| In recent years,the new energy based on distribution has gradually entered the sight of all countries due to the exhaustion of traditional fossil energy.Microgrid technology comes into being at this time because renewable energy has a lot of randomness and intermittency.Energy storage technology,as an important support for the development of microgrid technology,is playing an increasingly important role.Due to the limitations of single energy storage devices,the combination of supercapacitor and battery is becoming more and more popular.Hybrid energy storage usually uses bidirectional DC-DC converter to connect DC busbar and accesses to large power grid through bidirectional DC-AC converter.Therefore,DC bus voltage stability control is related to later connection with large power grid.In the energy storage system,the stable of DC busbar voltage is mainly realized by the control technology of the DC-DC converter.However,most of the traditional control strategies for hybrid power DC-DC converters are now based on the exact model without considering the uncertainties and disturbance effects,so it is difficult to achieve good control of bus voltage.In view of the above deficiencies,this paper focuses on the study of hybrid energy storage converter control under the influence of uncertainties based on robust H? control.The main contents are as follows:At first,this paper studies the working principles and mathematical models of battery and supercapacitor,which determin the equivalent circuit models of battery and super capacitor.The energy conversion strategy and power allocation method for hybrid energy storage are studied.Secondly,this paper studies the robust H? control theories which applies to bidirectional DC-DC converter and introduces the multicell model with uncertain parameter.The essence of robust control,the LMI technology and the region pole assignment are mainly introduced.The design method of robust H? controller,which considers the region pole assignment,is obtained by mastering these theories.Thirdly,According to the bidirectional DC-DC converter working mode,small signal state space modeling of DC-DC converter in the hybrid energy storage is built,which influences the establishment of the super capacitor and batterys' multicell model including uncertain parameters.Different steady state working points are designed in the model to improve the stability of system parameters.Based on the multi cell model and using the H?control theory,the influence of the uncertain parameters on the busbar voltage is transformed into a mathematical problem of optimizing the H? norm.By configuring the closed loop poles in the desired disk domain,the dynamic response characteristics of the bus voltage are improved.Then,the performance is compared with the traditional PI controller.Finally,A hybrid energy storage simulation platform based on MATLAB/Simulink is built.The robust H? controller and the traditional PI controller designed in this paper are compared.The simulation results show that the robust H? control can better stabilize the bus voltage and provide good dynamic performance under the influence of uncertain parameters. |
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