The paper describes a special system that makes it possible to generate electric and heat energy by utilising alternative, renewable and waste energies, in most cases, applying the principle of co-generation. The solution is based on a system that consists of a high-speed turbine, coupled to a three-phase permanent magnet synchronous generator, an AC/AC converter and a supervisory control unit. The function of the system is to utilise the energy content of some working medium by a special turbine that partially converts the energy content of the working medium into electric energy by the generator and the AC/AC converter. The electric power generated by the system can be fed back to the utility mains or it can be used in stand-alone mode to supply a selected group of loads. The paper focuses on the utilisation of waste energy that can be obtained during pressure reduction of saturated or superheated steam, furthermore the basic control strategies and principles of two basic modes of operation are also presented.