is the equivalent secondary winding L S The secondary side excitation voltage, I P is the equivalent primary winding L P The primary excitation current, I S is the equivalent secondary winding L S The secondary side excitation current, R P is the primary winding L P Internal resistance, R S is the primary winding L S The internal resistance of the primary excitation voltage U is obtained by ignoring the loss resistance and according to Kirchhoff's voltage law. P and secondary excitation voltage U S The relationship with the current fundamental wave is as follows:

[0097]

[0098] Where Z p , Z s are the equivalent impedances of the primary winding and the secondary winding, respectively, expressed as:

[0099]

[0100] According to equations (1)-(2), the current I P and I S The expression is:

[0101]

[0102] According to the above formula, the expressions of the output active power and reactive power of the primary winding and the secondary winding can be obtained as follows:

[0103]

[0104] Where:

[0105]

[0106] As can be seen from Equation (4), the direction of system energy transmission is determined by the phase difference θ between the voltages of the primary winding and the secondary winding. By adjusting θ, soft switching of the primary and secondary converters can be achieved. In order to analyze the zero voltage switching (ZVS) condition, it is necessary to establish a time domain model of the full-bridge output current while considering harmonics. The specific derivation process is as follows:

[0107]

[0108] The optimal phase angle θ for all power switches on the primary and secondary sides to achieve ZVS can be expressed as:

[0109] θ=max(θ1,θ2) (7)

[0110] like Figure 2 As shown, the loss of the resonant network is expressed as:

[0111]

[0112] According to the above formula, the system power factor can be expressed as:

[0113]

[0114] Where, P O is the output power.

[0115] Define T ac is the ratio of the primary excitation voltage to the secondary excitation voltage. The calculation process is expressed as:

[0116]

[0117] By solving η net Relative to T ac The derivative of is used to obtain the excitation voltage ratio that maximizes the system efficiency. The specific solution process is as follows:

[0118]

[0119] From the above formula, we can see that in order to obtain the maximum system efficiency, the primary side excitation voltage and the secondary side excitation voltage should be equal. According to formulas (10)-(11), it can be concluded that α and β should satisfy:

[0120]

[0121] The primary phase angle α and the secondary phase angle β are used to achieve the matching of the excitation voltage. For a given output power P O , the optimal α and β can be expressed as:

[0122]

[0123] Based on the triple phase shift strategy, and based on the relationship among the primary phase angle α, the secondary phase angle β, and the difference phase angle θ, the primary phase angle α and the difference phase angle θ are determined in turn after the secondary phase angle β is obtained.

[0124] It should be noted that the implementation of the triple phase shift strategy in the framework of the wireless power transmission system can only achieve zero voltage turn-on of the primary converter under the condition of minimum reactive power, but it will bring a large reactive power to the secondary converter; the high current stress of the secondary converter input leads to an increase in both turn-on loss and turn-off loss. The above two reasons limit the further improvement of system efficiency. Therefore, after determining the differential phase angle θ, the present application further adjusts the capacitance value on the secondary side according to the differential phase angle θ to achieve compensation of the output characteristics, and ultimately aims to reduce the current on the secondary side.

[0125] Optionally, the secondary capacitor module includes a switch-controlled capacitor; and adjusting the capacitance value of the secondary capacitor module according to the target capacitance value includes:

[0126] Determining switching parameters of the switch-controlled capacitor according to a target capacitance value;

[0127] According to the switch parameter, a control signal is sent to the switch-controlled capacitor, so that the switch-controlled capacitor adjusts its capacitance value connected in series to the secondary winding based on the control signal.

[0128] Among them, refer again to Figure 1 and Figure 2 , with switch-controlled capacitor C S MOS tube S a and MOS tube S b As an example of its control switch, since the MOS tube S a and MOS tube S b Turning on at zero voltage further minimizes switching losses.

[0129] Among them, the switch controls the capacitor C S By changing the MOS tube S a and MOS tube S b The control angle S is used to adjust the capacitance value. Cx The Fourier decomposition of the switch control capacitor C without considering the higher harmonics S Capacitance value C eq It can be expressed as:

[0130]

[0131] Optionally, proportional-integral control is performed on the voltage of the secondary power supply to obtain a secondary phase angle of the secondary voltage, including:

[0132] The voltage of the secondary power supply is compared with the reference voltage to obtain a voltage comparison result.

[0133] The reference voltage is usually the expected value set by the system, while the voltage of the secondary power supply is the actual value.

[0134] The voltage comparison result is subjected to proportional-integral control to obtain the secondary side phase angle.

[0135] Among them, proportional-integral control is PI control.

[0136] Among them, if the voltage of the secondary power supply is less than the reference voltage, it means that the current active power on the secondary side is lower than the expected value. Therefore, it is necessary to increase the corresponding secondary phase angle to increase the secondary voltage corresponding to the secondary capacitor module. Finally, through the transmission of the secondary converter, the voltage of the secondary power supply is increased to achieve closed-loop control.

[0137] Optionally, proportional-integral control is performed on the comparison result to obtain the secondary side phase angle, including:

[0138] Get the secondary current corresponding to the secondary voltage;

[0139] Compare the secondary current with the reference current to obtain a current comparison result;

[0140] Proportional-integral control is performed on the current comparison result and the voltage comparison result to obtain the secondary side phase angle.

[0141] Among them, in the previous embodiment, only the voltage comparison is considered to realize the control of the voltage outer loop, while in this embodiment, the current inner loop is controlled based on the voltage outer loop, and finally the dual-loop PI control is realized.

[0142] In summary, the wireless power transmission method proposed in this application is based on triple phase shift strategy, adjustable capacitor compensation and dual-loop PI control to achieve the control of the entire wireless power transmission system. Figure 5 As shown, it includes PWM generator 1 on the primary side, PWM generator 2 and PWM generator 3 on the secondary side. The secondary side control logic is used to implement the switch control capacitor C S The capacitor adjustment control and the secondary power supply current I o and voltage V s By adjusting the secondary phase angle (in Figure 5 Specifically, β s) and the difference phase angle θ to adjust the current I o and voltage V s The corresponding reference current I o_ref and reference voltage V s_ref Synchronous. When the wireless power transmission system operates in constant voltage output mode, in steady state, the voltage of the secondary power supply V s Maintaining the desired value, the reactive power on both sides is minimized, and the purpose of zero voltage switching is guaranteed. If the load changes on the secondary side, it will cause voltage deviation, such as V s <V s_ref , the PI controller of the secondary converter increases the voltage V of the secondary power supply by increasing the secondary phase angle s The primary side control logic adjusts the primary side phase angle according to the secondary side phase angle (in Figure 5 Specifically, β P ) to optimize the load matching, so θ changes with β P and β s The change of β eventually achieves zero voltage switching. P , β s and θ adjust the switch control capacitor C S The control angle S is set to achieve minimum reactive power and low current stress. Finally, by controlling these four variables, efficiency optimization and constant voltage will be effectively achieved.

[0143] This application uses a dual closed-loop PI control, where the voltage outer loop is mainly used to ensure the stability of the entire converter system by stabilizing the output voltage and enhancing the system's anti-interference performance. By using a PI regulator, the output voltage can be free of static error; the main control function of the current inner loop is to quickly track the leakage inductance current given value and enhance the system's dynamic performance. This application first lists the process based on single-loop control, referring to Figure 5 , the specific control process is as follows Figure 6 shown.

[0144] The transfer function G from the current regulator control to the state sd The standard form of (s) is:

[0145]

[0146] The equivalent control block diagram of the current inner loop is as follows: Figure 7 As shown, the PI regulator transfer function of the current loop is:

[0147]

[0148] Where K pi is the proportional coefficient of the current inner loop PI regulator, K liis the integral link coefficient, from which the open-loop transfer function of the current loop can be expressed as:

[0149]

[0150] The main function of the voltage outer loop controller is to enhance the anti-interference performance of the system. Therefore, unlike the current inner loop, the response speed of the voltage outer loop is usually 1 / 20 to 1 / 5 of the response speed of the current inner loop. To simplify the design, it is approximately assumed that when the voltage outer loop is working, the current inner loop remains unchanged as a link in the voltage outer loop. In this way, 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. The control block diagram of the voltage outer loop can be obtained as follows: Figure 8 As shown, PI is the PI regulator of the voltage outer loop, which is expressed as:

[0151]

[0152] The open-loop transfer function of the voltage outer loop is obtained as:

[0153]

[0154] Where G opi (s) is the open-loop transfer function of the current inner loop designed in the previous section.

[0155] According to a third aspect of the present application, a power system is provided, comprising the wireless power transmission system in any one of the above embodiments.

[0156] The power system of the embodiment of the present application can adopt a secondary capacitor module with adjustable capacitance value for the secondary side, so that the capacitance value of the secondary capacitor module can be adjusted according to the determined differential phase angle to achieve the purpose of compensating for the output characteristics of the wireless power transmission system, thereby reducing the output current of the secondary capacitor module, that is, the input current of the corresponding secondary converter, and ultimately reducing the current stress and switching loss on the secondary side.

[0157] According to a fourth aspect of the present application, a vehicle is provided, comprising a power system according to any one of the above embodiments.

[0158] The vehicle of the embodiment of the present application can adopt a secondary capacitor module with adjustable capacitance value for the secondary side, so that the capacitance value of the secondary capacitor module can be adjusted according to the determined differential phase angle to achieve the purpose of compensating for the output characteristics of the wireless power transmission system, thereby reducing the output current of the secondary capacitor module, that is, the input current of the corresponding secondary converter, and ultimately reducing the current stress and switching loss on the secondary side.

[0159] The vehicle may be a pure electric vehicle, a plug-in hybrid vehicle, a range-extended hybrid vehicle or other new energy vehicle, and this application does not make any specific restrictions on this.

[0160] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0161] In the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0162] The embodiments, implementation methods and related technical features of the present application can be combined and replaced with each other without conflict.

[0163] The above are only preferred embodiments of the present application and do not constitute any form of limitation to the present application. In the embodiments of the present application, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, please refer to the relevant content of other embodiments. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of the technical solution of the present application.

Claims

1. A wireless power transmission system, characterized in that: It includes a transformer module, a primary capacitor module connected in series with the primary winding of the transformer module, and a secondary capacitor module connected in series with the secondary winding of the transformer module; The capacitance value of the secondary capacitor module is adjusted based on the differential phase angle to reduce the output current of the secondary capacitor module; The difference phase angle is a difference between a primary phase angle of a primary voltage corresponding to the primary capacitor module and a secondary phase angle of a secondary voltage corresponding to the secondary capacitor module.

2. The wireless power transmission system according to claim 1, wherein: The secondary side capacitor module includes a switch-controlled capacitor; The switch-controlled capacitor includes a first access terminal and a second access terminal connected in series with the secondary winding, and a controlled terminal for receiving a control signal and for adjusting a capacitance value connected in series to the secondary winding according to the control signal.

3. The wireless power transmission system according to claim 2, wherein: The switch-controlled capacitor includes a secondary capacitor and a control switch; The first access terminal of the control switch and the first terminal of the secondary capacitor are electrically connected to a first common terminal, and the first common terminal serves as the first access terminal of the switch control capacitor; The second access terminal of the control switch and the second end of the secondary capacitor are electrically connected to a second common terminal, and the second common terminal serves as the second access terminal of the switch control capacitor; The controlled end of the control switch serves as the controlled end of the switch-controlled capacitor.

4. The wireless power transmission system according to claim 3, characterized in that: The control switch includes a first MOS transistor.

5. The wireless power transmission system according to claim 4, characterized in that: The control switch further includes a second MOS tube; The drain of the first MOS transistor and the first end of the secondary capacitor are electrically connected to the first common end, the source of the first MOS transistor is electrically connected to the source of the second MOS transistor, and the drain of the second MOS transistor and the second end of the secondary capacitor are electrically connected to the second common end; The gate of the first MOS transistor serves as the first controlled end of the switch-controlled capacitor and is used to receive a first control signal; The gate of the second MOS transistor serves as the second controlled end of the switch-controlled capacitor and is used to receive a second control signal.

6. The wireless power transmission system according to any one of claims 1 to 5, characterized in that: The wireless power transmission system further includes a primary side converter and a secondary side converter; The primary converter is electrically connected to the primary capacitor module, and is used to realize energy transmission between the primary power supply and the primary capacitor module; The secondary converter is electrically connected to the secondary capacitor module to achieve energy transmission between the secondary power supply and the secondary capacitor module.

7. The wireless power transmission system according to claim 6, characterized in that: The primary side converter includes a third MOS transistor, a fourth MOS transistor, a fifth MOS transistor and a sixth MOS transistor; The drain of the third MOS transistor and the drain of the fourth MOS transistor are respectively used to be electrically connected to the positive electrode of the primary power supply, the source of the third MOS transistor is respectively electrically connected to the drain of the fifth MOS transistor and the first end of the primary capacitor module, the second end of the primary capacitor module is electrically connected to the first end of the primary winding, the source of the fourth MOS transistor is respectively electrically connected to the drain of the sixth MOS transistor and the second end of the primary winding, and the source of the fifth MOS transistor and the source of the sixth MOS transistor are respectively used to be electrically connected to the negative electrode of the primary power supply.

8. The wireless power transmission system according to claim 6, characterized in that: The secondary side converter includes a seventh MOS transistor, an eighth MOS transistor, a ninth MOS transistor and a tenth MOS transistor; The drain of the seventh MOS transistor and the drain of the eighth MOS transistor are respectively used to be electrically connected to the positive electrode of the secondary power supply, the source of the seventh MOS transistor is respectively electrically connected to the drain of the ninth MOS transistor and the first end of the secondary capacitor module, the second end of the secondary capacitor module is electrically connected to the first end of the secondary winding, the source of the eighth MOS transistor is respectively electrically connected to the drain of the tenth MOS transistor and the second end of the secondary winding, and the source of the ninth MOS transistor and the source of the tenth MOS transistor are respectively used to be electrically connected to the negative electrode of the secondary power supply.

9. A wireless power transmission method, characterized in that: Applied to the wireless power transmission system according to any one of claims 1 to 8, the wireless power transmission method comprises: Obtaining the difference phase angle; Determining a target capacitance value of the secondary capacitor module according to the difference phase angle; The capacitance value of the secondary capacitor module is adjusted according to the target capacitance value to reduce the output current of the secondary capacitor module.

10. The wireless power transmission method according to claim 9, wherein: Before obtaining the difference phase angle, the wireless power transmission method further includes: Get the voltage of the primary power supply and the voltage of the secondary power supply; Performing proportional-integral control on the voltage of the secondary power supply to obtain a secondary phase angle of the secondary voltage; performing phase shift control on the voltage of the primary power supply, the voltage of the secondary power supply, and the secondary phase angle to obtain a primary phase angle of the primary voltage; The differential phase angle is obtained according to the difference between the primary phase angle and the secondary phase angle.

11. The wireless power transmission method according to claim 10, wherein: The performing proportional-integral control on the voltage of the secondary power supply to obtain a secondary phase angle of the secondary voltage includes: Comparing the voltage of the secondary power supply with a reference voltage to obtain a voltage comparison result; Proportional-integral control is performed on the voltage comparison result to obtain the secondary side phase angle.

12. The wireless power transmission method according to claim 11, wherein: The performing proportional-integral control on the comparison result to obtain the secondary side phase angle includes: Obtaining a secondary current corresponding to the voltage of the secondary power supply; Comparing the secondary current with a reference current to obtain a current comparison result; Proportional-integral control is performed on the current comparison result and the voltage comparison result to obtain the secondary side phase angle.

13. The wireless power transmission method according to claim 10, wherein: The performing phase shift control on the voltage of the primary power supply, the voltage of the secondary power supply, and the secondary phase angle to obtain the primary phase angle of the primary voltage includes: Triple phase shift control is performed on the voltage of the primary power supply, the voltage of the secondary power supply, and the secondary phase angle to achieve zero voltage switching of the wireless power transmission system and obtain the primary phase angle.

14. The wireless power transmission method according to claim 9, wherein: The secondary side capacitor module includes a switch-controlled capacitor; The adjusting the capacitance value of the secondary capacitor module according to the target capacitance value includes: determining a switching parameter of the switch-controlled capacitor according to the target capacitance value; A control signal is sent to the switch-controlled capacitor according to the switch parameter, so that the switch-controlled capacitor adjusts its capacitance value connected in series to the secondary winding based on the control signal.

15. A power system, characterized in that: A wireless power transmission system comprising the wireless power transmission system according to any one of claims 1 to 8.

16. A vehicle, characterized in that: Including the power system described in claim 15.

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