Autonomous wireless power transmission system with anti-offset and anti-detuning characteristics

Abstract

The invention discloses an autonomous wireless power transmission system with anti-offset and anti-detuning characteristics. The autonomous wireless power transmission system comprises a transmitting device and a receiving device, the transmitting device comprises a negative resistor, a transmitting coil, a transmitting coil equivalent internal resistor, a switched capacitor and a sampling and control circuit; the negative resistor, the transmitting coil, the transmitting coil equivalent internal resistor and the switched capacitor are connected in series; the negative resistor is composed of a direct-current power supply and a high-frequency controlled inverter; the sampling and control module is used for sampling the amplitude and phase of the current of the transmitting coil and generating control signals of the high-frequency controlled inverter and the switched capacitor; the receiving device comprises a load resistor, a receiving coil, a receiving coil equivalent internal resistor and a receiving resonant capacitor which are connected in series. The output characteristics of the system are not influenced by the coupling coefficient and the resonance frequency deviation, the system is controlled only by the transmitting end, a wireless communication module is not needed, and the system has the advantages of being simple in structure, reliable in control, high in anti-interference characteristic and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless power transmission, and in particular to an autonomous wireless power transmission system with anti-deviation and anti-detuning characteristics. Background Art

[0002] Wireless power transmission technology is a power transmission technology that directly transmits power to the load through space. Compared with plug-in contact power supply, wireless power transmission technology can achieve complete electrical isolation between the power supply and the load without any physical contact. It has high flexibility, convenience and safety. It has been widely used in portable consumer electronic devices, electric vehicles, drones and other fields. In practical applications, due to the relative position offset of the transmitter and the receiving position, the influence of the ferrite shielding layer, the manufacturing error of the resonant capacitor, temperature drift, etc., the coupling coefficient and the resonant frequency will inevitably shift. However, the output characteristics of the existing wireless power transmission system are easily affected by the coupling coefficient and the resonant frequency offset. Therefore, anti-offset and anti-detuning are key issues that need to be solved in the industrialization process of wireless power transmission technology. There are currently three main solutions for the change of coupling coefficient, including coupling coil design, compensation topology design and closed-loop control. The first two methods have limited control accuracy, and closed-loop control usually requires the addition of DC-DC converters and wireless communication equipment, which has problems such as complex structure and high cost. For resonant frequency disturbances, the solutions are mainly divided into two categories: one is to achieve tuning through frequency conversion. The second is to adjust the resonant frequency by changing the equivalent capacitance or inductance of the compensation network, including inductor-capacitor arrays, switch capacitors, and variable inductors. The above solutions usually determine whether the system is in a resonant state by whether the phase angle between the input voltage and current is zero, and whether the input current and output power reach the maximum value. However, when the resonant frequency of the resonant network at the receiving end is disturbed and the coupling coefficient changes at the same time, although the above control objectives are achieved, it is impossible to guarantee that the system obtains stable and efficient transmission characteristics. The present invention constructs an autonomous wireless power transmission system based on the simplified series-series compensation structure to achieve a constant output that is independent of the coupling coefficient and the resonant frequency, and only uses the transmitter control without the need for a wireless communication module. It has the characteristics of simple structure, reliable control, and strong anti-interference characteristics. In practical applications, it has significant advantages, especially in situations where the receiving end equipment requires integration and lightweight. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide an autonomous wireless power transmission system with anti-deviation and anti-detuning characteristics. By controlling the resistance value of the negative resistor to be constant, stable control of the output characteristics is achieved, so that the system output is not affected by changes in the coupling coefficient and the resonant frequency offset.

[0004] To achieve the above-mentioned purpose, the technical solution provided by the present invention is: an autonomous wireless power transmission system with anti-offset and detuning characteristics, the system comprising a transmitting device and a receiving device; the transmitting device comprises a transmitting circuit, a switching capacitor and a sampling and control circuit; the transmitting circuit comprises a negative resistor, a transmitting coil and an equivalent internal resistance of the transmitting coil, and the negative resistor, the transmitting coil, the equivalent internal resistance of the transmitting coil and the switching capacitor are connected in series; the negative resistor is composed of a DC voltage source and a high-frequency controlled inverter to provide energy for the system; the capacitance of the switching capacitor is adjustable; the input end of the sampling and control module is connected to the transmitting circuit, and the output end thereof is connected to the high-frequency controlled inverter and the switching capacitor respectively; the sampling and control module samples the effective value and phase of the transmitting coil current, and generates control signals of the high-frequency controlled inverter and the switching capacitor; the receiving device comprises a load resistor, a receiving coil, an equivalent internal resistance of the receiving coil and a receiving resonant capacitor connected in series.

[0005] Furthermore, the output characteristic of the high-frequency controlled inverter is equivalent to a negative resistance, that is, when the non-associated reference direction is selected, the output voltage fundamental component of the high-frequency controlled inverter and the output current fundamental component thereof maintain the same phase, that is, satisfying the following formula:

[0006]

[0007] In the formula, is the phase difference between the output voltage fundamental component of the high-frequency controlled inverter and its output current fundamental component, is the phase of the fundamental component of the output voltage of the high-frequency controlled inverter, is the phase of the fundamental component of the output current of the high-frequency controlled inverter.

[0008] Furthermore, the parameters of the system meet the following conditions:

[0009]

[0010] In the formula, -R N is the negative resistance, R L is the load resistance value, R P is the equivalent internal resistance of the transmitting coil, R S is the equivalent internal resistance of the receiving coil, β is the detuning ratio, is the inherent resonant frequency of the transmitting device, is the inherent resonant frequency of the receiving device, L P and L S are the inductance values ​​of the transmitting coil and the receiving coil respectively, C P and C S are the capacitance values ​​of the switch capacitor and the receiving resonant capacitor, respectively, k PS is the coupling coefficient between the transmitting coil and the receiving coil, and ω is the operating frequency of the system.

[0011] Furthermore, the resistance value of the negative resistor is always kept constant, and the capacitance value of the switch capacitor is adaptively changed according to the required resistance value of the negative resistor.

[0012] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0013] 1. It has stable output characteristics, and the system output is not affected by the coupling coefficient and resonant frequency deviation.

[0014] 2. Based on the simplest compensation topology, the control does not require wireless communication equipment, and has the characteristics of low cost and reliable control.

[0015] 3. Based only on transmitter control, it is suitable for situations where the receiving device requires integration and lightweight. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A structural block diagram of an autonomous wireless power transmission system with anti-deviation and detuning characteristics provided in an implementation manner.

[0017] Figure 2 An equivalent circuit diagram of an autonomous wireless power transmission system with anti-offset and detuning characteristics provided in an implementation manner.

[0018] Figure 3 Schematic diagram of the preferred circuit topology structure of the negative resistor mentioned in the implementation manner.

[0019] Figure 4 Schematic diagram of the preferred circuit topology structure of the switch capacitor mentioned in the implementation manner.

[0020] Figure 5 4 is a steady-state operating waveform diagram of the high-frequency controlled inverter in an implementation manner.

[0021] Figure 6 4 is a steady-state operating waveform diagram of the switch capacitor in the implementation manner. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0023] like Figure 1As shown, this embodiment discloses an autonomous wireless power transmission system with anti-offset and detuning characteristics, including a transmitting device and a receiving device; the transmitting device includes a transmitting circuit, a switching capacitor and a sampling and control circuit; the transmitting circuit includes a negative resistor, a transmitting coil and an equivalent internal resistance of the transmitting coil, and the negative resistor, the transmitting coil, the equivalent internal resistance of the transmitting coil and the switching capacitor are connected in series; the negative resistor is composed of a DC voltage source and a high-frequency controlled inverter to provide energy for the system; the capacitance of the switching capacitor is adjustable; the input end of the sampling and control module is connected to the transmitting circuit, and the output end thereof is connected to the high-frequency controlled inverter and the switching capacitor respectively; the sampling and control module samples the effective value and phase of the transmitting coil current, and generates control signals of the high-frequency controlled inverter and the switching capacitor; the receiving device includes a load resistor, a receiving coil, an equivalent internal resistance of the receiving coil and a receiving resonant capacitor connected in series.

[0024] Figure 2 This is the equivalent schematic diagram of this system. Figure 2 We can get:

[0025]

[0026] In the formula, are the current vectors of the transmitting circuit and the receiving circuit respectively, -R N is the negative resistance, R L is the load resistance value, R P is the equivalent internal resistance of the transmitting coil, R S is the equivalent internal resistance of the receiving coil, is the inherent resonant frequency of the transmitting device, is the inherent resonant frequency of the receiving device, L P and L S are the inductance values ​​of the transmitting coil and the receiving coil respectively, C P and C S are the capacitance values ​​of the switch capacitor and the receiving resonant capacitor, respectively, k PS is the coupling coefficient between the transmitting coil and the receiving coil, and ω is the operating frequency of the system.

[0027] The detuning ratio β is defined as:

[0028]

[0029] According to formula (1) and (2), we can get:

[0030]

[0031] Combining equations (1) and (3), the system operating frequency can be obtained as:

[0032]

[0033] In the formula, ω H and ω L Represent the high-frequency and low-frequency branches respectively, k C Express the critical coupling coefficient:

[0034]

[0035] The output power and transmission efficiency are:

[0036]

[0037] According to (3), when the resistance of the negative resistor is -R N When β is constant, the detuning ratio β remains constant and is independent of the coupling coefficient and the system resonant frequency. In addition, combining (5) and (6), it can be seen that when β is fixed, the system output power and transmission efficiency remain constant. Therefore, by controlling the resistance value of the negative resistor to remain constant, a constant output independent of the coupling coefficient and the resonant frequency can be achieved. Optionally, the resistance value of the negative resistor can be controlled by adjusting the capacitance of the switch capacitor or the voltage across the negative resistor according to the effective value of the transmitting coil current obtained by sampling. It can be seen that during the control process, there is no need for the receiving end to feedback information through the wireless communication device.

[0038] In order to further illustrate the advantages of the present invention, in this embodiment, an autonomous wireless power transmission system with anti-drift and detuning characteristics is designed. The negative resistor and the switch capacitor are respectively adopted as follows Figure 3 and Figure 4 The circuit topology shown in the figure, where Q 1 -Q 4 , S 1 -S 2 The resistance of the negative resistor is controlled by adjusting the capacitance of the switch capacitor, and the capacitance of the switch capacitor is controlled by controlling the power switch S 1 and S 2 The on-off of Figure 3 The circuit topology shown in the figure constructs a negative resistor, which can effectively improve the utilization rate of DC voltage and is beneficial to the realization of high-power negative resistor. Figure 4 The circuit topology shown is a switched capacitor, which is useful for implementing a power switch S 1 -S 2 Soft switching operation improves system efficiency.

[0039] Figure 5 is the steady-state operating waveform of the high-frequency controlled inverter in the embodiment. G1-4 and V G2-3 They are power switch devices Q 1 , Q 4 and Q 2 , Q 3It can be seen that the inverter output voltage is in phase with its output current, and the inverter always operates in the soft switching and unity power factor state, which can significantly improve system efficiency, reduce reactive power, and improve energy utilization.

[0040] Figure 6 is the steady-state operating waveform of the high-frequency controlled inverter in the embodiment. G1 and v G2 They are power switch devices S 1 and S 2 The driving signal, d 1 π represents the conduction angle of the switching device. It can be seen that the power switching device S 1 and S 2 Turning on at the current zero point can significantly reduce switching losses.

[0041] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An autonomous wireless power transmission system with anti-deviation and anti-detuning characteristics, characterized in that: The system comprises a transmitting device and a receiving device; the transmitting device comprises a transmitting circuit, a switching capacitor and a sampling and control circuit; the transmitting circuit comprises a negative resistor, a transmitting coil and an equivalent internal resistance of the transmitting coil, and the negative resistor, the transmitting coil, the equivalent internal resistance of the transmitting coil and the switching capacitor are connected in series; the negative resistor is composed of a DC voltage source and a high-frequency controlled inverter to provide energy for the system; the capacitance of the switching capacitor is adjustable; the input end of the sampling and control module is connected to the transmitting circuit, and the output end thereof is connected to the high-frequency controlled inverter and the switching capacitor respectively; the sampling and control module samples the effective value and phase of the transmitting coil current, and generates control signals of the high-frequency controlled inverter and the switching capacitor; the receiving device comprises a load resistor, a receiving coil, an equivalent internal resistance of the receiving coil and a receiving resonant capacitor connected in series.

2. The autonomous wireless power transmission system with anti-deviation and anti-detuning characteristics according to claim 1, characterized in that: The output characteristic of the high-frequency controlled inverter is equivalent to a negative resistance, that is, when the non-associated reference direction is selected, the output voltage fundamental component of the high-frequency controlled inverter and the output current fundamental component thereof are in phase, that is, the following formula is satisfied: In the formula, is the phase difference between the output voltage fundamental component of the high-frequency controlled inverter and its output current fundamental component, is the phase of the fundamental component of the output voltage of the high-frequency controlled inverter, is the phase of the fundamental component of the output current of the high-frequency controlled inverter.

3. The autonomous wireless power transmission system with anti-deviation and anti-detuning characteristics according to claim 1, characterized in that: The parameters of the system meet the following conditions: In the formula, -R N is the negative resistance, R L is the load resistance value, R P is the equivalent internal resistance of the transmitting coil, R S is the equivalent internal resistance of the receiving coil, β is the detuning ratio, is the inherent resonant frequency of the transmitting device, is the inherent resonant frequency of the receiving device, L P and L S are the inductance values ​​of the transmitting coil and the receiving coil respectively, C P and C S are the capacitance values ​​of the switch capacitor and the receiving resonant capacitor, respectively, k PS is the coupling coefficient between the transmitting coil and the receiving coil, and ω is the operating frequency of the system.

4. The autonomous wireless power transmission system with anti-deviation and anti-detuning characteristics according to claim 1, characterized in that: The resistance value of the negative resistor is always kept constant, and the capacitance value of the switch capacitor changes adaptively according to the required resistance value of the negative resistor.

Images