Abstract:In this paper, a real-time robust closed-loop control scheme for controlling the velocity of a Direct Current (DC) motor in a compound connection is proposed. This scheme is based on the state-feedback linearization technique combined with a second-order sliding mode algorithm, named super-twisting, for stabilizing the system and achieving control goals. The control law is designed to track a periodic square reference signal, being one of the most severe tests applied to closed-loop systems. The DC motor drives a squirrel-cage induction generator which represents the load; this generator must work above the synchronous velocity to deliver the generated power towards the grid. A classical proportional-integral (PI) controller is designed for comparison purposes of the time-domain responses with the proposed second-order sliding mode (SOSM) super-twisting controller. This robust controller uses only a velocity sensor, as is the case of the PI controller, as the time derivative of the velocity tracking variable is estimated via a robust differentiator. Therefore, the measurements of field current and stator current, the signal from a load torque observer, and machine parameters are not necessary for the controller design. The validation and robustness test of the proposed controller is carried out experimentally in a laboratory, where the closed-loop system is subject to an external disturbance and a time-varying tracking signal. This test is performed in real time using a workbench consisting of a DC motor-Alternating Current (AC) generator group, a DC/AC electronic drive, and a dSPACE 1103 controller board.

The authors propose robust non-linear controllers for a wind system. The proposed controllers are based on a combination of the block control linearisation and super-twisting algorithm, as a second-order sliding mode technique. The main control loop is designed to regulate the electromagnetic torque and stator power factor of a doubly-fed induction generator which is connected to the grid. The generator is mechanically coupled with a DC motor, which can emulate the wind turbine operation. Therefore, an auxiliary control loop is designed to control the DC motor velocity. Additionally, a grid-side converter controller is proposed to regulate the DC-link voltage into AC/DC/AC converter, and displacement factor of the energy flow between the rotor and the grid. A robust stability analysis of the complete closed-loop system under external disturbances is presented. The robustness of the proposed control schemes is validated in real time using a workbench, which consists of a motor-generator group, AC/DC/AC electronic drive and dSPACE DS 1104 controller boards.

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In this paper, we propose a sliding mode -based controller for a wind power system where an induction generator is connected to an infinity bus. To ensure robustness of the closed -loop system with respect to perturbations and plant parameter variations, first, we applied the conventional sliding mode (SM) control technique. Secondly, an integral sliding SM control is designed to reduce a chattering effect. Both the control schemes are proposed to control the electromagnetic torque and the stator reactive power of a wound rotor induction generator coupled with a wind turbine across a gear box. The performance of the designed controllers is validated through simulations.Index Terms-sliding mode control, power system, wound rotor induction generator. I. NOMENCLATUREL s = stator self inductance per phase L r = rotor self inductance per phase L m = magnetization inductance L sm = mutual inductance between two phases of stator L rm = mutual inductance between two phases of rotor L sr = mutual inductance between stator and rotor phase L ls , L lr = leakage stator and leakage rotor inductances R s , R r = stator and rotor resistance per phase i ds , i qs , i dr , i qr = stator and rotor currents in the axes d and q v ds , v qs , v dr , v qr = stator and rotor voltages in the axes d and q T e = electromagnetic torque T m = turbine torque T eref = reference electromagnetic torque Q s = stator reactive power Q sref = reference stator reactive power P m = mechanic power established by turbine fp s = stator power factor ω m = generator shaft velocity ω s , ω r = supply and rotor frequency θ r = rotor position P = number of poles pair J' tb = total inertia referred to generator side .A sincere gratefulness to CINVESTAV (Advanced Investigation Center of National Polytechnic Institute), and UACJ (Juarez City Autonomous University). This work was supported by PROMEPTeaching Staff Improvement Program) under grants 103.5/06/1974. [omorfin][louk][canedoj]@gdl/cinvestav.mx Cinvestav, Guadalajara. Av. Científica No. 1145, Col. El Bajío; Zapopan, Jalisco. México. CP 45010. Tel +52(33) 3777 3600, Fax +5(33) 3777 3609.v = wind velocity ρ = air density R, A = radius and sweep area of the wind turbine C p = power coefficient N gb = velocity relation in gear box λ = tip speed and wind velocity relation II. INTRODUCTION NE of operation modes of the wind power generating systems is featured by the variable-speed and constantfrequency where maximum-power-capturing of the wind must be reached [1]. In this application, the wound rotor induction (WRI) generator is typically used. This generator runs around synchronous speed drawing the magnetizing current from the electric network; therefore, this machine needs two sources: an unidirectional source for magnetizing the stator, and another, a bidirectional source that supplies current into the wound rotor to control the generator. The typical configuration of the rotor supply consists of two voltage-fed current-regulated inverters connected back to back through a direct current link and a capacito...

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