Study of Supercapacitor Energy Storage Converter with Unbalanced and Nonlinear Loads

A novel topology structure of supercapacitor energy storage converter (ESC) is presented with two cascaded bidirectional DC/DC converters connected to a bidirectional DC/AC converter. It can promote the energy utilization rate of supercapacitor and improve the ability of powering unbalanced and nonlinear loads. The effect of the midpoint voltage fluctuation of the cascaded connected DC bus capacitors on output voltage is analyzed, followed by the influence mechanism unbalanced and nonlinear loads. The control strategy to restrain the unbalance and zero sequence harmonic is proposed. The theoretical analysis and the proposed method are verified through simulations and experiments on a 100kVA supercapacitor ESC prototype.