Measurements, Models, Systems and Design

531 s.

Quasi Type-1 PLL With Tunable Phase Detector for Unbalanced and Distorted Three-Phase Grid

International audienc

Frequency Adaptive Parameter Estimation of Unbalanced and Distorted Power Grid

Grid synchronization plays an important role in the grid integration of renewable energy sources. To achieve grid synchronization, accurate information of the grid voltage signal parameters are needed. Motivated by this important practical application, this paper proposes a state observer-based approach for the parameter estimation of unbalanced three-phase grid voltage signal. The proposed technique can extract the frequency of the distorted grid voltage signal and is able to quantify the grid unbalances. First, a dynamical model of the grid voltage signal is developed considering the disturbances. In the model, frequency of the grid is considered as a constant and/or slowly-varying but unknown quantity. Based on the developed dynamical model, a state observer is proposed. Then using Lyapunov function-based approach, a frequency adaptation law is proposed. The chosen frequency adaptation law guarantees the global convergence of the estimation error dynamics and as a consequence, ensures the global asymptotic convergence of the estimated parameters in the fundamental frequency case. Gain tuning of the proposed state observer is very simple and can be done using Matlab commands. Some guidelines are also provided in this regard. Matlab/Simulink based numerical simulation results and dSPACE 1104 board-based experimental results are provided. Test results demonstrate the superiority and effectiveness of the proposed approach over another state-of-the art technique

Grid current control for active-front-end electric propulsion systems in AC ship microgrids

This article proposes a finite control set (FCS) current controller for grid-tied converters, specifically tailored to meet the characteristics of ac ship microgrids in all-electric ships (AESs). Contrary to a pulsewidth modulator (PWM)- based design, which often employs an LCL filter, the proposal is able to meet applicable harmonic regulations using an L filter with the same total inductance as the LCL filter and the same switching frequency required by PWM-based solutions. Moreover, the proposed design provides a low sensitivity in a wide frequency range from dc to the switching frequency of the power converter. This low sensitivity permits to quickly attenuate low-order disturbances and it is particularly convenient in marine applications with a weak grid, where the frequent connection and disconnection of high power nonlinear loads can significantly affect the voltage waveform qualityXunta de Galicia | Ref. GPC-ED431B 2020/03Agencia Estatal de Investigación | Ref. PID2019-105612RB-I0

Enhanced Frequency Adaptive Demodulation Technique For Grid-Connected Converters

This paper presents an enhanced frequency adaptive demodulation technique for grid-synchronization of grid-connected converters (GCC) in variable frequency condition. Demodulation works by generating demodulated voltages which contain undesired double frequency components. As a result, high-order low-pass filters (LPF) with high cutoff frequency are required to eliminate the undesired components. This reduces the dynamic performance. Frequency adaptive demodulation technique enhances the dynamic performance by rejecting the double frequency components as opposed to filtering, however, at the cost of additional computational complexity. This paper overcomes this problem by using double demodulation without recreating the double frequency component for rejection purpose. This reduces the computational complexity significantly. Suitability of proposed method is verified through numerical simulation and experimental study. Comparative study with existing frequency adaptive demodulation and second-order generalized integrator phase-locked loop (SOGI-PLL) techniques demonstrate the validity and performance improvement by the proposed technique

Coordinate Transformation-Free Observer-Based Adaptive Estimation of Distorted Single-Phase Grid Voltage Signal

© 2013 IEEE. This paper studies the phase and frequency estimation problem of single-phase grid voltage signal in the presence of DC offset and harmonics. For this purpose, a novel parameterized linear model of the grid voltage signal is considered where the unknown frequency of the grid is considered as the parameter. Based on the developed model, a linear observer (Luenberger type) is proposed. Then using Lyapunov stability theory, an estimator of the unknown grid frequency is developed. In order to deal with the grid harmonics, multiple parallel observers are then proposed. The proposed technique is inspired by other Luenberger observers already proposed in the literature. Those techniques use coordinate transformation that requires real-time matrix inverse calculation. The proposed technique avoids real-time matrix inversion by using a novel state-space model of the grid voltage signal. In comparison to similar other techniques available in the literature, no coordinate transformation is required. This significantly reduces the computational complexity w.r.t. similar other techniques. Comparative experimental results are provided with respect to two other recently proposed nonlinear techniques to show the dynamic performance improvement. Experimental results demonstrate the suitability of the proposed technique