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In this paper, it is shown that the application of a dynamic brake or thyristorcontrolled braking resistor (TCBR) at the generator terminals enhances the power transfer limit over a transmission line greatly. Two types of dynamic brake configuration have been considered here: a 3-phase, bidirectional, fullwave, Y-connected, phase controlled conventional brake and a 3-phase, fullwave, thyristor-controlled rectifier bridge. A simple rule-based '' ON-OFF'' control law based on the local measurement of generator output power and its derivative is proposed in this paper. Detail digital simulation studies using the PSCAD/EMTDC package have been carried out. It was found that with the insertion of the dynamic brake circuit and its associated control, the system is able to recover following 3-line-to-ground faults even at very heavy power transfer levels, which is not possible otherwise.

The operation of HVDC converters is discrete in nature. It is, therefore, proper to take into account the discrete behavior of converter operation while developing the system model for small signal stability analysis. This paper presents the development of such a system model, which also explicitly includes the effect of phase angle of respective AC bus voltages. A modular approach has been adopted for the formulation of complete state space system model. Utilizing the system model, the stability is examined in the controller parameter plane using eigenvalue analysis. The stability domains thus obtained are validated through detailed dynamic digital simulation.