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

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.

A Control Scheme to Suppress Circulating Currents in Parallel-Connected Three-Phase Inverters

“…However, PI controllers have difficulties when the regulated variables have frequency contents close to the crossover frequency of the loops, which is the case of the low-frequency harmonics of the circulating currents. To address this issue, second-order generalized integrators (SOGI) [24] have been added to the o-channel controllers to increase their gain at the frequency of the circulating currents' low-frequency harmonics, resulting in PI + SOGI o-channel controllers. As it will be seen in the simulation and experimental results section, when the powers provided by the parallel inverters are balanced, the circulating currents present third-order harmonics (150 Hz) and their odd multiples, with the ninth one being the most significant harmonic (450 Hz).…”

Dynamic Voltage Restorer with a Novel Robust control strategy to improve Power Quality issues in Distribution Network

“…Voltage transients, prolonged voltage shifts, brief voltage variations, voltage imbalances, waveform distortions, and voltage flicker are the primary contributors to inadequate power quality [4]. To ensure uniform power quality standards, the Institute of Electrical and Electronics Engineers (IEEE) and the International Electromechanical Commission (IEC) have established comprehensive guidelines.…”

“…According to these guidelines, a sag is defined as a reduction in the root mean square (rms) voltage or current that persists from 0.5 cycles to 1 minute [3], and the power frequency during a sag range between 0.1 and 0.9 pu. On the other hand, a swell is characterized by an increase in rms voltage or current lasting from 0.5 cycles to 1 minute [4], with the power frequency ranging between 1.1 and 1.8 pu. Voltage fluctuations lasting less than a minute encompass voltage sags, swells, and interruptions, as depicted in Figure 1 [5]- [6].…”

“…However, a common issue with traditional SMC is the occurrence of chattering, which can affect control performance [12]. To tackle this challenge, a range of algorithms has been employed to mitigate chattering effects, including real-twisting, super-twisting, smoothsuper twisting, optimum, suboptimal, global, integral, and state-observer algorithms [4], [13]- [15]. These algorithms aim to reduce or eliminate the oscillations and rapid changes in control signals that can occur in certain control systems, helping to achieve more stable and efficient performance.…”

Voltage Sag Detection and Compensation Signal Extraction for Power Quality Mitigation Devices

“…Synthetic and real signals of PQDs were utilized to validate and test the proposal, and the results from these cases demonstrated effective detection and categorization of PQDs. An average of absolute error integrated second-order generalizedintegrator frequency-locked loop (SOGI-FLL) based method was also introduced [26]. The average absolute error was obtained using a low-pass filter.…”