Application of a discrete time (DT) sliding mode controller (SMC) in the control structure of the primary controller of a three-phase LCL grid inverter is presented. The design of the inverter side current control loop is performed using a DT linear model of the grid inverter with LCL filter at output terminals. The DT quasi-sliding mode control was used due to its robustness to external and parametric disturbances. Additionally, in order to improve disturbance compensation, a disturbance compensator is also implemented. Also, a specific anti-windup mechanism has been implemented in the structure of the controller to prevent large overshoots in the inverter response in case of random disturbances of grid voltages, or sudden changes in the commanded power. The control of the grid inverter is realized in the reference system synchronized with the voltage of the power grid. The development of the digitally realized control subsystem is presented in detail, starting from theoretical considerations, through computer simulations to experimental tests. The experimental results confirm good static and dynamic performance.

Modern control techniques of electrical drives (EDs) use robust control algorithms. One of such algorithms is variable structure control (VSC) with sliding mode (SM). SM control needs more information on the controlled plant than the conventional PI(D) control. Valid mathematical model of the controlled plant is necessary for the SM controller design. Generalized mathematical model of two-phase electrical machine and its adaptation to direct current (DC) and induction motor (IM) are given in this paper, employed in the cascade control structure. Also, the basic SM control theory and discrete-time controller design approach, developed by the authors, are given. Finally, experimentally realized examples of speed and position control of DC and IM are given as an illustration of the efficiency of the promoted EDs controller design via discrete-time VSC.

Abstract The paper proposes a discrete-time sliding mode controller for single input linear dynamical systems, under requirements of the fast response without overshoot and strong robustness to matched disturbances. The system input saturation is imposed during the design due to inevitable limitations of most actuators. The system disturbances are compensated by employing nonlinear estimation by integrating the signum of the sliding variable. Hence, the proposed control structure may be regarded as a super-twisting-like algorithm. The designed system stability is analyzed as well as the sliding manifold convergence conditions are derived using a discrete-time model of the system in the δ-domain. The results obtained theoretically have been verified by computer simulations.