Research Of Distributed State Estimation In Power System

The interconnection of power systems is a inevitable trend with the development of future power system, correspondingly, we require the EMS to control the system better. SE(State Estimation) is the pivotal part of EMS, the algorithm of SE is related to the speed and precision in calculating directly. For a large-scale power system ,the conventional centralized state estimation methods have reached a stage in which substantial improvements in either speed or numerical robustness are unlikely. So we must open up new SE methods to adapt to the development of future power systems. Although the decentralized control techniques have not yet applied to power system ,however, they probablywill be the main trend in the future because the decentralized control has obvious advantages over the centralized control for the large-scale interconnected systems.In the thesis, for adapting to the decentralized control techniques, we proposed the distributed state estimation(DSE) method, established the corresponding math model, and we made observability analysis after studying the conventional and hierarchical methods. The main idea of the distributed SE method is "multi-processor to multi-area". Compared with the hierarchical methods, the distributed SE method has following advantages :1) Inherent parallel characteristics quicken the calculating speed. In DSE method a large system has been decomposed into tow or more subsystems, these subsystems can be solved and made observability analysis solely.2)The DSE method has no central controlling computer. It realizes the information communication through the message passing pattern, and eliminates the bottleneck problem of thehierarchical methods in the process of data transferring.3) The DSE method modified the results of the boundary buses by the coordinate function, thus it ensures the calculating precision generally.The disadvantage of DSE method is that its time-consuming is serious because of the limit of the network's speed, especially there are large numbers of boundary buses. But with the quick development of the high data communication technique ,its practicability will be very promising.After calculating the WSCC-9 system based on local area network consisting of single computer and used the software platform PVM, it showed that the DSE method is successful when the redundancy was proper and asynchronous computation was used.