JPH1094264A - Uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rationally supply power to a load that requires a backup operation for a specified period of time after the occurrence of a service interruption and a load that ordinarily operates on commercial power supply and requires a backup operation for a short period of time after the occurrence of a service interruption. SOLUTION: When an alternating-current power supply 1 is under normal conditions, an alternating-current reference voltage in phase with the commercial voltage of the alternating-current power supply 1 is output from a reference voltage circuit 21 according to a synchronizing signal output from a synchronization circuit 26. An alternating-current voltage in phase with the commercial voltage is output from an inverter 3. A load 4 is supplied with the alternating- current reference voltage and the alternating-current voltage, and a load 7 is supplied with the commercial voltage of the alternating-current power supply 1 through a change-over switch 6. If the alternatingcurrent power supply 1 is judged to be interrupted at a service interruption detection circuit 25 and a command S2 is output, the load 7 is supplied with the output voltage of the inverter 3 through the change-over switch 6 only for a short time.

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 for converting an AC voltage to a DC voltage and then converting the AC voltage to a constant voltage AC voltage, and more particularly to an uninterruptible power supply for supplying power to two types of loads. .

[0002]

2. Description of the Related Art FIG. 4 shows an uninterruptible power supply (hereinafter referred to as UPS). This UPS converts an AC (commercial) voltage received from an AC power supply 1 into a converter 2
After the DC voltage is once converted into a DC voltage, the inverter 3 converts the DC voltage into AC power having a constant voltage and constant frequency again to supply stable power to the load 4.

An AC voltage received from an AC power supply 1 is input via a circuit breaker 8 and applied to a converter 2 via a resistor 9 → a switch 11 → a reactor 12. The converter 2 is a half-bridge circuit composed of switch elements 2a and 2b in which diodes 2c and 2d are connected in anti-parallel.
The input AC voltage is rectified by the diodes 2c and 2d, and charges the capacitors 13 and 14 to the peak value of the AC voltage with the polarity shown. That is, converter 2 functions as a voltage doubler rectifier circuit. This DC voltage is applied to the voltage detector 18.
When the DC voltage reaches a predetermined value, the switch 10 is closed via the switch operation circuit 19 and both ends of the resistor 9 are short-circuited. Converter control unit 20 compares voltage reference Vd ^* with signal Vd detected by voltage detector 18 to output a gate signal for performing PWM control on switch elements 2a and 2b. To a value corresponding to the voltage reference Vd ^* .

The inverter 3 is a half-bridge circuit composed of switch elements 3a and 3b in which diodes 3c and 3d are connected in anti-parallel. The inverter 3 converts the DC voltage of the capacitors 13 and 14 into an AC voltage by PWM control. The ripple voltage is removed by the capacitor 16 to output a constant voltage and constant frequency AC voltage. The voltage reference circuit 21 generates an AC voltage reference Va ^* having a constant frequency and a constant amplitude, and the inverter control unit 23 controls the inverter 3 by comparing the voltage reference Va ^* with the signal Va detected by the voltage detector 22. And outputs a PWM signal for performing the operation.

When a power failure occurs in the AC power supply 1, the power failure detection circuit 25 switches the changeover switch 11 to the battery 5 side, and the converter 2 operates as a step-up chopper.
Supplies DC power, and the backup operation is performed for a predetermined compensation time. Note that the switch 17 supplies the AC voltage of the AC power supply 1 directly to the load 4 when only the load that does not require the backup operation or when performing maintenance on the UPS.

[0006]

In the above conventional UPS, when various loads are connected as the load 4, it is necessary to use a UPS having a total capacity of all the loads. Further, depending on the load, there is a load that requires a backup operation for several minutes when a power failure occurs, and a load that requires a relatively short backup operation. In addition, depending on the load, the power supply may normally be operated with a commercial power supply, but there is a case where it is desired to perform the backup operation for a short time (for example, 500 ms) from the time of the power failure.

In the case of supplying power to such various loads, the conventional UPS needs to supply power to all loads in a normal operation state. Problem.

The present invention has been made on the basis of the above-described problem. The first load requires a backup operation for a predetermined time from the time of the occurrence of a power failure, and operates with a commercial power supply in a normal operation. It is an object of the present invention to provide an economical uninterruptible power supply that rationally supplies power to a second load that requires a backup operation only for a short time, reduces the device capacity, and is downsized.

[0009]

To achieve the above object, an uninterruptible power supply according to the present invention comprises: a converter for converting a first AC voltage supplied from an AC power supply into a DC voltage; An inverter for converting to an AC voltage; a battery for supplying power for maintaining the DC voltage when a power failure of the AC power supply is detected; and a voltage reference generator for outputting an AC voltage reference in phase with the first AC voltage. Means, and inverter control means for controlling the inverter by comparing the AC voltage reference with the second AC voltage detection value, and usually supplies the second AC voltage to a first load and the second load And a switching unit for supplying the second AC voltage to the second load for a predetermined time when a power failure of the AC power supply is detected.
(Claim 1) Further, the predetermined time is set within a range permitted by a short-time overload rating of the converter and the inverter. (Claim 2) The apparatus further includes voltage detection means for determining a power failure when the first AC voltage of the AC power supply is equal to or lower than a predetermined voltage, and outputting an operation command to the switching means, wherein the voltage detection means determines that the power failure has occurred. At this time, the predetermined voltage is set within a range of a normal operation voltage of the second load. (Claim 3) Further, the switching means is normally connected to the first AC voltage side, and is connected to the second AC voltage side for a predetermined time when a power failure of the AC power supply is detected. And supplies power to the second load via the changeover switch. (Claim 4) Further, the changeover switch comprises a contact type changeover switch and a semiconductor switch connected between the inverter output side and the second load side, and when a power failure of the AC power supply is detected, the contact switch is formed. Set the system changeover switch to the second
The semiconductor switch is connected to the AC voltage side and the semiconductor switch is turned on for a predetermined time. (Claim 5) Further, the apparatus further comprises synchronization detecting means for detecting a phase of the first AC voltage of the AC power supply and outputting a synchronization signal, wherein the voltage reference generating means is in phase with the first AC voltage based on the synchronization signal. Output the AC voltage reference. (Claim 6) Further, the converter includes two first switch elements, each of which has a first diode connected in anti-parallel and connected in series, and two serially connected first switch elements at both ends of the two first switch elements. Two capacitors and the first two capacitors
The inverter is constituted by a reactor having one end connected to a connection point of a switch element, and the inverter is configured such that the two capacitors are connected in series with two second switch elements connected in series with second diodes connected in anti-parallel. The first AC voltage is applied to a series connection point between the other end of the reactor and the two capacitors, and
The second AC voltage is output between a connection point between the second switch elements and a series connection point between the two capacitors. (Claim 7)

[0010]

FIG. 1 shows an embodiment of an uninterruptible power supply according to the present invention. In FIG. 1, reference numeral 6 denotes a changeover switch connected to the AC power supply 1 in a normal operation state, and 7 denotes a commercial voltage (first AC voltage) of the AC power supply 1 which is normally supplied to the inverter 3 for a short time when a power failure occurs. A load (second load) to which the output voltage (second AC voltage) is supplied, and 26 is a synchronous circuit that outputs a signal synchronized with the commercial voltage. The other components are the same as those in the related art (FIG. 4), and are denoted by the same reference numerals, and description thereof is omitted.
However, the voltage reference circuit 21 generates an AC voltage reference Va ^* having a constant amplitude synchronized with the signal output from the synchronization circuit 26, and the power failure detection circuit 25 switches the switch 11 to the battery 5 when the power failure of the AC power supply is detected. Side, and outputs a command to switch the changeover switch 6 to the output side of the inverter 3 for a predetermined time.

In the above configuration, when the AC power source 1 is normal, the commercial voltage of the AC power source 1
After being converted into a DC voltage by the inverter 3, it is converted into an AC voltage which is converted into a constant voltage by the inverter 3, supplied to the load 4 (first load) via the changeover switch 17, and switched to the load 7 (second load). The commercial voltage of the AC power supply 1 is supplied via the switch 6. In this case, the AC voltage reference Va ^* having a constant amplitude output from the voltage reference circuit 21 is phase-synchronized controlled by a synchronization signal output from the synchronization circuit 26, synchronized with the phase of the commercial voltage of the AC power supply 1, and in phase with the commercial voltage. AC voltage reference Va
^* Is outputted, the AC voltage of the utility voltage in phase are outputted from the inverter 3.

When a power failure occurs in the AC power supply 1, the changeover switch 11 is switched to the battery 5 side by a command from the power failure detection circuit 25, and the converter 2 uses the DC power supplied from the battery 7 to connect the The inverter 3 continuously outputs an AC voltage while the DC voltage of the inverter 14 is kept constant to perform a backup operation, and the load 4 is continuously supplied with a constant-voltage AC voltage. Also,
The power failure detection circuit 25 switches the changeover switch 6 to the output side of the inverter 3 immediately after detecting the power failure, and operates so as to return to the original state after a predetermined time. Therefore, the commercial voltage of the AC power supply 1 is normally supplied to the load 7 (second load), and when a power failure occurs in the AC power supply 1, the output voltage of the inverter 3 is supplied for a certain time from the time of the power failure.

When the AC power supply 1 fails, the synchronous circuit 2
6, the voltage reference circuit 21 maintains the synchronous phase immediately before the power outage.
^* Is output continuously.

FIG. 2 shows an example of the operation when the AC power supply 1 fails at time t1.
s, the command for the changeover switch 11 is S1, the command for the changeover switch 6 is S2, the AC voltage supplied to the load 4 is Va1, and the AC voltage supplied to the load 7 is Va2.

When AC power supply 1 is normal, that is, at time t
Before 1 the changeover switch 6 is connected to the AC power supply 1 side,
The commercial voltage Vs is supplied as the AC voltage Va2 supplied to the load 7. When the AC power supply 1 loses power at time t1, the changeover switch 11 is connected to the battery 5 by the command S1 output from the power failure detection circuit 25, and the changeover switch 6 is moved to the output side of the inverter 3 by the command S2 for a fixed time T1 ( 2 until time t2). Therefore, load 7
Is supplied from the inverter 3 from time t1 to time t2. Load 4
, The AC voltage output from the inverter 3 is always supplied as Va1.

The predetermined time T1 is determined by the characteristics of the load 7, and it is sufficient that the time required for safely performing the power saving evacuation process is set, for example, to 500 ms. The converter 2 and the inverter 3 usually have a short-time overload capability under rated operating conditions.
In the case of an overload rating of 00%, 200% power can be supplied to the load 7, and the device capacity is reduced by 1 / compared to the conventional method.
It can be 3.

Accordingly, it is possible to rationally supply power to a system in which a load 4 requiring a normal backup operation time when a power failure occurs and a load 7 which requires only a short backup time within an allowable range of overload capacity. This makes it possible to reduce the capacity and reduce the size, and to provide an inexpensive uninterruptible power supply with reduced cost. (Claims 1, 2, 4, 6, 7) FIG. 3 shows an embodiment of a power supply circuit for a load 7. Reference numeral 6 denotes a contact type changeover switch, 6a denotes a semiconductor switch, and when a power failure of the AC power supply 1 is detected, a command S
2, the contact type changeover switch 6 is connected to the inverter output side for a predetermined time and the semiconductor switch 6a is turned on for a predetermined time. The contact type changeover switch 6 has an operation delay time of 10 ms or more at the time of switching, but the semiconductor switch 6a operates with a delay time of 1 ms or less, so that the switching can be performed almost without interruption.
(Claim 5) In addition, a contact 6b that is always closed is inserted between the inverter output side and the changeover switch 6, and when a power failure of the AC power supply 1 is detected, the contact 6b is opened after a predetermined time and the inverter 3 is opened. It can be configured to protect against overload.

The power failure detection circuit 25 determines that a power failure has occurred when the commercial voltage of the AC power supply 1 falls below a predetermined voltage, based on the operation limit voltage required from the characteristics of the load 7, and performs the switching operation described above. In addition, the operation of the device serving as the load 7 when the commercial voltage is abnormally lowered can be protected.
(Claim 3)

[0019]

According to the uninterruptible power supply of the present invention, the first load that requires the backup operation for a predetermined time from the time of the occurrence of the power failure and the commercial power supply in the normal operation, and a short time from the time of the occurrence of the power failure Power can be rationally supplied to the second load that requires only the backup operation, the device capacity can be reduced and the size can be reduced, the cost can be reduced, and the economic efficiency can be improved. it can.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of an uninterruptible power supply according to the present invention.

FIG. 2 is a time chart for explaining the operation of the embodiment.

FIG. 3 is a main part configuration diagram of an embodiment of an uninterruptible power supply according to claim 5 of the present invention.

FIG. 4 is a configuration diagram of a conventional uninterruptible power supply.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... AC power supply 2 ... Converter 3 ... Inverter 2a, 2b, 3a, 3b ... Switch element 2c, 2d, 3c, 3d ... Diode 4 ... First load 5 ... Battery 6 ... Switch 6a ... Semiconductor switch 6b ... Contact (switch) 7) Second load 8 ... Circuit breaker 9 ... Resistance 10 ... Switch 11 ... Changeover switch 12, 15 ... Reactor 13, 14,
DESCRIPTION OF SYMBOLS 16 ... Capacitor 17 ... Changeover switch 18 ... Voltage detector (DC) 19 ... Switch operation circuit 20 ... Converter control unit 21 ... Voltage reference generation circuit 22 ... Voltage detector (AC) 23 ... Inverter control unit 25 ... Power failure detection circuit 26 ... Synchronous circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H02M 7/219 H02M 7/219 7/5387 7/5387 A

Claims (7)

[Claims] A converter for converting a first AC voltage supplied from an AC power supply to a DC voltage; an inverter for converting the DC voltage to a second AC voltage; and an inverter for detecting a power failure of the AC power supply. A battery for supplying power for maintaining a voltage, voltage reference generating means for outputting an AC voltage reference having the same phase as the first AC voltage, and comparing the AC voltage reference with the second AC voltage detection value. An inverter control means for controlling the inverter, usually supplying the second AC voltage to a first load and supplying the first AC voltage to a second load, and detecting a power outage of the AC power supply. An uninterruptible power supply, further comprising switching means for supplying the second AC voltage to the second load for a predetermined time. 2. The uninterruptible power supply according to claim 1, wherein the predetermined time is set within a range allowed by a short-time overload rating of the converter and the inverter. 3. The uninterruptible power supply according to claim 1, further comprising a voltage detecting means for judging a power failure when the first AC voltage of the AC power supply is lower than a predetermined voltage, and outputting an operation command to the switching means. An uninterruptible power supply, wherein the predetermined voltage is set within a range of a normal operating voltage of the second load. 4. The uninterruptible power supply according to claim 1, wherein the switching means is normally connected to the first AC voltage side, and when a power failure of the AC power supply is detected, the switching means is provided for a predetermined time. (2) An uninterruptible power supply device comprising a changeover switch connected to the AC voltage side, and supplying power to the second load via the changeover switch. 5. The uninterruptible power supply according to claim 4, wherein the changeover switch comprises a contact-type changeover switch and a semiconductor switch connected between an inverter output side and a second load side. When a power outage is detected, the contact type changeover switch is set to the second
An uninterruptible power supply connected to an AC voltage side and turning on the semiconductor switch for a predetermined time. 6. The uninterruptible power supply according to claim 1, further comprising: synchronization detection means for detecting a phase of the first AC voltage of the AC power supply and outputting a synchronization signal, wherein the voltage reference generation means includes a synchronization signal generator. An uninterruptible power supply unit that outputs an AC voltage reference having the same phase as the first AC voltage based on the AC power. 7. The uninterruptible power supply according to claim 1, wherein the converter includes two first switch elements, each of which has a first diode connected in antiparallel and connected in series,
The two first switch elements connected in series include two capacitors connected in series at both ends thereof, and a reactor having one end connected to a connection point of the two first switch elements. A second diode is connected in series and two second switch elements are connected in series to the two capacitors connected in series, and the first AC voltage is connected to the other end of the reactor. The second AC voltage is output between a connection point of the two second switch elements and a connection point of the two capacitors in series, which is applied to a series connection point of the two capacitors. Uninterruptible power system.