Search

Wind turbine generators in a windfarm are connected by underground cables. Lightning sometimes strikes a nacelle or a blade. Lightning overvoltages due to a direct lightning strike to the system cause damages in the underground cable. Many parameters should be investigated to establish a rational lightning protection design for wind power generation system. Numerical simulation is a useful method to discuss the influence of the parameters on the lightning overvoltages. This paper uses an Electro-Magnetic Transients Program for the lightning surge analysis. This paper discusses the influence of grounding method of metallic sheath of the cable and grounding resistance on the lightning overvoltages for the direct lightning strike to the generation system. [ABSTRACT FROM AUTHOR]

In order to solve the problems of global warming and depletion of energy resource, renewable energy systems such as wind generation are getting attention. However, wind power fluctuates due to variation of wind speed, and it is difficult to perfectly forecast wind power. This paper describes a method to use power forecast data of wind turbine generators considering wind power forecast error for optimal operation. The purpose in this paper is to smooth the output power fluctuation of a wind farm and to obtain more beneficial electrical power for selling. [ABSTRACT FROM AUTHOR]

This paper presents the operation under fault and protection of multi DC smart grids connected to the DC transmission line. The smart grid consists of wind turbine and photovoltaic generators, controllable loads, generator side and grid side inverters. The voltage stability of the DC bus voltage is attained by applying the power consumption control of controllable loads, the power control of grid connected converter and power control of renewable plants. On the other hand, the fault protection for short-circuit and low resistance ground fault at the DC transmission line was sighted. Simulation results based on PSIM are provided to demonstrate the effectiveness of the system. [ABSTRACT FROM AUTHOR]

The output power fluctuation of such renewable energy power plants as a wind-turbine generator and a photovoltaic system results in frequency deviation and terminal voltage fluctuation. Furthermore, these power fluctuations also affect the turbine shafting of diesel generator and gas-turbine generators, which are the main power generation systems in isolated islands. This article presents a control strategy that achieves torsional torque suppression and power system stabilization. Since the measurement of torsional torque is difficult technically, and there is uncertainty in mechanical constants of the shaft torsional system, the torsional torque is estimated by using a linear quadratic regulator observer with a parameter identification system. The simulation results validate the effectiveness of the proposed control system. [ABSTRACT FROM AUTHOR]

The control of wind-energy conversion systems (WECSs) is still a challenging task for design engineers. Despite being ubiquitous in the wind industry, the performance of classical proportional–integral–derivative controllers is not ideal, and they require additional notch filters to handle turbine nonlinearity. This has triggered interest toward advanced control concepts that are multiobjective and multivariable. With optimality, feedback, and robustness being prerequisites in developing control policies that guarantee high-integrity and fault-tolerant control systems, \cal H\infty control theory has become a standard design method of choice over the past two decades and is gaining prominence in industrial (and WECS) control applications. Based on the linear matrix inequality approach, this paper presents a comprehensive and systematic way of applying the \cal H\infty control design algorithm for automatically gain-scheduling the linear-parameter-varying turbine plant along parameter trajectories. Control seeks to regulate both power and voltage via a synthesis of two controllers, namely, pitch and generator torque, respectively, for a megawatt-class WECS. Digital simulations executed in a MATLAB/Simulink environment ascertain that the control paradigm meets the objectives of optimizing power conversion throughout the operating envelope, as well as eliminating power oscillations through system damping. [ABSTRACT FROM AUTHOR]

Currently, there are several published reports on wind farms (WFs) for controlling output power by using pitch angle control. In addition, to reduce the adverse effects of frequency deviations, battery energy storage systems (BESSs) are introduced to small power systems. In this context, this paper presents a frequency control method by the WF and the BESS using load estimation. The load is estimated by a disturbance observer. The frequency deviations in low and high frequency domain are reduced by the WF using pitch angle control and battery charge/discharge, respectively. By using the proposed method, the reduction of the rated capacity of the BESS is possible. Furthermore, for the pitch angle control system of each WTG in the WF, generalized predictive control (GPC) is applied to achieve robust control performance. The effectiveness of the proposed method is verified by numerical simulation. [ABSTRACT FROM AUTHOR]

Effective utilization of renewable energies such as wind energy instead of fossil fuels is desirable. Wind energy is not constant and windmill output is proportional to the cube of the wind speed, which causes the generated power of wind turbine generators (WTGs) to fluctuate. In order to reduce the output power fluctuation of wind farms, this paper presents an output power leveling control strategy for a wind farm based on both the average wind farm output power and the standard deviation of the wind farm output power, a cooperative control strategy for WTGs, and pitch angle control using a generalized predictive controller (GPC) in all WTG operating regions. Simulation results using an actual detailed model for wind farm systems show the effectiveness of the proposed method. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 31– 41, 2007; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/eej.20448 [ABSTRACT FROM AUTHOR]

A hybrid power system uses many wind turbine generators in isolated small islands. The output power of wind turbine generators is mostly fluctuating and has an effect on system frequency. In order to solve this problem, we propose a new power system using renewable energy in small, isolated islands. The system can supply high-quality power using an aqua electrolyzer, fuel cell, renewable energy; and diesel generator. The generated hydrogen by an aqua electrolyzer is used as fuel for a fuel cell. The simulation results are given to demonstrate the availability of the proposed system in this paper. [ABSTRACT FROM AUTHOR]

Abstract: Operation of variable speed wind turbine generator (WTG) in the above-rated region characterized by high turbulence intensities demands a trade-off between two performance metrics: maximization of energy harvested from the wind and minimization of damage caused by mechanical fatigue. This paper presents a learning adaptive controller for output power leveling and decrementing cyclic loads on the drive train. The proposed controller incorporates a linear quadratic Gaussian (LQG) augmented by a neurocontroller (NC) and regulates rotational speed by specifying the demanded generator torque. Pitch control ensures rated power output. A second-order model and a stochastic wind field model are used in the analysis. The LQG is used as a basis upon which the performance of the proposed paradigm in the trade-off studies is assessed. Simulation results indicate the proposed control scheme effectively harmonizes the relation between rotor speed and the highly turbulent wind speed thereby regulating shaft moments and maintaining rated power. [Copyright &y& Elsevier]