A multi-stage magnetic resonance WPT system power flow regulation method based on current phase configuration

Abstract

The present application relates to the technical field of multi-stage magnetic resonance wireless power transfer (WPT), and specifically discloses a multi-stage magnetic resonance WPT system energy flow regulation method based on current phase configuration, aiming at the problems of active reverse sending and system detuning caused by the complex coupling relationship of the coils of the existing multi-stage magnetic resonance WPT system, presetting the current phase of each stage of coil, and obtaining a phase conversion matrix according to the conversion variable of the coil current phasor; multiplying the original impedance matrix with the phase conversion matrix, and transferring the multi-stage coil current phase relationship to the equivalent impedance matrix; taking the voltage imaginary part of each stage of coil loop as zero, and inversely deducing the expression of each stage of coil current; substituting the coil loop containing the compensation capacitor in the voltage real part into each stage of coil current, and solving the compensation capacitor of the corresponding coil loop; and obtaining the mathematical analytical relationship between the system power, efficiency and the to-be-optimized variable, so as to regulate the power of each stage of coil loop and the system efficiency by configuring the to-be-optimized variable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of multi-stage magnetic resonance wireless power transfer (WPT), and in particular to a multi-stage magnetic resonance WPT system energy flow regulation method based on current phase configuration. BACKGROUND

[0002] Wireless power transfer based on near-field magnetic coupling resonance is a new emerging power supply technology that is safe, flexible and free of wire contact, and can adapt to various harsh weather environments, and has been widely used in the fields of biomedical, consumer electronics, electric vehicles and intelligent industry. The current power grid safety requires a large number of modern monitoring equipment to be put into operation, and the working state of the power transmission network can be remotely observed through the monitoring equipment. In recent years, some scholars have combined wireless power supply systems with insulators to form a wireless power supply system based on insulators to supply power to monitoring equipment. The structure of the insulator does not change, but it has both insulation and energy transmission electrical properties. In order to solve the problem of transmission distance limitation of the WPT system, more and more scholars take multi-relay coil structure and domino coil structure to increase the transmission distance of the system. The current long-distance wireless power transfer method is to add a relay side structure unit between the energy transmitting end structure unit and the energy receiving end structure unit, and to use the magnetic coupling resonance of the relay coil to realize energy transmission at a long distance. With the increase of the number of elements, the coupling relationship between the multi-stage coils becomes very complex, resulting in active back feeding from the later stage coil to the former stage coil, and causing system detuning and transmission efficiency reduction. Therefore, how to control the power flow between the coils and ensure efficient transmission of system power is crucial for the operation of the multi-stage magnetic resonance WPT system. At present, there is no simple and effective solution to the energy flow regulation of the multi-stage magnetic resonance WPT system. SUMMARY

[0003] The present application provides a multi-stage magnetic resonance WPT system energy flow regulation method based on current phase configuration, which solves the technical problem that the existing multi-stage magnetic resonance WPT system has power back feeding under complex cross coupling, resulting in system detuning and transmission efficiency reduction.

[0004] To solve the above technical problems, the present application provides a multi-stage magnetic resonance WPT system energy flow regulation method based on current phase configuration, which includes a transmitting coil loop, n-2 relay coil loops and a receiving coil loop arranged in sequence, and the key lies in that the energy flow regulation method includes the following steps:

[0005] S1, a circuit impedance model U=ZI of the multi-stage magnetic resonance WPT system is established, U and I represent a voltage matrix and a current matrix composed of voltages and currents of each stage coil respectively, and Z is an impedance matrix describing the impedance relationship between the n-stage magnetic resonance coils;

[0006] S2, determine the partial relay coil phase as an optimization variable, and preset the remaining coil current phase as a constant;

[0007] S3, phase decomposition is performed on the coil current at each level to obtain a corresponding phase conversion matrix T, and an equivalent impedance matrix Z is obtained based on the phase conversion matrix T T = ZT and the converted current matrix I T = T -1 I;

[0008] S4, based on the current phase in I T , extract the elements or the real part or the imaginary part of the elements at the corresponding position of Z T , and construct a permutation matrix Z T0 based on Z T0 , to obtain the coil current expression I T = Z T0 -1 U;

[0009] S5, construct the coil loop voltage equation at the n levels, and solve the coil loop voltage equation corresponding to the element term containing the compensation capacitor in Z T , to obtain the analytical solution of the corresponding compensation capacitor and substitute it into I T = Z T0 -1 U to obtain a new coil current expression, and substitute the new coil current expression into the remaining coil loop voltage equations to solve the analytical solution of the remaining compensation capacitors;

[0010] S6, based on the currently determined information, obtain the relationship between the coil loop power at each level, the system transmission efficiency and the optimization variable, and based on the relationship, control the coil loop power at each level and the system efficiency by configuring the optimization variable.

[0011] Further, the step S2 specifically comprises the following steps:

[0012] S21, taking the transmit coil loop alternating current input voltage as the reference 0 phase, and setting the transmit coil current phase as 0°;

[0013] S22, when the system requires constant voltage output, the current phase of the receive coil is set as 0° or -180°; when the system requires constant current output, the current phase of the receive coil is set as 90° or -90°;

[0014] S23, set the current phase of the partial relay coil as 0°, 90°, -90° or -180°, and the current phase of the remaining relay coil as the optimization variable θ k .

[0015] Further, in step S3, the phase conversion matrix T is composed of phase conversion coefficients of the coils of each stage, and the phase conversion coefficients of the coils of each stage are valued according to the following rules:

[0016] The conversion coefficient corresponding to the coil current with phase of 0°, 90°, -90°, -180° is 1, i.e. the phase of the coil current is not changed before and after conversion;

[0017] The conversion coefficient corresponding to the coil current with phase of θ k and 0°<|θ k |<90° is cosθ k +jsinθ k , and the phase of the coil current after conversion is 0°;

[0018] The conversion coefficient corresponding to the coil current with phase of θ k and 90°<|θ k |<180° is -cos(180°-θ k )+jsin(180°-θ k ), and the phase of the coil current after conversion is 0°.

[0019] Further, in step S4, the permutation matrix Z T0 is constructed according to the following rules:

[0020] The real part of the diagonal element of the equivalent impedance matrix Z T is taken as the diagonal element of the permutation matrix Z T0 ;

[0021] For the coil loop with current phase of 0° and -180°, when the phase of the coil current coupled therewith is also 0° and -180°, the real part of the corresponding element of the equivalent impedance matrix Z T is taken as the element at the corresponding position of the permutation matrix Z T0 ; when the phase of the coil current coupled therewith is 90° and -90°, the imaginary part of the corresponding element of the equivalent impedance matrix Z T is taken as the element at the corresponding position of the permutation matrix Z T0 ;

[0022] For the coil loop with current phase of 90° and -90°, when the phase of the coil current coupled therewith is 0° and -180°, the imaginary part of the corresponding element of the equivalent impedance matrix Z T is taken as the element at the corresponding position of the permutation matrix Z T0 ; when the phase of the coil current coupled therewith is also 90° and -90°, the real part of the corresponding element of the equivalent impedance matrix Z T is taken as the element at the corresponding position of the permutation matrix Z T0 .

[0023] Further, in the step S6, based on the information determined at present, a relationship between the power of each level coil loop and the variable to be optimized is derived, specifically:

[0024] According to the phase conversion matrix T and the new coil current expression I T The reduced coil current matrix before conversion is I = TI T ;

[0025] The column elements in the impedance matrix Z are multiplied by the row elements in the current matrix I, and then multiplied by the conjugate of the current of each coil loop respectively, to obtain the power expression of the coupling between each level coil loop.

[0026] Further, the compensation capacitor of each level coil loop is in series with the coil.

[0027] Further, in step S1, the voltage matrix U is a column vector composed of the voltages of each level coil, and the current matrix I is a column vector composed of the currents of each level coil.

[0028] Further, in step S1, the impedance matrix Z is an n×n square matrix, and the element Z ij The value rule is:

[0029] When i=j≠n, Z ij is equal to R i +j(ωL i -1 / ωC i );

[0030] When i=j=n, Z ij is equal to R n +j(ωL n -1 / ωC n )+R Leq ;

[0031] When i≠j, Z ij is equal to jωM ij ;

[0032] Where, ω represents the working angular frequency of the system, I i , R i , L i , C i represent the current of each level coil, internal resistance, inductance and compensation capacitor in turn, M ij represents the mutual inductance between the i-th level coil and the j-th level coil, R Leq represents the AC equivalent load of the receiving end, i,j=1,2,…,n.

[0033] The application provides a multi-stage magnetic resonance WPT system current flow regulation method based on current phase configuration. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 is a 5-stage magnetic resonance WPT system circuit topology diagram provided by the embodiment of the application;

[0035] Figure 2 is a flow chart of a multi-stage magnetic resonance WPT system current flow regulation method based on current phase configuration provided by the embodiment of the application;

[0036] Figure 3 is a current phase diagram before phase configuration provided by the embodiment of the application;

[0037] Figure 4 is an active power flow diagram before phase configuration provided by the embodiment of the application;

[0038] Figure 5 is an output voltage diagram before phase configuration provided by the embodiment of the application;

[0039] Figure 6 is a current phase diagram under the first phase configuration provided by the embodiment of the application;

[0040] Figure 7 is an active power flow diagram under the first phase configuration provided by the embodiment of the application;

[0041] Figure 8 is an output voltage diagram under the first phase configuration provided by the embodiment of the application;

[0042] Figure 9 is a current phase diagram under the second phase configuration provided by the embodiment of the application;

[0043] Figure 10 is an active power flow diagram under the second phase configuration provided by the embodiment of the application;

[0044] Figure 11 is the output voltage diagram under the 2nd phase configuration provided by the embodiment of the present application;

[0045] Figure 12 is the current phase diagram under the 3rd phase configuration provided by the embodiment of the present application;

[0046] Figure 13 is the active power flow diagram under the 3rd phase configuration provided by the embodiment of the present application;

[0047] Figure 14 is the output voltage diagram under the 3rd phase configuration provided by the embodiment of the present application;

[0048] Figure 15 is the output power comparison diagram when the phase configuration changes provided by the embodiment of the present application;

[0049] Figure 16 is the transmission efficiency comparison diagram when the phase configuration changes provided by the embodiment of the present application. DETAILED DESCRIPTION

[0050] The embodiments of the present application will be described in detail below with reference to the accompanying drawings. The embodiments are given only for the purpose of illustration and should not be understood as limiting the present application. The accompanying drawings are used for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present application, because many changes can be made to the present application without departing from the spirit and scope thereof.

[0051] Before describing the energy flow regulation method of the multi-stage magnetic resonance WPT system of the present application, the structure of the multi-stage magnetic resonance WPT system will be briefly introduced. The multi-stage magnetic resonance WPT system comprises a transmitting coil loop, n-2 relay coil loops and a receiving coil loop arranged in sequence. The transmitting coil loop comprises an equivalent AC source, a transmitting coil compensation network and a transmitting coil, the relay coil loop comprises a relay coil and a relay coil resonance network, and the receiving coil loop comprises a receiving coil, a receiving coil compensation network and an equivalent AC load. The equivalent AC source is generally equivalent to a DC source and a high-frequency inverter. The equivalent AC load is generally equivalent to a rectifier filter circuit and a load resistor. The transmitting coil compensation network, the relay coil resonance network and the receiving coil compensation network adopt the same structure of compensation network. In order to facilitate energy flow regulation, the compensation network of the present embodiment adopts a series compensation capacitor. The circuit structure of the multi-stage magnetic resonance WPT system when n=5 is shown in FIG. 1, wherein I Figure 1 i , R i , L i , C i represent the coil current, internal resistance, inductance and compensation capacitor of each stage, respectively, and M ij ​(mij≠0) represents mutual inductance between the i-th stage coil and the j-th stage coil, R Leq represents the AC equivalent load of the receiving end, i, j = 1, 2, …, n, U in represents a DC source, MOS tubes S1 to S4 are connected into a high-frequency inverter, U inv represents the AC voltage of the inverter output. Diodes D1 to D4 are connected into a full-bridge rectifier, and a filter capacitor C f together constitute a rectifier filter circuit. R L represents a load resistance, I out and U out respectively represent the system output current and voltage.

[0052] Based on the above multi-stage magnetic resonance WPT system, the embodiment of the application provides a multi-stage magnetic resonance WPT system energy flow regulation method based on current phase configuration, as shown in the flowchart of Figure 2 , comprising the steps of:

[0053] S1, establishing a circuit impedance model U=ZI of the multi-stage magnetic resonance WPT system, U and I respectively represent a voltage matrix and a current matrix composed of voltages and currents of each stage coil, and Z is an impedance matrix describing the impedance relationship between the n-stage magnetic resonance coils;

[0054] S2, determining part of the relay coil phase as an optimization variable, and presetting the current phase of the remaining coils as a constant;

[0055] S3, phase-decomposing the current of each stage coil to obtain a corresponding phase conversion matrix T, and obtaining an equivalent impedance matrix Z T =ZT and a converted current matrix I T =T -1 I based on the phase conversion matrix T;

[0056] S4, based on each current phase in I T , extracting elements or real parts or imaginary parts of the elements at corresponding positions of Z T to construct a permutation matrix Z T0 , obtaining the current expression I T =Z T0 of each stage coil based on Z T0 -1 U;

[0057] S5, constructing a voltage equation of the n-stage coil loop, and solving the coil loop voltage equation corresponding to the element term containing the compensation capacitor in the real and imaginary parts of Z T to obtain the corresponding compensation capacitor analytical solution and substitute it into I T =Z T0 -1Uget a new coil current expression, substitute the new coil current expression into the remaining coil loop voltage equations, and solve the analytical solution of the remaining compensation capacitors;

[0058] S6, based on the currently determined information, derive the relationship between the power of each stage coil loop, the system transmission efficiency and the to-be-optimized variable, and based on the relationship, regulate the power of each stage coil loop and the system efficiency by configuring the to-be-optimized variable.

[0059] The multi-stage magnetic resonance WPT system based on current phase configuration can flow regulation method provided by the application can preset the phase of each stage coil current according to the zero phase angle input of the system transmitting end and the output performance requirement of the load end, and obtain a phase conversion matrix according to the conversion variable of the coil current phasor. By multiplying the original impedance matrix and the phase conversion matrix, the phase relationship of the multi-stage coil current is transferred to the equivalent impedance matrix. With the voltage imaginary part of each stage coil loop as zero, the expression of each stage coil current is derived in reverse, and then the coil loop containing the compensation capacitor in the voltage real part is substituted into each stage coil current, so that the compensation capacitor corresponding to the coil loop is solved, and the mathematical analytical relationship between each stage coil current and the compensation capacitor and the to-be-optimized variable is obtained. The application realizes the zero phase angle input and constant voltage output of the system through the accurate calculation of the compensation capacitor of each stage coil loop, and finds the energy flow regulation method through the quantitative relationship between the phase variable and the transmission power and efficiency, and improves the transmission power and efficiency of the system.

[0060] The following will be described in detail.

[0061] (1) Step S1

[0062] Step S1 determines the circuit impedance model U=ZI of the multi-stage magnetic resonance WPT system:

[0063]

[0064] Wherein, the voltage matrix is a column vector composed of the voltages of each stage coil. The current matrix is a column vector composed of the currents of each stage coil.

[0065] The impedance matrix Z is an n*n square matrix, and the element Z ij The value rule is:

[0066] Z ij =jωM ij , i≠j,

[0067]

[0068] That is:

[0069] When i = j ≠ n, Z ij i.e. Z ii equals R i +j(ωL i -1 / ωC i );

[0070] When i = j = n, Z ij i.e. Z ii equals R n +j(ωL n -1 / ωC n )+R Leq ;

[0071] When i ≠ j, Z ij equals jωM ij ;

[0072] Wherein, ω represents the working angular frequency of the system.

[0073] Taking n = 5 as an example, the corresponding circuit impedance model is described as follows:

[0074]

[0075] Wherein,

[0076] (2) Step S2

[0077] Step S2 is to determine that the phase of the partial relay coil is a to-be-optimized variable, and the phases of the remaining coil currents are preset as constants. Here, the to-be-optimized variable is at least two.

[0078] The step S2 specifically includes the following steps:

[0079] S21, taking the AC input voltage of the transmitting coil loop as the reference 0 phase, the phase of the transmitting coil current is set to 0°, so that the voltage and current phases of the transmitting end coil loop are in phase, and zero-phase angle input of the transmitting end is realized;

[0080] S22, when the system requires constant voltage output, the current phase of the receiving coil is set to 0° or -180°; when the system requires constant current output, the current phase of the receiving coil is set to 90° or -90°;

[0081] S23, the current phase of the partial relay coil is set to 0°, 90°, -90° or -180°, and the current phase of the remaining relay coils is the to-be-optimized variable θ k .

[0082] Taking n = 5, realizing constant voltage output, k = 2, 4 as an example, the step S2 specifically includes the following steps:

[0083] S21, taking the transmit coil loop AC input voltage as the reference 0 phase, the transmit coil current phase is set to 0°;

[0084] S22, the current phase of the receiving coil is set to -180°, so that the system outputs constant voltage;

[0085] S23, the current phase of the second relay coil (the third stage coil) is set to -90°, the current phases of the first relay coil (the second stage coil) and the third relay coil (the fourth stage coil) are the to-be-optimized variables θ2 and θ4, and the corresponding coil currents are represented as I2 ∠ θ2, I4 ∠ θ4.

[0086] (3) Step S3

[0087] In this step S3, the phase conversion matrix T is composed of the phase conversion coefficients of the coils of each stage, and the phase conversion coefficients of the coils of each stage are valued according to the following rules:

[0088] The conversion coefficient corresponding to the coil current with a phase of 0°, 90°, -90° or -180° is 1, that is, the coil current phase is unchanged before and after conversion;

[0089] The conversion coefficient corresponding to the coil current with a phase of θ k and 0°< |θ k |<90° is cosθ k +jsinθ k , and the coil current phase after conversion is 0°;

[0090] The conversion coefficient corresponding to the coil current with a phase of θ k and 90°< |θ k |<180° is -cos(180°-θ k )+jsin(180°-θ k ), and the coil current phase after conversion is 0°.

[0091] After extracting the phase conversion matrix T, the equivalent impedance matrix and the converted current matrix of the multi-stage magnetic resonance WPT system are further obtained in the form:

[0092]

[0093]

[0094] wherein,

[0095] After the coil current phase relationship is transferred to the equivalent impedance matrix, the coil current phase of the multi-stage magnetic resonance WPT system is only 0°, 90°, -90° or -180°.

[0096] According to the above example, the phase decomposition of the 5th level coil current is specifically:

[0097] (1) The phases of the 1st, 3rd and 5th levels are respectively 0°, -90° and -180°, and the conversion coefficients corresponding to the coil currents are 1.

[0098] (2) The phase θ2 of the 2nd level coil current is unknown, which is distributed between the 1st and 3rd level coil currents, so the value range is -90°<θ2<0°, and the conversion coefficient corresponding to the 2nd level coil current is cosθ k +jsinθ k , and the phase of the converted coil current is 0°.

[0099] (3) The phase θ4 of the 4th level coil current is unknown, which is distributed between the 3rd and 5th level coil currents, so the value range is -180°<θ2<-90°, and the conversion coefficient corresponding to the 4th level coil current is -cos(180°-θ k )+jsin(180°-θ k ), and the phase of the converted coil current is 0°.

[0100] The phase conversion matrix T of the 5-level magnetic resonance WPT system is obtained:

[0101]

[0102] According to the phase conversion matrix, the system impedance matrix can be equivalent to:

[0103]

[0104] After the phase decomposition of the current, the matrix formed by the coil currents of each level is:

[0105]

[0106] (4) Step S4

[0107] In this step S4, the inverse derivation of the expression of the coil current of each level depends on a permutation matrix Z T0 , which is an n-order full rank matrix, and the relationship between the converted coil current I T and the permutation matrix is:

[0108] I T =Z T0 -1 U

[0109] The rule for constructing the permutation matrix Z T0 is:

[0110] The real part of the diagonal element of the equivalent impedance matrix Z T is taken as the permutation matrix ZT0 diagonal elements of the equivalent impedance matrix Z

[0111] For the coil loops with current phase of 0° and -180°, when the coil current phase coupled therewith is also 0° and -180°, the equivalent impedance matrix Z T the real part of the corresponding element as the permutation matrix Z T0 the element at the corresponding position; when the coil current phase coupled therewith is 90° and -90°, the equivalent impedance matrix Z T the imaginary part of the corresponding element as the permutation matrix Z T0 the element at the corresponding position;

[0112] For the coil loops with current phase of 90° and -90°, when the coil current phase coupled therewith is 0° and -180°, the equivalent impedance matrix Z T the imaginary part of the corresponding element as the permutation matrix Z T0 the element at the corresponding position; when the coil current phase coupled therewith is also 90° and -90°, the equivalent impedance matrix Z T the real part of the corresponding element as the permutation matrix Z T0 the element at the corresponding position.

[0113] According to the above example, the permutation matrix Z T0 is constructed by the following steps:

[0114] The equivalent impedance matrix Z T is extracted by the real part of the diagonal elements, as the permutation matrix Z T0 is the diagonal elements of the equivalent impedance matrix Z T0ii = real(Z Tii ), i = 1, 2, …, 5, real() represents the real part;

[0115] For the 1st, 2nd, 4th and 5th coil loops with current phase of 0° and -180°, when they are coupled with each other, the equivalent impedance matrix Z T is extracted by the real part of the corresponding elements, as the elements of the permutation matrix Z T0 ; on the contrary, when the 3rd coil coupled therewith is with current phase of -90°, the equivalent impedance matrix Z T is extracted by the imaginary part of the corresponding elements, as the elements of the permutation matrix Z T0 , imag() represents the imaginary part;

[0116] For the 3rd coil loop with current phase of -90°, all of the 1st, 2nd, 4th and 5th coils coupled therewith are with current phase of 0° and -180°, then the equivalent impedance matrix Z T is extracted by the imaginary part of the corresponding elements, as the elements of the permutation matrix Z T0 .

[0117] Therefore, the permutation matrix of the 5-stage magnetic resonance WPT system is expressed as:

[0118]

[0119] The specific form is:

[0120]

[0121] Based on the permutation matrix Z T0 The coil current of each stage can be derived, which is determined by the values of all coil resistances and mutual inductances, load, current phases θ2 and θ4, self-inductance and compensation capacitance of the 2nd stage coil, and self-inductance and compensation capacitance of the 4th stage coil.

[0122] (5) Step S5

[0123] The element item with real and imaginary parts containing compensation capacitance in the equivalent impedance matrix is always located on the diagonal line of the matrix, and is caused by the phase decomposition of the coil current of the corresponding loop, and the specific form can be expressed as:

[0124] Z kk (cosθ k +jsinθ k ), or Z kk (-cos(180°-θ k )+jsin(180°-θ k ))

[0125] According to the coil current backstepping method as described above, the compensation capacitance can be obtained according to the diagonal element characteristics of the permutation matrix Z T0 , which is the compensation capacitance of the corresponding coil loop. Thus, the to-be-solved compensation capacitance can be obtained according to the coil loop voltage equation group with current phase decomposition.

[0126] In the parameter design of the multi-stage magnetic resonance WPT system, the coil self-inductance, mutual inductance and resistance parameters are generally known, and the compensation capacitance resonated therewith is a to-be-solved quantity. In order to obtain the coil current independent of the to-be-solved compensation capacitance, the following steps are needed:

[0127] To eliminate the compensation capacitance in the coil current expression I T , the element item with real and imaginary parts containing compensation capacitance in the equivalent impedance matrix and the matrix row (coil loop) where it is located need to be determined first;

[0128] The coil loop voltage equation group of such matrix row is constructed simultaneously, and the compensation capacitance in the coil current expression I T can be solved;

[0129] Substitute the compensation capacitance into the existing coil current expression, and the purpose of eliminating the compensation capacitance parameter can be achieved. Substitute the new coil current expression I T Substitute the coil loop voltage equation, and solve the compensation capacitance of the remaining coil loop.

[0130] Based on the above example, in order to obtain the coil current independent of the compensation capacitance to be solved, the following steps need to be taken:

[0131] First, determine the element item in the equivalent impedance matrix that contains the compensation capacitance in the real and imaginary parts and the matrix row (coil loop) where it is located, i.e. the 2nd row and the 4th row;

[0132] Construct the coil loop voltage equation group of the 2nd row and the 4th row:

[0133]

[0134] The equation group contains 2 equations and 2 compensation capacitances C2 and C4 to be solved. Solving the equation group gives the analytical solution of the compensation capacitances C2 and C4, and the analytical solution of C2 and C4 is an expression about θ2 and θ4.

[0135] Substitute the solved compensation capacitances C2 and C4 of the 2nd and 4th coils into the existing coil current expression, and the purpose of eliminating the compensation capacitance parameter can be achieved. Substitute the new coil current expression I T Substitute the voltage equations of the 1st, 3rd and 5th coil loops, and solve the analytical solutions of the compensation capacitances C1, C3 and C5. Similarly, the analytical solutions of C1, C3 and C5 are expressions about θ2 and θ4.

[0136] (6) Step S6

[0137] The coil current and the compensation capacitance have a clear mathematical analytical relationship with the current phases θ2 and θ4. The coil current before conversion is obtained according to the phase conversion matrix T:

[0138] I(θ2,θ4)=T(θ2,θ4)I T

[0139] Based on the system impedance matrix, the induced coupling voltage in each level of coil loop is:

[0140] G ij (θ2,θ4)=Z ij (θ2,θ4)I j (θ2,θ4)

[0141] In the above formula, I j represents the jth level coil current, G ij represents the induced voltage of the jth level coil in the ith level coil.

[0142] Further, the power calculation formula of each stage coil loop is obtained:

[0143] P ij (θ2,θ4)=real(G ij (θ2,θ4)I i * (θ2,θ4))

[0144] where I i * is the conjugate of the i-th stage coil current, P ij represents the active power flow exchanged between the j-th stage coil and the i-th stage coil, and the power flow is an expression with respect to the optimization variables θ2 and θ4. According to the quantitative relationship between the power distribution of each stage coil loop and the current phase, the energy flow regulation of the multi-stage magnetic resonance WPT system can be achieved by configuring the current phase. The system efficiency is calculated according to the input and output power:

[0145]

[0146] where R Leq is the AC equivalent load of the receiving end, and U inv is the AC voltage output by the inverter. It can be seen that the system input, output power and transmission efficiency are also expressions with respect to the optimization variables θ2 and θ4, and by changing the values of θ2 and θ4, the system transmission power and efficiency can be regulated.

[0147] (7) Experimental simulation

[0148] In order to verify the effectiveness of the energy flow regulation method provided by the present application, the following is a numerical simulation verification of a 5-stage magnetic resonance WPT system.

[0149] The parameters of the 5-stage magnetic resonance WPT system, such as the self-inductance of the coil, mutual inductance, system operating frequency, DC input voltage, etc., are shown in Table 1.

[0150] Table 1

[0151]

[0152] It is known from the foregoing derivation that the current phase of the 2nd and 4th stage coils has a quantitative relationship with the system power and efficiency, and the configuration of the current phase is achieved by adjusting the compensation capacitors of each stage coil loop. Based on the reverse solving process of energy flow → current phase → compensation capacitor, the present application takes the current phase as an intermediate quantity, and finally finds the compensation capacitor that meets the system power and efficiency requirements, thereby realizing the energy flow regulation of the system. Therefore, under different current phase configurations, the compensation capacitors of each stage coil, the input and output power, and the power flow between each stage coil can be calculated in sequence according to the method of the present application.

[0153] In contrast, firstly, according to the traditional harmonic matching method, namely C... i =1 / ω 2 L i The calculated compensation capacitors for each coil stage are C1 = 3.73e-09, C2 = 3.67e-09, C3 = 3.68e-9, C4 = 3.75e-09, and C5 = 3.71e-09. The corresponding coil currents are I1 = 0.7888 + 0.1588i, I2 = 0.2135 - 0.9956i, I3 = -0.6907 - 0.4150i, I4 = -0.5671 + 0.7941i, and I5 = 0.5392 + 0.6269i. Their phase relationships are as follows: Figure 3 As shown. At this time, the system's input power is 21.3W, the output power is 20.5W, the AC / AC (alternating current to alternating current) transmission efficiency is 96.2%, and the power flow between each stage of the coil is as follows. Figure 4 As shown. From Figure 4 As can be seen, according to the traditional matching method, both the 4th and 5th stage coils feed active power back to the 1st stage coil, and the 5th stage coil also feeds active power back to the 2nd stage coil, resulting in a reduction in system output power. Furthermore, by changing the load value, the system output voltage curves under load variations of 20-100Ω are obtained, as shown below. Figure 5 As shown, the system cannot achieve zero-phase input and constant voltage output.

[0154] To configure the current phases of the first to fifth stage coils as θ1 = 0°, θ2 = -30°, θ3 = -90°, θ4 = -150°, and θ5 = -180° respectively, based on the system parameter values ​​in Table 1, the calculated compensation capacitors for each stage coil are C1 = 3.19e-09, C2 = 3.52e-09, C3 = 7.91e-10, C4 = 3.62e-09, and C5 = 3.11e-09. The coil currents for each stage are I1 = 1.0172 + 0.0000i, I2 = 1.5473 - 0.8934i, I3 = 0.0000 - 0.0615i, I4 = -1.5913 - 0.9188i, and I5 = -0.9270 - 0.0000i. Their phase relationships are as follows: Figure 6 As shown, the system achieves zero-phase input. At this point, the system's input power is 27.5W, output power is 25.8W, and AC / AC transmission efficiency is 93.8%. The power flow between each stage of the coil is as follows: Figure 7 As shown. From Figure 7 It can be seen that under this current phase configuration, the active power of each stage of the coil is always transferred from the preceding stage to the following stage, and there is no active power backfeed. Furthermore, by changing the load value, the system output voltage curves for loads varying from 20-100Ω are obtained, as shown below. Figure 8It can be seen that the output voltage of the system varies in the range of 1.7V, which indicates that the system has constant voltage output characteristics.

[0155] To configure the current phase of the first to fifth stage coils as θ1=0°, θ2=-45°, θ3=-90°, θ4=-135°, θ5=-180°, according to the system parameter values in Table 1, the calculated compensation capacitances of the coils are C1=3.42e-09, C2=3.32e-09, C3=2.57e-9, C4=3.41e-09, C5=3.38e-09, and the current phases of the coils are I1=0.9800+0.0000i, I2=0.7964-0.7964i, I3=0.0000-0.4659i, I4=-0.8186-0.8186i, I5=-0.9227+0.0000i, as shown in Figure 9 It can be seen that the system achieves zero phase input. At this time, the input power of the system is 26.5W, the output power is 25.5W, the AC / AC transmission efficiency is 96.5%, and the power flow among the coils is as shown in Figure 10 It can be seen that the system achieves zero phase input. At this time, the input power of the system is 26.5W, the output power is 25.5W, the AC / AC transmission efficiency is 96.5%, and the power flow among the coils is as shown in Figure 10 It can be seen that in this current phase configuration, the active power of each stage coil is always transmitted from the previous stage to the next stage, and there is no active power return. In addition, by changing the load value, the system output voltage curve under the load change of 20-100Ω is obtained, as shown in Figure 11 It can be seen that the output voltage of the system varies in the range of 1.7V, which indicates that the system has constant voltage output characteristics.

[0156] To configure the current phase of the first to fifth stage coils as θ1=0°, θ2=-60°, θ3=-90°, θ4=-120°, θ5=-180°, according to the system parameter values in Table 1, the calculated compensation capacitances of the coils are C1=3.59e-09, C2=2.91e-09, C3=3.24e-9, C4=2.99e-09, C5=3.56e-09, and the current phases of the coils are I1=0.9540+0.0000i, I2=0.3643-0.6310i, I3=0.0000-1.1558i, I4=-0.3717-0.6438i, I5=-0.9117+0.0000i, as shown in Figure 12 It can be seen that the system achieves zero phase input. At this time, the input power of the system is 26.5W, the output power is 25.5W, the AC / AC transmission efficiency is 96.5%, and the power flow among the coils is as shown in Figure 13 It can be seen that the system achieves zero phase input. At this time, the input power of the system is 26.5W, the output power is 25.5W, the AC / AC transmission efficiency is 96.5%, and the power flow among the coils is as shown in Figure 13It can be seen that in this current phase configuration, the active power of each stage coil is always transmitted from the previous stage to the next stage, and there is no active reverse sending. In addition, by changing the load value, the system output voltage curve under the condition that the load changes from 20 to 100Ω is obtained, as shown in Figure 14 It can be seen that the output voltage of the system changes in the range of 0.5V, indicating that the system has constant voltage output characteristics.

[0157] By comparing the coil current and energy flow distribution results of the above three phase configurations, it can be seen that as the phase difference between I1 and I2, I4 and I5 increases, the current amplitude of I2 and I4 gradually decreases, and the amplitude of I3 gradually increases; the active power transmitted from the first stage coil to the second stage coil gradually decreases, the active power transmitted from the first stage coil to the third stage coil gradually increases, and the active power transmitted from the first stage coil to the fourth and fifth stage coils gradually decreases; the active power transmitted from the second stage coil to the third stage coil gradually increases, the active power transmitted from the second stage coil to the fourth and fifth stage coils gradually decreases; the active power transmitted from the third stage coil to the fourth and fifth stage coils gradually increases; the active power transmitted from the fourth stage coil to the fifth stage coil gradually decreases. Therefore, by configuring the phase of the current of each stage coil, not only zero phase angle input and constant voltage output are achieved, but also the energy flow size transmitted by each stage coil can be effectively regulated, and the transmission efficiency and transmission power of the system can be adjusted, as shown in Figure 15 and Figure 16 The maximum AC / AC transmission efficiency of the system can reach 97.3%, and the maximum transmission power can reach 25.8W.

[0158] In summary, the multi-stage magnetic resonance WPT system energy flow regulation method based on current phase configuration provided by the embodiment of the application can transfer the current phase relationship to the equivalent impedance matrix by presetting the phase of the current of each stage coil, based on the equivalent impedance substitution matrix constructed to meet the voltage-current relationship of the multi-stage system, the expression of the current of each stage coil is inversely deduced, and the mathematical relationship between the compensation capacitors of each stage coil and the to-be-optimized variables is also analyzed. Not only does the system remain in a resonant state, but also active reverse sending is avoided, zero phase angle input at the transmitting end and constant voltage output characteristics at the output end are achieved, and the transmission power and transmission efficiency of the system are effectively improved.

[0159] The above embodiments are the preferred embodiments of the application, but the embodiments of the application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations and simplifications made without departing from the spirit and principles of the application shall be equivalent replacement methods, and all shall be included in the protection scope of the application.

Claims

1. A method for energy flow control in a multi-stage magnetic resonant waveguide (WPT) system based on current phase configuration, wherein the multi-stage WPT system comprises a transmitting coil circuit, n-2 relay coil circuits, and a receiving coil circuit arranged sequentially, characterized in that, The energy flow regulation method includes the following steps: S1. Establish the circuit impedance model of the multi-stage magnetic resonant WPT system: U = ZI, where U and I represent the voltage matrix and current matrix composed of the voltage and current of each stage coil, respectively, and Z is the impedance matrix describing the impedance relationship between the n-stage magnetic resonant coils. S2. Determine the phase of some relay coils as variables to be optimized, and preset the current phase of the remaining coils as constants; S3. Perform phase decomposition on the current of each stage of the coil to obtain the corresponding phase transformation matrix T, and obtain the equivalent impedance matrix Z based on the phase transformation matrix T. T =ZT and the transformed current matrix I T =T -1 I; S4, based on I T Extract Z from each current phase in the data. T The permutation matrix Z is constructed from the real or imaginary parts of the elements at the corresponding positions. T0 Based on Z T0 The expressions for the currents of each coil stage are obtained. ; S5. Construct the voltage equation for the n-stage coil circuit and solve for Z. T The coil circuit voltage equation corresponding to the element whose real and imaginary parts both contain the compensation capacitor is obtained, and the corresponding analytical solution for the compensation capacitor is substituted into... The new coil current expression is obtained. Substitute the new coil current expression into the voltage equations of the remaining coil circuits to solve for the analytical solutions of the remaining compensation capacitors. S6. Based on the currently determined information, derive the relationship between the power of each coil circuit, the system transmission efficiency, and the variable to be optimized, and based on this relationship, adjust the power of each coil circuit and the system efficiency by configuring the variable to be optimized.

2. The energy flow control method for a multi-stage magnetic resonant WPT system based on current phase configuration according to claim 1, characterized in that, Step S2 specifically includes the following steps: S21. With the AC input voltage of the transmitting coil circuit as the reference phase 0, the phase of the transmitting coil current is set to 0. o ; S22. When the system requires constant voltage output, the current phase of the receiving coil is set to 0. o or -180 o When the system requires constant current output, the current phase of the receiving coil is set to 90°. o or -90 o ; S23. Set the current phase of some relay coils to 0. o 90 o -90 o or -180 o The current phase of the remaining relay coils is the variable to be optimized, θ. k .

3. The energy flow control method for a multi-stage magnetic resonant WPT system based on current phase configuration according to claim 2, characterized in that, In step S3, the phase conversion matrix T is composed of the phase conversion coefficients of each stage of the coil, and the phase conversion coefficients of each stage of the coil are selected according to the following rules: Phase 0 o 90 o -90 o -180 o The conversion factor corresponding to the coil current is 1, meaning that the phase of the coil current remains unchanged before and after the conversion; Phase θ k And 0 o <|θ k |<90 o The conversion factor corresponding to the coil current is cosθ k +jsinθ k After conversion, the coil current phase is 0. o ; Phase θ k And 90 o <|θ k |<180 o The conversion factor corresponding to the coil current is -cos(180). o -θ k ) + jsin(180 o -θ k After conversion, the coil current phase is 0. o .

4. The energy flow control method for a multi-stage magnetic resonant WPT system based on current phase configuration according to claim 3, characterized in that, In step S4, the permutation matrix Z is constructed. T0 The rules are: Extracting the equivalent impedance matrix Z T The real part of the diagonal elements is used as the permutation matrix Z. T0 The diagonal elements; For current phase 0 o and -180 o The coil circuit, when the phase of the coil current coupled with it is also 0. o and -180 o At that time, extract the equivalent impedance matrix Z. T The real part of the corresponding element is used as the permutation matrix Z. T0 The element at the corresponding position; when the phase of the coil current coupled to it is 90°. o and -90 o At that time, extract the equivalent impedance matrix Z. T The imaginary part of the corresponding elements is used as the permutation matrix Z. T0 The element at the corresponding position; For a current phase of 90° o and -90 o The coil circuit, when the phase of the coil current coupled to it is 0 o and -180 o At that time, extract the equivalent impedance matrix Z. T The imaginary part of the corresponding elements is used as the permutation matrix Z. T0 The element at the corresponding position; when the phase of the coil current coupled to it is also 90°. o and -90 o At that time, extract the equivalent impedance matrix Z. T The real part of the corresponding element is used as the permutation matrix Z. T0 The element at the corresponding position.

5. The energy flow control method for a multi-stage magnetic resonant WPT system based on current phase configuration according to claim 4, characterized in that, In step S6, based on the currently determined information, the relationship between the power of each coil circuit and the variable to be optimized is derived, specifically: Based on the phase transformation matrix T and the new coil current expression I T Restore the coil current matrix before conversion ; Multiply the column elements of the impedance matrix Z by the corresponding row elements of the current matrix I, and then multiply each by the conjugate of the current in each coil loop to obtain the power expression for the coupling between each coil loop.

6. A method for energy flow control of a multi-stage magnetic resonant WPT system based on current phase configuration according to any one of claims 1 to 5, characterized in that: The compensation capacitors of each stage of the coil circuit are connected in series with the coil of that stage.

7. The energy flow control method for a multi-stage magnetic resonant WPT system based on current phase configuration according to claim 6, characterized in that: In step S1, the voltage matrix U is a column vector composed of the voltages of each coil stage, and the current matrix I is a column vector composed of the currents of each coil stage.

8. The energy flow control method for a multi-stage magnetic resonant WPT system based on current phase configuration according to claim 7, characterized in that, In step S1, the impedance matrix Z is an n×n square matrix, and the element Z in the i-th row and j-th column is... ij The rules for selecting values ​​are as follows: When i = j ≠ n, Z ij equal ; When i = j = n, Z ij equal ; When i≠j, Z ij equal ; in, I represents the operating angular frequency of the system. i R i L i C i The following figures represent the current, internal resistance, inductance, and compensation capacitor of each coil stage, respectively. M ij R represents the mutual inductance between the i-th coil and the j-th coil. Leq Let i,j = 1,2,…,n, represent the AC equivalent load at the receiving end.

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