New fast arctangent approximation algorithm for generic real-time embedded applications

Fast and accurate arctangent approximations are used in several contemporary applications, including embedded systems, signal processing, radar, and power systems. Three main approximation techniques are well-established in the literature, varying in their accuracy and resource utilization levels. Those are the iterative coordinate rotational digital computer (CORDIC), the lookup tables (LUTs)-based, and the rational formulae techniques. This paper presents a novel technique that combines the advantages of both rational formulae and LUT approximation methods. The new algorithm exploits the pseudo-linear region around the tangent function zero point to estimate a reduced input arctangent through a modified rational approximation before referring this estimate to its original value using miniature LUTs. A new 2nd order rational approximation formula is introduced for the first time in this work and benchmarked against existing alternatives as it improves the new algorithm performance. The eZDSP-F28335 platform has been used for practical implementation and results validation of the proposed technique. The contributions of this work are summarized as follows: (1) introducing a new approximation algorithm with high precision and application-based flexibility; (2) introducing a new rational approximation formula that outperforms literature alternatives with the algorithm at higher accuracy requirement; and (3) presenting a practical evaluation index for rational approximations in the literature. - 2019 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The publication of this article was funded by the Qatar National Library.Scopu

Reservoir stress path and induced seismic anisotropy: Results from linking coupled fluid-flow/geomechanical simulation with seismic modelling

We present a workflow linking coupled fluid-flow and geomechanical simulation with seismic modelling to predict seismic anisotropy induced by nonhydrostatic stress changes. We generate seismic models from coupled simulations to examine the relationship between reservoir geometry, stress path and seismic anisotropy. The results indicate that geometry influences the evolution of stress, which leads to stress-induced seismic anisotropy. Although stress anisotropy is high for the small reservoir, the effect of stress arching and the ability of the side-burden to support the excess load limit the overall change in effective stress and hence seismic anisotropy. For the extensive reservoir, stress anisotropy and induced seismic anisotropy are high. The extensive and elongate reservoirs experience significant compaction, where the inefficiency of the developed stress arching in the side-burden cannot support the excess load. The elongate reservoir displays significant stress asymmetry, with seismic anisotropy developing predominantly along the long-edge of the reservoir. We show that the link between stress path parameters and seismic anisotropy is complex, where the anisotropic symmetry is controlled not only by model geometry but also the nonlinear rock physics model used. Nevertheless, a workflow has been developed to model seismic anisotropy induced by non-hydrostatic stress changes, allowing field observations of anisotropy to be linked with geomechanical models

Small-Signal Stability Analysis and Parameters Optimization of Virtual Synchronous Generator for Low-Inertia Power System

The stable operation of converter-interfaced generation (CIG) units is paramount for ensuring resilience in low-inertia power systems. This paper presents a comprehensive small-signal modeling and stability analysis framework for grid-connected virtual synchronous generators (VSGs), integrating: an LCL-filter interfaced power converter, active/reactive power loop (APL/RPL) controllers, and dual-loop PI-based current and voltage control. Through systematic eigenvalue analysis and parameter sensitivity studies, complemented by time-domain verification in MATLAB/SIMULINK, we demonstrate the decisive influence of VSG control parameters on low-frequency oscillation (LFO) damping characteristics, transient frequency stability metrics, including the rate of change of frequency (ROCOF), maximum frequency deviation (fnadir), overshoot, and settling time. We further propose a hybrid Particle Swarm Optimization (PSO) algorithm with a multi-objective cost function to optimize VSG controller gains. The optimized design achieves an 83% reduction in ROCOF, a 90% improvement in frequency deviation, and a non-oscillatory power response. These results quantitatively validate that proper VSG gain tuning can significantly enhance dynamic performance and frequency stability in inertia-constrained grids. The proposed methodology offers practical insights for designing resilient CIG-dominated power systems.Qatar University and Iberdrola S.A. as part of its Innovation Department Research Studies (Grant Number: QUEX-CENG-IBERDROLA-22/23 and QUEX-CENG-IBERDROLA-IDC). Qatar National Library through Open Access Funding

High-gain DC-DC converters for high-power PV applications: Performance assessment

Conventional non-isolated DC-DC converters provide limited practical gains at high duty cycles due to their parasitic losses. Such trend is not suitable for renewables grid integration due to the high required gain, while isolated DC-DC converters utilize costly and lossy high-frequency transformers with limited power capability. Alternatively, connecting conventional DC-DC converters in different combinations can provide higher gains, up to MVDC levels in PV applications, while maintaining adequate efficiency margin through design optimizations. This paper addresses cascaded and/or series connection of DC-DC converter modules as a solution to the high gain requirement, and provides a performance assessment based on Cuk and Single-Ended Primary Inductor Converter (SEPIC) topologies. Theoretical analyses are performed, and their trends are experimentally-verified by lab-scale prototypes. � 2018 IEEE.Scopu

Robust Sliding Mode Controller Design for DC-DC Converters with Adaptive Gains

Conventional DC-DC converters are an industry standard in several fields such as in solar PV applications for maximum energy extraction. However, the inherent non-linearity in these conventional types (e.g., boost, buck and buck-boost) makes it necessary to develop robust control techniques that can maintain the desired system operation in the presence of system disturbances. Variable Space Structure (VSS) controllers are convenient for such systems as their switching nature matches the DC-DC converters operational principle, and the Sliding Mode Control (SMC) mechanism may be employed in this context. This paper proposes an adaptive SMC method for the fourth order SEPIC converter, based on altering the sliding surface dynamics to continuously adjust the gains and drive the system to slide along an adaptive sliding surface to achieve stable converter operation. The mathematical model of the fourth order SEPIC is derived and the proposed adaptive SMC approach is simulated in MATLAB/Simulink. It is shown that one can achieve enhanced performance compared to the conventional SMC methods in the presence of system disturbances. The same methodology employed to SEPIC can also be expanded to other converters.Scopu

Assessment of isolated and non-isolated DC-DC converters for medium-voltage PV applications

The potential of Photovoltaic (PV) panels as a main tool of harnessing solar energy is increasing with the advancements in their power conditioning and conversion stages that vary based on applications. This paper focuses on the conversion of a 22kW PV array output from low-voltage to medium-voltage level (400V to 7kV). This high voltage conversion ratio is difficult to achieve using conventional single-stage DC-DC converters. Thus, different alternatives are proposed and compared here, namely, the Parallel-Input Series-Output (PISO) connection of two different stages using both isolated (full-bridge) and non-isolated DC-DC converters. The converters are compared on the basis of efficiency, footprint, components rating and reliability. Thus, the isolated DC-DC converter system efficiency was estimated at 797%, compared to 93 % for the non-isolated system, keeping into account the variations in terms of the filtering capacitor requirements to maintain a constant minimal voltage ripple at the output which is in favor of the non-isolated systems. ? 2017 IEEE.ACKNOWLEDGMENT This publication was made possible by the National Priority Research Program (NPRP) award [NPRP6-244-2-103] from the Qatar National Research Fund (QNRF); a member of the Qatar Foundation. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of QNRF

Using RAPD markers for genetic analysis in Three Species of Datura in Iraq

The study amis to develop the evidence genetic of active substances for several kinds of the Datura plant (Datura sp.), So it was procedure steps to isolated the Genomic DNA from leaf of Datura specis    it is (Datura metel, Datura innoxia and Datura stramonium).(&#x0D;  Has been used 51 primers in the experiments of the RAPD markers, but did not show 17 primers including any amplified band while showed in genomic in Datura plants, and 34 primers show results Differentiated locations where all the primers gave a differentiated binds Polymorphic band These results have been invested to study genetic variability among the species involved in study.&#x0D;  &#x0D; http://dx.doi.org/10.25130/tjps.23.2018.165</jats:p