HSCU-Based 31-Level Multilevel Inverter Design With Soft Charging Capability

Abstract

In this paper, a two-stage hybrid switched capacitor (SC)-based MLI topology is proposed to overcome the fundamental problems of conventional multilevel inverters (MLIs) such as high-power component count and the need for multiple DC sources. First, the proposed hexagonal switched capacitor unit (HSCU) achieves 300% voltage gain and does not require any additional balancing circuitry. This structure can generate three different DC bus voltages from a single DC source using only four power switches, two diodes and two capacitors. A 31-level SC-MLI topology is developed by coupling two HSCUs with a PUC circuit in a hybrid structure. Capacitors generate high peak currents in the charging loops. The proposed HSCU suppresses the charging current peaks with soft charging cell (SCC). The results show that SCC successfully reduces the current peaks and improves the circuit performance. The proposed topology achieves 96.14% efficiency while significantly reducing the number of components and is found to offer a lower cost solution compared to existing studies in literature. The performance of the proposed SC-MLI is verified by simulation and experimental results, and the output waveform integrity is maintained in tests at different frequencies, modulation indices and load conditions. The results prove that this topology is low-cost, highly efficient and suitable for practical applications.