The Research Of Harmonic Detection Methods For Ship Electronic Power System

At present, with the wide application of non-linear equipment in various kinds of electrical and electronic devices, especially the spread of ship shaft generator system. Harmonic pollution in ship electronic power system is becoming more and more serious, power quality comes down and different kinds of fault and accident happen continually. As a result, to prevent the harmonic disturbance and improve the power quality, real-time measurement and analysis of harmonic component produced by power network is very important, and it is essential to the safe operation of the ship power grid.This thesis systematically introduces the methods of measurement and analysis on ship electronic power system harmonic, and gets some conclusions. The thesis includes the following contents:Firstly, some basic conception of the harmonic is introduced resumptively. It summarizes the main methods of harmonic detection for ship electronic power system, indicates the problem that existed, and analyses the status quo and future direction of the research. Then educes the current commonly used Fourier harmonic analysis algorithm detailedly, analyses the efficiency of FFT algorithm and DFT algorithm, and discusses the harmonic analysis under synchronous sampling and non-synchronous sampling.Secondly, as the characteristics of the ship electronic power system, it is almost impossible to achieve synchronous sampling. Aimed at the problem that it is easy to bring the frequency spectrum leaks and fence effect when Fourier algorithm is adopted to analyse harmonic in non-synchronous sampling, this paper presents the method of window spectrum with FFT algorithm. In the case of many weak signals exist in ship electronic power system, using power spectrum has some special merit compared to traditional amplitude spectrum. And there are preferable feasibilities on accuracy and speed by using Hanning window combined with improved cycle method - Welch method to estimate the power spectrum. Finally, a harmonic detection devices based on singlechip dsPIC30F4011 is designed. And the relevant procedure of harmonic analysis is debuged in MPLAB IDE integrated development environment. The software has passed the preliminary debugging, and man-machine dialogue can be realized in virtue of the UART serial communication module in dsPIC30F4011.