Small-Signal Modeling and Analysis of Converter Interactivity in 48 V DC Grid

Abstract

Due to the flexibility of realization in decentralized form, environmentally genial, and the easy integration with renewable energy sources, storage units, and loads, the direct current (DC) microgrid has shaped as a subject matter worldwide. In a DC microgrid structure, the concurrent operation among multiple DC-DC converters, connected in parallel fashion across the common DC bus, realizes substantially with the average current information-based droop control technique. However, such control logic requires two minimal controllers with an inter-reliant design process to implement the overall control action. Considering the coupling effect during converter operation, this paper analyses the implementation of a mixed-signal peak current information-based droop control logic for the parallel connected converter system. A thorough small signal and switch-based modeling process for the interconnected systems are carried out with consideration of resistive and constant power loads. Adaptability to modeling with a first-order approximation-based approach makes the methodology easy for the design of the controller and stability analysis process in a parallel connected converter system. The veracity of the designed model is verified using simulation studies. A hardware prototype with two boost converters operating in parallel and feeding power to a resistive load and a buck converter (behaving as a constant power load) is fabricated to study the performance of the designed controller, along with the effect of different transient events on overall system performance.