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Control Interactions in Power Systems with Multiple VSC HVDC Converters

Boek - Dissertatie

Power systems are facing the most important transition since their origin. A massive amount of renewable generation is being installed and the participation of consumers in the energy system is intensified. The consequent intermittence in power flows leads to increasing needs of flexibility and controllability. These needs can be covered thanks to the use of power electronics. Particularly, power electronics converters are being interfaced at generation, transmission and consumer levels. At the same time, traditional installations such as synchronous machines are being phased out.From the dynamic perspective, power electronics present different and faster dynamics and controls compared to traditional installations. Indeed, the fast control loops of these devices impact a wider range of frequencies and reach significantly higher frequencies than the control loops of traditional installations. With the massive installation of converters in the network, converter dynamics will become more prevalent and these dynamics can interfere with each other and the network hence leading to stability problems. Particularly, converter dynamics impact on the system damping at high frequencies. As a consequence, the interaction between converter control dynamics and network electromagnetic dynamics results in an emerging instability problem, the so-called electromagnetic or harmonic stability. This problem has already appeared with the installation of first VSC HVDC connections in the high-voltage network.This work provides the necessary tools and methodologies to analyse analytically in the frequency-domain control interactions in meshed networks with multiple converters. The focus lies on addressing the electromagnetic instability by use of the impedance-based stability criterion and wideband models of components. Consequently, this work also provides recommendations about the necessary representation of elements and shows the misleading estimations of traditional and currently extended practices and models for power system analysis. Finally, different control techniques to mitigate control interactions are proposed.
Toegankelijkheid:Open