A new switched-capacitor multilevel inverter with soft start and quasi resonant charging capabilities

• Published in: International journal of electrical power & energy systems 2022-02, Vol.135, p.107412, Article 107412
• Main Authors: Khan, Md N.H., Barzegarkhoo, R., Siwakoti, Y.P., Khan, S.A., Li, L., Blaabjerg, F.
• Format: Article
• Language: English
• Subjects: H-bridge; Multilevel inverter; Quasi-resonant circuit; Soft charging
• ISSN: 0142-0615; 1879-3517
• DOI: 10.1016/j.ijepes.2021.107412

•Has the capability to boost the voltage, and thus, it requires reduced dc-link supply compared to existing topologies.•It requires a minimum number of components compared to the conventional topologies. This topology requires only seven active switches, a diode, a capacitor, and an inductor to generate 5 L voltage output.•It has soft-start and quasi resonant charging capability. Thus, it reduces the charging current through the capacitor and input inrush current.•The voltages stress on the switched-capacitor do not exceed the input dc voltage. As a result, it reduces the size of the capacitors. Moreover, the circuit does not require any additional sensor or control strategy to balance the capacitor voltages.•It can operate with both leading and lagging power factors. Thus, it can provide reactive power support to the grid when necessary. Switched-capacitor multilevel inverters (SCMLIs) are gaining widespread attention in recent decades due to their simple design, voltage boosting capability, and inherent capacitor voltage balancing feature. However, the advantages offered by SCMLIs come at the cost of employing a higher number of active and passive components and capacitor voltage balancing issues with an inrush current profile. This paper introduces a novel configuration of SCMLIs with a lower number of power components with inherent voltage boost. The basic 5-level topology consists of a single capacitor, an inductor, a diode, and seven active switching elements. To improve the transient response and the inrush current profile of the converter, a soft start and quasi-resonant charging capability has been explored and implemented. Considering the inherent capacitor voltage balancing of the proposed SCMLI, a new finite control set-model predictive control (FCS-MPC) method with a single objective and a less computational burden is also developed, which contributes to injecting a fully controlled current for the grid-connected applications. The proposed topology is compared with other existing five-level inverter topologies to show its superior capabilities/advantages. And finally, the performance of the proposed topology and its associated FCS-MPC mechanism are validated by the measurement results.