Development of Frequency Fixed Sliding Discrete Fourier Transform Filter Based Single-Phase Phase-Locked Loop

Abstract

The single-phase phase-locked loop (PLL) is essential for the stable operation and control of single-phase grid-connected converters. However, in practical applications, the grid voltage is usually affected by harmonics and dc offset, which will cause errors in the output of the PLL. Therefore, using sliding discrete Fourier transform filter (SDFT) as a prefilter, this paper proposes an improved single-phase synchronous reference frame PLL with a fixed sampling frequency, which can accurately and quickly obtain the grid parameters under distorted grid conditions. Most importantly, the paper theoretically analyzes phase and amplitude errors generated by SDFT for the first time and a quantitative compensation method is proposed, which is straightforward to be used by a reader. Finally, the proposed PLL is compared with other PLLs through simulation and experiments. The experimental results show the effectiveness and practicability of the proposed method.INDEX TERMS Sliding discrete Fourier transform filter (SDFT), phase-locked loop (PLL), dc offset, harmonic.

Rapid Extraction of the Fundamental Components for Non-Ideal Three-Phase Grid Based on an Improved Sliding Discrete Fourier Transform

“…The frequency-domain methods usually refer to Fourier transform-based techniques [12][13][14][15], within which the sliding discrete Fourier transform (SDFT) has gained wide applications in recent years for its efficient iteration and easy digital implementation. In [16], the SDFT was used for harmonic detection in the three-phase grid-tie inverter system; besides, SDFT has been often used in cooperation with the phase-locked loop for the stable operation and control of the grid-connected converters [17,18]. Although the SDFT algorithm is computationally efficient, this method still might have drawbacks, e.g., a slow dynamic performance and sensitivity to the frequency, and types of measures have been researched to make improvements [19], and types of improvements have been carried out in [20].…”