Research On Coordinated Control Strategy For Microgrid Voltage Optimization

Microgrid which is one of the research hotspots in the field of distributed power generation,provides an effective way to solve the process of large-scale new energy generation generated into the power grid.With the continuous development of microgrid technology,the voltage control of microgrid and the precise distribution of reactive power load need to be studied deeply.This paper draws on the experience of voltage control structure of traditional island microgrid,and conducts corresponding research on voltage optimization control of multi-bus complex microgrid.The main work and achievements of this paper are as follows:(1)Extensively researching the existing inverter control structure and voltage control strategy of the microgrid,then comparing and summarizing the advantages and disadvantages of the microgrid as well as the applications;Elaborated in detail of the local control and secondary voltage and frequency control consisting of the hierarchical control strategy in an islanded microgrid,at the same time,the effectiveness of the control strategy is verified by simulation.(2)There are many bus nodes in the isolated microgrid,and the voltage levels of the nodes are different.In order to select the pilot nodes that can represent and reflect the voltage levels of the whole network to achieve the control of the voltage state of the whole network,this paper proposes a method of selecting pilot nodes which is suitable for islanded microgrid.Meanwhile,a power flow calculation method with secondary voltage and frequency control is designed for the power flow calculation part for the selection of pilot nodes.Finally,an example is given to verify the effectiveness of the proposed power flow optimization algorithm and the selection of the pilot nodes under different load conditions and disturbance factors,respectively.(3)In order to make up for the defects of the traditional hierarchical control strategy and make full use of the reactive power adjustment capability of the distributed power generation units in the microgrid,this paper proposes a multi-time scale voltage coordinated control strategy for multi-bus complex microgrid.The control strategy includes objective function,equal constraints,unequal constraints and iterative algorithm.In order to perform the voltage optimization control more accurate,the proposed power flow optimization algorithm is used as its equal constraints,and the pilot node selected in the microgrid is used as the secondary voltage control node.Finally,the correctness of the proposed tertiary voltage optimization control strategy is verified on the Matlab/Simulink simulation platform.