Delta Operator SMVSC for T-Type Three-Level Inverter System

Aiming at the problems of low control accuracy caused by internal parameter perturbations and external disturbances in the T-type three-level inverter system, a novel sliding mode variable structure control (SMVSC) strategy is addressed based on Delta operator in this article. Delta operator sampling is an effective discretization approach, which can unify continuous-time systems and discrete-time systems. First, the mathematical model of the T-type three-level inverter system in the synchronous rotating coordinate is established and corresponding discretization mathematical model based on Delta operator is obtained. Then, the switching function is selected, the reaching condition is analyzed, and a novel exponential reaching law is proposed based on Delta operator. Next, two types of Delta operator sliding mode variable structure controllers for T-type three-level inverter systems without uncertainties and with uncertainties are designed. Finally, comparing the proposed Delta operator SMVSC strategy with PID control, model predictive control, and deadbeat control, the simulation and experimental results demonstrate the Delta operator SMVSC strategy has some superiority in high adaptivity and robustness, moreover, output voltages steady-state errors approach zero equilibrium state, and transient responses are good dynamic performance.