A PLL-Less Voltage Sensorless Direct Deadbeat Control for a SiC Grid-Tied Inverter With LVRT Capability Under Wide-Range Grid Impedance
Xiaofeng Dong, Hui Li
Abstract
SiC grid-tied inverters can reduce interface filter size and weight to reduce cost and achieve fast dynamics, but pose control challenges, such as stability as well as large current overshoots during low-voltage ride-through (LVRT) transients. In this article, a direct deadbeat prediction control is developed for SiC grid-tied inverters with <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> filter. By predicting grid voltage without voltage sensor and removing phase-lock loop (PLL), the proposed control can improve the stability of SiC grid-tied inverters. An online adaptive parameter identification algorithm is further developed to allow the inverter to maintain stability under wide-range grid impedance to enhance the control robustness. A unity-cycle delay compensation strategy is presented to eliminate the delay time effect. The stability of the proposed voltage sensorless PLL-less direct deadbeat control method is proved based on the Lyapunov stability theory. In addition, the proposed control allows the seamless implementation of LVRT with inrush current significantly mitigated. The proposed control method has been implemented and verified on a 5-kW SiC inverter with 50-kHz switching frequency. The experimental results of steady state and transients under different grid impedances as well as LVRT are presented to verify its validity.