Modular multilevel converter synchronous control method and system based on capacitor voltage

Through the modular multi-level converter synchronization control method based on capacitance voltage, the combination of capacitance voltage control outer ring and power control inner ring is solved, and the stability and cost problems of modular multi-level converter in weak AC systems are achieved, and fast response and efficient synchronization control are achieved.

CN120389632APending Publication Date: 2025-07-29CHINA EPRI ELECTRIC POWER ENG CO LTD +1
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Patent Information

Application Number
CN202410122269.0
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2024-01-29
Publication Date
2025-07-29

AI Technical Summary

Technical Problem

The existing modular multi-level converters are difficult to operate stably under weak AC systems, the control parameter design is difficult, the dynamic stability is poor, and the cost increases due to the increase in DC-side capacitance.

Method used

The modular multi-level converter synchronization control method based on capacitance voltage is adopted, and the active power command unit is calculated through the capacitance voltage control outer ring and applied it to the power control inner ring to realize the synchronous control of the modular multi-level converter and the power grid, avoiding the use of second-order low-pass filters.

Benefits of technology

It realizes stable operation under weak AC systems, improves control response speed and dynamic stability, reduces the overshoot of the control system, and avoids the cost problems caused by the increase in DC-side capacitance.

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Abstract

The invention provides a modular multilevel converter synchronous control method and system based on capacitor voltage, and the method comprises the steps: controlling an outer ring through the capacitor voltage based on a capacitor voltage average per unit value and a capacitor voltage instruction per unit value of a modular multilevel converter, calculating to obtain an active power instruction per unit value of the AC side of the modular multilevel converter; the active power instruction per unit value and the active power measurement per unit value of the AC side of the modular multilevel converter act on a power control inner ring, and synchronous control of the modular multilevel converter and a power grid is carried out; according to the method, the active power instruction per unit value of the AC side of the modular multilevel converter is calculated, so that the average capacitor voltage value of the sub-module as control feedback input does not have frequency doubling fluctuation in the subsequent synchronous control of the converter and the power grid, and an additional filter is not needed; the problem that the dynamic stability is poor due to the fact that a second-order low-pass filter needs to be additionally arranged when capacitor energy control is adopted is solved.
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