Study On The Mode Switching Control Strategy For Microgrid

In recent years, environmental and energy issues have become more severe. Powersystem plays an important role in energy conservation, emission reduction and energysustainability, which is the lifeblood of modern energy society. Distributed powergeneration system which makes full use of clean and renewable is the primary means toachieve a low-carbon economy power sectors. Distributed generation system has manysignificant advantages in the overall efficiency, energy diversification, environmentalprotection, energy conservation, resource conservation, supply reliability and other aspects.However, when distributed generation in grid-connected mode, may cause power quality,protection, security, stability and a series of systemic problems. In order to effectively dealwith these problems, the concept of microgrid is proposed. Microgrid is made up ofdistributed power supply, energy storing device, powers conversion device, related to theload, monitoring device, and protective device of assembled small power distributionsystem. Microgrid can either in grid-connected mode, also come out from the main grid inislanding mode. No matter what kind of work mode, microgrid provides reliable powersupply for important load.Therefore, stability in two kinds of modes is the basic conditions for security andreliable operation of the microgrid. And it is very important that analysis and designing thecontrollers which can make the system stable. In this paper, based on the grid-connectedoperating mode and islanding operating mode of microgrid, reasonable and appropriatecontrol methods are proposed and designed. First, based on microgrid power electronicinterface technology, the mathematical model of the grid-connected mode and islandingmode are established. According to Lyapunov stability theory, the robust controllers ofgrid-connected mode and islanding mode are designed, and the simulation verifies thecorrectness and effectiveness of control methods. Second, study on the stability ofmicrogrid switching from grid-connected mode to islanding mode, and the switchingsystem mode is established. Then analysis of the stability of the switching system anddesign the controller, making the microgrid smoothly and stably switching from grid-connected mode to islanding mode. Final, the simulation model of the switchingsystem is built in MATLAB/Simulink soft, and the simulation results verify thecorrectness and effectiveness of system controller.