Novel Cascaded Seven-Level Inverter With Embedded Voltage Boosting for Renewable Energy Applications

This paper proposes a novel seven-level inverter for renewable energy applications with voltage boosting capability. The proposed inverter is based on a full-bridge (FB) inverter, whose two half-bridge legs are cascaded with a three-level T-type (3LTT) inverter, respectively. It is supplied by a single dc source in series with an input inductor. The inductor is charged by the dc source internally through the FB inverter without using extra switches. It then transfers energy to capacitors that directly supply the 3LTT inverters. Auxiliary circuits for balancing the voltages of capacitors are not required, since each capacitor can be charged by the inductive dc-link with the same step-up average voltage. Carrier-based phase-shift pulse-width modulation (PWM) scheme is applied to the FB inverter to produce an inductive-charge duty ratio and generate suitable voltage gain. The operating principles of the proposed inverter are described. Key inverter parameters including voltage gain and voltage stresses on devices are analyzed and compared with those of the prior-art solutions. Simulations and experimental results verify the feasibility of the proposed single-stage dc-to-ac power conversion for producing a boosted seven-level output voltage with relatively high efficiency.