A Robust Frequency Estimation Technique Based on Three Consecutive Samples for Single-Phase Systems (original) (raw)
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IET Generation, Transmission & Distribution, 2015
This study proposes a robust technique for accurate estimation of single-phase grid voltage fundamental amplitude and frequency. The technique relies on a quadrature signal generator (QSG) based on a fixed frequency tuned second-order generalised integrator (SOGI) and an infinite-impulse-response differentiation filter (DF). The DF is used to estimate the fundamental frequency from the instantaneous phase angle obtained from the generated orthogonal voltage waveforms. The estimation technique is robust and offers an easy tuning process as there is no interdependent loop between the orthogonal voltage system and the frequency estimation. Additionally, the technique is computationally efficient and can also reject the negative effects caused by the direct current offset and harmonics. Furthermore, the frequency estimation is less sensitive to harmonics when compared with a similar technique relying on the QSG based on the fixed frequency tuned SOGI and leastsquares method. Simulation and real-time experimental results are provided to validate the robustness of the proposed technique.
IEEE Transactions on Industrial Informatics, 2017
This paper proposes a robust technique for the single-phase grid voltage fundamental amplitude, frequency and phase angle estimation under distorted grid conditions. It is based on a demodulation method tuned at a fixed frequency. It does not have stability issue due to an open loop structure, does not require real-time evaluation of trigonometric and inverse trigonometric functions, and also avoids the use of look-up table. It can provide accurate estimation of the singlephase grid voltage fundamental parameters under DC offset and harmonics. When compared with a frequency adaptive demodulation technique, the proposed one is less affected by DC offset, can provide faster frequency estimation and also avoids interdependent loop, trigonometric and inverse trigonometric functions operation. Simulation and experimental results are presented to verify the performance of the proposed technique.
Single-Phase Grid Voltage Frequency Estimation Using Teager Energy Operator-Based Technique
IEEE Journal of Emerging and Selected Topics in Power Electronics, 2015
This paper reports the performance of a technique for the estimation of single-phase grid voltage fundamental frequency under distorted grid conditions. The technique combines a Teager energy operator with a frequency adaptive band-pass filter. The Teager energy operator is based on three consecutive samples and is used to estimate the fundamental frequency. The band-pass filter relies on a recursive discrete Fourier transform (RDFT) and an inverse RDFT, and is used to extract the normalised amplitude of the grid voltage fundamental component. The technique is computationally efficient and can also reject the negative effects caused by DC offset and harmonics. It requires less computational effort, can provide faster estimation and is also less affected by harmonics as compared to a technique relying on the RDFT based decomposition of the single-phase system into orthogonal components. The performance of the technique is verified by using both simulation and experimental results.
A Modified Demodulation Technique for Single-Phase Grid Voltage Fundamental Parameters Estimation
IEEE Transactions on Industrial Electronics, 2014
This paper proposes a modified demodulation technique to provide accurate estimation of the single-phase grid voltage fundamental amplitude, frequency, and phase angle under distorted grid conditions. A quadrature oscillator is combined with a demodulation technique for rejecting oscillations at second harmonic generated by the demodulation of the fundamental voltage component; thus, it can provide more accurate estimation, as compared to a conventional one, using same-order and cutoff-frequency-based infinite-impulse-response low-pass filters after the demodulation stage. It also does not require a separate frequency estimation algorithm for adaptive demodulation as the frequency is obtained from the estimated initial phase by using a differentiation operation and an integral controller. The technique is relatively simple and can also reject the negative effects caused by harmonics under a wide range of fundamental frequency variation as specified by the standard requirements. When compared with a quadrature phase-locked loop technique, the proposed one provides improved estimation of the fundamental voltage parameters. The performance of the proposed technique is verified using both simulation and experimental results.
A unified method is presented which allows toestimate all harmonic components, DC-offset and fundamen-tal frequency in arbitrarily distorted single-phase grids us-ing a frequency-adaptive observer (FAO) consisting of modi-fied Second-Order Generalized Integrators (mSOGIs), a DC-Integrator (DCI) and a modified Frequency Locked Loop(mFLL). DCI and mSOGIs are tuned by pole placement which allows for an arbitrarily fast detection of DC-offset and harmonic components if the fundamental frequency is known. If the fundamental frequency must be estimated as well, a mFLL with Gain Normalization (GN), Rate Limitation (RL), Anti-Windup (AW) strategy and low-pass filters (LPF) must be employed. The effectiveness of the proposed FAO is validated by experimental results and its enhanced performance is shown by comparisonsto existing estimation methods.
IEEE Open Journal of the Industrial Electronics Society, 2020
A unified method is presented which allows to estimate dc-offset, all harmonic components <italic>and</italic> fundamental frequency in arbitrarily distorted single-phase grids using a <italic>Frequency Adaptive Observer (FAO)</italic> consisting of <italic>modified Second-Order Generalized Integrators (mSOGIs)</italic>, an adaptive <italic>DC-Integrator (DCI)</italic> and a <italic>modified Frequency Locked Loop (mFLL)</italic>. DCI and mSOGIs are tuned by <italic>pole placement</italic> which allows for an arbitrarily fast detection of dc-offset and harmonic components if the fundamental frequency is known. If the fundamental frequency must be estimated as well, an mFLL with <italic>Gain Normalization (GN)</italic>, <italic>Rate Limitation (RL)</italic>, <italic>Anti-Windup (AW)</italic> strategy and <italic>low-pass filters (LPF)</italic> must be employed. The e...
Robust Estimation of Voltage Harmonics in a Single-Phase System
IET Science, Measurement & Technology, 2019
A frequency adaptive technique relying on a linear Kalman filter (KF) is presented here for robust estimation of voltage harmonics under variable frequency conditions in a single-phase system. A relatively simple frequency-locked loop (FLL) is combined with the linear KF (LKF-FLL) to achieve frequency adaptive ability and avoid the use of a non-linear KF. In contrast to the non-linear extended KF (EKF), the LKF-FLL technique has several advantages such as robustness, linearity, simple tuning, having fewer states, requiring no derivative actions, while offering low complexity, excellent convergence, and computational efficiency. When compared to the non-linear extended real KF, it can generate a faster dynamic response and more accurate steady-state estimation of the harmonics under frequency variations. It can also provide an improved estimation for off-nominal frequency conditions when compared to the discrete Fourier transform (DFT) method. The effectiveness of the technique is verified by various simulated and real-time experimental case studies.
2013 4th IEEE International Symposium on Power Electronics for Distributed Generation Systems (PEDG), 2013
This paper proposes a robust technique for accurate estimation of single-phase grid voltage fundamental amplitude and frequency under harmonics. The proposed technique relies on a quadrature signal generator based on a fixed frequency tuned second-order generalized integrator. A differentiation filter is used to estimate the fundamental frequency from the instantaneous phase angle derived from the generated orthogonal voltage systems. The estimated fundamental frequency is then used to obtain the actual fundamental voltage amplitude from the orthogonal voltage systems. The proposed technique does not rely on interdependent loops offering stability and easy tuning process. The technique can reject the negative effects caused by the presence of the harmonics. Experimental results are provided to validate the performance of the proposed technique.
IEEE Transactions on Instrumentation and Measurement, 2010
A new technique for estimation of the instantaneous frequency based on simultaneous sampling of three-phase voltage signals is presented. The structure consists of two decoupled modules: the first is for adaptive filtering of input signals, and the second is for frequency estimation. A suitable and robust algorithm for frequency estimation is obtained. This technique provides better performance, compared with the technique based on a single-phase signal in relation to waveforms with noise. The technique is particularly important when asymmetric sags generate zero voltage in one of the three phases. In addition, it allows the measurement of the instantaneous frequency value of real signals for single-or three-phase systems. To demonstrate the performance of the developed algorithm, computer-simulated data records and calibrator-generated signals are processed. The proposed algorithm has been put to test with distorted three-phase voltage signals.
IEEE Access, 2020
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.