Generator Based Wind Energy Conversion Research Articles

Wind Velocity Sensorless Maximum Power Point Tracking Algorithm in Grid-connected Wind Energy Conversion System

This article proposes a wind velocity sensorless hill-climb searching algorithm in the grid-connected field-oriented controlled permanent magnet synchronous generator based wind energy conversion system. The proposed method improves the speed and accuracy of initial tracking. Pseudo-optimum points are used to track the exact optimum points using the power versus speed characteristics of a wind turbine for various wind velocities. This research emphasizes that the pseudo-optimum points using the power versus speed characteristics are always less than and much nearer to the exact optimum points. The small-step forward tracking after pseudo-optimum points improves the accuracy of this algorithm. Moreover, this method improves the tracking speed for various wind velocities. The system used for this research consists of a back-to-back sinusoidal pulse-width modulation converter between the generator and the grid. The performance of the proposed method is analyzed mathematically and verified by simulation using MATLAB/Simulink software (The Mathworks, Natick; Massachusetts, USA).

A New Three-mode Maximum Power Point Tracking Algorithm for Doubly Fed Induction Generator Based Wind Energy Conversion System

This paper proposes a new algorithm for maximum power point tracking of a wind energy conversion system, which is based on a doubly fed induction generator. The algorithm has three modes. In the first mode, the maximum power point is tracked and also the output power is smoothed. Once the turbine operating point reaches the optimal point, the second mode is activated to fix the speed of the turbine. In addition, this mode has a self-tuning capability. When the turbine operating point is far from the optimal value, the third mode is activated. In this mode, the optimal power curve along with the fuzzy logic is used to bring the turbine operating point rapidly to a point near the maximum power point. To verify the accuracy of the proposed algorithm, a large wind energy conversion system is simulated, and the simulation results are compared with the perturbation and observation algorithm.

Reliability comparison of power electronic converters for grid-connected 1.5kW wind energy conversion system

This work presents reliability analysis of the power electronic converters for grid-connected permanent magnet generator-based 1.5 kW wind energy conversion system based on the semiconductor power losses. The power converters examined are: the intermediate boost converter (IBC), the intermediate buck-boost converter (IBBC), the back-to-back converter (BBC) and the matrix converter (MC). The aim is to determine which power electronic converter yields the highest mean time between failures (MTBF) and reliability in terms of power losses of the semiconductor devices with a predetermined wind speed. In view of this, a furled wind turbine model is developed and used to generate power for different wind speeds. Afterwards, a relation between the wind speed and MTBF is established to evaluate the reliability of the power electronic converters. The power loss model presented in this paper has taken into account the conduction and switching losses of the semiconductor devices within each converter. The analysis reveals that efficiency and MTBF of an IBC are much higher compared to the other converters considered in this research. The investigation is extended to identify the least reliable component within the converters. It is shown that the inverter has the dominant effect on the system reliability for the converters. This research indicates that IBC with a simple rectifier is a much better option for grid-connected permanent magnet generator based wind energy conversion system.

Disturbances Rejection and Harmonics Reduction of Doubly Fed Induction Generator Based Wind Energy Conversion Systems

Although the doubly fed induction generator has many advantages over other configurations of wind energy conversion systems, it is not only susceptible to low power quality but also generates some power quality problems, such as harmonics. Proliferation of non-linear loads and high-scale penetration of doubly fed induction generator based turbines in the near future make disturbance rejection and harmonic reduction of these systems important issues. Therefore, this article aims to reduce the effects of the grid power quality problems on doubly fed induction generators and power quality problems caused by the doubly fed induction generator itself. To achieve this goal, the capability of the grid-side converter is extended by means of adding an active filtering function based on the voltage-detecting method. By this way, the fatal effects of system voltage disturbances and instantaneous active power oscillations can be reduced. Moreover, the proposed system is capable of damping out harmonic propagation phenomenon that is of great concern in offshore wind farms. In this system, to reduce harmonics emission of the doubly fed induction generator and further improve of its performance, a noise-shaping modulator, named ΣΔ, is utilized for modulation of rotor- and grid-side converters. Simulation results demonstrate the efficiency of proposed strategy.

Solid-state controller for an IAG-based stand-alone wind energy conversion system

This paper deals with an implementation of voltage and frequency controller (VFC) for isolated asynchronous generator-based three-phase autonomous wind energy conversion system. The focus of the proposed work is to provide a feasible solution for rural communities to serve their electricity needs. The least mean square algorithm is used for the extraction of active and reactive power components of the load currents. A three-leg voltage-sourced converter with a battery energy storage system is used as a VFC. The control algorithm is implemented using a digital signal processor. The steady-state and dynamic performances of VFC are demonstrated through test results under static and dynamic loads.

A New Maximum Power Point Tracking Technique for Permanent Magnet Synchronous Generator Based Wind Energy Conversion System

A new maximum power point tracking technique for permanent magnet synchronous generator based wind energy conversion systems is proposed. The technique searches for the system optimum relationship for maximum power point tracking and then controls the system based on this relationship. The validity of the technique is theoretically analyzed, and the design procedure is presented. The primary merit of the proposed technique is that it does not require an anemometer or preknowledge of a system, but has an accurate and fast response to wind speed fluctuations. Moreover, it has the ability of online updating of time-dependant turbine or generator parameter shift. The validity and performance of the proposed technique are confirmed by MATLAB/Simulink simulations and experimentations.

FIS/ANFIS Based Optimal Control for Maximum Power Extraction in Variable-speed Wind Energy Conversion System

An optimal control for maximizing extraction of power in variable-speed wind energy conversion system is presented. Intelligent gradient detection by fuzzy inference system (FIS) in maximum power point tracking control is proposed to achieve power curve operating near optimal point. Speed rotor reference can be adjusted by maximum power point tracking fuzzy controller (MPPTFC) such that the turbine operates around maximum power. Power curve model can be modelled by using adaptive neuro fuzzy inference system (ANFIS). It is required to simply well estimate just a few number of maximum power points corresponding to optimum generator rotor speed under varying wind speed, implying its training can be done with less effort. Using the trained fuzzy model, some estimated maximum power points as well as their corresponding generator rotor speed and wind speed are determined, from which a linear wind speed feedback controller (LWSFC) capable of producing optimum generator speed can be obtained. Applied to a squirrel-cage induction generator based wind energy conversion system, MPPTFC and LWSFC could maximize extraction of the wind energy, verified by a power coefficient stay at its maximum almost all the time and an actual power line close to a maximum power efficiency line reference.

Reliability analysis of grid connected small wind turbine power electronics

Grid connection of small permanent magnet generator (PMG) based wind turbines requires a power conditioning system comprising a bridge rectifier, a dc–dc converter and a grid-tie inverter. This work presents a reliability analysis and an identification of the least reliable component of the power conditioning system of such grid connection arrangements. Reliability of the configuration is analyzed for the worst case scenario of maximum conversion losses at a particular wind speed. The analysis reveals that the reliability of the power conditioning system of such PMG based wind turbines is fairly low and it reduces to 84% of initial value within one year. The investigation is further enhanced by identifying the least reliable component within the power conditioning system and found that the inverter has the dominant effect on the system reliability, while the dc–dc converter has the least significant effect. The reliability analysis demonstrates that a permanent magnet generator based wind energy conversion system is not the best option from the point of view of power conditioning system reliability. The analysis also reveals that new research is required to determine a robust power electronics configuration for small wind turbine conversion systems.