Single-Phase 15-Level Switched-Capacitor Boost Multilevel Inverter Topology for Renewable Energy Applications

Abstract

Galvanic isolation is a vital part of a grid-connected solar PV system. With the growth of multilevel inverters for grid-connected applications, the multilevel inverters having isolation are not sufficiently discussed in the literature. In this paper, a 15-level isolated multilevel inverter topology requiring only thirteen switches is proposed. The envisaged configuration includes two cells, designated as upper and lower cells. The upper cell includes a standard H-bridge, and the lower cell is a switched capacitor-based 5-level inverter. The outputs of the lower and upper cells are supplied to the load through single-phase isolation transformers. The proposed single-phase isolated inverter requires reduced switches to generate 15-level AC output voltage with a voltage gain of 7. In comparison to the MLIs mentioned in the literature, the switches connected in the proposed inverter experienced less voltage stress. The proposed inverter construction is contrasted with state-of-the-art MLIs described in the literature. PLECS software is used to simulate the inverter under various working environments, the proposed MLI able to maintain capacitor voltage balance and generate good power quality even at low values of modulation index. The experimental results achieved on a low-power laboratory prototype are utilized to validate the proposed inverter’s performance. The claimed efficiency of the inverter calculated using simulation results is found to be 97.1%. However, the efficiency calculated using experimental results is 96.4% at 700W.

Keywords

• Multilevel inverter
• switched capacitor (SC)
• self-voltage balancing
• boost capability
• isolated converter