Measurement Of Interharmonics In Power Systems Based On Wavelet Transform

With the widely use of all kinds of power electronic instruments , the situation of harmonics in power system become more and more serious. Interharmonics' frequencies are not an integer of the fundamental, and the effects of them cause an increasing interest among electrical power engineers.When we use the traditional harmonic analysis methods, such as Fourier transform, to analyze harmonics and interharmonics, the interharmonics component will result in a phenomenon of frequency spectrum leakage. So we need to find a new method to analyze signals that contain interharmonics. This paper makes a summary of the existing analysis methods of harmonic and interharmonics , and compare their advantages and disadvantages.The wavelet transform is developed to achieve both good time and frequency position. It is used in harmonic analysis recently. But aliasing in traditional wavelet transform cause measurement error, so we need to investigate new wavelet-based methods for more accurate and robust detection . This paper analyzes the physical essence of aliasing in discrete wavelet transform , and propose a new method to reduce aliasing . This new method demand less calculation amount than the existing methods that is used to reduce aliasing. Simulation result proves that it can effectively eliminate aliasing and provide a vigorous mean for power systemharmonic analysis.Aiming at the demand of power system and the practical application, we design a new power system harmonic analyzer. This paper develops the man-machine interface of the analyzer, which is based on the Texas Instrument Company's MSP430 microprocessor.