Multi-Criteria Decision Analysis Approach for DC Microgrid Bus Selection

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Saaty’s comparison note (Saaty and Vargas, 2012)

Significance level	1	3	5	7	9	2, 4, 6, 8
Definition	Equally important	Moderate important	Strong important	Very strong important	Extreme important	Moderate values

Alternatives and criteria

Alternatives	A1	Unipolar microgrid	Figure 1
	A2	Bipolar microgrid	Figure 2
	A3	Ring topology	Wang et al. (2023)
	A4	Multi-terminal topology	Bouchekara et al. (2023)
	A5	Multi-bus topology	Dali et al. (2022)
Criteria	C1	Cost
	C2	Protection
	C3	Resilience

Consumer scenarios

Scenarios	S1	S2	S3	S4	5S	S6	S7
Combined criteria	C1 = C2 = C3	C2 > C3 > C1	C2 > C1 > C3	C3 > C2 > C1	C3 > C1 > C2	C1 > C2 > C3	C1 > C3 > C2

Data from scientific articles

Criterion alternatives	Cost (20%)	Short-circuit resilience (40%)	Protection complexity (30%)
Unipolar DC MG	Economical for basic setups	Limited	Low
Bipolar DC MG	Moderate	Enhanced redundancy (20%)	Moderate
Ring topology	Moderate	Self-healing capabilities (30%)	Moderate
Multi-terminal	High	Adaptive energy management (20%)	High
Multi-bus	High	Fault isolation and modular replacement (30%)	High

Cost component comparison (Eskander and Silva, 2023; Jena et al_, 2021)

Component	PV	Wind (1 kW)	Boost	Buck	AC/DC	Bid- conv	Balancer converter	Circuit breaker	Cables (3 kW)	Total cost
Topology
Unipolar DC MG (3 kW)	€2,000 (CS6K-300)	€2,500 (Bergey Excel)	€350 (Energy Skylla)	€200 (MeanWell)	€800 (SMA Sunny Island)	€800 (SMA Sunny Island)	Not required	€150 (ABB S202)	€200 (Sola Cable)	€6,150
Bipolar DC MG (3 kW)	€2,000 (CS6K-300)	€2,500 (Bergey Excel)	€350 (E. Skylla)	€200 (MeanWell)	€800 (SMA Sunny Island)	€800 (SMA Sunny Island)	€600 (Victron Energy BMV-702)	€150 (ABB S202)	€200 (Solar Cable)	€11,07

Microgrids in the literature (Kumar and Prabha, 2022; Punitha et al_, 2024)

Topology	Type	Characteristics	Usage frequency (%)
AC microgrid	AC	Standard, widely used, less efficient for DC systems	25
Unipolar DC microgrid	DC	Simple, low-cost, suitable for small-scale systems	13
Bipolar DC microgrid	DC	More reliable, reduces losses compared to unipolar	12
Multi-terminal DC	DC	Connects multiple sources and loads, modular	11
Multi-bus DC	DC	Flexible load distribution and efficient control	10
Ring DC	DC	High resilience, continuous power supply	10
Radial DC	DC	Simple, but vulnerable to faults; low redundancy	5
Mesh DC	DC	High reliability, but complex control	4
Star DC	DC	Centralised, best for small systems	3

Microgrids and bus characteristics

Topology	Unipolar DC microgrid	Bipolar DC microgrid
Bus parameters	Single positive rail and ground	Positive, neutral and negative rails
Bus voltage	Single voltage (positive to ground)	Three-wire voltage (positive, neutral and negative)
Bus complexity	Simpler, with fewer components	More complex, with more components for balancing
Protection	Simple overcurrent/short-circuit protection	More complex, requiring balancing and fault detection for both rails
Voltage levels	300 V	±200 V
Power of sources	Pv (2 kW), wind (1 kW)	Pv (2 kW), wind (1 kW)
Load options	One voltage level per load, Load 1 (2 kW)	Load 2 (1 kW), load 3 (1 kW)