JPH05115136A - Instantaneous voltage drop compensator - Google Patents

Abstract

PURPOSE:To prevent unnecessary backward bias voltage from being supplied to the load by controlling the generation period of the backward voltage for forced extinction of arc of a thyristor switch to the minimum necessary one at the time of detection of an instantaneous voltage drop, in a serial- compensating instantaneous voltage drop compensator wherein an inverter device is used. CONSTITUTION:This equipment is provided with an instantaneous value detecting circuit 26 which sample-holds an instantaneous value of a conduction current of a thyristor switch 2 at the time of detection of an instantaneous voltage drop of an AC power supply 1, a backward bias period setting circuit 32 which variably sets a backward bias voltage supplying period according to the magnitude of the instantaneous value and which generates a control signal for forced extinction of arc during the backward bias period, and a control switching circuit 34 which controls an inverter device 18 to the output of the backward bias voltage while the control signal is generated and controls the inverter device 18 to the output of a compensating AC when the generation of the control signal is finished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving an inverter device when an AC voltage supplied to a load is momentarily dropped and forcibly extinguishing a thyristor switch forming a constant power supply path, and then The present invention relates to an instantaneous voltage compensator that serially compensates for a decrease in load voltage by compensating AC.

[0002]

2. Description of the Related Art Conventionally, this type of series compensation type instantaneous voltage drop compensating device is generally shown in FIG. 3 as described in the specification and drawings of the application of Japanese Patent Application No. 61-196216. It is configured. Then, when the voltage of the AC power supply 1 such as a system power supply (hereinafter referred to as power supply voltage) is normal, the antiparallel thyristors 2a and 2b of the thyristor switch 2 for the normal power supply path are alternately triggered in synchronization with the power supply voltage, The AC power supply 1 is supplied to the load 3 via the switch 2.

Further, the AC power source 1 is input to the rectifier 5 via the power transformer 4, and the rectified output of the rectifier 5 charges the energy storage capacitor 6. Further, the power supply voltage is detected by the voltage detection transformer 7, and this transformer 7
The phase synchronization circuit 8 forms a synchronization pulse in synchronism with the secondary side detection voltage Vi, and the reference sine wave generation circuit 9 supplies a reference sine wave voltage Vs having an amplitude corresponding to the rated power supply voltage based on this pulse. Occurs in synchronization with.

Further, the voltage drop detection circuit 10 repeats integration of, for example, 1/4 cycle of the difference between the voltages Vi and Vs, compares the integrated value with a reference value for voltage drop detection, and based on the comparison result, the power supply voltage. Occurrence of a momentary voltage drop (hereinafter referred to as a momentary voltage drop) is detected. In addition, the detection circuit 10
When the power supply voltage is normal, the switching control circuit 11 to which the drop detection signal a is input does not output a timer signal b described later to the thyristor drive circuit 12, and as a result, the drive circuit 12 alternately switches the thyristors 2a and 2b. Trigger on.

Next, the power source voltage is reduced to t ₀ as shown in FIG. 4 (a) due to an instantaneous drop such as lightning damage, and at t ₁ (b) in FIG.
When the decrease detection signal a is output, the switching control circuit forms the timer signal b shown in FIG. 6D and the reverse bias command signal c shown in FIG. 7E in synchronization with the rise of the detection signal a. , (F) in the figure, which is synchronized with the trailing edge of this signal c.
The gate signal d in the compensation output period of is formed.

Then, the timer signal b is set to a width of about 2 seconds, which is longer than the occurrence period of the instantaneous voltage drop, and the drive circuit 12 stops the trigger (thyristor drive) of the thyristors 2a and 2b by the generation of the signal b.

At this time, the thyristor 2a or 2b in the ON state supplies the power supply current to the load 3 until it is forcibly extinguished by the reverse bias voltage described later, and the current flowing through the thyristor switch 2 (hereinafter referred to as thyristor current) is 4 (c). The command signal c is composed of a mono-multi pulse of a predetermined reverse bias period τ ₀ (t _{1 to} t ₂ ) for forced arc extinction, and the gate signal d falls in synchronization with the timer signal b.

Then, the reverse bias generation circuit 13 operates in response to the command signal c, and the generation circuit 13 causes the adder 14 to operate.
The inverter drive circuit 15 is supplied with the control signal e for forced extinction of the switch 2 shown in FIG.

That is, based on the detection current of the current detection transformer 16 provided in the power supply path between the AC current 1 and the switch 2, the polarity detection circuit 17 supplies the current to the generation circuit 13 of the AC power supply 1 (hereinafter referred to as power supply current). When the polarity detection signal f of) is supplied and the command signal c is input, the generating circuit 13 sets the reverse bias period τ ₀ of forced extinction set to surely extinguish the commutation of the thyristors 2a and 2b. A control signal e having a polarity corresponding to the power supply current is generated.

The drive circuit 15 based on the control signal e
The inverter device 18 operates by the energy stored in the capacitor 6 under the control of the
Secondary side 19a provided in parallel with the switch 2 via
, A reverse bias voltage substantially corresponding to the peak value of the power supply voltage is generated, and at this voltage, the switch 2 is t _x (t ₁ <t _y ≦
It is extinguished by force at t ₂ ) and turns off. The polarity of the reverse bias voltage is also determined by the control signal e, and when the load current flows through the switch 2 in the direction of arrow I in FIG. 3, the reverse bias voltage is turned off to turn off the thyristor 2b. Occurs in the direction of arrow Vh.

Furthermore, when the reverse bias period τ ₀ ends and the command signal c is no longer output, the gate signal d turns on the gate circuit 20 for drive control, and the voltages Vi and Vs.
The output signal of the subtracter 21 based on the difference between the two, that is, the control signal g of the compensation amount corresponding to the decrease amount of the power supply voltage is
0, supplied to the drive circuit 15 via the adder 14, and the control input of the inverter device 18 is switched from the control signal e to g at t ₂ .

Based on the control signal g, the output of the inverter device 18 after t ₂ becomes a compensating AC corresponding to the amount of decrease in the power supply voltage as shown in FIG. 4 (h), and this compensating AC is the AC power supply 1 Are serially combined and supplied to the load 3, and the drop of the load voltage shown in FIG.

Reference numerals 22 and 23 in FIG. 3 denote capacitors and resistors that form a harmonic elimination filter, and eliminate the harmonics of the output of the injection transformer 19. Further, after t ₃ when the detection signal a ends, the gate circuit 20 is turned off and the control signal g
Is cut off, the control circuit 11 turns off the gate signal b, operates the drive circuit 12, and returns to the normal operating state.

[0014]

In the case of the above-mentioned conventional compensator, the reverse bias period τ ₀ is sufficient to surely turn off the switch 2 even if the currents of the thyristors 2a and 2b have the rated peak values. Set for a long period.

That is, when the thyristors 2a and 2b are extinguished by the reverse bias voltage, the extinction time ΔT until the thyristor current decreases and turns off is approximately ΔI / ΔT as shown in FIG. 5 (a). = E / L (ΔI is the current, E is the reverse bias voltage, L is the leakage inductance of the injection transformer 19) and becomes longer in proportion to the current flowing through the thyristor switch 2 (thyristor current) at that time.

Therefore, the reverse bias period τ ₀ is set to the substantially longest expected extinction time ΔT.

In this case, if the thyristor current during forced extinction is smaller than the rated peak value based on the state of the load 3, the current phase, etc., as shown in FIG.
_The thyristors 2a and 2b turn off in a time sufficiently shorter than ₀ ,
After that, the reverse bias voltage is combined in series with the AC power supply 1 and supplied to the load 3 until the output of the inverter device 18 is switched to the compensation AC.

[0018] Then, for example, by a reverse bias voltage t ₁ ~t ₂ in FIG. 4 (h), the thyristor 2a or 2b in the figure t _x is turned off, the subsequent reverse bias voltage to the t _x ~t ₂ It is supplied to the load 3. Then, the load voltage by the reverse bias voltage of t _x ~t ₂ is greatly disturbed as shown in FIG. 4 (i), there is a problem that can not be performed stably compensation, for example, the load 3 is in a thyristor converter for performing phase control if there is,
A malfunction of the load 3 occurs.

The present invention provides an instantaneous voltage drop compensating device for preventing the supply of unnecessary reverse bias voltage by variably setting the reverse bias period according to the magnitude of the current flowing through the thyristor switch at the time of detecting a voltage sag. The purpose is to provide.

[0020]

In order to achieve the above-mentioned object, in the instantaneous voltage drop compensating device of the present invention, the instantaneous value for sampling and holding the instantaneous value of the energizing current of the thyristor switch at the time of detecting the voltage sag is detected. A value detection circuit and a reverse bias period for supplying a reverse bias voltage depending on the magnitude of the instantaneous value are variably adjusted to long and short, and a reverse bias period is generated to generate a control signal for forced arc extinction. A bias period setting circuit and a control switching circuit that controls the inverter device to output the reverse bias voltage during the generation period of the control signal and controls the inverter device to output the compensation AC when the generation of the control signal ends.

[0021]

In the momentary voltage drop compensating device of the present invention constructed as described above, when a voltage sag is detected, the instantaneous value detection circuit determines the magnitude of the current (thyristor current) flowing through the thyristor switch at that time. It is detected as an instantaneous value. Furthermore, based on the detected instantaneous value, the reverse bias period setting circuit variably sets the reverse bias period to a length suitable for the magnitude of the instantaneous value, and the control signal for forced extinction is set during the set reverse bias period. Occur.

Then, the control switching circuit controls the inverter device to output the reverse bias voltage only during the generation period of the control signal for the forced extinction, and then to the output of the compensation AC. At this time, the reverse bias period becomes the minimum necessary period for forcibly extinguishing the thyristor switch, so that unnecessary reverse bias voltage is not supplied to the load.

[0023]

EXAMPLE One example will be described with reference to FIGS. 1, the same reference numerals as those in FIG. 3 indicate the same or corresponding ones, and the difference from the conventional apparatus in FIG.
Instantaneous value detection circuit 26 formed by full wave rectifier 24 and sample hold circuit 25, variable resistor 27, integrator 28, comparator 29, inverter 30, gate circuit 3 for period adjustment
The reverse bias period setting circuit 32 formed by 1 and the OR gate 33 that adds and corrects the gate signal d in the compensation control period of the switching control circuit 11 with the output signal γ of the comparator 29 are added.

An inverter-driven control switching circuit 34 is formed by the adder 14, the gate circuit 20, and the OR gate 33. The variable resistor 27 is connected to the DC power supply terminal 3
A DC voltage of 5 is applied, and the divided voltage of this voltage is generated in the switching piece as an integral reference voltage.

[0025] Then, when the voltage sag occurs in the same manner t0 the case of FIG. 4, drop detection signal a from detecting circuit 10 to t ₁ as shown in Figure based on the detection of the instantaneous drop 2 (a) is outputted, On the basis of this detection signal a, the switching circuit 11 causes the timer signal b rising to t ₁ and the reverse bias command signals c and t ₂ of the constant period τ ₀ (= t _{1 to} t ₂ ) of FIG.
The gate signal d in the correction output period shown in FIG. Further, based on the command signal c, the generation circuit 13 is shown in FIG.
A control signal e for forced extinction for a fixed period τ ₀ similar to the conventional one shown in (e) is formed, and this signal e is supplied to the gate circuit 31.

On the other hand, the rectifier 24 full-wave rectifies the detected current of the transformer 16 to form a full-wave rectified signal of the current (thyristor current) of the thyristor switch 2 shown in FIG.
This rectified signal is supplied to the sample hold circuit 25.

This sample-hold circuit 25 is triggered by the rising edge of the detection signal a to sample-hold the full-wave rectified signal, and the hold signal of the instantaneous value of the thyristor current at the time t ₁ shown in FIG. α is supplied to the comparator 29. In addition, the integrator 2 receives the reverse bias command signal c.
8 operates during the period τ ₀ of this command signal c, and the variable resistor 27
The integrated reference voltage, which has been converted to a constant voltage, is integrated.

At this time, the integration time constant is the reverse bias voltage,
E based on the leakage inductance L of the injection transformer 19
/ L, and the output signal β of the integrator 28 is shown in FIG.
As shown in, the linear increase is made with the slope of E / L. Then, the comparator 29 compares the hold signal α with the output signal β by using the output signal β as a reference signal (reference signal), and t _x ~ of β ≧ α
At t ₂ , the correction comparison signal γ shown in FIG. 2 (h) is output.

By the way, there is a relation of E / L = ΔI / ΔT as explained in FIGS. 5A and 5B, and in the equation of ΔI = (E / L) ΔT derived from this relational expression, The instantaneous value ΔI is detected as the hold signal α, and (E / L) Δ
T changes along the output signal β according to the magnitude of the extinguishing period ΔT. Therefore, based on the comparison of the signals α and β, the period τ
Of ₀ , the required extinction period ΔT is obtained as a period τ _x from t ₁ to t _x when α = β.

Then, the comparator 29 outputs the comparison signal γ during an unnecessary period t _{x to} t ₂ of the period τ ₀ , and this signal γ
The inverted signal γ ^* of the inverter 30 of FIG.
Are supplied to the gate circuit 31. Gate circuit 31 to the output signal gamma ^* supply period of the stops output of the gate signal e, variable adjustment to the adder control signal e period tau ₀ to the control signal ε period tau _x in FIG. 2 (j) It outputs to 14.

Therefore, the setting circuit 32 variably adjusts the reverse bias period for forcibly extinguishing the thyristor switch 2 to long or short depending on the magnitude of the instantaneous value ΔI of the thyristor current to obtain the required forcible extinguishing period τ _x . The control signal ε of this period τ _x is set and the adder 14 of the control circuit 34 is used instead of the control signal e.
Is supplied to the drive circuit 15 via.

Due to this supply, the drive circuit 15 is t ₁ to t _x.
In the period τ _x , the inverter device 18 is controlled to output a reverse bias voltage, and the reverse bias voltage turns off the thyristor switch 2 by forcibly extinguishing it by applying a proper voltage without excess or deficiency.

Further, the comparison signal γ is supplied to the OR gate 33 of the control circuit 34, the gate signal d is added and corrected by the comparison signal γ by the gate 33, and the rising edge is corrected to t _x as shown in FIG. 2 (k). The gate signal δ (= d + γ) is supplied to the gate circuit 20 instead of the gate signal d.

Then, the gate circuit 20 turns on at t _x when the gate signal δ rises, and instead of the control signal ε, the control signal g
Is supplied to the drive circuit 15 via the adder 14 and the thyristor switch 2 is turned off, and at the same time, the inverter device 18
Is switched to the output of compensation AC to control.

Therefore, the application of the undesired reverse bias voltage to the load 3 as in the conventional device is prevented from t _{x to} t ₂ ,
As shown by the solid line in FIG. 2 (l), the load voltage is free from the disturbance caused by the reverse bias voltage as in the load voltage of the conventional device indicated by the broken line.

[0036]

Since the present invention is constructed as described above, it has the following effects. When an instantaneous voltage drop is detected, the instantaneous value detection circuit 26 detects the magnitude of the energizing current (thyristor current) of the thyristor switch 2 as an instantaneous value, and the reverse bias period circuit 32 switches depending on whether the instantaneous value is large or small. The reverse bias period for forced arc extinguishing of No. 2 is variably adjusted to be long or short, and the control signal ε for forced extinction of the required period τ _x is generated, and the control switching circuit 34 generates the control signal ε. Inverter device 18 only for period τ _x
Is controlled to the output of the reverse bias voltage, and the inverter device 18 is switched to the output of the compensation AC at the same time as the generation period τ _x ends, so that the instantaneous voltage drop occurs and the inverter device 18 reverses the voltage after the switch 2 is turned off. Since the bias voltage is not output, unnecessary reverse bias voltage is prevented from being supplied to the load 3, disturbance of the load voltage is prevented, and stable compensation can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of an instantaneous voltage drop compensating device of the present invention.

2 (a) to (l) are timing charts for explaining the operation of FIG.

FIG. 3 is a block diagram of a conventional device.

4A to 4J are timing charts for explaining the operation of FIG.

5A and 5B are explanatory diagrams of extinguishing an arc of a thyristor switch.

[Explanation of symbols]

 1 AC power supply 2 Thyristor switch 3 Load 18 Inverter device 19 Injection transformer 26 Instantaneous value detection circuit 32 Reverse bias period setting circuit 34 Control switching circuit

Claims (1)

[Claims] 1. When detecting an instantaneous voltage drop of an AC power supply, the on-triggering of a thyristor switch for a constant power supply path between the power supply and the load is stopped to detect the polarity of the current supplied from the power supply to the load. A reverse bias voltage for forcibly extinguishing the original inverter device is supplied to an injection transformer provided in parallel with the switch to turn off the switch, and then the output of the inverter device is compensated corresponding to the voltage drop amount of the power supply. In an instantaneous voltage drop compensating device that controls the alternating current and serially compensates the decrease of the load voltage with the compensating alternating current, an instantaneous value detection circuit that samples and holds the instantaneous value of the energizing current of the thyristor switch at the time of the detection, The reverse bias period for supplying the reverse bias voltage is variably adjusted to be long or short according to the magnitude of the instantaneous value, and the reverse bias period is forcibly turned off during the reverse bias period. And a reverse bias period setting circuit for generating a control signal for controlling the inverter device to output the reverse bias voltage during the generation period of the control signal. An instantaneous voltage drop compensating device comprising: a control switching circuit for controlling the output.