RU2673335C2 - Device of the analog sensor of the reactive component of the alternating current - Google Patents

Abstract

FIELD: measuring equipment.SUBSTANCE: device of the analog sensor of the reactive component of the alternating current relates to measuring equipment and can be used as a reactive component of an alternating current for automatic or manual control of the reactive power of the load unit of the power supply system. Signal at the sensor output can be used as feedback for automatic control, it must be proportional to the reactive component of the alternating current, positive for inductive and negative for capacitive nature of the load. Primary sensors are the intermediate current transformer and the voltage transformer of one phase of the network. In the current channel, the voltage proportional to the current downstream of the low-pass and high-pass frequency filters by means of a comparator and a sawtooth voltage generator, is converted into short pulses that are sent to the base of a bipolar transistor controlling optocouplers, connected in parallel, which, in the open state, shunt the feedback loop of the pulse-phase converter made on the operational amplifier, while the feedback circuit is not shunted on a short time interval for measuring the sinus of the phase angle between current and voltage. In the voltage channel, the reference voltage of the sinusoidal shape is formed, which is fed to the input of the phase shifter, from which the voltage is applied to the input of the pulse-phase converter, at the output of which a signal proportional to the sinus of the shear angle between voltage and current in the form of short pulses is obtained, this signal is filtered and fed to the input of a multiplier chip. Second input of this chip is fed with rectified and filtered voltage proportional to the current of the measured network.EFFECT: as a result of multiplication, a voltage proportional to the reactive component of the current is obtained, and the output voltage can be either positive or negative, and no additional amplification of the output voltage is required.1 cl, 12 dwg

Description

The invention relates to devices of measuring equipment and can be used as a sensor for the reactive component of alternating current during automatic or manual control of the reactive power of the load node of the power supply system.

Reactive power in the load node can be inductive or capacitive in nature, while the current accordingly lags or outperforms the phase of the mains voltage. The signal (constant voltage) at the output of the sensor can be used as feedback for automatic control of reactive power compensation, it must be proportional to the reactive component of the alternating current, positive for inductive and negative for capacitive load.

The source of the first analogue (A.M. Bryantsev, V. N. Mozherin. Sensor of active (reactive) current. USSR author's certificate. 949525, 06/19/1980. 3629739 / 24-21 (22) 03.08.83 (46) 15. 10.85. Alma-Ata Energy Institute) describes the developed device, the structural diagram of which is shown in Fig. 1, and time diagrams in fig. 2.

“The device contains a current transformer 1 (Fig. 1), a phase-sensitive converter consisting of a current-limiting resistor 2 and a scaling resistor 3, forming a voltage divider, as well as a measuring capacitor 4, a triac 5 and a storage capacitor 6, a control pulse shaper 7, a switch 8. Number 9 in the diagram indicates the network load.

The primary winding of the current transformer 1 is included in the phase circuit (eg, “C”) of the monitored network. The first of the anode-cathode terminals of the triac 5 through a current-limiting resistor 2 is connected to the first terminal of the secondary winding of the current transformer 1. The output of the driver 7 of the control pulses is connected to the control electrode circuit of the triac 5.

Switch 8 is connected between the phases of the controlled network and the input of the driver 7 of the control pulses.

A scaling resistor 3 and a measuring capacitor 4 are connected in parallel between the first anode-cathode terminals of the triac 5 and the second terminal of the secondary winding of the current transformer 1. A storage capacitor 6 is connected between the second anode-cathode terminal of the triac 5 and the second terminal of the secondary winding of the current transformer 1 and is connected to the output terminals of the sensor by its plates.

If the current transformer 1 is included in the phase “C” circuit, then in position “A” of switch 8, the input of the driver 7 of the control pulses is connected to phase “C” and neutral “0” of the three-phase network, and in position “P” with phases “A” "And" B "three-phase network.

Resistors 2 and 3, capacitors 4 and 6 have parameters that satisfy the following conditions.

The time constant of the network of capacitors 4 and 6 through the resistance of the open triac R _C should be no less than an order of magnitude less than the duration of the control pulse t _{AND of the} driver 7, i.e.

where C ₄ and C _{6 are} capacitances of capacitors 4 and 6.

As a result, the triac 5 closes after the end of the action of the control pulse, since both its anode-cathode outputs will have the same potential, and the current flowing through the triac 5, by the time the end of the action of the control pulse will be zero.

The fulfillment of condition (1) allows you to expand the measurement range of the active (reactive) component of the current in angle ϕ of the phase difference between current and mains voltage from 0 to π without additional switching in the sensor circuit, i.e. ultimately provides increased reliability of the sensor.

The time constant of the charge circuit of the capacitor 4 through the resistor 2 should be no less than an order of magnitude less than the duration of the period T of the mains voltage:

The fulfillment of condition (2) provides the required speed of the sensor.

The active (reactive) current sensor operates as follows.

In the presence of a controlled alternating current I in the primary winding of the current transformer 1, a current proportional to the controlled primary current also flows through the capacitor 4 in the circuit of its secondary winding. In this case, a voltage U is formed on the capacitor 4, which is proportional to the controlled current I, but shifted by its phase by an angle π / 2.

This voltage, taking into account the presence of an angle ϕ of the phase shift between the current I and the voltage of the controlled phase of the network is:

where X _C4 is the resistance of the capacitor 4 at the frequency of the controlled current, I _m is the amplitude value of the controlled current, K ₁ is the transformation coefficient of the current transformer 1.

When measuring the reactive component of the controlled current I, switch 8 is translated into position "P".

In this case, the voltage U _AB, which is reference in this case, is shifted by an angle π / 2 relative to the voltage U _{C, is} supplied to the input of the driver 7 of the control pulses. The control pulses unlock the triac 5 at the time of the passage of the rising curve of the reference voltage U _AB through a zero value.

If the measuring voltage U _{4 is} ahead of the reference U _OP by the angle ϕ, the control pulse unlocks the triac 5 with a delay by the angle ϕ with respect to the moment of the transition of the rising curve of the measuring voltage U ₄ through the zero value. In this case, a voltage U _{6 of} positive polarity is formed on the capacitor 6, equal to

and proportional to the reactive component of the controlled current at an active-inductive load. "

The disadvantages of the first analogue are:

1. The statement that “a voltage U is formed on the capacitor 4, which is proportional to the controlled current I, but shifted in phase by an angle π / 2” when condition (2) is satisfied, it is necessary to take into account the active resistance 2 and the inductive resistance of the secondary the current transformer windings in an equivalent equivalent circuit, so the phase angle will not be π / 2, for example, if R ₂ C ₄ = 0.001 s, which is an order of magnitude less than the period, the phase shift will be Δϕ = -arctgωT = -17.43 ° °, not π / 2.

2. Expression (4) does not take into account the voltage drop when the capacitor 6 is charged at the active resistance 2 connected in series with the capacitors 4 and 6.

3. If voltmeters with different resistances are connected to the output of the device parallel to the capacitor 6, then due to the different capacitor discharge circuit formed, we will get different values of the readings of the devices.

Thus, it is impossible to calibrate this device with a certain accuracy, for example, it is impossible to accurately calculate the magnitude of the reactive current at a given measured output voltage.

At the source of the second analogue (V.V. Tropin, V.A. Kuzmenko, D.S. Mologin, O.S. Panova, Reactively-sensitive reactive power sensor for controlling a static reactive power compensator. Application: 2012100347/07, application: 01.10.2012 patent publication: 07.20.2013. Closed Joint-Stock Company Joint Venture Ansaldo-VEI JSC.) Describes the developed device, the structural diagram of which is shown in Fig. 3.

"The inventive reactive power sensor contains a multiplier 1, multiplying the current signal of a given phase of the network load and the reference voltage, the vector of which is in phase with the vector of this phase of the load; a set of notch filters 2, cascaded to the output of the multiplier 1; a low-pass filter 3, the input of which is connected to the output of the last stage of the notch filters; phase corrector 4 connected to the output of the low-pass filter 3.

A differentiator 5 is connected to the input of the multiplier 1. Differentiator 5 can be made in the form of an operational amplifier DA with negative feedback through a resistor R, to the inverting input of which the input signal passes through capacitor C, and the non-inverting input of which is connected to a common bus (“zero point” )

The technical result is to increase the operational efficiency of the reactive power sensor by measuring not only the reactive component of the load current, but also measuring the derivative of its active component of the current, which is inherently the reactive power of the dynamic load mode, which generally increases the accuracy of compensation (suppression) using STK voltage fluctuations in the mains with on-load tap-changer causing flicker. The technical result is achieved by the fact that the reactive power sensor containing the multiplier of the current signals of this phase of the on-load tap-changer and the reference sinusoidal voltage, cascade notch filters connected to the output of the multiplier, a low-pass filter connected to the output of the last notch filter of the cascade, and a phase corrector connected with the output of the low-pass filter, according to the invention further comprises a differentiator, to the input of which a current signal is connected, and the output is connected to the current input, multiply ator, the reference voltage vector in phase multiplier vector phase of the load voltage. In this case, the differentiator is made in the form of an operational amplifier (DA) with negative feedback through a resistor (R), to the inverting input of which the current signal is supplied through the capacitor (C), and the non-inverting input of which is connected to the common bus (“zero point”).

Phase corrector 4 can be made in the form of a set of series-connected smoothing-forcing links, each of which consists of an operational amplifier, the non-inverting input of which is connected to a common point through a serial RC target, and through the parallel RC target to the output terminal of the operational amplifier, which is the output of the smoothing-forcing link, the input of which is the non-inverting input of the operational amplifier.

Conclusion on the second analogue.

The differentiator at the input leads the total current to a phase shift relative to the voltage by the angle + π / 2, so it is impossible to accurately obtain the magnitude of the reactive component of the current at a given measured output voltage. Obviously, this sensor has limited use, only with a sharply alternating increase or decrease in the total load current to compensate for reactive power.

The source of the third analogue (Benin V.L. and Kizilov V.U. Static measuring transducers of electric power. M. "Energy", 1972.) provides schemes, the principle of operation and analytical conclusions of power converters with a sinusoidal reference voltage, using the properties of trigonometric functions .

, транзистор открыт в течение интервала времени, когда

. Транзистор Т₁ является ключевым элементом амплитудного модулятора, питаемого выпрямленным синусоидальным напряжением

, которое пропорционально току в измеряемой цепи. На рис. 4(б-д) приведены кривые наиболее характерных напряжений и токов в приведенной схеме множительно-делительного устройства при условии, что напряжения u₁ и u₃ синусоидальны и сдвинуты по фазе на угол γ».“In fig. 4a (scanned copy), the transistor T _{1 is} controlled by the difference between the direct current I ₂ and the rectified sinusoidal current

, the transistor is open during the time interval when

. Transistor T ₁ is a key element of an amplitude modulator powered by a rectified sinusoidal voltage

, which is proportional to the current in the measured circuit. In fig. 4 (bd), the curves of the most characteristic voltages and currents in the multiplier-divider circuit shown are shown, provided that the voltages u ₁ and u _{3 are} sinusoidal and phase-shifted by an angle γ ”.

The following is an analytical proof that the average voltage u _H at the resistor r _H (Fig. 4e) is proportional to the active power in the measured circuit.

In fig. 5 (scanned copy) is a schematic diagram of a converter based on a multiplier divider shown in Fig. four.

In the diagram, the primary sensors are a CT current transformer, the load of which is the active resistance r _T , and a VT voltage transformer, from the first secondary winding of which the voltage is rectified by a rectifier V ₂ and filtered by a circuit r ₂ , c ₂ , from the second secondary winding the voltage is supplied to the base of transistors T ₂ , T ₃ to create rectangular pulses in the secondary winding of the TM transformer. The rectangular pulse generator is powered by voltage U ₀ from the voltage regulator CH. A rectangular voltage u _M from the secondary winding of the TM is converted into a sinusoidal reference voltage using a passive low-pass filter L ₁ , L ₂ , C ₁ , which is phase shifted by this filter by approximately 90 °. fine adjustment of the phase shift by 90 ° is carried out by the chain r _ϕ , C _ϕ , L _ϕ .

The disadvantages of the third analogue are: the complexity of the technical implementation of a passive low-pass filter L ₁ , L ₂ , C ₁ , especially in the manufacture of inductors, it is unlikely to obtain a reference sinusoidal voltage using one filter stage.

The analysis shows that the device (Fig. 5) does not have amplitude modulation, nor does it have multiplication and division. By multiplication is meant, if you increase the voltage, for example, twice, the current strength also doubles, and the power increases four times, respectively, the duration and amplitude of the pulses increase twice, and the output voltage quadruples - this is impossible called multiplication, since it is difficult to make proportionality of voltage - pulse duration and current - pulse amplitude. The output signal is low, with additional gain required.

The first and third analogues contain the same principle of measuring the instantaneous value of a trigonometric function that varies according to a sinusoidal law by measuring this value over a short period of time. The smaller the length of time, the more accurate the measurement, however, the average value at the output of the sensor will be small, and an additional voltage amplifier is required.

The reactive component of the alternating current I _P is determined by the formula

where I is the current strength in the network (full current), ϕ is the phase angle between the voltage voltage.

In the claimed invention, it is necessary to measure the sine of the phase angle angle between the current and voltage, therefore, as a prototype, a device using the properties of trigonometric functions is adopted.

In the source of the prototype "V.S. Osipov, I.A. Shaidurov, A.N. Tatarnikov. The device of the analog sensor power factor. Utility Model Patent No. 143538, Application No. 2013159060, Priority 12/30/2013, Registered 06/23/2014 ”The diagrams, principle of operation and analytical conclusions of the device of the analog power factor sensor, where the measurement is performed using the properties of trigonometric functions, are presented.

The block diagram of the device of the analog sensor of the power factor is shown in Fig. 6, a schematic diagram in which the elements are dotted and marked in accordance with the structural diagram is shown in Fig. 7.

In the current channel, the primary sensor is an intermediate current transformer 1, the secondary winding of which is connected to the load resistance. The voltage from this resistance U ₁ , which is proportional to the current, is fed to the input of two series-switched low-pass filters 2, 3 of the second order with zero bias, the output of which is the first harmonic with a constant component U ₂ . The resulting signal is fed to a high-pass filter 4, which passes only the variable component U ₃ . The obtained first harmonic component is supplied simultaneously to two channels. In the first channel, the variable signal U ₄ is phase-shifted by the phase shifting device 5 by (8-10) °, from which it is fed to the input of the comparator 6 to convert the sinusoid into rectangular pulses. In the second channel, the alternating signal U _{3 is} fed to the comparator 7 without phase shift also to obtain rectangular pulses. Positive pulses are emitted from the outputs of both comparators by diodes, which are normalized by AND elements - NOT U ₅ , U ₆ . The pulses from the AND - elements do NOT arrive at the inputs of the exclusive OR 8, at the output of which U ₇ short pulses (8-10) °, which are then inverted to U _{8 by the} AND - NOT 9 element, from which they are sent to the base of the transistor pulse-phase, amplitude transducer 10.

In the voltage channel, the primary sensor is a voltage transformer 11, the alternating voltage from which is converted into rectangular bipolar pulses by the comparator 12. From the comparator, the pulses are fed to the input of the integrator 13, the output of which will be a triangular voltage, which is better and more accurately converted to a reference sinusoidal voltage using two successively connected low-pass filters 14, 15. The resulting sinusoidal voltage is fed to the input of the phase shifter 16, with which you can change phase to be widely variable resistor. Then, the reference voltage is supplied to the input of a precision rectifier 17, from which the voltage in the form of positive half-waves U ₉ is supplied to the collector of a transistor of a pulse-phase, amplitude converter 10. From the output of which pulses are fed to a DC filter and amplifier 18, to the output of which U ₁₀ can measuring device 19 must be connected.

The thus obtained reference voltage in the form of positive half-waves of a sinusoidal shape is used as a trigonometric function from which in the form of short pulses a signal is obtained proportional to the cosine of the angle of shift between voltage and current or power factor.

The rectangular signal from the current measuring channel and the sinusoidal signal from the voltage measuring channel are supplied to the signaling device 20, which gives information about the lag or leading in phase of the current from the voltage. The LED lights when the current lags behind the voltage and does not light when the current is ahead of the voltage.

The purpose of the invention is the device of an analog sensor of the reactive component of alternating current with an analog output voltage proportional to the reactive component of alternating current can be used as a feedback sensor in the automatic control of reactive power compensation by changing the excitation current of synchronous motors, or switching compensating devices. In this case, the sensor must have high speed (time constant 0.04 s.), The error is not more than 3%, the output voltage level is not less than 5.0 V in the nominal operating mode of the power supply system, the ability to calculate the transmission coefficient, the output voltage must be proportional to the reactive component of alternating current, positive for inductive and negative for capacitive nature of the load.

The technical result is achieved by the fact that in the device of the analog sensor of the reactive component of the alternating current, a sawtooth voltage generator and two optocoupler transistors are used to obtain short pulses of stable duration, the pulse-phase converter is made on an operational amplifier, a reference sinusoidal voltage is generated, which is used as a trigonometric function for determining the sine of the phase angle between the current and voltage, a multiplying micro circuit, while this does not require additional signal amplification, which reduces the measurement error.

In the claimed invention, the structural diagram of the device of the analog sensor of the reactive component of the alternating current is shown in Fig. 8, a schematic diagram in which the elements are dotted and indicated in accordance with the structural diagram is shown in Fig. 9.

Circuit Elements:

1 - an intermediate current transformer connected to a load resistor, on which the voltage is proportional to the current of the measured circuit;

2 - low-pass filter in the current channel, second order, with zero bias and with a follower at the output;

4 - high-pass filter, passing without attenuation the frequency of 50.0 Hz. and not passing a constant component of current;

11 - voltage transformer with an output of 6.0 V;

12 - the comparator on the operational amplifier is not inverting;

13 - integrator to obtain a bipolar voltage of a triangular shape;

14, 15 - two series-connected low-pass filters in the voltage channel, second order, with zero bias and with a follower at the output;

18 is a linear filter on an operational amplifier to isolate a constant component;

21 - inverter comparator on an operational amplifier;

22 - sawtooth voltage generator on an operational amplifier;

23 - zero organ (comparator) on the operational amplifier with an offset;

24 - two optocoupler transistors connected in opposite directions, connected simultaneously by one bipolar transistor;

25 - high-pass filter, passing without attenuation the frequency of 50.0 Hz. and not passing a constant component of current;

26 - two phase shifters connected in series for phase shift in the direction of advance and lag;

27 - Pulse-phase Converter on an operational amplifier with adjustable gain;

28 - precision rectifier with a filter, adjustable gain and positive output voltage;

29 - multiplier device (integrated circuit).

In the current channel, the primary sensor is an intermediate current transformer 1, the secondary winding of which is connected to the load resistance. The voltage from this resistance U ₁ , proportional to the current, is fed to the input of a second-order low-pass filter 2 with zero bias. The resulting signal is fed to a high-pass filter 4, which passes only the variable component U ₂ . The obtained first harmonic component is fed to a comparator 21, at the output of which, taking into account the included diode, there will be positive pulses rectangular U ₃ through a half-cycle. These pulses are fed to the base of the transistor of the sawtooth voltage generator 22, the output of which will be sawtooth voltage U ₄ through a half-cycle. The voltage U ₄ is supplied to the input zero of the organ 23, where it is added to the negative bias voltage, the change in the value of which controls the duration of the pulses U ₅ taking into account the diode at the output of the organ zero. The voltage U ₅ is supplied to the base of the bipolar transistor controlling the optocoupler transistors 24 connected in parallel, which shunt in the open state the feedback circuit of the pulse-phase converter 27 made on an operational amplifier, while the feedback circuit is not shunted for a short period of time measuring the sine of the phase angle shear between current and voltage.

The voltage diagrams are shown in Fig. 10 with indication of stresses at test points.

In the voltage channel, the primary sensor is a voltage transformer 11, the alternating voltage from which is converted into rectangular bipolar pulses by the comparator 12. From the comparator, the pulses are fed to the input of the integrator 13, the output of which will be a triangular voltage, which is better and more accurately converted to a reference sinusoidal voltage using two series-connected low-pass filters 14, 15. The voltage from the filters is supplied to the high-pass filter 25 to exclude the DC component. The resulting sinusoidal voltage is supplied to the input of two phase shifters 26 connected in series for phase shift in the direction of advancing and lagging, which is necessary for the commissioning mode. From the output of the phase shifters, a reference alternating voltage is supplied to the input of the pulse-phase converter 27, the output of which will be short pulses U ₆ (Fig. 11) at the time intervals when the feedback is not bypassed, they will be repeated after a period and are proportional to the sine of the phase angle shear between current and voltage. These pulses can be both positive and negative, their average value can be zero in the absence of a phase shift.

The thus obtained reference voltage of a sinusoidal shape is used as a trigonometric function from which in the form of short pulses a signal is obtained proportional to the sine of the angle of shift between voltage and current.

Figure 11 shows the timing diagrams of the impulses for measuring the sine of the phase angle with the stresses at the control points.

From the current channel after the high-pass filter 4, a voltage proportional to the total current is supplied to a precision rectifier 28 with an output voltage filter, which is fed to one input of the multiplying device 29. A voltage after the filter 18 is proportional to the sine of the phase shift angle between the current and voltage to the second input.

At the output of the multiplying device 29 we obtain a voltage proportional to the reactive component of the alternating current.

Thus, for example, with a primary 400/5 current transformer, we obtain a transmission coefficient of 40 A / V. If the phase shift, for example, is 30 °, then at a current of 400.0 A in the primary network, we get 5.0 V at the output of the multiplier, and the reactive component will be 40 × 5 = 200.0 A.

Comparison of the proposed solution not only with the prototype, but also with other technical solutions in the art allowed us to identify signs that do not match the claimed solution, which allows us to conclude that the invention has an inventive step. The invention is industrially applicable, because it can be used as a sensor for reactive power control systems of power supply systems. The inventive device meets the criterion of "novelty."

ADJUSTMENT SCHEME MODE

In commissioning mode, a current of 5 A is passed in the primary circuit of the current transformer, the secondary winding is closed by a variable resistor, with the help of which the voltage on this resistor is set equal to the voltage from the voltage transformer. Then the current transformer is turned off and the voltage from the voltage transformer is fed to the current input, that is, equal voltages to both inputs. The zero-organ bias resistor sets the pulses U ₅ approximately in duration equal to 0.05 of the duration of the period. A leading phase shifter + 90 ° is set by the oscillator resistor on the oscilloscope, then the voltage at the output of the filter 18 is set by the resistor of the amplifier 27, for which the gain is two, equal to U ₇ = 1.0 V. Then, the phase shifter resistor 26 sets the zero phase shift, when this voltage at the output of the filter 18 is zero. The rectifier resistor 28 sets a voltage of 10.0 V at a current of a current transformer of 5.0.A. Then, the multiplier microcircuit is set up, in which the proportionality coefficient is set equal to unity.

Balancing the multiplier chip consists of three stages:

Stage 1. The terminal X is connected to a common wire, the terminal Y is supplied with voltage from the middle terminal of the potentiometer connected by the extreme terminals with plus and minus power. Potentiometer resistance 20-40 kOhm. Thus, we can apply voltage Y from the plus of the supply to the minus to the Y output. We measure the voltage at the output of the microcircuit (leg 2). We adjust the potentiometer connected to terminal X _CM so that the output voltage does not depend on the voltage at input Y.

Stage 2. The terminal Y is connected to a common wire, the terminal X is supplied with voltage from the middle terminal of the same potentiometer, from which the voltage was applied to X at the previous stage. We measure the voltage at the output of the microcircuit (leg 2). We adjust the potentiometer connected to terminal Y _CM so that the output voltage does not depend on the voltage at input X.

Stage 3. Terminals X1 and Y1 are connected to a common wire. We measure the voltage at the output of the microcircuit (leg 2). We adjust the potentiometer connected to the terminal Z _CM so that the output voltage is early zero.

SCHEME ELEMENTS

Phase shifter

The phase shifter (Fig. 12) consists of two series-connected links with amplification factors at any frequencies, with R ₂ = R ₃ equal to 1.0 and transfer functions of the form

Phase Equations

ϕ ₁ (ω) = - 2arctg (ω (R ₅ + R ₄ ) С) ϕ ₂ (ω) = 180-2arctg (ωR ₁ C)

From these equations, setting C = 0.22 μF, we obtain that for

R ₅ = 1.0 kOhm, R ₄ = 0, it will be ϕ ₁ = -7.9 °, and at ϕ ₂ = + 110 ° we will find R ₁ = 10.0 kOhm.

To make a negative phase shift of -130 °, we find R ₄ = 33. kOhm.

As a result, we get a range from -27.9 ° to + 102.1 °.

List of documents cited in the search report

The search was carried out in the search system www.fips.ru in the query areas “Analog sensor for reactive current, power”, “Device for measuring reactive current, power”. "Sensor reactive current component."

In total, more than 12 abstracts were viewed, as well as open press materials and materials on the Internet. Of these, the most suitable topics were analyzed, the following works:

1 A.M. Bryantsev, V.N. Moserin. Active (reactive) current sensor. USSR copyright certificate. 949525, 06/19/1980. 3629739 / 24-21 (22) 03.08.83 (46) 15. 10.85. Alma-Ata Energy Institute

2 V.V. Tropin, V.A. Kuzmenko, D.S. Mologin, O.S. Panova. Suddenly variable load reactive power sensor for controlling a static reactive power compensator. Application: 2012100347/07, application filing: 01/10/2012 Patent publication: 07/20/2013. Closed Joint-Stock Company Joint Venture Ansaldo-VEI JSC.

3. V.L. Benin, V.U. Kizilov Static measuring transducers of electric power. M. "Energy", 1972.

4 V.S. Osipov, I.A. Shaidurov, A.N. Tatarnikov. The device of the analog sensor power factor. Utility Model Patent No. 143538, Application No. 2013159060, priority December 30, 2013, registered June 23, 2014

Analysis of devices in the given sources

In [1], a description is given of an active (reactive) current sensor, the essence of which lies in the fact that at the moments when the sinusoid of the mains voltage passes through zero, short control pulses are applied to the triac, which opens and the storage capacitor is quickly charged with a voltage proportional to the current at a given moment in time , the voltage at which is the output value proportional to the active (reactive) current.

The given sensor does not allow to accurately measure the magnitude of the reactive current. The device, for example, does not take into account the voltage drop across the active resistance connected in series with the capacitor. It is difficult to calibrate this device with a certain accuracy, for example, it is impossible to accurately calculate the magnitude of the reactive current at a given measured output voltage. The output voltage will be different at different values of the load resistance of the sensor due to the discharge of the storage capacitor.

In [2], a reactive power sensor of an abruptly variable load for controlling a static reactive power compensator is described. In the device, the input of the multiplying element is supplied with voltage and current through a differentiator. After the multiplying device, filters of various types are connected in series.

It is obvious that the differentiator leads the total current to a phase shift relative to the voltage by approximately the value of the angle + π / 2, therefore it is impossible to accurately obtain the value of the reactive component of the current at a given measured output voltage. This sensor has limited use, only with a sharply variable load to compensate for reactive power

In [3], an active power sensor is presented with the keywords “time is a medium-power pulse converter”, “a transistor is a key element of an amplitude modulator”, “a multiplier-divider device using the properties of trigonometric functions”, which can only work in circuits with sinusoidal forms of current and voltage. By multiplication is meant, if you increase the voltage, for example, twice, the current strength also doubles, and the power increases four times, respectively, the duration and amplitude of the pulses increase twice, and the output voltage quadruples - this is impossible call multiplication, since it is difficult to make the proportionality of the signals, in addition, the measurement can be performed in only one quadrant.

In [4], an analogue power factor sensor is described. The sensor has a current channel and a voltage channel. A reference sinusoidal voltage is generated in the voltage channel, which, after a precision rectifier, is applied to the collector circuit of the transistor. In the current channel with the help of an exclusive OR, short control pulses are formed in each half-cycle, which are fed to the base of the transistor, thereby allowing the current to pass through the collector for a short period of time. The output voltage in the form of short pulses depends on the phase between the current and the voltage and the magnitude of the reference voltage and is proportional to the power factor. In this case, the properties of trigonometric functions are used.

In the claimed invention, the definition of the reactive component of the alternating current I _P = I sin ϕ is associated with the measurement of the sine of the shear angle between the current and voltage, therefore, the analog power factor sensor is adopted as a prototype, these sensors have similar elements of the device, but also significant differences, since the installation of additional devices and the measurement of the odd function are required, therefore, it should take both positive and negative values.

Claims (1)

The device of the analog sensor of the power factor in the current channel from the load resistor of the current transformer voltage is supplied to two series-connected active low-pass filters of the second order with zero bias to isolate the voltage of the first harmonic proportional to the current that is supplied to the high-pass filter of the first order in the voltage channel from the transformer AC voltage is supplied to the input of the comparator, from which rectangular polarity bipolar pulses are supplied to the integrator, the triangular shape from which is fed to two series-order active low-pass filters of the second order with zero bias to obtain a reference sinusoidal voltage, the output filter is a linear filter on an operational amplifier, characterized in that in the current channel after the high-pass filter, the voltage is applied to one comparator , the positive component from the output of which is supplied to the input of a sawtooth voltage generator, the output voltage of the generator is compared with the bias voltage I’m at the input of the organ’s zero, as a result, at the output of the organ’s zero, short pulses are formed in each period, which open the transistor in the circuit of two optocoupler transistors, the emitter-collector junctions of which are connected counterclockwise, the feedback circuit of the pulse-phase converter made on an operational amplifier, a high-pass filter is installed in the channel of the reference voltage, from which the voltage is supplied to the input of two phase shifters in series, from which e voltage is applied to the input of the pulse-phase converter, from the output of which a voltage proportional to the sine of the angle of shift between the current and voltage is supplied to the DC filter, and then it is fed to one of the inputs of the multiplier chip, in addition, the precision channel is installed in the current channel after the high-pass filter a rectifier with a DC filter, the voltage from which is supplied to the second input of the multiplying microcircuit, at the output of which the voltage is proportional to the reactive component of the alternating current.

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