Novel low voltage ride-through strategy for doubly-fed variable-speed pumped storage units using negative sequence demagnetization

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Liu, Zhichang and Yin, Xin and Qiao, Jian and Yao, Wei and Yin, Xianggen and Yang, Ning and Xiao, Fan (2026) Novel low voltage ride-through strategy for doubly-fed variable-speed pumped storage units using negative sequence demagnetization. International Journal of Electrical Power and Energy Systems, 178. 111980. ISSN 0142-0615 (https://doi.org/10.1016/j.ijepes.2026.111980)

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Abstract

Doubly-fed variable-speed pumped storage units (VSPSUs) offer significant flexibility for renewable energy integration; however, their extended speed range increases the risk of encountering inherent hydraulic instability zones, such as the hump and S-shaped regions, during transients. Existing LVRT studies primarily target DFIG-based wind turbines and often overlook the massive inertia, hydro-mechanical–electrical coupling, and specific hydraulic constraints of VSPSUs. This paper first derives LVRT requirements tailored to VSPSUs by considering their operating boundaries and inertia characteristics. A quantitative analysis reveals that negative-sequence stator flux is the primary driver of rotor overvoltage/current during asymmetrical faults. To address these challenges, a novel LVRT strategy is proposed that integrates negative-sequence demagnetization with a hydraulic-stability-oriented control logic based on quasi-PIR control. The method prioritizes reactive current injection, and when the hydraulic stability margin decreases, the control objective is adaptively shifted toward hydraulic protection by regulating the q-axis rotor current, ensuring that the operating trajectory avoids entering the hump and S-shaped unstable regions. Finally, PSCAD/EMTDC simulations and experimental results demonstrate that the proposed method effectively limits rotor electrical stress while significantly enhancing grid support. Crucially, the results confirm that the VSPSU maintains stable operation without violating hydraulic safety boundaries, even under severe voltage sag conditions.

ORCID iDs

Liu, Zhichang, Yin, Xin, Qiao, Jian, Yao, Wei, Yin, Xianggen, Yang, Ning ORCID logoORCID: https://orcid.org/0009-0006-9665-0850 and Xiao, Fan;
CORE (COnnecting REpositories)