A phase angle synchronization method for electric vehicle wireless charging system

Abstract

The application discloses a phase angle synchronization method of an electric vehicle wireless charging system, which realizes rectification input voltage and current phase angle synchronization of a secondary side of the system. A main circuit of the vehicle wireless charging system comprises a DC power supply, a high-frequency inverter, a primary side compensation network, a coupling mechanism, a secondary side compensation network, a rectifier, a filter capacitor and a battery load which are sequentially and electrically connected, and the coupling mechanism comprises a primary side coil and a secondary side coil. The high-frequency inverter adopts a full-bridge inverter circuit, and the rectifier is a half-controlled rectifier bridge adopting a bridge-type half-controlled rectification circuit. A controller is used to control the half-controlled rectifier bridge to realize real-time phase angle synchronization control of the electric vehicle wireless charging system based on a SOGI phase-locked loop. Sampling input of the SOGI is i LF2 , a feedback quantity of the phase-locked loop is an output quantity of the phase-locked loop, and the output quantity of the phase-locked loop is θ rec . The half-controlled rectifier bridge is a controlled object of the phase-locked loop. The half-controlled rectifier bridge has two input parameters: θ rec and β rec .

Description

Technical Field

[0001] This invention relates to the technical field of wireless charging, specifically to a phase angle synchronization method for a wireless charging system for electric vehicles. Background Technology

[0002] With the development of new energy technologies, electric vehicles are gradually becoming the main force replacing gasoline-powered vehicles. The advantages of electric vehicles, such as low energy consumption, low pollution, energy efficiency, and reliability, will benefit the future development and innovation of the electric vehicle industry, making it possible for every household to use electric vehicles for transportation.

[0003] Charging electric vehicles using traditional plug-in power supply methods is prone to dangers and problems such as aging wiring, electrical leakage and fire, and equipment failure. With the continuous development of wireless power transmission technology in the electric vehicle field, wireless charging will become the main trend for electric vehicles due to its advantages of low energy consumption, high efficiency, stability and safety.

[0004] Wireless charging for electric vehicles generally uses magnetically coupled resonant technology. In order to maximize the system's transmission power, a DLCC topology magnetically coupled resonant wireless power transmission system is generally used. This topology has advantages such as high transmission power, strong anti-offset capability, and strong safety and stability. The resonant frequency of the system is 85.5kHz.

[0005] In magnetically coupled resonant wireless power transfer systems, both the primary and secondary circuits are resonant circuits, with their corresponding voltages and currents in phase. To ensure the synchronization of the primary and secondary voltage and current phases, and thus maintain the synchronization of the phase of the switching transistors in the secondary rectifier bridge arm and the resonant current flowing through them, synchronous rectification can be achieved, reducing conduction losses on the switching transistors. However, in practice, since the primary and secondary sides of the system require two sets of controllers, current technology cannot guarantee the synchronization of the secondary voltage and current phase angles. To ensure the synchronization of the secondary voltage and current phases, it is urgent to develop a method for the secondary rectifier bridge of this system that can achieve a fast and accurate response to current information even when faced with large current harmonics. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a phase angle synchronization method for a wireless charging system for electric vehicles. On one hand, it collects the input current of the secondary rectifier bridge and then uses a phase angle synchronization method based on SOGI (Synchronous Loop Induction Gain) to track changes in phase difference, thereby achieving phase angle synchronization of the rectified input voltage and current on the secondary side of the system. On the other hand, the collected current signal can be filtered after passing through SOGI, which not only saves the cost of adding filters to the circuit but also enables more accurate phase angle synchronization.

[0007] A phase angle synchronization method of an electric vehicle wireless charging system, characterized in that: the main circuit of the vehicle wireless charging system comprises a direct current power supply, a high-frequency inverter, a primary compensation network, a coupling mechanism, a secondary compensation network, a rectifier, a filter capacitor and a battery load connected in sequence, and the coupling mechanism comprises a primary coil and a secondary coil; the high-frequency inverter adopts a full-bridge inverter circuit, and the rectifier is a half-controlled rectifier bridge adopting a bridge-type half-controlled rectification circuit;

[0008] The controller is used to control the half-controlled rectifier bridge to realize real-time phase angle synchronization control of the electric vehicle wireless charging system based on a SOGI phase-locked loop;

[0009] The sampling input of the SOGI is i LF2 , the feedback quantity of the phase-locked loop is , and the output quantity of the phase-locked loop is θ rec ;

[0010] The half-controlled rectifier bridge is a controlled object of the phase-locked loop; the half-controlled rectifier bridge has two input parameters: θ rec and β rec ;

[0011] Among them, i LF2 is the input current of the half-controlled rectifier bridge; is the phase angle of i LF2 ; θ rec is the phase angle of the rectified input voltage u ab ; and β rec is the phase shift angle of the rectified input voltage u ab .

[0012] Further characterized in that:

[0013] The structure of the SOGI comprises a proportional element, a first integral element and a second integral element connected in series, an input signal i LF2 is input from the input end of the proportional element, an output signal v α is output after passing through the first integral element, and an output signal v β is output after passing through the second integral element, wherein the sampling current i LF2 has the same amplitude and phase as the output signal v α , and the output signal v β has the same amplitude as the output signal v α and a phase lag of 90°.

[0014] The structure of the phase-locked loop comprises a Park transformation unit, a PI controller, an integral element and a remainder element, two input ends of the Park transformation unit are connected with the output signal v α of the SOGI and the output signal v β , and the output signal of the phase-locked loop is θ rec;

[0015] The direct-axis component transfer function and the quadrature-axis component transfer function of the SOGI structure are respectively:

[0016]

[0017]

[0018] Wherein, k is a damping factor, ω0 is an undamped natural frequency, and s is a Laplace operator;

[0019] The phase-locked loop output signal θ rec is in phase with the sampling signal i LF2 . rec Simultaneously controls the turn-on and turn-off of the half-controlled rectifier bridge switch tubes S5 and S6, thereby controlling the phase and duty cycle of the rectified input voltage u ab In each time period [0, 2π], when β rec < θ rec < π, S5 is turned off, and is turned on in the remaining time, when θ rec > π + β rec , S6 is turned off, and is turned on in the remaining time.

[0020] Preferably, the phase shift angle β rec is controlled in the range of [0, π].

[0021] The phase-locked loop output signal θ rec is in phase with the sampling signal i LF2 .

[0022] After the application, the advantages are as follows: the primary and secondary power in the electric vehicle wireless charging system will be affected by the frequency deviation to cause oscillation, so it is necessary to use a phase-locked loop to solve the problem, and an open-loop phase-locked loop needs to add a filter to filter the sampling signal to improve the phase-locked accuracy, which has the disadvantages of high cost, low phase-locked accuracy, slow response, etc. The application discloses a phase angle synchronization method of an electric vehicle wireless charging system based on a SOGI phase-locked loop, utilizes a phase tracking technology based on a SOGI (second-order generalized integrator) phase-locked loop, establishes a mathematical model, deduces the phase angle difference between the phase of the output voltage and the sampling current and tracks the phase angle difference, and can realize phase angle synchronization. Finally, the application uses simulation software to build a simulation model, and verifies that the proposed phase angle synchronization method has excellent feasibility and stability.

[0023] The method of directly measuring the phase angle of the sampling current saves the cost of additional hardware circuit, and improves the accuracy and response speed of phase synchronization tracking due to the filtering effect of SOGI. Therefore, aiming at the problems of high current harmonic distortion rate and low phase detection accuracy in the LCC-LCC topology wireless power transmission system, the application provides a phase angle synchronization method of the automobile wireless charging system based on SOGI phase-locked loop, which adopts the SOGI phase-locked loop to detect the phase angle of the input current of the rectifier bridge, obtains the output characteristics of the SOGI structure through the transfer function of the SOGI structure, and then uses the phase-locked loop to track the change of the phase angle difference, so as to realize the phase angle synchronization of the input voltage and current of the rectifier bridge. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is the main circuit schematic diagram of the system corresponding to the application;

[0025] Figure 2 It is the main circuit equivalent circuit schematic diagram of the system corresponding to the application;

[0026] Figure 3 It is the phase synchronization control block diagram of the application;

[0027] Figure 4 It is the SOGI output signal and input signal waveform comparison diagram of the application;

[0028] Figure 5 It is the phase-locked loop output waveform and SOGI input signal waveform comparison diagram of the application;

[0029] Figure 6 It is the rectifier bridge switch tube driving waveform and phase-locked loop output waveform comparison diagram of the application;

[0030] Figure 7 It is the rectifier bridge input voltage and current waveform diagram of the application;

[0031] The names corresponding to the serial numbers in the figure are as follows:

[0032] DC power supply 1, high-frequency inverter 2, primary side compensation network 3, coupling mechanism 4, secondary side compensation network 5, rectifier 6, filter capacitor and battery load 7. DETAILED DESCRIPTION

[0033] A phase angle synchronization method of an electric vehicle wireless charging system is seen Figures 1-7 , in specific implementation: the automobile wireless charging system is an LCC-LCC topology wireless power transmission system, and the main circuit of the LCC-LCC topology wireless power transmission system is seen Figure 1) includes DC power supply 1, high frequency inverter 2, primary side compensation network 3, coupling mechanism 4, secondary side compensation network 5, rectifier 6, filter capacitor and battery load 7, coupling mechanism includes primary side coil, secondary side coil; high frequency inverter 2 adopts full-bridge inverter circuit, rectifier 6 is half-controlled rectifier bridge adopting bridge half-controlled rectification circuit;

[0034] DC power supply 1, high frequency inverter 2, primary side compensation network 3, primary side coil combination forms primary side mechanism; secondary side coil, secondary side compensation network 5, rectifier 6, filter capacitor and battery load 7 combination forms secondary side mechanism;

[0035] In specific embodiments, the DC input voltage V DC of the system is 400V, the driving frequency ω d of the system is 85.5kHz, the compensation inductance L f1 in the primary side compensation network is 25μH, the compensation capacitor C f1 is 138.6nF, the compensation capacitor C P is 123.8nF, the transmitting coil L P is 53μH, the receiving coil L S is 53μH, the compensation inductance L f2 in the secondary side compensation network is 25μH, the compensation capacitor C f2 is 138.6nF, the compensation capacitor C S is 123.8nF, wherein the transmitting coil and the receiving coil are both wound by litz wire to reduce the resistance value of the coil;

[0036] Figure 2 The equivalent circuit schematic diagram of the LCC-LCC topology wireless power transmission system main circuit is shown, in this embodiment, the mutual inductance M between the coils is 14.5μH, the filter capacitor C filter is 500μF, the battery load R L is 20Ω, then the equivalent load R eq is about 16.2Ω.

[0037] The controller is used to control the half-controlled rectifier bridge to realize real-time phase angle synchronization control of the electric vehicle wireless charging system based on SOGI phase-locked loop;

[0038] Referring to Figure 3 , the phase synchronization control block diagram is shown, the sampling input of SOGI (second-order generalized integrator) is i LF2 , the feedback quantity of the phase-locked loop is , and the output quantity of the phase-locked loop is θ rec ;

[0039] The half-controlled rectifier bridge is the controlled object of the phase-locked loop; the half-controlled rectifier bridge has two input parameters: θ rec and βrec ;

[0040] Among them, i LF2 This is the input current of the semi-controlled rectifier bridge; is i LF2 Phase angle; θ rec It is the rectified input voltage u ab Phase angle; β rec The rectified input voltage u ab The phase shift angle.

[0041] Figure 3 The SOGI structure consists of a proportional element, a first integral element, and a second integral element connected in series, with the input signal being i. LF2 The signal is input from the input terminal of the proportional element, and output as a signal v after passing through the first integral element. α After the second integration stage, the output signal v β .

[0042] refer to Figure 4 The diagram shown compares the SOGI output signal and input signal waveforms, where the sampling current i LF2 With output signal v α Same amplitude and same phase, output signal v β With SOGI output signal v α In comparison, it has the same amplitude but a 90° phase lag;

[0043] Figure 3 The structure of the intermediate phase-locked loop includes a Park converter unit, a PI controller, an integrator, and a remainder converter. The two inputs of the Park converter unit are connected to the SOGI output signal v. α With SOGI output signal v β ;

[0044] The direct-axis and quadrature-axis transfer functions of the SOGI structure are as follows:

[0045]

[0046]

[0047] Wherein, the damping factor k takes the value of 1.414, the undamped natural frequency ω0 takes the value of 2*π*85500, and s is the Laplace operator;

[0048] refer to Figure 5 The diagram shows a comparison between the phase-locked loop (PLL) output waveform and the SOGI input signal waveform. The PLL output signal is θ. rec Phase-locked loop output signal θ rec With sampled signal i LF2In-phase; in this embodiment, the output range of the phase-locked loop output signal is [0, 2π], and the phase shift angle β rec The control value is 0.5π;

[0049] Reference Figure 6 The rectifier bridge switch tube driving waveform diagram is shown in the figure, and the phase-locked loop output signal θ rec And the phase shift angle β rec Simultaneously control the turn-on and turn-off of the half-controlled rectifier bridge switch tubes S5 and S6, and in each time period [0, 2π], when 0.5π < θ rec <π, S5 is turned off, and is turned on for the rest of the time, when θ rec >1.5π, S6 is turned off, and is turned on for the rest of the time; thereby controlling the phase and duty cycle of the rectified input voltage u ab ;

[0050] The output rectifier bridge voltage waveform is shown in the figure Figure 7 .

[0051] In this embodiment, the phase of the voltage signal output by the phase-locked loop is almost consistent with the phase of the collected current signal, and the phase angle synchronization of the input voltage and current of the secondary rectifier bridge is realized.

[0052] The beneficial effects are as follows: the primary and secondary power in the electric vehicle wireless charging system will be affected by the frequency deviation to cause oscillation, so it is necessary to use a phase-locked loop to solve this problem, and an open-loop phase-locked loop needs to add a filter to filter the sampling signal to improve the phase-locked accuracy, which has the disadvantages of high cost, low phase-locked accuracy and slow response. The application discloses an electric vehicle wireless charging system phase angle synchronization method based on a SOGI phase-locked loop, which utilizes a phase tracking technology based on a SOGI (second-order generalized integrator) phase-locked loop, establishes a mathematical model, deduces the phase angle difference between the output voltage and the sampling current, and tracks the phase angle difference, so that the phase angle synchronization can be realized. Finally, the application uses simulation software to build a simulation model, and verifies that the proposed phase angle synchronization method has excellent feasibility and stability.

[0053] The method of directly measuring the sampling current phase angle saves the cost of additional hardware circuits, and on the other hand, since the SOGI itself has a filtering effect, the accuracy and response speed of the phase synchronization tracking are improved. Therefore, in view of the problems of high current harmonic distortion rate and low phase detection accuracy in the LCC-LCC topology wireless power transmission system, the application proposes an electric vehicle wireless charging system phase angle synchronization method based on a SOGI phase-locked loop, which uses a SOGI phase-locked loop to detect the phase angle of the rectifier bridge input current, obtains the output characteristics of the SOGI structure through the transfer function of the SOGI structure, and then uses the phase-locked loop to track the phase angle difference, so that the phase angle synchronization of the rectifier bridge input voltage and current is realized.

[0054] It will be obvious to a person skilled in the art that the application is not limited to the details of the foregoing exemplary embodiments and can be implemented in other concrete forms without departing from the spirit or essential characteristics of the application. The embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims to the identity of the reference signs therein.

[0055] Furthermore, it should be understood that although the description is made on the basis of the embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A phase angle synchronization method for an electric vehicle wireless charging system, characterized in that: The main circuit of the automobile wireless charging system comprises a DC power supply, a high-frequency inverter, a primary compensation network, a coupling mechanism, a secondary compensation network, a rectifier, a filter capacitor and a battery load connected in sequence, the coupling mechanism comprises a primary coil and a secondary coil, the high-frequency inverter adopts a full-bridge inverter circuit, and the rectifier is a half-controlled rectifier bridge adopting a bridge-type half-controlled rectification circuit; The controller is used for controlling the half-controlled rectifier bridge to realize real-time phase angle synchronization control of the electric automobile wireless charging system based on a SOGI phase-locked loop; Wherein the sampling input of SOGI is i LF2 , the feedback quantity of the phase-locked loop is , and the output quantity of the phase-locked loop is θ rec ; The half-controlled rectifier bridge is a controlled object of the phase-locked loop; the half-controlled rectifier bridge has two input parameters: θ rec and β rec ; wherein i LF2 is the input current of the half-controlled rectifier bridge; is i LF2 is the phase angle of the input current θ rec is the rectified input voltage u ab is the phase angle of the rectified input voltage β rec is the phase shift angle of the rectified input voltage u ab is the phase shift angle of the rectified input voltage The phase-locked loop output signal θ rec The phase-locked loop output signal β rec Simultaneously controls the turn-on and turn-off of the half-controlled rectifier bridge switch tubes S5 and S6, thereby controlling the phase and duty cycle of the rectified input voltage u ab In each time period [0, 2π], when β rec θ rec S5 is turned off, and is turned on at other times, and when θ rec >π+ β rec S6 is turned off, and is turned on at other times.​ 2. The phase angle synchronization method for a wireless charging system of an electric vehicle according to claim 1, characterized in that: The structure of the SOGI comprises a proportional link, a first integral link and a second integral link connected in series, and the input signal is i LF2 The input signal from the input end of the proportional link is output after passing through the first integral link v α The output signal is output after passing through the second integral link v β Wherein the sampling current i LF2 is in phase with the output signal v α The output signal v β is in phase with the output signal v α and has the same amplitude but a 90° phase lag.

3. The phase angle synchronization method for a wireless charging system of an electric vehicle according to claim 2, characterized in that: The structure of the phase-locked loop comprises a Park transformation unit, a PI controller, an integral element and a remainder element, two input ends of the Park transformation unit are connected with output signals of SOGI respectively v α and the output signal v β , the phase-locked loop output signal is θ rec .

4. The phase angle synchronization method for a wireless charging system of an electric vehicle according to claim 3, characterized in that: The direct-axis component transfer function and the quadrature-axis component transfer function of the SOGI structure are respectively: ； where k is a damping factor, ω 0 is the undamped natural frequency and s is the Laplace operator.

5. The phase angle synchronization method of a wireless charging system for an electric vehicle according to claim 4, wherein The phase shift angle β rec The control range is [0, π].

6. The phase angle synchronization method for a wireless charging system of an electric vehicle according to claim 3, characterized in that: The phase-locked loop output signal θ rec with the sampling signal i LF2 in phase.

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