Efficiency analysis of an energy conversion system for a variable speed small hydropower plant

Abstract

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 the 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. The synchronous generator excited by permanent magnets (PMSG) characterizes higher and more stable efficiency characteristic, in relation to the generated power, then mostly used in SHPs asynchronous machine. This paper investigates the efficiency of an example SHP solution. The researched system is based on an innovative generation unit (hydro-set) containing a propeller turbine integrated with the PMSG. In order to obtain the high efficiency in a wide range of water flow the variable speed operation method has been used. This solution requires a Power Electronic Unit in the energy conversion system to match the load and control the power flow from the generator to the grid. Efficiency analysis concerns all elements of the energy conversion system. Presented results comes from the real SHP of 150kW nominal power.