Frequency Control In Hydro-dominant Power Systems With PV And BESS

Over the past twenty years,ultra-low frequency oscillation(ULFO)has been observed in many hydro-dominant power systems worldwide,threatening the reliability,security,and stability of power systems.The stability of hydro units is poor and provides negative damping due to the water hammer effect and an inadequate setting of the governor’s Proportional-Integral-Derivative(PID)parameters.To solve this problem,this study proposes a frequency control strategy based on virtual inertia control(VIC)of a de-loaded photovoltaic system(PV)and a Battery Energy Management system(BESS).Firstly,a small-signal model consisting of a hydropower unit,a de-loaded PV unit,and BESS was established.Secondly,the damping provided by each unit in the ultra-low frequency band was analyzed using the damping torque.Next,a multi-machine model was established to study the impact of PV and BESS on ULFO.Finally,time-domain simulation results based on MATLAB/SIMULINK show that PV and BESS can participate in the primary frequency regulation(PFR),provide positive damping,and effectively suppress ULFO.