On the Key Factors of Frequency Stability in Future Low-Inertia Power Systems

The integration of high-penetration of renewable generation has caused sustained reduction of system inertia but also create new capability for frequency regulation. The common understanding is the loss of inertia is the main reason why the system frequency stability deteriorates. In this paper, considering swing dynamics with the primary frequency control, we identify the key factors that mostly affect frequency stability through sensitivity analysis on maximum frequency deviation. Surprisingly, we find that the droop coefficient of the primary frequency control has the most significant influence on the frequency response and hence the frequency stability, while the inertia is the least important, which is somewhat opposite to the common sense. Simulations on the simplified Northwest Chinese power system empirically justify our theoretical results well.