Battery voltage equalisation using single‐phase 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 normaldv/normaldt, 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 normaldv/normaldt 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.

Model predictive and SoC balancing control of a CHB inverter in battery energy storage application using reward functions

“…The H‐bridge with relatively high SoC is given priority to discharge in discharging mode, and the H‐bridge with relatively low SoC is given priority to charge in charging mode. In Pirooz et al, 27 a sorting and FCS‐MPC‐based SoC balancing method is presented, which is flexible and can be designed easily. However, the above methods are only suitable for inner‐phase SoC balancing.…”