Power System Probabilistic Security Assessment Based On Small Signal Stability Region

Interconnection and deregulation have been the trend of modern power systems nowadays. On one hand, power grid becomes more and more complicated. On the other hand, power systems are operated even more close to their stability limits for more profits and there are more uncertainties in the deregulation environment. So power system security and stability have been paid much more attention. Small signal stability is the ability that power system can sustain some small fluctuates and can return to its precondition. Small signal stable is a basic requirement for the power system daily operation. In this thesis, power system probabilistic security assessment based on small signal stability region (SSSR) is tentatively studied. Main work of this thesis is as following:Firstly, theory of power system small signal stability is briefly reviewed. Then, a probabilistic security index with its calculation algorithm is presented. In the proposed algorithm, power injections are treated as random variables with truncated normal distribution. And, combined cumulants and Cram-Charlier expansion are used to calculate the probabilistic security index. This method makes use of the topological characteristic of small signal stability region and the region boundary information. It is different from the traditional analytical and numerical methods.Secondly, the proposed method is validated by two benchmark systems: WSCC 3-generator-9-bus system and New England 10-generator-39-bus system. The calculation results reveal the effectiveness of the given method. The influences of the load level varying, operating point shifting and time delay to the calculation result of the probabilistic index are also discussed.Finally, we simply discuss the application of the probabilistic security index in power system operation and parameter optimization, such as, optimizing the generation dispatch schedule, optimal control to the parameter excursion, etc.