Although microgrids facilitate the increased penetration of distributed generations (DGs) and improve the security of power supplies, they have some issues that need to be better understood and addressed before realising the full potential of microgrids. This paper presents a comprehensive list of challenges and opportunities supported by a literature review on the evolution of converter-based microgrids. The discussion in this paper presented with a view to establishing microgrids as distinct from the existing distribution systems. This is accomplished by, firstly, describing the challenges and benefits of using DG units in a distribution network and then those of microgrid ones. Also, the definitions, classifications and characteristics of microgrids are revised according to their specific roles to provide a sound basis for novice researchers to undertake ongoing research on microgrids.

Background: Laparoscopic cholecystectomy has become the treatment of choice for symptomatic gall stone disease. But post operative pain may prolong hospital stay and increase morbidity. The aim of the study was to find out the effect of port site infiltration of Bupivacaine in reducing post operative pain following routine laparoscopic cholecystectomy. Materials and methods: This is a double blind randomized controlled trial conducted in the Department of Surgery, Chittagong Medical College Hospital, Bangladesh. A total 200 patients underwent routine laparoscopic cholecystectomy were enrolled in the study. All patients are assigned in two groupscontrol group (Infiltration of 20 ml normal saline at port site) and Bupivacaine group (20 ml Bupivacaine at port site). Both groups are followed at 4 hrs, 12 hrs and 24 hrs after operation to assess the intensity of pain by using Visual Analogue Pain Scale (VAS). Time regarding the first analgesic request by the patients, total dose of analgesic, days of return to normal day to day activities and normal works were also recorded. Results: The mean age of control group and Bupivacaine group were 41.64 and 37.54 years respectively. At 4hrs post operative mean pain score were 6.76 and 5.62 respectively (p value 0.015). At 12 hrs mean pain score were 4.4 and 3.88 respectively (p value 0.001). At 24hrs pain score were 2.66 and 2.08 respectively (p value 0.002). Mean time of first analgesic required were 4.8hrs and 7hrs respectively (p value 0.000). Mean duration of hospital stay were 2.26 days and 2.22 days respectively (p value 0.371). Total dose of analgesic required were 12 and 9 between the groups respectively (p value 0.000). Mean time of return to normal day to days activities were 3.98 days and 2.98 days respectively (p value 0.000). Return to normal work after 6.98 days and 6.46 days respectively between the groups (p value 0.008) that is statistically significant. Conclusion : Infiltration of Bupivacaine at port site at post operative period of laparoscopic cholecystectomy patients significantly reduces pain than control group. It helps patients for early mobilization, early return to normal activities and works. Thus it reduces overall cost and morbidity of symptomatic cholelithiasis patients. JCMCTA 2017 ; 28 (2) : 64-68