The article considers the problem of improving power efficiency of the diesel generator power plants as one of the priority objectives for development of low power generation in Russia. Improving energy efficiency for autonomous facilities is directly related to the optimization of hydrocarbon fuel consumption by marine diesel engines. It is possible to optimize the fuel consumption of internal combustion engines by creating variable-speed diesel generators (VSDG), which are diesel-generator units with semiconductor converters, i.e. systems with valved generators. Optimization of specific fuel consumption by VSDG is provided by the forced regulation of the rotational speed of the shaft of the internal combustion engine in accordance with its multi-parameter characteristic in the shared load conditions of the power plant. The synchronous electric machine is used as a generator as part of a ship power station. Its use in the classic constant-speed diesel generators is more preferable than an asynchronous electric machine. In the development of VSDG - valved power plant - the use of an electric machine with a phase rotor as a generator is technically justified, because the installed capacity of the frequency converter in the rotor circuit of an asynchronous generator with a phase rotor is determined by the sliding power and, with a limited range of speed control, SDGV significantly reduces the installed capacity of the electrical equipment. Such power topology of a ship’s power plant is called VSDG based on a dual-power machine. There has been proposed to consider a variant of a ship power plant based on VSDG with a dual-power machine. Its functional diagram and mathematical model are developed. A structural diagram is presented and dynamic modes of the amplitude and frequency of the generated voltage are modeled during electrical load switching.