The method of automated control of voltage fluctuations and current

 

The invention relates to measuring technique and can be used in the process of measuring and monitoring key indicators of quality of electrical energy. The technical result consists in process automation measurement and active control of vibrations of voltage and current. To achieve a technical result provide measurements of voltage fluctuations, which are in the form of analog curves of the main characteristics of electrical energy. Determine the effective values of voltage and current for half of the period changes of these values at the frequency of the main harmonic component, which is used to obtain information about the quantitative assessment of the magnitude of change of voltage and current, as well as in the determination of the amplitude-frequency characteristics of the visual analyzer of human - dose flicker voltage and current. When exceeding the guideline values of the quality of electrical energy formed a control signal corresponding corrective devices. 3 Il.

The invention relates to electrical engineering and can be used as an integral part of a comprehensive active and variations made to measure only voltage. This assessment can be considered objective, if we assume that the power system consist only of linear elements, when the form of the current practically does not differ from the shape of the voltage. But on modern power systems, which include more and more non-linear elements, you can't say that. Therefore, in modern power systems along with the assessment of voltage fluctuations for objective quality control voltage should be measured and fluctuations in the current.

Fluctuations in voltage and current is considered short-term (length of up to one minute) deviations of these values from the nominal values. Moreover, these deviations must be established. Therefore, the duration of the evaluation of the levels of voltage and current should not be less than ten minutes. Only when these conditions are met, you can count on the objectivity of judgments about the levels of voltage and current.

In accordance with the applicable interstate standard GOST 13109-97 “standards for the quality of electric energy in power supply systems for General use” [1] voltage fluctuations are measured by two indicators of the quality of electric energy: the size is Kim technical solution to the proposed method for automated control of the oscillations of voltage and current can be called flickermeter [2]. Such technical solution is implemented in the device ERIS-KE.02 developed in LLC “energy control”. However, this device is intended only for the passive control of the quality of electrical energy, that is only for the registration of the quantitative characteristics of these indicators and, in the best case, to check the conformity of their normative values.

The objective of the invention is the formation of an algorithm for automated active control of vibrations of voltage and current, i.e. the creation algorithm of signal control devices for adjusting the levels of voltage and current. Such devices can be, for example, a smoothing device.

The technical result is achieved by the fact that the initial data algorithm for active control of vibrations of voltage and current are analog curves of these characteristics of the electrical energy converted in the analog-to-digital Converter into a set of discrete values, from which to retrieve the current values of voltage and current for half of the period changes of these values at the frequency of the main harmonic component required for ituano-frequency characteristics of the visual analyzer man dose flicker voltage and current. When breaking the normative values of these indicators of quality of electrical energy formed a control signal corresponding corrective devices. Automation of active control of vibrations of voltage and current is provided by the use of computers.

To determine the level of fluctuations is quite affordable recommendations applicable on the territory of Russia inter-governmental standard [1].

The fluctuations in international standard recommends determined by the formula

where Uiand Ui+1- effective values of two adjacent extrema voltage curve; UMr.- current nominal value of the analyzed voltage.

Used in the formula (1) voltage Uiand Ui+1presents their current values defined on each half-cycle of the fundamental frequency. The procedure for determining these values can be realized by performing calculation according to the formula

where T0the period of the harmonic component of the voltage, u is the instantaneous value analysisreveals preliminary decomposition of the analog values of voltage and current in discrete already at the initial stage of analysis, the mathematical formulation for determining the effective value of voltage (2) can be represented in a different form:

where N0- the number of quantizations (discrete values) for the period changes in the main harmonic component of the analyzed voltage; upthe voltage at p-th quantization;t - value of one quantization determined by the formula

Formula (3) subject to the equality (4) will appear in the form

Determining the effective values of the analyzed voltage for each half period of the harmonic component of this voltage should be within ten minutes. Then you need to fix the facts short-term (less than one minute) voltage deviations from their nominal values. If the duration of the voltage deviation exceeds one minute, then here you should talk about another indicator of the quality of electric energy, namely the voltage deviation.

Further in the formula (1), we can determine the magnitude of the amplitude of the recorded voltage fluctuations.

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where kU- the normative value of the amplitude of the voltage fluctuations.

Such calculations should be performed for assessment of fluctuations in the current.

The procedure of estimating the magnitude of the current fluctuations should start with a definition of the effective values of the analyzed current for each half period of the harmonic component by the formula

where ip- the value of current when the p-th quantization.

You should then determine the magnitude of fixed current oscillation:

where Iiand Ii+1- effective values of two adjacent extrema current; Ii+1- current nominal value of the analyzed current.

Next, you should perform the verification of compliance is calculated by the formula (8) the magnitude of current oscillation their normative values:

where kI- standard value fluctuations in a current.

The violation of the inequalities (6) or (9) is the reason for the formation of the control signal corresponding corrective devices or signal to perform other technical by definition, provided in the applicable international standard [1], it turns out that the flicker is a subjective perceptions of the fluctuations of the light flux of the artificial light sources caused by voltage fluctuations in the power grid, the supply of these sources.

From the same source of information, it follows that the dose of flicker is the measure of susceptibility to the effects of flicker for a set period of time.

Here it is said that time is the perception of flicker is minimum time for the subjective human perception of flicker caused by voltage fluctuations in a certain form.

Here, apparently, it is appropriate to make the amendment concerning the fact that fluctuations of the light flux caused by fluctuations of electric energy, which is characterized not only by voltage, and current.

Dose flicker should be measured by flickermeter. The implementation of this instrument for automated active control of vibrations of voltage and current is extremely difficult. It should go on the search for the analytical determination of the dose of flicker. The situation is complicated by the subjective nature of this measure of quality of electrical energy.

In this case, it makes sense to use the ILO purely individual character. Here, apparently, it is appropriate to use the average of the amplitude-frequency characteristic shown in [2]. This characteristic is duplicated in Fig.1.

In this case, one of the most acceptable formula for determining the dose flicker voltage can be represented as:

where q(f) is the value of the ordinate the amplitude-frequency characteristics of the visual analyzer of the oscillation frequency; Tu- the measuring period doses flickertSU.

Minimum measuring period to determine by the formula (10) short-term dose of flicker under applicable at present to the international standard defined by the time interval in 10 (ten) minutes. The amplitude of oscillations, judging by the above, also measured for the same time interval.

Talk about a dose of flicker can only go in if during this period a number of voltage fluctuations. Only in this case you can judge the frequency of these oscillations and to determine it by the formula

where n is the number of vibrations at which estate and follows from the amplitude-frequency characteristics, is depicted in Fig.1, to define necessary for the formula (10) the ordinate.

The amplitude of the voltage fluctuations according to the recommendations of the current interstate standards is determined for each half period of the harmonic component of the voltage. If the frequency of the main harmonic component of the voltage is equal to 50 (fifty) hersam, half of its period will be 10 (ten) milliseconds; the time interval is equal to 10 (ten) minutes, is 60000 (sixty thousand) of these half-periods.

Considering the above-mentioned formula (10) can be represented in more than acceptable for this case as:

where k is the number of registered during the measurement cycle the magnitude of voltage fluctuationsU.

Next, after determining the numerical values of short-term dose of flicker, you should check its compliance with its regulatory value inequality

where kSU- normative (valid) value of short-term dose flicker voltage.

Violation of this inequality is the reason for the formation of the control signal, Coverity the stability of this indicator of the quality of electric power and to determine long dose flicker. For this purpose it is necessary to continue the procedure described above measurements.

To determine the long-term dose flicker full range of measurements, short-term (ten-minute) dose flicker should be repeated for 11 (eleven) times, that is, the measurement cycle is increased to two hours. Quantitatively long dose flicker voltage is determined by the formula

wheretSUishort - term dose of flicker voltage at the i-th time interval.

Long dose flicker voltage is usually standardized. Verification of compliance with this indicator of the quality of electric power is performed by inequality

where kLUthe maximum value allowed long dose flicker voltage.

The so-determined dose of flicker voltage and its duration.

The current fluctuations also have an impact on the visual analyzer man. In modern power systems, as mentioned above, fluctuations in power may not be repeated fluctuations of stress. So it makes sense to evaluate and dose flicker current.

Dose flickies.

So, the initial formulation dose flicker current is

For the case of short-term dose of flicker current sense be defined like this:

where k is the number of registered during the measurement cycle the magnitude of current fluctuationsI.

Before the described procedure should be set to the standard value of short-term dose flicker current kSI.

Verification of compliance of the actual short-term dose of flicker current its normative value is performed by the inequality

Long dose flicker current is formed of twelve consecutive measurements of transient doses flicker:

wheretSIishort - term dose of flicker current on the i-th time interval.

For long-term dose flicker should also establish normative values, verification of compliance which must be performed according to the inequality

where k

This is the algorithm for active control of the level of fluctuations of voltage and current, which is implemented in modern computing. It should be borne in mind that the amplitude-frequency characteristic of the visual analyzer should be set in advance, at least in the form as shown in Fig.1, and stored in a memory of the respective processor.

Sources of information

1. Norms of quality of electric energy in power supply systems General purpose: GOST 13109-97. - Minsk: the interstate Council for standardization, Metrology and certification, 1998. - 31 S.

2. Zielonko I. C. Indicators of power quality and control in industrial plants. - 2nd ed., revised and enlarged extra - M.: Energoatomizdat, 1986. - 168 C.

Faure is th use of computer equipment, which consists in comparing the actual magnitude of fluctuations and doses flicker voltage and current with the normative values of these quantities, characterized in that the procedure for determining the actual magnitude of fluctuations and doses flicker voltage and current precedes the conversion of the analog values of voltage and current in a discrete, identifying geometric mean values of voltage and current for every half period of their changes, and then reveals the fact that fluctuations in voltage and current, is determined by the amplitude of their oscillations and using the amplitude-frequency characteristics of the visual analyzer of a person are determined by short-term and then long dose flicker voltage and current, while exceeding the actual value of the magnitude of fluctuations and doses flicker voltage and current of the normative values formed a control signal correcting device.



 

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