Research On Consensus-Based Control Strategy For Microgrid Cluster

With the consumption of traditional fossil energy,the energy crisis and environmental problems are becoming increasingly serious.Vigorously developing the new energy industry has become an indispensable part of social development.Microgrid,as an important means of integrating distributed generators(DGs),has become the focus of power system research due to its flexibility,economy and environmental friendliness.However,in some regions with scattered energy sources,single microgrid may be limited by its insufficient capacity and affected by the randomness of power generation,thus affecting the quality of power.Therefore,in order to improve the stability of the power system,scholars connect the neighboring microgrid to form a microgrid cluster system that can exchange energy with each other.microgrid cluster system can not only improve the penetration of distributed power generation,but also reduce the energy loss caused by energy exchange between subnets through appropriate operation mode.droop control is commonly used in island microgrid.Droop control is a kind of deviation control,so it is necessary to introduce secondary control to eliminate the deviation.Traditional secondary control requires the central controller(MGCC)to collect and process DG information,which is less flexible and vulnerable to single point of failure.However,with the development of Multi-Agent System(MAS),using distributed consistency theory to solve the shortcomings of traditional secondary control has become the focus of current research.Therefore,this paper mainly focuses on the application of multi-agent consistency theory in microgrid system and microgrid cluster system.The main research contents and work of this paper are as follows:(1)In view of the limitations of the traditional secondary control,the reasons for the deviation in the droop control are first analyzed,and then the consistency algorithm and the leader-follower consistency algorithm are introduced into the secondary control of the microgrid.Through the sparse communication network,the frequency deviation in the droop control can be calculated and compensated,and at the same time,the active power distribution will not be affected.In view of the conflict between voltage recovery and reactive power distribution caused by line impedance mismatch,the control method of intermediate voltage consistency is adopted to achieve voltage recovery and reactive power accurate distribution at the common point.Finally,the stability of the proposed frequency/active power controller and voltage/reactive power controller is proved by Lyapunov stability theory.(2)In view of the fact that the traditional droop control cannot realize the economic optimization in the microgrid cluster control,the generation cost of distributed generation is introduced into the droop control,and the Lagrange function method is used to analyze that the economic optimal control can be achieved when the micro-increment rate of distributed generation is consistent.Then,the group consistency theory is used to realize the local economic optimal control of the subnets in the micro-electric network group system,and the stability of the proposed control strategy is proved by the Lyapunov stability theory.(3)Aiming at the problems of loss and overload that may be encountered in the operation of the microgrid cluster system,an improved microgrid cluster operation control strategy is proposed.Under the premise of considering the distributed power overload protection and subnet overload protection,a reasonable selection of the control mode and operation mode of the micro-electric network group system can effectively improve the stability of the system and reduce the loss caused by the factor network energy exchange in the micro-electric network group system.