Primary frequency regulation performance in hydropower systems: Precise quantification and holistic enhancement under wide-range operation

Numerous hydropower units are shifting to wide-range operation (WRO, head variation is over 7 % of the rated head, and power adjustment range is more than 50 % of the rated power.), which increases the risk of failing the primary frequency regulation (PFR) assessments from the power grid. To precisely quantify and holistically enhance the PFR performance. Firstly, a flexible hydro-turbine regulation system (HTRS) simulation platform with modular subsystem switching is established to facilitate various operating conditions and comparative studies. Secondly, Prony identification is introduced to determine the stable range of the complex nonlinear HTRS, which saves more than 90 % calculation time and is more accurate compared to traditional methods. On this basis, the influence of operating conditions and major nonlinear factors on the system stability are analyzed. Finally, the regulation rise time, stable time, and integrated electricity isotropic performance indexes for PFR are designed to quantitatively evaluate the regulating quality and assessment status under WRO, with further integrated optimization of control parameters. Results indicate that the risk of units failing PFR assessments is higher during low-head operation, with the main cause being a decrease in regulation speed. Following optimization, units successfully pass the PFR assessment in all operating conditions, with the three performance indexes improved by an average of 12.1 %, 78.9 %, and 87.8 % under WRO, respectively. This study offers a reliable tool and essential guidance for analyzing and optimizing the regulation performance of hydropower units under WRO.