Model Of Induction Generator Research Articles

Dynamic Modeling of Wound-Rotor Slip-Ring Induction Generator with Switched-Excitation Capacitance and Chopper Resistance Across Bridge Rectifier in the Rotor Circuit

This paper presents a novel external secondary self-excitation capacitance and chopper resistance across the diode bridge rectifier in the rotor circuit to control the voltage and frequency of 3-phase, wound-rotor, slip-ring, induction generator (WRSRIG). The problem related to the excitation- capacitance from the rotor side is the required large excitation capacitance to enhance the generator performance in a wide - range. In the present proposed method, a dynamic excitation capacitance is used in the H-Bridge inverter circuit connected in series with a chopper resistance across a 3-phase diode bridge rectifier in the rotor circuit. The duty ratios of the H-bridge thyristor elements and the thyristor chopper element are varied to emulate the excitation-capacitance as well as external-rotor resistance values dynamically, and to be used as terminal voltage and its frequency control. The dynamic excitation-capacitance is used to control the terminal voltage, while the dynamic external rotor resistance is used to control the generator speed (frequency). To study the performance of the WRSRIG a dynamic model is presented in this paper in D-Q axes rotating synchronously in a reference frame. The dynamic model takes into account all the machine parameters, such as stator and rotor - iron core losses, stator and rotor - stray load losses, dynamic saturation of the magnetizing inductance, rotor harmonic losses generated due to switching action of the bridge rectifier, reduction voltage in the rotor circuit due to the over-lap phenomenon and rotor external resistance losses. The new proposed equivalent circuit of the WRSRIG will become an efficient method for studying the performance characteristics of the generator and to be used as a suitable tool for an algorithm of the vector control analysis.

A novel strategy for fault location in shunt-compensated double circuit transmission lines equipped by wind farms based on long short-term memory

Parallel lines are one of the main parts of the power systems due to their capability of increasing the transmitted power and reliability of the power network. However, due to their complexity, fault location in these transmission lines has always been a potential problem. Furthermore, when the wind farms are connected to the power networks, a new challenge is created for the fault location algorithms. The reason is that the impedance changes continuously in these wind power plants. Moreover, the Static Var Compensator (SVC), which is used for compensation in transmission lines, can cause problems in accurate calculation of the fault location in power transmission lines. Accordingly, this paper presents a new method based on Long Short-Term Memory (LSTM) networks for source impedance and other network parameters estimation, which are key parameters to calculate the fault location accurately. The simulations are accomplished using PSCAD and Python software on a sample two-circuit network. This network consists of two parallel lines, a wind farm, and a synchronous generator to supply the network's power. The double-fed induction generator (DFIG) model is considered as the wind farm in the studied network. The results obtained from the tests clearly illustrate the applicability of the proposed method to estimate fault location and source impedance with high accuracy. • A fast and accurate fault location algorithm is achieved using Long Short-Term Memory (LSTM) networks. • Determining the location of different fault types in two circuit transmission lines. • Accurate performance for the location of different fault types under nosy conditions. • Estimation of the source impedance with a much smaller error value.

PERFORMANCE ASSESS OF SELF-EXCITED IG DRIVEN BY WIND TURBINE WORKING WITH FC-TCR

This work presented a self-excited induction generator (SEIG) model controlled by an (FC-TCR) fixed capacitor-thyristor control reactor consisting of a large fixed capacitor in parallel with a thyristor controlled reactor in series with the constant inductance. Induction machines were used because they are capable of working at different speeds. The 3-phase IG was driven by the prime mover that represents the wind turbine. Also, constant voltage and frequency were obtained, regardless of the change in velocity, by using proportional integration (PI control) for each of them. This type of generator is used in isolated rural areas far from power transmission lines. The voltage and frequency are analyzed for each wind speed proposed in the model and calculating the required excitation amplitude and torque required to drive the induction generator. Therefore, it is now a key interest to develop an efficient, viable, economic, and controllable induction generator for harnessing energy from renewable sources. The strategy of control was implemented with MATLAB/Simulink.

Current Sensor Fault Detection and Isolation in Doubly Fed Induction Generator

Fault Detection and Isolation (FDI) is gaining interest as a means to increase the reliability and availability of efficient systems. Measuring sensors used for data acquisition are more prone to failures. The main objective of this paper is to provide model based FDI for current sensor fault closed-loop controlled Doubly Fed Induction Generator (DFIG) model connected to power grid. The sensor fault was detected and isolated by two methods including Unknown Input Observer (UIO) on reduced order DFIG model and fuzzy logic. The results show improvement in computational speed during online monitoring when the fault isolation is performed on reduced order models.

Transfer function-based analysis of harmonic and interharmonic current summation in type-III wind power plants using DFIG sequence impedance modeling

This paper presents a new Transfer Function (TF)-based approach to evaluate the summation of complex harmonic and interharmonic current primary emissions in a wind power plant. A comprehensive impedance modeling of a doubly-fed induction generator including the Phase Locked Loop (PLL), induction generator, and current control loops of the converters is included in the TFs. A small-signal impedance modeling consisting of positive/negative-sequence modeling up to 50th harmonic order is adopted. The updated TF models are then used to calculate the contribution of each wind turbine to the total harmonic and interharmonic current distortions at the point of interconnection. Three phase angle distribution patterns are also presented to assess the stochastic behavior of the harmonic and interharmonic currents using the concept of “aggregation factor”. The variations of the aggregation factor with the PLL bandwidth are also investigated. Besides, the obtained primary emission TFs are used to adjust α-exponent in IEC 61000-3-6 summation rule. Analytical results are presented and compared to the simulation results where it is concluded that the proposed approach is more accurate than the previous approaches of TF modeling and related phase angle distribution patterns.

Stability and dynamic analysis of doubly-fed variable speed pump turbine governing system based on Hopf bifurcation theory

The stability of a doubly-fed variable speed pump-turbine governing system (VSPTGS) under the condition of small power disturbance was investigated. First, a novel model of the VSPTGS in turbine mode and pump mode is proposed based on the electromechanical transient model of the doubly-fed induction generator (DFIG). Then, the algebraic stability criteria of the system in turbine mode and pump mode are derived using Hopf bifurcation theory. Furthermore, the stability domain of the speed controller parameters is obtained when the power controller parameters are determined, and the dynamic behavior of the system is analyzed using bifurcation diagrams and numerical simulation. Finally, the power controller parameters are varied to study the influence of these parameters on the stability domain. The results show that Hopf bifurcation of a VSPTGS is subcritical. When the parameters of the power controller are fixed, the stability domain in pump mode is larger than that in turbine mode. The stability in turbine mode only depends on the speed controller parameters, whereas the stability in pump mode depends on both the speed controller parameters and the power controller parameters.

Dynamic characteristics analysis of a high-speed-level gear transmission system of a wind turbine considering a time-varying wind load and an electromagnetic torque disturbance

A high-speed-level gear transmission system model of a wind turbine is presented considering a time-varying wind load and an electromagnetic torque disturbance, along with eccentricity, dynamic backlash, and friction force. The auto-regressive model is employed for simulating the time-varying wind load in the realistic wind field as external excitation. A doubly fed induction generator model of the wind turbine is established to calculate the disturbance quantity of electromagnetic torque. The nonlinear differential equations of the system are strictly deduced using Lagrange equation and solved by the fourth-order Runge-Kutta method. The effect of friction on the dynamic response of the high-speed-level gear transmission system is analyzed with the time-varying wind load and the electromagnetic torque disturbance. These results show that the friction force is critical because frequency amplitude and components can be changed by it. The friction force also enlarges vibration displacement. The low-frequency components in the vertical direction are affected gravely by the friction force without electrical disturbance. In addition, sidebands exist in the vicinity of the low-frequency parts as the electromagnetic torque disturbance appears at the output end. The amplitude of the low-frequency component is further increased because of electromagnetic torque disturbance. This shows the frequency characteristics of the slight gear system fault. The study offers some fresh references into the design and diagnosis of the gear system.

Non stationary‐ARMA flicker model for squirrel cage induction generators based wind farms

Time varying nature of the wind power is studied previously considering different time intervals from seconds to days. However for power quality problems such as flicker, a model which considers the extremely fast variations is essential. Here by using large number of actual records, a time-varying model is proposed which considers the extremely short-time variations of wind active and reactive powers. The wind farm is modelled as a current source with time varying amplitude and phase which change every 0.01 s. Autoregressive moving-average (ARMA) models are utilized to model the variations and ARMA coefficients are calculated for every record. Same to the actual behaviour, the proposed model is non-stationary as the ARMA order and coefficients are different at every run of the model. The proposed model is confirmed through utilizing several applications which need the power time series with extremely short sampling intervals. The following studies are performed by using the actual data and then the proposed model: power spectral density of active and reactive power variations, instantaneous flicker, short term flicker (Pst), estimating the Pst using the maximum value of the instantaneous flicker, estimation of cumulative Pst for multiple wind turbines, and the impact of SVC on flicker mitigation.

Control and Investigation of Operational Characteristics of Variable Speed Wind Turbines with Doubly Fed Induction Generators

This article deals with the analysis, modeling, and control of the doubly-fed induction generator (DFIG) for wind turbines. The DFIG wind turbine can deliver more energy to the grid. There are some different methods to modify the DFIG system in order to accomplish the stator reactive power proposed. One of these methods is to modify the DFIG system for nominal voltage to evaluate cost and materials-efficiency consequences. A specific control strategy is implemented according to the vector control strategy. The proportional-integral (PI) regulators used are simple and precise controllers. This type of regulation, which is closed-loop rotor currents, allows adjustment of the sliding of the DFIG. This gives a good adjustment of the powers of the stator and the rotor. The percentage error of the simulation is less than 2 %. The results obtained in these investigations show that it is possible to adjust the powers of the stator, even with a variation of the parameters. The developed method will allow achieving the maximum efficiency of the wind energy conversion chain. The objective of this article is to optimize the quality of energy generated by wind turbines by controlling the reactive stator power and reducing the losses of the energy of the reactive stator power, which must be a physically minimal value. The results will be presented in the Matlab - Simulink environment.

Steady-State Analysis Based on Space Vector Model of Self-Excited Induction Generators

In order to attain more optimization for the procedure of transient and steady-state operation performance analysis and evaluation of self-excited induction generators (SEIGs), the paper converts the state-space transient mathematic model with real domain into the space vector transient model with complex domain based on the same two-phase stationary reference frame, described by which the physical systems can apply extendedly the holistic analysis approach based on Lyapunov stability theory proposed in real domain. Through equivalent analysis, the extended form of the steady-state conditions and its mathematic description into the complex domain is obtained, that is, the extended quasi limit cycle and the steady-state operating points. The analytic calculation for the extended steady-state condition provides successively the analytic solutions of exciting capacitance, stator frequency, as well as the extended steady state conditions under given rotor speed and magnetizing inductance. The practical calculation example verifies correctness and effectiveness of the approach and the analytic solution of the extended steady-state condition, with engineering reference values.

Application of New Co-simulation in System Simulation of Doubly-fed Induction Generator

This paper proposes a doubly-fed induction generator (DFIG) model built on three simulation platforms: Maxwell, Simplorer and Simulink. It can solve the overall modeling problem of the DFIG system effectively. In this paper, the generator physical simulation model (rotating shaft, rotor, stator and winding) are first established in Maxwell. Then, the internal (stator/rotor winding) and external circuit of DFIG are connected in Simplorer. The external circuit includes converter (generator side and grid side), filter, transformer and grid. Moreover, both the generator-side converter and the grid-side converter are controlled by Simulink. Finally, the simulation calculation study on the 5.5kW DFIG are carried out to validate the theoretical analysis. It is shown that SAGE causes distortion of the air gap magnetic field, the magnetic flux density (MFD) is inversely related to air gap changes. In addition, with the increase of SAGE, the curve of electromagnetic torque (EMT) moves down and rotor unbalanced magnetic pull (UMP) fluctuations become more obvious. The model can simulate the DFIG system accurately and effectively. And the simulation results are consistent with the theoretical derivation, which proves the validity of the model. This provides an effective method for the whole simulation and fault analysis of DFIG system.

Cooperative control strategy for distributed wind-storage combined system based on consensus protocol

To realize real-time wind farm output power regulation with power-sharing among storage devices that have different state of charges (SoCs), this paper proposes the cooperative control of the distributed wind-storage combined systems (WSCSs). It firstly establishes the mathematical model of doubly-fed induction generator (DFIG) and hybrid energy storage system (HESS) and implements the controls for two devices, respectively. Secondly, based on the power consensus protocol, an active power cooperative control strategy of the distributed WSCSs is proposed. It ensures that the energy storage devices can cooperatively compensate for wind power according to their different capacities to regulate the output power of the wind farm (WF) in real-time. At the same time, the high- and low- frequency power fluctuations can be effectively shared by the supercapacitors (SCs) and batteries, overcoming the deficiencies of the conventional battery energy storage system (BESS). Then, considering that the SoCs of the batteries are not identical, this paper further proposes a DFIG grid-side reference power adjustment strategy based on consensus protocol. It guarantees that each HESS can effectively achieve power-sharing while regulating the output power according to the SoCs of batteries. Finally, simulations in PSCAD/EMTDC under various scenarios are conducted to demonstrate the effectiveness of the proposed control strategy.

Modeling and stability analysis of three- and six-phase asymmetrical grid-connected induction generator

This paper presents the development of linearized model of asymmetrical six-phase grid-connected induction generator (GCIG) for small-signal stability. The developed linearized model has been used to obtain the eigenvalue to evaluate generator stability with respect to parameter variation of the machine in comparison with its three-phase counterpart. During the analysis, suitability of six-phase induction generator for higher output power has been accessed. Instability tendency during low electrical output power can be avoided through closed loop operation of the machine. Hence, the indirect field-oriented control scheme for asymmetrical six-phase GCIG has been proposed for stable operation with higher reliability. The key analytical results have been demonstrated with its experimental validation.

Improved Current Controlled Doubly Fed Induction Generator Model with Grid Integration Under Sub and Super Synchronous Conditions

This paper presents the development and experimental verification of the mathematical model of wind turbine and Doubly Fed Induction Generator (DFIG) using the current control and voltage estimation method between the DC link. The rotor of the induction generator (IG) is rotated with the wind turbine at a specific speed. The DFIG is directly coupled with a grid station and the synchronization between DFIG and the grid station is controlled by setting two converters: Machine Side Converter (MSC) implemented with the rotor side and Grid Side Converter (GSC) implemented with the grid. PI controllers have been utilized in the control loops and the parametric range is extracted to maximize the mechanical power transferred to the IG rotor. The model is tested under three conditions DFIG running at super synchronous speed, synchronous speed, and under synchronous speed using MATLAB Simulink. In the end, the same model is also tested through a series of experiments using lab modules. The results show that the proposed model is much simplified and accurate as compared to previous versions available in the literature.

Equivalent Modeling of Dfig-Based Wind Farms for Sub-Synchronous Resonance Analysis

The order of the detailed model of doubly-fed induction generator (DFIG) wind farms are too high and the simulation is difficult. Most of the existing research has used a single-machine equivalent model and clustering aggregation model for equivalence and few papers have explored the principles and equivalent conditions of the single-machine equivalent model under sub-synchronous resonance (SSR). Due to this reason, this paper equates DFIG wind farms connected with series compensated transmission network to two separate units based on the principle of matrix similarity transformation and the mathematical model and physical model of each unit has been studied. Then, the DFIG wind farm equivalent model’s validity is analyzed in number difference and collecting line difference based on linearization analysis. Finally, the system model is built in EMTDC/PSCAD, the damping analysis method is used to test the equivalent model’s validity and further reveal the mechanism of the system’s unstable operation. The results show that: the equivalent model can effectively reduce the system dimension and accurately reflect the dominant oscillation characteristics of DFIG wind farm under SSR; when SSR occurs, the damping coefficient of DFIG wind farm is negative under the oscillation frequency.

Control by second order sliding modes for a double-fed induction generator for a wind turbine

In recent years, the consumption of electrical energy in the world has increased, increasing the construction of power plants that operate with fossil fuels, which emit a large amount of CO2. Due to this polluting process, it is important to generate efficient alternatives. In this work the model of the double-feed induction generator for a wind turbine is exposed, to which the control by second order sliding modes will be applied to its state variables and these results will be compared with the classic proportional-integral-derivative technique of control. In this work it was found that the responses of the system with a second order sliding mode control compared to a control of the proportional-integral-derivative type, have a shorter establishment time and a slower behavior over time; in some cases the waveforms of the signals have a vibration effect at the moment of the response, but despite this, the response is not affected due to the wind speed to which the turbine is subjected, and reduces quickly system error at any instant of time. Whereas with a proportional-integral-derivative controller, some state variables can be highly dependent on wind speed.

Modeling and analysis of multiphase induction generator used in AC & DC hybrid microgrid generating system

Modeling and analysis of multiphase induction generator used in AC & DC hybrid microgrid generating system

Modeling and Analysis of Multiphase Induction Generator used in AC & DC Hybrid Micro Grid Generating System

Modeling and Analysis of Multiphase Induction Generator used in AC & DC Hybrid Micro Grid Generating System

A New Control Strategy of Dual Stator Induction Generator with Power Regulation

In this paper modelling and analysis of stand-alone dual stator induction generator (DSIG) with non-identical parameters under a new method has been done. The induction machine has two sets of stator three-phase windings spatially shifted by 30 electrical degrees. One supplied power to the DC load via a rectifier bridge and AC capacitors, and the other was connected to the battery banks by an inverter to store energy and restore it to regulate the power of the first stator in weak wind. We develop the steady state model and show the performances of different configurations by the simulation results.

Modelling and comparison analysis of grid‐connected DFIG‐based wind farm in weak grid

This study proposes a generic method for modelling and comparison analysis of grid-connected double-fed induction generator (DFIG)-based wind farms in a weak grid. A detailed model of DFIG in a weak grid is established and used as a benchmark. Specifically, the detailed model consists of the mechanical part, generator part, rotor side converter, and phase-locked loop (PLL). Two simplified models of grid-connected DFIG-based wind farms in a weak grid are compared with the detailed model to investigate the mechanism of sub-synchronous oscillation (SSO) as well as the influential factors through linear system analysis. The first simplified model ignores shafting dynamics, stator flux dynamics, and PLL dynamics. The same assumptions are used in the latter, except that PLL dynamics are considered. Time-domain simulation and eigenvalue analysis are used to verify the accuracy of the simplified models. The block diagrams of the linearised system are derived based on the proposed model, and the oscillation mechanism is explained by linear system analysis. Through eigenvalue analysis and the root locus method, the influences of the parameters of the DFIG and its controllers on the system stability are identified and analysed.