Control Of Doubly Fed Induction Generator Research Articles

Double Fed Induction Generator Control Design Based on a Fuzzy Logic Controller for an Oscillating Water Column System

Oscillating water column (OWC) systems are water power generation plants that transform wave kinetic energy into electrical energy by a surrounded air column in a chamber that changes its pressure through the waves motion. The chamber pressure output spins a Wells turbine that is linked to a doubly fed induction generator (DFIG), flexible devices that adjust the turbine speed to increase the efficiency. However, there are different nonlinearities associated with these systems such as weather conditions, uncertainties, and turbine stalling phenomenon. In this research, a fuzzy logic controller (FLC) combined with an airflow reference generator (ARG) was designed and validated in a simulation environment to display the efficiency enhancement of an OWC system by the regulation of the turbine speed. Results show that the proposed framework not only increased the system output power, but the stalling is also avoided under different pressure profiles.

Fractional Order Controller based Maximum Power Point Tracking Controller for Wind Turbine System

The wound rotor type Doubly Fed Induction Generator (DFIG) based adjustable velocity wind generator system is the most promising wind turbine system in the wind industry. A fractional-order proportional-integral-derivative (FOPID) based modified Incremental Conductance (INC) maximum power point tracking (MPPT) controller is proposed for DFIG based wind turbine (WT) system. The simulation of the proposed MPPT controller for DFIG based wind turbine system has been carried out in MATLABTM/SIMULINK with buck converter and resistive load for varying wind speed conditions. The FOMCON toolbox with the Nedler-Mead optimization algorithm is used to design an optimized Fractional order controller. Simulation results of the suggested controller are compared with conventional Perturb and Observe (P&O), INC, INC with integral action (INC-Integral) MPPT methods. The simulation results show that the proposed INC-FOPID MPP tracking controller is more efficient and produces more output power as compared to other MPPT techniques.

Fixed switching frequency scheme for current predictive control of DFIG

This paper suggests a new current predictive control algorithm for the wind-driven doubly-fed induction generator (DFIG) based on space vector modulation (SVM) with fixed switching frequency. Combining the current predictive controller and SVM has the benefits of a predictive controller, and fixing the switching frequency improves the output waveform quality. However, if classical predictive control is used, the computational burden will still be high. The proposed algorithm uses SVM to fix the switching frequency of the rotor side converter. Additionally, by using an incremental algorithm, the proposed technique prevents examining all inputs over the prediction horizon. As a result, in the proposed current predictive algorithm the computational time is significantly reduced. The detailed state-space model of DFIG and rotor side converter are used to execute the predictive algorithm. The proposed algorithm uses the rotor current to predict the next behavior of the DFIG, and then, by using SVM, the duty cycles of 2-level voltage source inverter are obtained. Finally, the proposed controller's responses are compared to those of the SVM-based field-oriented control strategy. Simulation results of the proposed controller on a two-level voltage source inverter under a balanced three-phase power system illustrate the satisfactory active and reactive power tracking and improved quality of the inverter outputs.

Performance analysis and enhancement of direct power control of DFIG based wind system

<span lang="EN-US">The paper proposes a complete modeling and control technique of variable speed wind turbine system (WTS) based on the doubly fed induction generator (DFIG). Two levels back-to-back converter is used to ensure the energy transfer between the DFIG rotor and the grid. The wind turbine to operate efficiently, a maximum power point tracking (MPPT) algorithm is implemented. Then, direct power control (DPC) strategy has been combined with the MPPT technique in order to guarantee the selection of the appropriate rotor voltage vectors and to minimize the active and reactive power errors. Finally, the simulation is performed by using MATLAB/simulink platform basing on 7.5KW DFIG wind generation system, and the results prove the effectiveness of our proposed control technique.</span>

Nonlinear rotor side converter control of DFIG based wind energy system

The present study proposes an alternative approach following command-filtered integral backstepping principle to control the rotor side converter (RSC) of a doubly-fed induction generator (DFIG) based wind energy conversion system (WECS). This controller provides better benefit compared to the classical backstepping controller; since the errors introduced by the input signal differentiation is eliminated. This controller essentially stabilises the rotor speed by controlling the electromagnetic torque. The global stability of the overall closed loop system is established using Lyapunov criteria. Moreover, the parameters of the controller are optimally selected using comprehensive learning particle swarm optimisation (CLPSO) technique. The performance of the controller is compared with two other controllers, which include a classical proportional integral derivative (PID) and ΔΣ–based PID. The results of comparative investigation demonstrate that the proposed command-filtered integral backstepping controller is superior and could effectively control the RSC under various fault conditions.

Analysis of SSO in DFIG grid with series compensation

Doubly fed induction generator (DFIG) has become the most widely used type of wind power generation due to its superior technical performance. Series compensation technology is widely used in large-scale and long-distance wind power transmission system because of its high cost performance and significant improvement of transmission capacity. However, it may cause subsynchronous oscillation (SSO). This paper first introduces the definition and harm of subsynchronous oscillation, and then analyzes the advantages and disadvantages of series compensation technology, as well as the mechanism and suppression measures of subsynchronous oscillation of DFIG connected system through series compensation. Through modeling and simulation analysis, the suppression effect of additional subsynchronous damping controller (SSDC) on subsynchronous oscillation of DFIG control system is verified.

Event triggered prescribed time convergence sliding mode control of DFIG with disturbance rejection capability

This paper proposes an event triggered sliding mode control method for direct power control (DPC) of doubly fed induction generator (DFIG). Conventional control approaches require the execution units to constantly update the control signal from the computing devices, which is unnecessary and requires extra communication and execution efforts for the control system. The event triggered control is able to determine the optimal time nodes to update the executed control signal with the event triggering condition. The event triggered mechanism is utilized in sliding mode control and the proposed method is employed for DPC of DFIG. Meanwhile, the prescribed time convergence principle is adopted for parameter selection of the controller. Subsequently, an extended state observer is designed to provide disturbance rejection capability for the DFIG. The Laypunov function method is employed to prove the convergence and stability of the system. Simulations and experimental studies are conducted to validate the performance of the proposed method. The experimental results indicate that the proposed method has superior performance in tracking precision, robustness against parametric disturbance and resource saving.

A Fast High-Precision Model of the Doubly-Fed Pumped Storage Unit

With an increase of renewable energy permeability in power grids, doubly-fed pumped storage units with excellent regulation performance have become a popular research topic. Current models of the doubly-fed pumped storage unit are mostly used in the study of electromagnetic transients while the generator model is complex and the pump-turbine system model is simple, which is not conducive to the research on electromechanical transients and pump-turbine control systems. To overcome this problem, a novel fast high-precision model of the doubly-fed pumped storage unit is proposed in this paper. First, a novel efficiency optimization method is proposed, and a high-precision variable speed control model of the pump-turbine is established according to the pump-turbine’s complete characteristic curves of. A doubly-fed induction generator (DFIG) control model is then used to construct a detailed model of the doubly-fed pumped storage unit. The DFIG control model is analyzed and simplified, and a fast high-precision model of a doubly-fed pumped storage unit is obtained. Finally, this fast high-precision model is verified in the turbine and pump modes. The results indicate that compared with the detailed model, the proposed fast high-precision model can better describe the characteristics of a variable speed unit. The new model is simple, has high accuracy and its simulation step (10−2 s) is larger than that of the detailed model (5 × 10−6 s), which makes the simulation speed improved effectively.

Enhanced Compensation Filter to Mitigate Subsynchronous Oscillations in Series-Compensated DFIG-Based Wind Farms

This paper presents a control strategy to mitigate subsynchronous oscillations (SSOs) in doubly-fed induction generator (DFIG)-based wind farms integrated into series-compensated transmission systems. The strategy has two parts: in the first one, a compensation filter based on the motion-induction amplification concept is proposed to increase the damping of the DFIG machine in the subsynchronous frequency range; in the second one, a proportional-integral (PI)-like controller is designed using an optimal quadratic technique to minimize the control effort and the additional rotor voltage required by the SSO damping action. The SSO mitigation strategy acts locally on the DFIG control system reducing the negative resistance the rotating machine presents to the grid at subsynchronous frequencies; this approach reduces the control dependence on the topology and resonance frequencies of the network. The control strategy is validated with a case study based on the Argentinian power system and evaluated in a wide range of operating conditions, showing that the DFIG control system can be enhanced to mitigate poorly damped SSOs and increase the penetration level of wind power in the system.

Disturbance-Observer-Based Control of DFIG in Island Mode for Microgrid Applications

This paper introduces a novel control approach for Doubly-Fed Induction Generator (DFIG) operating in island mode based on the cascaded control structure with disturbance estimation. The control of the DFIG is a challenging task due to its inherent nonlinearity, fast dynamics, and unpredictable disturbances acting on the system. The proposed control structure involves a nominal controller for plant and disturbance observer (DOB) in each of the inner and outer control loop. The first-order disturbance observers are designed to estimate the time-varying and unknown disturbances. With disturbance estimation, the nominal linear dynamics is obtained in both loops. This enables the same approach for designing controllers for the inner and outer loop which significantly simplifies implementation. The controllers are designed based on the demanded error dynamics and ensure stable operation of the system, while proposed DOBs estimate disturbances including external load. Finally, the effectiveness and quality of the proposed control structure were verified through numerical simulations in terms of external disturbances rejection and closed-loop tracking performance.

Active and Reactive Powers Control of DFIG Based WECS Using PI Controller and Artificial Neural Network Based Controller

The purpose of this study is to improve the control performance of a Doubly Fed Induction Generator (DFIG) in a Wind Energy Conversion System (WECS) by using both of the conventional Proportional-Integral (PI) controllers and an Artificial Neural Network (ANN) based controllers. The rotor-side converter (RSC) voltages are controlled using a stator flux oriented control (FOC) to achieve an independent control of the active and reactive powers, exchanged between the stator of the DFIG and the power grid. Afterward, the PI controllers of the FOC are replaced with two ANN based controllers. A Maximum Power Point Tracking (MPPT) control strategy is necessary in order to extract the maximum power from the of wind energy system. A simulation model was carried out in MATLAB environment under different scenarios. The obtained results demonstrate the efficiency of the proposed ANN control strategy.

Impact of active power recovery rate of DFIG wind farms on first swing rotor angle stability

The first swing rotor angle stability is still an important stability challenge for modern power systems integrated with a large number of renewable energy-based sources, such as wind farms and solar-photovoltaic farms. Therefore, innovative strategies must be developed to exploit the full potential of doubly fed induction generators (DFIGs) to improve the first swing rotor angle stability in the system. This study presents a new active power logic (APL) controller for DFIGs which can reduce the active power during the fault and slowly recover it after the fault to allow synchronous generators to increase the electrical power during and after the fault; thus, enabling synchronous generators to improve the first swing rotor angle stability. The feasibility of the proposed control scheme is investigated via theoretical analysis and simulation studies. The reliability and voltage stability test system is used to demonstrate the effectiveness of the proposed scheme for local and remote faults and increased DFIG penetration conditions. The comparative results show that the proposed APL controller of the DFIG improves the first swing rotor angle stability, specifically when the DFIGs are located near the synchronous generators.

Limited-Position Set Model-Reference Adaptive Observer for Control of DFIGs without Mechanical Sensors

Operations of the doubly-fed induction generators (DFIGs) without mechanical sensors are highly desirable in order to enhance the reliability of the wind generation systems. This article proposes a limited-position set model-reference adaptive observer (LPS-MRAO) for control of DFIGs in wind turbine systems (WTSs) without mechanical sensors, i.e., without incremental encoders or speed transducers. The concept of of the developed LPS-MRAO is obtained from the finite-set model predictive control (FS-MPC). In the proposed LPS-MRAO, an algorithm is presented in order to give a constant number of angles for the rotor position of the DFIG. By using these angles, a certain number of rotor currents can be predicted. Then, a new quality function is defined to find the best angle of the rotor. In the proposed LPS-MRAO, there are not any gains to tune like the classical MRAO, where a proportional-integral is used and must be tuned. Finally, the proposed LPS-MRAO and classical one are experimentally implemented in the laboratory and compared at various operation scenarios and under mismatches in the parameters of the DFIG. The experimental results illustrated that the estimation performance and robustness of the proposed LPS-MRAO are better than those of the classical one.

Modeling and Performance Improvement of Direct Power Control of Doubly-Fed Induction Generator Based Wind Turbine through Second-Order Sliding Mode Control Approach

A second-order sliding mode (SOSM)-based direct power control (DPC) of a doubly-fed induction generator (DFIG) is introduced in this research paper. Firstly, the DFIG output powers are regulated with the developed SOSM controller-based DPC scheme. The Super Twisting Algorithm (STA) has been used to reduce the chattering phenomenon. The proposed strategy is a combination of the Lyapunov theory and metaheuristics algorithms, which has been considered to identify the optimal gains of the STA-SOSM controllers. The Lyapunov function method is employed to define the stability regions of the controller parameters. On the other hand, the metaheuristics algorithms are mainly employed to select the fine controllers’ parameters from the predefined ranges. A Thermal Exchange Optimization (TEO) method is used to compute the optimal gain parameters. To prove the superiority of the proposed TEO, its obtained results have been compared with those obtained by other algorithms, including particle swarm optimization, genetic algorithm, water cycle algorithm, grasshopper optimization algorithm and harmony search algorithm. Moreover, the results of the introduced TEO-based SOSM controller have been also compared with the Proportional-Integral (PI)-based vector control and the conventional sliding mode control-based DPC. Moreover, an empirical comparison is carried out to investigate the indication of every metaheuristics method by employing Friedman’s rank and Bonferroni tests. The main findings indicate the effectiveness of STA-SOSM control for system stability and power quality improvement. The ripples in the active and reactive powers are minimized and the harmonics’ distortions of stator and rotor currents are improved. Besides, the STA-SOSM controller shows a superior performance of control in terms of chattering phenomenon elimination.

Control of Doubly-fed Induction Generator with Extended State Observer under Unbalanced Grid Conditions

Under unbalanced grid condition, in a doubly-fed induction generator (DFIG), voltage, current, and flux of the stator become asymmetric. Therefore, active-reactive power and torque will be oscillating. In DFIG controlling rotor side converter (RSC) aims to eliminate power and torque oscillations. However, simultaneous elimination of the power and torque oscillations is not possible. Also, grid side converter (GSC) aims to regulate DC-Link voltage. In this paper, in order to regulate DC-Link voltage, an extended state observer (ESO) based on a generalized proportional-integral (GPI) controller, is employed. In this controlling method, DC-Link voltage is controlled without measuring the GSC current, and due to using the GPI controller, the improved dynamic response is resistant against voltage changes, and the settling time is reduced. A versatile rotor position computation algorithm (RPCA) is utilized to measure the rotor speed. This algorithm is simple, yet it is accurate and is resistant to changes in the resistance of the rotor and stator. The simulations are implemented by MATLAB software in the synchronous positive and negative sequence reference (d-q).

Real-Time FPGA-Based HIL Emulator of Power Electronics Controllers Using NI PXI for DFIG Studies

This article presents a high-performance hardware-in-the-loop (HIL) system aimed to assist experts in developing and testing power electronics control board and their logic with real-time (RT) models of both electrical and mechanical components. For demonstrating the effectiveness of this system for HIL testing, a new industrial doubly-fed induction generator (DFIG) control board is tested based on a comprehensive wind energy conversion model developed in MATLAB/Simulink hardware description language (HDL) coder and LabVIEW environment. The interaction between MATLAB/Simulink and LabVIEW is accomplished by National Instrument (NI) intellectual property (IP) integration node, which loads very high-speed integrated circuit hardware description language (VHSIC-HDL or VHDL) codes (that enable those two software exchange RT data). LabVIEW implements a VHDL code of electrical model with fixed-point variables on an R-Series reconfigurable input/output (I/O) field-programmable gate array (FPGA) module on NI-PXIe 7858R installed on NI PXIe 1062Q chassis, and the mechanical models deployed in its PXIe 8133 central processing unit (CPU). Finally, through a uniquely developed interface board, the HIL emulator connects to an external DFIG control board. In FPGA, the model and other communicational and logging components’ step-time in each iteration is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5.0~\mu \text{s}$ </tex-math></inline-formula> . For verifying the results, a comparison is made between the proposed emulator system and Typhoon HIL602+ as a commercially available HIL system. It is proven that there is little or no significant deviation between the outputs of two systems. The proposed HIL emulator does not have the limitation of commercial HIL systems in adding custom-made new components.

Parallel model predictive direct power control of DFIG for wind energy conversion

This paper presents a parallel model predictive power control (PMPPC) method of doubly-fed induction generator (DFIG) for variable-speed wind turbine applications (VSWT). The use of a hysteresis controller and a predefined switching table will inevitably lead to select a non-optimal voltage vector in terms of minimizing power errors, power ripple and THD currents. In this research paper, a new approach of direct power control (DPC) of DFIG based model predictive direct power control is developed by minimizing two cost functions to select the voltage vectors for stator active and reactive power in synchronously manner and consequently the optimal switching vector state of two-level voltage source inverter (2L-VSI). The proposed PMPPC control scheme takes full advantage and the power regulation objective of DFIG is confirmed by the simulation results compared to the DPC and PPC methods.

Design and Analysis of Grid-Interactive DFIG Based WECS for Regulated Power Flow

This article presents the sharing of reactive power between two converters of a doubly fed induction generator (DFIG) based wind energy conversion system interacting with the grid. The rotor side converter (RSC) control of DFIG is designed for sharing of reactive power at below rated wind speeds, which essentially reduces the amount of rotor winding copper loss. However, at rated wind speed, the RSC control is designed to maintain the unity power factor at stator terminals and to extract rated power without exceeding its rating. Further, the reduction in rotor winding copper loss due to reactive power distribution is demonstrated with an example. Moreover, the grid side converter (GSC) control is designed to feed regulated power flow to the grid along with reactive power support to DFIG and to the load connected at point of common coupling. Moreover, the GSC control is designed to compensate load unbalance and load harmonics. The battery energy storage connected at dc link of back-to-back converters, is used for maintaining the regulated grid power flow regardless of wind speed variation. The system is modeled and its performance is simulated under change in grid reference active power, varying wind speed, sharing of reactive power, and unbalanced nonlinear load using SimPowerSystems toolbox of MATLAB. Finally, a prototype is developed to verify the system steady state and dynamic performance. Moreover, system voltages and currents are found sinusoidal and balanced, and their total harmonic distortions are as per the IEEE 519 standard.

Robust nonlinear control of wind turbine driven doubly fed induction generators

This paper presents the active and reactive powers control of a doubly fed induction generator (DFIG) connected to the grid utility and driven by a wind turbine, this machine allowing a large speed variation and so a large range of wind is achieved. Traditionally vector control is introduced to the DFIG control strategies, which decouples DFIG active and reactive powers, and reaches good performances in the wind energy conversion systems (WECS). However, this decoupling is lost if the parameters of the DFIG change. In this direction, a robust control scheme based on the nonlinear input-output linearizing and decoupling control strategy for the rotor side converter (RSC) of the WECS is presented. Simulation results show that the proposed control strategy provides a robust decoupled control and perfect tracking of the generated active and reactive powers of the wind turbine driven DFIG with a low THD rate of the generated currents.

An Intelligent Control Scheme for DFIG Wind Farm to Control the Voltage Fluctuations

&lt;p&gt;In this project we investigates the control of doubly-fed induction generator (DFIG) based wind farms for compensating voltage fluctuations in weak networks. Under an unbalanced power grid voltage conditions, the DFIG’s stator side active power, reactive power, and electromagnetic torque will generate twice-multiplied frequency pulse quantities. The proposed control methodology exploits the potential of the series-DFIG scheme to avoid that grid voltage unbalances compromise the machine operation, and to compensate voltage unbalances at the point of common coupling (PCC), preventing adverse effects on loads connected next to the PCC. The modeling of the system has been discussed and also the system parameters are plotted. MATLAB Simulink has been used as the tool to evaluate the system. The grid parameter variations are also discussed.&lt;/p&gt;