Research Of Hierarchical Cooperative Control For DC Microgrid And Its Cluster

As a new autonomous power system that can effectively integrate renewable energy,Microgrid is a research hotspot in recent years.Divided by bus type,microgrid can be mainly divided into DC and AC.Among them,the DC microgrid has the advantages of no need to control voltage frequency and phase,high power quality,etc,and is usually used in a power system including a DC load or a specific sensitive load.At the same time,with the development of microgrids,more and more microgrids are connected to the main grid,and these microgrids can be connected to each other to form a microgrid clusters.Due to the gradual increase of the renewable energy penetration rate in the microgrid system,the volatility of the system power generation becomes obvious.This problem combined with the volatility of the microgrid load demand will significantly affect the stable operation and power quality of the microgrid.Based on the above problems,it is necessary to study the control methods of DC microgrids and their clusters.Based on the actual engineering requirements,this paper studies the control methods of DC microgrids and their clusters.The main work content is as follows:1.This paper proposes a hierarchical cooperative control metho for DC microgrid,which requires the use of hybrid energy storage system.The method consists of two stages: the primary control and the sencondary control.The primary control consists of autonomously operated distributed generator(DG)and super capacitor(SC)with plug-and-drop characteristics.The secondary control is centralized.The battery can be controlled to charge or discharge by the Microgrid Center Controller(MGCC)to realize the sencondary target.This method can maintain the power balance inside the microgrid and provides inertia support during system dynamics2.Based on the hierarchical cooperative control method of a single microgrid,this paper proposes a cluster level hierarchical cooperative control method for microgrid clusters.Under the control of the method,a single microgrid within the microgrid cluster can be operated independently or interconnected with each other.The primary control of the cluster-level hierarchical cooperative control mainly ensures the stable operation of a single microgrid in the microgrid cluster.The secondary control realizes the DC bus voltage regulation and the power flow of the tie-line by coordinating and controlling the DGs and HESS in each sub-microgrid.Finally,this paper uses Typhoon and RT-Lab to build an electromechanicalelectromagnetic transient hybrid real-time simulation platform,which verifies the effectiveness of the above method on multiple time scales.