Voltage control by tap-changing transformers for a radial distribution network

Voltage control is of interest to many researchers, and is currently being considered by many utilities for implementation in their energy control centres. Transformers with tap-changing facilities constitute an important means of controlling voltage throughout the system at all voltage levels. A new method for determining the minimal changes in transformer taps to control voltage levels is presented. The problem to be solved is cast into a nonlinear constraint optimisation. The constraints are tackled in the minimisation algorithm by forming the Lagrangian. Necessary conditions for optimality are derived and solved using the Newton–Raphson method.