*3.2. Batteries*

The battery is one of the main components of the BESS. It is in the battery that energy is stored. There are various battery types integrated into generation, transmission, distribution, and end-consumer worldwide. Each type may use the system differently. Battery selection is mainly focused on the BESS application (e.g., applications that demand more power and energy) and cost-effectiveness ratio due to the high proportion of the battery's monetary value to the total cost of the project (about 50–60%) [19].

LFP batteries were used in the BESS. The LFP battery pack has an output voltage of 51.2 V and a capacity of 180 Ah. Fourteen battery packs are grouped in series in a cluster, totaling an output voltage of 716.8 V and a capacity of 180 Ah. The BESS contains 10 clusters in parallel, leading to an output voltage of 716.8 V and a capacity of 1800 Ah.

#### *3.3. BMS*

The BMS plays a vital role in the BESS. The integration of the BESS with the wind generation bus means that multiple batteries are connected in parallel, improving safety and reliability.

The BMS is designed to provide safe operations by monitoring the voltages, currents, and temperature of the cells in the batteries. In addition, the BMS offers the following functions [19–21]:


#### *3.4. EMS*

The EMS is responsible for continuously relevant BESS data acquisition and storage, such as voltage, frequency, active and reactive power, power factor, battery cell voltage, etc. This data acquisition and storage can be either in local or remote forms. Additionally, the EMS receives the control setpoints to allow changes in the BESS operating modes and subsystems. The BESS applications of this project are power smoothing, frequency control, voltage control, and power factor correction. Lastly, it contains manual control for active and reactive power injection and absorption.

EMS controls BESS to regulate battery recharges and discharges to achieve optimal efficiency generation requirements. All battery cells are individually monitored to ensure any deviation in performance is detected and corrected before problem occurrences. The EMS can be viewed remotely as needed and communicate with CPFL's local SCADA.
