Novel orthogonal signal generator for single phase PLL applications

Abstract

Single-phase phase-locked loops (PLLs) are used in various types of power electronics applications, including voltage source inverters, pulse width modulation rectifiers and different types of grid-tied power converter utilities. The orthogonal signal generators (OSGs), used in single-phase PLLs, are generally based on various types of filters, and they need to operate robustly in relation to the grid voltage disturbances and frequency variations. In this study, a novel OSG is proposed based on a modified first-order all-pass filter, which enables the PLL phase detector to operate at different response speeds, tuned by means of a single parameter. The PLL is experimentally verified and compared with a number of conventional solutions. Tests include responses to phase angle disturbances, frequency steps, and PLL input voltage distortions. Results show that a novel OSG filter enables faster PLL responses when compared with several conventional OSG filters, all designed to have the same disturbance attenuation at double fundamental frequency.