One of the inventors' concepts relates to a power generation system, comprising a diesel engine and an exhaust system. The exhaust system comprises a first oxidation catalyst, a fuel reformer, and a LNT. A fuel injector is configured to inject fuel downstream of the oxidation catalyst, but upstream of the reformer. Preferably, the first oxidation catalyst is located near the engine. The first oxidation catalyst can extend the range of exhaust temperatures at which the aftertreatment devices operate by raising the temperature through reactions with residual hydrocarbons in the exhaust. The first oxidation catalyst also stabilizes the reformer operation by reducing the exhaust oxygen concentration. In a preferred embodiment, the engine operation is changed for LNT regenerations to increase the hydrocarbon content of the exhaust.