Control strategies for power oscillation damping using STATCOM systems and advanced filtering

Power oscillations pose a non-negligible threat to the stability of the grid. Static synchronous compensators (STATCOMs) allow the damping of power oscillations to prevent the loss of synchronism and maximize power systems' transmission capacity. However, the power oscillation damping control via reactive power (POD-Q) with STATCOMs shows undesirable fluctuations in its reactive power output whenever a generator's mechanical power is ramped. The common control scheme includes high-pass filtering of its input signal to distinguish power oscillations from changes in the system's operating point. In literature, washout filters are widely applied to perform high-pass filtering. We improve the high-pass filtering in POD-Q control to reduce the STATCOM's reaction to changes in generator's mechanical power. Therefore, we adapt filters used in Power System Stabilizers to POD-Q control. Furthermore, we propose a step filter and a cascaded washout filter. The different filters are compared and evaluated with respect to defined design criteria regarding their phase and magnitude responses. The filter's response to a ramp input, as well as its ability to contribute to power oscillation damping, are of main interest. Both, the step filter and the cascaded washout filter can significantly reduce the reactive power fluctuations compared to a washout filter while mechanical power changes occur.