Online Power Metering And Analysing Based On DSP

With the fast development of power electronics technology, harmonic pollution of power system becomes serious day by day and power quality is attached more importance. On the one hand, it puts forward a higher request to the accuracy of high-voltage power measurement, which relates the interests of power plants, power supply departments and power consumers; on the other hand, online monitor of power quality and using condition, which can reduce a great deal of field check work using the monitored results, has a great significance to power girds' safely running and reasonable charging.Using TMS320F2812 DSP as its core processor as well as combining FIR digital anti-aliasing filter algorithm, FFT algorithm and Ethernet communication technology, this paper designs and implementes a system which is online power metering and analysing.The main work of this paper as follows:First of all, it introduces the research status of power metering and analysing algorithm, analyzes the technical indicators of this system in detail, and then proposes the FIR digital anti-aliasing filter and FFT algorithm applied in this paper.On design of hardware, TI's TMS320F2812 DSP is chosen and its peripheral circuits are designed according to requirements of algorithm. Processing circuit converts three phases voltage and current on the second side of high-voltage transformers to 0-5V signals. This paper uses PLL technology to track signal frequency and control synchronous sampling, samples the converted voltage and current synchronously by use of ADS8364. As for communication circuit, it uses Ethernet control chip RTL8019AS to complete real-time field datas report and remote management. What's more, this system takes fully account of the influence from device selection, sampling methods, PCB routing technology, scene shielding&grounding, and other relating technology to the system's accuracy, which provides a guarantee to the sampling and metering accuracy.On design of software, this paper achieves accurate measurement of frequency based on DSP capturing multiplied signal of PLL and arithmetic average filter; The multiplied signal of PLL is responsible for controlling the action of ADS8364. This paper puts forward a real-time zero calibration method to track the ripple of ground and improve the accuracy of sample results effectively. FIR DF filter out high harmonics of digital signals after A/D converting, then FFT algorithm analyses the harmonic content of the power grid and waveform's distortion rate. This paper adopts Q format calibration to improve fixed-point DSP's floating-point calculation speed and accuracy by use of IQmath functions. At last, this paper cuts the integrated TCP/IP protocol and realizes ARP, IP, ping function of ICMP and UDP protocol, and finally completes real-time communication with PC.Online power metering and analyzing system runs stably during test operation in Shandong Elctric Power Research Institute. This system can achieve high accuracy of power metering and analyzing, it can promise a 0.05 grade metering accuracy of voltage RMS, current RMS and active power, as well as accurate results of harmonic analysis.