Comparative analysis of NRF-PLL and GDSC-PLL synchronization algorithms

Abstract

The connection of renewable or alternative energy sources requires the use of several hardware and software technologies, which have been studied in the related FAPESP thematic project. One of the required tools for correct operation of distributed generation systems is the synchronization algorithm for the connection of grid-tied converters. In this context, several algorithms have been proposed in the last years, each one with its advantages and disadvantages from the operational or computational point of view. In particular, we highlight the algorithms known as PLL (Phase-Locked-Loop), widely used to realize the synchronization of voltage and current of power generating elements with the voltage and current of the distribution network. These techniques are immune to distortions in the power grid and, when necessary, allow to identify the positive sequence component in three-phase networks, even for distorted and unbalanced networks. Among different techniques, some have been highlighted in the international literature, such as: Generalized Delayed Signal Cancelation (GPL) and NRF-PLL (Natural Reference Frame). The NRF-PLL was proposed by the advisor of this project and co-authors and it is based on instantaneous vector algebra for a three-phase structure, which aims to synthesize a three-dimensional unit vector that is ideally orthogonal to the measured fundamental voltage vector. GDSC-PLL [5] is a method that aims at canceling some components of the input signal, in order to make the algorithm less susceptible to waveform disturbances and asymmetries of the signals. Although the techniques are very different from each other, in general, the algorithms aim to detect the frequency and phase angle of the input signal, with the maximum possible immunity with respect to distortions and asymmetries. Thus, the main goal of this project is to compare in detail the design and performance of the mentioned algorithms (NRF-PLL and GDSC-PLL). Characteristics such as: design difficulty, dynamic response, computational effort, performance under different operating conditions and compliance with distributed generation standards will be evaluated.