**Acknowledgements**

This work is supported by a research grant from the National Science and Engineering Research Council (NSERC) of Canada, the Atlantic Innovation Fund

higher than the other operational modes because all DG units are operating during this mode. Moreover, this mode has two generation sources which are assumed as

**Sub-systems Distribution parameters Sub-systems parameters Reliability** WT rotor *θtp βtp Pciw Pcow Rtp*

Gearbox *θgb βgb ωwt,s ωwt,*<sup>m</sup> *Rgb*

Generator *θ<sup>g</sup> β<sup>g</sup> Pg,ciw Pg,cow Rg*

IPE system *θIPE βIPE τciw τcow RIPE*

**DG units Reliability DG units Reliability** WT system *Rwts* HGU *RHGU*

WPGS *RWPGS* SU *RSU*

**Microgrid operational modes Reliability** Grid-connected mode *RMSRM*<sup>1</sup>

Isolated microgrid with WPGS: number of WTs in WPGS (1, 2, 3, 4) *RMSRM*<sup>2</sup>

Isolated microgrid without WPGS *RMSRM*<sup>3</sup>

*Reliability results of different subsystems in a variable-speed wind generator system.*

1560.58 1.422 77 3000 0.9068

13.73 3.33 4.1 18.4 0.9107

1354 1.4142 73 2850 0.9266

1.158 2.658e-5 0.0202e-4 0.4821e-4 0.8144

0.6232 0.85

0.9998 0.8144

0.9999

0.94, 0.97, 0.99, 0.997

0.99

On the other hand, MSR during isolated microgrid with WPGS varies depending on the number of WT system operating in the WPGS. It is worth mentioning that in an isolated microgrid system, all WTs in WPGS do not operate due to stability issues. This issue will occur since all WTs in WPGS will require reactive power for their operation during isolated mode. However, in an isolated mode, there is no such reactive power generation source to provide sufficient reactive power for all nine WT systems. Thus, the reliability calculation is carried out for a different number of WT systems in the WPGS, and the various reliability indices are found. On the other hand, it is important to note that the minimum reliability index found

highly reliable in power generation and supply.

*Reliability results of distributed generation units.*

*Reliability and Maintenance - An Overview of Cases*

is 0.94, which is high.

**186**

**Table 1.**

**Table 2.**

**Table 3.**

*Reliability results of microgrid system.*

(AIF) of Canada, and Memorial University of Newfoundland. The author also would like to acknowledge the utility company, Newfoundland Power, Canada, for providing the system information and data.

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