JPH04312330A - Uninterruptible power supply - Google Patents

Abstract

PURPOSE:To sustain operation of a system regardless of starting surge current of load or overcurrent due to short circuit fault on the load side. CONSTITUTION:In an uninterruptible power supply normally fed with commercial power comprising a first load 2 to be fed with power from a commercial power supply 1 and a second load 8 to be directly fed with power through a direct supply circuit provided with a circuit breaker 7 when the commercial power supply 1 is normal while fed with power from a battery 5 through an inverter 6 upon interruption of the commercial power supply 1, the circuit breaker is constituted of a high speed circuit breaker 7 for instantaneously interrupting the load current at an arbitrary level lower than a predetermined level and a high speed switch 11 having higher overcurrent resistance than the high speed circuit breaker 7 and connected in parallel therewith. The high speed switch 11 can interrupt current at zero-cross point and can start current supply at an arbitrary time point. Furthermore, means 12 for turning the high speed switch 11 ON at the time of overcurrent is also provided.

Description

[Detailed description of the invention]

[Purpose of the invention]

0001

[Industrial Application Field] The present invention is applicable to an uninterruptible power supply system with a constant commercial power supply system that directly supplies load power through a high-speed breaker when the commercial power supply is normal. This invention relates to an uninterruptible power supply system with a constant commercial power supply system that operates in the event of an instantaneous overcurrent caused by a short-circuit accident on the side.

0002

[Prior Art] In recent years, a large number of distributed computers have been introduced for FA and OA, but uninterruptible power supplies are increasingly being used as a countermeasure against problems such as instantaneous voltage drops and power outages in commercial power supplies. ing. The basic methods of uninterruptible power supplies can be classified into two types: a continuous inverter power supply method and a continuous commercial power supply method.

[0003] The continuous inverter power supply method is a method in which commercial power is converted to direct current via a rectifier, and then reversely converted to alternating current by an inverter to supply power to the load. This method uses a storage battery connected to the DC circuit for backup. In this method, even when the commercial power supply is normal, power is always supplied to the load via the inverter, so the output is extremely stable. Conversely, even when the commercial power source is healthy, power is supplied to the load via two converters, a rectifier and an inverter, which has the disadvantage that the operating efficiency of the device deteriorates.

On the other hand, in the constant commercial power supply system, when the commercial power supply is normal, the commercial AC power supply is directly supplied to the load via a switch, and the inverter is stopped. In this method, in the event of an instantaneous voltage drop in the commercial power supply voltage or a power outage, the inverter is activated at the same time as the switch is turned off, and the power in the storage battery is reversely converted by the inverter to continue supplying power to the load. This method has drawbacks such as difficulty in detecting various power outage modes of commercial power sources, resulting in instantaneous interruptions in the output, and output characteristics being affected by AC input conditions, but this method is especially useful in places like Japan where the power supply situation is good. It is advantageous in terms of operational efficiency, small size, and low cost, and can be used satisfactorily for specific loads.

[0005] Next, the configuration of a conventional uninterruptible power supply system of a constant commercial power supply type will be explained using FIG. In the same figure, 1
is a commercial power supply, 2 is a first load connected in parallel to the uninterruptible power supply and directly connected to AC power supply 1, 3 is an isolation transformer,
4 is a charger that is composed of a thyristor and has a function of charging the storage battery 5 and can adjust the DC output voltage; 6 is an inverter that converts DC to AC; 7 is a high-speed breaker that is composed of transistors; and 8 is an uninterruptible power supply. A second load connected to the output of the device. Further, 9 is a current detector that detects the load current flowing through the second load, and 10 is an overcurrent protection circuit.

Next, the operation of an uninterruptible power supply system with a constant commercial power supply system will be explained with reference to FIG. 4. When the commercial power supply 1 is normal, power is supplied from the commercial power supply 1 to a relatively unimportant first load 2. However, power is supplied to the second load 8 that requires uninterrupted operation via the high-speed breaker 7, and the storage battery 5 is charged by the charger 4 via the isolation transformer 3. Next, when an instantaneous voltage drop or power outage occurs in the voltage of the commercial power supply 1 due to a lightning strike or a ground fault, a power outage detection circuit (not shown) instantly detects the power outage and at the same time sets the high-speed circuit breaker 7 to a non-conducting state. The inverter 6 is activated, the DC power of the storage battery 5 is reversely converted by the inverter 6, and the load power supply is continued, so that the second load 8 can be made uninterrupted.

Here, the high-speed breaker 7 between the commercial power supply 1 and the second load 8 is not a device such as a thyristor that switches at the zero point of the current, but a high-speed breaker such as a transistor that can quickly interrupt any current value. The reason for this is that the thyristor cannot be switched off for up to half a cycle due to the timing of a power outage in the commercial power supply 1, so power from the storage battery 5 is supplied to the second load 8 via the inverter 6, and Inverter 6, high speed breaker 7
This is because there is a period in which the power is reversely supplied and power is also supplied to the first load 2. Here, the load capacity of the second load 8 is selected in accordance with the capacity of the uninterruptible power supply, but the capacity of the first load 2 cannot be limited and is several tens of times the capacity of the device. This is because the inverter 6 will come to a protective stop due to overload during the maximum half cycle when the thyristor is turned off, considering the load capacity. In particular, when considering the configuration of the high-speed circuit breaker 7, semiconductor circuit breakers such as transistor circuit breakers, thyristor circuit breakers, and GTO circuit breakers are applied, but thyristor circuit breakers require a commutation circuit using an auxiliary thyristor; Since circuit breakers require gate circuits, transistor circuit breakers are used in large numbers because they are smaller, lighter, and more economical than uninterruptible power supplies with a capacity of several tens of kilowatts (KVA). There is.

[0008]

[Problem to be Solved by the Invention] Now, if we consider the startup of an uninterruptible power supply system that uses a transistor breaker as the high-speed circuit breaker 7 and uses a constant commercial power supply system, the startup is performed by switching the AC input (not shown). By closing the circuit, power supply to the second load 8 is started via the high-speed circuit breaker 7, but the second load 8 has a main load such as a computer. , the computer is a capacitor input type rectifying load, and generally when the power is turned on, a current of about 10 to 20 times the steady load capacity flows as a rush current to the load. Also, if a short circuit occurs in a part of the second load 8 while the commercial power supply 1 is supplying power to the second load 8, the short circuit current will reach several tens of times as much as the fuse. It is common to disconnect the short circuit by using another protection circuit that can disconnect the circuit in the event of an overcurrent such as a leak. However, since the high-speed breaker 7 between the commercial power supply 1 and the second load 8 is composed of a transistor, it is difficult to allow such a startup current or short-circuit current to flow due to the overcurrent withstand capacity of the transistor. This is not possible, and the overcurrent protection circuit 10 turns off the high-speed breaker 7 using the load current detection circuit 9 to provide protection such as preventing damage to the transistor. but,
Although it is possible to prevent damage to the transistor by turning off the high-speed breaker 7, the power supply to the second load 8 will be stopped, and the original purpose of the uninterruptible power supply, which is to provide uninterrupted operation of the load, will be lost. You will end up getting lost.

[0009] Therefore, the object of the present invention has been made in view of this point, and is to provide an uninterruptible power supply system with a constant commercial power supply system, which is designed to prevent instantaneous inrush current into the load at the time of device startup or due to a short circuit accident on the load side. To provide an uninterruptible power supply that does not stop power supply to a load even when an excessive current flows. [Structure of the invention]

0010

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a first load supplied with power from a commercial power source, and a direct power supply via a direct transmission circuit equipped with a breaker when the commercial power source is normal. In the uninterruptible power supply system of a constant commercial power supply type, which includes a second load that is supplied with power from a storage battery through an inverter during a power outage of the commercial power supply, the breaker is configured to reduce the load current to an arbitrary value below a predetermined value. A high-speed breaker that can shut off the current instantaneously depending on the current value is connected in parallel with a high-speed switch that can shut off when the current passes through the zero point and has a higher overcurrent tolerance than the high-speed breaker that can start flowing the current at any time. means for turning on the high-speed switch when the load current flowing through the second load exceeds a predetermined value; and means for turning on the high-speed switch when a voltage drop or power outage of the commercial power supply is detected. The device is characterized in that it is equipped with a means for turning off the power.

[0011]

[Function] According to the present invention, when the commercial power supply fails, the high-speed breaker is turned off to prevent reverse flow from the inverter to the first load on the commercial power supply side via the high-speed breaker. When power is being supplied directly from the commercial power source to the second load,
When a momentary overcurrent flows, the high-speed switch is turned on and the overcurrent is diverted from the high-speed breaker to the high-speed switch, allowing the uninterruptible power supply to continue operating without stopping. be.

0012

[Embodiment] An embodiment of the present invention will be described below with reference to FIG. Components in this figure that are given the same numbers as those in FIG. 4, which is an embodiment of the prior art, have the same functions, so their explanations will be omitted.

The difference between FIG. 1 and FIG. 4 is that a high-speed switch 11 is connected in parallel with a high-speed breaker 7, and an overcurrent detection circuit 12 is configured to enable on/off control of the high-speed switch 11. It is a point. An example of a detailed circuit of this overcurrent detection circuit 12 is configured as shown in FIG. Ru. Also, the other input of the comparator 123 has an overcurrent reference 1.
22, and the comparator 123 compares the magnitude of the two input signals. The output signal of the comparator 123 is input to the sequence control circuit 124 to control the operation mode of the uninterruptible power supply.
Block and deblock signals according to the code. That is, when the operation mode is commercial power supply, the signal is deblocked and the thyristor of the high speed switch 11 is fired via the gate amplifier 125, and when the operation mode is inverter power supply, the signal is blocked. The thyristor of the high-speed switch 11 is configured to be in an off state.

Next, the operation of the present invention will be explained with reference to FIG. The operation mode of the uninterruptible power supply is a commercial power supply mode in which power is supplied to the second load 8 from the commercial power supply 1 via the high-speed breaker 7, and the operation mode is a commercial power supply mode in which power is supplied to the second load 8 from the commercial power supply 1 via the high-speed breaker 7.
If a short-circuit accident occurs on the side, the load current rises rapidly at time t0, and the overcurrent detection circuit 12 rises at time t1.
When a predetermined current value I1 set by an internal overcurrent reference 122 is exceeded, the output of the comparator 123 is inverted and a firing signal is given to the thyristor of the high speed switch 11. Therefore, from time t1, the short-circuit current is supplied to the short-circuit location via the high-speed switch 11, so that the current of the high-speed breaker 7 can be suppressed to an extremely low level. On the other hand, the load branch circuit on the second load 8 side is equipped with an overcurrent protection function such as a fuse, and by supplying overcurrent to the short circuit point via the high speed switch 11, the short circuit is normally prevented. The point is disconnected from the main circuit for half to a few cycles. Here, assuming that the short circuit is disconnected within half a cycle, the current falls below the overcurrent reference 122 at time t2, and the firing command to the high-speed switch 11 is turned off. Since the thyristor is configured using a thyristor, the thyristor is turned off when the main current of the thyristor crosses zero.

As explained above, when the commercial power supply 1 has a power outage, the high-speed breaker 7 is turned off, and the inverter 6 supplies power to the first load 2 on the commercial power supply side via the high-speed breaker 7. In addition, in the event of a momentary overcurrent, a high-speed switch 11 connected in parallel with the high-speed breaker 7 is turned on, and the overcurrent is commutated from the high-speed breaker 7 to the high-speed switch 11. Therefore, if the configuration is configured with only a high-speed breaker as explained in the conventional example, the overcurrent capacity of the high-speed breaker 7 is small against instantaneous overcurrent, so the load power supply is stopped and the high-speed breaker There is no need to protect the switch 7, and it is possible to continue supplying power to the load via the high-speed switch 11 which has a large overcurrent tolerance against overcurrent.

[0016]

As explained above, according to the present invention, in an uninterruptible power supply system with a constant commercial power supply system, when a commercial power supply fails, the inverter supplies power to the first load on the commercial power supply side. A high-speed breaker is installed that can cut off the current at high speed to prevent reverse current flow, and in the event of a momentary overcurrent,
By igniting a high-speed switch with a large overcurrent capacity that is connected in parallel with the high-speed breaker, the overcurrent is diverted from the high-speed breaker to the high-speed switch side, reducing the inrush current to the load at the time of device startup and the load side. It is possible to provide an uninterruptible power supply device that can continue operation without stopping the operation of the system in response to an overcurrent caused by a short circuit accident.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention.

FIG. 2 is a block diagram showing a specific example of the overcurrent detection circuit in FIG. 1;

FIG. 3 is a time chart diagram for explaining the operation sequence of the uninterruptible power supply against overcurrent according to the present invention.

FIG. 4 is a block diagram of a conventional uninterruptible power supply system that uses commercial power supply all the time.

[Explanation of symbols]

1... Commercial power supply, 2... First load, 3... Isolation transformer, 4...
Charger, 5...Storage battery, 6...Inverter, 7...High speed breaker, 8...Second load, 9...Current detector, 10...Overcurrent protection circuit, 11...High speed switch, 12...Overcurrent detection circuit ,
121... Rectifier circuit, 122... Overcurrent reference, 123... Comparator, 124... Sequence circuit, 125... Gate amplifier circuit.

Claims (1)

[Claims] Claim 1: A first load supplied with power from a commercial power source; when the commercial power source is normal, power is directly supplied through a direct transmission circuit equipped with a breaker, and when the commercial power source is out of power, power from a storage battery is transferred through an inverter. In the uninterruptible power supply system of a constant commercial power supply type, which consists of a second load that is supplied with power by A high-speed switch having a higher overcurrent withstand capacity than the high-speed breaker, which can be cut off when the current flows through the second load and can start flowing the current at any time, is connected in parallel, and the load current flowing to the second load is An uninterruptible power supply characterized by comprising means for turning on the high-speed switch when a predetermined value is exceeded, and means for turning off the high-speed breaker when a voltage drop or power outage of the commercial power supply is detected. Device.