Simplified Prediction Model of Frequency Nadir for Power Systems Penetrated With Renewable Energy

Frequency nadir is an important indicator that measures the post-disturbance frequency stability of power systems, which is vital for fast frequency support and control of future power systems penetrated with renewable energy. This paper proposes a simplified frequency nadir prediction model. A frequency analysis model is first proposed, in which the frequency response characteristics of the synchronous generators with governors, renewable energy generators, and loads are simplified in a reasonable manner. In this way, the Rate of Change of Frequency (ROCOF) can be described in the form of second-order polynomial of frequency. Afterwards, an analytical prediction model of frequency nadir is deduced, which is exactly the roots of the quadratic equation. This prediction model is simple, accurate and has the potential for real-time applications. Finally, the simulation results in IEEE 39 bus power system verify the effectiveness of the proposed frequency nadir prediction model.