Multi-level PT type wireless power transmission system

Abstract

The invention discloses a multi-level PT type wireless power transmission system, and the system comprises a primary loop which comprises a DC power supply, a three-level inverter, a primary resonant capacitor, and a transmitting coil; the secondary loop comprises a secondary resonant capacitor, a receiving coil, a rectifying circuit, a filter capacitor and a load; the transmitting coil and the receiving coil realize energy transmission of the primary side loop and the secondary side loop; the coupling model gain rate # imgabs0 # of the multi-level PT type wireless power transmission system is cos (alpha / 2) times of that of a full-bridge inversion PT symmetric WPT system. The introduced three-level inverter generates three-level voltage, and harmonic components of the three-level voltage are fewer, so that the voltage utilization rate is improved, and meanwhile, the device stress borne by an inverter switching tube is reduced; digital control is introduced, the duty ratio is adjustable, and compared with a traditional PT type WPT system with a single transmitting coil and a single receiving coil, more advantages are achieved.

Description

Technical Field

[0001] The invention relates to the field of wireless power transmission, and in particular to a multi-level PT type wireless power transmission system. Background Art

[0002] Wireless Power Transmission (WPT) refers to a technology that converts electrical energy into other forms of energy through the transmitter, and then collects and converts the energy into electrical energy at the receiver, which can achieve wireless power transmission over a certain distance. Wireless power supply has unique advantages in many occasions, such as walls, underwater, and biological bodies, where construction is difficult and where highly flexible equipment is charged. Different from 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 is mainly based on closed-loop modulation. The self-excited oscillation drive circuit has a 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) wireless power transfer (WPT) system meet the constant power and constant efficiency characteristics when the coupling coefficient changes in the PT working area. The inverter output of the traditional control scheme is a square wave voltage, which will have problems such as insufficient power utilization, uncontrollable output voltage amplitude, large switching loss, and high stress on the device, which limits the application scenarios of the PT type WPT system. Summary of the invention

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

[0005] The technical solution adopted by the present invention to solve the technical problem is: to provide a multi-level PT type wireless power transmission system, to introduce a three-level inverter to replace the full-bridge inverter in the full-bridge inverter PT symmetrical WPT system, and the multi-level PT type wireless power transmission system comprises:

[0006] The primary circuit includes a DC power supply, a three-level inverter, a primary resonant capacitor, and a transmitting coil;

[0007] The secondary circuit includes a secondary resonant capacitor, a receiving coil, a rectifier circuit, a filter capacitor and a load;

[0008] The transmitting coil and the receiving coil realize the energy transmission between the primary loop and the secondary loop; the coupling model gain rate of the multi-level PT type wireless power transmission system It is cos(α / 2) times of the full-bridge inverter PT symmetrical WPT system, and its output voltage is adjustable; L1 represents the inductance 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 circuit, the three-level inverter is composed of two bridge arms connected in series, one bridge arm includes a first switch tube and a second switch tube connected in series, and the other bridge arm includes a third switch tube and a third switch tube connected in series; the two bridge arms are connected in series in parallel with a 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 connected in series, and the midpoint of the first branch is grounded; the source of the second switch tube is connected to one end of the primary parasitic resistor, the other end of the primary parasitic resistor is connected to one end of the primary resonant capacitor, the other end of the primary resonant capacitor is connected to one end of the primary coil, and the other end of the primary coil is grounded;

[0010] The primary circuit also includes a second branch formed by a first freewheeling diode and a second freewheeling diode connected in series, and the midpoint of the second branch is grounded; the cathode of the first freewheeling diode is connected to the source of the first switch tube, and the anode of the second freewheeling diode is connected to the source of the third switch tube.

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

[0012] A midpoint of one bridge arm of the rectifier circuit is connected to one end of the secondary resonant capacitor, the other end of the secondary compensation capacitor is connected to the secondary parasitic resistor, the other end of the secondary parasitic resistor is connected to one end of the 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 the filter capacitor, and the filter capacitor is connected in parallel with the load.

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

[0015] The input current i of the primary 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, it is input into the digital sampling access terminal of the digital signal processor;

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

[0017] After the zeroth I / O port to the third I / O port of the digital signal processor are connected to the driver board, driving signals of the first to fourth switch tubes are generated until the system stably operates in the PT area, and the duty cycle is arbitrarily given at this operating frequency.

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

[0019] Preferably, the capacitance values ​​of the first voltage-dividing capacitor, the second voltage-dividing capacitor, the primary-side resonant capacitor and the secondary-side resonant 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 selected to be 0.2Ω.

[0023] The present invention has the following beneficial effects: the present invention proposes a multi-level PT type wireless power transmission system, and applies coupled mode theory to analyze the working principle of the system. Compared with the traditional self-excited oscillation control PT type WPT system, the three-level inverter of this structure generates a three-level voltage with fewer harmonic components, thereby improving the power supply utilization rate; at the same time, the device stress borne by the inverter switch tube is reduced; in addition, the drive circuit introduces a digital signal processor (DSP) output to generate a three-level control signal, and the output is flexible and controllable.

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the present invention is not limited to the embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a system principle diagram of an embodiment of the present invention;

[0026] Figure 2 is a system equivalent circuit diagram of an embodiment of the present invention;

[0027] Figure 3 A schematic diagram of a three-level voltage generated by a three-level inverter according to an embodiment of the present invention;

[0028] Figure 4 This is a comparison diagram of theoretical results and experimental results of the working frequency f of an embodiment of the present invention changing with the coupling coefficient k;

[0029] Figure 5 1 is a comparison diagram of theoretical results and experimental results of output power PL and transmission efficiency η of an embodiment of the present invention as a function of coupling coefficient k;

[0030] Figure 6 It is a steady-state waveform diagram of the DSP output signal, the DSP sampling input voltage and the transmitting coil current of the embodiment of the present invention;

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

[0032] Figure 8 The waveforms of the inverter output voltage and the transmitting coil current of the embodiment of the present invention at different duty cycles are shown in FIG. 1 , wherein (a) is a duty cycle D=0.5; (b) is a duty cycle D=0.4; (c) is a duty cycle D=0.3; (d) is a duty cycle D=0.2; and (e) is a duty cycle D=0.1. DETAILED DESCRIPTION

[0033] like Figure 1 As shown, the multi-level PT type wireless power transmission system consists of a DC power supply, a three-level inverter, a primary resonant capacitor, a transmitting coil, a receiving coil, a secondary resonant capacitor, a rectifier circuit, a filter capacitor and a load; wherein the primary loop includes a DC power supply, a three-level inverter and a primary resonant capacitor, and the secondary loop includes a secondary resonant capacitor, a rectifier circuit, a filter capacitor and a load;

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

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

[0036] The embodiment of the present invention is simplified to obtain its equivalent circuit, such as Figure 2 As shown; then based on the coupled mode theory, the typical dynamic equation is given as follows:

[0037]

[0038] The corresponding characteristic equation is

[0039]

[0040] For the three-level voltage generated by the three-level inverter, such as Figure 3 As shown, the Fourier series expansion is:

[0041]

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

[0043] In this example, the parameters are designed as follows:

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

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

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

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

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

[0049] See also Figures 4 to 5 The experimental results show that the multi-level PT type wireless power transmission system proposed in the embodiment of the present invention satisfies the constant power and constant efficiency characteristics in the PT region.

[0050] See also Figure 6 to Figure 7 The experimental results show that the multi-level PT type wireless power transmission system proposed in the embodiment of the present invention can generate a driving signal by DSP to achieve digital control.

[0051] See also Figure 8 From the experimental results, it can be concluded that compared with the PT-type WPT system with a single transmitting coil and a single receiving coil using a self-excited oscillation control circuit, the three-level voltage duty cycle generated by the multi-level PT-type wireless power transmission system proposed in the embodiment of the present invention is adjustable, and at the steady-state operating frequency corresponding to a fixed duty cycle of 0.5, the three-level PT symmetrical system can still operate in the PT region.

[0052] It can be seen from the above that the multi-level PT type wireless power transmission system proposed in the present invention introduces digital control and has an adjustable duty cycle, which has more advantages than the traditional PT type WPT system with a single transmitting and receiving coil.

[0053] It can be seen that the present invention proposes a multi-level PT type wireless power transmission system in view of the problems of the prior art. Compared with the traditional self-excited oscillation control, the three-level inverter of this structure generates a three-level voltage with fewer harmonic components, thereby improving the power supply utilization rate; at the same time, it reduces the device stress borne by the inverter switch tube; in addition, the drive circuit introduces a digital signal processor (DSP) output to generate a three-level control signal, and the duty cycle is flexible and controllable. This solution can also be extended to other application occasions of the multi-level PT symmetrical WPT system.

[0054] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-level PT type wireless power transmission system, characterized in that: A three-level inverter is introduced in the full-bridge inverter PT symmetrical WPT system to replace the full-bridge inverter. The multi-level PT type wireless power transmission system includes: The primary circuit includes a DC power supply, a three-level inverter, a primary resonant capacitor, and a transmitting coil; The secondary circuit includes a secondary resonant capacitor, a receiving coil, a rectifier circuit, a filter capacitor and a load; The transmitting coil and the receiving coil realize the energy transmission between the primary loop and the secondary loop; the coupling model gain rate of the multi-level PT type wireless power transmission system It is cos(α / 2) times of the full-bridge inverter PT symmetrical WPT system, and its output voltage is adjustable; L1 represents the inductance 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.

2. The multi-level PT type wireless power transmission system according to claim 1, characterized in that: In the primary circuit, the three-level inverter is composed of two bridge arms connected in series, one bridge arm includes a first switch tube and a second switch tube connected in series, and the other bridge arm includes a third switch tube and a third switch tube connected in series; the two bridge arms are connected in series in parallel with a 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 connected in series, and the midpoint of the first branch is grounded; the source of the second switch tube is connected to one end of the primary parasitic resistor, the other end of the primary parasitic resistor is connected to one end of the primary resonant capacitor, the other end of the primary resonant capacitor is connected to one end of the primary coil, and the other end of the primary coil is grounded; The primary circuit also includes a second branch formed by a first freewheeling diode and a second freewheeling diode connected in series, and the midpoint of the second branch is grounded; the cathode of the first freewheeling diode is connected to the source of the first switch tube, and the anode of the second freewheeling diode is connected to the source of the third switch tube.

3. The multi-level PT type wireless power transmission system according to claim 1, characterized in that: In the secondary loop, the rectifier circuit is composed of two bridge arms connected in parallel, one bridge arm is composed of a third diode and a fourth diode connected in series, and the other bridge arm is composed of a fifth diode and a sixth diode connected in series; A midpoint of one bridge arm of the rectifier circuit is connected to one end of the secondary resonant capacitor, the other end of the secondary compensation capacitor is connected to the secondary parasitic resistor, the other end of the secondary parasitic resistor is connected to one end of the 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; The two bridge arms are connected in parallel with the filter capacitor, and the filter capacitor is connected in parallel with the load.

4. The multi-level PT type wireless power transmission system according to claim 3, characterized in that: The primary circuit 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 circuit; a digital signal processor is introduced to generate a drive circuit control signal, specifically: The input current i of the primary 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, it is input into the digital sampling access terminal of the digital signal processor; When the input detection of the digital signal processor is a high level, the first I / O port and the second I / O port of the digital signal processor output a high level; when the input detection of the digital signal processor is a low level, the first I / O port and the second I / O port of the digital signal processor output a low level; the first I / O port and the third I / O port of the digital signal processor are complementary to the signals of the zeroth I / O port and the second I / O port of the digital signal processor respectively; After the zeroth I / O port to the third I / O port of the digital signal processor are connected to the driver board, driving signals of the first to fourth switch tubes are generated until the system stably operates in the PT area, and the duty cycle is arbitrarily given at this operating frequency.

5. The multi-level PT type wireless power transmission system according to claim 3, characterized in that: The voltage value of the DC voltage source is 100V.

6. The multi-level PT type wireless power transmission system according to claim 3, characterized in that: The capacitance values ​​of the first voltage-dividing capacitor, the second voltage-dividing capacitor, the primary-side resonant capacitor and the secondary-side resonant capacitor are 100uF, 100uF, 35.06nF and 35.06nF respectively.

7. The multi-level PT type wireless power transmission system according to claim 3, characterized in that: The inductance values ​​of the transmitting coil and the receiving coil are 100uH and 100uH respectively.

8. The multi-level PT type wireless power transmission system according to claim 3, characterized in that: The capacitance value of the filter capacitor is 100uF.

9. The multi-level PT type wireless power transmission system according to claim 3, characterized in that: The primary side parasitic resistance and the secondary side parasitic resistance are both selected to be 0.2Ω.

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