Analysis of the Dynamic Behavior of a Self-Commutated BTB System During Line Faults

This paper deals with a 50-MW self-commutated back-to-back (BTB) system intended for power-flow control between two ac transmission networks. It focuses on the dynamic behavior of the BTB system during single-line-to-ground and double-line-to-ground faults. Attention is particularly paid to the dc magnetic flux deviation in the grid and converter transformers, and the circulating current inside the grid transformers, which would produce undesirable effects on the system. Theoretical equations related to the amount of circulating current and the dc magnetic flux deviation are derived. The theoretical results developed in this paper are confirmed by computer simulation.