Centralized control of energy storages for voltage support in low-voltage distribution grids
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This paper presents a centralized voltage control scheme for unbalanced low-voltage grids experiencing over voltage problems due to high PV power penetration. Voltage control is primarily achieved by remotely controlling the active power of the distributed battery energy storage systems, which are owned by the customers. Reactive power capability of the converters are utilized for voltage control when sufficient kW capacity is not available. Distribution system operator has the control over these battery energy storage systems during the hours of high PV penetration. A method for fair utilization of battery energy storage systems by considering both rated power and energy capacity of the storage units is proposed. Delays caused by communication and computations are taken into consideration in the design of the real time controller. Results from a simulation study is presented to validate effectiveness of the real-time control scheme. The results show that the control scheme can successfully maintain the voltages at critical nodes within required limits. 1 minute computational and communication delay does not adversely affect the real time controller performance under the varying load and generation conditions considered in this paper. The utilization factor (total energy circulated through each battery units normalized to their rated energy capacity) justifies the fair utilization of battery storage units for voltage support.