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In many power systems, the increased penetration of inverter-based renewable generation will cause a decrease in kinetic energy storage, leading to higher frequency excursions after a power disturbance. This is the case of the future Nordic Power System (NPS). The look-ahead study reported in this paper shows that the chosen units participating in Frequency Containment Reserves (FCR) cannot keep the frequency above the prescribed threshold following the outage of the largest plant. This analysis relies on a detailed model of the Northern European grid. The latter is compared to the classical single-mass equivalent, and the impact of voltage-dependent loads is assessed in some detail. Next, the paper focuses on emergency power control of the HVDC links that connect the NPS to the rest of the European grid, which can supplement or even replace part of the FCR. The proper tuning of that control is discussed. Finally, the analysis is extended to the HVDC links connecting the future North Sea Wind Power Hub under two configurations, namely low and zero inertia. The impact of outages in the latter sub-system is also assessed. The material to simulate the system with industrial software is made publicly available. [ABSTRACT FROM AUTHOR]

Fundamental sensor feedback limitations for improving rotor angle stability using local frequency or phase angle measurement are derived. Using a two-machine power system model, it is shown that improved damping of inter-area oscillations must come at the cost of reduced transient stability margins, regardless of the control design method. The control limitations stem from that the excitation of an inter-area mode by external disturbances cannot be estimated with certainty using local frequency information. The results are validated on a modified Kundur four-machine two-area test system where the active power is modulated on an embedded high-voltage dc link. Damping control using local phase angle measurements, unavoidably leads to an increased rotor angle deviation following certain load disturbances. For a highly stressed system, it is shown that this may lead to transient instability. The limitations derived in the paper may motivate the need for wide-area measurements in power oscillation damping control. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive analysis of the impact that supplementary power control of an HVDC link has on the electromechanical dynamics of power systems. The presented work addresses an interesting phenomenon that may occur when an HVDC power controller is installed to support frequency stability. In specific cases, a high gain HVDC frequency controller could deteriorate system damping. The given analytical study is the first of its kind that addresses this issue by including both: (i) the important higher-order generator dynamics that affect small signal stability simultaneously with an HVDC control as well as (ii) the available local angle/frequency input signals of the controller. The methodological approach here analytically formulates the impact an HVDC control has on the single generator dynamics. Furthermore, the relationship between the damping/synchronizing coefficients and the HVDC gain is explicitly derived when a frequency proportional HVDC controller is installed. The derived expressions confirm that, indeed, there is an optimal HVDC gain with respect to the damping coefficient and a typically positive impact of the HVDC controller on the synchronizing component. Finally, the developed theoretical foundation is demonstrated by the tools of linear and nonlinear analysis in a one-machine system case study. [ABSTRACT FROM AUTHOR]