Wireless power transmission system with mode switching and parameter optimization design method

Abstract

The invention discloses a wireless electric energy transmission system with mode switching and a parameter optimization design method, and relates to the technical field of wireless electric energy transmission. According to the system, a series hybrid compensation topology network is designed, the quantitative relation between the series hybrid compensation topology network and the working frequency of the system is constructed, the working mode is controlled by taking the working frequency as a variable, and all system parameters are constructed. Due to the fact that the quantitative relation between the output current and the system parameters is established, the hybrid topology has the load-independent output characteristic, and the system parameters can be directly solved according to constraint conditions. Besides, a parameter optimization design method is constructed based on the system, and comprises the steps of establishing a mutual inductance fluctuation retention ratio, combining a current fluctuation ratio as a constraint, taking the maximum mutual inductance fluctuation retention ratio as an optimization target, improving the anti-offset capability of the system, simplifying parameter design and ensuring efficient output of a constant current mode. The method can be popularized to other hybrid topologies, is adaptive to different asymmetric magnetic coupling mechanisms, and achieves the maximization of the multi-direction dislocation tolerance.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and particularly to a wireless power transmission system with mode switching and a parameter optimization design method. Background Art

[0002] Wireless power transmission (WPT) is a technology that uses spatial electromagnetic changes to achieve contactless power transmission. This technology solves the limitations of traditional wired and contact power transmission methods and has attracted the attention of more and more researchers. In addition, WPT has been developing towards high efficiency, high power, and high applicability. Limited by the fact that the transmission distance greatly affects the system transmission power and system efficiency, the general application of WPT technology still lies in using the near-field effect of the electromagnetic field (EMF) to achieve short-distance power transmission.

[0003] According to the transmission channel, WPT technology using the near-field effect of the electromagnetic field can be divided into two categories. Among them, capacitive power transfer (CCPT) is a representative example of electric-field-coupled WPT technology, while inductive wireless power transfer (IPT) is a representative example of magnetic-field-coupled WPT technology. Compared with magnetic-field-coupled technology, electric-field-coupled technology is limited by its finite transmission distance, and the magnetic-field-coupled transmission channel shows a wider transmission range in the near-field environment. Currently, this technology has been applied in fields such as unmanned aerial vehicles, portable electronic devices, implantable medical devices, and electric vehicles. However, in the actual application of IPT systems, the offset of the receiving coil will cause a sharp drop in the output efficiency and reliability of the system. Therefore, improving the misalignment tolerance is one of the key issues in IPT technology research.

[0004] Regarding the output fluctuation problem of IPT systems, current research has been carried out from aspects such as hybrid topologies, parameter optimization, control strategies, and magnetic coupling mechanisms. In terms of hybrid topologies, such as series hybrid compensation structures, variable inductor topologies, and clamping circuits, etc. Reconfigurable topologies are used to ensure stable output under weak coupling conditions. However, the sensitivity of the compensation parameters in the hybrid topology may still cause the output characteristics to drift, and it is difficult to achieve zero-voltage switching (ZVS) operation of the inverter switching tubes. In terms of parameter optimization, methods such as particle swarm optimization algorithms, multi-objective optimization methods, and frequency tuning strategies are used to achieve high-efficiency output under coupling and load fluctuations. However, the misalignment tolerance improved by relying solely on parameter optimization methods is often limited. In terms of control strategies, there are hybrid controls such as phase-shift modulation and frequency tracking, and double-loop decoupling control, etc. However, the increase in system control complexity leads to a sharp drop in the reliability and stability of the system within a wide coil offset range. In terms of the design of magnetic coupling mechanisms, the mutual inductance fluctuation caused by lateral offset is suppressed by increasing the size gap between the receiving coil and the transmitting coil, and an intermediate coil is constructed in the middle to improve the system misalignment tolerance. Nevertheless, due to the limited anti-offset ability of traditional coupling mechanisms, and adding an intermediate coil will increase the volume of the coupler, thus increasing system losses and reducing the system transmission efficiency. Summary of the Invention

[0005] The object of the present invention is to provide a wireless power transmission system with mode switching and a parameter optimization design method, aiming to solve or improve at least one of the above technical problems.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] A wireless power transmission system with mode switching includes: a series hybrid compensation topology network composed of a full-bridge inverter circuit, a primary compensation network, a coupling coil, a secondary compensation network, and a rectifier filter circuit; wherein, the primary compensation network includes: a primary series compensation capacitor C p1 , a primary loop compensation capacitor C p2 , a primary branch compensation capacitor C p0 , and a compensation inductor L p0 ; wherein, the primary branch compensation capacitor C p0 and the compensation inductor L p0 are connected in parallel to form a primary branch;

[0008] The input end of the full-bridge inverter circuit is connected to a DC voltage source U D , one end of the primary series compensation capacitor C p1 is connected to the output end contact point A of the full-bridge inverter circuit, and the output end contact point B of the full-bridge inverter circuit is respectively connected to the primary loop compensation capacitor C p2 and one end of the primary branch; the primary series compensation capacitor C p1 , the primary loop compensation capacitor C p2 , and the other end of the primary branch are all connected to the primary input end of the coupling coil; the secondary output end of the coupling coil is connected to the input end of the secondary compensation network, the output end of the secondary compensation network is connected to the input end of the rectifier filter circuit, and the output end of the rectifier filter circuit is connected to a battery load R L .

[0009] Optionally, the coupling coil specifically includes: a primary first transmitting coil L p1 , a primary second transmitting coil L p2 , a secondary first receiving coil L s1 , and a secondary second receiving coil L s2 ;

[0010] The primary first transmitting coil L p1 and the primary second transmitting coil L p2 are connected in series in the same direction, and the secondary first receiving coil L s1 and the secondary second receiving coil L s2They are connected in series in the same direction, and electromagnetic coupling occurs between the two coils on the primary side and the two coils on the secondary side;

[0011] Among them, one end of the first transmitting coil L on the primary side p1 is connected to the series compensation capacitor C on the primary side p1 The other end of the first transmitting coil L on the primary side p1 is respectively connected to the primary side branch and one end of the second transmitting coil L on the primary side p2 One end of the second transmitting coil L on the primary side p2 is connected to the loop compensation capacitor C on the primary side p2 The other end of the first receiving coil L on the secondary side s1 and the second receiving coil L on the secondary side s2 are both connected to the secondary side compensation network.

[0012] Optionally, the secondary side compensation network specifically includes: a secondary side series compensation capacitor C s1 , a secondary side loop compensation capacitor C s2 , a secondary side branch series compensation capacitor C x , a secondary side branch parallel compensation capacitor C s0 and a compensation inductor L s0 ; among them, the secondary side branch parallel compensation capacitor C s0 and the compensation inductor L s0 are connected in parallel to form a secondary side branch;

[0013] One end of the secondary side series compensation capacitor C s1 is connected to one end of the first receiving coil L on the secondary side s1 , and the other end is connected to the contact point C of the rectifier filter circuit; one end of the first receiving coil L on the secondary side s1 is respectively connected to one end of the second receiving coil L on the secondary side s2 and the secondary side branch series compensation capacitor C x ; the other end of the secondary side branch series compensation capacitor C x is connected to one end of the secondary side branch; the other end of the second receiving coil L on the secondary side s2 is connected to one end of the secondary side loop compensation capacitor C s2 ; the other end of the secondary side loop compensation capacitor C s2 and the other end of the secondary side branch are both connected to the contact point D of the rectifier filter circuit.

[0014] Optionally, when the operating frequency of the wireless power transfer system is f1, the operating mode 1 of the wireless power transfer system is:

[0015] The primary side series compensation capacitor C in the primary side compensation network p1, the primary side branch compensation capacitor C p0 , the compensation inductor L p0 and the primary side first transmitting coil L in the coupling coil p1 form a series resonance network; the primary side loop compensation capacitor C in the primary side compensation network p2 , the primary side branch compensation capacitor C p0 , the compensation inductor L p0 and the primary side second transmitting coil L in the coupling coil p2 form a series resonance network; the secondary side series compensation capacitor C in the secondary side compensation network s1 , the secondary side branch series compensation capacitor C x , the secondary side branch parallel compensation capacitor C s0 , the compensation inductor L s0 and the secondary side first receiving coil L in the coupling coil s1 form a series resonance network; the secondary side loop compensation capacitor C s2 , the secondary side branch series compensation capacitor C x , the secondary side branch parallel compensation capacitor C s0 and the compensation inductor L s0 and the secondary side second receiving coil L in the coupling coil s2 form a series resonance network.

[0016] Optionally, when the operating frequency of the wireless power transfer system is f2, the operating mode 2 of the wireless power transfer system is:

[0017] The primary side series compensation capacitor C in the primary side compensation network p1 , the primary side loop compensation capacitor C p2 and the primary side first transmitting coil L in the coupling coil p1 , the primary side second transmitting coil L p2 form a series resonance network; the secondary side series compensation capacitor C in the secondary side compensation network s1 , the secondary side loop compensation capacitor C s2 and the secondary side first receiving coil L in the coupling coil s1 , the secondary side second receiving coil L s2 form a series detuned network.

[0018] The present invention also provides a parameter optimization design method for a wireless power transfer system with mode switching. Based on the above system, it includes:

[0019] Step 1: Set the DC input voltage U according to the working conditions D , the rated output current I0, the battery load R L , the system output current fluctuation ratio δ and the system operating frequency f1 in operating mode 1;

[0020] Step 2: According to the resonance states of the primary and secondary compensation networks in operating mode 1 and operating mode 2, respectively obtain the quantitative relationships between the constant-current equations and the compensation parameters of the wireless power transfer system;

[0021] Step 3: According to the design requirements of the coupling coils in the wireless power transfer system, use finite element simulation software to obtain the self-inductance values of the primary first transmitting coil L p1 and the primary second transmitting coil L p2 , the self-inductance values of the secondary first receiving coil L s1 and the secondary second receiving coil L s2 , and the mutual inductance values under different offset states, and use curve fitting to analyze the relationship between the main coupling mutual inductances M1 and M2;

[0022] Step 4: Define the mutual inductance retention ratio λ, and according to the constant-current equations of the wireless charging system in operating mode 1 and operating mode 2, as well as the set system output current fluctuation ratio δ and the system operating frequency f1 in operating mode 1, calculate the output current retention ratio relationship in operating mode 1, the system operating frequency f2 in operating mode 2, and the output current retention ratio relationship;

[0023] Step 5: According to the quantitative relationships between the primary and secondary compensation parameters in operating mode 1 and operating mode 2, and the optimized values of the mutual inductance retention ratios in operating mode 1 and operating mode 1, complete the setting of the compensation element parameters.

[0024] Optionally, the definition formula of the system output current fluctuation ratio δ in Step 1 is as follows:

[0025]

[0026] where, I Omax represents the maximum allowable transmitted current of the wireless power transfer system, I Omin represents the minimum allowable transmitted current of the wireless power transfer system, and the following relationship is stipulated:

[0027]

[0028] where, I0 represents the rated output current.

[0029] Optionally, Step 2 specifically includes:

[0030] Calculate the constant-current equation of the wireless power transfer system in operating mode 1:

[0031]

[0032] where, A = L peq / ω1C seq, B = ω1, where ω1 is the operating angular frequency when the system operating frequency is f1, i.e., ω1 = 2πf1, and U in is the output voltage of the full-bridge inverter circuit, and L peq is the equivalent inductance value of the primary-branch compensation capacitor C p0 and the compensation inductor L p0 , and C seq is the equivalent capacitance value of the secondary-branch series compensation capacitor C x , the secondary-branch parallel compensation capacitor C s0 and the compensation inductor L s0 . M1 represents the mutual inductance value between the primary first transmitting coil L p1 and the secondary first receiving coil L s1 . M2 represents the mutual inductance value between the primary second transmitting coil L p2 and the secondary second receiving coil L s2 ;

[0033] Calculate the constant-current equation of the wireless power transfer system in operating mode 2:

[0034]

[0035] where ω2 is the operating angular frequency when the system operating frequency is f2, i.e., ω2 = 2πf2;

[0036] In operating mode 1, there are the following relationships between the compensation parameters of the wireless power transfer system:

[0037]

[0038] where C p1 represents the capacitance value of the primary series compensation capacitor, C p2 represents the capacitance value of the primary loop compensation capacitor, C p0 represents the capacitance value of the primary-branch compensation capacitor, L p0 represents the inductance value of the primary-branch compensation inductor, C s1 represents the capacitance value of the secondary series compensation capacitor, C s2 represents the capacitance value of the secondary loop compensation capacitor, C x represents the capacitance value of the secondary-branch series compensation capacitor, C s0 represents the capacitance value of the secondary-branch parallel compensation capacitor, L s0 represents the inductance value of the secondary-branch parallel compensation inductor, L p1 represents the inductance value of the primary first transmitting coil, L p2 represents the inductance value of the primary second transmitting coil, L s1 represents the inductance value of the secondary first receiving coil, L s2 represents the inductance value of the secondary second receiving coil;

[0039] In working mode 2, the following relationships exist among the compensation parameters of the wireless power transfer system:

[0040]

[0041] Among them, C p1 represents the capacitance value of the primary side series compensation capacitor, C p2 represents the capacitance value of the primary side loop compensation capacitor, C p0 represents the capacitance value of the primary side branch compensation capacitor, L p0 represents the inductance value of the primary side branch compensation inductor, C s1 represents the capacitance value of the secondary side series compensation capacitor, C s2 represents the capacitance value of the secondary side loop compensation capacitor, C x represents the capacitance value of the secondary side branch series compensation capacitor, C s0 represents the capacitance value of the secondary side branch parallel compensation capacitor, L s0 represents the inductance value of the secondary side branch parallel compensation inductor, L p1 represents the inductance value of the first primary side transmitting coil, L p2 represents the inductance value of the second primary side transmitting coil, L s1 represents the inductance value of the first secondary side receiving coil, L s2 represents the inductance value of the second secondary side receiving coil.

[0042] Optionally, the definition formula of the mutual inductance retention ratio λ in step four is as follows:

[0043]

[0044] Among them, M min represents the minimum mutual inductance value of the coupling mechanism within the output current fluctuation ratio δ, and M0 represents the main coupling mutual inductance when the coupling mechanism is directly aligned;

[0045] The definition formula of the system output current retention ratio Δ is as follows:

[0046]

[0047] Among them, I O represents the output current of the wireless power transfer system, and I0 represents the rated output current of the wireless power transfer system when the coupling mechanism is directly aligned.

[0048] According to the specific embodiments provided by the present invention, the following technical effects are disclosed by the present invention:

[0049] The present invention discloses a wireless power transmission system with mode switching and a parameter optimization design method. The system includes designing a series hybrid compensation topology network, establishing a quantitative relationship with the system operating frequency, controlling the operating mode with the operating frequency as a variable, and constructing all system parameters. Due to establishing a quantitative relationship between the output current and system parameters, the hybrid topology has a load-independent output characteristic, and the system parameters can be directly solved according to the constraint conditions. In addition, a parameter optimization design method is constructed based on this system, including establishing a mutual inductance fluctuation retention ratio, jointly using the current fluctuation ratio as a constraint, and taking the maximum mutual inductance fluctuation retention ratio as the optimization goal to improve the anti-offset ability of the system, simplify the parameter design, and ensure efficient output in the constant current mode. This method can be extended to other hybrid topologies, adapt to different asymmetric magnetic coupling mechanisms, and maximize the multi-directional misalignment tolerance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0051] Figure 1 It is a schematic diagram of the main circuit architecture of the wireless power transmission system with mode switching in this embodiment;

[0052] Figure 2 It is the equivalent circuit diagram of the system in operating mode 1 in this embodiment;

[0053] Figure 3 It is the equivalent circuit diagram of the system in operating mode 2 in this embodiment;

[0054] Figure 4 It is the flowchart of the steps of the parameter design method of the wireless power transmission system in this embodiment;

[0055] Figure 5 It is the design schematic diagram of the system output current - coupled mutual inductance curve in operating mode 1 in this embodiment;

[0056] Figure 6 It is the design schematic diagram of the system output current - coupled mutual inductance curve in operating mode 2 in this embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0057] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0058] The purpose of the present invention is to provide a wireless power transmission system with mode switching and a parameter optimization design method, aiming to solve or improve at least one of the above technical problems.

[0059] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0060] As Figure 1 shown, the present invention provides a wireless power transmission system with mode switching, including: a full-bridge inverter circuit, a primary compensation network, a coupling coil, a secondary compensation network, and a rectifier filter circuit.

[0061] The input end of the full-bridge inverter circuit is connected to the DC voltage source U D , and the output end is connected to the input end of the primary compensation network. The output end of the primary compensation network is connected to the primary input end of the coupling coil. The secondary output end of the coupling coil is connected to the input end of the secondary compensation network. The output end of the secondary compensation network is connected to the input end of the rectifier filter circuit; the output end of the rectifier filter circuit is connected to the battery load R L .

[0062] The primary compensation network includes a primary series compensation capacitor C p1 , a primary loop compensation capacitor C p2 , a primary branch compensation capacitor C p0 , and a compensation inductor L p0 ;

[0063] The coupling coil includes a primary first transmitting coil L p1 , a primary second transmitting coil L p2 , a secondary first receiving coil L s1 , and a secondary second receiving coil L s2 ;

[0064] The secondary compensation network includes a secondary series compensation capacitor C s1 , a secondary loop compensation capacitor C s2 , a secondary branch series compensation capacitor C x , a secondary branch parallel compensation capacitor C s0 , and a compensation inductor L s0 .

[0065] In the primary compensation network:

[0066] The primary-side series compensation capacitor C p1 One end of which is connected to an output terminal of the full-bridge inverter circuit, and the other end is connected to one end of the primary-side first transmitting coil L p1 ;

[0067] The primary-side loop compensation capacitor C p2 One end of which is connected to the other output terminal of the full-bridge inverter circuit, one end of the primary-side branch compensation capacitor C p0 One end of the compensation inductor L p0 One end of the primary-side loop compensation capacitor C p2 The other end is connected to one end of the primary-side second transmitting coil L p2 ;

[0068] The primary-side branch compensation capacitor C p0 And the compensation inductor L p0 One end of which is connected to the end where the full-bridge inverter circuit is connected to the primary-side loop compensation capacitor C p2 The primary-side branch compensation capacitor C p0 And the compensation inductor L p0 The other end is connected to the end where the primary-side first transmitting coil L p1 And the primary-side second transmitting coil L p2 Are connected;

[0069] In the secondary-side compensation network:

[0070] The secondary-side series compensation capacitor C s1 One end of which is connected to an input terminal of the rectifier and filter circuit, and the other end is connected to one end of the secondary-side first transmitting coil L s1 ;

[0071] The secondary-side loop compensation capacitor C s2 One end of which is connected to the other input terminal of the rectifier and filter circuit, one end of the secondary-side branch parallel compensation capacitor C s0 One end of the compensation inductor L s0 One end of the secondary-side loop compensation capacitor C s2 The other end is connected to one end of the secondary-side second transmitting coil L s2 ;

[0072] The secondary-side branch parallel compensation capacitor C s0 And the compensation inductor L s0 One end of which is connected to the end where the rectifier and filter circuit is connected to the secondary-side loop compensation capacitor C s2 The secondary-side branch parallel compensation capacitor C s0 And the compensation inductor L s0 The other end is connected to one end of the secondary-side branch series compensation capacitor C x ;

[0073] The secondary-side branch series compensation capacitor Cx One end of it is connected to the shunt compensation capacitor C of the secondary branch s0 and the compensation inductor L s0 One end of the series compensation capacitor C of the secondary branch x The other end is connected to the first secondary transmitting coil L s1 and the second secondary transmitting coil L s2 at the connected end.

[0074] As Figure 2 and Figure 3 shown, by controlling the operating frequency of the wireless power transfer system, the system can enter two operating modes, which respectively correspond to different magnetic coupling mechanism offset methods, namely operating mode 1 and operating mode 2;

[0075] Furthermore, by coupler design, make M p , M S approach zero to form self-decoupling; by coupler design, make M 12 and M 21 approximate to zero to form cross-decoupling.

[0076] As Figure 2 shown, when the operating frequency of the wireless power transfer system is f1, that is, operating mode 1:

[0077] The primary series compensation capacitor C in the primary compensation network p1 , the primary branch compensation capacitor C p0 and the compensation inductor L p0 and the first primary transmitting coil L in the coupling coil p1 form a series resonance network; the primary loop compensation capacitor C in the primary compensation network p2 , the primary branch compensation capacitor C p0 and the compensation inductor L p0 and the second primary transmitting coil L in the coupling coil p2 form a series resonance network; the secondary compensation network includes the secondary series compensation capacitor Cs1, the secondary branch series compensation capacitor Cx, the secondary branch parallel compensation capacitor Cs0 and the compensation inductor Ls0 and the first secondary receiving coil Ls1 in the coupling coil form a series resonance network; the secondary loop compensation capacitor Cs2, the secondary branch series compensation capacitor Cx, the secondary branch parallel compensation capacitor Cs0 and the compensation inductor Ls0 and the second secondary receiving coil Ls2 in the coupling coil form a series resonance network. Specifically:

[0078]

[0079] In the formula, ω1 is the operating angular frequency when the system operating frequency is f1, that is, ω1 = 2πf1, L peq is the primary branch compensation capacitor C p0and compensating inductor L p0 is the equivalent inductance value, C seq is the series compensating capacitor C in the secondary branch x , the parallel compensating capacitor C in the secondary branch s0 and compensating inductor L s0 is the equivalent capacitance value

[0080] At this time, the constant current equation of the wireless power transfer system in Mode 1:

[0081]

[0082] In the formula, A = L peq / ω1C seq , B = ω1, ω1 is the working angular frequency when the system working frequency is f1, U in is the output voltage of the full-bridge inverter circuit, M1 represents the mutual inductance value between the first primary transmitting coil L p1 and the first secondary receiving coil L s1 , M2 represents the mutual inductance value between the second primary transmitting coil L p2 and the second secondary receiving coil L s2 is the mutual inductance value

[0083] The current I p1 flowing through the first transmitting coil L p1 and the current I p2 flowing through the second transmitting coil L p2 in Mode 1 are expressed as follows:

[0084]

[0085] In the formula, R eq represents the equivalent AC resistance before the rectifier bridge

[0086] Furthermore, when M1→0, M2→0, I p1 and I p2 are respectively equal to:

[0087]

[0088] It can be seen from Equation (4) that when the receiving coil deviates from the working area or is removed (no load), the current flowing through the transmitting coil L p1 and the current of the transmitting coil L p2 will not increase sharply, avoiding the risk of overcurrent in the transmitting coil when the receiving coil deviates from the working area or is removed (no load).

[0089] Furthermore, the input impedance Z in of the system in Mode 1 can be expressed as:

[0090]

[0091] As can be seen from Equation (5), the imaginary part of the input impedance Z of the system in is equal to zero, that is, the input impedance of the system is purely resistive, which indicates that a zero phase difference between the primary input current and the input voltage can be achieved. This system has a zero phase angle output characteristic and does not generate reactive power. Fine-tuning the insensitive compensation parameters is expected to achieve zero-voltage turn-on of the inverter switching tubes.

[0092] As Figure 3 shown, when the operating frequency of the wireless power transfer system is f2, that is, operating mode 2:

[0093] The primary series compensation capacitor C in the primary compensation network p1 , the primary loop compensation capacitor C p2 and the primary first transmitting coil L in the coupling coil p1 , the primary second transmitting coil Lp2 form a series resonance network; the secondary series compensation capacitor C in the secondary compensation network s1 , the secondary loop compensation capacitor C s2 and the secondary first receiving coil L in the coupling coil s1 , the secondary second receiving coil L s2 form a series detuning network;

[0094] Specifically:

[0095]

[0096] In the formula, ω2 is the operating angular frequency when the operating frequency of the system is f2, that is, ω2 = 2πf2.

[0097] At this time, the constant current equation of the wireless power transfer system in mode 2:

[0098]

[0099] In the formula, ω2 is the operating angular frequency when the operating frequency of the system is f2.

[0100] The current I p1 flowing through the first transmitting coil L p2 and the current I p flowing through the second transmitting coil L

[0101]

[0102] In the formula, R eq represents the equivalent AC resistance before the rectifier bridge.

[0103] Furthermore, the input impedance Z of the system in mode 2 in can be expressed as:

[0104]

[0105] As can be seen from Equation (5), the input impedance Z of the system in is inductive, indicating that the system is expected to achieve zero-voltage turn-on of the inverter switching transistors.

[0106] In Equations (2) to (9), U in represents the output voltage of the full-bridge inverter circuit, and U in = U D ; R eq represents the equivalent AC resistance before the rectifier bridge, and R eq = R L .

[0107] As Figure 4 shown, this embodiment provides a wireless power transfer system with mode switching, which is feasible for different coupling mechanisms, including the following steps:

[0108] Step 1: Set the DC input voltage U D , the rated output current I0, the battery load R L , the system output current fluctuation ratio δ, and the system operating frequency f1 in Mode 1 according to the working condition requirements;

[0109] Step 1 specifically includes:

[0110] The definition formula of the system output current fluctuation ratio δ is as follows:

[0111]

[0112] In Equation (1), I Omax represents the maximum allowable current that the wireless power transfer system can transfer, and I Omin represents the minimum allowable current that the wireless power transfer system can transfer, and it is stipulated that they have the following relationship:

[0113]

[0114] In Equation (2), I0 represents the rated current transferred by the wireless power transfer system.

[0115] Step 2: Obtain the constant-current equation of the wireless power transfer system and the quantitative relationship between the compensation parameters respectively according to the resonance states or relationships of the primary and secondary compensation networks in Mode 1 and Mode 2;

[0116] Step 2 specifically includes Equations (1) to (2) and Equations (6) to (7).

[0117] Step 3: According to the design requirements of the coupling coils in the wireless power transfer system, obtain the primary first transmitting coil L with the help of finite element simulation software p1, the second primary emission coil L p2 and the first secondary receiving coil L s1 , the second secondary receiving coil L s2 of the self-inductance value and the mutual inductance value under different offset states, and use curve fitting to analyze the relationship between the main coupling mutual inductances M1 and M2;

[0118] Step three specifically includes:

[0119] When the main coupling mutual inductances M1 and M2 are not always equal during the offset process of the coupling mechanism, use Mode 1. The relational expression of M1 and M2 analyzed by curve fitting is as follows:

[0120] M1 = CM2 b (12)

[0121] Among them, M1 represents the mutual inductance value between the first primary emission coil L p1 and the first secondary receiving coil L s1 , M2 represents the mutual inductance value between the second primary emission coil L p2 and the second secondary receiving coil L s2 ; The values of C and b are determined by the actual fitting effect, and it is necessary to ensure that the coefficient of determination R of the fitting curve 2 > 0.99.

[0122] When the main coupling mutual inductances M1 and M2 are always equal during the offset process of the coupling mechanism in other directions, use Mode 2, that is, the relational expression of M1 and M2 is as follows:

[0123] M1 = M2 (13)

[0124] Step four: Define the mutual inductance retention ratio λ, and according to the constant current equations of the wireless charging system under Mode 1 and Mode 2, as well as the set system output current fluctuation ratio δ and the system operating frequency f1 under Mode 1, calculate the output current retention ratio relational expression under Mode 1, the system operating frequency f2 under Mode 2, and the output current retention ratio relational expression;

[0125] Step four specifically includes:

[0126] The definition formula of the system mutual inductance retention ratio λ is as follows:

[0127]

[0128] In formula (14), M min represents the minimum mutual inductance value of the coupling mechanism within the output current fluctuation ratio δ range, and M0 represents the main coupling mutual inductance when the coupling mechanism is directly aligned. The definition formula of the system output current retention ratio Δ is as follows:

[0129]

[0130] In formula (15), IO Denote the output current of the wireless power transfer system as \(I\), and the rated output current of the wireless power transfer system with the coupling mechanism in perfect alignment as \(I_0\). Combining Equation (2) and Equation (12), the relationship of the system output current retention ratio \(\Delta\) in Mode 1 is as follows:

[0131]

[0132] In Equation (16), the parameters \(B\), \(C\), \(b\), and \(M_0\) can all be determined by the system operating conditions and the coupling coil design. That is, the system output current retention ratio \(\Delta\) in Mode 1 only depends on the system mutual inductance retention ratio \(\lambda\) and the parameter \(A\).

[0133] As Figure 5 shown, to ensure that the output current of the wireless power transfer system is within the system output current fluctuation ratio \(\delta\) set by the operating conditions, that is, to limit the system output current retention ratio \(\Delta\), the constraint conditions are as follows:

[0134]

[0135] Equation (17) shows that within the output current fluctuation ratio \(\delta\), the system can select the optimal parameter \(A\) to minimize the value of the system mutual inductance retention ratio \(\lambda\), that is, to maximize the system misalignment tolerance.

[0136] Combining Equation (2) and Equation (13), the relationship of the system output current retention ratio \(\Delta\) in Mode 2 is as follows:

[0137]

[0138] In Equation (18), the system output current retention ratio \(\Delta\) in Mode 2 only depends on the system mutual inductance retention ratio \(\lambda\).

[0139] As Figure 6 shown, to ensure that the output current of the wireless power transfer system is within the system output current fluctuation ratio \(\delta\) set by the operating conditions, that is, to limit the system output current retention ratio \(\Delta\), the constraint conditions are as follows:

[0140]

[0141] Equation (19) shows that the minimum value of the system mutual inductance retention ratio \(\lambda\) that the system can achieve within the output current fluctuation ratio \(\delta\) can be determined by the system operating conditions.

[0142] Step Five: According to the quantitative relationship between the primary and secondary compensation parameters in the working Mode 1 and working Mode 2, and the optimized values of the mutual inductance retention ratios of Mode 1 and Mode 1, complete the tuning of the compensation element parameters.

[0143] Step Five specifically includes:

[0144] The calculation formula for the system working angular frequency \(\omega_2\) in Mode 2 is as follows:

[0145]

[0146] Combining Equation (1) and Equation (6) and the optimal parameter A selected in Step 4, the compensation parameters of the primary-side compensation network and the secondary-side compensation network of the system can be obtained.

[0147] Therefore, the present invention has the following beneficial effects:

[0148] 1. By designing a series hybrid compensation topology network, the present invention constructs a quantitative relationship between the compensation topology network and the operating frequency of the system, uses only the operating frequency as a variable to control the operating mode of the system, and constructs all the wireless charging system parameters including compensation parameters, constant current frequency, and mutual inductance of the coils. Moreover, since a quantitative relationship between the output current and the wireless charging system parameters is constructed, it is ensured that the hybrid topology has an inherently load-independent output, and all the wireless charging system parameters can be directly solved by the constraint conditions.

[0149] 2. By establishing a mutual inductance fluctuation retention ratio, the present invention realizes that, on the premise of meeting the basic conditions, combining the current fluctuation ratio as a constraint condition and taking the maximum mutual inductance fluctuation retention ratio as the optimization goal, so that the overall anti-offset ability of the system reaches the global maximum. During this period, there is no need to introduce other iterative or optimization algorithms additionally, simplifies the multi-variable optimization problem into a single-variable optimization problem, realizes the rapid determination of all the wireless charging system parameters, simplifies the parameter design steps of the wireless charging system, and ensures the efficient output of the constant current mode of the wireless charging system under coupling fluctuations.

[0150] 3. The wireless charging system parameter optimization design method provided by the present invention can be applied to asymmetric magnetic coupling mechanisms, can be extended to other hybrid topologies, and is feasible for different magnetic coupling mechanisms, and can realize the maximization of the misalignment tolerance in multiple directions of the magnetic coupling mechanism.

[0151] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same and similar parts among the various embodiments can be referred to each other.

[0152] Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A wireless power transmission system with mode switching, characterized in that, Including: A series hybrid compensation topology network composed of a full-bridge inverter circuit, a primary side compensation network, a coupling coil, a secondary side compensation network, and a rectifier and filter circuit; wherein, the primary side compensation network includes: a primary side series compensation capacitor C p1 , a primary side loop compensation capacitor C p2 , a primary side branch compensation capacitor C p0 , and a compensation inductor L p0 ; wherein, the primary side branch compensation capacitor C p0 and the compensation inductor L p0 are connected in parallel to form a primary side branch; The input end of the full-bridge inverter circuit is connected to the DC voltage source U D One end of the primary series compensation capacitor C p1 is connected to the output terminal contact point A of the full-bridge inverter circuit, and the output terminal contact point B of the full-bridge inverter circuit is respectively connected to the primary loop compensation capacitor C p2 and one end of the primary branch; the other ends of the primary series compensation capacitor C p1 , the primary loop compensation capacitor C p2 and the primary branch are all connected to the primary input end of the coupling coil; the secondary output end of the coupling coil is connected to the input end of the secondary compensation network, the output end of the secondary compensation network is connected to the input end of the rectifier filter circuit, and the output end of the rectifier filter circuit is connected to the battery load R L is connected.

2. The wireless power transmission system with mode switching according to claim 1, characterized in that, The coupling coil specifically includes: a primary first transmitting coil L p1 , a primary second transmitting coil L p2 , a secondary first receiving coil L s1 , and a secondary second receiving coil L s2 ; The first primary-side transmitting coil L p1 and the second primary-side transmitting coil L p2 are connected in series in the same direction. The first secondary-side receiving coil L s1 and the second secondary-side receiving coil L s2 are connected in series in the same direction, and electromagnetic coupling occurs between the two coils on the primary side and the two coils on the secondary side; Among them, one end of the primary first transmitting coil L p1 is connected to the primary series compensation capacitor C p1 , and the other end of the primary first transmitting coil L p1 is respectively connected to the primary branch and one end of the primary second transmitting coil L p2 . The other end of the primary second transmitting coil L p2 is connected to the primary loop compensation capacitor C p2 ; both the secondary first receiving coil L s1 and the secondary second receiving coil L s2 are connected to the secondary compensation network.

3. The wireless power transmission system with mode switching according to claim 2, characterized in that, The secondary side compensation network specifically includes: a secondary side series compensation capacitor C s1 , a secondary side loop compensation capacitor C s2 , a secondary side branch series compensation capacitor C x , a secondary side branch parallel compensation capacitor C s0 and a compensation inductor L s0 ; wherein, the secondary side branch parallel compensation capacitor C s0 and the compensation inductor L s0 are connected in parallel to form a secondary side branch; The secondary-side series compensation capacitor C s1 has one end connected to one end of the first secondary-side receiving coil L s1 , and the other end is connected to the contact point C of the rectifying and filtering circuit; the other end of the first secondary-side receiving coil L s1 is respectively connected to one end of the second secondary-side receiving coil L s2 and the secondary-side branch series compensation capacitor C x ; the other end of the secondary-side branch series compensation capacitor C x is connected to one end of the secondary-side branch; the other end of the second secondary-side receiving coil L s2 is connected to one end of the secondary-side loop compensation capacitor C s2 ; the other end of the secondary-side loop compensation capacitor C s2 and the other end of the secondary-side branch are both connected to the contact point D of the rectifying and filtering circuit.

4. The wireless power transmission system with mode switching according to claim 3, wherein When the operating frequency of the wireless power transfer system is f1, the operating mode 1 of the wireless power transfer system is: The primary series compensation capacitor C in the primary compensation network p1 , the primary branch compensation capacitor C p0 , the compensation inductor L p0 and the primary first transmitting coil L in the coupling coil p1 form a series resonance network; the primary loop compensation capacitor C in the primary compensation network p2 , the primary branch compensation capacitor C p0 , the compensation inductor L p0 and the primary second transmitting coil L in the coupling coil p2 form a series resonance network; the secondary series compensation capacitor C in the secondary compensation network s1 , the secondary branch series compensation capacitor C x , the secondary branch parallel compensation capacitor C s0 , the compensation inductor L s0 and the secondary first receiving coil L in the coupling coil s1 form a series resonance network; the secondary loop compensation capacitor C s2 , the secondary branch series compensation capacitor C x , the secondary branch parallel compensation capacitor C s0 and the compensation inductor L s0 and the secondary second receiving coil L in the coupling coil s2 form a series resonance network.

5. The wireless power transmission system with mode switching according to claim 3, wherein, When the operating frequency of the wireless power transfer system is f2, the operating mode 2 of the wireless power transfer system is: The primary series compensation capacitor C in the primary side compensation network p1 , the primary loop compensation capacitor C p2 and the primary first transmitting coil L in the coupling coil p1 , the primary second transmitting coil L p2 form a series resonance network; the secondary series compensation capacitor C in the secondary side compensation network s1 , the secondary loop compensation capacitor C s2 and the secondary first receiving coil L in the coupling coil s1 , the secondary second receiving coil L s2 form a series detuned network.

6. A parameter optimization design method for a wireless power transmission system with mode switching, based on the system described in any one of claims 1-5, characterized in that, Including: Step 1: Set the DC input voltage U according to the working conditions requirements D , the rated output current I0, the battery load R L , the system output current fluctuation ratio δ, and the system operating frequency f1 in operating mode 1; Step 2: According to the resonance states of the primary and secondary compensation networks in operating mode 1 and operating mode 2, respectively obtain the quantitative relationship between the constant current equation of the wireless power transfer system and the compensation parameters; Step 3: According to the design requirements of the coupling coils in the wireless power transmission system, the self-inductance values of the primary first transmitting coil L p1 , the primary second transmitting coil L p2 , the secondary first receiving coil L s1 , and the secondary second receiving coil L s2 , and the mutual inductance values in different offset states are obtained by using finite element simulation software, and the curve fitting is used to analyze the relationship between the main coupling mutual inductances M1 and M2; Step 4: Define the mutual inductance retention ratio λ, and according to the constant current equations of the wireless charging system in operating mode 1 and operating mode 2, as well as the set system output current fluctuation ratio δ and the system operating frequency f1 in operating mode 1, calculate the output current retention ratio relationship in operating mode 1, the system operating frequency f2 in operating mode 2, and the output current retention ratio relationship; Step 5: According to the quantitative relationship between the primary and secondary compensation parameters in operating mode 1 and operating mode 2, and the optimized value of the mutual inductance retention ratio in operating mode 1 and operating mode 1, complete the setting of the compensation element parameters.

7. The parameter optimization design method of the wireless power transmission system with mode switching according to claim 6, characterized in that The definition formula of the system output current fluctuation ratio δ in Step 1 is as follows: Among them, I Omax represents the maximum current value allowed to be transmitted by the wireless power transmission system, and I Omin represents the minimum current value allowed to be transmitted by the wireless power transmission system, and it is stipulated that there is the following relationship: Where, I0 represents the rated output current.

8. The parameter optimization design method of the wireless power transmission system with mode switching according to claim 6, characterized in that The definition formula of the mutual inductance retention ratio λ in Step 4 is as follows: Among them, M min represents the minimum mutual inductance value of the coupling mechanism within the output current fluctuation ratio δ, and M0 represents the main coupling mutual inductance when the coupling mechanism is directly aligned; The definition formula of the system output current retention ratio Δ is as follows: Among them, I O represents the output current of the wireless power transfer system, and I0 represents the rated output current of the wireless power transfer system with the coupling mechanism being exactly aligned.

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