Md. Shamim Reza

Accurate Estimation of Single-Phase Grid Voltage Parameters Under Distorted Conditions

This paper presents an accurate technique for the estimation of single-phase grid voltage fundamental amplitude and frequency. The technique consists of a quadrature signal generator (QSG) and a discrete Fourier transform (DFT). The frequency information required by the QSG based on a second-order generalized integrator (SOGI) is estimated using the spectral leakage property of the DFT. The presented DFT operation does not require real-time evaluation of trigonometric functions. The frequency estimation is less affected by the presence of harmonics when compared to similar techniques based on QSG-SOGI such as the phase-locked loop and the frequency-locked loop. Moreover, unlike these techniques, the DFT-based QSG-SOGI (DFT-SOGI) technique does not create any interdependent loops, thus increasing the overall stability and easing the tuning process. The effectiveness of the proposed technique has been validated on a real-time experimental setup.

Power System Frequency Estimation by Using a Newton-Type Technique for Smart Meters

This paper proposes a single-phase grid voltage fundamental frequency estimation technique for smart meters. The technique relies on a nonlinear Newton-type algorithm and a recursive differentiation filter (NTA-DF). It can reject the negative effects caused by dc offset, harmonics, notches, and spikes. When compared with a NTA technique based on least-squares (NTA-LS), the proposed one reduces matrix dimensions, avoids matrix inversion, and is computationally efficient, thus requiring less hardware and associated cost for real-time implementation. Moreover, unlike the NTA-LS technique, the NTA-DF shows less sensitivity to the presence of harmonics. Simulation and experimental results are presented to verify the performance of the proposed technique.

Power quality analysis using piecewise adaptive Prony's Method

This paper proposes the application of the piecewise adaptive Pronys Method for power quality (PQ) analysis. The singular value decomposition (SVD) and least square (LS) techniques are used for estimating modal components present in the Prony modelled grid voltage waveform. The conventional Prony spectrum equation is also modified to show the accurate average amplitude of each modal component in the frequency domain. The proposed modification of the conventional Prony spectrum equation eliminates the problems of threshold setting and zero value of damping factor of each modal component. PQ analysis is performed by using synthetically generated voltage waveforms based on an adaptive algorithm. The simulation results presented in this paper show that the Prony analysis can be an efficient tool for PQ assessment.

A Modified Demodulation Technique for Single-Phase Grid Voltage Fundamental Parameter Estimation

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.

Grid voltage offset and harmonics rejection using second order generalized integrator and kalman filter technique

This paper proposes the application of second order generalized integrator (SOGI) and Kalman filter (KF) technique for the rejection of DC offset and harmonics from the distorted grid voltage waveform. The SOGI is used to estimate the orthogonal waveforms of grid voltage fundamental frequency component. On the other hand, the linear Kalman filter (LKF) is used to reject the DC offset and harmonics present in the distorted grid voltage waveform. The resonance and harmonic frequencies of the SOGI and LKF, respectively, are provided by the frequency locked loop (FLL). The proposed technique provides better results to reject the DC offset and harmonics as compared to the multiple SOGI (MSOGI) technique. The improved performance of the proposed technique is due to the use of LKF which not only rejects the DC offset and harmonics but also non-sensitive to the change of SOGIs gain. Synthetically generated grid voltage waveforms are used in MATLAB/Simulink to depict the superior performance of the proposed SOGI-LKF technique as compared to the MSOGI with/without offset rejection technique.

Instantaneous power quality analysis using frequency adaptive kalman filter technique

This paper proposes the application of frequency locked loop (FLL) based Kalman filter (KF) technique for frequency adaptive instantaneous power quality (PQ) analysis. In the proposed technique, the FLL is integrated with the linear Kalman filter (LKF) to estimate the time-varying grid fundamental frequency. The LKF is used to estimate the orthogonal waveforms of fundamental and harmonics components present in the distorted grid voltage waveform based on the fundamental angular frequency extracted by the FLL. The amplitude of grid fundamental frequency component obtained by the LKF is fed to the extended Kalman filter (EKF) to extract the instantaneous voltage flicker. The proposed FLL based KF technique tracks the time-varying grid voltage parameters instantaneously, adaptively and accurately. Moreover, the proposed technique has reduced the complexity and convergence time of the KF as the grid fundamental angular frequency is extracted separately by the FLL. Synthetically generated grid voltage waveforms are used in MATLAB/Simulink to demonstrate the effective application of the proposed technique. The simulation results show that the proposed technique can be used as an efficient technique for frequency adaptive instantaneous PQ assessment.

A Robust Technique for Single-Phase Grid Voltage Fundamental and Harmonic Parameter Estimation

This paper reports a frequency-adaptive robust technique for the accurate estimation of the single-phase grid voltage fundamental and harmonic parameters. The technique is based on the discrete Fourier transform and a cascaded delayed signal cancellation strategy. There is no stability issue in the technique, since it does not contain any type of feedback loop. It can also be flexibly configured to estimate the parameters of the fundamental and/or one/multiple harmonic(s) from the grid voltage waveform distorted by various harmonics. Moreover, it does not require evaluation of trigonometric and inverse trigonometric functions for implementing on real-time digital signal processor. However, it needs computationally demanding high-order finite-impulse-response filters. The simulation and real-time experimental results are provided to verify the performance of the proposed technique.

Accurate estimation of grid voltage parameters using singular value decomposition technique

This paper presents the comparison of results between the singular value decomposition (SVD) and the least square (LS) techniques and also proposes the application of the SVD technique for extracting the parameters of the grid voltage waveform. With a small size window, the proposed SVD technique can extract amplitudes and phase angles of all the frequency components present in the Prony modelled grid voltage waveform more accurately than the LS technique. Moreover, the proposed technique has the ability to estimate the grid voltage parameters accurately from the singular matrix, where the LS technique fails. The SVD technique is applied on the Vandermonde matrix formed by the known damping factors and frequencies of the Prony modelled grid voltage waveform in order to estimate the amplitudes and phase angles. Moreover, an algorithm, which avoids the rooting of higher order polynomial, is presented to estimate the unknown harmonic frequencies from the harmonically distorted grid voltage waveform, where the fundamental frequency is estimated from a predicted fundamental frequency variation zone. Synthetically generated grid voltage waveforms are used in MATLAB to depict the superior performance of the proposed SVD technique over the LS technique.

Frequency adaptive instantaneous power quality analysis using frequency locked loop based Kalman filter technique

This paper proposes the application of frequency locked loop (FLL) based on the second order generalized integrator (SOGI) and a Kalman filter (KF) for frequency adaptive instantaneous power quality (PQ) analysis. The FLL tracks the time-varying grid voltage fundamental frequency adaptively. The orthogonal waveforms of fundamental and harmonic components of grid voltage waveform are extracted using the quadrature signal generator (QSG)-SOGI and a linear Kalman filter (LKF), respectively. The fundamental voltage amplitude is obtained from the orthogonal voltage waveforms as provided by the QSG-SOGI and is fed to an extended Kalman filter (EKF) to extract the instantaneous flicker level (IFL). The proposed SOGI-FLL-KF technique provides accurate instantaneous results for PQ analysis based on the measurement of phasor quantities. Synthetically generated grid voltage waveforms are used in MATLAB/Simulink for instantaneous PQ analysis by the proposed SOGI-FLL-KF technique. The simulation results show that the proposed technique can be used as an effective technique for frequency adaptive instantaneous PQ assessment.

A Demodulation-Based Technique for Robust Estimation of Single-Phase Grid Voltage Fundamental Parameters

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 single-phase 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.