A Voltage Support Strategy Based on a Per-Phase Controlled Inverter in Faulty Networks

The independence of reactive current injection from the active power produced by distributed generators makes the inverters a key element in improving grid stability, particularly during grid faults. This paper proposes a new per-phase control strategy for three-phase inverters during asymmetrical and symmetrical grid fault conditions. The control strategy guarantees the safe operation of the inverter during voltage sags. As a result, the grid is better supported since the voltage at the point of common coupling is improved in each phase independently. In particular, this paper introduces a new control strategy to raise the Point of Common Coupling voltage based on the voltage reduction in each phase and to avoid undervoltage during grid fault conditions. Simulation results verify the effectiveness of the proposed method. The simulations are carried through Matlab environment.