Introduction. Actuality of theme
Aims and tasks of the research
Planned practical result
Improvement of a flicker-model
Conclusion
List of references
Abstract
RUS | ENG
Andrushkevich Olga
Faculty:Electrotechnical
Speciality:Electrical networks and systems
Theme of master's work:
Electromagnetic compatibility
Improvement of a flicker-model
Leader of work: Dmitrieva Elena
Email: andrushkevich@rambler.ru
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Introduction. Actuality of theme |
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Introduction. Actuality of theme
In normal conditions in the network of electric power distribution there are fast voltage fluctuations caused by connecting and disconnecting of different loads. In addition, there is such electric power consuming equipment, which uses an electric current unevenly, electric power use changes depending on the stages of duty cycle.
The similar loadings result in the origin of repetitive changes of supply voltage called "voltage fluctuation ". Naturally, that in practice these fluctuation tries to be limited, retaining them in such a range as not inconvenience for the users of electric energy.
The device which consumes the electric power and which is the most sensible to voltage fluctuation, is an incandescent lamp.
Aims and tasks of the research
The rapid changes voltage ("fluctuations") on the terminals of lamps cause fluctuation of luminosity, which negatively influences labour productivity and health of people. Estimation of consequences of voltage fluctuation is executed by the design of the system "lamp-sight-brain". In this system the reaction of sight of Y(t) is designed by a linear weighing filter (WF). Structure of WF in a flicker-model from [1,2] was grounded on the basis of experimental researches in area of frequencies of fluctuation more than 0,05 Hz. The concept of dose of flicker Рs is related to estimation of feeling of flicker S(t). Desire to formalization of basic experimental data resulted in substantial complication of nonlinear part of flicker -model, which does not delay development of exact methods of calculation of doses of flicker, but it makes the use of concept of dose of inaccessible for the wide circle of engineers.
Basic tasks are:
Planned practical result
We try to receive an improved flicker -model. The improvement involves including block of slow adaptation in to the already existent flicker-model. That will allow to get reliable information of increase of flicker in all frequency range from 0,001 to 35 Hz.
Improvement of a flicker-model
The existing model of flicker -model from [1,2] WF consists of three linear filters: HF - high-frequencies with threshold frequency 0.05 Hz, PF are perceptions of frequencies, LF - lower frequencies with threshold frequency 35 Hz (fug.1).
Figure 1. Flow diagram of existing model of flicker Filter HF is a real differentiate link 1 with the parameter of Тв=3,1831 s and transmission function
The following links are included in the filter of PF: 2 is swaying with a transitivity k=1,74802 and permanent in time of Тк1=0,015418 c, Тк2=0,017385 c, 3 is forcing with Тф=0,069811 c, 4 and 5 are no periodical (inertia) link of the first order with Тн1=0,12989 s and Тн2=0,007267 s, 6 is differentiate with permanent in time of Тк2. Transmission function of filter of PF
Filter of lower frequencies 7 is the filter of Batervorta with permanent in time of Тб1=0,0023537 s, Тб2=0,004573 s, Тб3=0,0064308 s, ТБ4=0,0087849 s and transmission function
And transmission function of WF corresponds to
a gain-frequency function (GFF) corresponds, with is given on fig.2 curve 1.
Figure 2. GFF weighing filters Fluctuation frequency in Hz is 120 times less than fluctuation frequency in 1/min. Maximum GFF, equal to unit, is achieved at resonant frequency 8,85 Hz.
НPresence of link 1 in WF results in the fast that curve 1 on a figure 2 tends to zero at small frequencies. The same is assumed that at small frequencies a flicker-effect is absent. However it contradicts the physiology of sight.
For its realization we will add an inertia link 9 to the link (fig.3) with the transmission function of 1/(Тк2s+1).
Figure 3 Structural scheme of the assumed WF
At the same time, for the maintenance of existing GFF the range of large frequencies, we will add a focusing link 10 with permanent in time of Тк2. At large frequencies slow adaptation influences a little, therefore GFF does not change practically, because work of transmissions functions of links 9 and 10 is equal to 1. Slow adaptation is designed by a link 11 and transmission function [3].
The change of structure of WF gives new GFF, a maximum Аam, which differs from 1. In this connection it is necessary to add the multiplier of 1/Аam. We will get expression for the transmission function of assumed WF A nominal multiplier is found from the condition of equality of GFF to 1 at resonance frequency.
Corresponding GFF is given to the curve 2 on fig.2. At frequencies more than 3 Hz it practically coincides with a curve 1. The account of slow adaptation allows to extend the range of flicker-model applicability to frequencies 0,0001 Hz and to avoid the unjustified understating of requirements to EMC in area of frequencies less than 3 Hz.
Conclusion Estimation of doses of flicker voltage for a standard lamp can not be spread on other types of lamps. To provide the authenticity of EMC estimations it is necessary to add the models of different lamps into a flicker-model, and in engineering calculations it is enough to use the coefficients of recalculation. List of references
The reason of this principle lack of existent flicker-model is in that GFF was set from data of questioning of examinees about their subjective reactions on fluctuation of luminosity. At such approach it is possible to get reliable results only in area of high-frequencies, where "rapid" adaptation of sight has the mean meanings. Conditioned by electric processes in the brain, it causes the noticeable subjective feelings on the people. Contrary at low frequencies the "slow " adaptation related to the photochemistry processes is determinant. Its action approximately 10 times weaker, therefore the subjective feelings show up insignificance.
For distribution of flicker -model applicability in the range of frequencies below 0,05 Hz it is assumed to take in account the phenomenon of slow adaptation. As both types of adaptation operate, it is necessary to select the link of rapid adaptation in WF and parallel it is necessary to include the link of by slow adaptation. Link 1 is not taken into consideration. Rapid adaptation is designed the real time of Та1 differentiate by a link with time permanent, which is tenth of milliseconds. We will accept, that Та1=Тк2(0,016 s - in [3]). In this case transmission function is
Is necessary to separate tasks of estimation of flicker influence on people. The concept of flicker dose is spread on the range of low frequencies of fluctuation with the help of the phenomenon of slow adaptation of sight. For this purpose the block of rapid adaptation of sight is selected in a weighing filter, parallel to which the block of slow adaptation is added
Existent procedure of measuring and calculation of flicker doses appears by itself unjustified difficult. It is desirable to pass from estimation of people discomfort to objective estimation of fatigue of man depending on the voltage dose.
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