Real-valued MUSIC algorithm for power harmonics and interharmonics estimation

Recently, advanced spectrum estimation methods, including the MUSIC (Multiple Signal Classification) algorithms, are being gradually employed for high-resolution power harmonics analysis. However, most of them are proposed to detect frequencies of complex-valued signals, so that any real-valued signal should be transformed into complex form. This data pre-treatment may lead to additional computation burden. In addition, the picket-fence effects also exist as in the FFT algorithm and cause poor frequency resolution. To overcome these drawbacks, a real-valued MUSIC algorithm is proposed for power harmonics analysis in this paper. The algorithm is based on the subspace decomposition theory and the computation of pseudospectrum is also provided. Additionally, to improve the measuring precision, the Newton-Raphson algorithm is adopted to optimize the harmonic frequencies significantly. Simulation results show that, in the real-valued MUSIC pseudospectrum, the spectral peaks of actual harmonic components can be more easily distinguished from the false peaks caused by noise, and the computational complexity is notably lower than that of the classic complex MUSIC, as well as the detecting accuracy is close to that of root-MUSIC algorithm which is quite time consuming. Experimental results prove that the proposed strategy is more suitable for high-resolution power harmonics estimation. Copyright (C) 2010 John Wiley & Sons, Ltd.