Voltage Support Scheme for Low Voltage Distribution Grids Under Voltage Sags

A grid-connected power electronics based distributed generator can act as an active element by providing support to the grid under various disturbances. In this paper, a voltage support scheme dedicated for distributed generators installed in the low voltage distribution network is proposed. The voltage support considers the resistive characteristics of the distribution line grid impedance in order to maximize its effectiveness. Therefore, the optimal active and reactive current references are estimated based on the resistance to reactance ratio (R/X). Moreover, a droop curve is suggested such that the intensity of voltage support will be defined according to the voltage drop conditions. The proposed voltage support concept is applied on a photovoltaic system to validate its operation. The effectiveness of the proposal is confirmed by means of simulations in a realistic low voltage distribution network.