Qualification: 
Ph.D, M.Tech, B-Tech

Dr. R. Saravanakumar currently serves as Assistant Professor (Senior Grade) at the department of Electrical and Electronics Engineering, School of Engineering, Amrita Vishwa Vidyapeetham, Bengaluru Campus. He has received his Bachelor degree of Electrical and Electronics Engineering from Anna University Chennai, India, in 2008. He has received his Master degree in the specialization of Control and Instrumentation Engineering in Anna University 2010 and Ph.D. degree in Control System Engineering from the Department of Electrical Engineering, National Institute of Technology Karnataka, Surathkal, India in 2016. He has worked as Post-Doctoral Fellow at IIT Roorkee. 

Publications

Publication Type: Conference Paper

Year of Publication Title

2018

Anjana Jain and R. Saravanakumar, “Comparative Analysis of DSOGI-PLL amp; Adaptive Frequency Loop-PLL for Voltage and Frequency control of PMSG-BESS based Hybrid Standalone WECS”, in 2018 8th International Conference on Power and Energy Systems (ICPES), Colombo, Sri Lanka, Sri Lanka, 2018.[Abstract]


3-phase PLL (phase-locked-loop) are the key elements for frequency & phase estimation of a balanced/disturbance voltage of the power system subjected to disturbances. Accurate measurement of generator speed in wind energy conversion system (WECS) is the most crucial task and it is worsening in disturbed voltage states. A dual-second-order-generalized-integrator (DSOGI)-PLL based control for load side bidirectional voltage source converter (VSC) is discussed in this paper for standalone hybrid variable speed WECS comprising of permanent magnet synchronous generator (PMSG) and & battery energy storage system (BESS). DSOGI-PLL based control scheme is presented here for voltage and frequency control. A MATLAB/Simulink-model is prepared for the system under study and a detailed simulation is performed. The effectiveness of the controller under study is checked by comparing it with Adaptive frequency loop-PLL based controller for different working conditions; like variable wind velocity, load variation, load disturbances, and faults. It is concluded from the simulation study that DSOGI-PLL gives comparative better performance during transient like: fault and unbalanced/disturbed voltage conditions. DSOGI-PLL removes the harmonics and disturbances from the signal (dq-axis component generation) as compared to Adaptive frequency loop-PLL. Proposed controller provides excellent control for VSC. BESS is able to perform load balancing during variations in wind-velocity and load.

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2018

R. Saravanakumar and Anjana Jain, “Design of Complementary Sliding Mode Control for Variable Speed Wind Turbine”, in 2018 8th International Conference on Power and Energy Systems (ICPES), 2018.[Abstract]


The wind turbine efficiency increases by controlling the rotor speed to its optimal value. A nonlinear controller, which is robust towards uncertainties in the dynamic plant model and unknown disturbances, is designed for better capture of rotor speed. This paper focuses on an effective wind speed based complementary sliding mode controller (CSMC) designed for wind turbine. The main objective of the controller is to extract the maximum power from wind at region 2 (below rated wind speed) with minimum oscillation on the drive train. The controller stability is validated by Lyapunov function. The proposed and existing control algorithms are validated using a FAST 600kW model which is developed by NREL (National Renewable Energy Laboratory). The efficacy of the proposed controller is validated by comparing it with typical nonlinear controller such as sliding mode and integral sliding mode controller. A detailed simulation is performed for typical and proposed control strategies for different mean wind speed profiles. The simulations results shows that, complementary sliding mode controller gives better performance than typical control strategies.

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2017

K. Matthew and R. Saravanakumar, “Design of Double Integral Sliding Mode Control for Variable Speed Wind Turbine at Partial Load Region”, in 2017 IEEE International Conference on Computational Intelligence and Computing Research (ICCIC), Coimbatore, India, 2017.[Abstract]


This work discusses the design of a nonlinear controller for a single mass model of a variable speed wind turbine without measurement of wind speed. Dynamic load on the drive train shaft plays a vital role in turbine lifespan. So the design of the nonlinear controller should pay more care in mitigation of transient load on the drive train shaft. The objective of the controller is to extract the optimal power with limited dynamic loads on the shaft. The above objectives are satisfied by tracking the reference rotor speed which is done by a nonlinear controller. Effective wind speed is obtained by Modified Newton Raphson (MNR), which is used for deriving the reference rotor speed. In this paper, a nonlinear controller, i.e. double integral sliding mode controller (DISMC) is proposed for the single mass model of a wind turbine at partial load region (below rated wind speed). Lyapunov candidate function is used for analyzing the stability of the proposed controller. The performance of the proposed controller is compared with conventional integral sliding mode controller (ISMC) in terms of performance parameters. The robustness of the controllers are analyzed in the presence of different input disturbances and different wind speed profiles. From results, it is found that DISMC can able to accommodate various input disturbance level up to 5kNm.

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2015

R. Saravanakumar and Jena, D., “Adaptive nonsingular terminal sliding mode control for variable speed wind turbine”, in 2015 IEEE 28th Canadian Conference on Electrical and Computer Engineering (CCECE), Halifax, NS, Canada, 2015.[Abstract]


In recent years wind energy is becoming more popular among other renewable sources due to more advanced technologies. Reduction in the cost of wind energy requires more efficient technology which is able to extract optimum power form the wind. The main focus of this work is to design a new adaptive controller for a variable speed wind turbine (VSWT) for maximizing turbine's energy capture. The generator torque is considered as the control input and it depends on the optimal rotor speed which is derived from the effective wind speed. From aerodynamic torque and rotor speed the effective wind speed is derived by Modified Newton Rapshon (MNR). Initially the conventional sliding mode controller (SMC) is considered. The control performance of SMC is compared with proposed Adaptive Nonsingular Terminal Sliding Mode Control (ANTSMC) for different level of random disturbances and actuator offset. The main advantage of ANTSMC is robustness to input disturbances and parametric uncertainties of the turbine. Both the controllers are tested for a single mass mathematical wind turbine (WT) model and validated through different mean wind speed with various random disturbances and actuator offset. Validation results show that the proposed control strategy is effective in terms of better energy capture and robustness to disturbances.

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2014

R. Saravanakumar and Jena, D., “ISMC based variable speed wind turbine for maximum power capture”, in International Conference on Control, Instrumentation, Energy and Communication (CIEC), 2014 International , Calcutta, India, 2014.[Abstract]


This paper presents the nonlinear control for variable speed wind turbine (WT) where the dynamics of WT is derived from single mass model. The main objective is to maximize the energy capture from the wind and reduce the drive train oscillations. In order to control the WT the generator torque is considered as the control input. This torque depends on the optimal rotor speed derived from the effective wind speed. The effective wind speed is estimated from aerodynamic torque and rotor speed by using modified Newton Rapshon (MNR). The conventional techniques such as aero dynamic torque feed forward (ATF) & Indirect speed control (ISC) which does not depend on the effective wind speed, are unable to track the dynamic aspect of the WT. The other disadvantages of the above conventional methods are more power loss and not robust with respect to disturbances and uncertainties. To overcome these weaknesses nonlinear controllers are found to be more suitable than the conventional controller. In this paper a sliding mode control with integral action i.e. integral sliding mode controller (ISMC) is applied to the WT and a modified Newton Rapshon is used to estimate the effective wind speed. The result shows the significance improvement in proposed controllers compared with existing controllers.

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2014

R. Saravanakumar and Jena, D., “Backstepping sliding mode control for variable speed wind turbine”, in Annual IEEE India Conference (INDICON), 2014 , 2014.[Abstract]


This paper presents the nonlinear control for variable speed wind turbine (VSWT). The dynamics of the wind turbine (WT) are derived from the single mass model. The control objective is to maximize the energy capture from the wind with reduced oscillation on the drive train. The generator torque is considered as the control input and it depends on the optimal rotor speed which is derived from the effective wind speed. The effective wind speed is estimated from the aerodynamic torque and rotor speed by using the modified Newton Rapshon (MNR). Initially the conventional sliding mode controller (SMC) is considered. The control performance of SMC was compared with Backstepping Sliding Mode Control (BSMC) for different level of disturbance. The conventional SMC and proposed BSMC are tested with mathematical model and validated through the different mean wind speed. The result shows the better performance of BSMC and robustness to disturbances.

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2013

D. Jena and R. Saravanakumar, “Second Order ISMC for Variable Speed Wind Turbine”, in 8th IEEE International Conference on Industrial and Information Systems (ICIIS), 2013, Peradeniya, Sri Lanka, 2013.[Abstract]


In this paper, a nonlinear controller is designed for variable speed wind turbine (WT) where the dynamics of the WT is derived for single mass model. The main aim of the controller is to extract the optimum power capture from the wind and minimize the transient load on low speed shaft. Modified Newton Rapshon (MNR) is used to estimate the effective wind speed and the optimal rotor speed is derived from it. The controller is used to track the optimal rotor speed by adjusting the generator torque which is acting as a control input to the WT. Existing controllers such as Nonlinear static state feedback with estimator (NSSFE) and Nonlinear dynamic state feedback with estimator (NDSFE) are unable to track the WT dynamics and introduces more transient on drive trains. In order to overcome the above drawbacks a nonlinear controller i.e. sliding mode control with integral action (ISMC) is used. In this paper an ISMC with MNR based wind speed estimator is used to control the single mass WT. The result shows the significance improvement in proposed controllers compared with NSSFE and NDSFE.

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2013

D. Jena and R. Saravanakumar, “Nonlinear estimation and control of wind turbine”, in IEEE International Conference on Electronics, Computing and Communication Technologies (CONECCT), 2013 , Bangalore, India, 2013.[Abstract]


Wind energy is one of the major renewable energy sources which continue to be one of the fastest growing power generation sectors. For variable speed operation of wind energy conversion system, it is required to generate the maximum power at below the rated speed using an authentic and powerful control strategy. Wind speed has the major impact on the dynamics and control of wind turbines. But in practice there is no accurate measurement of effective wind speed available for direct measurement. In this paper a new technique is proposed for optimal power generation of wind turbine below rated speed without estimating the wind speed. An extended Kalman filter (EKF) is used to estimate the rotor speed and a proportional (P) controller is used to track the error between the measured and estimated rotor speed. The output of the P controller is the estimated aerodynamic torque. The estimated aerodynamic torque and the rotor speed act as an input to the aerodynamic torque feed-forward (ATF) controller. The output of the ATF controller is the generated torque. As the aerodynamic torque is highly dependent on the wind speed so it cannot be controlled. So we have to control the generated torque by using ATF for generating optimal power output. Finally the estimated outputs are validated through correlation analysis.

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2010

M. Dhivya, Matthew, K., Prabhu, M., and R. Saravanakumar, “Position control of DC motor using advanced soft computing technique”, in Second National Conference on Signal Processing, Communications and VLSI Design – NCSCV’10, 2010.[Abstract]


The aim of this paper is to design a position controller of a DC motor by selection of a PID parameters using BFOA. The model of a DC motor is considered as a third order system. And this paper compares two kinds of tuning methods of parameter for PID controller. One is the controller design by the BFOA second is the controller design by the Ziegler and Nichols method. It was found that the proposed PID parameters adjustment by the BFOA is better than the Ziegler & Nichols’ method. The proposed method could be applied to the higher order system also.

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Publication Type: Journal Article

Year of Publication Title

2018

Anjana Jain, R. Saravanakumar, Shankar, S., and Dr. Vanitha V., “Adaptive SRF-PLL Based Voltage and Frequency Control of Hybrid Standalone WECS with PMSG-BESS”, International Journal of Emerging Electric Power Systems, vol. 19, no. 6, 2018.[Abstract]


The variable-speed Permanent Magnet Synchronous Generator (PMSG) based Wind Energy Conversion System (WECS) attracts the maximum power from wind, but voltage-regulation and frequency-control of the system in standalone operation is a challenging task A modern-control-based-tracking of power from wind for its best utilization is proposed in this paper for standalone PMSG based hybrid-WECS comprising Battery Energy Storage System (BESS). An Adaptive Synchronous Reference Frame Phase-Locked-Loop (SRF-PLL) based control scheme for load side bi-directional voltage source converter (VSC) is presented for the system. MATLAB/Simulink model is developed for simulation study for the proposed system and the effectiveness of the controller for bi-directional-converter is discussed under different operating conditions: like variable wind-velocity, sudden load variation, and load unbalancing. Converter control scheme enhances the power smoothening, supply-load power-matching. Also it is able to regulate the active & reactive power from PMSG-BESS hybrid system with control of fluctuations in voltage & frequency with respect to varying operating conditions. Proposed controller successfully offers reactive-power-compensation, harmonics-reduction, and power-balancing. The proposed scheme is based on proportional & integral (PI) controller. Also system is experimentally validated in the laboratory-environment and results are presented here.

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2016

R. Saravanakumar and Debashisha, J., “Nonlinear control of wind turbine with optimal power capture and load mitigation”, Energy Systems, vol. 7, no. 3, pp. 429–448, 2016.[Abstract]


The main control objectives associated with the variable speed wind turbine is to extract maximum power at below rated wind speed (region 2) and to regulate the power at above rated wind speed (region 3). This paper proposes a nonlinear framework to achieve the above two control objectives. The paper discusses about the application of an integral sliding mode control (ISMC) in region 2 and a fuzzy based proportional integral (PI) control in region 3. Same ISMC is adopted for the stable switching between operating regions (transition region 2.5) and the control input maintains the continuity at the instant of switching. Lyapunov stability criterion is used to prove the stability of ISMC. The controllers are tested for different wind speed profiles with different turbulence component. Finally the performances of the proposed controllers are tested with nonlinear Fatigue, Aerodynamics, Structures, and Turbulence WT model and the results are compared with the existing baseline + PI controllers.

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2016

R. Saravanakumar and Jena, D., “Control Strategy to Maximize Power Extraction in Wind Turbine”, Distributed Generation & Alternative Energy Journal , vol. 31, no. 4, pp. 27-49 , 2016.[Abstract]


This article deals with nonlinear control of variable speed wind turbine (VSWT), where the dynamics of the wind turbine (WT) is obtained from a single mass model. The main objective of this work is to maximize the energy capture form the wind with reduced oscillation on the drive train. The generator torque is considered as the control input to the WT. In general the conventional control techniques such as Aerodynamic Torque Feed-Forward (ATF) and Indirect Speed Control (ISC) are unable to track the dynamic aspect of the WT. To overcome the above drawbacks the nonlinear controllers such Sliding Mode Controller (SMC) and SMC with integral action (ISMC) with the estimation of effective wind speed are proposed. The Modified Newton Raphson (MNR) is used to estimate the effective wind speed from aero dynamic torque and rotor speed. The proposed controller is tested with different wind profiles with the presence of disturbances and model uncertainty. From the results the proposed controller was found to be suitable in maintaining a trade-off between the maximum energy capture and reduced transient on the drive train. Finally both the controllers are validated by using FAST (Fatigue, Aerodynamics, Structures, and Turbulence) WT simulator.

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2016

R. Saravanakumar and Jena, D., “Nonlinear control of a wind turbine based on nonlinear estimation techniques for maximum power extraction”, International Journal of Green Energy, vol. 13, no. 3, pp. 309-319, 2016.[Abstract]


This work proposes nonlinear estimators with nonlinear controllers, for variable speed wind turbine (VSWT) considering that either the wind speed measurement is not available or not accurate. The main objective of this work is to maximize the energy capture from the wind and minimizes the transient load on the drive train. Controllers are designed to adjust the generated torque for maximum power output. Estimation of effective wind speed is required to achieve the above objectives. In this work the estimation of effective wind speed is done by using the Modified Newton Rapshon (MNR), Neural Network (NN) trained by different training algorithms and nonlinear time series based estimation. Initially the control strategies applied was the classical ATF (Aerodynamic torque feed forward) and ISC (Indirect speed control), however due their weak performance and unmodeled WT disturbances, nonlinear static and dynamic feedback linearization techniques with the above wind speed estimators are proposed.

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2015

R. Saravanakumar and Jena, D., “Load Mitigation and Optimal Power Capture for Variable Speed Wind Turbine in Region 2”, Journal of Renewable Energy, 2015.[Abstract]


This paper proposes the two nonlinear controllers for variable speed wind turbine (VSWT) operating at below rated wind speed. The objective of the controller is to maximize the energy capture from the wind with reduced oscillation on the drive train. The conventional controllers such as aerodynamic torque feedforward (ATF) and indirect speed control (ISC) are adapted initially, which introduce more power loss, and the dynamic aspects of WT are not considered. In order to overcome the above drawbacks, modified nonlinear static state with feedback estimator (MNSSFE) and terminal sliding mode controller (TSMC) based on Modified Newton Raphson (MNR) wind speed estimator are proposed. The proposed controllers are simulated with nonlinear FAST (fatigue, aerodynamics, structures, and turbulence) WT dynamic simulation for different mean wind speeds at below rated wind speed. The frequency analysis of the drive train torque is done by taking the power spectral density (PSD) of low speed shaft torque. From the result, it is found that a trade-off is to be maintained between the transient load on the drive train and maximum power capture.

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2015

R. Saravanakumar and Debashisha, J., “Backstepping sliding mode control of a variable speed wind turbine for power optimization”, Journal of Modern Power Systems and Clean Energy, vol. 3, no. 3, pp. 402–410, 2015.[Abstract]


To optimize the energy capture from the wind, wind turbine (WT) should operate at variable speed. Based on the wind speed, the operating regions of the WT are divided into two parts: below and above the rated wind speed. The main aim at below rated wind speed is to maximize the energy capture from the wind with reduced oscillation on the drive train. At above rated wind speed, the aim is to maintain the rated power by using pitch control. This paper presents the control of WT at below rated wind speed by using backstepping sliding mode control (BSMC). In BSMC, generator torque is considered as the control input that depends on the optimal rotor speed. Usually, this optimal rotor speed is derived from effective wind speed. In this paper, effective wind speed is estimated from aerodynamic torque and rotor speed by using the modified Newton Rapshon (MNR) algorithm. Initially, a conventional sliding mode controller (SMC) is applied to the WT, but the performance of the controller was found to be less robust with respect to disturbances. Generally, WT external disturbance is not predictable. To overcome the above drawback, BSMC is proposed and both the controllers are tested with mathematical model and finally validated with the fatigue, aerodynamics, structures, and turbulence (FAST) WT simulator in the presence of disturbances. From the results, it is concluded that the proposed BSMC is more robust than conventional SMC in the presence of disturbances.

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2015

D. Jena and R. Saravanakumar, “A review of estimation of effective wind speed based control of wind turbines”, Renewable and Sustainable Energy Reviews, vol. 43, pp. 1046-1062, 2015.[Abstract]


This paper provides a comprehensive literature review on the estimation of effective wind Speed (EEWS), and EEWS based control techniques applied to wind turbine (WT). Several numbers of good publications have reported the EEWS based control of wind turbine. Wind speed is a driving force for the wind turbine system. In general wind speed measurement is carried out by anemometer which is located at the top of the nacelle. The optimal shaft speed is derived from the exact measurement of wind speed to extract the optimal power output at below rated wind speed. The wind speed provided by the anemometer is measured at a single point of the rotor plane which is not the accurate effective wind speed. At the same time anemometer increases the overall cost, maintenance and reduce the reliability of the overall system. So an accurate EEWS based control technique is required for WT systems to get the optimal power output. In this paper, a detailed description and classification of EEWS and some EEWS based control techniques have been discussed which is based on control strategy and complexity level of WT system. All most all previous work estimates the wind speed using EEWS techniques such as Kalman filter (KF), extended Kalman filter (EKF), neural network (NN) etc., and then different control techniques are applied. In the last section of this paper integral sliding mode control (ISMC) of a WT at below rated speed region is considered. Operating points are determined by proper estimation of effective wind speed, and modified Newton Raphson (MNR) is employed to estimate this. Finally simulation results are presented with a comparison between proposed ISMC, sliding mode control (SMC) and classical controllers such as aerodynamic torque feed forward (ATF) and indirect speed control (ISC).

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2015

R. Saravanakumar and Jena, D., “Validation of an integral sliding mode control for optimal control of a three blade variable speed variable pitch wind turbine”, International Journal of Electrical Power & Energy Systems, vol. 69, pp. 421-429, 2015.[Abstract]


Reduction in cost of wind energy requires most efficient control technology which can able to extract optimum power from the wind. This paper mainly focuses on the control of variable speed variable pitch wind turbine (VSVPWT) for maximization of extracted power at below rated wind speed (region 2) and regulation of extracted power when operating at above rated wind speed (region 3). To extract maximum power at below rated wind speed torque control is used whereas to regulate rated power at above rated wind speed pitch control is used. In this paper a nonlinear control i.e. integral sliding mode control (ISMC) is proposed for region 2 whereas a conventional proportional–integral (PI) control is adapted for region 3 of a VSVPWT. The proposed controller is combined with modified Newton Raphson (MNR) wind speed estimator to estimate the wind speed. The stability of the proposed ISMC is analyzed using Lyapunov stability criterion and the control law is derived for region 2 which is also adapted for the transition period between region 2 and region 3 (region 2.5). The dynamic simulations are tested with nonlinear FAST (Fatigue, Aerodynamics, Structures, and Turbulence) wind turbine (WT). The simulation results of ISMC are presented and the control performance is compared with conventional SMC and existing controllers such as aerodynamic torque feed forward control (ATF) and Indirect speed control (ISC). It is seen that especially in region 2.5, ISMC gives better performance compared to all other controllers.

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2014

D. Jena and R. Saravanakumar, “Adaptive Fuzzy Sliding Mode Control of Variable Speed Wind Turbine for Maximum Power Extraction”, WSEAS Transactions on Power Systems, vol. 9, 2014.[Abstract]


This paper deals with nonlinear control of variable speed wind turbine (VSWT), where the dynamics of the wind turbine (WT) is obtained from single mass model. The main objective of this work is to maximize the energy capture form the wind with reduced oscillation on the drive train. The generator torque is considered as the control input to the WT. In general the conventional control techniques such as Aerodynamic torque feed forward (ATF) and Indirect speed control (ISC) are unable to track the dynamic aspect of the WT. The nonlinear controllers such as nonlinear dynamic state feedback linearization with estimator (NDSFE) and nonlinear static state feedback linearization with estimator (NSSFE) are not robust with respect to model uncertainty and disturbances. To overcome the above drawbacks a Fuzzy Sliding mode controller (FSMC) with the estimation of effective wind speed is proposed. The Modified Newton Raphson (MNR) is used to estimate the effective wind speed from aero dynamic torque and rotor speed. The proposed controller is tested with different wind profiles with the presence of disturbances and model uncertainty. From the results the proposed controller was found to be suitable in maintaining a trade-off between the maximum energy capture and reduced transient on the drive train.

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2014

R. Saravanakumar and Jena, D., “Variable speed wind turbine for maximum power capture using adaptive fuzzy integral sliding mode control”, Journal of Modern Power Systems and Clean Energy, vol. 2, no. 2, pp. 114–125, 2014.[Abstract]


This paper presents a nonlinear control approach to variable speed wind turbine (VSWT) with a wind speed estimator. The dynamics of the wind turbine (WT) is derived from single mass model. In this work, a modified Newton Raphson estimator has been considered for exact estimation of effective wind speed. The main objective of this work is to extract maximum energy from the wind at below rated wind speed while reducing drive train oscillation. In order to achieve the above objectives, VSWT should operate close to the optimal power coefficient. The generator torque is considered as the control input to achieve maximum energy capture. From the literature, it is clear that existing linear and nonlinear control techniques suffer from poor tracking of WT dynamics, increased power loss and complex control law. In addition, they are not robust with respect to input disturbances. In order to overcome the above drawbacks, adaptive fuzzy integral sliding mode control (AFISMC) is proposed for VSWT control. The proposed controller is tested with different types of disturbances and compared with other nonlinear controllers such as sliding mode control and integral sliding mode control. The result shows the better performance of AFISMC and its robustness to input disturbances. In this paper, the discontinuity in integral sliding mode controller is smoothed by using hyperbolic tangent function, and the sliding gain is adapted using a fuzzy technique which makes the controller more robust.

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2014

R. Saravanakumar and Jena, D., “Control of variable speed variable pitch wind turbine at above and below rated wind speed”, Journal of Wind Energy, vol. 2014, 2014.[Abstract]


The paper presents a nonlinear approach to wind turbine (WT) using two-mass model. The main aim of the controller in the WT is to maximize the energy output at varying wind speed. In this work, a combination of linear and nonlinear controllers is adapted to variable speed variable pitch wind turbines (VSVPWT) system. The major operating regions of the WT are below (region 2) and above rated (region 3) wind speed. In these regions, generator torque control (region 2) and pitch control (region 3) are used. The controllers in WT are tested for below and above rated wind speed for step and vertical wind speed profile. The performances of the controllers are analyzed with nonlinear FAST (Fatigue, Aerodynamics, Structures, and Turbulence) WT dynamic simulation. In this paper, two nonlinear controllers, that is, sliding mode control (SMC) and integral sliding mode control (ISMC), have been applied for region 2, whereas for pitch control in region 3 conventional PI control is used. In ISMC, the sliding manifold makes use of an integral action to show effective qualities of control in terms of the control level reduction and sliding mode switching control minimization.

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