Small Wind Energy Conversion Systems Research Articles

Study of the Contribution to the Robust Control of a Small Variable Speed Wind Turbine Based on Permanent Magnet Synchronous Generator: Comparison between PI Controller and Sliding Mode Controller

This paper deals with a small wind energy conversion system based on PMSG in isolated sites. The aim is to model the wind chain conversion system based on the management and the control by means of PI and sliding mode controllers. A comparison between the control strategies proved the performance of the second technique in ensuring the stability of DC bus voltage irrespective to the fluctuation of the wind. The different simulation results of all the conversion chains realized under the MATLAB/SIMULINK environment, allowed the evaluation of the suggested system’s performance.

Small Wind Turbine Sensorless MPPT: Robustness Analysis and Lossless Approach

The configuration permanent-magnet synchronous generator with a diode bridge is frequently used in small wind energy conversion systems due to its reliability and low cost. In order to perform a sensorless maximum power point tracking, a suitable method consists of imposing the relationship between the dc current and the dc voltage in optimum operation. However, this strategy requires having knowledge of the system parameters, which are inaccurately known and can vary in real applications. Thus, the optimum curve is not precisely obtained, leading to power losses. This paper evaluates to what extent the power is reduced due to parameter errors. It is shown how the power can be drastically decreased due to some parameter variation, whereas it is not affected by others such as the resistance, which can then be neglected in order to simplify the model. Simulation results for an actual wind profile validate the theoretical analysis.

Wind Potential Analysis in Brasov Built Environment

Implementing renewables in the built environment represents a must, considering the target of Nearly Zero Energy Buildings set by the European legal frame, starting with 2020. One specific feature of the built environment is that it additionally imposes constraints, and can distort the renewable energy potential, particularly the wind energy. Therefore, the development of optimized, efficient small wind turbines requires on-site monitoring and, further on, models developed/adjusted according to these. Thus, the main purpose of this study is the analysis of the available wind potential in the built environment – particularly in theColinaCampus of the Transilvania University, in order to implement small wind energy conversion systems. Wind data are collected during one year (2013) from the meteorological station from Brasov - Ghimbav (located 8 km far from Brasov), and from a second weather station, which is mounted on the rooftop of the university building in Brasov city (University hill). The results indicate that the area has a promising wind potential for the implementation in this built environment of small-sized wind turbines, which can start operating from 0.8 m/s and producing electricity from min. 1.8 m/s.

Three-Stage Static Power Converter for Battery Charging Feasible for Small Wind Energy Conversion Systems

This paper presents the analysis, design, simulation, and experimental results for a three-stage static power converter for battery charging feasible to small wind energy conversion systems. The system employs a boost converter cascaded with a Graetz bridge that allows the implementation of a maximum power point (MPP) tracker and the reduction of the mechanical speed under overvoltage conditions across the batteries. Moreover, a buck converter is connected in series with the boost stage to ensure a constant voltage bus between the aforementioned topologies. Thus, it is possible to extract the maximum power over the entire wind speed range, and battery charging can be realized through conventional techniques. The complete design of the proposed battery charger including power, control, and supervisory circuits is presented and developed, considering a 300-W system, with the possibility of charging battery banks rated at 12 or 24 V. Simulation results are presented to prove the existence of MPPs in the wind generator. Finally, experimental results of the developed prototype required to validate the functionality of the proposed study are presented and discussed.

<inline-formula><tex-math>${\cal L}_1$</tex-math></inline-formula> Adaptive Speed Control of a Small Wind Energy Conversion System for Maximum Power Point Tracking

This paper presents the design of an L 1 adaptive controller for maximum power point tracking (MPPT) of a small variable speed wind energy conversion system (WECS). The proposed controller generates the optimal torque command for the vector-controlled generator-side converter based on the wind speed estimation. The proposed MPPT control algorithm has a generic structure and can be used for different generator types. In order to verify the efficacy of the proposed L 1 adaptive controller for the MPPT of the WECS, a full converter wind turbine with a squirrel cage induction generator is used to carry out case studies using MATLAB/Simulink. The case study results show that the designed L 1 adaptive controller has good tracking performance even with unmodeled dynamics and in the presence of parameter uncertainties and unknown disturbances.

Control of Wind Conversion System Used in Autonomous System

The topology based on permanent magnet generator (PMSG) and diode bridge rectifier is frequently used in small wind energy conversion system since it is robust and easy to control. This paper presents a robust control for the wind conversion system based on PMSG and boost DC/DC converter in the aim to maintain the generator rectified voltage at a reference voltage corresponding to the reference power imposed by the supervisory module. The reference power control is guaranteed without measuring the wind speed. The sufficient conditions for state feedback stabilizing designed controller are given in terms of solutions to a linear matrix inequality (LMI) and H∞. Simulation tests results are carried out for this wind conversion system topology which operates in a multi-source system, in order to visualize the feasibility of the proposed method.

Modeling of small wind turbines based on PMSG with diode bridge for sensorless maximum power tracking

The Permanent Magnet Synchronous Generator (PMSG) with diode bridge is frequently used in small Wind Energy Conversion Systems (WECS). This configuration is robust and cheap, and therefore suitable for small WECS. In order to achieve Maximum Power Point Tracking (MPPT) with no mechanical sensors, it is possible to impose the relationship between the DC voltage and the DC current on the optimum operating points. However, this relationship is difficult to calculate theoretically since the whole system is involved. In fact, as there is no model of the whole system in the literature, the optimum curve IL∗(Vdc) is obtained with experimental tests or simulations. This paper develops an accurate model of the whole WECS, thereby making it possible to relate the electrical variables to the mechanical ones. With this model, it is possible to calculate the optimum curve IL∗(Vdc) from commonly-known system parameters and to control the system from the DC side. Experimental results validate the theoretical analysis and show that maximum power is extracted for actual wind speed profiles.

A sensorless fuzzy-based maximum power point tracker for micro and small wind energy conversion systems

Abstract This paper deals with a small wind energy conversion system (WECS), equipped with a variable-speed wind turbine and a fuzzy Takagi-Sugeno-Kang (TSK) wind estimator is proposed for the maximum power extraction. Using the estimated wind speed, which is usually obtained employing anemometers, a fuzzy-based control system is able to determine and regulate rotor speed for the maximum power extraction. The adoption of a sensorless strategy, especially for small size wind generation systems, leads to lower costs and improved reliability of the overall system.

The integrated design of a permanent-magnet generator for small wind energy conversion system

This paper presents the integrated design, analysis and performance test of a 1.4 kW, radial-flux, permanent-magnet generator applied to small wind energy conversion system (WECS). In a small WECS, the three major components, i.e., turbine, generator and converter, need to be considered all together to gain a maximum overall efficiency, instead of only chasing high performance of individual components. Therefore, the integrated design approach developed for generators in this paper simultaneously considers the characteristics of turbine blades and power electronics for maximum electrical power generation. Finite element analysis (FEA) is employed to verify the design. The performance test shows that the generator prototype has an efficiency of 91% at the design operating condition and the output satisfies the requirement.

Modeling and Simulation of Grid Connected Permanent Magnet Generator (PMG)-based Small Wind Energy Conversion Systems

A small scale wind energy conversion system has tremendous diversity of use and operating conditions, and consequently is evolving rapidly along with the large scale wind energy conversion system for generation of electricity in either stand-alone or grid connected applications. In recent years, the grid connected small wind turbine industry is primarily dominated by the Permanent Magnet Generator (PMG) machines. The power conditioning systems for grid connection of the PMG-based system requires a rectifier, boost converter and a grid-tie inverter. Such system should be based on an appropriate control strategy to control the aerodynamic power during high wind speed, maximum power production, and maximum power flow to the grid at all operating conditions. This paper presents mathematical modeling and control strategy for the grid connected PMG-based small wind turbine systems. Furling control and expected dynamics are adopted with the wind turbine for aerodynamic power control, while the optimum speed of the PMG is followed to ensure maximum power production. A novel controller is derived from the optimum speed information that promise maximum power flow to the grid by controlling the boost converter output voltage and current through the duty cycle. It is found that the proposed modeling and control strategy is feasible and results are verified through simulation.

Design and Performance Evaluation of a Grid Connected Small Wind Energy Conversion System

The power conditioning system for grid connection of a Permanent Magnet Generator (PMG)-based small wind energy conversion system requires a rectifier, boost converter and a grid-tie inverter. Such system should be based on an appropriate control strategy to control the aerodynamic power during high wind speed, maximum power production, and maximum power flow to the grid at all operating conditions. This paper presents mathematical modeling and control strategy for the grid connected PMG-based small wind energy conversion system. Furling control and expected dynamics are adopted with the wind turbine for aerodynamic power control, while the optimum speed of the wind turbine is followed to ensure the maximum power production. A novel controller is derived from the optimum speed information that promises maximum power flow to the grid by controlling the boost converter output voltage and current through the duty cycle. It is found that the proposed modeling and control strategy is feasible and results are verified through simulation as well as laboratory experimentation.

Power Electronics Reliability Comparison of Grid Connected Small Wind Energy Conversion Systems

This work presents a power electronics reliability comparison of the power conditioning system for both the Permanent Magnet Generator (PMG) and Wound Rotor Induction Generator (WRIG)-based small Wind Energy Conversion Systems (WECS). The power conditioning system for grid connection of the PMG-based system requires a rectifier, boost converter and a grid-tie inverter, while the WRIG-based system employs a rectifier, a switch and an external resistor in the rotor side with the stator directly connected to the grid. Reliability of the power conditioning system is analyzed for the worst case scenario of maximum conversion losses at a predetermined wind speed. The analysis reveals that the Mean Time Between Failures (MTBF) of the power conditioning system of a WRIG-based small wind turbine is much higher than the MTBF of the power conditioning system of a PMG-based small wind turbine. The investigation is extended to identify the least reliable component within the power conditioning system for both systems. It is shown that the inverter has the dominant effect on the system reliability for the PMG-based system, while the rectifier is the least reliable for the WRIG-based system. This research indicates that the WRIG-based small wind turbine with a simple power conditioning system is a much better option for small wind energy conversion system.

Experimental Comparison of Performances of Grid Connected Small Wind Energy Conversion Systems

This paper presents an experimental comparative study of performances in terms of efficiency on two possible grid connected small wind turbine systems. One of the systems is based on Permanent Magnet Generator (PMG) and the other system is based on Wound Rotor Induction Generator (WRIG). The Power Conditioning System (PCS) for grid connection of the PMG-based system requires a rectifier, boost converter and a grid-tie inverter, while the WRIG-based system employs a rectifier, a switch and an external resistance in the rotor side with the stator directly connected to the grid. Experimental test benches for both systems are implemented using Wind Turbine Emulator (WTE) and Maximum Power Point Tracking (MPPT) control strategy. The procedure for calculate the PCS losses, energy capture and energy loss is presented. The expected efficiency of the systems is investigated for wind distributions at eight sites in Newfoundland and Labrador. It is shown that a WRIG-based system could provide 5% higher efficiency in contrast to a PMG-based system and could be an optimum alternative in the small wind energy domain.

Productivity of small wind turbines for various wind potentials conditions: application in Bulgaria and Corsica

Less or more accurate power curve models are generally used to simulate the wind turbine electrical production versus the available wind speed. However, if such models are adapted to large machines, this is not the case for small ones. The objective of this paper is to study the impact of different small-scale wind turbines power curves and wind distributions on the electrical production. An inventory of small wind turbines available on the market shows a great diversity of technical specifications and power curves and among them, eight types of power curves have been selected as representative of the available small machines. The influence of wind distribution and wind turbines power curves on the estimated production is shown. Lastly, a comparison of small wind energy conversion systems (WECS) performances on various sites in Bulgaria and Corsica is performed and shows that, for a same rated wind turbine power, in a same location, the electrical production varies greatly depending on the wind turbine power curve.

Dynamic response analysis of small wind energy conversion systems (WECS) operating with torque control versus speed control

Dynamic response analysis of small wind energy conversion systems (WECS) operating with torque control versus speed control

Performance Comparison of Grid Connected Small Wind Energy Conversion Systems

A small scale Wind Energy Conversion System (WECS) has tremendous diversity of use and operating conditions, and consequently is evolving rapidly along with the large scale WECS for generation of electricity in either on grid or off grid applications. In recent years, the grid connected Small Wind Turbine (SWT) industry is primarily dominated by the Permanent Magnet Generators (PMGs) based topology. The Power Conditioning Systems (PCS) for grid connection of the PMG based topology requires a rectifier, boost converter and a grid-tie inverter. However, a small wind turbine may be based on Wound Rotor Induction Generators (WRIGs). The WRIG based topology can employ a rectifier, a chopper and an external resistor in the rotor side while the stator is directly connected to the grid. These two topologies have diverse losses that fluctuate with the wind speed. This paper presents a comparative study of a PMG and WRIG based topologies for SWT systems. The study employs numerical simulation to investigate the conversion losses for both topologies. It is demonstrated that a WRIG based topology offers less losses than a PMG based topology. The comparison is further enhanced by investigating the annual energy capture, annual energy loss and efficiency for the wind speed data and Weibull distribution of three different locations of Newfoundland, Canada. The study shows that a WRIG based topology is an optimum alternative in terms of performance characteristics within a slip variation of 15%.

Energy capture by a small wind-energy conversion system

Furling is the most common method used by the small wind-turbine industry to control the aerodynamic power extraction from the wind. A small wind-turbine with furling mechanism and its resulting dynamics are modelled using Matlab/Simulinkplatform in this paper. The model simulates regulating the speed of the wind-turbine via a load-control method. Tip-speed ratio and hill-climbing control methods for maximum-power extraction from a small wind-turbine are investigated. Two dynamic controllers are designed and their behaviours simulated. In the first method, the controller uses the wind-speed and rotor speed information to control the load in order to operate the wind-turbine at its optimal tip-speed ratio. In the second method, the controller compares the output power of the turbine with the previous power, and controls the load based on the power difference. In order to determine a suitable control strategy for the small wind-energy conversion system, several tests are performed. Wind-speed versus power-curve and annual energy capture of the system for each control method are determined for wind conditions in St. John’s, Newfoundland. The annual energy-capture is determined using the bin’s power-curve method. Wind-speed data and Rayleigh distribution of St. John’s, Newfoundland are used to determine the annual energy-capture. The results of the simulations indicate that the energy capture of a wind-turbine depends not only on the control strategy but on the wind-speed and Rayleigh distribution. The results of the investigation lead to the conclusion that the hill-climbing method of control results in a greater annual energy-output.

Optimisation of a small non controlled wind energy conversion system for stand-alone applications

This article proposes a method to optimize the design of a small fixed-voltage wind energy conversion system (WECS). The system is composed of commercially available elements which are: a small horizontal axe wind turbine, a onestage gearbox, a permanent magnet synchronous generator, a diode bridge and a battery bank. As there are no controlled devices on the system, the design must be carefully done to find the configuration that maximizes both, the system utilization and the system's output power. Using the mechanical and the electrical power equations, an optimization problem is proposed. This problem is aimed to find the optimal combination of the gearbox ratio and the battery voltage in order to extract the maximum amount of energy form the WECS. The mechanical power is modelled using a new proposed power coefficient function approximation. The constrained optimization problem is then solved by a MATHEMATICA© genetic algorithm based routine. Results are shown and discussed.

Preliminary experimental study of a small reverse osmosiswind-powered desalination plant

The paper describes the work carried out in the development of a small wind-powered desalination plant. Analternative control system was studied to serve as a direct interphase between a reverse osmosis desalination plant and a small wind energy conversion system. The main purpose was to reduce or eliminate the need for an energy storage system (usually, a battery bank). In order to achieve this objective, an experimental prototype of a desalination plant and a wind generator simulator were developed. The systems were evaluated under laboratory-controlled conditions and subjected to field trials. The experimental plant desalinates highly saline seawater (35,000 mg/L) at a rate of approximately 0.4 m 3/d. This amount of potable water is sufficient to supply the basic water demands in a small community in an isolated location. The paper also describes the identification of technical problems associated with operating a desalination plant with an intermittent source of energy (wind).

Reliability evaluation of small stand-alone wind energy conversion systems using a time series simulation model

Reliability evaluation of small stand-alone wind energy conversion systems using a time series simulation model