Browsing by Author "Ahmed, Hafiz"

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Enhanced Control of Superconducting Magnetic Energy Storage Integrated Upqc for Power Quality Improvement in Ev Charging Station
(Elsevier, 2023) Celik, Dogan; Ahmed, Hafiz
Distribution-grid connected electric vehicle charging stations draw nonlinear current, which causes power quality issues including harmonic distortion, DC-link fluctuation etc. Recent literature found that a unified power quality conditioner with superconducting magnetic energy storage (UPQC-SMES) can alleviate charging induced power quality issues. However, the performance improvement can be greatly enhanced by suitably designed control strategy. In this paper, an effective control approach is proposed for the UPQC-SMES system. In the proposed method, an all-pass filter based quasi type-1 phase-locked loop is proposed, which can robustly detect voltage sag/swell for the control of UPQCs series converter. A robust sequence estimator based on exponential forgetting factor cost function is developed for nonlinear load current sequence estimation to be used inside UPQCs parallel converter control system. Finally, a nonlinear proportional-integral controller is applied to make the system fast responsive with lower DC-link ripple compared to a conventional linear proportional-integral controller. The combined use of SMES and nonlinear proportional-integral controller can significantly eliminate the voltage fluctuation in DC-link and reduce the size and cost of the DC-link capacitor, making the system more efficient. To enable grid-friendly charging operation, the proposed control strategy considers harmonic currents elimination, reactive power compensation, power factor improvement, restoring sags and swells of the grid voltage and mitigation of DC-link voltage fluctuations. Comparative verification results show that the total harmonic distortion by the proposed method always remained between 1.0 similar to 1.5% irrespective of the test cases, while the conventional approach could contain the distortion to less than 5% in some cases only.
Enhanced Upqc Control Scheme for Power Quality Improvement in Wave Energy Driven Pmsg System
(IEEE-Inst Electrical Electronics Engineers Inc, 2025) Ahmed, Hafiz; Celik, Dogan
This article focuses on enhancing power quality (PQ) in a wave energy-driven permanent magnet synchronous generator (PMSG) system with unbalanced and highly inductive nonlinear loads using a unified power quality conditioner (UPQC). Our proposed control system improves voltage quality, compensates for reactive power, and mitigates harmonics. It ensures constant voltage amplitudes during supply voltage faults, achieving harmonic rejection, reactive power compensation, and enhanced voltage quality through the UPQC's parallel converter. Compared to previous methods, we introduce a frequency-fixed second-order generalized integrator (FFSOGI) quasi-type-1 PLL for efficient load harmonics extraction and source voltage fault detection. Additionally, a robust nonlinear proportional-integral (N-PI) controller, with a feedforward term, regulates the DC-link voltage swiftly and mitigates fluctuations. Our approach ensures compliance with IEEE standards for source current and load voltage harmonics. Comprehensive PSCAD/EMTDC results, utilizing experimental torque and power data from a wave energy converter at the Australian Maritime College model test pool, highlight the advantages of our proposed approach over conventional methods.
Kalman Filter-Based Super-Twisting Sliding Mode Control of Shunt Active Power Filter for Electric Vehicle Charging Station Applications
(Ieee-inst Electrical Electronics Engineers inc, 2023) Celik, Dogan; Ahmed, Hafiz; Meral, Mehmet Emin
Electric vehicle (EV) charging stations draw nonlinear currents, which makes the distribution network unbalanced, distorted, and results in power quality (PQ) issues. These PQ issues are mitigated in this work through high-performance control of the shunt active power filter (SAPF). In the proposed method, a linear Kalman filter (LKF) has been applied to grid voltage and load current signals for harmonic and disturbance robust estimation purpose. Unlike the conventionally used orthogonal vector model, in this work, phase angle vector model together with a simple to tune phase-locked loop (PLL) has been considered for the LKF implementation. DC-link voltage regulation and charging of the DC-link capacitor has been obtained by proposing a Luenberger observer-based super twisting sliding mode control (ST-SMC), which has fast dynamic response and lower voltage ripples compared to similar other existing control methods. This results in significant reduction in size, cost and loss together with lifetime enhancement of the DC-link capacitor. Rigorous sensitivity analysis is conducted to analyze the robustness of the developed method. The proposed control technique achieves fast response time and satisfy the harmonic requirements as specified in the IEEE Std. 519 under various grid and load disturbances. Comparative quasi-real time validation results are presented by using digital signal processor (DSP) based processor-in-the-loop (PIL) with another recently proposed control strategy to verify the performance enhancement by the developed method.
A Review of Energy Storage Systems for Facilitating Large-Scale Ev Charger Integration in Electric Power Grid
(Elsevier, 2025) Celik, Dogan; Khan, Muhammad Adnan; Khosravi, Nima; Waseem, Muhammad; Ahmed, Hafiz
The swift increase in electric vehicle (EV) into modern power grids presents both significant opportunities and challenges, particularly in maintaining power quality (PQ) and managing peak loads. This review synthesizes current research, providing a comprehensive analysis of the pivotal role of energy storage systems (ESS) in enabling large-scale EV charger integration while addressing critical PQ issues. A key contribution is the comparative evaluation of various ESS typologies-battery ESS (BESS), hybrid ESS (HESS), and distributed ESS (DESS)-each offering distinct advantages in mitigating PQ challenges such as harmonic distortion, voltage regulation, and peak demand control. Ensuring compliance with IEEE-519 standards is emphasized as vital for maintaining grid reliability and high PQ standards. This review paper further examines the diverse impacts of plug-in electric vehicles (PEVs) on power grids, including their charging and storage characteristics, which influence grid stability and efficiency. It highlights the transformative potential of vehicle-to-grid (V2G) technology, which facilitates bidirectional power flow to support grid stabilization, energy balancing, and ancillary services. Additionally, it addresses the mitigation of harmonic distortion from PEV charging, preserving transformer performance and lifespan, and explores strategies to manage large-scale PEV integration through predictive and adaptive control techniques. This study introduces innovative approaches to improving grid recovery following disturbances and evaluates the synergistic integration of renewable energy sources with PEVs to foster sustainable energy systems. Models for PEV interaction with microgrids are also discussed, emphasizing their role in enhancing energy resilience and grid flexibility. This paper underscores the critical role of advanced energy management strategies (EMS) in optimizing EV-grid integration and improving overall system efficiency. These strategies include rule-based EMSs employing fixed rules, fuzzy logic, and wavelet transforms; optimization-based EMSs utilizing techniques such as dynamic programming, genetic algorithms, model predictive control, and particle swarm optimization; and intelligent EMSs leveraging neural networks and reinforcement learning for adaptive and predictive control. By outlining innovative solutions and highlighting the importance of strategic collaboration among utilities, policymakers, researchers, and technology developers, this review provides a comprehensive roadmap for overcoming the technical, economic, and regulatory challenges associated with EV charger integration, laying the groundwork for a reliable, efficient, and sustainable energy future.
Sliding Mode Based Adaptive Linear Neuron Proportional Resonant Control of Vienna Rectifier for Performance Improvement of Electric Vehicle Charging System
(Elsevier, 2022) Ahmed, Hafiz; Celik, Dogan
With a strong expansion of transportation electrification, electric vehicle charging systems are becoming very important part of the electrified powertrain. This paper proposes a sliding mode based adaptive linear neuron (ADALINE)-proportional resonant (PR) control solution to enhance performance of Vienna rectifier (VR), an AC-DC converter, as a charger for series-linked battery packs of electric vehicles (EVs) operating under unbalanced and distorted grid conditions. A sliding-mode control (SMC) has been utilized for the fast and robust regulation of DC-link voltage while ADALINE-PR control is proposed to regulate the source current errors through the real-time adaptation of the controller gains. Another contribution of this paper is to derive reference current signals without complex positive and negative sequences component separation, coordinate transformation and phase-locked loop. Besides, constant and pure battery current during charging/discharging is achieved in contrast to the previous studies. The proposed control algorithm achieves superior dynamic and steady-state performances and eliminate harmonics of source currents and ripples in active power, DC-link voltage and battery current compared to the existing studies. The proposed method has been implemented in a digital signal processor (DSP) TMS320F28335 within a processor in the loop (PIL) quasi-real-time setting. Extensive comparative results demonstrate the effectiveness of proposed control algorithm.