A 13-level inverter based on switched-capacitor technique is proposed in this work. It consists of ten transistors, four diodes and four capacitors with self-balanced voltages. The ten transistors form two H-bridges and one half bridge resulting in simple structure and easy design of gate drivers. With a hybrid of level-shifted and phase-shifted PWM algorithm, voltage ripples of capacitors and low harmonic components of output voltage are suppressed simultaneously. Compared with the existing solutions, the proposed 13-level inverter has simpler structure and the lower cost per level. Experimental results demonstrate that the proposed inverter has the advantages of high boosting factor, self-balanced capacitor voltages, low harmonics and high efficiency. And the maximum efficiency is up to 97.2%.

To explore single-phase micro inverter with boosting ability, simple structure, low cost and high power density, a new structure of multilevel inverter (MLI) is proposed in this paper. With this structure, two half-bridge modular switched-capacitor circuits are arranged on both left- and right-sides of a dc source. Circuit configuration of this MLI can be bilaterally symmetrical and this benefits to modular design and voltage stress reduction of inverting bridges. Additionally, in order to reduce voltage ripple of capacitors and total harmonic distortion of output voltage simultaneously, a hybrid pulse width modulation strategy is developed to improve the performance of this MLI. As a result, capacitors of this MLI can be replenished repeatedly when they are taken as voltage sources to generate different voltage levels. Circuit configuration, operation principle, modulation, power loss and voltage ripple are analyzed in detail. Both simulation and experimental results are provided to demonstrate the effectiveness of the proposed MLI and modulation strategy.