2,638 research outputs found
The health and development of children born to older mothers in the United Kingdom: observational study using longitudinal cohort data
Objective: To assess relations between childrenβs health and development and maternal age.
Design: Observational study of longitudinal cohorts.
Setting: Millennium Cohort Study (a random sample of UK children) and the National Evaluation of Sure Start study (a random sample of children in deprived areas in England), 2001 to 2007.
Participants: 31β257 children at age 9 months, 24β781 children at age 3 years, and 22β504 at age 5 years.
Main outcome measures: Childhood unintentional injuries and hospital admissions (aged 9 months, 3 years, and 5 years), immunisations (aged 9 months and 3 years), body mass index, language development, and difficulties with social development (aged 3 and 5 years).
Results: Associations were independent of personal and family characteristics and parity. The risk of children having unintentional injuries requiring medical attention or being admitted to hospital both declined with increasing maternal age. For example, at three years the risk of unintentional injuries declined from 36.6% for mothers aged 20 to 28.6% for mothers aged 40 and hospital admissions declined, respectively, from 27.1% to 21.6%. Immunisation rates at nine months increased with maternal age from 94.6% for mothers aged 20 to 98.1% for mothers aged 40. At three years, immunisation rates reached a maximum, at 81.3% for mothers aged 27, being lower for younger and older mothers. This was linked to rates for the combined measles, mumps, and rubella immunisation because excluding these resulted in no significant relation with maternal age. An increase in overweight children at ages 3 and 5 years associated with increasing maternal age was eliminated once maternal body mass index was included as a covariate. Language development was associated with improvements with increasing maternal age, with scores for children of mothers aged 20 being lower than those of children of mothers aged 40 by 0.21 to 0.22 standard deviations at ages 3 and 4 years. There were fewer social and emotional difficulties associated with increasing maternal age. Children of teenage mothers had more difficulties than children of mothers aged 40 (difference 0.28 SD at age 3 and 0.16 SD at age 5).
Conclusion: Increasing maternal age was associated with improved health and development for children up to 5 years of age
Plasmon channels in the electronic relaxation of diamond under high-order harmonics femtosecond irradiation
We used high order harmonics of a femtosecond titanium-doped sapphire system
(pulse duration 25 fs) to realise Ultraviolet Photoelectron Spectroscopy (UPS)
measurements on diamond. The UPS spectra were measured for harmonics in the
range 13 to 27. We also made ab initio calculations of the electronic lifetime
of conduction electrons in the energy range produced in the UPS experiment.
Such calculations show that the lifetime suddenly diminishes when the
conduction electron energy reaches the plasmon energy, whereas the UPS spectra
show evidence in this range of a strong relaxation mechanism with an increased
production of low energy secondary electrons. We propose that in this case the
electronic relaxation proceeds in two steps : excitation of a plasmon by the
high energy electron, the latter decaying into individual electron-hole pairs,
as in the case of metals. This process is observed for the first time in an
insulator and, on account of its high efficiency, should be introduced in the
models of laser breakdown under high intensity
ΠΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΡΡ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Π΅ΠΉ ΡΠ»Π΅ΠΊΡΡΠΎΡΠ½Π΅ΡΠ³ΠΈΠΈ Π΄Π»Ρ Π²ΡΡΠ°Π²Π½ΠΈΠ²Π°Π½ΠΈΡ Π³ΡΠ°ΡΠΈΠΊΠ° Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΠΉ
In this article, the authors consider the possibility of using a hybrid energy storage system to even out the load profile of the enterprise. Solving the problem of rational use of energy storage taking into account the initial variable load schedule will significantly reduce not only the cost of electricity consumption by the enterprise, but also the costs of its production. Detailed characteristics of batteries with various types of electrolytes and supercapacitors are given. A model of the active scheme of a hybrid electric energy storage system consisting of a lithium-ion battery and a supercapacitor unit with the corresponding characteristics is presented. The model was carried out by using the SimPowerSystems software in MatLab. During the simulation, the temperature and the aging effects and of the batteries were not taken into account. The selfdischarge parameter of the battery was also not presented. As a result of the simulation, discharge characteristics of supercapacitors and batteries were obtained based upon which the expediency of their combined use for leveling load profiles of various types was substantiated. The paper presents the results of the simulation of operating modes of a hybrid energy storage device, combining the advantages of two types of energy storage devices, as well as a diagram of delivered power to the network, corresponding to the specified parameters. The paper provides a mathematical description of the increasing power by hybrid storage system resulting from the combined use of supercapacitors and batteries. The paper presents the dependence of the power increase ratio on the frequency and the pulse current duty ratio, which proves that the maximum possible output power of the hybrid storage system can be several times greater than the power of a single battery having the same parameters
Conical refraction healing after partially blocking the input beam
In conical refraction, when a focused Gaussian beam passes along one of the
optic axes of a biaxial crystal it is transformed into a pair of concentric
bright rings at the focal plane. We demonstrate both theoretically and
experimentally that this transformation is hardly affected by partially
blocking the Gaussian input beam with an obstacle. We analyze the influence of
the size of the obstruction both on the transverse intensity pattern of the
beam and on its state of polarization, which is shown to be very robust
Evo-devo of human adolescence: beyond disease models of early puberty
Despite substantial heritability in pubertal development, much variation remains to be explained, leaving room for the influence of environmental factors to adjust its phenotypic trajectory in the service of fitness goals. Utilizing evolutionary development biology (evo-devo), we examine adolescence as an evolutionary life-history stage in its developmental context. We show that the transition from the preceding stage of juvenility entails adaptive plasticity in response to energy resources, other environmental cues, social needs of adolescence and maturation toward youth and adulthood. Using the evolutionary theory of socialization, we show that familial psychosocial stress fosters a fast life history and reproductive strategy rather than early maturation being just a risk factor for aggression and delinquency. Here we explore implications of an evolutionary-developmental-endocrinological-anthropological framework for theory building, while illuminating new directions for research
Investigation of the effect of combined thermomechanical processing on the brass microstructure evolution and the microhardness change
The article investigates the effect of combined thermomechanical processing, including pre-heat treatment and radial-shear rolling on the brass microstructure evolution and the microhardness change. The microstructure analysis of heat-treated samples according to various modes showed that the most optimal heat treatment before radialshear rolling for L63 brass is annealing at a temperature of 500 Β°C. As a result of combined thermomechanical processing, a gradient structure was obtained, so in the resulting rods with a diameter of 16 mm in the surface layer, a structure with an average grain size of 9 ΞΌm was obtained. In rods with a diameter of 12 mm, a fineβgrained, equalgrained structure of 3 ΞΌm was obtained in the surface layer
Investigation of the effect of combined thermomechanical processing on the brass microstructure evolution and the microhardness change
The article investigates the effect of combined thermomechanical processing, including pre-heat treatment and radial-shear rolling on the brass microstructure evolution and the microhardness change. The microstructure analysis of heat-treated samples according to various modes showed that the most optimal heat treatment before radialshear rolling for L63 brass is annealing at a temperature of 500 Β°C. As a result of combined thermomechanical processing, a gradient structure was obtained, so in the resulting rods with a diameter of 16 mm in the surface layer, a structure with an average grain size of 9 ΞΌm was obtained. In rods with a diameter of 12 mm, a fineβgrained, equalgrained structure of 3 ΞΌm was obtained in the surface layer
ΠΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΠ΅ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΡΡ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Π΅ΠΉ ΡΠ»Π΅ΠΊΡΡΠΎΡΠ½Π΅ΡΠ³ΠΈΠΈ Π΄Π»Ρ Π²ΡΡΠ°Π²Π½ΠΈΠ²Π°Π½ΠΈΡ Π³ΡΠ°ΡΠΈΠΊΠ° Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΠΉ
In this article, the authors consider the possibility of using a hybrid energy storage system to even out the load profile of the enterprise. Solving the problem of rational use of energy storage taking into account the initial variable load schedule will significantly reduce not only the cost of electricity consumption by the enterprise, but also the costs of its production. Detailed characteristics Β of Β batteries Β with Β various Β types Β of Β electrolytes Β and Β supercapacitors Β are Β given. A model of the active scheme of a hybrid electric energy storage system consisting of a lithium-ion battery and a supercapacitor unit with the corresponding characteristics is presented. The model was carried out by using the SimPowerSystems software in MatLab. During the simulation, the temperature and the aging effects and of the batteries were not taken into account. The selfdischarge parameter of the battery was also not presented. As a result of the simulation, discharge characteristics of supercapacitors and batteries were obtained based upon which the expediency of their combined use for leveling load profiles of various types was substantiated. The paper presents the results of the simulation of operating modes of a hybrid energy storage device, combining the advantages of two types of energy storage devices, as well as a diagram of delivered power to the network, corresponding to the specified parameters. The paper provides a mathematical description of the increasing power by hybrid storage system resulting from the combined use of supercapacitors and batteries. The paper presents the dependence of the power increase ratio on the frequency and the pulse current duty ratio, which proves that the maximum possible output power of the hybrid storage system can be several times greater than the power of a single battery having the same parameters.Π ΡΡΠ°ΡΡΠ΅ ΡΠ°ΡΡΠΌΠ°ΡΡΠΈΠ²Π°Π΅ΡΡΡ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½ΠΎΡΡΡ ΠΏΡΠΈΠΌΠ΅Π½Π΅Π½ΠΈΡ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΠΎΠ³ΠΎ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Ρ ΡΠ»Π΅ΠΊΡΡΠΎΡΠ½Π΅ΡΠ³ΠΈΠΈ Π΄Π»Ρ Π²ΡΡΠ°Π²Π½ΠΈΠ²Π°Π½ΠΈΡ Π³ΡΠ°ΡΠΈΠΊΠ° Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΡ. Π Π΅ΡΠ΅Π½ΠΈΠ΅ Π·Π°Π΄Π°ΡΠΈ ΡΠ°ΡΠΈΠΎΠ½Π°Π»ΡΠ½ΠΎΠ³ΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Π΅ΠΉ ΡΠ½Π΅ΡΠ³ΠΈΠΈ Ρ ΡΡΠ΅ΡΠΎΠΌ ΠΈΡΡ
ΠΎΠ΄Π½ΠΎΠ³ΠΎ ΠΏΠ΅ΡΠ΅ΠΌΠ΅Π½Π½ΠΎΠ³ΠΎ Π³ΡΠ°ΡΠΈΠΊΠ° Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΠΏΠΎΠ·Π²ΠΎΠ»ΠΈΡ ΡΡΡΠ΅ΡΡΠ²Π΅Π½Π½ΠΎ ΡΠ½ΠΈΠ·ΠΈΡΡ Π½Π΅ ΡΠΎΠ»ΡΠΊΠΎ Π·Π°ΡΡΠ°ΡΡ Π½Π° ΠΏΠΎΡΡΠ΅Π±Π»Π΅Π½ΠΈΠ΅ ΡΠ»Π΅ΠΊΡΡΠΎΡΠ½Π΅ΡΠ³ΠΈΠΈ ΠΏΡΠ΅Π΄ΠΏΡΠΈΡΡΠΈΠ΅ΠΌ, Π½ΠΎ ΠΈ Β Π·Π°ΡΡΠ°ΡΡ Β ΠΏΡΠΈ Β Π΅Π΅ Β ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΡΡΠ²Π΅. Β ΠΡΠΈΠ²ΠΎΠ΄ΡΡΡΡ Β ΠΏΠΎΠ΄ΡΠΎΠ±Π½ΡΠ΅ Β Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΈ Π°ΠΊΠΊΡΠΌΡΠ»ΡΡΠΎΡΠ½ΡΡ
Π±Π°ΡΠ°ΡΠ΅ΠΉ Ρ ΡΠ°Π·Π»ΠΈΡΠ½ΡΠΌΠΈ ΡΠΈΠΏΠ°ΠΌΠΈ ΡΠ»Π΅ΠΊΡΡΠΎΠ»ΠΈΡΠΎΠ² ΠΈ ΡΡΠΏΠ΅ΡΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠΎΡΠΎΠ². ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π° ΠΌΠΎΠ΄Π΅Π»Ρ Π°ΠΊΡΠΈΠ²Π½ΠΎΠΉ ΡΡ
Π΅ΠΌΡ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΠΎΠ³ΠΎ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Ρ ΡΠ»Π΅ΠΊΡΡΠΎΡΠ½Π΅ΡΠ³ΠΈΠΈ, ΡΠΎΡΡΠΎΡΡΠ΅Π³ΠΎ ΠΈΠ· Π»ΠΈΡΠΈΠΉ-ΠΈΠΎΠ½Π½ΠΎΠΉ Π±Π°ΡΠ°ΡΠ΅ΠΈ ΠΈ Π±Π»ΠΎΠΊΠ° ΡΡΠΏΠ΅ΡΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠΎΡΠΎΠ² Ρ ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΡΡΠΈΠΌΠΈ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠ°ΠΌΠΈ. Β ΠΠΎΠ΄Π΅Π»Ρ Β ΡΠ°Π·ΡΠ°Π±ΠΎΡΠ°Π½Π° Β Ρ Β ΠΏΠΎΠΌΠΎΡΡΡ Β ΠΏΠ°ΠΊΠ΅ΡΠ° Β ΠΏΡΠΈΠΊΠ»Π°Π΄Π½ΡΡ
Β ΠΏΡΠΎΠ³ΡΠ°ΠΌΠΌ Β SimPowerSystems Π² MatLab. ΠΡΠΈ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΠΈ Π½Π΅ ΡΡΠΈΡΡΠ²Π°Π»ΠΈΡΡ ΡΠ΅ΠΌΠΏΠ΅ΡΠ°ΡΡΡΠ½ΡΠΉ ΡΡΡΠ΅ΠΊΡ ΠΈ ΡΡΡΠ΅ΠΊΡ ΡΡΠ°ΡΠ΅Π½ΠΈΡ Π°ΠΊΠΊΡΠΌΡΠ»ΡΡΠΎΡΠ½ΡΡ
Π±Π°ΡΠ°ΡΠ΅ΠΉ, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΡ ΠΎΡΠ½ΠΎΡΠΈΡΠ΅Π»ΡΠ½ΠΎ ΡΠ°ΠΌΠΎΡΠ°Π·ΡΡΠ΄Π° Π°ΠΊΠΊΡΠΌΡΠ»ΡΡΠΎΡΠ½ΠΎΠΉ Π±Π°ΡΠ°ΡΠ΅ΠΈ. Π ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΠΏΠΎΠ»ΡΡΠ΅Π½Ρ Ρ
Π°ΡΠ°ΠΊΡΠ΅ΡΠΈΡΡΠΈΠΊΠΈ ΡΠ°Π·ΡΡΠ΄Π° Π±Π»ΠΎΠΊΠΎΠ² ΡΡΠΏΠ΅ΡΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠΎΡΠΎΠ² ΠΈ Π°ΠΊΠΊΡΠΌΡΠ»ΡΡΠΎΡΠ½ΡΡ
Π±Π°ΡΠ°ΡΠ΅ΠΉ, Π½Π° ΠΎΡΠ½ΠΎΠ²Π°Π½ΠΈΠΈ ΠΊΠΎΡΠΎΡΡΡ
Π²ΡΡΠ²Π»Π΅Π½Π° ΡΠ΅Π»Π΅ΡΠΎΠΎΠ±ΡΠ°Π·Π½ΠΎΡΡΡ ΠΈΡ
ΡΠΎΠ²ΠΌΠ΅ΡΡΠ½ΠΎΠ³ΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ Π΄Π»Ρ Π²ΡΡΠ°Π²Π½ΠΈΠ²Π°Π½ΠΈΡ Π³ΡΠ°ΡΠΈΠΊΠΎΠ² Π½Π°Π³ΡΡΠ·ΠΊΠΈ ΡΠ°Π·Π»ΠΈΡΠ½ΡΡ
ΡΠΈΠΏΠΎΠ². ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Ρ ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΡ ΠΌΠΎΠ΄Π΅Π»ΠΈΡΠΎΠ²Π°Π½ΠΈΡ ΡΠ΅ΠΆΠΈΠΌΠΎΠ² ΡΠ°Π±ΠΎΡΡ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΠΎΠ³ΠΎ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Ρ ΡΠ½Π΅ΡΠ³ΠΈΠΈ, ΡΠΎΠ²ΠΌΠ΅ΡΠ°ΡΡΠ΅Π³ΠΎ Π΄ΠΎΡΡΠΎΠΈΠ½ΡΡΠ²Π° Π΄Π²ΡΡ
ΡΠΈΠΏΠΎΠ² Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Π΅ΠΉ ΡΠ½Π΅ΡΠ³ΠΈΠΈ, Π° ΡΠ°ΠΊΠΆΠ΅ ΠΏΠΎΠ»ΡΡΠ΅Π½ Π³ΡΠ°ΡΠΈΠΊ ΠΎΡΠ΄Π°Π²Π°Π΅ΠΌΠΎΠΉ Π² ΡΠ΅ΡΡ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ, ΡΠΎΠΎΡΠ²Π΅ΡΡΡΠ²ΡΡΡΠΈΠΉ Π·Π°Π΄Π°Π½Π½ΡΠΌ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠ°ΠΌ. ΠΡΠΈΠ²Π΅Π΄Π΅Π½ΠΎ ΠΌΠ°ΡΠ΅ΠΌΠ°ΡΠΈΡΠ΅ΡΠΊΠΎΠ΅ ΠΎΠΏΠΈΡΠ°Π½ΠΈΠ΅ ΠΏΡΠΎΡΠ΅ΡΡΠ° ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΡ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΠΎΠ³ΠΎ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»Ρ Π² ΡΠ΅Π·ΡΠ»ΡΡΠ°ΡΠ΅ ΡΠΎΠ²ΠΌΠ΅ΡΡΠ½ΠΎΠ³ΠΎ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ Π±Π»ΠΎΠΊΠΎΠ² ΡΡΠΏΠ΅ΡΠΊΠΎΠ½Π΄Π΅Π½ΡΠ°ΡΠΎΡΠΎΠ² ΠΈ Π°ΠΊΠΊΡΠΌΡΠ»ΡΡΠΎΡΠ½ΡΡ
Π±Π°ΡΠ°ΡΠ΅ΠΉ. ΠΠΎΡΡΡΠΎΠ΅Π½ Π³ΡΠ°ΡΠΈΠΊ Π·Π°Π²ΠΈΡΠΈΠΌΠΎΡΡΠΈ ΠΊΠΎΡΡΡΠΈΡΠΈΠ΅Π½ΡΠ° ΡΠ²Π΅Π»ΠΈΡΠ΅Π½ΠΈΡ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ ΠΎΡ ΡΠ°ΡΡΠΎΡΡ ΠΈ Π²Π΅Π»ΠΈΡΠΈΠ½Ρ ΠΊΠΎΡΡΡΠΈΡΠΈΠ΅Π½ΡΠ° Π·Π°ΠΏΠΎΠ»Π½Π΅Π½ΠΈΡ ΠΈΠΌΠΏΡΠ»ΡΡΠ½ΠΎΠ³ΠΎ ΡΠΎΠΊΠ°, ΠΊΠΎΡΠΎΡΡΠΉ ΠΏΠΎΠΊΠ°Π·ΡΠ²Π°Π΅Ρ, ΡΡΠΎ ΠΌΠ°ΠΊΡΠΈΠΌΠ°Π»ΡΠ½ΠΎ Π²ΠΎΠ·ΠΌΠΎΠΆΠ½Π°Ρ Π²ΡΡ
ΠΎΠ΄Π½Π°Ρ ΠΌΠΎΡΠ½ΠΎΡΡΡ Π³ΠΈΠ±ΡΠΈΠ΄Π½ΠΎΠΉ Π½Π°ΠΊΠΎΠΏΠΈΡΠ΅Π»ΡΠ½ΠΎΠΉ ΡΠΈΡΡΠ΅ΠΌΡ ΠΌΠΎΠΆΠ΅Ρ Π±ΡΡΡ Π² ΡΠ°Π·Ρ Π±ΠΎΠ»ΡΡΠ΅ ΠΌΠΎΡΠ½ΠΎΡΡΠΈ ΠΎΠ΄ΠΈΠ½ΠΎΡΠ½ΠΎΠΉ Π±Π°ΡΠ°ΡΠ΅ΠΈ Ρ ΡΠ°ΠΊΠΈΠΌΠΈ ΠΆΠ΅ ΠΏΠ°ΡΠ°ΠΌΠ΅ΡΡΠ°ΠΌΠΈ
Improving the efficiency of autonomous electrical complex with renewable energy sources by means of adaptive regulation of its operating modes
Renewable energy sources are gradually becoming useful in mining industry. They are actively used in remote, sparsely populated areas to power shift settlements, geological and meteorological stations, pipeline equipment, mobile cell towers, helicopter pads lighting, etc. In comparison with diesel generators, systems with renewable sources do not require fuel transportation, have short payback periods and flexible configuration for different categories of electrical loads. The main obstacles to their spread are instability of generation and high cost of produced electricity. One of the possible ways to solve these problems is to develop new technologies, increase power density of generators and energy storage systems. The other way represents energy saving and rational use of affordable resources. The new solutions for implementation of the second method are proposed in this work. The object of the study is autonomous DC electrical complex with photovoltaic and wind power sources. In such systems the generated power from renewable sources is transferred to consumers via intermediate DC bus, the voltage level of which affects the power losses in the process of power transmission. The vast majority of complexes have a problem that their DC bus voltage is constant, while the optimum voltage level with lowest losses varies depending on the generated and consumed power. Therefore, electrical complexes potentially lose a part of the transmitted energy. To avoid this, a special algorithm was added to automatically adjust DC bus voltage to optimum level according to changes in working conditions. An additional contribution to efficiency improvement can be made by dynamic change of operating frequency in power converters depending on their load. The evaluation based on results of computer simulation showed that in a complex with rated power 10 kW active power losses during its lifetime can be reduced by 2-5 %
Operation of a Single-phase Autonomous Inverter as a Part of a Low-power Wind Complex
The article discusses the experience of operating a wind power complex with a low-power wind power installa- tion (5 kW), the use of which is promising for powering remote oil production facilities, exploration and other types of mining operations. The structure of the studied complex and its characteristics, technical problems that have arisen during operation for 6 years are given. The elements of the wind energy complex β the battery charge regulator and the inverter-converter are considered. The consequences of the mechanical regulator failure of battery charge are con- sidered and recommendations for its replacement are presented. The issues of diagnostics and repair of one of the main elements of the complex β the inverter-converter, its component β DC link are highlighted in detail. Oscil- lograms of the output voltage of the inverter-converter are presented for different capacities of the DC link and the images of the repaired inverter-converter are given. Recommendations are given on choosing an inverter-converter and setting up the operating modes of the wind energycomplex
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