Frequency converter-driven oscillations in weak grids : explanation and damping improvement

Wu, Guanglu and Sun, Huadong and Zhao, Bing and Xu, Shiyun and Zhang, Xi and Egea Àlvarez, Agustí and Wang, Shanshan and Li, Gen and Li, Yingbiao and Zhou, Xiaoxin (2021) Frequency converter-driven oscillations in weak grids : explanation and damping improvement. IEEE Transactions on Power Systems. ISSN 0885-8950 (In Press)

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Low-frequency oscillations have been reported in several weak-grids-connected voltage-source-converter(VSC) systems. Although efforts have been devoted to understand the parametric and sensitivity impact of the VSC controller gains, a general formulation of the oscillation mechanism is still missing. Using transfer function dynamic modelling approach, we find that the outer loop active power control’s bandwidth mainly determines the oscillation frequency. The PLL introduces a large phase lag around the frequency of the PLL bandwidth in weak grids which decreases the oscillation damping. A simple but effective PI+Clegg integrator (CI) compensator is proposed to replace the standard outer loop active power controller compensating the PLL’s phase delay and increase the oscillation damping. The results are verified in a real time digital simulator.


Wu, Guanglu, Sun, Huadong, Zhao, Bing, Xu, Shiyun, Zhang, Xi, Egea Àlvarez, Agustí ORCID logoORCID:, Wang, Shanshan, Li, Gen, Li, Yingbiao and Zhou, Xiaoxin;