The parameter estimation of inter-harmonics in power system

Inter-harmonics frequency is not the integer multiples of the fundamental and the amplitude of inter-harmonics is far less than the amplitudes of fundamental and harmonic, so it´s difficult to estimate inter-harmonics because of its´ characters. The nonuniformly sampling can estimate the signal frequencies because of its many advantages, such as avoiding aliasing in signal analysis, processing signals with components whose frequencies exceed the Nyquist limit, and higher frequency analysis; however, the nonuniformly sampling exists the noise in spectrum analysis, so it´s difficult to estimate the low amplitude signals. In this paper, a new method based on nonuniformly sampling and Least Square is proposed to estimate the parameters of inter-harmonics. This method estimates the frequency of maximal amplitude signal firstly, then suppress the noise in spectrum analysis by eliminating the maximal amplitude signal estimated by LS, so the low amplitude signals can be estimated; in addition, the application of LS can estimate the amplitude and phase of the signals. The result of experiments show that the proposed method can estimate the inter-harmonics exactly, even if the frequencies of inter-harmonics are near the fundamental frequency and the amplitudes of inter-harmonics are far less than the amplitudes of fundamental.