Browsing by Author "Ovaska, Seppo J., Prof., Aalto University, Department of Electrical Engineering, Finland"

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Methodologies for development of series-hybrid powertrains to non-road mobile machineries
(2013) Liukkonen, Matti
School of Electrical Engineering | Doctoral dissertation (article-based)
This dissertation is about the assessment and development methodologies of series-hybrid powertrains to non-road mobile machineries. The development and optimization of alternative powertrains require computational methodologies for different fidelity levels in order to maintain manageability and effectiveness of analyses. This dissertation uses a multi-stage modeling approach for a large-signal analysis of system-level designs. A small-signal approach is proposed for the stability assessments of DC-buses in power-electronics systems. The multi-stage modeling approach is used systematically for assessments of the diesel- electric powertrain with the power buffering by the active ultracapacitor. These assessments include design and validation of energy management algorithms for the powertrain. This energy management is described as the indirect power buffering, due to low-level controls of converters. The partial differential equations and the Monte Carlo method are used for error and sensitivity analyses of these assessments. Knowledge of achievable accuracies and restrictions of the multi-stage approach have been attained with experiments and assessments. The multi-stage modeling approach is used for evaluations of feasibilities and features of powertrain options in a non-road mobile machinery case. Mutual relations of the features of powertrain options, such as size, weight, cost, and efficiency, are concluded. This knowledge is a base for the choice between powertrain options, and enables optimization of the powertrain with respect to a single feature. The significance of this approach is on the management of the complex entity, i.e., the design of complete series-hybrid powertrains. A systematic approach for the dynamic modeling of DC-buses in power-electronics systems is introduced. This approach facilitates designs of load and source converter controllers in such a system. It can be used to derive the maximum lengths of the DC-bus cabling, as well as the minimum values and distribution of the DC-bus capacitances.