Inductance Parameter-Free Current Control of NPC Converters Via Period-Based Time Delay Estimation

This article presents a high-performance control strategy for three-level neutral-point-clamped (NPC) converters without dependence on the inductance parameter. In the current tracking loop, an adaptive-gain period-based time delay estimator is developed to compensate for periodic uncertainties, cooperating with a generalized super-twisting controller (GSTC) to guarantee fast, smooth, inductance parameter-free, and finite-time convergent current tracking. For the voltage regulation loop, a reset GSTC is proposed to suppress voltage overshoot while ensuring the rapid dynamic response. A peaking-free filtered high-gain observer is integrated to enhance voltage tracking robustness and mitigate the impact of measurement noise, with the estimated voltage incorporated into the overall control framework. Rigorous stability analysis is provided for the proposed controllers and observer, and experimental validation confirms their superior voltage and current control performance.