The large-scale integration of renewable energy sources poses significant challenges to the stable operation of existing power systems. Flexible interconnection devices can facilitate local consumption of renewable energy and help alleviate these challenges through dynamic power flow regulation. However, current flexible AC interconnection solutions often face difficulties in balancing reliability with cost-effectiveness in engineering applications. To address this issue, this paper introduces a novel direct series flexible interconnection topology that eliminates the need for a series transformer. The equivalent circuit for this topology is developed, and its principles for steady-state power flow control and transient fault ride-through are analyzed. A theoretical model is derived based on the equivalent circuit analysis, from which a phase-separated steady-state control strategy is proposed. In addition, a graded transient control strategy featuring three levels of protection—current limiting, blocking, and tripping—is introduced. The proposed control strategies are validated through experimental data from the Huzhou Flexible AC Interconnection Demonstration Project, demonstrating their effectiveness during minor voltage dips and severe faults.