Cycle-by-Cycle "Soft" Current Limiting Methods for ANPC Inverters
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    Abstract:

    [Objective] With the rapid development of new energy, the weak anti-interference capability of new energy inverters intensifies the risk of cascading grid disconnection after fault disturbances, posing new challenges to current risk prevention and control technologies for protection. This paper investigates the cycle-by-cycle (CBC) current limiting control methods for the fault condition of active neutral point clamped (ANPC) inverters when an AC side short circuit occurs. [Methods] In traditional CBC current limiting control methods, all switching devices of the inverter were turned off when the current exceeded the over-current threshold. However, this frequently triggered current limiting control, resulting in high current change rate di/dt of switching devices, and excessive current flowing through the anti-parallel diode of the insulated gate bipolar transistor (IGBT), which failed to effectively protect the switching devices in the inverter. Between the control strategy of forcibly turning off all switching devices and the new energy grid disconnection accidents caused by allowing over-current to develop, this paper proposed a technology that controlled the inverter in an intermediate state—partial-switching-off CBC "soft" current limiting control technology. When the control was triggered, the specified switching devices were turned off while the remaining ones were kept on. Finally, a simulation model was established using MATLAB/Simulink to verify the proposed CBC current limiting control method. [Results] The results indicated that this method could effectively reduce the number of triggers, lower the di/dt of the switching devices, and decrease the current peak value of the internal switching devices in the inverter, thereby enhancing the reliability of the inverter. Compared with the full-switching-off CBC current limiting method, the trigger cycles of the partial-switching-off CBC "soft" current limiting were longer, and the trigger frequency was lower. Moreover, the CBC "soft" current limiting method limited the peak current of the switching devices to a lower level, which was beneficial for improving the reliability of the inverter and optimizing the CBC current limiting control method. [Conclusion] The proposed CBC "soft" current limiting control method for ANPC inverters can effectively control inverter current under short-circuit faults, improve the inverter’s short-circuit fault ride-through capability, and provide technical support for the safe operation of new energy grid connection.

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Weng Tingting, Li Xiaohua, Yu Jiang, Kong Fei, Liu Huadong, Sun Xiaoyu, Ge Benjun. Cycle-by-Cycle "Soft" Current Limiting Methods for ANPC Inverters[J]. Electric Machines & Control Application,2026,53(5):420-431.

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History
  • Received:December 18,2025
  • Revised:March 04,2026
  • Adopted:
  • Online: May 29,2026
  • Published:
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