New design approach improves smart meter performance

Aguilera

New design approach improves smart meter performance [Copy link]

After the mature smart grid is built, smart meters will have the functions of automatic query and remote meter reading, and can also realize automatic power off. However, at present, domestic smart meters mainly use PLC to transmit data to the Internet, and RF communication is not yet used. This article discusses the breakthroughs in the design of smart meters and what needs to be improved in terms of functions.

　　1 Breakthrough in the design of smart meters
　　As shown in Figure 1, in the smart grid electricity consumption information collection system, smart meters are located between power users and information collection on-site terminals. They mainly provide, manage and transmit power user electricity consumption information and are the lowest-level terminal equipment of the smart grid.

Figure 1 Smart meter and electricity consumption information collection system

　　1.1 Information provision: Breakthrough in metering technology
　　From a functional point of view, traditional meters only require active energy measurement, while smart meters can achieve more metering and measurement functions, such as grid voltage, current, power, frequency and other parameters. The core task of the meter is energy measurement, but energy measurement is no longer the only function of smart meters. Smart meters need to provide more parameters of power usage status, and collect, analyze and interactively manage this information to generate useful information, which the power system can then use to make better power consumption decisions and optimize power system configuration in real time.
　　From a performance point of view, the accuracy level of traditional meters is low. With the development of metering technology, smart meters have greatly improved in terms of metering accuracy, dynamic range and other indicators. They can also be more accurate in starting and running, and can realize software calibration to greatly improve production efficiency. In fact, the accuracy level provided by current smart meters, especially smart single-phase meters, has far exceeded the national standard requirements.
　　From a reliability point of view, traditional meters, especially inductive meters, have relatively poor anti-interference performance, anti-theft performance, temperature performance and other aspects. Some illegal users can easily interfere with the normal operation of meters through simple means, thereby achieving the purpose of stealing electricity. Smart meters use leading modern integrated circuit design technology to ensure accurate and reliable measurement under strong interference and wide temperature range, effectively protect the rights and interests of power grid companies and legal users, and realize fair and just electricity use.
　　1.2 Information management: a breakthrough in intelligent management
　　Traditional meters do not have MCU or MCU only undertakes very simple management functions. Its information is displayed through a character wheel, and it can only provide electricity data to users, and cannot perform intelligent management of electricity collection.
　　The MCU system of the smart meter is responsible for the storage, display and transmission of electricity information. Through the effective management of storage modules, clock modules, encryption modules, metering modules, communication modules, prepaid cards, etc., smart meters can realize the management of electricity usage methods such as prepayment, multiple rates, and tiered electricity prices, realize the management of safety measures such as automatic closing and opening, automatic alarm, and realize the management of information transmission such as automatic control and automatic meter reading.
　　With smart meters, power users can change their electricity usage habits, choose electricity usage methods and time according to electricity usage information, improve energy efficiency, reduce energy waste, and realize the rational use of electricity.
　　With smart meters, power grid companies can use smart meters to monitor electricity consumption information, timely discover existing problems or even power failures, and provide electricity consultation for users; the power demand of each household can be grasped in detail, and the power generation and distribution equipment can be adjusted according to the demand, balancing the power consumption during peak and trough demand periods, forming a timely interaction between power generation, distribution and power consumption, and reducing large-scale power outages and power outages that affect normal social production and life.
　　1.3 Information transmission: Breakthrough in communication technology
　　Traditional meters are isolated terminals in the power grid, and power consumption information is collected by manual meter reading, and efficiency and reliability cannot be guaranteed. Smart grids rely on various communication methods to integrate smart meters into a unified network. As smart terminal nodes of smart grids, smart meters can realize automatic meter reading, automatic control and other functions, greatly improving efficiency and reliability.
　Common communication methods for smart grids include power line carrier, 485, GPRS, small wireless, optical fiber, etc. These communication methods have their own advantages and disadvantages. The communication mode will be selected according to the final application. For example, carrier and 485 are generally used between smart meters and collectors/concentrators, and GPRS, optical fiber, etc. are generally used between collectors/concentrators and master stations.

　　2. Functional areas for smart meters to be improved and challenges they face
　　The development of smart meters requires higher-performance devices, among which the SOC chip that integrates many functions is the most eye-catching. As shown in Figure 2, the smart meter with high-performance SOC as the core, coupled with prepaid cards, encryption chips, LCD displays, communication modules, etc., constitutes the main body of the new generation of smart meters. The development of smart meters has put forward new requirements for some of the key modules, as described below.

Figure 2 Smart meter application with new SOC as the core

　　2.1 Information provision: areas where metering technology needs to be improved
　　From the perspective of the stability of metering solutions, the field application conditions of smart meters are very complex, and the conditions such as temperature, humidity, pressure, and interference are ever-changing. Smart meters are products that have only been developed and produced in recent years. Their reliability in field installation and operation, as well as the faults and quality problems exposed during use, are all facing challenges. At present, tens of millions of smart meters have been installed, and a lot of field experience has been accumulated. However, due to the great price pressure faced by meter manufacturers, smart meter solutions are emerging in an endless stream, and core chips are constantly replaced with lower-priced products. The experience accumulated in the early stage cannot be effectively passed on due to the replacement of solutions. The reliability and long-term stability of metering solutions will become a major challenge for smart meters in the future.
　　From the perspective of new developments in power equipment and power consumption environments, more and more loads show dynamic distortion load characteristics, such as steel, metallurgy, high-speed rail, mechanical processing, electric vehicle charging stations, etc. among industrial users, and illegal energy savers among civilian users. These loads are added to the power grid, resulting in a large amount of harmonics and DC, and they show the characteristics of rapid changes. At present, all electric meters are static electric meters. From national standards, measurement methods to calibration devices, the entire system can only guarantee accurate measurement under steady-state load. How to deal with harmonic conditions and accurate measurement under dynamic load will become the area where future measurement technology needs to be improved. In addition, the application of new energy also poses challenges to measurement technology. The measurement methods and standards of distributed power generation systems need to be continuously improved and developed in the future. In the future, new measurement technologies can be developed for these special application occasions and fully promoted when the final conditions are ripe.
　　From the perspective of the demand for measurement parameters, smart meters currently already have parameters such as voltage RMS, current RMS, neutral current, active power, voltage line frequency, power factor, etc. In the future, more power parameters may need to be provided for power quality monitoring and power management, such as harmonic content, flicker, etc.

　　2.2 Information management: areas where intelligent management needs to be improved
　　As the smart grid system introduces more and more functions, the functions of smart meters are becoming more and more complex, and the tasks that smart meters need to control and the data they need to process are also increasing significantly. For example, higher security, tampering protection and detection performance are required; the number of upgrades needs to be increased to ensure timely information updates; remote real-time control is required to achieve remote switching and remote flow control; more complex encryption algorithms are required. Therefore, according to the requirements of the application and the load of the MCU core, smart meters will migrate to 32-bit cores in the future, and higher requirements will be placed on program memory (generally embedded FLASH). Although 8-bit machines are still the mainstream of smart meters, it is certain that 8-bit machines cannot meet the needs of future smart meters. The meter industry needs to meet the growing demand on a higher performance platform as early as possible.
　　Another challenge for smart meters is their life expectancy. Inductive meters have a long service life. If smart meters are to achieve a service life of 10 or even 15 years, batteries are one of the keys. The battery is used to power the meter’s timing and display when the meter loses power. This places demands on low-power SOCs, especially the power consumption when the meter loses power. The power consumption of MCU standby, automatic temperature compensation RTC, LCD display, etc. needs to be controlled at microamperes, so that the battery can maintain a life of more than 10 years.

　　2.3 Information transmission: areas where communication technology needs to be improved
　　The rise of smart meters depends largely on the development of communication modes supported by smart meters. At present, the mainstream communication modes of smart meters are carrier and 485, as shown in Figure 1. Other communication modes, such as RF, optical fiber, GPRS, etc., have not yet become mainstream due to cost considerations. However, the 485 mode and the carrier mode have their inherent disadvantages. The 485 mode is complex and the cost is slightly higher. The carrier mode has the lowest cost but the worst real-time performance and reliability.
　　In the future, smart meters need to have two-way real-time communication, secure communication functions, detection and prevention of fraudulent activities, high data transmission speed, and low network cost. The current single communication mode does not have all of the above characteristics, so the development of future communication technology is a key to the development of smart grids. Smart grids need to choose appropriate communication methods according to the final application requirements.

　　2.4 What else can smart meters do?
　　The essential task of smart meters is to serve as a scale for power grid companies to charge electricity users, with the aim of achieving accurate and reliable measurement of electricity.