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The combination of supercapacitors (SCs) with Li-ion Batteries (LIBs) and Lead-Acid Batteries (LABs) as hybrid ESSs (HESSs) have widely been proposed for Microgrid (MG) applications. The SCs of HESSs eliminate the stress of surge currents on LIBs and LABs, which increases their life cycles, and decreases their life cycle costs and hence decreases the HESSs operational costs. However, the active topology of HESS, which is the most commonly used configuration, requires an extra SC and an extra DC/DC converter in comparison to the Battery Energy Storage (BESS) topology, which increases the HESS capital cost. This paper tries to investigate that the hybridization of LABs and LIBs with SCs is economically effective or not for applications in islanded MG. In this regard, an energy management and frequency control (EMFC) scheme is proposed for the operation of MG in islanded mode. Using the simulations of the proposed EMFC scheme for islanded MG, the size of main components of LIB ESS (LIBESS), LAB ESS (LABESS), LIB-SC HESS (LISHESS) and LAB-SC HESS (LASHESS) are calculated. The numerical results show that for a 10-year period operation in islanded MG, the LISHESS and LASHESS impose less cost than LIBESS and LABESS. Also, the LISHESS is cheaper (almost 11%) than LASHESS.

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System operators have the option to trade balancing reserves among countries and operators. In order to trade balancing reserves with other system operators the markets should be harmonized. While the spot and intraday markets are already harmonized within the Nordics, the balancing markets still display differences. The differences can be subtle, yet they may play a significant role for the planning, operation, modelling and control of the power system. In this paper, we conduct a thorough literature review on Nordic balancing markets and summarize the market rules and requirements. This review can help operators and modellers to better represent the Nordic power system.