Research On Control Strategy Of Multi-Microgrid Under Distribution Network

At present,in order to further improve the efficiency of renewable energy utilization and eliminate the impact of grid-connected new energy power with high permeability,multi-microgrid as one of the effective schemes to absorb renewable energy has been widely concerned.How to use the optimal coordinated control strategy to realize the energy mutual benefit between microgrids has become a hot research issue in the power field.Therefore,this thesis takes the microgrid and the multi-microgrid under the distribution network as the research object,and studies the coordinated control strategy of the multi-microgrid in order to realize the energy supply between the microgrids and ensure the safe and stable operation,which has theoretical significance and practical value.Based on the working principle and topology of typical microgrid,the mathematical models of photovoltaic power generation,wind power generation,energy storage device and load are established,and the comprehensive mathematical model of microgrid as an independent unit connected to distribution network is given.In order to solve the problem of frequency change caused by disturbance power in microgrid,a non-error frequency modulation control strategy of microgrid based on auto-disturbance rejection technology and constant power control is presented.The auto-disturbance rejection technology is introduced into the PI link of power and current double-loop control.The internal and external disturbances of the system are eliminated by dynamic compensation linearization,the frequency overshoot is reduced,and the steady-state recovery speed of the system is improved.The effectiveness of the control strategy given in this thesis is verified by the simulation of PI control and ADRC.Based on the research of microgrid,the coordinated control strategy of multi-microgrid system is compared and analyzed.In order to solve the problem of energy supply between multi-grid,a master-slave control strategy of multi-microgrid based on fuzzy control is proposed.The fuzzy control of multi-microgrid is divided into main microgrid and slave microgrid respectively.Taking the power and power deviation rate of each microsource and load in the microgrid as the input of fuzzy control,the corresponding fuzzy set and membership function are given,and the fuzzy rules are worked out.The output power of each energy storage unit in the multi-microgrid is obtained by fuzzy reasoning,the energy supply between the microgrids is reasonably distributed.The effectiveness of the control strategy given in this thesis is verified by simulation.