All-day coordinated optimal scheduling in distribution grids with PV penetration

This paper presents an approach for the optimal scheduling of reactive power of photovoltaic (PV) inverters, tap position of on-load tap changers (OLTCs), and switch states of shunt capacitors (SCs) in distribution grids. The proposed method determines a day-ahead scheduling strategy containing continuous, discrete, and Boolean control variables. The optimization problem is formulated as a mixed-integer nonlinear programming (MINLP) problem with the objective of minimizing both the node voltage deviations and active power losses. The maximum allowable number of operations for OLTCs and SCs is constrained in predefined limits. Due to the operation limits of OLTCs and SCs, this multi-period optimal scheduling problem is time-coupled. The pattern search algorithm and the genetic algorithm are applied to solve the proposed optimization problem. Both the algorithms are improved with the multi-start framework for global optimization. The feasibility of the proposed method is examined on the modified IEEE 34-node test feeder and the modified IEEE 123-node test feeder. The performances of the proposed approach are verified in the case of forecast errors of PV generation and load demand.