A multi-level pt type wireless power transfer system

Abstract

The application discloses a kind of multi-level PT type wireless power transmission systems, comprising: original side loop, containing direct-current power supply, three-level inverter, original side resonance capacitor, transmitting coil;Secondary loop, containing secondary resonance capacitor, receiving coil, rectifier circuit, filter capacitor and load;The transmitting coil and receiving coil realize the energy transmission of original side loop and secondary loop;The coupling model gain rate of the multi-level PT type wireless power transmission system is the cos (alpha / 2) times of full-bridge inverter PT symmetry WPT system.The three-level inverter introduced in the application generates three-level voltage, which has fewer harmonic components, thereby improving voltage utilization rate, while reducing the device stress borne by inverter switch tube;The duty cycle of the digital control introduced in the application is adjustable, and compared with the PT type WPT system of traditional single transmitting single receiving coil, it has more advantages.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of wireless power transmission, in particular to a multi-level PT type wireless power transmission system. BACKGROUND

[0002] Wireless Power Transmission (WPT) refers to a technology that converts electrical energy into other forms of energy by a transmitting end, and then collects and converts the energy into electrical energy by a receiving end, which can realize wireless power transmission at a certain distance. Wireless power supply has unique advantages in many occasions, such as charging occasions with great construction difficulty and high flexibility, such as walls, underwater and organisms. Unlike traditional wired charging, coil offset is a typical problem unique to electric vehicle wireless charging systems. At present, the research on constant output under coil offset mainly uses closed-loop modulation. The self-oscillation driving circuit has fast response speed, but compared with digital signal processing control, it has the disadvantage of insufficient control freedom.

[0003] The transmitting and receiving coils in the parity-time (PT) type wireless power transmission (WPT) system satisfy the constant power and constant efficiency characteristics when the coupling coefficient changes in the PT working area. The output of the inverter in the traditional control scheme is a square wave voltage, which has problems such as insufficient power utilization, uncontrollable output voltage amplitude, large switching loss, and large stress on the device, which limits the application scenarios of the PT type WPT system. SUMMARY

[0004] The purpose of the present application is to solve the problems in the prior art.

[0005] The technical scheme adopted by the present application to solve its technical problems is to provide a multi-level PT type wireless power transmission system, which introduces a three-level inverter instead of a full-bridge inverter in a full-bridge inverter PT symmetric WPT system. The multi-level PT type wireless power transmission system comprises:

[0006] The primary side circuit comprises a DC power supply, a three-level inverter, a primary side resonance capacitor, and a transmitting coil.

[0007] The secondary side circuit comprises a secondary side resonance capacitor, a receiving coil, a rectifier circuit, a filter capacitor, and a load.

[0008] The transmitting coil and the receiving coil realize energy transmission of the primary side circuit and the secondary side circuit; the coupling model gain rate of the multi-level PT type wireless power transmission system is cos(α / 2) times that of the full-bridge inverter PT symmetric WPT system, and the output voltage is adjustable; L1 represents the inductance value of the transmitting coil, V DC represents the voltage value of the DC power supply, and α represents the level phase angle of the three-level inverter.

[0009] Preferably, in the primary side loop, the three-level inverter is composed of two bridge arms in series, one bridge arm comprises a first switch tube and a second switch tube in series, and the other bridge arm comprises a third switch tube and a fourth switch tube in series; the two bridge arms are connected in parallel with the DC power supply, and are connected in series with a first voltage dividing capacitor and a second voltage dividing capacitor to form a first branch, the midpoint of the first branch is grounded; the source electrode of the second switch tube is connected to one end of a primary side parasitic resistor, the other end of the primary side parasitic resistor is connected to one end of a primary side resonance capacitor, the other end of the primary side resonance capacitor is connected to one end of a primary side coil, and the other end of the primary side coil is grounded;

[0010] In the primary side loop, a second branch composed of a first freewheeling diode and a second freewheeling diode in series is further included, and the midpoint of the second branch is grounded; the cathode of the first freewheeling diode is connected to the source electrode of the first switch tube, and the anode of the second freewheeling diode is connected to the source electrode of the third switch tube.

[0011] Preferably, in the secondary side loop, the rectifier circuit is composed of two bridge arms in parallel, one bridge arm is composed of a third diode and a fourth diode in series, and the other bridge arm is composed of a fifth diode and a sixth diode in series;

[0012] The midpoint of one bridge arm of the rectifier circuit is connected to one end of a secondary side resonance capacitor, the other end of the secondary side compensation capacitor is connected to a secondary side parasitic resistor, the other end of the secondary side parasitic resistor is connected to one end of a receiving coil inductor, and the other end of the receiving coil inductor is connected to the midpoint of the other bridge arm of the rectifier circuit;

[0013] The two bridge arms are connected in parallel with a filter capacitor in parallel, and the filter capacitor is connected in parallel with a load.

[0014] Preferably, the primary side loop is a variable frequency circuit, and the switching frequencies of the first to fourth switch tubes are controlled to be consistent with the current frequency of the primary side loop; a digital signal processor is introduced to generate a driving circuit control signal, specifically:

[0015] The input current i of the primary side circuit p After being converted into a voltage signal by a current transformer, a zero-crossing comparison is performed to obtain a square wave signal, and after phase compensation and voltage division processing are performed on the square wave signal, the digital sampling access end of the digital signal processor is input;

[0016] When the input detection of the digital signal processor is high level, the first I / O port and the second I / O port of the digital signal processor output high level; when the input detection of the digital signal processor is low level, the first I / O port and the second I / O port of the digital signal processor output low level; the first I / O port and the third I / O port of the digital signal processor are respectively complementary to the zeroth I / O port and the second I / O port of the digital signal processor;

[0017] The first I / O port to the third I / O port of the digital signal processor is connected to the driving plate to generate the driving signals of the first to fourth switching tubes, until the system is stably operated in the PT area, and the duty cycle is arbitrarily given at the working frequency.

[0018] Preferably, the voltage value of the direct current voltage source is 100V.

[0019] Preferably, the capacitance values of the first voltage dividing capacitor, the second voltage dividing capacitor, the primary side resonance capacitor and the secondary side resonance capacitor are 100uF, 100uF, 35.06nF and 35.06nF respectively.

[0020] Preferably, the inductance values of the transmitting coil and the receiving coil are 100uH and 100uH respectively.

[0021] Preferably, the capacitance value of the filter capacitor is 100uF.

[0022] Preferably, the primary side parasitic resistance and the secondary side parasitic resistance are both 0.2Ω.

[0023] The application has the following beneficial effects: the application provides a multi-level PT type wireless power transmission system, the working principle of the system is analyzed by using the coupling mode theory, compared with the traditional self-excited oscillation control PT type WPT system, the three-level inverter of the structure generates a three-level voltage, the harmonic component is less, and the power utilization rate is improved; meanwhile, the device stress borne by the inverter switching tube is reduced; in addition, the digital signal processor (DSP) output is introduced into the driving circuit to generate a three-level control signal, and the output is flexible and controllable.

[0024] The application will be further described in detail in combination with the drawings and embodiments, but the application is not limited to the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a system principle diagram of the embodiment of the application;

[0026] Figure 2 It is a system equivalent circuit diagram of the embodiment of the application;

[0027] Figure 3 It is a three-level voltage generated by the three-level inverter of the embodiment of the application;

[0028] Figure 4 It is a comparison diagram of the theoretical result and the experimental result of the working frequency f changing with the coupling coefficient k of the embodiment of the application;

[0029] Figure 5 It is a comparison diagram of the theoretical result and the experimental result of the output power PL and the transmission efficiency η changing with the coupling coefficient k of the embodiment of the application;

[0030] Figure 6 The steady-state waveform diagram of the DSP output signal, the sampling input voltage of the DSP and the transmitting coil current of an embodiment of the present application;

[0031] Figure 7 The transmitting coil current schematic diagram of an embodiment of the present application, wherein (a) is the overall waveform diagram of the transmitting coil current transient process, and (b) is the partial enlarged diagram of the transmitting coil current transient process;

[0032] Figure 8 The inverter output voltage and the transmitting coil current waveform diagram of an embodiment of the present application under different duty ratios, wherein (a) is the duty ratio D=0.5; (b) is the duty ratio D=0.4; (c) is the duty ratio D=0.3; (d) is the duty ratio D=0.2; and (e) is the duty ratio D=0.1. DETAILED DESCRIPTION

[0033] As shown in Figure 1 , the multi-level PT type wireless power transmission system is composed of a direct current power supply, a three-level inverter, a primary side resonant capacitor, a transmitting coil, a receiving coil, a secondary side resonant capacitor, a rectifier circuit, a filter capacitor and a load; wherein the primary side loop comprises the direct current power supply, the three-level inverter and the primary side resonant capacitor, and the secondary side loop comprises the secondary side resonant capacitor, the rectifier circuit, the filter capacitor and the load.

[0034] In the primary side loop, the direct current power supply V in is connected in parallel with two series bridge arms of the three-level inverter: the switch tube Q1 and the switch tube Q2 form one bridge arm, and the switch tube Q3 and the switch tube Q4 form another bridge arm; the positive pole of the direct current power supply V in is connected to the drain of the switch tube Q1, the source of the switch tube Q1 is connected to the drain of the switch tube Q2, the source of the switch tube Q2 is connected to the drain of the switch tube Q3, the source of the switch tube Q3 is connected to the drain of the switch tube Q4, and the source of the switch tube Q4 is connected to the negative pole of the direct current power supply V in . The direct current power supply V in is also connected in parallel with a first branch formed by the series connection of the voltage dividing capacitors C1 and C2, and the midpoint of the first branch is grounded, that is, the negative pole of the voltage dividing capacitor C1 and the negative pole of the voltage dividing capacitor C2 are connected and grounded; the negative pole of the diode D1 is connected to the source of the switch tube Q1, the positive pole of the diode D2 is connected to the source of the switch tube Q3, and the positive pole of the diode D1 and the negative pole of the diode D2 are both grounded; the drain of the switch tube Q2 is connected to one end of the primary side parasitic resistance r p , the other end of the primary side parasitic resistance r p is connected to one end of the primary side resonant capacitor C p , and the other end of the primary side resonant capacitor C p is connected to one end of the primary side coil L p . The other end of the primary side coil L pThe other end of the secondary side loop is grounded to form a complete loop.

[0035] The secondary side loop comprises a receiving coil inductance L s , a secondary side parasitic resistance r s , a secondary side compensation capacitor C s , a rectifier circuit, a filter capacitor C f and a load R L . The rectifier circuit comprises diode D3, diode D4, diode D5 and diode D6; the anode of diode D3 is connected to the cathode of diode D4, the anode of diode D4 is connected to the anode of diode D6, the cathode of diode D6 is connected to the anode of diode D5, and the cathode of diode D5 is connected to the cathode of diode D3; one end of the receiving coil inductance L s is connected to the secondary side parasitic resistance r s , the other end of the secondary side parasitic resistance r s is connected to one end of the secondary side compensation capacitor C s , the other end of the secondary side compensation capacitor C s is connected to the midpoint of one bridge arm of the rectifier circuit (the connection between diode D3 and diode D4), and the midpoint of the other bridge arm of the rectifier circuit (the connection between diode D5 and diode D6) is connected to the other end of the inductance L s ; the cathode of diode D3 is connected to one end of the filter capacitor C f , the other end of the filter capacitor C f is connected to the anode of diode D4; the filter capacitor C f is connected in parallel with the load R L to form a complete loop.

[0036] The equivalent circuit of the embodiment of the application is simplified as shown in Figure 2 ; then based on the coupling mode theory, the typical dynamic equation is given as follows:

[0037]

[0038] The corresponding characteristic equation is

[0039]

[0040] The three-level voltage generated by the three-level inverter is shown in Figure 3 , and the Fourier series expansion is:

[0041]

[0042] The gain coefficient of the three-level output voltage in the characteristic equation is It can be seen that the gain coefficient of the multi-level PT type wireless power transmission system is cos(α / 2) times of the full-bridge inverter PT symmetric WPT system, so that the output voltage of the structure inverter is adjustable. Compared with the traditional self-oscillation control PT symmetric WPT system, the three-level inverter of the structure generates a three-level voltage, which has fewer harmonic components, thereby improving the voltage utilization rate; at the same time, the device stress borne by the inverter switch tube is reduced; in addition, the digital signal processor (DSP) output is introduced into the driving circuit to generate a three-level control signal, and the output is flexible and controllable.

[0043] The parameter design in the example is as follows:

[0044] 1) Select the DC voltage source V DC 100V;

[0045] 2) Select four capacitors C1, C2, C p , C s 100uF, 100uF, 35.06nF, 35.06nF;

[0046] 3) Select two inductors L1, L2 as 100uH, 100uH;

[0047] 4) Select the filter capacitor C f 100uF;

[0048] 5) Select the primary and secondary parasitic resistances r p , r s 0.2Ω;

[0049] According to the experimental results of Figure 4 to Figure 5 , it can be concluded that the multi-level PT type wireless power transmission system proposed in the embodiment of the application meets the constant power and constant efficiency characteristics in the PT region.

[0050] According to the experimental results of Figure 6 to Figure 7 , it can be concluded that the multi-level PT type wireless power transmission system proposed in the embodiment of the application can generate a driving signal by a DSP to realize digital control.

[0051] According to the experimental results of Figure 8 , it can be concluded that compared with the PT type WPT system of a single transmitting coil and a single receiving coil using a self-oscillation control circuit, the multi-level PT type wireless power transmission system proposed in the embodiment of the application generates a three-level voltage with adjustable duty cycle, and the three-level PT symmetric system can still work in the PT region at a fixed duty cycle of 0.5 corresponding to the steady-state working frequency.

[0052] From the above, the multi-level PT type wireless power transmission system introduced by the application introduces digital control, and the duty cycle is adjustable, and has more advantages than the traditional PT type WPT system with a single transmitting and single receiving coil.

[0053] It can be seen that the application proposes a multi-level PT type wireless power transmission system to solve the problems in the prior art. Compared with the traditional self-excitation oscillation control, the three-level inverter of the structure generates a three-level voltage, which has fewer harmonic components, thereby improving the power utilization rate; meanwhile, the device stress borne by the inverter switch tube is reduced; in addition, the driving circuit introduces a digital signal processor (DSP) output to generate a three-level control signal, and the duty cycle is flexible and controllable. The scheme can also be popularized to other application occasions of the multi-level PT symmetric type WPT system.

[0054] The above is only a preferred embodiment of the application, and is not used to limit the application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall be included in the protection scope of the application.

Claims

1. A multi-level PT type wireless power transfer system, characterized by, The application discloses a three-level inverter PT type wireless power transmission system. The primary side loop comprises a DC power supply, a three-level inverter, a primary side resonance capacitor and a transmitting coil. The secondary side loop comprises a secondary side resonance capacitor, a receiving coil, a rectifier circuit, a filter capacitor and a load. The transmitting coil and the receiving coil realize energy transmission of the primary loop and the secondary loop; the coupling model gain rate of the multi-level PT type wireless power transmission system , for the full-bridge inverter PT symmetric WPT system times, and the output voltage is adjustable represents the inductance value of the transmitting coil, represents the voltage value of the direct current power supply, and α represents the level phase angle of the three-level inverter In the primary side loop, the three-level inverter is composed of two bridge arms in series, one bridge arm comprises a first switch tube and a second switch tube in series, and the other bridge arm comprises a third switch tube and a fourth switch tube in series. The two bridge arms are connected in series and are connected in parallel with the DC power supply, and are connected in parallel with a first branch formed by a first voltage dividing capacitor and a second voltage dividing capacitor in series, and the midpoint of the first branch is connected to the ground. The source electrode of the second switch tube is connected to one end of a primary side parasitic resistor, the other end of the primary side parasitic resistor is connected to one end of the primary side resonance capacitor, the other end of the primary side resonance capacitor is connected to one end of the primary side coil, and the other end of the primary side coil is connected to the ground. The input current of the primary side loop After the transformation into voltage signal through the current transformer, the zero-crossing comparison is performed to obtain a square wave signal, and after the phase compensation and voltage division of the square wave signal, the digital sampling access end of the digital signal processor is input. The primary side loop further comprises a second branch formed by a first freewheeling diode and a second freewheeling diode in series, and the midpoint of the second branch is connected to the ground. The cathode of the first freewheeling diode is connected to the source electrode of the first switch tube, and the anode of the second freewheeling diode is connected to the source electrode of the third switch tube.

2. The multi-level PT-type wireless power transfer system of claim 1, wherein, The primary side loop is a variable frequency circuit, the switching frequency of the first to fourth switch tubes is controlled to be consistent with the current frequency of the primary side loop. A digital signal processor is introduced to generate a driving circuit control signal, specifically: When the input detection of the digital signal processor is high level, the first I / O port and the second I / O port of the digital signal processor output high level; when the input detection of the digital signal processor is low level, the first I / O port and the second I / O port of the digital signal processor output low level; the first I / O port and the third I / O port of the digital signal processor are respectively complementary to the zeroth I / O port and the second I / O port of the digital signal processor.

3. The multi-level PT-type wireless power transfer system of claim 2, wherein, The zeroth I / O port to the third I / O port of the digital signal processor are connected to a driving board to generate the driving signals of the first to fourth switch tubes, until the system is stably operated in the PT area, and the duty cycle is arbitrarily given at the working frequency.

4. The multi-level PT-type wireless power transfer system of claim 2, wherein, In the secondary side loop, the rectifier circuit is composed of two bridge arms in parallel, one bridge arm is composed of a third diode and a fourth diode in series, and the other bridge arm is composed of a fifth diode and a sixth diode in series.

5. The multi-level PT-type wireless power transfer system of claim 2, wherein, The midpoint of one bridge arm of the rectifier circuit is connected to one end of the secondary side resonance capacitor, the other end of the secondary side compensation capacitor is connected to a secondary side parasitic resistor, the other end of the secondary side parasitic resistor is connected to one end of the receiving coil inductance, and the other end of the receiving coil inductance is connected to the midpoint of the other bridge arm of the rectifier circuit.

6. The multi-level PT-type wireless power transfer system of claim 2, wherein, The two bridge arms are connected in parallel and are connected in parallel with the filter capacitor, and the filter capacitor is connected in parallel with the load.

7. The multi-level PT-type wireless power transfer system of claim 2, wherein, The voltage value of the DC voltage source is 100V. The capacitance values of the first voltage dividing capacitor, the second voltage dividing capacitor, the primary side resonance capacitor and the secondary side resonance capacitor are respectively 100uF, 100uF, 35.06nF and 35.06nF. The inductance values of the transmitting coil and the receiving coil are respectively 100uH and 100uH. The capacitance value of the filter capacitor is 100uF. The primary side parasitic resistor and the secondary side parasitic resistor are both 0.2Ω.

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