Variable Speed Wind Energy Conversion Research Articles

A single current sensor based adaptive step size MPPT control of a small scale variable speed wind energy conversion system

Due to the limited size and lower environmental impact, a small-scale wind energy conversion system (WECS) is a promising alternative for remote locations and residential areas where installing large wind turbines is not feasible. This system employs a permanent magnet synchronous generator (PMSG) as a variable speed wind generator due to its advantages such as high torque density, gearless, and require no external excitation, etc. This article proposes a single load current sensor-based adaptive step size (LCAS) maximum power point extraction (MPPT) method which utilizes the load current information to track the maximum power. This method does not require rotor speed information and knowledge of the turbine parameters. Also, this article uses a simple and cost-effective switch mode rectifier topology (AC–DC and DC–DC boost converters) for the PMSG-based variable speed WECS. The proposed method is validated in a 1.5 kW test rig using an OPAL-RT digital signal controller and also compared with various fixed step size (FSS) MPPT algorithms at various operating conditions. Extensive experimental work has been carried out for the LCAS MPPT method that confirms the tracking efficiency is better and tracking speed is faster along with the improved steady state as well as transient performance.

Design and Experimental Verification of PUC Multilevel Inverter-Based PMSG Wind Energy Conversion System

In this study, a wind energy conversion system is designed using a three-phase permanent magnet synchronous generator, a six-diode bridge rectifier, a DC–DC boost converter, an inverter, and a load. The proposed inverter is a Packed U-Cell-based multilevel inverter having five or seven voltage levels at the output. It is also a topology that is not widely used in wind energy applications. Furthermore, a dual-mode PI-PI control technique is proposed to regulate the auxiliary capacitor voltage in the PUC MLI. The inverter is designed and simulated for a permanent magnet synchronous generator-based variable speed wind energy conversion system. Additionally, the design and experimental application of the proposed system is carried out in a laboratory environment. In the experimental application, the rated voltage of the Packed U-Cell multilevel inverter is chosen as 45 V. The switching frequency of the multilevel inverter is set to 4 kHz, and a generator with rated power of 700 W is selected. The output voltage of the generator is varied between 25 V and 35 V through an induction motor. This varying voltage is increased to 45 V using a DC–DC boost converter. Finally, it is observed that the power generated by the permanent magnet synchronous generator is successfully transferred to the load and the designed system operates with low harmonic content.

A novel combined FFOC-DPC control for wind turbine based on the permanent magnet synchronous generator

The quality of the electrical energy produced from renewable energies is a preponderant need sought by electricity producers. It is in this vision that this present article tries to design a control that combines two control algorithms in order to improve the operation of a variable speed wind energy conversion system (VSWECS). Interestingly, combined control brings together fuzzy field oriented control (FFOC) with direct power control (DPC). The complete conversion chain includes the 1.5 MW permanent magnet synchronous generator (PMSG) and two full-scale mounted back-to-back power converters. Compared to FOC method based on the classical PI regulator, the proposed FFOC scheme is employed to guarantee a better performance between the effect of artificial intelligence (AI) and the simplicity of the standard regulator. This is because the FFOC smart control algorithm is used to control the machine-side-converter (MSC). The DPC control algorithm which uses a relatively low sampling frequency of around 5 kHz is proposed to estimate the active and reactive powers injected into the grid through the grid-side converter (GSC). In addition to the simplicity of implementation and the reduced simulation time, the combination of the FFOC-DPC control algorithm is very reassuring in terms of stability, robustness and tracking of set-points. The overall control scheme is simple to implement and the simulation results clearly show that the proposed control system offers very good performance in terms of total harmonic distortion (THD), which does not exceed 1.49%, a wave of well-balanced injected electric current, and a power factor almost equal to unity. Therefore, the proposed solution is finally compared with other alternatives to validate the results developed by the MATLAB/Simulink platform and consequently guarantee the improvement of the variable speed direct drive WECS.

Wind Energy Conversion System Based PMSG for Maximum Power Tracking and Grid Synchronization Using Adaptive Fuzzy Logic Control

This paper proposes an adaptive fuzzy logic based Maximum Power Point Tracking (MPPT) for Permanent Magnet Synchronous Generator (PMSG) based variable speed Wind Energy Conversion System (WECS). The control algorithm, online updates the scaling factors of the Fuzzy Logic Controllers (FLCs) at a high convergence speed. The adaptive FLC is in cooperated along with field-oriented control of PMSG to track the maximum power. The WECS is connected to the grid through a back-to-back converter. The grid side inverter is controlled by voltage-oriented control along with FLC, so that power quality standards of the grid are maintained. The performance of the system is verified using MATLAB Simulink and it is validated that power coefficient of WECS abide at its optimum value with dynamic conditions in wind speed. The WECS provides full reactive power support for the system with a unity power factor operation at the grid. The active power sharing of WECS to the grid/load changes with the availability of wind power.

Sensorless passivity based control of doubly-fed induction generators in variable-speed wind turbine systems based on high gain observer

The current study presents a robust sensorless control using passivity based control (PBC) combined with high gain observer (HGO). The proposed controller is applied to control the generated doubly-fed induction generator (DFIG) active and reactive power installed on a variable speed wind energy conversion system. The control objective is used to regulate independently the DFIG stator active and reactive power, which are decoupled by using the field oriented control technique. Additionally, this process leads to reduce the cost of control scheme by eliminating the speed sensor. Firstly, the DFIG is modeled under the port controlled Hamiltonian (PCH) model, as well as the method of simultaneous injection damping. Then, the DFIG is further modeled by assignment passivity based on the simultaneous injection damping and assignment (SIDA-PBC) control of the obtained model under such conditions and a comparison with the fuzzy sliding mode controller is carried out. Furthermore, the HGO is selected in order to estimate the rotor position and the speed from the measurement of the DFIG currents and voltages, and compared with fuzzy sliding mode observer. For testing the proposed control scheme performance, a 1.5 MW DFIG system is developed and simulated using MATLAB/Simulink. The obtained results demonstrate the effectiveness of the proposed control scheme in the presence of various DFIG parameters variation. Additionally, the control objective is achieved without speed sensor.

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.

Experimental Validation of Direct Predictive Control of Variable Speed Wind Energy Conversion System Based on DFIG

The paper presents the design and the implementation of a direct predictive control of a variable speed wind energy conversion system. The conversion chain uses a Doubly Fed Induction Generator DFIG whereas the control method is based on a Finite States Model Predictive Control FS-MPC. The proposed control method selects the optimal switching state of the two levels back to back power converter that minimizes the cost function, where this optimal voltage vector is applied on the output of the power converter in next sampling time. The proposed predictive control strategy uses only one sample time prediction and it is intuitive since it is very simple for implementation. In order to adjust the measured rotor currents to track their references, the error between orthogonal rotor current components predictions to their computed values used to select the optimal vector and applied on the power converter in rotor side CSR in next sampling time. On other side, based on the error between the active and reactive power prediction and their references of the electrical grid, the predictive algorithm control of the gird side converter CSG kept the Dc-link voltage constant and guarantee that the whole system functioning with unity power factor. The experimental results confirm the advantages of using this structure for wind energy conversion system and the effectiveness of the proposed control strategy.

Diagnosing multiple short circuit switches faults in wind turbine doubly-fed induction generator

In the current paper, the inverter feeding doubly fed induction generator (DFIG) in the case of short circuit switches fault is presented. Defects diagnosis is based on the so-called the Lissajous curves of DFIG rotor currents. For this purpose, the modeling of the variable speed wind energy conversion chain based on the DFIG, is firstly introduced, after that a description of the voltage source inverter operating mode is presented. Finally, rotor currents Lissajous curves are analyzed in case of a non-defective and defective inverter. Simulation results were achieved using MATLAB^®- SIMULINK^® package, thus confirming the efficiency of the proposed method.

Grid Connected Bidirectional Converter Based Ems System with Model Predictive Control

In this paper, the bidirectional converter that performs DC-DC power conversion is integrated with the variable speed wind energy conversion system’s grid system. Generally, the voltage quality is reduced, and fluctuation in outputs is performed in renewable energy sources. The stable operation and power generation with fluctuation and power demand in the variable are ensured by developing the energy management system (EMS). In this proposed method, the bidirectional converter’s control is accomplished using the proportional-integral-derivative (PID) controller, which controls the power fluctuation from the WECS to maintain constant. The DC-AC voltage conversion is achieved using the model predictive controller (MPC), which controls both power and voltage. This proposed power and voltage controller enhances the stable AC voltage supply and improves the proper power flow. The proposed method, which is validated in simulation is simple, and the results are obtained using MATLAB/Simulink.

New design and comparative study via two techniques for wind energy conversion system

Introduction. With the advancements in the variable speed direct drive design and control of wind energy systems, the efficiency and energy capture of these systems is also increasing. As such, numerous linear controllers have also been developed, in literature, for MPPT which use the linear characteristics of the wind turbine system. The major limitation in all of those linear controllers is that they use the linearized model and they cannot deal with the nonlinear dynamics of a system. However, real systems exhibit nonlinear dynamics and a nonlinear controller is required to handle such nonlinearities in real-world systems. The novelty of the proposed work consists in the development of a robust nonlinear controller to ensure maximum power point tracking by handling nonlinearities of a system and making it robust against changing environmental conditions. Purpose. In the beginning, sliding mode control has been considered as one of the most powerful control techniques, this is due to the simplicity of its implementation and robustness compared to uncertainties of the system and external disturbances. Unfortunately, this type of controller suffers from a major disadvantage, that is, the phenomenon of chattering. Methods. So in this paper and in order to eliminate this phenomenon, a novel non-linear control algorithm based on a synergetic controller is proposed. The objective of this control is to maximize the power extraction of a variable speed wind energy conversion system compared to sliding mode control by eliminating the phenomenon of chattering and have a good power quality by fixing the power coefficient at its maximum value and the Tip Speed Ratio maintained at its optimum value. Results. The performance of the proposed nonlinear controllers has been validated in MATLAB/Simulink environment. The simulation results show the effectiveness of the proposed scheme, suppression of the chattering phenomenon and robustness of the proposed controller compared to the sliding mode control law.

Dynamic Performance Analysis of a Grid-Connected Doubly-Fed Induction Generator

In the field of wind energy, the doubly fed induction generator (DFIG) is commonly used in variable speed wind energy conversion systems (WECS). This paper presents a review of various topologies, configurations, power converters and control schemes used with the operation of the DFIG. The operation of DFIG based on both slip ring and brushless arrangement has been discussed. The grid integration of DFIG and its influence on system stability, system reliability, power quality and power transmission is reviewed.

Novel insight on temporary frequency support of variable speed wind energy conversion system

AbstractIn the recent decade, temporary frequency support derived from variable speed wind turbine generator has been drawing increasing attention in the electronic‐growing power system. Frequency nadir and rate of change of frequency are two key indicators temporary frequency support strives to improve. This paper proposes a novel insight on frequency regulation of wind power. Note that considerable part of load is shared by synchronous generators and wind turbine generator and the system frequency still will be dominated by the former for a period of time. Simultaneously taking the frequency regulation characteristic of synchronous and power balance into account, a novel frequency regulation scheme aiming at improving system's frequency regulation performance is proposed and tested in a 7‐machine power system with an aggregated wind farm on MATLAB/Simulink to investigate what inherently determines the performance of frequency regulation. Results show that with differential cooperation of synchronous generator and doubly fed induction generator, frequency nadir and rate of change of frequency can be partially improved. Particularly, regarding to handling the issue of control delay, an appropriately slower action upon detecting a frequency event may not screw up it but contribute to a higher frequency nadir, which benefits from the spontaneous cooperation of synchronous generator and wind power with constraint of power balance.

Towards a global nonlinear control strategy for DFIG-based wind turbine in a high wind energy penetrated system

Variable speed wind turbines offer several advantages compared to those with fixed speed, especially as far as it concerns their ability to capture energy efficiently. To benefit from these features, the power transmitted to the electrical grid must reach its optimum. In this context, this paper proposes a nonlinear controller, so as to control the overall variable speed wind energy conversion system (VS-WECS). This latter consists of a wind turbine rotor, a doubly fed induction generator (DFIG), an AC/DC/AC converter, and the electrical grid. The proposed controller is based on the sliding mode technique aiming at controlling the stator power, the grid side reactive power and regulating the DC-link voltage, in order to manage the flow of energy between the wind turbine system and the power grid as well as to improve the dynamic system and transient stability. The performance of the 2MW grid-connected DFIG wind turbine system is checked with MATLAB/SimPowerSystems environment and examined under fixed and variable wind speed profiles to confirm the reliability and validity of the control strategy.

Enhancement of Low Voltage Ride Through Capability of Doubly Fed Induction Generator Based Wind Turbine Using Fuzzy Logic Controller

Combined impact of environmental issues and policies of utilities has led to generation of clean and sustainable energy. Solar and wind energies are prominent and can provide bulk amount of electrical energy. Vast number of resources and more electrical energy density are attractive features of wind energy. Generation of bulk amount of wind energy especially offshore wind energy is attracting utilities to incline towards wind energy. Variable speed wind energy conversion systems employing Doubly fed induction generators offers several advantages such as maximum power generation and independent control of active and reactive powers. Doubly fed induction generator-based wind energy system became the first choice of power system operators due to its low-cost power electronic convertors. Stringent grid codes adopted by various countries made Low voltage ride through a serious problem for electric utilities as well as DFIG manufacturers. Many researchers tried to address the problem of low voltage ride through. In initial stages, crowbar circuits were used. Later Low voltage ride through was addressed using additional hardware such as STATCOM. Artificial intelligent controllers were used to minimize the effect of ride through. A comprehensive review, of different issues allied with low voltage ride through of doubly fed induction generator-based wind energy conversion system is presented in this article.

Fuzzy logic based optimal tip speed ratio MPPT controller for grid connected WECS

Abstract This paper proposes a fuzzy logic based optimal tip speed ratio controlled maximum power point tracking for grid connected variable speed wind energy conversion system. The general system includes a three bladed fixed pitch turbine, permanent magnet synchronous generator (PMSG), three phase uncontrolled rectifier, DC boost chopper, PWM inverter and fuzzy logic controller (FLC). The PMSG is modelled in dq–synchronous reference frame theory. The combination of uncontrolled rectifier and DC chopper is employed to acquire the maximum power by controlling the generator. The dc output voltage of the boost converter is converted into ac voltage by PWM inverter. Fuzzy logic controller is applied to both grid side converter for grid voltage control and generator side converter for optimal tip speed control. Grid side controller is employed to vary the modulation index of PWM inverter to keep up constant grid voltage and generator side controller is utilized to stay up the tip speed ratio at an optimal value to operate the system at maximum power point. The effectiveness of the proposed system is verified through extensive simulation results using MATLAB/SIMULINK environment.

Modeling of Variable Speed Wind Turbines with Doubly Fed Induction Generator for Studying Steady State Operation (Dept.E)

Wind energy conversion has emerged as a viable alternative to meet the increased demand for energy resources in recent years. Wind (arms interconnected to power system bring new challenges to power system op eration. It is imperative to study the impact of variable speed wind turbine coupled to doubly fed induction generator DFIG on utility grid op eration. A mathematical model has been developed to evaluate the steady state performance of the variable speed wind energy conversion system with DFIG. In addition a steady state converter (rectifier-inverter) model as a function of siring angles of the rectifier and inverter is developed and used directly to calculate the influence of DFIG on power system operation through power flow solution. These units are modeled as P-Y bus(es) to manage the reactive power generation inside the wind farmi. The paper presents and validates a model of DFIG suitable for operation in steady state mode and not only able to support voltage by feeding reactive power but also to fulfill grid requirement. The p roposed algorithm is imp lemented and applied to the IEEE 26-bus system and the number of the equivalent wind turbines generating units WTGU at each generating bus is demonstrated and injected as P-V bus(es). The impact of WTGUs on active and reactive power of own generating bus(es) and slack bus at different wind speeds is also investigated.

Variable gain high order sliding mode control approaches for PMSG based variable speed wind energy conversion system

Variable gain high order sliding mode control approaches for PMSG based variable speed wind energy conversion system

Nonlinear Active Disturbance Rejection Control for Improving Low-Voltage Ride Through Capability of DFIG-Based WECS

As recorded in the grid codes of different global power grid operators, Variable Speed Wind Energy Conversion Systems (VS-WECS) based on Doubly Fed Induction Generator (DFIG) supplying into the utility grid should meet the new requirements during Low Voltage Ride Through (LVRT). In this paper, a new non-linear ADRC control is mobilized to improve the control of the DFIG-based VS-WECS in order to overcome the effects of the voltage sags. The simulation results in MATLAB-Simulink environment will be established to illustrate the relevance of control designed to make production by a VS-WECS based on DFIG able to meet the requirements of grid code during LVRT.

Control of PMSG based variable speed wind energy conversion system connected to the grid with PI and ADRC approach

This paper presents the modeling and simulation of wind energy Conversion System using the Permanent Magnet Synchronous Generator (PMSG). <br /> The objectives are: to extract the maximum power of the wind speed by controlling the electromagnetic torque of the PMSG, to maintain constant the DC-link voltage despite the wind speed variations and to attain the unity power factor. In order to ensure a regulation with high performance and a good robustness against the internal and the external disturbances, a new control strategy called the Active Disturbance Rejection Control (ADRC) is used. Therefore, the Analysis and simulation of the ADRC and PI controllers are developed with MATLAB/Simulink software. The performance of these controllers is compared in term of references tracking, robustness <br /> and grid faults.

A Proposed Strategy for Power Management of a Standalone Wind Energy Conversion System with Storage Battery

Several strategies have been suggested to optimize power extracted from the Standalone Variable Speed Wind Energy Conversion System (SVSWECS) using a Squirrel Cage Induction Generator (SCIG). Where, many of them use the battery as a storage unit for future use. However, the latter is assumed as an ideal component and that no maximum charging or critical limit. With the considered strategy, the generated wind power can be managed using a fast and reliable fully rugged electrical control. Indeed, the use of reliable Power Management and Control (PMC) algorithm where the battery current is well controlled. However, this solution allows maintaining the system operation in two stable modes.The considered system consists of an SCIG connected mechanically to the wind turbine through a gearbox, and electrically through a PWM rectifier to the DC bus capacitor, the latter is connected to the load and the battery through a PWM inverter and buck-boost converter respectively. In this paper, to approach the system to reality, a new PMC is proposed using a purely reliable electrical control. The Direct Torque Control (DTC) is used. The latter is combined with the Maximum Power Point Tracking (MPPT) technique and the State Of Charge (SOC) of battery. The important key of the proposed control strategy are the SOC and the sign of the difference between the generated and the demanded powers. The obtained simulations results are assessed and carried out using MATLAB/Simulink package and show the effectiveness and the performance of the proposed algorithm.