8 results on '"Davoudi, Ali"'
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2. Multi-Resolution Modeling of Power Electronics Circuits Using Model-Order Reduction Techniques.
- Author
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Davoudi, Ali, Jatskevich, Juri, Chapman, Patrick L., and Bidram, Ali
- Subjects
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POWER electronics , *ELECTRIC circuits , *CONVERTERS (Electronics) , *KRYLOV subspace , *ORDINARY differential equations - Abstract
Highly detailed models of power-electronic converter circuits can be slow to simulate due to the wide disparity in transient time scales. This paper presents a framework for multi-resolution simulation of switching converter circuits by providing an appropriate amount of detail based on the time scale and phenomenon being considered. In this approach, a detailed full-order model that accounts for the higher-order effects of components, parasitics, switching nonlinearity (e.g., saturated inductors), switching event detection, etc., is constructed first. Efficient order-reduction techniques are then used to extract several lower order models for the desired resolution of the simulation. The simulation resolution can be adjusted as needed even during a simulation run time. The state continuity across different resolutions and switching events is ensured using appropriate similarity transforms. The proposed high-fidelity model of converter is verified with hardware measurement and is used to verify different simulation resolutions. The proposed methodology is demonstrated to achieve orders of magnitudes improvement in simulation speed. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
3. Small-Signal Stability-Constrained Optimal Power Flow for Inverter Dominant Autonomous Microgrids.
- Author
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Pullaguram, Deepak, Madani, Ramtin, Altun, Tuncay, and Davoudi, Ali
- Subjects
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ELECTRICAL load , *MICROGRIDS , *SEMIDEFINITE programming , *LYAPUNOV stability , *REDUCED-order models , *STABILITY criterion - Abstract
This article details and solves a small-signal stability-constrained optimal power flow (SSSC-OPF) for inverter-based ac microgrids. To ensure a sufficient stability margin during optimal generation, a small-signal stability constraint is embedded into the conventional OPF formulation. This condition is enforced using a Lyapunov stability equation. A reduced-order model of the microgrid is adopted to alleviate the computational burden involved in solving the resulting SSSC-OPF. Even then, the resulting stability conditions are highly nonlinear and cannot be handled using the existing methods. To tackle the nonconvexity in the SSSC-OPF due to the presence of the nonlinear stability constraint, two distinct convex relaxation approaches, namely semidefinite programming and parabolic relaxations, are developed. A heuristic penalty function is added to the objective function of the relaxed SSSC-OPF, which is solved sequentially to obtain a feasible point. While off-the-shelf tools fail to produce any feasible point within hours, the proposed approach enables us to solve the SSSC-OPF in near real time. The efficacy of the proposed SSSC-OPF is evaluated by performing numerical studies on multiple benchmarks as well as real-time studies on a microgrid system built in a controller/hardware-in-the-loop setup. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Induction Machine Parameterization From Limited Transient Data Using Convex Optimization.
- Author
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Yadav, Ajay Pratap, Madani, Ramtin, Amiri, Navid, Jatskevich, Juri, and Davoudi, Ali
- Subjects
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INDUCTION machinery , *PARAMETERIZATION , *MACHINERY , *PARAMETER estimation , *STATORS , *SYSTEM identification , *TRANSIENT analysis , *POLYNOMIAL chaos - Abstract
This article identifies the parameters of an induction machine using limited and nonintrusive observations of available input voltages, stator currents, and the rotor speed. Parameter extraction is formulated as a nonconvex estimation problem, which is then relaxed to a convex conic optimization problem. While the resulting relaxation could exhibit a satisfactory performance, there might be cases where the solution of convex relaxation fails to satisfy the dynamic equations of the machine. This is remedied through a local search approach initiated using the solution obtained from the relaxed problem. The proposed method is experimentally verified on a squirrel-cage induction machine with missing measured data. Using the measured signals as the benchmark, time-domain transients produced by the parameters estimated using the proposed method show almost 20% better match compared to time-domain transients produced by the parameters obtained via conventional testing. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
5. Alternative Time-Invariant Multi-Frequency Modeling of PWM DC-DC Converters.
- Author
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Behjati, Hamid, Niu, Lei, Davoudi, Ali, and Chapman, Patrick L.
- Subjects
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DC-to-DC converters , *TIME-domain analysis , *FLOQUET theory , *FREQUENCY-domain analysis , *CLOSED loop systems - Abstract
A time-invariant multi-frequency modeling technique is proposed for pulse-width-modulated (PWM) dc-dc converters. The proposed methodology distinguishes between different types of modulation carrier signals (e.g., sawtooth and isosceles triangle carriers). A straightforward systematic procedure is proposed to automatically convert the conventional state-space time-variant model to the proposed time-invariant model. Hence, high-order time-invariant models can be easily developed for system design and stability analysis purposes. Closed-loop time-domain and open-loop frequency-domain responses extracted from a laboratory-scale Cuk converter have verified the proposed methodology. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
6. Hardware-Assisted Simulation of Voltage-Behind-Reactance Models of Electric Machines on FPGA.
- Author
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Yadav, Ajay Pratap, Xu, Siyuan, Schafer, Benjamin Carrion, and Davoudi, Ali
- Subjects
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ELECTRIC machines , *ELECTRIC machinery , *INDUCTION motors , *SYNCHRONOUS generators , *GATE array circuits , *SYNCHRONOUS electric motors , *FIELD programmable gate arrays - Abstract
This paper studies the acceleration of numerical simulations executed on Field-Programmable Gate Arrays (FPGAs) for electric machines presented by voltage-behind-reactance (VBR) models. In VBR models, the stator dynamics are modeled in abc coordinates, while the rotor dynamics are formulated in qd reference frame. Both induction motors and synchronous generators, operating without and with magnetic saturation, are considered. Once VBR models of these machine types are reviewed, their dynamic models are discretized using Runge-Kutta numerical routines. The detailed mapping of such discrete models to FPGA is provided using High-Level Synthesis, which directly converts untimed descriptions into VHDL or Verilog. An automated method finds the fastest FPGA architecture by finding the best set of synthesis options. Experimental results show that our FPGA-based acceleration flow leads to about 92-168 times average simulation speed-up for various machine types compared to the MATLAB simulation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
7. Model Validation of PWM DC–DC Converters.
- Author
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Beg, Omar Ali, Abbas, Houssam, Johnson, Taylor T., and Davoudi, Ali
- Subjects
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CASCADE converters , *ELECTRIC current converters , *ROTARY converters , *PULSE width modulation transformers , *ELECTRONIC modulation - Abstract
This paper presents hybrid automaton modeling, comparative model validation, and formal verification of stability through reachability analysis of pulse width modulation (PWM) dc–dc converters. Conformance degree provides a measure of closeness between the proposed hybrid automata models and experimental data. Nondeterminism due to variations in circuit parameters is modeled using interval matrices. In direct contrast to the unsound and computationally-intensive Monte Carlo simulation, reachability analysis is introduced to overapproximate the set of reachable states and ensure stable operation of PWM dc–dc converters. Using a 200 W experimental prototype of a buck converter, hybrid automata models of open-loop, and hysteresis-controlled converters are first validated against experimental data using their conformance degrees. Next, converter stability is formally verified through reachability analysis and informally validated using Monte Carlo simulations and experimental results. [ABSTRACT FROM PUBLISHER]
- Published
- 2017
- Full Text
- View/download PDF
8. Application of Balanced Realizations for Model-Order Reduction of Dynamic Power System Equivalents.
- Author
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Ramirez, Abner, Mehrizi-Sani, Ali, Hussein, Dalia, Matar, Mahmoud, Abdel-Rahman, Mohamed, Jesus Chavez, J., Davoudi, Ali, and Kamalasadan, Sukumar
- Subjects
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ELECTROMAGNETIC pulses , *ELECTRIC networks , *FREQUENCY-domain analysis , *DYNAMICAL systems , *WIND power plants , *ASYMPTOTIC controllability - Abstract
This paper reviews and applies the balanced realization (BR) theory to obtain reduced-order models from dynamic system equivalents of electric power networks. BR allows obtaining reduced-order models via a process in which the original asymptotic stable system is internally balanced. The balanced system is truncated according to its dominant dynamics. It can be proven that the truncated, that is, reduced-order, system is also stable. This paper applies the BR method to dynamic system equivalents represented as frequency-dependent network equivalents (FDNEs). Furthermore, it shows that an assumed reduced-order FDNE can be further reduced via the BR process. Four case studies, involving one transmission network and three wind power plants, are presented. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
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