Doubly-fed Induction Generator Power Research Articles

High proportion of new energy power system frequency and voltage support and regulation technology based on doubly fed induction generator

Abstract With the increasing proportion of new energy in power systems, issues regarding system voltage, inertia, and primary frequency regulation have become increasingly severe. In response to control and grid safety issues, a high proportion of new energy power system frequency and voltage support and regulation technology based on a doubly fed induction generator (DFIG) is proposed. The voltage-magnetic link equation of DFIG is theoretically derived, and the control principles of active and reactive power of DFIG are proposed. The support and regulation characteristics of improving the voltage of new energy substations are studied. Verification is conducted through large-scale grid simulation and on-site measurements.

High performance of variable-pitch wind system based on a direct matrix converter-fed DFIG using third order sliding mode control

In this paper, a full nonlinear control of a variable-pitch wind system (VPWS) based on the doubly fed induction generator (DFIG) fed by a direct matrix converter (DMC) has been presented. In this context, The MPPT has been implemented using the third order sliding mode control (TOSMC) in order to ensure maximum power provided by the wind turbine on the one side, on the other side the pitch control has been implemented in order to limit the power extracted to its nominal value. Moreover, a TOSMC has been incorporated into the direct flied-oriented control (DFOC) to ensure high-performance control of the active and reactive power of DFIG. To examine the performance of the TOSMC, a comparative study was performed between this last type and the first and second order sliding mode controllers. The obtained results affirmed the high performance provided by the TOSMC compared to lower order sliding mode controllers.

Comparative Study of Robust RSC Control of Doubly Fed Induction Generator Based Wind Turbine under Grid Frequency and Voltage Variations

The configuration of a grid-connected doubly fed induction generator (DFIG) for wind energy generation systems consists of direct coupling of the generator stator windings with the grid and partial coupling of the rotor through power converters. This structure makes the system sensitive to the fault grid. Thus, robust control techniques are required to deal with the undesirable transient sequences in the network. In this paper, two robust controllers have integrated to regulate the stator active and reactive power of DFIG based wind turbine. Then, they have been tested and compared to verify their performances when abnormal grid networks have occurred. Firstly, we used high order sliding mode (HOSM) based Super Twisting, which keeps the same conventional sliding mode performances, such as fast dynamic response and redundancy to the extern disturbances, with a simple design and chattering reduction. Secondly, we implement the backstepping control approach which is known for its robustness in transient sequences. A number of simulations have carried out to evaluate the ride-through performance of both control strategies in case of low grid voltage dips and grid frequency variations.

Small signal stability and dynamic performance investigation on multi-machines power system including DFIG wind farm

<p>The boundless potential of wind power in augmenting global energy production is a promising prospect. The efficient design and cost-effectiveness of doubly fed induction generator (DFIG) wind systems make them an optimistic solution for incorporating wind power on a massive scale. However, integrating these systems into power grids poses several challenges, including power system stability. This study examines the small signal stability and dynamic performance of a modified Western System Coordinating Council (WSCC) 9-bus system including a DFIG wind farm using load flow analysis, and both electromechanical oscillations and eigenvalue analysis. Three case studies were conducted based on the DFIG location and power increment.The simulation is carried out with the aid of the power system analysis toolbox (PSAT) that operates within the MATLAB environment. The study’s findings suggest that the perturbation and location of the DFIG relative to the system’s load have a minimal influence on the overall system’s stability and efficiency. However, when considering damping ratio, power angle, and rotor speed deviations, generators 1 and 2 with the perturbed DFIG installed on bus 8 are the most sensitive units to instability. Hence, larger perturbations and different DFIG’s location influence on power systems necessitates further analysis.</p>

Dual Converter Operating With Floating Capacitors Connecting Open-End Winding Doubly-Fed Induction Generator to the DC Microgrid

This paper presents a novel configuration to connect a three-phase doubly-fed induction generator (DFIG) to the dc microgrid. The proposed topology connects an uncontrolled con- verter and a full-controlled converter in series with the generator stator windings in an open-end winding (OEW) configuration. The full-controlled converter is connected to an independent dc link based on floating capacitors. The paper discusses the converter operating principles, pulse-width modulation (PWM), DFIG power control, and the floating capacitors' voltage reg- ulation. The work compares the proposed and conventional systems regarding current harmonic distortions, torque ripple, and semiconductor losses. Simulations and experiments show steady-state and transient results for a 0.56-kW DFIG operating at the rated power. Finally, it was verified that the proposed topology presents lower power losses and low-distorted voltages and currents over the DFIG stator windings.

An Advanced Control Performance of a Sophisticated Stand-Alone Wind-Driven DFIG System

To supply resident loads far from the grid, a stand-alone wind system with a small-scale wind turbine and battery storage can be used. The traditional configuration of the system has a permanent-magnet synchronous generator (PMSG). Other alternative configurations use doubly fed induction generator (DFIG). The systems with DFIG have variable speed operation with a limited speed range which reduces the captured power from the wind turbine. Also, there is a rotor-side converter (RSC) which carries the reactive power of DFIG, in addition to the slip power. In this paper, an improved system configuration with DFIG is controlled by an advanced control scheme. By this advanced scheme, the speed range is increased such that maximum power operation of wind turbine is obtained for complete range of wind speed, and volt-ampere (VA) requirements of RSC are reduced by the operation at nearly zero-slip power.

Steady-State Load Flow Model of DFIG Wind Turbine Based on Generator Power Loss Calculation

Penetration of wind power plants (WPPs) in the electric power system will complicate the system load flow analysis. Consequently, the traditional load flow algorithm can no longer be used to find the solution to the load flow problem of such a system. This paper proposes a doubly fed induction generator (DFIG)-based WPP model for a load flow analysis of the electric power system. The proposed model is derived based on the power formulations of the WPP—namely, DFIG power, DFIG power loss, and WPP power output formulas. The model can be applied to various DFIG power factor operating modes. In the present paper, applications of the proposed methods in two representative electric power systems (i.e., IEEE 14-bus and 30-bus systems) have been investigated. The investigation results verify the proposed method’s capability to solve the load flow problem of the system embedded with DFIG-based variable-speed WPPs.

Power loss minimization assessment of a doubly fed induction generator with variable core resistance for wind turbines operation

<p class="Default">This paper assesses the efficiency level and power loss minimization of a doubly fed induction generator (DFIG). A modified DFIG equivalent circuit with multi-core resistance connected in parallel was adopted. State-space differential equations of the DFIG was developed incorporating iron and copper loss components while a minimum flux linkage that aids in the minimization of the overall losses was derived. Simulation results showed that losses were minimized when the equivalent core resistances were connected in parallel with minimum permissible current flow. The results obtained during a transient disturbance showed that at different core resistance values of Rfe = 0.75Ω and 0.25Ω, different efficiency values of 83.45% and 41.21% were realized. An unconstrained optimization test carried out on the DFIG variable parameters showed that the DFIG power loss model was controllable with a positive definite value of 691.9801 and 2.9156〖e〗^(+5) for the leading principal determinants of the Hessian matrix. All simulation processes were achieved in MATLAB/Simulink 2020.</p>

Constant Power Factor Model of DFIG-Based Wind Turbine for Steady State Load Flow Studies

DFIG (Doubly Fed Induction Generator)-based WPP (Wind Power Plant) is the most popular type of wind-driven electric power generation configuration. The main reason for its popularity is that the DFIG system can capture wind energy more optimally than other WPP configurations. Due to the increasing penetration of WPP in power systems, the need to study its impact on power system performance is becoming increasingly important. To enable such a study to be conducted properly, the first and probably the most crucial step is to model all system components (including the WPP). This paper proposes a new steady state model of DFIG-based WPP for load flow analysis. The proposed model is derived based on DFIG power formulas (i.e., DFIG stator and rotor power formulas). The model in the present work is simple and can easily be incorporated into load flow analysis. Representation of the DFIG in both sub-synchronous and super-synchronous conditions can be carried out by using a single mathematical model. Furthermore, since DFIG can be operated at a constant power factor (i.e., unity, leading, or lagging power factor), this important feature is also considered in the proposed model development.

Improving DFIG performance under fault scenarios through evolutionary reinforcement learning based control

The doubly fed induction generator (DFIG) usually experiences high rotor current and DC capacitor link voltage spikes during system fault events. In this paper, a novel data-driven approach is proposed to enhance DFIG performance under fault scenarios. An advanced reinforcement learning algorithm called guided surrogate-gradient-based evolution strategy (GSES) is used to control the DFIG power and capacitor DC-link voltage by adjusting the optimal reference signals. This controller is able to prevent the DFIG rotor from over-current risk and maintain grid-connected operation. The proposed GSES-based control algorithm was evaluated through simulations on a 3.6-MW DFIG in the PSCAD/EMTDC software. Results have validated the effectiveness of the proposed GSES-based control algorithm in improving DFIG performance under various fault scenarios.

Virtual inertia control parameter regulator of doubly fed induction generator based on direct heuristic dynamic programming

The most widely applied doubly-fed induction generator (DFIG) leads to insufficient frequency regulation ability of power system. The virtual inertia control can adjust the active power of DFIG according to frequency fluctuation. However, the frequent changes in power flow and operating point bring great challenges to traditional virtual inertia controller with fixed parameters. Direct Heuristic Dynamic Programming (Direct HDP) based control parameter regulator is proposed in this paper to obtain the optimal control parameters when the operation condition changes. Compared with the initial parameters, the response has been significantly improved after adaptive optimization by the proposed method when the system operating point changes.

Robust control of wind turbine based on doubly-fed induction generator optimized by genetic algorithm

In this research paper we will cover the study of the modelling and the control methods of the variable speed wind turbine based on doubly-fed induction generator (DFIG). It represents the most stressed structure given its distinctive characteristics. To control the electrical powers generated by this system independently, the vector control with the stator flux orientation is founded according to two techniques: i) the control of the powers by the backstepping technique and ii) the robust control based on the active disturbances rejection control. After the synthesis of the controllers of those two methods, their performances will be tested and compared to evaluate their effectiveness. We are mainly interested in the robustness test of the two control strategies with respect to the internal parameters’ fluctuation of the generator. The computing of the different parameters regulators of these two strategies is carried out using a genetic algorithm. This computing method makes it possible to arrive at an optimal solution of the DFIG power control. The different parts are simulated using MATLAB/Simulink environment.

Constant Voltage Model of DFIG-Based Variable Speed Wind Turbine for Load Flow Analysis

At present, the penetration of wind-driven electric generators or wind power plants (WPPs) in electric power systems is getting more and more extensive. To evaluate the steady state performances of such power systems, developing a valid WPP model is therefore necessary. This paper proposes a new method in modeling the most popular type of WPP, i.e., DFIG (doubly fed induction generator)-based WPP, to be used in power system steady state load flow analysis. The proposed model is simple and derived based on the formulas that calculate turbine mechanical power and DFIG power. The main contribution of the paper is that, in contrast to the previous models where the DFIG power factor has been assumed to be constant at unity, the constant voltage model proposed in this paper allows the power factor to vary in order to keep the voltage at the desired value. Another important contribution is that the proposed model can be implemented in both sub-synchronous and super-synchronous conditions (it is to be noted that most of the previous models use two different mathematical models to represent the conditions). The case study is also presented in the present work, and the results of the study confirm the validity of the proposed DFIG model.

An Active Voltage Coordinate Control Strategy of DFIG-Based Wind Farm with Hybrid Energy Storage System

In a power system with wind farms, the point of common coupling (PCC) usually suffers from voltage instability under large wind speed variations and the load impact. Using the internal converter of a doubly fed induction generator (DFIG)-based wind turbine to provide voltage support auxiliary service is an effective scheme to suppress the voltage fluctuation at PCC. To satisfy the reactive power demand of the connected grid, an active voltage coordinate control strategy with the hybrid energy storage system of the wind farm is proposed. The dynamic reactive power balance model is established to show the interaction between the reactive power limitation of the wind farm and the reactive power compensation demand of the grid. This indicates the initial conditions of the active voltage coordinate control strategy. According to the critical operating point and the operation state of the DFIG, the active and reactive power coordinate control strategy composed of active ω-β coordinate control and active β control is proposed to enhance the reactive power support capability and stabilize the grid voltage. To compensate the active power shortage, an auxiliary control strategy based on the hybrid energy storage system is introduced. The simulation results show that the proposed strategy can suppress the voltage fluctuation effectively and make full use of primary energy.

Real-Time Emulation of a Grid-Connected Wind Energy Conversion System Based Double Fed Induction Generator Configuration under Random Operating Modes

This paper presents the design, modeling, simulation and the experimental implementation of a 1.5 kW relatively low-cost wind energy conversion system (WECS) based on the double fed induction generator (DFIG) configuration. In the preliminary experiments, we test the DFIG power control under fixe speed by applying the vector control principle, then we insert the physical emulator presented in the controlled DC motor in order to simulate the static-dynamic behaviors of a real wind turbine with the use of the Tip Speed Ratio TSR based MPPT algorithm to extract the maximum available power on the emulator. The proposed structure is simulated using MATLAB Simulink environment, the obtained results are validated experimentally on our laboratory setup. We also develop an application with MATLAB AppDesigner that calculates the operating point of our system at steady state and visualize the power transfer, current, voltage and electromagnetic torque values of the DFIG and the DC motor before starting the stimulation or the experimental manipulation. The MPPT, the DC motor control and the DFIG power control algorithms are implanted in C, embedded on a dSPACE DS1104 control board. The obtained results confirm the reliability of the proposed WECS to manage all the probable operating modes, also the effectiveness of the physical simulator in the role of wind turbine emulation.

Improved hardware implementation of a TSR based MPPT algorithm for a low cost connected wind turbine emulator under unbalanced wind speeds

This paper presents the design, modeling, and the experimental build of a 1.5 kW relatively low-cost wind turbine emulator (WTE), based on the variable speed wind power system concept with partly rated power converters. The turbine simulator is composed of a controlled DC motor (DCM) in order to manage the static-dynamic behavior of a real wind turbine, including an ideal gearbox. This emulator is integrated into a connected wind energy conversion system chain (WECS), based on the double fed induction generator (DFIG) configuration. The latter ensures the electromechanical conversion. It allows the transfer of active and reactive power to the power grid during hypo and hyper synchronous modes. The aerodynamic emulation principle requires controlling the DC armature current with a PI controller. This leads to an electrical drive that applies a shaft torque identical to the wind turbine transmission drive train. The current reference is calculated as function of the static settings of the wind turbine and real wind speed data gives different operating points. In addition, this paper also proposes to test the TSR (Tip Speed Ratio) based MPPT algorithm to extract the maximum available power on the emulator by adjusting the rotational speed according to the actual given wind speed data. The MPPT, the DC motor control and the DFIG power control algorithms are implanted in C language, using dSPACE DS1104 control board, meanwhile simulations are done using MATLAB/Simulink. The experimental and simulation results show the effectiveness of using the controlled DC motor to emulate the wind turbine and also the great performances of the proposed MPPT structure to achieve the extraction of the maximum instantaneous power available on the drive shaft.

Simulation Studies of Control Systems for Doubly Fed Induction Generator Supplied by the Current Source Converter

The control system for a Doubly Fed Induction Generator (DFIG) supplied by a grid-connected Current Source Converter (CSC) is presented in this paper. Nonlinear transformation of DFIG model to the multi-scalar form is proposed. The nonlinear control strategy of active and reactive power of DFIG is realized by feedback linearization. In the proposed control scheme, the DFIG model and CSI parameters are included. Two Proportional-Integral (PI) controllers are dedicated for the control of the respective active and reactive powers. The control variables are the dc-link input voltage vector and the angular speed of the inverter output current. The proposed control approach is characterized by satisfactional dynamics and provides enhanced quality of the power transferred to the grid. In the simulation, evaluation of the characteristic operating states of the generator system, correctness of the feedback linearization and the dynamics of active and reactive power control loops are studied. Simulation results are adequately provided.

Modified Control Technique of DFIG for Power Quality Improvement

In this paper, a modified control technique for doubly fed induction generator (DFIG) is presented to improve its power quality by controlling (minimizing) grid current harmonics. The problems of harmonics injection in grid current, especially due to the presence of nonlinear loads, are very crucial. The proposed control technique can transfer the power from grid to DFIG and vice versa and can also control the DC link voltage (Vdc ) against wide variations in wind speeds. The maximum power point tracking (MPPT) is used in rotor side converter (RSC) to control the power flow through the DFIG. The MPPT extracts the maximum electromagnetic torque Tem from wind energy even during wide variations in wind speeds. A comparison of hysteresis current control (HCC) and space vector pulse width modulation (SVPWM) techniques for harmonic mitigation is presented considering all wind speeds. Also, the control technique for RSC and GSC is discussed in detail in this paper. Finally, the performance of the modified control technique to improve DFIG power quality is checked with the help of MATLAB/SIMULINK software considering 2.6 MW DFIG connected to a power grid.

Power fuzzy adaptive control for wind turbine

In recent years, wind energy has become one of the most promising renewable energy sources. The doubly-fed induction generator (DFIG) is currently the most common type of generator used in wind farms. This paper describes an approach for the independent control of the active and reactive power of the variable-speed DFIG. This paper deals with the control of the active and reactive powers in a DFIG designed for a wind system. The simulation model including a 7 KW - DFIG driven by a wind turbine, a PWM inverter and the proposed control strategy are developed and implemented using Matlab Simulink.

A DFIG-based wind energy conversion system (WECS) for LVRT enhancement using a hybrid approach: an efficient MEHRFA technique

This paper proposes a hybrid algorithm-based control model for enhancing the low voltage ride through (LVRT) capability of the doubly fed induction generator (DFIG) system. The hybrid algorithm is the combined execution of both modified elephant herding algorithm (MEHA) and random forest (RF) algorithm, and hence the technique is named as MEHRFA. The purpose of the proposed control technique ensures the LVRT capability in the DFIG-based WECS at voltage drop and fault conditions. Here, MEHA approach is used as offline manner to identify the ideal solutions from the available searching space and creates the training dataset. In the MEHA technique, multiple parameters are considered which are related to LVRT such as, voltage, real and reactive powers and current. Utilizing these parameters, the objective function is characterized and solved by MEHA method. In light of the accomplished dataset, the RF performs and predicts the best possible control signals for machine-side converter and grid-side converter. In this manner, the LVRT capability of DFIG system and power quality issues has been enhanced with the assistance of proposed technique. The proposed procedure is implemented in MATLAB/Simulink working platform, and the exhibition is assessed by utilizing the comparison analysis with existing techniques.