Testing basic performance of a very small wind turbine designed for multi-purposes

A very small wind turbine system for multi-purposes was developed and its performance was reported in this paper. The rotor diameter of the turbine is 500 mm. The tests of the energy output, turbine speed, power coefficient, and torque of turbine were carried out for a wide rage of free stream velocity. The flow around the wind turbine and the influence of the turbulence were investigated with a particle image velocimetry. Experimentally obtained power coefficient was 0.4 in maximum and 0.36 in the rated running condition, respectively. The tip speed ratio corresponding to the optimum driving condition was 2.7. Comparing with the other commercial turbines, the performance was excellent at a slow turbine speed. By the flow visualization and PIV measurement around the wind turbine, the approaching flow velocity and the accelerated flow field passing the blade tip was obtained. It was confirmed that the actual flow passed through the blades was about 20% slower than the ideal flow. Tip vortex shed from the blade tip was also visualized clearly.     

Second law analysis of wind turbine power plants: Cesme, Izmir example

In this study, the energy and exergy efficiency results of the Wind Turbine Power Plants (WTPPs) are presented. Exergy, energy and technical availability analysis are performed. The case study includes the actual system data taken from the system in Cesme, Izmir WTPP. General energy, exergy and other performance parameters are also presented. Investigated WTPP is Turkey’s first installed (1998) wind plant (1.50 MW) located in Izmir. Exergy efficiency of the power plant found to be between 0% and 68.20%. The monthly average technical availabilities are 96.11%, 98.71%, 98.52% for turbine 1, turbine 2, and turbine 3, respectively. Furthermore, authors developed some correlations, which are capable of predicting the values of exergy efficiencies of the WTPP for different power factor value.     

Model simplification and optimization of a passive wind turbine generator

In this paper, the design of a “low cost full passive structure” of wind turbine system without active electronic part (power and control) is investigated. The efficiency of such device can be obtained only if the design parameters are mutually adapted through an optimization design approach. For this purpose, sizing and simulating models are developed to characterize the behavior and the efficiency of the wind turbine system. A model simplification approach is presented, allowing the reduction of computational times and the investigation of multiple Pareto-optimal solutions with a multiobjective genetic algorithm. Results show that the optimized wind turbine configurations are capable of matching very closely the behavior of active wind turbine systems which operate at optimal wind powers by using a MPPT control device.     

Evaluation of small wind turbines in distributed arrangement as sustainable wind energy option for Barbados

The island of Barbados is 99% dependent on fossil fuel imports to satisfy its energy needs, which is unsustainable. This study proposes a 10 MW distributed wind energy scheme using micro wind turbines (WT) of horizontal (HAWT) and vertical axis (VAWT) configurations. These units are rated less than 500 W, and the scheme is hereafter referred to as mWT10. mWT10 is compared to the proposed 10 MW medium WT farm by the Barbados Light & Power Company (BL&P). The economic bottom line is the levelized cost of electricity (LCOE). The results highlight the BL&P proposal as the best economic option at BDS$0.19 per kWh, while that of both mWT10 configurations exceeds the conventional cost of BDS$0.25 by two to nine times. This is attributed to significantly higher relative installation and operational costs. However, the financial gap between mWT10 LCOE and the retail price of electricity is much smaller due to a large fuel surcharge passed on to each customer. Annual additional benefits of using wind energy include: greenhouse gas emissions savings of 6–23 kt of carbon dioxide; and anavoided fuel costs of BDS$1.5–5.3 million.

The distributed mWT10 using HAWTs competes directly with the BL&P farm, however, it provides these benefits without the visual or ecological impacts of the larger machines. Conversely, VAWTs have features that favour a visually discrete and widely repeatable scheme but suffer relatively high costs. Therefore, this study illustrates the great potential of small wind turbines to be competitive with conventional wind farms, thus challenging the small wind industry to meet its potential by producing reliable and robust machines at lower cost.     

并网中小型风电系统最大功率跟踪控制

针对目前中小型风力发电系统发电效率低,提出了一种新型拓扑结构,即机侧采用三相PWM整流器,网侧采用单相PWM逆变器。在对永磁同步发电机数学模型和风力机最佳输出功率进行分析的基础上,采用转子磁链定向控制技术,实现对发电机输出的有功功率的控制,进而实现对风力发电机最大功率的跟踪控制;同时,在单相系统中引入"虚拟电路",使网侧单相变流电路参数可以转化到旋转坐标系下,实现无静差控制。通过仿真试验验证了控制策略的可行性。     

Analysis and synthesis of sliding mode control for large scale variable speed wind turbine for power optimization

The problem of designing a nonlinear feedback control scheme for variable speed wind turbines, without wind speed measurements, in below rated wind conditions was addressed. The objective is to operate the wind turbines in order to have maximum wind power extraction while also the mechanical loads are reduced. Two control strategies were proposed seeking a better performance. The first strategy uses a tracking controller that ensures the optimal angular velocity for the rotor. The second strategy uses a Maximum Power Point Tracking (MPPT) algorithm while a non-homogeneous quasi-continuous high-order sliding mode controller is applied to ensure the power tracking. Two algorithms were developed to solve the tracking control problem for the first strategy. The first one is a sliding mode output feedback torque controller combined with a wind speed estimator. The second algorithm is a quasi-continuous high-order sliding mode controller to ensure the speed tracking. The proposed controllers are compared with existing control strategies and their performance is validated using a FAST model based on the Controls Advanced Research Turbine (CART). The controllers show a good performance in terms of energy extraction and load reduction.     

Displacement of the maximum power point caused by losses in wind turbine systems

The energy yield of wind turbines is to a large extent determined by the performance of the Maximum Power Point Tracking (MPPT) algorithm. Conventionally, they are programmed to maximize the turbines power coefficient. However, due to losses in the generator and converter, the true optimal operating point of the system shifts. This effect is often overlooked, which results in a decreased energy yield. Therefore, in this paper, the wind turbine system is modeled including the dominant loss components to investigate this effect in detail. By simulations and experiments on a wind turbine emulator, it is shown that the location of the maximum power point is significantly affected for low wind speeds. For high wind speeds, the effect is less pronounced. The parameter of interest is the increase in yearly energy output with respect to the classical MPPT method, which is calculated in this paper by including a Rayleigh wind speed distribution. For typical average wind speeds, the energy yield can increase with 1–2%. There is no cost associated with operating the turbine in the overall MPP, making it worthwhile to include this effect. The findings are implemented in an MPPT algorithm to validate the increased performance in a dynamic situation.     

并网风电机组输出电能闪变和谐波指标的比较与分析

对根据IEC 61400-21标准进行测试的四款风电机组,即750 kW定桨失速型机组、2 MW变速恒频全馈机组、2.5 MW变速恒频双馈机组和运达（WD77-1500 A/1500 kW）变速恒频双馈机组的电能质量测试和评估报告进行了分析,通过比较风电机组闪变的测量值、谐波电流值,可对各种风电机组在不同方面的性能有一定的了解。     

Production price of hydrogen from grid connected electrolysis in a power market with high wind penetration.

In liberalized power markets, there are significant power price fluctuations due to independently varying changes in demand and supply, the latter being substantial in systems with high wind power penetration. In such systems, hydrogen production by grid connected electrolysis can be cost optimized by operating an electrolyzer part time. This paper presents a study on the minimization of the hydrogen production price and its dependence on estimated power price fluctuations. The calculation of power price fluctuations is based on a parameterization of existing data on wind power production, power consumption and power price evolution in the West Danish power market area. The price for hydrogen is derived as a function of the optimal electrolyzer operation hours per year for four different wind penetration scenarios. It is found to amount to 0.41–0.45 €/Nm³. The study further discusses the hydrogen price sensitivity towards investment costs and the contribution from non-wind power sources.     

A fuzzy control strategy for power smoothing and grid dynamic response enrichment of a grid‐connected wind energy conversion system

This paper concentrates on the output power smoothing and the grid dynamic response enhancement of a grid‐interactive MW‐class permanent magnet synchronous generator‐based wind energy conversion system (WECS). A simple fuzzy controller method is applied to improve the overall performance of the WECS. The proposed method can retrieve the storing kinetic energy from the inertia of a wind turbine, perfectly. As a result, it can ensure a proficient power smoothing of the variable speed WECS. On the other hand, the grid side inverter is controlled by the fuzzy controller. This approach can reduce the fluctuation of DC link voltage and can deliver a smooth power to the power grid. The proposed method is compared with two other methods such as the maximum power point tracking control method and the without fuzzy controller method. A simple shunt circuit also includes in the DC link circuit. Therefore, during the system fault condition, the WECS can perform a stable operation. Effectiveness of the proposed method is verified by numerical simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

Performance and viability analysis of small wind turbines in the European Union

Nowadays, wind energy plays a key role as a sustainable source of energy and wind turbines are a relevant source of power for many countries world-wide. In such a context, this paper investigates the technical and economic feasibility of small wind turbines for five of the main European Union countries (France, Germany, Italy, Spain and The Netherlands). Ten commercial turbines with rated power from 2.5 kW to 200 kW are evaluated considering their installation and operative conditions. Several parameters most affecting wind turbine performances are evaluated and the estimation of the annual cash flows during the expected plant life-time are determined as a function of both the installation location (wind speed probability distribution, national incentive scheme and tax level) and the wind turbine characteristics (rated power curve, maintenance, installation and shipping costs). The obtained data are presented and discussed through a parametric analysis based on the Net Present Value capital budget approach, showing the conditions making these systems profitable or non-profitable and explaining the relative motivations. Moreover, the analysis outcomes are further investigated highlighting the dependence of the turbine profitability from the considered parameters, including a comparative analysis among the five analyzed European countries.     

Dynamic model of wind energy conversion systems with PMSG-based variable-speed wind turbines for power system studies

In order to study the impact of a wind farm on the dynamics of the power system, a significant issue is to develop appropriate equivalent models that allow characterizing the dynamics of all individual wind turbine generators (WTGs) composing the park. In this sense, with the advance of power electronics, direct-driven permanent magnet synchronous generators (PMSGs) have drawn increased interest to wind turbine manufacturers due to their advantages over other variable-speed WTGs. These include the possibility of multi-pole design with a gearless construction that offers slow speed operation and reduced maintenance since no brushes are used, elimination of the excitation system, full controllability for maximum wind power extraction and grid interface, and easiness in accomplishing fault-ride through and grid support. In this way, this paper presents a comprehensive dynamic equivalent model of a wind farm with direct-driven PMSG wind turbines using full-scale converters and its control scheme. The proposed simplified modelling is developed using the state-space averaging technique and is implemented in the MATLAB/Simulink environment. The dynamic performance of the wind farm and its impact on the power system operation is evaluated using the phasor simulation method.     

In fault ride through reactive current rise time requirements of various European grid codes—analysis based on a full‐converter wind turbine

The European transmission system operators specify grid codes to ensure a safe and reliable operation of the electrical power system, even during grid faults. Wind power plants have to comply with such specific requirements prior to installation and operation. Some of the requirements, however, are open to interpretation, especially because of lack of specification, and therefore, they pose technical challenges to full‐converter wind turbines. In fact, different interpretations leave it open to debate on whether a requirement can be fulfilled or not. The rise time requirement across some European grid codes is discussed in this paper. First the uncertainties in some transmission system operators' definitions of rise time, step response time and settling time are presented, and then a comparative analysis is performed among calculation methods, such as instantaneous reactive current in alpha‐beta reference frame, direct and quadrature reference frame and root mean square of the positive sequence component. The comparison results of both ideal cases and randomly selected measurements from actual full‐converter wind turbine field tests show that the rise time of the reactive current is significantly affected by the calculation methods. This effect in some cases can make the difference between fulfilling the requirement or not. As a result of that, it is highlighted in this paper the need for a common understanding of the rise time requirements between industry and system operators, based on clear technical fundamentals. Copyright © 2015 John Wiley & Sons, Ltd.     

Experimental study of the functionality of a semisubmersible wind turbine combined with flap-type Wave Energy Converters

In the present paper the functionality of the Semisubmersible wind energy and Flap-type wave energy Converter (SFC) is examined experimentally. In order to study the functionality of the SFC, the focus is on operational environmental conditions. SFC is a combined concept that utilizes offshore wind energy and ocean wave energy for power production. Details are presented as far as the physical modelling of the wind turbine with the use of a redesigned small-scale rotor and of the Power Take-Off mechanism of the Wave Energy Converters (WECs) with the use of a configuration that is based on a mechanical rotary damper. Tests with quasi-static excitation, motion decay, regular and irregular waves without and with wind that is uniform are conducted on an 1:50 scale physical model. The experimental data are compared with numerical predictions obtained by a fully coupled numerical model using Simo/Riflex tool. A good agreement is observed between experimental and numerical predictions. The combined operation of WECs doesn't affect the tension of mooring lines nor the acceleration of nacelle and the bending moment in tower's base. The produced power of the WECs of the SFC and consequently the functionality of the SFC is estimated.     

Power flow control of grid connected hybrid renewable energy system using hybrid controller with pumped storage

This paper presents a grid-connected HRES using a hybrid controller with PHS for optimal power flow control and minimizing the production cost. The novelty of the proposed approach is the joined execution of the SSA and CSA named as SSA-CS are apparently a very new metaheuristic algorithm. Moreover, the proposed method is the cost-effective power production of the microgrids and effective utilization of renewable energy sources without wasting the available energy. Here, the energy sources in particular PV system, WT, MT and battery with PHS are utilized to generate the power of the MG system. In the proposed approach, the required power demand of the energy system is predicted by the ANN technique. After that, the production cost minimization is done in view of the anticipated load demand by utilizing the optimization approaches to be a specific SSA-CS algorithm. The result of the proposed approach is actualized in the MATLAB/Simulink working platform. The performance of the proposed approach is examined by comparing the current methodologies such as SSA and PSO with the proposed SSA-CS approach. The simulation results show that the proposed method generates maximum power and furthermore the proposed framework has less production cost in light of the power demand.