A new cascaded asymmetrical multilevel inverter based on switched dc voltage sources

Abstract

Multilevel inverters are now becoming an important element for medium-voltage high-power applications. A low switch count multilevel inverters are currently attracting more attention due to its high efficiency, low cost, and easy control. This paper proposes a new single-phase cascade asymmetrical multilevel inverter topology based on switched dc voltage sources which is capable of achieving a higher number of output levels using fewer number of switches, driver circuits, and dc voltage sources. Other advantages include the inherent generation of negative voltage levels and lower voltage stress across the switches. Three different approaches in selecting the magnitude of the sources for the cascade connection has been included to produce a higher number of voltage levels. Furthermore, the power loss and fault-tolerant analysis of the proposed basic module has also been discussed. To set the benchmark of the proposed multilevel inverter structure, a comparison with several recently proposed topologies is carried out. The comparison has been carried out for the basic module, generalized structure, and cascade connection. The proposed topology gave improved parameters for all three categories. Fundamental switching frequency modulation technique is used to achieve high-quality output voltage waveforms with lower harmonic contents and reduced switching losses. Finally, the operation and performance of the proposed basic module and its cascade connection for two modules are presented together with experimental results in several steady-state and dynamic operating conditions.