SIMULATION

Modeling of power electronics circuits presents significant challenges due to the non-linear time-varying behaviour of this kind of system. It is common practice to operate with families of models of different complexity depending on the analysis goal. In this paper we propose a wavelet-based approach as a unifying framework able to provide multi-resolution capabilities and consequently significant flexibility to the modeling process. The comparison with more classical approaches to power converter modeling demonstrates how this approach can be considered an extension of formalizations such as state-space averaging. Simulation results for both DC-DC and DC-AC power converters, including soft-switching configurations, are presented as sample applications. The discrete-time formulation makes this approach particularly suitable for design and analysis of converters operated with digital controllers.

A hybrid wind/photovoltaic generation system is designed to supply power demand. The aim of this design is minimization of the overall cost of the generation scheme over 20 years of operation. Full demand supply is modeled as constraint for optimization problem. Characteristic equations of the system components and solar radiation and wind speed datasets are assumed to be deterministic, i.e. uncertainties are ignored. The system's costs include investment, replacement, and operation and maintenance costs during 20 years of system lifetime. All system components are commercially available, and actual prices are used. Wind and radiation datasets are for the North West region of Iran (Ardebil province). A Particle Swarm Optimization (PSO) algorithm is used to solve the optimization problem. Results indicate superiority of the PSO algorithm, in terms of speed and convergence to global optimum solution, over a Genetic Algorithm that is conventionally exploited in literature.

The DC load flow is a rapid and approximate solution method for the determination of lines active power flows in power systems. In this paper, the HVDC (High Voltage Direct Current) links and FACTS (Flexible AC Transmission Systems) devices have been modeled in the DC load flow analysis. In order to evaluate the performance of the proposed method, the proposed DC load flow results have been compared with the AC or AC-DC load flow results of DIgSILENT software. It is shown that the proposed DC load flow is accurate enough for power system studies.

In an attempt to investigate blood unit ordering policies, researchers have created a discrete-event model of the UK National Blood Service (NBS) supply chain in the Southampton area of the UK. The model has been created using Simul8, a commercial off-the-shelf (COTS) discrete-event simulation package (CSP). However, as more hospitals were added to the model, it was discovered that the length of time needed to perform a single simulation severely increased. It has been claimed that distributed simulation, a technique that uses the resources of many computers to execute a simulation model, can reduce simulation runtime. Further, an emerging standardized approach exists that supports distributed simulation with CSPs. These CSP Interoperability (CSPI) standards are compatible with the IEEE 1516 standard, the High Level Architecture (HLA), the de facto interoperability standard for distributed simulation. To investigate if distributed simulation can reduce the execution time of NBS supply chain simulation, this paper presents experiences of creating a distributed version of the CSP Simul8 according to the CSPI/HLA standards. It shows that the distributed version of the simulation does indeed run faster when the model reaches a certain size. Further, we argue that understanding the relationship of model features is key to performance. This is illustrated by experimentation with two different protocols implementations (using Time Advance Request (TAR) and Next Event Request (NER)). Our contribution is therefore the demonstration that distributed simulation is a useful technique in the timely execution of supply chains of this type and that careful analysis of model features can further increase performance.