JPH0769747B2 - AC constant voltage device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention selectively selects the output of each tap of a transformer with a tap by the point of a bidirectional thyristor or by extinguishing the arc, and the voltage of an AC power supply. The present invention relates to an AC constant voltage device that supplies a constant voltage AC to a load regardless of fluctuations.

[Conventional technology]

Conventionally, in order to make a power supply alternating current of a load such as OA equipment a constant voltage, for example, Japanese Patent Laid-Open No. 53-81928 (G05F 1/20) discloses a transformer with a tap and a plurality of bidirectional thyristors. In addition, based on the detection of the voltage fluctuation of the primary side AC power supply of the transformer, each thyristor is selectively selected and ignited, and the output of each tap of the transformer is switched to the load and supplied. Is listed.

By the way, when switching the tap output by igniting each thyristor, in order to prevent damage due to simultaneous turning on of multiple thyristors, the thyristor of the target tap after commutation extinguishing of the thyristor that has been turned on by the already ignited It is necessary to shift to the ignition control of.

And, in the case of the AC constant voltage device described in the above publication, the characteristics of the thyristor that spontaneously commutates due to the zero cross of the energizing current are used, and when the tap output is switched, it is turned on by the already ignited by the tap switching control. The thyristor at the target tap is ignited in synchronism with the zero crossing of the AC power supply voltage after the thyristor has commutated and extinguished by natural commutation by stopping the supply of the gate signal for ignition to the existing thyristor. Is supplying the gate signal of.

[Problems to be Solved by the Invention]

When extinguishing the thyristor by natural commutation as described above,
The time required for extinguishing arc depends on the cycle (frequency) of the AC power supply, and when the load current flowing through the thyristor in the ON state is in the delay phase, the thyristor is extinguished in commutation after the zero crossing of the voltage. .

Therefore, it takes about one cycle of AC power supply (about 20 msec at 50 Hz) from detection of voltage fluctuation of AC power supply to extinction of already ignited thyristor, and it is ensured that multiple thyristors are turned on at the same time. In order to prevent it, it is necessary to control the firing of the thyristor of the target tap after the zero crossing of the load current is detected or after the preset long extinction period of one cycle or more.

Therefore, there is a problem that the tap output cannot be rapidly switched, and the output AC is in an uncontrolled state for a long period of at least about one cycle, and during that time, an excessive or excessive voltage application adversely affects the load. is there.

Incidentally, in the publication, based on the zero-cross detection of the voltage of the AC power supply, it is described only to ignite the thyristor of the target tap in synchronization with the zero-cross of the voltage of the AC power supply,
In this case, tap output cannot be switched quickly, and
Due to the delay in the phase of the load current described above, multiple thyristors may turn on at the same time, so the voltage between taps is regulated. Controls need to be complex and specialized.

An object of the present invention is to provide an AC constant voltage device capable of reliably preventing simultaneous turning-on of a plurality of thyristors and enabling quick switching of tap outputs.

[Means for Solving the Problems]

Means for achieving the above object will be described below with reference to FIG. 1 corresponding to one embodiment.

As shown in FIG. 1, the present invention provides a transformer 2B connected to an AC power source 1 with a plurality of output taps T ₁ , T ₂ , ..., T _n-1 , Tn,
A plurality of bidirectional thyristors are provided at each of the output taps T _{n-1 to} T _n.
While connecting one end of each of S ₁ , S ₂ , ..., S _n-1 , and Sn,
The other end of each thyristor S ₁ -Sn is connected to the output terminal 3, and by tap switching control based on the detection of the voltage fluctuation of the power supply 1,
The ignition control of the already ignited thyristor is stopped, and after the commutation of the thyristor is extinguished, the control proceeds to the ignition control of the thyristor of the target output tap, and a constant voltage AC is supplied to the load connected to the output terminal 3. In the AC constant voltage device, each thyristor S ₁ ~
The secondary winding L ₂ is inserted between the connection point at the other end of Sn and the output terminal 3, and the intermediate tap Tm of the primary winding L ₁ is grounded. Two semiconductor switches Qc and Qd for positive and negative commutation provided between the power source and both ends of the primary winding L ₁ and the termination of the ignition control of the already ignited thyristor and the power source 1 Both switches Qc and Qd are selectively momentarily turned on depending on whether the voltage is positive or negative, and each thyristor S _{1 is} driven by the induced energy in the secondary winding L _2.
~ The technical means of providing a commutation control circuit for forcibly extinguishing Sn is extinguished.

[Action]

With the above-described configuration, in the AC voltage regulator of the present invention, when the voltage of the power supply 1 fluctuates, the commutation control circuit switches the ignition control of the already-ignited thyristor at the same time. Qc and Qd are selectively turned on instantaneously, and at this time, the energization direction of the primary winding L ₁ of the reactor 4 is reversed by turning on each of the switches Qc and Qd, and the energization of the primary winding L ₁ is reversed. The already fired thyristor is reverse-biased by the induced energy in the secondary winding L ₂ whose polarity reverses depending on the direction, and the thyristor is immediately extinguished by forced commutation.

Therefore, the commutation extinction of the already ignited thyristor can be performed instantly for several 100 μsec depending on the characteristics of the thyristor without depending on the cycle of the power supply 1, and after the ignition control of the already ignited thyristor is stopped. By immediately shifting to the firing control of the thyristor of the target output tap, simultaneous turning on of a plurality of thyristors can be prevented and tap output can be switched instantaneously.

〔Example〕

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

As shown in FIG. 1, a single-winding transformer 2B is connected to an AC power source 1 of 50V or 60V system, and this transformer 2B is provided with an input tap T _{i at a} predetermined turn position as a tap on the primary side. In addition, n output taps T ₁ , T ₂ , ..., T _n-1 , Tn are provided as secondary-side taps for switching n stages of tap output.

The highest voltage output tap Tn forms one end of the winding 2B.

Then, the input tap Ti and the input side common terminal of the other end of the winding 2B
Based on the power supply voltage applied between Ti ′, a voltage corresponding to the tap position is generated between each output tap T _{1 to} Tn and the output-side common terminal T _{0 at} the other end of the winding 2B. The same voltage as the power supply voltage is generated at the output tap T ₁ provided at the predetermined turn position.

Furthermore, n tridirectional thyristors S ₁ , S ₂ , ..., S _{n-1 of} three terminals formed by triacs and reversible connections of two unidirectional thyristors at each output tap T _{1 to} Tn. , Sn are each one end connected to the other end of the thyristors S ₁ to Sn is connected to one output terminal 3 through the reactor 4 for commutation energy implant, an alternative for the thyristors S ₁ to Sn Based on the firing control, the alternating current of the voltages of the output taps T _{1 to} Tn is output between the output terminal 3 and the other output terminal 3 ′ connected to the common terminal T ₀ .

In the reactor 4, the secondary winding L ₂ is inserted between the other end of each thyristor S _{1 to} Sn and the output terminal 3, and the intermediate tap Tm of the primary winding L ₁ is grounded.

Further, a noise absorbing capacitor Ca and a resistor Ra forming an AC absorber are provided between the output terminals 3 and 3 '.

Next, each thyristor S _{1 to} Sn when switching output taps
In order to obtain the energy for the reverse bias of, the AC of the power supply 1 is transformed and full-wave rectified by the small and small-capacity power supply transformer 15 and the diodes De, Df for rectification, and the diodes De, D
The rectified output of f constantly charges the large-capacity smoothing integration capacitor Cb that forms the DC power supply.

Further, since the direction of feeding the charging energy of the capacitor Cb to the primary winding L ₁ is switched, the polarity of the induced energy of the secondary winding L ₂ is switched depending on whether the voltage of the power source 1 is positive or negative.
Two NPN type transistors Qc and Qd forming two semiconductor switches for positive and negative commutation are respectively inserted between Cb and one end and the other end of the primary winding L ₁ .

The collectors of both transistors Qc and Qd are connected to a capacitor Cb via a connection resistor Rb, and the emitters are connected to one end of a primary winding L ₁ via backflow prevention diodes Dg and Dh, respectively.
It is connected to each of the other ends.

On the other hand, detection of voltage fluctuation of the power supply 1 and each thyristor S _{1 to} Sn
Point, the voltage of the power supply 1 is detected by the detection transformer 6, and the detection output of the secondary side of the transformer 6 is input to the DC conversion circuit 7 and the synchronous pulse generation circuit 8. A DC voltage based on the AC voltage of the power supply 1 is output from the conversion circuit 7 to the integration circuit 9, and the positive and negative sync pulses of the voltage of the power supply 1 are generated from the generation circuit 8 to the integration circuit 9 at intervals sufficiently shorter than one cycle, for example, Output every 1/4 cycle.

The integrator circuit 9 repeats the integration of the output of each 1/4 cycle of the conversion circuit 7, and the integrated voltage of the integrator circuit 9 is the determination circuit.
Output to 10.

This judging circuit 10 is the integrated voltage of the integrating circuit 9 and the detection reference power source.
An error from the reference voltage of 11 is calculated, and the difference voltage between the integrated voltage as the detection voltage of the voltage fluctuation of the power supply 1 and the reference voltage is output to the decoder circuit 12.

Then, the decoder circuit 12 converts the input differential voltage into n-bit selection data that selectively selects _{one of the} output taps T _{1 to} Tn according to the polarity and magnitude of the voltage,
The selection data is supplied to the tap switching command circuit 13.

Further, the command circuit 13 detects the presence or absence of switching of the output taps T _{1 to} Tn based on the selection data input every 1/4 cycle, and based on this detection result, each thyristor S ₁
A gate signal for firing is alternatively output to the gates G of ~ Sn.

This gate signal causes each of the thyristors S ₁ to S ₁ to generate a constant voltage AC of the rated voltage of the power source 1 between the output terminals 3 and 3 '.
Sn is selectively fired and turned on, and a constant voltage AC is supplied to the load between the output terminals 3 and 3 '.

Then, for example, when the voltage of the power supply 1 drops and changes during the firing control of the thyristor S ₁ , based on the output of the integrating circuit 9,
The decision circuit 10 detects a voltage drop within an extremely short time of 1/4 cycle, and at this time, based on the selection data of the decoder circuit 12, the command circuit 13 switches the tap output, for example, from the output tap T ₁ to the output tap. Detect switching to Tn.

By the way, when the tap output switching is detected, the command circuit
13 cuts off the gate signal of the already fired thyristor S ₁ and at the same time outputs a commutation command signal to the commutation drive circuit 14.

Further, the drive circuit 14 switches the outputs based on the positive and negative sync pulses of the generation circuit 8 to make the commutation command signal from the drive circuit 14 a positive side and a negative side on-signal as transistors Qc and Qd.
Outputs instantaneously (several 100 μsec) to the bases Bc and Bd of.

As a result, when tap switching occurs in the positive half cycle of the voltage of the power supply 1, the commutation control circuit formed by the command circuit 13 and the drive circuit 14 causes the thyristor S _{1 that has} already been ignited based on the interruption of the gate signal. At the same time as the ignition control is stopped, the transistor Qc is instantly turned on.

At this time, based on the conduction polarity of the primary winding L ₁ , the secondary winding
L ₂ in in FIG. +, - polarity indicated by, i.e. thyristors S ₁ ~
The connection point of the Sn-induced energy polarity to positive occurs, the induced energy is injected as commutation energy thyristors S _1, are forced commutation extinguishing thyristor S ₁ is reverse biased to turn off immediately.

Then, after the extinction of the commutation of the thyristor S ₁ , when the output of the ON signal of the drive circuit 14 ends, the command circuit 13 outputs a gate signal to the thyristor Sn of the target output tap Tn designated by the selection data, and the thyristor S1. Several hundred microseconds from S ₁ off
Immediately after a delay, the thyristor Sn is switched to the ignition control, the thyristor Sn is turned on, and the tap output is switched.

Therefore, the detection of the voltage drop to the end of tap output switching can be done in an instant of several 100 μsec, and furthermore, after the extinguished thyristor S ₁ is extinguished by the forced commutation extinction, the thyristor of the target output tap Tn is S _n is fired and the thyristor
Neither S ₁ nor Sn will be on at the same time.

In the negative half cycle of the voltage of the power source 1, the transistor Qd is turned on by the ON signal on the negative side of the drive circuit 14, and the polarity of the induced energy of the secondary winding L ₂ is opposite to the positive half cycle. Then, the induced energy of the opposite polarity causes the commutated extinction of the already ignited thyristor in the same manner as in the positive half cycle, and the output taps are switched.

In addition, the flow of commutation energy to the load is blocked by the reactor 4, and the commutation extinguishing and ignition generate a few hundred μs.
The noise of ec is absorbed by the capacitor Ca and the resistor Ra.

Further, it goes without saying that the switching direction of the output taps changes as the voltage of the power source 1 rises and falls.

The waveforms of the voltage and current of the output AC when the voltage of the power source 1 rises and rises are as shown by the solid lines in FIGS. 2 (a) and 2 (b), respectively. ), The broken lines show the waveforms of abnormal voltage and current due to fluctuations, and τ shows the tap output switching period of several 100 μsec.

By the way, the capacitance and the like of the capacitor Cb are set in advance so that the commutation extinction of the thyristors S _{1 to} Sn can be surely performed regardless of the voltage fluctuation of the power supply 1.

Then, both commutation extinguishing thyristor S ₁ to Sn is performed on the basis of the charging energy of the capacitor Cb, it is not necessary or subjected to a weighted capacitance of the capacitor for each tap output, moreover, rolling the transformer 2B The device is formed with almost no adjustment, without the need to provide special taps for extinguishing the flow.

By the way, it goes without saying that various transformers such as a single-turn transformer and a transformer having primary and secondary windings may be used instead of the transformer 2B.

Further, the method of detecting the voltage fluctuation of the power supply 1 may be different from that of the embodiment.

Further, as the DC power supply, a rectified output of an AC power supply of a different system from the power supply 1 or a battery power supply may be used.

〔The invention's effect〕

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

2 between the plurality of bidirectional thyristors S _{1 to} Sn connected to the output taps T _{1 to} Tn of the transformer 2B and the output terminal 3, respectively.
A reactor 4 for injecting commutation energy into which the secondary winding L ₂ is inserted is provided, and when the output tap is switched based on the detection of the voltage fluctuation of the AC power supply 1, the ignition control of the already ignited thyristor is stopped. At the same time, depending on whether the voltage of the AC power supply 1 is positive or negative, two semiconductor switches Qc, Qd for positive and negative commutation provided on the primary winding L ₁ of the reactor 4 are selectively momentarily turned on, Based on the direct current of the direct current power supply, induced energy is generated in the secondary winding L ₂ of the reactor 4 in which the polarity is inverted depending on whether the alternating current power supply 1 is positive or negative, and the induced energy causes each thyristor S ₁ ...
By reverse biasing Sn and extinguishing the already ignited thyristor by commutation, the winding configuration of the transformer 2B and tap switching control are not complicated, and there is no adjustment regardless of the output tap. It is possible to inject the induced energy as the flow energy into the thyristors S _{1 to} Sn to instantaneously commutate and extinguish the thyristors that have already been ignited, and immediately shift to the ignition control of the thyristor of the target tap.

Furthermore, even if the load current is in a lag phase, the commutated extinction of the already fired thyristor is ensured by forced commutation extinction, preventing the simultaneous turn-on of multiple thyristors and outputting instantaneously. It is possible to switch the taps, prevent non-control of the output AC based on the switching of the output taps, and supply the constant voltage AC to the load.

[Brief description of drawings]

FIG. 1 is a connection diagram of one embodiment of an AC constant voltage device of the present invention,
FIGS. 2A and 2B are output AC voltage and current waveform diagrams for explaining the operation of FIG. 1 ... AC power supply, 2B ... Transformer, 3 ... Output terminal, 4 ...
… Reactor for injecting commutation energy, Qc, Qd… Transistors as semiconductor switches for positive and negative commutation, S _{1 to} Sn
…… Bidirectional thyristor, T _{1 to} Tn …… Output tap.

Continuation of front page (56) Reference JP-A-51-101847 (JP, A) JP-A-61-281312 (JP, A) JP-A-62-127911 (JP, A)

Claims (1)

[Claims] 1. A transformer connected to an AC power supply is provided with a plurality of output taps, one end of each of the plurality of bidirectional thyristors is connected to each output tap, and the other end of each of the thyristors is an output terminal. Connected, by tap switching control based on the detection of the voltage fluctuation of the power supply, stop the ignition control of the already ignited thyristor, and after the commutation extinction of the thyristor, shift to the ignition control of the thyristor of the target output tap. In an AC constant voltage device that supplies constant voltage AC to a load connected to the output terminal, a secondary winding is inserted between a connection point at the other end of each thyristor and the output terminal, and a primary winding A reactor for injecting commutation energy, in which the center tap of the wire is grounded, two semiconductor switches for positive and negative commutation provided between the DC power supply and both ends of the primary winding, respectively. Firing service Simultaneously with the stoppage of the ignition control of the lister, the both switches are selectively momentarily turned on depending on whether the voltage of the AC power supply is positive or negative, and the commutation of each of the thyristors is forced by the induced energy of the secondary winding. An AC constant voltage device comprising a commutation control circuit for extinguishing an arc.