A Modular Algorithm Based on the Minimum-Cost-Path Problem for Optimizing LTC Operations in Photovoltaic Integrated Distribution Systems

This paper presents a novel modular voltage control algorithm for optimal scheduling of adistribution system’s load tap changers to minimize the number of tap changes while maintaining avoltage deviation (VD) around a desired target. To this end, a bi-objective optimal voltage regulation(OVR) problem is addressed in two distinct stages. First, the operational constraint on the load tapchanger is removed to form a single-objective OVR problem relating to the voltage. The solutionobtained in this stage is ultimately utilized to determine the penalty value assigned to the distancefrom the optimal (solely in terms of voltage) control value. In the second stage, the optimal schedulingproblem is formulated as a minimum-cost-path problem, which can be efficiently solved via dynamicprogramming. This approach allows the identification of optimal scheduling that considers both thevoltage-related objective as well as the number of load tap changer switching operations with noadded computational burden beyond that of a simple voltage optimization problem. The methodimposes no restriction on the load tap changer’s operation and is tested under two different targetfunctions on the standard IEEE-123 test case. The first attains a nominal voltage with a 0.056 p.u.voltage deviation and the second is the well-known conservation voltage reduction (CVR) case with a0.17 p.u. voltage deviation. The method is compared to an evolutionary-based algorithm and showssignificant improvement in the voltage deviation by a factor of 3.5 as well as a computation timeacceleration of two orders of magnitude. The paper demonstrates the effectiveness and potential ofthe proposed method as a key feature in future cutting-edge OVR methods.