Study on Primary Frequency Regulation Capability and System Stability of Hydropower Units

Abstract

As an important frequency regulation unit, the hydropower unit plays an important role in the stable operation of the power grid. At present, most of the hydropower units pursue the primary frequency regulation (PFR) assessment index, ignoring the system stability. This could lead to ultra-low frequency oscillation in a high proportion hydropower area, such as the Yunnan power grid. Therefore, this paper studies the relationship between the PFR and the stability of the system. Firstly, the mathematical model of the hydropower unit is established, and the judgment criteria for satisfying the PFR assessment and system stability are obtained through theoretical analysis, indicating that the PFR capability of the unit is related to the control parameter $K_{I}$. Then, according to the judgment criteria of system stability, the functional relationship between the system parameters $T_{\mathrm{a}}$ and $T_{\mathrm{w}}$ of different types of hydropower units and the maximum value of the control parameter K_I is obtained by fitting, and the judgment criteria that the unit can satisfy both the PFR assessment and system stability is obtained by using the judgment criteria of PFR assessment. At the same time, it shows that most of the Francis and Kaplan units and all the tubular units cannot satisfy the PFR assessment and system stability at the same time. Finally, on the premise of considering a 20% regulation margin, combined with the fitting function, the PFR assessment formula that satisfies the system stability in a high proportion hydropower area is proposed.