JPH0937564A - Uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a continuous supply of power to a load without a drop of output voltage or instantaneous cut of power by providing a power supply with an overcurrent controlling means which lowers the output current of an inverter in response to the output of a comparing means and a means which switches a switching circuit to the commercial power supply side. SOLUTION: A device has a comparing circuit 14 which determines whether the current of an inverter 4 reaches a preliminarily set current limit value, an overcurrent controlling circuit 15 which lowers the output current of the inverter 4 immediately after it is detected that the current of the inverter 4 exceeds the set current limit value and the inverter 4 comes to an overcurrent state, and a signal generating circuit 16 which turns on a semiconductor switch 11 when the inverter current reaches the current limit value. When the comparing circuit 14 detects an overcurrent state, the signal generating circuit 16 turns on the semiconductor switch 11 to allow power to be supplied from the commercial power supply. By this method, power is supplied to a load from the inverter until the inverter comes to its limitations and short power is supplied from the commercial power supply. Therefore, power can be continuously supplied to the load without stopping a converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply unit composed of a converter, an inverter and a switching circuit, and more particularly to an uninterruptible power supply unit capable of switching to a commercial power supply.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing an example of a conventional uninterruptible power supply device. In the figure, 1 is a commercial power source,
2 is an AC reactor, 3 is a converter, 4 is an inverter
, 5 is a smoothing capacitor, 6 is a control circuit, 7 is a current detector, 8 is an inverter transformer, 9 is a filter capacitor, 10 is a contactor, 11 is a semiconductor switch, and 12 is a load.

Generally, in the uninterruptible power supply, a storage battery is connected to these in parallel with the smoothing capacitor 5, but it is not shown here. Reactor 2, converter 3, inverter
The converter 4, the smoothing capacitor 5, the control circuit 6, the inverter transformer 8 and the filter capacitor 9 make up one set.

The contactor 10 and the semiconductor switch 11 are used to switch the power supply to the load 12 to either the converter 13 or the commercial power supply 1. Normally, the contactor 10 is connected to the converter 13 side, and the electric power of the load 12 is supplied through the converter 13. The converter 13 is a control circuit 6
Therefore, the commercial power source 1 is operating synchronously.

When the conversion device 13 is inspected for maintenance or when the conversion device 13 fails for some reason, the semiconductor switch 11 having no operation delay is ignited.
The power supply to the load 12 is wrapped by the conversion device 13 and the commercial power supply 1, and then the contactor 10 that has a delay in operation because it is a mechanical contact is switched from the conversion device 13 side to the commercial power supply 1 side.

When the converter 13 completes the failure recovery or maintenance inspection, the contactor 10 is switched from the commercial power source 1 side to the converter 13 side to wrap the power supply, and the semiconductor switch 11 is extinguished. Converter 1 from the commercial power source 1 side
It is returned to the 3 side and power is supplied to the load 12. With the operation of these examples, the power supply to the load is not interrupted. When it is detected that the overload is equal to or higher than a predetermined level during the period in which the conversion device 13 is supplying electric power, Japanese Patent No. 1750
No. 086 “Inverter protection method”, the semiconductor switch 11 is ignited and at the same time the thyristor in the converter 13 is varied in ignition phase so that the output voltage depends on the voltage of the commercial power supply 1. Then, the current is rapidly reduced to a predetermined level, and an overload current (start-up inrush current of a motor, a transformer, etc.) is supplied from the commercial power supply 1.

[0007]

However, in this method, although the converter 13 is not stopped, the load 12 is not fed, and the load 12 is fed only by the commercial power source 1. Therefore, the reliability as an uninterruptible power supply cannot be improved.

Further, since the means for reducing the inverter current is the firing angle control using the thyristor, the inverter current cannot be instantaneously reduced. In this method, the conversion device 1
The element forming the inverter 4 in 3 is a thyristor, and its firing angle is controlled to control the output voltage. When the converter 13 stops the power supply due to the overcurrent on the load side and switches to the commercial power source 1, the ignition angle control using the thyristor cannot perform high-speed switching of 3.3 ms (at HZ) or more. For example, even if an overcurrent is detected immediately after the 1-phase gate is turned on, the gate block (G
B) cannot be performed. Therefore, when switching to the commercial power source 1, a voltage drop on the load side of 3.3 ms width occurs. Therefore, in the worst case, due to this switching, a momentary interruption may occur and the UPS may not function.

According to the present invention, the conversion device is constituted by using an element such as an IGBT capable of high-speed switching as a switching element forming the inverter and using high-speed control such as PWM control for the inverter control. When 13 detects an overcurrent on the load side, it immediately performs gate blocking and switches to the commercial power supply 1. For example, the PWM control cycle is 7
If the frequency is kHz, the gate ON / OFF of each phase is 142
Since it is performed in .mu.s, the gate block is delayed by 142 .mu.s even when the overcurrent is detected immediately after switching. Compared with the ignition angle control (3.3 ms) used for the above thyristor control, the voltage drop on the load side is very small, and the influence of momentary interruption does not affect the load. Therefore, the object of the present invention was made in view of the above points,
Even when an overcurrent exceeding a predetermined level due to load application or a short circuit on the load side is detected while the converter 13 is supplying electric power, the inverter current is instantly narrowed to within a predetermined range, and IG capable of high-speed switching
P is composed of elements such as BT and control of the inverter.
By using high-speed control such as WM control, it is possible to suppress the flow of excessive current from the inverter and to turn on the thyristor switch of the switching circuit, so that the load voltage can be maintained and within one cycle of the output voltage. With the aim of providing an uninterruptible power supply that is also effective against short-time overcurrent, and that does not stop the converter and stop protection, and that can continue load power supply without output voltage drop or instantaneous interruption. To do.

[0010]

In order to achieve the above object, the present invention provides a converter for converting an alternating current supplied from a commercial power source into a direct current, and the converter. In the uninterruptible power supply unit configured to select the output of the converter composed of the inverter for converting the direct current into the alternating current and the commercial power supply by the switching circuit to supply power to the load, the current of the inverter Current detection means for detecting
Comparing means for detecting that the output of the current detecting means exceeds a predetermined value and becoming an overcurrent, and overcurrent controlling means for responding to the comparing means and reducing the output current of the inverter at the time of overcurrent, Means for switching the switching circuit from the converter side to the commercial power source side in response to the comparing means.

The invention according to claim 2 is a converter comprising a converter for converting an alternating current supplied from a commercial power source into a direct current and an inverter for converting a direct current of the converter into an alternating current. In an uninterruptible power supply in which either the output or the commercial power supply is selected by a switching circuit to supply power to a load, current detection means for detecting the current of the inverter and output of the current detection means Comparison means for detecting that an overcurrent has exceeded a predetermined value, overcurrent control means for responding to the comparison means to throttle the output current of the inverter at the time of overcurrent, and whether the inverter is powered. And a means for responding to the determining means and the comparing means for switching the switching circuit from the converter side to the commercial power source side under an overcurrent condition and a power running condition. Is characterized by.

Further, a third aspect of the present invention is a converter comprising a converter for converting alternating current supplied from a commercial power source into direct current and an inverter for converting direct current of the converter into alternating current. In an uninterruptible power supply in which either the output or the commercial power supply is selected by a switching circuit to supply power to a load, current detection means for detecting the current of the inverter and output of the current detection means Comparing means for detecting an overcurrent exceeding a predetermined value, overcurrent control means for responding to the comparing means to throttle the output current of the inverter at the time of overcurrent, and comparing means and the load. And a means for switching the switching circuit from the converter side to the commercial power source side in response to a load state change signal obtained before turning on or adding a load.

Further, the invention according to claim 4 is a converter for converting an alternating current supplied from a commercial power source into a direct current,
A plurality of converters each including an inverter for converting direct current of the converter into alternating current are connected in parallel, and the output of the plurality of converters connected in parallel and one of the commercial power supplies are selected by a switching circuit. In the uninterruptible power supply device configured to supply power to the load, each of the conversion devices detects current of the inverter and current detection means, and the output of the current detection means exceeds a predetermined value to generate an overcurrent. And comparing means for detecting that the output current of the inverter is reduced when an overcurrent occurs in response to the comparing means, and the output of each of the comparing means is applied to a plurality of units. Of the inverters, a means for switching the switching circuit from the plurality of conversion devices connected in parallel to the commercial power supply side when more than half of the inverters are in an overcurrent state is provided. To do.

[0014]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing an embodiment of the invention described in claim 1. Components having the same functions as those in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 1 shows a comparison circuit 14 for determining whether or not the current of the inverter 4 has reached a preset current limit value in FIG. 6, and the current of the inverter 4 has a preset current limit value. When the overcurrent condition is exceeded, the comparison circuit 1
4, an overcurrent control circuit 15 that instantaneously throttles the output current of the inverter 4 when it is detected, and a signal for turning on the semiconductor switch 11 when the inverter current reaches the current limit value. A signal generating circuit 16 for generating is added.

The comparison circuit 14 detects that the inverter current detected by the current detector 7 is within the current limit value.
Further, the overcurrent control circuit 15 performs overcurrent control for instantaneously reducing the inverter current. This is, for example, the control circuit 6
Among them, when the voltage control or the current control is performed by PI control, it has a function of holding this integration operation for a certain period. When the comparison circuit 14 is in the overcurrent detection state, the signal generation circuit 16 turns on the semiconductor switch 11 so that power can be supplied from the commercial power supply 1.

Of the load current from the commercial power source 1 at the time of overload,
The load voltage is maintained by the commercial power source 1 and the converter 13 is not stopped by making it possible to supply the power shortage with respect to the inverter current. By this operation, the inverter 4 loads the load 12 up to the current of the limit capacity.
Power is supplied to the load 12, and the shortage is supplied from the commercial power supply 1. Therefore, the power supply to the load 12 can be continued without stopping the conversion device 13, and the power as an uninterruptible power supply device can be obtained. The reliability of supply can be improved.

Next, an embodiment of the invention described in claim 2 will be described with reference to FIG. 2 in which the same parts as those in FIG. In FIG. 2, a comparison circuit 1 for determining whether or not the current of the inverter 4 has reached a preset current limit value.
4, an overcurrent control circuit 15 that instantaneously throttles the inverter current when the current is excessive, and a determination circuit 17 that determines whether the inverter current is running or regenerated under the conditions of the inverter current throttling.
A signal generation circuit 1 for turning on the semiconductor switch 11 when the inverter current reaches the current limit value and the inverter 4 is in power running.
6 is provided.

According to the second aspect of the present invention configured as shown in FIG. 2, the current of the inverter 4 is detected by the current detector 7 to determine whether the power from the inverter 4 to the load 12 is power running or regenerative. When the electric power is regenerated from the load 12 to the converter 13 side by the determination circuit 17, the signal that does not turn on the semiconductor switch 11, the semiconductor switch is supplied only when the electric power is supplied from the inverter 4 to the load 12. A signal for turning on 11 is output. The signal generating circuit 16 sets the semiconductor switch 11 in a state in which power can be supplied from the commercial power source 1 side only when the inverter current reaches the current limit value and the inverter current flows from the inverter 4 to the load 12. . In the power running state from the inverter 4 to the load 12, the circuit becomes equivalent to the circuit of FIG. 1 and the same effect can be expected.

FIG. 3 is a block diagram showing another embodiment of the invention described in claim 2. In FIG. In the embodiment of FIG. 2, whether the inverter 4 is in power running or regenerative is determined by detecting the output current of the inverter 4, but as shown in FIG. 3, the input current of the load 12 is detected. The same effect can be obtained even if it is performed.

The load detector 12 detects the current of the load 12 by the current detector 18, and the load current is transferred from the load 12 to the converter 13 side by the judgment circuit 19 which judges whether the power from the converter 13 to the load 12 is power running or regenerative. Is being regenerated, a signal for not turning on the semiconductor switch 11 and a signal for turning on the semiconductor switch 11 are sent to the signal generating circuit 16 only when power is being supplied from the converter 13 to the load 12. In the signal generation circuit 16, the inverter current reaches the current limit value,
Moreover, only when the load current flows from the converter 13 to the load 12, the semiconductor switch 11 is brought into a state in which power can be supplied from the commercial power source 1 side. In the powering state from the converter 13 to the load 12, the circuit becomes equivalent to the circuit of FIG. 1 and the same effect can be expected.

Next, an embodiment of the invention described in claim 3 will be described with reference to FIG. 4, in which the same parts as those in FIG. In FIG. 4, a comparison circuit 1 for determining whether or not the current of the inverter 4 has reached a preset current limit value.
In response to the comparator circuit 14, the inverter 4 responds to the overcurrent control circuit 15 and the comparator circuit 14 which instantaneously reduce the inverter current when the current of the inverter 4 is in the overcurrent state.
Determination circuit 21 which gives a command signal for turning on the semiconductor switch 11 to the signal generation circuit 16 when the current reaches the current limit value and is in an overcurrent state. A load state change signal obtained before turning on or additional turning on of the load 12 is applied.

According to the third aspect of the present invention configured as described above, when the inverter 4 is in the overcurrent state, the semiconductor switch 11 is turned on. Is applied to the determination circuit 21, the load 12 is then turned on or additionally turned on. Therefore, at that time, if the semiconductor switch 11 is turned on in advance, an excessive starting current is generated from the commercial power source 1. Can be supplied.

Next, an embodiment of the invention described in claim 4 will be described with reference to FIG. 5, in which the same parts as those in FIG. In FIG. 5, a comparator circuit 14a for determining whether or not the current of the inverter 4a has reached a preset current limit value, an overcurrent control circuit 15a for instantaneously reducing the inverter current when the current is excessive, and an inverter. When the output currents of the inverters 4a, 4b ... Are received by the signal generation circuit 16a which turns on the semiconductor switch 11 when the output current reaches the current limit value and the outputs of the respective signal generation circuits 16a, 16b. A majority circuit 20 is provided for turning on the semiconductor switches 11 when more than half are in the state of turning on the semiconductor switches 11.

According to the invention of claim 4 configured as shown in FIG. 5, the decision circuit 20 receives the outputs from the respective signal generating circuits 16a, 16b ... From the respective inverters 4a, 4b. The semiconductor switch 11 is turned on when the semiconductor switch 11 is turned on. However, when the number is less than half, the semiconductor switch 11 is not turned on by compensating the current with the other conversion device 13 in parallel operation.
When a plurality of converters 13 are operating in parallel and more than half of them are in the state of turning on the semiconductor switch 11, the circuit becomes equivalent to the circuit of FIG. 1 and the same effect can be expected.

[0026]

As described above, according to the inventions of claims 1 to 4, when the inverter current of the power supply system is detected and the inverter current reaches the current limit value, the instant By performing the current drooping control and turning on the semiconductor switch to supply power from the commercial power supply, high-performance power conversion can be performed without stopping the power supply from the conversion device.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an uninterruptible power supply device according to the invention described in claim 1.

FIG. 2 is a configuration diagram showing an embodiment of the uninterruptible power supply device of the invention according to claim 2;

FIG. 3 is a configuration diagram showing another embodiment of the uninterruptible power supply device according to the present invention.

FIG. 4 is a configuration diagram showing an embodiment of the uninterruptible power supply device of the invention according to claim 3;

FIG. 5 is a configuration diagram showing an embodiment of the uninterruptible power supply device of the invention according to claim 4;

FIG. 6 is a configuration diagram showing a conventional uninterruptible power supply.

[Explanation of symbols]

1 ... Commercial power supply 2 ... AC reactor 3 ... Converter 4 ... Inverter 5 ... Smoothing capacitor 6 ... Control circuit 7 ... Current detector 8 ... Inverter transformer 9 ... Filter capacitor 10 ... Contactor 11 ... Semiconductor switch 12 ... Load 13 ... Conversion Device 14 ... Comparison circuit 15 ... Overcurrent control circuit 16 ... Signal generation circuit 17 ... Judgment circuit 18 ... Load current detector 19 ... Judgment circuit 20 ... Majority decision circuit 21 ... Judgment circuit

Claims (4)

[Claims] 1. A converter for converting an alternating current supplied from a commercial power supply into a direct current, and an output of a conversion device including an inverter for converting a direct current of the converter into an alternating current, and any one of the commercial power supply. In the uninterruptible power supply device which is selected by the switching circuit to supply power to the load, current detecting means for detecting the current of the inverter, and the output of the current detecting means exceeds a predetermined value to cause an overcurrent. Comparing means for detecting that the output current of the inverter is reduced when an overcurrent is responsive to the comparing means, and the switching circuit is responsive to the comparing means from the conversion device side to the above An uninterruptible power supply characterized by comprising means for switching to a commercial power supply side. 2. A converter for converting an alternating current supplied from a commercial power source into a direct current and an inverter for converting a direct current of the converter into an alternating current, and one of the commercial power source. In the uninterruptible power supply device which is selected by the switching circuit to supply power to the load, current detecting means for detecting the current of the inverter, and the output of the current detecting means exceeds a predetermined value to cause an overcurrent. Comparing means for detecting that the output current of the inverter is reduced in response to the comparing means, and an overcurrent control means for reducing the output current of the inverter at the time of overcurrent;
Determining means for determining whether the power is running or regenerating, and means for responding to the determining means and the comparing means, switching the switching circuit from the converter side to the commercial power source side under an overcurrent condition and a power running condition. An uninterruptible power supply characterized by having. 3. A converter for converting an alternating current supplied from a commercial power source into a direct current, and an output of a converter comprising an inverter for converting the direct current of the converter into an alternating current, and any one of the commercial power sources. In the uninterruptible power supply device which is selected by the switching circuit to supply power to the load, current detecting means for detecting the current of the inverter, and the output of the current detecting means exceeds a predetermined value to cause an overcurrent. Comparison means for detecting that the output current of the inverter has been reduced in response to the comparison means, and an overcurrent control means for reducing the output current of the inverter, and before the comparison means and the load are turned on or additional loads are turned on. And a means for switching the switching circuit from the converter side to the commercial power source side in response to the load state change signal obtained in FIG. 4. A plurality of converters connected in parallel, each of which is composed of a converter for converting an alternating current supplied from a commercial power source into a direct current and an inverter for converting the direct current of the converter into an alternating current, and the parallel connection. In the uninterruptible power supply device in which the output of the plural converters and one of the commercial power supplies are selected by the switching circuit to supply power to the load, each converter converts the current of the inverter. A current detecting means for detecting, a comparing means for detecting that the output of the current detecting means exceeds a predetermined value and becomes an overcurrent, and an output current of the inverter at the time of overcurrent in response to the comparing means. The switching circuit is connected in parallel when the output of each of the comparison means is applied, and more than half of the plurality of inverters are in an overcurrent state. Commercial power supply from multiple converters An uninterruptible power supply comprising a means for switching to the side.