Variable resonant network for multi-frequency multi-load wpt system and control method thereof

Abstract

The application provides a variable resonance network for a multi-frequency multi-load WPT system and a control method thereof, wherein the variable resonance network comprises a transmitting coil, n switch capacitor components and n-1 switch inductor components; each switch capacitor component is formed by connecting a tuning capacitor and a short-circuit switch in parallel; each switch inductor component is formed by connecting a tuning inductor and an open-circuit switch in series; the first switch capacitor component is connected in series with the transmitting coil; the i+1th switch capacitor component is connected across the ith switch capacitor component after being connected in series with the ith switch inductor component, i=1~n-1; and the resonance frequency is adjusted by changing the states of the short-circuit switches and the open-circuit switches. The effect is that the dynamic transformation of the resonance network can be realized, so as to meet the power supply requirements of multiple loads at any frequency and any number, and the resonance frequency can be changed through the change of the resonance network, so as to compensate the reactive power of the system, and the system can be efficiently operated.

Description

TECHNICAL FIELD

[0001] The present application relates to wireless power transfer technology, in particular to a variable resonant network for a multi-frequency multi-load WPT system and a control method thereof. BACKGROUND

[0002] Wireless power transfer (WPT) technology has been widely used in electric vehicles, consumer electronics, household appliances and other fields due to its high efficiency and flexibility. For some special application scenarios, the system often adopts a multi-frequency multi-load operation mode. For example, a multi-frequency multi-load wireless power transfer system based on multi-modulation wave composite SPWM control is disclosed in Chinese patent 202010342975.8.

[0003] Research on multi-frequency multi-load wireless power transfer systems mainly focuses on how to make the inverter output multi-frequency power. Research on the resonant network of multi-frequency multi-load wireless power transfer systems is less. Currently, some researchers have proposed multi-frequency resonant networks with multiple resonant frequencies to achieve multi-frequency power transmission while maintaining high system efficiency. Some researchers have proposed transmitting multi-frequency power without using a resonant network, which allows for flexible switching of frequencies. However, these studies still have the following shortcomings.

[0004] (1) In the case of not using a resonant network, there will be a large amount of reactive power in the system.

[0005] (2) In the case of using a multi-frequency resonant network, the resonant frequency of the resonant network is fixed due to the determination of the resonant network parameters, which results in a fixed transmission frequency of the system and the inability to supply power to loads of other frequencies. When the load frequency changes, the efficiency of the system will be greatly reduced. SUMMARY

[0006] Based on the above needs, the primary purpose of the present application is to propose a variable resonant network for a multi-frequency multi-load WPT system that can adjust the resonant frequency of the resonant network by adjusting the switch state to meet the wireless power transfer requirements of different load conditions when the receiving frequency of the load side changes, while maintaining high power and efficiency of the system.

[0007] To achieve the above purpose, the specific technical solutions adopted by the present application are as follows:

[0008] A variable resonant network for a multi-frequency multi-load WPT system, the key of which is that it includes a transmitting coil, n switch capacitor components and n-1 switch inductor components, where n is a positive integer greater than 1, wherein:

[0009] Each switched capacitor assembly consists of a tuning capacitor and a short-circuit switch connected in parallel, and each switched inductor assembly consists of a tuning inductor and a circuit breaker connected in series. The first switched capacitor assembly is connected in series with the transmitting coil, and the (i+1)th switched capacitor assembly is connected in series with the ith switched inductor assembly and then connected across the ith switched capacitor assembly, i = 1 to n-1. The resonant frequency is adjusted by changing the state of each short-circuit switch and each circuit breaker.

[0010] Optionally, both the short-circuit switch and the circuit breaker are fully controlled switching devices using MOSFT or IGBT.

[0011] Optionally, both the short-circuit switch and the circuit breaker are connected to the control module. Each short-circuit switch is configured with a corresponding off-angle, and each circuit breaker is configured with a corresponding on-angle. The control module changes the capacitance value of the corresponding switching capacitor component by adjusting the size of the off-angle, and the control module changes the inductance value of the corresponding switching inductor component by adjusting the size of the on-angle.

[0012] Optionally, when the variable resonant network needs to operate at n resonant frequencies, let the corresponding resonant frequencies be f1, f2, ..., fn. n The corresponding periods are T1, T2...T n The control module then controls the short-circuit switch and the open-circuit switch at a switching frequency of f = 1 / T, where T is T1, T2...T n The least common multiple of .

[0013] Based on the above-described structural design of the variable resonant network, another objective of this invention is to provide a control method for the variable resonant network used in a multi-frequency, multi-load WPT system as described above, the key of which is:

[0014] For single-frequency application scenarios, the circuit breakers in all switching inductor components are normally open, and the transmitting coil and the first switching capacitor component form a first series resonant circuit. The resonant frequency is changed by controlling the turn-off angle of the short-circuit switch in the first switching capacitor component.

[0015] For multi-frequency applications, the required frequency is determined by controlling the state of the circuit breakers in each switching inductor component to connect to the corresponding number of resonant circuits. The desired resonant frequency is achieved by controlling the turn-off angle of the short-circuit switches in each switching capacitor component and the turn-on angle of the circuit breakers in each switching inductor component.

[0016] Optionally, the capacitance values ​​of each tuning capacitor in the n switched capacitor components are different, and the self-inductance values ​​of each tuning inductor in the n-1 switched inductor components are different.

[0017] Optionally, the tuning capacitances of the n switch capacitor components are of the same capacitance value, the self-inductance values of the tuning inductances of the n-1 switch inductor components are of the same value, the equivalent capacitance value of the corresponding switch capacitor component is adjusted by controlling the off angle of the short-circuit switch in the switch capacitor component, and the equivalent inductance value of the corresponding switch inductor component is adjusted by controlling the on angle of the open-circuit switch in the switch inductor component.

[0018] Optionally, the tuning capacitances of the n switch capacitor components are of the same capacitance value, the self-inductance values of the tuning inductances of the n-1 switch inductor components are of the same value, the equivalent capacitance value of the corresponding switch capacitor component is adjusted by controlling the off angle of the short-circuit switch in the switch capacitor component, and the equivalent inductance value of the corresponding switch inductor component is adjusted by controlling the on angle of the open-circuit switch in the switch inductor component. m m m c

[0019] The self-inductance values of the tuning inductances of the n-1 switch inductor components are L m m m l

[0020] The effects of the present application are as follows:

[0021] The present application provides a variable resonant network for a multi-frequency and multi-load WPT system and a control method thereof. The variable resonant network is composed of switching devices, and can realize dynamic transformation of the resonant network, thereby meeting the power supply requirements of any frequency and any number of loads. Meanwhile, the resonant frequency can be changed through the change of the resonant network, thereby compensating for the reactive power of the system, and enabling the system to operate efficiently. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the description of the embodiments or the prior art will be briefly introduced.

[0023] Figure 1 FIG. 1 is a topological structure diagram of a variable resonant network in an embodiment of the present application;

[0024] Figure 2 FIG. 2 is a circuit schematic diagram of a multi-frequency and multi-load wireless power transmission system applying the variable resonant network in an embodiment of the present application;

[0025] Figure 3 FIG. 3 is an equivalent circuit schematic diagram of the system in a dual-frequency working state;

[0026] Figure 4 FIG. 4 is an equivalent circuit schematic diagram of the system in a single-frequency working state.​​​​​​​​

[0027] Figure 5 is a circuit schematic diagram of a switch device and a fixed value capacitor constituting a switched capacitor component;

[0028] Figure 6 is a circuit schematic diagram of a switch device and a fixed value inductor constituting a switched inductor component;

[0029] Figure 7 is a C sc / C a change relationship diagram with alpha c changing;

[0030] Figure 8 is a L sc / L a change relationship diagram with alpha l changing. DETAILED DESCRIPTION

[0031] The embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0032] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in the present application should be understood as the usual meaning understood by the skilled person in the field to which the present application belongs.

[0033] The present embodiment provides a variable resonant network for a multi-frequency multi-load WPT system, as shown in Figure 1 , comprising a transmitting coil, n switched capacitor components and n-1 switched inductor components, n being a positive integer greater than 1, wherein:

[0034] Each switched capacitor component is formed by a tuning capacitor and a short-circuit switch in parallel, and each switched inductor component is formed by a tuning inductor and an open-circuit switch in series. The first switched capacitor component is connected in series with the transmitting coil, the i+1th switched capacitor component is connected across the i th switched capacitor component after being connected in series with the i th switched inductor component, i = 1 ~ n-1, and the resonant frequency adjustment is realized by changing the state of each short-circuit switch and each open-circuit switch. The size of n can be determined according to the number of required frequencies in the application scenario of the system.

[0035] As can be seen from Figure 1 , L1 is the transmitting coil, the n switched capacitor components correspond to n tuning capacitors C1 ~ C n and n short-circuit switches S c1 ~ S cn , and the n-1 switched inductor components correspond to n-1 tuning inductors L2 ~ L nand n-1 circuit breakers S l2 ~S ln The structure allows for the adjustment of the resonant network frequency by controlling the switching of various switching devices, based on actual needs, thereby changing the values ​​of the switching capacitor and switching inductor.

[0036] In this embodiment, Figure 1 The variable resonant network shown is used in multi-frequency, multi-load wireless power transfer systems, and its circuit is as follows: Figure 2 As shown, from Figure 2 As can be seen, the system includes a DC power supply 1, a high-frequency inverter circuit 2, a resonant network 3, a secondary-side receiving circuit 4, and a multi-modulation inverter control circuit 5. The DC power supply 1, high-frequency inverter circuit 2, variable resonant network 3, and secondary-side receiving circuit 4 are cascaded in sequence. The multi-modulation inverter control circuit 5 and the high-frequency inverter circuit 2 in the system can generate electrical energy containing different frequencies. The output frequency can be changed through the controller. Let the control signal be:

[0037] u r =u1+u2+...+u n =a1sin(2πf1t)+a2sin(2πf2t)+...a n sin(2πf n t)

[0038] Figure 2 The resonant network 3 in the system shown adopts Figure 1 The variable resonant network shown corresponds to L1 as the transmitting coil, and the secondary receiving circuit 4 contains n receiving circuits, where L... s1 C s1 Constructing a resonant network with frequency f1...L sn C sn The frequency of formation is f n The resonant network has parameters that satisfy:

[0039]

[0040] from Figure 2 It can be seen that when S l2 When disconnected, the system operates in single-frequency mode, and the inverter outputs single-frequency power. At this time, it can be controlled via S... c1 This changes the resonant frequency of the resonant network, and the controller alters the inverter's output frequency, thus enabling frequency switching in single-frequency mode. When S... l2 Activation, S l3 ~S ln When disconnected, S l2 Together with a corresponding inductor, they form a switching inductor. The system operates in dual-frequency mode, and the inverter outputs dual-frequency power. At this time, it can be controlled via S... c1, S c2 , S l2 to change the resonant frequency of the resonant network, the frequency of the inverter output is changed through the controller, so as to realize the switching of the working frequency in the dual-frequency mode. Similarly, when S l2 ~S ln are all turned on, S l2 -S ln and the corresponding inductors form a switched inductor, and the system works in an n-frequency mode, and the inverter output contains electrical energy of n frequencies. At this time, S c1 ~S cn and S l2 ~S ln can be used to change the resonant frequency of the resonant network, and the frequency of the inverter output is changed through the controller, so as to realize the switching of the working frequency in the n-frequency mode. Figure 3 The equivalent circuit schematic diagram of the system in the dual-frequency working state is shown; Figure 4 The equivalent circuit schematic diagram of the system in the single-frequency working state is shown.

[0041] In specific implementation, the short-circuit switch and the open-circuit switch are both MOSFT or IGBT fully controlled switching devices, and the short-circuit switch and the open-circuit switch are both connected to the control module. Each short-circuit switch is provided with a corresponding off angle, and each open-circuit switch is provided with a corresponding on angle. The control module changes the capacitance value of the corresponding switched capacitor assembly according to the size of the off angle, and at the same time, the control module changes the inductance value of the corresponding switched inductor assembly according to the size of the on angle. From Figure 5 and Figure 6 It can be seen that each switch is composed of two reverse series connected switching devices, and the switching frequency of each switch is f. In each cycle, the switching device S c1 ~S cn is turned off for an angle of α c1 ~α cn , and the switching device S l2 ~S ln is turned on for an angle of α l2 ~α ln .

[0042] Taking the switched capacitor assembly shown in Figure 5 as an example, the switching device and the fixed value capacitor form a switched capacitor. The fixed value capacitor is C a , the equivalent capacitor is C sc , and the off angle of the switching device is α c . By controlling the off angle of the switching device, the equivalent capacitance value can be transformed in the range of (C a , +∞), Figure 7 The change relationship diagram of C sc / C a with α c is shown.

[0043] by Figure 6 Taking the shown switching inductor assembly as an example, the switching device and the fixed inductor together form the switching inductor. The set capacitance is L. a The equivalent inductance is L sc The conduction angle of the switching device is α l By controlling the conduction angle of the switching device, the equivalent inductance value can be transformed within a range of (L). a (+∞), Figure 8 Showing L sc / L a With α l A diagram showing the relationship between the changes.

[0044] In practical implementation, when the variable resonant network needs to operate at n resonant frequencies, let the corresponding resonant frequencies be f1, f2, ..., fn. n The corresponding periods are T1, T2...T n The control module then controls the short-circuit switch and the open-circuit switch according to the switching frequency f = 1 / T, where T is T1, T2...T n The least common multiple of the resonant frequency. The resonant frequency of a resonant network is determined by its capacitance and inductance. First, calculate the resonant frequency of the network without any switching devices, and then use the formula to transform the resonant frequency based on this. S c1 ~S cn At frequency f, the turn-off angle in each cycle is α. c1 ~α cn S l2 ~S ln At frequency f, the conduction angle in each cycle is α. l2 ~α ln Different conduction angles correspond to different inductance values. Different turn-off angles correspond to different capacitance values.

[0045] This embodiment also mentions a control method for a variable resonant network in a multi-frequency, multi-load WPT system. Specifically, for a single-frequency application scenario, the circuit breakers in all switching inductor components are normally open, and the transmitting coil and the first switching capacitor component form a first series resonant circuit. The resonant frequency is changed by controlling the turn-off angle of the short-circuit switch in the first switching capacitor component.

[0046] For multi-frequency applications, the required frequency is determined by controlling the state of the circuit breakers in each switching inductor component to connect to the corresponding number of resonant circuits. The desired resonant frequency is achieved by controlling the turn-off angle of the short-circuit switches in each switching capacitor component and the turn-on angle of the circuit breakers in each switching inductor component.

[0047] In implementation, the capacitance values of the tuning capacitors in the n switch capacitor components are different, and the self-induction values of the tuning inductors in the n-1 switch inductor components are different. According to the configuration of the constant value elements with different parameters, each resonant circuit can meet the resonant requirements of different frequencies after being connected to the system, or the capacitance values of the tuning capacitors in the n switch capacitor components and the self-induction values of the tuning inductors in the n-1 switch inductor components are the same, and the equivalent capacitance values of the corresponding switch capacitor components are adjusted by controlling the off angles of the short-circuit switches in the switch capacitor components, and the equivalent inductance values of the corresponding switch inductor components are adjusted by controlling the on angles of the open-circuit switches in the switch inductor components.

[0048] When the resonant frequency of the variable resonant network changes, the parameters of the corresponding elements in the circuit can be determined in the following manner:

[0049] In the single frequency case: the elements in the circuit are C1 and L1, the initial resonant frequency is f1, and the changed resonant frequency is f1', and let Then the changed L'1=L1.

[0050] In the dual frequency case: the elements in the circuit are C1, L1, C2 and L2, the initial resonant frequencies are f1 and f2, and the changed resonant frequencies are f1' and f2', and let Then the changed resonant frequencies are:

[0051]

[0052] According to the changes of the switch capacitance values and the switch inductance values, the off angles and the on angles can be determined in the following manner: the capacitance values of the tuning capacitors in the n switch capacitor components are C m , and if the equivalent capacitance value C' m of the corresponding switch capacitor component after adjustment is xC m , then the off angle a c of the short-circuit switch in the switch capacitor component satisfies The self-induction values of the tuning inductors in the n-1 switch inductor components are L m , and if the equivalent inductance value L' m of the corresponding switch inductor component after adjustment is yL m , then the on angle a l of the open-circuit switch in the switch inductor component satisfies

[0053] In order to better understand the technical effects of the present application, the following simulation experiments are performed by configuring the relevant parameters according to the circuit structure shown in Figures 2-4 .

[0054] First, let n=2. Then the circuit is equivalent to Figure 3As shown, in this example, it is assumed By derivation, we have:

[0055]

[0056] Where L1, C1, L2, C2 are the parameters of the resonant network before switching at frequencies f1, f2. L1', C1', L2', C2' are the parameters of the resonant network after switching at frequencies f1', f2'. As can be seen, under the condition of meeting the set conditions, the resonant frequency of the resonant network changes, and only the capacitance value needs to be changed.

[0057] The simulation process is designed according to the following three experimental paths:

[0058] Experiment 1: Frequency switching under single frequency and single load (S12 is disconnected)

[0059] According to the circuit system shown in Figure 4 , the parameter selection is shown in Table 1:

[0060] Table 1: Parameter configuration table for frequency switching under single frequency and single load

[0061]

[0062] Where the internal resistance of the transmitting coil R p is 0.08Ω, the internal resistance of the receiving coil R s is 0.08Ω, the DC power supply is 48V, and the system output power Coil loss

[0063] Experiment 2: Frequency switching from single frequency and double load to double frequency and double load (S l2 from disconnected to on) According to the circuit system shown in Figure 3 , the parameter selection is shown in Table 2:

[0064] Table 2: Parameter configuration table for frequency switching from single frequency and double load to double frequency and double load

[0065]

[0066] Where the internal resistance of the transmitting coil R p is 0.08Ω, the internal resistance of the receiving coil R s1 is 0.08Ω, the internal resistance of the receiving coil R s2 is 0.08Ω, and the DC power supply is 48V. The system output power Coil loss

[0067] Experiment 3: Frequency switching under double frequency and double load (S l2 on)

[0068] According to the circuit system shown in the table 3, the parameter selection is shown in the table 3: Figure 3

[0069] Table 3: Frequency switching parameter configuration table in the case of double frequency and double load

[0070]

[0071] Where the transmitting coil resistance R p is 0.08Ω, the receiving coil resistance R s1 is 0.08Ω, the receiving coil resistance R s2 is 0.08Ω, and the DC power supply is 48V. The output power coil loss

[0072] According to the above experiment, the system efficiency reactive power and power factor as a comparison parameter, the experimental results are shown in the table 4:

[0073] Table 4: simulation result data comparison and analysis table

[0074]

[0075] It can be seen that in the three cases of single frequency to single frequency, single frequency to double frequency, and double frequency to double frequency, the efficiency before and after switching is basically unchanged, and the system efficiency is relatively high. At the same time, the variable resonant network can dynamically compensate the reactive power of the system, so that the power factor of the system is relatively high.

[0076] Based on the above simulation results, it can be shown that the multi-frequency and multi-load wireless power transmission system using variable resonant network can realize flexible frequency switching, and can maintain high efficiency before and after frequency switching. At the same time, it can also flexibly compensate the reactive power, so that the power factor of the system is relatively high.

[0077] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and such modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and such changes should be covered in the scope of the claims and the specification of the present application.​

Claims

1. A variable resonant network for a multi-frequency multi-load WPT system, characterized by: The variable resonant network comprises a transmitting coil, n switch capacitor components and n-1 switch inductor components, wherein n is a positive integer greater than 1. Each switch capacitor component is formed by a tuning capacitor and a short-circuit switch in parallel, each switch inductor component is formed by a tuning inductor and an open-circuit switch in series, the first switch capacitor component is connected in series with the transmitting coil, the i+1th switch capacitor component is connected across the ith switch capacitor component after being connected in series with the ith switch inductor component, i = 1 ~ n-1, and the resonant frequency is adjusted by changing the states of the short-circuit switches and the open-circuit switches. The short-circuit switches and the open-circuit switches are connected to a control module, each short-circuit switch is provided with a corresponding off angle, each open-circuit switch is provided with a corresponding on angle, the control module adjusts the capacitance of the corresponding switch capacitor component by adjusting the size of the off angle, and the control module adjusts the inductance of the corresponding switch inductor component by adjusting the size of the on angle. When the variable resonant network needs to work at n resonant frequencies, let the corresponding resonant frequencies be f1, f2, … f n , and the corresponding periods be T1, T2, … T n , respectively, then the control module controls the short-circuit switch and the open-circuit switch at a switching frequency of f = 1 / T, where T is the least common multiple of T1, T2, … T n .

2. The variable resonant network for multi-frequency multi-load WPT systems of claim 1, characterized in that: The short-circuit switches and the open-circuit switches are MOSFT or IGBT fully controlled switching devices.

3. The control method of the variable resonant network for the multi-frequency multi-load WPT system according to claim 1, characterized in that: for a single-frequency application scenario, the open-circuit switches in all switch inductor components are in a normally open state, the transmitting coil and the first switch capacitor component form a first series resonant circuit, and the resonant frequency is changed by controlling the off angle of the short-circuit switch in the first switch capacitor component; for a multi-frequency application scenario, according to the number of required frequencies, a corresponding number of resonant circuits are connected by controlling the states of the open-circuit switches in the switch inductor components, and the required resonant frequencies are changed by controlling the off angle of the short-circuit switch in the switch capacitor component and the on angle of the open-circuit switch in the switch inductor component.

4. The control method of a variable resonant network for a multi-frequency multi-load WPT system according to claim 3, characterized in that: The capacitances of the tuning capacitors in the n switch capacitor components are different, and the self-inductances of the tuning inductors in the n-1 switch inductor components are different.

5. The control method of a variable resonant network for a multi-frequency multi-load WPT system according to claim 3, characterized in that: The capacitances of the tuning capacitors in the n switch capacitor components are the same, and the self-inductances of the tuning inductors in the n-1 switch inductor components are the same, the equivalent capacitance of the corresponding switch capacitor component is adjusted by controlling the off angle of the short-circuit switch in the switch capacitor component, and the equivalent inductance of the corresponding switch inductor component is adjusted by controlling the on angle of the open-circuit switch in the switch inductor component.

6. The control method of a variable resonant network for a multi-frequency multi-load WPT system according to claim 5, characterized in that: The capacitance of each tuning capacitor in n switched capacitor components is C m If the equivalent capacitance C' m of the switched capacitor component after adjustment is xC m , then the off angle α c of the short-circuit switch in the switched capacitor component satisfies The self-inductance of each tuning inductor in the n-1 switch inductance components is L m If the equivalent inductance L' m of the corresponding switch inductance component after adjustment is yL m , then the conduction angle α l of the circuit breaker switch in the corresponding switch inductance component satisfies

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