Application Of Hybrid Energy Storage Technology Based On Power Battery In Off-Grid Of Microgrid

The output power of the distributed power supply, such as photovoltaic power, the wind power, etc. is random and intermittent in the microgrid along with changes of external environment, which may challenge the power quality and the stable running of the grid beyond doubt. The service life of the storage battery may be reduced greatly as a result of random change of load at the same time; while the hybrid energy storage of super-capacitor and the storage battery fully utilize the complementary characteristics. Moreover, the recycling line of the power battery is disconnected seriously although it is safe,reliable and has long service life; then how to reduce the running cost of the system becomes the important problem required to solve urgently.The actual characteristics of PV and wind power generation in the institute were analyzed, and the gradient utilization technology of the power battery was research deeply in the text on the basis of microgrid demonstration project participated during the practical process in Jiangxi Electric Power Research Institute. Moreover, the capacity and the energy utilization ratio of the battery system could be improved effectively by using the optimization and grouping technologies of the lithium batteries connected serially and in parallel, and the way for research and manufacturing of two hybrid energy storage systems was paved by building the PV energy storage model, the wind energy storage model and the hybrid energy storage model in presence of the PSCAD software.The AC parallel and DC parallel hybrid energy storage systems were researched respectively from three aspects including the topological structure, the technical parameters and the simulated analysis after screening and grouping of serial connection and parallel connection of the power batteries, and the stable charging of the hybrid energy storage structure in the grid-connected mode and the capability of keeping stable frequency and voltage and meeting the quality requirements to the power of the energy storage structure in the grid-disconnected mode when facing different loads, such as step pulse load, the imbalance load, etc.In the microgrid structure composed of the PV power, the wind power and the hybrid energy storage combining with the power battery, the wave properties of the system and all units were analyzed respectively under the control strategies, such as droop control, constant voltage and constant frequency, etc., and the running characteristics of the new and old battery were analyzed for two hybrid energy storages respectively by taking the master-slave control and the peer-to-peer control as strategies during switching between connection and disconnection of the grid. Moreover, the simulation result verified that this microgrid structure can handle sudden switching of the load and random change of the distributed power supply and ensure safe and stable running of the system while implementing smooth switching; therefore, the running cost of the system can be reduced.