A control method of a wireless power transmission system for bidirectional AC / DC power transmission

Abstract

The application discloses a kind of bidirectional AC / DC wireless power transmission system control methods, the system is in the direct current input front side of traditional SS compensation wireless charging system Joining a full-bridge circuit and AC filter circuit, can realize power AC / DC and DC / AC bidirectional transmission.When working in AC / DC direction, the voltage phase relationship and impedance characteristic phase shift control of SS compensation wireless charging system under natural constant current frequency are used to control the latter circuit, without additional PFC circuit and AC side current sampling, power factor correction function is realized, and has constant voltage output and constant current output capability.When reverse operation, the system can realize power DC / AC transmission.Compared with the traditional bidirectional AC / DC wireless power transmission system, the system has the advantages of low cost and high efficiency, and the control method is easy to implement.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology, specifically relating to a control method for a two-way AC / DC wireless power transmission system. Background Technology

[0002] Currently, the penetration rate of new energy vehicles in China has exceeded 10%, meaning that the proportion of electrification in the increase of automobiles exceeds 10%, and it is expected to exceed 30% by 2025. With the advancement of the "dual-carbon" target, energy-side transformation will enable electric vehicles to use renewable energy, providing power to electric vehicles through grid-to-vehicle (G2V) transmission. Simultaneously, new energy vehicles can achieve vehicle-to-grid interaction by connecting to the grid, with power flowing from electric vehicles to the grid (V2G), playing a role in peak shaving and valley filling of the grid load. Wireless power transfer offers advantages over traditional plug-in charging in terms of portability, flexibility, and safety, and wireless charging technology has attracted widespread attention in recent years.

[0003] Non-resistive loads can cause a phase difference between the grid voltage and the sinusoidal current absorbed from the grid, resulting in energy backflow and reduced energy efficiency. Nonlinear components cause grid voltage distortion, generating harmonics and electromagnetic radiation. This leads to a decrease in grid power supply capacity and increased losses. Therefore, a power factor correction (PFC) circuit is generally required on the grid connection side to achieve high power factor and low harmonic distortion. Traditional bidirectional AC / DC wireless power transfer systems consist of a bidirectional AC / DC circuit and a wireless power transfer system. Summary of the Invention

[0004] In view of the above-mentioned problems, this invention provides a control method for a bidirectional AC / DC wireless power transfer system. In forward operation, without the need for an external PFC circuit and without AC-side current sampling, it achieves a high power factor during AC / DC power transfer, and through closed-loop control, the DC output side achieves constant voltage and constant current output functions. In reverse operation, the wireless charging section operates in open-loop constant voltage mode, and DC / AC power transfer is achieved through SPWM modulation of the full-bridge Q1-Q4.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A control method for a bidirectional AC / DC wireless power transfer system, characterized in that the system includes an AC-side filter capacitor C. f1 AC side filter inductor L f1 AC side damping resistor R f AC side filter inductor L f2 AC side filter capacitor C f2The first power frequency switch Q1, the second power frequency switch Q2, the third power frequency switch Q3, the fourth power frequency switch Q4, and the first high-frequency switch S on the primary side. P1 The second high-frequency switch S on the primary side P2 The third high-frequency switch S on the primary side P3 The fourth high-frequency switch S on the primary side P4 Primary side series compensation capacitor C P Primary coil L P Secondary coil L S Secondary side series compensation capacitor C S Secondary side first high-frequency switch S S1 Secondary side second high-frequency switch S S2 Secondary side third high-frequency switch S S3 The fourth high-frequency switch S on the secondary side S4 Output filter capacitor C o Load R L .

[0007] Preferably, during forward operation, Q1 to Q4 of the full-bridge converter operate as power frequency rectification, and the full-bridge S... P1 ~S P4 And the whole bridge S S1 ~S S4 This is a fixed-frequency phase-shift modulation method. It consists of passive components (L...). f1 ,R f ,L f2 C f2 High-frequency filtering for AC measurements is performed using R. f Parallel L f1 The passive damping element is formed in this form, reducing resonance between LC circuits and thus reducing the input current THD. Utilizing the characteristic that the secondary resonant cavity output voltage phase leads the primary resonant cavity output voltage phase by 90° at the natural constant current frequency of the SS-compensated wireless charging system, phase-shift control is used to make the fundamental component of the primary resonant cavity input voltage track the input voltage. Power factor correction is achieved without the need for an external PFC circuit or sampling of the AC side current. By sampling the output current or output voltage, filtering it through a notch filter, and then using a proportional-integral controller, constant voltage or constant current output in the AC / DC direction of the system is achieved. The SS-compensated wireless charging system includes: a high-frequency switching transistor S... P1 ~S P4 Primary side series compensation capacitor C P Primary coil L P Secondary coil L S Secondary side series compensation capacitor C S Secondary side high-frequency switch S S1 ~S S4 .

[0008] Preferably, during forward operation, it is necessary to sample the grid input voltage V. gird The phase θ of the grid voltage is obtained through a phase-locked loop, from which the modulation of power frequency transistors Q1 to Q4 and the secondary side full-bridge S can be obtained. S1 ~S S4 The inner phase shift value D S Simultaneously, it is necessary to sample the output voltage V. o (or output current I) o The filtered voltage signal V is obtained after passing through a notch filter. o * (current signal I) o * Then, compare it with the required output voltage V of the system. oref (or output current I) oref The difference is used to obtain the error, which is then used to obtain the primary side full-bridge S through a proportional-integral controller. P1 ~S P4 The inner phase shift value D P And the outward phase value D between the primary side full bridge and the secondary side full bridge PS Finally, the modulation signals of all the switching transistors were obtained.

[0009] Preferably, during reverse operation, the full bridge S S1 ~S S4 It operates as a high-frequency inverter, full-bridge S P1 ~S P4 Utilizing uncontrolled rectification via a body diode, the full-bridge inverters Q1-Q4 operate as sinusoidal inverters. Employing SS-compensated wireless charging systems, the output characteristics of a constant voltage source are similar to those of a constant voltage source operating at a natural constant voltage frequency. Capacitor C... f2 The signal above contains a voltage signal with high-frequency ripple. By sampling the peak value of the AC output voltage and adjusting the amplitude of the modulation fundamental wave in a closed loop, the reverse transmission of electrical energy between DC and AC is achieved.

[0010] Preferably, the AC output voltage V needs to be sampled during reverse operation. ac The peak value V of the AC output voltage is obtained through a phase-locked loop. ac.peak With the required peak AC voltage V peak.ref The peak value U of the modulated wave is obtained by subtraction and calculation using a proportional-integral converter. CM After being multiplied by the sine factor Sin(ω) by the multiplier o t) yielded the sinusoidal modulation signal U M Modulation signal U M With carrier U C The comparison output yields the drive signals for Q1 to Q4 of the full-bridge circuit. The secondary-side high-frequency switching transistor S... S1 ~S S4 It only needs to operate at the system's natural constant voltage frequency f cv Another full bridge SP1 ~S P4 No control is required; rectification is achieved solely through the body diode without control.

[0011] The present invention offers the following advantages: When the system operates in the forward direction, power factor correction can be achieved without the need for an external PFC circuit or sampling of the AC input current. Furthermore, the DC bus voltage does not require a large capacitor. The system can also perform reverse power transmission, transferring energy from the battery load to the grid. Compared to traditional bidirectional AC / DC wireless power transfer systems, it reduces the need for PFC inductors, large DC bus capacitors, and AC current sampling design, resulting in lower circuit costs and easier control implementation. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the bidirectional AC / DC wireless power transfer system according to an embodiment of the present invention;

[0013] Figure 2 This is a block diagram of the voltage closed-loop control when the system is operating in the forward direction, according to an embodiment of the present invention.

[0014] Figure 3 This is a block diagram of the current closed-loop control during forward operation of the system according to an embodiment of the present invention;

[0015] Figure 4 This is a block diagram of high-frequency tube modulation during the reverse operation of the system according to an embodiment of the present invention;

[0016] Figure 5 This is a block diagram of the power frequency tube modulation when the system is operating in reverse according to an embodiment of the present invention;

[0017] Figure 6 The output voltage (V) of the system in this embodiment of the invention when the load is cut off under a constant voltage of 300V during forward operation. o Waveform;

[0018] Figure 7 The output current (I) of the system in this embodiment of the invention when the load is cut off under a constant voltage of 300V during forward operation. o Waveform;

[0019] Figure 8 The system of this embodiment of the invention outputs a constant voltage AC input voltage (V) under a certain load during forward operation. gird Waveform, AC input current (I) in ) Amplify the waveform;

[0020] Figure 9 For the system of this embodiment of the invention, the constant voltage output voltage of the primary side resonant cavity under a certain load during forward operation is (V) P ) and primary side resonant cavity current (I P Waveform;

[0021] Figure 10 The output current (I) of the system under constant current of 3.5A during forward operation in this embodiment of the invention is as follows: o Waveform;

[0022] Figure 11 The output voltage (V) of the system under constant current of 3.5A during forward operation and load shedding in this embodiment of the invention. o Waveform;

[0023] Figure 12 The system of this embodiment of the invention outputs a constant current AC input voltage (V) under a certain load during forward operation. gird Waveform, AC input current (I) in ) Amplify the waveform;

[0024] Figure 13 For the system of this embodiment of the invention, the primary side resonant cavity voltage (V) under a certain load is output as a constant current during forward operation. P ) and primary side resonant cavity current (I P Waveform;

[0025] Figure 14 The system of this embodiment operates in reverse under a certain load with an AC input voltage (V). ac Waveform;

[0026] Figure 15 The system of this embodiment operates in reverse under a certain load with AC input current (I) ac Amplify the waveform. Detailed Implementation

[0027] 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, not all, of the embodiments of the present invention. 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.

[0028] Reference Figure 1 The diagram shown is a schematic diagram of the system structure of the bidirectional AC / DC wireless power transfer system control method according to an embodiment of the present invention. The AC side filter capacitor C... f1 AC side filter inductor L f1 AC side damping resistor R f AC side filter inductor L f2 AC side filter capacitor C f2 The first power frequency switch Q1, the second power frequency switch Q2, the third power frequency switch Q3, the fourth power frequency switch Q4, and the first high-frequency switch S on the primary side. P1 The second high-frequency switch S on the primary side P2The third high-frequency switch S on the primary side P3 The fourth high-frequency switch S on the primary side P4 Primary side series compensation capacitor C P Primary coil L P Secondary coil L S Secondary side series compensation capacitor C S Secondary side first high-frequency switch S S1 Secondary side second high-frequency switch S S2 Secondary side third high-frequency switch S S3 The fourth high-frequency switch S on the secondary side S4 Output filter capacitor C o Load R L .

[0029] In one embodiment of the present invention, Figure 2 Figure 3 These are the voltage closed-loop control block diagram and the current closed-loop control block diagram of the system during forward operation, respectively, according to an embodiment of the present invention. During forward operation, Q1 to Q4 of the full-bridge rectifier operate at power frequency, and the full-bridge S... P1 ~S P4 And the whole bridge S S1 ~S S4 For fixed-frequency phase-shift modulation, passive devices (C) f1 ,L f1 ,R f ,L f2 C f2 This is used to filter the high-frequency switching ripple in the subsequent stage. Utilizing the characteristic that the secondary resonant cavity output voltage of the SS-compensated wireless charging system operates at its natural constant current frequency with a phase lead of 90° over the primary resonant cavity output voltage, phase-shift control is used to make the fundamental component of the primary resonant cavity input voltage track the input voltage. Power factor correction is achieved without the need for an external PFC circuit or sampling of the AC side current. By sampling the output current or output voltage, filtering it through a notch filter, and then using a proportional-integral controller, constant voltage or constant current output in the AC / DC direction of the system is achieved. The SS-compensated wireless charging system includes: a high-frequency switching transistor S... P1 ~S P4 Primary side series compensation capacitor C P Primary coil L P Secondary coil L S Secondary side series compensation capacitor C S Secondary side high-frequency switch S S1 ~S S4 .

[0030] like Figure 2 and Figure 3 As shown, during forward operation, it is necessary to sample the grid input voltage V. girdThe phase θ of the grid voltage is obtained through a phase-locked loop, from which the modulation of power frequency transistors Q1 to Q4 and the secondary side full-bridge S can be obtained. S1 ~S S4 The inner phase shift value D S Simultaneously, it is necessary to sample the output voltage V. o (or output current I) o The filtered voltage signal V is obtained after passing through a notch filter. o * (current signal I) o * Then, compare it with the required output voltage V of the system. oref (or output current I) oref The difference is used to obtain the error, which is then used to obtain the primary side full-bridge S through a proportional-integral controller. P1 ~S P4 The inner phase shift value D P And the outward phase value D between the primary side full bridge and the secondary side full bridge PS Finally, the modulation signals of all the switching transistors were obtained.

[0031] In one embodiment of the present invention, Figure 4 and Figure 5 This is a block diagram of the switching transistor modulation during reverse operation of the system according to an embodiment of the present invention. During reverse operation, the full-bridge S... S1 ~S S4 It operates as a high-frequency inverter, full-bridge S P1 ~S P4 Utilizing uncontrolled rectification via a body diode, the full-bridge inverters Q1-Q4 operate as sinusoidal inverters. Employing SS-compensated wireless charging systems, the output characteristics of a constant voltage source are similar to those of a constant voltage source operating at a natural constant voltage frequency. Capacitor C... f2 The signal above is a voltage signal with high-frequency ripple. This characteristic is used to enable the full-bridge S... S1 ~S S4 It operates at a natural constant voltage frequency. Due to capacitor C... f2 These are small-value filter capacitors; at this point, the bus voltage still carries high-frequency ripple. Passive components (L) f1 ,R f ,L f2 C f1 It is used to simultaneously filter out the ripple of the high-frequency transistor in a sinusoidal inverter and the high-frequency voltage ripple on the bus voltage. By sampling the peak value of the AC output voltage and adjusting the amplitude of the modulation fundamental wave in a closed loop, the reverse transmission of electrical energy between DC and AC is achieved.

[0032] like Figure 4 As shown, the AC output voltage V needs to be sampled when working in reverse. ac The peak value V of the AC output voltage is obtained through a phase-locked loop. ac.peak With the required peak AC voltage V peak.refThe peak value U of the modulated wave is obtained by subtraction and calculation using a proportional-integral converter. CM After being multiplied by the sine factor Sin(ω) by the multiplier o t) yielded the sinusoidal modulation signal U M Modulation signal U M With carrier U C The comparison output yields the drive signals for Q1 to Q4 of the full-bridge circuit. For example... Figure 5 As shown, the secondary side high-frequency switch S S1 ~S S4 It only needs to operate at the system's natural constant voltage frequency f cv Another full bridge S P1 ~S P4 No control is required; rectification is achieved solely through the body diode without control.

[0033] See Figure 6 and Figure 7 It is the output voltage V when the 300V constant voltage output is turned off during forward operation. o and output current I o Waveform. Figure 8 and Figure 9 It is the AC input voltage V under a certain load when the output voltage is 300V constant voltage in forward operation. gird Waveform, AC input current I in Magnified waveform, primary side resonant cavity voltage V P and the primary side resonant cavity current I P Waveform. The system has the ability to output constant voltage while implementing PFC function.

[0034] See Figure 10 and Figure 11 When operating in the forward direction, the output voltage V is the constant current output of 3.5A when the load is cut off. o and output current I o Waveform. Figure 12 and Figure 13 The AC input voltage V under a certain load when the output is a constant current of 3.5A in positive direction. gird Waveform, AC input current I in Magnified waveform, primary side resonant cavity voltage V P and the primary side resonant cavity current I P Waveform. The system has the capability of constant current output while implementing PFC functionality.

[0035] See Figure 14 and Figure 15 When operating in reverse, the AC output voltage V under a certain load is... ac and output current I ac The waveform shows that the system has reverse DC / AC functionality.

[0036] It should be understood that the exemplary embodiments described herein are illustrative and not restrictive. Although one or more embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A control method for a bidirectional AC / DC wireless power transfer system, characterized in that, The system includes AC side filter capacitor C f1 AC side filter inductor L f1 AC side damping resistor R f AC side filter inductor L f2 AC side filter capacitor C f2 The first power frequency switch Q1, the second power frequency switch Q2, the third power frequency switch Q3, the fourth power frequency switch Q4, and the first high-frequency switch S on the primary side. P1 The second high-frequency switch S on the primary side P2 The third high-frequency switch S on the primary side P3 The fourth high-frequency switch S on the primary side P4 Primary side series compensation capacitor C P Primary coil L P Secondary coil L S Secondary side series compensation capacitor C S Secondary side first high-frequency switch S S1 Secondary side second high-frequency switch S S2 Secondary side third high-frequency switch S S3 The fourth high-frequency switch S on the secondary side S4 Output filter capacitor C o Load R L ; During forward operation, Q1~Q4 of the full-bridge converter operate as power frequency rectification, and the full-bridge S... P1 ~ S P4 And the whole bridge S S1 ~ S S4 For fixed-frequency phase-shift modulation, passive devices (C) f1 ,L f1 ,R f ,L f2 C f2 Used to filter the high-frequency switching ripple in the subsequent stage; The SS-compensated wireless charging system includes: a high-frequency switching transistor S... P1 ~ S P4 Primary side series compensation capacitor C P Primary coil L P Secondary coil L S Secondary side series compensation capacitor C S Secondary side high-frequency switch S S1 ~ S S4 In forward operation, utilizing the characteristic that the secondary resonant cavity output voltage phase leads the primary resonant cavity output voltage phase by 90° under the natural constant current frequency of the SS-compensated wireless charging system, phase-shift control is used to make the fundamental component of the primary resonant cavity input voltage track the input voltage. Power factor correction is achieved without the need for an external PFC circuit or sampling of the AC side current. By sampling the output current or output voltage, filtering it through a notch filter, and then using a proportional-integral controller, constant voltage or constant current output in the AC / DC direction of the system is achieved. (Full-bridge S) S1 ~ S S4 It operates as a high-frequency inverter, full-bridge S P1 ~ S P4 Using uncontrolled rectification with body diodes, the full-bridge inverters Q1~Q4 operate as sinusoidal inverters, with passive components (C) f1 ,L f1 ,R f ,L f2 ,) is used to filter high-frequency switching ripple on the AC side output.

2. The control method for a bidirectional AC / DC wireless power transfer system as described in claim 1, characterized in that, In reverse operation, the SS-compensated wireless charging system operates at a natural constant voltage frequency, exhibiting output characteristics similar to a constant voltage source. Capacitor C... f2 The voltage signal carrying high-frequency ripple is sampled, and the amplitude of the modulated fundamental wave is adjusted in a closed loop to realize the reverse transmission of electrical energy from DC to AC.

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