Study on Splitting Criterion Based on Improvement <i>ucosφ</i>

Abstract

In this paper, according to the splitting criterion ucosφ, the effectiveness and boundedness of the improvement method is studied. As the oscillation center may be an isolated dot or exists in a section of the splitting, this paper has proposed the thought of false oscillation center and introduced the relative degree coefficient of oscillation k which reflects the degree of effect on the tie lines. The tie lines being cut off should be sorted based on the value of k. If the system recovers stable, the tie lines remained should not be cut off. It is vital to the control of the splitting and reducing the losses of accidents. In the end, the simulation is given in the IEEE 10 Generator 39 Bus System which proves the correctness and effectiveness of this method.

Research on the Unstable Branch Screening Method for Power System With High-Proportion Wind Power

“…In addition, according to Yang (Yang et al, 2013), the unequal voltage on both sides of the branch is one of the reasons for the migration of out-of-step center. When the voltage amplitude on both sides of the branch is unequal, the out-of-step center migrates to the side where the voltage amplitude is smaller.…”

“…According to the conclusion in Section 2, when the out-of-step oscillation occurs, one or more branches loses stability, resulting in a sharp drop of voltage at each point of the branches. Considering that the voltage reduction at the oscillation center is the most severe (Yang et al, 2013), so the voltage of the oscillation center can be used to measure the stability margin of a branch. However, if the oscillation center is not on the branch due to the oscillation center migration, the voltage at one end of the branch is the minimum voltage, which is much greater than the oscillation center voltage.…”

“…The above methods can prejudge the transient stability of the grid quickly using generator information such as rotor angle, but the further application in the emergency control such as the splitting control is limited because the splitting section cannot be determined directly. Therefore, some scholars designed some new instability criterion using the branch response information, such as ucosφ criterion (Yang et al, 2013;Zhang et al, 2021), phase angle criterion (Regulski et al, 2018;, bus voltage frequency criterion (Zhang et al, 2019;Yang et al, 2022), apparent impedance differential method (Sreenivasachar, 2021;Shen and Raksincharoensak, 2021b) and so on. Compared with methods using generator response information, these methods can not only prejudge the unstable state of the system, but also accurately capture the unstable branches and the splitting section.…”