Research On Power System Transient Stability Probability Analysis And Control

The primary purpose of power system transient stability analysis is to check that if each machine in a power system can keep synchronization under large disturbance (such as contingency, load shed, shed machine, and re-closing actions etc.). If each machine can keep synchronization with others and with an acceptable voltage and frequency level, then the system is stable under this situation. In power system planning, designing, and running, lots of works must be done on transient stability analysis, because once a power system losts transient stability, it will lead to wide spread break out, and bring huge damage to national economy. Transient stability analysis can also research and review the effect of each stability action and the performance of stability control, so it is of important significance. This paper has done some works on contingency screening, sensitivity analysis and emergency control. According to uncertainty fractions of power systems, this paper proposed a method of probabilistic transient stability analysis, and many improvements have been achieved. This paper proposed a new method for fast contingency screening based on BCU method. In the process of computation of BCU method, we can get some key data in some key points such as fault clearing point, exit point, minimum grads point, and controlling UEP etc., and set filter on each point. According to computing result, this fault screening method is fast and reliable. This paper proposed an energy margin sensitivity analysis method based on trajectory sensitivity. The expression of energy margin is given using full differential formula. And the energy margin sensitivity is calculated by state variable sensitivity computation in fault clearing point and controlling UEP. Compared with other methods, this sensitivity method is more actual and reliable. In order to deal with the stochastic characters of fault location, fault type, fault clearing time, and load level etc., this paper proposed a transient stability probability analysis method based on curve fitting. Based on the history data of a power system, this method analysis the probability distribution of the fault location and type, and developed the stability probability computation formula. Compared with Monte-Carlo simulation method, this method evidently decreased the computation affords, and the error was limited in an accept level. This paper also proposed a method of computing the probability distribution of fault critical clearing time using Gram-Charlier expansion series. When bus loads are stochastic variables, then the critical fault clearing time is also a stochastic variable. By using the sensitivity of critical clearing time to load, the relationship between critical clearing time and load can be linearized. Gram-Charlier expansion and the property of center moments and the cumulate can be easily used to compute out the probability distribution of fault critical clearing time. Compared with Monte-Carlo simulation method, this method can evidently decreased the computation affords. This paper proposed a distributed coordinated control strategy based on Multi-Agent system theory. As the development of power system and promotion of marketing, the control mode of power systems will change from centralized mode to distributed mode. This paper proposed a distributed coordinated control strategy, and the actual example shows the effect of this method.