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Öğe Computation of PI Controllers Ensuring Desired Gain and Phase Margins for Two-Area Load Frequency Control System with Communication Time Delays(Taylor and Francis Inc., 2018) Sönmez Ş.; Ayasun S.This article deals with computation of all proportional-integral (PI) controllers which achieve the desired frequency-domain specifications namely, gain and phase margins (GPMs) of a traditional two-area load frequency control (LFC) system with constant communication delays. An efficient graphical method based on extracting the boundaries of stability regions in PI controller parameter space having user defined GPMs is proposed to obtain GPMs based stability regions. Regions are determined for a wide range of GPMs and time delay. The theoretical region boundaries are validated using a powerful numerical method known as the quasi-polynomial mapping-based root finder (QPmR) and time-domain simulations. Results indicate that the proposed scheme gives faster disturbance rejection and desired frequency response as compared to the recently developed scheme for LFC systems with communication delays. © 2018, Copyright © Taylor & Francis Group, LLC.Öğe Delay-dependent stability analysis of hybrid power systems with time delays(Institution of Engineering and Technology, 2016) Sezer H.; Erol H.; Ayasun S.It is essential to transmit measurements from remote terminal units (RTU) to control centre and control signals from the control centre to plant side, in load frequency control (LFC). Constant delays exist for used media in the conventional communication channels. Those delays would degrade the dynamic performance of LFC system. This paper investigates the delay-dependent stability of the LFC scheme for renewable energy power generation/storage/delivery subsystem. The investigated renewable energy power generation/storage/delivery subsystems include photovoltaic system (PV), wind turbine generator (WTG), fuel cell (FC) system and ultra-capacitor (UC) bank as energy storage system. In this paper, time delay effects of hybrid power systems are analysed by modelling the system via Matlab/Simulink.Öğe Effects of PWM chopper drive on the torque speed characteristic of DC Motor(2008) Gelen A.; Ayasun S.This paper describes a MATLAB/Simulink realization of the DC motor speed control method by controlling the voltage applied to the armature circuit using a pulse width modulated (PWM) chopper drive. Torque-speed characteristics are obtained for different values of switching frequency to demonstrate its effect on the linearity of the characteristic. The proposed simulation model is developed as a part of a software laboratory to support and enhance undergraduate electric machinery courses at Nigde University, Nigde, Turkey.Öğe Evaluation of the static performance of a simulation-stimulation interface for power hardware in the Loop(2003) Ayasun S.; Fischl R.; Chmielewski T.; Vallieu S.; Miu K.; Nwankpa C.This paper gives an evaluation framework of the static performance of a Simulation-Stimulation Interface (SSI) for Power Hardware in the Loop (PHIL) applications. The PHIL system is a hybrid system consisting of Hardware-Under-Test (HUT) connected to a Virtual Rest of the Power System (VROPS) via a Simulation-Stimulation Interface (SSI). The SSI maps the discrete time input/output signals of the VROPS to the continuous time power input/output signals of the HUT. Ideally, the performance of the PHIL should be the same as the actual power system consisting of the HUT connected to the Rest of the System hardware. The evaluation of the PHIL performance is made in terms of its electric power matching capability. Since the SSI is the key component affecting the power matching, this paper evaluates the effect of the SSI parameters on the static performance of PHIL, specifically, the power system loadability/maximum power transfer. The results are illustrated using P-Q curves of simple 2-bus l? system consisting of a generator, line and RL load. An experimental system was used to generate the baseline data for the simulation that was performed using Simulink. The study concentrated on the effect of time delay encountered in the SSI and VROPS processing on the maximum power transfer (i.e., P-Q curves) of the PHIL relative to that of the experimental system. The results show the decrease in maximum power transfer capability as the time delay increases to 1 msec. © 2003 IEEE.Öğe Gain and phase margins based delay-dependent stability analysis of two-area LFC system with communication delays(Institute of Electrical and Electronics Engineers Inc., 2018) Sönmez Ş.; Ayasun S.This paper investigates the effect gain and phase margins (GPM) on delay-dependent stability analysis of a two-area load frequency control (LFC) system with communication delays. An frequency-domain based exact method that takes into account both gain and phase margins is utilized to determine stability delay margins in terms of system and controller parameters. A gain-phase margin tester (GPMT) is introduced to the LFC system as to take into gain and phase margins in delay margin computation. For a wide range of proportional - integral (PI) controller gains, time delay values at which LFC system is both stable and have desired stability margin measured by gain and phase margins are computed. The time-domain simulation studies indicate that delay margins must be determined considering gain and phase margins to have a better dynamic performance in term of fast damping of oscillations, less overshoot and settling time. © 2017 EMO (Turkish Chamber of Electrical Enginners).Öğe Gain and phase margins based stability analysis of micro grid systems with time delay by using Rekasius substitution [Zaman gecikmeli mikro-şebeke sistemlerin Rekasius yerine koyma yöntemiyle kazanç ve faz payı tabanlı kararlılık analizi](Gazi Universitesi Muhendislik-Mimarlik, 2019) Gündüz H.; Ayasun S.; Sönmez Ş.This paper investigates the delay-dependent stability of a micro-grid system with constant communication delay considering not only stability but also gain-phase margins (GPMs). A gain-phase margin tester is introduced to the micro-grid system as to take into GPMs in delay margin computation. A frequency domain analytical method, Rekasius substitution, is utilized to compute the GPMs based stability delay margins. The method aims to calculate all possible purely complex roots of the characteristic equation for a finite positive time delay. The approach first transforms the characteristic polynomial of the micro-grid system with transcendental terms into a regular polynomial. Routh-Hurwitz stability criterion is then implemented to compute the purely imaginary roots with the crossing frequency and stability delay margin. For a wide range of proportional-integral controller gains and GPMs, time delay values for which the micro-grid system is both stable and has desired stability margin measured by GPMs are computed. The accuracy of complex roots and delay margins are verified by using an independent algorithm, QPMR (the quasi-polynomial mapping-based root finder) algorithm and time-domain simulations, respectively. Simulation studies indicate that delay margins must be determined by considering GPMs to have a better dynamic performance in term of fast damping of oscillations, less overshoot and shorter settling time. © 2019 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Öğe Impact of demand response on stability region of single-area LFC system with communication delay(Institute of Electrical and Electronics Engineers Inc., 2018) Ayasun S.; Nwankpa C.O.This paper investigates the impact of dynamic demand response (DR) on the stability region depicted on the controller parameter space of a single-area load frequency control (LFC) system with communication time delays. An effective and simple graphical method is implemented to compute all stabilizing Proportional Integral (PI) controller gains of DR loop for a given time delay. The approach is based on extracting stability region and the stability boundary locus in the PI controller parameter space. © 2017 EMO (Turkish Chamber of Electrical Enginners).Öğe Probability of small-signal stability of power systems in the presence of communication delays(2009) Ayasun S.; Nwankpa C.O.This paper presents a probabilistic approach to evaluate the small-signal stability of power systems in the presence of communication delays. An exact method is first proposed to determine the relationship between delay margin and system parameters such as the system load. The delay margin is then modeled as a random variable and the probability density function (PDF) of the delay margin is determined based on the PDF of the load using a Monte Carlo simulation approach. The communication delays are assumed to be uniformly distributed in a practical range and the probability of system being small-signal stable for a given time delay is determined using the estimated PDF of the delay margin. The proposed method is applied to a single-machine-infinite bus (SMIB) power system with an exciter.Öğe Stability of a two-area automatic generation control system with communication delays(2009) Ayasun S.; Nwankpa C.O.This paper investigates the effect of time delays on the stability of a two-area automatic generation control (AGC) system. The time delays are due to the use of measurement devices and communication links for sending and receiving control signals. The maximum amount of time delay known as the delay margin that the system can tolerate without becoming unstable is determined using Matlab/Simulink. The effect of integral controller gain on delay margin is analyzed.Öğe Symbolic analysis and simulation for power system dynamic performance assessment(2005) Ayasun S.; Dafis C.; Nwankpa C.; Kwatny H.This paper presents a MATLAB-based Voltage Stability Toolbox (VST) designed to analyze bifurcations, voltage stability problems and nonlinear observability in electric power systems. VST combines proven computational and analytical capabilities of stability and observability theory, symbolic implementation and graphical representation capabilities of MATLAB and its Toolboxes. The motivation for developing the package is to provide a flexible simulation environment for ongoing research conducted at Drexel University's Center for Electric Power Engineering (CEPE), and to enhance undergraduate/graduate power engineering courses. VST is a very flexible tool for load flow, small-signal and transient stability, bifurcation and observability analysis. To illustrat 1e the capabilities of VST, simulations using the IEEE 14 bus system are presented. ©2005 IEEE.
