Optimal Management of an Energy Storage Unit in a PV-Based Microgrid Integrating Uncertainty and Risk  
[PERSON]  
1 Department of Electrical Engineering and Automation, Aalto University, 02150 Espoo, Finland; [EMAIL_ADDRESS]  
[PERSON]  
1 Department of Electrical Engineering and Automation, Aalto University, 02150 Espoo, Finland; [EMAIL_ADDRESS]  
[PERSON]  
2 UNIDEMI--Department of Mechanical and Industrial Engineering, Faculty of Science and Technology (FCT), New University of Lisbon, 2829-516 Caparica, Portugal; [EMAIL_ADDRESS]  
[PERSON]  
3 ESTIA Institute of Technology, ESTIA, F-64210 Bidart, France; [EMAIL_ADDRESS]  
[PERSON]  
4 Faculty of Engineering, University of Porto, and INESC TEC, 4200-465 Porto, Portugal  
Correspondence: [EMAIL_ADDRESS] (E.P. ); [EMAIL_ADDRESS] (J.P.S.C. )4  
the dynamic operation and control of microgrid hybrid power systems including a PV system, fuel cell power, wind, and static VAR compensator is investigated. A power planning method is proposed in ref. [10] to minimize the storage, utility, loads, and generation cost, as well as the worst-case transaction cost due to uncertainties of renewable energy resources. This type of grid can be connected to the interconnected main electrical power system by means of a coupling point with the local utility for parallel operation [11]. It is also essential that the microgrid has the ability to automatically respond by disconnecting during disturbances coming from the main grid or from the local grid itself. Within the microgrid, generation and demand integrate a way to enable consumers to manage their power flows for the optimization of performance, cost, and reliability during interconnected system changes [12]. The majority of the currently existing electrical power systems were installed many decades ago and in such a manner that it only allows the power to flow unidirectionally from generation units to load centers. This may result in operating the power system near the maximum loading point [13] that, by increasing the negative impacts of end-users on producing emissions [14,15] and endangering the voltage stability, decreases the system flexibility [16]. As a consequence, several requirements became necessary for a flexible power system due to the expansion and use of renewable energy sources in an effective way [17,18]. This will lead to an increase in microgrids with the purpose of enabling bidirectional power flow between power generation and final customers which is expected to play a key role in future power networks. Renewable energy sources such as PV and wind can be connected to the distributed generations (DG) units and supply the loads and/or charge the energy storage system through the microgrid technology, which is capable to operate in grid-connected or in islanded operating modes in different operating conditions. Consequently, the energy storage devices are becoming an inevitable element of the grid which could lead to the improvement of the grid reliability and resiliency, and could reduce the necessity to build new transmission or distribution lines [19,20]. This source of energy can be used to smooth the power demand and reduce the power fluctuations of the renewable energy sources during the periods of absence of sufficient energy sources on the generation side. In addition, when considering the long-term, energy storage devices also could have great advantages from an economical point of view, since they can absorb the inexpensive excess power throughout off-peak periods and then release it during on-peak hours while the price of the electricity is high. Regarding the various kinds of energy storage technologies, they are known to have different response times which can support the power system requirements in different time scales [21]. So, by considering a short time period, fast-response energy storage devices can alleviate variations between demands and generation units. However, an efficient use of storage systems will be difficult to achieve, unless a well organized management system is applied to them.