Damping of voltage harmonics and transient voltage distortions with a STATCOM

Inhalt:
In addition to providing reactive power and dynamic voltage support, a static compensator (STATCOM) can be used to actively damp both quasi-stationary voltage harmonics and transient voltage distortions following grid events. The damping of quasi-stationary, pre-selected voltage harmonics is state or the art and already implemented in real projects. Frequency selective control methods are generally used for this purpose. For extended damping capability it is advantageous if the STATCOM mimics an ohmic resistance for voltage components deviating from the fundamental grid frequency. It thereby burdens the cause of the undesired voltage components, which significantly dampens them. This paper presents and discusses the implementation of such a concept. The developed damping function allows to damp voltage harmonics in a wider range without pre-selection of specific harmonic orders or restriction to quasi-stationary grid situations. The presented implementation effectively damps also transient voltage distortions of any waveform that occur during grid events like short circuits or line switching. In effect, the STATCOM control manipulates the non-fundamental part of the currents in such a way that they are in phase with the corresponding voltage components. The required actuating voltage is determined model-based and realised dynamically applying feedforward control. In addition to describing the concept of the damping function and its integration into the overall STATCOM control, its effectiveness is illustrated using selected simulation results.