Synchronous machine-turbine drive system with indirect speed control

Dynamic properties of a hybrid system are analyzed that has been developed to generate electric energy by utilizing alternative, renewable and waste energies. 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 utilize the energy content of some working medium by a special turbine that converts the energy content of the working medium into electric energy by the generator and the AC/AC converter. The alternative renewable energy sources may include solar energy (direct solar steam system or solar energy with heat exchanger), geothermal energy (with or without heat exchanger) and energy obtained from biomass. Various waste energy sources can also be utilized by applying the system such as the energy that can be obtained during the process of pressure reduction in steam, gas and fluid networks. 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 analyses a novel control strategy and principle of the system to ensure optimum performance and economy by using a special solution for ensuring the power equilibrium in the combined mechanical-electric drive.