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

Abstract

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.

Integrated turbine-generators for hydropower plant – a review

“…The power losses of the turbine set based on the measurements of the actual hydro set amounted to even 10% of the generator rated power depending on the size of the slot and the rotational speed of the turbine. Analytical calculations verifying the wetfracture value are presented in the article [13]. It The change of the Reynolds number value depending on the angular velocity does not significantly change the hydraulic resistance coefficient.…”

“…In this solution, instead of the turbine rotor blade control system, a variable rotational speed was used through the use of a power electronic converter. This solution has been thoroughly tested and analysed by among others the authors of this study [11][12][13][14]. Fig.…”

Alternative Solutions for Small Hydropower Plants

“…In this design, a variable rotational speed achieved by using a power electronics converter replaced turbine runner blade regulation. This topology was carefully examined and analyzed by the authors [11][12][13]. All the solutions described above refer to assembling a hydraulic turbine inside a synchronous generator, which is called "full integration."…”