Distributed control strategies for a cascaded multi-level H-bridge inverter for battery energy storage systems

The modular nature of multilevel cascaded converters is compromised by centralised control and communication architectures. This thesis introduces a distributed control and communication strategy for cascaded converters, where each submodule (SM) determines its switching and control actions based on local voltage measurements. The dynamic system's state-space model is derived, and an observer-based full-state feedback controller is employed for current regulation, achieving performance comparable to centralised control. The design principles use discrete linear-quadratic regulator (LQR) theory and a Luenberger Observer (LO) to estimate state variables. Experimental results on a single-phase grid-connected seven-level cascaded converter validate the proposed control and communication architecture's effectiveness.