Safe Reactive Power Production Schemes For the Grid-Connected Converters Affected by the Voltage Unbalances

Following the increase in the installed power of the distributed generation systems, voltage support became essential requirement defined by the respective regulations. During the voltage unbalances generation units should stay connected and supply the grid with the reactive power. However, as the voltage falls below the nominal value, the reactive power production margin should be also decreased so that the excessive increase in the phase currents is prevented. Therefore, algorithms that generate the maximized reactive power reference that would not cause the overcurrent protection triggering are proposed. The first algorithm allows for the reactive power production to be prioritized, contrary to the active power production. The second algorithm enables the reactive power reference generation in context of keeping the power factor the same before and during the fault. The third approach offers the safe production of positive and/or negative reactive power components. The hardware-in-the-loop setup was used to test the algorithms' behaviour.