Dynamic performance of a STATCOM under grid disturbances for two different linear controllers

The aim of this paper is to present a comparative stability study between vectorial control (VC) and power-synchronization control (PSC) related to a STATCOM under different grid disturbances. Both of them are linear control methods of grid-connected voltage source converters (VSC´s). VC is a very well known control method based on the dq decomposition to control the instantaneous active and reactive power independently. On the other hand, PSC is a novel method which uses the internal synchronization mechanism in AC systems, similar to the operation of a synchronous machine [1], [2]. By using this type of control, the VSC avoids the instability caused by a phase-locked loop (PLL) in weak AC systems [1]. The comparison between both control methods is verified through time simulations in the discrete domain under several grid disturbances as active and reactive power steps, grid impedance steps and voltage dips.