Research On Under Frequency Load Shedding Of Power Systrm

Under Frequency Load Shedding (UFLS) is an effective method to prevent the frequency reduction and maintain stability of power system. When system collapses, it will help the frequency back up to the normal range quickly by dropping excessive load in time.this paper summarizes the static and dynamic characteristics of frequency in power system with theoretical deduction and stimulation. For instance, the static characteristic of frequency exerts inhibiting effect on the change of system frequency; the dynamic characteristic of frequency is more complex due to its time and space distribution features. In addition, it has a close relationship with the system structure and operation mode.This paper proposes an UFLS scheme based on the dynamic frequency of integral.This scheme can determine the first action frequency and the amount of load shedding each round automatically and it can avoid the negative effect of frequency oscillation in multi-machine power systems. To assign the setting load shedding amount each round to each code reasonably, this paper focuses on the distribution of load shedding amount based on the sensitivity of the active power vacancy. This sensitivity can reflect the effect of removing certain load node on frequency recovery With the simulation process, it verifies the effectiveness of the setting load shedding each round and the distribution scheme of load shedding.Nevertheless, given the practical UFLS cases, it should not only consider the power sensitivity of load node but also need to take the importance of each load code, the cost of load shedding and other factors into account. Therefore, this paper applies entropy method to analyze the influences of various factors and concludes the sequence of load shedding by weighting comprehensively. With a series of simulation examples, the result shows the advantages of proposed scheme that considers comprehensive factors and makes the frequency recover well. This scheme is superior to the traditional methods referring to the effect of load shedding.