Wireless power transmission system frequency tracking method based on second-order generalized integrator phase-locked loop

Abstract

The invention discloses a wireless power transmission system frequency tracking method based on a second-order generalized integrator phase-locked loop, and aims to solve the problems of resonant frequency drift and transmission efficiency reduction caused by parameter change of a system. According to the method, an output voltage signal of the inverter is detected, a second-order generalized integrator phase-locked loop is used for carrying out orthogonal decomposition and phase error extraction, and a new driving signal is generated to control the working frequency of the inverter, so that the system tracks and locks the resonant frequency in real time. Only a single voltage signal is needed, the system structure is simplified, it is ensured that the system rapidly recovers and stably works in the resonance state when the load and coupling state changes, and the transmission efficiency and reliability are remarkably improved. The method is simple in step, has a remarkable effect on efficiency improvement, and has good economical efficiency and practicability.

Description

A Frequency Tracking Method for Wireless Power Transfer Systems Based on a Second-Order Generalized Integrator Phase-Locked Loop Technical Field

[0001] This invention relates to the field of wireless power transfer technology, specifically a frequency tracking method for wireless power transfer systems based on a second-order generalized integrator phase-locked loop. Background Technology

[0002] Wireless power transfer technology, also known as contactless power transmission, is a novel power supply technology that enables the transmission of electrical energy from the power source to the load without electrical contact, using media such as spatial magnetic fields, electric fields, microwaves, or lasers. Among these technologies, inductive wireless power transfer based on the principle of magnetic coupling resonance shows broad application prospects in fields such as wireless charging of electric vehicles, home appliances, medical implantable devices, and portable electronic products due to its advantages of high transmission power, high efficiency, and adaptability to medium transmission distances.

[0003] In magnetically coupled resonant wireless power transfer systems, the system's energy transfer efficiency is closely related to its operating state. The system achieves its highest energy transfer capability and efficiency when operating at its resonant frequency. However, in practical applications, system parameters such as the relative position and angle of the coupling coils, as well as dynamic changes in the load, cause the actual resonant frequency to drift. If the system continues to operate at a fixed preset frequency, it will deviate from the actual resonant point, resulting in reduced system transfer efficiency and potentially causing increased stress on power devices and severe overheating. Therefore, to ensure efficient and stable power transfer across the entire operating range, real-time and precise tracking and control of the system's resonant frequency—i.e., frequency tracking—is crucial.

[0004] Currently, existing methods for frequency tracking can be mainly divided into two categories: hardware detection and software phase-locked loop (PLL). Hardware detection methods typically detect the voltage and current signals on the inverter output side, and obtain their phase relationship through hardware comparison circuits or zero-crossing detection circuits. This allows them to determine whether the system is in a resonant state and adjust the inverter's drive frequency accordingly. While these methods offer fast response times, they are susceptible to circuit parameter deviations and electromagnetic interference, resulting in limited detection accuracy and increased hardware complexity and cost.

[0005] To overcome the shortcomings of hardware-based methods, phase-locked loop (PLL) technology based on software algorithms has been introduced into frequency tracking. Traditional synchronous reference coordinate system (SRF-PLL) PLLs are widely used due to their simple structure and good phase-locking performance under steady-state conditions. However, in scenarios like wireless power transmission systems with complex operating conditions and frequent changes in load and coupling states, the grid voltage or inverter output signal is easily mixed with a large amount of harmonics and DC components. Traditional SRF-PLLs are highly sensitive to these interferences, and their phase-locking accuracy and dynamic response speed will significantly decrease, leading to frequency tracking deviations or even loss of lock-in, making it impossible to guarantee the system's continuous and stable operation at the optimal resonant point.

[0006] Therefore, there is an urgent need for a method that can maintain high accuracy and robustness in frequency tracking under complex environments in order to improve the overall performance of wireless power transmission systems. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention aims to provide a frequency tracking method for a wireless power transmission system based on a second-order generalized integrator, which aims to solve the problem of the actual resonant frequency of the system drifting and the resulting reduction in system transmission efficiency.

[0008] A frequency tracking method for wireless power transfer systems based on a second-order generalized integrator phase-locked loop includes the following steps:

[0009] Step 1: Construct the circuit topology diagram of the SS-type wireless power transfer system;

[0010] Step 2: Construct the equivalent circuit of mutual inductance of the SS-type wireless power transmission system, analyze and calculate the equivalent impedance of the transmitting and receiving ends of the system, and calculate the primary and secondary current values ​​through Kirchhoff's laws. Further, the input and output power of the system can be calculated, thereby determining the transmission efficiency of the system.

[0011] Step 3: Construct the block diagram and structural diagram of the second-order generalized integrator phase-locked loop frequency tracking.

[0012] Step 4: Obtain the output voltage of the inverter and send it into the second-order generalized integrator phase-locked loop. Finally, the output phase angle is generated and sent into the PWM to generate a new drive signal. The new drive signal controls the inverter's operating frequency to the new resonant frequency after detuning, so that the wireless power transmission system is in a resonant state, thereby improving the transmission efficiency.

[0013] As a further technical solution of the present invention, step 1 includes:

[0014] Step 1.1: Construct the circuit topology diagram of the SS-type wireless power transmission system. The circuit topology specifically includes: DC power supply (1), high-frequency inverter module (2), primary side resonant capacitor (3), primary side parasitic resistor (4), transmitting coil (5), receiving coil (6), secondary side resonant capacitor (7), secondary side parasitic resistor (8), rectifier and filter module (9), and load (10).

[0015] The DC power supply is connected to the input terminal of the high-frequency inverter module. The output terminal of the high-frequency inverter is connected to the input terminal of the transmitting coil through the primary resonant capacitor and the primary parasitic resistor. The output terminal of the transmitting coil module is set opposite to the input terminal of the receiving coil module. The output terminal of the receiving coil module is connected to the input terminal of the rectifier module. The output terminal of the rectifier and filter module is connected to the system load.

[0016] Step 1.2: The DC power supply outputs a suitable DC voltage, which is then used by the high-frequency inverter to obtain a high-frequency voltage with zero phase. After passing through the primary-side compensation capacitor, the input voltage is output from the transmitting coil to the receiving coil. The rectifier module converts the high-frequency AC power into DC power, and the load is connected to the output of the rectifier module to absorb power.

[0017] As a further technical solution of the present invention, step 2 includes:

[0018] Step 2.1, analyze the equivalent circuit of the mutual inductance of the SS-type wireless power transmission system, and obtain the equivalent impedances Z1 and Z2 of the primary and secondary sides respectively:

[0019]

[0020] In the formula, R1 and R2 represent the parasitic resistances of the transmitter and receiver, respectively, and L1 and L2 are the coil inductances of the transmitter and receiver, respectively. L This is the load resistance.

[0021] Step 2.2, write Kirchhoff's equations for the two loops of the primary and secondary sides:

[0022]

[0023] In the formula, Us is the high-frequency power supply, and I1 and I2 are the current values ​​of the transmitter and receiver, respectively.

[0024] Step 2.3, according to the above formula, we can obtain I1 and I2 as follows:

[0025]

[0026] Step 2.4 further allows us to calculate the system's input and output power and efficiency as follows:

[0027]

[0028] For ease of analysis, let L1=L2=L and C1=C2=C;

[0029] When the system satisfies the electromagnetic resonance condition φL = 1 / φC, the imaginary parts of Z1 and Z2 approach zero, which can be simplified to:

[0030]

[0031] At this point, the system is in a resonant state, with a purely resistive impedance. The phase difference between the inverter output voltage and output current is in phase, and the apparent power at the inverter input is almost entirely converted into active power for transmission, resulting in maximum system transmission efficiency. When the impedance is inductive or capacitive, the system is in a detuned state, with a significant phase shift between the inverter output voltage and current. The proportion of reactive power in the input power increases, and the transmission efficiency decreases.

[0032] As a further technical solution of the present invention, step 3 includes:

[0033] Step 3.1: Construct a control block diagram based on frequency tracking using a second-order generalized integrator phase-locked loop. The control topology specifically includes: a DC power supply (1), a high-frequency inverter module (2), a primary resonant capacitor (3), a primary parasitic resistor (4), a transmitting coil (5), a receiving coil (6), a secondary resonant capacitor (7), a secondary parasitic resistor (8), a rectifier module (9), a load (10), a voltage detection module (11), a second-order generalized integrator phase-locked loop module (12), and a PWM drive module (13).

[0034] The connection method of module (1) to module (10) is the same as in step 1.1, and will not be repeated here;

[0035] In addition, the voltage detection module (11) is connected to the output terminal of the high-frequency inverter module (2), the output terminal of the voltage detection module is connected to the input terminal of the second-order generalized integrator phase-locked loop, and the output of the second-order generalized integrator phase-locked loop is connected to the PWM drive module (13), and the output terminal of the PWM drive is connected to the high-frequency inverter module to form a closed loop.

[0036] Step 3.2: Construct the structure diagram of the second-order generalized integrator phase-locked loop. The structure of the second-order generalized integrator phase-locked loop specifically includes: a second-order generalized integrator (1), a Park transform (2), a PI controller (3), and an integration module (4).

[0037] The output of the second-order generalized integrator is connected to the Park transform, and the output of the Park transform is connected to the PI control module. The output value of the PI control module is superimposed with the initial resonant angular frequency, which is fed into the integration module on one hand and fed back to the second-order generalized integrator module on the other. The integration module outputs a new phase angle and feeds it back to the Park transform.

[0038] As a further technical solution of the present invention, step 4 includes:

[0039] The voltage detection circuit first acquires the inverter output voltage signal u. g The data is then fed into a second-order generalized integrator module for orthogonal decomposition to generate the positive-sequence voltage component u in a two-phase stationary coordinate system. α and u β Then, the above components are transformed to a rotating coordinate system using the Park transformation, where the cross-axis component u... q This signal is used as an indicator of the system phase error. After being processed by the PI controller, this error signal outputs an angular frequency correction value. This correction value is added to the preset initial resonant angular frequency ω0 to obtain the real-time phase-locked loop angular frequency ω. PLL ω PLL On one hand, it feeds back to the second-order generalized integrator unit to update its center frequency parameter; on the other hand, it generates a phase signal q¢ through the integration stage and feeds it back to the Park transform matrix. q When the phase signal q¢ equals zero, it drives the PWM module to generate the inverter switching signal, thereby accurately locking the system's resonant frequency. This puts the wireless power transmission system in a resonant state, improving transmission efficiency.

[0040] The beneficial effects of this invention are:

[0041] The frequency tracking method based on a second-order generalized integrator phase-locked loop (PLL) employed in this invention offers significant advantages over traditional PLL technology. This method only requires detecting a single voltage signal output from the inverter. The second-order generalized integrator module orthogonally decomposes this signal into in-phase and quadrature-axis components, eliminating the need for additional current signal detection and phase comparison, thus simplifying the system structure. Furthermore, its inherent bandpass filtering characteristics effectively suppress high-order harmonics and random noise interference in the input signal, providing a cleaner input for the PLL and resolving the issues of unlocking or instability caused by signal interference in traditional PLLs. This design enables the system to quickly and accurately lock and track the actual resonant frequency in real time when parameters such as the transmitter capacitor or coil inductance drift, ensuring that the inverter output voltage and current remain in phase. This allows the system to quickly recover and stabilize in resonant operation, significantly improving the efficiency and reliability of wireless power transmission. By employing the aforementioned second-order generalized integrator PLL frequency tracking control strategy, this invention achieves efficient and stable operation of the system under various operating conditions. Simulation results show that when the transmitter parameters change, such as a capacitor change of ±20nF or an inductance change of ±8μH causing system detuning, the frequency tracking mechanism of this invention can act quickly to restore and maintain the system transmission efficiency above 90%. Attached Figure Description

[0042] Figure 1 shows the circuit topology of the SS-type wireless power transfer system;

[0043] Figure 2 shows the equivalent circuit of mutual inductance in an SS-type wireless power transmission system.

[0044] Figure 3 is a block diagram of frequency tracking based on a second-order generalized integrator phase-locked loop.

[0045] Figure 4 is a structural diagram of a second-order generalized integrator phase-locked loop;

[0046] Figure 5 is the Bode plot of the transfer function of the second-order generalized integrator;

[0047] Figure 6 shows the inverter output voltage and current under detuning without frequency tracking control.

[0048] Figure 7 shows the inverter output voltage and current under frequency tracking control when detuned;

[0049] Figure 8 shows the system transmission efficiency when the transmitter capacitance changes;

[0050] Figure 9 shows the system transmission efficiency when the self-inductance of the transmitting coil changes. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] Example 1

[0053] This embodiment provides a frequency tracking control strategy for a wireless power transfer system based on a second-order generalized integrator. The method specifically includes the following steps:

[0054] Step 1: Construct the circuit topology diagram of the SS-type wireless power transfer system;

[0055] Referring to the circuit topology diagram of the SS-type wireless power transmission system shown in Figure 1, the circuit topology specifically includes: DC power supply (1), high-frequency inverter module (2), primary side resonant capacitor (3), primary side parasitic resistor (4), transmitting coil (5), receiving coil (6), secondary side resonant capacitor (7), secondary side parasitic resistor (8), rectifier and filter module (9), and load (10).

[0056] The DC power supply is connected to the input terminal of the high-frequency inverter module. The output terminal of the high-frequency inverter is connected to the input terminal of the transmitting coil through the primary resonant capacitor and the primary parasitic resistor. The output terminal of the transmitting coil module is set opposite to the input terminal of the receiving coil module. The output terminal of the receiving coil module is connected to the input terminal of the rectifier module. The output terminal of the rectifier and filter module is connected to the system load.

[0057] The primary-side DC input voltage Us of the system is 24V, the resonant frequency of the system is 85kHz, the transmitting coil L1 and the receiving coil L2 are wound with Litz wire to reduce the resistance of the coils, the inductance of both is 35.07μH, and the mutual inductance M between L1 and L2 is 8.092μH, the primary-side resonant capacitor C1 and the secondary-side resonant capacitor C2 are both 99.98nF, the primary and secondary parasitic resistances are both 0.15Ω, and the load resistance is 10Ω.

[0058] Step 2: Analyze the equivalent circuit of the mutual inductance of the SS-type wireless power transmission system to determine the system's transmission efficiency.

[0059] When the high-frequency power supply U S When operating at angular frequency ω, analyzing Figure 2, the equivalent impedances Z1 and Z2 of the primary and secondary sides are obtained as follows:

[0060]

[0061] In the formula, R1 and R2 represent the parasitic resistances of the transmitter and receiver, respectively, and L1 and L2 are the coil inductances of the transmitter and receiver, respectively. L This is the load resistance.

[0062] Write Kirchhoff's equations for the two loops on the primary and secondary sides:

[0063]

[0064] According to the above formula, I1 and I2 can be obtained as follows:

[0065]

[0066] Furthermore, the system's input and output power and efficiency can be calculated as follows:

[0067]

[0068] For ease of analysis, let L1=L2=L and C1=C2=C;

[0069] When the system satisfies the electromagnetic resonance condition φL = 1 / φC, the imaginary parts of Z1 and Z2 approach zero, which can be simplified to:

[0070]

[0071] At this point, the system is in a resonant state, with a purely resistive impedance. The phase difference between the inverter output voltage and output current is in phase, and the apparent power at the inverter input is almost entirely converted into active power for transmission, resulting in maximum system transmission efficiency. When the impedance is inductive or capacitive, the system is in a detuned state, with a significant phase shift between the inverter output voltage and current. The proportion of reactive power in the input power increases, and the transmission efficiency decreases.

[0072] Step 3: Construct the control block diagram and the structure diagram of the second-order generalized integrator phase-locked loop for frequency tracking.

[0073] A control block diagram based on frequency tracking using a second-order generalized integrator phase-locked loop is constructed. The control topology is shown in Figure 3: DC power supply (1), high-frequency inverter module (2), primary resonant capacitor (3), primary parasitic resistance (4), transmitting coil (5), receiving coil (6), secondary resonant capacitor (7), secondary parasitic resistance (8), rectifier module (9), load (10), voltage detection module (11), second-order generalized integrator phase-locked loop module (12), PWM drive module (13);

[0074] The connection method between module (1) and module (10) is the same as in step 1, and will not be repeated here;

[0075] In addition, the voltage detection module (11) is connected to the output terminal of the high-frequency inverter module (2), the output terminal of the voltage detection module is connected to the input terminal of the second-order generalized integrator phase-locked loop, and the output of the second-order generalized integrator phase-locked loop is connected to the PWM drive module (13), and the output terminal of the PWM drive is connected to the high-frequency inverter module to form a closed loop.

[0076] The structure of the second-order generalized integrator phase-locked loop is shown in Figure 4. The output of the second-order generalized integrator is connected to the Park transform, and the output of the Park transform is connected to the PI control module. The output value of the PI control module is superimposed with the initial resonant angular frequency, which is fed into the integration module on one hand and fed back to the second-order generalized integrator module on the other. The integration module outputs a new phase angle and feeds it back to the Park transform.

[0077] Step 4: Obtain the inverter's output voltage and feed it into a second-order generalized integrator phase-locked loop (PLL). This generates an output phase angle, which is then fed into the PWM to produce a new drive signal. This new drive signal controls the inverter's operating frequency to the new resonant frequency after detuning, thus putting the wireless power transmission system in a resonant state and improving transmission efficiency.

[0078] The voltage detection circuit first acquires the inverter output voltage signal u. g The data is then fed into a second-order generalized integrator module for orthogonal decomposition to generate the positive-sequence voltage component u in a two-phase stationary coordinate system. α and u β Then, the above components are transformed to a rotating coordinate system using the Park transformation, where the cross-axis component u... q This signal is used as an indicator of the system phase error. After being processed by the PI controller, this error signal outputs an angular frequency correction value. This correction value is added to the preset initial resonant angular frequency ω0 to obtain the real-time phase-locked loop angular frequency ω. PLL ω PLL On one hand, it feeds back to the second-order generalized integrator unit to update its center frequency parameter; on the other hand, it generates a phase signal q¢ through the integration stage and feeds it back to the Park transform matrix. q When the phase signal q¢ equals zero, it drives the PWM module to generate the inverter switching signal, thereby achieving accurate locking of the system's resonant frequency, thus putting the wireless power transmission system in a resonant state and improving transmission efficiency.

[0079] The following analysis further examines the second-order generalized integrator phase-locked loop:

[0080] As shown in Figure 4, the voltage detection circuit first acquires the inverter output voltage signal u. gThe data is then fed into the SOGI unit for orthogonal decomposition to generate the positive sequence voltage component u in the two-phase stationary coordinate system. α and u β .

[0081] When the input signal frequency is equal to the center frequency of the second-order generalized integrator, its output is a pair of signals u with strictly orthogonal characteristics. α and u β The following equation is the transfer function of a second-order generalized integrator:

[0082] From D(s) and Q(s), we know that u α Always ahead of u in phase β The angle is 90°.

[0083] Figure 5 shows the Bode plot of the transfer function of a second-order generalized integrator.

[0084] The Bode plot shown in Figure 5 indicates that the second-order generalized integrator has certain filtering characteristics and can effectively suppress harmonic components in the input signal.

[0085] u α and u β The above components are transformed to a rotating coordinate system using the Park transformation:

[0086]

[0087] Assuming input voltage u g =V cosq. When the input signal frequency equals the center frequency, the output of the second-order generalized integrator can be expressed as:

[0088]

[0089] We can solve for:

[0090]

[0091] Analysis shows that:

[0092] (1) When u q When the value is greater than 0, q¢ lags behind q, and the PI controller increases the angular frequency correction value.

[0093] (2) When u q When q' is less than 0, q' leads q, and the PI controller reduces the angular frequency correction value.

[0094] (3) When u qWhen q¢ = 0, q¢ is synchronized with q. At this time, the output phase q¢ can achieve frequency tracking by controlling the switching transistor of the inverter circuit through the PWM drive circuit.

[0095] The simulation results are analyzed below:

[0096] (1) When the capacitance value is reduced from 99.98nF to 89.98nF, the system will become detuned. Figures 6 and 7 show the output voltage and current waveforms of the inverter without frequency tracking and with frequency tracking control system, respectively.

[0097] As shown in Figure 6, in a system without frequency tracking control, the phase difference between the inverter output voltage and current is not zero when the resonant capacitor changes, indicating a detuned state. The essence of this detuning is that the impedance characteristics deviate from purely resistive behavior, requiring the inverter to output additional reactive power to compensate for the phase difference, directly leading to a significant reduction in active power transmission efficiency. In Figure 7, after adopting frequency tracking control, the phase difference between the inverter output voltage and current is zero, and the system is in a resonant state. As can be seen from the waveform, the amplitude of the current sine wave is significantly increased, and the current period is strictly synchronized with the voltage square wave period. In this state, impedance matching is optimal, and transmission efficiency is maximized.

[0098] (2) During the simulation, the self-inductance of the transmitting coil was kept constant at 35.07μH. The value of the primary resonant capacitance was changed, and the transmission efficiency was calculated for both the case without frequency tracking control and the case with frequency tracking control. The results are shown in Figure 8.

[0099] As shown in Figure 8, when capacitor C1 equals 99.98nF, the system is in a resonant state, and the efficiency of the system using frequency tracking technology is similar to that of the system without frequency tracking. However, when the capacitor value deviates from 99.98nF, that is, when C1 is in the range of 79.98nF-99.98nF and 99.98nF-119nF, the system is in a detuned state. The efficiency of the system without frequency tracking shows a significant downward trend, while the efficiency of the system using frequency tracking technology is always maintained above 90%.

[0100] (3) During the simulation, the transmitter capacitance was kept constant at 99.98nF. The self-inductance of the transmitter coil was changed, and the transmission efficiency was calculated for both the case without frequency tracking control and the case with frequency tracking control. The results are shown in Figure 9.

[0101] As shown in Figure 9, when the inductance L1 is equal to 35.07 μH, the system is in a resonant state. At this time, the efficiency of the system using frequency tracking technology is similar to that of the system without frequency tracking. However, when the inductance value deviates from 35.07 μH, that is, when L1 is in the range of 27.07 μH-35.07 μH and 35.07 μH-43.07 μH, the system is in a detuned state. The efficiency of the system without frequency tracking decreases significantly, while the efficiency of the system using frequency tracking technology can be maintained above 90%.

[0102] In summary, the frequency tracking control method based on a second-order generalized integrator phase-locked loop adopted in this invention can quickly track the resonant frequency of the system when the compensation capacitor and coil self-inductance change, so as to restore the system to the resonant state and ensure the transmission efficiency of the system.

[0103] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented in software, the above embodiments can be implemented, in whole or in part, as a computer program product. Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution.

Claims

1. A frequency tracking method for a wireless power transfer system based on a second-order generalized integrator phase-locked loop, comprising the following steps: Step 1: Construct the circuit topology of the SS-type wireless power transfer system. Step 2: Construct the equivalent circuit of the mutual inductance of the SS-type wireless power transfer system, analyze and calculate the equivalent impedance of the transmitter and receiver, and calculate the primary and secondary current values ​​using Kirchhoff's laws. Further, the system's input and output power can be calculated, thus determining the system's transmission efficiency. Step 3: Construct the block diagram and structure diagram of the second-order generalized integrator phase-locked loop (PLL) based on frequency tracking. Step 4: Obtain the inverter's output voltage and feed it into the second-order generalized integrator PLL. This generates an output phase angle, which is then fed into the PWM to generate a new drive signal. This new drive signal controls the inverter's operating frequency to the new resonant frequency after detuning, thus putting the wireless power transfer system in a resonant state and improving transmission efficiency.

2. The frequency tracking method for a wireless power transfer system based on a second-order generalized integrator phase-locked loop according to claim 1, characterized in that, Step 1 includes: Step 1.1, constructing the circuit topology of the SS-type wireless power transmission system. The circuit topology specifically includes: a DC power supply (1), a high-frequency inverter module (2), a primary resonant capacitor (3), a primary parasitic resistor (4), a transmitting coil (5), a receiving coil (6), a secondary resonant capacitor (7), a secondary parasitic resistor (8), a rectifier and filter module (9), and a load (10). The DC power supply is connected to the input terminal of the high-frequency inverter module, the output terminal of the high-frequency inverter is connected to the input terminal of the transmitting coil through the primary resonant capacitor and the primary parasitic resistor, the output terminal of the transmitting coil module is opposite to the input terminal of the receiving coil module, the output terminal of the receiving coil module is connected to the input terminal of the rectifier module, and the output terminal of the rectifier and filter module is connected to the system load. Step 1.2, the DC power supply outputs a suitable DC voltage, which is then used by the high-frequency inverter to obtain a high-frequency voltage with zero phase. After passing through the primary compensation capacitor, the transmitting coil outputs the input voltage to the receiving coil. The rectifier module converts the high-frequency AC power into DC power, and the load is connected to the output of the rectifier module to absorb power.

3. The frequency tracking method for a wireless power transfer system based on a second-order generalized integrator phase-locked loop according to claim 1, characterized in that, Step 2 includes: Step 2.1, analyzing the equivalent circuit of the mutual inductance of the SS-type wireless power transmission system, and obtaining the equivalent impedances Z1 and Z2 of the primary and secondary sides respectively: In the formula, R1 and R2 represent the parasitic resistances of the transmitter and receiver, respectively, and L1 and L2 are the coil inductances of the transmitter and receiver, respectively. L Let the load resistance be denoted as ; Step 2.2, write Kirchhoff's equations for the two loops on the primary and secondary sides: In the formula, Us is the high-frequency power supply, and I1 and I2 are the current values ​​at the transmitting and receiving ends, respectively; Step 2.3, according to the above formula, I1 and I2 can be solved as follows: Step 2.4 further calculates the system's input and output power and efficiency as follows: For ease of analysis, let L1=L2=L and C1=C2=C. When the system satisfies the electromagnetic resonance condition λL=1 / λC, the imaginary parts of Z1 and Z2 approach zero, which can be simplified to: At this point, the system is in a resonant state, the system impedance is purely resistive, the phase difference between the inverter output voltage and output current reaches the same phase, the apparent power at the inverter input is almost completely converted into active power for transmission, and the system transmission efficiency is at its maximum. When the impedance is inductive or capacitive, the system is in a detuned state, a significant phase shift occurs between the inverter output voltage and current, the proportion of reactive power in the input power increases, and the transmission efficiency decreases.

4. The frequency tracking method for a wireless power transfer system based on a second-order generalized integrator phase-locked loop according to claim 1, characterized in that, Step 3 includes: Step 3.1, constructing a control block diagram based on frequency tracking of a second-order generalized integrator phase-locked loop. The control topology specifically includes: a DC power supply (1), a high-frequency inverter module (2), a primary resonant capacitor (3), a primary parasitic resistor (4), a transmitting coil (5), a receiving coil (6), a secondary resonant capacitor (7), a secondary parasitic resistor (8), a rectifier module (9), a load (10), a voltage detection module (11), a second-order generalized integrator phase-locked loop module (12), and a PWM drive module (13); wherein, the connection method of module (1)-module (10) is the same as in step 1.1, and will not be repeated here; in addition, the voltage detection module (11) is connected to the output terminal of the high-frequency inverter module (2), and the output terminal of the voltage detection module is connected to... The input of the second-order generalized integrator phase-locked loop is connected, while the output of the second-order generalized integrator phase-locked loop is connected to the PWM drive module (13). The output of the PWM drive is connected to the high-frequency inverter module to form a closed loop. Step 3.2: Construct the structure diagram of the second-order generalized integrator phase-locked loop. The structure of the second-order generalized integrator phase-locked loop specifically includes: a second-order generalized integrator (1), a Park transform (2), a PI controller (3), and an integration module (4). The output of the second-order generalized integrator is connected to the Park transform, and the output of the Park transform is connected to the PI control module. The output value of the PI control module is superimposed with the initial resonant angular frequency. On the one hand, it is sent to the integration module, and on the other hand, it is fed back to the second-order generalized integrator module. The integration module outputs a new phase angle and feeds it back to the Park transform.

5. The frequency tracking method for a wireless power transfer system based on a second-order generalized integrator phase-locked loop according to claim 1, characterized in that, Step 4 includes: the voltage detection circuit first acquires the inverter output voltage signal u. g The data is then fed into a second-order generalized integrator module for orthogonal decomposition to generate the positive-sequence voltage component u in a two-phase stationary coordinate system. α and u β Then, the above components are transformed to a rotating coordinate system using the Park transformation, where the cross-axis component u... q Used as an indicator of system phase error, this error signal is processed by a PI controller, which outputs an angular frequency correction value. This correction value is added to the preset initial resonant angular frequency ω0 to obtain the real-time phase-locked loop angular frequency ω. PLL ω PLL On one hand, the signal is fed back to the second-order generalized integrator unit to update its center frequency parameter; on the other hand, the phase signal q¢ is generated through the integration stage and fed back to the Park transform matrix, u. q When the phase signal q¢ equals zero, it drives the PWM module to generate the inverter switching signal, thereby achieving accurate locking of the system's resonant frequency, thus putting the wireless power transmission system in a resonant state and improving transmission efficiency.

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