Battery voltage equalisation using Singlephase cascaded H-bridge converters

Abstract

This research demonstrates modular battery storage systems’ voltage balancing using cascaded H-bridge (CHB) converters. The main principle is to maintain AC-side high-quality power absorption or injection, while on the DC-side independent battery units’ voltages get balanced. The CHB converter operates in inversion or rectification modes to discharge the storage system to an AC load/grid, or to charge it from an AC source, respectively. To achieve this goal, several challenges as high-differential mode dv/dtdv/dt, and dealing with semiconductors voltage drop also arise which should get tackled through feasible controller design. Model predictive control (MPC), as a flexible technique capable of multi-parameter controlling, is used to achieve the beforementioned system objectives in a simple, efficient, and scalable manner. The proposed MPC-based algorithm is an AC current controller, which handles DC-side voltage equalisation and introduces adjacent CHB voltage levels to reduce dv/dtdv/dt and performs switches voltage loss modelling all in a single control block. An additional linear controller based on multi-carrier pulse width modulation is also implemented for comparison with the MPC-based design. Experimental prototyping and simulation results validate the feasibility of this approach.