An Integral Sliding Mode Stator Current Control for Industrial Induction Motor

An integral sliding mode control (ISMC) for stator currents of the induction motor (IM) is developed in this work. The proposed controller is developed in the d-q synchronous reference frame, by using the indirect field-oriented control (FOC) method. Robust asymptotic tracking of stator current components in the presence of model uncertainties and current coupling disturbance terms has been guaranteed by using an enhanced ISMC surface. More precisely, the stationary error of stator currents has been eliminated, and the accuracy of the regulators has been enhanced. According to the Lyapunov approach, it has been proven that the stator currents tracking happens asymptotically, and consequently, the stability of each loop has been demonstrated. Simulation and experimental results show the capability of the new controller in diminishing system chattering and increasing the robustness of the designed scheme, considering the variation of the plant parameters and current disturbance terms. It has been illustrated that compared with the conventional ISMC and PI regulators, the proposed current controllers provide smoother control actions and excellent dynamics. In addition, because of the precise control over the rotor flux, the rotor flux weakening method is employed to run the motor at a higher speed than the rated value.The University of the Basque Country (UPV/EHU) [grant number PIF 18/127] has funded the research in this paper

An improved predictive current control for IM drives

In Finite Control Set-Model Predictive Control (FCS-MPC), the model of the induction machine (IM) is expressed in the a b or d q reference frame, and then the back-EMF is estimated based on the applied voltage vectors. In this work, the d-q reference frame is used but unlike the existing method, the esti- mated back-EMF is calculated by filtering the voltage vectors. Moreover, the work studies the importance of the discretization method on the predictive control behavior of IM. It has been demonstrated that the mentioned enhancements lead to an efficient Total Harmonic Distortion value for stator current (THD i) and torque ripple reduction compared to the conventional methods. The proposed Predictive Current Controller (PCC) has been validated experimentally by using a commercial IM of 7:5½kW controlled by a dSpace 1103 real-time control board running with sample frequencies from 10½kHz to 80½kHz . The test results validate the developed controller’s ability to meet the control objectives in a whole range of speeds, loads, and sampling frequencies.The authors wish to express their gratitude to the Gipuzkoako Foru Aldundia through the project Etorkizuna Eraikiz 2022–2023, the Basque Government through the project EKOHEGAZ (ELKARTEK KK-2021/00092), the Diputacion Foral de Alava (DFA) through the project CONAVANTER, and to the UPV/EHU through the project GIU20/063 for supporting this work

An Enhanced Sliding Mode Speed Control for Induction Motor Drives

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.The University of the Basque Country (UPV/EHU) [grant number PIF 18/127] has funded the research in this pape

Variable structure control for maximum wind power extraction

EuroPES 2009The actual wind turbines are provided with adjustable speed generators.Iike the double feed induction generator, that are capable to work in variable speed operations. One of the main advantage of adjustable speed generators is that they improve the system efficiency compared to fixed speed generators because twbine speed is adjusted as a function of wind speed to maximize output power. However this systems requires a suitable speed controller in order to track the optimal wind turbine speed reference. In this work, it is proposed a sliding mode control for variable speed wind turbines. The robustness analysis of the proposed controller under disturbances and pararneter uncertainties is provided using the Lyapunov stability theory and simulated results show that the proposed controller provides a good performance

Generalized Predictive Control Scheme for a Wind Turbine System

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.The University of the Basque Country (UPV/EHU) (grant number PIF 18/127) has funded the research in this paper

Grid Frequency and Amplitude Control Using DFIG Wind Turbines in a Smart Grid

Wind-generated energy is a fast-growing source of renewable energy use across the world. A dual-feed induction machine (DFIM) employed in wind generators provides active and reactive, dynamic and static energy support. In this document, the droop control system will be applied to adjust the amplitude and frequency of the grid following the guidelines established for the utility’s smart network supervisor. The wind generator will work with a maximum deloaded power curve, and depending on the reserved active power to compensate the frequency drift, the limit of the reactive power or the variation of the voltage amplitude will be explained. The aim of this paper is to show that the system presented theoretically works correctly on a real platform. The real-time experiments are presented on a test bench based on a 7.5 kW DFIG from Leroy Somer’s commercial machine that is typically used in industrial applications. A synchronous machine that emulates the wind profiles moves the shaft of the DFIG. The amplitude of the microgrid voltage at load variations is improved by regulating the reactive power of the DFIG and this is experimentally proven. The contribution of the active power with the characteristic of the droop control to the load variation is made by means of simulations. Previously, the simulations have been tested with the real system to ensure that the simulations performed faithfully reflect the real system. This is done using a platform based on a real-time interface with the DS1103 from dSPACE.This research was funded by the Basque Government through the project SMAR3NAK (ELKARTEK KK-2019/00051), the Diputación Foral de Álava (DFA) through the project CONAVAUTIN 2 and the University of the Basque Country (UPV/EHU) through (PPGA20/06)

Sliding mode control of an active power filter with photovoltaic maximum power tracking

Nowadays, the increase in solar energy installations as a source of energy is growing considerably. The connection to the grid of these installations generally injects all the power obtained from the panel as active power, making zero the reactive power. The same power injection system can be used to achieve a unit power factor if the active filter feature is integrated in it. In this paper, an active power filter (APF) that can control both, the MPP (maximum power point) of a photovoltaic system (PV) and the power factor of a nonlinear load connected to the grid using a three phase DC/AC power inverter with new sliding mode controllers is presented. Perturbation–observation (P&O) is the used MPPT algorithm and three Sliding Mode Controllers (SMC) are used to regulate the DC voltage of the PV and the current d and q components of the active filter using the PQ theory. With a SMC, no exact knowledge of the model parameters is required and it offers good behavior against unmodeled dynamics, insensitivity to parameter variations and good rejection of external disturbances. The space vector pulse wide modulation (SVPWM) of 7 and 5 segments is implemented in order to check the efficiency and grid current ripple. Several experimental tests have been carried in different conditions, concluding that the presented system provides an efficient maximum power tracking and a good power filter characteristic.The authors are very grateful to the UPV/EHU by its support through the project PPGA18/04, to the Basque Government by its support through the project ETORTEK KK-2017/00033 and to the Gipuzkoako Foru Aldundia by its support through the project Etorkizuna Eraikiz 2019

Effective generalized predictive control of induction motor

In this document it is presented and experimentally validated a new linear predictive regulator to control the mechanical speed and the rotor flux of induction motor (IM). The regulator is developed in the synchronous reference frame and it provides a very good dynamic performance and guarantees fulfilment with the current constraints, to avoid over currents in stator windings. This predictive controller employs the minimum necessary dynamic model of the motor to get minor computational cost, in which the rotor flux and the load torque are estimated, and in spite of important parametric uncertainties, the performance is excellent. Moreover, the predictive regulator anticipates the response and compensates the mechanical dead time of the speed induction motor drive, getting better results than the classic speed PI control scheme. This control scheme incorporates the space vector pulse width modulation (SVPWM) with two proportional–integral​ (PI) current controllers, where the rest of dynamics of motor (stator) is controlled and voltage constraints are implemented, ensuring that the modulator always works in the linear area, to prevent distortion in the resulting stator currents. From the experimental tests that have been carried out, it can be concluded that the presented controller provides an effective and robust mechanical velocity and rotor flux tracking, from low to high speed range, with a high accuracy.The authors wish to express their gratitude to the Basque Government through the project SMAR3NAK (ELKARTEK KK-2019/00051), to the Diputación Foral de Álava (DFA) through the project CONAVAUTIN 2, to the Gipuzkoako Foru Aldundia (GFA) through the project ETORKIZUNA ERAIKIZ 2019 and the UPV/EHU for supporting this research work

A real time sliding mode control for a wave energy converter based on a wells turbine

Due to the nonlinear dynamics and uncertainties usually present in wave energy conversion systems, the efficiency of these devices can be enhanced employing a robust control algorithms. Wave energy converters are constructed using electric generators of variable velocity, like double feed induction generator (DFIG) since they may improve the system efficiency to generate power when compared to fixed speed generators. The main reason is that this generators with variable speed may adapt the speed of the turbine in order to maintain the optimal flow coefficient values which improves the efficiency of the Wells turbine. However, a suitable speed controller is required in these systems first in order to avoid the stalling phenomenon and second in order to track the optimal turbine reference velocity that optimizes the power generation. In this paper a real time sliding mode control scheme for wave energy conversion systems that incorporate a Wells turbine and a DFIG is proposed. The Lyapunov stability theory is used to analyse the stability of this control scheme under parameter uncertainties and system disturbances. Next, the proposed control scheme is validated first by means of some simulation examples using the Matlab/Simulink software and second using a real-time experimental platform based on a dSPACE DS1103 control board.The authors are very grateful to the UPV/EHU by its support through the projects PPGA18/04 and UFI11/07 and to the Basque Government by its support through the project ELKARTEK KK-2017/00033. The authors also would like to thank the anonymous reviewers who have helped to improve the initial version of this paper

A Real-Time Sliding Mode Control for a Wind Energy System Based on a Doubly Fed Induction Generator

In this paper, a real time sliding mode control scheme for a variable speed wind turbine that incorporates a doubly feed induction generator is described. In this design, the so-called vector control theory is applied, in order to simplify the system electrical equations. The proposed control scheme involves a low computational cost and therefore can be implemented in real-time applications using a low cost Digital Signal Processor (DSP). The stability analysis of the proposed sliding mode controller under disturbances and parameter uncertainties is provided using the Lyapunov stability theory. A new experimental platform has been designed and constructed in order to analyze the real-time performance of the proposed controller in a real system. Finally, the experimental validation carried out in the experimental platform shows; on the one hand that the proposed controller provides high-performance dynamic characteristics, and on the other hand that this scheme is robust with respect to the uncertainties that usually appear in the real systems.The authors are very grateful to the Basque Government by the support of this work through the project S-PE12UN015 and S-PE13UN039 and to the UPV/EHU by its support through the projects GIU13/41 and UFI11/07