151. Harmonic Instability in MMC-HVDC Converters Resulting From Internal Dynamics.
- Author
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Li, Tan, Gole, Aniruddha M., and Zhao, Chengyong
- Subjects
- *
FREQUENCY changers , *ELECTRIC current converters , *PHASOR measurement , *ELECTRIC controllers , *ELECTRICAL harmonics - Abstract
This paper reveals the existence of poorly damped resonant modes in the modular multilevel converter (MMC) that can result in harmonic instability. A small-signal model based on dynamic phasors is introduced which takes into consideration the dynamics of internal variables, such as circulating arm currents, which have a tendency for a large second harmonic component and module capacitor voltage ripple, which has other harmonic components. The small-signal model is validated by comparison with the electromagnetic transient simulation of a detailed model. It is shown that the use of an active circulating current suppressing scheme can effectively improve the damping of internal harmonic modes in comparison with a passive filter used for the same purpose. The damping of internal harmonic modes has been shown to be significantly impacted by the gains of the MMC's outer-loop controller but is less sensitive to the ac system strength or the gain of the phase-locked loop. A larger arm resistance also increases the damping of these internal modes. [ABSTRACT FROM PUBLISHER]
- Published
- 2016
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