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Energies 2017, 10(3), 280;

An Efficient Phase-Locked Loop for Distorted Three-Phase Systems

College of Electrical and Information Engineering, Hunan University, Changsha 410082, China
School of Information Science and Engineering, Central South University, Changsha 410083, China
Author to whom correspondence should be addressed.
Received: 6 December 2016 / Accepted: 20 February 2017 / Published: 27 February 2017
(This article belongs to the Special Issue Power Electronics and Power Quality)
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This paper proposed an efficient phase-locked loop (PLL) that features zero steady-state error of phase and frequency under voltage sag, phase jump, harmonics, DC offsets and step-and ramp-changed frequency. The PLL includes the sliding Goertzel discrete Fourier transform (SGDFT) filter-based fundamental positive sequence component separator (FPSCS), the synchronousreference-frame PLL (SRF-PLL) and the secondary control path (SCP). In order to obtain an accurate fundamental positive sequence component, SGDFT filter is introduced as it features better filtering ability at the frequencies that are integer times of fundamental frequency. Meanwhile, the second order Lagrange-interpolation method is employed to approximate the actual sampling number including both integer and fractional parts as grid frequency may deviate from the rated value. Moreover, an improved SCP with single-step comparison filtering algorithm is employed as it updates reference angular frequency according to the FPSC, which promises a zero steady-state error of phase and improves the frequency tracking speed. In this paper, the mathematical model of the proposed PLL is constructed, its stability is analyzed. Also, design procedure of the control parameters is presented. The effectiveness of the proposed PLL is confirmed by experimental results and comparison with advanced pre-filtering PLLs. View Full-Text
Keywords: distorted grid conditions; SGDFT; Lagrange-interpolation method; frequency adaption; SC distorted grid conditions; SGDFT; Lagrange-interpolation method; frequency adaption; SC

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Cao, Y.; Yu, J.; Xu, Y.; Li, Y.; Yu, J. An Efficient Phase-Locked Loop for Distorted Three-Phase Systems. Energies 2017, 10, 280.

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