365 research outputs found
Repetitive current control of two-level and interleaved three-phase PWM utility connected converters
No full textThis thesis is mainly concerned with investigations into digital repetitive current controlof two-level and interleaved utility connected PWM converters. The research ismotivated by the relatively poor performance of classical (PI) controllers when theutility voltage harmonic distortion is high. This is due to the low gain, and poordisturbance rejection of the PI controller at the utility harmonic frequencies. Repetitivefeedback controllers have the ability to track or reject periodic disturbances, such asutility harmonics, as they naturally have high gains at the utility voltage harmonicfrequencies, assuming that these frequencies do not change.Repetitive controllers (RC) are known for being sensitive to variations in systemparameters and disturbance frequency, which in practice renders them either ineffectiveor unstable. Another challenge arises from the memory requirements of RC in case ofthe absence of even harmonics, which can make its practical implementation difficultand expensive. In addition, another problem that has not been investigated extensivelyin the literature is that the effectiveness of RC is severely limited by the limitedbandwidth of the plant (the utility connected converter and its filter). Theoreticalanalysis and simulation results presented in this thesis show that RC could noteffectively reject disturbances at frequencies above the closed loop system bandwidth.The design of the converter's output filter bandwidth and the values of its componentsneed to be selected carefully, to enable RC to be used effectively.The research in this thesis focuses on investigating the practical implementation andperformance limits of two types of repetitive controllers (conventional and oddharmonics),used for current control of two-level utility connected converter with LCLoutput filter. The odd-harmonic repetitive controller halves the memory requirementand offers higher gains only at odd harmonic frequencies of interest. The overall controlscheme consists of the traditional classical tracking controller with a dual loop feedbacksystem and RC. The results indicate that the repetitive controller improves the steadystate error and the total harmonic distortion of the output current, provided that theplant's bandwidth is sufficiently large.Finally, a repetitive controller for an interleaved utility connected converter has beendesigned and investigated in this study. The interleaved converter system has higherbandwidth than the two-level converter, which improves the effectiveness of RC. Itprovides good disturbance rejection compared to classical controllers which results inlow output current THD. The RC was demonstrated to be robust despite uncertainty inutility impedance, while achieving a fast almost zero error convergence. The proposedRC has been experimentally implemented using a DSP and the results indicate that thequality of output current complies with international standards on harmonic limits andmatches simulation results obtained from the Matlab/Simulink model of the system
Hydraulic simulations to evaluate and predict design and operation of the Chashma Right Bank Canal
No full textIrrigation systems / Irrigation canals / Flow control / Velocity / Canal regulation techniques / Hydraulics / Simulation models / Design / Operations / Crop-based irrigation / Distributary canals / Water delivery / Policy / Protective irrigation / Water allocation / Water requirements / Sedimentation / Water distribution / Equity / Water conveyance / Pakistan / Chashma Right Bank Canal
Active control of vibrations of a tall structure excited by external forces
No full textThis paper is concerned with active control of vibrations of tall structures subjected to strong wind or earth quake shocks using an active mass damper (AMD). A linear black box model of the systems is obtained from an experimental scale model of the structure. Two alternative control systems, and associated observers are designed and their performance assessed theoretically and experimentally
Battery energy storage systems for energy arbitrage: market selection and price forecasting optimization
No full textThe rapid integration of variable renewable energy (VRE) sources into electricity grids has disrupted traditional power market dynamics and created new opportunities for grid-scale battery energy storage system (BESS) ventures. This thesis presents an integrated, data-driven framework for optimizing the investment and operational decision-making processes of battery energy storage system-enabled energy arbitrage (BESS-EA) systems. The first component develops a novel energy arbitrage feasibility (EAF) scoring methodology to evaluate the locational suitability of 29 European electricity markets. Using eight years of hourly wholesale electricity price data (2015–2023) along with regulatory, volatility, and macroeconomic indicators—including electricity supply-origin risk (ESOR), GDP per capita (purchasing power parity), and index of economic freedom (IEF)—the EAF score facilitates standardized, cross-country investment assessment across five investor preference scenarios. Results identify Estonia and Luxembourg as optimal BESS-EA markets across five scenarios.
The second component addresses the critical challenge of electricity price forecasting for bid optimization by introducing a hybrid long short-term memory (LSTM) and exponentially weighted moving average (EWMA) architecture. Trained on Austria's market data, the model achieves a root mean square error (RMSE) of €1.2207/MWhe and incorporates 95% bootstrap confidence intervals for risk quantification. By simultaneously capturing long-term temporal trends and short-term volatility patterns, the model supports robust intraday BESS bid decisions in wholesale and ancillary service markets
Improved power quality in grid-connected inverters using robust sliding mode control techniques
No full textGrid-connected inverters (GCI) play a crucial role in injecting DC power from renewable resources into the utility grid; moreover, the quality of the power transferred to the grid largely depends on the effectiveness of the adopted control strategy. This research proposed a novel super-twisting double integral sliding mode control (SMC) algorithm for a three-phase grid-connected inverter with an inductive-capacitive-inductive (LCL) filter. In this study, the control algorithm is first derived based on the system’s dynamic mathematical model. Then, extensive simulation studies are carried out in MATLAB and Simulink software to validate its performance. Furthermore, the controller effectiveness is rigorously assessed under challenging conditions, including a 400% grid impedance variation, a 66% system parametric variation, grid frequency variation, and higher-order grid harmonic components. In the worst-case scenario, the total harmonic distortion (THD) of the grid current stays below 2.6%, demonstrating the controller's effectiveness in enhancing the power quality supplied to the grid.
In the second control technique a novel integral terminal sliding mode control (IT-SMC) for a grid-connected three-phase inverter is presented to overcome the adverse effects of external disturbances on the power being injected into the grid. The integral terminal SMC guarantees finite-time convergence, minimal overshoot, and chattering-free operation. In the mathematical design of the controller, a derivative term is introduced in the capacitor voltages to achieve a better damping effect and prevent overshoot. Additionally, the integral of the grid and inverter current error is incorporated into the sliding surface to achieve precise tracking of the current reference. A 3-kW system is designed using the MATLAB/Simulink tool to analyze the controller’s performance. The grid-current quality and the stability of the controller are analyzed under
conditions of grid voltage distortions, impedance variations, and filter resonance frequency. Experimental results confirm that the designed controller ensures nearly zero steady-state error, low grid current harmonics, rapid dynamic response, and system stability under weak grid conditions, thereby significantly improving the power quality supplied to the grid.
The third control method is constructed while integrating the sliding mode control (SMC) algorithm with proportional resonant harmonic compensators (PR-HCs) for a three-phase GCI with an LCL filter, offering a promising solution for injecting power generated from DC sources into the utility grid. The existing controllers exhibit a notable tendency toward GCI system instability when facing system with simultaneous occurrence of parameter mismatches, distorted grid voltage, and resonance frequency events. The proposed SMC+PR-HC method inserts a loop of PR-HCs in parallel with the SMC control loop, significantly suppressing unwanted grid current harmonic components. Furthermore, a combined SMC and PR-HC control law is appropriately derived to analyze system stability using linear control theory approach. The performance of the proposed control method is validated using MATLAB/Simulink platform while considering the grid impedance variation, grid voltage fluctuation, filter parametric change, and the resonance frequency of ƒₛ ̸ 6.Finally, experimental results demonstrate that the proposed controller ensures minimal steady-state error, low grid current harmonics, rapid dynamic response, and system stability, even under ultra-weak grid conditions, leading to significant power quality improvement.Includes bibliographical reference
Human Capital and Economic Growth in Pakistan
No full textPakistan’s economy has grown faster on average than many other low- and middleincome countries over the past two decades. But several countries in Southeast Asia have fared even better. This paper focuses on factors that explain Pakistan’s relative growth performance. In addition to more traditional factors believed to determine growth, this paper looks particularly at the role of differences in the quality of human capital. The cross-country empirical results suggest that accumulation of physical capital and improvements in the quality of institutions have the largest pay-offs in terms of achieving higher growth, but that better education and health care also have a significant impact. Investment in these areas will increase the possibility of Pakistan entering a virtuous cycle of high growth and improved living conditions for the population.
The Reluctant Fundamentalist de Mohsin Hamid. Un récit de radicalisation ?
No full textThe 9/11 attacks in 2001 resulted in significant geopolitical, social, legal, and political consequences, primarily within the United States; however, they also sparked literary responses. This article examines how Mohsin Hamid explores the theme of ideological radicalization in his novel The Reluctant Fundamentalist (2007). It analyzes how the author manipulates conventional discourses and representations of terrorism and radicalization to ensnare the reader, presenting them with a mirror of their own radicality. The conclusion raises questions about what would constitute the specifically literary radicality of a novel, drawing on a proposition by Justine Huppe.Los atentados del 11 de septiembre de 2001 tuvieron importantes consecuencias geopolíticas, sociales, jurídicas y políticas, principalmente en Estados Unidos, pero también provocaron reacciones literarias. En este artículo presentamos e interrogamos el modo en que Mohsin Hamid juega con el tema de la radicalización ideológica en su novela The Reluctant Fundamentalist (2007). Analizaremos cómo el autor utiliza el discurso y las representaciones convencionales del terrorismo y la radicalización para atrapar al lector y sostener un espejo ante su propio radicalismo. Siguiendo el trabajo de Justine Huppe, la conclusión del articulo propone algunas interrogaciones con respecto a eso que se podría identificar como una radicalidad específicamente literaria en la novela.Les attentats du 11 septembre 2001 ont eu des conséquences géopolitique, sociale, juridique et politique importantes, en premier lieu aux États-Unis ; mais ils ont aussi suscité des réactions littéraires. Cet article constitue une vignette qui présente et interroge la façon dont Mohsin Hamid joue avec le thème de la radicalisation idéologique dans son roman The Reluctant Fundamentalist (2007). On y analysera comment l’auteur travaille des discours et des représentations convenues du terrorisme et de la radicalisation afin de piéger le lecteur, et lui présenter un miroir de sa propre radicalité. La conclusion ouvre un questionnement sur ce qui constituerait la radicalité spécifiquement littéraire d’un roman, à partir d’une proposition de Justine Huppe
Comparative analysis of Dr. Mohsin Khan and Maulawi Sher Ali's translation of surah Adh Dhuha and Ash Sharh
No full textBeing a Quran translator is not an easy activity, because Al Quran has a very beautiful language with high literature. Of course translating the Qur'an has a different level of difficulty with translating other texts. Both Dr. Mohsin Khan and MaulawiSher Ali have translated the Qur'an very well, so it is easy to be understood by the reader from a word. This is because both translators translate the Qur'an accurately and can answer the problems of life with the point of view of the Quran. Described in plain language and not complicated. The main problem in this research is the differences and similarities of semantic aspects that influence the translation of the work of Dr. Mohsin Khan and MaulawiSher Ali. The results of this study indicate that the lexical semantic translation style that influences the difference and its perspectives is in terms of its purpose. In translating the Qur'an, Dr. Mohsin Khan and MaulawiSher Ali are not only influenced by linguistic factors, but are also influenced by extralinguistics factors such as circumstances when translating and the science background of both translators in translating the Qur'an. In translating the Qur’an verses, Dr. Mohsin Khan is simple. This can be seen in his translation work. The first interpretation is done by giving the meaning of the verses of the Qur'an, then giving a global interpretation, without beginning with the explanation of the meaning of the word. By not adding many notes in his commentary, as if Dr. Mohsin Khan wants to invite readers to focus on dialogue with god. While MaulawiSher Ali in translating Quran verse many provide footnotes or other translation options. With the explanation, the author has the opinion that what is done by MaulawiSher Ali is to clarify and facilitate the reader in understanding the meaning of the verses of Quran
Advanced model predictive control and power conversion strategies for flux-switching permanent magnet synchronous machines
No full textModern electric drive systems, particularly in electric vehicles (EVs), renewable energy, aerospace, and
industrial automation, demand efficient power conversion and robust motor control. Flux Switching Permanent
Magnet Synchronous Machines (FSPMSMs) are gaining attention due to their high torque density, enhanced
thermal performance, and durable structural design. However, their nonlinear behavior, parameter fluctuations,
and susceptibility to external disturbances present significant control challenges. Conventional approaches like
Field Oriented Control (FOC) and PI controllers often fall short in maintaining optimal performance under
dynamic conditions.
To address these limitations, Model Predictive Current Control (MPCC) has emerged as a viable solution,
offering improved dynamic response, reduced torque ripple, and better current regulation. Despite its
advantages, MPCC's reliance on accurate system modeling makes it prone to uncertainties. This research
introduces a novel integration of Sliding Mode Control (SMC) into the speed loop, enhancing the system's
ability to reject disturbances and adapt to varying conditions. The proposed MPCC SMC strategy demonstrates
faster transient response, increased stability, and greater reliability, making it well suited for demanding
FSPMSM applications. The approach is validated through high fidelity simulations using OPAL RT
Technologies’ OP5707XG simulator. In addition to advanced motor control , a stable high voltage DC supply is
crucial for efficient FSPMSM operation. Many energy sources, such as batteries, fuel cells, and photovoltaic
(PV) panels, produce low voltage DC power, requiring an efficient step up converter for high performance
motor drives. Traditional boost converters face challenges like extreme duty cycles, high conduction losses, and
reduced efficiency, limiting their suitability. To address these issues, this research explores the Cubic Semi
SEPIC Converter (C³SSC), a novel high gain, non isolated DC DC topology capable of achieving ultra high
voltage conversion with moderate duty cycles, reduced switching losses, and improved efficiency. A laboratory
tested prototype of the C³SSC confirms its high gain capability and practical viability for power conversion
applications. While MPCC SMC ensures robust control of the FSPMSM, the C³SSC efficiently provides the
necessary high voltage DC supply, enabling stable, efficient, and reliable motor operation. This research
integrates advance d motor control with high performance power conversion, enabling next generation electric
drives for sustainable transport, automation, and renewable energy.Includes bibliographical reference
A SURREALIST READING OF MOHSIN HAMID'S EXIT WEST
No full textThe study aims at exploring the surrealist elements in Mohsin Hamid's novel Exit West. It analyzes the motifs and a technique employed by Hamid, and discusses how they contribute to the overall themes of displacement, migration, and identity in the novel. The study also examines how Hamid uses surrealist imagery, dream-like sequences, and unconventional perspectives to depict the characters' experiences of dislocation and otherness. The knowledge of the elements of surrealism will add depth and nuance to the novel's exploration of complex and timely issues. Using a close reading approach to the selected passages, the paper evaluates the ways in which the author employs surrealist techniques to challenge conventional notions of time, space, and reality, and to convey the experiences of displacement, migration, and the erosion of identity. Through the knowledge of surrealism in the context of the novel, the readers can gain a greater understanding of the power of the imagination to shape their understanding of the world and human experience
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