Model Of Induction Generator Research Articles

A Technique for Mitigating Thermal Stress and Extending Life Cycle of Power Electronic Converters Used for Wind Turbines

Over the last two decades, various models have been developed to assess and improve the reliability of power electronic conversion systems (PECs) with a focus on those used for wind turbines. However, only few studies have dealt with mitigating the PECs thermo-mechanical effects on their reliability taking into account variations in wind characteristics. This work critically investigates this issue and attempts to offer a mitigating technique by, first, developing realistic full scale (FS) and partial scale (PS) induction generator models combined with two level back-to-back PECs. Subsequently, deriving a driving algorithm, which reduces PEC’s operating temperature by controlling its switching patterns. The developed switching procedure ensures minimum temperature fluctuations by adapting the variable DC link and system’s frequency of operation. It was found for both FS and PS topologies, that the generator side converters have higher mean junction temperatures where the grid side ones have more fluctuations on their thermal profile. The FS and PS cycling temperatures were reduced by 12 °C and 5 °C, respectively. Moreover, this led to a significant improvement in stress; approximately 27 MPa stress reduction for the FS induction generator PEC.

Transient Analysis of the Self Excited Induction Generator Subjected to Grid Disturbances

The present paper analyzes the consequences of short grid voltages interruptions on grid-connected self-induction generator, particularly, on the currents and electromagnetic torque of the generator. These effects depend on several variables such as the phase difference between the grid voltages and those of the generator, the magnitude of the grid voltage and the generator currents at the instant of reconnection to the grid. The approach has been used for studying the effects of these grid disturbances on the self-excited induction generator; is a numerical approach. In the numerical approach, which is based on the dynamic d-q model of the induction generator, the effect of magnetic saturation is accurately accounted for. This numerical model has been validated by experimental measurements taken from an induction generator test bench. The analysis focuses on the amplitudes of the peaks of the currents and torque during short interruptions especially at the reconnection of the grid voltage. The results obtained from the numerical model are compared to the measured ones. Full Text: PDF DOI: http://dx.doi.org/10.11591/telkomnika.v16i2.8756

Modeling and Analysis of Six-phase Self-excited Induction Generator Using Mixed Stator Current and Magnetizing Flux as State-space Variables

A simple two-axis (d-q) model of a saturated six-phase self-excited induction generator, aimed at a stand-alone renewable energy generation, is analyzed using mixed stator current and magnetizing flux as state-space variables. This new set of orthogonal transformation (dq0) is characterized with a four-saturation-element solely in-built system matrix. Selection of this model using proposed mixed variables is justified by its simplicity. Performance equations for the given machine use the magnetizing inductance (Lm) at steady state and the dynamic inductance (L). In view of simplifying the analysis, the effects of common mutual leakage inductance (Llm) and cross-saturation coupling (Lldq) across the d-q-axis of each stator have been pretermitted. The mathematical model presented herein has been verified by simulation results using a fourth-order Runge-Kutta subroutine. Analytical results were also validated by experimental results and were found to be in good agreement.

Fault Diagnosis of an Induction Generator in a Wind Energy Conversion System Using Signal Processing Techniques

In this article, a contribution to fault diagnosis of an induction machine in a wind energy conversion system in closed-loop operation using a combination between short-time Fourier transform and discrete wavelet transform algorithms is proposed. An on-line fault diagnostic technique based on stator currents analysis of the squirrel-cage induction generator is proposed to detect and localize abnormal electrical conditions that indicate, or may lead to, a stator or rotor failure in a squirrel-cage induction generator. This technique also permits identification of a fault severity factor and consequently helps to determine the best choice of corrective maintenance. Furthermore, a generalized model of the squirrel-cage induction generator is used to simulate both the rotor and stator faults, taking iron losses, main flux, and cross-flux saturation into account. The efficiency of diagnostic procedure in closed-loop operation of the wind energy conversion system under non-stationary operating conditions is illustrated with simulation results.

Modeling of a Dual Stator Induction Generator with and Without Cross Magnetic Saturation

This paper discusses general methods of modelling magnetic saturation in steady-state, two-axis (d & q) frame models of dual stator induction generators (DSIG). In particular, the important role of the magnetic coupling between the d-q axes (cross-magnetizing phenomenon) is demonstrated, with and without cross-saturation. For that purpose, two distinct models of DSIGs, with and without cross-saturation, are specified. These two models are verified by an application that is sensitive to the presence of cross-saturation, to prove the validity of these final methods and the equivalence between all developed models. Advantages of some of the models over the existing ones and their applicability are discussed. In addition, an alternative is given to evaluate all saturation factors (static and dynamic) by just calculating the static magnetizing inductance which is simply the magnitude of the ratio of the magnetizing flux to the current. The comparison between the simulation results of the proposed model with experimental results gives a good correspondence, especially at startup.

Transient Stability of Wind Turbine Adopting a Generic Model of DFIG and Singularity-Induced Instability of Generators/Units With Power–Electronic Interface

A generic model of grid-connected doubly-fed induction generator (DFIG)-type wind turbines represented by differential-algebraic equations (DAE) is proposed for short-term transient-stability analysis. From the view of analytical research, vital simplifications are made to the complex physical model of DFIGs, whereas characteristic dynamics are still preserved. When the connection between the wind turbine and grid is weak, transient voltage collapse caused by singularity-induced instability (SII) is observed and analyzed adopting the generic model. In addition, it is shown that collapse might also occur when state variables of the dynamical system get out of control when the connection between the wind turbine and grid is stiff, where fast drop of dc-bus voltage occurs. Critical indices for evaluating transient-stability performances of the DFIG are proposed and parameter sensitivity analysis is carried out. Physical meanings of SII in generators/units with power–electronic interface in vector-oriented control frame are generalized. Novel interaction between the grid and these nonconventional generators/units is highlighted.

Analysis of Saturated Self-Excited Dual Stator Induction Generator for Wind Energy Generation

This paper presents the modeling of saturated dual stator induction generator (DSIG) for analysis of its transient and dynamic behavior for stand-alone operation. In the analytical model, the effect of common mutual leakage reactance between the two three-phase winding sets and the cross saturation have been considered. For this purpose, a detailed description of a procedure to introduce magnetic saturation in found models is presented. Paper also discusses the possibility of DSIG for supplying two individual loads by presenting the results of analytical and experimental study of transient behavior under various operating conditions. Use of such models leads to more accurate predictions in industrial drives, especially wind driven power generation systems. This is verified by experimental lab tests.

Condition Monitoring and Fault Detection in Wind Turbine Based on DFIG by the Fuzzy Logic

Doubly-fed induction generator is widely used in wind turbine conversion systems. Several research works are being made to efficiently approve existing condition monitoring and fault detection techniques for these systems. The condition monitoring of these systems becomes more and more important, the main obstacle in this task is the lack of an accurate analytical model to describe a faulty DFIG in the majority of the research tasks. In this paper, we present the monitoring strategy of short-circuit fault between turns of the stator windings and open stator phases in doubly-fed induction generator by fuzzy logic technique. The stator condition monitoring is diagnosed based on the root mean square values of current magnitude in addition to the knowledge expressed in rules and membership function. The proposed strategy is verified using simulations performed via the model of Doubly-fed induction generator built in Mat Lab ® SIMULINK.

Adaptive Fuzzy Gain Scheduling of PI Controller for Control of the Wind Energy Conversion Systems

In this work, the Wind Energy Conversion Systems (WECS) based on doubly fed induction generator (DFIG) model is built. First, we consider the vector control strategy of the active and reactive powers in order to ensure an optimum operation. The whole system is presented in d-q-synchronous reference frame. After, the design of Adaptive Fuzzy Gain Scheduling of Proportional Integral Controller (AFGPI) for WECS is described, where the optimization by Fuzzy rules is utilized online to adjust the parameters of PI controller based on the error and its first derivative. Finally, the control of the active and reactive power using fuzzy-PI controller is simulated using software Matlab/Simulink, studies on a 1.5 MW DFIG wind generation system compared with conventional proportional integral controller. Performance and robustness results obtained are presented and analyzed.

The Analytical Simulation of Squirrel Cage Induction Generator-Rectifier System Based on SPWM

In the full power wind power system, the cage induction wind generator-rectifier system can be regarded as a independent part if the DC voltage could be always controlled constant by inverter part. The prospective AC voltage and frequency of induction generator is dependent on the specific speed and input power, which is obtained by use of SPWM. All rectifier switching state and the alternating moments can be calculated by switching function given by SPWM control. This paper focuses on how to use analytical methods to calculate the process of alternately switching the state of the system. Furthermore, the dynamic mathematical model of induction generator is studied and derived under different states, which is suitable for analytical method on base of Laplace transform.

Doubly-fed wind turbine generator control: A bond graph approach

In this contribution, a bond graph doubly-fed wind turbine generator control is proposed. The control law is derived from the inverse model of the doubly-fed induction generator, which allows a different structure for the torque control to be obtained. The bond graph methodology and the concept of bicausality are applied to derive the control law. The robustness of the proposed control is verified and the simulation of the complete model is conducted for constant and variable wind speed operation conditions, respectively.

Diagnosis of Wind Energy System Faults Part I : Modeling of the Squirrel Cage Induction Generator

Generating electrical power from wind energy is becoming increasingly important throughout the world. This fast development has attracted many researchers and electrical engineers to work on this field. The authors develop a dynamic model of the squirrel cage induction generator exists usually on wind energy systems, for the diagnosis of broken rotor bars defects from an approach of magnetically coupled multiple circuits. The generalized model is established on the base of mathematical recurrences. The winding function theory is used for determining the rotor resistances and the inductances in the case of n- broken bars. Simulation results, in Part. II of this paper, confirm the validity of the proposed model.

Full-Scale Modeling, Control, and Analysis of Grid-Connected Wind Turbine Induction Generators With Back-to-Back AC/DC/AC Converters

A model-based dynamic analysis of a variable-speed wind generator system consisting of an induction generator connected to the grid through a full power frequency converter is conducted. To this end, a nonlinear modeling of the entire system is used in a manner that permits a novel controller design with common structure for both the generator- and grid-side converters. The proposed controller, acting directly on the duty-ratio inputs of the converters, ensures the boundedness of the duty-ratio signals in the permitted range although its structure is independent from the system parameters and open to different control objectives. Therefore, maximum power point tracking and power factor correction are easily implemented. Furthermore, the controller is proven to guarantee stability of the whole system under field- or near-field-oriented conditions without needing any flux measurement or estimation. Hence, the main contribution established by this approach is that a rigorous stability analysis taking into account the generator, converters, dc link, and controller dynamics is presented on the basis of a complete system modeling and controller design approach. The theoretical analysis and controller effectiveness are confirmed via extended simulation results for a commercial size 2-MW induction generator operating under varied wind speed conditions and are further validated on a similar system with real-time results.

Study on Application of STATCOM in Dynamic Reactive Power Compensation of Wind Farm Integration

As an increasing proportion of wind power in power grid, reactive power problem has become the most important problems in wind power integration. But as a result of wind power is a kind of intermittent energy sources, and put it into use in a large scale only just beginning. Many urgent problems which affect on system stability need to be resolved, such as voltage stability, reactive power compensation. This paper discussed the problems which around the reactive power compensation and angle stability issues while wind power integration. The reactive power compensation device named STATCOM instead of traditional capacitance. Establish the mathematical model of the Doubly-Fed Induction Generator (DFIG) and Static Synchronous Compensator (STATCOM) [3]. In order to meet the wind farm can transport reactive power quickly and continuously after fault. Establish the control strategy of DFIG combined with STATCOM [1]. Using the software MATLAB to simulate the wind power grid model and control system, verifies the rightness and effectiveness of model and STATCOM reactive power compensation effect for wind power integration.

Ad ‐ hoc analytical solution based on local linearisations for doubly‐fed induction generator wind turbine electromechanical simulations

This study presents a new methodology to solve the wind turbine modelling based on doubly-fed induction generator (DFIG) technology. The proposed solution allows us to simulate simultaneously a significant number of individuals DFIG submitted to different wind-speed profiles, minimising the computational time costs and avoiding excessive simplifications in comparison with previous solutions. For this proposal, a third-order induction generator model has been considered by the authors. The rotor current-control loops have been modelled through standard PI regulators, discussing in detail rotor voltage expressions and values of the parameters. The global non-linear equation system has been rearranged in state-space forms, by means of local linearisations and using two different software-packages that enable symbolic computation in a collaborative manner. The analytical results have been compared facing a traditional discretised solving methodology to assess the suitability of the proposed solution under different wind-speed conditions. Indeed, simulated and real-measured wind profiles have been considered for this purpose. Finally, a comparison of computational time costs for different time steps, including the effect of the number of wind turbines, is also included in this study.

Control Strategies for DFIG Based Grid Connected Wind Energy Conversion System

This paper deals with the modelling and control of a doubly-fed Induction generator (DFIG) based grid connected wind energy conversion system .Back to back Pulse width modulated insulated gate bipolar transistors(IGBT) based voltage source converters(VSC) have been used for the control. The complete mathematical analysis of stator flux oriented control and stator voltage oriented control of DFIG based wind system has been done. Maximum power tracking has been done through rotor speed control. The proposed electromechanical system is modelled and simulated in MATLAB using Simulink and Sim power system toolboxes. The performance of the system for both the control strategies is presented to demonstrate the difference between the two.

Steady State Modeling and ANFIS Based Analysis of Self-Excited Induction Generator

Self-excited induction generator (SEIG) has the ability to generate power at varying speed, which facilitates its application for wind energy conversion in remote and windy areas. Estimation of the generator behavior under actual operating conditions is essential, but the SEIG analysis with conventional techniques take long time with fatigued mathematical procedures. This paper presents a new technique for the performance analysis of a three phase SEIG supplying an isolated resistive load using adaptive neuro-fuzzy inference system (ANFIS). Proposed ANFIS model has been implemented to predict the effect of prime mover speed, capacitance and load on generated voltage of SEIG. Experimental data is used for the training of ANFIS. Results obtained from the trained have been compared with the experimental results. The comparison confirms the validity and accuracy of the ANFIS based modeling of induction generator.

Performance Analysis of a Controller for Doubly-Fed Induction Generators Based Wind Turbines Against Parameter Variations

This paper deals with modeling, analysis, and control of the Doubly-Fed Induction Generator (DFIG) for wind turbines. A model of a DFIG is developed in a rotating d-q axis frame. When the resistance and mutual inductance of DFIG are varying, the risk of the rotor failure is arising. To quantify the rotor current controller performances, transfer functions are derived and analyzed. The design of the current closed-loop control is analyzed according to the rotor current and voltage response. Simulation results of the time domain responses prove a strong robustness of our designed control system under parameter uncertainties. The disturbance rejection performance of the system decreases when the mutual inductance changes with small or large values. The results of the study ensure the operation safety of the wind power generation units, helping the reduction of the failure rate and improving the operation reliability.

Modeling and simulation of static loads for wind power applications

This study aims to model and simulate static nonlinear loads with wind power generation to evaluate the impact of load models on wind power systems. Nonlinear loads are modeled as exponential load model, ZIP load model and combination of exponential/ZIP with an induction motor. The wind power generator is represented with a reduced-order doubly fed induction generator (DFIG) model. Developed models have been implemented in a grid-integrated wind power plant and simulated in MATLAB/SIMULINK. The effects of nonlinear loads into wind power plant are investigated in terms of bus voltages, angular speed, electrical torque, and d---q stator axes currents. Additional analyses are conducted to compare the behaviors of full- and reduced-order DFIG models under a selected loading condition. The results of this study indicate that the response of a system with DFIG is dependent of the load modeling and reduced-order DFIG model shows more stable trend than full-order DFIG model.

Toward a Comprehensive Model of Large-Scale DFIG-Based Wind Farms in Adequacy Assessment of Power Systems

With the current focus on energy and environment, efficient integration of renewable energies, especially wind energy into power systems, is becoming essential. Furthermore, to fully capture wind potentials and to recognize the unique characteristics associated with wind energy in power systems adequacy analysis, a profound inquiry is required. In this way, this paper tries to establish a comprehensive analytical approach for reliability modeling of doubly-fed induction generator (DFIG)-based wind farms. First, the most impressive components of wind turbines are introduced. It then continues with integrating developed state space model of wind turbines and their production uncertainties, thereby allowing a wind farm to be represented as a multistate model in analytical studies. To this end, a well-known clustering method, fuzzy c-means clustering, is employed to find the optimal states. The model priorities are then put under investigation via two various case studies, the RBTS and the IEEE-RTS. A wind farm in the northern region of Iran with its historical data is utilized to validate the main features of the proposed analytical model more efficiently. The adequacy studies at Hierarchical Level one (HLI) of the modified test systems are presented and general conclusions are then drawn.