Woodward (Germany)

In der Vergangenheit waren stets Bestrebungen zur Emissionsreduzierung – umgesetzt durch kontinuierlich verscharfte Abgasgesetzgebungen – Treiber fur Neuentwicklungen im Bereich der Diesel-Einspritzsysteme fur Grosmotoren. So lagen die ersten elektronisch angesteuerten Common-Rail Einspritzsysteme im Grosmotorenbereich 1997 bei 1200 bar Systemdruck. Durch eine stetige Weiterentwicklung wurde der Druck innerhalb der darauffolgenden zehn Jahre bis auf 1800bar angehoben.

New requirements for the validation of simulation models based on measurements in many grid codes show that existing generic approaches for generator and converter models of doubly fed generator systems (DFG) may not be accurate enough. The authors show that by applying a detailed analysis of the generator equations and the converter control design, a reduction of the model complexity is possible while maintaining a high level of accuracy. The generator model presented in this paper allows an improved representation of the stationary and dynamic response of wind turbines equipped with DFG systems especially during grid faults and during voltage recovery. The model is designed to represent modern DFG systems independently of vendor specific hardware and software. The results of simulations are compared to measurements of a voltage dip involving wind turbines. The generator model has been proposed as extension to the WECC/IEEE generator models and has been accepted as reference for IEC TC88 working group 27 (standard IEC 61400-27-1) on modeling and model validation of wind turbines.

When soil is compacted in layers by rollers, vibrating plates, or rammers, the horizontal earth pressures within the compacted soil mass are increased. Charts are presented that can be used to estimate compaction‐induced earth pressures quickly and reliably. These charts are developed using the hysteretic theory developed by Duncan and Seed, with a computer program called EPCOMP2. The charts offer the advantages of being easy to use, and providing very rapid results, while retaining most of the accuracy of the detailed computer analyses. Because earth pressures can be estimated quickly, it is easy to evaluate the effects of changes in the factors that influence the magnitudes of the compaction‐induced earth pressures. Comparisons of earth pressures calculated using these charts with the results of computer analyses indicate that the values calculated using the charts are sufficiently accurate for practical purposes. Field measurements of compaction‐induced earth pressures indicate that the horizontal eart...