DC-Side Secondary Ripple Suppression Method for Cascaded H-Bridge Systems Based on H-Bridge Power Device Reuse

With the rapid development of power electronics and the increasing maturity of device manufacturing processes, cascaded multilevel converters have gained widespread attention in the field of energy storage due to their ability to achieve high-voltage, high-power output by combining low-voltage, low-capacity modules. However, in cascaded H-bridge (CHB) systems, significant second-order ripple power on the DC side poses serious challenges to battery lifespan and system stability. To address this issue, this paper proposes a novel ripple suppression topology that reuses existing H-bridge power devices to achieve DC-side second-order ripple power mitigation—without the need for additional switching components. By implementing a specific control strategy on a single bridge leg, the system effectively realizes a Buck-type active power filter (APF) function. The proposed method reduces system cost and complexity while maintaining stability. The effectiveness of the topology and control approach is verified through simulation in MATLAB/Simulink. Results demonstrate significant improvements in DC voltage quality, including a reduction in total harmonic distortion (THD) and suppression of second-order harmonics, validating the feasibility and superiority of the proposed method.