Research On Control Strategy Of Microgrid Group Based On Consistency Algorithm

With the continuous development of the type and scale of distributed generation(DG),the microgrid(MG)used to coordinate various distributed power sources such as wind power and photovoltaics has been vigorously developed globally.Micro-grid systems generally have problems such as weak energy consumption capacity and weak anti-interference ability.Therefore,linking multiple microgrids adjacent to each other geographically to form a microgrid cluster(MGC)system can effectively solve the above-mentioned problems in the microgrid.Designing a micro-grid cluster system and performing reasonable intelligent control can play an important role in energy transformation and supply-side reform,and provide a new development direction for a new generation of smart grids.This article aims at the AC micro-grid system and performs coordinated control on the micro-grid based on the droop control of the micro-grid,mainly from the following aspects:(1)The stable operation of the microgrid is the premise and foundation of the stable operation of the microgrid.Therefore,the three-phase voltage inverter mathematical model is established for each DG in the microgrid under the dq rotating coordinate system,and the "three-loop control" strategy of droop control and voltage and current double closed-loop control is used to achieve DG voltage and frequency stability and active power.Of points.Based on the analysis of inverter circulating current,the problem of uneven distribution of reactive power in each DG in the microgrid due to the presence of line impedance is discussed.The above problems are usually solved by virtual impedance.Finally,a method of synchronizing multiple DGs in parallel to form a microgrid is outlined.(2)Based on the discussion of graph theory and the problem of multi-agent consistency,for the problem of uneven distribution of reactive power in the microgrid,an adaptive virtual impedance based on consistent reactive current is designed.This method does not requireprior knowledge of line impedance The size can adaptively adjust the size of the virtual impedance to complete the accurate distribution of reactive power of each DG in the microgrid.For a micro-grid group system that includes multiple micro-grids,a group consistency algorithm is used to coordinate and control each micro-grid to achieve energy coordination between the micro-grids,precise control of voltage and frequency within the group,and accurate distribution of active and reactive power in proportion.This control method does not require central control participation,and only requires one-way communication between distributed power sources in each micro-grid,which greatly reduces the complexity and economic cost of the system.Finally,build a micro-grid group simulation model with three micro-grids in MATLAB / Simulink,firstly conduct an experimental simulation of the independent operation of the micro-grid,verify that the proposed method can ensure the independent and stable operation of the micro-grid,and then perform micro-grid group simulation and Compared with the simulation results of the consistency algorithm,the simulation results show that the micro-network group with the consistency algorithm has a significant improvement in voltage convergence effect and reactive power distribution compared with the micro-network group without the consistency algorithm.(3)Because the consistency algorithm based on multi-agent system adopted by the micro-network group system in this paper belongs to peer-to-peer control,the system needs all DGs in the micro-network group system to implement synchronous coordination in the process of coordinated control.Therefore,during the operation of the micro-grid group,even if the micro-grids are not overloaded,all DGs in the group need to be synchronously linked,which will cause unnecessary network losses and fluctuations.Therefore,this paper proposes an improved microgrid operation mode.When the microgrids in the microgrid system are not overloaded,the microgrids maintain independent operation,and when a microgrid in the system is overloaded,each microgrid performs ring parallel operation.Realize the mutual energy between the microgrids and jointly bear the load.When entering the micro-grid mode,considering the situation that a micro-grid needs power outage maintenance or needs to leave the micro-grid due to a fault,the micro-grid system is added to the micro-grid power outage detection and power removal to make the faulty micro-grid It can be smoothly cut,whichenhances the flexibility of the operation mode of the micro-network group system and ensures the stable operation of the micro-network group system.Finally,build the microgrid overload detection and microgrid fault outage detection system modules in the microgrid group in MATLAB / Simulink,and verify the effectiveness of the proposed method through simulation experiments.