Multi-objective Optimal Placement of Three-Phase Step Voltage Regulator Considering Voltage Unbalance

The trend of energy decarbonization accelerates the transition towards decentralized power distribution systems. However, the growth of distributed generation and loads may increase voltage unbalance in distribution systems. Consequently, it is essential to plan and operate the systems considering voltage unbalance to avoid some problems caused by unacceptable voltage unbalance. This paper proposes an optimal placement method for three-phase individually controlled step voltage regulators (
$3\phi \text{SVRs}$
) considering voltage unbalance. A multi-objective bi-level optimization model is constructed to consider optimal placement and operation simultaneously. The optimal placement considers the trade-off between distribution losses and device costs, while the optimal operation minimizes the losses under the constraints of the voltage profile. Cooperative operation with a load ratio control transformer (LRT) is also incorporated in the optimization problem. The proposed method is tested using the IEEE 123 node test feeder. Results identify optimal placements for each number of devices and allow placement according to the preferences of distribution system operators.