In order to accurately detect subsynchronous harmonics in new energy-intensive regions

a combinatorial optimization algorithm based on windowed and interpolated fast Fourier transform（FFT） algorithm and all-phase FFT（apFFT） is proposed. A convolution operation is performed on the Hanning window with a narrow main lobe width and the 4-terms 3-order Nuttall window with good side lobe characteristics to obtain a hybrid-convolution window function

and a rectification formula of the triple-spectrum-line is obtained based on the window function and applied to detect amplitude and frequency parameters. Moreover

a phase-difference spectrum-correction algorithm is derived by using the differences between the FFT and apFFT phase spectra and applied to extract phase parameters. The simulation data and practical application results show that the algorithm can accurately achieve harmonic parameters estimation and suppress the interference between the spectra

and it can effectively realize subsynchronous components detection in a certain area of Xinjiang. The research can provide a data basis for the research of subsequent subsynchronous oscillation monitoring strategy.