Seminario Anual de Automática, Electrónica industrial e Instrumentación - SAAEI 2013, Madrid (Spain). 10-12 July 2013
Summary:
Harmonic extraction algorithms are widely used in the industry for electrical measurements. For real-time applications, algorithms such as the Fast Fourier Transform (FFT) and the Kalman Filter (KF) are frequently used. Unfortunately, FFTs impose certain restrictions to the sample time and yields inaccurate results in case of small frequency variations. KF overcomes some of these problems, but have a high computational cost and an unexpected behaviour if there is any un-modelled harmonics in the signal. This paper proposes a robust method to compute harmonic components in real-time with a moderate computational cost. The proposed method is based on Multiple Reference Frames rotating at each harmonic frequency. Once rotated, each harmonic is a DC magnitude in the corresponding rotating frame and can be extracted using a low-pass filter. The main contribution of this paper is the method proposed to transform the measured signals with a minimum use of trigonometric functions. Accordingly, the computation time is drastically reduced and the implementation on a DSP becomes very simply. The proposed algorithm, based on Moivre’s theorem, is valid for both three- and single-phase signals. The algorithm has been tested on a 5 kVA prototype of a Series Active Power Filter. The results reveal that harmonics can be accurately estimated in a reasonable time with low computational cost.
Keywords: Power conversion harmonics, digital signal processing, power quality, power harmonic filters.
Publication date: 2013-07-10.
Citation:
J. Roldán-Pérez, M. Ochoa, A. García-Cerrada, J. Zamora, Efficient real-time computation of harmonics in power systems using multiple reference frames, Seminario Anual de Automática, Electrónica industrial e Instrumentación - SAAEI 2013, Madrid (Spain). 10-12 July 2013.
