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88 Hybrid-Renewable Energy Systems in Microgrids

Figure 5.6 Components for multi level inverters.

It can clearly be inferred that the number of components of the topology is lower
than other topologies. Fig. 5.6 shows the required components versus different voltage
levels as mentioned in Table 5.3.
As the most important part in multilevel inverters are the power semiconductor
switches which define the reliability and control complexity, the number of required
switches against the required voltage levels is depicted in Fig. 5.7 for the topologies
in Table 5.3.

2 Evolution of hybrid multilevel inverters

More hybrid topologies are proposed in recent years that generally work with the same
principle of operation. A successful and pioneer researcher in this field is Prof. E. Ba-
baei who has developed many hybrid multilevel inverters in recent years. In 2011 he
proposed the following hybrid topology (#2) [7]. As can be observed from the circuit

Table 5.3 Number of Components for 3 Phase Inverters

Inverter type NPC Flying capacitor Cascade RV
Main switches 6(N−1) 6(N − 1) 6(N − 1) 3((N − 1) + 4)
Main diodes 6(N−1) 6(N − 1) 6(N − 1) 3((N − 1) + 4)
Clamping diodes 3(N − 1)(N − 2) 0 0 0
DC bus (N − 1) (N − 1) 3(N − 1)/2 (N − 1)/2
capacitors/
isolated
supplies
32 Flying capacitors 0 3 (N − 1)(N − 2) 0 0
2
1 27
272 Total numbers (N − 1)(3N + 7) (N − 1)(3N + 20) (N − 1) (13N + 35)/2
12
2 2