Optimal power control for a variable-speed generator integrated in series hybrid vehicle.

In series hybrid electric vehicles, the fossil energy source is composed of an electrical generator driven by an internal combustion engine. Compared to constant speed control, variable speed control of the electrical generator improves the vehicle’s energetic efficiency and releases the battery load. Such control is extremely sensitive because of the nonlinearities. In a plug-in hybrid vehicle, in addition to the obvious inherent variable speed nonlinearity, the large range of battery voltage variation increases the complexity of the controller design. Moreover, in our case, to take advantage of the variable speed feature, the generator load has transient constraints because it must follow the vehicle load. In equivalent applications, for the electrical side, usually there is a use of high-frequency control strategies, based on the generator’s three phases current and voltage acquirement. This paper investigates a low-frequency power control strategy through model-based method for a specific power electronics vehicle architecture. Starting with an adaptive PID based controller to tackle the non-linearity issues, the paper explains progressively the reasons and choices that lead to design a sliding hybrid fuzzy logic controller. The designed controller demonstrates good performance in power tracking and permits to reduce the fuel consumption.