Hardware-in-the-loop based testing of wind turbine controllers for transient stability enhancement

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Traditionally, electrical power systems have been based on fossil-fuel fired generation plants to satisfy the load demand. However, due to environmental targets for significant CO2 reduction, a gradual decommission of the aforementioned plants is observed whereas renewable energy sources are gaining gradually increasing momentum, which entails radical changes in the dynamic behavior of electrical power systems. Among the existing renewable energy technologies, variable speed wind generators which utilize full–scale power electronics units, are a preferred technological solution to tackle the variability of renewable energy. Increasing renewable power generation caused a reduction of system inertia and short circuit capacity. This reduction challenges the rotor angle stability of remaining synchronous generators when large disturbance occur. This paper presents a study on modifications of the outer control loops of the grid side converter of wind generators type IV to limit the magnitude of the first rotor angle swing while increasing the overall damping performance of a power system. The study includes a comparison between three different wind generation controllers. Namely, a basic Low Voltage Right Through (LVRT) with a post-fault ramp in the active power injection strategy, a voltage dependent active power injection scheme and a Supplementary Damping control (SDC) method are examined and tested through a power hardware-in-the-loop (PHIL) based test bench. It has been found that SDC supports quick damping of oscillations and high reduction of magnitude of the first swing with respect to the other two control schemes.