This paper presents the improvements of the hosting capacity of photovoltaics (PVs) and electric vehicles (EVs) in a stand-alone microgrid (MG) with an energy storage system (ESS) by consider-ing a model predictive control (MPC) based energy management system. The system is configured as an MG, including PVs, an ESS, a diesel generator (DG), and several loads with EVs. The DG is controlled to operate at rated power and the MPC algorithm is used in a stand-alone MG, which supplies the energy demanded for several loads with EVs. The hosting capacity of the load in-cluding the EV and PVs can be expanded through the ESS to the terminal node of the microgrid. In this case, the PVs and the load can be connected in excess of the capacity of the diesel genera-tor, and each bus in the feeder complies with the voltage range required by the grid. The effec-tiveness of the proposed algorithm to resolve the hosting capacity is demonstrated by numerical simulations.

With the intention of keep the customer voltage within a nominal voltage boundary (the South Korea voltage regulation in range of 220 V ± 6% for a single phase), the SVR (step voltage regulator) method in the primary feeder has been seriously systematized for the scheduled tap time delay (from a minimum of 120 s to a maximum of 900 s). The voltage must be compensated for the primary feeder during the tap delay time of SVR. However, when RES (renewable energy resource) is connected with the primary feeder, the customer voltage could exceed the nominal voltage boundary. Therefore, in order to keep the secondary feeder voltage within the nominal voltage boundary at all the time, this paper proposed a novel voltage control method in the primary feeder using coordinated controls between ESS (energy storage system) and SVR. Through the simulations based on PSCAD/EMTDC which is analysis tool of power system, it is confirmed that the proposed algorithm can effectively control the customer voltage within allowable limitation.

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The introduction of electrical vehicle charging infrastructure including electric vehicle (EV) charger renewable energy resource at the secondary feeder in a distribution system has been increased as one of countermeasure for global environmental issues. However, the electric vehicle charging (EVC) infrastructure may act as the peak load in the distribution system, which can adversely impact on the voltage stability when the electric vehicle is quickly charged. Therefore, to keep within the limit capacity of a secondary feeder and allowable limit for the feeder voltage, this paper proposes a stabilization method by an energy storage system (ESS) control strategy at the secondary feeder to not exceed the upper limit or fall below the lower limit. In addition, this paper presents an estimation method to keep the proper standard value of the state of charge (SOC). From the simulation results, the voltage stabilization operation by the ESS should make the feeder voltages of the distribution system (secondary feeder) introduced EVC infrastructure keep better voltage conditions. In addition, the estimation method was able to keep the proper standard value confirming that the SOC of the ESS when it is in standby can be kept within the proper reference range. Therefore, it is confirmed that this strategy is an effective tool to solve the voltage problems by ESS.