A New Orthogonal Signal Generator with DC Offset Rejection for Single-Phase Phase Locked Loops

Abstract

This paper presents a new orthogonal signals generator (OSG) with DC Offset rejection for implementing a phase locked loop (PLL) in single-phase grid-connected power systems. An adaptive filter (AF) based on the least mean square (LMS) algorithm is used to constitute the OSG in this study. The DC offset in the measured grid voltage signal can be significantly rejected in the developed OSG technique. This generates two pure orthogonal signals that are free from the DC offset. As a result, the DC offset rejection performance of the presented single-phase phase locked loop (SPLL) can be enhanced. A mathematical model of the developed OSG and the principle of the adaptive filter based SPLL (AF-SPLL) are presented in detail. Finally, simulation and experimental results demonstrate the feasibility of the proposed AF-SPLL.

An Accurate Orthogonal Signal Generator for Voltage Control in Synchronous Reference Frame of Stand-Alone Single-Phase Voltage Source Inverters

“…In other words, an orthogonal signal is generated from the original single-phase signal. To perform this, various OSG techniques have been proposed [14][15][16][17][18][19][20][21][22][23]. Time delay based OSG (TD-OSG) is the mostly used method [14,15].…”

“…The wellrecognized and established OSGs are based on the first and second order all-pass filter (APF) [1,16,17], Hilbert transform (HT) [15,18], and second order generalized integrator (SOGI) [18,19]. Other OSGs based on the adaptive filter [20], modified first-order APF [1], fixed frequency tuned SOGI and an infinite-impulse-response differentiation filter [21] have been recently investigated. An arbitrary phase delay OSG [22] and a frequency-adjustable OSG [23] are also developed.…”