Abstract
In recent times, much attention has been paid to small hydropower plants (SHPs) with variable speed operation and different control techniques. Control complexity in SHPs is mainly caused by specific steady-state features of the water turbine, the long time constants of the hydraulic system and significant seasonal and/or aging-related deterioration in the system performance. This paper presents the most important features of the turbine model from a control point of view. It classifies control techniques for SHPs with variable speed operation in terms of the turbine type and SHP function (run-of-the-river and reservoir). Furthermore, various control methods are analysed taking into account the complexity of the method, dynamics, adaptability and applicability. The novelty of this study is the proposal of a simple, universal analytical formula, which, based on the basic dimensions of the turbine, determines the optimal operating curve. The proposed formula is verified on a real SHP 150 kW by comparison with measurements in the form of operational characteristics. The analysis of the annual energy production confirms the effectiveness of the approximation precision, yielding only 1% production losses, and shows an advantage of variable speed over constant speed in annual energy production of 16%.
Highlights
Most of the local resources allowing the construction of high-power hydropower plants in Europe, as well as in the remaining parts of the world have been already utilised
The dynamic features of an small hydropower plants (SHPs) hydraulic system are mainly influenced by the dominant time constant of the water mass that fills the inlet and outlet pipes and turbine chamber
An important aspect affecting the operational profitability of variable speed SHPs is the selection of the optimal operation curve
Summary
Most of the local resources allowing the construction of high-power hydropower plants in Europe, as well as in the remaining parts of the world have been already utilised. The possibility of adjusting speed to mimic actual hydrological conditions widens the operating (e.g., water head—H, turbine discharge—Q) [12] This is especially important in low-power systems, range investment exploitation can be reduced by usingpoints simple propeller with fixed of suchwhere hydro-sets andand increases theircosts efficiency at operating far fromturbines the nominal values [13]. Of these of studies analysed energy empiricalspeed formulas This can be of the maininreasons for themost ineffectiveness the methodology conversion systems with a specific water turbine modelled in a simplified manner ortobythe empirical because the turbine influences the features of the system the most significantly compared power electronic and generator [19,20]. Hydro-Set addition,Features the efficiency of a turbine operating at constant and variable rotational speed is compared
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