Modeling method of channel model for underwater wireless power and data synchronous transmission system

Abstract

In order to solve the technical problem that the existing modeling method ignores the difference between the seawater environment and the air environment, and the difference in the coil equivalent resistance caused by the low-frequency power carrier and the high-frequency data carrier on the modeling accuracy, resulting in inaccurate modeling of the channel model, and causing deviations in the design and implementation of the data transmission circuit in the underwater wireless power and data synchronous transmission system, the present invention proposes a modeling method for the channel model of the underwater wireless power and data synchronous transmission system. When establishing a channel model for the underwater wireless power and data synchronous transmission system, the present invention considers the influence of the eddy current loss caused by seawater on the channel, and the influence of the low-frequency power carrier and the high-frequency data carrier on the channel, thereby improving the accuracy of the channel model and reducing the design and implementation deviations of the data transmission circuit in the underwater wireless power and data synchronous transmission system.

Description

Technical Field

[0001] The invention relates to the technical field of power supply circuit system and electric communication. Background Art

[0002] In the process of underwater wireless charging, data interaction is usually required to achieve closed-loop control and system status monitoring of the wireless charging system. Compared with traditional WIFI, acoustic, optical and other communication methods, wireless power and data synchronous transmission technology based on magnetic field coupling has the advantages of low transmission delay, reliable transmission, high integration, etc., and is the mainstream direction of current research.

[0003] At present, the data transmission circuit in the underwater wireless power and data synchronous transmission system is designed by using the channel model established in the air environment. When establishing the channel model in the air environment, it is mainly for the scenario where the data carrier is low-frequency, and it is approximately assumed that the coil equivalent resistance caused by the data carrier and the coil equivalent resistance caused by the power carrier are equal. However, the inventors of the present invention have found that this method of using the channel model established in the air environment ignores the difference between the seawater environment and the air environment, and the influence of the difference in the coil equivalent resistance caused by the low-frequency power carrier and the high-frequency data carrier on the modeling accuracy.

[0004] On the one hand, seawater is conductive, while the conductivity of air is close to 0. Therefore, during underwater wireless power and data synchronous transmission, the alternating electromagnetic field excited by the coil will generate eddy current loss in the seawater. If the eddy current loss is ignored during modeling, the established channel model will be inaccurate, resulting in deviations in the design and implementation of the data transmission circuit in the underwater wireless power and data synchronous transmission system.

[0005] On the other hand, the eddy current loss caused by seawater is not only related to the current in the coil, but also to the operating frequency of the underwater wireless power and data synchronous transmission system. In addition to the power carrier, the coil current of the underwater wireless power and data synchronous transmission system also has a data carrier. When the underwater communication rate needs to be increased, the data carrier frequency must be increased. At this time, the data carrier frequency and the power carrier frequency are quite different. The coil equivalent resistance values ​​caused by these two carriers will be significantly different. If the coil equivalent resistance caused by the power carrier is still used to equal the coil equivalent resistance caused by the data carrier, the channel model will be inaccurate, resulting in deviations in the design and implementation of the data transmission circuit in the underwater wireless power and data synchronous transmission system. Summary of the invention

[0006] In order to solve the technical problem that the existing modeling method ignores the difference between the seawater environment and the air environment, and the influence of the difference in the coil equivalent resistance caused by the low-frequency electric energy carrier and the high-frequency data carrier on the modeling accuracy, resulting in inaccurate modeling of the channel model, and causing deviations in the design and implementation of the data transmission circuit in the underwater wireless power and data synchronous transmission system, the present invention proposes a modeling method of the channel model of the underwater wireless power and data synchronous transmission system.

[0007] The technical solution of the present invention is:

[0008] A modeling method for a channel model of an underwater wireless power and data synchronous transmission system, wherein the underwater wireless power and data synchronous transmission system comprises an electric power transmission circuit and a data transmission circuit; the electric power transmission circuit comprises an inverter, a primary side compensation circuit, a coupler consisting of a primary side coil and a secondary side coil, a secondary side compensation circuit and a rectifier; the data transmission circuit comprises a data modulation circuit, a data injection circuit, the coupler, a data extraction circuit and a data demodulation circuit;

[0009] The particularity thereof is that the modeling method comprises the following steps:

[0010] Step 1: Calculate the equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier;

[0011] Step 1.1 calculate the electric field strength excited by the coil in the seawater medium;

[0012] The coils are regarded as multiple concentric current-carrying rings, and the superposition theorem is used to obtain the electric field intensity induced by the primary coil and the secondary coil in the seawater medium:

[0013]

[0014]

[0015] In the formula,

[0016] and are the electric field strengths excited by the primary coil and the secondary coil in the seawater medium respectively;

[0017] and are the total number of turns of the primary coil and the secondary coil respectively;

[0018] and They are the first The turns and the secondary coil The electric field strength induced by the turns in the seawater medium is calculated based on the general solution of the electric field strength induced by a single current-carrying ring in the seawater medium; the general solution of the electric field strength is:

[0019]

[0020] In the formula, is an imaginary unit, is the frequency of the alternating current in the coil, is the magnetic permeability of seawater, is the radius of the current-carrying ring, is the current-carrying ring current, is the separation constant, is the first-order Bessel function of the first kind, and is the cylindrical coordinate, is the spatial wave number, is a natural constant, is the unit circumferential vector;

[0021] Step 1.2 Calculate the eddy current loss equivalent resistance of the primary coil and secondary coil corresponding to the data carrier:

[0022]

[0023]

[0024] In the formula,

[0025] is the data carrier frequency;

[0026] and are the eddy current loss equivalent resistances of the primary coil and the secondary coil corresponding to the data carrier respectively;

[0027] is the electrical conductivity of seawater;

[0028] It is the area where eddy current loss occurs;

[0029] and are the currents on the primary coil and the secondary coil respectively;

[0030] Step 1.3 Calculate the equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier:

[0031]

[0032]

[0033] In the formula, and are the equivalent resistances of the primary coil and the secondary coil corresponding to the data carrier respectively; and are the AC resistances of the primary coil and the secondary coil corresponding to the data carrier respectively;

[0034] Step 2: Equivalent resistance of the primary coil and the secondary coil obtained in step 1 and , establish a mathematical model of the channel model.

[0035] Furthermore, step 2 is specifically as follows:

[0036] The inverter and its front-stage power supply, the rectifier and its rear-stage load are regarded as short-circuited, and the equivalent resistance of the primary coil and the secondary coil obtained in step 1 is and , calculate the input impedance of the data extraction circuit, the reflected impedance of the secondary compensation circuit to the input impedance of the data extraction circuit, the secondary input impedance, the reflected impedance of the primary compensation circuit to the secondary input impedance, the primary input impedance, the reflected impedance of the data injection circuit to the primary input impedance, the carrier voltage source input impedance and input current of the data injection circuit, the primary coil current, the secondary coil current, the data receiving circuit current, and the voltage on the equivalent resistance of the data demodulation circuit, and then derive the gain function expression of the channel model, which is the mathematical model of the channel model.

[0037] Furthermore, the underwater wireless power and data synchronous transmission system is an underwater wireless power and data synchronous transmission system based on LCC-LCC topology, and the mathematical model of the established channel model is:

[0038]

[0039] In the formula,

[0040] is the equivalent resistance of the data demodulation circuit;

[0041] To extract the mutual inductance of the primary and secondary inductances in the data circuit;

[0042] The mutual inductance of the primary and secondary inductors in the data injection circuit;

[0043] The mutual inductance between the primary coil and the secondary coil in the coupler;

[0044] A compensation capacitor for the data extraction circuit;

[0045] is the input impedance of the data extraction circuit;

[0046] is the secondary input impedance;

[0047] is the primary input impedance;

[0048] The carrier voltage source input impedance of the data injection circuit;

[0049] in,

[0050]

[0051] ;

[0052] In the formula,

[0053] and are the self-inductances of the primary coil and the secondary coil in the coupler respectively;

[0054] and They are primary side series compensation capacitor and secondary side series compensation capacitor respectively;

[0055] and They are primary side parallel compensation capacitor and secondary side parallel compensation capacitor respectively;

[0056] and They are primary side compensation inductance and secondary side compensation inductance respectively;

[0057] Secondary inductance for data injection circuits;

[0058] The primary inductance in the data extraction circuit;

[0059] is the input impedance of the data extraction circuit Reflected impedance of the secondary side compensation circuit;

[0060] is the secondary input impedance The reflected impedance of the primary compensation circuit.

[0061] The advantages of the present invention are:

[0062] When establishing a channel model for an underwater wireless power and data synchronous transmission system, the present invention takes into account both the influence of eddy current loss caused by seawater on the channel and the influence of low-frequency power carrier and high-frequency data carrier on the channel, thereby improving the accuracy of the channel model and reducing the design and implementation deviation of the data transmission circuit in the underwater wireless power and data synchronous transmission system, which has guiding significance for the design of the underwater wireless power and data synchronous transmission system. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 This is a principle block diagram of an underwater wireless power and data synchronous transmission system. The power supply and load in the figure do not belong to the underwater wireless power and data synchronous transmission system. The power supply is an underwater charging base station, and the load is an underwater equipment battery pack.

[0064] Figure 2 It is a principle block diagram of underwater wireless power and data synchronous transmission system to realize data transmission.

[0065] Figure 3 It is an equivalent simplified circuit diagram of the existing underwater wireless power and data synchronous transmission system based on LCC-LCC topology.

[0066] Figure 4 Yes Figure 3 The equivalent circuit diagram of the inverter and its upstream power supply, rectifier and its downstream load after being regarded as short-circuited.

[0067] Figure 5 It is a flow chart of the method of the present invention. DETAILED DESCRIPTION

[0068] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0069] like Figure 1 As shown, the underwater wireless power and data synchronous transmission system includes an inverter, a primary compensation circuit, a coupler composed of a primary coil and a secondary coil, a secondary compensation circuit, a rectifier, a data modulation circuit, a data injection circuit, a data extraction circuit and a data demodulation circuit. Among them, the inverter, the primary compensation circuit, the coupler, the secondary compensation circuit and the rectifier are sequentially arranged to form a power transmission circuit, and the data modulation circuit, the data injection circuit, the coupler, the data extraction circuit and the data demodulation circuit are sequentially arranged to form a data transmission circuit.

[0070] like Figure 2 Shown Figure 1 The principle block diagram of realizing data transmission in the wireless channel is Figure 1The data injection circuit, coupler and data extraction circuit in the wireless communication system are composed of the digital baseband signal, which enters the wireless channel after passing through the modulator and operational amplifier to realize data transmission. The signal extracted from the wireless channel is restored to the digital baseband signal after passing through the filter and demodulator to realize data reception. In the process of mathematical modeling of the channel model, the data modulation circuit and the data demodulation circuit can be equivalent to the AC signal source and the resistive load respectively.

[0071] In order to more clearly illustrate the modeling method of the present invention, the existing underwater wireless power and data synchronization transmission system based on LCC-LCC topology is briefly described here. Figure 1 A specific embodiment of Figure 3 As shown in FIG. 1 , the existing underwater wireless power and data synchronous transmission system based on the LCC-LCC topology includes an inverter, a primary compensation circuit, a coupler for power and data transmission, a secondary compensation circuit and a rectifier. The inverter is simplified to consist of four NMOS transistors. ~ The full-bridge circuit composed of is an equivalent substitute. The coupler is represented by a pair of loosely coupled transformers. and are the self-inductance of the primary and secondary coils, and are the equivalent resistances of the primary and secondary coils, respectively. is the mutual inductance between the primary coil and the secondary coil. is the primary compensation inductor, and They are the primary parallel compensation capacitor and the primary series compensation capacitor, For the secondary side compensation inductance, and The rectifier consists of four Schottky diodes. ~ and filter capacitors Indicates. The data signal is injected and extracted by inductive coupling. is the equivalent voltage source of the data modulation circuit, and are the primary inductance and secondary inductance in the data injection circuit, respectively, and their mutual inductance is , A compensation capacitor for the data injection circuit; and are the primary inductance and secondary inductance in the data extraction circuit, respectively, and their mutual inductance is , is the compensation capacitor of the data extraction circuit, is the equivalent resistance of the data demodulation circuit. The compensation circuit has various forms, and different combinations of primary and secondary compensation circuits can achieve different circuit characteristics.

[0072] by Figure 3 As an example, the underwater wireless power and data synchronization transmission system based on the LCC-LCC topology shown in FIG. Figure 5 The method for establishing a channel model in the present invention specifically comprises the following steps:

[0073] Step 1: Calculate the equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier;

[0074] Step 1.1 calculate the electric field strength excited by the coil in the seawater medium;

[0075] The coil is regarded as multiple concentric current-carrying rings, one current-carrying ring corresponds to one turn in the coil. The electric field strength excited by a single current-carrying ring in seawater is generally solved as follows:

[0076]

[0077] In the formula, is an imaginary unit, is the frequency of the alternating current in the coil, that is, the frequency of the alternating current in a single current-carrying loop, is the magnetic permeability of seawater, is the radius of the current-carrying ring, is the current-carrying ring current, is the separation constant, is the first-order Bessel function of the first kind, and is the cylindrical coordinate, is the spatial wave number, is a natural constant, is a unit circumferential vector.

[0078] Based on the general solution of the electric field strength induced by a single current-carrying ring in the seawater medium, the superposition theorem can be used to obtain the electric field strength induced by the primary coil and the secondary coil in the seawater medium:

[0079]

[0080] In the formula, and are the electric field strengths excited by the primary coil and the secondary coil in the seawater medium, and are the total number of turns of the primary coil and the secondary coil respectively, and They are the first The turns and the secondary coil The electric field strength induced by the turns in the seawater medium.

[0081] Step 1.2 calculates the eddy current loss equivalent resistance of the coil corresponding to the data carrier;

[0082] The eddy current loss power generated by the coil in the seawater medium is:

[0083]

[0084] In the formula, is the total eddy current loss power generated by the primary coil and the secondary coil, is the seawater conductivity, is the area where eddy current loss occurs, is the eddy current loss power of the primary coil, is the eddy current loss power of the secondary coil.

[0085] The eddy current loss power of the primary coil and the secondary coil is regarded as the heat loss caused by the resistance in series with the coil. The resistance corresponding to the heat loss is called the eddy current loss equivalent resistance, which is expressed as:

[0086]

[0087] in

[0088]

[0089] In the formula, is the equivalent resistance of the eddy current loss on the primary coil, is the equivalent resistance of the eddy current loss on the secondary coil, is the current on the primary coil, is the current in the secondary coil.

[0090] The power carrier and data carrier correspond to different eddy current loss equivalent resistances, which can be expressed as:

[0091]

[0092] In the formula, Power carrier frequency, is the data carrier frequency; is the eddy current loss equivalent resistance corresponding to the power carrier, It is used when deriving the formula of the power transmission part. The present invention is a modeling for the data transmission part, so it is not involved in the subsequent steps. ; It is the eddy current loss equivalent resistance corresponding to the data carrier.

[0093] Therefore, the eddy current loss equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier are:

[0094]

[0095] Step 1.3 calculates the coil AC resistance corresponding to the data carrier;

[0096] Coil AC resistance The calculation formula is:

[0097]

[0098] In the formula, is the vacuum permeability, is the wire radius, is the coil radius, is the number of coil turns, is the wire conductivity, is the wire length, is the frequency of the alternating current in the coil.

[0099] Similarly, referring to the expression of eddy current loss equivalent resistance, the copper loss equivalent resistance corresponding to the power carrier and data carrier can be obtained, that is, the coil AC resistance:

[0100]

[0101] In the formula, is the coil AC resistance corresponding to the power carrier, It is used when deriving the formula for power transmission. The present invention is a modeling for the data transmission part, so it is not involved in the subsequent steps. ; is the coil AC resistance corresponding to the data carrier.

[0102] Similarly, the primary coil AC resistance corresponding to the data carrier can be expressed as , the secondary coil AC resistance corresponding to the data carrier can be expressed as , substitute the wire radius of the primary coil and the secondary coil, the coil radius, the number of coil turns, the wire conductivity and the data carrier frequency in the coil into the coil AC resistance The calculation formula can be obtained and .

[0103] Step 1.4 calculates the equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier;

[0104] Since the coil loss in the underwater wireless power and data synchronous transmission system is mainly composed of two parts: copper loss and eddy current loss, the equivalent resistance of the primary coil in the coupler is and the secondary coil equivalent resistance It can be expressed as:

[0105]

[0106] Therefore, for the data transmission circuit part of the underwater wireless power and data synchronous transmission system, the primary coil equivalent resistance corresponding to the data carrier is and the secondary coil equivalent resistance for:

[0107]

[0108] In the formula, and They are the primary coil AC resistance and the secondary coil AC resistance corresponding to the data carrier respectively; and They are the equivalent resistances of the eddy current losses corresponding to the data carrier on the primary coil and the secondary coil respectively.

[0109] Step 2: Establish a gain function expression of the channel model, which is the mathematical model of the channel model;

[0110] According to the superposition theorem, when analyzing data links, Figure 3 The inverter and its front-stage power supply, rectifier and its back-stage load in the circuit are considered to be in short-circuit state. At this time, the equivalent circuit is as follows: Figure 4 shown.

[0111] After equivalence, we can get:

[0112] Input impedance of the data extraction circuit And its reflected impedance to the secondary compensation circuit They are:

[0113]

[0114]

[0115] In the formula, Is an imaginary unit.

[0116] Secondary input impedance And its reflected impedance to the primary compensation circuit They are:

[0117]

[0118]

[0119] Primary input impedance and its reflected impedance to the data injection circuit They are:

[0120]

[0121]

[0122] Then the carrier voltage source input impedance of the data injection circuit can be obtained: and input current They are:

[0123]

[0124]

[0125] Primary coil current for:

[0126]

[0127] Secondary coil current for:

[0128]

[0129] The data receiving circuit current is:

[0130]

[0131] Finally, the equivalent resistance of the data demodulation circuit is derived The voltage on is:

[0132]

[0133] According to all the formulas derived in step 2 above, we can get Figure 3 The gain function expression of the channel model of the underwater wireless power and data synchronous transmission system shown in FIG. 1 , that is, the mathematical model of the channel model is as follows:

[0134] .

Claims

1. A modeling method for a channel model of an underwater wireless power and data synchronous transmission system, wherein the underwater wireless power and data synchronous transmission system comprises an electric power transmission circuit and a data transmission circuit; the electric power transmission circuit comprises an inverter, a primary side compensation circuit, a coupler consisting of a primary side coil and a secondary side coil, a secondary side compensation circuit and a rectifier; the data transmission circuit comprises a data modulation circuit, a data injection circuit, the coupler, a data extraction circuit and a data demodulation circuit; the channel model refers to a mathematical model of a data transmission channel in the underwater wireless power and data synchronous transmission system; It is characterized in that The modeling method comprises the following steps: Step 1: Calculate the equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier; Step 1.1 calculate the electric field strength excited by the coil in the seawater medium; The coils are regarded as multiple concentric current-carrying rings, and the superposition theorem is used to obtain the electric field intensity induced by the primary coil and the secondary coil in the seawater medium: In the formula, and are the electric field strengths excited by the primary coil and the secondary coil in the seawater medium respectively; and are the total number of turns of the primary coil and the secondary coil respectively; and They are the first The turns and the secondary coil The electric field strength induced by the turns in the seawater medium is calculated based on the general solution of the electric field strength induced by a single current-carrying ring in the seawater medium; the general solution of the electric field strength is: In the formula, is an imaginary unit, is the frequency of the alternating current in the coil, is the magnetic permeability of seawater, is the radius of the current-carrying ring, is the current-carrying ring current, is the separation constant, is the first-order Bessel function of the first kind, and is the cylindrical coordinate, is the spatial wave number, is a natural constant, is the unit circumferential vector; Step 1.2 Calculate the eddy current loss equivalent resistance of the primary coil and secondary coil corresponding to the data carrier: In the formula, is the data carrier frequency; and are the eddy current loss equivalent resistances of the primary coil and the secondary coil corresponding to the data carrier respectively; is the electrical conductivity of seawater; It is the area where eddy current loss occurs; and are the currents on the primary coil and the secondary coil respectively; Step 1.3 Calculate the equivalent resistance of the primary coil and the secondary coil corresponding to the data carrier: In the formula, and are the equivalent resistances of the primary coil and the secondary coil corresponding to the data carrier respectively; and are the AC resistances of the primary coil and the secondary coil corresponding to the data carrier respectively; Step 2: Equivalent resistance of the primary coil and the secondary coil obtained in step 1 and , establish a mathematical model of the channel model; The inverter and its front-stage power supply, the rectifier and its rear-stage load are regarded as short-circuited, and the equivalent resistance of the primary coil and the secondary coil obtained in step 1 is and , calculating the input impedance of the data extraction circuit, the reflected impedance of the secondary compensation circuit to the input impedance of the data extraction circuit, the secondary input impedance, the reflected impedance of the primary compensation circuit to the secondary input impedance, the primary input impedance, the reflected impedance of the data injection circuit to the primary input impedance, the carrier voltage source input impedance and input current of the data injection circuit, the primary coil current, the secondary coil current, the data receiving circuit current, and the voltage on the equivalent resistance of the data demodulation circuit, and then deriving the gain function expression of the channel model, which is the mathematical model of the channel model; The underwater wireless power and data synchronous transmission system is an underwater wireless power and data synchronous transmission system based on LCC-LCC topology, and the mathematical model of the established channel model is: In the formula, is the equivalent resistance of the data demodulation circuit; To extract the mutual inductance of the primary and secondary inductances in the data circuit; The mutual inductance of the primary and secondary inductors in the data injection circuit; The mutual inductance between the primary coil and the secondary coil in the coupler; A compensation capacitor for the data extraction circuit; is the input impedance of the data extraction circuit; is the secondary input impedance; is the primary input impedance; The carrier voltage source input impedance of the data injection circuit; in, ； In the formula, and are the self-inductances of the primary coil and the secondary coil in the coupler respectively; and They are primary side series compensation capacitor and secondary side series compensation capacitor respectively; and They are primary side parallel compensation capacitor and secondary side parallel compensation capacitor respectively; and They are primary side compensation inductance and secondary side compensation inductance respectively; Secondary inductance for data injection circuits; The primary inductance in the data extraction circuit; is the input impedance of the data extraction circuit Reflected impedance of the secondary side compensation circuit; is the secondary input impedance The reflected impedance of the primary compensation circuit.

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