With the rapid development of computer technology, network technology and large-scale integrated circuits, the dynamic signal analysis system has a trend toward network development. Embedded System with computer technology, chip technology and software as the core has once again become the hot spot of current research and application. Compared with general-purpose computer systems, the biggest feature of embedded systems is that they are purposeful and pertinent, that is, the development and design of each embedded system has its own special applications and specific functions, and usually has high real-time performance and power consumption. Low, small size, high integration, low cost, etc.
The remote electric energy data acquisition terminal (ERTU) is an intermediate device between the main metering station and the tariff device (electric energy meter) in the electric energy billing system, which mainly completes the functions of electric energy data collection, processing, storage and forwarding. . The application of embedded technology in the power system has a long history. As early as a few years ago, China has begun to introduce the embedded real-time operating system (Real TIme OperaTIon System-RTOS) as the core power grid monitoring system. With the continuous improvement of power system automation in recent years and the rapid development of embedded technology, embedded technology has become more and more widely used in various fields such as data acquisition, status monitoring, automatic devices, microcomputer protection, and distributed control. Due to its own decentralized power users and the need for network management, the application of embedded technology will greatly improve system performance.
2 Overview of Embedded Electric Energy Harvesting SystemElectric energy harvesting system has broad application prospects as a technical support for electric power marketing and commercial operation of power grids in the future. The system is mainly composed of four parts: the computer system at the main station, the power collector at the plant station, the multi-function electronic electricity meter and the information communication network, involving professional knowledge in electronics, computers, communications, networks, and power systems.
With the establishment of the electricity market and the development of information technology, new characteristics have emerged in the development of electric energy acquisition systems: (1) The degree of networking is higher, and the remote electric energy data acquisition terminal (ERTU) has multiple interfaces and built-in Modem, It should also have network functions, a network interface, and comply with TCP/IP standard protocols; data transmission is safe and reliable, with user-oriented information query functions and auxiliary information release functions; (2) Automatic meter reading ARM (AutomaTIc Reading Meter) is The power supply department collects the electricity consumption recorded by the electric energy meter installed at the user's place to the business department through remote measurement, transmission and computer systems, instead of manual meter reading and a series of follow-up work.
The realization of ARM will overcome the time-consuming, laborious, error-prone and difficulties of meter reading at home by manual meter reading, and will help improve the level of power distribution automation; (3) The use of embedded CPU and embedded real-time in the remote electrical energy data acquisition terminal (ERTU) Multi-task RTOS constitutes a complete embedded system. On the basis of RTOS, combined with embedded Web server technology, it can realize real-time and dynamic interactive query functions and provide strong support for the decision-making analysis of power management personnel. ERTU uses timing or real-time start of meter reading tasks, reads the power information and event information in the smart energy meter through the RS-485 bus, and supports standard RS-485 serial data output. Each ERTU device can be connected to multiple RS-485 buses, so that multiple meter information can be collected at the same time. According to the development of the above-mentioned electric energy acquisition system, a new type of electric energy acquisition terminal has been developed in the system research. Its hardware adopts the popular PC104-based CPU, which can ensure high-speed and high-reliability operation. The design can easily expand the interface. The electronic disk is used as the storage medium to ensure that data is not lost after power failure; its control platform adopts real-time embedded LINUX operating system, multi-process/thread design, and each program module runs concurrently , Can greatly improve system efficiency. The smart meter corresponding to each electric energy metering point measures the electric energy, and the data acquisition system collects and stores the electric energy meter in a round-robin manner. The collected data is transmitted to the main station system through a dedicated line, that is, the mobile company's GPRS network, through the GPRS network Remote communication with the control center. The data acquisition system is designed with a plug-in structure of functional modules, which is mainly composed of interface modules, RS-485 acquisition modules, main control modules, and remote communication modules (Modem). Each module is connected and managed through the main control module. The collection device adopts the method of starting the meter reading task regularly, and can also use the remote control mode to read the electrical energy information stored in the smart meter through the RS-485 bus, and store the event information in the collection device in time intervals. The data acquisition system has the ability to convert different watt-hour meter protocols. For different watt-hour meters, the corresponding acquisition program is written and a program library is established.
3 Main functions of the embedded electric energy acquisition systemThe developed new electric energy collection system integrates data collection, storage, processing, wireless uploading and other functions. The system can collect 32/64 pulse input signals with a pulse scanning period of 10ms, a sampling resolution of not less than 40ms, and hardware filtering. At the same time, the software performs filtering processing according to the type and pulse width of the electric energy meter. The electric energy acquisition system provides 4 RS-485 interfaces, each RS-485 interface can be connected to 32 multi-function electronic energy meters, and can also be extended. The reading interval is set remotely by the master station, or can be set on the collection system side. Each data read from the electric energy meter is added to the time information and stored as data with time stamp. The time information of the power collection system is through the GPS module in the system For precise time service, the collection system completes time calibration through the GPS clock and can perform broadcast time calibration on multifunctional electronic energy meters. The embedded electrical energy collection system can communicate with pulse and pulse meter terminals, or with The digital interface is a fully electronic energy meter terminal communication, and a GPRS interface is provided at the same time, supporting the TCP/IP protocol, and uploading to the main station server through the GPRS network. The functional structure diagram of the system is shown in Figure 1.
4.1 The hardware structure of the data acquisition unit
The hardware core of the system uses the standard PC104 "mezzanine bus" mode and embedded operating system to provide the operating platform of the application program, which improves the standardization of software and hardware design and the reusability of the system. The microprocessor adopts the Intel486 processor platform, and its speed It is 100MHz and can be changed by program; it includes an Ethernet interface, supports TCP/IP protocol, and the memory is divided into two parts: 512kB FLASH EPROM (used to run programs and storage of various intermediate variables); a 64MB Disk On Chip The electronic disk (used to store the collected energy data, can be expanded to 1G at most). A 4-channel multi-serial port card with PC104 interface, using multi-serial ports to expand 8 serial ports to connect to local electric energy meters, the system also uses the following user interface equipment: a monochrome LCD screen compatible with standard LCD interface, display resolution Rate 320&TImes;240; input keyboard connected with PC-AT keyboard interface, used as user input device.
It can be seen from the above that the main PC peripheral devices are concentrated on a relatively small motherboard, which includes: CPU, memory, bus controller, standard serial communication port, standard parallel communication port, standard IDE disk drive interface, standard VGA driver chip, LCD interface, mouse/keyboard interface, Watchdog monitoring chip. With a motherboard plus power supply, display and storage devices, a powerful and compact industrial-grade PC is formed.
4.2 System timing module
The time of the data acquisition unit is calibrated by the synchronous time signal output by the GPS standard module. The GPS module communicates with the data acquisition unit through the RS-232 interface. The electric energy data collected from the electric energy meter is added to the time information and stored in the electronic disk. Then upload the energy data with time stamp to the master station.
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