Showing papers on "Power system simulation published in 2000"

Electric Power System Applications of Optimization

Abstract: Electric power system models power flow computation constrained optimization and applications linear programming and applications interior point methods non-linear programming dynamic programming Lagrange relaxation decomposition method optimal power flow unit commitment genetic algorithm epilogue.

Pseudo-chronological simulation for composite reliability analysis with time varying loads

Abstract: This paper presents a new methodology to evaluate loss of load indices, with particular emphasis on LOLC (loss of load cost) assessment, for composite generation and transmission systems considering time varying loads for different areas or buses. The proposed approach, named pseudo-chronological simulation, retains the computational efficiency of nonsequential Monte Carlo simulation and the ability to model chronological load curves in sequential simulation. It considers the actual blocks of unsupplied energy per consumer class, per bus, and the respective duration, to accurately characterize the interruption process. Case studies on the IEEE-MRTS (Modified Reliability Test System) and the BSS (Brazilian South-Southeastern System) are presented and discussed.

Robust tuning of power system stabilizers in multimachine power systems

Abstract: Summary form only given as follows. This paper demonstrates the robust tuning of power systems stabilizers for power systems, operating at different loading conditions. A classical lead-lag power system stabilizer is used to demonstrate the technique. The problem of selecting the stabilizer parameters is converted to a simple optimization problem with an eigenvalue-based objective function, which is solved by a tabu search algorithm. The objective function allows the selection of the stabilizer parameters to optimally place the closed-loop eigenvalues in the left-hand side of a vertical line in the complex s-plane. The effectiveness of the stabilizers tuned using the suggested technique, in enhancing the stability of power systems, is confirmed through eigenvalue analysis and simulation results.

Voltage stability analysis: V-Q power flow simulation versus dynamic simulation

Abstract: Summary form only given as follows. Several analysis methods are available for long-term voltage stability. The V-Q curve power flow method is widely used by Western Systems Coordinating Council utilities, and has some advantages. Long-term dynamic simulation with proper modeling, however, is clearly the most accurate simulation method. We compare the two methods for wintertime voltage stability problems in the Portland, Oregon USA load area. Results from the V-Q method can be misleading. The same is true of other power flow program based analysis employing conventional modeling. Results from these power flow methods may be pessimistic, causing overdesign or overly conservative operation.

State-space system identification-toward MIMO models for modal analysis and optimization of bulk power systems

Abstract: This paper provides an introduction to a reduced-order, small-signal identification approach to modal analysis and control of large power systems. Being based on system-wide responses to low-energy pulse excitations generated using conventional time-domain simulation software such as PSS/E or EMTSP, it readily takes full advantage of the large built-in model database. The proposed multi-input-multi-output (MIMO) minimal realization reveals naturally the dominant modes attached specifically to a given device, as well as the transfer functions relating selected measurement and observation sites. It plays a complementary role to direct computation of the full-scale linearized model using a comprehensive program such as MASS, after a summary of the theoretical work initiated at Hydro-Quebec in the early 1990s to promote this approach and put it into routine use, we present the main challenges in developing a production grade computer code. Detailed examples inspired by actual network studies at Hydro-Quebec are discussed, the most complex of them involving the identification of a 125th order MIMO model with 26 inputs and 26 outputs.

Dynamics of distribution networks with distributed generation

Abstract: This paper discusses the results of case studies which assess transient and small-signal stability of distributed generators connected to utility distribution networks. It also presents an investigation of the interaction between the controllers of individual generators. Case studies are based on different levels of generation penetration and a variety of operating conditions of both the networks and the generators. Transient stability and small-signal stability were assessed using commercially available power system simulation software. The interaction between the controllers is initially examined using eigenanalysis. A novel approach, i.e., individual channel analysis and design (ICAD), is then utilised to obtain an insight into the dynamics of the multivariable control problem.

Theory and applications of power system blockset, a MATLAB/Simulink-based simulation tool for power systems

Abstract: This paper presents a unified framework for power system simulation using a Simulink environment. The modeling and simulation of power systems under Simulink are described and discussed. Application examples for power systems including power networks, power electronics and electric machines are presented and compared with two popular simulation packages (EMTP, PSpice).

Modeling and simulation of the power transformer faults and related protective relay behavior

Abstract: The modeling of power transformer faults and its application to performance evaluation of a commercial digital power transformer relay are the objectives of this study. A new method to build an EMTP/ATP power transformer model is proposed in this paper. Detailed modeling of the transformer relay is also discussed. The transient waveforms generated by ATP under different operating conditions are utilized to evaluate the performance of the transformer relay. The computer simulation results presented in this paper are consistent with the laboratory test results obtained using an analog power system model.

Hybrid systems view of power system modelling

Abstract: The large disturbance behaviour of power systems often involves complex interactions between continuous dynamics and discrete events. The paper proposes a differential-algebraic-discrete (DAD) model structure which captures those interactions in a systematic way. It is shown that the model is a realization of a general hybrid system model. The DAD model opens up opportunities for the application to power systems of hybrid system results in stability analysis and control. The paper presents a practical approach to implementing the DAD model structure.

The operation of an inverter-assisted single-phase induction generator

Abstract: The enhancement of the operability range of a stand-alone single-phase induction generator scheme with an inverter-battery system connected to the auxiliary winding is the theme of this paper. The reactive power requirement of the load connected to the main winding is met by the inverter system operating with either of two proposed pulsewidth modulation techniques, in the process of which the load voltage and frequency are regulated. The proposed schemes have potential application as power sources for autonomous systems and for utility interface to single-phase power system grids. Simulation and calculation results of the generator system connected to an impedance and motor loads, confirmed with some experimental results, are also set forth to validate some of the conclusions of the paper.

Performance evaluation of thyristor based static transfer switch

Abstract: Industrial customers are becoming more sensitive to variations of utility supply systems due to the growing demand for process controls in automated plants. One option to increase reliability and quality of AC power is to provide sensitive customers with access to two independent power sources. In this paper, a fast thyristor based static transfer switch (STS) is proposed which employs fast voltage-detection and thyristor gating strategies to connect the customer to either of the two sources. Performance of the designed STS system is evaluated using the Electromagnetic Transients for DC (EMTDC). Simulation results are verified by comparing them with experimental results.

Digital simulation of power systems and power electronics using the MATLAB/Simulink Power System Blockset

Abstract: The Power System Blockset (PSB) is a graphic tool that allows schematics and simulation of power systems to be built in the Simulink environment. The blockset uses the MATLAB/Simulink environment to represent common components and devices found in electrical power networks. Simulink's variable-step event-sensitive integration algorithms allow increased accuracy in zero-crossing detection of currents as compared with fixed step algorithms. One important feature of the Power System Blockset which has been introduced with version 2.0 is its ability to simulate either with continuous variable time-step integration algorithms or with a discretized system. For small and medium size systems, variable time steps algorithms are usually faster because the number of steps will be less than with a fixed-time step method. However, for large systems which contain many states or many nonlinear blocks such as power electronic switches, it is advantageous to discretize the electrical system. Both the continuous integration and fixed-time step methods are illustrated. The graphic interface of Simulink provides a user-friendly environment where the power circuit and control system are represented in the same diagram. The results are displayed while the simulation is running. The processing power of MATLAB allows the designer to perform complex post-processing on simulation results. This special technical session presents the features of the Power System Blockset and its applications in the simulation of power systems and power electronics systems.

Modeling of FACTS in power system studies

Abstract: In complex interconnected power systems, technical problems in load flows and stability can be expected, and these problems are aggravated by the requirements of a liberalized energy market. Extended interconnected systems experience stability problems and inter-area oscillations, which can lead to system interruptions. Furthermore, long distance AC transmission requires reactive power compensation, introducing stability constraints that limit transmitted power. These conditions can be improved by the use of FACTS controllers. These improvements can be predicted by the proper simulation of FACTS controllers, which include all controls and a detailed representation of the system. Hence, this paper discusses FACTS controller models used through various analysis and design steps on FACTS projects. Examples of application studies of these controllers are also presented.

A neural network based power system stabilizer suitable for on-line training-a practical case study for EGAT system

Abstract: This paper presents the development of a neural network based power system stabilizer (PSS) designed to enhance the damping characteristics of a practical power system network representing a part of Electricity Generating Authority of Thailand (EGAT) system. The proposed PSS consists of a neuro-identifier and a neuro-controller which have been developed based on functional link network (FLN) model. A recursive on-line training algorithm has been utilized to train the two neural networks. Simulation results have been obtained under various operating conditions and severe disturbance cases which show that the proposed neuro-PSS can provide a better damping to the local as well as interarea modes of oscillations as compared to a conventional PSS.

A model of fossil fueled plant with once-through boiler for power system frequency simulation studies

Abstract: A model of a fossil fueled generating power plant with a once-through boiler for power system frequency simulation studies is presented. In the model, the plant control system is modeled to represent the fundamental response of the coordinated boiler-turbine control in the large-size supercritical plants under changes in the system frequency. The model is based on a survey of configurations of the plant control systems used in the major units commercially operated in Japan. The values of the parameters in the model are described through the comparisons with plant responses in a field test and with simulation results from a detailed model of the plant manufacturer. Sample simulation results from the model are presented for demonstrating the fundamental response of the once-through plants under change in system frequency.

Effects of FACTS devices on static voltage stability

Abstract: This paper presents a study of FACTS devices mainly static VAr compensator (SVC) and controlled series compensator (CSC). Their steady-state modeling and effects on power system performance have been studied. It also studies static stability improvement of a power system and hence power flow improvement in the network. Standard stability evaluation technique has been used to identify the optimum place for the implementation of flexible AC transmission system (FACTS) devices and the effects of FACTS on system loadability has been studied and presented here. The technique to identify the optimum location for the placement of FACTS devices is based on the concept of maximum power transferring capability of the lines and buses. The study has been carried out on the IEEE 24 and 118 bus test systems. Study reveals that incorporation of FACTS devices significantly enhanced system stability as well as power transfer capability of the system.

A simulation tool for the design of the electrical supply system of high-speed railway lines

Abstract: The design of the electrical supply system of high-speed railway lines involves the selection of the single phase system (one or two active conductors: 1/spl times/25 kV or 2/spl times/25 kV), the design of the catenary, and the location and sizing of the substations and the autotransformers in case of a 2/spl times/25 kV system. The electrical system should be designed so the train voltages are in the admissible range and the conductor currents and transformer powers are smaller that their rated values. This paper presents a simulation tool for the design of the electrical supply system of high-speed railway lines. The tool is composed of two main modules: (1) the simulator of the railway line; and (2) the electrical system simulator. The railway line simulator determines the position and power consumption of each train at each time step provided the line operation policy. The electrical system simulator solves the AC network at each time step and provides the catenary and train voltages, the conductor currents and the transformer power flows.

Innovative techniques in modeling UPFC for power system analysis

Abstract: The unified power flow controller (UPFC) is a flexible AC transmission system (FACTS) device capable of controlling line flows and terminal voltage. In order to analyze its true effects on power systems, it is important to model its constraints due to various ratings and operating limits. Innovative techniques are introduced in this paper for fast power flow convergence with various UPFC control modes and simultaneous multiple limits enforcement, while the line side bus remains explicitly accessible. An efficient algorithm is developed for applying the line side voltage limits, which avoids the possible hunting between shunt and series converters of UPFC. Control models with similar constraints are also developed for stability studies. Simulations are performed using EPRI's Power System Analysis Package (PSAPAC).

Modeling and operation of a 10 kW photovoltaic power generator using equivalent electric circuit method

Abstract: The output power of a photovoltaic power generator system (PV system) changes continuously as it strongly depends on the weather condition (solar radiation and temperature). Large fluctuations of output of PV system result in fluctuation and hence of harmonics in the inverter output. The PV systems are usually connected to the power grid lines, therefore, it is necessary to simulate the effects of the PV power systems on the commercial distribution line. In this paper, the authors have modeled a 10 kW PV module using current-voltage characteristic of a PV module by estimating its equivalent electrical circuit parameters.

An extensible genetic algorithm framework for problem solving in a common environment

Abstract: The authors describe an object-oriented framework for solving mathematical power system programs using genetic algorithms (GAs). The advantages of this framework are its extensibility, modular design and accessibility to existing programming code. The framework also incorporates a graphical user interface that may be used to build new GAs as well as run GA simulations. Two power system problems are solved by implementing genetic algorithms using the said framework. The first is a continuous optimization problem and the second an integer programming problem. The authors illustrate the flexibility of the framework as well as its other features on their test problems.

Decentralized stability-enhancing control of synchronous generator

Abstract: Summary form only given, as follows. This paper describes new structures for stability-enhancing excitation controllers designed using a nonlinear multi-machine system model and Lyapunov's direct method. Two control structures are presented: a hierarchical structure in which the AVR is the master controller and the PSS the slave controller and a traditional structure in which the PSS constitutes a supplementary loop to the main AVR. Both controllers are shown to be robust, as the damping they introduce into the system is insensitive to changes in both the system topology/parameters and the pattern of network flows. Each individual controller contributes positively to the overall system damping with no undesirable interaction between controllers. These features should allow a decentralized approach to the design of the AVR+PSS. Such a design approach is compatible with the new competitive market structures and should result in savings on commissioning costs. Simulation results for a multi-machine power system are presented that confirm the above and show that the two control structures are very effective in damping both local and inter-area power swings.

A method for linking different modeling techniques for accurate and efficient simulation

Abstract: This paper presents a new method for accurate linking of diverse simulation techniques. The method employs a functional modeling (FM) approach and facilitates linking of different simulation techniques as well as combining separate simulation engines. In addition, the presented method enables system decomposition with freely selected cuts as well as natural and efficient parallel computations. Discussion of advantages and various applications is also included.

State of the arts of the modern heuristics application to power systems

Abstract: In this paper, the application techniques of such modern heuristics methods as genetic algorithm, simulated annealing, tabu search, etc. to power systems operation and planning which are published in IEEE PES Transactions between 1990 and 1999 are systematically surveyed, and the state of the art of these techniques are outlined.

A new framework for estimation of generator dynamic parameters

Abstract: Summary form only given as follows. The accuracy of generator dynamic parameters is one of the crucial factors in correctly simulating the power system transient phenomena. This paper proposes a general procedure for estimating the generator dynamic parameters from measurements. The proposed procedure employs a gradient based simulation optimization technique to estimate the parameters. Effectiveness of the simulation optimization method is shown in some examples for estimating the exciter and governor model parameters. Impacts of noise and parameter uncertainties are briefly discussed in the paper.

Analysis of a voltage instability incident in the Greek power system

Abstract: The paper reports on a 1996 incident in the Greek power system that had all the characteristics of voltage instability and the subsequent analyses and countermeasures. Voltage stability analysis is performed by both NTUA and ULg software tools that give identical simulation results. After the upgrades performed by PPC a considerable increase in the maximum power that can be fed to the Athens area is achieved. Finally, secure operation limits of the upgraded system are calculated.

Reactive tabu search for distribution load transfer operation

Abstract: This paper presents a reactive tabu search for distribution load transfer operation. The load transfer operation at steady-state operation and planning aims at reconfiguring the target network for various purposes including loss minimization. On the contrary, the operation at restoration is called service restoration and aims at minimizing out-of-service area as quickly as possible. Both operations can be formulated as combinatorial optimization problems to divide the target network into several sub-networks, where each one has only one power source. The effectiveness of the proposed reactive tabu search is compared with other modern heuristic approaches (MHAs) on typical distribution systems with promising results.

Using the powerful SABER simulator for simulation, modeling, and analysis of power systems, circuits, and devices

Abstract: Power systems are some of the most difficult types of designs to simulate. They contain high frequency switching of currents and voltages into inductors and across capacitors, multiple feedback loops (voltage, current, motor speed, etc), nonlinear magnetics, high power device models, DSP, motors, generators, fuses, power distribution, thermal modeling, nonlinear sources (battery, solar array, etc), and loads. In addition, schematic capture, post processing of the waveforms, links to critical tools, and a powerful mixed-signal mixed technology modeling language are needed. There is no one tool that can provide 100% of capabilities to 100% of the engineers, however there is no single tool more powerful than SABER. This paper shows how SABER provides all the above capability and more.

Control concept of Unified Power Line Conditioner

Abstract: The Unified Power Line Conditioner (UPLC) with integrated series and parallel active filters is a universal solution featuring most power quality problems in distribution systems. This paper outlines the central concept of UPLC. The series active filter is controlled to maintain the load terminal voltage at required level with sinusoidal waveform, while the parallel active filter is specialized for mitigating the harmonics and the imbalance of the nonlinear loads. The exchanging power between the two active filters is limited to minimum. The control concept of UPLC is introduced and analyzed, with the simulation results to demonstrate the proposed approach.

A synergetic approach to the modeling of power electronic systems

Abstract: The authors introduce a synergetic approach, which brings great improvements in computer modeling and simulation of power electronic systems. Essentially, the process involves synthesis of control laws that result in collapse of (at least two) initially high-dimension models into a single model of lower-dimension. The technique requires creation of state space attractors, artificial manifolds, that reflect the desirable operating regimes of the dynamic system. They explain the process and give example results.