A Sliding Mode Approach to Enhance the Power Quality of Wind Turbines Under Unbalanced Voltage Conditions

An integral terminal sliding mode-based control design is proposed in this paper to enhance the power quality of wind turbines under unbalanced voltage conditions. The design combines the robustness, fast response, and high quality transient characteristics of the integral terminal sliding mode control with the estimation properties of disturbance observers. The controller gains were auto-tuned using a fuzzy logic approach.The effectiveness of the proposed design was assessed under deep voltage sag conditions and parameter variations. Its dynamic response was also compared to that of a standard SMC approach.The performance analysis and simulation results confirmed the ability of the proposed approach to maintain the active power,currents, DC-link voltage and electromagnetic torque within their acceptable ranges even under the most severe unbalanced voltage conditions. It was also shown to be robust to uncertainties and parameter variations, while effectively mitigating chattering in comparison with the standard SMC.

Decoupling Adaptive Sliding Mode Observer Design for Wind Turbines Subject to Simultaneous Faults in Sensors and Actuators

This paper proposes an adaptive sliding mode observer(ASMO)-based approach for wind turbines subject to simultaneous faults in sensors and actuators.The proposed approach enables the simultaneous detection of actuator and sensor faults without the need for any redundant hardware components.Additionally,wind speed variations are considered as unknown disturbances,thus eliminating the need for accurate measurement or estimation.The proposed ASMO enables the accurate estimation and reconstruction of the descriptor states and disturbances.The proposed design implements the principle of separation to enable the use of the nominal controller during faulty conditions.Fault tolerance is achieved by implementing a signal correction scheme to recover the nominal behavior.The performance of the proposed approach is validated using a 4.8 MW wind turbine benchmark model subject to various faults.Monte-Carlo analysis is also carried out to further evaluate the reliability and robustness of the proposed approach in the presence of measurement errors.Simplicity,ease of implementation and the decoupling property are among the positive features of the proposed approach.

Tube-based Model Reference Adaptive Control for Vibration Suppression of Active Suspension Systems

Dear editor,With the developments of industrial automation in recent years,vehicle suspension systems have received a great deal of attention in industry and academia due to their critical role in the chassis performance of vehicles[1].The suspension system is expected to guarantee the vehicle’s maneuverability and provide satisfactory ride comfort by absorbing the vibrations arising from the road surface excitations and ensuring road-holding capability and suspension safety.Motivated by the desirable performance of the model reference adaptive control(MRAC)approach,various literature studies have investigated its performance in diverse linear and nonlinear practical systems[2].

Fault-tolerant flight control design for effective and reliable aircraft systems

Effectiveness in flight control is achieved by maintaining specified performance despite the presence of faults and reliability implies taking the necessary measures to correct the fault before it leads to substantial performance deterioration and instability.In order to achieve both effectiveness and reliability,in this paper,we propose a fault-tolerant control(FTC)approach that is able to simultaneously compensate for actuator faults,model mismatch and parameter variations in aircraft systems.The proposed control design successfully combines the properties of active and passive FTCs to accommodate faults while retaining acceptable system performance.A passive baseline controller is designed using sliding mode theory and an active controller is designed using a model reference adaptive approach.The proposed control paradigm retains system performance under fault free conditions and triggers corrective measures only when necessary,hence ensuring flight effectiveness and enhancing system’s reliability.The proposed approach was validated using an aircraft system subject to a wide range of fault scenarios.Comparison analysis of the system performance,when only the passive controller is considered,was also carried out to highlight the effectiveness of the proposed approach.The obtained results show that the proposed fault-tolerant flight controller is able to maintain acceptable performance and retain system stability even in the event of major loss in actuator effectiveness.