Constant-power PT symmetrical wireless electric energy transmission system with anti-offset and load change characteristics

Abstract

The invention discloses a constant-power PT symmetrical wireless power transmission system with anti-offset and load change characteristics. The constant-power PT symmetrical 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 and a transmitting resonant capacitor; the negative resistor is composed of a direct-current power supply, a high-frequency inverter and an emission sampling control module; the receiving device comprises a receiving coil, a receiving coil equivalent internal resistor, a receiving resonant capacitor, a high-frequency controllable rectifier, a receiving sampling control module and a load resistor. According to the wireless power transmission system, when the coupling coefficient and the load resistance change, constant output power and transmission efficiency can be kept, complex compensation topology and a wireless communication module are not needed, and the wireless power transmission 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 field of wireless power transmission, and in particular to a constant power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics. Background Art

[0002] Wireless power transmission technology achieves complete electrical isolation between the power source and the load, eliminating any physical contact. It offers high flexibility, convenience, and safety, and has been widely adopted in applications such as portable consumer electronics, electric vehicles, and drones. In practical applications, the coupling coefficient inevitably varies due to offsets in the relative positions of the transmitter and receiver. Furthermore, when the load is a battery, the load resistance changes as the battery charge increases during charging. However, the output power and transmission efficiency of existing wireless power transmission systems are highly susceptible to the coupling coefficient and load resistance. Therefore, robustness against offset and load variations are key challenges that need to be addressed in the industrialization of wireless power transmission technology. Currently, there are three main approaches to address variations in the coupling coefficient and load resistance: coupling coil design, compensation topology design, and closed-loop control. The first two approaches have limited control accuracy, while closed-loop control typically requires the addition of a DC-DC converter and wireless communication equipment, resulting in complex and costly structures. Furthermore, existing solutions struggle to maintain constant transmission efficiency despite variations in the coupling coefficient and negative resistance.

[0003] The present invention constructs a constant-power PT symmetrical wireless power transmission system based on a simplified series-series compensation structure, achieving constant transmission efficiency and output power that are independent of the coupling coefficient and load resistance, without requiring a wireless communication module. It has the characteristics of simple structure, reliable control, and strong anti-interference characteristics. Summary of the Invention

[0004] The purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and provide a constant-power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics. The system is powered by negative resistance and achieves stable control of the output power by controlling the resistance value of the equivalent AC load resistor to be constant, so that the system output power and transmission efficiency are not affected by changes in the coupling coefficient and load resistance.

[0005] To achieve the above-mentioned purpose, the technical solution provided by the present invention is as follows: a constant power PT symmetrical wireless power transmission system with resistance to offset and load variation, comprising a transmitting device and a receiving device; the transmitting device comprises a negative resistor, a transmitting coil, an equivalent internal resistance of the transmitting coil and a transmitting resonant capacitor connected in series; the negative resistor is composed of a DC power supply, a high-frequency inverter, and a transmitting sampling control circuit to provide energy for the system; the transmitting sampling control circuit comprises a transmitting zero-crossing comparator and a transmitting control circuit, the transmitting zero-crossing comparator samples the phase of the transmitting coil current, and the transmitting control circuit generates a control signal of the high-frequency inverter according to the sampled transmitting coil current phase; the receiving device comprises a receiving coil, a receiving coil, etc. The receiving coil, the receiving coil equivalent internal resistance and the receiving resonant capacitor are connected in series and then connected to the input port of the high-frequency controlled rectifier; the output port of the high-frequency controlled rectifier is connected to the load resistor; the receiving sampling control circuit includes a receiving zero-crossing comparator, a receiving control circuit and a DC voltage and current sampling circuit; the receiving zero-crossing comparator samples the phase of the receiving coil current, the DC voltage and current sampling circuit samples the output DC voltage and output DC current, and the receiving control circuit generates a control signal for the high-frequency controlled rectifier according to the phase of the receiving coil current, the output DC voltage and output DC current.

[0006] Furthermore, the output characteristic of the high-frequency inverter is equivalent to a negative resistance, that is, when a non-correlated reference direction is selected, the output voltage fundamental component of the high-frequency inverter and the output current fundamental component thereof are kept in phase; the input characteristic of the high-frequency controlled rectifier is equivalent to a positive resistance, that is, when a correlated reference direction is selected, the input voltage fundamental component of the high-frequency controlled rectifier and the input current fundamental component thereof are kept in phase, that is, the following formula is satisfied:

[0007]

[0008] Where, is the phase difference between the fundamental component of the output voltage of the high-frequency inverter and the fundamental component of its output current, is the phase of the fundamental component of the output voltage of the high-frequency inverter, is the phase of the fundamental component of the output current of the high-frequency inverter; is the phase difference between the fundamental component of the input voltage of the high-frequency controlled rectifier and the fundamental component of its input current, is the phase of the fundamental component of the input voltage of the high-frequency controlled rectifier, is the phase of the fundamental component of the input current of the high-frequency controlled rectifier.

[0009] Furthermore, the parameters of the proposed wireless power transmission system meet the following conditions:

[0010]

[0011] Where R N is the resistance of the negative resistor, R ac is the equivalent input resistance of the high-frequency controlled rectifier circuit, that is, the equivalent AC load resistance, R P is the equivalent internal resistance of the transmitting coil, R S is the equivalent internal resistance of the receiving coil, is the detuning ratio, is the inherent resonant frequency of the transmitter, is the inherent resonant frequency of the receiving device, L P and L S are the inductances of the transmitting coil and the receiving coil, C P and C S are the capacitance values of the switching capacitor and the receiving resonant capacitor, k PS is the coupling coefficient between the transmitting coil and the receiving coil.

[0012] Furthermore, the ratio of the input voltage to the effective value of the fundamental component of the input current of the high-frequency controlled rectifier circuit is always kept constant, that is, R ac Always keep it constant.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0014] 1. It has constant output power. The system output power is not affected by the coupling coefficient and load resistance.

[0015] 2. It has constant transmission characteristics, and the system transmission efficiency is not affected by the coupling coefficient and load resistance.

[0016] 3. Based on the simplest compensation topology, the control does not require wireless communication equipment, and has the characteristics of low cost and reliable control. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural block diagram of a constant power PT symmetrical wireless power transmission system with anti-offset and load variation characteristics provided in an implementation manner.

[0018] Figure 2 1 is an equivalent circuit diagram of a constant power PT symmetrical wireless power transmission system with anti-offset and load variation characteristics provided in an embodiment.

[0019] Figure 3 Schematic diagram of the preferred circuit topology structure of the negative resistor proposed in the embodiment.

[0020] Figure 4 Schematic diagram of the preferred circuit topology of the high-frequency rectifier circuit in the embodiment.

[0021] Figure 5 is the steady-state operating waveform of the high-frequency inverter in the implementation method.

[0022] Figure 6 : is the steady-state operating waveform of the high-frequency rectifier circuit in the implementation method.

[0023] Figure 7 k PS =0.2,R L =5Ω when the key simulation waveforms of the proposed wireless power transmission system.

[0024] Figure 8 k PS =0.2,R L =10Ω when the key simulation waveforms of the proposed wireless power transmission system.

[0025] Figure 9 k PS =0.4,R L =5Ω when the key simulation waveforms of the proposed wireless power transmission system.

[0026] Figure 10 k PS =0.4,R L =10Ω when the key simulation waveforms of the proposed wireless power transmission system. DETAILED DESCRIPTION

[0027] To further illustrate the content and features of the present invention, specific implementation schemes of the present invention are described in detail below with reference to the accompanying drawings, but the implementation and protection of the present invention are not limited thereto.

[0028] like Figure 1As shown, the present embodiment provides a constant power PT symmetrical wireless power transmission system with anti-offset and load variation characteristics, including a transmitting device and a receiving device; the transmitting device includes a negative resistor, a transmitting coil, an equivalent internal resistance of the transmitting coil and a transmitting resonant capacitor connected in series; the negative resistor is composed of a DC power supply, a high-frequency inverter, and a transmitting sampling control circuit to provide energy for the system; the transmitting sampling control circuit includes a transmitting zero-crossing comparator and a transmitting control circuit, the transmitting zero-crossing comparator samples the phase of the transmitting coil current, and the transmitting control circuit generates a control signal of the high-frequency inverter according to the sampled transmitting coil current phase; the receiving device includes a receiving coil, an equivalent internal resistance of the receiving coil, A receiving resonant capacitor, a high-frequency controlled rectifier, a receiving sampling control circuit, and a load resistor; the receiving coil, the receiving coil equivalent internal resistance, and the receiving resonant capacitor are connected in series and then connected to the input port of the high-frequency controlled rectifier; the output port of the high-frequency controlled rectifier is connected to the load resistor; the receiving sampling control circuit includes a receiving zero-crossing comparator, a receiving control circuit, and a DC voltage and current sampling circuit; the receiving zero-crossing comparator samples the phase of the receiving coil current, the DC voltage and current sampling circuit samples the output DC voltage and output DC current, and the receiving control circuit generates a control signal for the high-frequency controlled rectifier based on the phase of the receiving coil current, the output DC voltage, and the output DC current.

[0029] Figure 2 This is the equivalent schematic diagram of the system. Figure 2 We can get:

[0030]

[0031] Among them, among them, are the current vectors of the transmitting circuit and the receiving circuit respectively; -R N is the negative resistance; R ac The resistance of the equivalent AC load resistor can be controlled by a high-frequency controlled rectifier and the load resistor R L Indicates; R P is the equivalent internal resistance of the transmitting coil, R S is the equivalent internal resistance of the receiving coil; ω0=ω P =ω S represents the circuit's natural angular frequency, is the inherent resonant frequency of the transmitter, 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, L P and L S are the capacitance values of the switching capacitor and the receiving resonant capacitor respectively; k PSis the coupling coefficient between the transmitting coil and the receiving coil; ω is the operating frequency of the system.

[0032] Equation (2) is a set of two-variable homogeneous linear equations about current. The necessary and sufficient condition for the existence of a non-zero solution is that the determinant of the corresponding matrix is zero. Therefore, the characteristic equation of the circuit is:

[0033]

[0034] Separating the imaginary and real parts of equation (2), we can obtain:

[0035]

[0036] Solving equation (3) yields the circuit's steady-state operating angular frequency:

[0037]

[0038] Among them, ω H and ω L Represent the high-frequency and low-frequency branches respectively, k C Express the critical coupling coefficient:

[0039] According to formula (1), the transmitting coil current can be calculated and receiving coil current The relationship is:

[0040]

[0041] In addition, according to formula (4), when the circuit is in the strong coupling region (k PS≥ k C ), the operating angular frequency is ω=ω H,L And ω≠ω0. At this time, from equations (3) and (5), we can get that in the strong coupling region (k PS≥ k C ) is:

[0042]

[0043] Where, I P and I S Represent the effective values of the transmitting coil current and the receiving coil current respectively.

[0044] V P =I P R N and V S =I S R ac Substituting into equation (6), we can get the voltage gain in the strong coupling region:

[0045]

[0046] According to equations (6) and (7), the system output power and transmission efficiency can be obtained as follows:

[0047]

[0048] From equations (8) and (9), we can see that when the equivalent AC load R ac When controlled to be constant, the system transmission efficiency and output power are related to the coupling coefficient k PS and the load resistor R L Not relevant.

[0049] In order to further illustrate the advantages of the present invention, in this embodiment, a constant power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics is designed. The high frequency inverter and high frequency controlled rectifier are respectively used as follows Figure 3 and Figure 4 The circuit topology shown in FIG. 1 , wherein Q1 - Q8 are power switching devices.

[0050] Figure 5 is the steady-state operating waveform of the high-frequency inverter in the embodiment. G1-4 and v G2-3 are the driving signals of power switching devices Q1, Q4 and Q2, Q3 respectively; v P Indicates the inverter output voltage, v P1 Represents the fundamental component of the inverter output voltage, V dc Represents the DC input voltage. It can be seen that the fundamental component of the inverter output voltage v P1 Its output current fundamental component i P Keeping the same phase, the inverter output characteristic can be equivalent to a negative resistance to ensure that the system meets the PT symmetry condition.

[0051] Figure 6 is the steady-state operating waveform of the high-frequency controlled inverter in the embodiment. G5 、v G6 、v G7 and v G8 are the driving signals for power switching devices Q5, Q6, Q7 and Q8 respectively; v S Represents the high-frequency controlled rectifier input voltage, v S1 Represents the fundamental component of the high-frequency controlled rectifier output voltage, D S Represents the rectifier duty cycle, V0 and I0 represent the DC output voltage and output current respectively. It can be seen that the fundamental component of the output voltage of the high-frequency controlled rectifier is the same as the fundamental component of its input current i S Keep the same phase, and by controlling the duty cycle of the high-frequency controlled rectifier, the equivalent AC load R can be adjusted in real time ac In this embodiment, the equivalent AC load Rac With the load resistor R L The relationship can be expressed as:

[0052]

[0053] Where, 0≤D S ≤1 represents the duty cycle of the high-frequency controlled rectifier.

[0054] In order to verify the accuracy of the proposed method, simulation verification is carried out based on the following parameters: transmitting coil inductance L P =100μH, receiving coil inductance L P =100μH, coupling coefficient k PS =0.2~0.4, transmitting resonant capacitance C P =5nF, receiving resonant capacitor C S =5nF, transmitting and receiving equivalent internal resistance R P =R S =0.1Ω, equivalent load R L =5-10Ω, input DC voltage V dc =30V. Equivalent AC load R ac Control is R ac =4Ω. Figure 7-10 Key simulation waveforms of the proposed wireless power transmission system under different loads and coupling coefficients. Figure 7-10 It can be seen that when the coupling coefficient and load change, the effective value of the transmitting coil current I P and the effective value of the receiving coil current I S Always remains unchanged, according to formula (8), the system transmission efficiency remains constant. In addition, according to Figure 7-10 It can be seen that the system output power remains constant when the coupling coefficient and load change. ac Constant, constant output power and transmission efficiency can be achieved, verifying the feasibility of the proposed scheme.

[0055] The above-described embodiments are only preferred embodiments of the present invention. The present invention provides a constant-power PT symmetrical wireless power transmission system with anti-offset and load variation characteristics. The present invention and its embodiments should not be limited to this. Therefore, all changes made according to the shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A constant power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics, characterized by: The system comprises a transmitting device and a receiving device; the transmitting device comprises a negative resistor, a transmitting coil, an equivalent internal resistance of the transmitting coil and a transmitting resonant capacitor connected in series; the negative resistor is composed of a DC power supply, a high-frequency inverter and a transmitting sampling control circuit to provide energy for the system; the transmitting sampling control circuit comprises a transmitting zero-crossing comparator and a transmitting control circuit, the transmitting zero-crossing comparator samples the phase of the transmitting coil current, and the transmitting control circuit generates a control signal of the high-frequency inverter according to the sampled transmitting coil current phase; the receiving device comprises a receiving coil, an equivalent internal resistance of the receiving coil, a receiving resonant capacitor, a high-frequency controlled rectifier, a receiving sampling control circuit circuit and a load resistor; the receiving coil, the receiving coil equivalent internal resistance and the receiving resonant capacitor are connected in series and then connected to the input port of the high-frequency controlled rectifier; the output port of the high-frequency controlled rectifier is connected to the load resistor; the receiving sampling control circuit includes a receiving zero-crossing comparator, a receiving control circuit and a DC voltage and current sampling circuit; the receiving zero-crossing comparator samples the phase of the receiving coil current, the DC voltage and current sampling circuit samples the output DC voltage and output DC current, and the receiving control circuit generates a control signal for the high-frequency controlled rectifier according to the phase of the receiving coil current, the output DC voltage and the output DC current.

2. The constant power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics according to claim 1, characterized in that: The output characteristic of the high-frequency inverter is equivalent to a negative resistance, that is, when a non-correlated reference direction is selected, the output voltage fundamental component of the high-frequency inverter and the output current fundamental component thereof are kept in phase; the input characteristic of the high-frequency controlled rectifier is equivalent to a positive resistance, that is, when a correlated reference direction is selected, the input voltage fundamental component of the high-frequency controlled rectifier and the input current fundamental component thereof are kept in phase, that is, the following formula is satisfied: Where, is the phase difference between the fundamental component of the output voltage of the high-frequency inverter and the fundamental component of its output current, is the phase of the fundamental component of the output voltage of the high-frequency inverter, is the phase of the fundamental component of the output current of the high-frequency inverter; is the phase difference between the fundamental component of the input voltage of the high-frequency controlled rectifier and the fundamental component of its input current, is the phase of the fundamental component of the input voltage of the high-frequency controlled rectifier, is the phase of the fundamental component of the input current of the high-frequency controlled rectifier.

3. The constant power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics according to claim 1, characterized in that: The parameters of the system meet the following conditions: Where R N is the resistance of the negative resistor, R ac is the equivalent input resistance of the high-frequency controlled rectifier circuit, that is, the equivalent AC load resistance, 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 transmitter, is the inherent resonant frequency of the receiving device, L P and L S are the inductances of the transmitting coil and the receiving coil, C P and C S are the capacitance values of the switching capacitor and the receiving resonant capacitor, k PS is the coupling coefficient between the transmitting coil and the receiving coil.

4. The constant power PT symmetrical wireless power transmission system with anti-drift and load variation characteristics according to claim 3, characterized in that: The ratio of the input voltage to the effective value of the fundamental component of the input current of the high-frequency controlled rectifier circuit is always kept constant, that is, R ac Always keep it constant.

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