Supporting transmission grid voltage control with active distribution grids using online feedback optimisation

The transition to decentralised electricity generation enables the integration of active distribution grids into transmission grid voltage control as an ancillary service. This study presents a mixed-integer online feedback reactive power controller. The controller iteratively optimises reactive power provision of distribution grids, minimising losses in the distribution grid while ensuring adherence to operational limits and voltage setpoints at interconnection nodes. The controller’s functionality is demonstrated using a high-voltage benchmark grid. The controller exhibits robust performance without requiring detailed knowledge of the distribution or transmission grid state. The results highlight the efficiency of online feedback optimisation in reactive power supply with minimal losses, supporting the economic and reliable provision of ancillary services.