Method for improving stability of network-forming converter by considering voltage and phase transients

By employing a hybrid current limiting strategy combining a circular current limiter and an adaptive virtual impedance, along with the virtual synchronous machine swing equation and power damping term, the overcurrent control blind zone problem of the grid-type converter under concurrent voltage and phase transient faults is solved, thereby improving the transient stability and stability boundary of the system.

CN121863374APending Publication Date: 2026-04-14HUZHOU ELECTRIC POWER SUPPLY CO OF STATE GRID ZHEJIANG ELECTRIC POWER CO LTD
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Patent Information

Application Number
CN202511727389.4
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2025-11-24
Publication Date
2026-04-14

AI Technical Summary

Technical Problem

When facing simultaneous voltage and phase transient faults, existing grid-type converters suffer from overcurrent control blind spots due to traditional current limiting methods, leading to a sharp deterioration in stability and a lack of analytical frameworks for complex faults.

Method used

A hybrid current limiting strategy combining a circular current limiter and adaptive virtual impedance is adopted. By combining the swing equation of the virtual synchronous machine and introducing a power damping term, the active power control loop is optimized, thereby improving system stability.

Benefits of technology

During faults, the current is strictly limited while the system damping characteristics are enhanced, significantly expanding the stability boundary, effectively addressing complex grid faults, and ensuring the safe and stable operation of the converter.

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Abstract

The invention discloses a method for improving stability of a network-forming converter by considering voltage and phase transients, which solves the problem of over-current control blind areas existing at the initial stage of a fault and at the moment of clearing in a traditional single current limiting method and overcomes the defect that the stability is sharply deteriorated when a traditional strategy is used for coping with a composite fault. The method comprises the following steps: S1, obtaining a virtual synchronous machine swing equation under a synchronous rotating coordinate system and an equivalent circuit model under the action of a circular current limiter; and S2, obtaining a nonlinear relation between the output power and the power angle of the converter, and analyzing a transient stability domain of the converter during a fault period. And S3, obtaining a mixed current limiting strategy, deducing an equivalent circuit model corresponding to the strategy, and further obtaining an output power expression corresponding to the strategy. And S4, obtaining a power damping term acting on an active power control loop, further obtaining a synchronization stability improvement strategy, and deducing a closed-loop model describing the system at the moment.
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