Mutual Inductance Detection Method and System for MC-WPT System Based on Frequency Modulation and Phase Shift Control

Abstract

This invention relates to the field of magnetically coupled wireless power transfer (MC-WPT) technology, specifically disclosing a method and system for detecting mutual inductance in an MC-WPT system based on frequency modulation and phase shift control. When the system experiences parameter drift and is no longer in a resonant state, frequency modulation control is used to ensure the power factor angle at the transmitting end is within a preset range, and phase shift control is used to ensure the phase angle at the receiving end is 90°, causing the system to resonate again. The mutual inductance between the coupling mechanisms is calculated based on the resonant frequency at this point, the fundamental output voltage of the transmitting end's full bridge, and the current in the resonant circuit of the receiving end, or vice versa. Due to the introduction of frequency modulation and phase shift control, this mutual inductance detection and measurement can be very accurate. Experiments have verified that the accuracy of mutual inductance detection using this invention is high.

Description

Technical Field

[0001] This invention relates to the field of magnetically coupled wireless power transfer (MC-WPT) technology, and more particularly to a mutual inductance detection method and system for MC-WPT systems based on frequency modulation and phase shift control. Background Technology

[0002] Due to their convenience and increasing transmission capacity, wireless power transmission systems are currently receiving widespread attention and application. However, during equipment operation, a series of unavoidable problems, such as capacitor parameter drift or system parameter changes, or problems caused by operational errors, may lead to system damage or even collapse. Therefore, the importance of parameter identification in MC-WPT systems is self-evident. Among these, mutual inductance identification in MC-WPT systems has always been a research hotspot, as mutual inductance is a crucial parameter affecting transmission power and efficiency.

[0003] Some literature proposes a black-box strategy to detect faults in system coupling mechanisms. While this method can obtain the approximate location of the fault, it cannot obtain accurate fault information, let alone identify mutual inductance. Other literature proposes a sensitivity analysis method for selecting a mutual inductance identification model for wireless charging of electric vehicles. Although this method can identify mutual inductance, the mutual inductance calculated according to the reference formula differs significantly from the actual system's mutual inductance. Still other literature proposes a coupling coefficient identification method that achieves maximum power transfer in WPT systems through impedance matching. While this method can detect the system's coupling coefficient k, it cannot separate the mutual inductance under capacitor and inductor parameter drift.

[0004] It is evident that current literature cannot accurately detect the mutual inductance of the MC-WPT system under parameter drift. Summary of the Invention

[0005] This invention provides a method and system for detecting mutual inductance in an MC-WPT system based on frequency modulation and phase shift control. The technical problem it solves is: how to accurately detect the mutual inductance of an MC-WPT system under parameter drift.

[0006] To address the above technical problems, this invention provides a mutual inductance detection method for an MC-WPT system based on frequency modulation and phase shift control, comprising the following steps:

[0007] A bidirectional MC-WPT system is constructed, comprising a primary side and a secondary side. The primary side includes a primary high-frequency inverter, and the secondary side includes a secondary high-frequency inverter. When transmitting electrical energy from the primary side to the secondary side, the primary side acts as the transmitter, the primary high-frequency inverter acts as the transmitter high-frequency inverter, the secondary high-frequency inverter acts as a full-bridge rectifier, and the secondary side acts as the receiver. Conversely, when transmitting electrical energy from the secondary side to the primary side, the secondary side acts as the transmitter, the secondary high-frequency inverter acts as the transmitter high-frequency inverter, the primary high-frequency inverter acts as a full-bridge rectifier, and the primary side acts as the receiver.

[0008] Set the system parameters so that the system's natural angular frequency is ω;

[0009] The key point is that this mutual inductance detection method also includes the following steps:

[0010] The transmitting end is excited with its natural angular frequency ω;

[0011] The system detects whether the power factor angle of the transmitter is within a preset range. If it is, it continues to be excited at the natural angular frequency ω. Otherwise, frequency modulation control is used to change the excitation frequency of the transmitter so that the power factor angle of the transmitter is within the preset range. At this time, the system angular frequency is ω. f And the phase angle of the receiving end is kept at 90° by phase shift control;

[0012] The mutual inductance between the coupling mechanism of the bidirectional MC-WPT system is calculated by obtaining the full-bridge fundamental output voltage of the transmitting end and the current of the resonant circuit of the receiving end; or, the mutual inductance between the coupling mechanism of the bidirectional MC-WPT system is calculated by obtaining the full-bridge fundamental output voltage of the receiving end and the current of the resonant circuit of the transmitting end.

[0013] Furthermore, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage of the transmitting end divided by the angular frequency ωf and then divided by the magnitude of the current in the resonant circuit of the receiving end.

[0014] Furthermore, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the modulus of the full-bridge fundamental output voltage at the receiving end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the transmitting end.

[0015] Furthermore, the steps for detecting the power factor angle at the transmitting end are as follows:

[0016] The active power P is obtained by sampling the current and voltage waveforms in the resonant slot of the transmitting end, multiplying the sampled current and voltage waveforms by an integrator, and integrating them over one cycle.

[0017] The reactive power Q is obtained by shifting the voltage waveform by 90°, multiplying it by the current waveform, integrating it over one cycle.

[0018] The power factor angle of the transmitter is calculated to be equal to the arctangent (Q / P).

[0019] Furthermore, the preset range of the power factor angle of the transmitting end is [0°, 10°].

[0020] The present invention also provides a mutual inductance detection system for an MC-WPT system based on frequency modulation and phase shift control, which is applied to the mutual inductance detection method for the MC-WPT system based on frequency modulation and phase shift control. The key features are: a first sensor, a second sensor, and a controller connecting the first sensor and the second sensor, wherein the controller is also connected to the primary high-frequency inverter and the secondary high-frequency inverter.

[0021] The first sensor is used to detect the full-bridge fundamental output voltage and the current of the resonant cavity on the primary side and send them to the controller;

[0022] The second sensor is used to detect the full-bridge fundamental output voltage and the current of the resonant cavity on the secondary side and send them to the controller;

[0023] The controller is used for:

[0024] The transmitting end is excited with its natural angular frequency ω;

[0025] Calculate whether the power factor angle of the transmitter is within the preset range. If it is, continue to excite with the natural angular frequency ω. Otherwise, use frequency modulation control to change the excitation frequency of the transmitter so that the power factor angle of the transmitter is within the preset range. At this time, the system angular frequency is ωf, and the phase angle of the receiver is made to be 90° through phase shift control.

[0026] The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is calculated based on the full-bridge fundamental output voltage of the transmitting end and the current of the resonant circuit of the receiving end; or, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is calculated based on the full-bridge fundamental output voltage of the receiving end and the current of the resonant circuit of the transmitting end.

[0027] In one embodiment, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the modulus of the full-bridge fundamental output voltage at the transmitting end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the receiving end.

[0028] In another embodiment, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the modulus of the full-bridge fundamental output voltage at the receiving end divided by the angular frequency ω. fThen divide by the magnitude of the current in the resonant circuit of the transmitting end.

[0029] In one embodiment, the step of calculating the power factor angle of the transmitter is as follows:

[0030] The active power P is obtained by multiplying the sampled current and voltage waveforms in the resonant slot of the transmitting end by an integrator and integrating them over one cycle.

[0031] The reactive power Q is obtained by shifting the voltage waveform by 90°, multiplying it by the current waveform, integrating it over one cycle.

[0032] The power factor angle of the transmitter is calculated to be equal to the arctangent (Q / P).

[0033] In one embodiment, the preset range of the power factor angle of the transmitting end is [0°, 10°].

[0034] The present invention provides a mutual inductance detection method and system for an MC-WPT system based on frequency modulation and phase shift control. When the system experiences parameter drift and is no longer in a resonant state, frequency modulation control is used to ensure the power factor angle at the transmitting end is within a preset range, and phase shift control is used to ensure the phase angle at the receiving end is 90°, causing the system to resonate again. The mutual inductance between the coupling mechanisms is calculated based on the resonant frequency at this point, the fundamental output voltage of the transmitting end's full bridge, and the current in the resonant circuit of the receiving end, or vice versa. Due to the introduction of frequency modulation and phase shift control, this mutual inductance detection and measurement can be very accurate. Experiments have verified that the accuracy of mutual inductance detection using the present invention is high. Attached Figure Description

[0035] Figure 1 This is a flowchart of the mutual inductance detection method for MC-WPT system based on frequency modulation and phase shift control provided in the embodiments of the present invention;

[0036] Figure 2 This is a topology diagram of the bidirectional SS-type MC-WPT system during forward transmission provided in an embodiment of the present invention;

[0037] Figure 3 This is a vector diagram of intracavity parameters provided in an embodiment of the present invention;

[0038] Figure 4 This is a structural diagram of the mutual inductance detection system of the MC-WPT system based on frequency modulation and phase shift control provided in an embodiment of the present invention;

[0039] Figure 5 This is a diagram showing the mutual inductance detection results at initial resonance provided in an embodiment of the present invention;

[0040] Figure 6This is a diagram showing the frequency increment and primary-side power factor angle control results at initial resonance provided in an embodiment of the present invention;

[0041] Figure 7 This is a diagram showing the mutual inductance detection results during re-resonance provided in an embodiment of the present invention;

[0042] Figure 8 This is a diagram showing the frequency increment and primary power factor angle control results during re-resonance provided in an embodiment of the present invention. Detailed Implementation

[0043] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0044] The mutual inductance detection method for MC-WPT systems based on frequency modulation and phase shift control provided in this invention embodiment is as follows: Figure 1 As shown, the steps include:

[0045] A bidirectional MC-WPT system is constructed, comprising a primary side and a secondary side. The primary side includes a primary high-frequency inverter, and the secondary side includes a secondary high-frequency inverter. When transmitting electrical energy from the primary side to the secondary side, the primary side acts as the transmitter, the primary high-frequency inverter acts as the transmitter high-frequency inverter, the secondary high-frequency inverter acts as a full-bridge rectifier, and the secondary side acts as the receiver. Conversely, when transmitting electrical energy from the secondary side to the primary side, the secondary side acts as the transmitter, the secondary high-frequency inverter acts as the transmitter high-frequency inverter, the primary high-frequency inverter acts as a full-bridge rectifier, and the primary side acts as the receiver.

[0046] Set the system parameters so that the system's natural angular frequency is ω;

[0047] The transmitter is excited with its natural angular frequency ω (the phase of the transmitter is always 0°, and the phase of the receiver is 90°. The power factor angle of the transmitter is 0-10°, and the power factor angle of the receiver is 180°).

[0048] The system detects whether the power factor angle of the transmitter is within a preset range ([0°, 10°]). If so, it continues to excite the transmitter using its natural angular frequency ω. Otherwise, it uses frequency modulation control to change the excitation frequency of the transmitter so that the power factor angle of the transmitter is within the preset range. At this time, the system angular frequency is ω. f And by using phase shift control, the phase angle of the receiver is kept at 90°;

[0049] Calculate the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system by obtaining the full-bridge fundamental output voltage at the transmitting end and the current in the resonant circuit at the receiving end; or, calculate the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system by obtaining the full-bridge fundamental output voltage at the receiving end and the current in the resonant circuit at the transmitting end.

[0050] The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage at the transmitting end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the receiving end. Alternatively, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage of the receiving end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the transmitting end.

[0051] The steps for detecting the power factor angle of the transmitter are as follows:

[0052] The active power P is obtained by sampling the current and voltage waveforms in the resonant slot of the transmitting end, multiplying the sampled current and voltage waveforms by an integrator, and integrating them over one cycle.

[0053] The reactive power Q is obtained by shifting the voltage waveform by 90°, multiplying it by the current waveform, integrating it over one cycle.

[0054] The power factor angle of the transmitter is calculated to be equal to the arctangent (Q / P).

[0055] The following section uses the MC-WPT system as an example to provide a more detailed explanation of the mutual inductance detection method for the MC-WPT system based on frequency modulation and phase shift control.

[0056] Figure 2 The diagram shows a typical bidirectional SS-type MC-WPT system during forward transmission (primary side to secondary side). This SS-type MC-WPT system includes a primary side and a secondary side. The primary side includes a DC power supply V connected in sequence. dc Primary high-frequency inverter (a full-bridge inverter composed of switching transistors S1 to S4), primary series compensation capacitor C p and primary coil L p (its current is I) p (Indicated), the secondary side includes sequentially connected secondary coils L s (its current is I) s (represented by) secondary series compensation capacitor C s Secondary high-frequency inverter (a full-bridge inverter consisting of switching transistors T1 to T4), filter capacitor C f and load resistance R L (its voltage is V) out (i.e., the system output voltage).

[0057] exist Figure 2 Middle,U p and U s These represent the fundamental output voltages of the primary and secondary full-bridge circuits, respectively. Wherein:

[0058]

[0059] Among them, V dp β represents the primary side DC input voltage. p V represents the phase shift angle inside the primary-side inverter. ds β represents the secondary-side DC output voltage. s δ represents the phase shift angle within the secondary-side inverter, and δ represents the phase angle by which the secondary-side rectified input voltage lags behind the primary-side inverter output voltage.

[0060] The system satisfies equation (3) at all times, and when the system is in resonance, it satisfies equation (4):

[0061]

[0062] Where ω represents the operating angular frequency of the system.

[0063] When the system is in resonance, the mutual inductance M is calculated by the following formula:

[0064]

[0065] Where ωf represents the angular frequency at which the system resonates under frequency modulation control.

[0066] In the resonant state, the system's transmission power is at its maximum. Therefore, without considering hard switching, most MC-WPT systems operate in a fully resonant state. In this state, only the effective values ​​of the voltage and current parameters of the resonant tank circuit and the angular frequency in the resonant state, as shown in equation (5), are needed to calculate the two sets of mutual inductances. However, when the system parameters change, such as temperature drift caused by long-term operation of the capacitor or changes in self-mutual inductance parameters caused by coupling mechanism deviation, the system will not maintain the resonant state, and therefore the system no longer satisfies equation (4). If equation (5) is still used to calculate the mutual inductance M, the calculated error may be very large. Therefore, in order to simplify the calculation process, this example takes some measures to make it return to the resonant state. In engineering practice and experimental research, this example adopts frequency modulation control (FM control) to make the system return to the resonant state.

[0067] When the system re-enters the resonant state through FM control, equation (5) is satisfied again, and the mutual inductance M can be recalculated through simple calculation. However, the working mechanism of FM control is to set the power factor angle to 0 or a small angle. When the power factor angle is a small angle that is not 0°, the resonant cavity exhibits weak inductance to reduce the peak voltage generated when the power tube is working, thereby reducing the current and voltage stress of electrical components in actual production. Although this operation will sacrifice the sensitivity of mutual inductance detection, simulation shows that the detection accuracy is still very high, so this operation is very practical. When the power factor angle is 0°, the system is in a fully resonant state. At this time, the sensitivity of mutual inductance detection will be very high, but the current and voltage stress of electrical components may be very large. Directly calculating the power factor angle by obtaining the detection results of the resonator voltage and resonator current phase requires high precision of the detection device, which will increase the detection cost in actual production. Therefore, this example introduces the PQ algorithm (P represents active power, Q represents reactive power) to calculate the power factor angle of the system more simply.

[0068] In FM control, the power factor angle of the primary side is controlled to 0° or a small angle by changing the operating frequency of the primary-side high-frequency inverter. After frequency modulation control, the phase angle of the secondary side is kept at 180° by secondary-side phase shift control to ensure that the system is in resonance. It should be noted that, as can be seen from equation (4), when and When the phase between them is 180°, because if Therefore, phase-shifting control can never control it. and The phase difference between them is 90°, and similarly, frequency modulation control can never control them. and The phase difference between them is 0°, so the combined effect of FM control and phase shift control is to make as well as In other words, in this state, the resonant cavity is in a resonant state, and the relationship between the vectors within the resonant cavity is as follows: Figure 3 As shown, that is and The phase difference between them is 180°. and The phase difference between them is 0°. and The phase difference between them is 90°.

[0069] The PQ algorithm calculates the power factor angle using the system's active power P and reactive power Q, without directly subtracting the voltage and current phases. The current and voltage waveforms in the resonant tank are obtained through a high-frequency sampling module, and the integrator integrates them separately over one cycle without directly subtracting the current and voltage phases. Since phase angle detection requires high accuracy from the sampling module, the PQ algorithm is introduced in this system. This system incorporates the PQ algorithm and FM control, allowing the power factor angle to be controlled by sampling the voltage and current information in the primary-side resonant tank, as shown in equations (6) and (7), where θ refers to the power factor angle on the primary side.

[0070]

[0071] That is, the steps for detecting the power factor angle of the transmitter are as follows:

[0072] The active power P is obtained by sampling the current and voltage waveforms in the resonant slot of the transmitting end, multiplying the sampled current and voltage waveforms by an integrator, and integrating them over one period T.

[0073] The reactive power Q is obtained by shifting the voltage waveform by 90°, multiplying it by the current waveform, integrating it over one cycle.

[0074] The power factor angle of the transmitter is calculated to be equal to the arctangent (Q / P).

[0075] This invention also provides a mutual inductance detection system for an MC-WPT system based on frequency modulation and phase shift control, applied to the aforementioned mutual inductance detection method for an MC-WPT system based on frequency modulation and phase shift control, such as... Figure 4 As shown, it includes a first sensor, a second sensor, and a controller connected to the first sensor and the second sensor. The controller is also connected to a primary high-frequency inverter and a secondary high-frequency inverter.

[0076] The first sensor is used to detect the full-bridge fundamental output voltage and the current of the resonant cavity on the primary side and send them to the controller;

[0077] The second sensor is used to detect the full-bridge fundamental output voltage and the current of the resonant cavity on the secondary side and send them to the controller;

[0078] The controller is used for:

[0079] The transmitting end is excited with its natural angular frequency ω;

[0080] Calculate whether the power factor angle of the transmitter is within a preset range. If so, continue excitation at the natural angular frequency ω; otherwise, use frequency modulation control to change the excitation frequency of the transmitter so that the power factor angle of the transmitter is within the preset range. At this time, the system angular frequency is ω. f And by using phase shift control, the phase angle of the receiver is kept at 90°;

[0081] The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system can be calculated based on the full-bridge fundamental output voltage at the transmitting end and the current in the resonant circuit at the receiving end; or, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system can be calculated by obtaining the full-bridge fundamental output voltage at the receiving end and the current in the resonant circuit at the transmitting end.

[0082] In this example, a bidirectional SS-type MC-WPT system was built in Matlab / Simulink. The parameters of the system resonant cavity are shown in Table 1.

[0083] Table 1 System Parameters

[0084]

[0085] When the SS topology initially maintains resonance, the waveform of parameter M calculated in this invention is as follows: Figure 5 As shown. This example can also detect the results of FM control. The frequency increment waveform is as follows. Figure 6 As shown, the yellow curve represents the power factor angle on the primary side, and the purple curve represents the frequency increment under frequency control. From Figure 6 As can be seen, the frequency increment curve under FM control initially oscillates. Since the system's natural resonant frequency is 85kHz, the maximum frequency increment is a small proportion of the natural frequency, so the system can still maintain normal operation. Finally, the waveform quickly stabilizes, with the frequency increment eventually settling at around -735Hz. To reduce the voltage spikes in the primary-side resonator, the primary-side power factor angle is controlled to a small angle (set to 10° in this simulation), giving the primary-side resonator weak inductance. This allows the charged capacitor to discharge more quickly, thereby reducing or even eliminating voltage spikes. The waveform curve in this example shows that the power factor angle eventually stabilizes at 9.95°. Figure 5 and Figure 6 It can be seen that the frequency modulation control and phase shift control of the present invention have relatively good control effects. Through two samplings, the calculated mutual inductances are 64.32uH and 63.66uH, respectively. Compared with the system setting mutual inductance of 64uH in Table 1, the error is small and the accuracy is above 99%. It can be seen that the present invention has a high accuracy in detecting mutual inductance.

[0086] Then, by changing the capacitance value of the primary-side resonant capacitor, the parameter change due to capacitor temperature drift during actual production is simulated. This is achieved by changing C... p The capacitance value was controlled to be 1.3 times the value under resonant conditions, thus preventing the primary-side resonator from being in a resonant state. The effects of frequency modulation control and phase shift control, as well as the calculated mutual inductance under their control, were then observed. Figure 7 For the mutual inductance calculation results, Figure 8This represents the control results of the power factor angle and frequency increment. (Through...) Figure 7 It can be observed that the sampling results of the two mutual inductance tests were 64.72uH and 64.29uH, respectively. The power factor angle eventually stabilized at around 9.60°, and the frequency increment stabilized at -456.1Hz. The detection results showed high accuracy and excellent control performance.

[0087] In summary, the mutual inductance detection method and system for MC-WPT systems based on frequency modulation and phase shift control provided in this invention, when the system experiences parameter drift and is no longer in a resonant state, employs frequency modulation control to ensure the power factor angle at the transmitting end is within a preset range, and employs phase shift control to ensure the phase angle at the receiving end is 180°, causing the system to resonate again. The mutual inductance between the coupling mechanisms is calculated based on the resonant frequency at this point, the fundamental output voltage of the full-bridge at the transmitting end, and the current in the resonant circuit at the receiving end, or vice versa. Due to the introduction of frequency modulation control and phase shift control, this mutual inductance detection measurement can be very accurate. Experiments have verified that the accuracy of mutual inductance detection using this invention is high.

[0088] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A mutual inductance detection method for MC-WPT systems based on frequency modulation and phase shift control, comprising the following steps: A bidirectional MC-WPT system is constructed, comprising a primary side and a secondary side. The primary side includes a primary high-frequency inverter, and the secondary side includes a secondary high-frequency inverter. When transmitting electrical energy from the primary side to the secondary side, the primary side acts as the transmitter, the primary high-frequency inverter acts as the transmitter high-frequency inverter, the secondary high-frequency inverter acts as a full-bridge rectifier, and the secondary side acts as the receiver. Conversely, when transmitting electrical energy from the secondary side to the primary side, the secondary side acts as the transmitter, the secondary high-frequency inverter acts as the transmitter high-frequency inverter, the primary high-frequency inverter acts as a full-bridge rectifier, and the primary side acts as the receiver. Set the system parameters so that the system's natural angular frequency is ω; Its features are, The mutual inductance detection method also includes the following steps: The transmitting end is excited with its natural angular frequency ω; The system detects whether the power factor angle of the transmitter is within a preset range. If it is, it continues to be excited at the natural angular frequency ω. Otherwise, frequency modulation control is used to change the excitation frequency of the transmitter so that the power factor angle of the transmitter is within the preset range. At this time, the system angular frequency is ω. f And the phase angle of the receiving end is kept at 90° by phase shift control; The mutual inductance between the coupling mechanism of the bidirectional MC-WPT system is calculated by obtaining the full-bridge fundamental output voltage of the transmitting end and the current of the resonant circuit of the receiving end; or, the mutual inductance between the coupling mechanism of the bidirectional MC-WPT system is calculated by obtaining the full-bridge fundamental output voltage of the receiving end and the current of the resonant circuit of the transmitting end.

2. The mutual inductance detection method for MC-WPT system based on frequency modulation and phase shift control according to claim 1, characterized in that: The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage of the transmitter divided by the angular frequency ωf and then divided by the magnitude of the current in the resonant circuit of the receiver.

3. The mutual inductance detection method for MC-WPT system based on frequency modulation and phase shift control according to claim 2, characterized in that: The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage at the receiving end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the transmitting end.

4. The mutual inductance detection method for MC-WPT system based on frequency modulation and phase shift control according to claim 3, characterized in that, The steps for detecting the power factor angle at the transmitter are as follows: The active power P is obtained by sampling the current and voltage waveforms in the resonant slot of the transmitting end, multiplying the sampled current and voltage waveforms by an integrator, and integrating them over one cycle. The reactive power Q is obtained by shifting the voltage waveform by 90°, multiplying it by the current waveform, integrating it over one cycle. The power factor angle of the transmitter is calculated to be equal to the arctangent (Q / P).

5. The mutual inductance detection method for MC-WPT system based on frequency modulation and phase shift control according to claim 4, characterized in that: The preset range of the power factor angle of the transmitter is [0°, 10°].

6. A mutual inductance detection system for an MC-WPT system based on frequency modulation and phase shift control, applied to the mutual inductance detection method for an MC-WPT system based on frequency modulation and phase shift control as described in any one of claims 1 to 5, characterized in that: It includes a first sensor, a second sensor, and a controller connecting the first sensor and the second sensor, the controller also being connected to the primary high-frequency inverter and the secondary high-frequency inverter; The first sensor is used to detect the full-bridge fundamental output voltage and the current of the resonant cavity on the primary side and send them to the controller; The second sensor is used to detect the full-bridge fundamental output voltage and the current of the resonant cavity on the secondary side and send them to the controller; The controller is used for: The transmitting end is excited with its natural angular frequency ω; Calculate whether the power factor angle of the transmitter is within a preset range. If so, continue excitation at the natural angular frequency ω; otherwise, use frequency modulation control to change the excitation frequency of the transmitter so that the power factor angle of the transmitter is within the preset range. At this time, the system angular frequency is ω. f And the phase angle of the receiving end is kept at 90° by phase shift control; The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is calculated based on the full-bridge fundamental output voltage of the transmitting end and the current of the resonant circuit of the receiving end; or, the mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is calculated based on the full-bridge fundamental output voltage of the receiving end and the current of the resonant circuit of the transmitting end.

7. The mutual inductance detection system of the MC-WPT system based on frequency modulation and phase shift control according to claim 6, characterized in that: The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage at the transmitting end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the receiving end.

8. The mutual inductance detection method for MC-WPT system based on frequency modulation and phase shift control according to claim 7, characterized in that: The mutual inductance between the coupling mechanisms of the bidirectional MC-WPT system is equal to the magnitude of the full-bridge fundamental output voltage at the receiving end divided by the angular frequency ω. f Then divide by the magnitude of the current in the resonant circuit of the transmitting end.

9. The mutual inductance detection system of MC-WPT system based on frequency modulation and phase shift control according to claim 8, characterized in that, The steps for calculating the power factor angle of the transmitter are as follows: The active power P is obtained by multiplying the sampled current and voltage waveforms in the resonant slot of the transmitting end by an integrator and integrating them over one cycle. The reactive power Q is obtained by shifting the voltage waveform by 90°, multiplying it by the current waveform, integrating it over one cycle. The power factor angle of the transmitter is calculated to be equal to the arctangent (Q / P).

10. The mutual inductance detection system of MC-WPT system based on frequency modulation and phase shift control according to claim 9, characterized in that: The preset range of the power factor angle of the transmitter is [0°, 10°].

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