System and method for controlling efficiency of multiple receiving coils of omnidirectional wireless power transmission system

Abstract

The invention discloses a multi-receiving-coil efficiency control system and method for an omnidirectional wireless power transmission system, and the system comprises a three-dimensional transmitting coil, three phase-shifting inverters, a receiving coil, a plurality of LCC compensation networks which are connected with one transmitting coil, the three-dimensional transmitting coil transmits electric energy to the receiving coil, the receiving coil is connected with a compensation capacitor, and the compensation capacitor is connected with the three-dimensional transmitting coil. The compensation capacitor is connected with the input of the synchronous rectification circuit. The output of the synchronous rectification circuit is connected with the buck-boost DC conversion circuit. The buck-boost DC conversion circuit is connected with the PI controller; the rectifying circuit is used for adjusting the direct-current output voltage on the load through the buck-boost direct-current conversion circuit; the PI controller is used for collecting the output voltage of the buck-boost DC conversion circuit; and the transmitting coil controller is used for collecting a mutual inductance value between the three-dimensional transmitting coil and the receiving coil, controlling the phase shift angles of the three phase shift inverters based on the mutual inductance value, and further controlling the transmission efficiency of the whole system. And the expected voltage output control problem of multiple receiving coils can be effectively solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless charging, and particularly relates to a multi-receiver coil efficiency control system and method for an omnidirectional wireless power transmission system. Background Art

[0002] With the continuous development of wireless charging technology, there are currently various types of wireless power transmission coil structures. Among them, the most common are planar two-coil or planar multi-coil structures. However, such coil structures often have the problem that when the distance between the coils changes or there is an offset, the transmission power and efficiency of the system are greatly reduced. This is because when the distance between the coils is far or there is an offset between the coils, the coupling coefficient will be greatly reduced, resulting in a relatively short transmission distance for these wireless power transmission coil structures.

[0003] The coil structure type of the omnidirectional wireless power transmission system is a three-dimensional wireless power transmission coil structure composed of three orthogonal coils, also known as a three-phase orthogonal omnidirectional wireless power transmission system structure. It can enable the transmitting coil to transmit power directionally to the receiving coil at any position in the space within a certain distance range. At the same time, by coordinating and controlling the current magnitudes of the three-dimensional transmitting coils, the direction and magnitude of the synthetic magnetic field of the wireless power transmission system can be changed, and simultaneous power supply to multiple receiving coils in multiple directions can be achieved. Currently, for the control method of the three-phase orthogonal omnidirectional wireless power transmission system, it mainly controls the output power when a single receiving coil is at any position in the space. When a single receiving coil changes in the space, according to the pre-calculated current amplitudes of the three-dimensional transmitting coils respectively, three inverter circuits are controlled to inject sinusoidal currents with the same frequency and the same phase into the three-dimensional transmitting coils, so as to achieve constant power output or point-to-point tracking control at the maximum efficiency point. However, there are few relevant reports on the control method for multiple receiving coils. How to achieve that multiple receiving coils simultaneously reach the desired output voltage while ensuring the highest overall efficiency of the system is a challenge for the control of the three-phase orthogonal omnidirectional wireless power transmission system. Summary of the Invention

[0004] To solve the problem of maximum efficiency transmission of the system with multiple receiving coils in the omnidirectional wireless power transmission system.

[0005] In a first aspect, the present invention provides a method for controlling the efficiency of multiple receiving coils in an omnidirectional wireless power transmission system, including: a three-dimensional transmitting coil, three phase-shifting inverters, and a receiving coil. The three-dimensional transmitting coil is composed of three circular transmitting coils; the output end of each phase-shifting inverter is connected to an LCC compensation network, and multiple LCC compensation networks are all connected to a transmitting coil. The three-dimensional transmitting coil transmits electric energy to the receiving coil. The receiving coil is connected to a compensation capacitor, and the compensation capacitor is connected to the input of a synchronous rectification circuit. The output of the synchronous rectification circuit is connected to a buck-boost DC conversion circuit; the buck-boost DC conversion circuit is connected to a PI controller;

[0006] The rectification circuit is used to convert the induced electromotive force generated by the receiving coil into a DC voltage by means of synchronous rectification of the high-frequency AC voltage, and adjust the DC output voltage on the load through the buck-boost DC conversion circuit;

[0007] The PI controller is used to collect the output voltage of the buck-boost DC conversion circuit and control the stability of its own output voltage based on the duty cycle of the buck-boost DC conversion circuit; by collecting the DC output voltage of the load of the receiving coil, control the duty cycle of the buck-boost DC conversion circuit;

[0008] The transmitting coil controller is used to collect the mutual inductance value between the three-dimensional transmitting coil and the receiving coil, and based on the mutual inductance value, control the phase-shifting angles of the three phase-shifting inverters to control the magnitude of the current of the three-dimensional transmitting coil, thereby controlling the transmission efficiency of the entire system.

[0009] Preferably, the three phase-shifting inverters are all full-bridge inverter structures composed of fully controlled devices, and the three phase-shifting inverters are connected to a DC voltage source.

[0010] In a second aspect, the present invention also provides a method for controlling the efficiency of multiple receiving coils in an omnidirectional wireless power transmission system. By using the omnidirectional wireless power transmission system multi-receiving coil efficiency control system described above, the following steps are implemented:

[0011] Step 1: Establish a mathematical model of the omnidirectional wireless power transmission system multi-receiving coil efficiency control system; based on the mathematical model, respectively obtain the mutual inductance values between the three transmitting coils and each receiving coil;

[0012] Step 2: Establish an expression for the transmission efficiency under multiple receiving coils based on the mutual inductance value; use the sequential quadratic programming method to determine the phase-shifting angles of the phase-shifting inverters corresponding to the three transmitting coils; based on the phase-shifting angles of the phase-shifting inverters, determine the input voltage of the transmitting coil; based on the input voltage of the transmitting coil, determine the current of the transmitting coil; control the voltage of the transmitting coil to control the magnitude of the currents of the three transmitting coils;

[0013] Step 3: Determine the input power of the system based on the phase shift angle of the phase-shifted inverter, the currents of the three transmitting coils, and the desired output voltage of the load.

[0014] Step 4: Determine whether the positions of the receiving coils have changed based on whether the input power changes; if the input power changes, it means that the position of one or more receiving coils has changed, and in this case, return to Step 1; if the input power remains unchanged, continue with Step 4.

[0015] Preferably, the expression for the transmission efficiency under multiple receiving coils is as follows:

[0016]

[0017] In the formula, P loss (Δ i ) represents the system power loss; U oj (Δ i ) represents the output voltage across the load resistor; D j (Δ i ) represents the duty cycle of the buck-boost DC conversion circuit as a function of the phase shift angle Δ i ; U oj * is the desired output voltage across the load resistor corresponding to the j-th receiving coil; D j represents the duty cycle of the buck-boost DC conversion circuit; Δ i represents the phase shift angles of the phase-shifted inverters, n represents the total number of receiving coils, s.t. is a mathematical symbol meaning subject to constraints, i.e., the content in s.t. is the constraint condition for the transmission efficiency.

[0018] Preferably, the input voltage of the transmitting coil is expressed as the following formula:

[0019]

[0020] Among them, U pi represents the input voltage of the transmitting coil; Δ i is the phase shift angle of the phase-shifted inverter corresponding to the i-th transmitting coil, π represents pi, and U dc represents the DC voltage source voltage.

[0021] Preferably, according to Kirchhoff's voltage law, establish a mathematical model for the multi-receiving coil efficiency control system of the omnidirectional wireless power transmission system.

[0022] One or more technical solutions provided in the present invention have at least the following technical effects or advantages:

[0023] A multi-receiver coil efficiency control system and method for an omnidirectional wireless power transmission system according to the present invention realizes the maximum efficiency transmission effect of the overall system by using a non-linear programming optimization method based on the mutual inductance detection result. The multi-receiver coil efficiency optimization control method has the characteristics of simple implementation and high control precision, can effectively solve the problem of controlling the desired voltage output of the multi-receiver coil, and at the same time reduces the additional loss of the system, greatly improving the transmission efficiency of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a structural diagram of a multi-receiver coil efficiency control system for an omnidirectional wireless power transmission system according to the present invention;

[0025] Figure 2 is an equivalent main circuit diagram of a multi-receiver coil efficiency control system for an omnidirectional wireless power transmission system according to the present invention;

[0026] Figure 3 is a flowchart of a multi-receiver coil efficiency control method for an omnidirectional wireless power transmission system according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0028] The present invention and its embodiments are described above, and this description is not restrictive. The actual embodiments are not limited thereto. In general, if those of ordinary skill in the art are inspired by it and design similar structural modes and embodiments without creative efforts without departing from the spirit of the present invention, they shall fall within the protection scope of the present invention.

[0029] Embodiment:

[0030] As Figure 1 shown, a multi-receiver coil efficiency control system for an omnidirectional wireless power transmission system according to the present invention includes: a three-dimensional transmitting coil, three phase-shifting inverters, and a receiving coil. The three-dimensional transmitting coil is composed of three circular transmitting coils; the output end of each phase-shifting inverter is connected to an LCC compensation network, and multiple LCC compensation networks are all connected to a transmitting coil. The three-dimensional transmitting coil transmits electric energy to the receiving coil. The receiving coil is connected to a compensation capacitor, and the compensation capacitor is connected to the input of a synchronous rectification circuit. The output of the synchronous rectification circuit is connected to a buck-boost DC conversion circuit; the buck-boost DC conversion circuit is connected to a PI controller;

[0031] The rectification circuit is used to convert the induced electromotive force generated by the receiving coil into a DC voltage by means of synchronous rectification of the high-frequency AC voltage, and adjust the DC output voltage on the load through the buck-boost DC conversion circuit;

[0032] The PI controller is used to collect the output voltage of the buck-boost DC conversion circuit and control the stability of its own output voltage based on the duty cycle of the buck-boost DC conversion circuit; by collecting the DC output voltage of the load of the receiving coil, it controls the duty cycle of the buck-boost DC conversion circuit to achieve different desired output voltages of multiple receiving coils in the wireless power transmission system.

[0033] The transmitting coil controller is used to collect the mutual inductance value between the three-dimensional transmitting coil and the receiving coil, and based on the mutual inductance value, control the phase shift angles of the three phase-shifted inverters to control the magnitude of the current in the three-dimensional transmitting coil, thereby controlling the transmission efficiency of the entire system.

[0034] First, the three-dimensional transmitting coil of the system is composed of three orthogonal circular transmitting coils, which are respectively denoted as transmitting coil 1, transmitting coil 2, and transmitting coil 3. Each of the three transmitting coils corresponds to a phase-shifted inverter (also known as a phase-shifted full-bridge inverter), and the output port of the phase-shifted inverter is connected to its respective transmitting coil through an inductor-capacitor-capacitor (LCC) compensation network. The controller of the transmitting coil adjusts the magnitude of the current in the transmitting coil by controlling the phase shift angle of the phase-shifted inverter corresponding to the transmitting coil. The receiving coil is composed of a circular coil, and there is one or more receiving coils in the system. The receiving coils are distributed in the surrounding space of the three-dimensional transmitting coil and are respectively denoted as receiving coil 1, receiving coil 2, …, receiving coil n. The receiving coil is connected to the synchronous rectifier circuit through its respective connected compensation capacitor, and the output of the synchronous rectifier circuit is connected to the buck-boost DC conversion circuit (abbreviated as the Buck-Boost circuit). For the control of the output voltage, according to the difference between the set desired voltage and the actual output voltage, the duty cycle of the Buck-Boost circuit is obtained through a proportional-integral (PI) controller, thereby achieving stable control of the output voltage of the buck-boost DC conversion circuit.

[0035] Controllers are respectively connected to the transmitting coil and the receiving coil, and the signals between them are transmitted between the controllers in a wireless communication manner. The output voltage and receiving coil current on the receiving coil side are sent to the controller of the transmitting coil through their corresponding controllers. The controller of the transmitting coil estimates the mutual inductance value between the transmitting coil and the receiving coil based on the output voltage information on the receiving coil side. The PI controller solves the phase shift angle of the phase-shifted inverter of the corresponding transmitting coil based on the mutual inductance estimation value, the output voltage on the receiving coil side, and the receiving coil current, thereby controlling the switching devices of the inverter corresponding to the transmitting coil to perform phase shift and achieving maximum transmission efficiency transmission of the system.

[0036] Figure 2It is the equivalent main circuit diagram of the efficiency control system for multiple receiving coils in an omnidirectional wireless power transmission system. The three phase-shifted inverters are all full-bridge inverter structures composed of fully controlled devices, and the three phase-shifted inverters are connected to a DC voltage source. The three phase-shifted inverters (Phase-shifted Inverter 1, Phase-shifted Inverter 2, Phase-shifted Inverter 3) share the same DC voltage source U dc . Phase-shifted Inverter 1 is composed of fully controlled power devices Q 11 , Q 12 , Q 13 , Q 14 . Phase-shifted Inverter 2 is composed of fully controlled power devices Q 21 , Q 22 , Q 23 , Q 24 . Phase-shifted Inverter 3 is composed of fully controlled power devices Q 31 , Q 32 , Q 33 , Q 34 . The output voltages of the three phase-shifted inverters are U p1 , U p2 , U p3 respectively; L f1 , C f1 , C p1 form the LCC filter of Transmitting Coil 1, L f2 , C f2 , C p2 form the LCC filter of Transmitting Coil 2, L f3 , C f3 , C p3 form the LCC filter of Transmitting Coil 3. The three-dimensional transmitting coils are respectively represented by L p1 , L p2 , L p3 . R p1 , R p2 , R p3 are the equivalent series resistances of the three transmitting coils respectively. The currents flowing through the three transmitting coils are I p1 , I p2 , I p3 respectively, and the currents flowing into the three LCC compensation networks are I f1 , I f2 , I f3 .

[0037] The receiving coils are respectively represented by L s1 , L s2 , …, L sn . R s1 , R s2 , …, R sn are the equivalent series resistances of each receiving coil, C s1 , C s2, …, C sn are the compensation capacitors for each receiving coil. The currents flowing through the receiving coils are I s1 , I s2 , …, I sn . The subsequent stage of the receiving coil is connected to a synchronous rectifier circuit and a Buck-Boost circuit. The output loads of each receiving coil are R L1 , R L2 , …, R Ln . The output voltages are U o1 , U o2 , …, U on , and the output currents are I o1 , I o2 , …, I on . Since the subsequent stage circuit is relatively complex, for the convenience of analysis, the equivalent resistances R eq1 , R eq2 , …, R eqn are used to represent the equivalent loads of each receiving coil.

[0038] The mutual inductances between the transmitting coil 1 and the n receiving coils are M 11 , M 12 , …, M 1n , the mutual inductances between the transmitting coil 2 and the n receiving coils are M 21 , M 22 , …, M 2n , and the mutual inductances between the transmitting coil 3 and the n receiving coils are M 31 , M 32 , …, M 3n . Since the three transmitting coils are orthogonal and the mutual inductance between them is very small, it is not considered.

[0039] Since the transmitting coil adopts an LCC compensation network and the receiving coils all adopt series compensation capacitors, according to the resonance condition of the resonance network, the resonance condition of each resonator is expressed by Equation (1).

[0040]

[0041] Among them, i = 1, 2, 3, representing the i-th transmitting coil. j = 1, 2, …, n, representing the j-th receiving coil, and ω0 is the operating frequency of the system. When the transmitting coil and the receiving coil satisfy the resonance condition of Equation (1), the system can reach the operating condition. For the receiving-side coil, since the induced electromotive force generated by the receiving coil is an AC signal, after passing through the rectifier, the equivalent resistance of the output load changes. For the convenience of representing the size of the receiving-side load. According to the power balance and the conversion relationship between AC and DC, the relationship between the equivalent load of the j-th receiving coil and the actual load resistance of the j-th receiving coil is expressed by Equation (2):

[0042]

[0043] Among them, D j is the duty cycle of the Buck - Boost circuit corresponding to the j - th receiving coil. R eqj represents the equivalent load of the j - th receiving coil, and R Lj represents the output load of the j - th receiving coil.

[0044] From Figure 2 the equivalent circuit diagram, according to Kirchhoff's voltage law, the mathematical models of the coil, inverter circuit, rectifier circuit, and buck - boost circuit of the system can be established, as shown in Equations (3) and (4).

[0045]

[0046] Among them, A represents the LCC compensation network matrix of the transmitting coil, B represents the mutual inductance reflection matrix, D represents the mutual inductance transfer matrix, and C represents the receiving coil matrix. I i is the transmitting coil current matrix, I j is the receiving coil current matrix, and U i is the input voltage matrix.

[0047]

[0048]

[0049] Among them, jω is the impulse - moment formula. A1, A2, A3 are intermediate variables, represented by A i ; B 11 , B 12 , B 1n , B 21 , B 22 , B 2n , B 31 , B 32 , B 3n are intermediate variables, represented by B ij ; C1, C2, C n are intermediate variables, represented by C j . The following are the specific expressions of A i , B ij , C j :

[0050]

[0051] Since the voltage U pi of the transmitting coil is controlled by the phase - shift angle of the phase - shift inverter, according to the fundamental - wave equivalent principle, the input voltage U pi of the transmitting coil can be expressed as Equation (5):

[0052]

[0053] where, Δ i is the phase shift angle of the phase shift inverter corresponding to the transmitting coil i, and π represents the pi.

[0054] Determine the output voltage of the load on the j-th receiving coil as shown in Equation (6):

[0055]

[0056] where, R dson is the on-resistance of the fully controlled power device of the synchronous rectifier and the Buck-Boost circuit of the receiving coil. M ij represents the estimated mutual inductance value between the transmitting coil i and the j-th receiving coil.

[0057] Assume that the spatial positions between each receiving coil and the transmitting coil remain unchanged within a period of time. As long as the output voltage of the load on the receiving coil is known, the mutual inductance values between the three transmitting coils and each receiving coil can be estimated respectively according to Equation (6). For the convenience of estimating the mutual inductance values between each transmitting coil and the receiving coil, and to avoid the mutual influence between each transmitting coil, the mutual inductance detection between the three transmitting coils and the j-th receiving coil is performed separately. Taking the transmitting coil 1 as an example, first set the effective value of the current flowing through the transmitting coil 1, for example, 1 A, and at the same time set the duty cycle of the Buck-Boost circuit to 0.5, and the other two transmitting coils do not work, that is, the currents are all zero. Then, from Equation (6), the output voltage U oj of the j-th receiving coil can be obtained, which is expressed by Equation (7):

[0058]

[0059] According to the detected output voltage U oj and the known phase shift angle Δ1 of the phase shift inverter corresponding to the transmitting coil 1 and the circuit parameters, the mutual inductance M 1j between the transmitting coil 1 and the j-th receiving coil can be calculated, as shown in Equation (8):

[0060]

[0061] Similarly, when only 1 A current is generated in the transmitting coil 1, the receiving coils at other positions will also induce different currents, thus generating output voltages on the corresponding loads. According to the detected output voltages U o1 、U o2 、…、U on of each receiving coil, the mutual inductance values M 1j between the transmitting coil 1 and each receiving coil can be obtained according to Equation (8), that is, M11 , M 12 , …, M 1n .

[0062] After the mutual inductance values between the transmitting coil 1 and each receiving coil are estimated, using the same method, only a current effective value of 1 A is generated for the transmitting coil 2, while the currents of the other two transmitting coils are both 0. Then, the mutual inductance M 2j between the transmitting coil 2 and the j-th receiving coil is as shown in Equation (9):

[0063]

[0064] Record the output voltage U of each receiving coil oj , and based on the known phase shift angle Δ2 of the phase shift inverter corresponding to the transmitting coil 2 and the circuit parameters, the mutual inductance values M 2j between the transmitting coil 2 and each receiving coil can be calculated, that is, M 21 , M 22 , …, M 2n .

[0065] After the mutual inductance values between the transmitting coil 2 and each receiving coil are estimated, using the same method, only a current effective value of 1 A is generated for the transmitting coil 3, while the currents of the other two transmitting coils are both 0. Then, the mutual inductance M 3j between the transmitting coil 3 and the j-th receiving coil is as shown in Equation (10):

[0066]

[0067] Record the output voltage U of each receiving coil oj , and based on the known phase shift angle Δ3 of the phase shift inverter corresponding to the transmitting coil 3 and the circuit parameters, the mutual inductance values M 3j between the transmitting coil 3 and each receiving coil can be calculated, that is, M 31 , M 32 , …, M 3n .

[0068] In summary, the estimated mutual inductance values between the three-dimensional transmitting coil and each receiving coil are obtained through the above method. The current I pi of the transmitting coil i, the current I fi of the LCC compensation network, and the current I sj of the j-th receiving coil obtained through wireless communication are as shown in Equation (11).

[0069]

[0070] The input power P inA of the system mainly includes the output power P oA , the coil loss Ploss_coil and the loss P of the power device loss_MOS . Thus, P inA can be expressed as Equation (12).

[0071]

[0072] The transmission efficiency of the system is η, which is expressed by Equation (13).

[0073]

[0074] Since the output voltage on the load corresponding to each receiving coil is constant, in order to maximize the transmission efficiency of the system, the loss of the system should be reduced as much as possible. It can be seen that the system can adjust the current magnitude of the three-dimensional transmitting coil and control the duty cycle of the Buck-Boost circuit on the receiving side so that each receiving coil can reach the required output voltage. However, there are many combinations of the current magnitudes of the three-dimensional transmitting coil that can achieve the desired output voltage of the system, but there is only one combination that achieves the maximum transmission efficiency. In order to ensure the output of the desired voltage and simultaneously achieve the maximum transmission efficiency of the system, it is necessary to control the phase shift angles of the phase shift inverters corresponding to the three transmitting coils to minimize the system loss and maintain the constant output voltage on the load. Thus, taking the minimum loss of the system as the optimization goal, the output power under the constant output voltage with a resistive load remains unchanged, that is, P oA is a constant value. Therefore, the optimization problem expression for the maximum transmission efficiency of the system with multiple receiving coils is established as shown in Equation (14).

[0075]

[0076] In the formula, P loss (Δ i ), U oj (Δ i ), D j (Δ i ) respectively represent the functions of the system power loss, the output voltage on the load resistance, and the duty cycle of the Buck-Boost circuit with respect to the phase shift angle Δ i . U oj * is the desired output voltage on the load resistance corresponding to the jth receiving coil. To ensure the normal operation of the system, the duty cycle D j of the Buck-Boost circuit is limited between 0.1 and 0.8, and the phase shift angles Δ i of each phase shift inverter are limited within the range of 0 to π / 2.

[0077] The above optimization problem is a typical non - linear programming problem. The present invention uses the existing sequential quadratic programming method to obtain the optimal solution. By solving the above optimization problem, the phase - shift angles Δ of the phase - shift inverters corresponding to the three transmitting coils are obtained. i The phase - shift angles Δ of the three inverters i can control the magnitudes of the currents of the corresponding transmitting coils. While satisfying the desired output voltages of each receiving coil, the control effect of maximizing the system transmission efficiency can be achieved simultaneously.

[0078] The output voltages across the resistive loads corresponding to each receiving coil need to be closed - loop controlled by their respective proportional - integral (PI) controllers to obtain the duty cycles D of the corresponding Buck - Boost circuits respectively. j

[0079] As Figure 3 shown in the flowchart of the optimization method for the maximum transmission efficiency of multiple receiving coils in a three - phase orthogonal omnidirectional wireless power transmission system, the specific implementation steps are divided into 4 steps, and the implementation steps are as follows:

[0080] Step 1: Establish a mathematical model of the efficiency control system of the omnidirectional wireless power transmission system with multiple receiving coils; based on the mathematical model, calculate the mutual inductance values between the three transmitting coils and each receiving coil respectively.

[0081] Step 1.1: First, establish its mathematical model according to the structure and parameters of the omnidirectional wireless power transmission system, and calculate the estimated mutual inductance values between transmitting coil 1 and each receiving coil. Specifically: Measure all circuit parameters, set the duty cycle of the Buck - Boost circuit of each receiving coil to 0.5, and at the same time adjust the phase - shift angle Δ1 of the phase - shift inverter corresponding to transmitting coil 1 so that the current I p1 flowing through transmitting coil 1 is 1 A, while keeping the currents of the other two transmitting coils at 0. After waiting for the output voltages of the corresponding loads of each receiving coil to stabilize, through wireless communication, the controller on the transmitting coil side obtains the output voltages U oj across the corresponding loads of each receiving coil at this time, and calculates the mutual inductance values M 1j between transmitting coil 1 and each receiving coil according to Equation (8), that is, M 11 , M 12 , …, M 1n .

[0082] Step 1.2, which is basically similar to Step 1.1, uses the same method to adjust the current of transmitting coil 2 so that the current I p2 flowing through transmitting coil 2 is 1 A, while keeping the currents of the other two transmitting coils at 0. After waiting for the output voltages of the corresponding loads of each receiving coil to stabilize, through wireless communication, the controller on the transmitting coil side obtains the output voltages U across the corresponding loads of each receiving coil at this time.​oj , calculate the mutual inductance value M between the transmitting coil 2 and each receiving coil according to Equation (9) 2j , that is, M 21 , M 22 , …, M 2n .

[0083] Step 1.3: Similar to Step 1.1, adjust the current of the transmitting coil 3 in the same way so that the current I flowing through the transmitting coil 3 p3 is 1 A, while maintaining the currents of the other two transmitting coils at 0. At this time, after waiting for the output voltages of the corresponding loads of each receiving coil to stabilize, through wireless communication, the controller on the transmitting coil side obtains the output voltages U oj of the corresponding loads of each receiving coil at this time, and calculate the mutual inductance value M between the transmitting coil 3 and each receiving coil according to Equation (10) 3j , that is, M 31 , M 32 , …, M 3n .

[0084] Step 2, based on the mutual inductance M between each coil obtained in the previous Step 1 ij , establish the transmission efficiency expression (14) of the system under multiple receiving coils, and solve the phase shift angles Δ1, Δ2, and Δ3 of the phase shift inverters corresponding to the three transmitting coils under the maximum transmission efficiency through the existing sequential quadratic programming method. Control the input voltage of the transmitting coil according to the phase shift angles of the phase shift inverters, thereby controlling the magnitudes of the currents of the three transmitting coils. Based on the mutual inductance M between each coil obtained in the previous Step 1 ij , establish the transmission efficiency expression (14) of the system under multiple receiving coils. By inputting the mutual inductance M ij between each coil into the existing sequential quadratic programming algorithm, solve the phase shift angles Δ1, Δ2, and Δ3 of the phase shift inverters corresponding to the three transmitting coils under the maximum transmission efficiency. Control the output voltage of the phase shift inverter through the solved phase shift angles, that is, the input voltage of the transmitting coil. And according to Equation (5), controlling the voltage of the transmitting coil can achieve the control of the magnitudes of the currents of the three transmitting coils.

[0085] Step 3: Control the phase shift inverters corresponding to the three transmitting coils according to the solved phase shift angles Δ1, Δ2, and Δ3 respectively. For each receiving coil, according to the desired output voltage U oj * on the load, control the duty cycle of the Buck - Boost circuit through a PI controller, and further determine the input power of the system;

[0086] Step 4: Based on whether the input power P inA changes, determine whether the positions of each receiving coil have changed. If the system input power PinA If a change occurs, it indicates that the position of one or more receiving coils has changed. In this case, return to step 1, re-estimate the mutual inductance values between the three transmitting coils and each receiving coil, and re-control the maximum transmission efficiency using the same process. If the system input power P inA remains unchanged, continue with the process of step 4. The phase shift angles of the phase shift inverters corresponding to the three transmitting coils remain unchanged, and the Buck-Boost circuit controls the output voltage on the load in a closed loop.

[0087] The present invention can finally realize an optimization method for the maximum transmission efficiency of multiple receiving coils in a three-phase orthogonal omnidirectional wireless power transmission system through steps 1 to 4.

[0088] Based on the structure of the three-dimensional transmitting coil and multiple receiving coils of the three-phase orthogonal omnidirectional wireless power transmission system, according to the transmission characteristics of the omnidirectional wireless power transmission system, the currents of the three-dimensional transmitting coil are independently controlled. By controlling the magnitudes of the currents of the three-dimensional transmitting coil, the magnitude and direction of the synthesized magnetic field of the three-dimensional transmitting coil can be changed, that is, the induced current of the receiving coil can be changed. When there are multiple receiving coils in the system, first estimate the mutual inductance values between each transmitting coil and the receiving coils through the mutual inductance detection method, and then establish an evaluation function of the system transmission efficiency based on the estimated mutual inductance values between the coils. Finally, it can be seen from the evaluation function that the maximum point of the system transmission efficiency is unique. Therefore, a non-linear function with a solution in the constraint conditions is established according to the characteristics of the evaluation function, and the non-linear programming method is used to optimize the solution of the maximum transmission efficiency point of the system, and finally realize the maximum efficiency transmission and the desired voltage output of the omnidirectional wireless power transmission system when there are multiple receiving coils.

[0089] It should be noted that the terms "first" and "second" in the present invention are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more unless otherwise specifically defined.

[0090] Although the present application has been described in conjunction with various embodiments herein, however, in the process of implementing the claimed present application, those skilled in the art can understand and achieve other variations of the disclosed embodiments by viewing the accompanying drawings, the disclosure content, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "one" does not exclude a plurality of cases.

[0091] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. A multi-receiver coil efficiency control system for an omnidirectional wireless power transmission system, characterized in that, Including: A three-dimensional transmitting coil, three phase-shifting inverters, and a receiving coil. The three-dimensional transmitting coil is composed of three circular transmitting coils; the output end of each phase-shifting inverter is connected to an LCC compensation network, and multiple LCC compensation networks are all connected to a transmitting coil. The three-dimensional transmitting coil sends electrical energy to the receiving coil. The receiving coil is connected to a compensation capacitor, and the compensation capacitor is connected to the input of a synchronous rectification circuit. The output of the synchronous rectification circuit is connected to a buck-boost DC conversion circuit; the buck-boost DC conversion circuit is connected to a PI controller. The rectification circuit is used to convert the induced electromotive force generated by the receiving coil into a DC voltage by means of synchronous rectification of a high-frequency AC voltage, and adjust the DC output voltage on the load through the buck-boost DC conversion circuit. The PI controller is used to collect the output voltage of the buck-boost DC conversion circuit, and control the stability of its own output voltage based on the duty cycle of the buck-boost DC conversion circuit; by collecting the DC output voltage of the load of the receiving coil, control the duty cycle of the buck-boost DC conversion circuit. The transmitting coil controller is used to collect the mutual inductance value between the three-dimensional transmitting coil and the receiving coil, and based on the mutual inductance value, control the phase-shifting angles of the three phase-shifting inverters, so as to control the magnitude of the current of the three-dimensional transmitting coil, and further control the transmission efficiency of the entire system.

2. The system according to claim 1, wherein The three phase-shifting inverters are all full-bridge inverter structures composed of fully controlled devices, and the three phase-shifting inverters are connected to a DC voltage source.

3. A method for controlling the efficiency of multiple receiving coils in an omnidirectional wireless power transmission system, characterized in that, Adopt the multi-receiving-coil efficiency control system of the omnidirectional wireless power transmission system as described in any one of claims 1-2, and implement the following steps: Step 1: Establish a mathematical model of the multi-receiving-coil efficiency control system of the omnidirectional wireless power transmission system; based on the mathematical model, respectively obtain the mutual inductance values between the three transmitting coils and each receiving coil. Step 2: Establish an expression of the transmission efficiency under multiple receiving coils based on the mutual inductance value; use the sequential quadratic programming method to determine the phase-shifting angles of the phase-shifting inverters corresponding to the three transmitting coils; based on the phase-shifting angles of the phase-shifting inverters, determine the input voltage of the transmitting coil; based on the input voltage of the transmitting coil, determine the current of the transmitting coil; control the voltage of the transmitting coil to control the magnitudes of the currents of the three transmitting coils. Step 3: Based on the phase-shifting angles of the phase-shifting inverters, the currents of the three transmitting coils, and the expected output voltage of the load, determine the input power of the system. Step 4: Judge whether the positions of the receiving coils have changed based on whether the input power changes; if the input power changes, it means that the position of one or more receiving coils has changed, and at this time, return to Step 1; if the input power remains unchanged, continue with Step 4.

4. The method according to claim 3, wherein The expression of the transmission efficiency under multiple receiving coils is as follows: minP loss (Δ i ) i = 1, 2, 3. j = 1, 2, …, n. where P loss (Δ i ) represents the system power loss; U oj (Δ i ) represents the output voltage across the load resistor; D j (Δ i ) represents the duty cycle of the buck-boost DC conversion circuit as a function of the phase shift angle Δ i ; U oj * is the desired output voltage across the load resistor corresponding to the j-th receiving coil; D j represents the duty cycle of the buck-boost DC conversion circuit; Δ i represents the phase shift angles of the respective phase-shifted inverters, n represents the total number of receiving coils, and s.t. is a mathematical symbol meaning subject to, i.e., the content in s.t. is the constraint condition for the transmission efficiency.

5. The method according to claim 3, wherein The input voltage of the transmitting coil is expressed as the following formula: Among them, U pi represents the input voltage of the transmitting coil; Δ i is the phase shift angle of the phase shift inverter corresponding to the transmitting coil i, π represents the pi, and U dc represents the voltage of the DC voltage source.

6. The method according to claim 3, wherein According to Kirchhoff's voltage law, establish a mathematical model of the multi-receiving-coil efficiency control system of the omnidirectional wireless power transmission system.

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