Current Control of Angle Controlled STATCOM

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 harmonic distortions may occur in STATCOM without PWM control. Selecting proper DC capacitor (Cdc) may keep negative-sequence current and harmonics low, and as a result, prevent over-currents within the STATCOM. However, the capacitor value depends on the type of distortion. In this paper, we propose and develop a current control strategy based on angle control, to prevent over-currents (and trips) in the VSC during and after system faults and harmonic distortions, and to ensure the STATCOM with small Cdc to supply required reactive power. Simulation results are presented for a 48-pulse VSC based plusmn100 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 and harmonic distortions.