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Currently, marine transportation in the world still uses fossil fuels. In addition to running low on supplies, fossil fuels also cause emissions that cause global warming. Sea transportation generates around 1,000 million tonnes of CO2 emissions. Therefore, the exploration of alternative energy is becoming a popular research direction. Several renewable energy sources include solar and wind energy. Indonesia has an average wind speed of above 8 m/s at sea. Also, the energy potential of the sun is around 4.8 kWh/m2. Based on the potential of these renewable energy sources, this study discusses the potential of renewable energy sources from sunlight and wind, which are implemented in the prototype catamaran ship. The results obtained from the experiment, the total energy of photovoltaic (PV) and wind turbine generators is 774 Wh. This energy can be used to charge a battery with a battery specification of 35Ah for 6 hours.

The risk of oscillation of grid-connected wind turbine generators (WTGs) is well known, making it all the more important to understand the characteristics of different WTGs and analyze their performance so that the problems’ causes are identified and resolved. While many studies have evaluated the performance of grid-connected WTGs, most lack clarity and precision in the modeling and simulation techniques used. Moreover, most of the literature focuses on a single mode of operation of WTGs to analyze their performances. Therefore, this paper updates the literature by considering the different operating conditions for WTGs. Using MATLAB/SIMULINK it expands the evaluation to the full range of vulnerabilities of WTGs: from the wind turbine to grid connection. A network representing grid-connected squirrel-cage induction generator (SCIG) and doubly-fed induction generator (DFIG) wind turbines are selected for simulation. The performances of SCIG and DFIG wind turbines are evaluated in terms of their energy generation capacity during constant rated wind speed, variable wind speed, and ability of fault-ride through during dynamic system transient operating conditions. The simulation results show the performance of DFIG is better than SCIG in terms of its energy generation capacity during variable wind speed conditions and active and reactive power control capability during steady-state and transient operating conditions. As a result, DFIG wind turbine is more suitable for large-scale wind power plants connected to weak utility grid applications than SCIG.

In many electrical grids, the share of renewable energy generation increases. As these generators are typically connected to the grid via inverters, the level of grid inertia decreases. Such grids may therefore suffer from high rates of change of frequency during power imbalances. Modern wind turbines can help in controlling the frequency in such grids by providing synthetic inertia. A controller to provide synthetic inertia with wind turbines was developed at the Wind Energy Technology Institute in collaboration with Suzlon Energy. For this controller the influence of providing synthetic inertia on the mechanical loads of the wind turbine is assessed for different grid frequency scenarios. Such a scenario-based load analysis has not been published before, especially as the scenarios are derived from real measurements. The effect of the loads strongly depends on the analyzed grid frequency behavior. Ten months of high quality grid frequency measurements of the Indian grid are analyzed in order to derive inputs for the load calculation. Different types of grid frequency abnormities are identified and categorized with respect to their severity. Based on the observed occurrences of the grid frequency abnormities, realistic scenarios for the load calculations are chosen. The load calculations are performed for a state-of-the-art Suzlon wind turbine generator. The load increases caused by the supply of synthetic inertia are calculated for individual components assuming an otherwise undisturbed power production of the wind turbine in turbulent wind. Furthermore, a hardware-in-the-loop test bench is used to show how the measured grid frequencies are actually perceived by the control system of a typical wind turbine. The original frequency data were recorded with high quality measurement equipment, which is faster and more accurate than a multi-function relay, often used in wind turbines. For exemplary time traces, the effect of the reduced measurement accuracy on the reaction of the wind turbine is shown. This aspect has not been investigated in the literature yet. The results show that wind turbines can provide synthetic inertia without a considerable effect on the lifetime of the wind turbine. However, there are still problems with providing synthetic inertia reliably at high power operating points, which have to be solved.

High temperature superconducting (HTS) technologies are expected to be a key enabler for lightweight and cost-effective direct-drive (DD) trains for large wind turbines. This paper reports the designing and basic experimental validation of the world's first full-scale DD HTS generator demonstrated on a commercial wind turbine. The HTS generator has its rotor with an HTS field winding working below 30 K, which is achieved by using off-the-shelf Gifford-McMahon cryocoolers. The stator of the generator is essentially conventional, except that the armature winding has four segments to limit fault torques in case of sudden short circuits due to converter failures. Compared to an existing DD permanent magnet generator on the turbine, the air gap shearing stress of the HTS generator is doubled, and the weight is reduced by 24%. The overall design requirements from the turbine integration perspective, as well as the topological considerations, are first described in this paper. The electromagnetic and cryogenic designs are then presented, followed by performance testing of HTS coils. The basic experimental validation shows that the cryogenic design is satisfactory and the measured no-load voltage matches the finite element calculation very well.

Innovations which help facilitate predictive maintenance strategies have the potential to greatly reduce costs associated with wind turbine O&M by driving efficiency and increasing wind turbine availability. This study uses multiple examples of the same generator bearing failure to provide insight into how condition monitoring systems can be used in to train machine learning algorithms with the ultimate goal of predicting failure and remaining useful life. Results show that by analysing high-frequency vibration data and extracting key features to train support vector machine algorithms, an accuracy of 67% can be achieved in successfully predicting failure 1–2 months before occurrence. This study reflects on the limitations surrounding a generalised training approach, taking advantage of all available data, showing that if too many different examples are considered of different wind turbines and operating conditions, the overall accuracy can be diminished.

As a powerful power system simulation software package, PSS/E has great advantage in large-scale power system simulation. However, in the PSS/E dynamic model, there is no low voltage ride through (LVRT) the model for the wind turbine generator, and that is why for engineering practice it less referred with regard to wind power simulation. According to the analysis of the principle of the PSS/E second generation generic model wind generator, this paper built the LVRT a model-based PSS/E second generation generic model for the wind generator with the help of Fortran, and the model has been verified. The model this paper has built enriches the dynamic model of PSS/E and has led to more reference to PSS/E in engineering practice for the study of power system simulation with fluctuant wind power.

Inverter-based resources (IBRs) exhibit different short-circuit characteristics compared to traditional synchronous generators (SGs). Hence, increased uptake of IBRs in the power system is expected to impact the performance of traditional protective relay schemes—set under the assumption of a SG-dominated power system. Protection engineers need to study these challenges and develop remedial solutions ensuring the effectiveness of system protection under higher levels of IBRs. To address this need, this paper studies the impact of IBRs on a variety of protective relay schemes including line distance protection, memory-polarized zero sequence directional protective relay element, negative sequence quantities-based protection, line current differential protection, phase comparison protection, rate-of-change-of-frequency, and power swing detection. For each protection function, potential misoperation scenarios are identified, and recommendations are provided to address the misoperation issue. The objective is to provide an improved understanding of the way IBRs may negatively impact the performance of traditional protection schemes as a first step towards developing future remedial solutions ensuring effective protection under high share of IBRs.

The EU-funded EcoSwing project addresses the world's first full-scale direct-drive (DD) high temperature superconducting (HTS) wind turbine generator. Before the generator was installed on a commercial wind turbine, the generator had been tested on the ground at the Dynamic Nacelle Testing Laboratory (DyNaLab) in Fraunhofer Institute for Wind Energy Systems (IWES), serving as an experimental validation of the generator design. This article is centered on the ground testing of the EcoSwing HTS generator, which includes corresponding tests for validating the generator's cryogenic design and electromagnetic performance. Despite one HTS coil with a defect limiting the operating current significantly, partial power production up to 1 MW at 14.5 rpm was reached. The critical auxiliary systems, i.e., vacuum system and rotary helium coupling, behaved as expected or even better than anticipated. The work reported in the article successfully validates the generator design, and also provides firsthand information prior to installing and testing the HTS generator on the wind turbine.

This paper analyses the electromechanical dynamics of the pole-piece rotors in a pseudo direct-drive wind turbine generator. The investigated generator has a rated power of 10 MW and was designed in the INNWIND.EU project. One way coupled finite element analysis (FEA) was used to calculate the rotor dynamic defections caused by electromagnetic forces in the air gap. Results show that the deflection exceeds the air gap length which is not mechanically feasible. To solve the problem, three structural modifications are proposed and tested in FEA to reduce the pole piece deflection significantly. The results of the three solutions are compared to idenfity the most promising one. It shows that a ribbed rotor piece topology is the most suitable option because it achieves a reasonable tradeoff between the torque generation and mechanical deflection.

Businesses are employing distributed generation techniques, such as wind turbines, to decarbonise their electrical energy supply by reducing their dependence on fossil-fuel-generated energy. This study investigates the effectiveness of a company making a €3,500,000 investment in a 3-MW on-site wind turbine to supply some or all of their factory electrical loads. The results should benefit the investing company and other potential investors by evaluating the economic, environmental, and social outcomes of the investment. A case study methodology was used. The study found that the payback period was six and a half years, and the turbine installation benefited the environment by offsetting 3,195 tonnes of CO2 per annum. As part of the power-quality analysis of the wind-turbine output, the short-term variability of the power output signal was calculated as the coefficient of variation values. The study found that the most stable power output is achieved when the turbine is generating at full output power (i.e., 3-MW). In addition to the existing range of traditional power quality parameters, the coefficient of variation parameter was found to be an essential aspect of electrical power quality and should be included in future practice.

This paper proposes a coordinated control scheme for wind turbine generators (WTGs) and energy storage in microgrids with high wind power penetration. The proposed scheme aimed to reduce the system frequency deviation caused by variations in wind power and loads. To stabilize the frequency, the WTG and energy storage system (ESS) are used for kinetic energy generation and electrical energy storage, respectively. When the WTG contributes excessively to frequency stabilization in the microgrid with a high wind power penetration, the system frequency may fluctuate considerably. Thus, it is necessary to adjust the contribution of a WTG and to share it with other sources. To achieve our objective, we proposed a coordinated control scheme between the WTG and ESS that shares their releasable and absorbable energies. The coordinated control consistently calculated the releasable and absorbable energies of the WTG and ESS and determined weight factors related to the energy ratios. Accordingly, the weight factors improved the ability of providing supporting frequency stabilization of the WTG and ESS by increasing the stored energy utilization. The performance of the scheme was investigated using MATLAB Simulink Electrical. The results show that the proposed coordinated control successfully stabilized the system frequency by calculating the appropriate contributions required from the WTG and ESS.

Purpose. The objective of research is to develop a version of combined mobile system of the main and backup power supply based on renewable and traditional energy sources for low-power consumers in regions distant from the main electricity grid; to describe the design of the proposed system; to develop a block diagram of the control and management algorithm for the system elements aimed at achieving more efficient energy supply to consumers in case of further implementation of the system,. Methodology. To attain the research objective, the following methods have been employed: the method of analytical processing of the reviewed materials on current state of alternative energetics, on problems related to energy supply for low-power remote consumers, and on ways of solving the problems identified by means of simulating potential uninterruptible power systems; the method of system analysis of complex estimation based on modern computer technologies as for the combined mobile system of the main and backup power supply potential. The results obtained. The expediency of development and further improvement of such combined power supply systems intended for low-power consumers with the purpose of providing the energy balance in the Dnipro region (Ukraine) has been revealed and proved. A version of the combined system based on traditional and renewable sources of power is proposed and described. The block diagram of the combined system controller algorithm is developed. The mechanism of action of the presented algorithm is determined, as well as the graphical dependences of the power factor on the speed of the wind turbine CP=f(Z), and of mechanical torque of the wind turbine on the coefficient of its speed M=f(Z) are obtained and analyzed. The results of calculation as for electric power generated by potential wind power plant W, [kWh] during the year are presented. Scientific novelty consists in the proposed block diagram of the control and management algorithm as regards the combined backup power supply system, that allows wind turbine engines and diesel units to alternately operate on a single generating unit. The practical value of study is further development of the system which provides guaranteed uninterruptible energy supply and distribution of electric energy intended for low-power energy consumers to satisfy their needs; increasing the efficiency, flexibility and reliability of the system and, ultimately, reducing the energy dependence of the country on the import of traditional fossil energy resources, the conversion of which leads to negative consequences for the country's ecology. The implementation of the proposed block diagram of the control and management algorithm will reduce the cost of the system and the cost of its maintenance, for example, current repairs, etc.

This paper presents a new operational strategy for a large-scale wind farm (WF) which is composed of both fixed speed wind turbines with squirrel cage induction generators (FSWT-SCIGs) and variable speed wind turbines with permanent magnet synchronous generators (VSWT-PMSGs). FSWT-SCIGs suffer greatly from meeting the requirements of fault ride through (FRT), because they are largely dependent on reactive power. Integration of flexible ac transmission system (FACTS) devices is a solution to overcome that problem, though it definitely increases the overall cost. Therefore, in this paper, a new method is proposed to stabilize FSWT-SCIGs by using VSWT-PMSGs in a WF. This is achieved by injecting the reactive power to the grid during fault condition by controlling the grid side converter (GSC) of PMSG. The conventional proportional-integral (PI)-based cascaded controller is usually used for GSC which can inject small amount of reactive power during fault period. Thus, it cannot stabilize larger rating of SCIG. In this paper, a suitable fuzzy logic controller (FLC) is proposed in the cascaded controller of GSC of PMSG in order to increase reactive power injection and thus improve the FRT capability of WF during voltage dip situation due to severe network fault. To evaluate the proposed controller performance, simulation analyses are performed on a modified IEEE nine-bus system. Simulation results clearly show that the proposed method can be a cost-effective solution which can effectively stabilize the larger rating of SCIG compared to conventional PI based control strategy.

The design and application of eddy current brakes (ECBs) should be simple; further, ECBs should be used semi-permanently. This study aimed to determine major parameters for designing an ECB that can be applied to a small-scale wind turbine generator. To this end, an ECB was developed that could actuate without additional power, thus improving the efficiency of the generator. A series of simulations were conducted for a parametric study to pre-design ECBs suitable for small wind turbines. The six parameters chosen were disk thickness, number of magnets, radial location of magnets from center of disk, magnet pole arrangement, magnetic flux density, and rotational speed. The simulations were conducted on COMSOL Multiphysics. The results indicated that the number of magnets and magnet pole arrangements can significantly affect the performance curve of ECBs. Moreover, the disk thickness and rotational speed are linearly proportional to the braking torque.

The integration of distributed generators (DGs) with flexible alternating current transmission systems (FACTS) can improve the performance of the grid system. In this study, we determine the location and optimal size of one type of DG, based on wind energy, with a shunt-FACTS control device called a static var compensator (SVC). The voltage profile is increase and the power loss reduced due to an improvement in performance from the maximizing load bus system scenario. Newton-Raphson power flow with a wind turbine generator (WTG) and SVC are formulated as a multi-objective problem called MLB system and minimizing system power loss (Ploss) by satisfying various system constraints, namely the loading limits, generation limits, voltage limits, and the small-signal stability. A variant of the genetic algorithm, called the non-dominated sorting genetic algorithm II (NSGA-II), is used to solve these conflicting multi-objective optimization problems. Modifications to the IEEE 14-bus standard and practical test system integrated to the WTG and SVC in the PSAT software are used as a test system. The simulation results indicate that the optimal allocation of the WTG and SVC, determined using the proposed technique, results in improved system performance, since all the specified constraints are met.

This work presents the characterization and assessment of wind energy potential in annual and monthly levels of the sites of Lomé, Accra and Cotonou located in the Gulf of Guinea, and the optimal characteristics of wind turbines to be installed on these sites. Studies of characterization and the wind potential of these sites from the wind speed data collected over a period of thirteen years at a height of 10 meters above the ground, show an annual average speed of 3.52 m/s for Lomé, 3.99 m/s for Cotonou and 4.16 m/s for Accra. These studies also showed that a monthly average speed exceeding 4 m/s was observed on the sites of Cotonou and Accra during the months of February, March, April, July, August and September and during the months of July, August and September on the site of Lomé. After a series of simulation conducted using the software named PotEol that we have developed in Scilab, we have retained that the wind turbines rated speeds of ~8 to 9 m/s at the sites of Lomé and Cotonou and ~ 9 to 10 m/s on the site of Accra would be the most appropriate speeds for optimal exploitation of electric energy from wind farms at a height of 50 m above the ground.Article History: Received May 26th 2016; Received in revised form August 24th 2016; Accepted August 30th 2016; Available onlineHow to Cite This Article: Salami, A.A., Ajavon, A.S.A , Kodjo, M.K. and Bédja, K. (2016) Evaluation of Wind Potential for an Optimum Choice of Wind Turbine Generator on the Sites of Lomé, Accra, and Cotonou Located in the Gulf of Guinea. Int. Journal of Renewable Energy Development, 5(3), 211-223.http://dx.doi.org/10.14710/ijred.5.3.211-223

This paper presents a dynamic modeling and control of doubly fed induction-generator (DFIG) based on the wind turbine systems. Active and reactive power control of the DFIG are based on the feedback technique by using the suitable voltage vectors on the rotor side. The rotor flux has no impact on the changes of the stator active and reactive power. The proposed controller is based on the feedback technique in order to reduce the oscillation of the generator. The control approach is estimated through the simulation result of the feedback controller assembled with DFIG wind turbines. It is applied by the feedback control based techniques in order to control the power flowing of DFIG and the power grid. Hence, an improved feedback control technique is adopted to get a better power flow transfer and to improve the dynamic system and transient stability. In stable condition, the improved performance of the controller, the proposed method is verified for the effectiveness of the control method is done in stable conditions.

As one of the important renewable energies, wind power has been exploited worldwide. Modeling plays an important role in the high penetration of wind farms in smart grids. Aggregation modeling, whose benefits include low computational complexity and high computing speed, is widely used in wind farm modeling and simulation. To contribute to the development of wind power generation, a comprehensive survey of the aggregation modeling of wind farms is given in this article. A wind farm aggregation model consists of three parts, respectively, the wind speed model, the wind turbine generator (WTG) model, and the WTG transmission system model. Different modeling and aggregation methods, principles, and formulas for the above three parts are introduced. First, the features and emphasis of different wind speed models are discussed. Then, the aggregated wind turbine generator (WTG) models are divided into single WTG and multi-WTG aggregation models, considering the aggregation of wind turbines and generators, respectively. The calculation methods for the wind conditions and parameters of different aggregation models are discussed. Finally, the WTG transmission model of the wind farm from the aggregation bus is introduced. Some research directions are highlighted in the end according to the issues related to the aggregation modeling of wind farms in smart grids.

As a consequence of the increasing renewable energy sources penetration, Transmission System Operators are facing critical stability challenges, e.g. lack of rotating inertia, frequency regulation and voltage control. In fact, majority of the recently installed renewable power plants are decoupled from the grid and are, therefore, unable to contribute to the grid stability in the case of network perturbations. In the world, wind energy represents one of the most interesting Renewable Energy Sources in terms of new installations. Two main categories of wind turbine exist: fixed speed and variable speed. In the second category, which is the market standard nowadays, Permanent Magnet Synchronous Generator and Doubly Fed Induction Generator are possible technologies. In particular, while the first one is fully decoupled from the grid, the second one is directly connected to the grid via the stator circuit and includes a power electronic converter to drive both magnitude and frequency of rotor currents. Differently from a fixed speed wind generator, the power converter enables the wind turbine to regulate the output power over a wide range of wind speeds to maximize the wind-to-electricity conversion efficiency. With the aim of preserving grid stability, recently connected wind turbines are required to contribute in the frequency and voltage regulation. In detail, the recently applied Italian connection standard for new type D wind power plants (i.e. rated power higher than 10 MW) imposes controllers for providing frequency and voltage support. The paper discusses the positive role that wind generators could have in terms of network stability if recent standards are correctly applied, making use of suitable simulations realized in the DIgSILENT PowerFactory environment. Doubly Fed Induction Generators have been considered, since this technology is currently the most widely used.

A serious disadvantage of coupling a solar PV and wind energies of a hybrid system into the main DC bus is the compatibility of the voltage. In fact the PV system response is faster than the wind system one. This can affect negatively on the whole hybrid system response especially in case of variable loads switching. In this paper a hybrid energy system consisting of two sources: wind turbine generator and photovoltaic solar, without energy storage is modeled and simulated using MATLAB/SIMULINK. Management of the obtained power is achieved through two adaptor switches in the DC output of both sources. Each subsystem switch is controlled in order to supply either a dump load or the consumers’ loads via an inverter. The objective is to obtain an acceptable (compromise) system response and to make it more compatible. A control strategy of those two switches is proposed to adapt the inputs of the sources to the output of the DC bus. Satisfying results have been obtained in terms of voltage response stability, precision and global compatibility achievement.

Future power systems face several challenges. One of them is the use of high power converters that decouple new energy sources from the AC power grid. This situation decreases the total system inertia affecting its ability to overcome system frequency disturbances. The wind power industry has created several controllers to enable inertial response on wind turbines generators: artificial, emulated, simulated, or synthetic inertial. This paper deals with the issues related to the emulated inertia of wind turbines based on full-converters and their effect on the under-frequency protection schemes during the recovery period after system frequency disturbances happen. The main contribution of this paper is to demonstrate the recovery period of under-frequency transients in future power systems which integrate wind turbines with emulated inertia capability does not completely avoid the worse scenarios in terms of under-frequency load shedding. The extra power delivered from a wind turbine during frequency disturbances can substantially reduce the rate of frequency change. Thus it provides time for the active governors to respond.

This paper proposes probabilistic generation assessment system introduction of renewable energy generators. This paper is focused on wind turbine generator and solar cell generator. The proposed method uses an assessment model based on probabilistic model considering uncertainty of resources (wind speed and solar radiation). Equivalent generation function of the wind and solar farms are evaluated. The equivalent generation curves of wind farms and solar farms are assessed using regression analysis method using typical least square method from last actual generation data for wind farms. The proposed model is applied to Korea Renewable Generation System of 8 grouped 41 wind farms and 9 grouped around 600 solar farms in South Korea.

The development and production of multiphase machines either generators or motors, specially five-phase, offers improved performance compared to three-phase counterpart. Five phase generators could generate power in applications such as, but not limited to, wind power generation, electric vehicles, aerospace, and oil and gas. The five-phase generator output requires converter system such as ac–dc converters. In this paper, a fully controlled 10-pulse line commutated rectifier, suitable to be engaged with wind energy applications, fed from five-phase source is introduced. A shunt active power filter (APF) is used to improve power factor and supply current total harmonic distortion (THD). Compared to three-phase converters, 6-pulse or 12-pulse rectifiers, the 10-pulse rectifier engaged with 5-phase source alleviate their drawbacks such as high dc ripples and no need for electric gear or phase shifting transformer. MATLAB/SIMULINK platform is used as a simulation tool to investigate the performance of the proposed rectifier.

In this paper, we propose a Four-Dimensional Variational (4D-Var) data assimilation framework for wind energy potential estimation. The framework is defined as follows: we choose a numerical model which can provide forecasts of wind speeds then, an ensemble of model realizations is employed to build control spaces at observation steps via a modified Cholesky decomposition. These control spaces are utilized to estimate initial analysis increments and to avoid the intrinsic use of adjoint models in the 4D-Var context. The initial analysis increments are mapped back onto the model domain from which we obtain an estimate of the initial analysis ensemble. This ensemble is propagated in time to approximate the optimal analysis trajectory. Wind components are post-processed to get wind speeds and to estimate wind energy capacities. A matrix-free analysis step is derived from avoiding the direct inversion of covariance matrices during assimilation cycles. Numerical simulations are employed to illustrate how our proposed framework can be employed in operational scenarios. A catalogue of twelve Wind Turbine Generators (WTGs) is utilized during the experiments. The results reveal that our proposed framework can properly estimate wind energy potential capacities for all wind turbines within reasonable accuracies (in terms of Root-Mean-Square-Error) and even more, these estimations are better than those of traditional 4D-Var ensemble-based methods. Moreover, large variability (variance of standard deviations) of errors are evidenced in forecasts of wind turbines with the largest rate-capacity while homogeneous variability can be seen in wind turbines with the lowest rate-capacity.

One of the main challenges in future power systems is the enormous integration of generation units using high power converters as interface, it decouples new power sources from the AC power grid, incapacitating a natural frequency response. This situation decreases the total system inertia affecting the ability of power system to overcome system frequency's disturbances. This paper evaluates two inertial controller for full-rated power converter wind turbines, Type 4: (A) releasing “hidden” inertia controller and (B) fast power reserve emulation. Simulations over a test system are used for a preliminary evaluation of the mentioned inertial controllers. The main contribution of this paper is to demonstrate the main differences between system frequency response (SFR) obtained by each inertial controller and how important is to match wind turbine and system characteristic to improve the SFR.

This electronic document is a “live” template. Based on the momentum-element theory, mathematical model of numerical simulation of the output characteristics is set up for resemble models of MW-scale wind turbine blades, which is under a test system with three different setting angles of 10.5°, 30.5°and 50.5°. The initial values of axial and tangential induction factors are determined by Newton-Raphson method, the powers P, power coefficients CP and torque coefficients CM of the three model test systems are simulated by programming in Matlab and Visual Basic. At the same time, characteristic output tests are carried out by in-truck test method of the three model test systems. The results show that each relative error of simulation and testing results of the model test systems is less than 10%; it proves that the simulation method is reliable and the testing results are reasonable.

The Bees Algorithm is a recently developed optimization technique that mimics the foraging behavior of honey bees in nature. This study investigates the use of the Bees Algorithm for the selection of the optimal operating speed parameters for wind power units. Three speed parameters need to be optimized, namely, the rated, cut-in, and cut-off (furling) speed of the turbine. The aim of the optimization process is to maximize the yearly power yield and turbine usage time. The choice of the best parameters depends from the wind frequency distribution at the site of installation. Eleven locations on the coastal areas of Egypt were chosen as case studies. The well-known Particle Swarm Optimization was used as a control optimization algorithm. A popular classical approach based on the manual optimization of the sole rated speed was used as baseline for the comparison of results. The optimization of all the three speed parameters and the use of intelligent optimization techniques represent the novelties of this paper. The study showed that the Bees Algorithm outperformed the other two optimization methods. The proposed algorithm was able to find speed parameters that greatly enhanced the power yield, without compromising the usage time or significantly increasing the capital costs. The comparison between the standard manual optimization method and the two intelligent optimization techniques proved the superiority of the latter ones.

Bearing current problems frequently appear in wind turbine systems, which cause wind turbines the break down and result in very large losses. This paper investigates and compares bearing current problems in three kinds of wind turbine generators, namely doubly-fed induction generator (DFIG), direct-drive permanent magnet synchronous generator (PMSG), and semi-direct-drive PMSG turbines. Common mode voltage (CMV) of converters is introduced firstly. Then stray capacitances of three kinds of generators are calculated and compared through the finite element method. The bearing current equivalent circuits are proposed and simulations of the bearing current are carried out. It is verified that the bearing currents of DFIGs are more serious than the two kinds of PMSG, while common mode current (CMC) of the direct-drive PMSG is much greater than the other two types of wind turbine generators.

Modern wind power plants are required and designed to ride through faults in electrical networks, subject to fault clearing. Wind turbine fault current contribution is required from most countries with a high amount of wind power penetration. In order to comply with such grid code requirements, wind turbines usually have solutions that enable the turbines to control the generation of reactive power during faults. This paper addresses the importance of using an optimal injection of active current during faults in order to fulfi l these grid codes. This is of relevant importance for severe faults, causing low voltages at the point of common coupling. As a consequence, a new wind turbine current controller for operation during faults is proposed. It is shown that to achieve the maximum transfer of reactive current at the point of common coupling, a strategy for optimal setting of the active current is needed.

This paper describes activities and main results of investigation for the Vlasina Wind Project, implemented within National Energy Efficiency Program, segment that deals with alternative and renewable energy sources. The main objective of the project was investigation of possibilities of wind energy generation in mountain areas of the Republic of Serbia. Problems of choice of location, measurement of wind energy potential, choice of type and unit size of wind turbine generators, as well as the interconnection of wind turbine generators and wind power plants to power system are considered. .

This study analyses an interconnection system based on differentially sinusoidal pulse width modulation, used for the interconnection to the grid of a variable speed wind turbine. The modulation technique used provides specific advantages in comparison with the commonly used sinusoidal pulse width modulation (SPWM) technique, such as lower DC bus voltage requirements, smaller switching losses for the same switching frequency as well as less higher harmonic content in the voltage waveforms produced. The respective control system is also described in detail. Thus this study provides a guide enabling the design of any interconnection system based on this modulation technique.

Electrical energy production based on wind power has become the most popular renewable resources in the recent years because it gets reliable clean energy with minimum cost. The major challenge for wind turbines is the electrical and the mechanical failures which can occur at any time causing prospective breakdowns and damages and therefore it leads to machine downtimes and to energy production loss. To circumvent this problem, several tools and techniques have been developed and used to enhance fault detection and diagnosis to be found in the stator current signature for wind turbines generators. Among these methods, parametric or super-resolution frequency estimation methods, which provides typical spectrum estimation, can be useful for this purpose. Facing on the plurality of these algorithms, a comparative performance analysis is made to evaluate robustness based on different metrics: accuracy, dispersion, computation cost, perturbations and faults severity. Finally, simulation results in MATLAB with most occurring faults indicate that ESPRIT and R-MUSIC algorithms have high capability of correctly identifying the frequencies of fault characteristic components, a performance ranking had been carried out to demonstrate the efficiency of the studied methods in faults detecting., Comment: 10 pages, 17 figures, 4 tables, journal paper

This paper concerns with wind turbine generator fault-tolerant control that avoids system shut- down and enables safe operation with less than nominal power production. We focus on generator stator isolation inter-turn fault that can be characterized before triggering the safety device and applied for any type of generator used in wind turbines. A low complexity model predictive tracking controller is proposed to achieve very accurate flux modulation that prevents the fault propagation while power delivery under fault is deteriorated as less as possible compared to healthy machine conditions. Presented fault- tolerant control strategy is developed taking into account its modular implementation and installation in available control systems of existing wind turbines to extend their life cycle and energy production. Simulation results for the case of a 700 kW wind turbine are presented.

Large offshore wind power plants may have multi-MW wind turbine generators (WTG) equipped with full-scale converters (FSC) and voltage source converter (VSC) based high voltaage direct-current (HVDC) transmission for gridconnection. The power electronic converters in theWTG-FSC and the VSC-HVDC allow fast current control in the offshore grid. This paper presents a method of controlling the negative sequence current injection into the offshore grid from the VSC-HVDC as well as WTG-FSCs. This would minimize the power oscillations and hence reduce the dc voltage overshoots in the VSC-HVDC system as well as in the WTG-FSCs; especially when the offshore grid is unbalanced due to asymmetric faults. The formulation for negative sequence current injection is mathematically derived and then implemented in electromagnetic transients (EMT) simulation model. The simulated results show that the negative sequencecurrent control mitigates the power oscillations and therefore limits the dc voltage excursions in the VSC-HVDC system during the asymmetric faults.

This paper addresses the representation of the wound rotor asynchronous generators by an equivalent synchronous generator, valid for short circuit current calculations. Modern wind power plants are required and designed to ride through faults in the network, subjected to fault clearing. Accurate knowledge of the wind turbine short circuit current contribution is needed for component sizing and protection relay settings during faults within the wind power plant collector system or in the external networks. When studying fault currents and protection settings for wind power installations, the industry standard is to employ software packages where generators are represented by their equivalent synchronous generator operational impedances. Hence, it is of importance to represent non-synchronous wind generators by an equivalent synchronous generator.

This paper addresses the representation of a wind power plant, based on wound rotor asynchronous generators, with a centralized voltage controller, by an equivalent transfer function, valid for small signal voltage control studies. This representation allows to investigate the influence of the centralized plant control gain and short circuit ratio on the system stability, for instance, by analyzing the zero-pole placement. Larger percentages of wind power penetration translate to more demanding requirements coming from the grid codes, for example voltage support at the point of connection has been introduced recently by several grid codes from around the world, making important to analyze this control when applied to wind power plants. The performance of the equivalent transfer function has been evaluated and compared using an equivalent grid with different short circuit ratios and active power injection levels, the cases have been simulated with PSCAD/EMTDC program. Results show that this equivalence can be used for short circuit ratios between 5 and 25 for obtaining an accurate representation of the system voltage dynamics.

This paper contributes a Markov chain Monte Carlo (MCMC) method for the direct generation of synthetic time series of wind power output. It is shown that obtaining a stochastic model directly in the wind power domain leads to reduced number of states and to lower order of the Markov chain at equal power data resolution. The estimation quality of the stochastic model is positively influenced since in the power domain, a lower number of independent parameters is estimated from a given amount of recorded data. The simulation results prove that this method offers excellent fit for both the probability density function and the autocorrelation function of the generated wind power time series. The method is a first step toward simple stochastic black-box models for wind generation.

Larger percentages of wind power penetration translate to more demanding requirements from grid codes. Recently, voltage support at the point of connection has been introduced by several grid codes from around the world, thus, making it important to analyze this control when applied to wind power plants.This paper addresses the analysis of two different voltage control strategies for a wind power plant, i.e. decentralized and centralized voltage control schemes.The analysis has been performed using the equivalent and simplified transfer functions of the system. Using this representation, it is possible to investigate the influence of the plant control gain, short circuit ratio, and time delays on thesystem stability, as well as the fulfillment of the design requirements.The implemented plant voltage control is based on a slope voltage controller, which calculates the references to be sent to the wind turbines, according to the slope gain and the difference between the reference and measured voltage at the point of connection.The results show that for a system where the time delay between the central control and the actuators is not negligible, the performance of a decentralized voltage control is better than the centralized one in terms of time reaction, disturbance rejection, and short-circuit ratio (SCR) dependency. However,for a system with reduced time delay (10 ms) the centralized scheme can have a performance similar to the decentralized one, in the SCR range of interest.