A single-phase H-type five-level Current Source Inverter

Abstract

Current Source Inverters (CSIs) have drawn growing attention in modern energy conversion systems due to their inherent voltage-boosting capability, reliable short-circuit protection, and smooth output current profiles. This dissertation investigates single-phase multilevel CSIs and systematically reviews the evolution of three-level, five-level, and seven-level topologies. The advantages and limitations of different five-level CSI configurations are further analyzed, and the trade-off between output current quality, circuit complexity, and efficiency indicates that the five-level CSI provides a suitable balance for practical applications. However, conventional five-level CSIs suffer from dc current imbalance, which necessitates complicated active balancing control schemes. Although a recently developed single-phase X-type five-level CSI successfully achieves inherent current balancing without complex external controllers, it requires significantly large DC inductors, which inevitably leads to increased system volume, higher manufacturing costs, and degraded efficiency. To overcome these limitations, this dissertation presents a novel single-phase H-type five-level CSI. The proposed topology retains the self-balancing capability for inductor currents while significantly reducing the required DC inductance across its full operating range. The operating principle, modulation scheme, passive component design, inductor current self-balancing, switch voltage stresses, and power losses of the proposed inverter are investigated. A comparative analysis is performed between the proposed H-type and X-type five-level CSIs in terms of required dc inductance, peak voltage of switches, semiconductor device count, and efficiency. Finally, the performance of the proposed inverter is verified through MATLAB/Simulink simulations and lab-scale experiments.