JPH04108390U - sine wave power supply - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent destruction of a pulse width modulation type inverter and its peripheral elements during overload without increasing the rated capacity of the pulse width modulation type inverter. [Structure] A switch element that short-circuits the output terminal of the pulse width modulation type inverter 7 is provided with a protection circuit 20 that makes the reference voltage for pulse width modulation zero with a small time constant when the sine wave AC power supply 1 becomes overloaded. 22, and a switch element control means 23 for making the switch element 22 conductive when the sine wave AC power source 1 becomes overloaded. [Effect] When the sine wave AC power supply 1 becomes overloaded,
The generation of the compensation voltage from the pulse width modulation type inverter 7 is temporarily stopped to prevent the pulse width modulation type inverter 7 from being overloaded. The output terminal of the pulse width modulation type inverter 7 is short-circuited and the pulse width modulation type inverter 7 is connected through the series injection transformer 4.
Prevent excessive current from flowing into.

Description

[Detailed explanation of the idea]

0001

[Industrial application field]

This idea is based on a sine wave generated by a commercial AC power supply or a large-capacity inverter device. A small capacity (about 1/10 of the rated capacity) is connected between the AC power supply and the load via a series injection transformer. ) is inserted and connected to the pulse width modulation type inverter to eliminate voltage fluctuations and distortion of the sine wave AC power supply. compensation, and supplies the rated voltage to the load regardless of voltage fluctuations or distortion of the sine wave AC power supply. This invention relates to a sine wave power supply device.

0002

[Conventional technology]

FIG. 3 shows a block diagram of an example of a conventional sine wave power supply device, and FIG. 4 shows a specific circuit diagram of a pulse width modulation type inverter, which is one of the components of the sine wave power supply device. As shown in FIG. 3, a conventional sine wave power supply device has a sine wave AC power supply 1 consisting of a commercial AC power supply or a large-capacity inverter device, a first winding _n1 of a series injection transformer 4, and a load switching circuit. A load 3 is connected via a switch 2. Both output terminals of a pulse width modulation type inverter (voltage type) 7 are connected to the second winding n ₂ of the series injection transformer 4 via a filter capacitor 5 and a filter reactor 6.

The DC power supplied to the pulse width modulation type inverter 7 is obtained by stepping down the voltage of a commercial AC power supply (not shown) with a transformer 10 , rectifying it with a full-wave rectifier 9 , and smoothing it with a DC capacitor 8 . I am gaining from this. Switching control of the pulse width modulation type inverter 7 is performed by an inverter control circuit 13 (which serves as an inverter control means). For example, as shown in FIG. 4, the pulse width modulation type inverter 7 includes four switching elements Q ₁ to Q 4 connected in a bridge type and diodes D 1 to D ₄ connected in antiparallel to the switching elements Q ₁ to Q ₄ .

0004 Then, this sine wave power supply device outputs power based on a command from the inverter control circuit 13. By the pulse width modulation type inverter 7 performing switching, the DC capacitor 8 The voltage fluctuation and distortion of the sine wave AC power supply 1 is controlled by using the DC voltage obtained at both ends of the It will output a voltage that compensates for the This voltage is applied by the series injection transformer 4. It is added to the voltage of the sine wave AC power supply 1 and is applied to the load 3.

[0005] The output voltage of the pulse width modulation type inverter 7 is controlled as follows. Ru. In other words, the voltage of the sine wave AC power supply 1 is detected through the voltage detection transformer 11. It will be done. Based on the secondary voltage of this transformer 11, the synchronous reference sine wave generation circuit 14 Synchronized with the voltage of the sine wave AC power supply 1 and corresponding to the rated voltage of the sine wave AC power supply 1 Generates a reference sine wave voltage. Then, in the arithmetic unit 19, from the reference sine wave voltage, To reduce the secondary voltage of the transformer 11 (corresponding to the current voltage of the sine wave AC power supply 1) Create a reference voltage for pulse width modulation.

[0006] The reference voltage for pulse width modulation is supplied to one of the comparators 18 through the multiplier 16. is applied to the other input terminal. The other input terminal of the comparator 18 is connected to a triangular wave generation circuit. A triangular wave voltage from 17 is applied. The comparator 18 is a reference lens for pulse width modulation. The pulse width modulation type inverter 7 can be configured by comparing the voltage of the pulse width modulation and the triangular wave voltage. A switching signal is generated to turn on and off the switching elements that constitute the switching element. The pulse width modulation type inverter 7 switches the switching elements based on the switching signal. By turning on and off the DC voltage obtained across the DC capacitor 8. As a source, it generates a compensation voltage corresponding to voltage fluctuations and distortion of the sine wave AC power supply 1, and Keep the voltage applied to 3 at the rated value.

[0007] Note that this compensation voltage is applied to the filter reactor 6 and the filter capacitor. 5, the carrier frequency component (triangular wave voltage frequency) during pulse width modulation is After the wave number components) are removed, the voltage of the sinusoidal AC power supply 1 is increased through the series injection transformer 4. is applied to the load 3 in a superimposed manner. Next, in this sine wave power supply, a protection circuit that protects against overload is introduced. The road 20 (which serves as a protection means) will be explained. Series injection change from sine wave AC power supply 1 The load current supplied to the load 3 through the voltage generator 4 and the switch 2 is It is detected by the flow device 12. The overload detector 15 presets the secondary output of the current transformer 12. The secondary output of current transformer 12 is within the range of positive and negative thresholds. (normal state), the switch 21 is kept switched to the a side.

At this time, the capacitor C is fully charged through the resistor R ₁ with a voltage of 1 pu, the voltage across the capacitor C is 1 pu, and the multiplier input to the multiplier 16 is 1.0. Therefore, the above-mentioned reference voltage for pulse width modulation is multiplied by 1.0 by the multiplier 16 and input to the comparator 18, which is the same state as if the multiplier 16 were not provided.

However, when an overcurrent flows through the load 3 for some reason and its value exceeds the threshold value described above, the overload detector 15 switches the switch 21 to the b side. As a result, the accumulated charge in capacitor C is discharged through resistor _R2 . At this time, since a resistor _R2 with a relatively small resistance value (small time constant) is used, the voltage of the capacitor C, that is, the input voltage to the multiplier 16, is as shown in FIG. , 1pu quickly drops to a voltage of 0pu.

0010 Therefore, an overcurrent flows through the load 3, which causes the voltage of the sine wave AC power supply 1 to drop. When the pulse width modulation is input to the multiplier 16 to compensate for the drop, The reference voltage increases, but the pulse input from the multiplier 16 to the comparator 16 increases. The reference voltage for pulse width modulation quickly becomes 0pu, and the pulse width modulation type inverter To prevent the output voltage of the inverter 7 from becoming zero and the pulse width modulation type inverter 7 to become overloaded. prevention and protection.

On the other hand, when the overcurrent to the load 3 disappears, the overload detector 15 returns the switch 21 to the a side. As a result, a voltage of 1 pu charges capacitor C through resistor R ₁ . At this time, since a resistor _R1 with a relatively large resistance value is used (large time constant), the voltage of the capacitor C, that is, the input voltage to the multiplier 16, is as shown in FIG. , the voltage gradually increases from 0 pu to 1 pu, and the pulse width modulation type inverter 7 returns to normal operation.

0012

[Problem that the idea aims to solve]

In the conventional sine wave power supply device as described above, the load 3 is a capacitor input rectifier ( (personal computer, etc.), immediately after turning on switch 2, the rated current is 2 A current with a peak value of ~3 times flows. At this time, the signal input to the comparator 18 Even if the reference voltage for pulse width modulation is zero, the peak value of overcurrent will be If it is large, the current flowing into the pulse width modulated inverter 7 through the series injection transformer 4 will increase. The breaker built into the pulse width modulated inverter 7 is triggered by an overcurrent trip due to the current. If the pulse width modulation type inverter 7 stops operating due to the The problem is that there is no.

For this reason, conventionally, the rated capacities of the switching elements Q ₁ to Q ₄ and the diodes D ₁ to _{D 4} constituting the pulse width modulation type inverter 7 are set large, so that the rating of the pulse width modulation type inverter 7 is effectively reduced. We have dealt with this by making it bigger. However, with such a measure, the switching elements Q ₁ to Q ₄ and the diodes D ₁ to D ₄ become expensive, and their losses also increase, resulting in problems in terms of economic efficiency.

Furthermore, when a short-circuit failure occurs on the load 3 side, an extremely large current flows from the sine wave AC power supply 1 to the load 3 through the series injection transformer 4, but this current is pulsed from the series injection transformer 4. It flows into the width modulation type inverter 7. At this time, even if the breaker built into the pulse width modulation type inverter 7 trips overcurrent, the current is passed through the freewheeling diodes D ₁ to _{D 4} connected in antiparallel to the switching elements Q ₁ to _{Q 4} to the DC capacitor 8. The voltage flows into the DC capacitor 8 and increases the voltage of the DC capacitor 8. As a result, there is a risk that the DC capacitor 8 itself or the switching elements Q ₁ to Q ₄ etc. may be destroyed.

[0015] Therefore, the purpose of this invention is to increase the rated capacity of pulse width modulated inverters. To prevent damage to pulse width modulated inverters and their peripheral elements during overload without causing damage. It is an object of the present invention to provide a sine wave power supply device that can prevent damage.

[0016]

[Means to solve the problem]

The sine wave power supply device of this invention uses a series injection transformer between the sine wave AC power source and the load. The first winding of the series injection transformer is inserted into the second winding of the series injection transformer. Both output terminals of the converter are connected. In addition, the pulse width corresponds to the voltage difference between the voltage of the sine wave AC power source and the reference sine wave voltage. Controlling a pulse width modulation type inverter based on the modulation reference voltage This compensates for voltage fluctuations and distortions in the sine wave AC power supply and maintains the voltage applied to the load at the rated value. Inverter control that generates a compensation voltage across the first winding of a series injection transformer We have measures in place.

[0017] Furthermore, by detecting the load condition of the sine wave AC power supply, the sine wave AC power supply can be When an overload occurs, the reference voltage for pulse width modulation is set to zero, and the sine The reference voltage for pulse width modulation is returned to its original state when the overload of the wave AC power source is removed. Protective measures have been put in place to restore the condition. Additionally, a switch element is installed to short-circuit both output terminals of the pulse width modulation type inverter. A switch that makes the switching element conductive when the sine wave AC power supply becomes overloaded. Element control means is provided.

[0018]

[Effect]

According to the configuration of this invention, when the sine wave AC power supply is overloaded, the protection means will operate. to quickly bring the reference voltage for pulse width modulation to zero, and also turn off the switch element. The slave control means operates to make the switch element conductive. Reference for pulse width modulation The zero voltage causes the generation of compensation voltage from the pulse width modulated inverter. A pause prevents overloading of the pulse width modulated inverter. Also, switch The output terminal of the pulse width modulation type inverter is short-circuited by the conduction of the Excessive current flows into the pulse width modulated inverter through the series injection transformer, resulting in DC This prevents the voltage across the capacitor from becoming excessive.

[0019] Once the overload condition of the sine wave AC power supply is resolved, the reference voltage for pulse width modulation returns to its original voltage, the switch element shuts off again, and the pulse width modulated inverter compensation operation is resumed.

[0020]

【Example】

An embodiment of this invention will be described based on FIGS. 1 and 2. This sine wave power supply As shown in Figure 1, there is a short circuit between both output terminals of the pulse width modulation type inverter switch element (anti-parallel connection circuit of two thyristors) 22 is connected, and a capacitor is connected. When the voltage across the capacitor C drops from 1.0 pu to, for example, 0.8 pu, turn on command signal At the same time, the voltage across capacitor C rises from 0pu to 0.1pu. A switch element control circuit (switch element control circuit) that stops generating the ON command signal when 23 (which acts as a control means) and an amplifier circuit 24 that amplifies the ON command signal. The ignition signal is supplied to the switch element 22 by the ignition command signal. Ru. Other configurations are similar to the conventional example shown in FIG.

[0021] Here, the operation of this sine wave power supply device will be explained. In this sine wave power supply device, the sine wave AC power supply 1 is normally operated (when not overloaded). ) pulse width modulation type inverter 7, its peripheral circuits, and inverter control circuit The voltage fluctuation/distortion compensation operation by the line 13 is the same as in the conventional example. Next, the protection circuit 20 and the switch element 22 during overload of the sine wave power supply device The operation of the switch element control circuit 23 will be explained with reference to FIG.

A load current supplied from the sine wave AC power supply 1 to the load 3 through the series injection transformer 4 and the switch 2 is detected by a current transformer 12 for current detection. The overload detector 15 compares the secondary output of the current transformer 12 (see FIG. 2(a)) with preset positive and negative thresholds L ₁ and L ₂ and determines whether the secondary output of the current transformer 12 is When it is within the range of positive and negative thresholds L ₁ and L ₂ (normal state), the switch 21 is kept switched to the a side.

At this time, the capacitor C is fully charged through the resistor R ₁ with a voltage of 1 pu, the voltage across the capacitor C is 1 pu, and the multiplier input to the multiplier 16 is 1.0. Therefore, the reference voltage for pulse width modulation mentioned above is input to the comparator 18 which is multiplied by 1.0 by the multiplier 16. This is the same state as (see FIG. 2(c)). Further, at this time, the switch element control circuit 23 does not generate the ON command signal (see FIG. 2(d)).

However, for some reason, an overcurrent flows through the load 3, and the secondary output of the current transformer 12 falls outside the range of the thresholds L ₁ and L ₂ as shown in FIG. 2(a). At a time (time t ₀ ), the overload detector 15 switches the switch 21 to the b side. As a result, the accumulated charge in capacitor C is discharged through resistor _R2 . At this time, since a resistor R ₂ with a relatively small resistance value is used (the time constant is small), the voltage of the capacitor C, that is, the input voltage to the multiplier 16 is as shown in FIG. 2 (b). As shown, the voltage quickly drops from 1 pu to 0 pu.

[0025] Therefore, an overcurrent flows through the load 3, which causes the voltage of the sine wave AC power supply 1 to drop. When the drop occurs, the pulse width modulation level of the output of the arithmetic unit 19 is used to compensate for the drop. Although the reference voltage increases, the pulse width input from the multiplier 16 to the comparator 16 The modulation reference voltage quickly becomes 0pu, as shown in Figure 2(c), and the The output voltage of the pulse width modulation type inverter 7 becomes zero, and the pulse width modulation type inverter 7 To prevent and protect the equipment from being overloaded.

Furthermore, when the voltage across the capacitor C, that is, the input voltage to the multiplier 16 begins to drop, the switch element control circuit 23 controls the voltage to decrease to 0.8 pu, as shown in FIG. 2(d). At the time of falling (time t ₁ ), an ON command signal is generated, the switching element 22 is made conductive, and both output terminals of the pulse width modulation type inverter 7 are short-circuited. This prevents current from flowing from the first winding n ₁ to the second winding n ₂ of the series injection transformer 1, and prevents the diode D ₁ forming the pulse width modulated inverter 7 from flowing into the second winding n 2 . - Prevents DC capacitor 8 from being charged through _D4 .

On the other hand, when the overcurrent to the load 3 disappears (time t ₂ ), the overload detector 15 returns the switch 21 to the a side. As a result, a voltage of 1 pu charges capacitor C through resistor R ₁ . At this time, since a resistor _R1 with a relatively large resistance value is used (large time constant), the voltage of the capacitor C, that is, the input voltage to the multiplier 16, is as shown in FIG. 2(b). As shown, the voltage gradually increases from 0 pu to 1 pu. Therefore, the reference voltage for pulse width modulation also gradually returns to its original amplitude as shown in FIG. 2(c). At this time, when the input voltage to the multiplier 16 exceeds 0.1 pu (time t ₃ ), the generation of the ON command signal from the switch element control circuit 23 stops as shown in FIG. 2(d), and the switch The gate signal to the element 22 is cut off, the switch element 22 is then self-extinguished, and the pulse width modulation type inverter 7 returns to normal operation. Note that in FIG. 2(c), the broken line indicates the reference voltage for pulse width modulation on the input side of the multiplier 16.

[0028] The sine wave power supply device of this embodiment has power when the sine wave AC power supply 1 is overloaded. A protection circuit 20 is provided to make the reference voltage for pulse width modulation zero, and the pulse width modulation type A switch element 22 is provided to short-circuit the output end of the inverter 7, and the sine wave AC power supply 1 is Switch element control means 23 that makes the switch element 22 conductive when overload occurs. is provided, so when the sine wave AC power supply 1 is overloaded, the pulse width modulation Immediately bring the reference voltage to zero and make the switch element 22 conductive. be able to.

[0029] Therefore, generation of the compensation voltage from the pulse width modulation type inverter 7 is temporarily stopped. , prevents overload of the pulse width modulation type inverter 7, and also prevents the pulse width modulation type inverter 7 from overloading. The output end of the inverter 7 is short-circuited and the pulse width modulated input is connected through the series injection transformer 4. It is possible to prevent excessive current from flowing into the inverter 7, and also It is possible to prevent the voltage across the sensor 8 from becoming excessive. As a result, the pulse width changes Pulse width modulation type during overload without increasing the rated capacity of the adjustable inverter 7 This can prevent damage to the inverter 7 and the DC capacitors 8, etc. around it. Ru. Therefore, a compact device can be realized.

[0030] In addition, in the above embodiment, the switch element 22 is a normal reverse blocking three-terminal silicate switch. Although we used a gate turn-off thyristor, power transistors, etc. can also be used. In this case, forced extinguishing is possible, so it is possible to simultaneously extinguish the ON command signal. The switch element 22 can be cut off at any time.

[0031]

[Effect of the idea]

According to the sine wave power supply device of this invention, when the sine wave AC power supply becomes overloaded, A protection means is provided to reduce the pulse width modulation reference voltage to zero, and the pulse width modulation type A switch element is installed to short-circuit the output end of the inverter to prevent the sine wave AC power supply from overloading. Since the switch element control means is provided to make the switch element conductive when the Zero the reference voltage for pulse width modulation when the sine wave AC power supply is overloaded. At the same time, the switch element can be made conductive.

[0032] Therefore, generation of compensation voltage from the pulse width modulated inverter is temporarily suspended. It prevents overloading of pulse width modulated inverters and Short-circuit the output of the converter and pass it through the series injection transformer to the pulse-width modulated inverter. It can prevent large currents from flowing in, and also reduce the voltage across the DC capacitor. can be prevented from becoming excessive.

[0033] As a result, overloads can be handled without increasing the rated capacity of the pulse width modulated inverter. This prevents damage to the pulse width modulated inverter and its surrounding elements during loading. can. Therefore, a compact device can be realized.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a sine wave power supply device according to an embodiment of the present invention.

FIG. 2 is a time chart of each part of the sine wave power supply device shown in FIG. 1;

FIG. 3 is a block diagram showing the configuration of a conventional example of a sine wave power supply device.

FIG. 4 is a circuit diagram showing a specific configuration of an inverter.

FIG. 5 is a time chart showing changes over time in an input signal to a multiplier.

[Explanation of symbols]

1 Sine wave AC power supply 2 switch 3 Load 4 Series injection transformer 5 Filter capacitor 6 Filter reactor 7 Pulse width modulation inverter 8 DC capacitor 9 Full wave rectifier 10 Transformer 11 Transformer 12 Current transformer 13 Inverter control circuit 14 Synchronous reference sine wave generation circuit 15 Overload detector 16 Multiplier 17 Triangle wave generator 18 Comparator 19 Arithmetic unit 20 Protection circuit 21 Switch 22 Switch element 23 Switch element control circuit

──────────────────────────────────────────────── ─── Continued from front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H02M 7/48 F 8730-5H

Claims (1)

[Scope of utility model registration request] 1. A first winding of a series injection transformer is inserted and connected between a sine wave AC power supply and a load, and both outputs of a pulse width modulation type inverter are connected to a second winding of the series injection transformer. of the sine wave AC power source by connecting the terminals and controlling the pulse width modulation type inverter based on the pulse width modulation reference voltage corresponding to the voltage difference between the voltage of the sine wave AC power source and the reference sine wave voltage. an inverter control means for generating a compensation voltage across the first winding of the series injection transformer to compensate for voltage fluctuations and distortions and maintain the voltage applied to the load at the rated value; By detecting the load state of the sine wave AC power source, when the sine wave AC power source becomes overloaded, the reference voltage for pulse width modulation is set to zero, and when the overload of the sine wave AC power source is eliminated, the pulse width modulation is performed. The sine wave power supply device is provided with a protection means for restoring the reference voltage to the original state, and a switch element is provided to short-circuit both output terminals of the pulse width modulation type inverter, so that the sine wave AC power supply is prevented from overloading. A sine wave power supply device comprising a switch element control means for making the switch element conductive when the switch element is turned on.