| Energy storage technology is an important measure to solve the intermittent and volatile problems of renewable energy in microgrids.At present,single-form energy storage technology cannot meet the requirements of power and energy at the same time.Therefore,Hybrid energy storage technology,a combination of different kinds of energy storage technology based on complementarity,has been valued and becomes a research hotspot.Hybrid energy storage technology is currently in the basic theoretical research and engineering demonstration stage.With the development of the energy storage industry,the research on hybrid energy storage technology is gradually deepening.Problems related to the optimization of microgrid operation with hybrid energy storage system(HESS)and the coordinated control of HESS have been studied in this paper,which are both significant in theoretical and in practical engineering.First of all,the characteristics of various types of energy storage technologies have been studied,and the complementarities among various energy storage technologies have been analyzed,ranging from technology,economy,security,environmental protection,and development potential.The indicators are weighted,using a combination of AHP and entropy-weighted methods,and then the combinations of hybrid energy storage technologies are evaluated in a fuzzy comprehensive manner.The optimal choice is made base on their development potential.Topological and steady-state analysis model are analyzed,which lays foundation for follow-up studies.The microgrid optimization scheduling model with HESS is established,considering standalone and grid-connected modes,taking into account the life-cycle conversion cost of HESS.While the goal is minimizing microgrid operating cost in the scheduling period,including power balance,conventional units standby and the limitations of charging and discharging of HESS.The model is then solved using an improved particle swarm algorithm based on natural selection.Based on the steady state analysis model of the hybrid energy storage system,the basic filter control strategy is used to rationally distribute power and energy between super capacitor and lithium battery.Compared to single energy storage,the use of HESS can reduce the operating costs of the microgrid,which have been confirmed by case studies based on MATLAB.At the same time,with the basic filter control strategy,the number of charging and discharging of the battery is effectively reduced,so that the operatingcost is reduced,and the optimal operation of the microgrid with HESS is also realized.The energy distribution control strategy is very important to improve the overall performance of HESS.For the aforementioned basic filter control strategy cannot achieve coordinated control of energy,a novel fuzzy coordination control strategy is proposed in this paper.The state of charge(SOC)of each part of HESS is analyzed,and the energyprioritized allocation criteria between the super capacitor and the lithium battery are formulated for different operating conditions.The energy coordination allocation strategy is formulated according to the energy distribution priority.Base on the fuzzy control theory,the energy coordination allocation strategy is implemented by a fuzzy controller.The charge/discharge status and SOC of the lithium battery,the SOC of the super capacitor,and the power demand instruction are taken as input by the fuzzy controller,and the reference correction power instruction of the lithium battery and super capacitor are taken as the output.Power instructions are adjusted by the fuzzy controller so that a coordinated distribution of energy is achieved.The overall performance of the system can be improved by the proposed control strategy,which is confirmed by case study.As a result,the number of charging and discharging of the lithium battery is reduced,and the operating cost of the system is saved. |
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