Design of a one-way communication based control scheme for power management unit in scalable DC microgrid architecture

Abstract

Renewable energy has gained much interest in recent years to keep the environment safe from ongoing climate change and become less dependent on fossil fuels. DC microgrids adapts nicely to distributed control ofrenewable energy sources to supply electricity in the remote regions. They ensure efficacious instantaneouspower sharing among differentdomestic Power Management Units (PMUs) along with maintaining stability of the grid voltage. Here design metricsand performance evaluation of a scalable DC microgrid aredocumented where asource converter initially complies with the efficient powersharing phenomenon among a set of two home PMUs. Thesource converter is connected with a Photovoltaic panel of 300W and uses Perturb and Observation (PO) method for executing Maximum Power Point Tracking (MPPT). A boost average DC-DC converter topology is used to enhance the voltage level ofthe source converter before transmission. The load converter consists of parallel PMUs. Each PMU isconstructed with high switching frequency based Full Bridge (FB)converter to charge an integrated Energy Storage System (ESS). The overall system is modeled and simulated onMATLAB/Simulink platform with ESSs in the form of Lead Acidbatteries connected to the load side of the FB converter circuitsand these batteries yield to support marginalized power utilities.The behavior of the system is tested in different solar insolationlevels along with several battery charging levels of 12 V and 36V to assess the power efficiency. In each testbed the efficiency isfound to be more than 93% which affirm the reliability of theframework and a look-up table is generated comprising the gridand load quantities for effective control of power transmission. Next the full bridge (FB) converter is used as the fanout node to lower the source-end voltage and to generate a dc bus of 48 V. Buck converter topology is used to design the PMUs and each PMU is controlled in a way to generate an output voltage suitable for a 12 V battery charging application. A one-way communication control based interface is designed to maintain the change in the solar irradiation level so that the more important units receive more power in a crisis situation. To make the system more sensible in case of long duration drop in solar irradiance level, a time based control scheme has been proposed which ensures that the turn off time is distributed evenly among the PMUs. The system works successfully for different irradiation pattern. The one-way communication based approach represent less circuit complexity and a cost effective control scheme for DC microgrid in the perspective of underprivileged people of Bangladesh.