Grid-connected Wind Energy Conversion System Research Articles

A Review of Fast Power-Reserve Control Techniques in Grid-Connected Wind Energy Conversion Systems

Grid-connected power-converter-interfaced systems have been sharing the responsibility of grid generation alongside conventional synchronous generators. However, these systems lack spinning reserves, leading to a decrease in system inertia and resulting in more pronounced frequency deviations during power imbalances. Therefore, grid codes require the active involvement of wind energy conversion systems in frequency control, aiming to constrain the frequency and rate of change of frequency variations within predefined limits. This paper reviews fast power-reserve control techniques without energy storage in wind energy conversion systems that do not depend on frequency or rate of change of frequency values. The resulting effects on system frequency, energy production, mechanical loadings, and electrical loadings are assessed. The techniques are classified in the maximum-power point-tracking region according to the power function during the transient response, such as constant, speed-, time-, or mechanical power-dependent methods. Both overproduction and underproduction stages are considered. Certain techniques are tested on simulation grids that include either hydro or no-reheat steam generators, followed by a comparative analysis.

Fractional-Order Extremum Seeking Based MPPT for Wind Energy Conversion System with PMSG and ANPC Inverter Using Model Predictive Control

In this paper, a real-time optimization-based extremum seeking (ES) approach is applied to a grid-connected PMSG-based wind energy conversion system (WECS) for maximum power point tracking (MPPT). The proposed model-free approach aims harness the output power of the WECS by controlling the system from the DC side, eliminating the need for speed sensor. Moreover, using fractional order calculus in ES improves the convergence speed and robustness compared with the conventional integer-order ES methods. Additionally, an MPC controller for the inner loop is designed to maintains fast transient response through ANPC inverter. Finally, the effectiveness of the proposed method is verified by simulating the WECS in MATLAB/Simulink environment. It was shown that the proposed method is feasible and robust under different weather conditions.

Control strategies and performance analysis of doubly fed induction generator for grid-connected wind energy conversion system

Control strategies and performance analysis of doubly fed induction generator for grid-connected wind energy conversion system

Performance improvement through nonlinear control design and power management of a grid-connected wind-battery hybrid energy storage system

This paper presents a study on the application of nonlinear control and optimal power management techniques in a grid-connected wind energy conversion system with battery storage. The objective is to efficiently supply power to a load while considering performance constraints. The energy system under investigation comprises a wind turbine, battery, AC-grid, and load. Power is delivered to the load through various converters and a DC-link. However, the intermittent nature of wind energy and frequent load fluctuations can negatively impact the battery's lifetime and charging performance. To address these challenges, a nonlinear controller and a novel energy management system are designed. The energy management system generates multiple energy flow scenarios to achieve equilibrium in energy distribution between the load and energy sources. This equilibrium aims to minimize overall system costs, ensure DC-grid stability, and enhance power quality. Two distinct operation modes are identified: i) MPPT mode, which utilizes an optimizer to maximize power extraction, and ii) adaptive power point tracking (APPT) mode, which considers demand-driven production and the state of charge (SOC) of the storage system. The convergence of the closed-loop control is formally analyzed, and simulation results confirm the improved performance of the proposed multi-criteria design for energy management.

Application of different MPPT algorithms for PMSG-based grid-connected wind energy conversion system

Renewable energy sources such as wind energy sources have become the most prominent area of research work over the last two decades. Extraction of maximum power and lowering of THD are still the main issues during the integration of wind energy sources to the grid due to the noncontrollable variability of wind energy sources and the application of power electronic devices as interfacing devices. The main objective of this paper is to utilize modern optimization techniques for extracting maximum power points and implementing a Multilevel inverter to obtain minimal THD. This paper has introduced Improved Grey Wolf Optimization with Levy Flight for tracking maximum power from WECS. This Levy flight concept is applied in combination with the improved hunting process of GWO for providing an efficacy solution and a high rate of convergence through global tracking. Distinct MPPT algorithms such as Perturb and Observe (P&O), Grey Wolf Optimization (GWO), and Levy Flight Grey Wolf optimization (LGWO) are presented, simulated, and analyzed using MATLAB/SIMULINK. These algorithms have been compared based on quantitative analysis to examine the stability, figure out performance, and verify the best algorithm among the proposed algorithms. The consequences of the comparison demonstrated the supercilious characteristic of LGWO in the matter of tracking GMPP, rate of convergence, and the time to catch GMPP. The multilevel inverter is utilized as an interfacing unit between wind energy sources and the grid. This power electronic-based multilevel inverter is the main source of harmonic generation. This harmonic has been reduced to 5.5% (THD) due to the application of a 23-level Cascaded H-bridge multilevel Inverter using MATLAB/SIMULINK software.

Design and implementation of finite control set MPC with an LCL filter for grid-tied PMSG based wind turbine

This paper presents a grid-connected wind energy conversion system (WECS) that leverages the benefits of a permanent magnet synchronous generator and a finite control set model predictive control (FCS MPC) strategy. Despite the advantages offered by FCS MPC, challenges such as fluctuations in switching frequency, steady-state errors, high computational demands, and limited prediction horizons still persist. To address the switching frequency issue, the study introduces an approach incorporating the switching control action within the cost function while preserving the finite character of FCS MPC. The weight factors for switching control are optimized to reduce the switching frequency fluctuations while addressing other control objectives, such as regulating the DC-link voltage and controlling the flow of active and reactive power. The grid currents on the d and q axes are controlled to limit the amount of active and reactive electricity entering the grid. The proposed system also includes a modified third-order LCL filter, which is optimized by the predictive controller’s regulation of switching frequency, reducing design complexities and ensuring effective performance. A simulation of the proposed WECS with FCS MPC and a modified LCL filter has been performed using the MATLAB/Simulink environment. The dSpace DS1202 controller has been used to create an experimental setup suitable for a lab setting. The simulation and experimental findings confirm the controller and filter’s effectiveness under dynamic and steady-state operating circumstances. This research provides a promising solution for future wind energy conversion systems, advancing the field and establishing a foundation for further exploration.

A novel application of adaptive filtering algorithm for LVRT capability enhancement of grid-connected DFIG-based wind energy conversion systems (WECS)

A novel application of adaptive filtering algorithm for LVRT capability enhancement of grid-connected DFIG-based wind energy conversion systems (WECS)

Design of Vector Control Strategies Based on Fuzzy Gain Scheduling PID Controllers for a Grid-Connected Wind Energy Conversion System: Hardware FPGA-in-the-Loop Verification

This paper presents a hardware implementation upon a Field Programmable Gate Array (FPGA) of improved Vector Control Strategies (VCSs) based on a Fuzzy Logic System (FLS) of a grid-connected wind energy conversion system. Usually, the classical VCS is based on fixed-gain Proportional Integral Derivative (PID) controllers, which are known to exhibit limited performance against the nonlinear behavior of wind systems, such as rapid fluctuations of the wind speed and uncertainties of the system parameters. In order to overcome this limitation, an improved VCS based on Fuzzy Gain Scheduling PID controllers (VCS-FGS-PID) is suggested in this work to guarantee good tracking, high accuracy and good robustness under system parameter variations. Indeed, the PID controller gains are tuned, in real-time, by the FLS. In addition, the proposed VCS-FGS-PID methods are implemented on the FPGA in order to reduce the delays and the period of the system of the control loop, thanks to its parallel processing. In fact, the performance of the suggested VCS-FGS-PID approaches are proved by digital simulation with the Xilinx system generator tool under Matlab/Simulink, in addition to an experimental hardware-in-the-loop implementation using the FPGA. The obtained results demonstrate that the proposed VCS-FGS-PID techniques offer better performance as regards good tracking and high accuracy and good robustness against stator resistance variability compared to VCS-PI.

High-Gain Observer-Based Advanced Nonlinear Control of a Grid-Connected Wind Energy Conversion System with Sensorless Maximum Power Point Tracking

This paper deals with the control development of a wind energy conversion system (WECS) interfaced to a utility grid by using a doubly fed induction generator (DFIG), a back-to-back (B2B) converter and an RL filter for optimal power extraction. The aim was to design a sensorless controller to improve the system reliability and to simultaneously achieve the regulation of the generator speed, reactive power and DC-link voltage. The proposed global control scheme combines: (i) a high-gain observer employed to estimate the generator speed and the mechanical torque, usually regarded as accessible, (ii) a sensorless MPPT block developed to provide optimal generator speed reference, which is designed on the basis of the mechanical observer and a polynomial wind-speed estimator and (iii) a finite-time controller (FTC) applied to the B2B converter to meet the output reference’s tracking objectives in a short predefined finite time by using the backstepping and Lyapunov approaches. The proposed controller performance is formally analysed, and its capabilities are verified by numerical simulations using a 2 MW DFIG wind turbine (WT) under different operating conditions.

Optimization of Proportional-Integral Controllers of Grid-Connected Wind Energy Conversion System Using Grey Wolf Optimizer Based on Artificial Neural Network for Power Quality Improvement

Optimization of Proportional-Integral Controllers of Grid-Connected Wind Energy Conversion System Using Grey Wolf Optimizer Based on Artificial Neural Network for Power Quality Improvement

Impact of a PMSG inter-turn short-circuits fault on a grid-connected variable-speed wind energy conversion system

This paper assesses the effect of an inter-turn short circuit fault in stator windings of a Permanent Magnet Synchronous generator (PMSG)-based variable speed wind energy conversion system (WECS) connected to the grid by a power converters interface. The objective is to assess the impact of the fault on the WECS performances. This study has two tasks. The first one details a dynamic modeling of different subsystems of the WECS. The mathematical model of the defective PMSG is also set up. The second one presents an appropriate control strategy for the power converters interface. The control of the PMSG-side converter aims to ensure the operation in maximum power point tracking. The grid-side control was also established by controlling the active and reactive powers to ensure the operation in unity power factor and keeping the DC bus voltage stable. The performance of the control design was tested under healthy and faulty conditions.

Thermal Analysis of Power Converters for DFIG-Based Wind Energy Conversion Systems during Voltage Sags

The doubly fed induction generator (DFIG) and back-to-back converter are very sensitive to power quality disturbances in grid-connected wind energy conversion systems (WECSs). Special attention has been given to protect the system from voltage sags, considering the introduction of several low-voltage ride-through (LVRT) techniques in the literature. However, only few works have really analyzed the behavior of power semiconductors during such phenomena in terms of the thermal stresses, whereas the existing studies are focused on balanced voltage sags only. In this context, this work presents a thermal profile analysis of power semiconductors in the grid-side converter (GSC) and rotor-side converter (RSC) considering a DFIG-based WECS submitted to symmetrical and asymmetrical voltage sags. The system is modeled using PLECS software and results on a 2.0 MW system are presented and thoroughly discussed. The results show that it is possible to meet the ride-through requirements during both balanced and unbalanced sags in terms of acceptable thermal stresses on the semiconductors as long as the back-to-back converter and its respective control system are properly designed.

Comparative Study between Flatness-Based and Field-Oriented Control Methods of a Grid-Connected Wind Energy Conversion System

Wind energy is an alternative to meet the growing energy demand. Control of wind turbines should help the reliability and stable operation of the power grid. Furthermore, they should respect the technical requirements according to the grid codes to inject the wind energy into the grid. In this paper, a well-known field-oriented control (FOC) method and a new control method based on the flatness properties (FBC) are presented and compared. These control methods are applied to a wind energy conversion system (WECS), which connects a variable-speed wind turbine (WT) based on a permanent magnet synchronous generator (PMSG) to the grid via a back-to-back converter. The main aim of both control methods is to extract the maximum power from the wind. For this purpose, the mathematical model of each subsystem, i.e., WT, PMSG, and electrical grid, is presented. To evaluate and to compare the dynamic behavior of the high-power wind energy conversion system, it is modeled and the control strategies are developed using SimPowerSystems Toolbox in MATLAB. The simulation results obtained in the time domain show that the FBC performs better at managing the energy in the studied system. Indeed, the proposed FBC is a high bandwidth control method with only one closed-loop control, which leads to a high dynamic performance. Therefore, that strategy can be used to provide ancillary services such as frequency control and spinning reserves according to the grid codes.

Ferroresonance Overvoltage Mitigation Using STATCOM for Grid-connected Wind Energy Conversion Systems

We present the ferroresonance overvoltage mitigation concerning the power systems of the grid-connected wind energy conversion systems (WECSs). WECS is considered based on a doubly-fed induction generator (DFIG). Ferroreso-nance overvoltage associated with a single-pole outage of the line breaker is mitigated by fast regulating the reactive power using the static compensator (STATCOM). STATCOM controller is introduced, in which two incorporated proportional-inte-gral (PI) controllers are optimally tuned using a modified flower pollination algorithm (MFPA) as an optimization technique. To show the capability of the proposed STATCOM controller in mitigating the ferroresonance overvoltage, two test cases are introduced, which are based on the interconnection status of the power transformer used with the grid-connected DFIGs. The results show that the ferroresonance disturbance can occur for the power transformers installed in the wind farms although the transformer terminals are interconnected, and neither side of the transformer is isolated. Furthermore, as a mitigation method of ferroresonance overvoltage, the proposed STATCOM controller succeeds in improving the system voltage profile and speed profile of the wind turbine as well as protecting the system components against the ferroresonance overvoltage.

Coordinated Control of Grid-Connected PMSG Based Wind Energy System With STATCOM and Supercapacitor Energy Storage

In this paper, two coordinated control schemes have been designed for a grid-connected permanent magnet synchronous generator-based wind energy conversion system with static synchronous compensator (STATCOM) and supercapacitor energy storage (SCES) under various operating conditions. The coordinated control scheme-I (CCS-I) integrated a SCES into the DC-link through a bidirectional DC/DC converter to stabilize the DC-link voltage under varying wind speed and grid disturbances. The coordinated control scheme-II (CCS-II) implemented a STATCOM at the point of common coupling (PCC) to enhance the grid voltage stability during the grid voltage sag or swell. In CCS-II the SCES balances the active power while reactive power support is extracted from the grid side converter (GSC). The STATCOM is only activated when the reactive power requirement by the PCC exceeds the support capacity of the GSC. The proposed coordinated control schemes have been experimentally implemented with a dSpace MicroLabBox. Results show that CCS-I and II ensured the uninterrupted operation of the wind energy system and satisfied grid code requirements under various operating conditions and grid disturbances.

Direct Power and Voltage Oriented Control Strategies of Grid-Connected Wind Energy Conversion System Based on Permanent Magnet Synchronous Generator

This article deals with the control techniques of a low-voltage grid-connected to wind power conversion system based on a permanent magnet synchronous generator (PMSG) using an indirect matrix converter (IMC). Details of the proposed strategies for both the rectifier and inverter stages of the IMC are presented. Thus, a rectifier control strategy based on voltage-oriented control using space vector modulation is proposed. In addition, the control objective of the direct power control (DPC) inverter is the regulation of the active powers of the PMSG according to references established on the basis of the maximum power point tracker (MPPT) of the wind turbine, and also a good tracking of the output reactive power to its reference ensures unit power factor (UPF). A numerical simulation investigation is conducted to investigate the fast-dynamic performance of the proposed control systems during the wind speed variation. The obtained results in simulation are then complemented with tests in laboratory environment, the DPC control system is implemented on a dSpace DS1104 real time board. Selective experimental results are presented using a laboratory prototype of the wind energy conversion system to demonstrate the resulting improvements of the developed system. The results achieved have been clearly responded to the follow-up of references even under fluctuating wind conditions, and show promising relevance of the proposed method.

Fault Analysis of PI and Fuzzy-Logic-Controlled DFIG-based Grid-Connected Wind Energy Conversion System

Fault Analysis of PI and Fuzzy-Logic-Controlled DFIG-based Grid-Connected Wind Energy Conversion System

Robust Neural Control of the Dual Star Induction Generator Used in a Grid-Connected Wind Energy Conversion System

This paper presents a field-oriented control (FOC) of a dual star induction generator (DSIG) applied in a grid-connected wind energy conversion system. Currently, the dual star induction machine (DSIM) is increasingly used among multiphase machines. The machine has two star-connections, sharing the same stator offset, by an electrical angle of 30° and fed by two parallel converters. Maximum power point tracking (MPPT) is illustrated in a first stage, in order to extract a maximum of power under fluctuating wind speed. In a second stage, vector control of a DSIG with FOC is described. Finally, voltage oriented control (VOC) is used to ensure the power factor unity on the grid side. The main contribution of the presented paper is the application of a simple architecture of an artificial neural network (ANN) controller in order to improve the robustness and stability of the system, especially against the parameter change. In comparison with the conventional control, which is known by its sensitivity, the proposed neural MPPT with neural FOC (NMPPT-NFOC) presents better performance under normal and abnormal conditions. The robustness and effectiveness of the proposed control has been validated through illustrative simulation results with different functional zones, and for fixed and variable wind speed.

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.

Nonlinear control of grid-connected wind energy conversion system without mechanical variables measurements

This article addresses the problem of controlling an overall wind energy conversion system (WECS) formed by a wind turbine connected to the grid via a doubly fed introduction generator (DFIG) and an AC/DC/AC converter. The main control objectives are fourfold: (i) designing an output feedback speed controller that makes the DFIG rotate at the optimal value delivered by the MPPT strategy, (ii) controlling the stator reactive power so as to be null, (iii) guaranteeing the DC-link voltage in the grid side converter to be at a given constant value, (iv) ensuring a unitary power factor. A high gain observer is synthesized, in order to provide estimated values of the mechanical variables. To achieve the control objectives, a sliding mode controller involving the mechanical observer is designed. The performance of the system configuration based on the 2MW-DFIG with the proposed controller is evaluated by a numerical simulation under a realistic wind profile using MATLAB/SIMULINK/SimPowerSystems environment.