Analysis of Smart Meters and Functional Meters

    Smart grid has attracted wide attention since Obama mentioned it in his new energy policy in 2009. In the same year, Liu Zhenya, general manager of State Grid Corporation of China, proposed the construction of "strong smart grid", which pointed out the direction for China's smart grid. As the user terminal of the power grid, the energy meter has also kept pace with the times. In addition to being prefixed with the word "smart" in front of its name, it has also been given more requirements and missions in addition to its traditional metering function.

　　Introduction to Traditional Electricity Meters

　　The earliest electricity meter was an induction mechanical energy meter (mechanical meter for short), which measures electricity by generating a magnetic field through an electric field, which generates a torque on a rotating disk. Traditional mechanical meters are only used as electricity metering instruments , with relatively simple functions, and their stability, accuracy, and sensitivity are difficult to control, requiring regular calibration. With the development of electronic technology, electronic electricity meters have been used more and more widely. Since electronic devices with integrated circuits as the core are used from measurement to data processing, the mechanical components used for a long time on the electricity meter have been eliminated, which greatly reduces the size of the electricity meter and greatly enhances its reliability and accuracy. With the use of single-chip microcomputers and smart chips in electricity meters, electricity meters have more and stronger functions, so they have developed multifunctional electricity meters such as time-sharing meters that can measure day and night, smart IC card prepaid meters, meters with infrared meter reading and remote meter reading functions, and anti-theft meters.

 

　　However, there is still a big difference between these multifunctional electricity meters and real smart meters. What should a real smart meter look like?

　　Smart Energy Meter Requirements

　　my country proposed the State Grid smart meter enterprise standard in October 2009, which set relatively clear requirements for smart meters. Although the standard has entered the stage of comprehensive revision this year, the basic requirements for smart meters are still clear, and they usually have the following functions.

　　1. Need to have two-way power transmission and metering functions

　　As the access point of the power grid, the power grid transmits safe and high-quality electricity to the user's electrical equipment through smart meters. With the widespread application of new energy, many distributed new energy sources, such as wind energy and solar energy, have been fully utilized at the user end. This micro-distributed energy can also be fed back to the power grid through smart meters and connected to the grid. Therefore, smart meters need to have the functions of two-way power transmission and metering.

　　Of course, with the support of the powerful computing power of the MCU inside the smart meter, the smart meter can also perform reliable power management, such as time-sharing management, user power consumption classification management, maximum load control, etc. Through these managements, preferential discounts are provided for some high-energy-consuming equipment to switch from peak power consumption hours to non-peak power consumption hours, achieving peak-shifting and avoiding peak power consumption, improving the operating efficiency of the power grid, and saving expenses for users.

    2. Two-way communication is required

　　This two-way communication includes two aspects: one is the two-way communication between the smart meter and the user interactive terminal, and the other is the two-way communication between the smart meter and the distribution network. As the connection unit between the user terminal and the power grid, the smart meter can manage the power consumption of the user terminal, and the user terminal can feed back the power consumption to the smart meter in real time; on the distribution network side, the smart meter can send the power consumption information to the distribution network through the communication network, and the distribution network can control the smart meter in real time through the communication network.

　　At present, the communication between smart meters and user terminals is mainly achieved through wireless communication methods such as ZigBee, WiFi, and some special buses such as M-Bus and power line modulation and demodulation. The user terminal is interconnected with the smart meter through the energy gateway; and the communication between the smart meter and the remote distribution network also has various forms, such as power line carrier communication (PLC), wireless network communication (WiMax, OFDM, etc.), communication network communication, etc. By the way, with the golden signboard of "smart grid", State Grid is also actively building its own exclusive power optical fiber communication network. It is believed that in the next few years, State Grid may build the fifth optical communication network after China Telecom, China Mobile, China Unicom and Radio and Television. [page]

　　3. Control function of load switch

　　With the help of remote communication function, users can remotely control the switching of various smart loads in their homes, such as air conditioners, washing machines, refrigerators, lighting, etc., through the Internet or mobile communication network. At the same time, remote monitoring and alarm can be achieved through the remote communication function of the smart meter.

　　Of course, there is no widely accepted definition of smart meters internationally, and many concepts are incomplete or unclear, which is why the State Grid smart meter enterprise standard has to be fully revised just two years after its implementation. However, if the above three requirements are met, it can basically be considered a smart meter.

　　Development of smart meters

　　The concept of smart meters has been very popular in recent years. On the surface, it is the State Grid Corporation of China and China Southern Power Grid that are promoting the construction of smart grids and the installation and transformation of smart meters. However, the actual leaders of "intelligence" are semiconductor giants with core technologies in the electronics field and some large IT companies.

　　We can see that semiconductor giants such as Freescale and Texas Instruments have complete solutions for smart meters, including the most basic metering, LCD display, extended communication, anti-theft functions, etc. In addition, they also participate in the formulation of various standards, such as ZigBee, power line carrier communication (PLC), ITU-T G.9955/9956 narrowband power line carrier communication standards, etc. The following is a brief introduction to some solutions and products of various semiconductor manufacturers on smart meters.

　　1. Freescale Semiconductor

　　It was transformed from the former Motorola Semiconductor Division. As one of the world's largest semiconductor companies, it has rich product lines in the automotive, consumer, industrial control, network and wireless communication fields, and has design, R&D, manufacturing and sales organizations in more than 30 countries and regions around the world.

　　In the field of smart meters, Freescale provides energy-saving 8-bit and 32-bit microcontroller solutions. Among them, the MZ series is specially customized for the new standards of China's smart grid, which integrates analog-to-digital converters, timers, up to 69 general-purpose input/output ports and multiple communication interfaces; the communication module can easily implement ZigBee applications through the MC1322x series RF low-power products; and in terms of anti-tampering, Freescale's NMA766x and NMA7455x series acceleration sensors can be easily designed.

    2. STMicroelectronics

　　As a global leading semiconductor manufacturer, STMicroelectronics also has a series of products to support the design of smart meters. In terms of microprocessors, the STM32 series based on the ARM Cotex-M core integrates a large number of resources, with optional Flash ranging from 16K to 1M, RTC reduced to 1uA, and supports up to 15 communication interfaces. The STM32W directly integrates the RF module on the chip, and users can directly design based on the IEEE 802.15.4 communication protocol on it; for power line carrier communication, STMicroelectronics has products such as ST7570, ST7580, and ST7590; and for the design specifically for energy metering, STMicroelectronics has STPM10 for single-phase meters, and STPMC1 and STPMS2 for three-phase meters.

　　3. Texas Instruments

　　As a long-established semiconductor manufacturer, Texas Instruments has a rich product line. After acquiring National Semiconductor, its technology in power management chips has become even more powerful. For smart meter applications, the microprocessor uses the MSP430 series; for RF ICs, CC2520 and CC2530 are second-generation 2.4GHz ZigBee chips that can be used for ZigBee AMI.

　　Smart Meter Market Outlook

　　The emergence of smart meters has greatly facilitated our lives. With the construction of smart grids, smart meters will surely enter thousands of households. However, the problems brought by smart meters cannot be ignored. For example, whether the radio waves emitted by them will affect human health, whether they will damage biological systems, whether the application of smart meters will cause privacy leakage, etc., are also issues that people are paying more and more attention to. Similarly, the promotion of smart meters is also a process of interest competition between the traditional power industry and emerging power manufacturers, such as semiconductor manufacturers and IT manufacturers. This is bound to be a difficult and long stage. In addition, whether the large-scale application of smart meters will affect national security, how to deal with the large amount of surplus manpower after automatic meter reading replaces manual meter reading, etc., these are all problems that smart meters must face and solve in the promotion.

　　There is still a big gap between reality and the future we envision, and there is still a long way to go in the development of smart meters.