Rotary equipment PT symmetric wireless power transmission system and constant power transmission method thereof

Abstract

The invention discloses a rotating equipment PT symmetrical wireless power transmission system and a constant power transmission method thereof, the system comprises a power source, an inversion module, a transmission coil module, a rectification module and a load, the power source and the inversion module are equivalent to a negative resistor externally, and the rectification module and the load are equivalent to an output resistor externally. The transmission coil module is composed of a transmitting coil and a receiving coil, and the system meets the PT symmetry condition. According to the deduced analytical expression of the output current, the fluctuation factor causing the fluctuation of the output power of the rotating equipment PT symmetric wireless power transmission system is analyzed, and the mutual inductance between the transmitting coil and the receiving coil is designed by taking elimination of the fluctuation factor as a target. By regulating and controlling the mutual inductance between the transmitting coil and the receiving coil, the amplitude of the output current can be kept constant, and then the constant power output characteristic of the system can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wireless power transmission, in particular to a rotating device PT-symmetry wireless power transmission system and a constant power transmission method thereof. BACKGROUND

[0002] Wireless power transmission technology is widely used in implantable medical devices, rotating device power supply, electric vehicle wireless charging and other fields due to its characteristics of no physical contact, safety and the like. The PT-symmetry-based wireless power transmission system can achieve constant transmission efficiency and output power independent of the coupling coefficient in the over-coupling region. Compared with the traditional magnetic coupling wireless power transmission system, the PT-symmetry wireless power transmission system can overcome the problem that the transmission characteristics are sensitive to the coupling coefficient in a wider transmission range, greatly enhancing the practicability of the wireless power transmission system.

[0003] However, the current PT-symmetry wireless power transmission system only maintains constant efficiency and constant power transmission in a discrete changing transmission range. In the case of rotating device power supply, the relative position between the transmitting coil and the receiving coil changes continuously and periodically. In this case, the output power of the system will fluctuate with the change of position, affecting the transmission characteristics of the system. The current solution to the output power fluctuation problem of the rotating device wireless power transmission system mainly adopts a multi-coil strategy and a scheme of constructing a cage-type or cylindrical magnetic coupling mechanism. Such schemes result in a large device size and are not suitable for occasions such as the space between the stator and rotor of the motor, where the space is small.

[0004] To solve the above problems, the mutual inductance between the transmitting coil and the receiving coil of the PT-symmetry wireless power transmission system is designed so that the constant power output can be maintained when the position of the receiving coil changes continuously with the rotating device, ensuring the output stability of the system. SUMMARY

[0005] The present application aims to overcome the current PT-symmetry wireless power transmission system for rotating devices, which causes output power fluctuation and output instability due to the continuous change of the relative position between the receiving coil and the transmitting coil, and the problem of the large size of the existing rotating device wireless power transmission system. A rotating device PT-symmetry wireless power transmission system and a constant power transmission method thereof are provided, which realizes the effect of constant output power by regulating the mutual inductance between the transmitting coil and the receiving coil.

[0006] To achieve the above object, the technical scheme provided by the application is as follows: a PT-symmetry wireless power transmission system of rotating equipment, which comprises a power source, an inverter module, a transmission coil module, a rectifier module and a load; the power source is composed of a direct-current voltage source, and the output end of the direct-current voltage source is connected with the input end of the inverter module; the inverter module is a voltage full-bridge inverter composed of four bridge arms, and the output end of the inverter module is connected with the transmitting coil of the transmission coil module; the transmission coil module comprises a transmitting coil and a receiving coil, the transmitting coil is equivalent to a series circuit formed by a transmitting coil resonant inductance, a transmitting coil internal resistance and a transmitting coil compensation capacitor, the receiving coil is equivalent to a series circuit formed by a receiving coil resonant inductance, a receiving coil internal resistance and a receiving coil compensation capacitor, and there is a coupling relationship between the transmitting coil and the receiving coil; the receiving coil is connected with the input end of the rectifier module; the rectifier module is a bridge rectifier circuit composed of four diodes, and the output end of the rectifier module is connected with the load; the voltage and current direction of the output end of the inverter module are non-correlation reference directions, and the power source and the inverter module are equivalent to a negative resistance to the outside; and the rectifier module and the load are equivalent to an output resistance to the outside.

[0007] Further, the modal of the transmitting coil and the receiving coil And is defined as: ; ; In the formula, represents the time variable of a function, and the time ; represents an imaginary unit, and satisfies ; and are the inductance values of the transmitting coil resonant inductance and the receiving coil resonant inductance respectively, and are the transmitting coil compensation capacitor value and the receiving coil compensation capacitor value respectively, is the current value flowing through the transmitting coil resonant inductance, is the current value flowing through the receiving coil resonant inductance, is the voltage value across the transmitting coil compensation capacitor, is the voltage value across the receiving coil compensation capacitor.

[0008] Further, when the system satisfies the PT-symmetry condition , the modal analytical expression of the transmitting coil and the receiving coil is: ; In the formula, , The natural resonant frequency of the transmitting coil and the receiving coil respectively, the natural resonant frequency of the system , The resistance value of the negative resistance, , The internal resistance value of the transmitting coil and the receiving coil respectively, The total gain rate of the transmitting coil, The total loss rate of the receiving coil, The resistance value of the output resistance; And The undetermined coefficient; let the parameter , The coupling rate between the modes And , The coupling coefficient between the transmitting coil and the receiving coil, The mutual inductance value of the transmitting coil and the receiving coil; the eigenvalue of the system is , The Bary phase ; The initial value , , The voltage value of the direct current voltage source.

[0009] Further, the analytical expression of the output current Of the receiving coil is: .

[0010] The application also provides a constant power transmission method of the PT-symmetric wireless power transmission system of the rotating device, comprising the following steps: 1) The fluctuation factor In the analytical expression of the output current affects the amplitude of the current, thereby causing the fluctuation of the output power, in order to obtain the output current with constant amplitude, the fluctuation factor Should be equal to a constant , that is ; 2) The equation Can be further written as: ; The initial value of the mutual inductance between the transmitting coil and the receiving coil should be equal to Therefore, the constant Is designed; 3) The mutual inductance between the transmitting coil and the receiving coil is designed so that the mutual inductance value satisfies: ; By adjusting the mutual inductance between the transmitting coil and the receiving coil, the fluctuation factor Can be a constant , so that when the transmitting coil and the receiving coil of the PT symmetric wireless power transmission system are constantly moving with the rotating device, the amplitude of the output current can always remain constant, at this time the amplitude of the output power is constant, and thus the system can realize constant power output.

[0011] Compared with the prior art, the present application has the following advantages and beneficial effects: 1. According to the derived output current analytical expression under the condition of time-varying circuit parameters, the fluctuation factor of the PT symmetric wireless power transmission system output current fluctuation caused by the rotating device movement is analyzed from the analytical expression , which can more accurately quantify the influence of the fluctuation of mutual inductance between the transmitting coil and the receiving coil on the system output characteristics.

[0012] 2. The present application designs a specific mutual inductance value expression that eliminates the fluctuation factor , and by adjusting the mutual inductance between the transmitting coil and the receiving coil, the purpose of keeping the output current constant amplitude can be achieved, and the controllability of the output current during the rotating device rotation is realized, and thus constant power output is achieved.

[0013] 3. The present application uses the method of adjusting the mutual inductance between the transmitting coil and the receiving coil to realize constant power transmission, which can avoid the large size of the device caused by the traditional wireless power transmission system for rotating devices using multiple coils or cylindrical magnetic cores, and is more suitable for a type of narrow space such as the motor stator and rotor. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the circuit principle diagram of the system of the present application.

[0015] Figure 2 is a simplified circuit diagram of the system of the present application.

[0016] Figure 3 , Figure 4 are respectively the output current and output power waveform simulation diagrams of the existing PT symmetric wireless power transmission system for rotating devices.

[0017] Figure 5 , Figure 6 are respectively the output current and output power waveform simulation diagrams of the PT symmetric wireless power transmission system of the present application for rotating devices. DETAILED DESCRIPTION

[0018] The present application will be further described in detail below in conjunction with the embodiments and the drawings, but the embodiments of the present application are not limited thereto.

[0019] As Figure 1The embodiment shown discloses a rotating equipment PT-symmetrical wireless power transmission system, comprising a power source, an inverter module I, a transmission coil module II, a rectifier module III and a load ; wherein the power source is composed of a direct current voltage source , the output end of which is connected with the input end of the inverter module I; the inverter module I is a voltage full-bridge inverter composed of four bridge arms 、 、 、 , the output end of which is connected with the transmitting coil of the transmission coil module II; the transmission coil module II comprises a transmitting coil and a receiving coil, wherein the transmitting coil is equivalent to a series circuit formed by a transmitting coil resonant inductance , a transmitting coil internal resistance and a transmitting coil compensation capacitor , the receiving coil is equivalent to a series circuit formed by a receiving coil resonant inductance , a receiving coil internal resistance and a receiving coil compensation capacitor , and the transmitting coil and the receiving coil have a coupling relationship, the receiving coil is connected with the input end of the rectifier module III; the rectifier module III is a bridge rectifier circuit composed of four diodes 、 、 、 , the output end of which is connected with the load . The voltage and current direction of the output end of the inverter module II are non-correlation reference directions, which are equivalent to a negative resistance to the outside together with the power source; the rectifier module III and the load are equivalent to an output resistance to the outside, and the simplified circuit diagram of the rotating equipment PT-symmetrical wireless power transmission system is shown as Figure 2 .

[0020] Definition 、 respectively represent the modalities of the transmitting coil and the receiving coil: (1) wherein represents the time variable of a function, the time ; represents an imaginary unit, which satisfies ; and respectively represent the inductance values of the transmitting coil resonant inductance and the receiving coil resonant inductance, and respectively represent the compensation capacitor values of the transmitting coil and the receiving coil, is the current value flowing through the transmitting coil resonant inductance and the receiving coil resonant inductance, The voltage value across the compensation capacitor is compensated for the transmitting coil and the receiving coil.

[0021] Figure 2 Under the conditions of high quality factor and weak coupling, the circuit model can be equivalent to the coupled mode model as follows: (2); wherein, R is the resistance value of the negative resistance, , Rt and Rc are the internal resistance values of the transmitting coil and the receiving coil respectively, Rout is the resistance value of the output resistance, Gt is the total gain rate of the transmitting coil, Gc is the total loss rate of the receiving coil, the natural resonant frequencies of the transmitting coil and the receiving coil are , and the natural resonant frequency of the system is , M is the mutual inductance value between the transmitting coil and the receiving coil, K is the coupling coefficient between the transmitting coil and the receiving coil, is the coupling rate between the modes and .

[0022] The PT-symmetric wireless power transmission system of the rotating device PT needs to meet the PT-symmetric condition: , Under the condition of meeting the PT-symmetric condition, the Hamiltonian matrix in the coupled mode model of formula (2) can be written as: (3); In a non-Hermitian system, there are eigen vectors and its adjoint eigen vector satisfy: (4); wherein, , is the transpose conjugate of the matrix , the Hamiltonian matrix of the system is a non-Hermitian operator, that is, .

[0023] The steady-state equation corresponding to formula (4) is: (5); wherein, , is the eigenvalue corresponding to the eigen vector , and is the adjoint eigen vector corresponding eigenvalue. Since the eigenvector and the adjoint eigenvector satisfy biorthogonality and completeness, i.e., for , , the ortho-normalization condition is satisfied and , and represent the transpose conjugate of and , respectively, the expression represents the inner product, and the expression represents the outer product, represents the Kronecker function, represents the identity matrix operator, and the summation symbol.

[0024] The general solution of the differential equations of the time-dependent Hamiltonian of the non-Hermitian system is a linear superposition of each eigenstate, which can be set as (6); where is an undetermined coefficient, and the exponential term is the Berry phase.

[0025] Taking the derivative of equation (6) gives (7); Taking the inner product of equation (7) with and using the ortho-normalization condition gives (8); When the adiabatic approximation condition is satisfied, we have (9); Solving the differential equation of equation (9) gives the Berry phase as (10); Let the vector composed of the modes be , and the coupled-mode differential equations of equation (2) can be simplified to (11); The general solution of equation (11) is (12); where .

[0026] Solving the eigenvalue gives the equation , which can be obtained as (13); where the parameter .

[0027] The eigenvector is obtained as (14); Similarly, the adjoint eigenvector is obtained as (15); Substituting equations (14) and (15) into equation (10), the Berry phase is derived as (16); The analytical expression of the mode of the transmitting coil and the receiving coil of the PT-symmetry wireless power transfer system of the rotating device is obtained from the general solution (12) as (17); where the undetermined coefficients , ; the initial value of the system is , , and the voltage value of the DC voltage source is V.

[0028] According to , the analytical expression of the output current of the receiving coil is (18); The fluctuation factor in the analytical expression of the output current affects the amplitude of the current, thereby causing the fluctuation of the output power. To obtain the output current with constant amplitude, the fluctuation factor should be equal to a constant , i.e. , and the equation can be further written as (19); The mutual inductance between the transmitting coil and the receiving coil should be equal to , and therefore the constant is designed.

[0029] According to equation (19), the mutual inductance between the transmitting coil and the receiving coil is designed so that the mutual inductance value satisfies (20); At this time, by adjusting the mutual inductance between the transmitting coil and the receiving coil, the fluctuation factor can be a constant , so that the amplitude of the output current can always remain constant when the transmitting coil and the receiving coil of the PT-symmetry wireless power transfer system of the rotating device are constantly moving with the rotating device.​

[0030] Output power The expression is: (twenty one); As can be seen from equation (21), the output power amplitude is constant, and the system achieves constant power output.

[0031] The following is a preferred example of the constant power transmission method for the PT-symmetric wireless power transmission system of the rotating device: the resonant inductance value of the transmitting coil is... The resonant inductance of the receiving coil is In the formula, The initial amplitude of the resonant inductance of the transmitting coil. The initial amplitude of the resonant inductance of the transmitting coil. Let be the frequency of the system's Hamiltonian variation. To satisfy the PT symmetry condition and ensure high-efficiency transmission, the resonant frequencies of the transmitting and receiving coils must be consistent, i.e., satisfy . And satisfy The system parameters are designed as shown in Table 1.

[0032] Table 1: System Parameters

[0033] Based on the parameters in Table 1, the constant power transmission method of the PT-symmetric wireless power transmission system of the rotating equipment is simulated and verified. Figure 3 , Figure 4 The waveforms are the output current and output power waveforms of an existing PT symmetrical wireless power transfer system applied to rotating equipment. The amplitudes of both current and power fluctuate periodically, and the fluctuation frequencies of current and power are related to the mutual inductance fluctuation frequency between the transmitting and receiving coils. Figure 5 , Figure 6 The waveforms show the output current and output power of the PT symmetrical wireless power transfer system of this invention when applied to rotating equipment, with both current and power amplitudes remaining constant. (Comparison) Figure 3 , Figure 4 and Figure 5 , Figure 6 It can be concluded that by using the PT symmetrical wireless power transmission system and its constant power transmission method of the present invention, and by designing and controlling the mutual inductance between the transmitting coil and the receiving coil, the PT symmetrical wireless power transmission system of the rotating equipment outputs a current with a constant amplitude, thus achieving constant power output characteristics.

[0034] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A PT-symmetric wireless power transfer system for a rotating device, characterized in that, The system comprises a power source, an inverter module (I), a transmission coil module (II), a rectifier module (III) and a load ( ). The power source is composed of a DC voltage source ( ), the output of which is connected with the input of the inverter module (I); the inverter module (I) is a voltage full-bridge inverter composed of four bridge arms ( , , , ), the output of which is connected with the transmitting coil of the transmission coil module (II); the transmission coil module (II) comprises a transmitting coil and a receiving coil, the transmitting coil is equivalent to a series circuit formed by a transmitting coil resonant inductance ( ), a transmitting coil internal resistance ( ) and a transmitting coil compensation capacitor ( ), the receiving coil is equivalent to a series circuit formed by a receiving coil resonant inductance ( ), a receiving coil internal resistance ( ) and a receiving coil compensation capacitor ( ), there is a coupling relationship between the transmitting coil and the receiving coil, the receiving coil is connected with the input of the rectifier module (III); the rectifier module (III) is a bridge rectifier circuit composed of four diodes ( , , , ), the output of which is connected with the load ( ); the voltage and the current direction of the output of the inverter module (II) are non-correlation reference directions, which are equivalent to a negative resistance ( ) with the power source; the rectifier module (III) and the load ( ) are equivalent to an output resistance ( ) to the outside.

2. The PT-symmetric wireless power transfer system of claim 1, wherein, Modality of the transmitting coil and the receiving coil and is defined as: ； ； In the formula, denotes the time variable of the function, time ; denotes the imaginary unit, which satisfies ; and are the inductance values of the transmit coil resonance inductance and the receive coil resonance inductance, respectively, and are the compensation capacitance values of the transmit coil and the receive coil, respectively, is the current value flowing through the transmit coil resonance inductance, is the current value flowing through the receive coil resonance inductance, is the voltage value across the transmit coil compensation capacitor, is the voltage value across the receive coil compensation capacitor.

3. The PT-symmetric wireless power transfer system of claim 2, wherein, When the system satisfies the PT symmetric condition , , the modal analytical expression of the transmitting coil and the receiving coil is: ； wherein , are the natural resonant frequencies of the transmitting coil and the receiving coil, respectively, the natural resonant frequency of the system , is the value of the negative resistance, , are the internal resistance values of the transmitting coil and the receiving coil, respectively, is the total gain rate of the transmitting coil, is the total loss rate of the receiving coil, is the value of the output resistance; and are the undetermined coefficients; let the parameters , be the coupling rate between the modes and , is the coupling coefficient between the transmitting coil and the receiving coil, is the mutual inductance value of the transmitting coil and the receiving coil; the eigenvalues of the system are , ; the Berry phase ; the initial value , , is the voltage value of the direct current voltage source.

4. The PT-symmetric wireless power transfer system of claim 3, wherein, The output current of the receiving coil The analytical expression for the output current of the receiving coil is: 。 5. The constant power transmission method of the PT-symmetric wireless power transmission system of the rotating device of claim 4, characterized by, comprising the steps of: 1) Fluctuation factor in analytical expression of output current of the receiving coil affects the amplitude of the current, thus resulting in fluctuations in the output power, in order to obtain an output current with constant amplitude, it is necessary to make the fluctuation factor equal to a constant i.e. ; 2) Equation Can be further written as: ； The mutual inductance between the transmitting coil and the receiving coil should be equal to The constant is therefore designed ; 3) designing the mutual inductance between the transmitting coil and the receiving coil such that the mutual inductance value satisfies: ； By regulating the mutual inductance between the transmitting coil and the receiving coil, the fluctuation factor is constant , so that when the transmitting coil and the receiving coil of the symmetrical wireless power transmission system of the rotating device PT move constantly with the rotating device, the amplitude of the output current can always remain constant, at this time the amplitude of the output power is constant, and the system can realize constant power output.

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