Second Order Sliding Mode Control of Three Phase Neutral Point Clamped Inverter in Stationary Frame

Grid-tied Neutral-Point-Clamped (NPC) inverters have been widely used in various applications recently. A superior control method is required to achieve the desired performance of a grid-connected NPC inverter. Accordingly, a second-order sliding mode control (SOSMC) method, which is designed in the stationary frame, is utilized for achieving this aim in this paper. The super-twisting second-order sliding mode control is used for solving the chattering problem of conventional first-order sliding mode control (FOSMC). In comparison to control methods which are applied in rotation frame, this method is not required transformation from rotating frame to a-b-c frame and vice versa and decoupling of d and q components. The Lyapunov stability analysis is used for designing of this controller. The performance of proposed method is evaluated by simulation results implemented in MATLAB/Simulink software. The performance of the SOSMC is also compared with FOSMC. The results show that the incorporation of SOSMC can improve current reference tracking of the NPC inverter in different scenarios.