The dependence of distributed generations (DGs) on climate conditions and fluctuating load demands are the challenges for the implementation of battery energy storage systems (BESSs) in islanded microgrids. BESS participation in system frequency regulation becomes one of the solutions to those challenges. Frequency regulation by BESS can be realized by applying the load-frequency control (LFC) in BESS. However, this participation clearly poses problems for the battery state of charge (SOC), as the battery is often overcharged or undercharged. In this paper, a control that maintains SOC at a certain level is introduced. This control strategy focuses on the battery operation function, which is determined from five control scenarios. All scenarios are achieved by applying the droop reference shifting method in the LFC to allow battery operation change. Control verification is carried out on an islanded microgrid system that experiences load demand changes and photovoltaic (PV) output power changes. The test results show that the SOC is maintained at 45–75% by applying load and PV power variations. The results correspond to the predetermined criteria control.

This research aims to know the effect of the Rotor Radius Ratio on the performance of the hybrid Vertical Axis Wind Turbine Savonius-Darrieus NREL S809 model using the Computational Fluid Dynamics method. Two-bladed Savonius is used as an internal rotor, and three-bladed Darrieus NREL S809 as an external rotor. Turbine model performance is analyzed through the value of the Moment Coefficient and Power Coefficient. The result shows that the increase in the Rotor Radius Ratio value causes an increase in the initial Moment Coefficient but a decrease in the maximum Power Coefficient value. At the initial TSR, the Rotor Radius Ratio 0.5 model has the best Moment Coefficient value among all variations but has the lowest maximum Power Coefficient value.

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The application of battery energy storage (BES) in microgrid systems has attracted much attention in recent years. It is because the BES is able to store excess power and discharge its power when needed. In islanded microgrid systems, BES is starting to be considered as a unit that can regulate the system frequency. The control used in the BES to display frequency regulation performance is called load-frequency control (LFC). However, this participation resulted in the large size of the battery and high expansion planning cost. In this paper, an advanced LFC control that has frequency limitation compared to traditional LFC is proposed. The proposed control implies droop control as the base and has frequency limitations. Compared to the traditional LFC, the proposed control can reduce the system expansion planning costs. A performance simulation was done to validate battery performance. The results of the numerical simulation showed that the proposed control participated in reducing the operation cost. It directly led to a reduction in the expansion planning cost. A study of battery selection was conducted to draw the practicality of the BES sizing solutions.

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