Modeling of HVDC Tie Links and Their Utilization in AGC/LFC Operations of Multiarea Power Systems

This paper presents the accurate modeling of HVdc links for the dynamic studies of automatic generation control/load frequency control (AGC/LFC) of the multiarea interconnected power system. In earlier AGC studies, HVdc links were simply modeled by using the first-order transfer function with system time constant Tdc. It was argued that Tdc is the time required by HVdc links to establish dc current after following a load disturbance in the power system. However, no mathematical or analytical justification was provided in support to the existing transfer function model of HVdc links. This paper presents the accurate modeling of HVdc links for AGC studies. The comparative analysis has also been performed to demonstrate error being accrued due to the use of the conventional model of HVdc links. Furthermore, this paper also implements the inertia emulation based control strategy in AGC, which allows us to harness the stored energy from the capacitance of HVdc links for AGC operations.