Reduced Voltage Stress and Spikes in Source Current of 7-Level Switched-Capacitor Based Multilevel Inverter

Various 7-level switched-capacitor (SC) based converters are reported in the literature which furnishes a voltage gain of 1.5. However, in these topologies, the voltage rating of switches is high and the switch count is more. Further, the charging and discharging action of the switched capacitors, lead to the production of spikes having a large magnitude in source current and charging currents supplied to switched capacitors. Due to this limitation, the SC-based Multilevel Inverter (SC-MLI) cannot be used for high-power applications. To resolve these issues, an SC-MLI in an Active-Neutral-Point-Clamped (ANPC) configuration is proposed in this paper which requires switches having reduced value of voltage stresses and the switch count of the proposed converter is less. Further, to reduce the magnitude of spikes in the source and charging current supplied to switched capacitors, a soft switching circuit is included in the proposed converter. The soft charging circuit includes an inductor and a diode in the charging path of the proposed converter which ensures soft charging of the switched capacitors. The proposed converter can significantly suppress the spikes appearing in the source current by including a small value of inductance connected to the soft charging circuit. The proposed topology requires a single dc source, 2 switched capacitors, and 8 switches to generate 7-level and does not require an auxiliary diode. The absence of an auxiliary diode leads to a further reduction in losses. If the value of the modulation index is reduced to a low value, the proposed topology can maintain the self-balancing of the capacitor voltage. To highlight the various key features of the proposed 7-level topology, its comparison with the recent converter topologies suggested in the literature is carried out. To validate the efficacy of the proposed 7-level SC-MLI, experimental results are included which are captured using a laboratory prototype for different values of soft charging inductor.

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Published in: IEEE Access
License: http://creativecommons.org/licenses/by/4.0
See article on publisher's website: https://dx.doi.org/10.1109/access.2023.3297496