An extended modeling of frequency security constraints for unit commitment model

Under the background of high proportion of renewable energy, the frequency security of the power system is facing challenges, which makes it necessary to consider and respond in the optimal dispatching. In this paper, the frequency security constraint is introduced into the basic unit commitment model and the unit commitment model considering the frequency security constraint is proposed. Different from the traditional research, a dynamic modeling method for the unbalanced power of the system is presented. Based on the system frequency response model of primary frequency response, the analytic and linearized frequency safety constraint sets are constructed for the frequency nadir, quasi steady frequency and maximum rate-of-change-of-frequency. The experimental results show that the proposed model not only ensures sufficient frequency security, but also fully considers the actual operation state of the frequency response unit. Compared with the traditional model whose unbalanced power is constant, the proposed model can save operating costs.