The Design And Development Of Multi-function Electrical Parameters Measuring Device Based On DSP

With the rapid increase of social electric power consumption and the massive use of electric power nonlinear load in power system, the harm brought by electric harmonics becomes more and more serious. As conventional electric metering device is unable to exactly measure electric energy under non-sinusoidal conditions, this paper deeply studied the theories relative to power parameters measurement, electric energy metering and harmonics measurement. A multi-function electrical parameters measuring device which is able to measure the harmonics is designed and developed based on those theories.Firstly, the paper detailedly introduces the AC sampling technology and the effect on the accuracy of electric parameters computation caused by synchronization error. The resolution methods that can eliminate synchronization error are deeply studied both on the hardware and software aspects. The computation algorithm for period average values such as voltage, current, active power, reactive power, etc. based on quasi-synchronous sampling technology is given. Considering that multi-function energy meter demands real-time harmonic analysis and only a few frequency components need to be calculated, the Goertzel algorithm is introduced to measure and analyze harmonics.Secondly, a specific hardware design of the electric energy metering module for multi-function energy meter is introduced. The hardware structure based on high-accuracy AD converter and high-performance DSP processor is given. Each part of the hardware circuit with its working process is also discussed.Thirdly, the system software is developed with hierarchical and modular development flow. The software implementation method and process of the digital algorithms introduced before are given. The execution efficiency of the program is greatly raised by using assembly language modules with C code.Finally, the experimental and testing platform is constructed and the validity of the digital signal processing algorithms is validated.The multi-function electrical parameters measuring device introduced in the paper works fine. The experiment results indicate that the electric parameters algorithm based on quasi-synchronous sampling technology and the harmonics measurement method based on Goertzel algorithm are correct and effective. Accompanied with a data management module, an integrated multi-function energy metering terminal will be implemented and it will have a promising future.