Electric Energy Metering System Based On Wireless Communication Technology

Electric energy metering facilitie is a significant component of power distribution domain. Its intelligentization is indispensable to that of distribution, and correspond the project of promoting the IOT (internet of things) industry, which is brought forward in the12th Five Year Plan. As an important tool to collect, record and transport power utility information, electric energy metering facilities are going to bring people’s life much convenience, when getting intelligentized. It’s imperative to research and develop intelligent power metering facilities (systems) with better performance, so as to meet the requirements for progress of society and science.Our government work reports made in March,2012has proposed the implementing of reform program for resident step tariff. Step tariff is going to reflect the value of energy, encourage rational and reduced power consumption. This electric energy metering system thus has chosen the charge mode of step tariff.This system combines advanced metering and communication technologies. The whole system is divided into two parts--data acquisition layer and gateway layer. The data acquisition layer is responsible for the acquisition and transmission of data, while the gateway layer is in charge of connecting two kinds of communication networks and collecting data sending from data acquisition layer. It is ZigBee network that serves the communication between the two layers. This ZigBee network is built according to star topology. The nodes belonging to data acquisition layer are installed by residents’houses, and tens of the nodes correspond to one node in gateway layer, which is the center of the star network and serves as the coordinator of the ZigBee network. Gateway layer and upper management center communicates across Ethernet. The former collect information sending from data acquisition layer and send it to the latter, playing the role of a gateway and thus realizing the communication between data acquisition layer and management center.In data acquisition layer, the electric power measurement chip AD71056, which is launched by ADI Company, has been chosen to measure residents’ single-phase power consumption. The output of this chip is proportional to the power consumption, thus a MCU can compute the power consumption by residents if connecting AD71056’s output as an input. The ZigBee chip CC2530has been chosen to fulfill functions such as acquiring power consumption information and transmitting data through wireless networks. CC2530has integrated a MCU inside, and thus simplify the design process. The data acquisition layer’s function is completed mainly by AD71056and CC2530, which acts as the coordinator of a ZigBee network in gateway layer. As the center of a ZigBee network, gateway layer executes the duties of data relay, data display and so on. The chip LM3S9B96, based on ARM Cortex-M3architecture, is selected to serve in gateway layer. LM3S9B96has integrated Ethernet MAC and PHY inside, which ensure the quality of communication through Ethernet. CC2530and LM3S9b96in gateway layer communicate through serial port and cooperate with each other to fulfill main functions of gateway layer. ZigBee network in this system is based upon Z-stack, which is released by TI Company. There is a SafeRTOS operating system ported into LM3S9B96. Z-stack and SafeRTOS have made the whole system more stable and reliable.At present this designed system can realize functions like building a star ZigBee network, transmitting data through ZigBee network, through serial port between CC2530and LM3S9B96, and through Ethernet between LM3S9B9and computer, as well as operating the touch screen.This electric energy metering system provides convenience for managers. Computer in management center is capable of work like report generation and print if the system gets further designed, which is going to simplify managers work and cut back expenses. When the LAN of the system accesses the Internet, managers can execute their responsibilities anywhere, anytime, and residents can carry out operations, for example payment, as long as they get access to internet. All in all, this system is important for the intelligentitzition of power distribution.