Enhancement of Power System Transient Response by Control of HVDC Converter Power

This paper examines enhancement of power system stability by control of real power which is injected into or taken from the AC system by the high-voltage direct current (HVDC) converter in transmission systems with HVDC transmission. It also investigates the influence of transient converter reactive power following a severe system disturbance with clearance together with the effect of system dynamic loads on system transient response. First, a new algorithm for damping power system oscillations which is based on modulation of active power injected into a node of the power system is described. The algorithm is based on the direct Lyapunov method which is used to process signals for supplementary control of an HVDC converter to damp AC system electromechanical oscillations to enhance power system stability. The algorithm is formulated to minimize time of dissipation of turbine-generator rotor oscillation energy which results from incidence andclearance of a system disturbance. The relationship between rotor slip and locally measured quantities is used in formulating the control strategy. The performance of a benchmark multimachine system with and without optimal HVDC converter control to enhance damping and power system stability is then illustrated. This is extended to include transient link reactive power which is consumed by the AC system by the converter in controlling rotor swing due to a severe transmission system disturbance with clearance, and the effect dynamic loads have on dynamic response of the system following a severe system disturbance.