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This article presents an improved model-based predictive current control for a surface permanent magnet synchronous generator (SPMSG), where the dynamic response time can be adjusted according to the characteristics of the application and that can operate in the overmodulation region. Moreover, the steady-state errors typically observed in other model predictive controls (MPCs) due to the uncertainties of the system and errors in the parameter values are removed in the proposed MPC. The proposed MPC was tested for the nED100 wind turbine of Norvento in MATLAB/Simulink environment. Besides, it was assessed in an 8.7 kW SPMSG laboratory prototype. The simulation and experimental results indicate that the proposed MPC works properly in an overmodulation region and the desired dynamic response time is achieved whereas the switching frequency is constant. [ABSTRACT FROM AUTHOR]

This paper proposes the design and development of a space vector pulse width modulated v/f controller in FPGA for a three-phase multilevel inverter. The complexity of the modulation scheme and the switching signal generation for motor drives rises with the increase in the number of levels of the inverter. Due to the sequential processing of instructions, microprocessors and digital signal processors are unable to execute short duration pulse width modulated switching signals in real-time, resulting in harmonic distortion. The proposed algorithm is implemented in FPGA to get a dynamic response and to improve the harmonic performance. All of the controller's modules are embedded in a single FPGA and operate in synchronism with a single clock. The controller is validated with a 4-Level inverter, which drives an open-end winding induction motor. Because of algorithm optimization, single clock synchronization, and FPGA parallel processing, the controller has less than 1% total harmonic distortion. There is no need for bulky and costly harmonic reduction filters with this design technique. The proposed scheme shows much better harmonic performance compared to other higherlevel schemes. [ABSTRACT FROM AUTHOR]

A great deal of previous research into wheel alignment has focused on techniques of the alignment, which involve big, bulky and high cost to maintain. Even though several approaches are required, the works are tedious and only performed in spacious area and trained mechanics. IoT is the alternatives due to the evolution of smartphone with numerous sensors to support and assist the research and development for IoT applications in vehicles. In this work, smaller and portable wheel alignment monitoring system is introduced by using communication protocol between sensors, microcontroller and mobile phone application. Thus, graphical user interface (GUI) is utilized to the system via wireless communication technology using TCP/IP Communication Protocol. The system has been tested to suit the functioning architecture system for the wheel alignment to provide the user awareness on early detection of wheel misalignment. In addition, the application has been successfully integrated with Android mobile application via TCP/IP communication protocol and view the results in smart phone in real-time. [ABSTRACT FROM AUTHOR]

This article presents a novel model predictive voltage control (MP VC) for a doubly fed induction generator (DFIG) without a speed sensor. The methodology of the considered MP VC is articulated on the direct voltage control by incorporating the deadbeat control principle within the model predictive topology. The derivation of the utilized cost function is accomplished in organized steps. The finite control set (FCS) principle is adopted to avoid the utilization of the pulsewidth modulation (PWM), which contributes to simplifying the system configuration. For estimating the rotor position, a robust estimator is proposed to achieve precise tracking of the rotor alignment, and thus, a perfect co-ordinates transformation can be achieved. To visualize the significance of the intended MP VC in regard to the classic model predictive techniques, accurate analysis of the DFIG dynamics under the proposed MP VC and model predictive direct torque control (MP DTC) is presented. The test results approve and reveal the predomination of the presented MP VC over the MP DTC. Furthermore, the effectiveness of the proposed sensorless scheme is verified for different ranges of speed operation. [ABSTRACT FROM AUTHOR]

Traditional model predictive control has difficulty in achieving satisfactory control performance when parameter identification is inaccurate or when a parameter changes. To solve this problem, this article proposed a new model-free predictive current control (MFPCC) scheme for a doubly fed induction generator (DFIG), which combines an ultra-local model with predictive current control (PCC). This method replaces the mathematical model of a DFIG with an ultra-local model and has strong parameter robustness. In addition, this method is suitable for the synchronization and power regulation processes of a DFIG, and it is also easy to apply to a DFIG with uncertain parameters. The proposed method is compared to traditional model-based deadbeat control with space vector modulation (SVM), and the presented experimental results confirm its superiority and effectiveness. [ABSTRACT FROM AUTHOR]

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The introduction of virtual-synchronous machine and generator as well as synchronous inverter (synchronverter), in recent years, has facilitated the integration of inverter-interfaced distributed energy resources (IIDERs) into the synchronous generator (SG) dominant microgrids and power grid. In this concept, the voltage source inverter (VSI) is controlled in such a way that it mimics the behavior of SG. To provide a reliable utilization of the IIDERs, a seamless transition of the VSIs between islanded and grid-connected operation modes is required. This paper integrates a novel virtual torque and virtual flux linkage-based synchronizing technique into the synchronverter controller to provide a plug ‘n’ play capability of the VSIs and their smooth transition between these two operating modes. Comprehensive mathematical modeling, design, and dynamic stability analysis as well as dSPACE-based real-time simulation are provided to validate the effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

The Brushless Doubly-Fed induction Generator (BDFG) has a commercial potential for wind power generation, due to its low maintenance cost. For simplicity, the Cascaded Brushless Doubly Fed induction Generator (CBDFG) topology is usually applied as a model for BDFG. The BDFG-based wind turbines must be synchronized and connected to the grid, without inrush current. This paper purposes an improved Direct Torque Control (DTC) method for smooth synchronization of BDFG. Since BDFG has a complicated model, due to the resistance and voltage source in its rotor loop, finding proper references for smooth synchronization is difficult. To overcome this difficulty, a new model for BDFG is proposed. Appropriate flux and torque references for the DTC scheme are proposed based on this model, in order to achieve grid synchronization without inrush current. A 2-MW BDFG is simulated to show the efficiency and accuracy of this proposed method. The experimental results of a 3-kW laboratory scale BDFG confirm the efficiency of this proposed method. [ABSTRACT FROM PUBLISHER]

The conventional direct torque control (DTC), based on the hysteresis controllers and the switching table, operates with a variable switching frequency, which decreases the conventional DTC performances, like the torque and flux ripples. Thus, the space vector modulation (SVM), used in the DTC, ensures a constant switching frequency and improves the DTC performances. The first aim of this paper is to present a comparison study between the DTC with an SVM (DTC-SVM) based on the Proportional Integral regulators (DTC-SVM-PI) and the DTC-SVM based on the sliding mode controllers (DTC-SVM-SMC). These two approaches are complex control algorithms which require faster micro-controllers; therefore the second objective of this paper is to present the implementation of the DTC-SVM-PI and the DTC-SVM-SMC on the Field Programmable Gate Array (FPGA), due to the parallel processing capability of the FPGAs. The two approaches are designed and simulated using the Xilinx System Generator (XSG) and implemented using an FPGA Virtex 5. The simulation results in the transient behavior and the steady state of the induction motor controlled by these two approaches are compared and discussed. The hardware FPGA implementation results show the effectiveness of the FPGA relative to the digital signal processor in terms of execution time. [ABSTRACT FROM AUTHOR]

For the doubly fed induction generator (DFIG)-based wind energy conversion system, the decaying flux and negative flux are the main reasons to cause the DFIG rotor overcurrent, during grid faults. The stator decaying flux characteristics versus the depth and instant of the stator voltage variation are analyzed first. On the basis of the stator flux performances, the enhanced control strategy is proposed to limit the decaying flux approximately into zero in half fundamental period by changing the stator voltage drop and recovery mode, and consequently the rotor transient current pulse is significantly reduced during grid faults. The experimental results based on the 7.5 kW DFIG setup are carried to validate the correctness and feasibility of the proposed strategy. Dynamic voltage restorer (DVR) can be one of the applications. With the proposed strategy, the DVR only works in a half fundamental period and its output voltage amplitude is half of the stator voltage variation, during the grid voltage drop and recovery, respectively. As a consequence, the DVR can be rated for lower power saving cost. The simulation results based on MATLAB/Simulink using a 2 MW DFIG and the experimental results based on the 7.5 kW DFIG validate the effectiveness and feasibility of the DVR-based low-voltage ride through strategy. [ABSTRACT FROM PUBLISHER]

This paper proposes a new control strategy of doubly fed induction generators (DFIGs) under unbalanced grid voltage conditions. The proposed controller includes a model predictive direct power control (MPDPC) method and a power compensation scheme. In MPDPC, the appropriate voltage vector is selected according to an optimization cost function, hence the instantaneous active and reactive powers are regulated directly in the stator stationary reference frame without the requirement of coordinate transformation, PI regulators, switching table, or PWM modulators. In addition, the behavior of the DFIG under unbalanced grid voltage is investigated. Next, a power compensation scheme without the need of extracting negative stator current sequence is developed. By combining the proposed MPDPC strategy and the power compensation scheme, distorted currents injected into the power grid by the DFIGs can be eliminated effectively. [ABSTRACT FROM PUBLISHER]

Cascaded brushless doubly fed induction machines have attracted much attention because of the elimination of slip rings and brushes. However, only limited works have been reported on the control strategies due to the complex machine modeling. Further developments of these kinds of machines are still under investigation, especially for wind energy applications. This paper proposes a new control strategy for cascaded brushless doubly fed induction generators (CBDFIGs) based on direct power control. The effects of voltage vectors on the output active and reactive powers are first investigated. A vector selection strategy is then proposed to achieve flexible power regulation. In addition, the behaviors of the CBDFIG under unbalanced grid voltage conditions are studied and a power compensation scheme is developed to improve the power quality. The effectiveness of the proposed control strategy is validated experimentally on a laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper presents an easy and a robust sensor fault detection and isolation (FDI) and fault tolerant control (FTC) of a single phase PWM rectifier for electrical railway traction application. Catenary current sensor and dc link voltage sensor failures are considered. The FDI method is based on observers and residual generation. The different FDI algorithm steps allow a good detection and isolation of the sensor fault and identify the faulty sensor. The reconfiguration strategy consists of two steps with open loop control and closed loop control working. Simulation results are presented to illustrate the good performance of the FTC procedure. Experimental results are also presented to show the effectiveness of the proposed FDI and FTC algorithms and good performances of the rectifier after the reconfiguration. [ABSTRACT FROM AUTHOR]

This paper presents modeling and simulation of Field Programmable Gate Array (FPGA) based Direct Torque Control (DTC) of Induction Motor Drive fed by Space Vector Modulation (SVM) based Voltage Source Inverter (VSI) which allows precise and quick control of induction motor without calling for complex control algorithms. Also this technique is found to yield low steady state torque ripples and current distortions. At the same time the technique retains fast transient response, associated with DTC. FPGA is chosen due to its fast proto typing, simple hardware and software design and provides reduction in execution time. [ABSTRACT FROM AUTHOR]

This paper presents the concept of dynamic reconfiguration between two sliding mode current controllers for synchronous motor drives. The first one is a Direct Sliding Mode (DSM) current controller, which is based on a switching table synthesized via sliding mode theory. The second one is an Indirect Sliding Mode (ISM) current controller that computes a reference voltage vector via sliding mode theory. The computed reference voltage is then applied to the terminals of the synchronous machine through a Pulse Width Modulation (PWM) process. This item studies and discusses the reconfiguration criteria and presents the main interest of using FPGA digital solutions for dynamic reconfiguration process implementation between the two sliding mode current controllers. Numerous experimental results are presented in order to confirm the interest and performances of the proposed reconfigurable sliding mode current controller. [ABSTRACT FROM PUBLISHER]

This paper presents the stability-improvement results of a synchronous generator (SG)-based one-machine infinite-bus system with a permanent-magnet SG (PMSG)-based offshore wind farm (OWF) and a doubly fed induction generator (DFIG)-based OWF using a static VAR compensator (SVC). The operating characteristics of the studied two OWFs are simulated by an equivalent aggregated PMSG driven by an equivalent wind turbine (WT) and an equivalent aggregated DFIG driven by an equivalent WT through an equivalent gearbox, respectively. A damping controller of the SVC is designed by using adaptive-network-based fuzzy inference system (ANFIS) to contribute adequate damping characteristics to the dominant modes of the studied SG under various operating conditions. A frequency-domain approach based on a linearized system model using root-loci technique and a time-domain scheme based on a nonlinear system model subject to various disturbances are both utilized to examine the effectiveness of the proposed control scheme. It can be concluded from the simulation results that the proposed SVC joined with the ANFIS damping controller is capable of improving the stability of the studied SG system subject to different disturbances. [ABSTRACT FROM PUBLISHER]

Predictive direct torque control of the electric motors has been well developed. It is simple and has excellent steady state and transient performance. However, further developments are still under investigation for applications in the field of power generation. This paper presents a predictive direct virtual torque and power control strategy for a doubly fed induction generator, which allows fast and smooth grid synchronization, and flexible active and reactive power regulation. In the no-load mode, predictive direct virtual torque control is employed to meet the grid synchronization conditions. In the grid-connected mode, predictive direct power control is utilized to achieve flexible active and reactive power regulation. To simplify the control system structure and improve the reliability, a sensorless rotor position scheme is proposed. Furthermore, a model-based predictive scheme is introduced to compensate for a one-step delay in the digital implementation. The proposed control strategy is very simple and robust. There is constant switching frequency, while the requirement of smooth and fast grid synchronization is fulfilled. The transition from no load to flexible power regulation is achieved without changing the switching table. The proposed control strategy was tested by simulation using MATLAB/Simulink and experimentally validated on a 20-kW laboratory prototype. [ABSTRACT FROM PUBLISHER]

This paper proposes a configuration of wind turbine using a doubly fed induction generator (DFIG) in single-sided grid connection. The stator of the machine is connected with a direct power grid, and the rotor is controlled by an inverter without any external power source. This is called a single external feeding of DFIG (SEF-DFIG). The conventional DFIG uses an additional grid power converter to regulate the rotor power; but in SEF-DFIG, the external source of a grid power is only connected to the stator windings. Due to this feature, the rotor-side inverter can be integrated on the rotor without any slip ring. In this paper, for applying the proposed scheme to the wind turbine, the performances of the generating operation are analyzed. The experimental results of a 2.4-kW DFIM system are presented to prove the feasibility of the proposed system and method. [ABSTRACT FROM PUBLISHER]

In this paper, we present a design method of Direct Torque Control based on hardware description language and FPGA implementation. The DTC, which is used to control induction machines, is designed through the description of Concordia transformation, torque and stator flux estimator, torque and stator flux comparator, stator flux position detector, switching table and Finite State Machine (FSM). The same algorithm is designed and simulated using MATLAB software tool to make a comparison with the proposed design on FPGA. Experimental test results of this drive control structure realized in FPGA are demonstrated. [ABSTRACT FROM AUTHOR]

The aim of this paper is to quantify the interest of using hardware field-programmable gate arrays (FPGAs) to implement complex control algorithms. As a benchmark, authors have chosen a sensorless speed controller for a synchronous motor. The estimation of the rotor position and speed is achieved using an extended Kalman filter (EKF), eliminating the need of their corresponding mechanical sensors. Due to the EKF complexity, such sensorless controller is systematically implemented in a software digital signal processor (DSP) device. The execution time is frequently evaluated to several tens or hundreds of microseconds. The motivation here is to prove that, when exploiting the treatment fastness of FPGAs (less than 6 \mu\s), it is possible to enhance the control bandwidth. To reach this objective, a comparison between the developed FPGA-based sensorless speed controller and its DSP-based counterpart is made. The same sensorless controller (with the same complexity) has been implemented in both cases. To prop up this comparison, simulation, hardware-in-the-loop, and experimental tests are presented. [ABSTRACT FROM PUBLISHER]

A recently proposed shaft position sensorless method for torque and reactive power control of the brushless doubly fed reluctance machine has proven successful in simulation studies. In this paper, its real-time performance has been evaluated on a custom-designed machine prototype. The preliminary experimental results have confirmed the viability of the scheme and represent a serious step toward the development of a generic virtually parameter independent controller for doubly excited machines. A wide range of applications is possible, including drive and generator systems with limited speed ranges (e.g., large pumps and wind turbines), where the cost savings of using a partially rated power electronic converter are significant. [ABSTRACT FROM PUBLISHER]

This paper describes the harmonic spectra of the cogging torque of a magnetic gear. The operating principle of this gear is described, and the transmission torque under operation in accordance with the gear ratio is mathematically formulated. In particular, the harmonic order of the cogging torque is described in detail. Moreover, the orders of the cogging torque of both rotors are verified by employing 3-D finite element method. The computed results are also then further verified by carrying out measurements on a prototype. Other harmonic components are observed in the computed and measured results, but it is discussed why they are contained in the cogging torque. [ABSTRACT FROM PUBLISHER]

This paper deals with the adaptive tuning of the stator inductance in a rotor-current-based Model Reference Adaptive System observer for the sensorless control of doubly fed induction machines. At first, the effect of mismatched parameters in this observer is discussed in order to show the considerable influence of the stator inductance on the accuracy of the estimated rotor position. Then, an adaptive tuning of the stator inductance is proposed and a small signal model is deduced in order to design the tuning loop. Moreover, a theoretical sensitivity and stability analysis is performed. Finally, the performances of the proposed scheme are experimentally investigated and validated. [ABSTRACT FROM AUTHOR]

This paper presents a control strategy for a doubly fed induction generator (DFIG) using an indirect matrix converter, which consists of an input side matrix converter and an output side voltage source converter (VSC). The capability of the input converter to generate different “virtual dc link” voltage levels is exploited. The commutation of the VSI with reduced voltage is illustrated for operating points where the output voltage demand is low without any deterioration of the current control performance. The proposed method leads to a reduction in the commutation losses in the output converter and reduced common-mode voltage. For the input converter, soft switching commutation is obtained by synchronizing the input and output converter pulsewidth-modulation patterns. This modulation strategy is particularly applicable in DFIG applications because the required rotor voltage decreases when the DFIG speed is close to the synchronous speed. The complete control strategy is experimentally validated using a 2-kW rig. [ABSTRACT FROM AUTHOR]

This paper proposes a new robust controller in a stationary reference frame for doubly fed induction generators (DFIGs) of grid-connected wind turbines. Initially, a DFIG dynamic model is derived from the voltage and flux equations in \alpha\beta coordinates, where uncertainties and disturbances intrinsic to the system are accounted for as perturbation terms are added to the nominal model. Then, a controller design procedure that guarantees the DFIG stability under uncertainties and disturbances at the grid side is presented in detail. It is demonstrated that a very fast dynamic behavior can be obtained with the proposed controller, which improves the transient response of the grid-connected DFIG, particularly under conditions of unbalanced voltage dips resulting from asymmetrical network faults. In order to conform with the fault ride-through capability requirements, this paper proposes a new reference strategy, which is divided into normal and fault operation modes. Experimental results are given to support the theoretical analysis and to illustrate the performance of the grid-connected DFIG with the proposed controller. [ABSTRACT FROM AUTHOR]

The increasing use of distributed power-generation systems, as with the case of wave-power-generation plants, requires a reliable fault-ride-through capability. The effects of grid fault include uncontrolled turbogenerator acceleration, dangerous rotor peak currents, and high reactive-power consumption so that the plant may contribute to the voltage dip. A simple solution is automatic disconnection from the grid, but this policy could lead to a massive power-network failure. This is why new Grid Codes oblige these systems to remain connected to the grid. In this paper, an oscillating-water-column-based wave-power-generation plant equipped with a doubly fed induction generator is modeled and controlled to overcome balanced grid faults. The improvement relies on the implementation of a control scheme that suitably coordinates the airflow control, the active crowbar, and the rotor- and grid-side converters to allow the plant to remain in service during grid fault, contributing to its attenuation by supplying reactive power to the network and complying with new Grid Code requirements. The simulated results show that it obtains a great reduction of the rotor currents, improving the transients and avoiding rotor acceleration. Similar results are obtained from the experimental implementation. [ABSTRACT FROM AUTHOR]