STATCOM Operation with Saturable Transformer Under Single Line to Ground Power System Faults

The STATCOM (synchronous static compensator) based on voltage source converter (VSC) is used for voltage regulation in transmission and distribution systems. The STATCOM can rapidly supply dynamic VARs required during system faults for voltage support. The "emergency PWM" strategy developed in this paper can prevent over-current and transformer saturation in the VSC during and after single line to ground system faults, and also meet the strict requirements of STATCOM losses and total system loss penalty. Simulation results are presented for a 48-pulse VSC based plusmn140 MVAR STATCOM connected to a 2-bus power system to validate the "emergency PWM" strategy to prevent VSC over-current and transformer saturation and to supply required reactive power under a single-line to ground (SLG) system faults. The proposed "emergency PWM" strategy is explained in terms of positive and negative sequence voltage for the system bus voltage and STATCOM generated voltage.