Three-Phase Multi-Function Meter Developed Based On The STM32 And The STN LCD

With the development of economy and society, and also the popularity of electrical equipment, the demand of power is growing rapidly, but more than half of the electricity comes from fossil energy, petrochemical power generation is bound to damage the environment. According to the national energy saving and emission reduction 12th five-year plan, country should be less dependence on fossil energy to develop new energy, moreover rapid development of distributed new energy power generation facilities need to join to power grid system; The use of various power electronic devices in power grid increases a lot of harmonic in it and this will affect the system stability. Therefore, there must be a system could solve these problems. So a set of high-efficiency terminal system which can both have electricity consuming and providing statistics data and harmonic components analysis need to be developed.The metering system in this paper can not only measure the fundamental main parameters of the power,but also can detect the harmonic components.The main work of this paper is as followed:1.In order to reduce the leakage barrier effect of the spectrum effectively, interpolation and windowing processing and FFT method is applied to meet the requirements of the system accuracy. The design in this paper has a smaller amount of computation and is real-time sampling compared with the traditional interpolation.2.On the hardware design, both the economic and engineering factors are considered, the design of the electric meter has low price, multi-function and high precision. Choosing the STM32F1XX series which have rich resources of the chip and interface, and it can handle large amounts of data. Choosing current transformer and the input voltage resistance series connection to alternate voltage transformer, this can save the the cost instrument while still meet the system requirement. To ensure the accuracy of data collection, the speed of op-amp chip must be fast and signal distortion should be low enough,which can stimulate amplitude and precision of the AD section. Choosing PCA82C250 chip to replace the RS485 conversion chip to improve the anti-interference ability of the system. Choosing STN dot matrix LCD multi-color display, add open circuit input and relay output, temperature measurement and sound alarm can enrich the meter.3.The standard protocol is developed in software base on the mod-bus to ensure the data accuracy and instruments versatility. The harmonic processing algorithms can get the data rapidly and accurately. Design of LCD multi-layer menu display, better to check the data and modify parameters.When the hardware finished and software designed, there must be a test by the standardized testing. Experimental results show that the design meets th e system requirements.