The article describes the diesel generator complex which consists of two diesel generators. In order to save fuel, it is advisable to choose one diesel generator of inverter type, i.e. to switch it to a variable speed mode. The buffer storage device is used as a part of the power plant in order to ensure the required parameters of the generated electricity under peak loads, as well as when the generator is operating at the limit of rated power. There has been given the control algorithm and transient processes of the charge / discharge of the buffer storage device in a diesel generator power plant. The power plant that consists of a classic diesel generator and a variable speed diesel generator unit (valved generator) has been chosen as an object research. A block diagram of the power plant conducting is proposed, as well as a power transformer topology of a variable-speed diesel generator based on a step-down pulse-width converter. There has been presented an algorithm for controlling the connection of a buffer storage device depending on its charge and the load power value both in stand-alone mode and in parallel operation of generator sets. In the MatLab Simulink computer environment a simulation model of a power plant was developed and transient processes of load switching, as well as charge / discharge of a buffer energy storage device were studied. An electrical circuit diagram of an experimental bench of a variable-speed diesel generator set is illustrated. The results of experimental studies of dynamic modes of operation on a prototype variable speed diesel generator with a power of 3.2 kW are also presented.