A Review of Control Techniques and Energy Storage for Inverter-Based Dynamic Voltage Restorer in Grid-Integrated Renewable Sources

Table 16

Quantitative and qualitative comparison of classical MLI topologies.

Indices		NPC MLI	FC MLI	CHB MLI
				Symmetric	Asymmetric
Quantitative	N sw	2(Nlel − 1)	2(Nlel − 1)	2(Nlel − 1)
	N so	1	1	(Nlel − 1)/2
	N dc	(Nlel − 1)	(Nlel − 1)	0	0
	N cd	(Nlel − 1)  (Nlel − 2)	0	0	0
	N cc	0	(Nlel − 1)  (Nlel − 2)/2	0	0
	V block	2(Nlel − 1)V	2(Nlel − 1)V	2(Nlel − 1)V	V
Qualitative	Complexity	Low	High	Medium	High
	Redundancy	Line	Phase and line	Phase	None
	Modularity	Yes	Yes	Yes	None
	Structure	Bulky	Bulky	Light	Light
	Source/switch utilization	Poor	Good	Good	Poor
	Fault tolerance	Medium	High	High	Low
	Cost	Low	High	Medium	Medium
Features		Switches are exposed to less voltage stress than, a single DC source	Fault-tolerant, modularity, single dc source, and natural charge balancing	Fewer components needed, fault-tolerant, modular, reliable, symmetric, and asymmetric structure
Limitations		Uneven blocking voltage across diodes	More switching losses, high clamping capacitors needed, and unbalanced voltage between clamping capacitors	Required more isolated dc supplies, lack of modularity due to asymmetry, and increases the components requirement
Applications		FACTS, DSTATCOM, UPFC, active filter, and low switching frequency applications	High switching frequency and high-velocity MV drive applications	HEVs, EVs, stand-alone PV systems, active filter, grid integrated PV, and WECS