KR900005423B1 - Impulse communtatio inverter - Google Patents

Abstract

The inverter for preventing the primary coil short of a transformer during the commutation of thyristors comprises a transformer (10) of which stcondary winding is connected to the load, thyristors (T1-4) triggered by "a" and "b" taps of the primary winding of the transformer, a commutation condenseer (c) connected between junctions of the thyristors an inductor (L) for energy absorption generated at the primary and secondary windings of the transformer, and commutation diodes (D1-2.).

Description

Impulse reflux inverter for uninterruptible power supplies

1 is a representative representative voltage reflux inverter.

2 is a typical representative current reflux inverter.

3A, 3B, 3C, and 3D are simplified illustrations of the four operating modes of FIG.

4A, 4B, and 4C are simplified illustrations of the three operating modes of FIG.

5 is a circuit diagram for improving the disadvantages of FIG.

6 is a circuit diagram for improving the disadvantages of FIG.

7 is a basic circuit diagram of the present invention.

8 is an input signal waveform diagram for controlling the thyristors used in the present invention.

9A, 9B, 9C, 9D, and 9E are simplified illustrations of the five operating modes of FIG. 7 of the present invention.

10A, 10B, 10C, and 10D are waveform diagrams of a space current, a capacitor voltage, a series inductor terminal voltage, and a series inductor secondary current during the period of reflux in the circuit of FIG.

11A and 11B are waveform diagrams showing examples of principles for controlling the magnitude of the output voltage in the present invention.

FIG. 12 is a diagram showing a ratio of fundamental wave component and harmonic component size as controlling "α" in FIG.

13 is a block diagram of a circuit for automatic voltage regulation in the present invention.

Figure 14a is a block diagram of a typical uninterruptible power supply.

Figure 14b is a block diagram of a powerless apparatus according to the present invention.

15 is a circuit diagram showing an example of an inverter for an uninterruptible power supply according to the present invention.

* Explanation of symbols for main parts of the drawings

1: Signal Generator 2,3: Signal Converter

4: reference signal generator 5: error amplifier

6: signal comparator 7: gate logic circuit

8: Thyristor Driver 9: Thyristor

10 converter 11 filter

12: feedback circuit 13: load

14 DC power

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low frequency inverter suitable for an uninterruptible power supply, in particular to an impulse reflux inverter consisting of a transformer and a thyristor, and a device including an automatic voltage regulator.

In general, the uninterruptible power supply that is used is composed of a separate inverter and automatic voltage regulator, and not only increases the volume and threshold, but also very low efficiency puts a lot of burden on the user. The efficiency is low, but can only be used for a short time rating, the present invention is able to supply a stable high-quality power at all times.

The juice switching device used in the present invention uses a thyristor, and has high efficiency and high reliability, and is almost free from capacity limitations compared to the typical inverters for uninterruptible power supply, and can always supply stable AC power. .

First, in order to understand the principle of the present invention, a representative inverter for a conventional uninterruptible power supply is shown in FIGS. 1 and 2.

1 is a voltage reflux inverter, the configuration of which is a DC power supply (V _s ), a transformer (T), a thyristor (Th ₁ , Th ₂ ), a diode (D ₁ , D ₂ , D ₃ , D ₄ ), a capacitor ( C) A series inductor is a basic configuration of an inverter, and its operation is the same as those of FIGS. 3A, 3B, 3C, and 3D. This inverter is simple in configuration and easy to control. This technology is published by ROBERT CHAUPRADE, IEEE Trans. Of Ind. July / AUGUST, IA-13, Vol. 4 (July, 1977), "Inverters for Uninterruptible Power Supplies. for Uninterruptible power supplies. " Therefore, the operation of this inverter is as follows.

In FIG. 3a, the current applied from the positive terminal of the DC power supply V _{s to} the terminal C of the transformer T is transferred from the diode D _{1 to the} thyristor Th ₁ through the terminal a. ¡Æ the circuit consists of the negative terminal of the inductor (L) and the direct current power supply (V _s ), and at this time, current flows through the capacitor (C) for reflux and is charged with twice the voltage of the direct current power supply (V _s ) do. There then look at the operation time period of claim 3b also represents the process of thyristor (Th ₂₎ to conduct, thyristors (Th ₁₎ to reflux (commutation), wherein thyristors until reflux (Th ₁₎ diodes ( D ₁ , D ₂ ) and the thyristors (Th ₁ , Th ₂ ) are all conducting, so a short circuit occurs momentarily, and the dyristi (Th ₁ ) is refluxed so that the voltage in the condenser (C) is reversed. In this case, the charging current flowing at this time may be very different depending on the conditions of the transformer secondary side AC load. Therefore, the reflux operation is very sensitive by the power factor of the AC load, and the size of the series inductor L is inevitably increased due to a momentary short circuit during the reflux period. Therefore, the most important reflux operation in the inverter is greatly changed by the influence of the load. Therefore, it is difficult to apply this inverter to a capacity of 15 [KVA] or more as described in "IEEE Application Bulletin IA-13 No. 4 (August 1977)".

In the following operation section 3c, after the thyristor Th ₁ is refluxed, the energy stored in the series inductor L is transferred through the diode D ₄ → transformer T terminal d → terminal c → A part of the DC power positive terminal is sacrificed, and some current flows from the transformer (T) terminal (d) to the diode (D ₂ ) to the thyristor (Th ₂ ) to the direct current inductor (L). The ratio of the currents is determined by the turns ratio of the terminal c and the terminal e at the tap terminal d of the transformer T. From this point on, the polarity of the induced voltage on the secondary side of the transformer is reversed. In the next section (d), the transformer terminal (c) → terminal (e) → diode (D ₂ ) → thyristors (Th ₂ ) → series inductor → DC power supply unit from the positive (+) terminal of DC power supply (V _s ). -) Current flows to the terminal. Thus, FIG. 3A-FIG. 3B-FIG. 3C-FIG. 3D are repeated, and AC power is supplied to a load. In view of the characteristics of this circuit, one of the two elements of the thyristor (Th ₁ ) and the thyristor (Th ₂ ) is necessarily conducting, and thus the output voltage cannot be controlled. However, to change the size of the direct current supply voltage (V _s), or not only can control the output voltage only by the turn ratio of the primary side and the secondary side of the transformer (T). In order to stop the two inverters it is required the thyristors (Q ₁₎ and the thyristor (Q ₂₎ as shown in Figure 6.

2 is a typical current reflux inverter of the related art, the configuration of which is a DC power supply (V _s ), a transformer (T), a thyristor (Th ₁ , Th ₂ ), a diode (D ₁ , D ₂ , D ₃ , D ₄ , D ₅ ), the capacitor C, the resonant inductor L, and the reactors Ld and Ls, and the operations thereof are the same as those in FIGS. 4A, 4B, 4C, and 4D. Like the inverter of FIG. 1, this inverter also has the characteristics that the structure is simple and it is easy to control. The characteristics of the inverter are described in detail in the book "Principles of Inverter Circuits" by BD Bedford and RG Hoft. The operation of this inverter is as follows.

Referring to FIG. 4A, from the positive terminal of the DC voltage V _s to the terminal of the reactor Ld, the terminal of the transformer T, the terminal a, the diode D ₁ and the thyristor Th. ₁ ) → The current flows to the negative terminal of the DC power supply ( _s ), and the resonant current flows from the terminal (c) of the transformer (T) to the diode (D ₂ ) to the resonance inductor (L) to the capacitor (C). The capacitor C is charged with twice the power supply voltage V _s .

In FIG. 4B, when the die thruster Th ₂ is conducted to open the conducting die thruster Th ₁ , the capacitor C resonant inductor L thyristor Th ₂ diode D _{2 is applied.} ) The diode (D ₁ ) → diode (D ₁ ) → the capacitor (C) is opened, and the thyristor (Th ₁ ) is opened. In this case, the diode (D ₁ , D ₂ ) is similar to the phenomenon shown in the reflux operation of the inverter shown in FIG. ), And the thyristors Th ₁ and Th ₂ are all conducted, and a short circuit occurs at the primary side of the transformer T. Due to this phenomenon, the voltage of the secondary load terminal of the transformer T becomes zero. At this time, the voltage of the DC power supply V _s is maintained by the reactor Ld. At this time, the energy accumulated in the reactor Ld is sacrificed to the DC power supply V _s through the diode D ₅ in a section where the flowing resonance current decreases, and the overshoot appears in the load after the reflux operation is completed. Limit the magnitude of the voltage. In FIG. 4, the reflux operation of the thyristor Th ₁ ends, and the voltage of both ends of the capacitor C is charged in the opposite direction by the resonant current, and the voltage direction of the load is also reversed. AC power is supplied to the load by a series of operations of FIG. 4A-FIG. 4B-FIG. 4C-FIG. 4D.

For the purpose of understanding the present invention, conventional voltage reflux inverters of FIGS. 1, 3a, 3b, 3c and 3d and current reflux inverters 2, 4a, 4b and 4c is shown, but each configuration is simple and easy to control, but the momentary short circuit of the transformer (T) primary winding occurs during the reflux operation. Due to the phenomenon, the size of the series inductor or reactor capacity is very large. Therefore, any one of the inverters of 15 [KVA] is always conducting, so that the voltage can not be adjusted by controlling the conduction section of the thyristor. Therefore, to adjust the voltage, it is necessary to change the size of the DC power supply (V _s ) or change the transformer tap. Otherwise, use a separate automatic voltage regulator or connect it externally. In addition, the output voltages of the inverters shown in FIG. 1 and FIG. 2 always have the same waveform of l in FIG. 11a. This waveform has a very large ratio of harmonic components to the fundamental wave since the thyristor conduction delay angle α becomes zero as shown in FIG. In addition, the inverters shown in FIGS. 1 and 2 are very sensitive to the load conditions during the reflux operation, making it difficult to use nonlinear loads, i.e., loads such as phase controlled rectifiers, and difficult to use by three-phase (3 °) wiring. Do. In addition, the conventional representative inverter shown in FIG. 1 and FIG. 2 requires a separate power device, as shown in FIG. 5 and FIG. Conventional representative inverters have the disadvantages described above.

In the present invention, unlike the conventional representative inverter as described above, the instantaneous short circuit of the transformer primary side winding does not occur during the reflux operation. Therefore, unlike the conventional inverter, the size of the series inductor or reactor can be very small, and the inverter capacity is also almost limited and can be increased. In addition, unlike the conventional inverter has a feature that does not require a separate automatic voltage regulator to adjust the size of the output voltage. In addition, as described above, since there is no short circuit of the primary side of the transformer during reflux, the reliability of the thyristor is greatly improved.

The basic diagram of the present invention is shown in FIG. The basic configuration is a transformer (T), a thyristor (T ₁ , T ₂ , T ₃ , T ₄ ), a series inductor (L), a reflux capacitor (C), a diode (D ₁ , D ₂ , D ₅ ) and It consists of a DC power source (V _s). The signal for operating the juice switching thyristors T ₁ , T ₂ , T ₃ , T ₄ shown in FIG. 7 is as shown in FIG. 8. The basic principle operated by this signal is shown in the operating section as shown in Figs. 9A, 9B, 9C and 9D. Referring to FIG. 9A, the transformer (T) terminal (c) → terminal (a) → die Lister (T ₁ ) → die lister (T ₃ ) → series inductor (L) at the positive (+) terminal of the DC power supply (V _s ). ) → DC power source (V _s) part (-) and the terminal circuit is composed of, wherein the direct-current power supply voltage (V _s) of twice the reflux condenser (C) for being charged, the thyristors (T ₂₎ is open .

In the next interval the 9b also, in order to reflux the thyristor (T ₃₎ in continuity are, when conducting the thyristor (T _4), thyristor (T ₃₎ is opened while the resonant current is a capacitor (C) → die The lister T ₄ ? Serial inductor L? Diode D ₁ ? Die lister T ₁ flows as shown in FIG. 10A, and energy is accumulated in the series inductor L by the increased current. When the resonant current I _r decreases in the next section 10c, when the voltage across the series inductor V _L changes and becomes equal to the negative DC voltage V _s , the circulating current I _f ) flows into the DC power supply (V _s ) positive (+), resulting in energy sacrifice. In this case, however, the ratio between the secondary winding and the primary winding of the series inductor L is 1: 1. In this case, the voltage across the reflux capacitor is as shown in FIG. 10B.

FIG. 10 shows stable operation when the test condition is 0.4 of load power factor (cosθ) and Lag (Lag). Referring to FIG. 10d of the next operation section, it can be seen that all the thyristors T ₁ to T _{4 of the} inverter are all open. Therefore, in the present invention, as shown in FIG. 11B, the conduction section can be controlled to adjust the output voltage. Unlike the conventional inverter, as shown in FIG. 12A, the magnitude of the harmonic components with respect to the fundamental wave of the output voltage is shown in FIG. 12B by controlling the conduction region α of the thyristors T. In particular, in FIG. 12B, the third harmonic component is shown to be very small at the conduction delay angle α around 30 °, and the synthetic harmonic component is least controlled when the conduction region angle is between 20 ° and 30 °. Is showing. Therefore, the present invention has a feature that can minimize the size of the transformer secondary filter. In the typical representative inverter, since the conduction delay angle α is zero, the third harmonic is 33% of the fundamental wave component, and the fifth harmonic is about 20%, so that the transformer secondary filter must be very large. There is a disadvantage. In Figure 9e of the following operating section, DC power supply (V _s ) → transformer (T) terminal (c) → terminal (b) → die Lister (T ₂ ) → die lister (T ₄ ) → series inductor (L) → DC power supply The circuit consists of the (V _s ) negative terminal, which changes the direction of the transformer secondary output voltage.

As described above, the present invention shows that there is no short circuit of the primary winding of the transformer during the reflux period of the die Lister (T). Therefore, the present invention further increases the reliability. In addition, the output voltage can be adjusted by controlling the conduction section of the thyristor T as in the section of FIG. 9d. Unlike the conventional inverter shown in FIG. 14a, a separate automatic voltage regulator is built in the uninterruptible power supply. There is no need to do it. The entire block diagram of the uninterruptible power supply according to the present invention is shown in FIG. 14B in large divisions.

In order to explain the principle of automatic voltage regulation in the present invention is shown in FIG. The basic configuration generates signals of reference signals 10 [KHZ] to 30 [KHZ] in the signal generator 1, supplies them to the signal converters 2 and 3, and uses them as carrier waves in the gate circuit 8 as well. The carrier uses a frequency higher than the final output frequency as a carrier to significantly reduce the size of the transformer used to insulate the isolation transformer between the gate circuit and the amplifying unit (distorter) 9 in the gate circuit 8. Doing.

By the signal supplied from the signal generator, the signal converter 2 generates a triangular wave corresponding to twice the output frequency and is supplied to the signal comparator 6. The signal converter 3 generates a square wave equal to the output frequency (inverter final output frequency) and is supplied to the gate logic circuit 7. At this time, the reference signal generator 4 generates a DC reference signal and is supplied to the error amplifier 5.

The pulse width corresponding to the difference between the two signals is generated in the signal comparator 6 in comparison with the output of the error amplifier 5 and the triangular wave of the signal converter 2. This signal is compared with the signal supplied from the signal converter 3 to generate a signal in the gate logic circuit 7 only when it is a positive signal of the same magnitude, and is supplied to the thyristor driver circuit 8. . At this time, the signal generator 1 also supplies carriers 10 to 30 KHZ to the thyristor driver 8. The two supplied signals are supplied to the thyristor 9 through an isolation transformer, and the thyristor 9 excites the primary winding of the transformer 10 to induce an output voltage on the secondary side of the transformer. At this time, the power required by the DC power supply (V _s ) 14 is supplied. The voltage induced on the secondary side of the transformer is supplied to the load 13 through the filter 11, at which time the output voltage of the filter 11 is detected and supplied to the feedback circuit 12. The supplied signal is changed into a DC voltage corresponding to the magnitude of the AC output voltage, and is supplied to the error amplifier 5. As a result, a closed loop is formed, and the DC voltage supplied from the reference signal generator 4 and the output voltage and error of the feedback circuit are amplified and supplied to the signal comparator 6. This is the basic principle of automatic output voltage adjustment. In particular, when the output voltage of the filter 11 is detected and its magnitude is larger or smaller than the reference voltage of the reference signal generator, the conduction section of the die thruster is controlled as shown in FIG. 11B to automatically control the voltage supplied to the load. Since the uninterruptible power supply according to the present invention is characterized in that it does not need a separate automatic voltage regulator unlike the conventional uninterruptible power supply in Figure 14b. FIG. 15 is a circuit diagram showing an embodiment of an inverter for an uninterruptible power supply according to the present invention.

As described above, the characteristics of the impulse reflux inverter according to the present invention are summarized as follows.

First, unlike the conventional method, there is no short circuit of the primary winding of the output transformer during the reflux operation.

Secondly, it is suitable for large power uninterruptible power supply.

Thirdly, the inverter output voltage is adjusted by controlling the conduction section of the thyristor, so that the automatic voltage regulator is included.

Fourth, the loss during reflux operation is very small, high efficiency operation is possible, and it is suitable for the constant voltage constant frequency [CVCF] type uninterruptible power supply.

Fifth, unlike the conventional inverter during reflux operation, there is no influence of the load power factor.

Sixth, since there is no short circuit during reflux operation, it is possible to improve the reliability of power devices (for example, the thyristor) and implement them at a low price, and unlike conventional inverters, it is easy to deal with overload or short circuit of load. Can protect the inverter.

Seventh, since the voltage waveform supplied to the load has less harmonic components than the conventional method, the filter size can be reduced.

Eighth, when used as an uninterruptible power supply, the number of power devices can be significantly reduced compared to the conventional method.

Ninth, three-phase (3 °) connection is easier than conventional methods.

Tenth, there is an advantage that the volume of the uninterruptible power supply is significantly reduced compared to the conventional method.

Claims (2)

In the impulse reflux type inverter, the thyristors T ₁ and T ₃ connected in series from the primary one terminal (a) of the transformer T to which the abutment load is connected to both ends of the secondary side, and are conducted in accordance with the second preferred input to their gate terminals. And a die Lister T ₂ and T ₄ connected in series from the primary terminal (b) of the transformer T and conducted in accordance with a control signal input to their gate terminal, and the die Lister T ₁ and T ₃ connection points and the die. A reflux capacitor C connected between the Lister T ₂ and T ₄ connection points, an energy storage primary side series inductor L connected from the die Listers T ₃ and T ₄ , and the primary side series inductor L and the transformer Diodes D ₁ and D ₂ respectively connected to both ends a and b of T, and the intermediate tap terminal c of the transformer T and the primary inductor L and diode, D ₁ , Secondary series Inductor L and a diode D ₅ is the impulse reflux inverter for an uninterruptible power supply, characterized in that consisting of the DC power supply V _s while a series connection being connected in parallel to its both ends. The impulse gliding inverter according to claim 1, wherein the die thrusters T ₃ and T ₄ are composed of elements having a faster switching speed than the die thrusters T ₁ and T ₂ .

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