Energy-Based Flatness Control for Islanded Hybrid Microgrids: Robustness Evaluation Under Uncertain Parameters and Measurement Noise

Abstract

In battery energy storage systems (BESSs) in microgrids, traditional proportional–integral (PI) controllers remain a popular choice for management. The PI-based system often fails during sharp transients and under sudden shifts in solar irradiance or load demands. PI-based systems typically exhibit sluggish recovery times and pronounced voltage overshoots. To overcome these limitations, this article develops a flatness-based control (FBC) framework designed to optimize the dynamic response and stability of an islanded hybrid microgrid powered by photovoltaic (PV) arrays and wind turbines. The core mechanism directly regulates the battery charging and discharging currents. This mechanism ensures that the DC-bus voltage strictly tracks its reference command regardless of fluctuations in load or weather profiles. Crucially, the structural resilience of this control architecture was rigorously assessed, with the simulation model subjected to severe 20% mismatches in physical parameters, specifically the main DC-bus capacitance and battery inductance, alongside continuous high-frequency Gaussian white noise injected into the measurement feedback channels. Three scenarios have been implemented in MATLAB/Simulink: variable weather conditions, realistic weather conditions, and parameter uncertainties with measurement noise. The comparison shows that the new FBC controller cuts the settling time down from 0.47 s with the regular PI controller to just 0.02 s, which is a 95.7% decrease. In addition, the proposed controller substantially mitigates transient voltage deviations and eliminates the 2.6% voltage overshoot observed with the PI controller. The rise time is also reduced by approximately 35%. These results demonstrate that the proposed FBC provides faster, overshoot-free, and more stable DC-bus voltage regulation under the investigated operating conditions.