The Online Power Quality Monitoring Device Developed Based On μc/OS-Ⅱ

Recently, the application of non-linear and high-power electrical equipment brings a large number of harmonic pollution to the grid. It not only influences the use of precision electrical equipment and the stability of power networks, but also reduces the accuracy of electric energy metering device. At present, the high-performance power quality monitoring device on the market is so expensive that can’t be used widely. Therefore, designing the power quality monitoring device which is precision and cheap is meaningful for the regulation of utility grid.Based on the development status and practical requirements of on-line power quality monitoring system, a design concept which adopts ARM Cotex-M3 as control center and ADE7880 as DSP core is proposed to set up hardware platform. On this basis, μc/OS-II embedded opration system was adopted as software core to manufacture a device which owns functions like measurement, harmonic analysis, storage, communication and display.Firstly, the sampling method, the measuring principle of electrical power system basic parameter and the algorithm of harmonic analysis are described in conformity with power quality standard of china. Based on the hardware platform, the sampling scheme, key data processing algorithm and additional function modules design used in this device are described detailedly in this paper. In the part of the sampling scheme, the sampling scheme used in this design scheme is compared with traditional sampling method in the simulation. The result demonstrates that this sampling scheme is helpful to reduce the spectrum leakage and noise effectively. As is well known, the algorithm computational complexity of traditional harmonic analysis is so large that the real-time performance of algorithm is depend on hardware.In order to solve this problem, the algorithm with adaptive real-time monitoring is adopted to improve the real-time performance of harmonic analysis.Secondly, the part of software design mainly introduces how to transplant μc/OSII to LPC1768 and the software architecture based on it. Ulteriorly, function module design and implementation like data acquisition, processing, storage and display are elaborated in this part.Finally, experiments about calibration accuracy, real-time capability, function and index are designed to test the performance of prototype.The experimental results show that the measurement error of RMS less than 0.5%, the frequency resolution is 0.01 Hz and the relative error of harmonic in the first 52 nd below 5%. These experiments prove that the scheduled result is attained and the aim of design is realized. The main power quality index monitored by prototype achieved the accuracy requirements about power quality monitoring device in standard of GB/T 19862 – 2005.