CT power taking-wireless power transmission system and output power optimization control method thereof
The impedance of the CT power withdrawal-wireless transmission system is adjusted through the DC/DC converter and the disturbance-observation MPPT algorithm, which solves the problem that the output power of the CT power withdrawal device is affected by the load characteristics, and maximizes the system output power and improves efficiency.
Patent Information
- Application Number
- CN202510555371.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-08-01
AI Technical Summary
The output power of the existing CT power-taking device is affected by its own load characteristics. When the overall equivalent impedance of the system is too small or too large, the output power will drop and cannot be maximized.
The DC/DC converter is used to adjust the equivalent impedance of the wireless power transmission system, and combined with the disturbance-observation MPPT algorithm, the impedance matching of the CT power withdrawal-wireless power transmission system is realized. Through the rectification and voltage stabilization circuit and the DC/DC converter optimization control, the output power of the CT device is adjusted.
The output power of the CT power withdrawal-wireless power transmission system is maximized, the system's transmission efficiency and adaptability are improved, and the control can be optimized under different load conditions.
Smart Images
Figure CN120414928A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of transmission line monitoring, and particularly relates to a CT power taking - wireless power transmission system and an optimization control method for its output power. Background Art
[0002] With the rapid development of China's power industry, the power grid coverage has been expanding day by day, and the safe and stable operation of the power system has become extremely important. Conducting on - line real - time monitoring of transmission cables is a necessary condition for the development of smart grids and an important means to improve the reliability of transmission lines. In practical applications, a variety of on - line monitoring devices are widely used to monitor various information of transmission conductors, such as electrical information (such as voltage, current, etc.), mechanical information (such as snow and ice coverage, cable galloping, etc.), and climate information (such as wind speed, flashover, pollution, etc.). However, these on - line monitoring devices usually require a stable and reliable power supply to support their long - term outdoor work. Currently, the commonly used power supply methods include battery power supply, solar / wind power supply, vibration power supply, electric field power supply, and magnetic field power supply, etc. However, the above - mentioned power supply methods all have certain deficiencies and there are certain limitations in their use.
[0003] Power supply solely by battery can only provide long-term power supply for low-power online monitoring devices, so it is not suitable for applications where the power consumption is as high as several watts, such as images and videos. Solar / wind energy is greatly affected by weather. For example, during the severe snowstorm in the south in 2008, stable power supply could not be obtained. The power generated by vibration energy harvesting and electric field energy harvesting is relatively small, usually below 0.1W, and is also not suitable for high-power online monitoring devices. In contrast, the magnetic field energy harvesting method that uses a current transformer (CT) to generate an induced voltage from the alternating magnetic field around high-voltage AC transmission wires and supply power to the online monitoring device can achieve a power supply of over 10W, which can meet the power consumption requirements of most online monitoring devices. On this basis, researchers proposed and improved the system architecture of CT power extraction - wireless power transmission. First, a CT device is used to pick up electrical energy from the power frequency magnetic field around the current-carrying wire through magnetic induction coupling, and then it is transmitted to the tower on the low-voltage side in the form of wireless power transfer (WPT), so as to supply power to the online monitoring device on the ground potential side without damaging the line insulation. Researchers optimized the design of the CT power extraction - wireless power transmission system from aspects such as system topology and wireless power transmission mechanism to improve the transmission efficiency of the system and its adaptability to outdoor environments. However, the above research mainly optimized the design of the wireless power transmission part, and only equivalent the CT power extraction device to a constant voltage source. In fact, under certain load current conditions, the output power of the CT power extraction device is also affected by its own load characteristics. In particular, when the equivalent impedance of the entire wireless power transmission system is too small or too large, it will cause a decrease in the output power of the CT power extraction device. Therefore, it is necessary to optimize the control of the CT power extraction - wireless power transmission system architecture to maximize the overall output power of the system. Summary of the Invention
[0004] The purpose of the present invention is to provide a CT power extraction - wireless power transmission system and its output power optimization control method, which are used to solve the problems that the output power of the existing CT power extraction device is affected by its own load characteristics, and when the equivalent impedance of the entire system is too small or too large, it will cause a decrease in the output power of the CT power extraction device, and the maximum output power cannot be achieved. By using the DC / DC converter in the CT power extraction control circuit to adjust the equivalent impedance of the wireless power transmission system to match the optimal load impedance of the CT device, the overall output power of the system can be maximized.
[0005] To achieve the above object, in a first aspect, the present invention provides a CT power extraction - wireless power transmission system, including a CT device, a CT power extraction control circuit, and a wireless power transmission conversion circuit. The CT device picks up electrical energy from the magnetic field around the current - carrying wire based on magnetic - field induction coupling. The CT power extraction control circuit includes a rectification and voltage - regulation circuit and a DC / DC converter. The rectification and voltage - regulation circuit is used to rectify and regulate the current flowing from the CT device to the load to obtain a DC voltage. The DC voltage is processed by the DC / DC converter to obtain an output voltage, and the output voltage is input to the wireless power transmission conversion circuit. The DC / DC converter is used to adjust the equivalent impedance of the wireless power transmission conversion circuit to maximize the output power of the CT device.
[0006] According to a CT power extraction - wireless power transmission system provided by the present invention, the DC / DC converter includes a capacitor C f1 , a switching tube S buck , a diode D buck , an inductor L buck , a capacitor C buck . The first end of the capacitor C f1 is connected to the first end of the switching tube S buck . The second end of the switching tube S buck is connected to the first end of the diode D buck and the first end of the inductor L buck . The second end of the inductor L buck is connected to the first end of the capacitor C buck . The second end of the capacitor C buck is connected to the second end of the diode D buck and the second end of the capacitor C f1 . By adjusting the duty cycle of the DC / DC converter through the control terminal of the switching tube S buck , the equivalent impedance of the CT power extraction - wireless power transmission system is adjusted. According to a CT power extraction - wireless power transmission system provided by the present invention, the matching adjustment of the equivalent impedance of the CT power extraction - wireless power transmission system is realized through a MPPT algorithm based on perturbation - observation. The specific process is as follows: Set the symbolic variable sgn 1 to 1, and the duty cycle of the DC / DC converter is zero; Increase the duty cycle and observe the current flowing through the inductorL buck The current I buck increases. If the current I buck increases, the sign variable sgn 1 remains unchanged, and the duty cycle continues to increase in the original direction; if the current I buck decreases, the sign of the sign variable sgn 1 is reversed, and the duty cycle is adjusted in the reverse direction; When the current I buck is less than the maximum allowable current, the sign variable sgn 2 is set to 1, and the duty cycle is adjusted according to the target of the current I buck increasing; when the current I buck is greater than or equal to the maximum allowable current, the sign variable sgn 2 is set to , and the duty cycle is adjusted according to the target of the current I buck decreasing. According to a CT power taking - wireless power transmission system provided by the present invention, a compensation capacitor is connected to the output end of the CT device C m .
[0007] According to a CT power taking - wireless power transmission system provided by the present invention, the rectifying and voltage - stabilizing circuit is a semi - active full - wave rectifying bridge.
[0008] According to a CT power taking - wireless power transmission system provided by the present invention, the wireless power transmission conversion circuit includes an inverter circuit, a transmitting - end resonant circuit, a receiving - end resonant circuit, and a rectifying circuit. The transmitting - end resonant circuit includes a transmitting coil L p1 , a compensation capacitor C p1 , and a parasitic internal resistance R p1 . The receiving - end resonant circuit includes a receiving coil L s1 , a compensation capacitor C s1 , and a parasitic internal resistance R s1 . The transmitting coil L p1 is coupled with the receiving coil L s1 , and the output end of the rectifying circuit is connected to a load. According to a CT power extraction - wireless power transmission system provided by the present invention, the inverter circuit is a full - bridge inverter or a half - bridge inverter. The inverter circuit is connected to the output voltage and outputs a square - wave voltage to excite the resonant circuit at the transmitting end.
[0009] According to a CT power extraction - wireless power transmission system provided by the present invention, the rectifier circuit is a full - bridge rectifier. The rectifier circuit is connected to the high - frequency electrical energy picked up by the resonant circuit at the receiving end and outputs direct - current electrical energy to supply the load. In a second aspect, the present invention provides an output power optimization control method for the CT power extraction - wireless power transmission system of the first aspect, including: The CT device picks up electrical energy from the magnetic field around the current - carrying wire based on magnetic - field induction coupling; The rectifier and voltage - stabilizing circuit rectifies and stabilizes the current flowing from the CT device to the load to obtain a direct - current voltage. The direct - current voltage is processed by a DC / DC converter to obtain an output voltage, and the output voltage is input to the wireless power - transmission conversion circuit; The DC / DC converter adjusts the equivalent impedance of the wireless power - transmission conversion circuit to maximize the output power of the CT device.
[0010] According to an output power optimization control method for the CT power extraction - wireless power transmission system provided by the present invention, the matching adjustment of the equivalent impedance of the CT power extraction - wireless power transmission system is realized through a perturbation - observation - based MPPT algorithm. The specific process is as follows: Set the symbolic variable sgn 1 to 1, and the duty cycle of the DC / DC converter to zero; Increase the duty cycle and observe the current L buck flowing through the inductor I buck to see if it increases. If the current I buck increases, the symbolic variable sgn 1 remains unchanged, and continue to increase the duty cycle in the original direction; if the current I buck decreases, the sign of the symbolic variable sgn 1 is reversed, and the duty cycle is adjusted in the reverse direction; When the current I buck is less than the maximum allowable current, set the symbolic variable sgn 2 to 1, and adjust the duty cycle according to the target of increasing the current I buck ; when the current I buck is greater than or equal to the maximum allowable current, set the symbolic variable sgn 2 to , and adjust the duty cycle according to the current I buckReduced target regulation duty cycle.
[0011] To achieve the maximum power output of the CT power extraction - wireless power transmission system, this invention optimizes and controls the architecture of the CT power extraction - wireless power transmission system to maximize the overall output power of the system. This invention provides a CT power extraction - wireless power transmission system that realizes the equivalent impedance regulation of the system based on a DC / DC converter and its output power optimization control method. Combined with the Maximum Power Point Tracking (MPPT) algorithm, it realizes the optimized control of the system output power. This invention has at least the following technical effects: 1. It proposes a CT power extraction - wireless power transmission system architecture based on DC / DC impedance transformation.
[0012] 2. It analyzes the basic characteristics of the power output of the CT device with the change of load, providing a theoretical reference for power optimization.
[0013] 3. Based on the MPPT optimization algorithm, it realizes the optimized control of the overall system output power under different load conditions. BRIEF DESCRIPTION OF THE DRAWINGS
[0014] To more clearly illustrate the technical solutions in this invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following - described drawings are some embodiments of this invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.
[0015] In the drawings: Figure 1 is the overall structure diagram of the CT power extraction - wireless power transmission system of this invention; Figure 2 is the circuit structure diagram of the CT power extraction - wireless power transmission system of this invention; Figure 3 is the simplified equivalent circuit diagram of the CT power extraction - wireless power transmission system of this invention; Figure 4(a) is the size diagram of the coupling coil of this invention; Figure 4(b) is the curve diagram of the internal resistance and transmission efficiency of the coil of this invention changing with the natural frequency; Figure 5(a) is the equivalent model diagram of the CT device of this invention; Figure 5(b) is the diagram of the output power of the CT device of this invention changing with the load; Figure 6 is the flow block diagram of the MPPT algorithm based on perturbation - observation of this invention; Figure 7(a) is the working waveform diagram of the wireless power transmission part of this invention; Figure 7(b) is the working waveform diagram of the transmitting - end circuit of this invention; FIG8( a ) is a graph showing the variation of the received power of the system according to the present invention with the duty cycle of the DC / DC converter; FIG8( b ) is a waveform diagram of the automatic impedance matching operation of the system of the present invention. DETAILED DESCRIPTION
[0016] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.
[0017] The following will describe some embodiments of the present invention in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.
[0018] See also Figure 1 The embodiment of the present invention provides a CT power supply-wireless power transmission system suitable for high-voltage transmission lines, and its overall structure is as follows Figure 1 As shown, it includes a CT device, a CT power supply control circuit and a wireless power transmission conversion circuit. The CT device picks up electrical energy from the magnetic field around the current-carrying conductor based on magnetic field inductive coupling. The CT power supply control circuit includes a rectifier and voltage regulator circuit and a DC / DC converter. The rectifier and voltage regulator circuit is used to rectify and stabilize the current flowing from the CT device to the load to obtain a DC voltage; the DC voltage is processed by the DC / DC converter to obtain an output voltage, which is input to the wireless power transmission conversion circuit; the DC / DC converter is used to adjust the equivalent impedance of the wireless power transmission conversion circuit to maximize the output power of the CT device.
[0019] The CT device, transmitter circuit, and transmitter coil are located on the high-voltage transmission line side, while the receiver coil, receiver circuit, and load device are located on the grounded tower side. The transmitter and receiver coils are separated by an insulator string, creating magnetic field coupling. This allows for efficient power transmission without compromising insulation between the high-voltage and low-voltage sides.
[0020] based on Figure 1 The overall structure of the CT power supply-wireless power transmission system shown in FIG. 1 is as follows: Figure 2 As shown in the figure, it mainly includes two parts: 1) CT power control circuit; 2) wireless power transmission conversion circuit.
[0021] It should be noted that the CT power extraction - wireless power transmission system of the present invention consists of three major parts: a CT device, a CT power extraction control circuit, and a wireless power transmission system. Among them, the wireless power transmission conversion circuit is the equivalent circuit of the wireless power transmission system.
[0022] Specifically, the DC / DC converter includes a capacitor C f1 , a switching tube S buck , a diode D buck , an inductor L buck , a capacitor C buck . The first end of the capacitor C f1 is connected to the first end of the switching tube S buck . The second end of the switching tube S buck is connected to the first end of the diode D buck and the first end of the inductor L buck . The second end of the inductor L buck is connected to the first end of the capacitor C buck . The second end of the capacitor C buck is connected to the second end of the diode D buck and the second end of the capacitor C f1 . By adjusting the duty cycle of the DC / DC converter through the control terminal of the switching tube S buck , the equivalent impedance of the wireless power transmission system can be adjusted.
[0023] The wireless power transmission conversion circuit includes an inverter circuit, a transmitting - end resonant circuit, a receiving - end resonant circuit, and a rectifier circuit. The transmitting - end resonant circuit includes a transmitting coil L p1 , a compensation capacitor C p1 , and a parasitic internal resistance R p1 . The receiving - end resonant circuit includes a receiving coil L s1 , a compensation capacitor C s1 , and a parasitic internal resistance R s1 . The transmitting coil L p1 is connected to the receiving coil L s1Coupling, the output terminal of the rectifying circuit is connected to the load.
[0024] For 1) the CT power-taking control circuit, I cord / n represents the total current generated by the CT device for power-taking, where I cord represents the load current passing through the current-carrying conductor, n represents the number of turns of the CT device. L m 、 R m respectively represent the exciting inductance and equivalent parallel resistance of the CT device. The exciting inductance can be measured through the "no-load experiment" L m and the parameter values of the equivalent parallel resistance R m . C m is the compensation capacitor for the exciting inductance L m . Under ideal conditions, through appropriate parameter adjustment, the compensation capacitor C m can completely compensate the exciting inductance L m , that is, Figure 2 the current L m flowing through the exciting inductance I Lm and the current C m flowing through the compensation capacitor I Cm cancel each other out. At this time, I cord / n is the sum of the current R m flowing through the equivalent parallel resistance I Rm and the current I out flowing from the CT device to the load. In this embodiment, the rectifying and voltage-regulating circuit is a semi-active full-wave rectifying bridge, which is composed of diodes D 1, D 2 and switching tubes Q 1, Q 2, and rectifies and voltage-regulates the current I out to obtain a stable DC voltage U 1. Next, it is composed of a capacitor C f1 、switching tube S buck, Diode D buck , Inductor L buck , Capacitor C buck A first - stage buck DC / DC converter composed of them has an output voltage U 2 is supplied to the subsequent wireless power transmission conversion circuit for use.
[0025] For 2) the wireless power transmission conversion circuit, in this embodiment, the inverter circuit is a full - bridge inverter, which is composed of a filter capacitor C f2 and switching tubes Q 3~ Q 6. It is connected to the output voltage U 2 and outputs a square - wave voltage to excite the transmitting - end resonant circuit. When the application scenario has high requirements for circuit size and cost, a half - bridge inverter can also be formed by using only one bridge arm. L p1 is the transmitting coil, and together with the transmitting - end compensation capacitor C p1 and the transmitting - end parasitic internal resistance R p1 constitute the transmitting - end resonant circuit. Correspondingly, the receiving - end resonant circuit is composed of the receiving coil L s1 , the receiving - end compensation capacitor C s1 and the receiving - end parasitic internal resistance R s1 constitute. Among them, there is mutual inductance L s1 between the receiving coil L p1 and the transmitting coil M . In this embodiment, the rectifier circuit is a full - bridge rectifier bridge, which is composed of diodes D s1 ~ D s4 and a filter capacitor C f3 . The rectifier circuit accesses the high - frequency electric energy picked up by the receiving - end resonant circuit and outputs DC electric energy to supply the load R L for use.
[0026] Based on the circuit structure shown in Figure 2 , the core work of the present invention is to use the DC / DC converter in the CT power - taking control circuit to adjust the equivalent impedance of the wireless power transmission system, so that the overall output power of the system is maximized.
[0027] For Figure 2 the circuit structure shown, the output voltage U2 and the full-bridge inverter are equivalently regarded as U AC_Inv , and the full-bridge rectifier bridge and the post-stage circuit of the system are regarded as a load as a whole R L_WPT , then the equivalent circuit of the simplified system can be obtained, as shown in Figure 3 . Here, for the full-bridge inverter, U AC_Inv and U The relationship between 2 is shown in Equation (1); for the half-bridge inverter, U AC_Inv The amplitude of will be halved.
[0028] (1) As shown in Figure 3 , the equivalent circuit of the simplified system includes two loops: the transmitting loop and the receiving loop. Using Kirchhoff's loop voltage law, the circuit equation of the system can be obtained, as shown in Equation (2): (2) Here, ω represents the angular frequency of the system, Z p and Z s respectively represent the total impedance of the transmitting loop and the receiving loop itself, as shown in Equation (3): (3) Then, from Equation (2), the current expression of each loop can be solved as shown in Equation (4): (4) Based on Equation (4), the input power and output power of the system can be obtained, as shown in Equations (5) and (6) respectively: (5) (6) Furthermore, the transmission efficiency of the system can be solved as shown in Equation (7): (7) In particular, when the receiver is in resonance, that is, when the reactance of the receiving coil L s1 and the capacitive reactance of the compensation capacitor C s1 are completely cancelled out, Equation (7) obtains the maximum efficiency value under specific load conditions, as shown in Equation (8): (8) The present invention designs a CT power extraction - wireless power transmission system for the 27 kV line of the railway catenary. First, on the premise that mechanical and installation conditions permit, the outer diameter of the coupling coil is increased, thereby increasing the mutual inductance between the transmitting coil and the receiving coil. M ; Then, the operating frequency of the system is optimized to improve the transmission efficiency of the system. Limited by mechanical conditions, the specifications of the coupling coil used in the present invention are shown in Figure 4(a), which is a circular solenoid coil with a diameter of 45 cm, 10 turns, and wound with 0.04×1200 - strand litz wire to reduce the internal resistance of the coil under high - frequency conditions. The inductance of the coil measured by an LCR meter is 101 μH, and the mutual inductance between the transmitting coil and the receiving coil is 7.2 μH at a transmission distance of 30 cm (meeting the requirements of 27 kV air insulation). On the other hand, the high - frequency internal resistance of the coupling coil measured by an LCR meter R coil The curve of the internal resistance varying with the operating frequency is shown as the black circular line in Figure 4(b). It can be seen that the higher the operating frequency, the greater the internal resistance value of the resonant inductor.
[0029] For a resonant wireless power transmission system, selecting an appropriate natural frequency is crucial for the transmission performance of the system. On the one hand, increasing the natural frequency can make the receiving end generate a higher reflected impedance at the transmitting end, thereby improving the transmission efficiency of the system; on the other hand, the increase in high - frequency internal resistance will also lead to the attenuation of the transmission efficiency. Therefore, when actually designing the system, it is necessary to optimize the natural frequency of the system to obtain an ideal transmission efficiency. Substituting the coil internal resistance in Figure 4(b) into Equation (8), the maximum transmission efficiency of the system under different natural frequency conditions can be calculated, and the calculation results are shown as the red square line in Figure 4(b). Among them, f nom represents the natural resonant frequency (nominal resonant frequency) of the system. It can be seen that when the natural resonant frequency is selected around 200 kHz, the system can obtain the highest transmission efficiency of 91.8%. Based on this result, a resonant capacitor with a capacitance value of 5 nF is selected to make the natural resonant frequency of the system 224 kHz. Finally, the key parameters of the wireless power transmission system are listed in Table 1.
[0030] Table 1 Key parameters of the wireless power transmission system
[0031] For Figure 2 The CT power extraction control circuit shown, its output power is equal to the product of the DC voltage and DC current output by the full - bridge rectifier. For an ideal CT device, it can be considered that its exciting inductance L m and the equivalent parallel resistance R m are both infinite, that is, the currentI Lm and I Rm are both zero. At this time, the CT device can be regarded as a current source output, I cord / n flows completely to the load. The larger the load impedance, the higher the load voltage (this is also the reason why the CT device is prohibited from being open-circuited), and the greater the system output power. However, for an actual CT device, the exciting inductance L m and the equivalent parallel resistance R m will have a certain shunting effect on I cord / n Even if the compensation capacitor C m can compensate the current generated by the exciting inductance L m to a certain extent, due to the inherent errors of the device parameters and the non-linearity of the exciting inductance L m under different working conditions, the exciting inductance L m cannot be completely compensated by the compensation capacitor C m Therefore, the CT device can be equivalent to the simplified model shown in Fig. 5(a), and its internal impedance Z m is composed of the parallel reactance jX m and the internal resistance R m Here, X m is L m and C m 's parallel equivalent impedance, which tends to infinity in the resonant state. The current passing through Z m will also be affected by the output voltage U m The larger U m is, the larger I Zm is, and the smaller the current R L_AC flowing to the load I RL_AC is, which is not conducive to improving the output power. Here, R L_AC is the total equivalent load of the rectifier bridge of the CT device and the subsequent circuit on the AC input side of the rectifier bridge.
[0032] Based on the simplified model shown in Fig. 5(a), the voltage across the load can be obtained. R L_AC across the load U L_AC is: (9) Furthermore, the load power across the load can be calculated as: R L_AC is: (10) The denominator in Equation (2)
[0033] is a function of the load R L_AC and the condition for it to reach the minimum value is shown in Equation (11): (11) On the other hand, according to the analysis in the existing literature ("Research and Design of Current Transformer Power Supply", Wang Zhibo, Hangzhou: Zhejiang University, 2015), there is a corresponding relationship between the equivalent load R L_AC on the AC input side of the rectifier bridge of the CT device and the actual load R L_DC on the DC output side, as shown in Equation (12): (12) Therefore, when R L_DC satisfies the condition shown in Equation (13), the power obtained by the load is the maximum.
[0034] (13) At this time, the maximum output power is shown in Equation (14): (14) Substituting the measured circuit parameters in Table 2 into Equation (14), the variation curve of the system output power with R L_DC can be obtained, as shown in Fig. 5(b). Generally speaking, as R L_DC increases, the system output power P L_CT shows a trend of first rising and then falling, and there is an optimal R L_DC value that makes the output power of the CT device the maximum. It should be noted that L m ` and Rm The value decreases gradually as the output voltage of the rectifier bridge of the CT device U increases. In Table 2, L m and R m the value is the measurement result when the output voltage of the CT rectifier bridge is 75 VDC.
[0035] Table 2 Key parameters of the CT device
[0036] In practical applications, the overall equivalent impedance of the system is affected by conditions such as the state of the receiving-end battery, mutual inductance M , and changes in device parameters, and does not necessarily match the optimal load in Equation (13). Therefore, Figure 2 a step-down DC / DC converter is added after the rectifier output of the CT device in R total to adjust the equivalent impedance of the system. Generally speaking, when the duty cycle of the DC / DC converter decreases, the total impedance of the DC / DC converter and the wireless power transmission system R total will increase; conversely, the total impedance of the DC / DC converter and the wireless power transmission system will decrease. In particular, when the duty cycle of the DC / DC converter is zero, Figure 2 the switch tubes of the semi-active full-wave rectifier bridge in Q 1, Q 2 need to be short-circuited for protection; when the duty cycle of the DC / DC converter is 1, R total reaches the minimum value and is equal to the impedance of the wireless power transmission system itself (less than R optimal ). Therefore, for the actual system, the impedance matching of the wireless power transmission system can be achieved by adjusting the duty cycle d of the DC / DC converter, thereby improving the overall output power of the system.
[0037] Assume that the impedance of the wireless power transmission system itself is R WPT , then R total can be represented by d and R WPT as shown in Equation (15): (15) Here, η dcdcIt represents the conversion efficiency of the DC / DC converter, which can be approximated as 1. As can be seen from Equation (15), as the duty cycle of the DC / DC converter gradually decreases from 1 to 0, R total it increases rapidly in a squared relationship, and the output power of the CT device will first increase and then decrease, and the maximum output power can be obtained under the condition of satisfying Equation (16).
[0038] (16) However, in practical applications, R WPT affected by various factors, it is always changing with time. For example, when the battery is fully charged and the receiving end is open, only the internal resistance of the transmitting end itself exists in the WPT system; when the battery is discharged, the receiving end will generate a large reflected impedance to the transmitting end. In addition, parameter drift of the resonant device, etc., will all affect R WPT the modulus value of. Therefore, the optimal duty cycle d optimal in Equation (16) is also changing with time. Therefore, the present invention designs a MPPT (Maximum Power Point Tracking) algorithm based on perturbation-observation to achieve the tracking of the optimal impedance.
[0039] As Figure 6 shown, the core of this perturbation-observation-based MPPT algorithm is to adjust the duty cycle of the DC / DC converter at the transmitting end so that the inductor current I buck of the DC / DC converter is the largest. First, by default, both symbolic variables sgn 1 and sgn 2 are 1, and the duty cycle of the DC / DC converter is zero. Then, the duty cycle is increased by Δd , and the new current L buck flowing through the inductor I buck is observed to see if it increases. If the current I buck increases, the symbolic variable sgn 1 remains unchanged, and the duty cycle continues to increase in the original direction. Conversely, if the current I buck decreases, the sign of the symbolic variable sgn 1 is reversed, and the duty cycle is adjusted in the opposite direction. In particular, the symbolic variable sgn 2 is used for overcurrent protection. When the current I buck is less than the maximum allowable current allowed by the device, the symbolic variable sgn 2 is 1, and the system operates according to the currentI buck Adjust the duty cycle with an increasing target. Conversely, the sign variable sgn is -1, and the system adjusts the duty cycle according to the current I buck decreasing target. According to the Figure 6 algorithm shown, the system can adjust the duty cycle in real time to maximize the output current of the DC / DC converter without exceeding the maximum allowable current permitted by the device.
[0040] To verify the feasibility and effectiveness of the CT power extraction - wireless power transmission system provided by the present invention, an experimental device was built. The system includes the following parts: 1) High - current generator: used to simulate the load current of the high - voltage transmission line; 2) CT device for power extraction, used to inductively extract power from the simulated wire; 3) Transmitter control circuit, integrating the rectification and voltage - stabilization circuit of the CT device, DC / DC converter, and high - frequency inverter for wireless charging on a circuit board; 4) Coupled resonance unit: realizing wireless power transmission in the way of magnetic - field coupled resonance; 5) Receiver rectifier bridge and load: using adjustable resistors to simulate loads with different resistances; 6) Oscilloscope and measurement probe.
[0041] Next, the overall working performance of the CT power extraction - wireless power transmission system was first tested. Among them, the receiver load was set to 20 Ω, the operating frequency of the high - frequency inverter was set to 219.3 kHz, the duty cycle of the transmitter DC / DC converter was set to 33.3%, and the load current of the simulated wire was set to 150 A. At this time, the working waveforms of the wireless power transmission part are shown in Figure 7(a). The amplitude of the resonant current of the transmitting coil in Channel 1 is 3.32 A, and the voltage amplitude of the high - frequency inverter (half - bridge inverter) in Channel 2 is 27.2 V. The two are in phase, so the output power of the inverter is 28.7 W. The amplitude of the resonant current of the receiving coil in Channel 3 is 1.68 A, and the voltage amplitude of the input of the receiver rectifier bridge in Channel 4 is 24.4 V, so the received power is 26.1 W. Further, according to the measured transmitting power and receiving power, the AC - to - AC transmission efficiency of the wireless power transmission system is 90.94%. On the other hand, the working waveforms of the transmitter circuit are shown in Figure 7(b). The amplitude of the voltage at the mid - point of the bridge arm of the DC / DC converter in Channel CH4 (i.e., the amplitude of the input voltage of the DC / DC converter) is 77.2 V, which is 2.92 times the amplitude of the output voltage of the half - bridge inverter in Channel CH2 (i.e., the amplitude of the output voltage of the DC / DC converter) of 26.4 V. At the same time, the average value of the inductor current of the DC / DC converter is 1.19 A. Looking at the impedance of the subsequent stage from the input end of the DC / DC converter, it can be equivalent to 194.8 Ω, that is, in Equation (13) R L_DCIt is 194.8 Ω. In this configuration, the system uses a single CT device to achieve a power output of 26.1 W under a load current of 150 A for the overall system.
[0042] Then, the power output characteristics of the system were tested at different duty cycles of the DC / DC converter. The test results are shown in Fig. 8(a). It can be seen that when the duty cycle is 33.33%, the overall output power of the CT power extraction - wireless power transmission system is the largest. Continuing to increase or decrease the duty cycle will cause a decrease in the output power. In particular, when the duty cycle is 1, that is, when the input and output of the DC / DC converter are directly connected, the overall output power of the system is only 6.19 W. It can be seen that the impedance matching method of adjusting the duty cycle of the DC / DC converter can increase the overall output power of the system by 321%.
[0043] Finally, the Figure 6 regulating effect of the impedance matching by the shown algorithm was tested. During the experiment, the total impedance of the system was adjusted by changing the resistance value of the receiving - end load resistor. Before time 1 in Fig. 8(b), the receiving - end load was 20 Ω. At t time 1, a 20 - Ω resistor was suddenly connected in parallel, making the receiving - end load suddenly change to 10 Ω. At this time, due to the decrease in the receiving - end load, the reflected impedance of the receiving end to the transmitting end increases. As can be seen from Fig. 8(b), t at time 1, the current of the transmitting end in the CH1 channel suddenly decreases, and the current of the receiving end in the CH3 channel begins to increase, reflecting the characteristic of the decrease in the receiving - end load. Next, during the period from t time 1 to t time 2, the input voltage of the DC / DC converter in the CH4 channel continuously decreases, and the output voltage of the inverter in the CH2 channel (i.e., the output voltage of the DC / DC converter) continuously increases, indicating that the system automatically increases the duty cycle, making the ratio of the input and output voltages of the DC / DC converter decrease. According to Equation (16), the t automatic matching is completed, and the matching time is 110 ms. R L_DC
[0044] The present invention proposes a CT power extraction - wireless power transmission system and its output power optimization control method. A first - stage DC / DC converter is used to perform impedance matching on the wireless power transmission system, enabling it to adapt to the optimal load impedance of the CT device. During the system design process, the operating parameters of the wireless power transmission system and the optimal load of the CT device are analyzed and optimized in sequence. Meanwhile, a MPPT optimization algorithm based on perturbation - observation is designed. Finally, the designed wireless power transmission system can achieve an AC - to - AC efficiency of 90.94%. The overall CT power extraction - wireless power transmission system can output 26.1 W of power under the condition of a primary - side current of 150 A. At the same time, when the load at the receiving end changes, the system can automatically optimize and match the load impedance, and the output power can be increased by 321% compared with the working condition without impedance matching.
[0045] Based on the same inventive concept, another embodiment of the present invention provides an output power optimization control method for the CT power extraction - wireless power transmission system of the foregoing embodiment, including: The CT device picks up electrical energy from the magnetic field around the current - carrying wire based on magnetic - field induction coupling; The rectification and voltage - stabilization circuit rectifies and stabilizes the current flowing from the CT device to the load to obtain a DC voltage; the DC voltage is processed by a DC / DC converter to obtain an output voltage, and the output voltage is input to the wireless power - transmission conversion circuit; The DC / DC converter adjusts the equivalent impedance of the wireless power - transmission conversion circuit to maximize the output power of the CT device.
[0046] Specifically, the matching adjustment of the equivalent impedance of the CT power extraction - wireless power transmission system is realized through a MPPT algorithm based on perturbation - observation. The specific process is as follows: Set the symbolic variable sgn 1 to 1, and the duty cycle of the DC / DC converter to zero; Increase the duty cycle and observe the current L buck flowing through the inductor I buck to see if it increases. If the current I buck increases, the symbolic variable sgn 1 remains unchanged, and continue to increase the duty cycle in the original direction; if the current I buck decreases, the sign of the symbolic variable sgn 1 is reversed, and the duty cycle is adjusted in the reverse direction; When the current I buck is less than the maximum allowable current, set the symbolic variable sgn 2 to 1, and adjust according to the current I buckAdjust the duty cycle with the goal of increasing; when the current I buck is greater than or equal to the maximum allowable current, set the symbolic variable sgn 2 to , and adjust the duty cycle with the goal of decreasing the current I buck .
[0047] In summary, for the traditional CT power extraction - wireless power transmission system, the CT device usually supplies power to the wireless power transmission system in the form of constant voltage, and this working mode is not conducive to improving the overall output power of the system. The present invention proposes a CT power extraction - wireless power transmission system and its output power optimization control method. Using a first - stage DC / DC converter, impedance matching is performed on the wireless power transmission system to make it adapt to the optimal load impedance of the CT device. First, the present invention conducts a modeling analysis on the wireless power transmission system and optimizes the parameter design, thereby improving the transmission efficiency of the system. Then, a model of the CT device is established, and the influence of the load impedance of the CT device on the output power is analyzed. Next, a set of MPPT optimization algorithm based on perturbation - observation is designed to achieve real - time control of impedance matching. Finally, the effectiveness of the proposed method is verified through experiments. The results show that the designed CT power extraction - wireless power transmission system can achieve an AC - to - AC efficiency of 90.94%, and the CT power extraction - wireless power transmission system as a whole can output 26.1 W of power under the condition of a primary - side current of 150 A. At the same time, when the load at the receiving end changes, the system can automatically achieve the optimization matching of the load impedance, and compared with the working condition without impedance matching, the output power can be increased by 321%.
[0048] After considering the specification and practicing the disclosed embodiments herein, those skilled in the art will readily conceive of other embodiments of the present invention. The present invention is intended to cover any variations, uses, or adaptations of the present invention, which follow the general principles of the present invention and include common general knowledge or conventional technical means in the technical field not disclosed by the present invention. It should be understood that the present invention is not limited to the exact structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present invention is only limited by the appended claims.
Claims
1. A CT power taking - wireless power transmission system, characterized in that, It includes a CT device, a CT power extraction control circuit and a wireless power transmission conversion circuit. The CT device picks up electrical energy from the magnetic field around the current-carrying wire based on magnetic field induction coupling. The CT power extraction control circuit includes a rectification and voltage stabilization circuit and a DC / DC converter. The rectification and voltage stabilization circuit is used to rectify and stabilize the current flowing from the CT device to the load to obtain a DC voltage. The DC voltage is processed by the DC / DC converter to obtain an output voltage, and the output voltage is input to the wireless power transmission conversion circuit. The DC / DC converter is used to adjust the equivalent impedance of the wireless power transmission conversion circuit to maximize the output power of the CT device.
2. The CT power extraction - wireless power transmission system according to claim 1, characterized in that, The DC / DC converter includes a capacitor C f1 , a switching transistor S buck , a diode D buck , an inductor L buck , a capacitor C buck , a capacitor C f1 The first end of the capacitor S buck is connected to the first end of the switching transistor S buck The second end of the switching transistor D buck is connected to the first end of the diode L buck and the first end of the inductor L buck The second end of the inductor C buck is connected to the first end of the capacitor C buck The second end of the capacitor D buck is connected to the second end of the diode C f1 and the second end of the capacitor S buck The duty cycle of the DC / DC converter is adjusted through the control end of the switching transistor , so as to adjust the equivalent impedance of the wireless power transmission conversion circuit.
3. The CT power taking - wireless power transmission system according to claim 2, wherein, The matching adjustment of the equivalent impedance of the CT power extraction - wireless power transmission system is realized through a perturbation - observation - based MPPT algorithm. The specific process is as follows: Set the symbolic variable sgn 1 to 1, and the duty cycle of the DC / DC converter is zero; Increase the duty cycle and observe the current flowing through the inductor L buck . I buck Whether it increases. If the current I buck increases, the sign variable sgn 1 remains unchanged and the duty cycle continues to increase in the original direction; If the current I buck decreases, the sign of the sign variable sgn 1 is inverted, and the duty cycle is adjusted in the reverse direction; When the current I buck is less than the maximum allowable current, set the symbolic variable sgn 2 to 1 and adjust the duty cycle in accordance with the goal of I buck increasing the current; When the current I buck is greater than or equal to the maximum allowable current, set the symbolic variable sgn 2 to , and adjust the duty cycle according to the target of decreasing current I buck .
4. The CT power-taking and wireless power transmission system according to claim 1, wherein The output terminal of the CT device is connected with a compensation capacitor C m .
5. The CT power taking - wireless power transmission system according to claim 1, characterized in that, The rectification and voltage stabilization circuit is a semi - active full - wave rectifier bridge.
6. The CT power-taking and wireless power transmission system according to claim 1, wherein The wireless power transmission conversion circuit includes an inverter circuit, a transmitting-end resonant circuit, a receiving-end resonant circuit, and a rectifier circuit. The transmitting-end resonant circuit includes a transmitting coil L p1 , a compensation capacitor C p1 , and a parasitic internal resistance R p1 . The receiving-end resonant circuit includes a receiving coil L s1 , a compensation capacitor C s1 , and a parasitic internal resistance R s1 . The transmitting coil L p1 is coupled with the receiving coil L s1 . The output end of the rectifier circuit is connected to a load.
7. The CT power extraction - wireless power transmission system according to claim 6, characterized in that The inverter circuit is a full - bridge inverter or a half - bridge inverter. The inverter circuit is connected to the output voltage and outputs a square - wave voltage to excite the transmitter resonant circuit.
8. The CT power-taking - wireless power transmission system according to claim 6, wherein The rectifier circuit is a full - bridge rectifier bridge. The rectifier circuit is connected to the high - frequency electrical energy picked up by the receiver resonant circuit and outputs DC electrical energy to supply the load.
9. An output power optimization control method for a CT power taking - wireless power transmission system as described in claim 2, characterized in that, It includes: The CT device picks up electrical energy from the magnetic field around the current - carrying wire based on magnetic field induction coupling. The rectification and voltage stabilization circuit rectifies and stabilizes the current flowing from the CT device to the load to obtain a DC voltage. The DC voltage is processed by the DC / DC converter to obtain an output voltage, and the output voltage is input to the wireless power transmission conversion circuit. The DC / DC converter adjusts the equivalent impedance of the wireless power transmission conversion circuit to maximize the output power of the CT device.
10. The output power optimization control method of the CT power taking - wireless power transmission system according to claim 9, characterized in that, The matching adjustment of the equivalent impedance of the CT power extraction - wireless power transmission system is realized through a perturbation - observation - based MPPT algorithm. The specific process is as follows: Set the symbolic variable sgn 1 to 1, and the duty ratio of the DC / DC converter is zero; Increase the duty cycle and observe the current flowing through the inductor L buck . I buck Whether it increases. If the current I buck increases, the sign variable sgn 1 remains unchanged, and continue to increase the duty cycle in the original direction; If the current I buck decreases, the sign of the sign variable sgn 1 is inverted, and the duty cycle is adjusted in the opposite direction; When the current I buck is less than the maximum allowable current, set the symbolic variable sgn 2 to 1, and adjust the duty cycle according to the target of increasing the current I buck increase; When the current I buck is greater than or equal to the maximum allowable current, set the symbolic variable sgn 2 to , and adjust the duty cycle according to the target of decreasing current I buck .