JP3070192B2 - Instantaneous voltage drop compensator - Google Patents

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 and forcibly extinguishing a thyristor switch forming a normal power supply line when an instantaneous voltage drop of an AC power supply supplied to a load occurs. The present invention relates to an instantaneous voltage compensator that compensates for a decrease in load voltage in series by a compensation AC.

[0002]

2. Description of the Related Art Conventionally, such a series-compensation type instantaneous voltage drop compensating apparatus has been disclosed in, for example, Japanese Patent Application No. 61-196216 as shown in FIG. It is configured. When the voltage of the AC power supply 1 such as a system power supply (hereinafter referred to as a 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. An AC power supply 1 is supplied to a load 3 via a switch 2.

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

Further, the voltage drop detection circuit 10 repeats the integration of, for example, 1/4 cycle of the difference between the voltages Vi and Vs, and compares the integrated value with a reference value of the voltage drop detection. Of the instantaneous voltage drop (hereinafter, referred to as an instantaneous voltage drop) is detected. 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 the 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. On trigger.

Next, the power supply voltage drops to t ₀ as shown in FIG. 4A due to an instantaneous drop due to lightning damage, and the power supply voltage drops to t ₁ in FIG.
Is output by the switching control circuit, a timer signal b shown in FIG. 3D and a reverse bias command signal c shown in FIG. (F) in synchronization with the fall of this signal c.
Of the compensation output period is formed.

The timer signal b is set to have a width of about 2 seconds which is longer than the period during which the instantaneous voltage drop occurs, and the generation of the signal b causes the drive circuit 12 to stop triggering the thyristors 2a and 2b (thyristor drive).

At this time, the thyristor 2a or 2b in the on state supplies the power supply current to the load 3 until the arc 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 shown in FIG. It changes as shown in FIG. The command signal c is a mono-multi pulse of a predetermined reverse bias period τ ₀ (t _{1 to} t ₂ ) for forced extinguishing, and the gate signal d falls in synchronization with the timer signal b.

Then, the reverse bias generating circuit 13 operates according to the command signal c.
The control signal e for forcibly extinguishing 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 generation circuit 13 with the current of the AC power supply 1 (hereinafter referred to as the power supply current). When the polarity detection signal f) is supplied and the command signal c is input, the generation circuit 13 causes the reverse bias period τ ₀ of forced arc extinguishing set to surely extinguish the thyristors 2a and 2b by commutation. A control signal e having a polarity corresponding to the power supply current is generated.

The driving circuit 15 based on the control signal e
, The inverter device 18 operates with the energy stored in the capacitor 6, and the primary side 19a of the injection transformer 19
Secondary side 19a provided in parallel with switch 2 through
The reverse bias voltage is generated corresponding to the peak value of approximately the power supply voltage, switch 2 in this voltage _{t x (t 1 <t y} ≦
At t ₂ ), the arc is forcibly extinguished and turned off. The polarity of the reverse bias voltage is also determined by the control signal e. When the load current flows through the switch 2 to the load 3 in the direction of arrow I in FIG. 3, the reverse bias voltage is turned off to turn off the thyristor 2b. In the direction of arrow Vh.

Further, when the reverse bias period τ ₀ ends and the command signal c is not output, the gate circuit 20 for drive control is turned on by the gate signal d, and the voltages Vi and Vs
The output signal of the subtracter 21 based on the difference between the two, ie, the control signal g of the compensation amount corresponding to the amount of decrease in the power supply voltage
0, via the adder 14 is supplied to the drive circuit 15, the control input of the inverter 18 is switched to g from the control signal e to t _2.

Then, based on the control signal g, the output of the inverter device 18 after t ₂ becomes a compensation AC corresponding to the amount of decrease in the power supply voltage as shown in FIG. Are combined in series and supplied to the load 3, and the load voltage shown in FIG.

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

[0014]

In the case of the conventional compensating device, the reverse bias period τ ₀ is sufficiently set so that the switch 2 is reliably turned off even if the current of the thyristors 2a and 2b is at the rated peak value. Set for a long period.

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

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

In this case, if the thyristor current at the time of forcible extinguishing is smaller than the rated peak value based on the state of the load 3 and the current phase, etc., the reverse bias period τ as shown in FIG.
_The thyristors 2a and 2b turn off in a time sufficiently shorter than ₀ ,
Thereafter, 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 The load 3 is supplied. 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 or the like of the load 3 occurs.

According to the present invention, there is provided an instantaneous voltage drop compensating apparatus which variably sets a reverse bias period in accordance with the magnitude of a current flowing through a thyristor switch upon detection of an instantaneous voltage drop, thereby preventing unnecessary reverse bias voltage from being supplied. The purpose is to provide.

[0020]

In order to achieve the above object, in the instantaneous voltage drop compensating device of the present invention, an instantaneous value of the current flowing through the thyristor switch at the time of detecting an instantaneous voltage drop is detected by sampling and holding. A value detecting circuit and a reverse bias period for supplying a reverse bias voltage according to the magnitude of the instantaneous value are variably adjusted to be long and short, and a reverse bias period for generating a control signal for forcibly extinguishing the arc is provided. 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 compensated AC when the generation of the control signal ends.

[0021]

With the instantaneous voltage drop compensator of the present invention configured as described above, when an instantaneous voltage drop is detected, the instantaneous value detection circuit reduces the current flowing through the thyristor switch (thyristor current) at that time. It is detected as an instantaneous value. Further, based on the detected instantaneous value, the reverse bias period is variably set to a length suitable for the magnitude of the instantaneous value by the reverse bias period setting circuit, and a control signal for forcibly extinguishing is set in the set reverse bias period. Occur.

The inverter is controlled by the control switching circuit to output the reverse bias voltage only during the generation period of the control signal for forcibly extinguishing the arc, and then to the output of the compensated AC. At this time, since the reverse bias period is the minimum necessary period for forced extinction of the thyristor switch, unnecessary reverse bias voltage is not supplied to the load.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment will be described with reference to FIGS. In FIG. 1, the same reference numerals as those in FIG. 3 denote the same or corresponding elements.
An instantaneous value detection circuit 26 formed by a full-wave rectifier 24 and a sample-and-hold circuit 25; a variable resistor 27; an integrator 28; a comparator 29; an inverter 30;
1 in that a reverse bias period setting circuit 32 formed by the circuit 1 and an OR gate 33 for adding and correcting 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.

The adder 14, the gate circuit 20, and the OR gate 33 form a control switching circuit 34 driven by an inverter. The variable resistor 27 is connected to the DC power supply terminal 3
5 is applied, and a 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, as with the detection signal a circuit 11 Setsu based on the prior art, a period of time _{τ 0 (= t 1 ~t 2} ) reverse bias command signal c of the upright climbing timer signal b and the drawing in t ₁ (c), t ₂
The gate signal d in the correction output period shown in FIG. Further, based on the command signal c, the generating circuit 13
A control signal e for forcibly extinguishing the arc for a fixed period τ ₀ is formed as in the conventional case shown in (e), and this signal e is supplied to the gate circuit 31.

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

The hold signal of the instantaneous value of the sample hold circuit 25 detects signal is triggered by the sample-and-hold the full-wave rectified signal by the rise of a, FIG. 2 (f) to indicate sag detection time t ₁ of the thyristor current is supplied to the comparator 29. Further, the integrator 2 is controlled by the reverse bias command signal c.
8 operates during the period τ ₀ of the command signal c,
Is integrated.

At this time, the integration time constant is a reverse bias voltage,
Based on the leakage inductance L of the injection transformer 19, E
/ L, and the output signal β of the integrator 28 is as shown in FIG.
As shown in FIG. The comparator 29 compares the hold signal alpha and output signal beta as a reference signal the output signal beta (reference signal), t the β ≧ α _x ~
and outputs a comparison signal γ for correction in FIG. 2 (h) to t _2.

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

The comparator 29 outputs a 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 in FIG.
Is supplied to the gate circuit 31. The gate circuit 31 stops outputting the gate signal e during the supply period of the output signal γ ^* , variably adjusts the control signal e in the period τ ₀ to the control signal ε in the period τ _x in FIG. 14 is output.

Accordingly, the setting circuit 32 variably adjusts the reverse bias period for forcibly extinguishing the thyristor switch 2 to be long or short depending on whether the instantaneous value ΔI of the thyristor current is large or small, and sets the required forcible extinguishing period τ _x to And the control signal ε of this period τ _x is replaced with the adder 14 of the control circuit 34 instead of the control signal e.
Is supplied to the drive circuit 15 via the.

With this supply, the drive circuit 15 operates from t ₁ to t _x
During the period τ _x , the inverter device 18 is controlled to output a reverse bias voltage, and the thyristor switch 2 is forcibly extinguished by an appropriate voltage application that does not have excess or shortage and is turned off by the reverse bias voltage.

The comparison signal γ is supplied to the OR gate 33 of the control circuit 34, and the gate signal d is added and corrected by the comparison signal γ by the gate 33, and the rising is corrected to t _x as shown in FIG. 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 the time _{tx at} which the gate signal δ rises, and the control signal g instead of the control signal ε.
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 compensation AC output for control.

Therefore, application of an unstable 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 not disturbed by a reverse bias voltage like the load voltage of the conventional device indicated by the broken line.

[0036]

Since the present invention is configured as described above, the following effects can be obtained. Upon detecting an instantaneous voltage drop, the instantaneous value detection circuit 26 detects the magnitude of the current flowing through the thyristor switch 2 (thyristor current) as an instantaneous value, and a reverse bias period circuit 32 switches the switch according to the magnitude of the instantaneous value. 2, the reverse bias period for forced arc extinguishing is variably adjusted to be long and short, and a control signal ε for forced extinguishing is generated for a required period τ _x , and the control switching circuit 34 generates the control signal ε. Inverter device 18 for period τ _x
The control output of the reverse bias voltage, because of the control by switching the generation period tau _x End inverter device 18 at the same time the output of the compensation AC, along with the instantaneous voltage drop occurs, the reverse from the inverter device 18 after off of the switch 2 No bias voltage is output, and unnecessary supply of a reverse bias voltage to the load 3 is prevented, so that disturbance of the load voltage is prevented and stable compensation can be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of an instantaneous voltage drop compensator according to the present invention.

FIGS. 2A to 2L are timing charts for explaining the operation of FIG.

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

FIGS. 4A to 4J are timing charts for explaining the operation of FIG. 3;

FIGS. 5 (a) and 5 (b) are explanatory diagrams for extinguishing a thyristor switch. FIG.

[Explanation of symbols]

 DESCRIPTION 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)

(57) [Claims] When an instantaneous voltage drop of an AC power supply is detected, an on-trigger of a thyristor switch for a normal power supply path between the power supply and a load is stopped to detect a polarity of a current supplied from the power supply to the load. After a reverse bias voltage for forced arc extinguishing of the inverter device is supplied to an injection transformer provided in parallel with the switch to turn off the switch, the output of the inverter device is compensated for by an amount corresponding to a voltage drop amount of the power supply. An instantaneous voltage drop compensating device that controls to an alternating current and series-compensates the drop of the load voltage with the compensated alternating current, wherein an instantaneous value detection circuit that samples and holds an instantaneous value of a conduction current of the thyristor switch at the time of the detection, and The reverse bias period for supplying the reverse bias voltage is set to be long or short by variably adjusting the instantaneous value according to the magnitude of the instantaneous value, and is forcibly erased during the reverse bias period. 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 that controls output.