Optimal Voltage-Support Control for Distributed Generation Inverters in RL Grid-Faulty Networks

During grid faults, the stability and reliability of the network are compromised, and the risk of a widespread disconnection of distributed generation power facilities is increased. Distributed generation inverters must support the power system to prevent this issue. Voltage support depends substantially on the currents injected into the grid and the equivalent grid impedance. This article considers these two aspects and proposes an optimal voltage-support strategy in RL grids. The control algorithm guarantees safe operation of the inverter during voltage sags by calculating the appropriate reference currents according to the equivalent impedance and the voltage sag characteristics, avoiding active power oscillations, and limiting the injected current to the maximum allowed by the inverter. Consequently, the grid can be better supported since the voltage at the point of common coupling is improved and the voltage support objectives are achieved. The proposed control strategy is validated through experimental tests in different grid scenarios. Throughout this article, it is assumed that the grid impedance is known, but the proposed solution requires calculating the grid impedance angle.