Convex approximations to the nonlinear AC Optimal Power Flow Problem

This report documents several formulations of the optimal power flow problem (OPF) that are implemented as part of the Network Innovation Allowance project: Application of convex optimisation to enhance National Grid’s NOA process. The code of formulations is made available on a GitHub repository [1]. The implemented models are tested on a 24-bus IEEE reliability test network and a 36-zone representative GB network. The results demonstrate that the convex approximation of the OPF problem can approximate the solution of the nonlinear OPF to good accuracy. Linear approximations to the OPF depends on the choice of initialisation and can only provide a good approximation if the initialisation is close to the optimal solution. The impact on voltages of committing a bank of capacitors is also demonstrated on the 36-zone network.