An Emergency Control Strategy of Short-Time HVDC for Frequency Stability

Abstract

With the increase of the proportion of the new energy resources, the rotational inertia of the power system decreases, which results in the risk of frequency instability increasing. In this paper, the method achieves an energy optimization control of high voltage DC transmission (HVDC) to improve the frequency stability. Firstly, according to the characteristics of the short-time overload of HVDC, the system frequency response model that considers the power support and starting-time is developed. The influence of different power support and starting-time on the frequency nadir is analyzed. It is found that there is an optimal starting-time for a given power support to maximize the frequency nadir, and the relationship between the power support and the maximum frequency nadir is not linearly increasing. Then, a optimization control method is proposed, which can not only recover the frequency nadir of the disturbed system above the threshold value of frequency stability with minimum energy, but also meet the security requirement of the frequency of interconnection system of HVDC. Simulation results demonstrate the effectiveness and correctness of proposed method.