Research On Hierarchical Fuzzy Control Strategy For Hybrid Storage System In Micro-grid

In modern power supply, the clean energy based on wind power and solar radiation has the characteristics of random output, intermittent outage and frequent power fluctuation. In this paper, lOkV AC micro grid, in order to stabilize the power fluctuation of distributed energy,reduce the adverse effects on the distributed energy micro grid operation and island operation for the purpose of charging and discharging of the micro grid hybrid energy storage system control strategy is studied.First, this paper analyzes the characteristics of distributed power fluctuations, the system output is divided into steady-state wave power, peak power fluctuation and fluctuation of power reciprocating three power fluctuation type, and according to the system requirements to stabilize the power fluctuation, the study found that the super capacitor and battery two are complementary, consisting of mixed storage can the system can effectively improve the throughput of power fluctuation, the power quality of the micro grid.Then, the composite structures with different energy storage devices are compared and analyzed, and a composite structure consisting of a two stage parallel structure containing a bidirectional DC/DC converter is used as a hybrid energy storage system for a centralized micro grid. Then, a three layer control model consisting of real-time state layer, logical operation layer and system control layer is designed. Among them, the real-time state layer is mainly used to collect the power fluctuation signal of the micro grid and the charging state of the supercapacitor, and to formulate the charging and discharging rules based on the principle of the super capacitor to do the power throughput first. The logical operation layer provides two control libraries: the control object library and the control algorithm library. The control object can be controlled object retrieval in different state of charge and discharge of super capacitor cycle of hybrid energy storage power coordinated control system throughput. At the same time,the self-tuning fuzzy PI controller is introduced in the system control layer, which can replace the traditional PI controller, and can control the nonlinear fluctuation of power and optimize the operation of the system.Finally, scenery storage micro grid model built in Matlab/Smiulink simulation platform for simulation using this paper, shows that the proposed hierarchical fuzzy control strategy can effectively stabilize the energy storage system to stabilize the DC voltage, distributed power fluctuations, to ensure the stable operation of grid connected and islanded mode, realize smooth load switching.