Improved control for DFIG based wind power system under voltage dips using ADRC optimized by genetic algorithms

Many countries have focused on the study of the electrical energy production using wind generators. These studies include maintaining the production under disturbed conditions at the grid connection point of wind farms, and maintaining production during voltage dips. Electrical grid operators have established different requirements for connecting renewable energy production systems to electrical grids. In this research paper, we are interested in the study of the wind power system based on the Doubly Fed Induction Generator during a voltage dip. We are also developing a control approach based on Active Disturbance Rejection Control and Genetic Algorithms, which aims to control the stator flux variations which should be taken into account during the current controllers computing. This control strategy will allow the wind power system to remain connected to the grid under voltage dips, and to resume the normal operation after the fault disappearance. The model of the wind power system and the proposed control strategy, are tested in the MATLAB-Simulink software

Comparative study of power smoothing techniques produced by a wind energy conversion system

This paper aims to present and compare two techniques used to smooth the injected power in the grid from a doubly-fed induction generator (DFIG) based conversion system. The first technique based on an inertial storage system while the second is founded on limiting the power captured by the wind turbine. The overall system composed of a wind energy conversion system (WECS) allowing to convert a wind power into electric power. It is controlled by two converters, grid side converter and a rotor side converter, both are controlled by sliding mode. The storage system is used to consume power which exceeds the setpoint due to storing it or producing more in the event of a lack, the system is controlled through the flywheel side converter by the sliding mode. Numerical simulations were carried out using Matlab/Simulink software

Advanced Dispatching of a Wind Farm Based on Doubly Fed Induction Generators for the Improvement of LVRT Capability by the ADRC Approach

This paper aims to explore a viable monitoring and management of active and reactive powers for a large-scale wind farm based on Doubly- Fed Induction Generators (DFIG) considering the volt- age Fault-Ride-Through capability (FRT), especially Low-Voltage-Ride-Through (LVRT) capability by using a new control strategy, known as Active Disturbance Rejection Control. This strategy uses real-time estima- tion and compensation of the generalized "total" dis- turbance before it affects the system. The wind farm supervisory unit is used to coordinate the control of the powers production by the entire wind farm, which must take into account the couplings between each wind gen- erator while producing the individual power commands. The turbine control units (local supervisory units) send the appropriate power references depending on the sit- uation. This can be to produce the maximum power, to manage the active and reactive power given by the Transmission System Operator (TSO) or to meet the requirements of the grid code (LVRT capacity). How- ever, to ensure the dispatching of the references of the active and reactive powers over the all wind generators of the wind farm and to satisfy the security of the power grid, we utilized mean of the proportional distribution algorithm. The effectiveness of the proposed supervisory approach and control strategies are tested and vali- dated through a multiples scenarios of simulations that are made under the MATLAB/Simulink Environment. The results obtained have demonstrated the efficiency and robustness of the control methods, and also the fact that they guarantee good performance and safety of the integration of wind farms into the grid while complying with the requirements of the grid code during power system faults

Contribution of magnetic resonance imaging in the diagnosis of talus skip metastases of Ewing's sarcoma of the calcaneus in a child: a case report

<p>Abstract</p> <p>Introduction</p> <p>Ewing's sarcoma of the calcaneus is rare. About thirty cases with calcaneus involvement have been reported in the literature. Talus skip metastases have rarely been described in the available literature</p> <p>Case presentation</p> <p>We report a case of a 14-year-old Moroccan boy, who presented with Ewing's sarcoma of his right calcaneus, diagnosed by swelling of the calcaneus evolving over a year. Radiography, computed tomography and magnetic resonance imaging showed an important tumoral process of the calcaneus and talus skip metastases. The diagnosis was confirmed with histology after a biopsy. In spite of amputation and postoperative chemotherapy, our patient died six months later due to secondary respiratory distress after lung metastasis.</p> <p>Conclusion</p> <p>Imaging, especially magnetic resonance, is important in the diagnosis of Ewing sarcoma and skeletal skip metastases. Treatment of Ewing's sarcoma consists of chemotherapy, radiation therapy and surgical resection depending on the stage and extent of the disease. With the exception of lesions in the calcaneus, the prognosis for disease-free survival of Ewing's sarcoma of the foot is excellent.</p

Coordinated Control Using Backstepping of DFIG-Based Wind Turbine for Frequency Regulation in High Wind Energy Penetrated System

The expansion of renewable generation has raised some red flags in terms of power system stability, control, and management. For instance, unlike traditional synchronous energy sources, the doubly-fed induction generator- (DFIG-) based wind turbines (WTs) do not instinctively act against frequency deviations. In fact, the power electronics interfacing the generator, merely controlled to warrant maximum wind power conversion, make its output power and mechanical speed immune to the characteristics of the electric network frequency. Moreover, significant wind power penetration (WPP) promotes the retirement of many traditional generation groups, consequently curtailing the power system corresponding inertia and displacing the primary reserves that are essential to retain the frequency within an acceptable range of variation. This paper explores different control approaches, using backstepping, allowing DFIG-based WTs to engage actively in frequency regulation using a coordinated control of the rotor speed and pitch angle to regulate the system during both partial- and full-load operation modes. The first method momentarily discharges part of the kinetic energy stored in the WT spinning masses, and the second method follows a deloaded operation characteristic, so as to keep a specific power reserve that can be automatically activated at the events of frequency excursions. A study case considering an isolated power system that consists of synchronous generators, DFIG-based wind farm, static load, and a sudden frequency disturbance was performed. The simulation result in a Matlab/Simulink environment highlights the robustness and capability of the coordinated control scheme to furnish, under variant operation conditions, active power aid, consequently lifting the frequency nadir up to a superior level than that obtained with 0% wind power penetration in the system

Robust Multiobjective Model Predictive Control with Computation Delay Compensation for Electric Vehicle Applications Using PMSM with Multilevel Inverter

The Three-Level Neutral-Point-Clamped (3L-NPC) inverter fed Permanent Magnet Synchronous Motor (PMSM) drive is an attractive configuration for high performance Electric Vehicle (EV) applications. For such configuration, due to their high performances, the Finite-Control-Set Model Predictive Control (FCS-MPC) is a very attractive control solution. The FCS-MPC scheme is based on the prediction of the future behavior of the controlled variables using the dynamic model of PMSM and the discrete nature of the 3L-NPC inverter. However, the parametric uncertainties and time-varying parameters affect the FCS-MPC algorithm performances. In this paper, robust FCS-MPC controls based on “dynamic error correction” (DEC) and “modified revised prediction” (MRP) are proposed to improve the FCS-MPC robustness without affecting the controller performances and complexity. The proposed strategies are improved also by multiobjective (MO) algorithm optimization and computation delay compensation. The simulation results included prove the performance in robustness and efficiency of the proposed robust FCS-MPC-DEC

Comparative Analysis between PI and Linear-ADRC Control of a Grid Connected Variable Speed Wind Energy Conversion System Based on a Squirrel Cage Induction Generator

This paper aims at contributing to the modeling and control of a variable speed Wind Energy Conversion System (WEC-System) based on a Squirrel Cage Induction Generator (SCI-Generator). The connection between the SCI-Generator and the main utility grid is achieved by back-to-back three phase power converters (Generator and Grid Side Converters). A new control strategy named the Active Disturbance Rejection Control (ADRC) is proposed and utilized to control the Wind Energy Conversion (WEC) system based on the SCI-Generator. The objective is to control both the generator and the grid side converters in order to operate the system and to ensure the connection with the power grid. The first converter is used to control the SCI-Generator speed and field to extract the available maximum power from the wind turbine by using a Maximum Power Point Tracking (MPPT) technique and, also, to ensure that the extracted power does not exceed its rated value in case of strong wind speeds; in this case a pitch actuator system is used to control the blades pitch angle of the wind turbine. The second converter is used to control the active and reactive powers injected into the utility grid as well as to regulate the DC-Link Voltage. This control takes into account the rejection of internal disturbances as the variation of electrical parameters (the resistance, the inductance…) and the external disturbances as voltage dips and frequency droops in the main grid. To test and validate the performances of the proposed controller, a series of simulations were developed under MATLAB/Simulink environment, and the results have demonstrated the effectiveness of the proposed control under different case of simulations

High order sliding mode control of active and reactive powers for DFIG based Wind turbine

Grid connected wind turbines are considered as a wise alternative to conventional energy sources; not only they are used to produce energy, but they have been recently operated in order to provide grid ancillary services such as stability and frequency control. In this paper we are going to deal with the famous doubly fed induction generator (DFIG) based Wind Energy Conversion Systems (WECS) for its variable speed operation and excellent power quality. The purpose of this study is to apply a High Order Sliding Mode Control (HOSMC) based on vector control and to compare the results with the first order sliding mode control (FOSMC) in order to evaluate the performances of stability and chattering elimination under normal conditions. Simulation results show the superiority of the SOSMC over the FOSMC in terms of robustness and chattering elimination

Novel Predictive Control for the IPMSM Fed by the 3L-SNPC Inverter for EVAs: Modified Lyapunov Function, Computational Efficiency, and Delay Compensation

This paper proposes a novel predictive strategy based on a model predictive control (MPC) for the interior permanent magnet synchronous motors (IPMSMs) driven by a three-level simplified neutral-point clamped inverter (3L-SNPC) for electric vehicle applications (EVAs). Based on the prediction of the future behavior of the controlled variables, a predefined multiobjective cost function incorporates the control objectives which are evaluated for every sampling period to generate the optimal switching state applied directly to the inverter without the modulation stage. The control objectives in this paper are tracking current capacity, neutral-point voltage balancing, common-mode voltage control, and switching frequency reduction. The principal concepts of the novel scheme are summarized as follows: first, the delay compensation based on the long horizon of prediction is adopted by a multilevel power converter structure. Second, based on the modified Lyapunov candidate function, both stability and recursive feasibility are ensured of the proposed predictive scheme. Third, the practicability of the real-time implementation is improved by the proposed “static voltage vector” (SVV) and “single state variation” (SSV) principles. Finally, the proposed concepts are implemented in the novel predictive control formulation as additional constraints without compromising the complexity and the good performances of the predictive controller. Therefore, only the switching states that guarantee the stability and the reduction of calculation burden criteria are considered in the evaluation of cost function. The proposed predictive scheme based on the “SVV” principle has demonstrated superior performance in simulation compared with the proposed scheme with the “SSV” principle. The computational burden and switching frequency rates are reduced by 35% and 56.22%, respectively