Nine-level voltage-doubler bi-polar module for multilevel DC to AC power conversion

Abstract

A major disadvantage of two-stage topologies of switched capacitors based multilevel inverters is the use of H-bridge switches which endure high peak-inverse-voltage (PIV). In such topologies, the H-bridge stage is preceded by a level-generation stage which synthesises unipolar voltage levels. In this work, a bi-polar module is proposed which can synthesise nine levels at the AC terminals with a single DC input. The proposed module uses power switches with PIV equal to that of the input DC source. Use of switched capacitors in each of the proposed module enables a voltage gain of two. Such bi-polar voltage-doubler modules can be easily connected in a cascaded fashion to increase the number of levels, without involving H-bridge switches. Working modes of the module ensure that the capacitors are self-balanced. A complete analysis of the proposed module is presented. Also, experimental results are presented for validation. In addition, a comparison with other topologies has been presented.