An improved droop control algorithm for load sharing and circulating current control for parallel DC-DC converters in standalone DC microgrid

Abstract

This paper discuss the relationship between load sharing and circulating current for parallel connected dc-dc converters. In the proposed algorithm a new figure-of-merit called Droop Index is introduced, which is a function of normalized current sharing difference and losses in the output side of the converters. This algorithm minimizes the circulating current and current sharing difference between the converters based on the virtual resistance, R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">droop</sub> values. This also eliminates the trade-off between current sharing difference and voltage regulation. By calculating negative R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">droop</sub> values, the algorithm gives better performance and low voltage regulation. The detailed analysis and design procedure are explained for two dc-dc boost converters connected in parallel. The effectiveness of proposed method is verified using MATLAB simulation.