Wide Frequency Range Second Harmonic Suppression in Cascaded H-Bridge Energy Storage Converters Using a Disturbance Observer

The Cascaded H-bridge energy storage converter provides power to ultra-high-speed linear motors. During motor acceleration and braking, rapid frequency-changing second harmonic currents are generated in the submodule inductance branches. To address this issue, this paper proposes an improved mathematical model for its submodules and utilizes a disturbance observer established based on this model to rapidly track this harmonic current. By employing control with disturbance current feedforward, variable-frequency second harmonic currents can be effectively suppressed without compromising the dynamic response speed of the DC-DC converter. Simulation results confirm the effectiveness of the proposed method.