This work addresses the problem of controlling the single-phase grid connected to the photovoltaic (PV) system via a three-level boost converter (TLBC) and half-bridge inverter (HBI) with an LCL filter, considering many difficulties like the nonlinearity of the system and a high-dimensional system. This study aims to achieve four main objectives: (i) ensure that the output voltage of the PV panel tracks its reference value given by the MPPT block based on the perturb and observe (P&O) algorithm; (ii) regulate the DC bus voltage to ensure injection of photovoltaic energy into the grid; (iii) guarantee power factor correction (PFC); (iv) ensure the balance between TLBC output capacitor voltages. The problem is dealt with using a nonlinear controller based on the backstepping approaches and Lyapunov stability. A filtered PI regulator ensures the power balance between the grid and the PV panel. The proposed controller performance is confirmed by simulation in MATLAB under standard and various climatic conditions.