Research On Consensus-Based Distributed Control Of Islanded Microgrids

Microgrid is an effective solution to solve the problem of distributed generators connecting to distribution network.In particular,in the islanded mode operation,microgrid can supply power to remote areas,as well as continue to supply power to important loads in the event of external grid failure,which has certain popularization value.However,due to the loss of support from the large power grid,changes in the environment can easily lead to instability of system voltage and frequency,so the control of islanded microgrid has become a difficult problem to be solved urgently.In order to solve the problems of voltage and frequency regulation and economic operation of the islanded microgrid,and simultaneously overcome the limitations of the traditional centralized control method,such as heavy computational burden,complex communication and insufficient flexibility,this thesis combines the distributed control method based on the finite-time consensus theory with the hierarchical control structure to formulate a distributed hierarchical control strategy for coordinated operation of distributed generators in the islanded microgrid.First,the primary droop control strategy is proposed,and a multi-loop controller of distributed generator inverters based on droop control is further designed,including the hardware part of the inverter,the outer-loop power controller and the inner-loop voltage and current controller,so as to realize the rapid response of distributed generator and stabilize the system voltage and frequency.Then,based on the finite-time consensus algorithm,the method of translating droop curve and the method of modifying voltage-reactive droop coefficient,this thesis puts forward a distributed secondary frequency control strategy and a distributed secondary voltage-reactive control strategy,respectively,to correct the system frequency and voltage offset caused by primary droop control in a distributed manner and realize the proportional distribution of reactive power.Finally,an economic dispatch model is established aiming at minimizing total power generation cost of the microgrid system,and the Lagrange dual decomposition method is used to solve the model.Furthermore,based on the finite-time consensus algorithm,a distributed economic dispatch method for islanded microgrid is proposed to enable each distributed generator to solve the optimal output active power locally and realize the economic operation of islanded microgrid.Each control layer above independently completes its own control task and exchanges information among the layers through communication links,thus jointly improving the security,stability and economic operation level of the islanded microgrid.Moreover,the proposed strategy does not require a central controller and can effectively solve the defects of poor reliability and low robustness of the centralized control method.The effectiveness and robustness of the proposed distributed hierarchical control strategy are verified by multi-scenario simulation analysis of the analog islanded microgrid system on the Matlab/simulink simulation platform.