Optimal Transient Control and Effects of a Small Energy Storage for a Diesel-Electric Powertrain

Abstract: Optimal control of a diesel-electric powertrain in transient operation as well as effects of adding a small energy storage to assist in the transients is studied. Two different types of problems are solved, minimum fuel and minimum time, with and without an extra energy storage. In the optimization both the output power and engine speed are free variables. For this aim a 4-state mean value engine model is used together with a model for the generator losses as well as the losses of the energy storage. The considered transients are steps from idle to target power with different requirements on produced energy, used as a measure on the freedom in the optimization before the requested power has to be met. For minimum fuel transients the energy storage remains unused for all requested energies, for minimum time it does not. The minimum time solution is found to both minimize the response time of the powertrain and also provide good fuel economy. For larger requested energies with energy storage the response time is immediate, with an energy storage of only 10-20Wh.