An approach to improve the penetration of sustainable energy using optimal transformer tap control

A method to secure the generator reactive power reserve by adjusting the transformer tap to improve the power system penetration of renewable energy has been proposed in this study. The tap is adjusted based on the voltage and reactive power sensitivity in the power system network. That is, the transformer tap sensitivity is calculated and analyzed to adjust the tap variation to gain sufficient or the least necessary amount of reactive power reserve. This method can be effective for generators without any margins in the reserves. The optimization problem based on the calculated sensitivities and effectiveness are presented. The optimum solution derived from such a problem provides the minimum control amount necessary to maintain the system voltage and dynamic reactive power reserve at their pre-specified levels to improve the power system acceptability of renewable energy. To demonstrate the effectiveness of the method proposed, a simulation has been performed for an IEEE-25 bus system. The results from simulations prove that the voltage has been well maintained while securing a dynamic reactive power reserve through optimal control based on the sensitivity analysis.