A multi-parameter online identification energy efficiency improvement method for an underwater wireless transmission system

Abstract

This invention discloses a multi-parameter online identification method for improving energy efficiency in underwater wireless transmission systems. First, a topology diagram of the underwater wireless power transmission system is constructed. During normal system operation, the voltage U1 and current I1 of the transmitting coil are acquired, and the input impedance is calculated. The equivalent circuit is then determined, and mutual inductance M and bridging capacitor C are established using voltage U1 and current I1. e and equivalent load R Le The equations for mutual inductance M and bridging capacitance C are solved. e and equivalent load R Le This technology enables multi-parameter identification. It requires no change to the system's drive frequency or the addition of complex circuitry, and can quickly and accurately identify mutual inductance, bridging capacitors, and loads. Then, based on the calculated bridging capacitor value, the system's operating state is determined. This method accurately controls the system's power and efficiency, improving the stability and reliability of the charging process.

Description

Technical Field

[0001] This invention belongs to the field of wireless power transmission technology, specifically a method for improving energy efficiency through online multi-parameter identification in underwater wireless transmission systems. Background Technology

[0002] Autonomous Underwater Vehicles (AUVs) play a vital role in both military and civilian applications, such as oceanographic surveying and underwater mine hunting. However, their limited endurance necessitates frequent recharging and, constrained by their payload capacity, hinders the realization of their unmanned and intelligent advantages. The emergence of wireless power transfer technology offers an effective solution to this problem, effectively preventing issues such as electrical leakage and water seepage, thus promoting the widespread application of AUVs.

[0003] In practical engineering applications, wave fluctuations can cause misalignment of the coils in a wireless power transmission system, altering the mutual inductance and bridging capacitance between the two coils. Changes in the energy receiving device also change the load. These changes in mutual inductance, bridging capacitance, and load negatively impact system transmission performance, reducing the lifespan of the equipment, decreasing transmission efficiency and power during charging, and causing instability and unreliability in the charging process. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-parameter online identification method for improving energy efficiency in underwater wireless transmission systems. This method can accurately control the system's power and efficiency, improving the stability and reliability of the charging process.

[0005] To achieve the above objectives, the present invention provides a method for improving the energy efficiency of an underwater wireless transmission system through multi-parameter online identification, comprising the following steps:

[0006] Step 1: Construct the topology of the underwater wireless power transmission system, including: a DC power supply, a DC-AC converter, a transmitting coil, a receiving coil, an AC-DC converter, and an equivalent load of a charging device; the DC power supply is connected to the input terminal of the DC-AC converter, the output terminal of the DC-AC converter is connected to the input terminal of the transmitting coil, the output terminal of the transmitting coil is positioned opposite to the input terminal of the receiving coil, the output terminal of the receiving coil is connected to the input terminal of the AC-DC converter, and the output terminal of the AC-DC converter is connected to the equivalent load of the charging device;

[0007] Step 2: When the system is working normally, obtain the voltage U1 and current I1 of the transmitting coil, and calculate the input impedance;

[0008] Step 3: Determine the equivalent circuit. The equivalent circuit includes voltage U1, with one end of voltage U1 connected in series with the primary-side compensation capacitor, parasitic resistance R1, and the primary-side transmitting coil compensation capacitor C. PPrimary-side transmitting coil compensation capacitor C P The other end splits into two paths, one of which is connected in series with the equivalent inductance L of the primary-side transmitting coil. P Parasitic resistance R of the primary transmitting coil P parasitic resistance R of the primary transmitting coil P The other end splits into two paths. One path is connected to voltage U1, forming the first mesh. The primary-side transmitting coil compensation capacitor C P The other series-connected capacitor C e bridging capacitor C e The other end splits into two paths, one of which is connected in series with the equivalent inductance L of the secondary transmitting coil. S Parasitic resistance R of the secondary transmitting coil S Parasitic resistance R of the secondary transmitting coil S The other end splits into two paths, one of which is connected in series with a bridging capacitor C. e 'Afterwards, the parasitic resistance R of the primary-side transmitting coil P The other path is connected to form a second mesh; a bridging capacitor C is connected. e The other path is connected in series with the secondary transmitting coil and the compensation capacitor C. S Parasitic resistance of the secondary compensation capacitor R2, and the equivalent load of the system R Le Ultimately, this is related to the parasitic resistance R of the secondary transmitting coil. S The other path is connected to form a third mesh; mutual inductance M and bridging capacitor C are established through voltage U1 and current I1. e and equivalent load R Le The equation;

[0009] Step four: Substitute the voltage U1 and current I1 obtained in step two into the equations from step three to solve for the mutual inductance M and the bridging capacitance C. e and equivalent load R Le To achieve multi-parameter recognition;

[0010] Step 5: Connect capacitor C across the identification system. e After determining the value, the system jumper capacitor C is used. e The magnitude of the value is used to analyze the operating state of the system and to optimize the performance of each operating state. The operating states include the operating state of the capacitor-decoupled underwater wireless power transfer system and the operating state of the capacitor-coupled underwater wireless power transfer system. The energy efficiency optimization includes constant current output characteristic optimization and maximum efficiency and output power point tracking.

[0011] As a further aspect of the present invention: the voltage U1 and current I1 in step two represent the voltage vector and current vector of the transmitting coil (3) during normal operation, respectively.

[0012] As a further aspect of the present invention: in step three, the mutual inductance M and the bridging capacitance C are solved. eand equivalent load R Le The equations are as follows:

[0013] The equation for solving the single-variable mutual inductance M is as follows:

[0014]

[0015] Z2 = -R p -jωL p +jωM (4)

[0016] Z3=-jωM (5)

[0017]

[0018] Z5 = -R s -jωL s +jωM (7)

[0019]

[0020] In the formula, j is the imaginary unit, ω is the system driving angular frequency, Z1, Z2, Z3, Z4, Z5 and Z6 are the impedances corresponding to the currents in each mesh in the equivalent circuit, and T1 is an intermediate variable;

[0021] Single variable bridging capacitor C e The solution is as follows:

[0022]

[0023] T2=MωB-L p C+jD+E (10)

[0024]

[0025] In the formula, T 2、 A, B, C, D, and E are intermediate variables;

[0026] Single-variable equivalent load R Le The solution is as follows:

[0027]

[0028] T3=B1-2Z2Z3Z5+Z1Z4Z5+C1 (13)

[0029]

[0030] In the formula, T 3、 A1, B1, C1, D1, and E1 are intermediate variables;

[0031] Multiple variables: mutual inductance M, bridging capacitance C eEquivalent load R Le Solving for:

[0032] Transforming equation (15) yields equation (17):

[0033]

[0034] The constructor is as shown in equation (17):

[0035]

[0036] In the formula, T is an intermediate variable. For the function Γ, the parameter region where the optimal solution occurs may not be within the numerical range that conforms to the actual engineering situation. Therefore, it is necessary to adjust the parameters M and C in the function Γ. e and R Le Constrain the range of M and C; e and R Le The range is set as shown in equation (18):

[0037]

[0038] The objective function is optimized to obtain the minimum value of the equation and the corresponding variables as shown in equation (19). At this time, the corresponding M1 and C e1 and R Le1 That is, the solution to equation (19)

[0039] Γ(M1, C e1 R Le1 )=min{Γ(M,C e R Le )}=0 (19).

[0040] As a further aspect of the present invention:

[0041] The DC-AC converter (2) adopts a single-phase full-bridge inverter circuit. During the mutual inductance M identification process, the output frequency of the DC-AC converter (2) remains constant, and the output voltage is a square wave with a fixed duty cycle. The output voltage satisfies the formula Among them U ab Let V be the fundamental effective value of the output voltage of the DC-AC converter (2). DC The output DC voltage value of the DC power supply (1);

[0042] The transmitting coil (3) includes transmitting coils L connected in series. P and compensation capacitor C P Compensation capacitor C P One end is connected to one output terminal of the DC-AC converter (2), and the compensation capacitor C P The other end is connected to the transmitting coil LP One end is connected; transmitting coil L P The other end is connected to the other output terminal of the DC-AC converter (2);

[0043] The receiving coil (4) includes transmitting coils L connected in series. S and compensation capacitor C S Compensation capacitor C S One end is connected to one input terminal of the AC-DC converter (5), and the compensation capacitor C S The other end is connected to the transmitting coil L S One end is connected; transmitting coil L S The other end is connected to the other input terminal of the AC-DC converter 5;

[0044] The AC-DC converter (5) includes a single-phase uncontrolled rectifier circuit and a filter capacitor C. filter Single-phase uncontrolled rectifier circuit and filter capacitor C filter Parallel connection; a single-phase uncontrolled rectifier circuit includes four uncontrolled diodes, two uncontrolled diodes form one bridge arm, there are a total of two bridge arms, and the two bridge arms are connected in parallel.

[0045] As a further aspect of the present invention: the multi-parameter online identification energy efficiency improvement method is applied to four working modes, with working mode one being when the cross-connected capacitor C... e and equivalent load R Le Given that the mutual inductance M is known, the expressions for the mutual inductance M can be obtained as (1) and (2) according to formulas (3)-(8); by performing mathematical analysis on formulas (1) and (2), solving the system of equations (1) yields the complex solutions a1 and a2 of the mutual inductance M, neglecting the negative roots. Since the imaginary parts of a1 and a2 are much smaller than the real parts, they can be ignored. It is assumed that the real parts of a1 and a2 are the solutions for the mutual inductance M; at the same time, considering that the actual mutual inductance is positive, taking the positive solutions of a1 and a2, the solution for the mutual inductance M can be obtained; the second working mode is when the mutual inductance M and the equivalent load R are... Le Given the given information, the bridging capacitor C can be solved using formulas (3)-(8). e The expressions are (9), (10), and (11). By performing mathematical analysis on equations (9), (10), and (11), the bridging capacitor C can be obtained. e The solution; the third working mode is in the mutual inductance M and the cross-connected capacitor C e Given the condition, the equivalent load R can be solved using formulas (3)-(8). Le The expressions are (12), (13), and (14). By performing mathematical analysis on equations (12), (13), and (14), the equivalent load R can be obtained. Le The solution; the fourth working mode is to connect the mutual inductance M and the bridging capacitor C. e and equivalent load R LeThe identification problem is transformed into an optimization problem of the above parameter values, and the problem of solving nonlinear equations is transformed into a numerical optimization problem of functions to realize the mutual inductance M and the bridging capacitor C. e and equivalent load R Le Simultaneous identification of multiple parameters.

[0046] As a further aspect of the present invention: the transmission characteristic equation of the capacitor-decoupled underwater wireless power transfer system includes:

[0047]

[0048] Z2 = -R p -jωL p +jωM (21)

[0049] Z3=-jωM (22)

[0050]

[0051] Z5 = -R s -jωL s +jωM (24)

[0052]

[0053] P out =|I3| 2 R Le (28)

[0054]

[0055] Where I1, I2, and I3 are the currents of each mesh, P out Let η be the system's output power, η be the system coil efficiency, and Z be the output power. in Given the input impedance, the impedance of each element of the impedance matrix can be obtained according to equations (20)-(25). Then, the current of each mesh of the capacitor-decoupled underwater wireless power transmission system can be solved according to equations (26) and (27). At this time, I2 is set to 0 to realize the cross-connection capacitor decoupling of the system. Then, the output characteristics of the system can be solved according to equations (28) to (30).

[0056] The transmission characteristic equations of a capacitively coupled underwater wireless power transfer system include:

[0057]

[0058] Z2 = -R p -jωL p +jωM (32)

[0059] Z3=-jωM (33)

[0060]

[0061] Z5 = -R s -jωL s +jωM (35)

[0062]

[0063] P out =|I3| 2 R Le (39)

[0064]

[0065] The impedance of each element of the impedance matrix can be obtained according to equations (31)-(36). Then, the current of each mesh of the capacitively coupled underwater wireless power transmission system can be solved according to equations (37) and (38). At this time, the I2 formula is derived and substituted into the system to realize the cross-capacitor coupling of the system. Then, the output characteristics of the system can be solved according to equations (39) to (41).

[0066] Based on the output characteristic formula of the capacitor-decoupled underwater wireless power transfer system, a constant current output is achieved. The expression for the system's output current during constant current output is:

[0067]

[0068] Based on the output characteristic formula of a capacitively coupled underwater wireless power transfer system, the maximum efficiency and output power tracking of the system are achieved; at this point, the expressions for the system's output power and coil efficiency are:

[0069] P out =|I3| 2 R Le (43)

[0070]

[0071] Compared with existing technologies, this invention provides a multi-parameter online identification method for improving the energy efficiency of underwater wireless transmission systems. This method, by obtaining the system input voltage U1 and current I1, can quickly solve for the mutual inductance M between the system coils and the bridging capacitance C. e and equivalent load R LeThis technology requires no change to the system's drive frequency or the addition of complex circuitry, enabling rapid and accurate identification of mutual inductance, bridging capacitors, and loads. Subsequently, the system's operating state is determined based on the calculated bridging capacitor value. Constant current optimization is performed on capacitor-decoupled underwater wireless power transfer systems, while maximum efficiency and maximum output power point tracking optimization are conducted on capacitor-coupled underwater wireless power transfer systems, providing more specific system-level energy efficiency optimization analysis. This method accurately controls system power and efficiency, improving the stability and reliability of the charging process. Attached Figure Description

[0072] Figure 1 This is a topology diagram of the underwater wireless power transmission system of the present invention.

[0073] Figure 2 This is the equivalent circuit diagram of the underwater wireless power transmission system topology of the present invention.

[0074] Figure 3 This is a flowchart of the single parameter identification process of the present invention.

[0075] Figure 4 This is a flowchart illustrating the multiple parameter identification process of the present invention.

[0076] Figure 5 This is a parameter identification diagram of the mutual inductance between the coils of the system of the present invention under various operating conditions.

[0077] Figure 6 This is a parameter identification diagram of the bridging capacitance between the coils of the system of the present invention under various operating conditions.

[0078] Figure 7 This is a parameter identification diagram of the system load of the present invention under various operating conditions.

[0079] Figure 8 This is a graph showing the solution of the maximum efficiency and maximum output power load curves of the capacitively coupled wireless power transmission system of the present invention.

[0080] Figure 9 This is a constant current output characteristic curve of the capacitor decoupled wireless power transfer system of the present invention.

[0081] In the diagram: 1. DC power supply, 2. DC-AC converter, 3. Transmitting coil, 4. Receiving coil, 5. AC-DC converter, 6. Equivalent load of charging device. Detailed Implementation

[0082] The invention will now be further described with reference to the accompanying drawings.

[0083] like Figure 1 As shown, a method for improving energy efficiency through multi-parameter online identification in an underwater wireless transmission system includes the following steps:

[0084] Step 1: Construct the topology of the underwater wireless power transmission system, including: DC power supply 1, DC-AC converter 2, transmitting coil 3, receiving coil 4, AC-DC converter 5, and equivalent load 6 of the charging device; DC power supply 1 is connected to the input terminal of DC-AC converter 2, the output terminal of DC-AC converter 2 is connected to the input terminal of transmitting coil 3, the output terminal of transmitting coil 3 is opposite to the input terminal of receiving coil 4, the output terminal of receiving coil 4 is connected to the input terminal of AC-DC converter 5, and the output terminal of AC-DC converter 5 is connected to equivalent load 6 of the charging device;

[0085] Step 2: When the system is working normally, obtain the voltage U1 and current I1 of the transmitting coil 3, and calculate the input impedance;

[0086] Step 3, determine the equivalent circuit, such as Figure 2 As shown, the equivalent circuit includes a voltage U1, with one end of voltage U1 connected in series with the primary-side compensation capacitor, parasitic resistance R1, and the primary-side transmitting coil compensation capacitor C. P Primary-side transmitting coil compensation capacitor C P The other end splits into two paths, one of which is connected in series with the equivalent inductance L of the primary-side transmitting coil. P Parasitic resistance R of the primary transmitting coil P parasitic resistance R of the primary transmitting coil P The other end splits into two paths. One path is connected to voltage U1, forming the first mesh. The primary-side transmitting coil compensation capacitor C P The other series-connected capacitor C e bridging capacitor C e The other end splits into two paths, one of which is connected in series with the equivalent inductance L of the secondary transmitting coil. S Parasitic resistance R of the secondary transmitting coil S Parasitic resistance R of the secondary transmitting coil S The other end splits into two paths, one of which is connected in series with a bridging capacitor C. e 'Afterwards, the parasitic resistance R of the primary-side transmitting coil P The other path is connected to form a second mesh; a bridging capacitor C is connected. e The other path is connected in series with the secondary transmitting coil and the compensation capacitor C. S Parasitic resistance of the secondary compensation capacitor R2, and the equivalent load of the system R Le Ultimately, this is related to the parasitic resistance R of the secondary transmitting coil. S The other path is connected, forming a third mesh; due to the bridging capacitor C e and the bridging capacitor C e The sizes are similar, so only the bridging capacitor C needs to be disconnected. e That's it. According to Kirchhoff's laws, a mutual inductance M is established through voltage U1 and current I1, and a bridging capacitor C is connected.e and equivalent load R Le The equation;

[0087] Step four: Substitute the voltage U1 and current I1 obtained in step two into the equations from step three to solve for the mutual inductance M and the bridging capacitance C. e and equivalent load R Le This enables multi-parameter recognition.

[0088] In step two, voltage U1 and current I1 represent the voltage vector and current vector of transmitting coil 3 during normal operation, respectively.

[0089] In step three, the mutual inductance M and the bridging capacitance C are calculated. e and equivalent load R Le The equations are as follows:

[0090] The equation for solving the single-variable mutual inductance M is as follows:

[0091]

[0092] Z2 = -R p -jωL p +jωM (4)

[0093] Z3=-jωM (5)

[0094]

[0095] Z5 = -R s -jωL s +jωM (7)

[0096]

[0097] In the formula, j is the imaginary unit, ω is the system driving angular frequency, and Z1, Z2, Z3, Z4, Z5, and Z6 are... Figure 2 The impedance corresponding to the current in each mesh is given, with T1 being an intermediate variable.

[0098] Single variable bridging capacitor C e The solution is as follows:

[0099]

[0100] T2=MωB-L p C+jD+E (10)

[0101]

[0102] In the formula, T 2、 A, B, C, D, and E are intermediate variables.

[0103] Single-variable equivalent load R Le The solution is as follows:

[0104]

[0105] T3=B1-2Z2Z3Z5+Z1Z4Z5+C1 (13)

[0106]

[0107] In the formula, T 3、 A1, B1, C1, D1, and E1 are intermediate variables.

[0108] Multiple variables: mutual inductance M, bridging capacitance C e Equivalent load R Le Solving for:

[0109] Transforming equation (15) yields equation (17):

[0110]

[0111] The constructor is as shown in equation (17):

[0112]

[0113] In the formula, T is an intermediate variable. For the function Γ, the parameter region where the optimal solution occurs may not be within the numerical range that conforms to the actual engineering situation. Therefore, it is necessary to adjust the parameters M and C in the function Γ. e and R Le Constrain the range of M and C. e and R Le The range is set as shown in equation (18).

[0114]

[0115] The maximum and minimum values ​​of each parameter depend on the parameter fluctuation limits in actual engineering conditions. Optimizing the objective function yields the minimum value of the equation and the corresponding variables, as shown in equation (19). At this point, the corresponding M1 and C... e1 and R Le1 It is the solution corresponding to equation (19).

[0116] Γ(M1, C e1 R Le1 )=min{Γ(M,C e R Le )}=0 (19)

[0117] DC-AC converter 2 uses a single-phase full-bridge inverter circuit. During the mutual inductance M identification process, the output frequency of DC-AC converter 2 remains constant, and the output voltage is a square wave with a fixed duty cycle, satisfying the formula... Among them U ab Let V be the fundamental RMS value of the output voltage of DC-AC converter 2. DC This is the output DC voltage value of DC power supply 1.

[0118] Transmitting coil 3 includes transmitting coils L connected in series. P and compensation capacitor C P Compensation capacitor C P One end is connected to one output terminal of DC-AC converter 2, and the compensation capacitor C P The other end is connected to the transmitting coil L P One end is connected; transmitting coil L P The other end is connected to the other output terminal of the DC-AC converter 2.

[0119] The receiving coil 4 includes transmitting coils L connected in series. S and compensation capacitor C S Compensation capacitor C S One end is connected to one input terminal of AC-DC converter 5, and the compensation capacitor C S The other end is connected to the transmitting coil L S One end is connected; transmitting coil L S The other end is connected to the other input terminal of the AC-DC converter 5.

[0120] The AC-DC converter 5 includes a single-phase uncontrolled rectifier circuit and a filter capacitor C. filter Single-phase uncontrolled rectifier circuit and filter capacitor C filter Parallel connection; a single-phase uncontrolled rectifier circuit includes four uncontrolled diodes, two uncontrolled diodes form one bridge arm, there are a total of two bridge arms, and the two bridge arms are connected in parallel.

[0121] The multi-parameter online identification method for energy efficiency improvement is applied to four operating modes. Operating mode one involves connecting a cross-connector capacitor C. e and equivalent load R Le Given that the mutual inductance M is known, the expressions for the mutual inductance M can be obtained as (1) and (2) according to formulas (3)-(8); by performing mathematical analysis on formulas (1) and (2), solving the system of equations (1) yields the complex solutions a1 and a2 of the mutual inductance M, neglecting the negative roots. Since the imaginary parts of a1 and a2 are much smaller than the real parts, they can be ignored. It is assumed that the real parts of a1 and a2 are the solutions for the mutual inductance M; at the same time, considering that the actual mutual inductance is positive, taking the positive solutions of a1 and a2, the solution for the mutual inductance M can be obtained; the second working mode is when the mutual inductance M and the equivalent load R are... LeGiven the given information, the bridging capacitor C can be solved using formulas (3)-(8). e The expressions are (9), (10), and (11). By performing mathematical analysis on equations (9), (10), and (11), the bridging capacitor C can be obtained. e The solution; the third working mode is in the mutual inductance M and the cross-connected capacitor C e Given the condition, the equivalent load R can be solved using formulas (3)-(8). Le The expressions are (12), (13), and (14). By performing mathematical analysis on equations (12), (13), and (14), the equivalent load R can be obtained. Le The solution; the fourth working mode is to connect the mutual inductance M and the bridging capacitor C. e and equivalent load R Le The identification problem is transformed into an optimization problem of the above parameter values, and the problem of solving nonlinear equations is transformed into a numerical optimization problem of functions to realize the mutual inductance M and the bridging capacitor C. e and equivalent load R Le Simultaneous identification of multiple parameters.

[0122] Step 5: Connect capacitor C across the identification system. e After determining the value, the system jumper capacitor C is used. e The magnitude of the value is used to analyze the system's operating state and to optimize performance for each operating state. Operating states include: the operating state of a capacitor-decoupled underwater wireless power transfer system and the operating state of a capacitor-coupled underwater wireless power transfer system. Energy efficiency optimization includes constant current output characteristic optimization, maximum efficiency, and output power point tracking.

[0123] The transmission characteristic equations of a capacitor-decoupled underwater wireless power transfer system include:

[0124]

[0125] Z2 = -R p -jωL p +jωM (21)

[0126] Z3=-jωM (22)

[0127]

[0128] Z5 = -R s -jωL s +jωM (24)

[0129]

[0130] P out =|I3| 2 R Le (28)

[0131]

[0132] Where I1, I2, and I3 are the currents of each mesh, P out Let η be the system's output power, η be the system coil efficiency, and Z be the output power. in Given the input impedance, the impedance of each element of the impedance matrix can be obtained according to equations (20)-(25). Then, the current of each mesh of the capacitor-decoupled underwater wireless power transmission system is solved according to equations (26) and (27). At this time, I2 is set to 0 to realize the cross-connection capacitor decoupling of the system. Then, the output characteristics of the system are solved according to equations (28) to (30).

[0133] The transmission characteristic equations of a capacitively coupled underwater wireless power transfer system include:

[0134]

[0135] Z2 = -R p -jωL p +jωM (32)

[0136] Z3=-jωM (33)

[0137]

[0138] Z5 = -R s -jωL s +jωM (35)

[0139]

[0140] P out =|I3| 2 R Le (39)

[0141]

[0142] The impedance of each element of the impedance matrix can be obtained according to equations (31)-(36). Then, the current of each mesh of the capacitively coupled underwater wireless power transmission system can be solved according to equations (37) and (38). At this time, the I2 formula is derived and substituted into the system to realize the cross-capacitor coupling of the system. Then, the output characteristics of the system can be solved according to equations (39) to (41).

[0143] Based on the output characteristic formula of the capacitor-decoupled underwater wireless power transfer system, a constant current output is achieved. The expression for the system's output current during constant current output is:

[0144]

[0145] Based on the output characteristic formula of a capacitively coupled underwater wireless power transfer system, the system's maximum efficiency and output power tracking are achieved. At this point, the expressions for the system's output power and coil efficiency are:

[0146] P out =|I3| 2 R Le (43)

[0147]

[0148] After identifying the bridging capacitor parameters, the system operates in different states depending on the size of the coupler's bridging capacitor. State 1: When the bridging capacitor is very small, the system's transmission characteristics are decoupled into a capacitor-free wireless power transfer system. In this state, the operating characteristics are similar to those in air, and the system's energy efficiency optimization goal is constant current output. State 2: When the bridging capacitor is not negligible, the system's transmission characteristics show a trend of first increasing and then decreasing with increasing load. The energy efficiency optimization goal then becomes finding the maximum efficiency point and the maximum output power point. The online mutual inductance identification method for underwater wireless power supply systems based on relay coils is applied to wireless power transfer in underwater AUVs.

[0149] Example:

[0150] Step 1: Construct as follows Figure 1 The circuit topology diagram of the underwater wireless power transmission system shown includes a DC power supply 1, a DC-AC converter 2, a transmitting coil 3, a receiving coil 4, an AC-DC converter 5, and an equivalent load 6 for a charging device. The DC power supply 1 is connected to the input terminal of the DC-AC converter 2, the output terminal of the DC-AC converter 2 is connected to the input terminal of the transmitting coil 3, the output terminal of the transmitting coil 3 is positioned opposite to the input terminal of the receiving coil 4, the output terminal of the receiving coil 4 is connected to the input terminal of the AC-DC converter 5, and the output terminal of the AC-DC converter 5 is connected to the equivalent load 6 for the charging device.

[0151] The system's DC input voltage V DC The voltage is 50V, the system drive frequency is 92.8kHz, and the transmitting coil L... P Receiver coil L S All coils are wound with Litz wire to reduce resistance; the inductance is 86.5uH; and the compensation capacitor C... P C S Both are 34nF. At a high frequency of 92.8kHz, the transmitting coil resistance R... P The resistance R of the receiving coil is 0.33W. S =0.45W, and the parasitic resistances R1 and R2 of the transmitting coil compensation capacitor and the receiving coil compensation capacitor are 0.1W. In this embodiment, it is assumed that the transmitting coil L... Pand relay coil L S The mutual inductance M between the transmitting and receiving coils is 34.335uH, and the equivalent bridging capacitance C between the transmitting and receiving coils is... e = 2.5426nF, system load R L =50W, then the equivalent load R Le ≈45W.

[0152] Step 2: When the system is working normally, obtain the voltage U1 and current I1 of the transmitting coil 3, and calculate the input impedance;

[0153] Step 3, determine the equivalent circuit, such as Figure 2 As shown, according to Kirchhoff's laws, a mutual inductance M is established through voltage U1 and current I1, and a cross-connected capacitor C is connected. e and equivalent load R Le The equations are used to solve for the single variable mutual inductance M according to formulas (1)-(8); the single variable bridging capacitance C is solved according to formulas (9)-(11). e The equivalent load R of a single variable is solved according to formulas (12)-(14). Le Multiple variables M, C e and R Le The solution is based on equations (15)-(18);

[0154] Step four: Substitute the voltage U1 and current I1 obtained in step two into the equations from step three to obtain the mutual inductance M in operating mode one and the bridging capacitor C in operating mode two. e The load R in working mode three Le M and C in working mode four e and R Le This enables the identification of multiple parameters; a workflow reference is provided. Figure 3 and Figure 4 The specific method is as follows:

[0155] In operating mode one, based on the obtained voltage U1 and current I1, calculate Z1, Z2, Z3, Z4, Z5, Z6 and T1 in formulas (2)-(8). Then substitute these parameters into formula (1) to obtain the mutual inductance M.

[0156] In operating mode two, based on the obtained voltage U1 and current I1, calculate Z1, Z2, Z3, Z4, Z5, Z6, T2, A, B, C, D, and E in formulas (3)-(8), (10), and (11). Then, substitute these parameters into formula (9) to obtain the bridging capacitor C. e .

[0157] In operating mode three, based on the obtained voltage U1 and current I1, calculate Z1, Z2, Z3, Z4, Z5, Z6, T3, A1, B1, C1, D1, and E1 in formulas (3)-(8), (13), and (14). Then, substitute these parameters into formula (12) to obtain the load R. Le .

[0158] In operating mode four, based on the obtained voltage U1 and current I1, calculate Z1, Z2, Z3, Z4, Z5, Z6 and T in formulas (2)-(8). Then substitute these parameters into formulas (17) and (19) to obtain the mutual inductance M and the bridging capacitor C. e and load R Le .

[0159] In this example, the mutual inductance M = 34.3352uH obtained through operating mode one has an error of 0.0005% compared to the set value of 34.335uH. The bridging capacitor C obtained through operating mode two... e = 2.46648nF, with an error of 2.9937% compared to the set value of 2.5426nF. The mutual inductance R obtained through operating mode three... Le =44.937Ω, with an error of 0.126% from the set value of 45Ω. The mutual inductance M = 34.3301uH and C obtained through operating mode four are... e =2.4480nF, R Le =44.9857Ω. The errors from the set values ​​are 0.0001%, 9.46%, and 0.0003%, respectively. (Reference to recognition results) Figures 5 to 7 By comparing the experimental values ​​with the assumed values, it can be found that the error is small, which fully demonstrates that the method used in this invention is feasible and effective.

[0160] Step 5: After identifying the system's cross-connection capacitance value, analyze the system's operating state based on the value of the cross-connection capacitance and optimize the performance for each operating state. The impedance of each element of the impedance matrix can be calculated using equations (20)-(25). Then, the current of each mesh in the capacitor-decoupled underwater wireless power transmission system is solved using equations (26) and (27). At this point, I2 is set to 0 to achieve cross-connection capacitance decoupling. Then, the output characteristics of the system are solved using equations (28) to (30). The impedance of each element of the impedance matrix can be calculated using equations (31)-(36). Then, the current of each mesh in the capacitor-coupled underwater wireless power transmission system is solved using equations (37) and (38). The I2 formula is derived and substituted into the system to achieve cross-connection capacitance coupling. Then, the output characteristics of the system are solved using equations (39) to (41).

[0161] Based on the bridging capacitor obtained in step 4, it can be observed that the system should be operating as a capacitively coupled underwater wireless power transfer system. Therefore, the system transmission characteristics are optimized according to the energy efficiency optimization objective of maximum power and maximum efficiency tracking.

[0162] in accordance with Figure 8 As can be seen, the system's output power, calculated based on the bridging capacitor's identification value, shows an increasing trend. Therefore, the maximum power corresponds to a load of 100 ohms, while the maximum efficiency (94.86501%) occurs at a load of 19 ohms. Thus, the system's energy efficiency optimization goal should be to pursue maximum efficiency. The load should be set to 19 ohms.

[0163] Then, the bridging capacitor is set to 0nF. At this point, the system is in the working state of a capacitor-decoupled underwater wireless power transfer system. The energy efficiency optimization goal is to achieve a constant current output from the system. Then, according to... Figure 9 It can be observed that after adjusting the system operating frequency, the system achieves constant current output under load fluctuation conditions.

[0164] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving energy efficiency through multi-parameter online identification in an underwater wireless transmission system, characterized in that, Includes the following steps: Step 1: Construct the topology of the underwater wireless power transmission system, including: a DC power supply, a DC-AC converter, a transmitting coil, a receiving coil, an AC-DC converter, and an equivalent load of a charging device; the DC power supply is connected to the input terminal of the DC-AC converter, the output terminal of the DC-AC converter is connected to the input terminal of the transmitting coil, the output terminal of the transmitting coil is positioned opposite to the input terminal of the receiving coil, the output terminal of the receiving coil is connected to the input terminal of the AC-DC converter, and the output terminal of the AC-DC converter is connected to the equivalent load of the charging device; Step 2: When the system is working normally, obtain the voltage of the transmitting coil. U 1 and current I 1. Calculate the input impedance; Step 3: Determine the equivalent circuit. The equivalent circuit includes voltage U1, with one end of voltage U1 connected in series with a primary-side compensation capacitor and parasitic resistor. R 1. Primary-side transmitting coil compensation capacitor C P Primary-side transmitting coil compensation capacitor C P The other end splits into two paths, one of which is connected in series with the equivalent inductance of the primary-side transmitting coil. L P parasitic resistance of the primary transmitting coil R P parasitic resistance of the primary transmitting coil R P The other end splits into two paths. One path is connected to voltage U1, forming the first mesh, and the primary-side transmitting coil compensation capacitor... C P Another series jumper capacitor C e bridging capacitor C e The other end splits into two paths, one of which is connected in series with the equivalent inductance of the secondary transmitting coil. L S Parasitic resistance of the secondary transmitting coil R S Parasitic resistance of the secondary transmitting coil R S The other end splits into two paths, one of which is connected in series with a bridging capacitor. C e ’ Parasitic resistance of the primary-side transmitting coil R P The other path is connected to form a second mesh; a bridging capacitor is connected. C e The other path is connected in series with the secondary transmitting coil compensation capacitor. C S Parasitic resistance of secondary-side compensation capacitor R 2. Equivalent load of the system R Le Ultimately, this is related to the parasitic resistance of the secondary transmitting coil. R S The other path is connected to form a third mesh; through voltage U 1 and current I 1. Establish mutual understanding M , bridging capacitor C e and equivalent load R Le The equation; Step 4, based on the voltage obtained in Step 2 U 1 and current I 1. Substitute the equations from step three into the system of equations to solve for the mutual inductance. M , bridging capacitor C e and equivalent load R Le To achieve multi-parameter recognition; Step 5: Connect the capacitor across the identification system. C e After determining the value, the system jumper capacitor is used. C e The value is used to analyze the system's operating state and optimize performance for each operating state. The operating states include: the operating state of a capacitor-decoupled underwater wireless power transfer system and the operating state of a capacitor-coupled underwater wireless power transfer system. The energy efficiency optimization includes constant current output characteristic optimization, maximum efficiency, and output power point tracking. When the operating state is a capacitor-decoupled underwater wireless power transfer system, the optimization objective is constant current output. When the operating state is a capacitor-coupled underwater wireless power transfer system, the optimization objectives are maximum efficiency and output power point tracking.

2. The method for improving energy efficiency through multi-parameter online identification of an underwater wireless transmission system according to claim 1, characterized in that, The voltage in step two U 1 and current I 1 represents the voltage vector and current vector of the transmitting coil during normal operation, respectively.

3. The method for improving energy efficiency through multi-parameter online identification of an underwater wireless transmission system according to claim 1, characterized in that, In step three, the mutual inductance is solved. M , bridging capacitor C e and equivalent load R Le The equations are as follows: Solving for mutual inductance of a single variable M The equation is as follows: ； In the formula, j is the imaginary unit. The driving angular frequency of the system. Z 1. Z 2. Z 3. Z 4. Z 5 and Z 6 represents the impedance corresponding to the current in each mesh of the equivalent circuit. T 1 is an intermediate variable; Single variable bridging capacitor C e The solution is as follows: ； In the formula, T 2、 A , B , C , D and E As an intermediate variable; Single-variable equivalent load R Le The solution is as follows: ； In the formula, T 3、 A 1. B 1. C 1. D 1 and E 1 is an intermediate variable; Multiple variables: mutual inductance M、 bridging capacitor C e Equivalent load R Le Solving for: Transforming equation (15) yields equation (17): ； The constructor is as shown in equation (17): ； In the formula, T is an intermediate variable. For the function G, the parameter region where the optimal solution occurs may not be within the numerical range that conforms to actual engineering conditions. Therefore, it is necessary to adjust the variables in the function G. M , C e and R Le Constrain the scope; M , C e and R Le The range is set as shown in equation (18): ； The objective function is optimized to obtain the minimum value of the equation and the corresponding variable as shown in equation (19). M 1. C e1 and R Le1 That is, the solution to equation (19) 。 4. The method for improving energy efficiency through multi-parameter online identification of an underwater wireless transmission system according to claim 1, characterized in that, The DC-AC converter uses a single-phase full-bridge inverter circuit, in mutual inductance M During the identification process, the output frequency of the DC-AC converter remains constant, and the output voltage is a square wave with a fixed duty cycle, satisfying the formula... :in U ab Let V be the fundamental effective value of the output voltage of the DC-AC converter. DC This refers to the output DC voltage value of the DC power supply. The transmitting coils include transmitting coils connected in series. L P and compensation capacitor C P Compensation capacitor C P One end is connected to one output terminal of the DC-AC converter, and the compensation capacitor... C P The other end is connected to the transmitting coil L P One end is connected; transmitting coil L P The other end is connected to the other output terminal of the DC-AC converter; The receiving coil includes transmitting coils connected in series. L S and compensation capacitor C S Compensation capacitor C S One end is connected to one input terminal of the AC-DC converter, and the compensation capacitor... C S The other end is connected to the transmitting coil L S One end is connected; transmitting coil L S The other end is connected to the other input terminal of the AC-DC converter; The AC-DC converter includes a single-phase uncontrolled rectifier circuit and a filter capacitor. C filter Single-phase uncontrolled rectifier circuit and filter capacitor C filter Parallel connection; a single-phase uncontrolled rectifier circuit includes four uncontrolled diodes, two uncontrolled diodes form one bridge arm, there are a total of two bridge arms, and the two bridge arms are connected in parallel.

5. The method for improving energy efficiency through multi-parameter online identification of an underwater wireless transmission system according to claim 1, characterized in that, The multi-parameter online identification method for energy efficiency improvement is applied to four operating modes. Operating mode one involves connecting a capacitor... C e and equivalent load R Le When the mutual inductance is known, it can be solved using formulas (3)-(8). M The expressions are (1) and (2); by performing mathematical analysis on equations (1) and (2), and solving the system of equations (1), we can obtain the mutual inductance with negligible negative roots. M Complex solutions a 1 and a 2, because a 1 and a The imaginary part of 2 can be ignored, and it is assumed that... a 1 and a The real part of 2 is the mutual inductance. M The solution value is obtained; considering that the actual mutual inductance is positive, we take... a 1 and a The positive solutions for 2 can be used to obtain mutual inductance. M The solution; Working mode two is in mutual inductance M and equivalent load R Le When the value is known, the bridging capacitor can be solved using formulas (3)-(8). C e The expressions are (9), (10), and (11). By performing mathematical analysis on equations (9), (10), and (11), the bridging capacitor can be obtained. C e The solution; Working mode three is in mutual inductance M and bridging capacitor C e Given the information, the equivalent load can be solved using formulas (3)-(8). R Le The expressions are (12), (13), and (14). By performing mathematical analysis on equations (12), (13), and (14), the equivalent load can be obtained. R Le The solution; Working mode four transforms the problem of solving nonlinear equations into a numerical optimization problem of functions to achieve mutual inductance. M , bridging capacitor C e and equivalent load R Le Simultaneous identification of multiple parameters.

6. The method for improving energy efficiency through multi-parameter online identification in an underwater wireless transmission system according to claim 1, characterized in that, In step five, the transmission characteristic equation of the capacitor-decoupled underwater wireless power transfer system includes: ； ； in I 1. I 2 and I 3 represents the current of each mesh cell. The system's output power, For the system coil efficiency, Z in Given the input impedance, the impedance of each element of the impedance matrix can be calculated according to equations (20)-(25). Then, the current of each mesh in the capacitor-decoupled underwater wireless power transfer system can be solved according to equations (26) and (27). I Setting 2 to 0 achieves decoupling of the system's cross-connect capacitor, and then the output characteristics of the system are solved according to equations (28) to (30); The transmission characteristic equations of a capacitively coupled underwater wireless power transfer system include: The transmission characteristic equations of a capacitively coupled underwater wireless power transfer system include: ； ； The impedances of each element of the impedance matrix can be obtained from equations (31)-(36). Then, the currents of each mesh in the capacitively coupled underwater wireless power transmission system can be solved from equations (37) and (38). At this point, the derivation is... I 2. The formula is substituted into the system to realize the cross capacitor coupling of the system, and then the output characteristics of the system are solved according to the formulas (39) to (41); Based on the output characteristic formula of the capacitor-decoupled underwater wireless power transfer system, a constant current output is achieved. The expression for the system's output current during constant current output is: ； Based on the output characteristic formula of a capacitively coupled underwater wireless power transfer system, the maximum efficiency and output power tracking of the system are achieved; at this point, the expressions for the system's output power and coil efficiency are: 。

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