8 results on '"Davoudi, Ali"'
Search Results
2. A Multiple-Input Multiple-Output DC–DC Converter.
- Author
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Behjati, Hamid and Davoudi, Ali
- Subjects
- *
DC-to-DC converters , *TOPOLOGY , *ARBITRARY waveform generators , *BUDGET , *SENSITIVITY analysis - Abstract
A multiple-input multiple-output dc–dc converter topology is proposed. This converter is able to accommodate an arbitrary number of sources and loads. The steady-state and dynamic characteristics of the proposed converter are analyzed. A controller scheme is proposed that enables budgeting the input powers coming from different energy sources, in addition to regulating the output voltages. Loss and efficiency modeling and sensitivity analysis to the underlying parameters are performed. Several case studies are presented to verify the analytical models and evaluate the performance of the proposed converter. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
3. 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
4. Topology-Cognizant Optimal Power Flow in Multi-Terminal DC Grids.
- Author
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Altun, Tuncay, Madani, Ramtin, and Davoudi, Ali
- Subjects
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ELECTRICAL load , *TRANSMISSION line matrix methods , *ELECTRIC lines - Abstract
In this paper, we propose a topology-cognizant optimal power flow (OPF) paradigm with additional safety constraints for multi-terminal direct current (MTDC) grids. The resulting formulation is concerned with the optimization of controller set-points, i.e., voltage and power levels at each bus, and the switching status of transmission lines that collectively referred to as grid topology. A pair of additional safety constraints are integrated into the problem formulation to prevent voltage violations caused by power fluctuations in between two controller set-point updates. Searching for a grid topology that offers more efficient operation leads to a mixed-integer nonlinear program (MINLP) which is computationally challenging due to: i) Non-convex power flow equations, (ii) Non-convex converter loss equations, and iii) Binary variables accounting for the operational status of transmission lines. Non-convexities of power flows and converter loss equations are tackled by means of a mixed-integer second-order cone programming (MISOCP) relaxation, while the optimal switching status of transmission lines are determined via a branch-and-bound search. Numerical results for the modified IEEE 14, 30, and 57-bus systems are used to verify the merits of the proposed method. Furthermore, this method is experimentally validated using the CIGRE B4 DC grid benchmark in a real-time hardware-in-the-loop platform. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
5. Dynamic Model Development and Variable Switching-Frequency Control for DCVM Cúk Converters in PFC Applications.
- Author
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Nasirian, Vahidreza, Karimi, Yaser, Davoudi, Ali, Zolghadri, Mohammad Reza, Ahmadian, Mahdi, and Moayedi, Seyedali
- Subjects
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ROTARY converters , *POWER capacitors , *VOLTAGE dependent capacitors , *SWITCHING circuits , *BATTERY chargers , *ELECTRIC motor efficiency - Abstract
A Cúk converter operating in discontinuous capacitor voltage mode (DCVM) is an inherent power factor correction converter. A reduced-order switch-network model of a Cúk converter in DCVM is developed, which is valid for both dc–dc and ac–dc applications. The model can be used for controller analysis and design. Moreover, a fast dynamic response controller is proposed, which is an integration of a switching-frequency control unit and a proportional-integral (PI) controller. The PI controller is in charge of duty ratio adjustment. In the proposed controller, unlike conventional PI controllers, switching frequency is no longer fixed and varies as load changes. The switching-frequency control unit reacts much faster than the PI controller and instantly compensates for the output voltage in case of drastic load change, thus significantly improving the transient response. Furthermore, the proposed control scheme keeps the switch voltage stress constant, which eases switch selection and improves converter reliability. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
6. Output Power Maximization and Optimal Symmetric Freewheeling Excitation for Switched Reluctance Generators.
- Author
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Nasirian, Vahidreza, Kaboli, Shahriyar, and Davoudi, Ali
- Subjects
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MAXIMUM entropy method , *ELECTRONIC excitation , *ELECTRIC generators , *RIPPLES (Fluid dynamics) , *ELECTRIC power - Abstract
Space constraint is a limiting factor for the widespread commercial adaptation of switched reluctance generators (SRGs). Maximizing the output power and minimizing the dc bus filter size are thus highly desired. The output power profiles of a typical SRG are determined by applying various excitation angles. Excitation for maximum output power is obtained while limiting the rms value of the phase currents. The dc bus current of an SRG drive, operating in single pulse mode, is highly distorted by low-frequency ripples. Introducing a freewheeling angle in the excitation pattern can lower the current ripple factor. A novel transform is proposed to establish a relationship between the conventional and the freewheeling excitation patterns. An optimal symmetric freewheeling excitation is accordingly proposed that uses an optimal freewheeling angle and minimizes the ripple factor of the dc bus current while keeping other operational variables intact. Consequently, the output power maximization and current ripple minimization processes are decoupled. This decoupling technique accelerates the overall optimization process. Numerical simulation and hardware measurements verify the proposed methodology. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
7. 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
8. Optimal Reconfiguration of DC Networks.
- Author
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Altun, Tuncay, Madani, Ramtin, Yadav, Ajay Pratap, Nasir, Adnan, and Davoudi, Ali
- Subjects
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NONLINEAR programming , *MATRIX converters , *POINT set theory , *EQUATIONS , *CONES - Abstract
In this paper, we consider the problem of optimizing voltage set points and switching status of components in direct current power networks subject to physical and security constraints. The problem is cast as a mixed-integer nonlinear programming with two sources of computational complexity: i) Non-convex power flow equations, and ii) The presence of binary variables accounting for the on/off status of network components. A strengthened second-order cone programming (SOCP) relaxation is developed to tackle the non-convexity of power flow equations, and a branch-and-bound search is employed for determining optimal network configurations. The efficacy of the proposed method in optimizing the operation while mitigating contingencies is experimentally validated in a real-time hardware-in-the-loop environment using IEEE benchmark data. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
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