139 research outputs found

    Analysis of potential low frequency resonance between a 1GW MMC HVDC and a nearby nuclear generator

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    Acknowledgements The conducted research is part of the corresponding author's PhD project which is funded by Réseau de Transport d'Électricité (RTE), France.Peer reviewedPostprin

    Ofshore Wind Park Control Assessment Methodologies to Assure Robustness

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    HVDC grids stability improvement by direct current power system stabilizer

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    High-voltage direct current breaker is among the essential components of high-voltage direct current grids. Such a breaker generally needs a direct current reactor to reduce the fault currents rate. However, direct current reactors have destructive effects on the multi-terminal high-voltage direct current grid dynamic stability, and in such a system, despite the variety of controllers, the system dynamics are highly sensitive to the operating point. Therefore, additional damping control will be needed. This paper proposes a modification to be applied to the traditional droop controller of high-voltage direct current grids to cope with the influence of these large reactors, improving the direct voltage stability and decreasing power variations in the transient events by introducing a direct current power system stabilizer. The proposed method for direct voltage control has been investigated through the analytical model of the system. Stability improvement has been studied following the application of the proposed method by investigating zeros, poles, and frequency response analysis. Moreover, a method is proposed for optimal design and optimal placement of direct current power system stabilizer. The system analysis and time-domain simulations demonstrate a decent damping improvement attained by the proposed method. All simulations and analytical studies are conducted on Cigré DCS3 test high-voltage direct current grid in MATLAB/Simulink

    Wide-area monitoring and control of future smart grids

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    Application of wide-area monitoring and control for future smart grids with substantial wind penetration and advanced network control options through FACTS and HVDC (both point-to-point and multi-terminal) is the subject matter of this thesis. For wide-area monitoring, a novel technique is proposed to characterize the system dynamic response in near real-time in terms of not only damping and frequency but also mode-shape, the latter being critical for corrective control action. Real-time simulation in Opal-RT is carried out to illustrate the effectiveness and practical feasibility of the proposed approach. Potential problem with wide-area closed-loop continuous control using FACTS devices due to continuously time-varying latency is addressed through the proposed modification of the traditional phasor POD concept introduced by ABB. Adverse impact of limited bandwidth availability due to networked communication is established and a solution using an observer at the PMU location has been demonstrated. Impact of wind penetration on the system dynamic performance has been analyzed along with effectiveness of damping control through proper coordination of wind farms and HVDC links. For multi-terminal HVDC (MTDC) grids the critical issue of autonomous power sharing among the converter stations following a contingency (e.g. converter outage) is addressed. Use of a power-voltage droop in the DC link voltage control loops using remote voltage feedback is shown to yield proper distribution of power mismatch according to the converter ratings while use of local voltages turns out to be unsatisfactory. A novel scheme for adapting the droop coefficients to share the burden according to the available headroom of each converter station is also studied. The effectiveness of the proposed approaches is illustrated through detailed frequency domain analysis and extensive time-domain simulation results on different test systems

    Robust coordinated damping control of power systems with multi-terminal vsc-hvdc system and facts

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    This thesis investigates the robust and coordinated design of multiple damping controllers to ameliorate the damping characteristics of a bulky power system. A new methodology is proposed in this thesis for VSC-MTDC and FACTS damping controllers based on multiple control objectives and system multi-model. The key feature of the methodology is the robust and coordinated performance of the damping controllers. The formulated BMI-based optimization problem is solved systematically via a two- step approach. System multi-model is established in the design for the robustness of the controllers under system disturbances and changing operating conditions. The sequential design of a series of SISO controllers with properly selected feedback signals minimizes the negative interactions among the controllers. The approach is applied to a three-terminal VSC-MTDC and subsequently exerted with one terminal of VSC-MTDC and a TCSC to incorporate multiple devices and examine the generality and feasibility of the design. Given the flexible internal control configuration of VSC converter, the assessment of the impact of the d-q decoupled control modes on the effectiveness and flexibility of the damping controllers is carried out. Real-Time Digital Simulator is used to examine the effectiveness and robustness of the damping controllers under various system operating conditions and disturbances

    Damping subsynchronous resonance oscillations using a VSC HVDC back-to-back system

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    A problem of interest in the power industry is the mitigation of severe torsional oscillations induced in turbine-generator shaft systems due to Subsynchronous Resonance (SSR). SSR occurs when a natural frequency of a series compensated transmission system coincides with the complement of one of the torsional modes of the turbine-generator shaft system. Under such circumstances, the turbine-generator shaft system oscillates at a frequency corresponding to the torsional mode frequency and unless corrective action is taken, the torsional oscillations can grow and may result in shaft damage in a few seconds. This thesis reports the use of a supplementary controller along with the Voltage Source Converter (VSC) HVDC back-to-back active power controller to damp all SSR torsional oscillations. In this context, investigations are conducted on a typical HVAC/DC system incorporating a large turbine-generator and a VSC HVDC back-to-back system. The generator speed deviation is used as the stabilizing signal for the supplementary controller. The results of the investigations conducted in this thesis show that the achieved control design is effective in damping all the shaft torsional torques over a wide range of compensation levels. The results and discussion presented in this thesis should provide valuable information to electric power utilities engaged in planning and operating series capacitor compensated transmission lines and VSC HVDC back-to-back systems
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