Distributed Coordinated Control For DC Microgrid Based On Finite-Time Consensus Algorithm

Microgrid technology represents the development trend of distributed energy supply system in the future.It is an important component of intelligent distribution and power system in the future.It is of great significance to promote energy conservation and emission reduction and achieve sustainable energy development.Compared with AC microgrid,DC microgrid can more efficiently and reliably accept distributed renewable energy generation systems,energy storage units,electric vehicles and other DC power loads,such as wind and light.At the same time,DC microgrid also has the advantages of low loss,simple structure and strong controllability.In this paper,the DC microgrid is taken as the research object.Around some key problems,a series of studies are carried out on the coordinated operation of the control units,the improved method of traditional droop control,the fast realization of bus voltage stability and economic maximization,and the energy interaction between the DC microgrid and the main network.The research results of this paper have theoretical guiding significance and practical application value for the related technologies of distributed control and optimal operation of DC microgrid.(1)First,a distributed coordinated control strategy is proposed for DC microgrid under island operation mode.The control strategy based on hierarchical structure,the introduction of the two voltage control and the cost of power generation operation control based on original droop control,the power generation unit only exchange information with the adjacent communication unit,through the finite-time consensus algorithm,finally realize the voltage stability and minimum generation cost control objectives.The proposed control strategy has the both advantages of hierarchical control and limited consistency control.It has high flexibility,robustness and good convergence.In order to verify the proposed control strategy,a DC microgrid model is built in this paper.Simulation of different scenarios such as power supply,load return and load fluctuation is carried out,and the effectiveness of the proposed method is verified by numerical examples.(2)Secondly,a hierarchical coordinated control strategy is proposed for a cluster of DC microgrids.Based on the finite-time consensus algorithm,the control objectives of load proportional distribution,DC bus voltage stability and global generation cost minimization are achieved.At the same time,in order to overcome the limitation of the finite-time consensus algorithm and improve the convergence speed,an estimated communication topology is proposed.The proposed topology ensures that the control strategy is completely distributed,that is,it does not need initial global information and has high reliability.This proposed control strategy is verified in one DC microgrid and a cluster of those containing 4 DC microgrids.The simulation results under different scenarios all indicate the effectiveness of the proposed methods.(3)Finally,the optimal operation control strategy of grid-connected DC microgrid is studied.After considering the energy exchange between the DC microgrid and the main network,a two level control strategy is proposed.The upper level is economic operation control,the control objective is to maximize the economy and the highest self-balancing rate;the lower level is voltage stability control,which achieves bus voltage stability by improving the droop control equation.The control strategy is solved by differential evolution algorithm for multi-objective optimization to get the global optimal solution.The simulation results of grid-connected DC microgrid show the effectiveness of the control strategy.