SU1638652A1 - Devise for measuring active power of sine currents - Google Patents

Abstract

The invention relates to a measurement technique, in particular, to devices for measuring the active power of alternating current. The purpose of the invention is improving the speed of the device for measuring active power. To achieve this goal, a phase link 6, an inverter 7, and an adder 4 are introduced into the device. The newly introduced blocks compensate for phase shifts, which causes the output signal to follow the change in electrical power almost without delay. The device also contains a current sensor 1 and voltage 2, a multiplier 3, and a high pass filter 5. 1 il.

Description

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p uL UIcos f-UlCOS ()

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The invention relates to a measurement technique and can be used in the development of high-speed measuring transducers of active power to a constant voltage.

The aim of the invention is to increase the speed of a device for measuring active power.

The drawing shows a diagram of the proposed device.

A device for measuring the active power of a sinusoidal current contains current and voltage sensors 1 and 2, the outputs connected to the inputs of multiplier 3, the output of which is connected to the first input of the adder 4 directly, and to the second input of the adder 4 through a series-connected high-pass filter 5, phase link 6 and inverter 7.

The device works as follows.

The signals of sensors 1 and 2, proportional to the instantaneous values of current i and voltage, and in the controlled circuit are fed to the inputs of the multiplier 3, at the output of which a signal is formed proportional to the instantaneous value of power p U i. For sinusoidal voltages and currents, the ratio is known

P UIcos Cf- UIcos (2tot cr), (1)

where U, I are the effective values of voltage and current; (p - phase shift between current

and voltage;

0} - angular frequency of the network; t - time

From relation (1) it follows that the active power in the controlled circuit (Pq UIcosCj) is equal to the sum of the instantaneous power and its harmonic component:

Pq p + UIcos (). (2

The selection of the harmonic component of the instantaneous power is carried out by the high-pass filter 5. The output signal of the high-pass filter 5 —UIcos (2 (Ot-Cp +) is phase-shifted relative to the harmonics

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five

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The instantaneous power -UIcos (2 (0t 4f)) magnitude (Jq. The signal from the output of filter 5 enters the phase link 6, which provides a phase shift of the signal by an amount equal in magnitude and opposite in sign to the phase shift of the signal in the filter 5. At the frequency of the harmonic component of the instantaneous power. At the output of the phase link 6, a signal is generated that is proportional to the harmonic component -UIcos (2 (0 t - (f) instantaneous power. This signal is inverted by an inverter 7, the output of which is the UIcos signal (2COt - (J). In adder 4, the signal is summed proportional to the instantaneous power p and its harmonic component UIcos (263t-CO, and, according to expression (2), a signal is continuously generated at the output of the adder that is proportional to the active power in the controlled circuit.

Thus, in comparison with the known delayed devices for measuring active power, in which information is updated periodically, the proposed device has a higher speed, there is practically no delay, and a continuous signal is generated at the output that is proportional to the active power in the monitored circuit.

Claims (1)

Invention Formula A device for measuring the active power of a sinusoidal current, containing current and voltage sensors connected by outputs to corresponding multiplier inputs, output connected to an input of a high-pass filter, characterized in that, in order to improve speed, a phase link, an inverter and an adder are entered into it, the first input of the adder is connected to the output of the multiplier, and the output of the high-pass filter is connected via a series-connected phase link and the inverter is connected to the second input of the adder.