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distributed-generation
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Active power management of multihybrid fuel cell/supercapacitor power conversion system in a medium voltage microgrid
, Article IEEE Transactions on Smart Grid ; Volume 3, Issue 4 , 2012 , Pages 1903-1910 ; 19493053 (ISSN) ; Hamzeh, M ; Mokhtari, H ; Karimi, H ; Sharif University of Technology
2012
Abstract
This paper proposes a hierarchical active power management strategy for a medium voltage (MV) islanded microgrid including a multihybrid power conversion system (MHPCS). To guarantee excellent power management, a modular power conversion system is realized by parallel connection of small MHPCS units. The hybrid system includes fuel cells (FC) as main and supercapacitors (SC) as complementary power sources. The SC energy storage compensates the slow transient response of the FC stack and supports the FC to meet the grid power demand. The proposed control strategy of the MHPCS comprises three control loops; dc-link voltage controller, power management controller, and load current sharing...
An interactive fuzzy multi-objective approach for short term DG planning
, Article International Journal of Innovative Computing, Information and Control ; Volume 8, Issue 6 , 2012 , Pages 4157-4175 ; 13494198 (ISSN) ; Ehsan, M ; Meyabadi, A. F ; Niknam, T ; Sharif University of Technology
2012
Abstract
This paper presents a short term multi-objective planning model for Distributed Generators (DGs) deployment in an electrical network. "Total Cost" and "Emission Cost" are two objective functions which have been going to be minimized in this model by finding the optimal schemes of sizing, placement and DG technologies over a short planning period (static planning). The proposed model can be used for a long term planning period (dynamic planning) in order to consider the timing concept. An interactive fuzzy satisfying method based on Chaotic Local Search and Modified Honey Bee Mating Optimization (CLS-MHBMO) is used to choose the final solution. The effectiveness of the proposed model and...
A high performance real-time simulator for controllers hardware-in-the-loop testing
, Article Energies ; Volume 5, Issue 6 , 2012 , Pages 1713-1733 ; 19961073 (ISSN) ; Karimi, H ; Etemadi, A ; Iravani, R ; Sharif University of Technology
2012
Abstract
This paper presents a high performance real-time simulator for power electronic systems applications and primarily intended for controller hardware-in-the-loop (CHIL) testing. The novelty of the proposed simulator resides in the massively parallel hardware architecture that efficiently exploits fine-grained parallelism without imposing severe communication overhead time that can limit the performance. The simulator enables the use of a nanosecond range simulation timestep to simulate power electronic systems. Through the use of this nanosecond range simulation timestep, the simulator minimizes the error arising from the intersimulation timestep switching phenomenon associated with CHIL. The...
A new control strategy for a multi-bus MV microgrid under unbalanced conditions
, Article IEEE Transactions on Power Systems ; Volume 27, Issue 4 , 2012 , Pages 2225-2232 ; 08858950 (ISSN) ; Karimi, H ; Mokhtari, H ; Sharif University of Technology
2012
Abstract
This paper proposes a new control strategy for the islanded operation of a multi-bus medium voltage (MV) microgrid. The microgrid consists of several dispatchable electronically-coupled distributed generation (DG) units. Each DG unit supplies a local load which can be unbalanced due to the inclusion of single-phase loads. The proposed control strategy of each DG comprises a proportional resonance (PR) controller with an adjustable resonance frequency, a droop control strategy, and a negative-sequence impedance controller (NSIC). The PR and droop controllers are, respectively, used to regulate the load voltage and share the average power components among the DG units. The NSIC is used to...
Stochastic modeling of the energy supply system with uncertain fuel price - A case of emerging technologies for distributed power generation
, Article Applied Energy ; Volume 93 , 2012 , Pages 668-674 ; 03062619 (ISSN) ; Saboohi, Y ; Sharif University of Technology
2012
Abstract
A deterministic energy supply model with bottom-up structure has limited capability in handling the uncertainties. To enhance the applicability of such a model in an uncertain environment two main issues have been investigated in the present paper. First, a binomial lattice is generated based on the stochastic nature of the source of uncertainty. Second, an energy system model (ESM) has been reformulated as a multistage stochastic problem. The result of the application of the modified energy model encompasses all uncertain outcomes together and enables optimal timing of capacity expansion. The performance of the model has been demonstrated with the help of a case study. The case study has...
Imperialist competition algorithm for distributed generation connections
, Article IET Generation, Transmission and Distribution ; Volume 6, Issue 1 , January , 2012 , Pages 21-29 ; 17518687 (ISSN) ; Ehsan, M ; Sharif University of Technology
2012
Abstract
This study proposes an imperialist competition algorithm (ICA) to maximise the benefits of distribution network operators (DNOs) because of the existence of distributed generation (DG) units. The sum of active loss reduction and network investment deferral incentives has been considered as the objective function to be maximised in this study. The optimal location and size of DG units in the network are found considering various techno-economical issues. The application of the proposed methodology in the UK under current Ofgem financial incentives for DNOs is investigated. The ability of the proposed approach in finding the optimal solution is validated by comparing the obtained results with...
Optimal tuning of linear controllers for power electronics/power systems applications
, Article Electric Power Systems Research ; Volume 81, Issue 12 , 2011 , Pages 2188-2197 ; 03787796 (ISSN) ; Edrington, C. S ; Mokhtari, H ; Sharif University of Technology
2011
Abstract
This paper presents a new method for tuning various linear controllers such as Proportional-Integral (PI), Proportional-Integral-Derivative (PID) and Proportional-Resonant (PR) structures which are frequently used in power electronics and power system applications. The linear controllers maintain a general structure defined by the Internal Model Principle (IMP) of control theory. The proposed method in this paper is twofold. The first perspective uses the well-known concept of the Linear Quadratic Regulator (LQR) to address the problem as a regulation problem. The Q matrix of the LQR design is then finely adjusted in order to assure the desired transient response for the system. The second...
μ-Synthesis control for an islanded microgrid with structured uncertainties
, Article IECON Proceedings (Industrial Electronics Conference), 7 November 2011 through 10 November 2011 ; November , 2011 , Pages 3064-3069 ; 9781612849720 (ISBN) ; Karimi, H ; Sharif University of Technology
2011
Abstract
This paper presents a robust control scheme for an islanded microgrid in the presence of structured uncertainties. The microgrid consists of parallel connection of two Distributed Generation (DG) units and a passive load. The DG units are connected to the passive load by using the power electronics converters. The microgrid model is structurally uncertain due to the large perturbations in the load parameters. To deal with the uncertainties, a Linear Fractional Representation (LFR) of the parametrically uncertain system is obtained. To achieve robust performance, the μ-synthesis approach is applied to the derived LFR model to design a μ controller. The resultant controller is structurally...
Probabilistic dynamic multi-objective model for renewable and non-renewable distributed generation planning
, Article IET Generation, Transmission and Distribution ; Volume 5, Issue 11 , 2011 , Pages 1173-1182 ; 17518687 (ISSN) ; Caire, R ; Hadjsaid, N ; Ehsan, M ; Sharif University of Technology
2011
Abstract
This study proposes a probabilistic dynamic model for multi-objective distributed generation (DG) planning, which also considers network reinforcement at presence of uncertainties associated with the load values, generated power of wind turbines and electricity market price. Monte Carlo simulation is used to deal with the mentioned uncertainties. The planning process is considered as a two-objective problem. The first objective is the minimisation of total cost including investment and operating cost of DG units, the cost paid to purchase energy from main grid and the network reinforcement costs. The second objective is defined as the minimisation of technical risk, including the probability...
Design of low order dynamic pre-compensators using convex methods
, Article Proceedings of the American Control Conference, 29 June 2011 through 1 July 2011, San Francisco, CA ; 2011 , Pages 3680-3685 ; 07431619 (ISSN) ; 9781457700804 (ISBN) ; Nejati, A ; Nobakhti, A ; Karimi, H ; Sharif University of Technology
2011
Abstract
Pre-compensators are used in multivariable control systems to reduce (or eliminate) open loop system interactions. Classical methods for the design of pre-compensator are traditionally based on static designs. Static pre-compensators are preferred for their simplicity, but are highly unsystematic in the amounts of achievable diagonal dominance. In many applications, only the more powerful dynamic pre-compensators are able to deliver the desired amounts of decoupling. This paper proposes a new method for the design of dynamic pre-compensators which is based on a Quadratic Programming (QP) optimization. Using the proposed approach the total pre-compensator is found through several smaller...
Stability analysis and experimental evaluation of a control strategy for islanded operation of distributed generation units
, Article IEEJ Transactions on Industry Applications ; Volume 131, Issue 8 , 2011 , Pages 1013-1022 ; 09136339 (ISSN) ; Karimi, H ; Iravani, R ; Sharif University of Technology
2011
Abstract
This paper presents stability analysis of a distributed generation (DG) controller (1), in an islanded mode, based on the Mapping Theorem and the Zero Exclusion Condition, and validates the results based on a laboratory scale experimental setup. The DG unit is interfaced to the host system through a voltage-sourced converter (VSC). The control strategy regulates the load voltage at the desired value in the islanded mode, despite uncertainties in the load parameters. The frequency of the island is controlled in an open loop manner by an internal oscillator. The experimental results show that the controller provides robust voltage control for a wide range of load parameters, and even maintains...
Control of microgrids: Aspects and prospects
, Article 2011 International Conference on Networking, Sensing and Control, ICNSC 2011, 11 April 2011 through 13 April 2011 ; April , 2011 , Pages 38-43 ; 9781424495702 (ISBN) ; Azizi, S ; Ranjbar, A. M ; Sharif University of Technology
2011
Abstract
A microgrid is a controllable component of the smart grid defined as a part of distribution network capable of supplying its own local load even in the case of disconnection from the upstream network. Microgrids incorporate large amount of renewable and non-renewable distributed generation (DG) that are connected to the system either directly or by power electronics (PE) interface. The diversity of technologies used in DGs and loads, high penetration of DGs, economic operation of DGs, dynamics of low-inertia conventional DGs and PE interfaced inertialess DGs and smart operation by means of enhanced communication infrastructure have raised challenges in widespread utilization of microgrids as...
Optimal distributed generation placement in a restructured environment via a multi-objective optimization approach
, Article 16th Electrical Power Distribution Conference, EPDC 2011, 19 April 2011 through 20 April 2011 ; April , 2011 , Page(s): 1 - 6 ; 9789644631498 (ISBN) ; Dehghanian, P ; Hosseini, S. H ; Sharif University of Technology
2011
Abstract
The increasing use of electrical energy in nowadays modern societies and industries has brought about a sharp need for more efficient means of electricity generation. It seems rather logical to increase the electricity production proportional to the increasing rate of the demand. Distributed Generation (DG) has been recently accepted to be one of the most efficient means of electricity generation, particularly near to the load centers. The DG has been also considered in the generation expansion planning of power systems. In this paper, three main factors associated with the DGs placement procedure is scrutinized through a multi-objective optimization approach. One of the main factors...
Multivariable control strategy for autonomous operation of a converter-based distributed generation system
, Article 2011 IEEE/PES Power Systems Conference and Exposition, PSCE 2011, 20 March 2011 through 23 March 2011, Phoenix, AZ ; March , 2011 , Page(s): 1 - 8 ; 9781612847870 (ISBN) ; Nobakhti, A ; Karimi, H ; Sharif University of Technology
2011
Abstract
This paper presents a control strategy for the autonomous (islanded) operation of a distributed generation (DG) unit. The DG unit supplies a balanced load through a voitage-sourced converter (VSC). To maintain the autonomous operation in the islanded mode, the DG unit should provide its dedicated load with a sinusoidal voltage with a constant magnitude and a constant frequency. The dynamic model of the islanded DG system is represented by a set of nonlinear equations. Since the objective is to regulate voltage and frequency of the islanded DG about their rated values, the nonlinear model is linearized about the operating point. The obtained linearized model represents a multivariable LTI...
Nondetection zone assessment of an active islanding detection method and its experimental evaluation
, Article IEEE Transactions on Power Delivery ; Volume 26, Issue 2 , 2011 , Pages 517-525 ; 08858977 (ISSN) ; Karimi, H ; Iravani, R ; Sharif University of Technology
2011
Abstract
This paper analytically determines the nondetection zone (NDZ) of an active islanding detection method, and proposes a solution to obviate the NDZ. The method actively injects a negative-sequence current through the interface voltage-sourced converter (VSC) of a distributed generation (DG) unit, as a disturbance signal for islanding detection. The estimated magnitude of the corresponding negative-sequence voltage at the PCC is used as the islanding detection signal. In this paper, based on a laboratory test system, the performance of the islanding detection method under UL1741 anti-islanding test conditions is evaluated. Then, determining the NDZ of the method and proposing the...
Robust control of an autonomous four-wire electronically-coupled distributed generation unit
, Article IEEE Transactions on Power Delivery ; Volume 26, Issue 1 , September , 2011 , Pages 455-466 ; 08858977 (ISSN) ; Yazdani, A ; Iravani, R ; Sharif University of Technology
2011
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...
Robust decentralized control for islanded operation of two radially connected DG systems
, Article 2010 IEEE International Symposium on Industrial Electronics, ISIE 2010, Bari, 4 July 2010 through 7 July 2010 ; July , 2010 , Pages 2272-2277 ; 9781424463916 (ISBN) ; Karimi, H ; Karimi Ghartemani, M ; The Institute of Electrical and Electronics Engineers (IEEE); IEEE Industrial Electronics Society (IES); IEEE Control Systems Society (CSS); Society of Instrument and Control Engineers (SICE-Japan); Politecnico di Bari ; Sharif University of Technology
2010
Abstract
A decentralized servomechanism controller for islanded (autonomous) operation of radial connection of two distributed generation (DG) units is proposed in this paper. Each DG unit utilizes a voltage-sourced converter (VSC) for interface to its dedicated load. The DG units and the loads are to operate in the islanded mode of operation. Each DG unit regulates the voltage of its dedicated load in a decentralized manner. In this paper, it is first shown that the radial connection of two DG units in the islanded mode constitutes an interconnected composite system consisting of two subsystems. Moreover, the paper shows that the overall islanded system can be controlled by the local controllers,...
Modeling, control and islanding detection of microgrids with passive loads
, Article Proceedings of EPE-PEMC 2010 - 14th International Power Electronics and Motion Control Conference, 6 September 2010 through 8 September 2010 ; September , 2010 , Pages T11107-T11112 ; 9781424478545 (ISBN) ; Karimi, H ; Nikkhajoei, H ; Terzija, V ; Sharif University of Technology
2010
Abstract
This paper presents a control scheme for microgrids with passive loads. The existing control techniques for distributed generation systems are designed to operate either in the grid-connected or in the islanded mode. In the grid-connected mode of operation, a currentcontrolled scheme based on d-q variables is used for the regulation of real and reactive powers of the converter. In the islanded mode of operation, the converter is controlled in the voltage-controlled mode. This paper deals with the modeling of both control schemes. Furthermore, reconnection from the islanded mode to the grid-connected mode based on the use of adequate Phase-Locked Loops (PLLs) has been demonstrated
Optimal placement and sizing of distributed resources for congestion management considering cost/benefit analysis
, Article IEEE PES General Meeting, PES 2010, 25 July 2010 through 29 July 2010, Minneapolis, MN ; 2010 ; 9781424483570 (ISBN) ; Abbaspour Tehrani Fard, A ; Rashidinejad, M ; Lee, K. Y ; Sharif University of Technology
2010
Abstract
Congestion management is one of the most important issues for secure and reliable system operations in deregulated electricity market. This paper presents a cost/worth analysis approach for optimal location and sizing of Distributed Resources (DRs) to mitigate congestion and increase security of the system. In order to reduce the solution space a priority of candidate buses is formed, then optimal location and sizing problem is discussed. To increase the accuracy of results, load duration curve is constituted and based on this curve different load levels are incorporated into this study. Proposed method considers economical factors such as congestion rent, deferred upgrading investment and...
Distributed generation placement for congestion management considering economic and financial issues
, Article Electrical Engineering ; Volume 92, Issue 6 , November , 2010 , Pages 193-201 ; 09487921 (ISSN) ; Abbaspour Tehrani Fard, A ; Rashidinejad, M ; Sharif University of Technology
2010
Abstract
Congestion management is one of the most important functions of independent system operator (ISO) in the restructured power system. This paper presents two new methodologies for optimal sitting and sizing of distributed generations (DGs) in the restructured power systems for congestion management. The proposed methodologies are based upon locational marginal price (LMP) and congestion rent that forms a priority list of candidate buses to reduce the solution space. The proposed priority list facilitates the optimal placement as well as the level of output power of DGs. The proposed methods are implemented on the IEEE 14-bus and IEEE 57-bus test systems to illustrate their effectiveness. An...