Cascaded multilevel inverter using series connection of novel capacitor-based units with minimum switch count
Abstract
In this paper a new family of cascaded multilevel inverters (CMLIs) which can generate a considerable number of output voltage levels with minimum number of required accompanying switching devices. Conceptually, each stage of proposed CMLI is composed of using a novel capacitor-based unit including two floating capacitors, one embedded dc voltage source and three power switches. In this case, the balanced voltage of integrated capacitors can be precisely provided as self-voltage balancing without using any auxiliary circuits, close loop systems and intricate modulation techniques. In addition, to reach different number of output voltage levels, four different algorithms pertaining to the symmetrical, binary asymmetrical, trinary asymmetrical and also hybrid patterns for determining the magnitude of isolated dc voltage sources are presented.
Existing method
The existing method describes a conventional types of MLIs are classified into three main configurations including diode clamp or neutral point MLIs, flying capacitor-multicell MLIs (FCMC-MLIs) and cascade H-bridge (CHB-MLIs) based on the symmetrical or asymmetrical patterns for the magnitude of their relevant dc voltage sources.
Proposed method
In this paper, a new basic unit is presented which comprises of one dc voltage source, two capacitors as dc-link energy sharing elements and only three power switches. Proposed basic unit named as capacitor-based unit.
Circuit diagram
Overall configuration of proposed 27-level inverter
Proposed hybrid topology
Advantages
1. An ability to generate three-level of output voltage (one positive level, one negative level and one zero level) without using the traditional full-H-bridge cell.
2. Generating all the output voltage levels by using just one dc power supply and self-charge balancing capability of capacitors during the positive and negative half cycles of output voltage waveform.
Applications
This can be used mainly in High voltage inverter applications.
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