MEMS is a general term for micro-electromechanical systems that integrate silicon-based micro-sensors, microprocessors, micro-actuators, and micro-automatic machines. The science and technology related to the development, manufacture and application of MEMS can be collectively referred to as MEMS technology. The emergence and development of devices and systems such as miniature fluxgates and micro-relays have provided a good opportunity for the development of electrical equipment. After analyzing the possibility of miniaturization and intelligentization of electrical equipment, this paper expounds the characteristics of microelectronics in electrical equipment and derives the characteristics of micro electrical equipment.
2 The rapid development of MEMS technology makes it possible to realize miniaturization and intelligentization of electrical equipment. MEMS is characterized by small size, light weight and stable performance. It adopts 1C technology, especially LIGA technology (ie deep X-ray etching, electroforming, plastic). Casting and other technologies), can be mass-produced, low cost and good performance consistency. The advantages of MEMS are low power consumption, high resonance frequency, short response time, high integration and high added value. It has functions such as transforming and transmitting various energy such as force, heat, sound, magnetic and chemical energy, and bioenergy. . After more than ten years of development, MEMS technology is expanding to three-dimensional processing represented by LIGA technology, from various element technologies to system integration, from basic exploration to practicalization. In 1990, T. Seitz of Switzerland first produced the world's first miniature fluxgate sensor using a microelectronic planar process. The fluxgate integrated the core and induction coil onto a single chip to form a fluxgate system. The abbreviation of an electromagnetic micro-relay developed by Swiss and Belgian scholars reported in the IEEE Journal in 1998, whose on-resistance is lower than 0.4! , open circuit resistance is greater than 10G! The on-time is about 0.2ms. In the field of MEMS, micro-operations such as electromagnetic micro-motors, generators, micro-pumps, micro-photoelectric switches, micro-relays, micro-tweezers, fluxgates, and magnetoresistive devices have been studied based on electromagnetic effects. Or sensors are moving toward systematization and arraying.
The current electrical components in the power system are bulky, costly, and low in automation. The theory and methods of control and protection based on such appliances are also quite backward. The development of high-tech, environmentally friendly appliances is a trend in all industries. In the low-voltage electrical part, micro-intelligence will not only change the control and management mode of the original system, but also expand the application range of the electrical appliance; in the middle and high-voltage parts, with the increase of the voltage level, the volume and cost will increase rapidly. The factors are particularly prominent, and it is more difficult to achieve according to the existing technical ideas. With the deepening of information technology, information acquisition (sensing) technology and information execution technology, the so-called "external device" technology have become the bottleneck of development, regardless of the miniaturization or performance-price ratio development, and their interfaces with the host ( Interface) has also become the key to hinder processing speed. The rapid development of MEMS technology and communication technology provides a technical basis for the miniaturization, intelligentization, low-cost and comprehensive automatic management of power system electrical components.
3 electrical equipment requirements for micro-electrical characteristics The current intelligent electrical components are mainly in the information acquisition part and the system-driven part; the fundamental reason for the low degree of automation is that the relationship between each other is not tight enough, and the communication is not very mature.
However, the development of communication technology has provided a good foundation for this part of the in-depth study. Relatively speaking, the micro-sensor and micro-actuator parts are very backward in terms of miniaturization, intelligence, and low price. Therefore, in the electrical equipment, it is necessary to constitute a micro-intelligent sensor system that effectively and reasonably collects data, and a micro-intelligent driver system that must establish an optimal driving effect must construct a fast and reliable communication system between the functional modules, thereby forming a distributed Large system.
3.1 Microsensor System This system should be able to collect data effectively and accurately, and accurately reflect system status information. According to the quantity that the power system needs to measure, the micro sensor selects the corresponding sensitive signal head of the physical signal, and integrates with the microprocessor and the communication component into the same chip to form a smart electrical device, which can be a current sensor, a voltage sensor, a temperature sensor, Pressure sensor, etc. From the current situation, to know the state quantity in the system, the information obtained by a single sensor is very limited, and the array sensor must be used to measure enough information. Therefore, array sensing is the application direction of the micro smart sensor in the power system.
For example, the current in the busbar is generally measured by a current transformer, but the current is measured by magnetism in the microelectronics. The semiconductor magnetic sensor head is integrated in the chip, but the accuracy of the magnetic field (measuring current) measured at a single point is difficult to meet the requirements. The measurement current is completed by multiple sensors in accordance with a certain topology structure to form an array sensing method. The sensor integrates a microprocessor to denoise, filter, linearize, and compensate the data. The integrated communication component performs data transmission at high speed and synchronously, and the current value can be obtained for display or protection in real time.
The micro-driver system's distributed drive achieves optimal results similar to micro-sensors. The micro-driver also integrates a microprocessor and communication components to form a micro-intelligent driver that can be operated according to the level and number of commands to achieve optimal results. However, the micro-actuator driving force is still very small. In the electrical equipment, the distributed driver must be built, that is, the array driver can be implemented according to the topology optimization theory to achieve the best driving effect with as few drivers as possible.
Communication system fast communication ensures that the functional modules are closely linked.
The communication system has two layers: the data exchange communication between the array sensing and the same level device where the array driver is located and between them and the upper layer device. This is the lower layer network communication; the system control center and the device center machine Inter-communication is a higher level of network communication. Although the distance between the low-level sensor and the actuator and the upper layer device are relatively close, but the distribution form is flexible, the micro-system itself is small in size and is not convenient for wired connection. Therefore, this layer of data exchange adopts the wireless local area network mode. Each microsystem pre-sets parameters to work together. The system control center and the device center machine realize high-speed communication, and the networking is flexible and convenient, the expansion is good, and the compatibility is good. It can be seen that whether it is from the analysis of power system reliability, real-time requirements, or the characteristics of distributed sensor systems and distributed drive systems, the requirements of high-speed and reliable communication systems are determined.
4 MEMS Characteristics in Electrical Equipment Intelligent systems are systems in which an array of devices or devices together can sense changes in the state of the system and make useful, optimized responses through a single device or array of devices.
Each intelligent sensor system and intelligent drive system can process data according to its own authority, make “decisionsâ€, and exchange data with other devices. The establishment of micro-intelligent appliances and their systems with microprocessor as the core and micro-sensors, micro-actuators and communication modules as peripheral devices has become one of the development directions of electrical equipment in the future. Therefore, the power system control and protection mode is completely different from the traditional mode of control and protection. It has no traditional concept of electrical devices and shows its own characteristics.
The system obtains various information as needed, and can control and protect according to the essential requirements. The sensor in this system is small in size and wireless communication, which is convenient for flexible installation and optimized layout. Different types of sensors are selected according to the control and protection theory, which is more in line with the original physical essence. For example, overload protection usually uses a thermal tripping device with a bimetal structure, while a microsensor system calculates heat by measuring current. Of course, a temperature sensor can be placed to directly measure temperature and protect.
The open system integrates and judges the acquired information to make optimal control and protection decisions. A distributed sensor system based on a high-speed communication system can be used for multiple upper-level devices, and the control center of the entire system or the central machine of the local network can make optimal control and protection decisions from the data obtained by the lower-layer devices. .
MEMS improve the control and protection reliability of electrical equipment. The intelligent micro-driver is executed hierarchically according to the degree of "authority" of the sender of the command, and can also be acted upon according to the number of commands, such as a command according to the master device or directly controlling the device; and some devices need to accept certain The number of commands is only actionable, such as self-learning, self-adaptation, and flexible adjustment according to the actual operation of the power system. This command acceptance mode of the driver can improve the reliability of the operation, and in particular, can avoid the situation in which the current microcomputer protection device malfunctions.
5 Conclusions The application of MEMS in electrical equipment is a complex project involving many disciplines, mostly cutting-edge disciplines at present, and the power system is both complex and demanding, and it is a relatively conservative system, which contains many needs to be deepened. Research issues, such as structural topology optimization design of micro-sensor systems and micro-driver systems; research on reliable and efficient communication mechanisms; research on management and calculation methods of distributed systems; research on power system control and protection theory and methods based on MEMS technology; Device integration technology, anti-jamming technology, etc. It is of far-reaching significance to study the application of microelectromechanical systems in electrical equipment. In theory, the control and protection strategies of power systems are more in line with the actual physical nature. The system is flexible, adaptable, and scientifically managed. The existing control and protection systems are incomparable; economically, production, installation, and commissioning are low. , high degree of intelligence, easy installation and commissioning. Therefore, it is feasible to implement new electrical equipment with modern science and technology.
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