Enhancement of the Transient Stability of AC/DC Power System by Controlling HVDC Power Flow

Abstract

HVDC power transmission employing power electronic device provides a wide range of control in power transmission. There are several possibilities to improve the transient stability in a power system. One adequate option is to use the high controllability of the HVDC if HVDC is available in the system. This paper presents a control strategy for HVDC to improve the transient stability. The strategy controls the power through the HVDC to make the system more transient stable during disturbances. Loss of synchronism is prevented by quickly producing sufficient decelerating energy to counteract accelerating energy gained during. In this study, the power flow in the HVDC link is modulated by adding an auxiliary signal to the current reference of the rectifier firing angle controller. This modulation control signal is derived from speed deviation signal of the generator using a PD controller, the use of a PD controller is appropriate since it has the property of fast response. The effectiveness of the proposed controller is demonstrated by a single machine-infinite bus system example. Simulation study on SimPowerSystems toolbox in the MATLAB is carried out to validate the concept.