A hybrid control method for two-load wireless charging system

Abstract

The present invention discloses a hybrid control method suitable for a two-load wireless charging system, comprising three control variables: the inverter bridge switching frequency, the inverter bridge duty cycle, and the switch capacitor for primary-side series compensation. The method comprises the following steps: real-time sampling of the inverter bridge output voltage and current, extracting the fundamental or higher harmonic components of the detection components to obtain the system input impedance, thereby identifying the multilateral mutual inductance parameters; compensating for the secondary-side equivalent leakage inductance, and calculating and updating the inverter bridge switching frequency; and calculating and updating the inverter bridge duty cycle and the switch capacitor value for primary-side series compensation based on the input impedance and output power requirements. The hybrid control method disclosed herein can ensure that, under conditions of varying loads or varying coupling coefficients, the total output power of the wireless charging system remains unchanged, the output power ratio between the loads remains unchanged, the input impedance remains weakly inductive, and the inverter bridge switch tube always achieves soft switching. The method is suitable for a two-load wireless charging system based on a "one-to-two" coupled coil.

Description

Technical Field

[0001] The present invention relates to a hybrid control method applicable to a two-load wireless charging system, and belongs to the field of electric energy conversion. Background Art

[0002] Existing multi-load wireless charging systems are based on two types: "many-to-many" coupled coils and "one-to-many" coupled coils. The "one-to-many" coupled coils offer smaller system size, cost, and weight, but their multilateral coupling makes system control more difficult. Not only is there coupling between the primary coil and each secondary coil, but there is also mutual coupling between the secondary coils. When the coupling coils shift or the load conditions change, the total output power of the multi-load wireless charging system changes, as does the output power ratio between the loads. This also alters the input impedance characteristics, causing hard switching in the inverter bridge switches and reducing system transmission efficiency. Summary of the Invention

[0003] The present invention aims to address the secondary-side cross-coupling problem in a two-load wireless charging system by providing a hybrid control method. The method includes three control variables: the inverter bridge switching frequency, the inverter bridge duty cycle, and the capacitance of the primary-side series compensation switch capacitor. This method ensures that, under varying loads or coupling coefficients, the total output power of the wireless charging system remains constant, the output power ratio between the loads remains constant, the input impedance remains weakly inductive, and the inverter bridge switches consistently achieve soft switching. The method is suitable for two-load wireless charging systems based on a "one-to-two" coupled coil arrangement.

[0004] The present invention provides a hybrid control method for a two-load wireless charging system, characterized by including three control variables: the inverter bridge switching frequency, the inverter bridge duty cycle, and the capacitance of the primary-side series compensation switch capacitor. The method includes the following steps:

[0005] Real-time sampling of the inverter bridge output voltage and current, extraction of the fundamental wave or higher harmonic components of the detection component to obtain the system input impedance, thereby identifying the multilateral mutual inductance parameters;

[0006] Compensate for the secondary side equivalent leakage inductance and calculate and update the inverter bridge switching frequency;

[0007] Based on the input impedance and output power requirements, calculate the switching capacitor value for updating the inverter bridge duty cycle and primary side series compensation.

[0008] In the above hybrid control method, the control of the three control variables is all performed on the primary side without the need for communication.

[0009] The above-mentioned two-load wireless charging system is based on a "one-to-two" coupled coil, with one winding on the primary side and one or two windings on the secondary side, and can output single load or multiple loads.

[0010] The above-mentioned multilateral mutual inductance parameter identification method samples the inverter bridge output voltage and current in real time, extracts the fundamental wave or higher harmonic component of the detection component to obtain the system input impedance, and thus identifies the multilateral mutual inductance parameters.

[0011] The above-mentioned multilateral mutual inductance parameters refer to the mutual inductance between the primary winding and the two secondary windings, as well as the mutual inductance between the two secondary windings.

[0012] The above extraction of the fundamental wave or higher harmonic component of the detection component can be performed by discrete Fourier transform or Goetzel algorithm.

[0013] The updating of the inverter bridge switching frequency is for the purpose of compensating the secondary side equivalent leakage inductance.

[0014] The above-mentioned switching capacitor is composed of a switching tube and a fixed capacitor, and its equivalent capacitance is controlled by controlling the conduction time of the switching tube.

[0015] Compared with the prior art, the main technical feature of the present invention is that it adopts a hybrid control method including the inverter bridge switching frequency, the inverter bridge duty cycle and the primary side series compensation switch capacitor, which can ensure that under the conditions of variable load or variable coupling coefficient, the total output power of the wireless charging system remains unchanged, the output power ratio between each load remains unchanged, the input impedance remains weakly inductive, and the inverter bridge switch tube always achieves soft switching; all controls are performed on the primary side and no communication is required. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG1 is a flow chart of a hybrid control method applicable to a two-load wireless charging system according to the present invention;

[0017] FIG2 is an embodiment of a hybrid control method applicable to a two-load wireless charging system;

[0018] Figure 3 shows the typical waveform of the switched capacitor;

[0019] Figure 4 Full-bridge inverter bridge phase-shift control waveform. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] FIG2 is an embodiment of a hybrid control method applicable to a two-load wireless charging system. in The high-frequency modulated AC voltage u is obtained through the full-bridge inverter bridge p , the primary resonant circuit uses a series switched capacitor C p To compensate, L p 、L s1 、L s2 is the self-inductance of the primary and secondary coils, M ps1 、M ps2 is the mutual inductance of the primary and secondary coupling coils, Ms1s2 The secondary resonant circuit uses a series capacitor C for the mutual inductance of the two secondary coupling coils. s1 、C s2 To compensate, R p 、R s1 、R s2 is the equivalent resistance of the primary and secondary coils, R L1 、R L2 There are two DC loads. The secondary resonant circuit can be selected arbitrarily. The switch capacitor C p It consists of two reverse series connected switching tubes Q1 and Q2 and a fixed capacitor C a 、C s The equivalent capacitance of the switch capacitor is controlled by controlling the conduction angle α of the switch tube. The typical waveform is shown in Figure 3. The switch tubes Q1 and Q2 can achieve zero current turn-on and zero switching loss.

[0022] In Figure 2, the output voltage u of the sampling inverter bridge is p and current i p , extract the fundamental or higher harmonic components of the two variables through discrete Fourier transform or Goetzel algorithm to obtain the input impedance Z in , and then calculate the multilateral mutual inductance parameter M according to the input impedance expressions (1) to (2) ps1 、M ps2 and M s1s2 This is step 1 of the hybrid control method of the present invention.

[0023]

[0024]

[0025] In order to compensate for the equivalent leakage inductance of the secondary side, the switching frequency ω of the inverter bridge is calculated and updated according to expression (3), so that the output power ratio of the two loads is as shown in expression (4), which is equal to the mutual inductance M of the two secondary coupling coils. s1s2 This is step 2 of the hybrid control method of the present invention.

[0026]

[0027]

[0028] The full-bridge inverter bridge adopts a phase-shift control strategy. The switch tube drive waveform and the inverter bridge output voltage and current waveform are shown in Figure 4. If the input impedance arg(Z in )>θ, then the soft switching of all switches in the inverter bridge can be realized. According to the input impedance requirement and the output power expression (5), the updated inverter bridge duty cycle d and the switching capacitor value C of the primary side series compensation are calculated. p This is step three of the hybrid control method of the present invention.

[0029]

[0030] In a two-load wireless charging system based on a "one-to-two" coupling coil, when the coupling coil position shifts or the load conditions change, the total output power of the two-load wireless charging system changes, the output power ratio between the loads changes, the input impedance characteristics change, the inverter bridge switches experience hard switching, and the system transmission efficiency decreases. To address this issue, the present invention proposes a hybrid control method for a two-load wireless charging system. This method utilizes a hybrid control method that includes inverter bridge switching frequency, inverter bridge duty cycle, and primary-side series compensation with a switched capacitor. This method ensures that, under varying loads or coupling coefficients, the total output power of the wireless charging system remains constant, the output power ratio between the loads remains constant, the input impedance remains weakly inductive, and the inverter bridge switches consistently achieve soft switching. All control is performed on the primary side, requiring no communication.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A hybrid control method for a two-load wireless charging system, characterized by: The control variables include the inverter bridge switching frequency, the inverter bridge duty cycle, and the capacitance value of the primary side series compensation switch capacitor. It includes the following steps: Real-time sampling of the inverter bridge output voltage and current, extraction of the fundamental wave or higher harmonic components of the detection component to obtain the system input impedance, thereby identifying the multilateral mutual inductance parameters; Compensate for the secondary side equivalent leakage inductance and calculate and update the inverter bridge switching frequency; Based on the input impedance and output power requirements, calculate and update the inverter bridge duty cycle and the switching capacitor value for primary side series compensation; The formula for determining the inverter bridge switching frequency ω is: L s1 、L s2 is the self-inductance of the secondary coil, C s1 、C s2 is the capacitance of the series capacitor, M ps1 、M ps2 is the mutual inductance of the primary and secondary coupling coils, M s1s2 The mutual inductance of the two secondary coupling coils ensures that the input impedance arg(Z in )>θ,Z in is the input impedance.

2. The hybrid control method for a two-load wireless charging system according to claim 1, wherein: In the hybrid control method, the control of the three control variables is all performed on the primary side without the need for communication.

3. The hybrid control method for a two-load wireless charging system according to claim 1, wherein: The two-load wireless charging system is based on a "one-to-two" coupled coil, with one winding on the primary side and one or two windings on the secondary side.

4. The hybrid control method for a two-load wireless charging system according to claim 1, wherein: The multilateral mutual inductance parameter identification method samples the inverter bridge output voltage and current in real time, extracts the fundamental wave or higher harmonic component of the detection component to obtain the system input impedance, and thus identifies the multilateral mutual inductance parameters.

5. The hybrid control method for a two-load wireless charging system according to claim 4, wherein: The multilateral mutual inductance parameters refer to the mutual inductance between the primary winding and the two secondary windings, and the mutual inductance between the two secondary windings.

6. The hybrid control method for a two-load wireless charging system according to claim 4, wherein: The extraction of the fundamental wave or higher harmonic component of the detection component is performed by discrete Fourier transform or Goetzel algorithm.

7. The hybrid control method for a two-load wireless charging system according to claim 1, wherein: The updating of the inverter bridge switching frequency is for the purpose of compensating for the secondary side equivalent leakage inductance.

8. The hybrid control method for a two-load wireless charging system according to claim 1, wherein: The switch capacitor is composed of a switch tube and a fixed capacitor, and its equivalent capacitance is controlled by controlling the conduction time of the switch tube.

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