JP3044822B2 - Power factor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention detects reactive power in a power system and, when the reactive power becomes delayed reactive power having a magnitude equal to or larger than a predetermined set value, inputs a phase advance capacitor to the power system. The present invention relates to a power factor control device for improving a load power factor by cutting off a phase advance capacitor when the reactive power becomes a leading reactive power equal to or more than a predetermined set value or a delayed reactive power equal to or less than a predetermined setting value.

[0002]

2. Description of the Related Art FIG. 2 shows a block diagram of a conventional power factor control apparatus of this kind. In FIG. 2, reference numeral 1 denotes one phase in a three-phase alternating current (R-phase, S-phase, T-phase) of a power system, and in this case, R
The current flowing in the phase is input via a current transformer CT, the voltage between the other two phases, in this case the S and T phases, is input via a transformer PT, and this current is converted into a reactive power based on the voltage. The output voltage V is converted into a DC voltage proportional to the value of the reactive power.
Reactive power voltage conversion circuit for outputting as _{OU T,} 2 is set phase advance determination levels lagging reactive power that must be put capacitor, determining the level of leading reactive power is required to block the phase advance capacitor that is set Condition setting circuit for setting operating conditions such as delay time and delay time, the reference numeral 3 designates the decision level of turning on / off the phase advance capacitor set by the operating condition setting circuit 2 and the output voltage V _{OUT of the} reactive power voltage conversion circuit 1. An on / off determining circuit for determining whether or not the reactive power of the power system has reached a level at which the phase-advancing capacitor is turned on / off, is used as a starting current of the motor when the motor is used as a load, for example. In order to prevent repetition of turning on and off the phase-advancing capacitor for a short-time load change, the reactive power is set during the delay time set by the operating condition setting circuit 2. A delay time circuit which does not generate an output unless the determination level of the input of the phase-advancing capacitor is continuously exceeded on the delay side; and 5, an on-off control for controlling on / off of the phase-advancing capacitor based on an output of the delay time circuit 4 Reference numeral 6 denotes an output circuit having a relay (not shown) that outputs contact signals C1 to C4 for turning on and off the phase advance capacitor in accordance with the output signal of the on / off control circuit 5.

The power factor control device shown in FIG. 2 uses an output voltage V
_When it is determined that _OUT has exceeded the determination level of the input of the phase advance capacitor, the determination output is output by the delay time circuit 4 for a predetermined time.
(For example, 10 minutes) After the delay, the on / off control circuit 5
Is input to As a result, the on / off control circuit 5 drives the output circuit 6 in a predetermined order to turn on the contact signals C1 to C1.
Output C4 and turn on the phase advance capacitor. When it is determined in the ON / OFF determination circuit 3 that the output voltage V _OUT of the reactive power voltage conversion circuit 1 exceeds the determination level of the cutoff of the phase-advancing capacitor, the output is passed through the delay time circuit 4 for a predetermined time. Thereafter, the on / off control circuit 5 operates, drives the output circuit 6, outputs the off contact signals C1 to C4, and shuts off the phase advance capacitor.

[0004]

As shown in FIG. 2, a current transformer CT is connected to the first and second terminals of the reactive power voltage conversion circuit 1.
Are connected to the secondary terminal k and the terminal l of the transformer PT, and the secondary terminal u and the terminal v of the transformer PT are connected to the third and fourth terminals of the reactive power voltage conversion circuit 1, respectively. The vector relationship between the current I _R flowing in the AC R phase and the phase voltages V _ST of the S phase and the T phase is represented by a solid line shown in FIG. In FIG. 3, I _R1 indicates a current at a power factor of 100%.

In this case, the principle of detecting the reactive power is expressed as follows using the principle of a single-phase wattmeter. That is, when the reactive power at a lagging power factor and q _1, the reactive power q ₁
Is given by the following equation (1).

[0006]

(Equation 1)

[0007] The power factor angle in the three-phase alternating current is theta ₁ since the angle with respect to the phase voltage V _R. Therefore, the detected delayed reactive power Q ₁ is converted into a three-phase value and becomes the following equation (2).

[0008]

(Equation 2)

Similarly to the above-mentioned delayed reactive power, the leading reactive power Q ₂ at the time of the leading power factor is also detected by the following equation (3).

[0010]

(Equation 3)

Accordingly, the output voltage V _OUT of the reactive power voltage conversion circuit 1 is a DC voltage proportional to the value of the reactive power represented by the above-mentioned equations (2) and (3), and has a characteristic shown by a solid line in FIG. Becomes Now, in FIG. 2, the terminals u and v on the secondary side of the transformer PT and the terminals 3 and 4 of the
When the connection with the No. 1 terminal becomes the reverse polarity as shown by the dotted line, the voltage V _ST as shown by the dotted line in FIG. At this time, since the reactive powers Q ₁ and Q ₂ have a relationship between the voltage V _ST and the R-phase current I _R1 or I _R2 , the delayed reactive power Q ₁ is represented by the following equation (4).

[0012]

(Equation 4)

The leading reactive power Q ₂ is given by the following equation (5).

[0014]

(Equation 5)

That is, the terminals u and u on the secondary side of the transformer PT
When the connection between v and the third and fourth terminals of the reactive power voltage conversion circuit 1 has the opposite polarity, the delay / advance is determined based on whether the polarity of the output voltage V _OUT of the reactive power voltage conversion circuit 1 is positive or negative. Are the opposite. In this case, the characteristic of the output voltage V _OUT of the reactive power voltage conversion circuit 1 is as shown by a dotted line in FIG. The same applies to the case where the connections between the secondary terminals k and l of the current transformer CT and the first and second terminals of the reactive power voltage conversion circuit 1 are reversed.

As described above, in the conventional apparatus shown in FIG. 2, when the secondary terminal of either the current transformer CT or the transformer PT and the wiring of the reactive power voltage conversion circuit 1 are erroneously connected to opposite polarities. Thus, the detection of the lag / lead reactive power is reversed. Such erroneous wiring is often overlooked at the facility, and if power is received with the phase sequence reversed, the erroneous connection will not be recognized until the power factor control device actually enters the operating state and drives the load. There is a disadvantage that there is no. In addition, there is a drawback that a power outage must be made once for rewiring of erroneous wiring.

Therefore, a first object of the present invention is to eliminate the above-mentioned disadvantages of the conventional device and to easily detect an erroneous wiring in which the input polarity of the current or voltage to the reactive power voltage conversion circuit is reversed. Another object of the present invention is to provide a power factor control device capable of notifying the erroneous wiring. Further, a second object of the present invention is to provide a power factor capable of performing a stable operation without requiring a wiring change even in the case of erroneous wiring in which the input polarity of a current or a voltage to a reactive power voltage conversion circuit is reversed. It is to provide a control device.

[0018]

In order to achieve the above-mentioned first object, a first invention of the present invention detects a reactive power of a power system and, based on a result of the detection, inputs a phase advance capacitor or In a power factor control device for shutting down and improving the power factor of the power system, a reactive power voltage conversion for detecting a reactive power from a transformed output of a current and a voltage of the power system and converting the reactive power to a voltage proportional to the reactive power. Circuit and this reactive power
An output judging circuit advances determines that the phase of the code or entered in the reactive power voltage conversion circuit than the magnitude current or voltage of the output voltage of the pressure transducer circuit is phase lead, advances the output decision signal of the proceeds output decision circuit And an erroneous input determination alarm circuit that outputs an alarm for erroneous wiring based on a logical product condition that all output signals for turning on and off the phase advance capacitor are output signals for shutting off, and the reactive power voltage Strange
If either the current input or the voltage input to the
In this case, an alarm is notified from the erroneous input determination alarm circuit .

Further, in order to achieve the above-mentioned second object, a second invention of the present invention detects reactive power of a power system, and turns on or off a phase-advancing capacitor based on the detection result. In a power factor control device for improving a power factor of a power system, an output voltage of a reactive power voltage conversion circuit that detects a reactive power from a transformed output of a current and a voltage of the power system and converts the reactive power into a voltage proportional to the reactive power. A leading output determination circuit that determines that the phase of the current or voltage input to the reactive power voltage conversion circuit is a leading phase based on the sign or magnitude of the leading output determination circuit; a leading output determination signal of the leading output determination circuit; An erroneous input determination alarm circuit that outputs an erroneous wiring alarm based on a logical AND condition that all of the input and output signals for disconnection are output signals for interruption and the output of the erroneous input determination alarm circuit Characterized by comprising a phase inversion instruction circuit for inverting the polarity of the current or voltage of the power system by operating the switching means based on.

[0020]

When a current or a voltage is input to the reactive power voltage conversion circuit with the opposite polarity, the reactive power voltage conversion circuit leads the reactive power as a leading power factor even though the load power factor of the power system is a lagging power factor. Outputs an output voltage proportional to. Based on the output voltage, the advance output determination circuit determines the advance power factor, and supplies the reverse input determination signal to the erroneous input determination alarm circuit. In the erroneous input judgment alarm circuit, the reverse polarity input judgment signal from the advance output judgment circuit and the output signal for turning on / off the phase advance capacitor are all output signals for shutting off, that is, the phase advance capacitor is turned on. When it is detected that the power factor is not at the leading power factor, it is determined that there is a reverse polarity input and an alarm is issued. By operating the switching means of the phase inversion instruction circuit based on this alarm, the polarity of the current input or voltage input of the power system is inverted, and the advance output determination circuit is reset.

[0021]

FIG. 1 is a block diagram of a power factor control device showing one embodiment of the present invention. 1 that are the same as or correspond to those shown in FIG. 2 are denoted by the same reference numerals. FIG.
2 is different from the conventional device of FIG. 2 in a lead output determination circuit 7, an erroneous input determination alarm circuit 8, and a phase inversion instruction circuit 9. Proceeds output determining circuit 7 determines whether or not the leading reactive power based on the output voltage V _OUT of the reactive power voltage conversion circuit 1, the reverse polarity input determination signal when the leading reactive power S ₂
Is supplied to one input of an AND circuit 83 of the erroneous input determination alarm circuit 8. The erroneous input determination alarm circuit 8 outputs signals a1 to a4 which are high when the contact signals C1 to C4 from the output circuit 6 are closing signals and are low when the contact signals C1 to C4 are shutoff signals, respectively. And a high-level signal S ₁ output from the AND circuit 82 when the contact signals of the output circuit 6 are all cut-off signals. issuing an alarm from the alarm circuit 81 conducts the aND circuit 83 by said opposite polarity input determination signal S ₂ and. The phase inversion circuit 9 has a changeover switch 91. By operating the changeover switch 91 to close it, the polarity of the output voltage _VOUT of the reactive power voltage conversion circuit 1 input to the make / break decision circuit 3 is inverted. outputs the reset signal S ₄ to the output judging circuit 7 proceeds to output an instruction signal S ₃ to determine Te.

In the power factor control apparatus shown in FIG. 1, terminals u and v on the secondary side of transformer PT and reactive power voltage conversion circuit 1
If the connection to terminals Nos. 3 and 4 is incorrectly wired as shown by the dotted lines, the output voltage V _OUT of the reactive power voltage conversion circuit 1 will be as shown in FIG. 4
, The voltage becomes negative as shown by the dotted line. The reactive power voltage conversion circuit 1 of the output voltage V _OUT is advanced to be the negative voltage output determining circuit 7 proceeds to output a reverse polarity input determination signal S ₂ determines as reactive power. When power is supplied to the load of the power system, that is, when the power factor control device shown in FIG.
C4 is a signal a1~a4 input from the output circuit 6 to the AND circuit 82 becomes all low level by that all-off signal, the AND circuit 82 is high level signal S ₁ is an AND circuit
83 is applied to one input. The other of the AND circuit 83 by the reverse polarity input judging circuit S ₂ is inputted from the output judging circuit 7 proceeds to the input of the AND circuit 83 operates the alarm circuit 81 conductive. The alarm circuit 81 notifies that the connection is made in the opposite polarity by a buzzer sound or a light emission display by a light emitting element such as an LED.

The output to the phase inversion when closed by operating the changeover switch 91 of the instructing circuit 9 a phase inversion command circuit 9 is turned-cutoff discrimination circuit 3 is a signal S ₃ operates on the basis of the notification output of the alarm circuit 81 I do. The turned-cutoff discrimination circuit 3 operates to input and inverted by an inverting circuit output voltage V _OUT of the reactive power voltage conversion circuit 1 when the signal S ₃ is inputted, is thereby connected to the opposite polarity Polarity returns to normal. The phase inversion instructing circuit 9 outputs the signal S ₃ and simultaneously outputs the reset signal S ₄ to the output determination circuit 7 to reset the advance output determination circuit 7.

In the above description, the case where the terminals u and v on the secondary side of the transformer PT input to the reactive power voltage conversion circuit 1 are erroneously wired, but the terminals k and l on the secondary side of the current transformer CT are described.
Is incorrectly wired, and the current input to the reactive power voltage conversion circuit 1 has the opposite polarity. Note that when both the current transformer CT and the transformer PT have opposite polarities, the phase relation is correctly connected as is apparent from the vector relations of I _R1 , I _R2 , and V _ST indicated by dotted lines in FIG. And it operates normally.

[0025]

As described above, according to the present invention,
Since the power factor of the power system when the phase-advancing capacitor is not turned on is generally a lagging power factor, an advanced output determination circuit for detecting advanced reactive power based on the output voltage of the reactive power voltage conversion circuit; An erroneous input judgment alarm circuit that issues an alarm when the reverse polarity input judgment signal is input from the advance output judgment circuit even though the output signals for turning on and off the phase capacitor are all output signals for shutting off Is provided, it is possible to report an erroneous wiring in which the current or voltage input to the reactive power voltage conversion circuit has the opposite polarity. Also,
By providing a phase inversion instruction circuit for inverting the polarity of the current or voltage of the power system by operating the switching means based on the notification from the erroneous input determination alarm circuit, the energized state is stopped and the erroneous wiring is connected. There is an effect that it is possible to obtain a power factor control device that does not need to be replaced and performs a stable operation in the energized state.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power factor control device showing one embodiment of the present invention.

FIG. 2 is a block diagram of a power factor control device showing a conventional example.

FIG. 3 is a vector diagram of current / voltage input for explaining the operation of the power factor control device.

FIG. 4 is a diagram illustrating a reactive power voltage conversion characteristic for explaining the operation of the power factor control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reactive power voltage conversion circuit 2 Operating condition setting circuit 3 Closing / shutdown determination circuit 4 Delay time circuit 5 On / off control circuit 6 Output circuit 7 Advance output determination circuit 8 False input determination alarm circuit 9 Phase inversion instruction circuit 91 Changeover switch CT Current flow Vessel PT transformer

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-55621 (JP, A) JP-A-1-136527 (JP, A) JP-A-1-286727 (JP, A) JP-A-2- 17827 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G05F 1/70

Claims (3)

(57) [Claims] 1. A power factor control device for detecting reactive power of a power system and for turning on or off a phase-advancing capacitor based on the detection result to improve a power factor of the power system. A reactive power voltage conversion circuit that detects reactive power from a transformed output with a voltage and converts the reactive power into a voltage proportional to the reactive power, and the reactive power voltage conversion circuit based on the sign or magnitude of the output voltage of the reactive power voltage conversion circuit. A leading output determining circuit for determining that the phase of the input current or voltage is the leading phase; a leading output determining signal of the leading output determining circuit and an output signal for turning on / off the phase-advancing capacitor are all used for blocking. An erroneous input judgment alarm circuit that outputs an alarm of erroneous wiring based on the AND condition of the output signal
And a current input and power supply to the reactive power / voltage conversion circuit.
If any of the pressure inputs have reverse polarity, the erroneous input judgment alarm
A power factor control device that issues a warning from a circuit . 2. A power factor control device for detecting a reactive power of a power system and for turning on or off a phase-advancing capacitor based on the detection result to improve a power factor of the power system. The phase of the current or voltage input to the reactive power voltage conversion circuit is determined based on the sign or magnitude of the output voltage of the reactive power voltage conversion circuit that detects the reactive power from the transformed output with the voltage and converts the reactive power into a voltage proportional to the reactive power. A leading output determination circuit for determining that the phase is a leading phase, and a logical product of a leading output determination signal of the leading output determination circuit and an output signal for turning on / off the phase advance capacitor being all an output signal for blocking. An erroneous input determination alarm circuit that outputs an alarm of erroneous wiring based on a condition, and a polarity of current or voltage of a power system by operating a switching unit based on an output of the erroneous input determination alarm circuit. Power factor control apparatus characterized by comprising a phase inversion instruction circuit for inverting. 3. The power factor control device according to claim 2,
A power factor control device, wherein the phase inversion instruction circuit outputs an instruction signal for inverting the sign of the output voltage of the reactive power voltage conversion circuit.