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In this paper, a distributed predefined-time fractional-order sliding mode controller (DPTFOSMC) is proposed for performance improvement of power system. The proposed DPTFOSMC is designed based on the multi-agent framework and distributed control theory, which can reduce the pressure of central controller in communication and calculation, thus obtaining fast and coordinated response. The DPTFOSMC can achieve the advantages of sliding mode control (SMC) with fast response and strong robustness for the power system. In addition, the power system under the proposed DPTFOSMC can be stabilized in stable range within a predefined time which is directly equal to the tunable parameter, thus meeting the high requirement for convergence time of the power system. The prescribed performance function (PPF) is carried out to design the DPTFOSMC, which can ensure that the power system can achieve the expected transient and steady responses. Meanwhile, fractional calculus is implemented to devise the DPTFOSMC to eliminate the chattering phenomenon of conventional SMC. The Lyapunov function is adopted to analysis the predefined-time stability of the power system under the proposed DPTFOSMC. Simulations are taken to validate the effectiveness and superior performance of the proposed DPTFOSMC for the power system. The results show that the DPTFOSMC can ensure the power system to achieve superior performances than the existing control methods. [ABSTRACT FROM AUTHOR]

This paper proposes a fractional-order sliding mode controller (FOSMC) for fixed-time stability of multimachine power systems. Fractional calculus has been applied in sliding mode control (SMC) to design FOSMC which can better suppress the chattering phenomenon than the traditional integer-order SMC. Hence, a FOSMC is proposed to regulate the excitation of synchronous generators to improve the transient stability of the power system. In addition, the FOSMC can maintain the multimachine power systems stabilization in an upper bound and measurable convergence time independent of the initial operating conditions of the power system. The Lyapunov function is implemented to demonstrate the stability of multimachine power systems under the FOSMC, and the upper bound convergence time of the power system is generally estimated. The New England 10-machine 39-bus power system is taken into simulation to test the effectiveness and superior performances of the FOSMC than the existing control methods under different operating conditions. Meanwhile, the FOSMC with different orders are presented to verify that the FOSMC can better restrain the chattering phenomenon than traditional integer-order SMC. Simulation results show that the FOSMC can effectively reduce the chattering phenomenon and ensure the power system stabilization in an upper bound time, thus enhancing the dynamic performances of the power system. [ABSTRACT FROM AUTHOR]

• A high-order sliding mode based direct power control (HOSM-DPC) scheme for doubly-fed induction generator. • A power compensation strategy for DFIG wind turbine under unbalanced grid voltage condition. • A novel power compensation strategy for DFIG with variable wind speed scenario. • A Lyapunov function based super-twisting algorithm for parameter design. This paper proposes a novel high-order sliding mode (HOSM) based control methodology for direct power control (DPC) of doubly-fed induction generator (DFIG) wind turbine which is operating under unbalanced grid voltage conditions. Firstly, a set power quality enhancement strategies are presented, incorporating six power compensation schemes corresponding to six selective control targets in both steady and variable speed conditions. Meanwhile, the DFIG output powers are regulated with the proposed HOSM-DPC scheme, wherein a super-twisting algorithm is employed to cope with the chattering phenomenon and simplify the controller structure. The Lyapunov function method is utilized to decide the stability region of the controller parameters. Experiments and simulations are conducted to prove the validity and the performance of HOSM-DPC, where the DPC method with lookup table and the first order sliding mode based DPC are incorporated for comparison purpose. The experimental tests fully reveal the effectiveness of HOSM-DPC in power quality improvement subjected to unbalanced grid voltage conditions, and the superior performance of HOSM-DPC in dynamic response, chattering phenomenon elimination and variable wind speed operation are also validated. [ABSTRACT FROM AUTHOR]

• A fractional order sliding mode control method for power quality enhancement of the (PMSG) wind turbine is proposed. • Two fractional order sliding mode controller are employed to control the MSC and GSC. • The Lyapunov function based stability analysis is conducted. This paper proposes a fractional order sliding mode control (FOSMC) method for permanent magnet synchronous generator (PMSG) to enhance its output power quality. The control scheme concludes the machine side converter (MSC) control and the grid side converter (GSC) control. In the MSC, the rotor side d-q axis currents are controlled by a novel fractional order sliding mode controller; in the GSC control, the output voltage and the DC-link voltage of the GSC are regulated by another fractional order sliding mode controller. Moreover, a stability analysis based on Lyapunov function is conducted to decide the controller coefficient boundaries. The gravitational search algorithm is used to obtain the optimal parameters. Subsequently, three simulations and three experimental case studies are conducted to show the effectiveness of FOSMC, and the performance of FOSMC is compared with conventional sliding mode control and proportional integral control methods. The simulation and experiment results reveal that FOSMC has faster time response, superior tracking precision in both steady state and variable wind speed conditions, and it shows stronger robustness against parametric disturbances over SMC and PI control. [ABSTRACT FROM AUTHOR]

• A FTFOSMC is proposed for performance enhancement of the PMSG wind turbine. • The proof is presented for the stabilization of the PMSG wind turbine under the proposed FTFOSMC. • The upper limited convergence time of the PMSG wind turbine under the FTFOSMC can be estimated. • The simulations are taken to validate the superior performance of the PMSG wind turbine under FTFOSMC. This paper proposes a fixed-time fractional-order sliding mode controller (FTFOSMC) for the permanent magnet synchronous generator (PMSG) wind turbine to enhance the power quality. The FTFOSMC is implemented in the rotor side converter (RSC) and the grid side converter (GSC) to stabilize the PMSG wind turbine within an upper limited convergence time and to improve the dynamic performances. The fractional-order calculus is taken to devise fractional-order controller and the expression of the FTFOSMC is a continuous description, which can better weaken the chattering phenomenon of conventional SMC. Meanwhile, fixed-time stability is adopted to ensure the stabilization of the PMSG wind turbine within an upper limited convergence time irrelated with the initial states. The detailed proof is presented to validate that the proposed FTFOSMC can ensure the PMSG wind turbine stable and estimate the upper limited convergence time through Lyapunov function. Finally, several cases, including peak power tracking and reactive power control, variable wind speeds, grid voltage disturbances and experimental verification, are studied to show the effectiveness, robustness and superiority of the FTFOSMC than the PI control. Simulation and experimental results show that the FTFOSMC can achieve superior dynamic performances than the PI control with shorter convergence time, less vibration, higher tracking accuracy and stronger robustness, thus improving power quality of the PMSG wind turbine. [ABSTRACT FROM AUTHOR]