A Novel Multi-Level Cascade Inverter with Reduced Switching Devices to Connect Renewable Energy Sources to the Grid

Abstract

Multi-level inverters (MLIs) have now become an essential component for medium and high power applications with medium voltage levels. Low switches multi-level inverters are very popular due to their high efficiency, low cost, and easy control for output with higher levels. In this paper, a new multi-level inverter structure based on a switched DC voltage source is proposed by reducing the number of switches for single-phase applications. The proposed structure can be used in grid-connected applications, such as grid connections for renewable energy sources. The proposed structure is developed with a higher number of levels at the output using a smaller number of devices. The proposed topology can also be used in symmetric and asymmetric configurations. Two switching methods including pulse width modulation (PWM) switching and ladder switching based on selective harmonic elimination (SHE) have been used to generate the output voltage. Comparative studies with multilevel inverters were presented recently to show the advantage of the proposed structure in terms of reducing the number of devices. Simulation and experimental results are presented to confirm the performance of the proposed topology. In addition, the performance of the proposed multilevel structure for energy transfer from renewable sources to the low-power grid has also been investigated.

Keywords

• multi-level inverter
• reduced semiconductor devices
• symmetric sources
• asymmetric sources
• pulse width modulation
• voltage stress on switches