12 results on '"Yazdani, Amirnaser"'
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2. A Power Mismatch Elimination Strategy for an MMC-Based Photovoltaic System.
- Author
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Bayat, Hasan and Yazdani, Amirnaser
- Subjects
- *
CONVERTERS (Electronics) , *PHOTOVOLTAIC power generation , *ELECTRIC power distribution grids - Abstract
This paper proposes a power mismatch elimination strategy for a medium-voltage modular multilevel converter (MMC) -based photovoltaic (PV) system. In the MMC-based PV system, each submodule of the MMC is energized by multiple PV generators, each interfaced with the dc port of the submodule by a corresponding isolated dual active bridge dc–dc converter. This configuration allows for a transformerless connection to the host grid and independent maximum power point tracking for the PV generators. The paper then proposes a power mismatch elimination strategy that ensures that the current delivered to the host grid is balanced in spite of unbalanced PV generator outputs. The proposed power mismatch elimination strategy employs a dc differential current to equalize the leg powers, and an ac differential current to stabilize the dc voltages of the submodules. The effectiveness of the proposed power mismatch elimination strategy is demonstrated by time-domain simulations conducted on a model of the PV system in PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
3. Fractional-Order Sliding-Mode Control of Islanded Distributed Energy Resource Systems.
- Author
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Delghavi, Mohammad B., Shoja-Majidabad, Sajjad, and Yazdani, Amirnaser
- Abstract
This paper proposes a voltage control strategy for islanded operation of dispatchable electronically coupled distributed energy resource (DER) systems, for remote (off grid) electrification systems. The proposed control strategy is based on fractional-order sliding-mode control, offers black-start functionality, maintains the quality of the output voltage of the host DER system in spite of unbalanced and/or distorted load currents, and ensures protection of the power-electronic interface to external faults. Moreover, the fractional derivative order of the controller can be used as an additional tuning parameter. Performance of the proposed control strategy is demonstrated through time-domain simulation of single- and multi-DER islanded networks, starting from black-start and subjected to various operating scenario, and it is also compared to the performance of a proportional-integral (PI)-based control strategy. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
4. An analysis of the three-level neutral-point clamped (NPC) inverter with two independent DC sources.
- Author
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Ghoddami, Hamidreza and Yazdani, Amirnaser
- Abstract
In addition to its other merits, the three-level neutral-point clamped (NPC) inverter allows two dc sources, which may be an advantage in photovoltaic systems for enhanced maximum power-point tracking capability and higher energy yield. This paper takes a look at the impact of power mismatch between the two dc sources on the performance of the inverter. The paper develops a mathematical model for the calculation of the inverter mid-point current (and its harmonic components), for three different pulse-width modulation (PWM) strategies. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
5. A bipolar two-stage photovoltaic system based on three-level neutral-point clamped converter.
- Author
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Ghoddami, Hamidreza and Yazdani, Amirnaser
- Abstract
This paper proposes a two-stage photovoltaic (PV) system for large-scale grid-connected applications. The proposed PV system consists of multiple dc-dc boost converters and one large inverter. The inverter is based on the neutral-point clamped (NPC) technology with a grounded dc-link midpoint. This enables a bipolar structure and doubles the net dc voltage, while the 600-V North American standard is respected. The boost converters independently control the dc voltages of their corresponding PV arrays, while their output voltages are regulated by the inverter. Further, they limit the dc-link voltage of the inverter if the power cannot be dispatched to the grid, for example, due to network faults or failure of the inverter. The proposed PV system also offers an enhanced MPPT performance and energy yield, due to its multi-MPPT capability. The NPC technology permits the employment of low-voltage switches for the inverter, despite the doubled net dc voltage. Principles of operation, mathematical model, and control schemes of the proposed PV system are described in the paper. Further, the performance of the proposed PV system is demonstrated through time-domain simulations and study cases that include system startup, normal operation, shading and partial shading scenarios, and various faults. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
6. An Efficient Single-Switch Quasi-Active PFC Converter With Continuous Input Current and Low DC-Bus Voltage Stress.
- Author
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Athab, Hussain S., Dah-Chuan Lu, Dylan, Yazdani, Amirnaser, and Wu, Bin
- Subjects
POWER electronics ,DIRECT currents ,ALTERNATING currents ,ELECTRONIC transformers ,ELECTRIC currents - Abstract
This paper proposes a novel single-switch quasi-active power factor correction (PFC) converter based on two flyback dc/dc modules. To achieve a high efficiency, part of the input power is directly transferred to the load by the first dc/dc module. The rest of the input power is stored in the dc-bus capacitor and reprocessed by the second dc/dc module. Together, the dc-bus capacitor and the second dc/dc module also serve as a regenerative snubber. Furthermore, a quasi-active PFC circuit is provided to improve the power factor and to ensure the continuous current mode (CCM) operation of the input inductor without the need for sophisticated feedforward sensing and control mechanism. The quasi-active PFC circuit is driven by a magnetic switch, through the tertiary winding of the transformer of the first flyback module. The input current harmonics of the proposed converter meet the IEC 61000-3-2 (Classes A, C, and D) requirements. The dc-bus capacitor voltage is always less than the input voltage regardless of the load condition and is fairly invariant to large variations of the input voltages. High power factor with CCM operation and fast output voltage regulation have been achieved through a single-loop controller. Operating principles, analysis, and experimental results are presented to verify the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
7. A Single-Stage Three-Phase Photovoltaic System With Enhanced Maximum Power Point Tracking Capability and Increased Power Rating.
- Author
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Ghoddami, Hamidreza and Yazdani, Amirnaser
- Subjects
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PHOTOVOLTAIC power systems , *ELECTRIC power systems , *MATHEMATICAL models , *POLYPHASE currents , *SYSTEM integration , *TIME-domain analysis , *VOLTAGE regulators , *POWER electronics - Abstract
This paper proposes a single-stage three-phase photovoltaic (PV) system that features enhanced maximum power point tracking capability, and an improved energy yield under partial shading conditions. Further, the proposed PV system can effectively double the maximum permissible dc voltage of a grounded conventional single-stage PV system, with no need for insulators, fuses, disconnects, and switchgear of a higher voltage class, with respect to safety/insulation standards or common system integration practices exercised for conventional grounded single-stage PV systems. The proposed PV system is realized through the parallel connection of an auxiliary half-bridge converter to the dc link of a conventional single-stage PV system and, therefore, is also an option for retrofit applications. This paper presents the mathematical model, principles of operation, and the control loops of the proposed single-stage PV system. The performance of the proposed single-stage PV system is demonstrated by time-domain simulation studies conducted on a detailed switched model in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
8. Multimode Control of a DFIG-Based Wind-Power Unit for Remote Applications.
- Author
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Bhuiyan, Faruk A. and Yazdani, Amirnaser
- Subjects
- *
WIND power , *POWER resources , *ENERGY storage , *COMPUTER software , *CONTROL boards (Electrical engineering) - Abstract
This paper proposes a multimode control strategy for a doubly fed induction generator-based wind-power unit, which enables operation in the islanded (autonomous) mode as well as the grid-connected mode. The configuration can be an option for electricity generation in remote communities with favorable wind conditions, but limited or unreliable connection to the grid. In the grid-connected mode, the proposed control enables the wind power unit to operate with or without battery energy storage, as desired. In case that the wind-power unit is augmented with battery energy storage, in the islanded mode, the proposed control strategy enables voltage and frequency regulation for the network, and parallel operation with constant-speed wind-power units, induction motor loads, and passive loads. The proposed control strategy employs a unified controller for all of the foregoing modes of operation and, therefore, relieves the need for switching between different controllers or reconfiguration of the hardware. The effectiveness and robustness of the proposed control strategy are demonstrated for faulted as well as normal operating conditions through simulation studies carried out on a detailed switched model of the system in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
9. A Control Methodology and Characterization of Dynamics for a Photovoltaic (PV) System Interfaced With a Distribution Network.
- Author
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Yazdani, Amirnaser and Dash, Prajna Paramita
- Subjects
- *
PHOTOVOLTAIC power systems , *ELECTRIC power distribution , *HIGH voltages , *ELECTRICAL load , *ELECTRIC controllers , *VOLTAGE regulators - Abstract
This paper proposes a control strategy for a single-stage, three-phase, photovoltaic (PV) system that is connected to a distribution network. The control is based on an inner current-control loop and an outer dc-link voltage regulator. The current-control mechanism decouples the PV system dynamics from those of the network and the loads. The dc-link voltage-control scheme enables control and maximization of the real power output. Proper feedforward actions are proposed for the current-control loop to make its dynamics independent of those of the rest of the system. Further, a feedforward compensation mechanism is proposed for the dc-link voltage-control loop, to make the PV system dynamics immune to the PV array nonlinear characteristic. This, in turn, permits the design and optimization of the PV system controllers for a wide range of operating conditions. A modal/sensitivity analysis is also conducted on a linearized model of the overall system, to characterize dynamic properties of the system, to evaluate robustness of the controllers, and to identify the nature of interactions between the PV system and the network/loads. The results of the modal analysis confirm that under the proposed control strategy, dynamics of the PV system are decoupled from those of the distribution network and, therefore, the PV system does not destabilize the distribution network. It is also shown that the PV system dynamics are not influenced by those of the network (i.e., the PV system maintains its stability and dynamic properties despite major variations in the line length, line X/R ratio, load type, and load distance from the PV system). [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
10. Modeling and Stability Analysis of a DFIG-Based Wind-Power Generator Interfaced With a Series-Compensated Line.
- Author
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Ostadi, Amir, Yazdani, Amirnaser, and Varma, Rajiv K.
- Subjects
- *
ELECTRIC controllers , *ELECTRIC lines , *EIGENVALUES , *MATHEMATICAL models , *ELECTRIC oscillators , *ELECTRIC generators , *MATHEMATICAL statistics - Abstract
This paper deals with modeling and stability analysis of a doubly-fed induction generator (DFIG)-based wind-power unit that is interfaced with the grid via a series-compensated transmission line. A detailed mathematical model is developed in this paper that takes into account dynamics of the flux observer, phase-locked loop (PLL), controllers of the power-electronic converter, and wind turbine. Using the model and based on eigenvalue/participation-factor analysis, the system and controller parameters that substantially influence the system stability have been identified. The developed model is validated through a comprehensive set of simulation studies in the Matlab/Simulink and PSCAD/EMTDC software environments. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
11. Iterative learning control of dispatchable grid-connected distributed energy resources for compensation of grid current harmonic distortions.
- Author
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Delghavi, Mohammad B., Yazdani, Amirnaser, and Alizadeh, Abdollah
- Subjects
- *
POWER resources , *ITERATIVE learning control , *REACTIVE power control , *ELECTRIC power distribution grids , *POWER electronics - Abstract
• A power regulation scheme is proposed for grid-connected DER units based on ILC. • The proposed control compensates the harmonic distortion of the grid current • The paper presents the mathematical model , as well as the control design methodology. • A MIMO ILC with perfect power tracking and harmonic rejection performance is proposed. This paper proposes a power regulation scheme for dispatchable grid-connected distributed energy resource (DER) units based on the iterative learning control (ILC) strategy. The proposed control provides fast and stable control of the real and reactive powers that the DER unit delivers to the grid. In addition, it compensates the harmonic distortion of the grid current caused by the local nonlinear loads and delivers a high quality power to the grid. To this end, the paper presents the mathematical model on which the proposed control is based, as well as the control design methodology. A new MIMO iterative learning control with perfect power tracking and harmonic rejection performance as well as minor measurement requirements is proposed. The performance of the proposed ILC strategy is demonstrated through time-domain simulation of a grid-connected DER unit under various operating scenarios, and it is compared with the performance of the conventional control based on the instantaneous power theory (IPT). [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
12. An integrated wind-photovoltaic-battery system with reduced power-electronic interface and fast control for grid-tied and off-grid applications
- Author
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Ghoddami, Hamidreza, Delghavi, Mohammad B., and Yazdani, Amirnaser
- Subjects
- *
PHOTOVOLTAIC power systems , *POWER electronics , *ELECTRON tube grids , *PROCESS control systems , *CASCADE converters , *MECHANICAL loads , *ELECTRIFICATION , *SIMULATION methods & models - Abstract
Abstract: This paper proposes an integrated wind-photovoltaic-battery hybrid system that features a simple power management strategy, requires a lower number of power-electronic converters, and eliminates the need for dump loads. Thus, it is expected to offer a lower cost and higher efficiency, and to enable easier integration with distribution networks, as compared with a set of three stand-alone system. The power management strategy of the proposed hybrid system enables (1) rapid control of the wind and photovoltaic (PV) power outputs for tightly regulating the battery current, (2) off-grid operation with black-start capability, (3) grid-connected operation, and (4) safe transition from the grid-connected mode to the off-grid mode, and vice versa, without a need for communications with the host grid. Further, the proposed hybrid system is expected to have plug-and-play and power sharing capabilities and, therefore, suited for multi-generator remote electrification systems. The effectiveness of the proposed hybrid system is demonstrated through time-domain simulation studies in the PSCAD/EMTDC software environment. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
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