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Power Systems (power + system)
Kinds of Power Systems Selected AbstractsAn efficient methodology for security assessment of power systems based on distributed optimal power flowEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2003D. Hur This paper presents an algorithm for the parallel solution of the security constrained optimal power flow (SCOPF) problem in a decentralized framework, consisting of regions, using a price-based mechanism that models each region as an economic unit. We first solve the distributed optimal power flow (OPF) problem to determine the maximum secure simultaneous transfer capability of each tie-line between adjacent regions by taking only the security constraints imposed on the tie-lines into account. In this paper, the line outage distribution factors (LODF) calculated at the current state are used to formulate the appended constraints. Once the secure transfer capability of each tie-line is determined, the intra-regional SCOPF is performed using the conventional linear programming (LP) approach. A description on the inclusion of security constraints with distributed OPF algorithm will be given, followed by the case study for Korea Electric Power System. [source] The dynamic characteristics of a thermal control system using latent heat: Comparison between analytical and experimental resultsHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2005Terushige Fujii Abstract The two-phase flow thermal control system, using latent heat of the internal fluid, has received a great deal of research interest as a method for heat removal on the space station and the Space Solar Power System (SSPS). The system has a much lower weight than the single-phase flow, and the temperature can be accurately controlled by changing the saturated pressure inside the loop. To date, this system has not been put into practical use. Numerical analyses were therefore used to investigate the dynamic responses of the loop and to investigate the operational characteristics of the thermal control system. A simulation model was constructed, and the results of the numerical analysis were compared with the experimental results. Good agreement was obtained between analytical and experimental results. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(8): 564,578, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20090 [source] High Frequency AC Power SystemNAVAL ENGINEERS JOURNAL, Issue 4 2008RAYMOND M. CALFO The Navy's Next Generation Integrated Power System (NGIPS) master plan calls for the evolution of the IPS system from its current medium voltage, 60 Hz state to a high-frequency, medium-voltage AC (HFAC) system in the next 10 years. Beyond that, and pending development of key protection components, a medium-voltage DC system will be considered for implementation. The master plan calls for power generation modules at three power levels across these systems: ,A low power level (2,5 MW) driven by a fuel-efficient diesel prime mover, ,A medium power level (10,15 MW) driven by a gas turbine, and ,A main propulsion power level (20,40 MW) driven by a gas turbine. EMD is currently developing a high-speed, high-frequency, liquid-cooled generator under contract with NAVSEA that will effectively demonstrate the mid-level generator for the HFAC system. It will be coupled directly to the output of a GE LM1600 Gas Turbine to provide a TG set with power density four times more favorable than conventional ATG sets. The generator development is proceeding favorably, with testing at the Navy's land-based test site (LBTS) expected to begin in July 2008. The technology embodied in the high-speed generator can be easily extrapolated to main turbine generator power levels. Given the availability of prime movers at appropriate speeds, the power generation modules for the HFAC system, at all three power levels, could be provided in a much shorter time frame than noted in the NGIPS master plan. This paper will explore the combinations of prime movers and advanced generators that would suit the three power generation modules of the HFAC system. A description of the prime mover and the generator used for each module will be provided to demonstrate the modest level of development needed. The performance parameters for each generation module will be provided, along with key characteristics and dimensions for the set. In the end, the paper will make the case that demonstration of a HFAC power generation system can be made in the short term, allowing the shipbuilding community to take advantage of the benefits of state-of-the-art power dense electrical generation. [source] Sensitivity Analysis of the Shipboard Integrated Power SystemNAVAL ENGINEERS JOURNAL, Issue 1 2008PRADYA PREMPRANEERACH Stochastic sensitivity analysis is a valuable tool in ranking inputs and in investigating the degree of interaction of its components. In this paper, we present stochastic simulation results for a shipboard integrated power system and study its sensitivity. Specifically, we apply sensitivity analysis to two high-fidelity models of shipboard subsystems, investigating open- and closed-loop control of the propulsion system. The results show that different inputs are most important for the open- and closed-loop control, with sensitivities that change dramatically in time as they reflect the transition from the fast electrical scales to slower mechanical scales. We also demonstrate how sensitivity analysis can be used to establish the robustness of the AC drive. [source] Proper Splitting of Interconnected Power SystemsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2010S. Najafi Non-member Abstract Power system islanding is the last defense line to protect power grids from incidence of wide-area blackout. As a wide-area control action, power system splitting is a comprehensive decision making problem that includes different subproblems. This paper introduces a novel approach for separation of the entire power system into several stable islands in different loading levels. The proposed method combines both the dynamic and the static characteristics of interconnected power network and determines the proper splitting schemes. The presented algorithm searches for proper islanding strategy in the boundary of primary determined coherent machines using Krylov subspace method and finds the proper splitting points by transferring some of the buses in one island to another island such that total load shedding is minimized. A spanning tree-based depth first search algorithm is used to find all possible combination of transferred buses. The presented method reduces the huge initial search space of islanding strategy considering dynamic characteristics of integrated power system and reduction of search space to only boundary network. The speed of the proposed algorithm is remarkably high and can be applied for islanding the power system in real-time. The presented algorithm is applied to IEEE 118 BUS test system. Results show the robustness, effectiveness, and capability of the algorithm to determine fast and accurate proper islanding strategy. Time domain simulation of the islanding strategies confirms that all the islands which are specified by the proposed method are stable. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Special Issue on Advanced Technology in Power SystemsIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 6 2007Dr. Toshihisa Funabashi No abstract is available for this article. [source] Recent Activities of HTS Power Application in KoreaINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 3 2007Minwon Park From April 2007, DAPAS (Development of the Advanced Power system by Applied Superconductivity technologies), which is a 10-year-long program, entered the final phase with 4 years. For the last 7 years, the significant achievement of DAPAS is that a 10 m long and 100 A critical current-coated conductor and core technologies of distribution line voltage class HTS power systems including cables, transformers, fault current limiters (FCLs), and motors have been developed. In particular, a 100 m length HTS power cable was installed and is operating well in the Gochang power system test center. Two different types of FCL were successfully developed and demonstrated very good results of fault current test with 22.9 kV distribution line voltage class. In the case of the HTS motor, it was well operated too on connecting to 2 units of a 1.1 MVA conventional induction motor each as a load. In addition, the coated conductor project team achieved a 30 m length and 185 A critical current-coated conductor tape after 6 months since the hardware was set up. [source] Coordinated voltage control of transformer taps with provision for hierarchical structure in power systemELECTRICAL ENGINEERING IN JAPAN, Issue 4 2009Yoshiki Nakachi Abstract Participation of distributed generators (DGs), such as wind turbines, cogeneration systems, etc., is a natural trend from an ecological point of view and will continue to increase. The outputs of these DGs mainly depend on weather conditions but do not correspond to the changes of electrical load demand necessarily. On the other hand, due to deregulation of the electric power market, the power flow in a power system will uncertainly vary with several power transactions. Thus, complex power flow by DGs or transactions will cause voltage deviation. It will be difficult to sustain the voltage quality by using conventional voltage/reactive power control in the near future. In this paper, in order to avoid such voltage deviation and to decrease the frequency of transformer tap operations, the coordinated voltage control scheme of transformer taps on account of hierarchical structure in the power system is proposed. In the proposed scheme, integral of voltage deviation at each layer bus is applied to decide the timing of each transformer tap operation. Numerical simulations confirm that the proposed scheme is able to respond to every condition on voltage deviation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 48,55, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20531 [source] Transient stability simulation of wind generator expressed by two-mass modelELECTRICAL ENGINEERING IN JAPAN, Issue 3 2008Yoshikazu Shima Abstract Recently, wind power generation is increasing worldwide. In wind power stations, induction machines are mostly used as generators. Since induction generators have a stability problem similar to the transient stability of synchronous machines, it is important to analyze the transient stability of power systems including wind generators. Although there have been some reports analyzing the transient stability problem, wind turbine and wind generator are, in most cases, modeled as a one-mass shaft system having total inertia constant. This paper presents simulation analyses of transient stability of power system including induction generator which is expressed by a two-mass shaft model and analyzes an effect of shaft system modeling on the transient stability characteristics. Simulations are performed by PSCAD/EMTDC in this study. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 162(3): 27,37, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20394 [source] Construction of Lyapunov function for power system based on solving linear matrix inequalityELECTRICAL ENGINEERING IN JAPAN, Issue 4 2007Atsushi Ishigame Abstract This paper presents construction of Lyapunov functions for power systems based on solving the Linear Matrix Inequality (LMI) derived from the Lyapunov stability theorem considering the dynamics of load characteristic and AVR control system. The proposed Lyapunov function is constructed as a quadratic form of state variables and an integral term which satisfies the curl equation and the sector condition. An induction machine and a synchronous machine are considered as load characteristics. One-machine one-load infinite bus system is considered taking into account the flux decay effects and AVR with one time constant of the generator. To verify the proposed Lyapunov function, the transient stability assessment is shown. The critical clearing times given by the proposed Lyapunov function are compared with those obtained by the numerical integration method, and they are shown to be practical. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 42, 50, 2007; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20328 [source] A study of economic evaluation of demand-side energy storage system in consideration of market clearing priceELECTRICAL ENGINEERING IN JAPAN, Issue 1 2007Ken Furusawa Abstract In Japan the electricity market will open on April 1, 2004. Electric utility, Power Producer and Supplier (PPS), and Load Service Entity (LSE) will join the electricity market. LSEs purchase electricity based on the Market Clearing Price (:MCP) from the electricity market. LSEs supply electricity to the customers that contracted with the LSEs on a certain electricity price, and one to the customers that introduced Energy Storage System (:ES) on a time-of-use pricing. It is difficult for LSEs to estimate whether they have any incentive to promote customers to introduce ES or not. This paper evaluates the reduction of LSEs' purchasing cost from the electricity market and other LSEs' purchasing cost by introducing ES to customers. It is clarified which kind of customers has the effect of decreasing LSEs' purchasing cost and how much MCP of the whole power system the demand-side energy storage systems change. Through numerical examples, this paper evaluates the possibility of giving the cost merit to both customers with energy storage systems and LSE by using real data for a year's worth of MCP. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 22,35, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20447 [source] Determining arresters best positions in power system for lightning shielding failure protection using simulation optimization approachEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2010B. Vahidi Abstract The lightning stroke to power system structures especially overhead lines makes severe damages and results in less reliable power supply. The invention of surge arresters was a revolution in these systems for protecting the precise equipments from lightning stroke overvoltages. Nowadays, with ever decreasing prices, using arrester not only for protecting certain instruments but also for decreasing total risk of flashover in overall network, is investigated by academic and industrial pioneers in this area. In this paper, our goal is to introduce a heuristic method for determining optimum positions for placing transmission lines surge arresters (TLSAs) with acceptable approximation, to get lowest possible value of shielding failure risk of flashover in a selected set of overhead lines. Simulation optimization based on neural net (i.e. Meta Model) and genetic algorithm (optimization algorithm) is invoked to suggest best positions for placing TLSAs. A case study on Kerman 230,kV network shows good achievement of simulation optimization for finding optimum positions of TLSAs. Comparison is also made with the results of transient simulation to reveal the effectiveness of the method. Copyright © 2008 John Wiley & Sons, Ltd. [source] Damping torque analysis for DC bus implemented damping control,EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2010W. Du Abstract Damping torque analysis is a well-developed technique for understanding and studying power system oscillations. This paper presents the applications of damping torque analysis for DC bus implemented damping control in power transmission networks in two examples. The first example is the investigation of damping effect of shunt voltage source converter (VSC) based flexible AC transmission systems (FACTS) voltage control, i.e. static synchronous compensator (STATCOM) voltage control. It is shown in the paper that STATCOM voltage control mainly contributes synchronous torque and hence has little effect on the damping of power system oscillations. The second example is the damping control implemented by a battery energy storage system (BESS) installed in a power system. Damping torque analysis reveals that when BESS damping control is realized by regulating exchange of active and reactive power between the BESS and power system, respectively, BESS damping control exhibits different properties. It is concluded by damping torque analysis that BESS damping control implemented by regulating active power is better with less interaction with BESS voltage control and more robust to variations of power system operating conditions. In the paper, all analytical conclusions obtained are demonstrated by simulation results of example power systems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Trends, challenges and opportunities in power quality researchEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2010Math H. J. Bollen Abstract This paper outlines a number of possible research directions in power quality. The introduction of new sources of generation will introduce the need for new research on voltage,magnitude variations, harmonic emission and harmonic resonance. Statistical performance indicators are expected to play an important role in addressing the hosting capacity of the power system for these new sources. The quickly growing amounts of power-quality data call for automatic analysis methods. Advanced signal-processing tools need to be developed and applied to address this challenge. Equipment with an active power-electronic interface generates waveform distortion at higher frequencies than existing equipment. The emission, spread, consequences and mitigation of this distortion require more research emphasis. The growing complexity of the power system calls for remote identification of system events and load transitions. Future DC networks, at different voltage levels, require the research on DC power quality next to AC power quality. Research on methods to describe and analyse time-varying harmonics has applications in a number of the above-mentioned issues. So does the use of hardware-in-the-loop (HIL) and real-time-digital simulation. Existing power quality standards should not form a barrier against future research; instead research should result in improved standards as well as completely new concepts. Examples are: voltage dips in three-phase systems, flicker due to non-incandescent lamps, and voltage variations on the timescale between 1,second and 10,minutes. All together, it is concluded in this paper that sufficient important and interesting research challenges and opportunities remain in the power quality area. Copyright © 2009 John Wiley & Sons, Ltd. [source] Power quality state estimationEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2010Neville R. Watson Abstract Due to the size and complexity of modern electrical power networks and the cost of monitoring and telecommunication equipment, it is unfeasible to fully monitor the system state. For this reason state estimation techniques are used. With strategically placed measurements, estimation techniques can determine the parameters at unmonitored locations. Fundamental frequency state estimation is now a standard tool in modern power systems. The emission and immunity levels of modern electrical equipment are different to that of the past, and this has resulted in power quality issues have become important. Knowledge of the source and location of the disturbances is desirable so that remedial action can be taken promptly. Recent contributions have extended the concept to: harmonic state estimation (HSE) and identification of harmonic sources, transient state estimation (TSE) and voltage sag state estimation (VSSE), which are all types of power quality state estimation (PQSE). This paper provides an overview of the state-of-the-art techniques currently available for PQSE in a large electrical power system. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of line routing and terminations on transient overvoltages in LV power installationsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 8 2009Ibrahim A. Metwally Abstract IEC 62305-4 gives the rules for the selection and the installation of surge protective devices (SPDs), where the maximum enhancement factor is considered to be equal to 2 in the worst case of open-circuit condition. The objective of the present paper is to check this relation for equipment connected to low-voltage (LV) power system. The LV power system is considered as TN-S system with different routings in three- and six-storey buildings. The terminals of apparatus are substituted by a variety of different loads, namely, resistances, inductances, and capacitances. All Maxwell's equations are solved by the method of moments (MoM) and the voltage is calculated at the apparatus terminals. The SPD itself is simulated by a voltage source at the ground floor. The results reveal that the voltage at the apparatus terminals may overshoot the SPD protection level by a factor of 3 irrespective of the number of floors and loops. Copyright © 2008 John Wiley & Sons, Ltd. [source] Application of differential evolution algorithm for optimal location and parameters setting of UPFC considering power system securityEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 7 2009Husam I. Shaheen Abstract Unified power flow controller (UPFC) is one of the most effective flexible AC transmission systems (FACTS) devices for enhancing power system security. However, to what extent the performance of UPFC can be brought out, it highly depends upon the location and parameters setting of this device in the system. This paper presents an approach based on evolutionary algorithms (EAs) techniques to find out the optimal placement and settings of UPFC for enhancing power system security under single line contingencies (N-1 contingency). Firstly, we perform a contingency analysis and ranking process to determine the most severe line outage contingencies considering line overloads and bus voltage limit violations as a performance index. Secondly, we apply an evolutionary optimization technique, namely: differential evolution (DE) to find out the optimal location and parameters setting of UPFC under the determined contingency scenarios. To verify our proposed approach and for comparison purposes, we perform simulations on an IEEE 14-bus and an IEEE 30-bus power systems. The results we have obtained indicate that DE is an easy to use, fast, and robust optimization technique compared with genetic algorithm (GA). Installing UPFC in the optimal location determined by DE can significantly enhance the security of power system by eliminating or minimizing the overloaded lines and the bus voltage limit violations. Copyright © 2008 John Wiley & Sons, Ltd. [source] Computation of time delay margin for power system small-signal stabilityEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 7 2009Saffet AyasunArticle first published online: 19 JUN 200 Abstract With the extensive use of phasor measurement units (PMU) in the wide-area measurement/monitoring systems (WAMS), time delays have become unavoidable in power systems. This paper presents a direct and exact method to compute the delay margin of power systems with single and commensurate time delays. The delay margin is the maximum amount of time delay that the system can tolerate before it becomes unstable for a given operating point. First, without using any approximation or substitution, the transcendental characteristic equation is converted into a polynomial without the transcendentality such that its real roots coincide with the imaginary roots of the characteristic equation exactly. The resulting polynomial also enables us to easily determine the delay dependency of the system stability and the sensitivities of crossing roots with respect to time delay. Then, an expression in terms of system parameters and imaginary root of the characteristic equation is derived for computing the delay margin. The proposed method is applied to a single-machine-infinite bus (SMIB) power system with an exciter. Delay margins are computed for a wide range of system parameters including generator mechanical power, damping and transient reactance, exciter gain, and transmission line reactance. The results indicate that the delay margin decreases as the mechanical power, exciter gain and line reactance increase while it increases with increasing generator transient reactance Additionally, the relationship between the delay margin and generator damping is found be relatively complex. Finally, the theoretical delay margin results are validated using the time-domain simulations of Matlab. Copyright © 2008 John Wiley & Sons, Ltd. [source] The assessment of the impacts of the security management in a competitive environmentEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2009Ettore Bompard Abstract Security management is of the utmost importance in power system and many efforts have been made on this issue since a reliable supply of electricity is crucial to the modern societies. The traditional approach adopted in Europe is based on the "n,,,1" steady-state security that is efficient, although restrictive, and can continue to play an important role also in the new competitive context. In this paper, three alternative market-based models for security consideration are introduced, according to preventive and corrective control approaches. The models are presented and analyzed in terms of their economic impacts on the market throughout a set of useful indexes that allows for a ranking of the advantages got from the re-enforcement of the lines. Moreover, the positive impacts of the phase-shifter (PS) installation for the security and congestion management are quantified and indexes are derived to assess their optimal location. The different models and the exploitation of the proposed indexes are illustrated with reference to a 34-bus test system. Copyright © 2008 John Wiley & Sons, Ltd. [source] On-line dynamic security assessment to mitigate the risk of blackout in the Italian power systemEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 8 2008Diego Cirio Abstract This paper provides a comprehensive survey of the major initiatives and research projects recently carried out by the Italian system operator, Cesi Ricerca, and Universities on power system monitoring, defense, and security assessment. The technological and methodological features of an advanced wide area measurement system (WAMS) are described and the main aspects of an adaptive system for event-based automatic load shedding are presented. Then preventive and corrective security assessment, with particular emphasis to dynamic security assessment,DSA, is introduced. Results from an EU project, where the Italian power system served as a test site for on-line experimentation, are reported. Considering the need for very fast assessment by stability indices, a complementary approach to the above "conventional" DSA, currently under way, is described in further detail. The methodology relies on a correlation model relating significant power system measurements with local loadability margins. Results of some tests on the Italian power system are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Autonomous power system for island or grid-connected wind turbines in distributed generationEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 7 2008Grzegorz Iwanski Abstract Modern power generation systems for wind turbines are often based on the rotor fed slip-ring machines. Power electronics converter provides the slip power, and also the reactive power for excitation of the generator during standalone operation. This way the isolated load can be supplied even if the grid has failed. Stator voltage in an autonomous operation is controlled using vectorial phase locked loop (PLL) structure; therefore the information about mechanical speed or angular position of the rotor is eliminated from the control method. The second PLL is also used for synchronization of the generated voltage with the grid voltage. Voltages synchronization is necessary for soft connection and protection of the supplied load from the rapid change of the supply voltage phase. The grid-connected doubly fed induction generator (DFIG) can be useful after grid fault; however, the mains outage detection methods are necessary for fast disconnection after grid failures. Copyright © 2008 John Wiley & Sons, Ltd. [source] Automatic generation control of multi-area power system using fuzzy logic controllerEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2008P. Subbaraj Abstract This paper presents an application of Fuzzy Logic Controller (FLC) with triangular and gauss membership functions to study Automatic Generation Control (AGC) of a four-area interconnected power system. Out of the four areas three have steam turbines and one has hydro turbine. All steam turbines in the system contain the reheat effect of non-linearity and hydro turbine contains upper and lower constraints for generation rate. The result proves that the performance of FLC with Gaussian membership function is better than that of conventional controller. Copyright © 2007 John Wiley & Sons, Ltd. [source] Dynamic COI-tracking concept for the control of generators in multi-machine power systemsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2008Zhou Lan Abstract In the conventional excitation control concept, the power angle and frequency of a generator are driven to a pre-designed operation point after the fault occurs. It is named as Constant Point Stabilization (CPS) concept in this paper. A novel concept, called dynamic Center of Inertia (COI)-tracking concept is proposed in this paper. In the concept, the power angle and frequency of each generator track the dynamic COI of the power system. Compared to CPS concept, a salient feature the suggested dynamic COI-tracking concept has is that the generators are not restricted to constant angle point or frequency any longer but track the dynamic COI trajectory of the system to keep synchronous in rotor angle and frequency. Wide area measurement system (WAMS) will be used to transform COI signals to each generator. The time delay within a certain limit of WAMS signals is permitted. To make comparison between the two concepts, the control system models based on the two concepts are first established. Then, using the back-stepping method, two robust controllers are designed to achieve the control objectives of the two concepts. At last, dynamic simulations are carried out based on a 2-area-4-machine test power system, and the control effects of the two controllers, together with that of the conventional AVR,+,PSS excitation system, are compared. Copyright © 2007 John Wiley & Sons, Ltd. [source] Maintaining the power balance in an ,empty network'EUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 5 2006M. Reza Abstract This paper presents the concept of an ,empty network' and shows how the power balance can be maintained in such a system. In this study, an ,empty network' is defined as a power system in which no rotating mass is present; all generators are grid-connected via power electronic interfaces. One generator creates a neat 50,Hz voltage that serves as a frequency reference for the other generators. Consequently, a power unbalance cannot be detected in the classical way, as an altered system frequency. Therefore, in this paper, voltage deviations are used to detect the power unbalances. Simple test systems that consist of 1, 2 and 3 buses are applied on a real time digital simulator (RTDS). A load jump is simulated to cause a power unbalance in the system. The study shows that by using voltage deviations as control signals, the power balance can be maintained in an empty network. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effects of intermediate load on damping of synchronous generatorEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2006P. Aree Abstract The transfer-function block-diagram model of a single-machine infinite-bus power system, originally developed by Heffron and Phillips, has been a popular analytical tool amongst power system engineers for explanation and assessment of synchronous generator dynamic behaviors. Since this model simply accounts for the generator field circuit with none of the damper circuits, it may not always give a realistic transient response. Moreover, the model considers only a grid-system load without local and intermediate loads. Hence, effects of these loads together with the damper circuits on electromechanical damping have not yet been completely studied. In this paper, the Heffron-Phillips's model has been advanced to incorporate an intermediate load plus one additional damper circuit in the q -axis. The upgraded model demonstrates a great influence of the intermediate load together with the q -axis damper circuit on the electromechanical damping and the dynamic interaction between the field and damper flux linkages. The study shows the key contributions of load to rise and fall of the damping. It appears that the electromechanical damping can be improved with regard to the unity power-factor load through increasing in the natural damping and decreasing in the automatic voltage regulator (AVR) negative damping torques. Nevertheless, the damping is mostly declined, when the load power factor is poor. Moreover, it is markedly changed in relation to various locations of load. The damping characteristics of synchronous generator are investigated using the eigenvalue and frequency response methods. Copyright © 2006 John Wiley & Sons, Ltd. [source] A study on a new AVR parameter tuning concept using on-line measured data with the real-time simulatorEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2006Joong-Moon Kim Abstract Automatic voltage regulator (AVR) parameter tuning for voltage control of power system generators has generally been performed with the analytic methods and the simulation methods, which mostly depend on off-line linear mathematical models of power system. However, due to the nonlinear nature of power system, the mathematical models of the excitation system may not be correct. So the excitation control system performances with the parameter set that is tuned by using the mathematical model, may not be appropriate for some operating conditions. This paper presents an AVR parameter tuning method using on-line measured data of the excitation control system with parameter optimization technique. As this method utilizes on-line operating data, it can overcome the limitation of model uncertainty problems of conventional method. To validate the proposed tuning concept, a scaled model excitation system is connected to the real-time power system simulator, and the proposed tuning concept is tested. Copyright © 2006 John Wiley & Sons, Ltd. [source] Systematic unbalanced interharmonic interaction analysis with power constraintsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 1 2005Jesús C. Contreras Sampayo Abstract This paper presents a systematic technique to solve for the harmonic and interharmonic interaction between a power system and several harmonic sources. The technique can potentially analyze any power electronic source that can be modeled as a piece-wise linear circuit. Harmonic source data is input to the procedure using a standard lumped parameter description. Two test cases are presented. The first test case shows the interaction between a static var compensator (SVC) and an HVDC in unbalanced operating conditions. The second test case analyzes a complete current source variable speed drive connected to a distribution network. Both test cases include power constraints. Copyright © 2005 John Wiley & Sons, Ltd. [source] The application of NN technique to automatic generation control for the power system with three areas including smes unitsEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2003A. Demirören The study includes an application of layered neural network controller to study automatic generation control (AGC) problem of the power system, which contains superconducting magnetic energy storage (SMES) units. The effectiveness of SMES unit over frequency oscillations improvement against load perturbations in power system is well known. In addition, the proposed control scheme provides the steady state error of frequency and inadvertent interchange of tie-lines to be maintained in steady state values. The power system considered has three areas two of which including steam turbines while the other containing a hydro turbine, and all of them contain SMES units, in addition. In the power system each area with a steam turbine contains the non-linearity due to reheat effect of the steam turbine and all of the areas contain upper and lower constraints for generation rate. Only one neural network (NN) controller, which controls all the inputs of each area in the power system, is considered. In the NN controller, back propagation-through-time algorithm is used as neural network learning rule. The performance of the power system is simulated by using conventional integral controller and NN controller for the cases with or without SMES units in all areas, separately. By comparing the results for both cases, it can be seen that the performance of NN controller is better than conventional controllers. [source] Successive expansion method of network planning applying symbolic analysis methodEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 4 2002kokljev The conventional power system network successive expansion planning method is discussed in the context of the new paradigm of competitive electric power, energy and service market. In sequel, the paper presents an application of the conceptually new computer program, based on the symbolic analysis of load flows in power system networks. The network parameters and variables are defined as symbols. The symbolic analyzer which models analytically the power system DC load flows enables the sensitivity analysis of the power system to parameter and variable variations (costs, transfers, injections), a valuable tool for the expansion planning analysis. That virtue could not be found within the conventional approach, relying on compensation methods, precalculated distribution factors, and so on. This novel application sheds some light on the traditional power system network expansion planning method, as well as on its possible application within the system network expansion planning in the new environment assuming the competitive electric power market. [source] Load frequency control for power system with reheat steam turbine and governor deadband non-linearity by using neural network controllerEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 3 2002H. L. Zeynelgil In this paper, a neural network (NN) controller is presented for load-frequency control of power system. The NN controller uses back propagation-through-time algorithm. In the power system, the reheat effect of the steam turbine and the effect of governor deadband non-linearity are considered by describing function approach in the state space model. By comparing the results of simulations, the performance of the NN controller is better than conventional controller. NN controller gives a shorter settling time and eliminates the necessity of parameter estimation time required in conventional adaptive control techniques. [source] | ||||||||||||||||