SU970252A1 - Method of measuring instantaneous values of narrow band signal complex envelopes - Google Patents

Description

The invention relates to a measurement technique and can be used in the construction of devices for measuring complex envelopes that vary in time with narrowband signals, such as voltage harmonics in three phase networks.

There is a method for extracting a narrowband complex envelope by synchronous detection, in this method the output signal carries information about the orthogonal components of complex envelope 1.

However, it is characterized by dynamic errors, which in the first approximation are proportional to the rate of change of the signal envelope.

In order to reduce the dynamic heaters, it is necessary to reduce the time constant of the filters connected to the outputs of the detectors, this leads to an increase in the ripple level of the rectified voltage.

The closest to the proposed technical essence and the problem to be solved is the method of resonatorless determination of the sine (cosine) component of the 2 nm signal spectrum.

The essence of this method is that they measure the averaged over the period of the product of the signal by sin kujt and cos kvM: that determine the real and the minimum of the complex envelope of the k-th harmonic.

This method allows one to accurately determine the complex amplitudes of periodic signals 2.

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However, when measuring signals with time-varying amplitudes, significant dynamic errors appear, which are proportional to the speed of change as measured.

15th harmonic, non-measurable Cth () harmonics.

The purpose of the invention is to reduce the dynamic error in the measurement of the complex envelope of a change in the magnitude of the UCB signal.

The goal is achieved by the fact that, according to the method of measuring the instantaneous values of the complex

25 narrowband signal envelopes, judged by two orthogonal components, formed by averaging the products of the narrowband signal by a sinusoidal.

Claims (2)

30 cosine signal, narrowband signal is pre-multiplied by an auxiliary signal, linearly increasing from zero to one in the first interval equal to the period of the highband signal and linearly decreasing in the second interval equal to the first, and the averaging is performed in the auxiliary signal interval. Fig. 1 shows a block diagram of a device implementing a method for measuring the instantaneous values of the complex envelopes of narrowband signals; figure 2 - timing diagrams of the operation of this device. A device for measuring the instantaneous values of the complex envelope of a narrowband signal comprises modulators 1-3, integrators 4 and 5 of the indication block b, generator 7 of quadrature sinusoidal voltages and generator 8 of linearly varying voltage. Input bus via modulator 1. connected to the inputs of the modulators 2 and 3, the outputs of which. through the integrator 4 and 5 are respectively connected to the display unit 6. The outputs of the generator 7 are connected to the second inputs of modulators 2 and 3, and the output of the module 8 to the second input of the modulator 1. The device works as follows. The narrowband signal U (t) (FIG. 2a is fed to the input of the modulator 1, to another input of which an auxiliary signal H (t) comes from the output of generator 8. The auxiliary signal H (t) varies from 0 to 1 in the interval time (-T, 0) and from 1 to O over the time interval (O, T) (Fig.26 where T is the period of the narrowband signal U (t). From the output of the modulator 1, the product of the signals U (t) H (t) (Fig. 2-6) is fed to modulators 2 and 3, to the second inputs of which the voltages sin (jut, cos (i) t, where O), respectively, come from generator output 1. Output voltages of modulators 2 and 3 averaged inte Taps 4 and 5 on the time interval- (-T, T) whose length is equal to twice the period of the narrowband signal U (t). At the end of this time interval, the integrator output voltages 4 and 5 are fixed by the display unit b, and the measurement result when it is timed to the middle of the interval (-T, t). In this case, if the input signal is equal to the sum of several narrowband signals that are multiples in frequency, the signal harmonics, i.e. iH; | ) si itKwt + VfKU), where Ai (t) is the amplitude, VK is the phase angle of the kth signal harmonic, then the 6th signal harmonics do not affect the measurement result of the kth complex harmonic envelope (). The method allows to significantly reduce the dynamic measurement errors of complex envelopes. In the particular case, with a linear change in the amplitudes of the harmonics, dynamic errors are completely absent. When the amplitudes change nonlinearly, the dynamic error is at least an order of magnitude smaller than that of the prototype, whose errors are determined by the first derivatives of the harmonic envelopes. The use of the proposed method for measuring voltage fluctuations of a three-phase network makes it possible to more accurately assess the quality of electricity in distribution networks. The method of measurement of the instantaneous values of the complex envelope of narrowband signals judged by two orthogonal components, formed by averaging the products of the narrowband signal by sine and cosine signals, characterized in that in order to reduce the dynamic error when measuring the complex envelope of narrowband signal, it is pre-multiplied by an auxiliary signal, linearly increasing from zero to one in the first interval It is equal to the period of the narrowband signal and linearly decreasing in the second interval equal to the first one, and the averaging is performed ta interval of the existence of the auxiliary signal. Sources of information taken into account in the examination 1.Gonorovsky I.S. Radio targets and signals. M., Sov. Radio, 1977, p. 467-469. 2. USSR author's certificate 420943, cl. G 01 R 23/00, 1974. u (t) 0--0- 1 at