Power System Risk Security Assessment Based On Probabilistic Modeling

With the rapid development of power demand, the power systems face a challenge and tough tasks, such as bulk capacity and long distance transmission, and large-scale power grid interconnection. Facing the more and more complex operation feature, traditional security assessment method has some weaknesses. The security assessment based on risk theory and probabilistic modeling can consider not only the uncertainty of power system, but also combining the occurring probability of the contingency and consequences.This paper discusses the security assessment from two points of view, namely steady state security and transient state security. The probabilistic model has been built. The likelihood and severity indices are presented. Quantitative analysis has been done.Probabilistic load flow (PLF) based on simulation method has been taken for the steady state security assessment. This paper presents the risk assessment about nonlinear a.c PLF considering correlation between stochastic variables. From the planning point, the discrete probability distribution has been taken for generator bus. The load model is following a normal distribution with annual average value as expected value and fluctuation range as standard deviation. The fault line model is calculated according to statistic data of different failure types. From the operation point, the load model is following a normal distribution with load forecast as expected value and forecasting error as standard deviation. Besides, weather model can also be considered. This paper employs Monte Carlo simulation to analyze the weakness point from periodic and real time operation.This paper uses time domain simulation method to evaluate the risk during electromechanical transient state process. This paper considers generator and load model, governor model, AC/DC hybrid power system with FACTS, and induction motor model. The stability analysis with generator angle's rolling curve has been done under the single fault and multiple faults. This paper presents a new acceleration algorithm for calculating the critical clearing time (CCT). This paper also presents some effective indices for the transient state security assessment considering the uncertainty factors.