J.R. Saenz

Modeling and control of a wind turbine driven doubly fed induction generator

This paper presents the simulation results of a grid-connected wind driven doubly fed induction machine (DFIM) together with some real machine performance results. The modeling of the machine considers operating conditions below and above synchronous speed, which are actually achieved by means of a double-sided PWM converter joining the machine rotor to the grid. In order to decouple the active and reactive powers generated by the machine, stator-flux-oriented vector control is applied. The wind generator mathematical model developed in this paper is used to show how such a control strategy offers the possibility of controlling the power factor of the energy to be generated.

Adaptive control of a fuel cell-microturbine hybrid power plant

Power producing systems containing a combination of high-temperature fuel cells and heat engines have the potential for very high efficiency in converting fossil fuel to AC electricity. Hybrid cycles are myriad and can include combinations of fuel cells with gas turbine engines, steam turbines, or even reciprocating engines The synergy realized by fuel cell/turbine hybrids derives primarily from using the rejected thermal energy and combustion of residual fuel from a fuel cell in driving the gas turbine. This leveraging of the thermal energy makes the high-temperature molten carbonate fuel cells ideal candidates for hybrid systems. Use of a recuperator contributes to thermal efficiency by transferring heat from the gas turbine exhaust to the fuel and air used in the system.

Reactive power control of a wind farm made up with doubly fed induction generators. II

Electrical systems endowed with variable generating units are called to dominate the electrical landscape in the near future and new tools are necessary to develop in order to work in this new environment. Wind power generation is becoming one of the most important renewable energy sources in Spain and consequently, the simulation of a wind farm power performance will be an essential tool for the location of new farms. Additionally, their active/reactive power regulation possibility can become very important in the decision making process for the generator-type that has to be implemented in each wind farm. The present papers presents two different algorithms for the regulation of wind farms made up with doubly fed induction machines (DFIM), simulation results of the developed algorithms and real results of the implementation in a farm located in the North of Spain. Part I presents the wind farm model and validation.

Comparison between discrete STFT and wavelets for the analysis of power quality events

Abstract This paper deals with the comparison of signal processing tools for power quality analysis. Two signal processing techniques are considered: the wavelet filters and the discrete short-time Fourier transforms. Then, examples of the two most frequent disturbances met in the power system are chosen. It is designed an adjustable speed drive with a six-pulse converter using EMTP/ATP and it is presented normal energizing of utility capacitors. The analysis is tested on a system consists of 13 buses and is representative of a medium-sized industrial plant. Finally, each kind of electrical disturbance is analyzed with example representing each tool. A qualitative comparison of results shows the advantages and drawbacks of each signal processing technique applied to power quality analysis.

Serum levels of polychlorinated dibenzodioxins and dibenzofurans and PCBs in the general population living near an urban waste treatment plant in Biscay, Basque Country.

Levels of PCDD/Fs and dioxin-like PCBs were measured in 16 pooled samples of serum from a total of 322 adults in the general population, to coincide with the start-up of a new municipal solid urban waste treatment plant in Biscay, Basque Country (Spain). Two hundred and eighty-three individual serum samples were also obtained, in which the most common PCBs (28, 52, 101, 118, 138, 153 and 180) were quantified. The samples were taken from four geographical zones: two from the metropolitan area of Bilbao, located less than 2 km from the plant and with high traffic density (Zones E1 and E2), a third located 5 km from the plant in an urban area of Bilbao, also with high traffic density (Zone C1) and the fourth located 20 km from the plant, in a municipality with minimal industrial activity and low traffic density (Zone C2), the latter two being out of the path of the prevailing winds. The median levels of dioxins+furans were similar by zone: E1=24.3, E2=27.3, C1=21.3, C2=18.8 pg g(-1) lipid (p=0.362); by sex: 20.2 vs. 22.6 pg g(-1) lipid in men and women (p=0.328); and by age: 20.8 vs. 21.3 pg g(-1) lipid in subjects aged 20-44 and 45-69 (p=0.505). No detectable levels of PCBs 52 and 101 were found. Significant differences by zone were found only for PCB 180 (p=0.041), with higher values in Zone C2, the zone with the lowest presumed contamination levels. Dioxin-like PCBs (p<0.001) and the most common PCBs (138, 153, 180) (p<0.001) were both statistically associated with age, higher values being found in the 45-69 age group.

Heavy metal levels (Pb, Cd, Cr and Hg) in the adult general population near an urban solid waste incinerator.

In 2005 an urban solid waste incinerator (SWI) was commissioned in Bilbao (Basque Country, Spain). Serum and urine samples were collected from 95 and 107 volunteers in 2006 and 2008 respectively, of which 62 were repeats from the same individuals. Blood lead levels (BPb) were determined, as were the concentrations of cadmium (Cd), chromium (Cr) and mercury (Hg) in urine (UCd, UCr and UHg). The town of Alonsotegi and a borough of Bilbao (Altamira, Rekalde) were considered to be close, less than 2 km from the plant, and correspond to an urban environment with high traffic density. The areas of reference were a borough of Bilbao (Santutxu-Zurbaran), 5 km from the plant, also in an urban area with high traffic density, and a small town with little industrial activity and low traffic density (Balmaseda) 20 km from the plant; neither of these is downwind from the site with respect to prevailing winds. There was a significant correlation for BPb, r=0.63 (p<0.001), between the two surveys. However, there was no linear correlation for the other three metals (UCd, UCr and UHg), between the two sampling periods (p>0.05). Multiple linear regression models did not show increases over time of the levels of BPb, UCd, UCr and UHg in the areas close to the SWI compared to those of areas located further away, after adjusting for confounding variables. These results reinforce the hypothesis that populations near modern plants for solid waste incineration do not manifest increased levels of heavy metals.

High-temperature conductors: a solution in the uprating of overhead transmission lines

The legislation currently in force that affects the construction of overhead electricity transmission or distribution lines establishes an extensive number of conditioning factors as regards licences, public exposition of projects, rights regarding the presentation of allegations, etc. For that reason, the period that can elapse between the time the need for the installation of a new line is detected and its coming into service amply exceeds the time regarded as permissible by the utility. In upgrading the capacity of a line, the possible options include installing a larger conductor on existing structures, increasing the operating voltage, increasing operating temperature, etc. Also, uprating process using high-temperature conductors is another possible solution. This paper presents the most important results of the COALPRET research project, whose dual aim has been to carry out a general study of the characteristics of electrical conductors with high temperature performance and low sag, and apply these studies to the specific overhead transmission line.

Neuro-fuzzy control for autonomous wind–diesel systems using biomass

This paper deals with the development of a neuro-fuzzy controller for a wind–diesel system composed of a stall regulated wind turbine with an induction generator connected to an ac bus-bar in parallel with a diesel generator set having a synchronous generator. A gasifier is capable of converting tons of wood chips per day into a gaseous fuel that is fed into a diesel engine. The controller inputs are the engine speed error and its derivative for the governor part of the controller, and the voltage error and its derivative for the automatic voltage regulator. These are readily measurable quantities leading to a simple controller which can be easily implemented. It is shown that by tuning the fuzzy logic controllers, optimal time domain performance of the autonomous wind–diesel system can be achieved in a wide range of operating conditions compared to fixed-parameter fuzzy logic controllers and PID controllers.

Reduced model of DFIGs wind farms using aggregation of wind turbines and equivalent wind

In this paper, a new reduced model of wind farms with doubly-fed induction generators wind turbines is proposed for representing all the wind turbines of a wind farm by one single equivalent wind turbine. The simulation results demonstrate the effectiveness of the proposed reduced model to represent the collective response of a wind farm in the point of common coupling to grid during power system dynamic simulations. This model can be used for voltage and angle stability investigations of large power system with an important reduction of the model order and computation time

Control system of doubly fed induction generators based wind turbines with production limits

Doubly fed induction generators based wind turbines are today one of the most widely used generation systems in wind farms due to the ability of variable speed operation and with decoupled control of active and reactive power. Nowadays these wind turbines are operating without generation limits, but the increasing wind power penetration in power systems must lead to that the wind farms have to operate with production limits imposed by the electrical system operators to maintain the stability of the electrical network. In this paper, a new control system of doubly fed induction generators based wind turbines is proposed for the control of active and reactive powers according to the imposed power limitations. This control system presents an active power controller, reactive power controller and pitch angle controller, in order to operate the wind turbine with optimum power efficiency or with limited active power and the demanded reactive power. This generation control provides a better grid integration of doubly fed induction generators