SOGI-FLL Grid Frequency Monitoring with an Error-Based Algorithm for a Better Response in Face of Voltage Sag and Swell Faults

Sajad Abdali Nejad,José Matas,Helena Martín,Jordi De La Hoz,Jordi Elmariachet

doi:10.3390/electronics10121414

Sajad Abdali Nejad, José Matas + Show 3 more

Open Access

https://doi.org/10.3390/electronics10121414

Copy DOI

Journal: Electronics	Publication Date: Jun 11, 2021
Citations: 7	License type: CC BY 4.0

Affiliation: Universitat Politècnica de Catalunya

Abstract

The SOGI-FLL (second-order generalized-integrator frequency-locked-loop) is a well-known and simple adaptive filter that allows estimation of the parameters of the grid voltage with a small computational burden. However, this structure has shown to be sensitive to the events of voltage sags and swell faults, especially to voltage sags that deeply distort the estimated frequency. In this paper an algorithm is proposed to face the fault that modifies the SOGI-FLLs gains in order to achieve a better transient response with a reduced perturbation in the estimated frequency. The algorithm uses the SOGI’s instantaneous and absolute error to detect the fault and change the SOGI-FLL gains during the fault. Moreover, the average of the absolute error is used for returning to normal operating conditions. The average value is obtained by means of a single low pass filter (LPF). The approach is easy to implement and represents a low computational burden for being implemented into a digital processor. The performance is evaluated by using simulations and real-time Typhoon Hardware in the Loop (HIL) results.

Highlights

The gains of the SOGI-FLL were adjusted by the Finite State Machine (FSM) at each part of the pattern according to the voltage sag/swell depth/height level to minimize the size of the perturbation in the estimated frequency
The structure of the SOGI-FLL is shown in Figure 1, where v g is the grid voltage, ωo is the center frequency of the SOGI filter, vd and vq are the in-phase and quadraturephase outputs and ω is the FLL estimated grid frequency acting as center frequency of the
This paper tried to improve the response of the SOGI-FLL to voltage sags and swells, since it is highly sensitive to these kinds of faults, especially to voltage sags

Summary

Introduction

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The gains of the SOGI-FLL were adjusted by the FSM at each part of the pattern according to the voltage sag/swell depth/height level to minimize the size of the perturbation in the estimated frequency. The approach is easier to implement than [32] since it doesn’t need to measure the depth or height of the voltage sag or swell, it uses a simpler algorithm employing less states and uses constant gains for the SOGI-FLL for dealing with the fault. In this algorithm, the use of the SOGI’s error allows a faster transient response to the fault event, since the error is directly affected by it, with no-delay, and allows differentiating voltage sags from voltage swells. The response of the proposed algorithm is better than the reported in [32], which is assessed using simulations and HIL test using MATLAB/Simulink and Typhoon HIL 402 platforms

SOGI-FLL Response to Voltage Sags and Swells

Reducing the Perturbation Impact by Means of a SOGI’s Error-Based Algorithm

Simulation and HIL Results

Conclusions