JP4134728B2 - Instantaneous voltage drop detection circuit and instantaneous voltage drop compensator using this circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a compensation device that detects an instantaneous voltage drop of a system voltage, detects that the voltage drop is equal to or greater than a predetermined value, and performs an instantaneous voltage drop detection and an undervoltage compensation to generate an alarm.
[0002]
[Prior art]
The conventional instantaneous voltage drop detection circuit measures the difference between the reference sine waveform and the system voltage, and detects the occurrence of the voltage drop when the integrated value of the difference exceeds the set value. (For example, refer to Patent Document 1).
[0003]
[Patent Document 1]
JP 2000-55947 A
[Problems to be solved by the invention]
The conventional instantaneous voltage drop detection circuit observes the difference between the reference sine waveform and the system voltage, and detects the occurrence of a voltage drop when the integrated value of the difference exceeds a set value. For this reason, for example, when a voltage drop occurs in the vicinity of the zero cross, the difference between the reference sine waveform and the system voltage waveform is small in spite of a predetermined voltage drop rate. The detection time differs depending on the angle. In addition, when a voltage drop slightly lower than the determination reference voltage occurs, an increase time of integration of the difference is required, and a detection time delay of at least 1/4 cycle occurs. For this reason, in a device that tries to compensate for an undervoltage such as an instantaneous voltage drop compensation device, there is a problem that the compensation start operation is delayed and the operation of the compensated device is hindered.
[0005]
The present invention has been made in order to solve such a problem, and voltage drop detection can be determined instantaneously regardless of the phase at which the voltage drop occurs, the degree of voltage drop, and the system voltage phase angle at which the voltage drop occurs. An object of the present invention is to provide a voltage drop detection circuit and an instantaneous voltage drop compensation device using the same.
[0006]
[Means for Solving the Problems]
The instantaneous voltage drop detection circuit according to the present invention includes a phase advance means for obtaining a cosine voltage signal by advancing the voltage signal of the AC power system by 90 degrees, and the system voltage signal and the cosine voltage signal are simultaneously sampled and quantized. From the ratio of the system voltage signal and the cosine voltage signal and the phase angle specifying means for specifying the phase angle sampled from the sign and the quantized system voltage signal and the cosine voltage signal corresponding to the specified phase angle A gain coefficient setting means for obtaining a gain coefficient of the inverse sine value or inverse cosine value of the phase angle of the selected system voltage signal or cosine voltage signal by selecting one of the basic calculation bases, and a reference voltage value for determination A reference setting means for setting, and the estimated voltage peak value and the reference voltage are obtained by multiplying the selected calculation-system voltage signal or cosine voltage signal by a gain coefficient to obtain an estimated voltage peak value. When the estimated voltage peak value <the reference voltage value by comparison with those which is adapted to output an instantaneous voltage drop detection signal.
[0007]
A voltage compensation unit that is connected between the AC power system and the load and generates a voltage that compensates for an instantaneous voltage drop; a switch provided in parallel with the voltage compensation unit; and a switch control unit that controls opening and closing of the switch; The voltage compensation means is activated and the switch is opened by an instantaneous voltage drop detection signal from the instantaneous voltage drop detection circuit.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a block diagram of an instantaneous voltage drop detection circuit and an instantaneous voltage drop compensation device according to Embodiment 1 of the present invention, FIG. 2 is a waveform diagram for explaining the operation of Embodiment 1 of the present invention, and FIG. It is a figure of the conversion table which shows the gain coefficient to specification of the sampling phase angle of this, and the estimated voltage peak value in an applicable phase angle. An instantaneous voltage drop detection circuit and an instantaneous voltage drop compensation device according to Embodiment 1 of the present invention will be described with reference to FIGS.
In FIG. 1, the voltage of the AC power system 1 to be monitored is converted into a voltage that can be measured by the transformer 2, and the secondary voltage of the transformer 2 is input to the voltage drop detection circuit 10. In the voltage drop detection circuit 10, the secondary voltage of the transformer 2 is input to the phase advance circuit 11 and the synchronization / period detection circuit 12. The phase advance circuit 11 advances the phase of the system voltage signal (Vsin) of the power system 1 by 90 degrees by a differential element to obtain a cosine voltage signal (Vcos).
[0009]
The synchronization / period detection circuit 12 performs period detection and synchronization determination of the system voltage signal (Vsin), and generates a sampling pulse from the sampling timing circuit 13 based on the signal. With the sampling pulse from the sampling timing circuit 13, the sampling circuit 14 A / D converts the system voltage signal (Vsin) and the cosine voltage signal (Vcos), and the system voltage signal (Vsin *) quantized as a sampling value of both. The cosine voltage signal (Vcos *) is obtained at the same time.
[0010]
The simultaneously sampled system voltage signal (Vsin *) and cosine voltage signal (Vcos *) are input to the phase angle specifying circuit 15, and the value of the ratio (Vsin * / Vcos *) of both signals is calculated. This calculated ratio is sent to the phase interval detection circuit 16 and the gain coefficient setting circuit 17 as a phase angle signal (Vph). Here, when calculating (Vsin * / Vcos *), the value of Vcos * becomes “0” when the phase angle is 90 degrees and 270 degrees, and the calculation becomes impossible, so the value is fixed to a finite value larger than the preceding and following phase angle values. By doing so, computation is possible.
[0011]
The phase interval detection circuit 16 specifies the phase angle at which sampling is performed as shown in the conversion table of FIG. 3 from the sign of the phase angle signal (Vph) and the magnitude of the numerical value, and the phase angle is 0 to 45 degrees. Phase interval signals (Vpsw) are generated corresponding to five types of phase intervals of 45 to 135 degrees, 135 to 225 degrees, 225 to 315 degrees, and 315 to 360 degrees. This phase interval signal (Vpsw) is a signal of “1” or “0” depending on the phase angle of the phase angle signal (Vph), and the signal switching circuit 18 that receives this signal has a value of the phase interval signal (Vpsw). When “1” is selected, the cosine voltage signal (Vcos *) is selected, and when the value is “0”, the system voltage signal (Vsin *) is selected and the selected sampling value is sent to the gain amplification circuit 19.
[0012]
Although the value of (Vsin * / Vcos *) is used for specifying the phase angle of the above sampling, it is also possible to use the value of (Vcos * / Vsin *). In this case, the phase interval and the positive / negative sign are different, but a corresponding one may be set from the relation of the trigonometric function.
[0013]
The phase angle signal (Vph) from the phase angle specifying circuit 15 is input to the gain coefficient setting circuit 17, and the gain coefficient (Vpg) is shown in the conversion table of FIG. 3 according to the value (phase angle is specified). Is sent to the gain amplifier 19. The gain amplifier 19 amplifies the selection signal (Vsw = Vsin * or Vcos *) from the signal switching circuit 18 with a gain coefficient (Vpg), and an estimated voltage wave corresponding to the maximum AC voltage of the power system 1 Calculate and output the high value (Vx).
[0014]
The gain coefficient (Vpg) is calculated based on the larger value of the sine wave (Vsin *) and cosine wave (Vcos *) of the system voltage signal according to the phase of the system voltage (Vsin). By calculating the gain, it is avoided that the amplification gain becomes an infinite or very large value.
[0015]
Here, the gain coefficient (Vpg) is a conversion coefficient for back-calculating the maximum value from the sine value or cosine value at a specific phase angle φ of the sine wave or cosine wave, and is (1 / Sinφ) or (1 / Cosφ ) Is calculated from the absolute value. The estimated voltage peak value (Vx) is obtained by calculating and estimating the maximum voltage value when the sine wave or cosine wave becomes the maximum value over time from the phase angle φ at the time of sampling.
Although the conversion tables in FIG. 3 are used for easy understanding, these tables deal with trigonometric functions, and it is possible to perform program calculation processing by the CPU from trigonometric functions.
[0016]
The estimated voltage peak value (Vx) from the gain amplifying circuit 19 is input to the comparison circuit 21, and the comparison circuit 21 estimates the reference set value (Vr) for determining a voltage drop preset in the reference setting circuit 23. Compare the voltage peak value (Vx).
When the reference set value (Vr)> the estimated voltage peak value (Vx), “1” is output to the determination signal (Vy), and when the reference set value (Vr) <the estimated voltage peak value (Vx), the determination is made. “0” is output to the signal (Vy). The judgment signal (Vy) is output at every sampling timing, but the nature of the judgment signal (Vy) varies depending on the value “1” or “0”. , “0” will be described below as a normal voltage signal (Vy0).
[0017]
When the system voltage is normal, the judgment set value (Vr) <estimated voltage peak value (Vx), and the judgment signal (Vy) from the comparison circuit 21 is continuously output as the normal voltage signal (Vy0). When a state of value (Vr)> estimated voltage peak value (Vx) occurs, an instantaneous drop occurrence signal (Vy1) is output at the sampling timing. When the judgment set value (Vr) <estimated voltage peak value (Vx) is restored, the normal voltage signal (Vy0) is output from the sampling timing.
While the system voltage (Vsin) is maintained above the predetermined voltage value, the estimated voltage peak value (Vx) is calculated as the maximum value, and the voltage drop detection signal (Vz) is “0” as normal voltage. "Is output. This is the same as a voltage return signal described later.
[0018]
When the normal voltage signal (Vy0) continues for a predetermined number of samplings (predetermined time) in the voltage drop determination unit 22 to which the determination signal (Vy) is input, “1” is set to the voltage drop detection signal as an instantaneous voltage drop detection. Outputs (Vz1). When the normal voltage signal (Vy0) is input to the determination signal (Vy), the voltage drop detection signal becomes “0”, and this is output as the voltage recovery signal (Vz0). The output determination of the voltage recovery signal (Vz0) is output when the normal voltage signal (Vy0) continues for a predetermined number or more from the low voltage state.
This prevents malfunctions due to spike noise from the system and short glitch pulses generated in the circuit.
[0019]
As described above, in the instantaneous voltage drop detection circuit 10 of the present invention, even when a voltage drop occurs at any phase (sampling phase), by detecting “1” of this voltage drop signal (Vz), The voltage drop can be detected instantaneously from the estimated voltage peak value (Vx) calculation by capturing the voltage fluctuation.
[0020]
Embodiment 2. FIG.
Next, an instantaneous voltage drop compensator using the above instantaneous voltage drop detection circuit will be described. In FIG. 1, 10 to 23 are the same as those in the first embodiment.
The voltage compensation device 30 is provided with a voltage compensation inverter 31 that generates a replenishment voltage from a battery power source or the like when the voltage of the power system 1 drops. The voltage compensation inverter 31 is controlled by an inverter control unit 32. A switch 33 is provided in parallel for bypass conduction when the voltage compensation inverter 31 is unnecessary. The switch 33 is controlled to be opened and closed by a switch control unit 34.
A voltage drop detection signal (Vz) from the voltage drop determination unit 22 and a determination signal (Vy) from the comparison circuit 21 are input to the inverter control unit 32 and the switch control unit 34, respectively.
[0021]
When the voltage of the power system 1 is in the normal range, the comparison circuit 21 is a normal voltage signal (Vy0), the voltage drop detection signal (Vz) from the voltage drop determination unit 22 is a voltage return signal (Vz0), and the switch 33 is closed. Thus, the voltage compensation inverter 31 is not operated, and power is supplied to the load through the switch 33.
When an instantaneous voltage drop occurs in the power system 1, a voltage sag occurrence signal (Vy 1) is output from the comparison circuit 21 to the switch control unit 34 and the inverter control unit 32 in accordance with the sampling timing. This first instantaneous voltage drop signal (Vy1) serves as a start warning signal for the switch 33 and the voltage compensation inverter 31.
[0022]
When the voltage drop generation signal (Vy1) continues for a predetermined number of samplings (predetermined time) or more, the voltage drop detection unit (22) outputs a voltage drop detection signal (Vz1) as an instantaneous voltage drop occurrence and detection. In response to the detection signal (Vz1), the switch 33 is opened, and the voltage compensation inverter 31 activated by the start notice signal compensates for the voltage drop and supplies a stable voltage to the load.
[0023]
When the power system 1 returns to the normal voltage from the voltage drop, the normal voltage signal (Vy0) is output from the comparison circuit 21 to the switch control unit 34 and the inverter control unit 32. The switch control unit 34 closes the switch 33 by this normal voltage signal (Vy0), that is, a return signal, and the voltage drop detection signal (Vz) “0” from the voltage drop determination unit 22 is connected to the bypass circuit of the switch 33. Upon confirmation, the inverter control unit 32 stops the operation of the voltage compensation inverter 31.
[0024]
Further, when the voltage drop occurrence signal (Vy1) from the comparison circuit 21 does not reach the predetermined sampling number in the voltage drop determination unit 22, the voltage drop occurrence signal (Vy1) is connected to the switch control unit 34. This is input to the inverter control unit 32 and becomes a start notice of the switch 33 and the voltage compensation inverter 31. However, the normal voltage signal (Vy0) is input by the voltage restoration of the power system 1 before the voltage decrease detection signal (Vz1) of the voltage decrease determination unit 22 is output. This normal voltage signal (Vy0) again becomes a return signal and the notice is released and the normal voltage is restored.
[0025]
In particular, since the switch 33 is accompanied by a mechanical operation, the response is delayed. In the above instantaneous voltage drop compensator, the voltage can be compensated in response to the instantaneous voltage drop at high speed by preparing for the start of operation with the advance notice of the instantaneous drop generation signal (Vy1) from the comparison circuit 21.
[0026]
Embodiment 3 FIG.
In the first embodiment, the voltage drop signal is transmitted by determining that the voltage value of the system voltage has become a predetermined value or less based on a predetermined reference voltage. Judgment based on the actual system voltage is effective.
Further, the system voltage value usually varies somewhat depending on the distance from the power source and the state of the load. Therefore, instead of using the estimated voltage peak value (Vx) corresponding to the fluctuating system voltage and the reference setting value (Vr) set in advance in the reference setting circuit 23 as a predetermined value, the reference for the instantaneous voltage drop is the voltage. It is easier and understandable to set the rate of decrease (for example,% display).
[0027]
FIG. 4 is a block diagram for explaining the third embodiment. The same reference numerals as those used in the second embodiment are the same. In the figure, the time integration circuit 3 obtains the average voltage value (Vsm) of the system voltage with a relatively long time constant (for example, 10 seconds). The average voltage value (Vsm) is digitally converted by the A / D converter 24 and input to the determination criterion calculation unit 25. The determination criterion calculation unit 25 provides the comparison circuit 21 with a reference setting value (Vr) calculated from the% setting value (for example, 80 to 100%) set by the% reference setting unit 26 and the average voltage value (Vsm). The comparison determination of the estimated voltage peak value (Vx) from the voltage drop detection circuit 10 and the reference set value (Vr) is as described above, and a description thereof is omitted.
[0028]
Next, the calculation contents of the determination criterion calculation unit 25 will be described. The average voltage value (Vsm) of the system voltage from the time integration circuit 3 is a simple average value of the waveform. The peak value of the waveform is calculated by the following equation, and the reference value (Vr) is set by adding the% setting value. .
Standard set value (Vr) = (Vsm) · (π / 2) · (% set value)
[0029]
Since the actual voltage of the power system 1 is obtained by the time integration circuit 3 as a criterion for determining the low voltage, and the allowable voltage drop rate is set as a% value (80 to 100%) from the% reference setting unit 26, the power The output of the instantaneous low voltage detection signal or the instantaneous voltage drop compensator can be operated based on the percentage rate with respect to the actual voltage of the system 1. As described above, determination criteria can be easily set.
[0030]
Embodiment 4 FIG.
FIG. 5 is a block diagram for explaining the fourth embodiment. The same reference numerals as those used in the second embodiment are the same. In the figure, the nominal voltage reference device 4 has a potential corresponding to the nominal voltage (generally effective value voltage) of the power system 1. Then, the potential (Vk) of the nominal voltage reference device 4 is converted in the voltage conversion circuit 5 to the homogeneous level of the average voltage which is the output of the time integration circuit 3. This is to obtain an average value by multiplying the effective value by a coefficient (0.727).
Then, the ratio calculation circuit 6 amplifies the system voltage with the amplifier 7 using the ratio of the calculation result of “nominal reference voltage value / system voltage average value (Vsm)” as an amplification gain, and inputs the signal to the voltage drop detection circuit 10 ( Vs). In formula,
(Vs) = (Vsin) x (0.727Vk) / (Vsm) = K · (Vk) · (Vsin) / (Vsm)
As a result, the system voltage signal normalized with respect to the nominal voltage (Vk) is input to the input signal (Vs) of the voltage drop detection circuit 10.
[0031]
In addition, a nominal voltage value and an allowable voltage drop rate (80 to 100%) are set in the reference setting unit 23, and the multiplication result of both is input to the comparison circuit 21 as a reference setting value (Vr). The subsequent operation is as described in the first embodiment.
[0032]
As described above, since the voltage can be determined by normalizing the system voltage value using the nominal voltage reference device 4, the allowable voltage reduction rate can be set by% setting. In addition, since an A / D converter that imposes a burden on the CPU for setting the reference voltage is not used, it is effective in increasing the speed of instantaneous low voltage detection.
[0033]
In the above description, the estimated voltage peak value is obtained from the voltage obtained at the time of sampling, and the determination reference is also set to a reference voltage value corresponding to the peak value. It is obvious that even if it is a certain effective value and average value, the same effect can be obtained.
[0034]
【The invention's effect】
As described above, the instantaneous voltage drop detection circuit according to the present invention sets the phase angle where the voltage has dropped and calculates and estimates the voltage peak value at that time, regardless of the phase at which the instantaneous voltage drop occurs. Compared with the reference set value, the voltage drop detection signal is output when the estimated voltage peak value <the reference voltage value, so the instantaneous voltage drop can be detected without delay in the instantaneous voltage drop. .
[0035]
In addition, the voltage compensation inverter and the switch control for switching to the voltage compensation inverter are activated by the voltage drop detection signal at the sampling timing from the above instantaneous voltage drop detection circuit to quickly compensate the voltage against the instantaneous voltage drop. Can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an instantaneous voltage drop detection circuit according to a first embodiment of the present invention and an instantaneous voltage drop compensation device according to a second embodiment.
FIG. 2 is a waveform diagram illustrating the operation of the present invention.
FIG. 3 is a conversion table showing the specification of the sampling phase angle and the gain coefficient to the estimated voltage peak value at the corresponding phase angle according to the present invention.
FIG. 4 is a configuration diagram of an instantaneous voltage drop detection circuit and an instantaneous voltage drop compensation device according to Embodiment 3 of the present invention;
FIG. 5 is a configuration diagram of an instantaneous voltage drop detection circuit and an instantaneous voltage drop compensation device according to Embodiment 4 of the present invention;
[Explanation of symbols]
1 Power system 3 Time integration circuit 4 Nominal voltage reference
6 ratio calculation circuit, 7 amplifier, 10 voltage drop detection circuit,
11 phase advance circuit, 12 synchronization / period detection circuit, 14 sampling circuit,
15 phase angle specifying circuit, 16 phase interval detection circuit,
17 gain coefficient setting circuit, 19 gain amplification circuit, 21 comparison circuit,
22 voltage drop determination unit, 23 reference setting circuit, 24 A / D converter,
25 judgment criterion calculation unit, 26% standard setting unit, 30 voltage compensation device,
31 voltage compensation inverter, 32 inverter control unit, 33 switch,
34 Switch control unit.

Claims (8)

  Phase advance means for obtaining the cosine voltage signal by advancing the phase of the system voltage signal of the input AC power system by 90 degrees, sampling means for quantizing and sampling the system voltage signal and the cosine voltage signal at the same time, Phase angle specifying means for specifying the phase angle obtained by sampling from the ratio and sign of the system voltage signal and cosine voltage signal, and the system voltage signal quantized corresponding to the specified phase angle; A signal switching means for selecting one of the basis of calculation after the cosine voltage signal, and a gain coefficient for obtaining a gain coefficient that is an inverse sine value or an inverse cosine value of the phase angle of the selected system voltage signal or cosine voltage signal. Setting means; gain amplifying means for calculating an estimated voltage peak value by multiplying the selected calculation-system voltage signal or cosine voltage signal by the gain coefficient; And a reference setting means for setting a reference voltage value, and an instantaneous voltage drop detection signal is output when the estimated voltage peak value is smaller than the reference voltage value by comparing the estimated voltage peak value with the reference voltage value. The instantaneous voltage drop detection circuit.   2. The instantaneous voltage drop detection circuit according to claim 1, wherein an instantaneous voltage drop detection signal is output when the state of estimated voltage peak value <reference voltage value continues for a predetermined number of samplings or for a predetermined time.   3. The instantaneous voltage drop detection circuit according to claim 1, wherein a return signal is output when the estimated voltage peak value> the reference voltage value is determined after outputting the instantaneous voltage drop detection signal. Time-integrating circuit that obtains the average voltage value for a predetermined time of the AC power system, reference setting means for inputting the reference setting as a voltage drop tolerance, and converting the above average voltage value into a peak value from the coefficient and the voltage drop tolerance 4. An instantaneous voltage drop detection circuit according to claim 1, further comprising a calculation means for setting the reference voltage value. Reference setting means for inputting the reference setting at a voltage drop allowable rate and a nominal voltage value, reference potential applying means for applying a reference potential corresponding to the nominal voltage value, and an average voltage value at a predetermined time of the AC power system The instantaneous voltage drop according to any one of claims 1 to 3, further comprising a time-integrating circuit to be obtained, and conversion means for normalizing a voltage signal of an AC power system from the average voltage value and the reference potential. Detection circuit. An instantaneous voltage drop detection circuit according to any one of claims 1 to 5 , a voltage compensation means connected between the AC power system and a load for generating a voltage to compensate for the instantaneous voltage drop, and in parallel with the voltage compensation means And a switch control means for controlling opening and closing of the switch, and the voltage compensation means is activated by the instantaneous voltage drop detection signal from the instantaneous voltage drop detection circuit and the switch control means is used to Instantaneous voltage drop compensator characterized by starting switch opening.   7. The instantaneous voltage drop compensator according to claim 6, wherein a start warning signal is output to at least switch control at the first sampling timing when the estimated voltage peak value <reference voltage value state occurs in the instantaneous voltage drop detection circuit.   When the voltage compensation means is in operation and the switch is in the open state, or when the instantaneous voltage drop detection circuit becomes the estimated voltage peak value> reference voltage value after the start warning signal is output, a return signal is sent to the voltage compensation means and the switch control means. 8. The instantaneous voltage drop compensator according to claim 6, wherein the instantaneous voltage drop compensator is output.

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