Design Method of Magnetic Induction Energy Harvesting Device Based on Combined Energy Harvesting from Three-Phase Power Cables

Abstract

The present invention discloses a design method for a magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables, including: establishing an equivalent circuit model of a three-phase combined magnetic field induction energy harvesting device containing a transformer, obtaining an accurate power analytical formula of the three-phase combined magnetic field induction energy harvesting device by using the superposition theorem, and analyzing the variation of the energy harvesting power with the transformer turns ratio, magnetic core air gap and load fluctuation under different transformer connection methods; comparing and analyzing the variation characteristics of the three-phase combined magnetic field induction energy harvesting power and the single-phase magnetic field induction energy harvesting power with the load, and providing the maximum energy harvesting power for a wide-range variable load by switching between the single-phase energy harvesting and three-phase combined energy harvesting modes. The present invention realizes the improvement of the three-phase combined magnetic field induction energy harvesting device in terms of output power and load access range, fills the blank in the mechanism and performance optimization of the three-phase combined energy harvesting of the magnetic field induction energy harvesting device, and has practical value and guiding significance.

Description

Technical Field

[0001] The present invention relates to the technology of magnetic field induction energy harvesting and power supply, and particularly to a design method of a magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables. Background Art

[0002] The advent of the new power system has pushed the power industry to a new height, promoted the deep integration of digital technology and the real economy, and empowered the transformation and upgrading of traditional industries. To promote the digitization of the main / secondary distribution network, a large number of digital monitoring devices and sensors need to be deployed on medium- and low-voltage feeders and transmission and transformation towers. Taking the medium-voltage distribution network as an example, as the proportion of distributed new energy generation connected to the distribution network continues to increase, the resilience safety line of the distribution network is constantly under new threats, the uncertainty of power quality and reliable power consumption is enhanced, and there is an urgent need to widely deploy digital monitoring terminals such as broadband measurement devices, voltage or current sensors, and construct an omni-directional "transparent power grid".

[0003] However, from the actual situation, except for a small number of distribution network feeder terminals that are equipped with DTU or FTU at the initial design stage, most medium- and low-voltage feeder terminals lack a ready-made and reliable power access point during installation. In addition, in the medium- and low-voltage distribution network environment, existing ambient energy harvesting technologies, such as wind energy, solar energy, thermoelectric energy harvesting, and electric field energy, are difficult to meet the continuous and reliable power supply of small- and medium-power online monitoring devices, which greatly restricts the on-demand deployment and flexible mobilization of online monitoring points. Therefore, in order to solve the real-time power supply problem of digital monitoring terminals under the condition of no ready-made power access point in the main / distribution network, it is urgent to study an effective, reliable, and high-power energy capture method. The current effective energy supply way for battery-free monitoring terminals on the medium- and low-voltage distribution network side is to collect the electromagnetic energy of the field source through a single-phase magnetic field induction energy harvesting device. Due to reasons such as insulation cost and too low output power of three-phase energy harvesting, existing research still focuses on magnetic field induction energy harvesting from single-phase power transmission and distribution lines. In particular, the electrical and non-electrical quantity states of power equipment such as medium- and low-voltage distribution network switch cabinets, distribution transformers, and distribution cables need to be monitored in real time online. However, compared with the current of high-capacity high-voltage transmission lines, the current of medium- and low-voltage feeders is relatively low, and the captured electromagnetic energy of the field source is too weak to maintain the stable operation of small- and medium-power online monitoring devices. In addition, due to the inconsistent supply current caused by the working mode switching of some online monitoring devices, its equivalent impedance fluctuates greatly. Or when the magnetic field induction energy harvesting device supplies energy to multiple online monitoring devices with different power consumption types simultaneously, its equivalent total impedance also has a step change due to the access or shutdown state of each online monitoring device. All the above situations will cause the online monitoring equipment to be unable to operate reliably at the rated power. The reason is that the output performance of the single-phase magnetic field induction energy harvesting device highly depends on the connected load, and its single-load characteristic is difficult to meet the high-power energy stable supply under the condition of load fluctuation, while the equivalent impedance of the online monitoring equipment usually fluctuates within a wide range under working conditions. Therefore, problems such as low power at low current of single-phase power transmission and distribution lines and large influence of output power on load fluctuation need to be solved urgently. Summary of the Invention

[0004] Object of the Invention: An object of the present invention is to provide a design method for a magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables, which collects the magnetic field energy around the three-phase power cables to supply energy to the wireless sensor system, and improves the load connection range and energy harvesting power of the magnetic field induction energy harvesting device.

[0005] Technical Solution: A design method for a magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables of the present invention includes the following steps:

[0006] S1. Establish an equivalent circuit model of a three-phase combined magnetic field induction energy harvesting device with a transformer, analyze the constraints among the three-phase combined magnetic field induction energy harvesting power and the transformer connection method, the structural dimensions of the energy harvesting magnetic core, the number of turns of the energy harvesting coil winding, the magnetic permeability of the energy harvesting magnetic core, the air gap of the energy harvesting magnetic core, the transmission line current, and the load parameters connected. Use the superposition theorem to obtain an accurate power analytical formula for the three-phase combined magnetic field induction energy harvesting device, and use the control variable method to analyze the influence of the transformer turns ratio, the magnetic core air gap, and the connected load on the three-phase combined magnetic field induction energy harvesting power;

[0007] S2. Compare and analyze the load variation characteristics of the three-phase combined magnetic field induction energy harvesting power and the single-phase magnetic field induction energy harvesting power, and provide the maximum energy harvesting power for a wide-range variable load by switching between the single-phase energy harvesting and the three-phase combined energy harvesting modes.

[0008] Furthermore, in step S1, the establishment of the equivalent circuit model of the three-phase combined magnetic field induction energy harvesting device with a transformer is specifically as follows:

[0009] Slip the selected first magnetic core A, second magnetic core B, and third magnetic core C onto the three-phase power cables respectively. Select the first transformer (1) and the second transformer (2). Connect the primary side of the first transformer (1) to the energy harvesting winding of the second magnetic core B, and connect the primary side of the second transformer (2) to the energy harvesting winding of the third magnetic core C. Connect one end of the secondary side of the first transformer (1) and one end of the secondary side of the second transformer (2). Connect the other end of the secondary side of the first transformer (1) to one end of the energy harvesting winding of the first magnetic core A, and connect the other end of the secondary side of the second transformer (2) to the other end of the energy harvesting winding of the first magnetic core A through the load. The primary and secondary side connection methods of the first transformer (1) and the second transformer (2) are the same-name end connection method or the different-name end connection method.

[0010] Furthermore, the use of the superposition theorem to obtain an accurate power analytical formula for the three-phase combined magnetic field induction energy harvesting device is specifically as follows: Analyze the current values flowing through the load when the line current of phase A is used as the excitation source, the line current of phase B is used as the excitation source, and the line current of phase C is used as the excitation source respectively, and calculate the current flowing through the load of the three-phase combined magnetic field induction energy harvesting device based on the superposition theorem.

[0011] Furthermore, when the line current of phase A is used as the excitation source:

[0012] Then, when only the line current of phase A exists, the load current I LA1 is expressed as:

[0013]

[0014] where I pA is the effective value of the line current of phase A, and N A$N$ is the number of turns of the energy-taking coil of the A-phase magnetic field induction energy-taking device, $a$ is the ratio of the current flowing through the energy-taking winding of core A to the exciting current of the A-phase magnetic field induction energy-taking device when only the A-phase line current exists, and $\alpha$ A is the included angle between the secondary-side voltage of the A-phase magnetic field induction energy-taking device and the current flowing through the energy-taking winding of core A when only the A-phase line current exists;

[0015] When the B-phase line current is used as the excitation source:

[0016] Then the load current $I$ when only the B-phase line current exists LA2 is expressed as:

[0017]

[0018] Among them, $N_1$ and $N_1$ # are the number of turns of the primary and secondary sides of the transformer connected to the B-phase energy-taking circuit respectively, $I$ pB is the effective value of the B-phase line current, $N$ B is the number of turns of the energy-taking coil of the B-phase magnetic field induction energy-taking device, $I$ LB is the current flowing through the energy-taking winding of core B when only the B-phase line current exists, $b$ is the included angle between the B-phase voltage and the current flowing through the energy-taking winding of core B when only the B-phase line current exists, and $\beta$ B is the included angle between the secondary-side voltage of the B-phase magnetic field induction energy-taking device and the current flowing through the energy-taking winding of core B when only the B-phase line current exists;

[0019] When the C-phase line current is used as the excitation source:

[0020] The load current $I$ when only the C-phase line current exists LA3 is expressed as:

[0021]

[0022] Among them, $N_2$ and $N_2$ # are the number of turns of the primary and secondary sides of the transformer connected to the C-phase energy-taking circuit respectively, $I$ pC is the effective value of the C-phase line current, $N$ C is the number of turns of the energy-taking coil of the C-phase magnetic field induction energy-taking device, $I$ LC is the current flowing through the energy-taking winding of core C when only the C-phase line current exists, $\gamma$ C is the included angle between the secondary-side voltage of the C-phase magnetic field induction energy-taking device and the current flowing through the energy-taking winding of core C when only the C-phase line current exists, and $c$ is the ratio of the current flowing through the energy-taking winding of core C to the exciting current of the C-phase magnetic field induction energy-taking device when only the C-phase line current exists;

[0023]

[0024] Among them, $L$ mAThe excitation inductance of the energy extraction device for the magnetic field induction of phase A is L mB The excitation inductance of the energy extraction device for the magnetic field induction of phase B is L mC The excitation inductance of the energy extraction device for the magnetic field induction of phase C. ω is the power frequency angular frequency, and R wA The internal resistance of the energy extraction device for the magnetic field induction of phase A is R wB The internal resistance of the energy extraction device for the magnetic field induction of phase B is R wC The internal resistance of the energy extraction device for the magnetic field induction of phase C is I mC The excitation current of the energy extraction device for the magnetic field induction of phase C is R L is the load impedance.

[0025] Based on the superposition theorem, the final current I flowing through the load LA is expressed as:

[0026]

[0027] where is the vector of I LA1 and is the vector of I LA2 and is the vector of I LA3 ; Γ1, Γ2, Γ3 are expressed as:

[0028]

[0029] α, β, γ are expressed as:

[0030]

[0031] Furthermore, based on the superposition theorem, the final current I flowing through the load LA in the formula, the sequential selection of the plus and minus signs is determined by the selection of the same-name or different-name terminals of the transformers connected to the magnetic field energy extraction circuits of phase B and phase C.

[0032] Furthermore, the control variable method is used to analyze the influence of the transformer turns ratio, the magnetic core air gap, and the connected load on the three-phase combined magnetic field induction energy extraction power; specifically:

[0033] The load output power P T2 is:

[0034] P T2 = I LA 2 R L

[0035] where R L is the load impedance, and I LA is the current flowing through the load during the three-phase combined magnetic field induction energy extraction, and I LAIt is related to the connection method of the same or different name terminals of the transformer, turns ratio, structural dimensions of the energy-taking magnetic core, number of turns of the energy-taking coil winding, magnetic permeability of the energy-taking magnetic core, air gap of the energy-taking magnetic core, current of the transmission line, and parameters of the connected load.

[0036] Further, step S2 specifically includes:

[0037] (1) Fix the dimensions of the energy-taking magnetic core, air gap of the magnetic core, number of turns of the energy-taking coil, turns ratio and wiring method of the first transformer 1 and the second transformer 2 for energy-taking access of phase B and phase C;

[0038] (2) According to the intersection point of the curves of the output power of single-phase single-core magnetic field induction energy extraction and three-phase combined magnetic field induction energy extraction changing with the load, obtain the load resistance value R at which the single-phase single-core magnetic field induction energy extraction and the three-phase combined magnetic field induction energy extraction correspond to each other and switch; s ;

[0039] (3) Monitor the load current and load voltage, calculate the load impedance according to Ohm's law. If the load impedance is less than Rs, the switching device S1 is closed, and the load is powered by single-phase single-core magnetic field induction energy extraction. On the contrary, if the load impedance is greater than R s , the switching device S2 is closed, and the load is powered by three-phase combined magnetic field induction energy extraction.

[0040] In an embodiment of the present invention, a design system for a magnetic field induction energy extraction device based on three-phase power cable combined energy capture includes:

[0041] An equivalent circuit model construction unit for establishing an equivalent circuit model of a three-phase combined magnetic field induction energy extraction device containing a transformer;

[0042] An analysis unit for analyzing the constraint relationship between the three-phase combined magnetic field induction energy extraction power and the connection method of the transformer, structural dimensions of the energy-taking magnetic core, number of turns of the energy-taking coil winding, magnetic permeability of the energy-taking magnetic core, air gap of the energy-taking magnetic core, current of the transmission line, and parameters of the connected load;

[0043] An energy extraction power calculation unit for obtaining an accurate power analytical formula of the three-phase combined magnetic field induction energy extraction device by using the superposition theorem, and analyzing the influence of the transformer turns ratio, magnetic core air gap, and connected load on the three-phase combined magnetic field induction energy extraction power by using the control variable method;

[0044] An energy extraction power optimization unit for comparing and analyzing the characteristics of the three-phase combined magnetic field induction energy extraction power and the single-phase magnetic field induction energy extraction power changing with the load, and providing the maximum energy extraction power for a load with a wide range of changes through the switching between the single-phase energy extraction and three-phase combined energy extraction modes.

[0045] In an embodiment of the present invention, an electronic device, the device includes:

[0046] A memory storing executable program code;

[0047] A processor coupled to the memory;

[0048] The processor calls the executable program code stored in the memory and executes the steps of the design method of the magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables as described above.

[0049] In one embodiment of the present invention, a computer-readable storage medium stores computer instructions that, when called, are used to execute the steps of the design method of the magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables as described above.

[0050] Advantageous effects: Compared with the prior art, the significant technical effects of the present invention are as follows: The combined three-phase magnetic field induction energy harvesting provides a new idea for improving the power of magnetic field induction energy harvesting, realizes the improvement of the output power and the load access range of the combined three-phase magnetic field induction energy harvesting device, fills the gap in the combined three-phase energy harvesting mechanism and performance optimization of the magnetic field induction energy harvesting device, and has practical value and guiding significance. Description of the Drawings

[0051] Figure 1 is the equivalent circuit diagram of the combined three-phase magnetic field induction energy harvesting device of the present invention;

[0052] Figure 2 is the current phase diagram of the combined three-phase magnetic field induction energy harvesting when the first transformer uses the opposite-end connection method and the second transformer uses the same-end connection method;

[0053] Figure 3 is the simulation diagram of the combined three-phase magnetic field induction, where (a) is the finite element model and (b) is the combined simulation circuit;

[0054] Figure 4 is the variation of the output power multiple of the combined three-phase magnetic field induction energy harvesting with the turns ratio of the transformer. Among them, (a) is when the turns ratio of the first transformer is 0.2, (b) is when the turns ratio of the first transformer is 0.4, (c) is when the turns ratio of the first transformer is 1, and (d) is when the turns ratio of the first transformer is 3;

[0055] Figure 5 is the variation of the output power multiple of the combined three-phase magnetic field induction energy harvesting with the air gap of the magnetic core;

[0056] Figure 6 is the variation of the output power multiple of the combined three-phase magnetic field induction energy harvesting with the load. Among them, (a) is when the turns ratio of the second transformer is 0.2, (b) is when the turns ratio of the second transformer is 0.4, (c) is when the turns ratio of the second transformer is 1, and (d) is when the turns ratio of the second transformer is 2;

[0057] Figure 7 It is a control diagram for improving the output power based on three-phase combined magnetic field induction energy harvesting. Among them, (a) is a control schematic diagram, and (b) is a control flow chart. Specific implementation manners

[0058] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0059] The present invention discloses an optimized design method for a magnetic field induction energy harvesting device based on three-phase power cable combined energy harvesting, including: establishing an equivalent circuit model of a three-phase combined magnetic field induction energy harvesting device containing a transformer, obtaining an accurate power analytical formula of the three-phase combined magnetic field induction energy harvesting device by using the superposition theorem, and analyzing the energy harvesting power under different transformer connection methods with respect to the transformer turns ratio, magnetic core air gap, and load fluctuation; proposing an output power improvement control strategy for wide-range load access based on three-phase magnetic field combined energy harvesting. The present invention realizes the improvement of the output power and the load access interval of the three-phase combined magnetic field induction energy harvesting device, fills the blank in the mechanism and performance optimization of the magnetic field induction energy harvesting device in three-phase combined energy harvesting, and has practical value and guiding significance.

[0060] As Figure 1 shown, a design method for a magnetic field induction energy harvesting device based on three-phase power cable combined energy harvesting of the present invention includes the following steps:

[0061] S1. Establish an equivalent circuit model of a magnetic field induction energy harvesting device for three-phase power cable combined energy harvesting containing a transformer, analyze the restrictive relationships between the three-phase combined magnetic field induction energy harvesting power and parameters such as the transformer connection method, the structural dimensions of the energy harvesting magnetic core, the number of turns of the energy harvesting coil winding, the magnetic permeability of the energy harvesting magnetic core, the air gap of the energy harvesting magnetic core, the transmission line current, and the connected load, obtain an accurate power analytical formula of the three-phase combined magnetic field induction energy harvesting device by using the superposition theorem, and focus on analyzing the influence of the transformer turns ratio, the magnetic core air gap, and the connected load on the three-phase combined magnetic field induction energy harvesting power by using the control variable method;

[0062] S2. Propose an output power improvement control strategy for wide-range load access based on three-phase combined magnetic field induction energy harvesting, including: comparing and analyzing the characteristics of the three-phase combined magnetic field induction energy harvesting power and the single-phase magnetic field induction energy harvesting power with respect to load changes, and providing the maximum energy harvesting power for a wide-range varying load by switching between the single-phase energy harvesting and the three-phase combined energy harvesting modes.

[0063] Further, step S1 specifically includes: Select three toroidal energy-taking cores, designated as the first core A, the second core B, and the third core C, and respectively sleeved on the three-phase power cables. The core material is a high-permeability material. Select two groups of transformers, designated as the first transformer 1 and the second transformer 2. Connect the primary side of the first transformer 1 to the energy-taking winding of the second core B, and connect the primary side of the second transformer 2 to the energy-taking winding of the third core C. Connect one end of the secondary side of the first transformer 1 and one end of the secondary side of the second transformer 2. Connect the other end of the secondary side of the first transformer 1 to one end of the energy-taking winding of the first core A, and connect the other end of the secondary side of the second transformer 2 to the other end of the energy-taking winding of the first core A through a load. The connection methods of the primary and secondary sides of the first transformer 1 and the second transformer 2 can be the same-name terminal connection method and the different-name terminal connection method. As Figure 1 shown is the equivalent circuit diagram of the three-phase combined magnetic field induction energy-taking device. i pA (t), i pB (t), i pC (t) are the line currents of phase A, phase B, and phase C respectively, and i mA (t), i mB (t), i mC (t) are the exciting currents of the magnetic field induction energy-taking devices of phase A, phase B, and phase C respectively, and i LA (t), i LB (t), i LC (t) are the currents flowing through the energy-taking windings of cores A, B, and C respectively. N A , N B and N C are the number of turns of the energy-taking coils of the magnetic field induction energy-taking devices of phase A, phase B, and phase C respectively. N1 and N1 # are the number of turns of the primary and secondary sides of the transformer (i.e., the first transformer 1) connected to the energy-taking circuit of phase B respectively. N2 and N2 # are the number of turns of the primary and secondary sides of the transformer (i.e., the second transformer 2) connected to the energy-taking circuit of phase C respectively. u A (t), u B (t), u C (t) are the induced voltages of the magnetic field induction energy-taking devices of phase A, phase B, and phase C respectively. Considering Figure 1 there are three current sources with different phases, the superposition theorem is used to calculate the current I LA flowing through the load, so as to obtain the load output power. Based on Figure 1 the three-phase combined magnetic field induction energy-taking circuit and the superposition theorem, taking the first transformer 1 using the different-name terminal connection method and the second transformer 2 using the same-name terminal connection method as an example, draw the current phase diagram of the magnetic field induction energy-taking circuit of each phase as shown in Figure 2 . I pA , I pB , I pC are the effective values of the line currents of phase A, phase B, and phase C respectively. ImA 、I mB 、I mC are the exciting currents of the magnetic field induction energy extraction devices for phase A, phase B, and phase C respectively. U A 、U B 、U C are the secondary side voltages of the magnetic field induction energy extraction devices for phase A, phase B, and phase C respectively. α, β, and γ are the phase difference angles between the secondary side currents and voltages of the magnetic field induction energy extraction devices for phase A, phase B, and phase C respectively. α A 、β B 、γ C are the phase difference angles between the secondary side voltages and the currents flowing through the energy extraction windings A, B, and C of the magnetic cores of the magnetic field induction energy extraction devices for phase A, phase B, and phase C respectively. I LA1 、I LA2 、I LA3 are the currents flowing through the energy extraction windings A, B, and C of the magnetic cores when only the line currents of phases A, B, and C exist respectively. The following analyzes the current flowing through the load of the three-phase combined magnetic field induction energy extraction device obtained based on the superposition theorem, and analyzes the current values flowing through the load when the line current of phase A is used as the excitation source, the line current of phase B is used as the excitation source, and the line current of phase C is used as the excitation source respectively.

[0064] (1) When the line current of phase A is used as the excitation source:

[0065]

[0066] Among them, I LA1 is the current flowing through the energy extraction winding A of the magnetic core when only the line current of phase A exists. I mA1 is the exciting current of the magnetic field induction energy extraction device for phase A. a is the ratio of the current flowing through the energy extraction winding A of the magnetic core to the exciting current of the magnetic field induction energy extraction device for phase A when only the line current of phase A exists. ω is the power frequency angular frequency. R L is the load resistance. R wA is the internal resistance of the magnetic field induction energy extraction device for phase A. R wB is the internal resistance of the magnetic field induction energy extraction device for phase B. R wC is the internal resistance of the magnetic field induction energy extraction device for phase C. L mA is the exciting inductance of the magnetic field induction energy extraction device for phase A. L mB is the exciting inductance of the magnetic field induction energy extraction device for phase B. L mC is the exciting inductance of the magnetic field induction energy extraction device for phase C.

[0067] Figure 2 In the triangle formed by the lengths of each side being I pA / N A 、I LA1 、I mA1 , according to the cosine theorem:

[0068]

[0069] Among them, α A is the included angle between the secondary side voltage of the magnetic field induction energy extraction device of phase A and the current flowing through the energy extraction winding of magnetic core A when only the line current of phase A exists.

[0070] Then, when only the line current of phase A exists, the load current I LA1 can be expressed as:

[0071]

[0072] In formula (3), α A is expressed as:

[0073]

[0074] (3) The line current of phase B is used as the excitation source:

[0075] According to Kirchhoff's voltage law, it can be obtained that:

[0076]

[0077] Among them, I LB is the current flowing through the energy extraction winding of magnetic core B when only the line current of phase B exists, I mB1 is the exciting current of the magnetic field induction energy extraction device of phase B, and b is the ratio of the current flowing through the energy extraction winding of magnetic core B to the exciting current of the magnetic field induction energy extraction device of phase B when only the line current of phase B exists;

[0078] In the triangle formed by the lengths of each side being I pB / N B 、I LB 、I mB1 According to the cosine theorem, it can be known that:

[0079]

[0080] Among them, β B is the included angle between the secondary side voltage of the magnetic field induction energy extraction device of phase B and the current flowing through the energy extraction winding of magnetic core B when only the line current of phase B exists.

[0081] Then, when only the line current of phase B exists, the load current I LA2 can be expressed as:

[0082]

[0083] In formula (7), β B is expressed as:

[0084]

[0085] (3) The line current of phase C is used as the excitation source:

[0086] Similarly, when only the line current of phase C exists, the load current I LA3 can be expressed as:

[0087]

[0088] In Equation (9), γ C is the included angle between the secondary-side voltage of the magnetic-field induction energy-taking device of phase C and the current flowing through the energy-taking winding of core C when only the line current of phase C exists; c is the ratio of the current flowing through the energy-taking winding of core C to the exciting current of the magnetic-field induction energy-taking device of phase C when only the line current of phase C exists.

[0089]

[0090] In summary, based on the superposition theorem, the final current I flowing through the load LA can be expressed as:

[0091]

[0092] In Equation (11), Γ1, Γ2, and Γ3 can be expressed as:

[0093]

[0094] In Equation (12), α, β, and γ are the phase difference angles between the secondary-side currents and voltages of the magnetic-field induction energy-taking devices of phases A, B, and C, respectively.

[0095]

[0096] The sequential selection of the plus and minus signs in Equation (11) is determined by the selection of the same-name or different-name terminals of the transformers connected to the magnetic-field energy-taking circuits of phases B and C. Table 1 shows the symbol selection of the calculation formula of I LA under different connection methods of each transformer.

[0097] Table 1 Symbol selection of the calculation formula of I LA under different connection methods of each transformer

[0098]

[0099] Then the load output power P T2 is:

[0100] P T2 = I LA 2 R L (14)

[0101] where R L is the load impedance, and ILA It is related to parameters such as the connection method of the same-name or different-name terminals of the transformer, the turns ratio of the first transformer 1 and the second transformer 2, the structural dimensions of the energy-taking core, the number of turns of the energy-taking coil winding, the magnetic permeability of the energy-taking core, the air gap of the energy-taking core, the current of the transmission line, and the connected load.

[0102] Establish the three-phase combined magnetic field induction simulation diagrams shown in (a) and (b) in Figure 3 . The outer radius, inner radius, and height of the core are 30 mm, 15 mm, and 30 mm respectively. The energy-taking core material is 1K107. The number of energy-taking turns of the first core A, the second core B, and the third core C is 50 turns. First, analyze the influence of the connection method and turns of the first transformer 1 and the second transformer 2 on the energy-taking power multiple under the simulation and calculation conditions. To simplify the analysis, fix the air gap of the core, the line current, and the connected load at 0.2 mm, 20 A respectively. Assume the output voltage is 3.3 V, the power consumption of the on-line monitoring device is about 100 mW, and set the connected impedance to 100 Ω. As shown in (a) to (d) in Figure 4 are the curves of the three-phase energy-taking power multiple varying with the transformer turns under four groups of N1 / N1 # typical values. Set G T as the ratio of the three-phase distributed energy-taking output power to the single-phase centralized energy-taking load output power of the same volume, that is, G T = P T2 / P T1 . Among them, P T1 is the energy-taking power after the energy-taking windings of the three cores are connected in sequence and sleeved on the single-phase power cable. By comparing (a) to (d) in Figure 4 , it can be seen that the simulation results are relatively close to the calculation results, which also verifies the correctness of the numerical calculation analytical formula. Some errors are due to the neglect of parameters such as coil leakage inductance and excitation resistance in the calculation process. When N1 / N1 # is 0.2, the transformer connection method is Scheme 3 and Scheme 4, and there is an optimal value for N2 / N2 # . When N1 / N1 # is 0.4, 1, and 3, the transformer connection methods are Scheme 1, Scheme 2, Scheme 3, and Scheme 4, and there are optimal values for N2 / N2 # in all cases. It should be noted that as can be seen from (c) in Figure 4 , when N1 / N1 # = N2 / N2 # = 1, the current vectors of the three-phase energy-taking device flowing through the load cancel each other out under the connection method of Scheme 1, and the synthesized current is 0, and there is no output power for the three-phase energy-taking. From this, it can be seen that the addition of non-equal turns ratio transformers can effectively prevent the ineffective energy-taking of the three-phase induction energy-taking device, and there are optimal turns ratios and transformer connection methods for the second transformer 2 under different turns ratios of the first transformer 1, so that the three-phase combined magnetic field induction energy-taking power has a maximum value.

[0103] Furthermore, since increasing the magnetic core air gap will improve the anti - saturation ability of the energy - taking magnetic core at the expense of part of the energy - taking power, if the power demand of the connected load is about milliwatt level, the air gap of the energy - taking magnetic core can be increased on the premise of meeting the load power demand. Therefore, in this section, the variation of the three - phase energy - taking output power multiple with the magnetic core air gap is analyzed. To facilitate intuitive analysis and simplify the circuit structure, the turns ratio of the first transformer is fixed at 1. If the electrical isolation of phase B is not considered, the transformer connected to the phase - B energy - taking circuit can be omitted in practical applications. Using the control variable method, the line current is still set at 20 A, and the connected load is 100 Ω. From Figure 4 Figure (c), it can be seen that the optimal turns ratio of the transformer connected to phase C is about 0.16, and the air gap variation range is set at 0.1 mm to 1 mm, as shown in Figure 5 is the curve of the three - phase energy - taking output power multiple varying with the magnetic core air gap. Under the current simulation and calculation parameter conditions, the power multiple almost increases linearly before the air gap reaches 0.2 mm. The power multiples of the three - phase energy - taking all increase with the increase of the magnetic core air gap, and when the transformers adopt the connection method of Scheme 4, the rising rate of the power multiple is relatively obvious. However, increasing the air gap will directly affect the energy - taking power of the energy - taking magnetic core. Therefore, in actual use, the magnetic core air gap should be determined according to the line current fluctuation range and the load power demand.

[0104] Considering the volatility of the connected load, the variation of the energy - taking power multiple with the transformer connection method and the connected load value is further analyzed. The line current is fixed at 20 A, and the air gap is fixed at 0.2 mm. To simplify the analysis, the control variable method is still used to fix the transformer connected to the phase - B magnetic - field induction energy - taking device at 1, as shown in Figure 6 Figures (a) - (d) show the variation of the single - phase energy - taking output power and the three - phase energy - taking output power with the load when the transformer connected to the phase - C magnetic - field induction energy - taking device is in different connection methods. Among them, P S is the single - phase single - magnetic - core magnetic - field induction energy - taking power.

[0105] The calculation results and simulation results of the output power variation curves under different transformer connection methods are almost the same, which also verifies the correctness of the theoretical analytical formula of the three - phase magnetic - field induction energy - taking power. When the turns ratio of the first transformer is 1, the output power variation curves of Scheme 2 and Scheme 3 are basically the same; in particular, when the turns ratios of the transformers connected to the phase - B and phase - C magnetic - field induction energy - taking devices are both 1, the output power variation curves of Scheme 2, Scheme 3, and Scheme 4 are basically the same, and the three - phase magnetic - field energy - taking method of Scheme 1 cannot obtain energy. In addition, both the single - phase magnetic - field induction energy - taking output power and the three - phase combined magnetic - field induction energy - taking output power have optimal values. When N2 / N2 # is 0.2 and 0.4, the output power of the three - phase magnetic - field induction energy - taking using Scheme 4 is the largest. When N2 / N2 #When it is 2, the output power is the largest when Scheme 2 or Scheme 3 is adopted for three-phase magnetic field induction energy harvesting. In particular, the energy harvesting power of single-phase single-core magnetic field induction energy harvesting is greater than that of any three-phase combined magnetic field induction energy harvesting method with transformer connection when the load is small. Therefore, the present invention proposes an output power boosting control strategy for wide-range load access based on three-phase combined magnetic field induction energy harvesting.

[0106] Further, as Figure 7 shown in (a) and (b) in

[0107] (1) Select the energy harvesting core size, core air gap, number of turns of the energy harvesting coil, turns ratio and wiring method of the first transformer 1 and the second transformer 2 for B-phase and C-phase energy harvesting access;

[0108] (2) According to the intersection point of the curves of the output power of single-phase single-core magnetic field induction energy harvesting and three-phase combined magnetic field induction energy harvesting with respect to the load, obtain the load resistance value (i.e., the threshold) R s ;

[0109] (3) Monitor the load current and load voltage, calculate the load impedance according to Ohm's law. If the load impedance is less than Rs, the switching device S1 is closed, and the single-phase single-core magnetic field induction energy harvesting is used to supply power to the load. On the contrary, if the load impedance is greater than R s , the switching device S2 is closed, and the three-phase combined magnetic field induction energy harvesting is used to supply power to the load.

[0110] In an embodiment of the present invention, a magnetic field induction energy harvesting device design system based on three-phase power cable combined energy capture includes:

[0111] An equivalent circuit model construction unit for establishing an equivalent circuit model of a three-phase combined magnetic field induction energy harvesting device containing a transformer;

[0112] An analysis unit for analyzing the restrictive relationships among the three-phase combined magnetic field induction energy harvesting power, transformer connection method, energy harvesting core structure size, number of turns of the coil energy harvesting winding, magnetic permeability of the energy harvesting core, energy harvesting core air gap, transmission line current, and load parameters;

[0113] An energy harvesting power calculation unit for obtaining an accurate power analytical formula of the three-phase combined magnetic field induction energy harvesting device by using the superposition theorem, and analyzing the influence of the transformer turns ratio, core air gap, and connected load on the three-phase combined magnetic field induction energy harvesting power by using the control variable method;

[0114] An energy harvesting power optimization unit for comparing and analyzing the characteristics of the three-phase combined magnetic field induction energy harvesting power and the single-phase magnetic field induction energy harvesting power with respect to the load change, and providing the maximum energy harvesting power for a wide-range variable load through the switching between the single-phase energy harvesting and three-phase combined energy harvesting modes.

[0115] In one embodiment of the present invention, an electronic device, the device comprising:

[0116] A memory storing executable program code;

[0117] A processor coupled to the memory;

[0118] The processor calls the executable program code stored in the memory and executes the steps of the design method of the magnetic field induction energy harvesting device based on the combined energy harvesting of three-phase power cables as described above.

[0119] In one embodiment of the present invention, a computer-readable storage medium stores computer instructions, and when the computer instructions are called, they are used to execute the steps of the design method of the magnetic field induction energy harvesting device based on the combined energy harvesting of three-phase power cables as described above.

Claims

1. A design method of a magnetic induction energy harvesting device based on combined energy harvesting from three-phase power cables, characterized in that, It includes the following steps: S1. Establish an equivalent circuit model of a three-phase combined magnetic field induction energy harvesting device with a transformer, analyze the constraint relationships between the three-phase combined magnetic field induction energy harvesting power and the transformer connection method, the structure size of the energy harvesting magnetic core, the number of turns of the energy harvesting coil winding, the magnetic permeability of the energy harvesting magnetic core, the air gap of the energy harvesting magnetic core, the transmission line current, and the load parameters connected. Use the superposition theorem to obtain an accurate power analytical formula for the three-phase combined magnetic field induction energy harvesting device, and use the control variable method to analyze the influence of the transformer turns ratio, the magnetic core air gap, and the connected load on the three-phase combined magnetic field induction energy harvesting power; S2. Compare and analyze the load variation characteristics of the three-phase combined magnetic field induction energy harvesting power and the single-phase magnetic field induction energy harvesting power, and provide the maximum energy harvesting power for a wide-range variable load by switching between the single-phase energy harvesting and three-phase combined energy harvesting modes. Specifically, it includes: (1) Select the size of the energy harvesting magnetic core, the magnetic core air gap, the number of turns of the energy harvesting coil, the turns ratio and connection method of the first transformer 1 and the second transformer 2 connected to the energy harvesting of phase B and phase C; (2)According to the intersection point of the curves of the output power of single-phase single-core magnetic field induction energy harvesting and three-phase combined magnetic field induction energy harvesting varying with the load, the load resistance value R corresponding to the mutual switching between single-phase single-core magnetic field induction energy harvesting and three-phase combined magnetic field induction energy harvesting is obtained s ; (3) Monitor the load current and load voltage, calculate the load impedance according to Ohm's law. If the load impedance is less than Rs, the switching device S1 is closed, and the single-phase single-core magnetic field induction energy harvesting is used to supply power to the load. On the contrary, if the load impedance is greater than R s , the switching device S2 is closed, and the three-phase combined magnetic field induction energy harvesting is used to supply power to the load.

2. The design method of a magnetic induction energy harvesting device based on combined energy harvesting of three-phase power cables according to claim 1, characterized in that In step S1, the equivalent circuit model of the three-phase combined magnetic field induction energy harvesting device with a transformer is established as follows: The selected first magnetic core A, second magnetic core B, and third magnetic core C are respectively sleeved on the three-phase power cables. The first transformer (1) and the second transformer (2) are selected. The primary side of the first transformer (1) is connected to the energy harvesting winding of the second magnetic core B, and the primary side of the second transformer (2) is connected to the energy harvesting winding of the third magnetic core C. One end of the secondary side of the first transformer (1) and one end of the secondary side of the second transformer (2) are connected. The other end of the secondary side of the first transformer (1) is connected to one end of the energy harvesting winding of the first magnetic core A. The other end of the secondary side of the second transformer (2) is connected to the other end of the energy harvesting winding of the first magnetic core A through a load. The primary and secondary side connection methods of the first transformer (1) and the second transformer (2) are the same-name end connection method or the different-name end connection method.

3. A design method of a magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables according to claim 1, characterized in that, Use the superposition theorem to obtain an accurate power analytical formula for the three-phase combined magnetic field induction energy harvesting device, specifically: analyze the current values flowing through the load when the phase A line current is used as the excitation source, the phase B line current is used as the excitation source, and the phase C line current is used as the excitation source, and calculate the current flowing through the load of the three-phase combined magnetic field induction energy harvesting device based on the superposition theorem.

4. A design method of a magnetic induction energy harvesting device based on combined energy harvesting of three-phase power cables according to claim 3, characterized in that When the phase A line current is used as the excitation source: Then, when only the line current of phase A exists, the load current I LA1 is expressed as: Among them, I pA is the effective value of the line current of phase A, N A is the number of turns of the energy-taking coil of the magnetic field induction energy-taking device of phase A, a is the ratio of the current flowing through the energy-taking winding of core A to the exciting current of the magnetic field induction energy-taking device of phase A when only the line current of phase A exists, α A is the included angle between the secondary-side voltage of the magnetic field induction energy-taking device of phase A and the current flowing through the energy-taking winding of core A when only the line current of phase A exists; When the phase B line current is used as the excitation source: Then, when there is only the line current of phase B, the load current I LA2 is expressed as: Among them, N1 and N1 # are the primary and secondary turns of the transformer connected to the B-phase energy-taking circuit respectively, I pB is the effective value of the B-phase line current, N B is the number of turns of the energy-taking coil of the B-phase magnetic field induction energy-taking device, I LB is the current flowing through the energy-taking winding of core B when only the B-phase line current exists, b is the ratio of the current flowing through the energy-taking winding of core B to the excitation current of the B-phase magnetic field induction energy-taking device when only the B-phase line current exists, β B is the angle between the secondary-side voltage of the B-phase magnetic field induction energy-taking device and the current flowing through the energy-taking winding of core B when only the B-phase line current exists; When the phase C line current is used as the excitation source: Load current I when only C-phase line current exists LA3 Expressed as: Among them, N2 and N2 # are the primary and secondary turns of the transformer accessing the C-phase energy-taking circuit respectively, I pC is the effective value of the C-phase line current, N C is the number of turns of the energy-taking coil of the C-phase magnetic field induction energy-taking device, I LC is the current flowing through the energy-taking winding of core C when only the C-phase line current exists; c is the ratio of the current flowing through the energy-taking winding of core C to the exciting current of the C-phase magnetic field induction energy-taking device when only the C-phase line current exists, γ C is the included angle between the secondary-side voltage of the C-phase magnetic field induction energy-taking device and the current flowing through the energy-taking winding of core C when only the C-phase line current exists; Among them, L mA is the excitation inductance of the magnetic field induction energy extraction device for phase A, L mB is the excitation inductance of the magnetic field induction energy extraction device for phase B, L mC is the excitation inductance of the magnetic field induction energy extraction device for phase C, ω is the power frequency angular frequency, R wA is the internal resistance of the magnetic field induction energy extraction device for phase A, R wB is the internal resistance of the magnetic field induction energy extraction device for phase B, R wC is the internal resistance of the magnetic field induction energy extraction device for phase C, I mC is the excitation current of the magnetic field induction energy extraction device for phase C, R L is the load impedance; The final current I flowing through the load based on the superposition theorem LA is expressed as: Among them, is the vector of I LA1 ; is the vector of I LA2 ; is the vector of I LA3 ; Γ1, Γ2, Γ3 are expressed as: α, β, γ are expressed as:

5. A design method of a magnetic field induction energy harvesting device based on combined energy harvesting of three-phase power cables according to claim 4, characterized in that The final current I flowing through the load based on the superposition theorem LA The sequential selection of the plus and minus signs in the formula is determined by the selection of the same-name or different-name terminals of the transformers connected to the magnetic field energy extraction circuits of phases B and C.

6. A design method of a magnetic field induction energy harvesting device based on combined energy harvesting from three-phase power cables according to claim 1, characterized in that Use the control variable method to analyze the influence of the transformer turns ratio, the magnetic core air gap, and the connected load on the three-phase combined magnetic field induction energy harvesting power. Specifically: Load output power P T2 is: P T2 = I LA 2 R L Among them, R L is the load impedance, and I LA is the current flowing through the load during the energy extraction by the combined three-phase magnetic field induction. I LA is related to the connection method of the same or opposite ends of the transformer, the turns ratio, the structural dimensions of the energy extraction magnetic core, the number of turns of the energy extraction coil winding, the magnetic permeability of the energy extraction magnetic core, the air gap of the energy extraction magnetic core, the current of the transmission line, and the parameters of the connected load.

7. A design system for a magnetic induction energy harvesting device based on combined energy harvesting from three-phase power cables, characterized in that, It includes: An equivalent circuit model construction unit for establishing an equivalent circuit model of a three-phase combined magnetic field induction energy harvesting device with a transformer; An analysis unit for analyzing the constraint relationships between the three-phase combined magnetic field induction energy harvesting power and the transformer connection method, the structure size of the energy harvesting magnetic core, the number of turns of the energy harvesting coil winding, the magnetic permeability of the energy harvesting magnetic core, the air gap of the energy harvesting magnetic core, the transmission line current, and the load parameters connected; An energy harvesting power calculation unit for using the superposition theorem to obtain an accurate power analytical formula for the three-phase combined magnetic field induction energy harvesting device, and using the control variable method to analyze the influence of the transformer turns ratio, the magnetic core air gap, and the connected load on the three-phase combined magnetic field induction energy harvesting power; The energy-taking power optimization unit is used to compare and analyze the characteristics of the energy-taking power of the three-phase combined magnetic field induction and the single-phase magnetic field induction with respect to load changes, and provide the maximum energy-taking power for a load with a wide range of changes by switching between the single-phase energy-taking and the three-phase combined energy-taking modes; specifically including: (1) Fix the energy-taking core size, core air gap, number of turns of the energy-taking coil, turns ratio and wiring method of the first transformer 1 and the second transformer 2 for the energy-taking access of phase B and phase C; (2) According to the intersection point of the curves of the output power of single-phase single-core magnetic field induction energy harvesting and three-phase combined magnetic field induction energy harvesting varying with the load, the load resistance value R corresponding to the mutual switching between single-phase single-core magnetic field induction energy harvesting and three-phase combined magnetic field induction energy harvesting is obtained. s ; (3) Monitor the load current and load voltage, calculate the load impedance according to Ohm's law. If the load impedance is less than Rs, the switching device S1 is closed, and the single-phase single-core magnetic field induction energy harvesting is used to supply power to the load. On the contrary, if the load impedance is greater than R s , the switching device S2 is closed, and the three-phase combined magnetic field induction energy harvesting is used to supply power to the load.

8. An electronic device, characterized in that, The device includes: A memory storing executable program code; A processor coupled to the memory; The processor calls the executable program code stored in the memory and executes the steps of the design method of the magnetic field induction energy-taking device based on the combined energy capture of three-phase power cables as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions, which are used to execute the steps of the design method of the magnetic field induction energy-taking device based on the combined energy capture of three-phase power cables as described in any one of claims 1-6 when the computer instructions are called.

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