A transformer-based piezoelectric energy harvester and power optimization method thereof

Abstract

The present application relates to piezoelectric energy technology field, especially to a kind of piezoelectric energy collector based on transformer and its power optimization method, comprising: measuring transformer box surface vibration signal, and the vibration signal collected is analyzed in time-frequency domain, and the vibration center frequency of monitoring point is obtained;Adjust the position of mass block on piezoelectric vibrator, make piezoelectric vibrator resonance frequency equal to vibration center frequency;Through signal generator, simulate transformer box surface vibration waveform, act on the piezoelectric energy collector after frequency modulation, measure its output characteristic, and the output power is optimized.The resonance frequency of piezoelectric vibrator is equal to this vibration center frequency in the present application, so as to be able to capture higher level of power generation power, and by simulating transformer surface vibration waveform, measuring its output characteristic, optimizing the output power, so as to better adapt to transformer surface, provide more stable electric energy for vibration sensor, improve service life and long-term monitoring effect.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric energy harvesting technology, and in particular to a transformer-based piezoelectric energy harvester and its power optimization method. Background Technology

[0002] During transformer operation, vibrations occur within the transformer itself. The vibration on the tank surface is the result of the coupling and superposition of signals from multiple vibration sources. Vibrations generated by the windings and core are transmitted to the tank surface through liquid and solid paths. Throughout the entire operation, the transformer experiences a relatively stable voltage, meaning the core vibration remains essentially constant. However, the current flowing through the windings varies considerably. Winding vibration is the result of the coupling and superposition of vibrations from multiple coils. Under different current magnitudes, the vibration response of coils at different locations differs, leading to varying contributions to the tank surface vibration. Therefore, under normal conditions, the differences in tank surface vibration are primarily caused by winding vibration.

[0003] Collecting vibration energy from transformers under normal operating conditions to power vibration measurement sensors can not only reduce the impact of installing online monitoring equipment on the safe and stable operation of transformers, but also enable self-powering to extend the single-use lifespan of the equipment.

[0004] Currently, there are three main methods for vibration energy recovery: electrostatic, electromagnetic, and piezoelectric. Electrostatic recovery converts mechanical energy into electrical energy using the principle of electrostatic induction; electromagnetic recovery converts mechanical energy into electrical energy using the principle of electromagnetic induction; and piezoelectric recovery converts mechanical energy into electrical energy using the positive piezoelectric effect of piezoelectric materials. Among these, piezoelectric vibration energy recovery has the highest energy density, and its simple structure makes it easy to integrate and miniaturize, allowing for widespread application in daily life and production. This gives it a significant advantage over electromagnetic and electrostatic methods. However, traditional cantilever beam fixed piezoelectric oscillators suffer from a narrow frequency band, and the power generation performance of the piezoelectric element is easily affected by the environmental vibration frequency. If the environmental vibration frequency deviates slightly from the resonant frequency of the piezoelectric oscillator, the power generation performance will rapidly decrease.

[0005] The information disclosed in this background section is intended only to enhance the understanding of the general background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a transformer-based piezoelectric energy harvester and its power optimization method, thereby effectively solving the problems in the background technology.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a power optimization method for a transformer-based piezoelectric energy harvester, comprising: The vibration signal on the surface of the transformer tank was measured, and the collected vibration signal was analyzed in the time and frequency domain to obtain the vibration center frequency at the monitoring point. Adjust the position of the mass block on the piezoelectric vibrator so that the resonant frequency of the piezoelectric vibrator is equal to the vibration center frequency; The vibration waveform of the transformer tank surface is simulated by a signal generator and applied to the frequency-modulated piezoelectric energy harvester to measure its output characteristics and optimize the output power.

[0008] Furthermore, vibration signals on the surface of the transformer tank are collected using an accelerometer.

[0009] Furthermore, in the time-frequency domain analysis, the vibration signal is subjected to Fourier transform to obtain a frequency-acceleration curve, and the vibration center frequency is the frequency corresponding to the point of maximum acceleration in the frequency-acceleration curve.

[0010] Furthermore, when adjusting the position of the mass block on the piezoelectric vibrator, the position of the mass block is adjusted by comparing the changing trends of the resonant frequency and open-circuit voltage, the load voltage and the generated power under different positions of the mass block.

[0011] Furthermore, the position of the mass block is adjusted by adjusting the distance between the mass block and the non-fixed end of the piezoelectric vibrator.

[0012] Furthermore, in the measurement of its output characteristics, a simulated vibration signal is input from the signal generator, and the amplitude of the input acceleration waveform is adjusted to the measured amplitude of the acceleration waveform by the power amplifier. The amplified signal is then provided to the exciter. The vibration excitation signal acting on the exciter drives the piezoelectric oscillator to vibrate. The piezoelectric energy harvester connects the output power to the load resistor box, and the open-circuit output voltage of the piezoelectric array is observed through an oscilloscope. The load voltage and load power output by the load resistor are also recorded.

[0013] Furthermore, different series and parallel combinations of piezoelectric oscillators in the piezoelectric energy harvester were obtained to obtain the load voltage and load power under different combinations, and the optimal series and parallel combination method was determined.

[0014] The present invention also includes a piezoelectric energy harvester, comprising a plurality of piezoelectric vibrators, which are combined in series and parallel. Each piezoelectric vibrator includes a substrate, a piezoelectric crystal, and a mass block. One end of the substrate is fixedly disposed on the surface of a transformer housing. The piezoelectric crystal is disposed on the substrate near the fixed end. The mass block is adjustablely disposed at a non-fixed end, and the distance between the mass block and the non-fixed end can be adjusted to adjust the position of the mass block. The piezoelectric energy harvester optimizes its power output using the method described above.

[0015] The beneficial effects of this invention are as follows: By measuring the vibration of the transformer tank surface, the vibration center frequency of the monitoring point is obtained. Based on the vibration center frequency, the position of the mass block on the piezoelectric vibrator is adjusted so that the resonant frequency of the piezoelectric vibrator is equal to this vibration center frequency. Therefore, when set at the monitoring point of the transformer tank, a higher level of power generation can be captured. Furthermore, by simulating the vibration waveform of the transformer surface and applying it to the frequency-modulated piezoelectric energy harvester, its output characteristics are measured and the output power is optimized. This allows for better adaptation to the transformer surface, providing more stable power to the vibration sensor, improving its service life and long-term monitoring effect. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart of the method in Example 1; Figure 2 This is a flowchart of the method in Example 2; Figure 3 This is a schematic diagram of the structure of a piezoelectric vibrator; Figure 4 shows the comparison of output characteristics at different locations in Example 2. a is the trend of resonant frequency change at different locations, b is the trend of open circuit voltage change at different locations, c is the trend of load voltage change with load resistance at different locations, and d is the trend of power generation change with load resistance at different locations. Figure 5 shows the vibration signal on the surface of the transformer tank in Example 2, where a is the time domain diagram of the measured vibration signal at monitoring point 1, b is the time domain diagram of the measured vibration signal at monitoring point 2, c is the frequency domain diagram of the measured vibration signal at monitoring point 1, d is the frequency domain diagram of the measured vibration signal at monitoring point 2, e is the simulated vibration signal waveform at monitoring point 1, and f is the simulated vibration signal waveform at monitoring point 2. Figure 6 A schematic diagram of the measurement; Figure 7 shows the power output of the piezoelectric energy collector after simulating transformer vibration in Example 2, where a is the power output of the piezoelectric energy collector at monitoring point 1 and b is the power output of the piezoelectric energy collector at monitoring point 2. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0019] Example 1: like Figure 1 As shown: A power optimization method for a transformer-based piezoelectric energy harvester includes the following steps: The vibration signal on the surface of the transformer tank was measured, and the collected vibration signal was analyzed in the time and frequency domain to obtain the vibration center frequency at the monitoring point. Adjust the position of the mass block on the piezoelectric vibrator so that the resonant frequency of the piezoelectric vibrator is equal to the vibration center frequency; The vibration waveform of the transformer tank surface is simulated by a signal generator and applied to the frequency-modulated piezoelectric energy harvester to measure its output characteristics and optimize the output power.

[0020] By measuring the vibration of the transformer tank surface, the vibration center frequency of the monitoring point is obtained. Based on the vibration center frequency, the position of the mass block on the piezoelectric vibrator is adjusted so that the resonant frequency of the piezoelectric vibrator is equal to this vibration center frequency. Therefore, when set at the monitoring point on the transformer tank, a higher level of power generation can be captured. Furthermore, by simulating the vibration waveform of the transformer surface and applying it to the frequency-modulated piezoelectric energy harvester, its output characteristics are measured, and the output power is optimized. This allows for better adaptation to the transformer surface, providing more stable power to the vibration sensor, improving its service life and long-term monitoring effect.

[0021] In this embodiment, an accelerometer is used to collect vibration signals from the surface of the transformer tank.

[0022] In the time-frequency domain analysis, the vibration signal is Fourier transformed to obtain the frequency-acceleration curve, and the vibration center frequency is the frequency corresponding to the maximum acceleration point in the frequency-acceleration curve.

[0023] To achieve higher power generation, better conversion of vibration energy is needed. However, during normal operation, transformers exhibit vibration differences due to winding vibration. Under electromechanical coupling, when the natural frequency of the winding is an integer multiple of the current excitation, parametric resonance multi-harmonic vibration occurs. The vibration frequency is an integer multiple of the current frequency. By obtaining the frequency-acceleration curve through Fourier transform of the vibration signal, the vibration center frequency is the frequency corresponding to the maximum acceleration in the frequency-acceleration curve. Thus, the resonant frequency of the piezoelectric vibrator is set to the frequency with the maximum vibration amplitude, thereby increasing the conversion of vibration energy.

[0024] Piezoelectric oscillators generate electrical energy using the piezoelectric effect of piezoelectric materials. When an external force is applied to a piezoelectric crystal, the mechanical force causes the crystal to bend and deform, resulting in internal polarization and the generation of oppositely polarized charges on the two surfaces of the crystal. Mechanical energy is then converted into electrical energy. The piezoelectric oscillator reaches its optimal power generation performance when it resonates, i.e., when the external excitation frequency is close to its resonant frequency.

[0025] As a preferred embodiment of the above, when adjusting the position of the mass block on the piezoelectric vibrator, the position of the mass block is adjusted by comparing the changing trends of the resonant frequency and open circuit voltage, the load voltage and the generated power under different positions of the mass block.

[0026] The position of the mass block is adjusted by adjusting the distance between the mass block and the non-fixed end of the piezoelectric vibrator.

[0027] In this embodiment, the output characteristics are measured by simulating a vibration signal from a signal generator, adjusting the amplitude of the input acceleration waveform to the measured amplitude of the acceleration waveform via a power amplifier, and providing the amplified signal to the exciter. The vibration excitation signal acting on the exciter drives the piezoelectric oscillator to vibrate. The piezoelectric energy harvester connects the output power to the load resistor box, observes the open-circuit output voltage of the piezoelectric array using an oscilloscope, and records the load voltage and load power output by the load resistor.

[0028] In this study, different series and parallel combinations of piezoelectric oscillators in the piezoelectric energy harvester were used to obtain the load voltage and load power under different combinations, and to determine the optimal series and parallel combination method.

[0029] Piezoelectric energy harvesters typically use multiple sets of piezoelectric oscillators. These sets of oscillators can output different power characteristics through different series and parallel connections. Therefore, by combining different series and parallel connections of piezoelectric oscillators in the piezoelectric energy harvester, the load voltage and load power under different combinations can be obtained, and the optimal series and parallel connection combination can be determined.

[0030] This embodiment also includes a piezoelectric energy harvester, which includes several piezoelectric vibrators. The piezoelectric vibrators are combined in series and parallel. Each piezoelectric vibrator includes a substrate, a piezoelectric crystal, and a mass block. One end of the substrate is fixedly disposed on the surface of the transformer housing. The piezoelectric crystal is disposed on the substrate near the fixed end. The mass block is adjustablely disposed on the non-fixed end, and the distance between the mass block and the non-fixed end can be adjusted to adjust the position of the mass block. The piezoelectric energy harvester optimizes power using the method described above.

[0031] Example 2: like Figure 2 As shown, this embodiment includes the following steps: Step 1: Measure the vibration signal on the surface of the transformer tank using an accelerometer, and perform time-frequency domain analysis on the collected vibration signal to obtain the vibration center frequency at the monitoring point; Step 2: By adjusting the position of the mass block, the resonant frequency of the piezoelectric vibrator is made equal to the vibration center frequency of the transformer monitoring point, so that its power generation reaches the optimal level. Step 3: Simulate the measured transformer vibration waveform using a signal generator, apply it to the frequency-modulated piezoelectric energy acquisition device, and measure its output characteristics.

[0032] In step 1, the test transformer is an on-load tap-changing power transformer of model SFSZ10-240000 / 220 that is in operation. After Fourier decomposition, the vibration center frequency of the monitoring point is found to be 200Hz.

[0033] The vibration amplitude and spectral characteristics of a transformer directly determine the center frequency and available vibration energy of the piezoelectric material.

[0034] like Figure 3 As shown, the piezoelectric substrate has a length*width*height of 30*10*0.2 mm and is made of beryllium bronze; the mass block is a pure tungsten block with a length*width*height of 3*10*3 mm; the piezoelectric wafer is an Sm-doped-PMN-PT piezoelectric ceramic with a length*width*height of 10*10*0.2 mm.

[0035] The position of the mass block can be changed within a range of x, which is 0.5-12.5 mm, where x represents the distance between the mass block and the non-fixed end. By comparing the trends of resonant frequency and open-circuit voltage at different positions, as well as the comparison of load voltage and power generation after load, the resonant frequency of the piezoelectric oscillator can be made 200 Hz by changing the position of the mass block.

[0036] In step 2, when the piezoelectric oscillator resonates, that is, when the external excitation frequency is close to its resonant frequency, its power generation performance reaches its optimal level.

[0037] As shown in Figures 4 to 7, the measurement method involves simulating the input of the transformer's measured vibration signal to the signal generator, adjusting the amplitude of the input acceleration waveform to the measured amplitude of the acceleration waveform through a power amplifier, and then providing the amplified signal to the exciter. The vibration excitation signal acting on the exciter drives the piezoelectric oscillator to vibrate. The piezoelectric energy harvester converts mechanical vibration energy into electrical energy based on the piezoelectric effect, connects the output electrical energy to the load resistor box, observes the open-circuit output voltage of the piezoelectric array through an oscilloscope, and records the voltage and power output from the load resistor.

[0038] In the description of this invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. "A plurality of" means two or more, unless otherwise explicitly specified.

[0039] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0040] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0041] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0042] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by, or in conjunction with, an instruction execution system, apparatus, or device (such as a computer-based system, a processor-included system, or other system that can fetch and execute instructions from, an instruction execution system, apparatus, or device). For the purposes of this specification, "computer-readable medium" can be any means that can contain, store, communicate, propagate, or transmit programs for use by, or in conjunction with, an instruction execution system, apparatus, or device. More specific examples (a non-exhaustive list) of computer-readable media include: an electrical connection having one or more wires (electronic device), a portable computer disk drive (magnetic device), random access memory (RAM), read-only memory (ROM), erasable and editable read-only memory (EPROM or flash memory), fiber optic devices, and portable optical disc read-only memory (CDROM). Alternatively, the computer-readable medium may be paper or other suitable media on which the program can be printed, since the program can be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, interpreting, or otherwise processing as necessary, and then stored in a computer memory.

[0043] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0044] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0045] The storage medium mentioned above can be a read-only memory, a disk, or an optical disk, etc. Although embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A power optimization method for a transformer-based piezoelectric energy harvester, characterized in that, Includes the following steps: The vibration signal on the surface of the transformer tank was measured, and the collected vibration signal was analyzed in the time and frequency domain to obtain the vibration center frequency at the monitoring point. Adjust the position of the mass block on the piezoelectric vibrator so that the resonant frequency of the piezoelectric vibrator is equal to the vibration center frequency; The vibration waveform of the transformer tank surface is simulated by a signal generator and applied to the frequency-modulated piezoelectric energy harvester to measure its output characteristics and optimize the output power. Vibration signals on the surface of the transformer tank are collected using an accelerometer. In the time-frequency domain analysis, the vibration signal is Fourier transformed to obtain a frequency-acceleration curve, and the vibration center frequency is the frequency corresponding to the maximum acceleration point in the frequency-acceleration curve. In the process of measuring its output characteristics, a simulated vibration signal is input from the signal generator, and the amplitude of the input acceleration waveform is adjusted to the measured amplitude of the acceleration waveform by the power amplifier. The amplified signal is then provided to the exciter, and the vibration excitation signal acting on the exciter drives the piezoelectric oscillator to vibrate. The piezoelectric energy harvester connects the output power to the load resistor box, and the open-circuit output voltage of the piezoelectric array is observed through an oscilloscope. The load voltage and load power output by the load resistor are also recorded.

2. The power optimization method for a transformer-based piezoelectric energy harvester according to claim 1, characterized in that, When adjusting the position of the mass block on the piezoelectric vibrator, the position of the mass block is adjusted by comparing the changing trends of the resonant frequency and open-circuit voltage, the load voltage and the generated power under different positions of the mass block.

3. The power optimization method for a transformer-based piezoelectric energy harvester according to claim 2, characterized in that, The position of the mass block is adjusted by adjusting the distance between the mass block and the non-fixed end of the piezoelectric vibrator.

4. The power optimization method for a transformer-based piezoelectric energy harvester according to claim 1, characterized in that, Different series and parallel combinations of piezoelectric oscillators in the piezoelectric energy harvester were used to obtain the load voltage and load power under different combinations, and the optimal series and parallel combination method was determined.

5. A piezoelectric energy harvester, characterized in that, It includes several piezoelectric vibrators, which are combined in series and parallel. Each piezoelectric vibrator includes a substrate, a piezoelectric crystal, and a mass block. One end of the substrate is fixedly disposed on the surface of the transformer housing. The piezoelectric crystal is disposed on the substrate near the fixed end. The mass block is adjustablely disposed at the non-fixed end, and the distance between the mass block and the non-fixed end can be adjusted to adjust the position of the mass block. The piezoelectric energy harvester is power optimized by the method described in any one of claims 1 to 4.

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