Multi-pulse STATCOM operation under unbalanced voltages

This work presents a study about static synchronous compensators (STATCOM) operating in electrical systems where the voltages are unbalanced and contain negative sequence components. In balanced systems the STATCOM has a very good performance, allowing compensation of capacitive or inductive reactive power with a fast transient response. However, when there are negative sequence components, the STATCOM has its performance diminished. An analytical analysis, using the instantaneous power theory and the switching functions technique, and simulations of a STATCOM quasi 48-pulses using the electromagnetics transients program (ATP-EMTP) show how STATCOM is affected by negative sequence components and how its performance is degraded. A proposal to improve the STATCOM performance under negative sequence unbalance is shown.