Enhanced Power Management System for Droop Control in a Grid Connected DC Microgrid

Abstract

This paper presents an enhanced power management system for a DC microgrid operating in the grid connected mode using droop control. The proposed power management technique acts over the energy storage system (ESS) regulating the power flow according to the state of charge of the battery bank. A voltage source converter (VSC) is applied to interface the DC microgrid and the AC utility grid. Since droop control is applied, no communication between the VSC and the energy storage unity is required. Customer loads and distributed generation are considered as part of the DC microgrid. The droop characteristic of the energy management system is modified to force the ESS to operate autonomously, providing the energy required by the load, while the AC grid only supplies or absorbs power during deficit or surplus of energy. A comparison between the proposed method and a conventional power management for droop control is performed. Simulation results indicate that the proposed system leads to a better control over the DC microgrid power flow, in a smooth DC bus voltage variation and in a better ESS state of charge regulation.