Harmonic injection due to negative phase sequence correction in static VAr compensators

Negative phase sequence voltages within a three phase power system are generally caused by unbalanced loads. Power utilities are generally required to limit the amount of negative phase sequence voltage on the grid because of the increased heating it causes in three phase machines. Static VAr compensators (SVCs) have been widely used to address unbalanced voltage problems in distribution, sub-transmission and transmission networks. An SVC can however introduce harmonic currents into the power system due to the power electronic switching of static reactive devices. These harmonic currents can also result in additional heating and degraded performance of connected loads. This paper investigates the relationship between SVC Negative Phase Sequence correction and third harmonic injection into the power system.