Research On Coordinated Control Method Of AC/DC Power Interface In AC/DC Hybrid Microgrid

AC/DC hybrid microgrid provides a more effective way for high density distributed energy access to distribution network.It has increasingly become a research hotspot in the field of microgrid.The AC / DC power interface,which is composed of multiple parallel AC/DC converters,is very important to maintain the dynamic balance of power in the hybrid microgrid.The power complementarity between AC and DC sub microgrids can be realized by controlling the bidirectional power flow on the AC/DC power interface.Considering the fluctuation and uncertainty of DG and the strong randomness of the load,it is necessary to study the power flexible control technology of AC/DC power interface.In order to realize the dynamic power balance and improve the power quality of the AC / DC hybrid microgrid,this paper studies the coordinated control of multiple AC/DC bidirectional converters on the AC/DC power interface.In this paper,the operation mechanism and operation mode of AC / DC hybrid micronetwork were studied.On one hand,based on the nonlinear optimal control theory,a coordinated optimal control strategy for the AC/DC power interface was proposed in this paper.The strategy proposed in this paper can make the transmitted power and DC voltage have optimal dynamic response characteristics.Besides,the strategy can also take into account both the power distribution and the optimal dynamic response.On the other hand,based on the time optimal control and fuzzy control theory,the time state coordination optimal control strategy was proposed in the island model.The control strategy took time and quadratic function as performance index,and designed time optimal controller and optimal state regulator respectively.In order to further realize coordination between the two controllers,an adaptive weight coefficient based on fuzzy control theory was introduced to coordinate proportion between the two controllers.The proposed strategy can take both state transition time and state adjustment process into account and achieve double optimization goals.Finally,combined with the first commercial AC / DC hybrid microgrid demonstration project in China,a simulation model was built,and the correctness and feasibility of the proposed control strategy were verified.