JPH03277140A - Device for compensating momentary voltage drop - Google Patents

Abstract

PURPOSE:To improve accuracy of compensation by a simple constitution by detecting change of a level in the output signal of a subtracter by means of the hysteresis characteristic of a comparator circuit and driving an inverter device so that the output signal of the subtracter is converged to a predetermined permissible range. CONSTITUTION:In a comparator circuit 20, the result of comparison is inverted from a positive direction compensation commanding low level to a negative direction compensation commanding high level, when the output signal of a subtracter 19 is increased to reach a positive side threshold value P, and from the high level to the low level, when the output signal of the subtracter 19 is decreased to reach a negative side threshold value N, by comparing action of the hysteresis characteristic based on the positive and negative side threshold values P, N preset in accordance with a permissible fluctuation range of load voltage. The output signal of the comparator circuit 20 is supplied to an inverter driving circuit 13 as a drive control signal having PWM waveform in accordance with the result of comparison.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a series compensation type instantaneous voltage drop compensator using an inverter device.

[Conventional technology]

Conventionally, this type of series compensation type instantaneous voltage drop compensator is configured as shown in Fig. 3 in the case of a single-phase configuration.
) voltage (hereinafter referred to as power supply voltage) is normal, the control device (2
The AC switch circuit (A) is connected to the feed line switching circuit (3)
4) anti-parallel connected thyristors (4p).

(4n) is triggered to fire.

This ignition trigger turns on the AC switch circuit (4) and closes the connection between the AC power source (1) and the load (5).
AC power (1) is supplied to a load (5) via an AC switch circuit (4).

Further, the AC power source (1) is rectified by a charging circuit (6), and the DC output of this charging circuit (6) charges an energy storage capacitor (7).

Furthermore, the secondary side detection signal VS proportional to the power supply voltage of the input side voltage detection transformer (8) is transmitted to the voltage drop detection circuit (9) of the control device (2A), the synchronous circuit Q□, the compensation amount determination circuit 01) is supplied to

The voltage drop detection circuit (9) repeats the integration of 1/4 cycle of the absolute value of the detection signal Vs in synchronization with the power supply voltage, for example, and compares the integrated value with a reference value, The occurrence of an instantaneous voltage drop of, for example, 10% or more is monitored and quickly detected.

Further, the synchronization circuit aO forms a synchronization pulse at the zero-crossing timing of the power supply voltage, for example, and supplies this pulse to the reference sine wave generation circuit (2).

This generation circuit 02 forms a reference sine wave signal Vsin of rated amplitude (reference amplitude) synchronized with the power supply voltage, and supplies this sine wave signal Vsin to the compensation amount determining circuit 01).

When the power supply voltage is normal, the voltage drop detection circuit (9)
No detection signal is output from the power supply path switching circuit (3) to the power supply path switching circuit (3), and the power feeding path switching circuit (3) turns on the AC switch circuit (4) as described above.

Next, when an instantaneous voltage drop occurs, the thyristors (4p) and (4n) are forced or naturally commutated by switching the feed path switching circuit (3) based on the detection signal of the voltage drop detection circuit (9). At the same time as the AC switch circuit (4) is turned off, the compensation amount determining circuit a°C and the inverter drive circuit operate.

At this time, the compensation amount determining circuit αD forms a signal of the difference (Vs − Vain) between the detection signal Vs and the reference sine wave signal Vsin in real time as a compensation amount signal, and this signal is input to the comparator circuit 0 for generating the pulse. supply to.

This comparator circuit 04) pulse-width modulates a triangular wave or sawtooth wave signal of a constant period and constant amplitude from the reference wave generating circuit with the output signal of the compensation amount determination circuit Ql), and generates a signal P corresponding to the compensation amount.
A WM waveform drive control signal is formed.

This drive control signal is converted into a drive signal for the inverter device 0G by the inverter drive circuit α3, and a semiconductor switching element (16a) such as a thyristor forms the power stage of the inverter device 00 based on this drive signal.

..., (16d) switches at high speed, and the inverter OQ converts the energy stored in the capacitor (7) into alternating current of the compensation amount.

This alternating current is generated as a compensation output between the output terminals Lx) and fy1 of the inverter device α0, and this output terminal (x)
, (y) is injected into the primary side (17a) of the injection transformer Q7).

The secondary side (17b) of the injection transformer α power is provided in parallel with the AC switch circuit (4), and the secondary side (17b)
forms the load supply path when an instantaneous voltage drop occurs, so
The AC power source (1) and the compensation output are combined in series and supplied to a load (5).

At this time, the drop in power supply voltage is compensated for by the compensation output, and the load voltage is compensated in series by the output of the inverter device 06.

[Problem to be solved by the invention]

In the case of the conventional compensation device, when an instantaneous voltage drop occurs, the compensation output of the inverter device OG is controlled to a magnitude corresponding to the amount of drop in the power supply voltage based on the signal (Vs-Vsin).

On the other hand, the load voltage actually decreases from the series composite voltage of the AC power source (1) and the compensation output due to a voltage drop based on the impedance of the injection transformer α force (hereinafter referred to as impedance drop).

Moreover, since the impedance force of the injection transformer 07) varies depending on the magnitude of the load current, etc., the amount of decrease in the load voltage varies depending on the state of the load (5), etc.

Therefore, even if the compensation output of the inverter aQ is formed to a size that accurately corresponds to the amount of drop in the power supply voltage, the load voltage will not be compensated to the rated voltage and will fluctuate, causing a problem in which highly accurate compensation cannot be performed. There is.

In addition, in order to drive the inverter device Q~ by PWM control, a complicated reference wave generation circuit α9 that generates a triangular wave or a silver wave is required separately from the reference sine wave generation circuit 03, and a complicated reference wave generation circuit α9 that generates a triangular wave or a silver wave is required. There are also features that require a control device (2A).

SUMMARY OF THE INVENTION An object of the present invention is to provide an instantaneous voltage drop compensator that performs PWM control on the drive of an inverter device with a simpler configuration than the conventional one, and that series compensates the load voltage with high precision while taking into account the impedance drop of the injection transformer. .

[Failure to solve the problem]

In order to achieve the object #J, in the instantaneous voltage drop compensator of the present invention, as shown in FIG. a reference sine wave generation circuit @ which outputs the voltage, a voltage detection transformer α8 which detects the load voltage, and a subtracter (which outputs a signal of the difference between the output signal Vz of the voltage detection transformer α~ and the reference sine wave signal Vsin); 19, when an instantaneous voltage drop is detected, the inverter device 0Q detects an increase or drastic change in the output signal of the subtracter q9 using hysteresis characteristics, and controls the inverter device 0Q so that the output signal of the subtracter I converges within a predetermined tolerance range. and a comparator circuit ω that generates a PWM waveform drive control signal for driving.

[Effect]

In the case of the compensator of the present invention configured as in #J, the output signal Vg changes in accordance with the load voltage reduced due to the impedance drop of the injection transformer α power.

Based on the (Vl-Vsin) output signal of the subtracter 09, when an instantaneous voltage drop occurs in the AC power supply (1), the inverter OQ adjusts the actual drop in the load voltage by the drive control signal of the comparator circuit. Generates a corresponding compensated output.

At this time, the compensation output becomes large enough to compensate for the sum of the power supply voltage drop and the impedance drop, and by series combination of the AC power supply (1) and the compensation output, the load voltage becomes the impedance of the injection transformer α force. It is compensated to approach the rated voltage with high precision without being affected by voltage drop.

By comparing the hysteresis characteristics of the comparison circuit (a) based on the subtracter-like output signal, it is possible to generate PWM waveforms without providing a special signal generation circuit for creating PWM pulses like a conventional reference wave generation circuit. A drive control signal is formed.

〔Example〕

One embodiment will be described with reference to FIGS. 1 and 2.

Fig. 1 differs from Fig. 3 in that it includes a voltage detection transformer on the output side that detects the load voltage, and a control device (2B) instead of the control device (2A) in Fig. 3. It is.

This control device (2B) is the compensation amount determining circuit 01 in Fig. 3).
and a comparison circuit for generating PWM parnu, and a subtracter α9.instead of the reference wave generation circuit a9. It is formed by providing a comparison circuit that operates with hysteresis characteristics.

Then, the secondary side output signal vl of the voltage detection transformer (to)
varies depending on the load voltage itself across the load (5), and is supplied to the subtractor q9.

This subtracter east is the reference sine wave generator circuit 0 from the output signal Vg.
3 reference sine wave signal Vsin is subtracted, (Vl-Vsi
A signal of n), that is, an AC waveform signal corresponding to the actual variation of the load voltage from the rated voltage is formed and supplied to the head of the comparison circuit.

Furthermore, the comparator circuit (A) has a positive threshold value P set in advance according to the allowable fluctuation range of the load voltage, and a negative threshold value MN.
(1Pl=lNl) When the output signal of the subtracter 09 increases and reaches the positive threshold P, the comparison result is changed from the low level for the positive direction compensation command to the negative direction. When the subtracter-like output signal decreases and reaches the negative threshold N, the comparison result is inverted from the high level to the low level tb K .

Then, the output signal of the comparison circuit 0 changes in binary level according to the comparison result, and this output signal is sent to the inverter drive circuit 03 as a drive control signal with a PWM waveform similar to the output signal of the comparison circuit 0 in FIG. Supplied.

Therefore, when an instantaneous voltage drop occurs in the AC power supply (1), the inverter drive circuit 03 is controlled by the power supply path switching circuit (3) based on the detection signal of the voltage drop detection circuit (9).
supplies a drive signal based on the drive control signal of the comparator circuit (2) to the inverter device α0 to drive it.

At this time, if the comparison result of the comparison circuit ■ is at a high level, the semiconductor switching elements (16b) and (160) are turned on, and the semiconductor switching elements (16a) and (16d) are turned on.
is controlled to be off, and if the comparison result is at a low level, the semiconductor switching elements (16a) and (LED) are controlled to be on, and the semiconductor switching elements (16b) and (16c) are controlled to be off.

And semiconductor switching elements (16a), (16d
), (16b), and (16c), the inverter device αQ is controlled so that the output signal of the subtracter 09 converges between the threshold values P and N, thereby forming a compensation output.

Then, the output signal of the subtracter 09 is an increase in the compensation output.

Since the compensation output changes in accordance with the change in the actual load voltage based on the change in the load voltage, the compensation output changes according to the broken lines +Δ■, - in the figure corresponding to the threshold values P and N, as shown by the solid line in Figure 2 fa). Δ
(2) It is varied so as to converge within the range of (2).

In addition, the dashed-dotted line in FIG. 2 fa) shows the characteristics at the rated load voltage.

Further, FIG. 2(b) shows the pressure of the comparator circuit (a) corresponding to the compensation output of fa) in the same figure.

Then, due to the compensated output including the impedance drop of the injection transformer α power, the load voltage becomes the above-mentioned broken line +Δ■.

The voltage is series compensated within the range of -ΔV, and the magnitude and waveform of the rated voltage are stably maintained.

Note that the compensation accuracy improves as the threshold values P and N are brought closer within a range in which the inverter device Q7) operates stably.

This allows for more accurate compensation than before with a simple configuration.

By the way, transistors or GTOs may be used as the semiconductor switching elements (16a) to (16d) in the output stage of the inverter device αG.

Even in the case of a multi-phase system such as three phases, the same effects as in the embodiment can be obtained by detecting the load voltage for each phase and controlling the compensation output.

The method of detecting an instantaneous voltage drop is not limited to the embodiment.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

Difference (V77) between the output signal Vz of the voltage detection transformer (to) and the reference sine wave signal Vsin of the reference sine wave generation circuit (6)
-Vsin) is formed by a subtracter a9, an increase or drastic change in the output signal of this subtracter 09 is detected by the hysteresis characteristic of the comparator circuit, and a drive control signal of the PWM waveform of this comparator circuit is used to generate a subtracter. Since the drive of inverter device 0Q was controlled when an instantaneous voltage drop occurred so that the output signal of 09 converged within a predetermined tolerance range, the compensation output of inverter device αQ took into account the voltage drop based on the impedance of the injection transformer. By series combination of the AC power supply (1) and the compensation output, the load voltage can be compensated to the magnitude and waveform of the rated voltage with an accuracy corresponding to the above-mentioned tolerance range.

Therefore, with a simple configuration that does not require a complicated signal generation circuit for creating PWM pulses, the influence of the voltage drop of the injection transformer 07) is eliminated when an instantaneous voltage drop occurs, and the load voltage is compensated to the rated voltage with high precision. This allows the compensation accuracy to be significantly improved.

[Brief explanation of drawings]

Figure 1 is a block diagram of one embodiment of the instantaneous voltage drop compensator of the present invention, Figure 2 (b) is a waveform diagram for the operation question in Figure 1, and Figure 3 is a block diagram of a conventional example. be. (1)...AC power supply, (sha)...control device, (4)
...AC switch circuit, (5)...load, ■...
Reference sine wave generation circuit, 03... inverter drive circuit,
OQ...Inverter device, α...Injection transformer, 0
Q: Output side voltage detection transformer, 09: Subtractor, ■: Comparison circuit.

Claims (1)

[Claims] (1) An AC switch circuit for a normal power supply line that is turned on when the voltage of the AC power supply is normal and closes between the AC power supply and the load, an inverter device for compensation power supply, and a primary side of the inverter device. Connected to the output terminal, 2
The next side includes an injection transformer installed in parallel with the AC switch circuit, and upon detection of an instantaneous voltage drop of the AC power source, the AC switch circuit is opened and the load power supply path is switched to the secondary side of the injection transformer. At the same time, the inverter device is driven to supply the compensated output of the inverter device to the primary side of the injection transformer, and the AC power source and the compensated output are serially combined on the secondary side of the injection transformer. An instantaneous voltage drop compensator that is supplied to a load and series-compensates the load voltage using the compensation output, comprising: a reference sine wave generation circuit that outputs a reference sine wave signal of rated amplitude synchronized with the AC power source; and a reference sine wave generating circuit that detects the load voltage. a subtracter that outputs a signal of the difference between the output signal of the voltage detection transformer and the reference sine wave signal, and a subtracter that outputs an increase or decrease change in the output signal of the subtracter when the instantaneous voltage drop is detected. and a comparison circuit that detects a hysteresis characteristic and generates a PWM waveform drive control signal for driving the inverter device so that the output signal of the subtracter converges within a predetermined tolerance range. Voltage drop compensator.