Performance improved during system fault of angle controlled STATCOM by current control

Voltage Source Converter (VSC) based STATCOM (Synchronous Static Compensator) is used for voltage regulation in transmission and distribution systems. Over-currents and trips of the STATCOM during and after system faults or bus voltage harmonic distortions may occur in STATCOM without PWM control. Selecting proper DC capacitor (Cdc) may keep negative-sequence and harmonic currents low, and as a result, prevent over-currents within the STATCOM. However, the capacitor value depends on the type of voltage distortion. In this paper, we propose and develop a current control strategy for an “angle controlled” STATCOM, to prevent over-currents (and trips) in the VSC during and after system faults and bus voltage distortions. Simulation results are presented for a 48-pulse VSC based ±100 MVAR STATCOM connected to a 2-bus power system. Simulation results validate the current control strategy to prevent VSC over-currents and to supply required reactive power under system fault.