Model Predictive Current Control for Grid-connected Inverter Considering the PLL Dynamics

Phase locked loop (PLL) is commonly used for grid synchronization in inverter system. The stability of the grid connected inverter system can be negatively affected by the PLL bandwidth and grid impedance easily. The use of large bandwidth PLL to yield fast response might deteriorate the system stability under high grid impedance conditions. In this work, a model predictive current control (MPC) method considering the PLL dynamics is proposed, which maintains the stability of the control in the case of high grid impedance with large band width of PLL which is compared and analyzed with the existing MPC method. Analyzed results demonstrate that the proposed control method is suitable for maintaining the system stability under various short circuit ratio conditions (SCR). The optimal controller gains are obtained using the linear matrix inequality (LMI) optimization-based model predictive control. Simulations are carried out to validate the performance of the proposed control scheme.