System Simulation Techniques Research Articles

Wide area network performance modeling of distributed energy management systems

A distributed energy management system consists of networked hardware and software capable of monitoring and controlling the operations of an electric utility. When several of these distributed systems are connected to each other via wide area network connections, then a truly geographically distributed environment exists where data between systems can be shared. Heavy communication network loads and transit time constraints on these large amounts of shared data are significant design considerations, especially in light of the fact that most power utilities have existing private networks or use leased voice grade circuits. Modeling of the wide area network aspects of interconnected energy management systems was seen as a way to identify potential communications problem areas between systems early in the design process. Modeling would also help verify that the hardware and software designs would accommodate the communications load and ensure that transit times were within the system's functional requirements. System stress case data was used in each model to simulate a worst-case data acquisition and dissemination environment. This paper describes the modeled configuration and provides specific details about the system simulation techniques used and the conclusions provided by the model to estimate transit times and line rates for WAN connections.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

MDS: A design methodology for switched reactance systems

There are many proven formal techniques for design and simulation of digital or analogue systems and circuits. Such techniques are rather cumbersome, and at times inefficient, when they are employed in the design of systems containing both analogue and digital sub-systems. This inefficiency, in the majority of cases, leads to separate design methodologies being employed and the designed sub-systems to be brought together at a later stage. The late merger of the designed sub-systems also results in further complications and incompatibilities. This paper proposes a technique, referred to as the MDS, for the design of switched reactance (inductive and capacitive) systems. The proposed method is applicable to both event-driven and predefined switching systems. The results submitted reflect the suitability of the method for both software simulation and hardware realisation techniques. It also plays an important role during the hardware debugging stage.

Efficient importance sampling techniques for simulation of multiuser communication systems

The problem of simulating error rates in direct sequence spread-spectrum code division multiple-access (CDMA) systems is examined. Due to the computational complexity required to simulate these systems, an importance sampling technique is developed based upon previous work by the authors. A conditional weighting function is derived such that the linear shift class of biasing densities can be employed. Results are given for a variety of detector structures and background noise distributions. It is shown that this biasing scheme can dramatically reduce the run time of realistic multiple-access simulations. >

Development of functional simulation model of CMOS memory

AbstractThe development of semiconductor integration has brought with it the system‐on‐chip era. The small‐quantity productions of diversified kinds of IC are required at the stage of ASIC (application specific IC). Thus, it has become important to reduce the design period for the mixed analog/digital circuit. The capacity of the CMOS memory continues increasing and is expected to expand from the Mbit level to the Gbit level. Then the parasitic effect will be a problem.This paper proposes a functional simulator based on the continuous system simulation technique. It is shown that the proposed simulation including the parasitic effect can effectively be applied to the functional design of CMOS memory, which has been unsatisfactory in the early circuit simulator.In the proposed method, CMOS memory is modeled based on the functional element model of the CMOS memory and the functional simulation can easily be realized considering the parasitic functional effect. This helps to improve the design quality and to reduce the design period.

A toolbox for power system dynamics and control engineering education and research

The design concept and use of the power system toolbox (PST), a Matlab-based power system dynamics simulation and control design package, are discussed. The motivation for developing the package was to provide a flexible environment for teaching power system simulation techniques and control design concepts to advanced undergraduate and graduate students, and for graduate students to perform research and development on power systems. The authors discuss the capabilities of PST and the software development philosophy. Sample applications are given. Some potential educational usage is suggested. The future enhancement to the package is outlined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Artificial intelligence based simulation in the design of a GDSS idea generation tool

Little research has been conducted on the software engineering design problems of group decision support systems (GDSS). We believe this has been due in part to the lack of powerful system design methodologies, such as Artificial Intelligence Based System Simulation (AISS) techniques and also, in part, due to a lack of research direction. The AISS design methodology described here is split into three stages: the specification of system boundaries using a System Entity Structure (SES), SES pruning and model synthesis using an expert system (ES), and the evaluation of candidate design models using discrete event simulation (DEVS). This paper presents an example of applying AISS to the design of a GDSS Idea Generation tool. Simulation results show that the selected model meets the design criterion of equitable distribution of comments among group participants.

Charge Susceptibility of the Two-Dimensional Hubbard Model near the Half-Filled Band -A Monte Carlo Study-

Using the quantum Monte Carlo simulation technique for the lattice fermion systems, we study the charge susceptibility of the two-dimensional Hubbard near the half-filled band. Lattice sizes up to 6×6 and inverse temperatures up to 6 t ( t : hopping parameter) are studied. We find that the behavior of the charge susceptibility is strongly dependent on the electron concentration at low temperature: the charge susceptibility is suppressed at the half-filled band, while it is considerably enhanced in non-half-filled band cases by the electron correlation. The above behavior of the charge susceptibility is quite similar to the recent Bethe-Ansatz result for the one-dimensional Hubbard model.

Functional simulation of color signal processor for VTR by digital dynamics simulation language

AbstractWith the development of semiconductor integration, the technology has arrived at the stage of the system‐on‐chip. With the widespread use of application specific IC (ASIC), the small‐quantity production of diversified types is required. Then it is important to reduce the design period for the mixed analog/digital circuit.VTR color signal processing LSI is a typical mixed analog/digital circuit. It has the scale of 500 analog elements and 800 digital elements, and it is too time‐comsuming to simulate the operation of the whole LSI by the conventional circuit simulator. Thus, a functional simulator is required for the large‐scale mixed analog/digital LSI.This paper proposes a functional simulation, employing techniques of continuous system simulation. The technique is applied to the design of a mixed analog/digital circuit, where the conventional method has been unsatisfactory, and the method is shown to be useful in the Functional design of the circuit. The method is based on the modeling of the mixed analog function/circuit, and can be applied to the VTR color signal processing LSI.The functional simulation can easily be performed with the complete knowledge of the analog function. Consequently, the method can contribute greatly to the quality improvement of the design and the reduction of the design period.

Improved importance sampling technique for efficient simulation of digital communication systems

An improved importance sampling technique for the efficient simulation of digital communication systems is proposed. Evaluation of low-probability error events by direct use of classical Monte Carlo (MC) simulation techniques usually involves a very large number of runs. Importance-sampling techniques make the low-probability events occur more frequently. The technique proposed here is based on optimized translations of the original probability densities. The only approximation needed in the optimizations is that of replacing the Q function by the simpler exponential expression. Detailed analytical evaluations of the estimation variances of the classical MC and the conventional and improved importance-sampling approaches for systems with memories and signals are presented and compared, showing the superior performance of the latter. Detailed numerical and simulation results are given. >

Three-phase modeling of unbalanced distribution systems during open conductors and/or shunt fault conditions using the bus impedance matrix

Abstract This paper presents a digital simulation technique for unbalanced three-phase distribution systems subjected to a shunt or a series fault. The method is also applicable to multiple faults which involve a shunt fault at one location and blown fuses or open conductors at another. The method utilizes the phase frame representation of network elements. The imbalance conditioned by large single-phase loads, untransposed feeders, conductor bundles, etc., is reflected in the polyphase impedance matrix. Consequently, line removals, additions, impedance changes, conductor and phase openings can be simulated by modifying the base-case impedance matrix. Thus, the proposed method makes it possible to analyze any type of single or multiple fault occurring anywhere in the system.

Efficient Numerical Simulation and Identification of Large Chemical Reaction Systems

New, highly efficient techniques for the numerical simulation and parameter identification of large chemical reaction systems are surveyed. The survey particularly addresses to chemists, which are understood to be potential users of the distributed software packages. These packages are written in the form of interactive dialogue systems - thus enabling chemists to concentrate on the chemistry of their problem. Large scale examples from chemical research environments are included.

Digital Simulation of Multiterminal HVDC Systems Using A Novel Converter Model

A technique for detailed dynamic simulation of multiterminal HVDC systems with associated controls is presented here. This utilizes a novel converter representation based on the analysis using graph theoretic framework. This enables the development of an efficient model of the converter during both normal and abnormal modes.

A fast and efficient digital simulation technique for control systems

The new simulation technique uses a digital compensator in the forward path immediately after the error detector in a typical closed loop system. This compensator contains two parameters which can be tuned to obtain very accurate results. This technique was used on a second order closed loop system with a non linear element in the forward path. The results show great improvement over the substitution methods (Halijak and Tustin). When another compensator was introduced in the feedback path, the results are comparable to the highly accurate T-integrator method.

Computer simulation calculations for one-dimensional magnetic systems, with some remarks on optimisation on the cray computer

Some of the novel aspects of the spin dynamics of one-dimensional magnetic systems are illustrated by a review of some recent studies of such systems. Emphasis is laid on the role played by computer simulation calculations in understanding the fundamental mechanisms, and advances in the simulation technique for magnetic systems are described. The impact, both actual and potential, of fast vector processors, such as the CRAY computer, is assessed, with reference to specific figures for increases in computational speed.

A technique for efficient simulation of large dynamic systems

A technique for efficient simulation of large dynamic systems

Simulation of continuous system models in industrial engineering

Many industrial engineering and operations research studies in the creation of continuous dynamic models; that is, models consisting of a system of ordinary differential equations. Such models arise frequently in the analysis of economic, inventory and production control systems. The area of Industrial Dynamics (more recently named Systems Dynamics) is specially oriented toward modeling and simulation of these dynamic systems. The purpose of this paper is to discuss briefly some of the current techniques for modeling and simulation of continuous systems and then to devote major attention to describing a number of difficulties encountered in the actual digital simulation. Finally, a number of specific suggestions will be offered to prevent the occurence of most of these problems.

A DDC-Design Based on a Digital Simulation Technique

Refering to the two-variable control system representing the pressure and the steam temperature control, respectively of a steam generator a design method of a DDC system is described. The control algorithms employed were selected according to a comparative simulation study. By dealing with this problem a digital simulation technique for sampling systems was developed. It is presented in brief.