Challenges and future trends of piezoelectric sensing technology

The fourth global industrial revolution is significantly changing the mode of power energy production and transmission, triggering the deep integration of the power energy industry and the Internet of things, making the construction of energy Internet an urgent need for China's new infrastructure. Energy Internet is built on a sensor comprehensive perception of source, network, storage, load power equipment running state signals on the basis of intelligent interconnection, state with the full awareness, information efficient processing, application and convenient features such as flexible, is to deal with external digital economy and Internet economy, social economic morphology change and complexity increases, such as internal networks morphology change at the heart of the action.

As the grid configuration gradually shifts from construction period to maintenance period, in addition to building a flexible, stable and safe energy network, it is more important to realize the real-time measurement and feedback adjustment of the grid state quantity, and then combine the subsequent analysis algorithm to realize the intelligent sensing of information and intelligent self-healing of faults. Sensing the state of power equipment through advanced sensing and measurement technologies is the basis for building ubiquitous energy Internet big data resources.

As the key component of device state sensing in power Internet of Things, sensor determines the overall technical level of safe operation of power system. With the continuous improvement of automation and intelligence of power grid, the demand of digitalization, miniaturization and convenience of power sensors is increasingly urgent, the core of which lies in the development of high-performance materials and their coordination with devices.

As with highly integration of sensors, piezoelectric sensors to achieve the mechanical - electrical signal conversion, passive, miniaturization, has advantages of strong anti-jamming capability, is perceived power equipment vibration, discharge status of key devices, such as in piezoelectric vibration sensors, ultrasonic sensors, surface acoustic wave sensor has been widely applied. In addition, there are new piezoelectric sensors such as piezoelectric temperature sensors and voltage sensors based on the coupling and conversion of physical quantities. The physical signals such as temperature, voltage and current are converted into vibration signals or acoustic signals, and the original signal value is deduced by measuring the converted physical quantities.

, however, is subject to material performance, components encapsulation, topology structure, such as piezoelectric sensor when actual operation still has low precision, poor stability and high misjudgment rate significantly, gradually difficult to adapt to the complex power grid operation environment, needs to be in rapid development of new materials, new sensor topology design, stability and improve life made a breakthrough, intelligent compensation, etc.

With the development of energy Internet, the sensor accuracy, reliability and stability of power equipment are required to be higher and higher. The piezoelectric sensor technology is faced with the following challenges:

(1) Accuracy. At present, there are contradictions among the frequency band width, sensitivity, structure volume and other factors of the sensor, and the resolution and sensitivity are still insufficient, and the misjudgment rate is high under complex working conditions.

(2) Stability. The key parameters of piezoelectric sensor depend on the polarization state of piezoelectric materials, and the performance of piezoelectric materials will be degraded by aging and fatigue under long-term electromechanical coupling, which seriously affects the long-term reliability of piezoelectric sensor components.

(3) Environmental adaptability. Most piezoelectric sensing devices operate in outdoor environments. The key piezoelectric materials are greatly affected by environmental factors such as temperature and humidity, which brings large measurement errors. Coupled with the comprehensive influence of structural heat adaptation and circuit matching, the sensor inevitably has problems such as temperature and frequency drift.

(4) Environmentally friendly. A large number of sensor components are used in the construction of energy Internet, which puts forward higher requirements for the environmental friendliness of sensor materials. PZT and other lead-based materials are still the mainstream materials of piezoelectric devices, especially commercial sensors. The overuse of lead has posed a potential threat to the environment. Although the piezoelectric coefficient of lead-free materials has been comparable to that of leaded materials, there are still some problems such as poor stability and depolarization, so it is difficult to realize practical application.

To solve the above problems, we need to make breakthroughs in the following aspects:

(1) Development of new piezoelectric materials. For multiple application scenarios of power grid, piezoelectric materials are needed to achieve synergistic improvement of piezoelectric properties such as piezoelectric coefficient, Curie temperature and electromechanical coupling coefficient. The development of environmentally friendly advanced piezoelectric materials combined with artificial intelligence methods to enhance their stability and environmental adaptability is a development trend in the field of piezoelectricity.

(2) Topology design of new piezoelectric sensor. The integrated design of sensor parts and materials for the sensing application of electric power equipment has become the development trend of intelligent piezoelectric devices in the future to realize the high coordination of sensing materials and devices and the high fusion of sensors and devices. It is urgent to develop a new sensor topology to improve the comprehensive performance of sensors.

(3) Intelligent compensation. In order to improve the piezoelectric performance and stability of piezoelectric materials and devices as much as possible, specific compensation (such as dynamic compensation network modification) should be made for the dynamic characteristics of sensors to eliminate the impact of errors and environmental factors. In addition, electromagnetic compatibility is also an important factor to ensure the safe and stable operation of piezoelectric sensor components in dense power equipment and strong electromagnetic environment.

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