Dynamic resonance analysis and oscillation damping of multiterminal DC grids

Liu, Yuchao and Raza, Ali and Rouzbehi, Kumars and Li, Binbin and Xu, Dianguo and Williams, Barry W. (2017) Dynamic resonance analysis and oscillation damping of multiterminal DC grids. IEEE Access, 5. pp. 16974-16984. ISSN 2169-3536 (https://doi.org/10.1109/ACCESS.2017.2740567)

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Voltage source converter (VSC) based multi-terminal high voltage direct current (VSC-MTDC) systems/grids are prone to system instability. This critical issue is overlooked in literature. In order to improve the system stability, this paper proposes an effective active damping method as a remedy to suppress voltage and power resonances in the VSC-MTDC grids by injecting damping signals into the inner current loops of VSC-MTDC stations. With dynamic regulation of the damping current, resonance is suppressed by power converter controllers without any additional current and voltage measurement. In this study, modeling and stability analysis of VSC-MTDC system/grid is presented considering the dc-side energy storage components, and control with a droop control structure. Then, single-frequency and multi-frequency resonance mechanisms of dc-bus voltage and power in the event of transients are analyzed. Later, stability effect of MTDC system/grid inductance and capacitance values to the resonance amplitude and frequency droop coefficients is investigated. A PSCAD/EMTDC platform is developed to conduct dynamic simulations, and a scaled-down four-terminal 20 kW experimental prototype is used to validate the effectiveness of proposed control methodology.