SU737846A1 - Method of determining effective value of non-sinusoidal voltage in switch-type sine voltage converters - Google Patents

Description

The invention relates to the field of electrical measurements in circuits with non-sinusoidal currents and voltages, and can be used to measure or determine the effective value of sinusoidal impulse moduli {ovannye currents and voltages in kyochevye converting devices, as well as in Ka4iecTBe transducers of the effective value of output value. , Research institute. . . . ,,. / /; -;

There is known a method for determining the effective stress S value of abbreviated aggregates under the azov regulation, in sync CTBIJH with approximation (1m of the stan of 1 m

; by -til- -; ; - -;, - ;; . : -: l BECAUSE effective value

; Because of the voltage of the npii to this condition of the approximate formula, the accuracy of the method is limited. The relatively complicated implementation of the measurement method

A large number of empirical coefficients, some of which are functions of the angle of control. In addition, the method is applicable only for a certain effective value, or stressful with phase regulation on the ohmic load. Phase regulation is just one type of pulse modulation. In converter technology, in addition to phase control, many other types of pulse modulation are used, for which this method is not applicable. In addition, the load of converting devices, as a rule, is not ohmic, but active-inductive.

. The closest technical solution to the invention is a method, c. according to which fashion; lyrbvaNyyo nff wives square,

15 are integrated and the square root of 2 is extracted from the obtained result.:. However, such a square is performed. The integration and integration of non-sinusoidal voltage requires the use of computational microscopic parameters, i.e.

carrying out a large number of cumbersome operations, which significantly complicates the known method.

The purpose of the invention is to simplify and

25 also extends the functional capabilities by measuring the power factor when the converter is operating on a resistive load.

This goal is achieved by

30 that with the method according to

 The modulated voltage is squared and integrated, the quadratic operation and integration is performed by applying the basic riapMO HKH, the cosine of the shear angle between the extracted main harmonic OHOHKOft voltage and the input transformer is determined, and the Vine is applied. the result is divided by the effective value of the input voltage, the square root is extracted from the value determined in this way, and the result is the root multiplied by the effect rms values of the input voltage and measured, and in that the measured value of the result.

The modulated voltage at the output of the converter can (written as

(one

) F ()

one

where U (t) is V, sinujt is the input voltage of the converter

0 is the voltage amplitude at the converter input;

ф (t) - unit modulating

function

The effective value of the voltage expressed by the formula (1) is equal to

11 2C,

(tVd

Substituting expression (1)

considering that (t.C.-t) tea

II I, i

  j.

where G. is the value of the input

for example, in relative units. On the other hand, by decomposition of the modulated voltage in the Fourier series, we obtain

e

A -T fUlU cosnujtdt

(four)

 2K h-lult S MUutdt.

Converting expression (4),

We get

- 1 jWF (t) cos p U) t.d-t I

"1C

(five

77t

I U (O (.- f)

..Hp-gf

hch

We introduce the notation: A.P. Reduced coefficient

Fourier series for the nth harmonic with cosine terms or the degree of shift of the nth harmonic;

Yj iJp ,, - the reduced coefficient p Ea Fourier dl. nth garmbyyi with sinusoidal terms or the degree of regulation of the nth harmonic.

737846

accepted designations

ill

t (M w Mi-di

(6)

-Go

taking into account the fact that UW - jj-- sinuut we get:

2-4-.

((.OFU) dt

(-)

Gh It about

Comparing formulas (3) and (7), we arrive at the final expression

 l- It is possible to determine the coefficient СГр as follows.

The effective value of the voltage of the first harmonic in the output (modulated) voltage is equal to

.,:

(9)

The cosine of the angle of displacement between the input voltage and the first harmonic in the modulated voltage is

soy h

But)

Multiplying formula (9) by (10), we get

- Ud-p

(HI)

The drawing shows a block diagram of a device implementing the method.

It consists of a filter 1 which isolates the main harmonic in a modulated voltage, a phase detector 2, a division unit 3, a root extraction unit 4, a multiplying device 5, an indicator 6 of the effective value of the measured voltage, a power factor indicator 7. on active load, key converter 8, load 9 converter.

At the output of filter 1, the voltage of the main harmonic is obtained.

..

 oi

Received Tension

° s.

arrives at the input of the phase detector 2, and the voltage of the network arrives at its second input e. At the output of the phase detector 2, a voltage proportional to U.j cost., Urfp is obtained. The received signal is fed to the input of the 3 division unit, and the network voltage is applied to the second input of the division unit. At the output of the division unit 3, a value proportional to Op is obtained. From the obtained value, the square root in block 4 is extracted. At the output of the multiplier device 5, a signal is obtained that is proportional to U -U- / dV, which is then inserted into the feedback circuit of the converters or you

Claims (2)

Claim 1. A method for determining the effective value of the non-sinusoidal voltage in the key transducers of the sinusoidal voltage, namely, that the measured modulated voltage is squared and integrated, characterized in that, for the sake of simplification, the operation of squaring and integration is performed by extracting the fundamental harmonic, the cosine of the angle is determined shear 'between the selected fundamental harmonic of the voltage and the input voltage of the converter, multiply the magnitude of the cosine angle of the angle of shift by the effective value In addition to the fundamental harmonic, the result obtained is divided by the effective value of the input voltage, the square root is extracted from the determined value in this way, and the result of the square root is multiplied by the effective value of the input voltage and measured. 2. The method according to claim 1, starting with the fact that, in order to measure the power factor during operation of the key converter for active load, measure the value of the square root extraction result by an indicator, the scale of which is calibrated in units of power factor.