Modelling and utilisation of frequency responsive TCSC for enhancing the frequency response of a low inertia grid

Abstract

The objective of this paper is to enhance the frequency resilience and wind penetration level of a low inertia power system by utilising frequency responsive Thyristor Controlled Series Capacitor (TCSC). In recent years, wind power integration has become prolific in numerous power grids around the world. As such, Synchronous Generators (SGs) are being substituted from the generation mix. Unlike conventional synchronous generators, variable speed Wind Turbine Generators (WTGs) generally do not participate in system frequency control without additional control strategy. When subjected to prolific wind generation and interconnection import from an adjacent grid, number of online SGs in a grid can be scant. During such a situation, a large contingency in the power importing zone may overload an AC interconnection. Consequently, the interconnection could trip due to loss of synchronism. It eventually may cause a system-wide blackout. In addition, due to the risk of network separation, non-synchronous wind penetration level is kept restricted in many power systems. To overcome these challenges, this paper proposes a frequency responsive TCSC model to increase interconnection transfer capability by reducing the line reactance. To this end, for determining optimal TCSC parameters, a strategy is outlined. Furthermore, a generalised expression is developed to find the maximum wind penetration level while maintaining the frequency response adequacy. The developed techniques are applied to a low inertia test system. Simulation results reveal that the risk of blackout is averted, and the maximum wind penetration level is significantly increased after deploying the frequency responsive TCSC.