Low-Voltage Stress Seven-Level Inverter Based on Symmetrical Capacitors

A step-up single-phase seven-level inverter is proposed in this article. The proposed multilevel inverter (MLI) uses one voltage source and two symmetrical capacitors. Two capacitors are provided with self-voltage balancing ability, eliminating the requirement for sensors or additional control loop. The proposed topology generates bipolar levels inherently without the use of inverting H-bridge, so that the total standing voltage of switches is greatly reduced. The blocking voltages of all the switches are limited to the input voltage, and thus the proposed topology has low-voltage stress. Furthermore, the proposed structure has the advantages of voltage-boosting capability and high efficiency. The maximum output voltage is 1.5 times the input voltage. The prominent merits make it suitable for distributed generation applications. In this article, the circuit configuration of the proposed topology, operation principle, and the phase disposition pulsewidth modulation (PD PWM) strategy are presented. Furthermore, the mathematical calculations of power loss and parameter comparisons are performed to demonstrate the superiority. Finally, the experimental results are presented to verify the feasibility of the proposed topology.