Wireless power transmission system and full-working-area soft switching modeling method thereof

Abstract

The invention provides a wireless electric energy transmission system and a full working area soft switching modeling method thereof, and relates to the technical field of wireless electric energy transmission, and the modeling method comprises the steps: building a wireless electric energy transmission system; establishing a state-space equation for the wireless power transmission system; dimensionality reduction decoupling is carried out on the state-space equation to obtain a mathematical model of the wireless power transmission system; simplifying the mathematical model of the wireless power transmission system, and establishing a second-order equivalent circuit of the wireless power transmission system; and in combination with the control waveform and the state track of the second-order equivalent circuit, calculating a current value at the conduction moment, and when the current value is less than zero, calculating a phase shift control strategy for realizing soft switching in the whole working domain of the wireless power transmission system. According to the method, the influence of the harmonic content on the soft switching is considered, the wireless power transmission system is modeled and analyzed by adopting dimension reduction decoupling and combining a visual state track, the efficiency of the wireless power transmission system is improved, and meanwhile, the thermal runaway risk is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wireless power transmission, and in particular to a wireless power transmission system and a full-operating-domain soft switch modeling method thereof. Background Art

[0002] In wireless power transmission systems, in order to maximize the active power transmission capability and minimize the volt-ampere capacity of the power electronic converter, the resonant frequency of the impedance matching network is usually configured to be equal to the system operating frequency (i.e., the switching frequency). However, under this condition, the inverter operates in a hard switching state, which increases the risk of thermal runaway of power devices and reduces system efficiency. Soft switching technology has been proven to be an effective solution to the above problems.

[0003] In the related art, the methods for realizing soft switching are all based on fundamental harmonic analysis (FHA), which ignores the influence of harmonics on soft switching, so it is impossible to establish an accurate mathematical model and control method for soft switching. Especially under light load, the rich harmonic content increases the risk of soft switching loss, significantly reducing system efficiency and endangering system stability and safety.

[0004] Therefore, how to solve the above problems has become one of the technical problems that need to be solved urgently at this stage. Summary of the invention

[0005] In order to solve the above technical problems, the present disclosure provides a wireless power transmission system and a full-operating-range soft switching modeling method thereof, so as to realize full-operating-range soft switching of the wireless power transmission system.

[0006] In a first aspect, the present disclosure provides a method for modeling a full-operating-domain soft switch of a wireless power transmission system, comprising:

[0007] Build a wireless power transmission system;

[0008] Establishing a state space equation for the wireless power transfer system;

[0009] Performing dimensionality reduction and decoupling on the state space equation to obtain a mathematical model of the wireless power transmission system;

[0010] Simplifying the mathematical model of the wireless power transmission system and establishing a second-order equivalent circuit of the wireless power transmission system;

[0011] Combined with the control waveform and state trajectory of the second-order equivalent circuit, the current value at the moment of conduction is calculated. When the current value is less than zero, the phase shift control strategy for realizing soft switching in the full working range of the wireless power transmission system is calculated.

[0012] Optionally, where:

[0013] The wireless power transmission system comprises a transmitting side unit and a receiving side unit;

[0014] The transmitting side unit comprises an inverter, a transmitting side coil and a transmitting side series compensation capacitor, wherein the inverter is electrically connected to the transmitting side coil and the transmitting side series compensation capacitor;

[0015] The receiving side unit includes a rectifier, a receiving side coil and a receiving side series compensation capacitor, and the rectifier is electrically connected to the receiving side coil and the receiving side series compensation capacitor.

[0016] Optionally, where:

[0017] The establishing of a state space equation for the wireless power transmission system comprises:

[0018] Establish the state-space equation of the resonant cavity:

[0019]

[0020] in,

[0021] v Cp (t) represents the voltage value of the transmitter-side series compensation capacitor;

[0022] v Cs (t) represents the voltage value of the series compensation capacitor at the receiving side;

[0023] i AB (t) represents the inverter output current;

[0024] i ab (t) represents the input current of the rectifier;

[0025] C p represents the capacitance value of the transmitter-side series compensation capacitor;

[0026] C s represents the capacitance value of the receiving-side series compensation capacitor;

[0027] L Ls represents the self-inductance value of the receiving side coil;

[0028] L Lp represents the self-inductance value of the transmitting side coil;

[0029] L m represents the mutual inductance value of the transmitting side coil and the receiving side coil;

[0030] V AB Indicates the effective value of the output voltage of the inverter;

[0031] Vab Indicates the effective value of the input voltage of the rectifier.

[0032] Optionally, where:

[0033] The step of performing dimensionality reduction and decoupling on the state space equation comprises:

[0034] Definition Ld ,i Lq , v Cd and v Cq Performing dimensionality reduction decoupling on the state space equation;

[0035]

[0036] Among them, A d , A q , B d and B q are all decoupling factors.

[0037] Optionally, where:

[0038] The dimensionality reduction and decoupling of the state space equation further includes defining:

[0039]

[0040] A d (L Ls +L m )-A d B d L m -B d (L Lp +L m )+L m =0,

[0041] A q (L Ls +L m )+A q B q L m -B q (L Lp +L m )-L m =0,

[0042] The state space equation is simplified, and the mathematical model of the wireless power transmission system is equivalent and simplified to:

[0043]

[0044] in,

[0045] C d =Cq =C s ,

[0046]

[0047] ΔV d Denotes the D-type equivalent input voltage, ΔV q It represents the q-type equivalent input voltage.

[0048] Optionally, where:

[0049] The second-order equivalent circuit includes a d-type series resonant circuit and a q-type series resonant circuit;

[0050] The d-type series resonant circuit and the q-type series resonant circuit are both independent LC series resonant circuits.

[0051] Optionally, where:

[0052] After establishing the second-order equivalent circuit of the wireless power transmission system, the following further comprises:

[0053] The mathematical model of the wireless power transmission system is solved and normalized according to the second-order equivalent circuit.

[0054] Optionally, where:

[0055] The step of calculating the current value at the moment of conduction by combining the control waveform and the state trajectory of the second-order equivalent circuit comprises:

[0056] According to the control waveform and the state trajectory of the second-order equivalent circuit, the instantaneous value of the inverter conduction current of the D-type series resonant circuit and the instantaneous value of the inverter conduction current of the Q-type series resonant circuit are calculated.

[0057] Optionally, where:

[0058] The current value at the moment of conduction is calculated using the following formula:

[0059]

[0060] in,

[0061] and Indicates the instantaneous value of the inverter conduction current of the wireless power transmission system;

[0062] and Indicates the instantaneous value of the rectifier conduction current of the wireless power transmission system;

[0063] and represents the instantaneous value of the inverter on-current of the D-type series resonant circuit;

[0064] and It represents the instantaneous value of the inverter on-current of the q-type series resonant circuit.

[0065] In a second aspect, based on the same inventive concept, the present disclosure provides a wireless power transmission system, which implements full-operating-range soft switching by adopting the full-operating-range soft switching modeling method of the wireless power transmission system described in the first aspect.

[0066] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0067] The present disclosure provides a wireless power transmission system and a method for modeling a soft switch in the entire working domain thereof, wherein the modeling method includes: constructing a wireless power transmission system; establishing a state space equation for the wireless power transmission system; performing dimensionality reduction and decoupling on the state space equation to obtain a mathematical model of the wireless power transmission system; simplifying the mathematical model of the wireless power transmission system and establishing a second-order equivalent circuit of the wireless power transmission system; combining the control waveform and state trajectory of the second-order equivalent circuit to calculate the current value at the moment of conduction, and when the current value is less than zero, calculating the phase shift control strategy for realizing soft switching in the entire working domain of the wireless power transmission system. This method takes into account the influence of harmonic content on soft switching, adopts dimensionality reduction and decoupling, and combines visual state trajectories to model and analyze the wireless power transmission system, which is beneficial to improving the efficiency of the wireless power transmission system and reducing the risk of thermal runaway. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0069] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0070] Figure 1 The figure is a flow chart of a method for modeling a full-operating-range soft switch of a wireless power transmission system provided by an embodiment of the present disclosure;

[0071] Figure 2 Shown is a schematic diagram of the principle of a wireless power transmission system provided by an embodiment of the present disclosure;

[0072] Figure 3Shown is a second-order equivalent circuit diagram of a wireless power transmission system provided by an embodiment of the present disclosure;

[0073] Figure 4 Shown is a schematic diagram of a control waveform of a wireless power transmission system provided by an embodiment of the present disclosure;

[0074] Figure 5 Shown is a schematic diagram of a state trajectory of a wireless power transmission system provided by an embodiment of the present disclosure;

[0075] Figure 6 The figure shows a schematic diagram of the input and output measurement results of a resonant cavity of a wireless power transmission system provided by an embodiment of the present disclosure;

[0076] Figure 7 The figure is a schematic diagram of the relationship between efficiency and output power of a wireless power transmission system provided by an embodiment of the present disclosure. DETAILED DESCRIPTION

[0077] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0078] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0079] The inventors found in their research that there are three methods for realizing soft switching in wireless power transmission systems: (1) frequency conversion control; (2) active tuning method for impedance matching network; and (3) phase shift modulation method.

[0080] Changing the switching frequency of the inverter in real time is the simplest and most feasible solution to achieve zero voltage switching (ZVS). However, there are many disadvantages, such as increased electromagnetic interference (EMI), reduced active power transmission capability, increased reactive power loss, and the switching frequency range is limited by wireless charging standards (such as SAE J2954 and Qi), making it difficult to promote and apply.

[0081] Active tuning methods for impedance matching networks include variable capacitors, variable inductors, and active rectifiers. Capacitor matrices and PWM (Pulse Width Modulation) controlled active capacitors can dynamically adjust their equivalent capacitance through reasonable control strategies to achieve soft switching operation. However, the equivalent capacitance of the capacitor matrix cannot be adjusted continuously, making it difficult to achieve precise soft switching control. The equivalent capacitance range of PWM controlled active capacitors is limited, making it impossible to achieve soft switching control over the entire operating range. Inductor matrices and PWM controlled active inductors are similar to variable capacitors, and they also have problems such as the inability to continuously adjust the equivalent inductance and the small adjustable range of the equivalent inductance. Compared with variable capacitors and variable inductors, active rectifiers can be equivalent to either resistance-inductance or resistance-capacitance, and the inductance or capacitance range is adjustable, which has been studied in depth.

[0082] Phase shift modulation methods, including single phase shift (SPS), dual phase shift (DPS) and triple phase shift (TPS), are effective ways to enable soft switching operation of bidirectional wireless power transmission systems. In particular, triple phase shift modulation technology has a wide soft switching control capability and has been widely used.

[0083] However, the above methods for realizing soft switching are all based on fundamental harmonic approximation (FHA), which ignores the influence of harmonics on soft switching, so it is impossible to establish an accurate mathematical model and control method for soft switching. Especially under light load, the rich harmonic content increases the risk of soft switching loss, significantly reduces system efficiency and endangers system stability and safety.

[0084] Therefore, how to solve the above problems has become one of the technical problems that need to be solved urgently at this stage.

[0085] In order to solve the above technical problems, the present disclosure provides a wireless power transmission system and a full-operating-range soft switching modeling method thereof, so as to realize full-operating-range soft switching of the wireless power transmission system.

[0086] Figure 1 FIG. 1 is a flow chart of a method for modeling a full-operating-domain soft switch of a wireless power transmission system provided by an embodiment of the present disclosure. Please refer to FIG. Figure 1 The present disclosure provides a method for modeling a full-operating-domain soft switch of a wireless power transmission system, comprising:

[0087] Step S01, building a wireless power transmission system;

[0088] Step S02: establishing a state space equation for the wireless power transmission system;

[0089] Step S03, performing dimensionality reduction and decoupling on the state space equation to obtain a mathematical model of the wireless power transmission system;

[0090] Step S04, simplifying the mathematical model of the wireless power transmission system and establishing a second-order equivalent circuit of the wireless power transmission system;

[0091] Step S05, combining the control waveform and state trajectory of the second-order equivalent circuit, calculating the current value at the moment of conduction, and when the current value is less than zero, calculating the phase shift control strategy for realizing soft switching in the entire working range of the wireless power transmission system.

[0092] It should be noted that the present disclosure provides a method for modeling a soft switch in the entire working range of a wireless power transmission system, including but not limited to steps S01 to S05. Soft switching is a switching method or device relative to hard switching. Soft switching is switched on and off when the voltage or current is zero (or close to zero) during the switching transition, which greatly reduces the switching loss and is conducive to improving the efficiency of the wireless power transmission system.

[0093] Specifically, the present disclosure provides a method for modeling switches in the entire working range of a wireless power transmission system. In step S01, a wireless power transmission system is built. The wireless power transmission system is a system that does not rely on traditional wire connections and realizes the transmission of electric energy from a charging source end to a load end through electromagnetic fields, electromagnetic waves, etc.

[0094] In step S02, a state space equation is established for the wireless power transmission system constructed in step S01. The state space equation is a mathematical model in modern control theory that describes the dynamic behavior of the system. In the power system, the state space equation can be used to describe the dynamic behavior of the power system. It should be noted that the full-operating-domain switch modeling method of the wireless power transmission system provided in the present disclosure takes the resonant cavity into consideration when establishing the state space equation. In this way, the influence of the harmonic content on the soft switch is taken into consideration, which is conducive to reducing the risk of soft switch loss and improving the stability and safety of the wireless power transmission system.

[0095] In step S03, the state space equation established in step S02 is subjected to dimensionality reduction and decoupling to obtain a mathematical model of the wireless power transmission system, thereby facilitating further analysis and processing of the wireless power transmission system.

[0096] In step S04, the mathematical model of the wireless power transmission system is simplified, and a second-order equivalent circuit of the wireless power transmission system is established according to the simplified mathematical model, so as to facilitate the subsequent calculation of the current value of the wireless power transmission system at the moment of conduction.

[0097] In step S05, the current value of the wireless power transmission system at the moment of conduction is calculated according to the second-order equivalent circuit established in step S04, combined with the control waveform and the state trajectory. The conditions for all power devices in the wireless power transmission system to achieve soft switching include: the current value of the power device at the moment of conduction is less than zero. Therefore, by calculating the current value of the wireless power transmission system at the moment of conduction, making the current value less than zero, the phase shift control strategy for soft switching of the wireless power transmission system in the entire working range can be calculated.

[0098] It should be noted that the soft switching modeling method for the full working range of the wireless power transmission system provided in the present invention takes into account the impact of harmonic content on soft switching, adopts dimensionality reduction decoupling, and combines visual state trajectories to model and analyze the wireless power transmission system, which is beneficial to improving the efficiency of the wireless power transmission system and reducing the risk of thermal runaway.

[0099] Figure 2 FIG. 1 is a schematic diagram showing a principle of a wireless power transmission system provided by an embodiment of the present disclosure. Please refer to FIG. Figure 1 and Figure 2 , in an optional embodiment of the present disclosure, the wireless power transmission system 100 includes a transmitting side unit 10 and a receiving side unit 20;

[0100] The transmitting side unit 10 includes an inverter 11, a transmitting side coil Lp and a transmitting side series compensation capacitor Cp, and the inverter 11 is electrically connected to the transmitting side coil Lp and the transmitting side series compensation capacitor Cp;

[0101] The receiving side unit 20 includes a rectifier 21, a receiving side coil Ls and a receiving side series compensation capacitor Cs, and the rectifier 21 is electrically connected to the receiving side coil Ls and the receiving side series compensation capacitor Cs.

[0102] Specifically, in the full-operating-domain soft-switch modeling method of the wireless power transmission system provided by the present disclosure, in step S01, a wireless power transmission system 100 is constructed, and the wireless power transmission system 100 includes a transmitting side unit 10 and a receiving side unit 20, and electric energy is transmitted from the transmitting side unit 10 to the receiving side unit 20. The transmitting side unit 10 includes an inverter 11, a transmitting side coil Lp and a transmitting side series compensation capacitor Cp, and the inverter 11 includes a power device Q AB1 , Q AB2 , Q AB3 and Q AB4 , the output voltage of inverter 11 is v AB (t), the output current of the inverter 11 is i AB (t). The receiving side unit 20 includes a rectifier 21, a receiving side coil Ls and a receiving side series compensation capacitor Cs. The rectifier 21 includes a power device Q ab1 , Q ab2 , Qab3 and Q ab4 , the input voltage of rectifier 21 is v ab (t), the input current of the rectifier 21 is i ab (t). The input and output DC voltages of the wireless power transmission system 100 are V dc.AB and V dc.ab .

[0103] It should be noted that Figure 2 The wireless power transmission system 100 shown in the figure is a wireless power transmission system based on the SS compensation network (Series-Series Compensating Network), which is a compensation network used in electronic circuits to improve circuit performance. The SS compensation network is usually composed of an inductor and a capacitor, which is connected at a specific position of the circuit to compensate for the circuit performance. In the SS compensation network, when the values ​​of the inductor and the capacitor satisfy a certain relationship, the circuit will resonate. The full-operating domain soft switching modeling method of the wireless power transmission system provided in the present disclosure takes into account the influence of harmonic content on the soft switch, and therefore, a wireless power transmission system 100 based on the SS compensation network is established.

[0104] Please continue to refer to Figure 1 and Figure 2 , for the above-mentioned wireless power transmission system 100, a state space equation is established. The present disclosure provides an optional implementation mode of establishing a state space equation for the wireless power transmission system 100, including:

[0105] Establish the state-space equation of the resonant cavity:

[0106]

[0107] in,

[0108] v Cp (t) represents the series compensation capacitor C on the transmitter side p Voltage value;

[0109] v Cs (t) represents the series compensation capacitor C on the receiving side s Voltage value;

[0110] i AB (t) represents the output current of the inverter 11;

[0111] i ab (t) represents the input current of the rectifier 21;

[0112] C p Indicates the transmitter side series compensation capacitor C p Capacitance value;

[0113] C s Indicates the series compensation capacitor C on the receiving side s Capacitance value;

[0114] L Ls Indicates the self-inductance value of the receiving side coil Ls;

[0115] L Lp Indicates the self-inductance value of the transmitting side coil Lp;

[0116] L m Indicates the mutual inductance of the transmitting side coil Lp and the receiving side coil Ls;

[0117] V AB represents the effective value of the output voltage of the inverter 11;

[0118] V ab Indicates the effective value of the input voltage of the rectifier 21.

[0119] It should be noted that this embodiment Figure 2 The wireless power transmission system 100 shown establishes a state-space equation. In order to realize soft switching of the wireless power transmission system 100 over the entire working range, the present disclosure considers the influence of harmonics on soft switching, establishes the state-space equation of the resonant cavity, and models and analyzes the wireless power transmission system 100.

[0120] Please continue to refer to Figure 1 and Figure 2 The present disclosure provides an optional implementation mode, in step S03, performing dimensionality reduction decoupling on the state space equation, including:

[0121] Definition Ld ,i Lq , v Cd and v Cq Decouple the state space equations by reducing their dimensionality;

[0122]

[0123] Among them, A d , A q , B d and B q are all decoupling factors.

[0124] It should be noted that i AB (t) and i AB Both represent the output current of the inverter 11; i ab (t) and i ab Both represent the input current of the rectifier 21; v Cp (t) and v Cp Both represent the transmitter side series compensation capacitor C pVoltage value; v Cs (t) and v Cs Both represent the receiving side series compensation capacitor C s The voltage value of the voltage. "(t)" represents the instantaneous value at time t. It should also be noted that the present disclosure defines i Ld ,i Lq , v Cd and v Cq The state space equation is decoupled by reducing the dimension. In formulas (5) to (8), i is used Ld ,i Lq , v Cd and v Cq Substitute the content on the other side of the equation, i Ld ,i Lq , v Cd and v Cq Has no practical meaning.

[0125] Specifically, by substituting formulas (5) to (8) into formulas (1) to (4), we can obtain:

[0126]

[0127] In order to further reduce the dimension and decouple the state space equation, the present disclosure provides an optional implementation method of reducing the dimension and decoupling the state space equation, further comprising defining:

[0128]

[0129] A d (L Ls +L m )-A d B d L m -B d (L Lp +L m )+L m =0 (15)

[0130] A q (L Ls +L m )+A q B q L m -B q (L Lp +L m )-L m =0 (16)

[0131] The state space equation is simplified, and the mathematical model of the wireless power transmission system 100 is equivalent and simplified to:

[0132]

[0133] in,

[0134] C d =C q =C s (twenty one)

[0135]

[0136] ΔV d Denotes the D-type equivalent input voltage, ΔV q It represents the q-type equivalent input voltage.

[0137] It should be noted that the purpose of setting formulas (21) to (27) is to further simplify the formulas. d , L d , L q , A v , B v , A u and B u Has no practical meaning.

[0138] Specifically, in this implementation, the state space equation is further decoupled by dimensionality reduction, and formulas (13) to (16) are defined. Formulas (28) to (31) can be derived from formulas (13) to (16):

[0139]

[0140] Substituting formulas (28) to (31) into formulas (9) to (12), Figure 2 The mathematical model of the wireless power transmission system based on the SS compensation network shown can be equivalent to:

[0141]

[0142] In order to further simplify the mathematical model, formulas (21) to (23) are set. Through formulas (21) to (23), formulas (32) to (35) are further simplified to formulas (17) to (20), that is, Figure 2 The mathematical model corresponding to the wireless power transmission system 100 shown in is simplified to formulas (17) to (20).

[0143] According to formulas (17) to (20), the second-order equivalent circuit of the wireless power transmission system 100 is established: Figure 3 FIG. 1 is a second-order equivalent circuit diagram of a wireless power transmission system provided by an embodiment of the present disclosure. Please refer to FIG. Figure 1 to Figure 3In an optional embodiment of the present disclosure, the second-order equivalent circuit 100 includes a D-type series resonant circuit and a Q-type series resonant circuit; the D-type series resonant circuit and the Q-type series resonant circuit are both independent LC series resonant circuits.

[0144] Specifically, according to formula (17) and formula (18), a d-type series resonant circuit is established, and according to formula (19) and formula (20), a q-type series resonant circuit is established, that is, Figure 2 The wireless power transmission system 100 shown is equivalent to two independent LC series resonant circuits. Figure 3 (a) shows a D-type series resonant circuit including a capacitor C d 、Inductance L d and the equivalent input voltage ΔV d ; Please refer to Figure 3 (b) shows a q-type series resonant circuit including a capacitor C q 、Inductance L q and the equivalent input voltage ΔV q With such an arrangement, the wireless power transmission system 100 is decoupled from a four-dimensional system into a second-order equivalent circuit 200 , which is beneficial for analyzing and processing the system, thereby facilitating the realization of full-range soft switching of the wireless power transmission system 100 .

[0145] Please continue to refer to Figure 1 to Figure 3 In an optional embodiment of the present disclosure, after establishing the second-order equivalent circuit 200 of the wireless power transmission system 100, the following further includes:

[0146] The mathematical model of the wireless power transmission system 100 is solved and normalized according to the second-order equivalent circuit 200 .

[0147] Specifically, according to Figure 3 , formulas (17) to (20) can be solved to obtain:

[0148]

[0149] In the formula, and They are Figure 3 (a) The D-type series resonant circuit and Figure 3 (b) The resonant frequency of the q-type series resonant circuit; and It represents characteristic impedance; and is the initial voltage value of the equivalent capacitor, and is the initial current value of the equivalent inductor.

[0150] After normalizing formulas (36) to (39), we can obtain:

[0151]

[0152] It should be noted that per-unit is also called normalization, which is a processing method widely used in the fields of power system and circuit analysis. Per-unit is a method of expressing physical quantities with relative values ​​(per-unit values). The per-unit value of a physical quantity is equal to the ratio of the actual value of the physical quantity to the selected reference value of the same unit. For example, for voltage U, its per-unit value is Among them U B It is the reference value of voltage. In the power system analysis, many different levels of voltage, current, power, impedance and other physical quantities are involved. After per unit normalization, physical quantities of different dimensions and orders of magnitude are converted into relatively simple per unit values ​​for calculation, which is further conducive to simplifying the calculation process and improving the versatility and practicality of the model.

[0153] After the second-order equivalent circuit 200 is established, the current value at the turn-on moment is calculated by combining the control waveform and the state trajectory of the second-order equivalent circuit 200 . Figure 4 FIG. 1 is a schematic diagram of a control waveform of a wireless power transmission system provided by an embodiment of the present disclosure. Figure 5 FIG. 1 is a schematic diagram of a state trajectory of a wireless power transmission system provided by an embodiment of the present disclosure. Please refer to FIG. Figure 1 to Figure 5 The present disclosure provides an optional implementation method for calculating the current value at the turn-on moment in combination with the control waveform and state trajectory of the second-order equivalent circuit 200, including: calculating the instantaneous value of the inverter turn-on current of the D-type series resonant circuit and the instantaneous value of the inverter turn-on current of the Q-type series resonant circuit according to the control waveform and state trajectory of the second-order equivalent circuit 200.

[0154] Specifically, Figure 4 The typical waveform of the wireless power transmission system based on the single phase shift modulation strategy is shown in FIG. The output voltage of the inverter 21 and the input voltage of the rectifier are both square waves with a duty cycle of 50%, and the phase angle between them is γ. dx Indicates the power device Q ABx (and Q abx ) conduction moment. Combined Figure 4 And formula (40) ~ (43), we can get the state trajectory of the d-type series resonant circuit and the q-type series resonant circuit, please refer to Figure 5 , Figure 5 (a) shows the state trajectory of a D-type series resonant circuit, Figure 5 (b) shows the state trajectory of the q-type series resonant circuit. The state trajectory of the d-type series resonant circuit and the q-type series resonant circuit are both composed of 4 arcs. dx and O qx is the center of the arc, and its coordinates are shown in Table 1. dxand R qx is the radius of the arc.

[0155] Table 1 Center of the state trajectory of the wireless power transmission system

[0156]

[0157] Figure 5 In (a), facing ΔO d1 O d2 P d1 , ΔO d1 O d3 P d4 , ΔO d2 O d4 P d2 , ΔO d3 O d4 P d3 Establishing the triangle side angle formula, we can get:

[0158]

[0159] In formulas (44) to (47), combined Figure 4 We can get:

[0160] θ d1 =θ d3 =γ (48)

[0161] θ d2 =θ d4 =π-γ (49)

[0162] Combination Figure 5 (a), the instantaneous value of the inverter conduction current of the D-type series resonant circuit can be calculated, and formula (50) can be obtained:

[0163]

[0164] Similarly, according to Figure 5 (b) Combined Figure 3 and Figure 4 , we can get:

[0165]

[0166]

[0167] It should be noted that in this embodiment, the instantaneous value of the inverter conduction current of the D-type series resonant circuit and the instantaneous value of the inverter conduction current of the Q-type series resonant circuit are calculated to facilitate the subsequent calculation of the current value at the moment of conduction of the wireless power transmission system.

[0168] Please continue to refer to Figure 1 to Figure 5In an optional implementation of the present disclosure, the current value at the moment of conduction is calculated using the following formula:

[0169]

[0170] in,

[0171] and represents the instantaneous value of the on-current of the inverter 11 of the wireless power transmission system 100;

[0172] and represents the instantaneous value of the on-current of the rectifier 21 of the wireless power transmission system 100;

[0173] and It represents the instantaneous value of the inverter conduction current of the D-type series resonant circuit;

[0174] and It represents the instantaneous value of the inverter on-current of the q-type series resonant circuit.

[0175] Specifically, the present disclosure calculates the instantaneous value of the inverter conduction current of the d-type series resonant circuit and the instantaneous value of the inverter conduction current of the q-type series resonant circuit by formula (50) and formula (55). Substituting formula (50) and formula (55) into formula (5) and formula (6), the power device Q in the inverter can be calculated. AB1 , Q AB2 , Q AB3 and Q AB4 , and the power device Q in the rectifier ab1 , Q ab2 , Q ab3 and Q ab4 Current at the moment of conduction and The condition for all power devices in the transmitting side unit 10 and the receiving side unit 20 to achieve soft switching is that their instantaneous turn-on current is less than 0, as shown in formulas (56) to (59). The phase shift control strategy that enables all power devices in the wireless power transmission system 100 to achieve precise soft switching can be calculated.

[0176] It should be noted that in order to verify the effect of the full working range soft switching modeling method of the wireless power transmission system provided by the present invention on achieving the full working range soft switching, the inventors Figure 2 A wireless power transmission system experimental platform was built, and the experimental results are as follows: Figure 6 and Figure 7 As shown, Figure 6FIG. 1 is a schematic diagram of a measurement result of a resonance cavity input and output of a wireless power transmission system provided by an embodiment of the present disclosure. Figure 7 FIG. 1 is a schematic diagram showing the relationship between the efficiency and output power of a wireless power transmission system provided by an embodiment of the present disclosure. Please refer to FIG. Figure 6 , Figure 6 The wireless power transmission system resonant cavity input and output voltage v is shown in AB (t) and v ab (t), and the current i AB (t) and i ab (t) waveform. Figure 6 It can be concluded that v AB (t) and v ab (t) are both square waves with a duty cycle of 50%, and Figure 4 The analysis in is completely consistent; and under different working conditions, the phase shift angle between the inverter 11 and the rectifier 21 can be calculated by formulas (56) to (59), so that v AB (t) Ahead i AB (t), and v ab (t) Lag i ab (t), that is, all power devices of the inverter 11 and the rectifier 21 have achieved precise soft switching.

[0177] At different voltage gains (V dc.ab / V dc.AB =0.8, 1 and 1.2) working conditions, Figure 7 The figure shows the relationship between the efficiency and output power of the wireless power transmission system. It can be concluded that the transmission efficiency increases with the increase of output power; at the same output power, the smaller the voltage gain, the greater the transmission efficiency; and the peak efficiency at rated output power is as high as 95.1%.

[0178] It should be noted that the soft switch modeling method for the entire working range of the wireless power transmission system provided in the present invention takes into account the impact of harmonic content on soft switching during the modeling and analysis process, adopts dimensionality reduction decoupling and normalized analysis methods, and combines visual state trajectories to model and analyze the wireless power transmission system, which is beneficial to improving the efficiency of the wireless power transmission system and reducing the risk of thermal runaway.

[0179] Please refer to Figure 2 Based on the same inventive concept, the present disclosure also provides a wireless power transmission system 100, which implements full-operating-domain soft switching by using any one of the wireless power transmission system full-operating-domain soft switching modeling methods provided in the embodiments of the present disclosure.

[0180] It should be noted that the embodiment of the wireless power transmission system 100 provided in the embodiment of the present disclosure can refer to the embodiment of the wireless power transmission system full working range soft switch modeling method, which will be repeatedly pointed out and will not be repeated. The wireless power transmission system 100 with full working range soft switching implemented by the wireless power transmission system full working range soft switch modeling method is conducive to improving system efficiency and reducing the risk of thermal runaway.

[0181] It can be seen from the above embodiments that the wireless power transmission system and the full-operating-range soft switch modeling method thereof provided by the present disclosure achieve at least the following beneficial effects:

[0182] The present disclosure provides a wireless power transmission system and a method for modeling a soft switch in the entire working domain thereof, wherein the modeling method includes: constructing a wireless power transmission system; establishing a state space equation for the wireless power transmission system; performing dimensionality reduction and decoupling on the state space equation to obtain a mathematical model of the wireless power transmission system; simplifying the mathematical model of the wireless power transmission system and establishing a second-order equivalent circuit of the wireless power transmission system; combining the control waveform and state trajectory of the second-order equivalent circuit to calculate the current value at the moment of conduction, and when the current value is less than zero, calculating the phase shift control strategy for realizing soft switching in the entire working domain of the wireless power transmission system. This method takes into account the influence of harmonic content on soft switching, adopts dimensionality reduction and decoupling, and combines visual state trajectories to model and analyze the wireless power transmission system, which is beneficial to improving the efficiency of the wireless power transmission system and reducing the risk of thermal runaway.

[0183] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0184] The above description is only a specific embodiment of the present disclosure, so that those skilled in the art can understand or implement the present disclosure. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for modeling soft switching of a wireless power transmission system over the entire working range, characterized in that: include: Build a wireless power transmission system; Establishing a state space equation for the wireless power transfer system; Performing dimensionality reduction and decoupling on the state space equation to obtain a mathematical model of the wireless power transmission system; Simplifying the mathematical model of the wireless power transmission system and establishing a second-order equivalent circuit of the wireless power transmission system; Combined with the control waveform and state trajectory of the second-order equivalent circuit, the current value at the moment of conduction is calculated. When the current value is less than zero, the phase shift control strategy for realizing soft switching in the full working range of the wireless power transmission system is calculated.

2. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 1, characterized in that: The wireless power transmission system comprises a transmitting side unit and a receiving side unit; The transmitting side unit comprises an inverter, a transmitting side coil and a transmitting side series compensation capacitor, wherein the inverter is electrically connected to the transmitting side coil and the transmitting side series compensation capacitor; The receiving side unit includes a rectifier, a receiving side coil and a receiving side series compensation capacitor, and the rectifier is electrically connected to the receiving side coil and the receiving side series compensation capacitor.

3. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 2, characterized in that: The establishing of a state space equation for the wireless power transmission system comprises: Establish the state-space equation of the resonant cavity: in, v Cp (t) represents the voltage value of the transmitter-side series compensation capacitor; v Cs (t) represents the voltage value of the series compensation capacitor at the receiving side; i AB (t) represents the inverter output current; i ab (t) represents the input current of the rectifier; C p represents the capacitance value of the transmitter-side series compensation capacitor; C s represents the capacitance value of the receiving-side series compensation capacitor; L Ls represents the self-inductance value of the receiving side coil; L Lp represents the self-inductance value of the transmitting side coil; L m represents the mutual inductance value of the transmitting side coil and the receiving side coil; V AB Indicates the effective value of the output voltage of the inverter; V ab Indicates the effective value of the input voltage of the rectifier.

4. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 3, characterized in that: The step of performing dimensionality reduction and decoupling on the state space equation comprises: Definition Ld ,i Lq , v Cd and v Cq Performing dimensionality reduction decoupling on the state space equation; Among them, A d , A q , B d and B q are all decoupling factors.

5. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 4, characterized in that: The dimensionality reduction and decoupling of the state space equation further includes defining: A d (L Ls +L m )-A d B d L m -B d (L Lp +L m )+L m =0, A q (L Ls +L m )+A q B q L m -B q (L Lp +L m )-L m =0, The state space equation is simplified, and the mathematical model of the wireless power transmission system is equivalent and simplified to: in, C d =C q =C s , ΔV d Denotes the D-type equivalent input voltage, ΔV q It represents the q-type equivalent input voltage.

6. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 5, characterized in that: The second-order equivalent circuit includes a d-type series resonant circuit and a q-type series resonant circuit; The d-type series resonant circuit and the q-type series resonant circuit are both independent LC series resonant circuits.

7. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 6, characterized in that: After establishing the second-order equivalent circuit of the wireless power transmission system, the following further comprises: The mathematical model of the wireless power transmission system is solved and normalized according to the second-order equivalent circuit.

8. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 7, characterized in that: The step of calculating the current value at the moment of conduction by combining the control waveform and the state trajectory of the second-order equivalent circuit comprises: According to the control waveform and the state trajectory of the second-order equivalent circuit, the instantaneous value of the inverter conduction current of the D-type series resonant circuit and the instantaneous value of the inverter conduction current of the Q-type series resonant circuit are calculated.

9. The method for modeling soft switches in the entire working range of a wireless power transmission system according to claim 8, characterized in that: The current value at the moment of conduction is calculated using the following formula: in, i QAB1(3) (t) and i QAB2(4) (t) represents the instantaneous value of the inverter conduction current of the wireless power transmission system; i Qab1(3) (t) and i Qab2(4) (t) represents the instantaneous value of the rectifier conduction current of the wireless power transmission system; i Ld,QAB1(3) ,i Ld,QAB2(4) ,i Ld,Qab1(3) and i Ld,Qab2(4) represents the instantaneous value of the inverter on-current of the D-type series resonant circuit; i Lq,QAB1(3) ,i Lq,QAB2(4) ,i Lq,Qab1(3) and i Lq,Qab2(4) It represents the instantaneous value of the inverter conduction current of the q-type series resonant circuit.

10. A wireless power transmission system, characterized in that: The full-operating-domain soft switching modeling method for a wireless power transmission system according to any one of claims 1 to 9 is adopted to realize full-operating-domain soft switching.

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