Real-Time Estimation of Power System Frequency Using a Three-Level Discrete Fourier Transform Method

• Main Authors: Soon-Ryul Nam, Seung-Hwa Kang, Sang-Hee Kang
• Format: Article
• Language: English
• Published: MDPI AG 2014-12-01
• Series: Energies
• Subjects: amplitude ratio; power system frequency; hardware implementation; real-time estimation; three-level discrete Fourier transform; zero-crossing problem
• Online Access: http://www.mdpi.com/1996-1073/8/1/79

This paper proposes a three-level discrete Fourier transform (DFT) method to provide an accurate estimate of power system frequency in real time. The first level decomposes a power system signal into two orthogonal cosine- and sine-filtered signals. The second and third levels are used to determine the amplitude ratio of the cosine- and sine-filtered signals without encountering the zero-crossing problem and with an increase in ability to suppress harmonics and inter-harmonics. The performance of the three-level DFT method is evaluated using computer-simulated signals with harmonics and inter-harmonics. The three-level DFT method is also implemented on a digital signal processor (DSP)-based hardware prototype, and its performance in the hardware implementation is evaluated using a real-time digital simulator (RTDS). The evaluation results show that the three-level DFT method can achieve real-time estimation of power system frequency with satisfactory performance.