Modeling, analysis, and design of novel control scheme for two-input bidirectional DC-DC converter for HESS in DC microgrid applications

摘要

This paper presents an advanced controller for multi-input bidirectional DC-DC power converter (MIPC) for hybrid energy storage system (HESS). When batteries are used for energy storage, their rates of charge and discharge are low, and this sets up current stress on the battery, decreasing its life. Supercapacitors (SC), with their higher power density, can react immediately to sudden fluctuations and can take care of this issue. However, SC alone cannot be used for storage, as they cannot supply power for longer durations. In HESS, batteries and supercapacitors are used together, as their contrasting characteristic makes them a perfect combination for energy storage. The HESS is interfaced with DC microgrid using MIPC. MIPC provides decoupled control of battery and SC power and also facilitates energy exchange between storage devices within the system. A controller is designed for DC microgrid application, with its operation modified to control both HESS charging and discharging operation, making it a unified controller. Conventional control schemes neglect uncompensated power from the battery system, and power sharing depends entirely on a low-pass filter (LPF). In the control scheme proposed in this paper, uncompensated power from the battery system is utilized to improve the SC system. This approach reduces the current stresses, increases the life cycle of the battery, improves the overall system performance to the step change in PV generation and load demand, and provides faster DC grid voltage regulation. Simulation and experimental results are developed for the proposed controller by varying photovoltaic (PV) generation and load demand, providing faster DC link voltage regulation.