JPH04368436A - Protective circuit for uninterruptible power supply system - Google Patents

Abstract

PURPOSE:To prevent the effect of an accident on a sound machine by inserting a diode polarity blocking currents in the direction of a common battery from a DC intermediate circuit. CONSTITUTION:When a smoothing capacitor 14 is short-circuited, short circuit currents are made to flow through a short-circuit point from a common battery 2, the short circuit currents are detected by a first current detector 18, and a battery breaker 17 is tripped. A first unintrruptible power equipment 30 is detached from a sound second uninterruptible power equipment 40 and the common battery 2. The voltage of the common battery 2 drops during a time when the short circuit currents are made to flow, but a reverse blocking diode 41 obstructs the flowing of currents through the short-circuit point from the second uninterruptible power equipment 40. Accordingly, the effect of an accident on the sound uninterruptible power equipment can be prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit for an uninterruptible power supply when a plurality of uninterruptible power supplies are operated in parallel by connecting backup batteries in common.

0002

[Prior Art] Fig. 3 is a circuit diagram showing a conventional example of a protection circuit for an uninterruptible power supply equipped with a common battery and operated in parallel. be. In this FIG. 3, the first uninterruptible power supply 10
is a thyristor rectifier 13 as a second power conversion means,
The main components include a smoothing capacitor 14, a transistor inverter 15 as a first power conversion means, and a filter 16 to convert AC power from an AC power supply 11 into AC power of a constant voltage and constant frequency, and to use this AC power as a common source. The DC intermediate circuit that connects the DC side of the thyristor rectifier 13 and the DC side of the transistor inverter 15 includes, in addition to the smoothing capacitor 14, a battery breaker 17 and a first A series circuit with the current detector 18 is connected, and the common battery 2 is connected through this series circuit. The second uninterruptible power supply 20 also has a thyristor rectifier 23 as a second power conversion means, a smoothing capacitor 24, a transistor inverter 25 as a first power conversion means, and a filter 26 as main components, and uses AC from an AC power supply 21. It converts electric power into AC power with a constant voltage and constant frequency, and supplies AC power with a constant voltage and constant frequency to the common load 3 while operating in parallel with the above-mentioned first uninterruptible power supply 10. The DC intermediate circuit of the power conversion means 20 and the common battery 2 are connected via a series circuit including a battery breaker 27 and a first current detector 28.

When the first uninterruptible power supply 10 and the second uninterruptible power supply 20 are operating in parallel, for example, if an accident occurs in which the smoothing capacitor 14 of the first uninterruptible power supply is short-circuited (the smoothing capacitor has a large static Generally, electrolytic capacitors are used because they require large capacitance, but these electrolytic capacitors are more easily damaged than other capacitors), from the common battery 2, and from the DC intermediate circuit of the second uninterruptible power supply 20 to the short-circuit point. Short-circuit current flows towards. The first current detector 18 detects this short circuit current and connects the battery breaker 1 to the battery breaker 1.
7, the first uninterruptible power supply 10 that caused the accident is disconnected from the common battery 2 and the healthy second uninterruptible power supply 20, and this second uninterruptible power supply 20 is connected to the common load 3. Continue to supply AC power.

0004

[Problem to be Solved by the Invention] When the above-mentioned short circuit accident occurs, it is necessary to detect the current flowing into the short circuit point from the time the accident occurs until the battery circuit breaker 17 completes cutting off the fault current. Since it takes a certain amount of time, there is a possibility that even the normal second uninterruptible power supply 20 will be drawn into this accident and stopped during this time. or,
Even if it does not stop, the DC intermediate circuit voltage of the normal second uninterruptible power supply 20 is decreasing during the accident period, so the moment the battery circuit breaker 17 opens and disconnects the accident machine,
There is a possibility that an excessive current rushes from the common battery 2 to the smoothing capacitor 24, and the first current detector 28 detects this rush current, causing the battery circuit breaker 27 to be cut off.

[0005] Therefore, an object of the present invention is to connect a plurality of uninterruptible power supplies to a common battery and operate them in parallel due to a failure of a particular uninterruptible power supply. The purpose is to prevent accidents from spreading to a healthy uninterruptible power supply through the circuits in the system.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the protection circuit of the present invention includes a rectifying means configured with a diode to convert an AC input into a DC, and a rectifier that converts an AC input into a DC and a desired voltage by inputting the DC. An uninterruptible power supply system comprising first power conversion means for converting the frequency into alternating current, and a smoothing capacitor connected to a DC intermediate circuit that connects the DC sides of these rectifying means and the DC side of the first power conversion means. An uninterruptible power supply in which multiple sets of power supplies are connected in parallel to supply the AC output of each uninterruptible power supply to a common load, and a common battery is provided in the DC intermediate circuit of each uninterruptible power supply. In,
Between the common battery and the DC intermediate circuit of each uninterruptible power supply, there is a series circuit including a polarity diode and circuit interrupting means for blocking current flowing from the DC intermediate circuit to the common battery, and A first current detection means for detecting current is connected separately, and the first
If the current detection means detects a current equal to or higher than the first predetermined value, it shall give an open circuit signal to the circuit breaking means, but instead of the rectification means, a second power converter converts the AC input into DC of a desired voltage. In the case of a circuit configuration in which the common battery can be charged using means, a semiconductor switch element through which a charging current flows is connected in antiparallel to the diode, and a second current that detects the current flowing through the semiconductor switch element. A detection means is provided, and if the second current detection means detects a current equal to or higher than a second predetermined value, an off signal is given to the semiconductor switch element.

[0007]

[Operation] In this invention, when an accident occurs in a specific uninterruptible power supply when a plurality of uninterruptible power supplies are equipped with a common battery and are operated in parallel, the common battery is connected to the accident machine. However, by blocking the flow of fault current from a healthy uninterruptible power supply to the faulty machine, the aim is to prevent the fault from spreading to the healthy machine. Between the DC intermediate circuit of the power failure power supply and the common battery, diodes with polarities that block current from flowing from the DC intermediate circuit toward the common battery are inserted separately. In addition, when the second power conversion means for supplying DC power to the DC intermediate circuit also serves as a charging device for charging the common battery, a semiconductor whose forward direction is from the DC intermediate circuit to the common battery is used. If a switch element is inserted and it is detected that the current flowing through this semiconductor switch element exceeds the charging current, this semiconductor switch element is immediately turned off, so that in the event of an accident, a healthy uninterruptible power supply returns to the point of failure. By blocking the supply of current, the aim is to prevent accidents from spreading to healthy machines.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention, in which two sets of uninterruptible power supplies are operated in parallel. That is, the first uninterruptible power supply 30 and the second uninterruptible power supply 40 are equipped with a common battery 2 common to both,
AC power is supplied to the common load 3 through parallel operation, and the common battery 2 and the common load 3 shown in FIG.
, AC power supplies 11 and 21, smoothing capacitors 14 and 24, transistor inverters 15 and 25 as first power conversion means, filters 16 and 26, and battery circuit breakers 17 and 2.
7 and the first current detectors 18 and 28 are the same as in the conventional example circuit already described in FIG.
Descriptions of these will be omitted.

In the first embodiment circuit shown in FIG. 1, each uninterruptible power supply has a DC intermediate circuit and a common battery 2.
reverse current blocking diodes 31 and 41 with polarity to block current in the two directions of the common battery are separately inserted into the circuit connecting the two, and thyristor rectifiers 13 and 2 are inserted separately.
3 is different from the conventional example circuit already described in FIG. be.

With such a circuit configuration, for example, when the smoothing capacitor 14 is short-circuited, a short-circuit current flows from the common battery 2 to the short-circuit point, and the first current detector 18 detects this short-circuit current and detects the short-circuit current from the battery. The circuit breaker 17 is tripped, and the first uninterruptible power supply 30 is disconnected from the healthy second uninterruptible power supply 40 and the common battery 2. While this short circuit current does not flow, the voltage of the common battery 2 decreases, but since the reverse current blocking diode 41 prevents the current from flowing from the second uninterruptible power supply 40 to the short circuit point, the spread of the accident is prevented. It can be prevented.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention, and shows a case where two sets of uninterruptible power supplies are operated in parallel as in the case of the circuit of the first embodiment described above. . That is, the first uninterruptible power supply 50 and the second uninterruptible power supply 60 are equipped with a common battery 2 that is common to both, and supply AC power to a common load 3 through parallel operation, which is illustrated in FIG. common battery 2, common load 3, AC power supply 1
1 and 21, thyristor rectifiers 13 and 23 as second power conversion means, smoothing capacitors 14 and 24, transistor inverters 15 and 25 as first power conversion means, filters 16 and 26, battery circuit breakers 17 and 27, and Since the names, uses, and functions of the current detectors 18 and 28 are the same as those of the conventional circuit described in FIG. 3, a description thereof will be omitted.

In the second embodiment circuit shown in FIG. 2, reverse current blocking diodes 31 and 41 are provided in the circuit connecting the DC intermediate circuit and the common battery 2 to prevent current from flowing in the direction of the common battery 2. are inserted separately, charging thyristors 51 or 61 as semiconductor switching elements are connected in antiparallel to the reverse current blocking diodes 31 and 41, and the currents of the charging thyristors 51 and 61 are detected. The conventional example already described in FIG. This is different from a circuit.

With this circuit configuration, when the smoothing capacitor 14 is short-circuited as in the case of the first embodiment circuit described above, the first current detector 18 detects the short-circuit current flowing from the common battery 2 to the short-circuit point. Upon detection, the battery circuit breaker 17 is tripped, and the first uninterruptible power supply 50 is disconnected from the healthy second uninterruptible power supply 60 and the common battery 2 . During the period until the battery circuit breaker 17 trips, the current flowing from the second uninterruptible power supply 60 to the short circuit point is blocked by the reverse current blocking diode 41. This causes current to flow from the second uninterruptible power supply 60 to the fault point. However, this charging thyristor 6
1 is necessary to charge the common battery 2 by using the thyristor rectifier 23 as a charger, and cannot be removed. Therefore, if the second current detector 63 detects that the current flowing through the charging thyristor 61 exceeds the second predetermined charging current value, the forced extinguishing circuit 62 is activated to immediately turn off the charging thyristor 61. to prevent current from flowing to the fault point. In addition, the forced arc extinguishing circuit 62
By turning on the built-in thyristor, the charge stored in the capacitor is applied as a reverse voltage to the charging thyristor 61 through a resonant circuit between this capacitor and the reactor, and this charging thyristor 61 is turned off. Since the operation of the forced arc extinguishing circuit 62 is unrelated to the present invention, its explanation will be omitted.

[0014]

[Effect of the invention] When multiple uninterruptible power supplies that share a common backup battery are operating in parallel, if an accident occurs in any of the uninterruptible power supplies, the common battery and other healthy batteries will be damaged. A large fault current flows from the power failure power supply to the fault point, but according to the present invention,
A reverse current blocking diode is separately inserted between the DC intermediate circuit of each uninterruptible power supply and the common battery to prevent current from flowing from a healthy uninterruptible power supply to the fault point. As a result, the accident spread until the fault current was cut off.
This has the effect of preventing even other healthy uninterruptible power supplies from becoming abnormal. In addition, if the uninterruptible power supply also serves as a charging device that charges the common battery, a semiconductor switching element is inserted between the DC intermediate circuit and the common battery for charging, and this semiconductor switching element is activated in the event of an accident. If the flowing current exceeds the charging current, this semiconductor switch element is immediately turned off, thereby preventing the accident from spreading to a healthy uninterruptible power supply.

[Brief explanation of the drawing]

[Fig. 1] A circuit diagram showing a first embodiment of the present invention.

[Fig. 2] A circuit diagram showing a second embodiment of the present invention.

[Figure 3] A circuit diagram showing a conventional example of a protection circuit for an uninterruptible power supply equipped with a common battery and operated in parallel.

[Explanation of symbols]

2 Common battery 3 Common load 4 Charging device 10 Uninterruptible power supply 12 Diode rectifier 13 as a rectifier
Thyristor rectifier 14 as second power conversion means
Smoothing capacitor 17 Battery circuit breaker 18 First current detector 20 Uninterruptible power supply 22 Diode rectifier 23 as a rectifier
Thyristor rectifier 24 as second power conversion means
Smoothing capacitor 27 Battery breaker 28 First current detector 30 Uninterruptible power supply 31 Backflow blocking diode 40 Uninterruptible power supply 41 Backflow blocking diode 50 Uninterruptible power supply 51 Charging thyristor 52 Forced extinguishing circuit 53 Second current detector 60 Uninterruptible power supply 61 Charging thyristor 62 Forced arc extinguishing circuit 63 Second current detector

Claims (2)

[Claims] 1. Rectifying means configured with diodes and converting AC input into DC; first power conversion means inputting this DC and converting it into AC with a desired voltage and frequency; and DC sides of these rectifying means. and a smoothing capacitor connected to a DC intermediate circuit that couples the DC side of the first power conversion means, and a smoothing capacitor connected to the DC intermediate circuit that connects the In an uninterruptible power supply that supplies an output to a common load and also connects a common battery to the DC intermediate circuit of each uninterruptible power supply, the connection between the common battery and the DC intermediate circuit of each uninterruptible power supply is In between, there is a series circuit consisting of a polar diode and circuit interrupting means for blocking current flowing from the DC intermediate circuit to the common battery, and a first circuit for detecting the current flowing through the diode.
A protection circuit for an uninterruptible power supply, characterized in that the first current detection means is separately connected to a current detection means, and when the first current detection means detects a current equal to or higher than a first predetermined value, an open circuit signal is given to the circuit breaking means. . Claim 2: A second converter for converting AC input into DC at a desired voltage.
A power conversion means, a first power conversion means for inputting this DC and converting it into AC of a desired voltage and frequency, and a DC side of these second power conversion means and a DC side of the first power conversion means are coupled. A plurality of sets of uninterruptible power supplies each consisting of a smoothing capacitor connected to a DC intermediate circuit are connected in parallel to supply the AC output of each uninterruptible power supply to a common load, and In an uninterruptible power supply in which a common battery is provided in the DC intermediate circuit of the power supply, a current flowing from the DC intermediate circuit to the common battery is connected between the common battery and the DC intermediate circuit of each uninterruptible power supply. a series circuit of a diode with a polarity to block the current and a circuit breaking means; a first current detection means for detecting the current flowing through the diode; a semiconductor switch element connected in antiparallel to the diode; A second current detecting means for detecting a flowing current is separately connected, and when the first current detecting means detects a current equal to or higher than a first predetermined value, an open circuit signal is given to the circuit breaking means, and the second current detecting means
A protection circuit for an uninterruptible power supply, characterized in that if the current detection means detects a current equal to or higher than a second predetermined value, it gives an off signal to the semiconductor switch element.