A robust direct flux and torque control (DFTC) technique of a doubly-fed induction generator (DFIG) for wind turbine applications (WTA) is presented in the paper. The main advantages of traditional DFTC control method are its simple structure, robust technique and good dynamic response compared to the field-oriented control (FOC). The use of a classical hysteresis comparator and a predefined lookup table will inevitably lead to select a nonoptimal rotor voltage vector in terms of reducing rotor flux errors, harmonic distortion (THD) current, and electromagnetic torque undulations. In this research work, a new approach of DFTC technique of DFIG based modified super-twisting algorithms (MSTA) and modified space vector modulation (MSVM) is developed by replacing the traditional lookup table and two hysteresis comparators. Theoretical principles of this method are presented along with simulation results. Analysis of DFTC-MSVM control scheme based MSTA controllers have been done in MATLAB/ Simulink environment. The machine (DFIG 1,5MW) is tested in association with a wind turbine. Simulation results are presented. The proposed DFTC control technique takes full advantage and the electromagnetic torque regulation objective of DFIG is confirmed by the numerical simulation results compared to the traditional DFTC control technique.
Background: The direct flux and torque control are a robust, simple, and alternative approach control formulation that does not require decomposition into symmetrical components; the direct flux and torque control schemes have been proved to be preponderant for doubly-fed induction generators due to the simple implementation. Aim: This work presents the minimization of electromagnetic torque and rotor flux undulations of doubly-fed induction generators using fractional-order super twisting algorithms and modified space vector modulation techniques. Methods: The main role of direct flux and torque control is to regulate and control the electromagnetic torque and rotor flux of doubly-fed induction generators for wind turbine systems. The direct flux and torque control is a traditional control algorithm and robust technique. Fractional-order super twisting algorithms are a new and proposed nonlinear controller; characterized by a robust controller and a simpler algorithm, which gives a good harmonic distortion of current compared to other methods. Novelty: The A fractional-order super twisting algorithm is proposed. Proposed nonlinear controller construction is based on the traditional super twisting algorithm and fractional calculus to obtain a robust controller and reduces the electromagnetic torque and rotor flux undulations of doubly-fed induction generators. We use in our study a 1.5 MW doubly-fed induction generator integrated into a single-rotor wind turbine system to minimizes the electromagnetic torque, stator current, rotor flux undulations. As shown in the results figures using fractional-order super twisting algorithms ameliorate effectiveness especially minimizes the electromagnetic torque and rotor flux, and minimizes harmonic distortion of stator current (0.16 %) compared to the traditional control scheme. Results: As shown in the results figures using fractional-order super twisting algorithms ameliorate effectiveness especially minimizes the electromagnetic torque and rotor flux, and minimizes harmonic distortion of stator current (0.16 %) compared to the traditional control scheme. Conclusion: The direct flux and torque control are a robust, simple, and alternative approach control formulation that does not require decomposition into symmetrical components; the direct flux and torque control schemes have been proved to be preponderant for doubly-fed induction generators due to the simple implementation.
A new nonlinear controller for direct flux and torque control (DFTC) of a doubly-fed induction generator (DFIG) based on a single-rotor wind turbine (SRWT) using the fractional-order second-order continuous sliding mode (FOSOCSM) controller is presented in this paper. Three different controllers are proposed to control the electromagnetic torque and rotor flux of the doubly-fed induction generator driven by a single-rotor wind turbine. The main goal of the proposed DFTC control structure is to improve the quality of the electromagnetic torque and stator current of the SRWT system by reducing electromagnetic torque undulations, stator current, and rotor flux undulations in the DFIG-SRWT systems. The mathematical model of the DFIG has been described. The descriptions of the modified space vector modulation (MSVM) strategy and the proposed FOSOCSM controller have been presented. The DFTC-MSVM control structure with proposed FOSOCSM controllers has been described. This proposed strategy has been shown to be robust and stable against parametric uncertainties and load electromagnetic torque. The validity, robustness, and effectiveness of the proposed DFTC-FOSOCSM technique are demonstrated through simulation studies in the MATLAB® software environment. Numerical simulation results demonstrate that the proposed DFTC control scheme with proposed FOSOCSM controllers has a faster transient response than traditional DFTC and DFTC with classical SOCSM controllers. Also, it reduces ripples in both electromagnetic torque of stator current, and rotor flux significantly compared to the classic technique and DFTC with traditional SOCSM controllers.
Direct torque control (DТС) is a method of controlling electrical machines that are widely used, and this is due to its simplicity and ease of use. However, this method has several issues, such as torque, rotor flux, and current fluctuations. To overcome these shortcomings and improve the characteristics and robustness of the DTC strategy of the doubly-fed induction generator (DFIG), a new DTC scheme based on the feedback control method (FCM) and space vector modulation (SVM) is proposed. In the proposed DTC technique, a proportional-integral controller based on feedback control theory is used to control and regulate the torque and rotor flux of the DFIG. On the other hand, the SVM technique is used to control the rotor side converter (RSC) to obtain a high-quality current. The simulation result shows that the proposed DTC technique has the advantages of faster dynamics and reduced harmonic distortion of current compared to the conventional technique.
Two new nonlinear techniques are proposed in this study for improving the performance and efficiency of the doubly-fed induction generator (DFIG)-based wind turbine systems. Direct torque control (DTC) is among the most widely used strategies for controlling DFIGs due to its many advantages, such as robustness, simplicity, and fast response dynamics. However, this control causes big ripples in both torque and flux. Furthermore, it has significant total harmonic distortion (THD). Several solutions are proposed to overcome these problems, including nonlinear techniques and intelligent strategies such as genetic algorithms. In this work, two different controllers are proposed to improve the performance of the DTC technique. Firstly, the second-order continuous sliding mode (SOCSM) based on fractional-order (FO) control, and secondly, the super twisting algorithm (STA) based on the FO technique. The biggest advantages of the proposed strategies are their durability and ease of execution. Based on the proposed controls, the DTC strategy can greatly improve generator performance in different operating conditions. This paper also provides a comparative analysis of DTC-FOSOCSMC, DTC, and DTC-FOSTA in terms of reference tracking, robustness, chattering reduction, and computational complexity, using mathematical theory and simulation carried out in Matlab/Simulink using a 1.5 MW DFIG-based wind turbine. The simulation results demonstrate the effectiveness and high performance of the proposed DTC techniques.
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