Abstract:

A novel control strategy for two-stage, three-phase Grid -Tied Photovoltaic (GTPV) systems is proposed in this paper to enhance the Power Quality under unbalanced grid faults. Power Quality related issues, such as injected currents and active and reactive power may be negatively impacted if a three-phase power converter operates under unbalanced grid voltage faults. The unbalanced fault causes double grid frequency oscillations in active power and reactive power and also injects non-sinusoidal currents into the grid. Similar variations in the DC-link voltage can occur in conventional two-stage GTPV inverters due to these double frequency oscillations of the injected active power. These oscillations of the dc-link voltage in such systems with an electrolytic capacitor can shorten the capacitor's lifespan and, consequently, the system as a whole. A method for creating a reference current, that can eliminate these oscillations at the dc-link and in the active power during unbalanced voltage sag, is a benefit of the proposed Low-Voltage Ride Through (LVRT) control strategy. Moreover, a reliable current limiting strategy is presented, that can proficiently anticipate overcurrent failure under grid faults. The performance of a 2-KW system using the proposed LVRT strategy is verified through MATLAB simulation.

Description:

Low-Voltage Ride-Through, Reference Current Generation, Dc-link voltage, Grid-Tied PV systems, Double frequency Oscillations, Voltage Sag