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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., Цель. Цель работы заключается в разработке мобильной комбинированной системы основного и резервного питания на основе возобновляемых и традиционных источников энергии для электропитания маломощных потребителей в отдаленных от общей электросети регионах; в описании конструкции предложенной системы; в разработке блок-схемы алгоритма контроля и управления элементами системы для достижения наиболее эффективного энергопитания потребителей при дальнейшем внедрении и совершенствовании системы.Методы исследования. Для проведения исследований использованы: метод аналитической обработки обзорных материалов по вопросу состояния развития альтернативной энергетики на современном этапе и существующих сегодня проблем, связанных с энергообеспечением маломощных отдаленных энергоустановок, а также путей решения обозначенных проблем за счет моделирования возможных систем бесперебойного питания; метод системного анализа комплексной оценки потенциала комбинированной мобильной системы основного и резервного питания на основе современных компьютерных технологий.Полученные результаты. Выявлена и доказана целесообразность создания и дальнейшего совершенствования систем комбинированного электропитания маломощных потребителей с целью обеспечения энергобаланса Днепровского региона (Украина). Предложен вариант конструкции комбинированной системы на основе традиционных и возобновляемых источников: в частности, разработана блок-схема алгоритма контроллера управления комбинированной системой. Определен механизм действия представленного алгоритма, а также полученны и проанализоват графические зависимости: коэффициента мощности от величины быстроходности ветроагрегата CP=f(Z); механического момента ветротурбины от коэффициента быстроходности М=f(Z). Представлены прогнозируемые результаты расчета выработки электроэнергии в течение года потенциальной ветроэлектроустановкой W, [кВт.ч].Научная новизна заключается в предложенной блок-схеме алгоритма контроля и управления комбинированной системой резервного электроснабжения, которая позволяет двигателям ветроустановки и дизельного агрегата попеременно работать на один общий электрогенератор.Практическая ценность работы состоит в создании системы гарантированного энергообеспечения и распределения электроэнергии для маломощных потребителей энергии различного назначения; повышении эффективности, гибкости и надежности системы и, в конечном счете, уменьшении энергетической зависимости страны от импорта традиционных ископаемых энергоресурсов, преобразование которых приводит к негативным последствиям для экологии страны. Внедрение предложенной блок-схемы алгоритма контроля и управления комбинированной системой резервного электроснабжения позволит снизить стоимость системы и затраты на ее обслуживание, например, текущий ремонт и тому подобное., Мета. Мета роботи полягає в розробці мобільної комбінованої системи основного і резервного живлення на основі відновлюваних і традиційних джерел енергії для електроживлення малопотужних споживачів у віддалених від загальної електромережі регіонах; в описанні конструкції запропонованої системи; в розробці блок-схеми алгоритму контролю і управління елементами системи задля досягнення найбільш ефективного енергоживлення споживачів при подальшому впровадженні та удосконаленні системи.Методи дослідження. Для проведення досліджень використані: метод аналітичної обробки оглядових матеріалів з питання стану розвитку альтернативної енергетики на сучасному етапі та існуючих на сьогодні проблем, щодо енергозабезпечення малопотужних віддалених енергоустановок, а також шляхів їх подолання завдяки моделюванню можливих систем безперебійного живлення; метод системного аналізу комплексної оцінки потенціалу комбінованої мобільної системи основного та резервного живлення на основі сучасних комп’ютерних технологій.Отримані результати. При аналізі матеріалів робіт відповідно до тематики дослідження, виявлено та доведено доцільність створення та подальшого удосконалення систем комбінованого електроживлення малопотужних споживачів з метою забезпечення енергобалансу Дніпровського регіону (Україна). Запропоновано варіант конструкції комбінованої системи на основі традиційних і відновлюваних джерел: зокрема, розроблено блок-схему алгоритму контролера управління комбінованою системою. Представлено механізм дії запропонованої блок-схеми алгоритму, а також отримані та проаналізовати графічні залежності: коефіцієнту потужності від величини швидкохідності вітроагрегату CP=f(Z); механічного моменту вітротурбіни від коефіцієнту швидкохідності реальної вітроустановки M=f(Z). Представлено результати розрахунку виробітку електроенергії, W, [кВт.год] протягом року потенційною вітроелектроустановкою.Наукова новизна полягає в запропонованій блок-схемі алгоритму контролю і управління комбінованою системою резервного електропостачання, яка дозволяє двигунам вітроустановки та дизельного агрегату поперемінно працювати на один загальний електрогенератор.Практична цінність роботи полягає у створенні системи гарантованого енергозабезпечення та розподілу електроенергії для малопотужних споживачів енергії різного призначення; підвищенні ефективності, гнучкості та надійності системи і, в кінцевому рахунку, зменшенні енергетичної залежності країни від імпорту традиційних викопних енергоресурсів, перетворення яких призводить до негативних наслідків щодо екології країни. Впровадження запропонованої блок-схеми алгоритму контролю і управління енергосистемою дозволить знизити витрати на її обслуговування, наприклад, поточний ремонт, тощо та, відповідно, вартість системи вцілому.

Наведено результати розрахунку технічних та економічних показників вітро- електростанцій із різнотипними вітрогенераторами за вітрових умов Карпатського регіону України для вибору оптимального обладнання. The paper presents the results of the calculation of technical and economic performance of various wind farms WTG with wind turbines for the real wind conditions in Ukrainian Carpathian region to choose the optimal equipment.

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.

The strategy to improve both efficiency and power quality of grid-connected wind turbine generator systems (WTGs) are presented. WTGs efficiency is improved by developing a variable speed control to obtain maximum power at all wind speeds. Variable speed control based on Adaptive Type-2 Fuzzy Sliding Mode Control (AFSMOC) is proposed by employing Very Sparse Matrix Converter (VSMC). Type-2 fuzzy system is used to improve the robustness of sliding mode control. VSMC can provide low harmonics in line current, so the power quality problems can be minimized. The simulation results shows that the AFSMOC can regulate the generator speed at optimum Tip Speed Ratio (TSR) with maximum error 2.5 rpm, so that the maximum power can be obtained at all wind speeds. VSMC also provide good performance with Total Harmonic Distortion (THD) of voltage 0.35% and THD of current 6,82%

Wind turbine generators (WTGs) are required to operate at different levels of voltage uctuations in the power grid. When the uctuations exceed the standard levels, i.e. over and under voltage, they affect the performance of WTGs. In this study, we estimate the distribution of over and under voltages by utilizing Extreme Value Analysis. Assuming voltage as a random variable, we show that the over and under voltages can be considered as extreme deviations from the probability distribution median. The results approve that extreme fluctuations in the voltage of one WTG follow Generalized Extreme Value distribution. Since different WTGs do not necessarily experience the same extreme events, the model is generalized to the wind farm scale to cover all probable variations. This is accomplished by assuming the parameters of the generalized model as random variables. The generalized model will be used in the WTG test center, in order to determine WTG's capability to withstand the fluctuations.

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. .

The authors have been making a study of an independent source system utilizing wind turbine generator in recent years. This system is composed of four main installations, that is, a wind turbine generator, a diesel engine generator, an electric water heater (or an electric power storage flywheel), and an alternating power control device. The strong points of this system is that it is possible to increase generating electric power, because the brushless three-phase synchronous induction generator with two stators and without exciter developed by authors is used as the wind turbine generator of this system. We have reported about the experimental results of electric power characteristics in steady state by using the simulated device of the proposed system up to now. In this experiment, the terminal voltage and the current of the proposed independent source system did not change and the quality of electric power was good when the wind turbine generator operates as a synchronous generator and also as an induction generator. In this paper, the experimental results of electric power characteristics in transient state of the simulated device are reported. In this experiment, the change of the terminal voltage and the current are extremely small and the electric power characteristics are very good while the operation of the wind turbine generator changes from synchronous generator driving to induction generator one and also in the opposite operation. The electric power characteristics of this simulated device in both steady and transient states are good; therefore this proposed system would be put to practical use.

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 presents a reliability-based approach to select appropriate wind turbine types for a wind farm considering site-specific wind speed patterns. An actual wind farm in the northern region of Iran with the wind speed registration of one year is studied in this paper. An analytic approach based on total probability theorem is utilized in this paper to model the probabilistic behavior of both turbines- availability and wind speed. Well-known probabilistic reliability indices such as loss of load expectation (LOLE), expected energy not supplied (EENS) and incremental peak load carrying capability (IPLCC) for wind power integration in the Roy Billinton Test System (RBTS) are examined. The most appropriate turbine type achieving the highest reliability level is chosen for the studied wind farm., {"references":["T. Ackermann, Wind Power in Power Systems, 1st ed. New York: John\nWiley and Sons, 2005.","S. Kennedy, \"Wind power planning: Assessing long term costs and\nbenefits,\" Energy Policy, vol. 33, pp. 1661-1675, 2005.","Z. M. Salameh and I. Safari, \"Optimum windmill -site matching,\" IEEE\nTrans. Energy Convers., vol. 4, no. 7, pp. 669-675, 1992.","H. Chen, R. Billinton, \"Determination of the optimum site-matching wind\nturbine using risk-based capacity benefit factors,\" IEE Proc-Gener.\nTransm. Distrib., vol. 146, no. 1, pp. 96-100, Jan. 1999.","R Billinton and R Allan, Reliability Evaluation of Power Systems, 2nd ed.\nNew York: Plenum, 1996.","F. C. Sayas, and R. N. Allan, \"Generation availability assessment of wind\nfarms,\" Proc. Inst. Elect. Eng., Gen., Transm., Distrib., vol. 143, no. 5, pp.\n507-518, Sep. 1996.","A. P. Leite, C. L. T. Borges, D. M. Falcão, \"Probabilistic wind farms\ngeneration model for reliability studies applied to Brazilian sites,\" IEEE\nTrans. Power Syst., vol. 21, no. 4, pp. 1493-1501, Nov. 2006.","R. Billinton and Y. Gao, \"Multistate wind energy conversion system\nmodels for adequacy assessment of generating systems incorporating wind\nenergy,\" IEEE Trans. Energy Convers., vol. 23, no. 1, pp. 163-170, Mar.\n2008.","P. Giorsetto and F. K. Utsurogi, \"Development of a new procedure for\nreliability modeling of wind turbine generators\", IEEE Trans. Power App.\nSyst., vol. 102, no. 1, pp. 134-143, Jan. 1983.\n[10] Online Available: http://www.vestas.com.\n[11] Online Available: http://www.gewindenergy.com/\n[12] Iranian Renewable Energy Organization Archives, Tehran, Iran.\n[13] R. Billinton, H. Chen, and R. Ghajar, \"Time-series models for reliability\nevaluation of power systems including wind energy,\" Microelectron. Rel.,\nvol. 36, no. 9, pp. 1253-1261, 1996.\n[14] R. Billinton, S. Kumar, N. Chowdhury, K. Debnath, L. Goel, E. Khan, P.\nKos, G. Nourbakhsh, and J. Oteng-Adjei, \"A reliability test system for\neducational purposes basic data,\" IEEE Trans. Power Syst., vol. 4, no. 4,\npp. 1238-1244, Aug. 1989."]}

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.

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.

This paper presents a novel fault tolerant converter topology for grid connected Wind Energy Conversion System (WECS) with Doubly Fed Induction Generator (DFIG). This topology allows fast fault detection and compensation of one of the semiconductors or drivers by using isolating and connecting devices. It is based on a unique redundant leg for both back to backconverters. We present a new detection algorithm, robust to false fault detection due to semiconductor switching. Simulation results are presented cases on both back-to-back converters and both hyper and hypo synchronous conditions.

平成5,6年度科学研究費補助金［一般研究(B)］, 研究概要：1.直径27m,定格出力1kWの小型水平軸風車3台よりなる研究用小型ウィンドファームを琉球大学工学部エネルギー機械工学ビル屋上に建設し,約1年にわたって性能特性,出力変動特性を調べた.その結果小型風車はその構造上,各風車毎の出力変動特性に独立性がかなり高く,複数台風車の出力を合計すればその変動率は単機の較べてかなり小さくなることを,理論的,実験的に確認した. 2.同上ウィンドファームに出力800Wの多結晶太陽電池パネルを増設し,風力発電システムと同一系統にした場合の各発電装置の出力特性および相互干渉を調べた.その結果太陽電池パネルの出力変動成分は風力発電のそれに比して,およそ2.0Hz以上の高周波数成分が多く,逆に低周波数成分は少ないという新しい知見を得,結果的に異種発電装置間の複合化も出力変動の減衰に効果的であることがわかった. 3.今後の普及型小型風力発電装置への提案として,直径40m,定格出力3kWの可変ピッチ小型風力発電装置を設計し,その製作を8割方完了した.これは,従来固定ピッチが大半であった小型機についても可変ピッチ方式を導入し,ステッピングモータ,ウォーム・ギアおよびマイクロコンピュータ制御によってより安定かつ安全な風力発電装置の開発をめざすものである. 4.以上の研究と並行して,沖縄県宮古島において実際に系統連系運転中の250kW風力発電機2機システムの出力変動特性を詳細に解析した.その結果,同島の5万kW系統容量に対して,1万kWすなわち20%までの風力発電システムの浸透は可能との結論を示した., (1) A small experimental wind farm consisting of three 2.7m diameter 1kW horizontal wind turbine generators (WTG) was constructed at top of a building of the Faculty of Engineering, University of the Ryukyus, and examined their performances and the characteristics of output fluctuation about a year. As the result, it is cleared that the fluctuation of small WTG is almost independent to each other because of their structural reason. Therefore, fluctuation ratio of the summed up output of the wind farm was confirmed to be smaller than that of the individual WTG output. (2) A 800W photovoltaic power panel was introduced to the above mentioned wind farm and investigated its fluctuation and the effect on the farm system. The fluctuation of the solar panel showed the higher components that the WTG in the higher frequency region than about 2.0Hz, and the lower components in the lower frequency region. So that it was cleared that the hybrid system of the different power generator also has the effect to reduce the total fluctuation ratio. (3) As a proposal of new small WTG,4.0m diameter 3kW and variable pitch WTG has been designed. The characteristics of the machine are the variable pitch with stepping motor, worm gearing system drive and micro computer control. Up to about 10m diameter WTG, we have planned to introduce this new system and to offer the stable and maintenance easy small wind turbine generators., 未公開:P.5以降（別刷論文のため）

In recent years, many wind turbine generation systems (WTGSs) have been installed in many countries from a point of view of grobal environment due to CO_2 emission. But wind turbine generator output and annual energy production are dependent on wind characteristic of each area and a kind of WTGS. Authors previous paper presented the analyses about annual electrical energy production and capacity facotor of WTGS for each area with different wind data. This paper presents a method to calculate each cost of WTGS component such as drive train system, generator and other equipments, and also evaluates generation cost that obtained from WTGS cost and annual electrical energy production. Based on these results, we consider the optimal kind of WTGS for each installation area from a economical point of view.

Several large offshore wind power plants (WPP) are planned in the seas around Europe. VSC-HVDC is a suitable means of integrating such large and distant offshore WPP which need long submarine cable transmission to the onshore grid. Recent trend is to use large wind turbine generators with full scale converters to achieve an optimal operation over a wide speed range. The offshore grid then becomes very much different from the conventional power system grid, in the sense that it is connected to power electronic converters only. A model of the wind power plant with VSC-HVDC connection is developed in PSCAD for time-domain dynamic simulation. This paper presents the modelling and simulation of such a system. A single line to ground fault has been simulated and fault currents for the grounded and ungrounded offshore grid system is obtained through simulation and then compared.

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.

In this decade, a significant amount of additional wind and solar power will be integrated in the Dutch high voltage grid. The 383 MW nearshore Wind Park Fryslân is foressen to be connected to the Dutch 110kV grid in 2020 through two 55km cable circuits. To quantify the risks of exceeding emission levels for both the TSO and the wind farm developer, harmonic voltage distortion studies must already be performed at an early phase of the project. Relevant data of wind farm components may not yet be available then and must therefore be estimated including data of the wind turbine generator (WTG). The objective of this paper is to assess the impact of a WTG converter impedance model on the harmonic impedance of the windfarm and subsequent harmonic voltage amplification. For this purpose, an analytical converter harmonic model with tunable parameters has been developed. A sensitivity study was performed in a case study of Wind Park Fryslân to analyse the impact of these parameters on the harmonic amplification at the Point of Connection with the 110 kV grid. The length and amount of array cables were also included in the study. The paper follows a step-wise approach where subsequently wind farm impedance, grid impedance and amplification factor have been calculated. It has been found that the WTG converter impedance model has a significant impact on the harmonic amplification of low harmonic orders (h=2 to h=10). Notably, not taking the converter impedance into account (infinite impedance) will result in both over- as well as underestimation of the harmonic amplification over the mentioned frequency range. It is shown that, when no WTG manufacturer has been selected yet, the analytical converter model provides a valid alternative for performing early-stage harmonic studies.

In the low frequency range, there are some couplings between the positive- and negative-sequence small-signal impedances of the power converter due to the nonlinear and low bandwidth control loops such as the synchronization loop. In this paper, a new numerical method which also considers these couplings will be presented. The numerical data are advantageous to the parametric differential equations, because analysing the high order and complex transfer functions is very difficult, and finally one uses the numerical evaluation methods. This paper proposes a numerical matrix-based method, which is not only able to deal with those mentioned numerical data, but also it is able to consider all couplings between the positive and negative sequences.