Keywords: ZigBee, communication module, wireless technology, power management system
1 Introduction As the construction of smart grids around the world is gradually unfolding, the client is an important part of the smart grid. The core content of the client includes smart distribution and energy management, smart appliances, power safety, and power metering. At present, the energy management system will consider a hybrid networking method of multiple communication technologies to overcome some of the deficiencies inherent in the existing technology, so as to meet the requirements of system performance and return on investment. At present, industrial Ethernet, power line carrier and wireless short-range communication are considered to be available solutions for AMR automatic meter reading systems. Among them, wireless short-range communication is a good solution for local communication networks. Long-distance communication such as industrial Ethernet, GPRS and CDMA can be used as a remote communication network. The hybrid networking in this way is recognized as a good solution Program. With the rise of an emerging short-range, low-rate wireless network technology, ZigBee technology, local wireless automatic meter reading systems based on ZigBee technology have become a hot spot. This article mainly introduces the design of a wireless module based on ZigBee technology and its application in ZigBee wireless automatic meter reading system.
2 Features of ZigBee technology
ZigBee wireless technology is characterized by low power consumption, low cost, low data rate, short distance, and high communication reliability. Its network topology mainly supports three types of self-organizing wireless networks, namely, star structure, mesh structure, and cluster tree structure, especially the mesh structure, which has strong network robustness. And system reliability. This makes ZigBee technology play a huge role in the wireless meter reading system with low power consumption, low cost, low data rate and strong reliability.
3 ZigBee wireless module design The ZigBee wireless module designed in this paper adopts the installation method of rail type installation, which can be conveniently installed on the 35mm standard rail, which enables the module to be flexibly installed in various distribution boxes and distribution cabinets. The appearance side view is shown in Figure 1. The technical specifications of the ZigBee wireless module are shown in Table 1.
Table 1 ZigBee wireless module technical indicators
ZigBee wireless modules are divided into two categories. Among them, the module that converts ZigBee signals to RS485 signals is called ZigBee acquisition module; and the module that converts ZigBee signals to Ethernet signals is called ZigBee network terminal. The central node in the network.
Figure 1 ZigBee module side view
3.1 Hardware design
The ZigBee wireless communication module is mainly composed of a switching power supply part, a ZigBee wireless transmission part and an interface conversion part, and its functional block diagram is shown in FIG. 2.
Figure 2 ZigBee communication module
The switching power supply circuit part mainly uses American PI company TOP221Y (TOPSwitch), using a flyback power conversion circuit to convert the AC power supply to the DC power supply we need; the wireless transmission part mainly uses the MC13213 chip, which is the second-generation freescale ZigBee chip With MCU chip and wireless transceiver inside, its schematic diagram is shown in Figure 3; the power amplifier uses SKY65336, which can support a maximum power amplification function of 20dbm, and its schematic diagram is shown in Figure 4; the signal conversion circuit is divided into RS485 conversion Circuit and Ethernet conversion circuit, the Ethernet part uses Zhou Ligong's IPORT Ethernet module.
Figure 3 Schematic diagram of MC13213
Figure 4 SKY65336 schematic diagram
3.2 Software design is shown in Figure 5 as a flow chart of the establishment of the ZigBee module network. The entire ZigBee network is initiated and established by the central node (ie, ZigBee network terminal module). And the ZigBee acquisition module with the same network ID as ZigBee can automatically join this ZigBee network, and each ZigBee acquisition module obtains its own independent network address. At this time, the entire ZigBee network is successfully established, and it is ready to send and receive data. The ZigBee network terminal transmits data by broadcasting.
Figure 5 ZigBee module network establishment flow chart
Figure 6 shows the flow chart of the data transmission of the ZigBee acquisition module. First, the ZigBee acquisition module receives data from the ZigBee network terminal module. Then judge whether it is the data passed to yourself, if it is your own data, upload the relevant reply data, if not, then forward the data from the ZigBee network terminal module in a broadcast manner according to the address in the routing table you found. After finishing all work, enter sleep mode and wait for the next visit.
Figure 6 ZigBee acquisition module data transmission flow chart
ZigBee acquisition module and ZigBee network terminal adopt transparent transmission, that is, directly convert Ethernet data into ZigBee signal, which does not add redundant data, only forward the data part, automatically remove the frame header and frame tail; RS485 signal conversion ZigBee The same principle applies to signals.
4 Based on the application of ZigBee power management system as shown in Figure 7 for the ZigBee power management system, the remote communication network in this paper uses industrial Ethernet network, the communication protocol of the meter in the network uses MODBUS-RTU protocol. The monitoring host in the entire system transmits the MODBUS-RTU command data to the ZigBee network center node through Ethernet according to the TCP / IP protocol. The network center node then transmits the command data frame to the broadcast mode through the single-point to multi-point communication mode. Each ZigBee collector in the ZigBee wireless network is passed to each meter on the 485 bus through the ZigBee collector. If the address of the meter matches the address involved in the command frame, a corresponding data reply is made and the original path is used. Return to the monitoring host.
Figure 7 ZigBee power management system
The entire system can monitor the energy measurement of various sub-items of the entire plant or the entire building, such as the power consumption of street lamps in a plant, the power consumption of various offices, the power consumption of various production lines, etc., and can also be in the form of reports Analyze the percentage of total energy consumption of each sub-item of the plant over a period of time, so that the factory can understand the energy consumption of each sub-item during this period to formulate a future energy management plan, which has achieved energy saving and reduction Consuming effect.
At present, the entire system is implemented in a manufacturing enterprise in Jiangyin. According to the principle of sub-metering, the incoming and outgoing lines of the plant area are sub-metered. Figure 8 is the power distribution diagram of the plant area. The entire system has all incoming lines The loop is monitored, and all use ZigBee acquisition modules for data acquisition and monitoring, which include parameters such as current, voltage, and energy, as well as some simple switch control. The system also monitors some branches, such as production lines, office buildings, air conditioners, etc., for comprehensive monitoring, so that the factory can understand various data in order to formulate more detailed energy-saving programs.
Figure 8 Power distribution diagram of the plant
At present, the entire ZigBee wireless energy management system uses 21 wireless modules, including 82 blocks of various types of meters. Figure 9 is a communication diagram in the ZigBee wireless energy management system, which lists all the meters included in the entire system. Among them, the 14 meters in the power distribution room are connected to a ZigBee acquisition module for wireless communication through the 485 bus. Each air-conditioning socket is more dispersed, and each uses a ZigBee acquisition module, etc. According to the discrete situation of the meter, the 485 bus is used to connect a module together, and the modules are connected separately. It is more flexible in this way, reducing the difficulties caused by wiring.
Figure 9 ZigBee wireless energy management system communication diagram
The whole system is running well and has been running on site for a while. Figure 10 is a trend diagram of the main incoming current over a period of time, which reflects the current situation of the plant during this period of time in real time, thus reflecting the load situation of the entire plant area.
Figure 10 Trend graph of main incoming current over time
Figure 11 shows the specific values â€‹â€‹of the parameters of the incoming circuit over a period of time. It records the three-phase voltage, current, active energy, non-functional energy, power factor, and frequency parameters of the incoming circuit in detail. The power summation of each circuit in the whole plant is shown in Figure 12, which records the power consumption of each circuit in a period of time, including the total power and branch power of each circuit cabinet.
Figure 11 Various parameters of the incoming circuit over a period of time
Figure 12 Summary of electrical energy of each circuit
5 Summary With the rapid development of wireless communication and ZigBee technology, the power management system based on ZigBee will gradually get people's attention. ZigBee can solve the problems of difficult wiring, high cost, difficult to maintain and upgrade in wired communication mode, and the networking flexibility is very high, the application prospect is very wide in the power management system, and also in the field of smart grid Application prospects.
The ZigBee wireless module introduced in this article has been successfully applied in the ZigBee wireless power system. The entire system has well monitored the various incoming circuits in the plant and can truly reflect the load of the plant, which will save energy and reduce emissions. Make due contributions. In order to make the ZigBee wireless energy management system better use its advantages, it is necessary to continuously optimize the hardware and software equipment in the system.
The article comes from: "Electric Drive Automation", Issue 3, 2011.
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About the Author:
Yu Jing, female, undergraduate, engineer of Wuhan Ankerui Electric Co., Ltd., the main research direction is intelligent power monitoring and power management system
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