In this paper, an enhanced Integral Sliding Mode Control (ISMC) for mechanical speed of an Induction Motor (IM) is presented and experimentally validated. The design of the proposed controller has been done in the d-q synchronous reference frame and indirect Field Oriented Control (FOC). Global asymptotic speed tracking in the presence of model uncertainties and load torque variations has been guaranteed by using an enhanced ISMC surface. Moreover, this controller provides a faster speed convergence rate compared to the conventional ISMC and the Proportional Integral methods, and it eliminates the steady-state error. Furthermore, the chattering phenomenon is reduced by using a switching sigmoid function. The stability of the proposed controller under parameter uncertainties and load disturbances has been provided by using the Lyapunov stability theory. Finally, the performance of this control method is verified through numerical simulations and experimental tests, getting fast dynamics and good robustness for IM drives.

In this paper, a generalized predictive control scheme for wind energy conversion systems that consists of a wind turbine and a doubly-fed induction generator is proposed. The design is created by using the maximum power point tracking theory to maximize the extracted wind power, even when the turbine is uncertain or the wind speed varies abruptly. The suggested controller guarantees compliance with current constraints by applying them in the regulator’s conceptual design process to assure that the rotor windings are not damaged due to the over-current. This GPC speed control solves the optimization problem based on the truncated Newton minimization method. Finally, simulation results, which are obtained through the Matlab/Simulink software, show the effectiveness of the proposed speed regulator compared to the widely used Proportional-integral controller for DFIG.

This paper considers the problem of robust output regulation of nonlinear systems in semi strict-feedback form in the presence of model uncertainties and nonvanishing disturbances. In the proposed procedure, two exosystems are considered to generate the disturbance and reference signals. In order to reduce both the conservatism of the control law and the chattering phenomena, a disturbance observer is designed for disturbance estimation instead of assuming the known upper bound for the disturbance. Moreover, a novel sliding surface is designed based on the tracking error to guarantee that the output of the system tracks the output of the exosystem. In this regard, some theorems are given and according to the Lyapunov approach, it is proved that the robust output regulation is guaranteed in the presence of model uncertainties and external disturbances. Finally, in order to show the applicability of the proposed controller, it is applied to the Van der Pol chaotic oscillator. Computer simulations verify the theoretical results and also show the effective performance of the proposed controller.

Achieving maximum power extraction and reliable power transfer from the wind turbine systems (WTS) to the grid network is essential. Hence, machine and grid-side converters utilize cascaded proportional-integral (PI) controllers to achieve the abovementioned objective. However, the conventional controller's performance gets delayed due to mismatched machine parameters and slow dynamic response. Therefore, this study aims to propose an advanced control method combining the predictive scheme principle and PI control's merits for maximizing the power extraction from permanent magnet vernier generator (PMVG) based WTS. For this purpose, a generalized predictive approach-based PI (GPC-PI) scheme is initially presented in the machine-side converter (MSC) to regulate the generator speed. Similarly, the same approach-based DC-link voltage (DLV) control is presented in the grid side converter (GSC) to handle the capacitor voltage and optimize the power delivery at the point of common coupling. Further, the stability conditions of designed controllers are verified by carrying out pole placement analysis. Finally, the superiority of the proposed methods is demonstrated using the simulation and experimental configuration of a grid-connected 5 kW PMVG-based WTS.

The purpose of this paper is to propose a controller for nonlinear systems to achieve robust asymptotic tracking of a class of reference signals, in the presence of matched and unmatched disturbances and model uncertainties. The disturbances and reference signals are generated using two linear exosystems. In the proposed controller, instead of using the upper bound of disturbances in the design process, their instantaneous values are estimated disturbance observer. Therefore, disturbance observer-based control (DOBC) methods are less conservative with respect to conventional approaches. In addition to the DOBC design, a new stepwise procedure based on backstepping technique and sliding mode control is proposed. In the proposed approach, in each step, estimations of disturbances and the upper bound of model uncertainties are used to compose virtual control laws; these virtual control laws compose the final control law. Finally, numerical and practical examples are simulated to show the efficiency of the proposed technique and also to verify the theoretical results.