The technology covered by the smart grid and the industries involved are very extensive. It has driven the development of many industries from concept to practice. Smart meters are one of the earliest markets to benefit. Because it is directly related to electricity consumption and is also a link between users and grid companies, smart meters have become the vanguard of the development of smart grids.
The difference between a smart meter and a traditional meter is that it is a two-way real-time communication, has interactive features, can provide real-time data, and provides the possibility of implementing tiered electricity prices. Therefore, the design of smart meters emphasizes stronger information processing, interaction, measurement and communication capabilities. In the smart grid standards promulgated by the State Grid Corporation of China, these indicators have also been specified in detail. In October 2009, the State Grid Corporation of China announced a new technology standard system for smart meters, consisting of 12 technical standards in four categories: functional specifications, technical specifications, type specifications, and safety certification specifications. The standard system has detailed regulations on metering, cost control, communication, power consumption, and electronic circuit wiring, appearance, etc., and puts forward higher requirements.
The chip of the smart electric meter involves control, measurement, encryption and communication chips (narrow wave communication). The control chip is the core of the whole program and is responsible for the most important functions such as tariff calculation, control display and communication. Domestic control chips are now mainly occupied by the two major manufacturers. The largest is Renesas Electronics, which accounts for more than 70% of the share; the other is domestic Fudan Microelectronics, which accounts for about 20% of the share. The solutions of these two manufacturers also represent the design solutions of domestic mainstream smart meter manufacturers.
Fudan Microelectronics FM3308 control chip
The domestic manufacturer Fudan Microelectronics has launched a group of FM33 series MCU chips specially designed for single-phase smart meters of the State Grid. Taking the representative FM3308 chip as an example, it illustrates the smart meter solution provided by Fudan Microelectronics. FM3308 is based on the mature 8051 core. The following figure is the national grid single-phase smart meter solution using FM3308.
Because Fudan Microelectronics' FM3308 chip is specially tailored for the national grid smart meter, it integrates various functions required by the smart meter, such as the MCU core, LCD driver, real-time clock, and I2C, 7816, and other interfaces on the chip Therefore, the smart meter design with FM3308 as the main control chip can make full use of the inherent hardware functions of the chip, simplify the peripheral design to the greatest extent, and reduce the system cost while ensuring that the overall design function meets the optimal performance.
The chip has built-in hardware real-time clock and liquid crystal drive circuit, so there is no need to add another real-time clock chip and liquid crystal drive chip, which can greatly reduce system cost and simplify peripheral circuit design.
The MCU clock is provided by the internal high-frequency / low-frequency oscillator, thus eliminating the traditional external crystal oscillator, which can simplify the peripheral circuit and improve reliability. The accuracy of the high-frequency (8MHz) oscillator in the FM3308 chip can reach 8MHz ± 0.5%, which fully meets the requirements of the energy meter. 3-way hardware serial interface is used for infrared, 485 meter reading and power line carrier communication respectively; 2-way 7816 interface is used for ESAM and IC card; I2C interface is used for external EEPROM memory chip.
Renesas Electronics' R8C / Lx series control chip
Renesas Electronics has been in the electricity meter market for more than ten years. It has the largest market share in China's electricity meter application main control chip market and provides customers with complete reference solutions.
Renesas Electronics' R8C / Lx series products integrate watchdog, internal reset circuit, built-in LCD driver, data flash memory, etc., which can not only save the cost of parts for customers, but also save the number of pins available for the chip, so that the chip can get the most Degree of utilization.
Renesas Electronics ’R8C / L38 products use a 3-serial design, enabling customers to achieve 485 communication, infrared and smart card communication; the built-in LCD driver meets the requirements of 4 * 40 segment codes, and reflects power usage information, battery information, and smart card usage in real time In the display terminal; the hardware SSC, I2C interface realizes the communication between the MCU and the clock chip and the metering chip; a large number of IO ports can meet the needs of buttons, cover opening, relays and so on.
SoC solution can be expected in the future
In the past, due to the restrictions of the State Grid specifications, the smart meter SoC solution cannot be adopted in China at present, but the latest specifications are not limited in this regard. As the SoC solution gradually matures and the bulk use in some foreign markets brings Demonstration effect, under the situation that the domestic electricity meter product cost pressure is increasing day by day, SoC scheme will make substantial breakthrough in the next 2 to 3 years.
The AS-I (i.e. actuator-sensor interface) bus belongs to the bus system at the bottom device level. It is a two-wire network for digital input and output, which complies with EN50295 and IEC62026-2 specifications.
Various types of digital devices can be connected, such as: Sensors, limit switches, buttons, valves, relays, light curtains and emergency stop switches, etc., and send signals to higher-level controls such as PC, PLC, CNC or DCS system. In general, AS-I does not require shielded cables and terminal resistors.
The unshielded two-wire cable used carries both the signal and the power. Generally speaking, the AS-I bus system is simple and reliable, easy to install and fast to configure, and is widely used in industrial automation fields such as logistics, automobile production, petrochemical industry, and elevator control.
The As-I Passive Distributor simple module is pierced and connected to the flat cable, which is suitable for installation in a narrow space, and can provide connection methods such as aviation connectors.
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