A frequency tracking method for magnetically coupled wireless power transmission system

Abstract

The present invention discloses a frequency tracking method for a magnetically coupled wireless power transmission system. The method uses an intersecting S transform to detect the phase difference between the primary current and voltage. First, the voltage signals and the voltage signals obtained by the primary current and voltage detection are respectively passed through a low-pass filter to obtain two sinusoidal signals. this Two discrete signals are sampled from the two channels, and then an intersecting S-transform is performed on the two discrete signals. The phase difference between the primary current and voltage is determined by extracting the transformation result. Finally, the operating frequency of the inverter switch is adjusted based on the phase difference to achieve the resonant frequency of the system, thus achieving frequency tracking. This invention can quickly and accurately achieve frequency tracking, providing conditions for the magnetically coupled wireless power transmission system to operate in a resonant state.

Description

Technical Field

[0001] The present invention relates to the field of resonant frequency tracking of a magnetically coupled wireless power transmission system, and in particular to a phase difference detection method for frequency tracking. Background Art

[0002] Wireless power transmission, also known as contactless power transmission, is a transmission mode that uses a wireless soft medium (such as electric fields, magnetic fields, and microwaves) to transfer electrical energy from a power source to a device. Magnetic coupling resonant wireless power transmission systems offer the advantages of high transmission efficiency and long transmission distances, and have significant application value in a wide range of fields, including electric vehicle charging, home appliances, medical equipment, and industrial applications. Therefore, research on magnetic coupling resonant wireless power transmission is of great practical significance.

[0003] The magnetically coupled resonant wireless power transmission system is a coupled system affected by the intersection of nonlinear multiple parameters, and the transmission performance of the system is greatly affected by changes in the system parameters. Among the many parameters, the operating frequency of the system is one of the key factors affecting the transmission performance of the system. Whether the system operates in a resonant state determines whether the system can transmit electrical energy efficiently, that is, the operating frequency and the resonant frequency need to be consistent during the operation of the system. However, when the parameters, load size and transmission distance of the resonant circuit change, the resonant frequency of the system will deviate from the original inherent resonant frequency. When the resonant frequency shifts, necessary control methods need to be adopted to keep the system operating frequency and the resonant frequency consistent to ensure efficient transmission of the system. Phase difference detection of the primary signal is the basis for frequency tracking. Traditional frequency tracking is implemented using analog phase-locked loop chips, but analog chips have poor noise resistance and low reliability, making it difficult to ensure reliable operation of the system. This patent provides an effective method to address this problem. Summary of the Invention

[0004] The present invention provides a frequency tracking method for a magnetically coupled wireless power transmission system, which is used to extract the phase difference between the primary current and voltage and provide support conditions for the system to operate in a resonant state.

[0005] The frequency tracking method of a magnetically coupled wireless power transmission system described in the present invention includes a low-pass filter module and an intersecting S-transformation module, wherein the low-pass filter module is used to filter the two main circuit current and voltage signals to generate two sinusoidal signals, and sample the two signals and output them to the intersecting S-transformation module.

[0006] The present invention discloses a method for frequency tracking a magnetically coupled wireless power transmission system, which uses an intersecting S-transform to detect the phase difference between the primary current and voltage of the main circuit of the magnetically coupled wireless power transmission system. The method comprises the following steps:

[0007] S1: Given the main circuit switching frequency f r=85kHz, error tolerance value E Φ , proceed to step S2;

[0008] S2: Use sensors and signal conditioning circuits to obtain the primary current of the magnetically coupled wireless power transfer system and primary voltage Two voltage signals and Go to step S3;

[0009] S3: and Through the cutoff frequency f c =100kHz analog low-pass filter, obtain two sinusoidal voltage signals f1(t) and f2(t), t represents time, and enter step S4;

[0010] S4: Sample f1(t) and f2(t) respectively to obtain discrete signals f1(n) and f2(n), where n is the sampling sequence number, and then proceed to step S5;

[0011] S5: Perform an intersecting S transform on the discrete signals f1(n) and f2(n) to obtain a complex vector CST(n), and proceed to step S6;

[0012] S6: Calculate the phase of CST(n) to obtain the phase vector Go to step S7;

[0013] S7: Calculate vector The average value of the middle segment is the phase difference Φ between f1(n) and f2(n), that is:

[0014]

[0015] Where N is a vector The total length of , round() is a rounding function, and the process goes to step S8;

[0016] S8: Determine whether Φ is less than the set error tolerance value E Φ If yes, go to step S10, if no, go to step S9;

[0017] S9: Update the main circuit switching frequency:

[0018] f r =f r +kΦ

[0019] Where k is the correction coefficient, and the process returns to step S2;

[0020] S10: output f r The value of is the resonant frequency of the magnetically coupled wireless power transmission system.

[0021] In the frequency tracking method of a magnetically coupled wireless power transmission system described in the present invention, the intersecting S-transformation module thereof adopts the following steps:

[0022] T1: Initialize the discrete Gaussian window g(n) and its frequency domain result G(m), and proceed to step T2;

[0023] T2: Input discrete signals f1(n) and f2(n), and proceed to step T3;

[0024] T3: Perform discrete Fourier transform on f1(n) and f2(n) to obtain F1(m) and F2(m), where m is the frequency domain sampling number, and then proceed to step T4;

[0025] T4: Press F1(m) or F2(m) to press m r After shifting, we get F1(m+m r ) and F2(m+m r ), m r is the frequency corresponding to f r The frequency domain frequency number is obtained, and step T5 is entered;

[0026] T5: Use the following formula to calculate the single vector S transform S of the two signals f1(n) and f2(n) respectively x (n):

[0027] S x (n) = IFFT{G[m]×F x (m+m r )}

[0028] Where IFFT() is inverse fast Fourier transform, x represents 1 or 2, and the process goes to step T6;

[0029] T6: Take the conjugate of S2(n) to get S2 * (n), proceed to step T7;

[0030] T7: S2 * Multiplying (n) with S1(n) yields the intersection S transform CST(n).

[0031] The beneficial effect of the present invention is that, by providing a frequency tracking phase difference detection method for a magnetically coupled wireless power transmission system, a good foundation can be provided for the magnetically coupled wireless power transmission system to operate in a resonant state, thereby overcoming the disadvantages of the hardware method such as high cost and complex circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a block diagram of an implementation method for a magnetically coupled wireless power transmission system according to the present invention.

[0033] Figure 2The figure is a flow chart of the frequency tracking method of the magnetic coupling wireless power transmission system of the present invention.

[0034] Figure 3 This is a flow chart of the intersecting S transform module of the present invention.

[0035] Figure 4 The present invention is described with examples. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be noted that the preferred embodiments are intended to further illustrate the present invention rather than to limit the scope of protection of the present invention.

[0037] The frequency tracking method of a magnetically coupled wireless power transmission system described in the present invention includes a low-pass filter module and an intersecting S-transformation module, wherein the low-pass filter module is used to filter the two original signals of the main circuit to generate two sinusoidal signals, and sample the two signals and output them to the intersecting S-transformation module.

[0038] Figure 1 This is a block diagram of the implementation method of the frequency tracking method of the magnetically coupled wireless power transmission system of the present invention. The topological structure is one of the four basic structures of wireless power transmission, which has the advantages of long transmission distance and strong load capacity. The circuit mainly includes a DC power supply, a high-frequency inverter link, a receiving and transmitting coil, a compensation network, a rectifier link, a filter and a load. The DC power is generated into a high-frequency current through the high-frequency inverter link and is sent to the transmitting coil. The transmitting coil and the receiving coil are coupled to generate an induced current of the same frequency on the secondary side, and then the rectifier and filter structure are used for consumption by the load. The frequency tracking method of the magnetically coupled wireless power transmission system of the present invention provides a phase difference Φ between the detected primary current and voltage, and outputs it to the controller. The controller adjusts the frequency of the PWM generator according to Φ and controls the inverter.

[0039] Figure 2 The steps adopted by the frequency tracking method of the magnetic coupling wireless power transmission system of the present invention are as follows:

[0040] S1: Given the main circuit switching frequency f r =85kHz, error tolerance value E Φ , proceed to step S2;

[0041] S2: Use sensors and signal conditioning circuits to obtain the primary current of the magnetically coupled wireless power transfer system and primary voltage Two voltage signals and Go to step S3;

[0042] S3: and Through the cutoff frequency f c =100kHz analog low-pass filter, obtain two sinusoidal voltage signals f1(t) and f2(t), t represents time, and enter step S4;

[0043] S4: Sample f1(t) and f2(t) respectively to obtain discrete signals f1(n) and f2(n), where n is the sampling sequence number, and then proceed to step S5;

[0044] S5: Perform an intersecting S transform on the discrete signals f1(n) and f2(n) to obtain a complex vector CST(n), and proceed to step S6;

[0045] S6: Calculate the phase of CST(n) to obtain the phase vector Go to step S7;

[0046] S7: Calculate vector The average value of the middle segment is the phase difference Φ between f1(n) and f2(n), that is:

[0047]

[0048] Where N is a vector The total length of , round() is a rounding function, and the process goes to step S8;

[0049] S8: Determine whether Φ is less than the set error tolerance value E Φ If yes, go to step S10, if no, go to step S9;

[0050] S9: Update the main circuit switching frequency:

[0051] f r =f r +kΦ

[0052] Where k is the correction coefficient, and the process returns to step S2;

[0053] S10: output f r The value of is the resonant frequency of the magnetically coupled wireless power transmission system.

[0054] Figure 3 The steps adopted by the intersecting S transform module of the present invention are:

[0055] T1: Initialize the discrete Gaussian window g(n) and its frequency domain result G(m), and proceed to step T2;

[0056] T2: Input discrete signals f1(n) and f2(n), and proceed to step T3;

[0057] T3: Perform discrete Fourier transform on f1(n) and f2(n) to obtain F1(m) and F2(m), where m is the frequency domain sampling number, and then proceed to step T4;

[0058] T4: Press F1(m) or F2(m) to press m r After shifting, we get F1(m+m r ) and F2(m+m r ), m r is the frequency corresponding to f r The frequency domain frequency number is obtained, and step T5 is entered;

[0059] T5: Use the following formula to calculate the single vector S transform S of the two signals f1(n) and f2(n) respectively x (n):

[0060] S x (n) = IFFT{G[m]×F x (m+m r )}

[0061] Where IFFT() is inverse fast Fourier transform, x represents 1 or 2, and the process goes to step T6;

[0062] T6: Take the conjugate of S2(n) to get S2 * (n), proceed to step T7;

[0063] T7: S2 * Multiplying (n) with S1(n) yields the intersection S transform CST(n).

[0064] Figure 4 This is an application example of the frequency tracking method of the magnetic coupling wireless power transmission system of the present invention. Figure 4 (a) is the current and voltage signal to be analyzed; Figure 4 (b) for Figure 3 In (a), the effect of the two signals passing through the filter shows that the phase error between the two paths does not change; Figure 4 (c) for using the method of the present invention to Figure 4 (b) The result of phase difference detection on the signal after passing through the filter.

[0065] The embodiments of the present invention described above are not intended to limit the scope of protection of the present invention. If various deformations or modifications are made to the embodiments of the present invention, they should be included in the scope of protection of the claims of the present invention as long as they are within the spirit and principles of the present invention.

Claims

1. A frequency tracking method for a magnetically coupled wireless power transmission system, comprising a low-pass filter module and an intersecting S-transform module, characterized in that Use the following steps: S1: Given the main circuit switching frequency f r =85kHz, error tolerance value E Φ , proceed to step S2; S2: Use sensors and signal conditioning circuits to obtain the primary current of the main circuit of the magnetic coupling wireless power transmission system and primary voltage Two voltage signals and Go to step S3; S3: and Through the cutoff frequency f c =100kHz analog low-pass filter, obtain two sinusoidal voltage signals f1(t) and f2(t), t represents time, and enter step S4; S4: Sample f1(t) and f2(t) respectively to obtain discrete signals f1(n) and f2(n), where n is the sampling sequence number, and then proceed to step S5; S5: Perform an intersecting S transform on the discrete signals f1(n) and f2(n) to obtain a complex vector CST(n), and proceed to step S6; S6: Calculate the phase of CST(n) to obtain the phase vector Go to step S7; S7: Calculate vector The average value of the middle segment is the phase difference Φ between f1(n) and f2(n), that is: Where N is a vector The total length of , round() is a rounding function, and the process goes to step S8; S8: Determine whether Φ is less than the set error tolerance value E Φ If yes, go to step S10, if no, go to step S9; S9: Update the main circuit switching frequency: f r =f r +kΦ Where k is the correction coefficient, and the process returns to step S2; S10: output f r The value of is the resonant frequency of the magnetically coupled wireless power transmission system.

2. A frequency tracking method for a magnetically coupled wireless power transmission system according to claim 1, characterized in that: Its intersecting S transform module uses the following steps: T1: Initialize the discrete Gaussian window g(n) and its frequency domain result G(m), and proceed to step T2; T2: Input discrete signals f1(n) and f2(n), and proceed to step T3; T3: Perform discrete Fourier transform on f1(n) and f2(n) to obtain F1(m) and F2(m), where m is the frequency domain sampling number, and then proceed to step T4; T4: Press F1(m) or F2(m) to press m r After shifting, we get F1(m+m r ) and F2(m+m r ), m r is the frequency corresponding to f r The frequency domain frequency number is obtained, and step T5 is entered; T5: Calculate the single vector S transform S of signals f1(n) and f2(n) respectively using the following formula: x (n): S x (n)=IFFT{G[m]×F x (m+m r )} Where IFFT() is inverse fast Fourier transform, x represents 1 or 2, and the process goes to step T6; T6: Take the conjugate of S2(n) to get S2 * (n), proceed to step T7; T7: S2 * Multiplying (n) with S1(n) yields the intersection S transform CST(n).

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