Abstract: In order to suppress the system resonance of the LCL-filtered NPC 3-level grid-connected inverter under the weak grid, improve the output power quality, and at the same time suppress the DC side midpoint voltage fluctuations. The prediction model of the inverter side current and the DC side midpoint voltage of the LCL-filtered 3-level grid-connected inverter is established under the weak grid. Aiming at the resonance problem of the LCL filter, the MPC-i₁u_{c_f} resonance suppression strategy is proposed from the perspective of prediction model, which using the fundamental frequency component of the capacitor voltage and eliminating the influence of resonance components on the system, and the resonance is suppressed when the inductance of the weak grid changes. Compared with the existing resonance suppression methods under model predictive control, the proposed method reduces the complexity of parameter design and is easy to implement in engineering. The experimental results show that under the weak grid conditions, the proposed method of MPC-i₁u_{c_f} can achieve system resonance suppression, and the grid-connected current can be well controlled, while taking into account the neutral voltage balance of the DC side.