Load-stabilized power control method for omnidirectional wireless power transmission system

Abstract

The load stabilization power control method for an omnidirectional wireless power transmission system disclosed in the present invention is specifically as follows: S1, constructing an objective function and constraints; S2, obtaining the maximum value of the DC side input power according to the sampled DC voltage and DC current; S3, obtaining the minimum value of the DC side input power according to the sampled DC voltage and DC current; S4, calculating the maximum power received by the load coil according to the maximum value of the DC side input power and the minimum value of the DC side input power determined by S2 and 3, and further calculating the square sum of the mutual inductance at the position of the load coil; S5, calculating the magnitude of the synthetic current vector amplitude when the required load power is required. This method can ensure that the load can receive a stable and controllable power flow at any position near the omnidirectional WPT system, avoiding the transmission of power to areas without loads, thereby reducing unnecessary power transmission and improving the transmission efficiency of the system.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless power transmission, and in particular relates to a load stabilization power control method for an omnidirectional wireless power transmission system. Background Art

[0002] Wireless Power Transfer (WPT) technology is a new charging technology with the advantages of easy operation, high safety and adaptability to relatively harsh conditions. In recent years, WPT technology has developed rapidly and has been gradually applied to consumer electronic products such as mobile phones, smart watches, tablets and laptops. However, for the wireless charging of these consumer electronic products, the traditional "stick-on-plate" charging method is adopted. When using, the charging device must be placed close to the charging panel, so that the load coil placed in the device is strictly aligned with the transmitting coil on the charging board, which greatly limits its convenience and user satisfaction.

[0003] In order to break these limitations, people have gradually explored and studied omnidirectional WPT technology, which is an improvement on the "stick-on" WPT technology based on unidirectional energy flow. It can obtain a higher degree of freedom in the wireless charging process and reduce the position sensitivity of the charging device. Among them, the omnidirectional WPT system based on the three-phase orthogonal transmitting coil has the characteristics of simple structure and easy control, and is being widely studied. The system adopts the excitation current control method, which can perform wireless power transmission for the load coil at any position within a certain range outside the transmitting coil. However, for the omnidirectional WPT system, as the position of the charging device changes in space, the offset between the transmitting coil and the load coil will inevitably occur. This offset will cause the mutual inductance between the coils to change, directly affecting the transmission power and efficiency of the system, and thus cannot provide stable and efficient electric energy for the charging device. For this reason, an output control method of the omnidirectional WPT system is needed to meet the stable power control of the system when the position of the charging device is not fixed, and provide stable and efficient electric energy for the charging device within a certain range of space, so as to improve the flexibility and reliability of the application of the wireless power transmission system. Summary of the invention

[0004] The purpose of the present invention is to provide a load stabilization power control method for an omnidirectional wireless power transmission system, which can ensure that the load can receive a stable and controllable power flow at any position near the omnidirectional WPT system, avoiding power transmission to areas without loads, thereby reducing unnecessary power transmission and improving the transmission efficiency of the system.

[0005] The technical solution adopted by the present invention is a load stabilization power control method for an omnidirectional wireless power transmission system, and the specific steps are as follows:

[0006] Step 1: Construct the objective function and constraints to determine the direction of the load coil;

[0007] Step 2: Adjust the direction of the synthetic current vector and perform current amplitude control. After the current is stable, obtain the maximum value of the DC side input power according to the sampled DC voltage and DC current.

[0008] Step 3: adjust the direction of the synthetic current vector again, perform current amplitude control, and after the current stabilizes, obtain the minimum value of the DC side input power according to the sampled DC voltage and DC current;

[0009] Step 4: Calculate the maximum power received by the load coil according to the maximum DC side input power and the minimum DC side input power determined in steps 2 and 3, and further calculate the square sum of the mutual inductance at the position of the load coil;

[0010] Step 5: Calculate the magnitude of the synthetic current vector amplitude when the load power is required according to the square sum of the mutual inductance at the load coil position obtained in step 4, adjust the direction of the synthetic current vector, and perform current amplitude control, so as to finally realize directional and stable power control of the load and ensure the maximum efficiency transmission at any position of the load coil.

[0011] The present invention is also characterized in that

[0012] Step 1 is as follows:

[0013] Step 1: Set the synthetic current vector amplitude I to a certain value I = I base The direction of the synthetic current vector is the elevation angle θ and the azimuth angle in the spherical coordinate system. According to the load coil direction detection principle: DC side input power P in The direction of the synthetic current vector corresponding to the maximum value is θ and That is the direction of the load coil θ * and Select the DC side input power P in The maximum value of the synthetic current vector θ and To optimize the variables, construct the objective function and constraints as follows:

[0014]

[0015] Execute the extreme value search algorithm to obtain the maximum point of the objective function At this time, θ * and Corresponding to the direction of the load coil in the spherical coordinate system.

[0016] Step 2 is as follows:

[0017] Keep the resultant current vector magnitude I = I base, adjust the direction of the synthetic current vector θ=θ * and As a result, the current amplitudes flowing into the three-phase transmitting coil for the first time are:

[0018]

[0019] Execute current amplitude control. After the current stabilizes, obtain the DC side input power according to the sampled DC voltage and DC current. At this time, the DC side input power P in Reaching the maximum value is expressed as:

[0020]

[0021] Among them, P coil is the ohmic loss of the three-phase transmitting coil; P inv is the loss of the three-phase inverter; ω is the system operating angular frequency; I base is the given synthetic current vector amplitude; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X4 is the equivalent reactance of the load coil; M 14 、M 24 、M 34 Respectively represent the mutual inductance of each phase transmitting coil and load coil.

[0022] Step 3 is as follows:

[0023] Keep the resultant current vector magnitude I = I base , adjust the direction of the synthetic current vector and As a result, the current amplitudes flowing into the three-phase transmitting coil for the second time are:

[0024]

[0025] Execute current amplitude control. After the current stabilizes, obtain the DC side input power according to the sampled DC voltage and DC current. At this time, the DC side input power P in Reaching the minimum is expressed as:

[0026] P in_min =P coil +P inv (twenty two)

[0027] Among them, P coil is the ohmic loss of the three-phase transmitting coil, P inv is the loss of the three-phase inverter.

[0028] Step 4 is as follows:

[0029] The maximum DC input power P determined by steps 2 and 3 in-maxThe minimum DC input power P in-min , calculate the maximum power P received by the load coil out-max for:

[0030] P out_max =P in_max -P in_min (twenty three)

[0031] According to the maximum power P received by the load coil out-max expression:

[0032]

[0033] Where, ω is the system operating angular frequency; I base is the given synthetic current vector amplitude; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X4 is the equivalent reactance of the load coil; M 14 、M 24 、M 34 Respectively represent the mutual inductance of each phase transmitting coil and load coil.

[0034] Let the square sum of the mutual inductance of each phase transmitting coil and load coil be The size of the square sum M of the mutual inductance of each phase transmitting coil and the load coil at this position is further calculated, which is calculated as follows:

[0035]

[0036] Step 5 is as follows:

[0037] According to the square sum of mutual inductance M at the load coil position obtained in step 4, calculate the required load power P load The composite current vector amplitude I obj The size of is calculated as follows:

[0038]

[0039] Among them, P load is the power required by the load; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X4 is the equivalent reactance of the load coil; M is the square sum of the mutual inductance of each phase transmitting coil and the load coil at this position;

[0040] Adjust the direction of the synthetic current vector θ=θ * and As a result, the current amplitudes that finally flow into the three-phase transmitting coil are:

[0041]

[0042] By performing current amplitude control, directional and stable power control of the load can be finally achieved, ensuring the maximum efficiency transmission at any position of the load coil.

[0043] The beneficial effects of the present invention are:

[0044] The method of the present invention transforms the nonlinear power control problem of the omnidirectional WPT system into a linear directional power control problem. Based on the detection of the direction of the load coil, the mutual inductance information is estimated according to the DC side parameters to obtain the real-time mutual inductance information of the transmitting coil and the load coil. According to the estimated mutual inductance information and the output power equation, a three-phase power supply coordinated control output power strategy is proposed, which can solve the output power fluctuation problem caused by the position movement of the load coil in the omnidirectional WPT system. The control strategy does not require wireless communication and additional detection circuits, and has the advantages of simple structure and convenient control. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a structural diagram of the omnidirectional WPT system based on a three-phase orthogonal transmitting coil of the present invention;

[0046] Figure 2 This is the circuit equivalent diagram of the omnidirectional WPT system based on the three-phase LCC-S compensation network of the present invention;

[0047] Figure 3 It is a flow chart of the load stabilization power control method for an omnidirectional wireless power transmission system of the present invention;

[0048] Figure 4 It is a waveform diagram of the maximum input power of the DC side of the load coil at position 1 in the simulation experiment of the present invention;

[0049] Figure 5 It is a waveform diagram of the minimum input power on the DC side of the load coil at position 1 in the simulation experiment of the present invention;

[0050] Figure 6 The maximum input power waveform diagram of the DC side when the load coil of the present invention is moved to position 2;

[0051] Figure 7 This is a waveform diagram of the minimum DC input power when the load coil of the present invention is moved to position 2;

[0052] Figure 8 The simulated waveform of each phase transmitting coil current modulated by the load coil at position 1 of the present invention; Fig. 9 yes Figure 8 A partial enlarged view

[0053] Fig.10 The load power simulation waveform of the load coil of the present invention at position 1;

[0054] Fig.11 The simulated waveform of each phase transmitting coil current modulated when the load coil of the present invention moves to position 2;

[0055] Fig.12 yes Fig.11 A partial enlarged view of point B in the middle;

[0056] Fig.13 The load power simulation waveform of the load coil of the present invention is moved to position 2. DETAILED DESCRIPTION

[0057] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] The present invention provides a load stabilization power control method for an omnidirectional wireless power transmission system, which is aimed at an omnidirectional WPT system based on a three-phase orthogonal transmitting coil and using a three-phase LCC-S compensation network. The principle is as follows: Figure 1 The structure diagram of the omnidirectional WPT system coil consists of three orthogonal transmitting coils and one loading coil. Among them, the YOZ plane represents the transmitting coil 1; the XOZ plane represents the transmitting coil 2; the XOY plane represents the transmitting coil 3; the elevation angle θ and azimuth angle θ at the center of the transmitting coil are The represents the load coil.

[0059] Assuming that the currents flowing into the three transmitting coils are I1, I2, and I3 respectively, according to the Biot-Savart law, the magnetic flux density at the center of each transmitting coil is is calculated as:

[0060]

[0061] Where N P is the number of turns of the coil; μ0 is the magnetic permeability of vacuum; is the unit vector in the three-dimensional coordinate system; R is the radius of the coil. The magnetic flux density at the center of each transmitting coil is The direction is always perpendicular to the plane of each transmitting coil, and the magnitude is always proportional to the current flowing into each transmitting coil.

[0062] Therefore, if Figure 1 As shown, the synthetic magnetic flux density at the center of the three-phase transmitting coil is Equal to the magnetic flux density at the center of each coil The vector sum of :

[0063]

[0064] It can be concluded that the synthetic magnetic flux density of the three-phase orthogonal transmitting coil is With the resultant current vector The direction is the same as that of the excitation current amplitude modulation method. Therefore, the magnetic flux density synthesized based on the excitation current amplitude modulation method is Can be oriented in any direction without physically moving the transmitting coil.

[0065] In order to achieve efficient power transmission, the present invention adopts an excitation current amplitude modulation method, where the current phase and frequency flowing into each transmitting coil are the same, but the amplitude is different. Directionally pointing Figure 1 The elevation angle θ and azimuth angle shown In the direction of, the current amplitudes I1, I2 and I3 of each transmitting coil should satisfy the corresponding relationship of the three-dimensional coordinates:

[0066]

[0067] Where I is the magnitude of the resultant current vector, θ and is the direction of the composite current vector in three-dimensional coordinates, where θ is the composite current vector The positive angle with the Z axis, It is the angle between the projection of the composite current vector I on the XOY plane and the positive direction of the X-axis.

[0068] Figure 2 The equivalent schematic diagram of the omnidirectional WPT system based on the three-phase LCC-S compensation network. dc is the DC voltage source of the system, I dc is the DC input current; Respectively represent the port output voltage of each phase inverter; Respectively represent the port output current of each phase inverter; Respectively represent the current flowing into each phase transmitting coil; Indicates the current flowing into the load coil; Q1~Q 12 are the power switches of three groups of single-phase bridge inverters; L1, L2, L3 are the inductances of the transmitting coils of each phase respectively; L f1 , C f1 , C1 constitute the LCC compensation network of the transmitting coil 1, L f2 , C f2 , C2 constitute the LCC compensation network of the transmitting coil 2, L f3 , C f3 , C3 constitute the LCC compensation network of the transmitting coil 3; C4 is the compensation capacitor of the load coil; R1, R2, R3 are the parasitic resistances of the transmitting coils of each phase respectively; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; M 14 、M 24 、M 34Respectively represent the mutual inductance of each phase transmitting coil and load coil; M 12 、M 23 、M 13 Represents the mutual inductance between the transmitting coils of each phase.

[0069] Since the three-phase transmitting coils are orthogonal to each other, the mutual inductance M between the transmitting coils of each phase is 12 、M 23 、M 13 are all 0. According to Kirchhoff's voltage law, the equivalent circuit relationship of the omnidirectional WPT system based on the three-phase LCC-S compensation network can be listed as follows:

[0070]

[0071] in:

[0072]

[0073] ω is the operating angular frequency, X1, X2, X3 are the equivalent reactances of the transmitting coils of each phase, and X4 is the equivalent reactance of the load coil.

[0074] According to formula (4), the current vector flowing into the load coil can be calculated for

[0075]

[0076] The amplitude of the current flowing into the load coil I4 is

[0077]

[0078] The load receiving power P can be calculated by formula (7): load for

[0079]

[0080] When the system parameters are determined, the load receiving power is M 14 、M 24 、M 34 and I, θ, Decision. 14 、M 24 、M 34 Depending on the relative positions of the transmitting coil and the loading coil, I, θ, It is determined by the current amplitudes I1, I2, and I3 flowing into the transmitting coils of each phase.

[0081] In order to eliminate wireless communication from the transmitting coil to the load coil, the relationship between the load coil power and the system input power is established. The system input power is also the DC side input power, which is determined by the inverter power loss P inv, the loss of compensation network P com , Ohmic loss P of the transmitting coil coil And the load coil receives power P out It consists of four parts.

[0082] Inverter loss P inv Including the conduction loss and switching loss of the power device, the inverter loss P can be calculated by formula (9): inv for

[0083]

[0084] To simplify the calculation, assume that the parameters of each transmitting coil are equal, and the resistance of the three transmitting coils is equal to R1 = R2 = R3 = R, and calculate the ohmic loss P of the transmitting coil coil for

[0085] P coil =P coil1 +P coil2 +P coil3 =I1 2 R+I2 2 R+I3 2 R=I 2 R (10)

[0086] Under resonant conditions, according to the law of conservation of energy, the power from input to output of the compensation network will not decay, that is, the loss of the compensation network P com is 0.

[0087] The power of the load coil is P out Including the received power of the load and the ohmic loss of the load coil, it is expressed as:

[0088]

[0089] Combining equations (9), (10) and (11), we can calculate the input power P on the DC side: in for

[0090]

[0091] When the magnitude of the composite current vector is determined to be I = I base When the inverter loss P inv , Ohmic loss P of the transmitting coil coil Both can be regarded as constants. Therefore, in the absence of communication feedback, the load coil receiving power information can be indirectly obtained by detecting the DC source input power information.

[0092] The transmission efficiency η can be calculated as

[0093]

[0094] Introducing variables K and γ, the load receiving power P load , DC source input power P in , the expression of transmission efficiency η is rewritten as

[0095]

[0096] In the formula, K and γ are expressed by formula (15):

[0097]

[0098] According to the analysis of formula (14), when the system is determined, the load receives power P load , DC side input power P in , the transmission efficiency η is related to the relative position M of each transmitting coil and loading coil 14 、M 24 、M 34 and the magnitude and direction of the resultant current vector I, θ, Multiple variables are involved and nonlinear.

[0099] When the direction of the synthetic current vector satisfies equation (16)

[0100]

[0101] Load receiving power P load , DC side input power P in , the transmission efficiency η can be expressed as:

[0102]

[0103] It can be obtained that the condition of equation (16) is that the direction of the synthetic current vector θ and The physical direction of the load coil is θ * and The condition satisfied when the composite current vector direction meets this condition is the condition satisfied when the load receives power P. load , DC side input power P in The transmission efficiency η is only related to the magnitude I of the synthetic current vector and the sum of the squares of the mutual inductance Therefore, by controlling the direction of the synthetic current vector to point to the direction of the load coil, the nonlinear power control problem in the omnidirectional WPT system can be converted into a linear directional power control problem. According to the load coil direction detection principle: when the synthetic current vector amplitude I = I base When the DC side input power P in The maximum load receiving power P can be achieved simultaneously loadThe maximum and transmission efficiency η are maximum, thus, according to the DC side input power P in The direction of the synthetic current vector corresponding to the maximum value is θ and Determine the direction of the load coil θ * and

[0104] Based on the above analysis, the system performs real-time detection of the input power on the DC side during normal operation. If the input power P on the DC side is detected in If there is a change, it means that the load receives power P load There is a change, that is, the position of the load coil has changed, and stable power control of the load needs to be performed.

[0105] The specific steps of a load stabilization power control method for an omnidirectional wireless power transmission system of the present invention are as follows: Figure 3 As shown:

[0106] Step 1: Construct the objective function and constraints to determine the direction of the load coil;

[0107] Step 1 is as follows:

[0108] Step 1: Set the synthetic current vector amplitude I to a certain value I = I base The direction of the synthetic current vector is the elevation angle θ and the azimuth angle in the spherical coordinate system. According to the load coil direction detection principle: DC side input power P in The direction of the synthetic current vector corresponding to the maximum value is θ and That is the direction of the load coil θ * and Select the DC side input power P in The maximum value of the synthetic current vector θ and To optimize the variables, construct the objective function and constraints as follows:

[0109]

[0110] Execute the extreme value search algorithm to obtain the maximum point of the objective function At this time, θ * and Corresponding to the direction of the load coil in the spherical coordinate system.

[0111] Step 2: Adjust the direction of the synthetic current vector and perform current amplitude control. After the current is stable, obtain the maximum value of the DC side input power according to the sampled DC voltage and DC current.

[0112] Step 2 is as follows:

[0113] Keep the resultant current vector magnitude I = Ibase , adjust the direction of the synthetic current vector θ=θ * and As a result, the current amplitudes flowing into the three-phase transmitting coil for the first time are:

[0114]

[0115] Execute current amplitude control. After the current stabilizes, obtain the DC side input power according to the sampled DC voltage and DC current. At this time, the DC side input power P in Reaching the maximum value is expressed as:

[0116]

[0117] Among them, P coil is the ohmic loss of the three-phase transmitting coil; P inv is the loss of the three-phase inverter; ω is the system operating angular frequency; I base is the given synthetic current vector amplitude; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X4 is the equivalent reactance of the load coil; M 14 、M 24 、M 34 Respectively represent the mutual inductance of each phase transmitting coil and load coil.

[0118] Step 3: adjust the direction of the synthetic current vector again, perform current amplitude control, and after the current stabilizes, obtain the minimum value of the DC side input power according to the sampled DC voltage and DC current;

[0119] Step 3 is as follows:

[0120] Keep the resultant current vector magnitude I = I base , adjust the direction of the synthetic current vector and As a result, the current amplitudes flowing into the three-phase transmitting coil for the second time are:

[0121]

[0122] Execute current amplitude control. After the current stabilizes, obtain the DC side input power according to the sampled DC voltage and DC current. At this time, the DC side input power P in Reaching the minimum is expressed as:

[0123] P in_min =P coil +P inv (twenty two)

[0124] Among them, P coil is the ohmic loss of the three-phase transmitting coil, P invis the loss of the three-phase inverter.

[0125] Step 4: Calculate the maximum power received by the load coil according to the maximum DC side input power and the minimum DC side input power determined in steps 2 and 3, and further calculate the square sum of the mutual inductance at the position of the load coil;

[0126] Step 4 is as follows:

[0127] The maximum DC input power P determined by steps 2 and 3 in-max The minimum DC input power P in-min , calculate the maximum power P received by the load coil out-max for:

[0128] P out_max =P in_max -P in_min (twenty three)

[0129] According to the maximum power P received by the load coil out-max expression:

[0130]

[0131] Where, ω is the system operating angular frequency; I base is the given synthetic current vector amplitude; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X4 is the equivalent reactance of the load coil; M 14 、M 24 、M 34 Respectively represent the mutual inductance of each phase transmitting coil and load coil.

[0132] Let the square sum of the mutual inductance of each phase transmitting coil and load coil be The size of the square sum M of the mutual inductance of each phase transmitting coil and the load coil at this position is further calculated, which is calculated as follows:

[0133]

[0134] Step 5: Calculate the magnitude of the synthetic current vector amplitude when the load power is required according to the square sum of the mutual inductance at the load coil position obtained in step 4, adjust the direction of the synthetic current vector, and perform current amplitude control, so as to finally realize directional and stable power control of the load and ensure the maximum efficiency transmission at any position of the load coil.

[0135] Step 5 is as follows:

[0136] According to the square sum of mutual inductance M at the load coil position obtained in step 4, calculate the required load power P load The composite current vector amplitude I objThe size of is calculated as follows:

[0137]

[0138] Among them, P load is the power required by the load; R4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X4 is the equivalent reactance of the load coil; M is the square sum of the mutual inductance of each phase transmitting coil and the load coil at this position.

[0139] Adjust the direction of the synthetic current vector θ=θ * and As a result, the current amplitudes that finally flow into the three-phase transmitting coil are:

[0140]

[0141] By performing current amplitude control, directional and stable power control of the load can be finally achieved, ensuring the maximum efficiency transmission at any position of the load coil.

[0142] The following is a simulation verification of the above invention content:

[0143] The power control concept of the omnidirectional WPT system is simulated and verified in MATLAB. The simulation conditions are that the direction of the load coil is known, and the mutual inductance of each transmitting coil and receiving coil has been simulated and calculated to ensure correctness, and the system model is built. Table 1 shows the specific simulation parameters.

[0144] Table 1 Specific simulation parameters

[0145]

[0146] When the receiving coil is located at position 1 (0.6m, 45°, 45°), the mutual inductance estimation process is as follows:

[0147] As described in step 2, when the composite current vector magnitude I is given base =2.7A, direction θ = 45° and When the current amplitude control is executed, the maximum input power waveform of the DC side under steady-state conditions is as follows: Figure 4 As shown, the maximum input power P on the DC side in_max =85.40W. As described in step 3, maintain the resultant current vector magnitude I base =2.7A, direction θ = 135° and When the current amplitude control is performed, the minimum input power waveform of the DC side under steady-state conditions is as follows: Figure 5 As shown, the minimum input power P on the DC side in_min =25.80W.

[0148] The estimated mutual inductance information M at position 1 is:

[0149]

[0150] Actual mutual inductance information M = 62.3403 × 10 -12 , relative error accuracy E r for:

[0151]

[0152] Similarly, when the load coil moves to position 2 (0.7 cm, 30°, 60°), the synthetic current vector amplitude I is given base =4.4A, direction θ = 30° and When the current amplitude control is executed, the maximum input power waveform of the DC side under steady-state conditions is as follows: Figure 6 As shown, the maximum input power P on the DC side in_max =90.2W. As described in step 3, maintain the resultant current vector magnitude I base =4.4A, direction θ = 120° and When the current amplitude control is performed, the minimum input power waveform of the DC side under steady-state conditions is as follows: Figure 7 As shown, the minimum input power P on the DC side in_min =32.6W.

[0153] The estimated mutual inductance information M at position 2 is:

[0154]

[0155] Actual mutual inductance information M = 23.31 × 10 -12 , relative error accuracy E r for:

[0156]

[0157] To this end, the feasibility of the proposed front-end mutual inductance information estimation method based on synthetic current vector direction control can be verified.

[0158] Finally, based on the estimated mutual inductance information, the power control is simulated. In order to make the load receive 50W power, when the load coil is at position 1, the synthetic current vector amplitude I calculated according to formula (26) is obj It should reach 2.7A, and the final current amplitude flowing into each phase transmitting coil should be

[0159]

[0160] The reference values ​​of the transmitting coil current of each phase are changed to 1.4A, 1.4A, and 1.9A respectively. The waveforms of the transmitting coil current of each phase obtained by simulation are as follows Figure 8-9 As shown in the figure, the current of each phase transmitting coil follows the given 1.4A, 1.4A, and 1.9A. At this time, the load power waveform is as follows Fig.10 As shown, the load power is close to 50W.

[0161] When the load coil moves from position 1 to position 2, the power of the load coil moved to position 2 is controlled according to the estimated mutual inductance information at position 2. In order to ensure that the load still receives 50W power, the synthetic current vector amplitude I obj The calculation should reach 4.4A, and the final current amplitude flowing into each phase transmitting coil should be

[0162]

[0163] First, keep the reference value of each phase transmitting coil current as the original 1.4A, 1.4A, and 1.9A. At 5ms, change the reference value of each phase transmitting coil current to 1.1A, 1.9A, and 3.8A respectively. The three-phase transmitting coil current waveform obtained by simulation is as follows Figure 11-12 As shown in the figure, the current of each phase transmitting coil follows the given requirement after 6ms. At this time, the load power waveform is as follows Fig.13 As shown, it can be seen that after the load coil moves from position 1 to position 2, if the current amplitude of each phase transmitting coil is still the given value at position 1, that is, the fixed synthetic current vector at the original position 1 is still used, the load receiving power is less than 20W. At 5ms, by performing directional power control on position 2, the load power reaches nearly 50W.

[0164] Therefore, the above simulation work proves that the mutual inductance can be estimated through the front-end information, and the stable power control of the load can be achieved based on the estimated mutual inductance information.

Claims

1. Load-stabilized power control method for omnidirectional wireless power transmission system, It is characterized in that The omnidirectional wireless power transmission system consists of three orthogonal transmitting coils and one loading coil. The YOZ plane represents the transmitting coil 1; the XOZ plane represents the transmitting coil 2; the XOY plane represents the transmitting coil 3; the loading coil is located at the center of the transmitting coil at an elevation angle θ and an azimuth angle θ. The transmitting coil 1, the transmitting coil 2 and the transmitting coil 3 are respectively connected to a DC power supply through an inverter; The specific steps are as follows: Step 1: Construct the objective function and constraints, perform the extreme value search algorithm on the objective function, and obtain the maximum value point of the objective function. At this time, θ * and The direction of the load coil corresponding to the spherical coordinate system; Step 2: Adjust the direction of the synthetic current vector and perform current amplitude control. After the current is stable, obtain the maximum value of the DC side input power according to the sampled DC voltage and DC current. Step 3: adjust the direction of the synthetic current vector again, perform current amplitude control, and after the current stabilizes, obtain the minimum value of the DC side input power according to the sampled DC voltage and DC current; Step 4: Calculate the maximum power received by the load coil according to the maximum DC side input power and the minimum DC side input power determined in steps 2 and 3, and further calculate the square sum of the mutual inductance at the position of the load coil; Step 4 is as follows: According to the maximum DC input power P determined in steps 2 and 3 in-max The minimum DC input power P in-min , calculate the maximum power P received by the load coil out-max for: P out_max =P in_max -P in_min (23) According to the maximum power P received by the load coil out-max expression: Where, ω is the system operating angular frequency; I base is the given composite current vector magnitude; R 4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X 4 is the equivalent reactance of the load coil; M 14 、M 24 、M 34 Respectively represent the mutual inductance of each phase transmitting coil and loading coil; Let the square sum of the mutual inductance of each phase transmitting coil and load coil be The size of the square sum M of the mutual inductance of each phase transmitting coil and the load coil at this position is further calculated, which is calculated as follows: Step 5: Calculate the magnitude of the synthetic current vector amplitude when the load power is required according to the square sum of the mutual inductance at the load coil position obtained in step 4, adjust the synthetic current vector direction, and perform current amplitude control, so as to finally realize directional stable power control of the load and ensure the maximum efficiency transmission at any position of the load coil; Step 5 is as follows: According to the square sum of mutual inductance M at the load coil position obtained in step 4, calculate the required load power P load The composite current vector amplitude I obj The size of is calculated as follows: Among them, P load is the power required by the load; R 4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X 4 is the equivalent reactance of the load coil; M is the square sum of the mutual inductance of each phase transmitting coil and the load coil at that position; Adjust the direction of the synthetic current vector θ=θ * and As a result, the current amplitudes finally flowing into the three-phase transmitting coil are: By performing current amplitude control, directional and stable power control of the load can be finally achieved, ensuring the maximum efficiency transmission at any position of the load coil.

2. The load stabilization power control method for an omnidirectional wireless power transmission system according to claim 1, It is characterized in that Step 1 is as follows: Step 1: Set the synthetic current vector amplitude I to a certain value I = I base The direction of the synthetic current vector is the elevation angle θ and the azimuth angle in the spherical coordinate system. According to the load coil direction detection principle: DC side input power P in The direction of the synthetic current vector corresponding to the maximum value is θ and That is the direction of the load coil θ * and Select the DC side input power P in The maximum value of the synthetic current vector θ and To optimize the variables, construct the objective function and constraints as follows:

3. The load stabilization power control method for an omnidirectional wireless power transmission system according to claim 2, It is characterized in that Step 2 is as follows: Keep the resultant current vector magnitude I = I base , adjust the direction of the synthetic current vector θ=θ * and As a result, the current amplitudes flowing into the three-phase transmitting coil for the first time are: Execute current amplitude control. After the current stabilizes, obtain the DC side input power according to the sampled DC voltage and DC current. At this time, the DC side input power P in Reaching the maximum value is expressed as: Among them, P coil is the ohmic loss of the three-phase transmitting coil; P inv is the loss of the three-phase inverter; ω is the system operating angular frequency; I base is the given composite current vector magnitude; R 4 is the parasitic resistance of the load coil; R L is the equivalent load resistance; X 4 is the equivalent reactance of the load coil; M 14 、M 24 、M 34 Respectively represent the mutual inductance of each phase transmitting coil and load coil.

4. The load stabilization power control method for an omnidirectional wireless power transmission system according to claim 3, It is characterized in that Step 3 is as follows: Keep the resultant current vector magnitude I = I base , adjust the direction of the synthetic current vector and As a result, the current amplitudes flowing into the three-phase transmitting coil for the second time are: Execute current amplitude control. After the current stabilizes, obtain the DC side input power according to the sampled DC voltage and DC current. At this time, the DC side input power P in Reaching the minimum is expressed as: P in_min =P coil +P inv (22) Among them, P coil is the ohmic loss of the three-phase transmitting coil, P inv is the loss of the three-phase inverter.

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