A Research Of Power Coordinated Control Strategy For DC Microgrids

Nowadays,with the gradual depletion of traditional energy and the increasing environmental pollution,renewable-energy-source-based distributed generation technology has attracted increasing attention from all over the world.Microgrid,which is a small-scaled power system,can solve the problem for distributed generations,such as connecting to the grid,random and intermittent output power,and low flexibility and efficiency.Therefore,it has great economic significance and social value.Compared with AC system,DC microgrid can integrate all kinds of distributed generations,energy storage units and AC/DC loads with higher energy efficiency and better reliability by eliminating the DC-AC converters.Currently,DC microgrid has been one of the hot areas in smart grid researches.This paper is organized as follows.Firstly,several common power electronic equipment in DC microgrid are introduced based on the topologies and control strategies.Secondly,the operation modes of DC system are analyzed,including the master-slave control and droop control.For the power coordination allocation problems among different sources,a power coordinated control strategy for DC microgrids is proposed,where the renewable energy sources can transform between MPPT mode and power limit mode,the energy storage systems can adjust the charging/discharging power under the same control scheme,and the grid-connected converters can realizes power exchange between DC and AC system by droop control.This strategy utilizes the DC bus voltage as a global indicator for power balance.Therefore,DC microgrids can realize distributed autonomous operation without extra communication links.Finally,the effectiveness of master-slave control,droop control and the proposed power coordinated control strategy is verified by Matlab/Simulink simulation.