Reliability Sensitivity Analysis to Frequency Stability Control System Based on Improved Probability Weighted Directed Graph

Difficulty to assess the risk of the frequency stability control system (FSCS) lies in its complex structure and expected function. In this paper, a risk assessment model to the FSCS is proposed. From the improved probability-based weighted directed graph firstly established, the weighted adjacency matrix is obtained. To find the connectivity of any two nodes, the weighted fully connected matrix is introduced by the path search algorithm since the weighted adjacency matrix has no Boolean property. When assessing the risk of the FSCS, considering its hierarchical structure, redundant configuration of stations and ‘non-point-to-point’ instruction transmission characteristics, the corrected topology with N-1 contingency of the FSCS is established. Then the risk indices are defined from two perspectives of only the FSCS itself and its functional characteristics, while the latter reflects the ability of the FSCS to ensure the security and stability of the AC/ultra-high voltage DC (UHVDC) power system. The sensitivities of the risk indices to the FSCS devices and UHVDC components are quantified based on the risk assessment model. The numerical results of the typical test system are provided to validate the practical value and accuracy of the proposed model.