99 results on '"Yazdani, Amirnaser"'
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2. 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
- Published
- 2021
- Full Text
- View/download PDF
3. An effective hybrid wind-photovoltaic system including battery energy storage with reducing control loops and omitting PV converter
- Author
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Najafi-Shad, Sajad, Barakati, S. Masoud, and Yazdani, Amirnaser
- Published
- 2020
- Full Text
- View/download PDF
4. A simple passive voltage-balancing scheme for three-phase induction generators interfaced with single-phase grids in micro hydroelectric systems
- Author
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Delghavi, Mohammad B. and Yazdani, Amirnaser
- Published
- 2016
- Full Text
- View/download PDF
5. A communication-based strategy for protection of microgrids with looped configuration
- Author
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Zamani, M. Amin, Sidhu, Tarlochan S., and Yazdani, Amirnaser
- Published
- 2013
- Full Text
- View/download PDF
6. Multimode control of a DFIG-based wind-power unit for remote applications
- Author
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Bhuiyan, Faruk A. and Yazdani, Amirnaser
- Subjects
Induction electric motors -- Design and construction ,Electric generators -- Design and construction ,Wind power -- Research ,Remote control -- Technology application ,Technology application ,Business ,Computers ,Electronics ,Electronics and electrical industries - Published
- 2009
7. 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
Eigenvalues -- Measurement ,Photovoltaic power generation -- Equipment and supplies ,Feedforward control systems -- Design and construction ,Electric current converters -- Design and construction ,Electric current converter ,Business ,Computers ,Electronics ,Electronics and electrical industries - 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). Index Terms--Control, eigenvalue analysis, feedforward, modal analysis, participation factor, photovoltaic (PV), power electronics, voltage-source converter (VSC).
- Published
- 2009
8. 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 generators -- Design and construction ,Induction electric motors -- Design and construction ,Eigenvalues -- Measurement ,Wind power -- Research ,Signal processing -- Methods ,Digital signal processor ,Business ,Computers ,Electronics ,Electronics and electrical industries - 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. Index Terms--Control, doubly-fed induction generator (DFIG), eigenvalue analysis, participation factor, power electronics, series compensation, small-signal analysis, wind power.
- Published
- 2009
9. Negative-sequence current injection for fast islanding detection of a distributed resource unit
- Author
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Karimi, Houshang, Yazdani, Amirnaser, and Iravani, Reza
- Subjects
Electric current converters -- Design and construction ,Voltage -- Measurement ,Phase-locked loops -- Design and construction ,Electric current converter ,Business ,Electronics ,Electronics and electrical industries - Abstract
This paper presents an active islanding detection method for a distributed resource (DR) unit which is coupled to a utility grid through a three-phase voltage-sourced converter (VSC). The method is based on injecting a negative-sequence current through the VSC controller and detecting and quantifying the corresponding negative-sequence voltage at the point of common coupling of the VSC by means of a unified three-phase signal processor (UTSP). UTSP is an enhanced phase-locked loop system which provides high degree of immunity to noise, and thus enable islanding detection based on injecting a small (< 3%) negative-sequence current. The negative-sequence current is injected by a negative-sequence controller which is adopted as the complementary of the conventional VSC current controller. Based on simulation studies in the PSCAD/EMTDC environment, performance of the islanding detection method under UL1741 anti-islanding test is evaluated, and its sensitivity to noise, grid short-circuit ratio, grid voltage imbalance, and deviations in the UL1741 test parameters are presented. The studies show that based on negative-sequence current injection of about 2% to 3%, islanding can be detected within 60 ms even for the worst case scenario. Index Terms--Distributed resource (DR), islanding detection, UL1741 test.
- Published
- 2008
10. A unified dynamic model and control for the voltage-sourced converter under unbalanced grid conditions
- Author
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Yazdani, Amirnaser and Iravani, Reza
- Subjects
Electric power distribution -- Research ,Electric current converters -- Research ,Electric current converter ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper introduces and develops i) a novel unified dynamic model, and ii) new control schemes for a grid-connected static energy conversion system that is based on the voltage-sourced converter (VSC) configuration. The model and the controls are applicable to both the conventional two-level and the three-level neutral point diode clamped (NPC) VSCs. The model is unified since it represents the dynamic behavior of the VSC with respect to both positive- and negative-sequence components, due to unbalanced grid conditions and disturbances. To develop the unified model, the concepts of 'generalized sinusoidal pulse-width modulation (SPWM)' and 'VSC sequence subsystems' are presented. Based on the negative-sequence subsystem control, a new control strategy, to either balance the ac line currents or to mitigate dc-bus voltage ripples, is introduced. Application of the developed model and the controls to a variable-speed wind-power unit is presented in the paper. Index Terms--Instantaneous symmetrical components, neutral point diode clamped (NPC) converter, sequence subsystems, unbalanced operation, voltage-sourced converter (VSC), wind power.
- Published
- 2006
11. A neutral-point clamped converter system for direct-drive variable-speed wind power unit
- Author
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Yazdani, Amirnaser and Iravani, Reza
- Subjects
Electric current converters -- Research ,Wind power -- Research ,Electric current converter ,Business ,Electronics ,Electronics and electrical industries - Abstract
Recent and ongoing developments in wind turbine technology indicate a trend towards utilization of high capacity (e.g., up to 5 MW) wind power units in large wind farms. Higher capacity of the wind turbine necessitates operation of the corresponding electric machine and the static converter system at higher voltages. This paper presents a neutral point diode clamped (NPC) converter system that inherently accommodates higher voltage and power ratings of a high capacity wind power unit. The overall control strategy of an NPC-based wind power unit and the details of the ac side and the dc side controls of the NPC converter system are also described. The generator-side NPC converter provides torque-speed control of the turbine-generator unit. The network-side NPC converter controls real and reactive power flow to the network and thus regulates the dc bus voltage and the ac side power-factor (or voltage) respectively. The paper also presents a new control approach to balance the dc capacitor voltages. The NPC converter system is augmented with a dc chopper that controls the synchronous generator field current. The NPC-based converter system is used to interface a 3 MW, direct-drive (gearless), synchronous machine based wind power unit to the utility grid. Performance of the overall NPC-based wind power unit, under the proposed controls, is evaluated based on time domain simulations in the power systems computer aided design (PSCAD) electromagnetic transient for DC (EMTDC) environment. Index Terms--Current control, dc-side voltage balancer, electromagnetic transients, neutral-point diode clamped (NPC) converter, variable-speed wind-power system.
- Published
- 2006
12. Dynamic model and control of the NPC-based Back-to-Back HVDC system
- Author
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Yazdani, Amirnaser and Iravani, Reza
- Subjects
Electric current converters -- Analysis ,Electric currents -- Analysis ,Electric current regulators -- Usage ,Voltage regulators -- Usage ,Electric current converter ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper presents a comprehensive model of the Back-to-Back (BtB) HVDC system based on the three-level Neutral-Point Diode Clamped (NPC) converter. Based on the developed model, a systematic design procedure for i) the ac-side controllers, ii) the voltage balancer of the dc-side capacitors, and iii) the net dc-bus voltage controller, are presented. The model is developed based on the generalized state-space averaging method and the principle of power balance. The developed model precisely describes the system dynamics if the ac grids are strongly or moderately stiff, and offers acceptable precision otherwise. The averaged nature of the model inherently renders itself for analysis in the SIMULINK/MATLAB environment, and thus provides a computationally efficient tool for the design and the performance evaluation of the control. The accuracy of the developed model and the controls are validated by comparing the results from MATLAB/SIMULINK with those obtained from the exact switching model of the system, based on digital time-domain simulation studies, using the PSCAD/EMTDC software package. Index Terms--Back-to-Back HVDC system, current control, generalized state-space averaging, multilevel converter, Neutral Point Diode Clamped (NPC) converter.
- Published
- 2006
13. An accurate model for the dc-side voltage control of the neutral point diode clamped converter
- Author
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Yazdani, Amirnaser and Iravani, Reza
- Subjects
Electric current converters -- Design and construction ,Electric controllers -- Design and construction ,Electric current converter ,Power controller ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
This paper presents an in depth analysis to show that the conventional power balance model for the dc-side control of the Neutral Point Diode Clamped (NPC) converter is not adequately accurate for all operating conditions. The inaccuracy is due to the fact that the instantaneous power of the ac-side inductors is assumed to be negligible in the power balance equation. This paper shows that this assumption obscures (i) the impact of operating point which is a direct consequence of the inherent nonlinear nature of the problem and (ii) the nonminimum-phase property of the plant in the rectifying mode of operation. Thus, the conventional dc-side control model may lead to unsatisfactory performance or even instability. To overcome the shortcoming, this paper also develops accurate nonlinear and linearized models for the dc-side controller design, including the impact of the ac-side interface reactors. The analytical results and the conclusions are validated by digital time-domain simulation of a study system in the PSCAD/EMTDC environment. The mathematical developments and conclusions of the paper are equally applicable to the conventional two-level VSC. Index Terms--Generalized state-space averaging, multilevel converter, neutral point diode clamped (NPC) converter, nonminimum-phase plant, power balance.
- Published
- 2006
14. A generalized state-space averaged model of the three-level NPC converter for systematic DC-voltage-balancer and current-controller design
- Author
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Yazdani, Amirnaser and Iravani, Reza
- Subjects
Electric current converters ,Electric current converter ,Business ,Computers ,Electronics ,Electronics and electrical industries - Abstract
A comprehensive dynamic model of the three-level Neutral Point Diode Clamped (NPC) converter, based on the generalized state-space averaging method, is presented. The developed model mathematically describes (i) the reason for and (ii) the impacts of the system parameter tolerances on the drift/imbalance of the DC-side capacitor voltages. Then, based on the developed model (i) a novel controller to prevent DC capacitor voltage drift/imbalance and (ii) a decoupled current controller in the dq-frame are designed. The paper also presents a feed-forward control to eliminate the coupling between the voltage balancer and the current controller. The accuracy of developed NPC converter model and the effectiveness of the proposed controls are verified by time-domain simulations of a study system in the PSCAD/EMTDC environment. Index Terms--Generalized averaging method, multi-level converter, neutral point voltage control, unipolar PWM.
- Published
- 2005
15. Modeling and Current-Mode Control of a DC–DC Modular Multilevel Converter.
- Author
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Kaler, Sandeep and Yazdani, Amirnaser
- Subjects
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CASCADE converters , *DC-to-DC converters , *DYNAMIC models , *VOLTAGE control , *INTEGRATING circuits , *INTEGRATED circuits - Abstract
This article presents a dynamic model and a current-mode control for a dc–dc modular multilevel converter with the ultimate aim of expanding the converter to a three-leg configuration to reduce the filtering requirements of the dc ports. A complete model of the converter including a systematic approach for the control of the power throughput is developed. It is then shown that the expansion from a single-leg to three-leg configuration requires no additional modeling, and that the three-leg converter significantly alleviates the filtering requirements on both the high-voltage and low-voltage sides. The proposed model and control technique are verified using simulation results based on the MATLAB / Simulink software environment for both the single and three-leg configuration. Further verification is carried out through a single-leg 1-kW experimental prototype. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
16. Decentralized Model-Based Predictive Control for DER Units Integration in AC Microgrids Subject to Operational and Safety Constraints.
- Author
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Perez-Ibacache, Ricardo, Cedeno, Angel L., Silva, Cesar A., Carvajal, Gonzalo, Aguero, Juan C., and Yazdani, Amirnaser
- Subjects
POWER resources ,REACTIVE power ,CONSTRAINED optimization ,VOLTAGE control ,MICROGRIDS ,VOLTAGE - Abstract
The dynamic performance of a microgrid is governed by the decentralized primary control strategy that is embedded in each of its hosted Distributed Energy Resource (DER) units. The primary control computes the voltage synthesized by the interfacing voltage-sourced converter such that the DER unit contributes active and reactive powers in support of the microgrid voltage amplitude and frequency. These operational requirements must be satisfied with respect to the converter safety and physical limitations, such as the limited magnitude of the converter output current and terminal voltage. In this paper, all the control requirements mentioned above are taken into account in a single constrained optimization problem using the framework of Model-based Predictive Control (MPC). Solving the primary control problem in this way allows the microgrid to respond to major disturbances such short-circuit faults and transitions between modes of operation, while the electronically-interfaced DER units operate within operational and safety limits. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
17. Adjustable Wind Farm Frequency Support Through Multi-Terminal HVDC Grids.
- Author
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Mehrabankhomartash, Mahmoud, Saeedifard, Maryam, and Yazdani, Amirnaser
- Abstract
In the future power systems, a large number of offshore wind farms will be connected to the AC grids through high voltage DC (HVDC) and multi-terminal DC (MTDC) grids. As wind power penetration level increases, complex grid codes and regulations will be imposed on wind turbines for frequency support. To follow any grid code and requirement for frequency support, two important features should be included in the wind turbine frequency support: i) It should be able to adjust the maximum additional power that the wind turbine temporarily provides for frequency support; ii) It should be capable of adjusting the time interval in which the wind turbine provides additional temporary power. The first feature is mainly important for reducing rate of change of frequency (RoCoF) and improving the frequency nadir while the second one is mainly important for fast frequency recovery from its nadir and improving the second frequency drop. This paper indicates that the conventional method cannot offer both of the two aforementioned features. To address this issue, two approaches are proposed for frequency support by wind turbines. The first one uses P-ω
r and P-ƒWF droops in each wind turbine controller, where P, ωr , and ƒWF represent the wind turbine power, rotor speed, and wind farm frequency. The second method employs P-ωr and P-ƒWF droops in each wind turbine controller. Performance and effectiveness of the proposed methods are evaluated by time-domain simulation studies on an MTDC grid in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]- Published
- 2021
- Full Text
- View/download PDF
18. Linear State-Feedback Primary Control for Enhanced Dynamic Response of AC Microgrids.
- Author
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Perez-Ibacache, Ricardo, Silva, Cesar A., and Yazdani, Amirnaser
- Abstract
This paper proposes a state feedback primary control strategy for microgrids with multiple distributed energy resource units, improving their transient behavior in both islanded and grid-connected modes of operation. To that end, the interaction of each distributed energy resource unit within the microgrid is modeled as a lumped dynamic system, which results to be nonlinear and multivariable. For the closed-loop control of such multivariable systems, the full state feedback formulation is preferred which requires a suitable state observer. For the design of the observer and feedback gains, the solution of the linear-quadratic estimation and regulation problems is considered. For simplicity, an approximate linear model at a representative operating point is derived. The linear quadratic Gaussian/loop-transfer recovery is adopted as the design procedure to optimize the trajectory of the state variables subject to a desirable actuation effort, in this case of the voltage amplitude and frequency, yielding a solution that is robust to model uncertainties. The effectiveness of the strategy is assessed through time-domain simulation on the CIGRE benchmark medium-voltage distribution network with three distributed energy resource units. These results are compared to those obtained with conventional static droop gains and with a state-of-the-art technique from the literature. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
19. An Enhanced Closed-Loop Control Strategy With Capacitor Voltage Elevation for the DC–DC Modular Multilevel Converter.
- Author
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Yang, Heng, Saeedifard, Maryam, and Yazdani, Amirnaser
- Subjects
CLOSED loop systems ,DC-to-DC converters ,CAPACITORS ,VOLTAGE control ,HIGH-voltage direct current transmission - Abstract
The dc–dc modular multilevel converter (MMC), derived from the ac–dc MMC, is an attractive converter topology for interconnection of medium-/high-voltage dc grids. The dc–dc MMC generates an ac voltage component in each arm to drive an ac circulating current for maintaining the energy balance of its submodule capacitors. The power transfer capability of the dc–dc MMC and the amplitude of the ac circulating current are closely coupled with the available arm ac voltage headroom. As the voltage conversion ratio of the dc–dc MMC deviates from 0.5, the power transfer capability of the converter diminishes. This paper proposes an enhanced closed-loop control strategy, which increases the power transfer capability and at the same time reduces the ac circulating current of the dc–dc MMC. Performance and effectiveness of the proposed control strategy are demonstrated by simulation studies in the MATLAB/Simulink as well as experiments conducted on a laboratory prototype. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
20. Sliding-Mode Control of AC Voltages and Currents of Dispatchable Distributed Energy Resources in Master-Slave-Organized Inverter-Based Microgrids.
- Author
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Delghavi, Mohammad B. and Yazdani, Amirnaser
- Abstract
This paper proposes a current-controlled voltage-mode control scheme for dispatchable electronically coupled distributed energy resource (DER) units based on sliding-mode control (SMC) strategy. The proposed control strategy provides fast and stable control on the terminal voltage and frequency of DER unit and ensures protection of the power-electronic interface to external faults. In addition it maintains the quality of the output voltage of the host DER unit in spite of unbalanced and/or distorted load currents. Performance of the proposed SMC strategy is demonstrated through time-domain simulation of a single islanded DER unit, starting from black-start and subjected to various operating scenarios, and it is compared to the performance of a proportional-integral (PI) based control strategy. Also a current-mode control strategy is proposed for DER units based on SMC. The performance of both voltage- and current-mode control strategies are demonstrated in a sample master-slave organized three-unit microgrid. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
21. 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
22. An Enhanced Steady-State Model and Capacitor Sizing Method for Modular Multilevel Converters for HVdc Applications.
- Author
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Oliveira, Rafael and Yazdani, Amirnaser
- Subjects
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CONVERTERS (Electronics) , *CAPACITORS , *VOLTAGE control , *HIGH-voltage direct current transmission , *ELECTRONIC modulation - Abstract
An analytical steady-state model of the modular multilevel converter (MMC) can be used for component sizing and assessment of the impact of different parameters on the MMC performance. Thus, this paper proposes an enhanced steady-state model for the MMC, which enables one to calculate the amplitudes of the harmonic components of MMC arm currents, submodule capacitor voltages, and arm voltages. In addition, the proposed model allows for the calculation of the amplitude and phase angle of the modulating signal, and it also presents a criterion for resonance of the arm currents. This is achieved by means of a polynomial function of the modulation index, and through checking the stability criteria established by the proposed model. The capability of formulating the modulating signal enables a more accurate calculation of the steady-state amplitudes of the variables, as compared to the previously published models. This paper also presents an accurate method of submodule capacitor sizing, based on the proposed steady-state model. The proposed method gives the exact value of the submodule capacitance (i.e., the capacitance that results in dc voltage fluctuations within a desired range) for a prespecified submodule capacitor voltage variation and a given circulating current amplitude. The stability criterion given by the proposed steady-state model, used for sizing the arm inductance, and the submodule capacitor voltage variation given by the proposed capacitor sizing method, used for sizing the submodule capacitor, allows for the determining of the operating limits of the MMC in terms of its parameters. Extensive simulation results are presented to demonstrate the efficacy of the proposed steady-state model and the capacitor sizing method. Further, the results obtained from the proposed capacitor sizing method are compared with experimental results from the literature. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
23. A Modular Multilevel Converter With DC Fault Handling Capability and Enhanced Efficiency for HVdc System Applications.
- Author
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Oliveira, Rafael and Yazdani, Amirnaser
- Subjects
- *
HIGH-voltage direct current converters , *ELECTRONIC telephone switching systems , *CAPACITORS , *TIME-domain analysis , *FAULT tolerance (Engineering) - Abstract
This paper proposes a modular multilevel converter (MMC) topology for high-voltage dc (HVdc) system applications. The proposed MMC employs two half-bridge converters, a cascade of networks that consist of electronic switches, and multiple capacitors. Thus, charged capacitors are inserted in series with the arm current path, for a desired level of the output ac voltage. The switches that must be turned
on are judiciously selected for the most efficient current path. The proposed MMC also offers dc-side fault handling capability. The paper compares the proposed MMC with the half-bridge submodule-based MMC, full-bridge submodule-based MMC, and clamp-double submodule-based MMC technologies. It is shown that the proposed MMC is more efficient than the three aforementioned MMC technologies, while it offers the same fault handling capability as that of an equivalent full-bridge-based MMC. Time-domain simulation studies confirm the effectiveness of the proposed MMC under various normal and faulted operating scenarios, using detailed as well as reduced models. [ABSTRACT FROM AUTHOR]- Published
- 2017
- Full Text
- View/download PDF
24. Optimal Location and Sizing of Fault Current Limiters in Mesh Networks Using Iterative Mixed Integer Nonlinear Programming.
- Author
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Yu, Peng, Venkatesh, Bala, Yazdani, Amirnaser, and Singh, Birendra N.
- Subjects
FAULT current limiters ,MESH networks ,MIXED integer linear programming ,ELECTRIC impedance ,SHORT circuits - Abstract
In some mature power systems located in densely populated areas, an increase in demand and supply is resulting in very high short-circuit levels that are either too close to or over the safe breaker operating limits. Fault current limiters (FCLs) built with advanced materials and methods are a potent solution in this situation wherein an in-line FCL offers a very low impedance and power loss under normal operating conditions, but a high impedance and hence a lower short-circuit current during faults. From a planning perspective for complex meshed networks where faults are concurrently fed from several sources, it is important to optimally locate and size FCLs, which is a difficult mixed integer nonlinear optimization challenge as commonly used location sensitivity index methods and heuristic search techniques seem inadequate. In this paper, an iterative mixed integer nonlinear optimization method is proposed to optimally locate and size FCLs in a power system by searching the entire solution space such that costs are the least and fault currents are curtailed to levels within breakers' limits, without prior knowledge of the best locations irrespective of the size of the system. The IEEE 9-bus, IEEE 30-bus, and a real North American 395-bus transmission system were chosen to test and demonstrate the proposed method. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
25. 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
26. Design and Transient Operation Assessment of Resonant FCLs in Bulk Power Systems.
- Author
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Alizadeh, Omid, Yazdani, Amirnaser, Venkatesh, Bala, and Singh, Birendra N.
- Subjects
- *
FAULT current limiters , *ELECTRIC power system faults , *ELECTRIC power systems , *ELECTRIC networks , *ELECTRIC transients , *HIGH voltages - Abstract
The increasing capacity of power systems and the continuing growth in interconnections within transmission networks to improve the reliability may cause the short-circuit fault current level of the equipment in the system, including the existing circuit breakers, to exceed their rated capacities. Therefore, the equipment must be either upgraded or replaced, which is costly and requires time-intensive procedures. Fault current-limiting techniques offer benefits to the system in such cases. Using passive elements, such as current-limiting reactors, is a well-known practice in power systems: however, they impact the power flow under normal operation, cause voltage drop, and might reduce the transient stability. Alternatively, resonant fault current limiters (RFCL) offer a dynamic solution based on proven technologies of current-limiting reactors and series capacitors. This paper presents a comprehensive framework to design RFCLs in bulk power systems. The presented approach uses a combination of mathematical analyses and numerical time-domain simulations to design the RFCL elements, and its effectiveness is assessed in test power systems. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
27. Stability Analysis of Vector-Controlled Modular Multilevel Converters in Linear Time-Periodic Framework.
- Author
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Chaudhuri, Nilanjan Ray, Oliveira, Rafael, and Yazdani, Amirnaser
- Subjects
CONVERTERS (Electronics) ,CAPACITORS ,STABILITY theory ,MATHEMATICAL models ,TIME-varying systems ,ELECTRIC power - Abstract
Stability analysis of average value models (AVMs) of vector-controlled modular multilevel converters (MMCs) is the subject matter of this paper. Stability analysis of fundamental frequency phasor-based AVMs of MMCs can be conducted in a traditional linear time-invariant framework through eigenvalue computation. This class of models does not consider circulating current control loop and hence fails to capture system instability that occurs in a certain range of gains of the circulating current controller. We propose stability analysis in a linear time-periodic (LTP) framework to solve this issue. To that end, a nonlinear AVM is presented that considers the submodule capacitor insertion dynamics and takes into account the output and the circulating current control schemes in the vector control approach. Upon linearization, an LTP model is derived from this averaged model. It is shown that the Poincar \acutee multipliers are indicative of system instability corresponding to a certain range of gains of the circulating current controller. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
28. An Energy Management Strategy for a DC Distribution System for Power System Integration of Plug-In Electric Vehicles.
- Author
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Tabari, Mansour and Yazdani, Amirnaser
- Abstract
This paper proposes an energy management strategy (EMS) for a dc distribution system for power system integration of plug-in electric vehicles (PEVs). The dc distribution system is intended to integrate electric vehicles in a parking lot with an ac grid through bidirectional dc–dc converters (battery chargers) and a central voltage-sourced converter. Using an online constrained optimization algorithm, the proposed EMS manages the power flow within the dc system. Thus, the PEV owners can charge or discharge their batteries based on the state-of-charge of the batteries and their upcoming trip plans. The EMS offers two energy exchange options to the PEV owners: 1) the fast energy exchange option for the owners wishing to minimize the energy exchange time; and 2) the optimal energy exchange option for the owners intend to either minimize their costs of charging or maximize their revenues through selling their stored energy. The proposed EMS seamlessly handles all charging/discharging requests from the PEV owners with different options and, at the same time, it takes into account the power demand and power generation limits of the ac grid to preclude under-voltage, over-voltage, and reverse power flow issues. Various energy exchange scenarios are simulated to demonstrate the effectiveness of the proposed EMS. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
- Full Text
- View/download PDF
29. A μ-based approach to small-signal stability analysis of an interconnected distributed energy resource unit and load.
- Author
-
Haddadi, Aboutaleb, Boulet, Benoit, Yazdani, Amirnaser, and Joos, Geza
- Subjects
DISTRIBUTED power generation ,FREQUENCY response ,POWER resources ,ELECTRIC inverters ,ELECTRIC power distribution grids ,ROBUST stability analysis - Abstract
The small-signal stability of an interconnected source and load can be analyzed using the frequency-response methods of stability analysis. Existing frequency-response methods of stability analysis introduce artificial conservativeness and do not explicitly address stability robustness against load perturbations, that is, by how much the load can change such that the system will remain stable in the small-signal sense. This paper presents a frequency-response method of stability analysis which provides a less conservative stability condition compared to existing methods, in the sense of having less restriction on the control system; further, the proposed method establishes a robust stability margin in terms of perturbations in load parameters. The proposed method is based on μ analysis, and models the source-load dynamic interaction via a closed-loop system of impedances and admittances. The proposed method is used to examine small-signal stability of an islanded subnetwork extracted from a university campus microgrid, composed of a distributed energy resource (DER) unit feeding a load, providing a study with realistic parameter values. Two case studies are presented to show the features of the proposed method, namely, reduced conservativeness and the establishment of a robust stability margin. Another example is provided to show the application of the proposed stability analysis method in a multi-DER-unit network. The findings of the frequency-domain analysis are illustrated through time-domain simulations around the operating point on the system under study. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
30. A Mitigation Strategy for Temporary Overvoltages Caused by Grid-Connected Photovoltaic Systems.
- Author
-
Ghoddami, Hamidreza and Yazdani, Amirnaser
- Subjects
- *
OVERVOLTAGE , *PHOTOVOLTAIC power systems , *ELECTRIC generators , *ELECTRONIC circuits , *TIME-domain analysis , *PREVENTION - Abstract
Widespread penetration of distributed generators (DGs) into the power system has aggravated the problem of temporary overvoltages (TOVs), which can inflict substantial damages on the DGs, equipment, and other customers. Through slight modifications to the power-electronic circuit and its control, this paper proposes a strategy for limiting the TOVs caused by single-stage grid-connected photovoltaic (PV) energy systems. This paper also proposes a reduced TOV mitigation strategy for applications where a somewhat less effective, but also less expensive, solution is acceptable. The effectiveness of the proposed TOV mitigation strategy is demonstrated through time-domain simulation studies conducted on a detailed switched model of a study PV system in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
31. A Mathematical Model for Stability Analysis of a DC Distribution System for Power System Integration of Plug-In Electric Vehicles.
- Author
-
Tabari, Mansour and Yazdani, Amirnaser
- Subjects
- *
MATHEMATICAL models , *ROBUST stability analysis , *DIRECT current in electric power distribution , *ELECTRIC power systems research , *ELECTRIC vehicles - Abstract
This paper proposes a systematic method for developing a model of a dc distribution system, based on the configuration of the system. The dc distribution system is assumed to host electric vehicles and photovoltaic modules, using dc–dc converters, and to integrate them with an ac power grid. The developed model is of the matrix form and, therefore, can be readily expanded to represent a dc distribution system of any desired number of dc–dc converters. The model captures both the steady-state and dynamic characteristics of the system and includes port capacitors of the converters, as well as the interconnection cables. Thus, it can be used for identifying the condition for existence of a steady state, as well as for stability analysis. This paper further proposes an alternative set of characteristic equations that are less computationally intensive than the original matrix representation, for example, for online stability assessment tasks. The adequacy of the proposed model has been demonstrated through a number of case studies conducted and compared in the PSCAD/EMTDC and MATLAB software environments. [ABSTRACT FROM PUBLISHER]
- Published
- 2015
- Full Text
- View/download PDF
32. Optimal sizing approach for islanded microgrids.
- Author
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Bhuiyan, Faruk A., Yazdani, Amirnaser, and Primak, Serguei L.
- Abstract
This study proposes a single‐objective optimal sizing approach for an islanded microgrid (IMG). The approach determines the optimal component sizes for the IMG, such that the life‐cycle cost is minimised while a low loss of power supply probability (LPSP) is ensured. As wind speed and solar irradiation exhibit both diurnal and seasonal variations, the proposed algorithm takes advantages of the typical meteorological year‐based chronological simulation and enumeration‐based iterative techniques. The mathematical models presented in this study for the IMG components consider the non‐linear characteristics as well as the reactive power. The LPSP is also formulated based on the supply‐demand balances of both real and reactive powers, and an economic evaluation model is presented. The proposed sizing approach identifies the global minimum, and simultaneously provides the optimal component sizes as well as the power management strategies. This study also presents a number of sensitivity analyses as well as comparisons with a commercial software package. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
33. A Transformerless DC–DC Converter With Large Voltage Ratio for MV DC Grids.
- Author
-
Athab, Hussain, Yazdani, Amirnaser, and Wu, Bin
- Subjects
- *
DIRECT currents , *ELECTRIC potential , *CAPACITORS , *VOLTAGE control , *RESONANCE - Abstract
This paper proposes a transformerless dc–dc converter, which features a large voltage ratio, for medium-voltage dc (MVDC) applications. The proposed converter combines a boost converter with a series-parallel resonant converter which enables soft switching of the power switches and diodes. Further, the power switches and diodes of the proposed converter experience lower voltage stresses compared to the other topologies. The proposed converter is modular and, therefore, permits series and/or parallel connection of multiple units for the desired voltage and/or power ratings. This paper discusses the principles of operation, analysis, and design of the proposed converter. Simulation and experimental results are presented to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
34. A Control Strategy for Power Regulation in a Direct-Drive WECS With Flexible Drive-Train.
- Author
-
Alizadeh, Omid and Yazdani, Amirnaser
- Abstract
The ever-increasing penetration of wind power into the electric power systems indicates the need that wind energy conversion systems (WECSs) should be able to regulate their output real power, since their participation in power-flow control is expected to be essential for power systems stability. On the other hand, the tendency to build larger WECSs at competitive costs encourages lighter and, consequently, more flexible drive-trains. However, a softer drive-train may give rise to undamped drive-train oscillations when the WECS exercises output power regulation. This paper proposes an enhanced control strategy that enables a direct-drive WECS based on the permanent magnet synchronous generator (PMSG) to damp its drive-train torsional mode, even if the output real power of the WECS is regulated. A procedure is presented for tuning of the proposed control to ensure the internal stability of the WECS, considering the impacts of the proposed control on the dynamic performance of the host WECS. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
35. Stability of a dc Distribution System for Power System Integration of Plug-In Hybrid Electric Vehicles.
- Author
-
Tabari, Mansour and Yazdani, Amirnaser
- Abstract
This paper proposes a method for enhancing the stability of a dc distribution system that integrates plug-in hybrid electric vehicles (PHEVs) with an ac power grid. The dc distribution system is interfaced with the host ac grid via a voltage-sourced converter and can also embed photovoltaic (PV) modules. Thus, bidirectional dc–dc electronic power converters act as battery chargers and interface the PHEVs with the dc distribution system, while PV modules are interfaced with the dc distribution system via unidirectional dc–dc converters. The dc distribution system is expected to be more efficient and economical than a system of ac–dc battery chargers directly interfaced with an ac grid, but it is prone to instabilities due to the constant-power property of the dc–dc converters. Using a nonlinear control strategy, the proposed stability enhancement method mitigates the issue of instability by altering the power setpoints of the battery chargers, bidirectional dc–dc converters, without a need for changing system parameters or hardware. The paper presents mathematical models for the original and modified systems and demonstrates that the proposed technique expands the stable operating region of the dc distribution system. Simulation results demonstrate the effectiveness of the proposed method for a study system in the PSCAD/EMTDC software environment. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
36. A Gain-Scheduled Decoupling Control Strategy for Enhanced Transient Performance and Stability of an Islanded Active Distribution Network.
- Author
-
Haddadi, Aboutaleb, Yazdani, Amirnaser, Joos, Geza, and Boulet, Benoit
- Subjects
- *
MATHEMATICAL decoupling , *ELECTRIC networks , *POWER resources , *VOLTAGE references , *VOLTAGE control , *EIGENVALUES - Abstract
This paper proposes a control strategy to enhance transient performance and stability of a droop-controlled active distribution network. The dependency of dynamics on the droop gains, steady-state power flow, and network/load is studied in a droop-controlled distributed energy resource (DER) unit. These dependencies result in poor transient performance or even instability of the network in the event of a disturbance in the system. To eliminate these dependencies, a gain-scheduled decoupling control strategy is proposed which reshapes the characteristics of conventional droop by means of supplementary control signals; these control signals are based on local power measurements and supplement the d- and q-axis voltage reference of each DER unit. The impact of the proposed control on the DER and network dynamics is studied by calculating the eigenvalues of a test active distribution system assuming proposed control. The proposed control is shown to stabilize the system for a range of operating conditions. The effectiveness of the proposed control is further demonstrated through simulations carried out in the PSCAD/EMTDC software environment, on the active distribution system under study. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
37. Investigations Into the Control and Protection of an Existing Distribution Network to Operate as a Microgrid: A Case Study.
- Author
-
Zamani, M. Amin, Sidhu, Tarlochan S., and Yazdani, Amirnaser
- Subjects
COUPLED transmission lines ,FAULT currents ,GRID computing ,SIMULATION methods & models ,CONTROL theory (Engineering) - Abstract
With the increasing attention to the concept of microgrids, it has become important to identify the requirements that enable an electric distribution network to operate as a microgrid. This paper studies a realistic distribution network to accomplish the following: 1) determine the conditions under which the network can operate as a microgrid and 2) present the control scenarios that allow the islanded operation of the network. In particular, the employment of electronically coupled distributed energy resources with the fault-ride-through and synchronization capabilities is investigated. Another objective of this paper is to propose practical protection strategies that are effective in both operational modes of a microgrid (i.e., the grid-connected mode and the islanded mode), considering the system constraints; the protection strategies provide the microgrid with acceptable reliability against different fault scenarios. The effectiveness of the control and protection strategies is demonstrated and discussed through a comprehensive set of simulation studies conducted in the PSCAD/EMTDC software environment. [ABSTRACT FROM PUBLISHER]
- Published
- 2014
- Full Text
- View/download PDF
38. An Efficient Single-Switch Quasi-Active PFC Converter With Continuous Input Current and Low DC-Bus Voltage Stress.
- Author
-
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
39. A Strategy for Real Power Control in a Direct-Drive PMSG-Based Wind Energy Conversion System.
- Author
-
Alizadeh, Omid and Yazdani, Amirnaser
- Subjects
- *
WIND energy conversion systems , *WIND power , *MAXIMUM power point trackers , *PERMANENT magnets , *MATHEMATICAL analysis - Abstract
As the penetration of wind energy into the power system continues to grow, wind energy conversion systems (WECSs) are increasingly expected to be able to control their output real power, while retaining their maximum power-point tracking (MPPT) capability. This paper proposes a simple real power control strategy, which augments the MPPT feature of modern WECSs, and is based on rapid torque control as opposed to the traditional pitch-angle control. This paper presents the implementation of the proposed control strategy for a direct-drive WECS that employs the permanent-magnet synchronous generator, even though the proposed method can also be extended to other classes of electronically interfaced WECSs. The paper also presents a parameter-tuning procedure for the proposed control strategy. The effectiveness of the proposed control strategy is demonstrated through mathematical analysis and time-domain simulation studies. [ABSTRACT FROM PUBLISHER]
- Published
- 2013
- Full Text
- View/download PDF
40. A Communication-Assisted Protection Strategy for Inverter-Based Medium-Voltage Microgrids.
- Author
-
Zamani, M. Amin, Yazdani, Amirnaser, and Sidhu, Tarlochan S.
- Abstract
This paper proposes a communication-assisted protection strategy implementable by commercially available microprocessor-based relays for the protection of medium-voltage microgrids. Even though the developed protection strategy benefits from communications, it offers a backup protection strategy to manage communication network failures. The paper also introduces the structure of a relay that enables the proposed protection strategy. Comprehensive simulation studies are carried out to verify the effectiveness of the proposed protection strategy under different fault scenarios, in the PSCAD/EMTDC software environment. [ABSTRACT FROM PUBLISHER]
- Published
- 2012
- Full Text
- View/download PDF
41. An Adaptive Feedforward Compensation for Stability Enhancement in Droop-Controlled Inverter-Based Microgrids.
- Author
-
Delghavi, Mohammad B. and Yazdani, Amirnaser
- Subjects
- *
FEEDFORWARD control systems , *DISTRIBUTED power generation , *STABILITY (Mechanics) , *ROBUST control , *ARTIFICIAL neural networks , *LEAST squares , *DISCRETE-time systems - Abstract
This paper proposes an adaptive feedforward compensation that alters the dynamic coupling between a distributed-resource unit and the host microgrid, so that the robustness of the system stability to droop coefficients and network dynamic uncertainties is enhanced. The proposed feedforward strategy preserves the steady-state effect that the conventional droop mechanism exhibits and, therefore, does not compromise the steady-state power sharing regime of the microgrid or the voltage/frequency regulation. The feedforward compensation is adaptive as it is modified periodically according to the system steady-state operating point which, in turn, is estimated through an online recursive least-square estimation technique. This paper presents a discrete-time mathematical model and analytical framework for the proposed feedforward compensation. The effectiveness of the proposed control is demonstrated through time-domain simulation studies, in the PSCAD/EMTDC software environment, conducted on a detailed switched model of a sample two-unit microgrid. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
42. A Protection Strategy and Microprocessor-Based Relay for Low-Voltage Microgrids.
- Author
-
Zamani, M. Amin, Sidhu, Tarlochan S., and Yazdani, Amirnaser
- Subjects
MICROPROCESSORS ,ELECTRIC relays ,ELECTRIC power system protection ,ELECTRIC fuses ,ELECTRIC fault location ,ELECTRIC breakdown ,DISTRIBUTED power generation ,ELECTRIC current grounding - Abstract
One of the major challenges associated with microgrid protection is to devise an appropriate protection strategy that is effective in the grid-connected as well as islanded mode of operation. This paper proposes a protection strategy based on microprocessor-based relays for low-voltage microgrids. Further, the structure of a new relay enabling the proposed protection strategy is presented. One of the salient feature of the developed protection scheme is that it does not require communications or adaptive protective devices. Moreover, it is to a large extent independent of the fault current magnitude and the mode of operation. Transient time-domain simulation studies are conducted to demonstrate the effectiveness of the proposed protection strategy and its enabling relay, using the PSCAD/EMTDC software package. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
43. Modeling Guidelines and a Benchmark for Power System Simulation Studies of Three-Phase Single-Stage Photovoltaic Systems.
- Author
-
Yazdani, Amirnaser, Di Fazio, Anna Rita, Ghoddami, Hamidreza, Russo, Mario, Kazerani, Mehrdad, Jatskevich, Juri, Strunz, Kai, Leva, Sonia, and Martinez, Juan A.
- Subjects
- *
PHOTOVOLTAIC power systems , *COMPUTER simulation , *ELECTRIC machinery -- Polyphase , *ELECTRIC power systems , *MATHEMATICAL models , *ELECTRIC current converters , *INTEGRATED circuits , *ELECTRIC networks - Abstract
This paper presents modeling guidelines and a benchmark system for power system simulation studies of grid-connected, three-phase, single-stage Photovoltaic (PV) systems that employ a voltage-sourced converter (VSC) as the power processor. The objective of this work is to introduce the main components, operation/protection modes, and control layers/schemes of medium- and high-power PV systems, to assist power engineers in developing circuit-based simulation models for impact assessment studies, analysis, and identification of potential issues with respect to the grid integration of PV systems. Parameter selection, control tuning, and design guidelines are also briefly discussed. The usefulness of the benchmark system is demonstrated through a fairly comprehensive set of test cases, conducted in the PSCAD/EMTDC software environment. However, the models and techniques presented in this paper are independent of any specific circuit simulation software package. Also, they may not fully conform to the methods exercised by all manufacturers, due to the proprietary nature of the industry. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
44. A Single-Stage Three-Phase Photovoltaic System With Enhanced Maximum Power Point Tracking Capability and Increased Power Rating.
- Author
-
Ghoddami, Hamidreza and Yazdani, Amirnaser
- Subjects
- *
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
45. Islanded-Mode Control of Electronically Coupled Distributed-Resource Units Under Unbalanced and Nonlinear Load Conditions.
- Author
-
Delghavi, Mohammad B. and Yazdani, Amirnaser
- Subjects
- *
DISTRIBUTED power generation , *ELECTRICAL load , *ELECTRIC power systems , *MATHEMATICAL models , *ELECTRIC networks , *TIME-domain analysis , *CONTROL theory (Engineering) , *DISTRIBUTED resources (Electric utilities) - Abstract
This paper proposes a voltage- and frequency-control strategy for the islanded operation of dispatchable electronically coupled distributed-resource units, based on a discrete-time mathematical model which is also valid for variable-frequency operation. The proposed control strategy utilizes a combination of deadbeat and repetitive control to enhance the performance of the control system under unbalanced and/or distorted load currents. Moreover, a new approach is proposed to maintain the effectiveness of the repetitive control under variable-frequency operational scenarios. Furthermore, the control strategy employs feedforward compensation techniques to mitigate the impact of load dynamics on the regulation process. The performance of the proposed control strategy is demonstrated for single- and multiunit islanded networks, through digital time-domain simulation studies in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
46. Robust Control of an Autonomous Four-Wire Electronically-Coupled Distributed Generation Unit.
- Author
-
Karimi, Houshang, Yazdani, Amirnaser, and Iravani, Reza
- Subjects
- *
ROBUST control , *DISTRIBUTED power generation , *ELECTRIC potential , *TRANSFER functions , *ELECTRIC power system control , *CASCADE converters , *FEEDBACK control systems - Abstract
This paper proposes a control strategy for the autonomous (islanded) operation of a four-wire, electronically-coupled distributed generation (DG) unit which can feed a highly unbalanced load, e.g., due to the presence of single-phase loads. In the grid-connected mode, the power-electronic interface of the DG unit enables the exchange of real and reactive power with the distribution network, based on the conventional dq-frame current control strategy. The current control scheme is disabled subsequent to the detection of an islanding event, and the proposed controller is activated. The proposed control strategy utilizes: i) an internal oscillator to maintain the island frequency and ii) a feedback control system to regulate the island voltage. The proposed control strategy provides a set of balanced three-phase voltages for the load, despite the load imbalance and parameters uncertainties. The proposed control strategy also guarantees robust stability, fast dynamic response to disturbances, and zero steady-state error. A stability analysis is also carried out to determine the robust stability margin of the closed-loop islanded system. Effectiveness of the proposed control strategy is evaluated based on time-domain simulation studies in the PSCAD/EMTDC software environment and verified based on laboratory experiments. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
47. Investigation of the Local Passive Anti-Islanding Scheme in a Distribution System Embedding a PMSG-Based Wind Farm.
- Author
-
El-Khattam, Walid, Yazdani, Amirnaser, Sidhu, Tarlochan S., and Seethapathy, Ravi
- Subjects
- *
PASSIVE electric networks , *ELECTRIC power distribution , *WIND power plants , *ELECTRIC relays , *MATHEMATICAL models , *DETECTION of electric discharges , *SYNCHRONOUS generators - Abstract
This paper evaluates the effectiveness of different commercial relay functions in a local passive anti-islanding process for a permanent-magnet synchronous generator (PMSG)-based wind farm which is interfaced with a radial distribution network. The results are obtained through a comprehensive set of real-time simulation studies, conducted on a detailed topological model of a single-machine equivalent of the PMSG-based wind farm and the network, using three different commercial relays. The paper introduces the study set-up and methodology and, additionally, details of the mathematical and simulation models of the PMSG-based wind farm. The models and the methodology presented in this paper can be used, directly or with minor modifications, for many other impact-assessment studies. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
48. A Mathematical Model and Performance Evaluation for a Single-Stage Grid-Connected Photovoltaic (PV) System.
- Author
-
Dash, Prajna Paramita and Yazdani, Amirnaser
- Subjects
- *
PHOTOVOLTAIC power systems , *ELECTRIC current converters , *ELECTRIC power distribution , *ELECTRIC transients , *MATHEMATICAL models , *ELECTRIC power systems - Abstract
This paper proposes a control strategy for important transients of a single-stage, three-phase, PV system that is connected to a distribution network. The proposed control strategy adopts an inner current-control loop and an outer DC-link voltage control loop. The current-control mechanism renders the PV system protected against external faults, enables control of the DC-link voltage and, therefore, controls/maximizes the PV system power output. The paper also proposes a feed-forward compensation strategy for the DC-link voltage control loop to mitigate the impact of the nonlinear characteristic of the PV array on the closed-loop stability, and to permit design and optimization of the DC-link voltage controller for a wide range of operating conditions. A mathematical model and a control design methodology are presented for the PV system, and it is shown that under the proposed control, the PV system fulfills the operational requirements of a grid-connected PV system. The effectiveness of the proposed control strategy and the most important transients of the PV system are evaluated through simulation studies conducted on a detailed switched model of the PV system in the PSCAD/EMTDC software environment. [ABSTRACT FROM AUTHOR]
- Published
- 2008
- Full Text
- View/download PDF
49. Editorial: Introduction to the Special Section on Dynamic Modeling, System Identification, Analysis, and Control of Renewable Distributed Energy Resources for Grid Integration.
- Author
-
Yazdani, Amirnaser and Fan, Lingling
- Published
- 2019
- Full Text
- View/download PDF
50. Capacitance health monitoring in the modular multilevel converter using a method with minimum number of sensors and computational burden.
- Author
-
Zoraghi‐Jedi, Mahsa, Barakati, Seyed‐Masoud, Rahmani‐Haredasht, Mohsen, Barahouei, Vahid, and Yazdani, Amirnaser
- Abstract
Summary This paper proposes a method for capacitance health monitoring (CHM) of submodule capacitors in modular multilevel converters (MMCs) that uses a reduced number of voltage sensors. In the proposed method, the MMC arms are divided into some groups of submodules and one voltage sensor is used for each group. In addition, a capacitor voltage estimation technique with minimal computational complexity is used to determine the capacitor voltage. The ratio of the estimated to measured capacitor voltage during positive arm current is also used to demonstrate a simple and efficient capacitance monitoring method. Moreover, contrary to the limitations associated with traditional CHM methods, the proposed method reduces the required voltage sensors and minimizes data exchange between the power system and the central processor. The effectiveness of the proposed method is validated through simulation and experimental results under various operating conditions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
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