Small Range Rapid Search Method Of DSR Based On The Combination Of Analytical Method And Fitting Methods

Interconnectedness and complexity of modern power system bring moreimportant significance to power system security and stability assessment. DynamicSecurity Region theory provides a new way to quantitatively analyze the power systemstability. Currently, there are two methods to determine the DSR boundary. The firstone is the fitting method, which is accurate and reliable, but costs too much time. Theother method is analytical method, based on a critical injection point, using analyticalderivation to determine DSR boundary quickly. This method is fast, but has a lowaccuracy.Power system probabilistic security assessment based on DSR can easily consideruncertain factors. Considering the uncertainty factor of the operating point injection,system instability probability can be simplified as a normal distribution. When makingsecurity analysis, we only concern the DSR boundary on the direction which theoperation point is most likely to overflow. For the directions with a low operating pointoverflow probability, it has no need to precisely measure the DSR boundary. Therefore,to measure the DSR boundary on the direction which the operating point is most likelyto overflow has a strong practical significance.This paper has analyzed the necessity of determining the small range DSRboundary and its theoretical basis. And we proposed a rapid search method of smallrange DSR. Firstly, we made use of the practical analytical method to determine theinitial value of the boundary hyper-plane, then repeatedly calculated the vertical linefrom the operating point to the hyper-plane and searched critical points around thepedal. Next, the improved analytical method was used to revise the already achievedhyper-plane until a most proximate hyper-plane was gained. This hyper-plane iscorresponding to the most likely overflowing direction of the operating point.Furthermore, a small range was determined and the fitting method was applied to getthe hyper-plane of small range DSR boundary.The method proposed in this paper uses the analytical method to estimate theinitial value and the fitting method to achieve accurate solution. It can significantlyreduce the number of unwanted search directions and rapidly determine the directionwhich the operation point is most likely to overflow, then solve the DSR boundary hyper-plane in a small range along this direction accurately. It fully combines theadvantages of both fitting method and analytical method which can get a betterestimation of the desired hyper-plane. In addition, it also makes a foundation for thefurther safety evaluation.