Frequency regulation of rectifier side AC system of an HVDC scheme using coordinated fuzzy logic control

Abstract

This paper presents a fuzzy logic controller for improving the frequency regulation of the rectifier side AC system of an HVDC scheme interconnecting two power systems. The controller coordinates the modulation of, the current in the DC scheme and the generator excitation of the rectifier side AC system, in response to rectifier side AC system frequency deviation. The fuzzy logic controller is designed without using any precise system model. Only the qualitative knowledge about the system is used in designing the controller. An iterative technique using steepest descent gradient search method is proposed in this paper for further tuning of the output gains of the controller to optimise a chosen objective function. Simulation results reveal that, a fuzzy logic controller can be successfully implemented to realise significant improvements in frequency regulation by coordinating the modulation of the DC current and generator excitation of the rectifier side AC system.