An Adaptive Modulation Technique to Improve the Power Quality of Single-Phase Single-Stage Current Source Inverters

Current source inverters (CSIs) are attractive options for battery energy storage systems (BESS) due to their inherent capabilities for voltage boosting and short-circuit protection. This article presents a single-phase, single-stage wide bandgap (WBG)-enabled CSI designed to serve as an interface between the battery and the ac load. By utilizing WBG anti-series connected pairs (ASCP) of MOSFETs, the proposed design provides reverse voltage blocking while reducing the losses compared to conventional CSI. However, incorporating ASCP of MOSFETs makes the proposed CSI vulnerable to inter-leg short circuit conditions when controlled using modulation techniques designed for conventional CSI. Additionally, like other single-phase inverters, the presence of double-frequency power ripples on the dc link adversely affects the output power quality of single-phase CSIs. To address the issue of inter-leg short circuit, as well as double-frequency power ripples simultaneously, this article introduces an adaptive modulation technique that ensures safe operation while effectively reducing the impact of low-frequency dc-link ripples on the ac side of the proposed CSI. However, the dc-link ripples are still present due to ac side power pulsations. By solving the latter issue, the proposed modulation technique significantly improves output power quality and allows for a smaller dc-link inductor. This article includes detailed derivations and analysis, along with a discussion on the challenges associated with the implementation of the proposed technique. The performance of the proposed adaptive modulation technique is evaluated through both MATLAB/Simulink simulations and experiments, with results validating the effectiveness of the proposed modulation technique.