Analysis And Research On Complex Power System Cascading Failures Considering Hidden Failure Of Protection

With the development of power grid interconnection, the overall grid security issues become increasingly prominent as well as the improvement of the operational economy. Some failure of the local power grid may spread to nearby regional power grid, which may induce cascading process and lead to serious consequences. The traditional methods have some limitation in aspects of analyzing cascading failures. Therefore, it is necessary to carry out the research of diagnosis, prevention and control approaches for cascading failures in power system.Based on in-depth analysis of the evolution process of cascading failure, involving its occurrence and development, the research of N-k contingency analysis considering of protection hidden failures, fault diagnosis and prevention and control methods for cascading failure have been carried out. The main efforts are listed as follows:1. On the basis of in-depth analysis of characteristic of cascading failures evolvement process, it is indicated that the emphasis of analysis and control should be put on the development stage of cascading failures, which is divided into initial phase, slow and fast cascade phase. The corresponding analysis and control focus are presented according to different characteristics of three phases.2. Kinds of hidden failure (HF) modes caused by protection element functionality defect or improper settings have been listed and analyzed for several types of typical protections with different operational principles. Based on that, one analytical mode of protection HF caused by protection element functionality defect with common features is presented. From which, the reason for protection malfunction caused by hidden failure has been revealed essentially.3. N-k contingency analysis method taking protection hidden failure into consideration is proposed, which can evaluate the effect of protection hidden failure on the system reliability. There exists a linkage between a first contingency (random initial fault) and a possible second outage due to hidden failures in protection systems, which could be exposed by multiple contingencies options and failure combinations. The method for culling the list of possible higher order (N-K) contingencies could be used to recognize vulnerable lines and key protections in the system, which is helpful to improve the system monitoring with priority.4. A diagnosis and analysis method for cascading failure based on complex event processing technology (CEP) is proposed by use of characteristics of fault events during cascading process, which focus on dynamic development trend of failures in power system. A hierarchy model for complex event processing and correlation analysis is developed. Successive failure events are correlated by analyzing the temporal, spatial and electrical correlation between them, which can offer tendency analysis of failure development and confirm the starting of cascading failure.5. Taken present hierarchical and network partition structure into consideration, drawn on existing system stable operational control experience, a framework of wide-area coordinated pre-control based on multi-agent system (MAS) is built, which is of engineering practice value. With the introduction of interfaces power flow algorithm under quasi-steady-state taken into account of generator response, power flow level of key transmission section can be controlled in advance from the system point of view by means of power transfer limit of cross-section calculated offline, which can prevent the development of fault occurred in local network, and thus ensure security and stability operation of the whole power grid.