Small-Signal Stability Analysis on Energy-Balancing Control of Modular Multilevel Converter Under Instantaneous Optimal Zero-Sequence Voltage Injection
Journal, IEEE Transactions on Power Electronics
D. -J. Kim, J. Park, A. Junyent-Ferré and S. Cui, “Small-Signal Stability Analysis on Energy-Balancing Control of Modular Multilevel Converter Under Instantaneous Optimal Zero-Sequence Voltage Injection,” in IEEE Transactions on Power Electronics, doi: 10.1109/tpel.2026.3745827.
Author
Dong-Joon Kim; Jaeyeon Park; Adrià Junyent-Ferré; Shenghui Cui
Abstract
This paper investigates a small-signal stability of energy-balancing control of a modular multilevel converter (MMC) under instantaneous optimal zero-sequence voltage injection (IO-ZSVI). Unlike conventional zero-sequence voltage (ZSV) injection schemes based on third-harmonic components, IO-ZSVI instantaneously determines the feasible ZSV range by considering the sum of the submodule capacitor voltages within each arm, namely the arm voltage, thereby enhancing the modulation margin and converter design flexibility. However, since the injected ZSV inherently depends on instantaneous arm voltages, IO-ZSVI introduces an unintended feedback loop into the MMC energy-balancing dynamics, which may lead to instability. To address this issue, a steady-state model of IO-ZSVI is firstly derived using steady-state arm-energy and arm-voltage models, and its inherent periodic characteristics are investigated. A small-signal model of IO-ZSVI is subsequently constructed within the framework of an averaged energy-balancing model of the MMC. The resulting model is used to analyze the small-signal stability over various operating conditions. Based on these findings, a novel design strategy for energy-balancing controllers compatible with IO-ZSVI is also proposed to ensure stable operation of the MMC under IO-ZSVI. Experiments carried out with a downscaled MMC experimental setup validate the theoretical analysis and demonstrate the effectiveness of the proposed controller design strategy.