Flexible transformer‐based multilevel inverter topologies

Abstract

Cascaded multilevel inverters (MLIs) have been proposed that utilise transformers in the basic unit. The proposed inverters primarily serve to step up the input voltages in addition to using lower number of components in comparison to traditional MLIs. In order to generate all voltage levels (even and odd) at the output, three different algorithms are proposed to determine the magnitude of DC voltage sources and transformer turn ratios. Also, the basic inverter unit was further developed and two new flexible MLI structures have been obtained. The developed structures increase the input voltage with no need for an additional boost converter. A reduction in the number of power switches, the peak inverse voltage, and the number of DC voltage sources are other advantages of the proposed topologies. Also, a simple cost model was developed and the dimensionless cost coefficient was determined. The overall cost of the proposed MLIs was compared to the similar MLIs from the literature. It was shown that the proposed MLI decrease the overall cost of the system if the cost coefficient is selected appropriately. To verify the performance of the proposed topologies simulated by the mathematical model; several lab-scale inverters were built and tested and good agreement was achieved.

A new single‐phase multilevel inverter with improved modulation technique

“…The issue of having several sources in an inverter can be overcome by using a transformer-based MLI (TMLI). [11][12][13][14][15][16][17][18] In TMLI, the total power required to provide an electrical load is alone supplied through a single DC source. Recent past several structures for TMLI have been presented.…”

“…[19][20][21][22][23][24][25] The key benefits of these TMLIs are to minimize the number of transformers, sources, and switches. Later topology in Gandomi et al 12 is suggested in high voltage and renewable energy applications. These flexible TMLI topologies have been presented to minimize component count, and these circuits use basic seven-level units to build the inverter.…”

“…To assess the benefits of the suggested 17L topology, a comparative examination was conducted between the presented structure and the recent existing transformer-based topologies. 12,[14][15][16][17][18][19][20][21][22][23][24][25]27 The outline of the comparison results is enrolled in Table 4. To make a sufficient examination between the inverter topologies with various voltage levels, the ratio of N s , N dr , N t , N dd , N c , and N dc over N l was utilized.…”

“…Furthermore, the suggested 17L inverter generates more voltage levels per device than topologies in previous studies. 12,[14][15][16][17][18][19][20][21][22][23][24][25] Further, the concern of total blocking voltages (TBV) is another aspect that is taken into consideration in the comparison. Blocking voltage is closely related to the size and cost of switches and ensuring that a switch has minimal overall blocking voltage means that the switch will have the smallest possible size and lowest cost.…”

Quadrature Voltage Compensation in the Isolated Multi-Modular Converter

“…Cascaded-transformer multilevel inverters (CTMIs) provide isolation through lowfrequency transformers [10][11][12][13][14][15]. They have several H-bridge converters connected in parallel to a single direct current (DC) source, while the cascaded connection is made on the secondary side of the transformers.…”