Miaoling Yang, Liangzong He, Yuanyuan Peng, Yixuan Li
In single-phase two-stage inverters, the bus capacitor plays a critical role in maintaining system stability by suppressing DC-link voltage ripple, absorbing harmonic currents, and regulating bus voltage. However, capacitor aging leads to parameter drift that significantly degrades control performance, making accurate online parameter identification essential for reliable operation. Current identification methods face the major limitations: they require specific operating conditions that interrupt normal converter function, impose substantial computational burdens and hardware costs, and depend on integer-order models that cannot accurately capture real capacitor behaviors. To overcome these challenges, this paper presents an innovative fractional-order capacitor online identification method that achieves rapid, precise parameter estimation during normal converter operation without requiring test signals or operational interruptions. The proposed approach offers three key advantages: first, it leverages a fractional-order model that more accurately represents capacitor dynamics; second it embeds a fractional-order recursive model into NN to achieve disturbance-free online identification; third, it enables real-time identification using only the inherent operating characteristics of the converter; and forth, it simultaneously facilitates second harmonic current suppression in the singlephase two-stage inverter used as our test case. Furthermore, the identified capacitor parameters can be directly utilized to optimize system control parameters, enhancing harmonic suppression performance. This work provides a practical framework for highprecision, low-cost online parameter identification that can be readily adapted to various power converter topologies, offering important implications for maintenance and control of aging power electronic systems.