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As China's AC transmission system with series capacitor and HVDC transmission technology are widely used in long-distance and large-scale power transmission network, sub-synchronous resonance (SSR) problem becomes more prominent. This paper studied induction generator effect (IGE) and torsional interaction (TI) of synchronous generator by focusing on amplitude and frequency modulation of synchronous generator's flux linkage. IGE involves only electric system dynamics, which will only cause amplitude modulation of flux linkage, resulting in one or two frequency component added in stator current of non-salient pole synchronous generator (NPSG) or salient pole synchronous generator (SPSG) respectively. TI involves both electric and mechanical system dynamics, which will cause both amplitude and frequency modulation of flux linkage, resulting in multiple sub and super-synchronous frequency components added in stator current by means of Bessel function. This result will provide a new reference to understand the SSR phenomena containing multiple frequency components in practical power system. The IEEE first benchmark model is used to demonstrate the accuracy of the analysis results.

As China's AC transmission system with series capacitor and HVDC transmission technology are widely used in long-distance and large-scale power transmission network, sub-synchronous resonance (SSR) problem becomes more prominent. This paper studied induction generator effect (IGE) and torsional interaction (TI) of synchronous generator by focusing on amplitude and frequency modulation of synchronous generator's flux linkage. IGE involves only electric system dynamics, which will only cause amplitude modulation of flux linkage, resulting in one or two frequency component added in stator current of non-salient pole synchronous generator (NPSG) or salient pole synchronous generator (SPSG) respectively. TI involves both electric and mechanical system dynamics, which will cause both amplitude and frequency modulation of flux linkage, resulting in multiple sub and super-synchronous frequency components added in stator current by means of Bessel function. This result will provide a new reference to understand the SSR phenomena containing multiple frequency components in practical power system. The IEEE first benchmark model is used to demonstrate the accuracy of the analysis results. [ABSTRACT FROM AUTHOR]

In recent years, with the development of high voltage direct current (HVDC) transmission technology, wind power integration with modular multiple converter-HVDC (MMC-HVDC) has been widely researched and applied. However, the conventional control methods on wind power integration cannot match the flexibility needing of loads. In this paper, a wind power integration system with permanent magnet direct-drive wind farm and full-bridge MMC is proposed. It has the characteristics of independent control of AC and DC current, which can realise the stable operation of the system under low DC voltage, so that to effectively avoid the accident of the wind turbine cut-off caused by the load reduce. When the DC voltage drops, the system can maintain a constant AC voltage at the wind power integration point, so that the wind farm can operate normally. Finally, the simulation results in PSCAD/EMTDC show that the proposed system and its control strategy are correct. [ABSTRACT FROM AUTHOR]

In recent years, with the development of high voltage direct current (HVDC) transmission technology, wind power integration with modular multiple converter-HVDC (MMC-HVDC) has been widely researched and applied. However, the conventional control methods on wind power integration cannot match the flexibility needing of loads. In this paper, a wind power integration system with permanent magnet direct-drive wind farm and full-bridge MMC is proposed. It has the characteristics of independent control of AC and DC current, which can realise the stable operation of the system under low DC voltage, so that to effectively avoid the accident of the wind turbine cut-off caused by the load reduce. When the DC voltage drops, the system can maintain a constant AC voltage at the wind power integration point, so that the wind farm can operate normally. Finally, the simulation results in PSCAD/EMTDC show that the proposed system and its control strategy are correct.