Calculation of the transient stability boundary of AC/DC inter‐connected system based on the stability margin of dynamic energy

Abstract

Concerning the transient power angle stability problem in AC/DC inter‐connected system caused by DC line grounding fault, a transient stability analysis method based on the stability margin of dynamic energy is proposed. First, the analytical expressions of the dynamic energy function before alpha retard, during alpha retard and after alpha retard are derived. According to the topologies of system and the integration intervals of energy function in different stages, the expressions of the acceleration energy, position energy and margin energy are obtained, which, respectively, reflect the rotating speed of system, the swing range of power angle and the system's ability of resisting in stability. Then, the surplus energy in the system is calculated by subtracting the sum of the acceleration energy and position energy from the margin energy, and the stability margin of the system is obtained. And then, the stability boundary of the system is derived. It is revealed that, if the stability margin is exactly right 0 at the end moment of alpha retard, the system is critical stable. Finally, hardware‐in‐the‐loop tests are conducted in RT‐LAB platform. The simulation results verify that, the stability margin reaches the minimal value at the end moment of alpha retard, and this value can clearly reflect the stability of system. Besides, the earlier the alpha retard starts or the longer the distance between the fault point and the rectifier outlet is, the better it is for the stability of system.

Power system stability margin prediction based on gradient lifting decision tree

“…To verify the precision of the proposed method, the proposed method in Reference [4] and Reference [5] is applied to forecast the stability margin of the target power system. The results of the forecast are shown in Figure 4.…”

“…The experimental results show that the method has good robustness and effectiveness. Reference [4] introduces a new method for transient stability analysis using dynamic energy stability margin. Then, according to the topology of the model and the integral interval of the energy function at each stage, the expressions of acceleration, position and edge energy are obtained.…”

Study on the time and duration of restart on the AC/DC interconnected system based on dynamic energy

“…When the optimal restart strategy is used, the variation of system dynamic energy is shown in Figure 12. It can be seen that the system enters the fault process at point A (t = 2.103 FIGURE 13 Impact of the restart time on system trajectory s), and the system dynamic energy gradually dissipates from an initial value of 14.58 p.u. Then the system enters the restart process at B (t = 2.416 s).…”

“…By integrating of voltage and current at each port of the system, the dynamic energy function can universally describe the stability of power systems. Reference [13] deduces the stability margin of the system by constructing a dynamic energy function, and provides a calculation method for the stability boundary of an AC/DC FIGURE 1 Diagram of an AC/DC interconnected system interconnected system based on the stability margin crossing the zero point as the stability boundary condition. Reference [14] analyses the receiving-end of AC/DC system based on dynamic energy, reveals that the trajectory of operating points passes new equilibrium point when the system is reclosed at the optimal reclosing time.…”

Transient stability emergency control for AC/DC grids considering successive commutation failures

“…In recent years, numerous scholars have conducted in-depth researches on TSEC and preventive control of AC/DC hybrid systems, whose works mainly focus on the generator rotor angle stability [7,8], but the successive CFs is rarely considered. In [9], a transient stability boundary calculation method of AC/DC system based on dynamic energy analysis is proposed, which yet ignores CFs. In [10], an online transient stability assessment method of AC/DC hybrid system considering CFs is proposed, which is lack of further research on TSEC.…”