A Simple Neutral-Point-Clamped Circuit for Active Balancing of Battery Modules and DC-Link Capacitor Voltages

This paper introduces a novel balancing circuit applicable to the active balancing of the state of charge of battery modules connected in series or to the active balancing of the capacitor voltages of dc-links formed by a series connection of capacitors. The balancing circuit is composed by one or two multilevel neutral-point clamped legs, an inductor and eventually a capacitor. Suitable modulation strategies to control the balancing are defined for three-levels in both the single-leg and the two-leg case. The topology and control can be extended to any number of levels and can be integrated into the powertrain of electric vehicles. Simulation results proof the good performance of the proposed circuit, modulation, and control principle.