Asymmetric Voltage Sag Compensation Capability of Dual Voltage Source Inverter

In this work, it is proposed an amendment in one of the operation modes of a nine switch inverter (NSI) which is used to interface a photovoltaic system and a series compensator for voltage sag mitigation. The NSI Fault Operation mode is commonly applied to correct balanced three-phase faults, whose occurrence is less than 10% of the overall faults affecting power grids. In the proposed NSI, a fourth wire allows the correction of asymmetric faults, which increases its performance and consequently makes the system more attractive. Furthermore, the modulation technique used in this mode must address the asymmetric corrections without interfering with the others NSI functionalities. Simulated results are presented and show that the method is promising. Experimental results corroborate this proposal.