DC-Link Voltages Digital Sampling for Cascaded H-Bridge Rectifiers With Single Voltage Sensor Under Loads Unbalanced Condition

Direct current (dc) voltage sensor in each cell of the cascaded H-bridge rectifier (CHBR) is traditionally indispensable for capacitor voltage balancing control. The cost of dc sensors will increase with the number of cells. This letter proposes a strategy for dc-voltage digital sampling based on sliding window recursive least square (RLS), which employs only one voltage sensor. Sliding window RLS is used to decouple voltage information within one sampling interval. For the actual situation where the modulation waves of cells are different, this method owns faster updating rate and higher detection precision compared to the existing multisampling method. A downscale test platform of the single-phase CHBR is built to verify the correctness and effectiveness of the proposed method. The result shows that better current quality and steadier dc voltage are achieved.