A nonlinear observer-based control strategy for hybrid energy storage systems to improve voltage disturbance rejection in DC microgrids

Abstract

This paper proposes an efficient nonlinear observer-based a simple and effective control approach for DC microgrids integrating hybrid energy storage systems (HESSs) composed of supercapacitors and batteries with photovoltaic (PV) generation. The study focuses on improving HESS performance in DC microgrids, particularly in achieving fast and accurate DC microgrid bus voltage control, improved dynamic response, enhanced disturbance rejection capabilities, and better HESS power allocation. The proposed scheme combines a proportional–integral (PI) voltage controller with a variable-gain Nonlinear High-Gain Observer (NHGO) that estimates and compensates external disturbances, including load changes and PV power fluctuations. Unlike conventional high-gain or extended-state observers, which negatively impacted by measurement noise that can only be mitigated by reducing observer gain, consequently weakening dynamic response, the NHGO overcomes this limitation by dynamically adjusts its gain to achieve fast disturbance estimation during transients while maintaining noise immunity in steady state.