A Study On DSP-Based Precise Real-Time Harmonics Measure Device In The Electric Power System

This paper analyses the harm of power system harmonics. It also points out the significance of harmonics measuring and the developing condition of harmonics measuring device, and points out the significance of the research of this paper.The researching intention of this paper is to establish a high precise and real time harmonics measuring system. This paper explains development about the theory of digital signal, and discusses the application of digital signal processing in the electric measurement. This paper also introduces the characteristics and the development of the digital signal processor. Base on the two points discussed above this paper brings forward the general designing idea which bases on the theory of digital signals and adopts the digital signal processor DSP.As a real time harmonics measuring device, it is important that it can real time measure various harmonics accurately. In order to the realize request above, after analyzing and comparing various harmonics analyzing method, this paper brings forward the harmonics analyzing method based on Fourier progression, which is fit for this system. In succession this paper analyses the various causes which reduce the precision of harmonics analyzing, it also compare various methods which can improve the precision of harmonics analyzing. According to the analysis and compare of all the methods of harmonics analysis in the power system, this paper introduces an adaptive sampling harmonic analysis method adapted to realization of precise real time harmonic analysis. This method adjusts sampling interval to trail after the power system frequency while harmonics analyzing, so that this method greatly reduces the spectrum leakage. This method requires to finish harmonics analysis between every sampling. Although it is much less then N2 the computation amount of DFT required, Nlog2 N of FFT is also too much for many DSPs to finish between every sampling. In order to solve this problem, This paper introduce recursive Hartely transform algorithm which is highly-efficient, simple and convenient to realize.In order to realize the arithmetic which mentioned above the system integrates TMS320LF2407 DSP and ADS8364 A/D CMOS chip. It utilizes the high speed performance of TMS320LF2407 DSP. It also utilizes the performance of high precision and ability of adjusting sampling rate of ADS8364. At the aspect of displaying, this paper brings forward the method of realizing connecting LCD controller IC by using I/O of LF2407 to simulate interface timing. At the aspect of communications, this paper brings forward the method to realize serial communication of many device. This paper adopts the real_time kernel to manage the software system. In addition this paper realizes the design of data collection module, keyboard module and data saving module.