Seamless Mode Control of Microgrid for Optimal Coordination of Conventional and Renewable Energy Resources

Abstract

The technological developments in the control strategy cause optimal coordination of conventional energy resources and renewable energy sources and increase the popularity of the AC microgrid (MG). This paper proposes a seamless mode transfer capability of MG to achieve optimal coordination between solar photovoltaic (PV)/battery/utility grid/diesel energy sources. The MG is controlled in such a way that the maximum power demand is fulfilled from a solar PV array; thereby, the optimum use of a clean energy source is targeted. Battery storage at the DC link manages the power variations from the solar PV array during the varying solar irradiations. In GC mode, the MG is synced to the three-phase power grid and thereby, the excess power generation is being fed to it, or the power deficiency is taken from it. Moreover, the MG is synchronized to a diesel engine generator (DEG) set as a standby energy source. The MG is synchronized to it only when the utility grid is not available, the battery state of charge (SOC) is under the lower limit and where PV array power is lower than the load power demand. In this way, the MG is controlled such that optimal coordination of various energy sources is performed in this paper. An improved second-order generalized integrator-frequency locked loop with DC offset rejection capability (SOGI-FLL-WDCRC) is developed in this paper for enhancing the quality of power injected to the utility grid even under abnormal grid conditions and mitigating the power quality (PQ) issues due to the connected nonlinear loads.