Search for: reactive-power
Total 82 records
Article European Transactions on Electrical Power ; Volume 17, Issue 1 , 2007 , Pages 61-79 ; 1430144X (ISSN) ; Vakilian, M ; Feuillet, R ; Hadj Said, N ; Sharif University of Technology
This paper presents a reactive power valuation method with regard to its effect on realization of MW transactions. The security constraint optimization model in which the objective function is maximization of transactions is solved by the genetic algorithm approach. The proposed scheme allocates a specific amount of MW transactions to each dynamic reactive power source. An index is introduced to derive VAr value from the calculated optimal parameters of power network. This index represents the system-wide effect of MVAr sources on MW transactions implementations. Application of proposed method has been illustrated using IEEE 30 and 14 bus test systems. Results are discussed and compared in...
Article Ain Shams Engineering Journal ; Volume 7, Issue 1 , 2016 , Pages 131-141 ; 20904479 (ISSN) ; Fotuhi Firuzabad, M ; Karimi, A ; Sharif University of Technology
Ain Shams University 2016
A risk-based approach for short term security assessment with voltage stability constraint is presented in this paper. This approach includes voltage-stability considerations in reactive power adequacy assessment of a composite power system. The proposed method is based on probabilistic criteria because deterministic risk criteria do not define consistently the true risk in the system. For risk calculation, in this paper, load and parametric uncertainties and system contingencies are considered. Then the effects of uncertainties and contingencies on bus voltage violation are calculated. The required reactive power is determined based on the calculated voltage violation in order to maintain...
Article IEEE Transactions on Power Delivery ; Volume 22, Issue 1 , 2007 , Pages 732-734 ; 08858977 (ISSN) ; Parniani, M ; Sharif University of Technology
The ability of static VAr compensators (SVC) to reduce the flicker caused by electric arc furnaces and other variable VAr loads depends on their speed, which is limited by delays in reactive power measurement and thyristor ignition. In this paper, a predictive method is proposed to compensate the delay time and, hence, to improve the SVC performance. Previous samples of the load reactive power are used to predict its future values. Predicted VAr is then applied as a reference for reactive power compensation. © 2006 IEEE
Article 2004 International Conference on Power System Technology, POWERCON 2004, 21 November 2004 through 24 November 2004 ; Volume 2 , 2004 , Pages 1067-1071 ; 0780386108 (ISBN) ; Parniani, M ; Fotuhi Firuzabad, M ; Sharif University of Technology
Distributed generation (DG) portion of power production is increasing more and more. DG poses different benefits and difficulties in a power system. Inadvertent islanding is a problem with DG which may cause health danger to line crew and can damage both DG and power system equipments. This paper investigates the effect of reactive power on ROCOF islanding detection method. Impacts of load power factor and load combination are studied using a sample test system. The paper offers a corrective method to cope with impacts of load reactive power. A way is suggested to locate DG such that the role of reactive power becomes a positive factor in islanding detection. © 2004 IEEE
A conceptual structure for value based assessment of dynamic reactive power support in power markets, Article Electric Power Systems Research ; Volume 77, Issue 7 , 2007 , Pages 761-770 ; 03787796 (ISSN) ; Vakilian, M ; Feuillet, R ; Hadj Said, N ; Sharif University of Technology
This paper presents a practical reactive power valuation method, for the purpose of the reactive power pricing, in which the VAr value is decomposed into two components. These components are basically different from those already employed in the literature. Using a security constrained optimization model, the proposed scheme allocates two specific amounts of MW transactions to each generator as a dynamic reactive power source. One of these allocated amounts represents the contribution of the VAr resource to the shipment of active power, while the other one represents the contribution to the protection of the system against voltage instability. The final VAr value is derived using the...
M.Sc. Thesis Sharif University of Technology ; Ehsan, Mehdi
Restructuring and privatization in power system such as any industry leads to better market operation and more social welfare. Since two decade the power system in many countries have changed from monopoly to free market. In a restructured network the technical and economical aspects should be considered together. Ancillary services are needed for any power system to be operated in an optimal and secure manner. Reactive power and voltage regulation is one of the most important ancillary services in the network. this service should be supplied by its providers through a competitive market and system operator determines the optimal dispatch among different bids. The cost of purchasing reactive...
Article World Applied Sciences Journal ; Volume 13, Issue 2 , 2011 , Pages 316-323 ; 18184952 (ISSN) ; Hashemnia, N ; Kashiha, A ; Sharif University of Technology
Nowadays, application of renewable energies has taken a rapid trend. Wind energy is among those mostly used for this purpose. Doubly Fed Induction Generators (DFIG) are widely used in wind power plants due to several advantages such as partial rating converter, capability of decoupled active and reactive power control, etc. Application of a suitable control strategy is of great importance in wind power plants. In this paper, the parameters of a hybrid controller are calculated using Particle Swarm Optimization (PSO) subjected to satisfying the required criteria in output active and reactive powers of a DFIG. In the proposed system Direct Power Controller (DPC), Variable Structure Controller...
Article Power Plants and Power Systems Control 2006 ; Volume 39, Issue 7 , 2007 , Pages 65-70 ; 9780080466200 (ISBN) ; Ranjbar, A. M ; Mozafari, A ; Amraee, T ; Sharif University of Technology
Elsevier Ltd 2007
This chapter proposes a methodology for optimal dispatch of bilateral electricity contracts, which may endanger the system voltage stability in light of short-term operational planning of a deregulated power system. In this framework the value that each owner of a transaction is willing to pay reflects how much the electricity contract is important to be implemented physically. The proposed model dispatches optimally the bilateral transactions regarding the prices offered by owners of bilateral contracts for reactive power and transmission capacity utilization in one hand and, the total operational costs of reactive power resources in the other hand. The model also includes the limits...
Article 2006 IEEE PES Transmission and Distribution Conference and Exposition: Latin America, TDC'06, Caracas, 15 August 2006 through 18 August 2006 ; 2006 ; 1424402883 (ISBN); 9781424402885 (ISBN) ; Amraee, T ; Ranjbar, A. M ; Mirjafari, M ; Shirani, A. R ; Sharif University of Technology
The participants in auction-based electricity markets need to take part in a competition way, which operates, based on the concept of supply and demand theory to buy or sell the electricity. However, to have a feasible market solution, reactive power services are necessary to support the transmission of power from generation to end-users. This paper presents a methodology for optimal reactive power procurement, consistent with the auction-based electricity market mechanism. The proposed reactive power market is run in subsequence of the primary electricity market, allowing active power modification in light of available transmission capacity and reactive power resources. The IEEE 30-bus test...
Article IEEE Systems Journal ; Volume 12, Issue 3 , 2018 , Pages 2782-2790 ; 19328184 (ISSN) ; Nouri, A ; Ghadimi, N ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2018
The main focus of this paper is to find an upgrade plan for a microgrid. This plan includes system lines' upgrades, the place, and size of the new capacitors and DERs. As usual, the planning process is begun with the load forecasting. The main objectives include minimization of system upgrade cost, loss cost, loss cost in peak load, and finally demand cost. The last objective is realized here using the tap changer of the main station transformer and reactive power support of the sources available or planned for the future of the grid. This is always referred to as the conservation of voltage reduction. In order to consider the effects of bus voltages on the system demand, the ZIP model for...
A novel islanding detection scheme for synchronous distributed generation using rate of change of exciter voltage over reactive power at DG-side, Article 2017 Australasian Universities Power Engineering Conference, AUPEC 2017 ; Volume 2017-November , 5 February , 2018 , Pages 1-5 ; 9781538626474 (ISBN) ; Bagheri, M ; Naderi, S. B ; Negnevitsky, M ; Jalilian, A ; Blaabjerg, F ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2018
Penetration of distributed generation (DG) in distribution networks is rapidly increasing. DGs' application enhances system's reliability and power quality. However, along their benefits, there are some issues. One of the most important issues of DGs' application is the islanding. This paper presents a novel passive islanding detection scheme for synchronous DG based. In the proposed scheme, rate of change of exciter voltage over rate of change of reactive power at the DG-side (dE/dQDG) is taken into account. In reality, the voltage and reactive power of load depend on the exciter of the synchronous generator. Therefore, due to lack of inertia, response of these parameters to small changes...
Article International Journal of Electrical Power and Energy Systems ; Vol. 56, issue , March , 2014 , p. 298-306 ; ISSN: 1420615 ; Fotuhi-Firuzabad, M ; Aminifar, F ; Lehtonen, M ; Sharif University of Technology
Recent investigations have revealed the significant role of reactive power in blackout events. The associated disturbances frequently emerge in the form of voltage instability and collapse. Due to the computational complexity of modeling and analysis of enormous contingencies, DC approximation of the power flow, without accounting the role of reactive power, is usually used to evaluate the contingencies and to mitigate the associated probable violations. This paper, at first, presents a linear power flow model based on an approximated version of AC power flow formulation. The proposed model is then used to develop an efficient reliability assessment approach which is capable of taking both...
Article IET Generation, Transmission and Distribution ; Volume 6, Issue 1 , January , 2012 , Pages 1-10 ; 17518687 (ISSN) ; Soroudi, A ; Ranjbar, A. M ; Sharif University of Technology
Owing to the local nature of voltage and reactive power control, the voltage control is managed in a zonal or regional basis. A new comprehensive scheme for optimal selection of pilot points is proposed in this study. The uncertainties of operational and topological disturbances of the power system are included to provide the robustness of the pilot node set. To reduce the huge number of probable states (i.e. combined states of load and topological changes), a scenario reduction technique is used. The resulted optimal control problem is solved using a new immune-based genetic algorithm. The performance of the proposed method is verified over IEEE 118-bus and realistic Iranian 1274-bus...
Article 2006 International Conference on Power System Technology, POWERCON2006, Chongqing, 22 October 2006 through 26 October 2006 ; 2006 ; 1424401119 (ISBN); 9781424401116 (ISBN) ; Amraee, T ; Ranjbar, A. M ; Mirjafari, M ; Shirani, A. R ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc 2006
The participants in auction-based electricity markets need to take part in a competition way which operates based on the concept of supply and demand theory to buy or sell the electricity. However, to have a feasible market solution, reactive power services are necessary to support the transmission of power from generation to end-users. This paper presents a methodology for optimal reactive power procurement, consistent with the auction-based electricity market mechanism. The proposed reactive power market is run in subsequence of the primary electricity market, allowing active power modification in light of available transmission capacity and reactive power resources. The IEEE 30-bus test...
Article International Review of Electrical Engineering ; Volume 5, Issue 5 , 2010 , Pages 2209-2216 ; 18276660 (ISSN) ; Habibi, M. R ; Khorasani, H ; Rashidinejad, M ; Sharif University of Technology
This paper establishes a simple and topological approach to track real and reactive power flow in electric transmission systems. The presented method utilizes the well-known Proportional Sharing Theorem in order to evaluate the contribution of each power source to grid elements' supplied input power. We have also put forward an approximate power tracing method for upgraded grids, using its own previously surveyed results. The main advantages of the proposed procedure, compared with conventional methods, are discussed extensively. The effectiveness of this approach has been studied and ascertained for small-scale power systems, showing prominent speed and accuracy
Prevention of distribution network overvoltage by adaptive droop-based active and reactive power control of PV systems, Article Electric Power Systems Research ; Volume 133 , 2016 , Pages 313-327 ; 03787796 (ISSN) ; Parniani, M ; Sharif University of Technology
Proliferation of grid-connected photovoltaic systems (PVSs) causes technical problems due to their variable and non-dispatchable generated power. High penetration of PVS in distribution networks can result in overvoltage in some operating conditions. Although this situation occurs rarely, it limits the installed capacity of PVS. In this paper, adaptive droop-based control algorithms are presented to regulate active and reactive power of PVS, with the objectives of loss minimization and increasing the PVS capacity installation without unallowable overvoltage. Operating voltage range of the PVS is divided into several intervals, and a specific control algorithm is presented for each of them....
Article Iranian Journal of Science and Technology, Transaction B: Engineering ; Volume 30, Issue 2 , 2006 , Pages 259-276 ; 03601307 (ISSN) ; Ranjbar, A. M ; Amraee, T ; Shirani, A. R ; Sharif University of Technology
This paper first proposes a competitive market structure for reactive power procurement and then develops a methodology for incorporating voltage stability problems into the model. The owners of electric transactions should participate in this competitive framework and submit their own firmness bids in ($/MW) to the Independent/System/Market Operator (ISOIMO). ISO clears the market for reactive energy regarding the value of each transaction and utilization cost of reactive power on one hand, and the impact of transaction amount on the voltage security of the power system on the other hand. Here, the voltage stability margin is incorporated into the power flow equations so that the security...
Article Proceedings of 2004 International Conference on Machine Learning and Cybernetics, Shanghai, 26 August 2004 through 29 August 2004 ; Volume 7 , 2004 , Pages 4234-4239 ; 0780384032 (ISBN) ; Arabian, H ; Mirjafari, M ; Sharif University of Technology
In this paper two novel search methods for solving optimal power flow (OPF) have been presented and compared. Electricity is undergoing a restructuring process, moving from integrated environment towards deregulation and reduced regulation all around the world. Electrical energy markets are going to be created as a consequence of this process. In order to meet technical issues, system operator would need to apply some ancillary services. Reactive power is one of the most important ancillary services, which should be injected to power network in order to decrease the total loss and control the voltage profile. The main goal of this study is to present a method based on a Locational Marginal...
Article Electric Power Components and Systems ; Volume 31, Issue 4 , 2003 , Pages 321-334 ; 15325008 (ISSN) ; Mahdavi, J ; Mokhtari, H ; Emadi, A ; Sharif University of Technology
Advanced static VAR compensators (ASVCs) are used to improve the transient stability of electric power systems. In this paper we present a new control strategy, which has superior performances compared to the conventional control techniques for these systems. The proposed method utilizes a novel current reference based on the transient energy function (TEF) approach. It also includes the voltage limits in the optimizing process using the Lyapunov theory and linear programming. In addition, it is optimized considering the permissible system conditions. A continuous control of the reactive power flow is also achieved. The proposed ASVC is modeled in single-machine and multimachine systems. In...
Design and implementation of TSC type SVC using a new approach for electrical quantities measurement, Article 2001 IEEE Porto Power Tech Conference, Porto, 10 September 2001 through 13 September 2001 ; Volume 2 , 2001 , Pages 262-267 ; 0780371399 (ISBN); 9780780371392 (ISBN) ; Alavi, M. H ; Marami, M ; Dehnavi, G. R ; Sharif University of Technology
In this paper, a compact algorithm for balancing the load and correction of power factor in three-phase three-wire system is presented. Susceptances of SVC in each phase are computed as a function of real and imaginary parts of line current. This calculation is based on unity power factor and elimination of negative sequence of currents. A laboratory prototype of Thyristor Switched Capacitor (TSC) at 380V and 45KVAR is designed and implemented. Also, a new approach for measuring active and reactive power, power factor and voltage is presented. This measuring technique is based on integration of current signal over a specific part of voltage signal period. Finally, a brief description of...