Sharif Digital Repository

Natural ventilation has been used to increase indoor air quality, remove pollutants, and remove heat absorbed in the building structure. Some architectural features such as wind-catcher systems are used to induce airflow into buildings, and openings equipped with louvers are employed to reduce solar daylight while allowing natural ventilation. Earlier studies on ventilated louvers and wind-catchers have shown the impact of the louvers’ opening positions and slat angles. However, their combination with each other has been less studied. This paper presents CFD simulations of cross-ventilation in a generic isolated building integrated with a one-sided roof-top wind-catcher and the outlet... 

This paper presents a multi-model robust control (MMRC) design for an offshore variable speed wind turbine with tension leg platform. The proposed control scheme covers the model uncertainty in the above rated wind speed, and it provides a reliable control for power regulation while minimizing the mechanical loads on the wind turbine structure. For this purpose, the above rated wind speed region is divided into several wind speed groups, and a set of linearized models are obtained from the Fatigue, Aerodynamics, Structures, and Turbulence (FAST) simulator for various mean wind speeds of each group. Using Weibull wind speed distribution, a nominal model with additive uncertainty is generated... 

Using natural draft dry air cooling systems in the power plant cycle is one of the proposed solutions for less water consumption. But the wind blowing will cause decreasement of cooling system performance in the power plants that work with the Rankin cycle. Therefore, it is important to know the right amount of wind speed to make the right decision to prevent reducing generating power or provide the right solution to improve the performance of the power plant cooling system. There are many methods of calibration of sensors in the world. But using optimization techniques or stochastic methods that do not require physical facilities and additional costs is almost a new approach. Therefore, in... 

Safe pitch angle-based pole–zero–gain scheduling, and controller blending of H∞ controllers for a variable-speed variable-pitch wind turbine in the full load region are introduced in this paper. The design methodology ensures proper model reduction and modification, canonical controller realization, and cancellation of the hidden coupling terms that emerge from these scheduling procedures to maintain the stability of the closed–loop dynamics during wind turbine operation. In contrast to previous multi-model designs that either involve scheduling of complex transfer functions or depend on less-reliable wind speed estimations, in the presented framework only a portion of the controller is... 

The capacity factor is an important wind turbine parameter which is ratio of average output electrical power to rated electrical power of the wind turbine. Another main factor, the AEP, the annual energy production, can be determined using wind characteristics and wind turbine performance. Lower rated power may lead to higher capacity factor but will reduce the AEP. Therefore, it is important to consider simultaneously both the capacity factor and the AEP in design or selecting a wind turbine. In this work, a new semi-empirical secondary capacity factor is introduced for determining a rated wind speed at which yearly energy and hydrogen production obtain a maximum value. This capacity factor... 

Providing ancillary services such as frequency support and power operating reserve by doubly fed induction gener-ator-based wind turbines has received considerable attention in the recent years, and several auxiliary controllers have been proposed to provide these services. In this paper, small-signal stability of wind turbines equipped with these controllers is assessed in presence of a frequency event and varying wind speed conditions. For this purpose, first, several auxiliary controllers are discussed, and a unified auxiliary controller (UAC) is proposed, which can represent all of these controllers simultaneously. Then, the overall transfer function from the wind speed to the wind... 

Optimization of wind farm (WF) layout has been studied in the literature with the objective of maximizing the wind energy capture. Based on the power spectrum density theorem, this paper shows that the WF layout affects not only the total harvested energy but also the level of power fluctuation, which, in turn, influences required capacity of battery energy storage system (BESS) needed to mitigate the inherent power fluctuation of the WFs. Since, both harvested energy level and BESS capacity directly influence the profit of WF owner, the effect of WF layout on these quantities is taken into account simultaneously, and WF layout optimization problem is redefined. Genetic algorithm is then... 

This study proposes a modified virtual inertial control (MVIC) scheme for doubly-fed induction generator (DFIG)based wind turbines (WTs), which both improves the frequency response of these renewable resources and enhances the power system oscillation damping capabilities. It is shown that the proposed control structure enables the WT to participate prudentially in system frequency regulation, which means the amount of WT kinetic energy released to the grid and its participation in system frequency support is alleviated as its stored energy decreases. The proposed control strategy is introduced conceptually, and its performance is verified analytically. Effects of wind speed variations on... 

Nowadays, the incorporation of wind power in electrical grids and electricity markets is grown. Due to the fluctuation of wind speed, one of the main challenges of wind power would be selling power directly to the wholesale markets. A method for solving this challenge is coordination of wind power with energy storages, cascaded hydro, or gas turbine units in bidding strategy and operation. By coordinating with gas turbine units, wind power can be incorporated in real-time markets with fewer capital costs. In this paper, a stochastic bi-level optimization is proposed for coordinated wind power and gas turbine units in the real-time market. The uncertainties of wind power, demands, rivals'... 

Nowadays, the incorporation of wind power in electrical grids and electricity markets is grown. Due to the fluctuation of wind speed, one of the main challenges of wind power would be selling power directly to the wholesale markets. A method for solving this challenge is coordination of wind power with energy storages, cascaded hydro, or gas turbine units in bidding strategy and operation. By coordinating with gas turbine units, wind power can be incorporated in real-time markets with fewer capital costs. In this paper, a stochastic bi-level optimization is proposed for coordinated wind power and gas turbine units in the real-time market. The uncertainties of wind power, demands, rivals'... 

This paper mainly focuses on operational reliability studies of modern power systems taking into consideration the effects of energy storage systems (ESSs). The aim is to develop a new evaluation tool to assess the effects of different factors such as penetration rate, operational strategies, and capacities of the ESSs in determining the role of these systems as a source of operating reserve. In this regard, at first, some modifications are made to the Pennsylvania-New Jersey-Maryland (PJM) method aimed to precisely model the short-term variability in output generation of wind farms in reliability studies. Then, this algorithm is employed to examine the effects of ESSs operating strategies... 

In this paper, the aeroelastic analysis of a large scale wind turbine rotor is performed with the aim of studying transient performance of turbine in extreme wind conditions, such as wind gusts and rapid yaw changes. The effect of the presence and/or lack of blade pitch control system on output power, rotor thrust, and blade deformation in sudden change of wind speed are investigated. The NREL 5 MW offshore wind turbine is used as the baseline case. In this regard, the modal approach is implemented for modeling the flexible blade structure with tension, bending and torsion degrees of freedom. The unsteady vortex lattice method is employed to obtain the aerodynamic loads. Moreover, the... 

Optimization of wind farm (WF) layout has been studied in the literature with the objective of maximizing the wind energy capture. Based on the power spectrum density (PSD) theorem, this paper shows that the WF layout affects not only the total harvested energy but also the level of power fluctuation, which in turn influences required capacity of battery energy storage system (BESS) needed to mitigate the inherent power fluctuation of the wind farms. Since both harvested energy level and BESS capacity directly influence the profit of WF owner, the effect of WF layout on these quantities are taken into account simultaneously and WF layout optimization problem is redefined. Genetic algorithm... 

This paper investigates the effects of two important factors, i.e., correlation of wind farms output with load and wind speed coincidence in determining the required static reserve in a high wind-penetrated power system. To this end, it suggests an analytical approach to involve the effects of these two factors in probabilistic analytical multi-state models of wind farms output generation. Based on an optimization framework with the objective of reaching the desirable level of correlation, the key idea is to calculate some joint probabilities for equivalent models of wind farms. As a result, these models become compatible with the ones for conventional generation units in adequacy studies of... 

Variable speed wind turbines are widely used in the modern power industry. These turbines that are usually driven by doubly fed induction generators (DFIG) contain two groups of controlling variables; mechanical variables like pitch angle, and electrical variables like rotor voltage. During the turbine operation, with variable wind speed, power must be managed in two different regimes; power optimization and power limitation. In the current research, initially a non-linear simulation, based on the general wind turbine dynamic model is presented. Then, the desired controllers for both pitch angle and generator voltage components are constructed. To validate turbine behavior and controller... 

Miscellaneous sorts of renewable energies, despite of their positive impacts on the power system operation cost and environmental concerns, could jeopardize the system reliability due to introducing significant degrees of intermittency and uncertainty. This challenge could be overcome by composing various sources of renewable energies with complimentary natures. This paper devises an explicit mathematical framework to compromise the contribution of wind and solar energies. The optimization problem is to maximize the system reliability subject to a fixed monetary investment associated with both wind and solar. The problem formulation is based on mixed-integer programming (MIP) format in which... 

This paper proposes a decentralized market-based model for long-term capacity investment decisions in a liberalized electricity market with significant wind power generation. In such an environment, investment and construction decisions are based on price signal feedbacks and imperfect foresight of future conditions in electricity market. System dynamics concepts are used to model structural characteristics of power market such as, long-term firms' behavior and relationships between variables, feedbacks and time delays. For conventional generation units, short-term price feedback for generation dispatching of forward market is implemented as well as long-term price expectation for... 

The purpose of this article is to develop a new method to estimate annual energy output for a given wind turbine in any region which should be easy to use and has satisfactory accuracy. To do this, hourly wind speeds of 25 different stations in Netherlands, output power curve of S47 wind turbine and fuzzy modeling techniques and artificial neural networks were used and a model is developed to estimate annual energy output for S47 wind turbine in different regions. Since this model has three inputs (average wind speed, standard deviation of wind speed, and air density of that region), this model is easy to use. The accuracy of this method is compared with the accuracy of conventional methods... 

This paper analytically investigates the effects of system and controller parameters and operating conditions on the dynamic and transient behavior of wind turbines (WTs) with doubly-fed induction generators (DFIGs) under voltage dips and wind speed fluctuations. Also, it deals with the design considerations regarding rotor and speed controllers. The poorly damped electrical and mechanical modes of the system are identified, and the effects of system parameters, and speed/rotor controllers on these modes are investigated by modal and sensitivity analyses. The results of theoretical studies are verified by time domain simulations. It is found that the dynamic behavior of the DFIG-based WT... 

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...