Abstract
A grid integration ratio of decentralized energy conversion systems (ECSs) in combination with renewable energy sources (RESs) has been recently increased in order to build up sustainable electrical power supply systems. Due to those changes, it can be predicted that the decentralized systems will change the conventional top-down power flow process to be the bidirectional process. Then the power flow can be reversed from distribution level to transmission level. To handle those significant changes, the cluster power systems approach has been developed and proposed to be the future of power systems. The strategy is to cluster the power systems in several areas, called cluster area. And the smart grid cluster controller (SGCC) unit is announced as a smart controller to operate the cluster based on each area. Presently, SGCC control functions have been published and proved that the SGCC can give an opportunity to establish control function down to local level. On the other hand, the cluster systems structure must be thoroughly considered to complete the clustering approach. Therefore, the cluster fractal model is proposed in this paper as a flexible and an adaptive model to organize the cluster network structure. According to fractal model, the internal structure of each cluster can be described by using the same network model. And the linkage to another cluster is allocated by the hierarchical system; superordinate, ordinate and sub-ordinate level. To this point of view, the fractal model has the flexibility to model the network of clustering power systems and ensures the bottom-up approach strategy. With the fractal model of cluster network structure and the SGCC, the cluster power systems philosophy will finally simplify the way for future smart gird.