Control algorithm for DSTATCOM to compensate consumer-generated negative and zero sequence voltage unbalance

Abstract

This paper presents a control algorithm, based on consumer-generated voltage imbalance assessment, for a distribution static synchronous compensator (DSTATCOM). The proposed algorithm quantifies, in the time-domain, the parcels of voltage unbalance due to the supplier (utility) and consumer using measurements of the instantaneous voltages and currents at the point of common coupling. Small-signals models are derived and used to design the controllers for the DSTATCOM in order to compensate for the negative and zero sequence voltages caused by the consumer. These controllers are designed in the synchronous reference frame, with two inner current loops and two outer voltage loops for each compensated sequence, to ensure the DSTATCOM tracks the reference voltages generated by the unbalance assessment algorithm. Digital simulation results obtained with an unbalanced distribution network are used to validate the proposed methodology. Through the comparison of the results obtained with and without the proposed unbalance assessment algorithm it is possible to conclude that the capacity of the compensator can be significantly reduced when only the unbalanced voltage parcel caused by the load is compensated.