Design Of Integrated Power Quality Monitoring Instrument Based On ARM

With the development of national economy and the building of Smart grids, large numbers of electrical equipment are used in power system, and therefore power quality problems has become an urgent issue to be solved in the construction of the smart grid. Power quality monitoring as a prerequisite to solve the problems, has received increasing attention.Currently, our country has made a series of standards on power quality according to relevant international standards, and power monitoring instruments also came into being, but product quality is mixed. Therefore, through the study of relevant national standards and combined with the current large used micro-controller based on ARM and today’s most characteristic features of current products, this issue designed a ground-easy to install, reliable, intelligent and networked power monitoring instruments.This paper strictly followed the national standards, and proposed the function and design specifications of the instrument according to the requirements of the cooperative units. This monitoring instrument can measure electric parameters on the electricity scene, such as each phase current, each phase voltage, power factor, active power, power, harmonics and so on. In addition, according to the user’s settings, it can set alarms and protective operations, and the alarm and status information can be recorded and inquired. In order to improve the accuracy of fault information, the instrument designed GPS clock synchronization circuit. System forms a real-time monitoring network which can quickly locate fault and alarm points through RS485bus. You can easily check the operational status of circuit, record and query alarm and fault operations. It extended a GPRS interface, which achieved long-distance data transmission via a wireless network.According to the functional requirements and design specifications of the instrument, hardware design uses a dual-CPU program. The main chip were used32-bit high-performance embedded microcontroller LPC1764FBD100, relies on its high-performance GPIO ports, SPI interface, UART interface, timers and other hardware resources. The A/D sample used a dedicated16-bit A/D converter ADS8556. It selected a8-bit high-performance embedded microcontroller P89LPC930as slaved chip, which achieved Modbus protocol and GPRS remote communications on the RS485bus. The system hardware and software design, including signal processing, data storage management, GPS synchronized timing, human-computer interaction, alarm, protection, communication and other modules in accordance with the modular approach. Hardware design bases on the microprocessor core of the system, according to system requirements, select the relevant functional chip, and design each circuit. Software design, which used a microcontroller powerful interrupt management mechanism for multi-tasking, achieved the orderly scheduling of software tasks.The introduction of the GPS module improved the accuracy of the instrument for SOE event records. This article briefly describes the GPS timing principle, the needs of the different behavior in the power system for time synchronization accuracy, and the traditional time synchronization method which has a big error and is difficult to achieve the power system requirements because of electromagnetic interference within the power station impact. This paper presents a GPS-synchronized timing achievement by using time information and pulse signal provided by GPS.Finally, the paper introduced the test results of the instrument function, error analysis and anti-jamming design, and proposed the improvement proposal for anti-jamming design.