Small Hydropower Plant With Integrated Turbine-Generators Working at Variable Speed

Present-day small hydropower plants (SHPs) have a large development potential because of the increasing interest in renewable resources and distributed energy generation; however, the variable hydrological conditions that are found in run-of-the-river projects require operations over a wide range of water flow and head variations. Special control methods and system topologies are needed to maintain the high efficiency of energy conversion systems. This paper presents a complete SHP solution based on an innovative generation unit (hydro-set): a propeller turbine is integrated with a permanent magnet synchronous generator working at a variable speed in a grid-connected system that utilises an ac/dc/ac converter. The main elements of this energy conversion system are described. A dedicated control strategy is proposed and verified. All of the results presented here originate from an actual 150-kW SHP that contains two innovative hydro-sets working in parallel on the same river.