A Stable and Ultrafast Control for Multiparallel Grid-Tied SiC Inverters With LVRT Capability Considering Cable Impedance

The stability of multi-paralleled grid-tied inverters remains a challenging issue especially during low-voltage ridethrough (LVRT) in the presence of grid impedance. SiC devicebased grid-tied inverters can achieve advantages such as higher efficiency, reduced size of interface filters, and fast dynamics; however, they can exacerbate this stability issue particularly when LVRT occurs along with high inrush current due to their low inertia characteristics. In this paper, a direct deadbeat control method without any PI control loop is proposed for multi-parallel grid-tied SiC inverters. The proposed control achieves instantaneous current regulations within switching cycles. In addition, it mitigates high inrush currents and maintains stability during LVRT transients without requiring mode transitions between normal and LVRT operation modes, thereby achieving an ultrafast response and seamless operation through this unified control method. The Lyapunov method is applied to analyze the multi-parallel inverter stability in the presence of grid impedance with proposed deadbeat control method. The inverter V-I trajectories during LVRT transients are derived to illustrate the ultrafast and stable feature of proposed control. Finally, the experimental results of two grid-tied SiC inverters operating at LVRT transients are provided to verify the advantages of the proposed control method.