This page has only limited features, please log in for full access.

Unclaimed
Hafiz Ahmed
Nuclear Futures Institute, Bangor University, Bangor, U.K.

Honors and Awards

The user has no records in this section


Career Timeline

The user has no records in this section.


Short Biography

The user biography is not available.
Following
Followers
Co Authors
The list of users this user is following is empty.
Following: 0 users

Feed

Journal article
Published: 07 July 2021 in IEEE Transactions on Instrumentation and Measurement
Reads 0
Downloads 0

Fast and accurate frequency estimation of an unbalanced three-phase power system in the presence of measurement offset is a challenging task. A simple to implement and tune method is proposed in this work through a delay-based linear-regression framework. Using two challenging scenarios, we verify the performance of our procedure in the presence of severe grid abnormalities, including voltage unbalance, harmonics, frequency jump, and dc offset. Comparative hardware-in-the-loop experimental results demonstrate the suitability of the proposed approach.

ACS Style

Hafiz Ahmed; Rosane Ushirobira; Denis Efimov. A Simple Frequency Estimator for Power Systems. IEEE Transactions on Instrumentation and Measurement 2021, 70, 1 -2.

AMA Style

Hafiz Ahmed, Rosane Ushirobira, Denis Efimov. A Simple Frequency Estimator for Power Systems. IEEE Transactions on Instrumentation and Measurement. 2021; 70 ():1-2.

Chicago/Turabian Style

Hafiz Ahmed; Rosane Ushirobira; Denis Efimov. 2021. "A Simple Frequency Estimator for Power Systems." IEEE Transactions on Instrumentation and Measurement 70, no. : 1-2.

Review article
Published: 25 June 2021 in Annual Reviews in Control
Reads 0
Downloads 0

Many systems in the natural and physical world often work in unison with similar other systems. This process of simultaneous operation is known as synchronization. In the past few decades, owing to this phenomenon’s importance, extensive research efforts have been made. However, many of the existing results consider the systems are identical and/or linear time-invariant, while practical systems are often nonlinear and nonidentical for various reasons. This observation motivated several recent studies on the synchronization of nonidentical (i.e., heterogeneous) nonlinear systems. This paper summarizes some recent results on the synchronization of heterogeneous nonlinear systems, as developed in the thesis (Ahmed 2016). First, the results on the synchronization of a particular class of robustly stable nonlinear systems are presented. Then, these results are applied to an example model known as Brockett oscillator. Finally, using the Brockett oscillator as a common dynamics, output oscillatory synchronization results are given for heterogeneous nonlinear systems of relative degree 2 or higher. An application example of Brockett oscillator for power-grid synchronization is also presented. Some outlooks are provided regarding future research directions.

ACS Style

Hafiz Ahmed; Rosane Ushirobira; Denis Efimov. On robust synchronization of nonlinear systems with application to grid integration of renewable energy sources. Annual Reviews in Control 2021, 1 .

AMA Style

Hafiz Ahmed, Rosane Ushirobira, Denis Efimov. On robust synchronization of nonlinear systems with application to grid integration of renewable energy sources. Annual Reviews in Control. 2021; ():1.

Chicago/Turabian Style

Hafiz Ahmed; Rosane Ushirobira; Denis Efimov. 2021. "On robust synchronization of nonlinear systems with application to grid integration of renewable energy sources." Annual Reviews in Control , no. : 1.

Original research paper
Published: 03 May 2021 in IET Generation, Transmission & Distribution
Reads 0
Downloads 0

Development of advanced grid‐synchronization technique for unbalanced and distorted grid is considered in this paper. In this context, self‐tuning filter (STF) is considered to extract the fundamental component from the measured unbalanced and distorted voltages. Standard STF considers balanced grid voltages which is not always possible to ensure in the actual power grid. To mitigate this issue, an extended STF is proposed by analyzing the standard STF in the state‐space framework. To make the proposed ESTF grid‐following, a robust open‐loop frequency estimator is also applied. The closed‐loop system enjoys excellent filtering benefit from the extended STF side while taking advantage of the fast convergence speed property of the open‐loop frequency estimation technique. Numerical simulation and experimental results with double second‐order generalized integrator phase‐locked loop are provided to validate the theoretical developments.

ACS Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. A Quasi open‐loop robust three‐phase grid‐synchronization technique for non‐ideal grid. IET Generation, Transmission & Distribution 2021, 1 .

AMA Style

Hafiz Ahmed, Samet Biricik, Mohamed Benbouzid. A Quasi open‐loop robust three‐phase grid‐synchronization technique for non‐ideal grid. IET Generation, Transmission & Distribution. 2021; ():1.

Chicago/Turabian Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. 2021. "A Quasi open‐loop robust three‐phase grid‐synchronization technique for non‐ideal grid." IET Generation, Transmission & Distribution , no. : 1.

Journal article
Published: 11 January 2021 in Applied Sciences
Reads 0
Downloads 0

Various faults and disturbances often make the grid unbalanced and distorted. To make the grid-connected converters resilient to unbalanced and distorted grid, real-time estimation of grid voltage sequences are essential. Adaptive-observer based grid-synchronization techniques are very suitable for this purpose. In this paper, a comparative analysis of three recently proposed adaptive observer-based grid-synchronization technique are presented for frequency estimation and sequence extraction. The considered techniques are: global adaptive observer, gain normalized adaptive observer, and second-order generalized integrator type adaptive observer. Following a fair and systematic gain tuning process, the performances are verified through extensive numerical simulation and experiments. Experimental results demonstrate the merits and demerits of the individual techniques. Academic researchers and industrial practitioners will find the results useful for the selection of adaptive observer-based grid-synchronization and sequence extraction techniques.

ACS Style

Hafiz Ahmed; Mohamed Benbouzid. Adaptive Observer-Based Grid-Synchronization and Sequence Extraction Techniques for Renewable Energy Systems: A Comparative Analysis. Applied Sciences 2021, 11, 653 .

AMA Style

Hafiz Ahmed, Mohamed Benbouzid. Adaptive Observer-Based Grid-Synchronization and Sequence Extraction Techniques for Renewable Energy Systems: A Comparative Analysis. Applied Sciences. 2021; 11 (2):653.

Chicago/Turabian Style

Hafiz Ahmed; Mohamed Benbouzid. 2021. "Adaptive Observer-Based Grid-Synchronization and Sequence Extraction Techniques for Renewable Energy Systems: A Comparative Analysis." Applied Sciences 11, no. 2: 653.

Journal article
Published: 19 November 2020 in IEEE Transactions on Industrial Electronics
Reads 0
Downloads 0

This paper presents a super twisting sliding mode control (ST-SMC) for single-phase dynamic voltage restorers (DVRs). Unlike the conventional first-order sliding mode controller, the proposed ST-SMC technique eliminates the need for differentiating the compensation voltage in the sliding surface function while keeping the merits of first-order SMC. As a consequence of employing ST-SMC, a continuous control signal is achieved from which the pulse width modulation (PWM) signals can be generated. In this case, the inverter operates at constant switching frequency. The stability analysis of ST-SMC is also presented. The reference compensation voltage needed in ST-SMC is estimated by using Brockett oscillator based frequency-locked loop. Theoretical considerations are verified through experimental results under ideal and distorted grid voltage conditions. The obtained results show that the ST-SMC has good dynamic performance and can maintain the load voltage at desired level under voltage sag, swell and harmonically distorted grid voltages.

ACS Style

Samet Biricik; Hasan Komurcugil; Hafiz Ahmed; Ebrahim Babaei. Super Twisting Sliding-Mode Control of DVR With Frequency-Adaptive Brockett Oscillator. IEEE Transactions on Industrial Electronics 2020, 68, 10730 -10739.

AMA Style

Samet Biricik, Hasan Komurcugil, Hafiz Ahmed, Ebrahim Babaei. Super Twisting Sliding-Mode Control of DVR With Frequency-Adaptive Brockett Oscillator. IEEE Transactions on Industrial Electronics. 2020; 68 (11):10730-10739.

Chicago/Turabian Style

Samet Biricik; Hasan Komurcugil; Hafiz Ahmed; Ebrahim Babaei. 2020. "Super Twisting Sliding-Mode Control of DVR With Frequency-Adaptive Brockett Oscillator." IEEE Transactions on Industrial Electronics 68, no. 11: 10730-10739.

Journal article
Published: 13 October 2020 in IEEE Transactions on Industrial Electronics
Reads 0
Downloads 0

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 cut-off 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 with out 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.

ACS Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. Enhanced Frequency Adaptive Demodulation Technique for Grid-Connected Converters. IEEE Transactions on Industrial Electronics 2020, 68, 11053 -11062.

AMA Style

Hafiz Ahmed, Samet Biricik, Mohamed Benbouzid. Enhanced Frequency Adaptive Demodulation Technique for Grid-Connected Converters. IEEE Transactions on Industrial Electronics. 2020; 68 (11):11053-11062.

Chicago/Turabian Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. 2020. "Enhanced Frequency Adaptive Demodulation Technique for Grid-Connected Converters." IEEE Transactions on Industrial Electronics 68, no. 11: 11053-11062.

Journal article
Published: 27 August 2020 in IEEE Transactions on Industrial Informatics
Reads 0
Downloads 0

In this context of grid synchronization, estimating the phase and frequency of the grid voltage signal is an interesting problem. Out of various techniques available in the literature, Linear Kalman Filter (LKF) is one of the most popular one. In this paper, we propose an alternative implementation of the LKF for grid synchronization application. The proposed implementation uses a linear parametric model of the grid voltage signal including DC offset. It does not involve any quadrature signal generation, rather it works by estimating the phase angle. This helps to estimate the unknown grid frequency directly from the phase angle. This clearly differentiates the proposed alternative implementation with respect to the existing implementations. Performance improvement by the proposed technique is verified extensively through comparative numerical simulation and experimental studies. Comparative results demonstrate the suitability of the proposed technique with respect to other state-of-the-art techniques namely SOGI-PLL and EPLL.

ACS Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. Linear Kalman Filter-Based Grid Synchronization Technique: An Alternative Implementation. IEEE Transactions on Industrial Informatics 2020, 17, 3847 -3856.

AMA Style

Hafiz Ahmed, Samet Biricik, Mohamed Benbouzid. Linear Kalman Filter-Based Grid Synchronization Technique: An Alternative Implementation. IEEE Transactions on Industrial Informatics. 2020; 17 (6):3847-3856.

Chicago/Turabian Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. 2020. "Linear Kalman Filter-Based Grid Synchronization Technique: An Alternative Implementation." IEEE Transactions on Industrial Informatics 17, no. 6: 3847-3856.

Journal article
Published: 07 June 2020 in Energies
Reads 0
Downloads 0

This paper studies the grid-synchronization problem of three-phase system. Second-order adaptive filters are a popular tool for grid-synchronization. In this context, reduced-order generalized integrator has attracted some attention in recent time. However, existing implementations cannot control directly the closed-loop poles (real and imaginary) of reduced-order generalized integrator. To overcome this limitation, this paper proposes a novel reduced-order generalized integrator structure. To make the proposed technique frequency adaptive, an open-loop frequency estimation technique is also used. Comparative performance analysis are provided over two other advanced and recently proposed techniques. Results demonstrate the suitability and effectiveness of the proposed technique.

ACS Style

Hafiz Ahmed; Samet Biricik; Elhoussin Elbouchikhi; Mohamed Benbouzid. Adaptive Filtering-Based Pseudo Open-Loop Three-Phase Grid-Synchronization Technique. Energies 2020, 13, 1 .

AMA Style

Hafiz Ahmed, Samet Biricik, Elhoussin Elbouchikhi, Mohamed Benbouzid. Adaptive Filtering-Based Pseudo Open-Loop Three-Phase Grid-Synchronization Technique. Energies. 2020; 13 (11):1.

Chicago/Turabian Style

Hafiz Ahmed; Samet Biricik; Elhoussin Elbouchikhi; Mohamed Benbouzid. 2020. "Adaptive Filtering-Based Pseudo Open-Loop Three-Phase Grid-Synchronization Technique." Energies 13, no. 11: 1.

Journal article
Published: 30 May 2020 in Electric Power Systems Research
Reads 0
Downloads 0

This paper aims to address the DC offset rejection problem in grid synchronization algorithm. A simple approach to estimate the unknown grid frequency in the presence of DC offset is proposed for this purpose. Some of the existing techniques available in the literature use either low-pass filter or an additional integrator to eliminate the DC offset. Both approaches require an additional parameter to tune. However, tuning the additional parameter is not straightforward. Moreover, tuning the overall system can be complicated due to the presence of DC offset rejection part. The proposed approach does not require any additional parameter to tune. By considering the orthogonal signal instead of the DC offset as an additional state, the proposed technique can efficiently estimate the unknown frequency of the grid. Application to both single and three-phase grids are provided. Comparative experimental results with DC offset rejection capable second-order generalized integrator (SOGI) phase-locked loop (PLL) (SOGI-PLL) demonstrate the effectiveness and suitability of the proposed technique.

ACS Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. Low-pass filtering or gain tuning free simple DC offset rejection technique for single and three-phase systems. Electric Power Systems Research 2020, 186, 106422 .

AMA Style

Hafiz Ahmed, Samet Biricik, Mohamed Benbouzid. Low-pass filtering or gain tuning free simple DC offset rejection technique for single and three-phase systems. Electric Power Systems Research. 2020; 186 ():106422.

Chicago/Turabian Style

Hafiz Ahmed; Samet Biricik; Mohamed Benbouzid. 2020. "Low-pass filtering or gain tuning free simple DC offset rejection technique for single and three-phase systems." Electric Power Systems Research 186, no. : 106422.

Journal article
Published: 13 May 2020 in Energies
Reads 0
Downloads 0

This paper deals with a comparative study of two phasor estimators based on the least square (LS) and the linear Kalman filter (KF) methods, while assuming that the fundamental frequency is unknown. To solve this issue, the maximum likelihood technique is used with an iterative Newton–Raphson-based algorithm that allows minimizing the likelihood function. Both least square (LSE) and Kalman filter estimators (KFE) are evaluated using simulated and real power system events data. The obtained results clearly show that the LS-based technique yields the highest statistical performance and has a lower computation complexity.

ACS Style

Yassine Amirat; Zakarya Oubrahim; Hafiz Ahmed; Mohamed Benbouzid; Tianzhen Wang. Phasor Estimation for Grid Power Monitoring: Least Square vs. Linear Kalman Filter. Energies 2020, 13, 2456 .

AMA Style

Yassine Amirat, Zakarya Oubrahim, Hafiz Ahmed, Mohamed Benbouzid, Tianzhen Wang. Phasor Estimation for Grid Power Monitoring: Least Square vs. Linear Kalman Filter. Energies. 2020; 13 (10):2456.

Chicago/Turabian Style

Yassine Amirat; Zakarya Oubrahim; Hafiz Ahmed; Mohamed Benbouzid; Tianzhen Wang. 2020. "Phasor Estimation for Grid Power Monitoring: Least Square vs. Linear Kalman Filter." Energies 13, no. 10: 2456.

Journal article
Published: 09 May 2020 in Sensors
Reads 0
Downloads 0

Atomic force microscopy (AFM) plays an important role in nanoscale imaging application. AFM works by oscillating a microcantilever on the surface of the sample being scanned. In this process, estimating the amplitude of the cantilever deflection signal plays an important role in characterizing the topography of the surface. Existing approaches on this topic either have slow dynamic response e.g., lock-in-amplifier or high computational complexity e.g., Kalman filter. In this context, gradient estimator can be considered as a trade-off between fast dynamic response and high computational complexity. However, no constructive tuning rule is available in the literature for gradient estimator. In this paper, we consider small-signal modeling and tuning of gradient estimator. The proposed approach greatly simplifies the tuning procedure. Numerical simulation and experimental results are provided to demonstrate the suitability of the proposed tuning procedure.

ACS Style

Hafiz Ahmed; Mohamed Benbouzid. Gradient Estimator-Based Amplitude Estimation for Dynamic Mode Atomic Force Microscopy: Small-Signal Modeling and Tuning. Sensors 2020, 20, 2703 .

AMA Style

Hafiz Ahmed, Mohamed Benbouzid. Gradient Estimator-Based Amplitude Estimation for Dynamic Mode Atomic Force Microscopy: Small-Signal Modeling and Tuning. Sensors. 2020; 20 (9):2703.

Chicago/Turabian Style

Hafiz Ahmed; Mohamed Benbouzid. 2020. "Gradient Estimator-Based Amplitude Estimation for Dynamic Mode Atomic Force Microscopy: Small-Signal Modeling and Tuning." Sensors 20, no. 9: 2703.

Journal article
Published: 20 April 2020 in IEEE Access
Reads 0
Downloads 0

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.

ACS Style

Hafiz Ahmed; Mominul Ahsan; Mohamed Benbouzid; Alhussein Albarbar; Mohammad Shahjalal; Samet Biricik. Coordinate Transformation-Free Observer-Based Adaptive Estimation of Distorted Single-Phase Grid Voltage Signal. IEEE Access 2020, 8, 74280 -74290.

AMA Style

Hafiz Ahmed, Mominul Ahsan, Mohamed Benbouzid, Alhussein Albarbar, Mohammad Shahjalal, Samet Biricik. Coordinate Transformation-Free Observer-Based Adaptive Estimation of Distorted Single-Phase Grid Voltage Signal. IEEE Access. 2020; 8 (99):74280-74290.

Chicago/Turabian Style

Hafiz Ahmed; Mominul Ahsan; Mohamed Benbouzid; Alhussein Albarbar; Mohammad Shahjalal; Samet Biricik. 2020. "Coordinate Transformation-Free Observer-Based Adaptive Estimation of Distorted Single-Phase Grid Voltage Signal." IEEE Access 8, no. 99: 74280-74290.

Journal article
Published: 08 April 2020 in IEEE Access
Reads 0
Downloads 0

Grid-connected converters are an important class of power electronic systems. Many power and energy applications require grid-connected converters. To control grid-connected converters, precise information of the grid voltage frequency and phase are required. Gradient estimators can be very useful in this regard. They are suitable to estimate the frequency and phase of the grid voltage signal. Various gradient estimators are already available in the literature e.g. regression-based techniques. However, most of them are designed by using the instantaneous estimation error as the cost-function. This amplifies the effect of noise in the estimated parameters. To overcome this issue, an integral cost-function is considered in this paper. The integral cost-function tries to minimize the estimation error over the integration window leading to reduce the effect of noise in the estimated frequency and phase. Moreover, the cost-function uses tunable forgetting factor to give more importance to recent data. The proposed gradient estimator assumes the grid frequency to be constant. However, in practice the frequency is variable with known nominal value. To overcome this problem, a frequency estimation block is coupled with the gradient estimator. The frequency estimation block uses the idea of phase-based frequency estimation. Comparative numerical simulation and experimental studies are performed to demonstrate the suitability of the proposed technique over three other advanced techniques from the literature.

ACS Style

Hafiz Ahmed; Ivan Salgado; Isaac Chairez; Mohamed Benbouzid. Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization. IEEE Access 2020, 8, 70693 -70702.

AMA Style

Hafiz Ahmed, Ivan Salgado, Isaac Chairez, Mohamed Benbouzid. Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization. IEEE Access. 2020; 8 (99):70693-70702.

Chicago/Turabian Style

Hafiz Ahmed; Ivan Salgado; Isaac Chairez; Mohamed Benbouzid. 2020. "Robust Gradient Estimator for Unknown Frequency Estimation in Noisy Environment: Application to Grid-Synchronization." IEEE Access 8, no. 99: 70693-70702.

Journal article
Published: 20 March 2020 in IEEE Transactions on Instrumentation and Measurement
Reads 0
Downloads 0

Many phase locked-loop (PLL) or frequency locked-loop (FLL) use quadrature signals (directly or indirectly) as the input variables. Generalized integrator (GI) is a popular quadrature signal generator (QSG) available in the literature. GI is also widely used in various industrial applications. In addition to being a QSG, GI also works as kind of band-pass filter. However, due to structural limitation, the dynamic tuning range is limited for the standard GI. The limitation arises from using only one gain in the direct-phase estimation dynamics while quadrature phase estimation dynamics doesn’t use direct feedback of the filter estimation error. Some attempts have already been made to overcome this limitation by adding direct feedback of the filter estimation error to quadrature phase dynamics as well. However, we have demonstrated in this paper that this kind of implementation has some frequency domain limitations. In this paper, we propose a novel GI type adaptive filter using coordinate transformation. The resulting structure maintains the same kind of filtering property of the standard GI at the transformed coordinates level while at the same time enhances the dynamic tuning range of standard GI. Details of the proposed technique, stability analysis and discussion on gain tuning are provided in this paper. Finally, comparative experimental results are provided with respect to GI-FLL to show the dynamic performance improvement. Experimental results demonstrate the suitability of the proposed technique.

ACS Style

Hafiz Ahmed; Mohamed Benbouzid. On the Enhancement of Generalized Integrator-Based Adaptive Filter Dynamic Tuning Range. IEEE Transactions on Instrumentation and Measurement 2020, 69, 7449 -7457.

AMA Style

Hafiz Ahmed, Mohamed Benbouzid. On the Enhancement of Generalized Integrator-Based Adaptive Filter Dynamic Tuning Range. IEEE Transactions on Instrumentation and Measurement. 2020; 69 (10):7449-7457.

Chicago/Turabian Style

Hafiz Ahmed; Mohamed Benbouzid. 2020. "On the Enhancement of Generalized Integrator-Based Adaptive Filter Dynamic Tuning Range." IEEE Transactions on Instrumentation and Measurement 69, no. 10: 7449-7457.

Journal article
Published: 01 March 2020 in Electronics Letters
Reads 0
Downloads 0

This Letter proposes demodulation type PLL for phase and frequency estimation of single-phase system that can reject DC offset. Using results from the adaptive estimation literature, this Letter proposes a linear parametric model-based initial phase angle estimation approach. Then by using differentiation and integration operation on the estimated initial phase angle, the frequency is estimated. This avoids the use of any low-pass filter unlike conventional demodulation-based technique. Moreover, unlike existing demodulation-based technique, the proposed technique can completely reject DC offset. Comparative experimental results, provided with state-of-the-art DC offset rejection-based enhanced phase locked-loop, clearly demonstrate the suitability of the proposed technique.

ACS Style

H. Ahmed; M. Benbouzid. Demodulation type single‐phase PLL with DC offset rejection. Electronics Letters 2020, 56, 344 -347.

AMA Style

H. Ahmed, M. Benbouzid. Demodulation type single‐phase PLL with DC offset rejection. Electronics Letters. 2020; 56 (7):344-347.

Chicago/Turabian Style

H. Ahmed; M. Benbouzid. 2020. "Demodulation type single‐phase PLL with DC offset rejection." Electronics Letters 56, no. 7: 344-347.

Original paper
Published: 27 February 2020 in Electrical Engineering
Reads 0
Downloads 0

Estimation of instantaneous phase and frequency of harmonics-polluted single-phase grid voltage signal have been studied in this paper. The proposed approach uses a frequency adaptive Luenberger-sliding mode observer. Using Lyapunov stability theory, a frequency adaptation law has been proposed. The proposed frequency adaptive observer technique is robust against various perturbations faced in the practical settings, e.g., discontinuous jump of phase, frequency and amplitude. Global stability analysis of the closed-loop observer has been performed. Experimental results demonstrate the effectiveness of the proposed technique over a state-of-the-art technique proposed in the literature.

ACS Style

Miao Lin Pay; Hafiz Ahmed. Parameter estimation of harmonics-polluted single-phase grid voltage signal. Electrical Engineering 2020, 102, 1351 -1359.

AMA Style

Miao Lin Pay, Hafiz Ahmed. Parameter estimation of harmonics-polluted single-phase grid voltage signal. Electrical Engineering. 2020; 102 (3):1351-1359.

Chicago/Turabian Style

Miao Lin Pay; Hafiz Ahmed. 2020. "Parameter estimation of harmonics-polluted single-phase grid voltage signal." Electrical Engineering 102, no. 3: 1351-1359.

Journal article
Published: 15 January 2020 in International Journal of Electrical Power & Energy Systems
Reads 0
Downloads 0

This paper proposes the estimation of parameters and symmetrical components of unbalanced grid using adaptive observer framework. Recent adaptive observers proposed in the literature doesn’t employ any gain normalization in their frequency estimation loop. This can be problematic in the presence of large voltage dip. This paper proposes a solution to overcome this limitation using a novel gain normalized - frequency-locked loop (GN-FLL). Technical details of GN-FLL, stability analysis and tuning are provided in this paper. Comparative experimental results with adaptive Luenberger observer, second-order generalized integrator - phase-locked loop (SOGI-PLL) and enhanced PLL (EPLL) are provided to demonstrate the effectiveness the proposed technique in the single-phase case. Comparative experimental results with double SOGI-FLL (DSOGI-FLL) and adaptive notch filter (ANF) are provided to demonstrate the effectiveness the proposed technique in the three-phase case.

ACS Style

Hafiz Ahmed; Miao Lin Pay; Mohamed Benbouzid; Yassine Amirat; Elhoussin Elbouchikhi. Gain normalized adaptive observer for three-phase system. International Journal of Electrical Power & Energy Systems 2020, 118, 105821 .

AMA Style

Hafiz Ahmed, Miao Lin Pay, Mohamed Benbouzid, Yassine Amirat, Elhoussin Elbouchikhi. Gain normalized adaptive observer for three-phase system. International Journal of Electrical Power & Energy Systems. 2020; 118 ():105821.

Chicago/Turabian Style

Hafiz Ahmed; Miao Lin Pay; Mohamed Benbouzid; Yassine Amirat; Elhoussin Elbouchikhi. 2020. "Gain normalized adaptive observer for three-phase system." International Journal of Electrical Power & Energy Systems 118, no. : 105821.

Journal article
Published: 06 January 2020 in IEEE Access
Reads 0
Downloads 0

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.

ACS Style

Hafiz Ahmed; Mohamed Benbouzid; Mominul Ahsan; Alhussein Albarbar; Mohammad Shahjalal. Frequency Adaptive Parameter Estimation of Unbalanced and Distorted Power Grid. IEEE Access 2020, 8, 8512 -8519.

AMA Style

Hafiz Ahmed, Mohamed Benbouzid, Mominul Ahsan, Alhussein Albarbar, Mohammad Shahjalal. Frequency Adaptive Parameter Estimation of Unbalanced and Distorted Power Grid. IEEE Access. 2020; 8 (99):8512-8519.

Chicago/Turabian Style

Hafiz Ahmed; Mohamed Benbouzid; Mominul Ahsan; Alhussein Albarbar; Mohammad Shahjalal. 2020. "Frequency Adaptive Parameter Estimation of Unbalanced and Distorted Power Grid." IEEE Access 8, no. 99: 8512-8519.

Journal article
Published: 01 January 2020 in IFAC-PapersOnLine
Reads 0
Downloads 0

This manuscript describes the design and numerical implementation of a novel composite differential neural network aimed to estimate nonlinear uncertain systems. A differential neural network (DNN) with a composite feedback matrix approximates the structure of non-linear uncertain systems. The feedback matrix is assumed to belong to a convex set as well as the free parameters of the DNN (weights) at any instant of time. Therefore, ɩ-different DNN works in parallel. A composite Lyapunov function finds the convex hull approximation of the set of DNN working together to improve the approximation capabilities of classical neural networks. The main result of this study shows the practical stability of the estimation error. Numerical simulations demonstrate the approximation capabilities of the composite DNN implemented in a Van Der Pol oscillator where the presence of high-frequency components makes difficult a classical DNN approximation.

ACS Style

Alejandro Guarneros; Iván Salgado; Manuel Mera; Hafiz Ahmed. Differential neural network identifier with composite learning laws for uncertain nonlinear systems. IFAC-PapersOnLine 2020, 53, 7897 -7902.

AMA Style

Alejandro Guarneros, Iván Salgado, Manuel Mera, Hafiz Ahmed. Differential neural network identifier with composite learning laws for uncertain nonlinear systems. IFAC-PapersOnLine. 2020; 53 (2):7897-7902.

Chicago/Turabian Style

Alejandro Guarneros; Iván Salgado; Manuel Mera; Hafiz Ahmed. 2020. "Differential neural network identifier with composite learning laws for uncertain nonlinear systems." IFAC-PapersOnLine 53, no. 2: 7897-7902.

Journal article
Published: 29 December 2019 in Advances in Electrical and Electronic Engineering
Reads 0
Downloads 0

Second-Order Generalized Integrator -- Frequency-Locked Loop (SOGI-FLL) is a popular technique available in the grid synchronization literature. This technique uses gain normalization in the frequency locked-loop. This increases the computational complexity. In this paper, we propose an alternative implementation to reduce the computational complexity of the SOGI-FLL. The proposed implementation modifies mainly the frequency locked-loop part and requires normalized voltage measurement. dSPACE 1104 board-based hardware implementation shows that the proposed implementation executes 20% faster than the standard implementation. This could be very beneficial for high switching frequency application e.g. >= 1MHz. In addition to the nominal frequency case, multi-resonant implementation is also proposed to tackle grid harmonics using a~simpler harmonic decoupling network. Small signal dynamical modeling and tuning are performed for both implementations. Dynamical equivalence is also established between the two implementations. Experimental comparative analysis demonstrates similar or better performance (depending on test scenarios) with respect to the standard implementation of the SOGI-FLL.

ACS Style

Hafiz Ahmed; Mohamed Benbouzid. Simplified Second-Order Generalized Integrator - Frequency-Locked Loop. Advances in Electrical and Electronic Engineering 2019, 17, 405 - 412 .

AMA Style

Hafiz Ahmed, Mohamed Benbouzid. Simplified Second-Order Generalized Integrator - Frequency-Locked Loop. Advances in Electrical and Electronic Engineering. 2019; 17 (4):405 - 412.

Chicago/Turabian Style

Hafiz Ahmed; Mohamed Benbouzid. 2019. "Simplified Second-Order Generalized Integrator - Frequency-Locked Loop." Advances in Electrical and Electronic Engineering 17, no. 4: 405 - 412.