Parameter design method for mc-wpt system in seawater environment

Abstract

This invention relates to the field of wireless power transmission, specifically a parameter design method for an MC-WPT system in a seawater environment, comprising the following steps: S1: Determine the transmission distance, seawater conductivity, required efficiency, and output power; S2: Determine the coupling mechanism dimensions and the maximum number of winding turns; S3: Determine the wire diameter and maximum current withstand value; S4: Set the initial value of the coil turns; S5: Determine the system eddy current loss and coil parameters through magnetic field simulation; S6: Determine whether the required efficiency is met; if so, proceed to S8; otherwise, proceed to S7; S7: Increase the number of coil turns by a preset step; if the maximum number of winding turns is not exceeded, return to S5; otherwise, return to S2; S8: Record the operating frequency and load, and calculate the resonant current; S9: Determine whether the maximum current withstand value is exceeded; if it is exceeded, return to S3; if not, the efficiency optimization index is completed. Designing the system parameters according to this method can effectively ensure that the system's transmission efficiency meets the preset requirements.

Description

Technical Field

[0001] This invention relates to wireless power transfer technology, and more particularly to a method for designing parameters of an MC-WPT system for use in a seawater environment. Background Technology

[0002] With the development of the marine equipment industry, underwater unmanned navigation devices have become more diversified. Regarding the energy supply issue of these devices, wireless power transfer technology has gradually replaced the original wet-plug technology, significantly improving the time and energy utilization of the vehicles. However, in the complex environment of seawater, the transmission efficiency of existing magnetically-coupled wireless power transfer (MC-WPT) is often affected. To address the problem of seawater eddy current losses, most existing technologies employ close-fitting tank-type or other short-range coupling mechanisms to improve transmission efficiency by avoiding seawater in the transmission gap; or by reducing coil current to reduce losses and improve efficiency.

[0003] For MC-WPT systems in seawater environments, existing efficiency improvement solutions typically have the following shortcomings:

[0004] (1) A two-to-one energy transfer mechanism is adopted to reduce losses by reducing coil current, but the efficiency improvement is not obvious and the cost increases.

[0005] (2) By adopting a close-range coupling method, the volume of seawater in the gap between the transmitter and receiver is reduced, thus reducing losses. However, the application scenarios are limited, and the structural design of the equipment coupling mechanism requires high precision.

[0006] (3) Efficiency can be improved by increasing self-inductance, but the effect is not obvious and the port voltage stress is large. Summary of the Invention

[0007] In view of this, the present invention provides a parameter design method for an MC-WPT system in a seawater environment. By analyzing the seawater eddy current loss, the influencing factors affecting energy transmission efficiency are determined. Then, the optimal efficiency of the system under specific operating conditions is solved to find the operating frequency and load of the system under the optimal efficiency, thereby achieving the parameter configuration for the optimal system efficiency.

[0008] To achieve the above objectives, the specific technical solution adopted by the present invention is as follows:

[0009] A method for designing parameters of an MC-WPT system for use in seawater environments, the key of which includes the following steps:

[0010] S1: Determine the transmission distance, seawater conductivity, required efficiency, and output power based on the requirements of the MC-WPT system in a seawater environment;

[0011] S2: Determine the dimensions of the coupling mechanism and the maximum number of winding turns;

[0012] S3: Determine the wire diameter and the corresponding maximum flow resistance value;

[0013] S4: Set the initial value for the number of coil turns;

[0014] S5: Determine the system eddy current loss and coil parameters under the current number of coil turns using magnetic field simulation software;

[0015] S6: Calculate whether the current optimal energy transmission efficiency of the system meets the required efficiency. If it does, proceed to step S8; otherwise, proceed to step S7.

[0016] S7: Increase the number of coil turns by a preset step. If the number of coil turns does not exceed the maximum number of winding turns after the increase, return to step S5 to redetermine the system eddy current loss and coil parameters under the current number of coil turns. If the number of coil turns exceeds the maximum number of winding turns after the increase, return to step S2 to redetermine the coupling mechanism size and the maximum number of winding turns.

[0017] S8: Record the operating frequency and load resistance value corresponding to the optimal efficiency, and calculate the resonant current of the transmitting coil and the resonant current of the receiving coil based on the output power;

[0018] S9: Determine whether the resonant current of the transmitting coil and the resonant current of the receiving coil exceed the maximum current withstand value. If they do, return to step S3 to redetermine the wire diameter and the corresponding maximum current withstand value. If they do not exceed the maximum current withstand value, complete the efficiency optimization index and use the obtained parameters as the MC-WPT system parameters in the seawater environment for configuration.

[0019] Optionally, the MC-WPT system in the seawater environment adopts an LCC-S topology. The primary side of the system includes a DC power supply, a high-frequency inverter module, an LCC compensation network, and a transmitting coil. The secondary side of the system includes a receiving coil, a secondary-side series compensation capacitor, a rectifier filter circuit, and a load resistor.

[0020] Optionally, the transmitting coil and the receiving coil adopt a symmetrical coupling structure, and are respectively laid with magnetic core and aluminum plate.

[0021] Optionally, in step S5, the eddy current loss of the system is equivalent to the internal resistance of the coil circuit using magnetic field simulation software, and an equivalent resistance R of the eddy current loss of the transmitting coil is introduced into the transmitting end in the equivalent circuit model of the system. ep In the equivalent circuit model of the system, the equivalent resistance R of the eddy current loss of the receiving coil is introduced at the receiving end. es .

[0022] Optionally, in the equivalent circuit model, according to R ep =R es =mω 2 The equivalent resistance of eddy current loss in the transmitting coil and the equivalent resistance of eddy current loss in the receiving coil are simulated, where m is the correlation coefficient determined by magnetic field simulation software and ω is the system operating angular frequency.

[0023] Optionally, the coil parameters determined by the magnetic field simulation software in step S5 include the internal resistance R of the transmitting coil. p The internal resistance R of the receiving coil s And system mutual inductance M.

[0024] Optionally, step S6 is performed according to:

[0025]

[0026] Calculate the current energy transfer efficiency of the system, where R eq This is the equivalent resistance of the load.

[0027] Optionally, in step S4, the initial value of the number of coil turns is set to 1, and in step S7, the number of coil turns is increased by a preset step of 1.

[0028] Optionally, after configuring other system parameters through step S9, proceed as follows:

[0029]

[0030] Calculate the current system output power. If the output power does not meet the system requirements, adjust the input voltage U1 to meet the system requirements. f is the system operating frequency.

[0031] The significant effects of this invention are:

[0032] This invention performs electromagnetic modeling on an MC-WPT system in a seawater environment to identify the manifestation of equivalent eddy current resistance. Then, based on the system's circuit topology, it clarifies the factors affecting transmission efficiency, thereby summarizing a parameter design method for an MC-WPT system in a seawater environment. Designing the system parameters according to this method can effectively ensure that the system's transmission efficiency meets the preset requirements. Attached Figure Description

[0033] Figure 1 This is a flowchart of a method in a specific embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the electromagnetic model of the MC-WPT system in a seawater environment;

[0035] Figure 3 The curves show the equivalent eddy current loss as a function of the square of the frequency under different electrical conductivity.

[0036] Figure 4 This is the equivalent circuit diagram of the MC-WPT system in a seawater environment;

[0037] Figure 5 This shows how efficiency changes with frequency under different loads. Detailed Implementation

[0038] The embodiments of the present invention are described in detail below with reference to the accompanying drawings. The embodiments are given for illustrative purposes only and should not be construed as limiting the present invention. The accompanying drawings are for reference and illustration only and do not constitute a limitation on the scope of patent protection of the present invention, because many changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0039] like Figure 1 As shown, this embodiment provides a method for designing MC-WPT system parameters for use in seawater environments, including the following steps:

[0040] S1: Determine the transmission distance S, seawater conductivity σ, and required efficiency η based on the requirements of the MC-WPT system in a seawater environment. max and output power P out This embodiment uses the LCC-S topology as an example for detailed explanation. The primary side of the system includes a DC power supply, a high-frequency inverter module, an LCC compensation network, and a transmitting coil. The secondary side of the system includes a receiving coil, a secondary-side series compensation capacitor, a rectifier filter circuit, and a load resistor.

[0041] S2: Determine the coupling mechanism size W and the maximum number of winding turns N. max The transmitting and receiving coils here typically employ a symmetrical coupling structure, with corresponding magnetic cores and aluminum plates. The size of the coupling mechanism and the maximum number of winding turns can be preliminarily determined based on the space available for the specific application equipment.

[0042] S3: Based on the power requirements of transmission, the wire diameter r and the corresponding maximum current-bearing value Imax can be preliminarily determined;

[0043] S4: Set the initial value of the number of coil turns N = 1;

[0044] S5: Determine the system eddy current loss and coil parameters under the current number of coil turns using magnetic field simulation software; treat the system eddy current loss as equivalent to the coil circuit resistance, and introduce an equivalent resistance R of the transmitting coil eddy current loss into the transmitting end in the system equivalent circuit model. ep In the equivalent circuit model of the system, the equivalent resistance R of the eddy current loss of the receiving coil is introduced at the receiving end. es According to R ep =R es =mω 2The equivalent resistance of eddy current loss in the transmitting coil and the receiving coil are simulated, where m is the correlation coefficient determined by magnetic field simulation software, and ω is the system operating angular frequency; other coil parameters include the internal resistance R of the transmitting coil. p The internal resistance R of the receiving coil s And system mutual inductance M;

[0045] S6: Calculate whether the current optimal energy transmission efficiency of the system meets the required efficiency. If it does, proceed to step S8; otherwise, proceed to step S7.

[0046] S7: Increase the number of coil turns by N = N + 1. If the number of coil turns does not exceed the maximum number of winding turns after increasing the number of coil turns, return to step S5 to redetermine the system eddy current loss and coil parameters under the current number of coil turns; if the number of coil turns exceeds the maximum number of winding turns after increasing the number of coil turns, return to step S2 to redetermine the coupling mechanism size and the maximum number of winding turns.

[0047] S8: Record the operating frequency and load resistance value corresponding to the optimal efficiency, and calculate the resonant current of the transmitting coil and the resonant current of the receiving coil based on the output power;

[0048] S9: Determine whether the resonant current of the transmitting coil and the resonant current of the receiving coil exceed the maximum current withstand value. If they do, return to step S3 to redetermine the wire diameter and the corresponding maximum current withstand value. If they do not exceed the maximum current withstand value, complete the efficiency optimization index and use the obtained parameters as the MC-WPT system parameters in the seawater environment for configuration.

[0049] To better understand the design concept of this invention, the working principle of the system will be further explained below.

[0050] like Figure 2 As shown, assuming the transmitting and receiving coils are completely identical, and the seawater medium in the region is uniform and homogeneous, then we obtain... Figure 2 The diagram illustrates the eddy current loss generation model. The eddy current electric field is generated based on the principle of electromagnetic induction and is rotational and source-free. Therefore, when discussing the combined eddy current voltage generated by the transmitting coil and the picking coil at any point within the seawater region, it is only necessary to analyze... and The phase difference θ is sufficient, and since the eddy voltage lags the excitation current by 90°, therefore... and The phase difference between them is also equal to θ.

[0051] Figure 2 In the diagram, consider a small current tube with length dl and cross-section dS at point T(x0,y0,z0). Assume the current density within it is... Then the current intensity I = jdS, and from the Biot-Savart formula, the magnetic field generated by this current element at the field point M(x,y,z) is:

[0052]

[0053] in It is the radial vector from the source point T to the field point M. It is along The unit vector of direction, and It is a function of the coordinates of the field point M(x,y,z). It is a function of the source point T(x0,y0,z0). The modulus is represented as:

[0054]

[0055] The magnetic field generated by the single-turn transmitting coil in M(x,y,z) for:

[0056]

[0057] List Maxwell's equations:

[0058]

[0059] In electromagnetism, the curl of the magnetic vector potential is the magnetic field, that is, we have From this, we can obtain the magnetic vector potential at point M. for:

[0060]

[0061] From Maxwell's equations, we can obtain:

[0062]

[0063] The induced electric field has zero curl, and the medium is homogeneous, therefore That is:

[0064]

[0065] Similarly, the eddy current voltage generated by the receiving coil at point M can be obtained as follows:

[0066]

[0067] Therefore, the total eddy current loss P generated by the transmitting and receiving coils can be obtained. e :

[0068]

[0069] in, θ represents the phase angle difference between the transmitting and receiving coil currents. Simulations show that this value is very small and can therefore be ignored. Thus, the eddy current loss is the sum of the losses generated by the transmitting and receiving coils individually. For multi-turn coils, the electric field strength generated at the field point retains only the circumferential component. Therefore, the eddy current loss generated by an N-turn coil can be obtained as follows:

[0070]

[0071] In the above equation, 'i' represents the loss generated by the i-th turn of the coil. Then, the eddy current resistance generated by the transmitting coil is:

[0072]

[0073] The equivalent eddy current resistance of the receiving coil can be calculated similarly. It can be seen that the equivalent eddy current resistance is independent of the coil current, and only depends on the frequency, conductivity, permeability, and the integral over the coil structure. For a specific coil structure, the integral term is a constant, and the equivalent eddy current resistance is linearly related to the square of the frequency and the conductivity.

[0074] Simulation verification was performed using MAXWELL 2022R1 software, and the results are as follows. Figure 3 As shown, through Figure 3 It can be seen that, under a given conductivity, the equivalent eddy current resistance and the square of the frequency are almost linearly related.

[0075] In this embodiment, the system adopts an LCC-S topology. Therefore, considering eddy current losses, the equivalent circuit model of the system can be expressed as follows: Figure 4 As shown.

[0076] Based on the above model, analyzing from AC side to AC side, when the system's operating frequency f and natural frequency f0 are satisfied, the system's input power P can be obtained. in Output power P out Efficiency η:

[0077]

[0078]

[0079]

[0080] Where ω=2πf, the equivalent resistance R before rectification. eq for:

[0081]

[0082] Therefore, when the operating conditions are determined, we can assume R ep =R es =mω 2The output power and efficiency can be obtained through simulation or experimentation, and can then be expressed as:

[0083]

[0084]

[0085] At this point, the efficiency η is a bivariate function of m and frequency f, and finding the most efficient function becomes a process of finding the maximum value of the efficiency function.

[0086] Therefore, in step S6, it can be done according to:

[0087]

[0088] Calculate the current energy transfer efficiency of the calculation system.

[0089] At the same time, after configuring other system parameters through step S9, you can proceed as follows:

[0090]

[0091] Calculate the current system output power. If the output power does not meet the system requirements, adjust the input voltage U1 to meet the system requirements.

[0092] To further verify the correctness of the above theory, the following simulation was conducted using a circular planar coil with a conductivity of 4 S / m, a coupling mechanism size of 700mm*700mm, a transmission distance of 35cm, and an output of 10KW. The efficiency versus frequency curves under different loads were obtained, as shown below. Figure 5 As shown.

[0093] pass Figure 5 It can be seen that once the coupling mechanism is defined, there exists an optimal frequency point for the MC-WPT system in a seawater environment under a specific load, resulting in optimal efficiency. Furthermore, at a specific frequency, the system efficiency can be adjusted by changing the load. Therefore, by first setting the parameters of the coupling mechanism using the method proposed in this invention, if the optimal efficiency can meet the preset requirements given the defined coupling mechanism parameters, the system design needs can be satisfied by adjusting the operating frequency or load.

[0094] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for designing parameters of an MC-WPT system for use in a seawater environment, characterized in that, Includes the following steps: S1: Determine the transmission distance, seawater conductivity, required efficiency, and output power based on the requirements of the MC-WPT system in a seawater environment; S2: Determine the dimensions of the coupling mechanism and the maximum number of winding turns; S3: Determine the wire diameter and the corresponding maximum flow resistance value; S4: Set the initial value for the number of coil turns; S5: Determine the system eddy current loss and coil parameters under the current number of coil turns using magnetic field simulation software; S6: Calculate whether the current optimal energy transmission efficiency of the system meets the required efficiency. If it does, proceed to step S8; otherwise, proceed to step S7. S7: Increase the number of coil turns by a preset step. If the number of coil turns does not exceed the maximum number of winding turns after the increase, return to step S5 to redetermine the system eddy current loss and coil parameters under the current number of coil turns. If the number of coil turns exceeds the maximum number of winding turns after the increase, return to step S2 to redetermine the coupling mechanism size and the maximum number of winding turns. S8: Record the operating frequency and load resistance value corresponding to the optimal efficiency, and calculate the resonant current of the transmitting coil and the resonant current of the receiving coil based on the output power; S9: Determine whether the resonant current of the transmitting coil and the resonant current of the receiving coil exceed the maximum current withstand value. If they do, return to step S3 to redetermine the wire diameter and the corresponding maximum current withstand value. If they do not exceed the maximum current withstand value, complete the efficiency optimization index and use the obtained parameters as the MC-WPT system parameters in the seawater environment for configuration.

2. The method for designing MC-WPT system parameters for seawater environments according to claim 1, characterized in that, The MC-WPT system in the seawater environment adopts an LCC-S topology. The primary side of the system includes a DC power supply, a high-frequency inverter module, an LCC compensation network, and a transmitting coil. The secondary side of the system includes a receiving coil, a secondary-side series compensation capacitor, a rectifier filter circuit, and a load resistor.

3. The method for designing MC-WPT system parameters for seawater environments according to claim 2, characterized in that, The transmitting coil and the receiving coil adopt a symmetrical coupling structure, and are respectively laid with magnetic core and aluminum plate.

4. The method for designing MC-WPT system parameters for seawater environments according to claim 2 or 3, characterized in that, In step S5, the eddy current loss of the system is equivalent to the internal resistance of the coil circuit using magnetic field simulation software. An equivalent resistance R for the eddy current loss of the transmitting coil is introduced into the transmitting end of the equivalent circuit model of the system. ep In the equivalent circuit model of the system, the equivalent resistance R of the eddy current loss of the receiving coil is introduced at the receiving end. es .

5. The method for designing MC-WPT system parameters for seawater environments according to claim 4, characterized in that, In the equivalent circuit model according to R ep =R es =mω 2 The equivalent resistance of eddy current loss in the transmitting coil and the equivalent resistance of eddy current loss in the receiving coil are simulated, where m is the correlation coefficient determined by magnetic field simulation software and ω is the system operating angular frequency.

6. The method for designing parameters of an MC-WPT system in a seawater environment according to claim 5, characterized in that, The coil parameters determined by the magnetic field simulation software in step S5 include the internal resistance R of the transmitting coil. p The internal resistance R of the receiving coil s And system mutual inductance M.

7. The method for designing parameters of an MC-WPT system in a seawater environment according to claim 6, characterized in that, In step S6, the procedure is as follows: Calculate the current energy transfer efficiency of the system, where R eq This is the equivalent resistance of the load.

8. The method for designing parameters of an MC-WPT system in a seawater environment according to claim 5, 6, or 7, characterized in that, In step S4, the initial value of the number of coil turns is set to 1, and in step S7, the number of coil turns is increased according to the preset step 1.

9. The method for designing parameters of an MC-WPT system in a seawater environment according to claim 7, characterized in that, After configuring other system parameters through step S9, follow these steps: Calculate the current system output power. If the output power does not meet the system requirements, adjust the input voltage U1 to meet the system requirements. f is the system operating frequency.

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