JP2016049011A - Uninterruptible power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To switch between an inverter and a bypass circuit in an asynchronous and uninterruptible manner in an uninterruptible power supply including a plurality of inverters each including a parallel control function and the bypass circuit.SOLUTION: The uninterruptible power supply includes: an inverter device in which the plurality of inverters are connected in parallel; the bypass circuit for supplying power from a bypass power source; and a power supply switching part which switches output of the inverter device and output from the bypass power source and supplies power to a load device. The power supply switching part includes: a first switch circuit that is connected to the inverter device; a second switch circuit that is connected to the bypass circuit; and a switch control circuit which controls ON/OFF of the first switch circuit and the second switch circuit. At normal times, the switch control circuit turns on the first switch circuit and turns off the second switch circuit. When the inverter device is abnormal, the switch control circuit turns off the first switch circuit, simultaneously turns on the second switch circuit and further turns off all the inverters.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an uninterruptible power supply, and more particularly to an uninterruptible power supply that includes a plurality of inverters having a parallel control function and a bypass circuit, and is capable of switching between an inverter and a bypass circuit without interruption.

An uninterruptible power supply that constantly supplies power to the inverter can supply stable AC power to the load at all times, and can supply stable AC power for a certain period even during a power outage, etc., so it is used to supply power to important loads . This uninterruptible power supply is provided with a bypass circuit for connecting a commercial power supply to a load, and is switched to the bypass circuit when the uninterruptible power supply is broken or inspected. Thereby, the power supply to the load is continued.
However, normally, in order to reduce disturbance to the load, when shifting from normal operation by the uninterruptible power supply to the AC power supply for bypass, the frequency of the bypass power supply is within the predetermined frequency range, and the inverter is the frequency of the bypass power supply. And switching is performed in a synchronized state in which the output frequencies and phases of the two are substantially the same.

  For example, it has been proposed to calculate and correct the operation frequency of the current command of the converter that performs instantaneous current control and the voltage command of the inverter that performs instantaneous voltage control, and to synchronize the converter and the inverter with a commercial AC power source. (Patent Document 1). According to this method, uninterruptible switching of the power supply device can be realized by performing uninterruptible switching with a commercial AC power supply.

  However, the method of Patent Document 1 is complicated in control because the converter and the inverter are synchronized with a commercial AC power supply. Moreover, when the inverter and the commercial AC power supply are not synchronized, switching cannot be performed without instantaneous interruption. Therefore, the conventional example shown in FIG. 6 proposes a method of switching between the inverter 102 and the bypass circuit 131 even when the output phase of the inverter and the AC voltage from the commercial power source have a voltage phase difference and is in an asynchronous state (patent). Reference 2). That is, even if the bypass circuit 131 includes the overcurrent suppression circuit unit 134 including the reactor 140 and the output voltage of the inverter 102 and the AC voltage from the commercial power supply 150 are in an asynchronous state, the inverter power supply is switched to the bypass power supply. Since the current flows to the load 151 and the inverter 102 via the reactor 140, the current value is equal to or less than the allowable current value of the inverter.

  In Patent Document 2, even when the inverter 102 and the commercial AC power supply 150 are not synchronized, when the inverter power supply is switched to the bypass power supply, no overcurrent flows through the inverter 102. Therefore, the inverter power supply is safely switched to the bypass power supply. Can be switched. However, Patent Document 2 requires a reactor 140 having a relatively large inductance in order to suppress overcurrent during switching. Moreover, since the current supplied to the load always flows in the reactor 140 during bypass power feeding, a reactor having a large current capacity is required. In particular, a large uninterruptible power supply device in which a plurality of inverters are connected in parallel has a large reactor. Further, when the overcurrent is suppressed, a voltage drop occurs, and the voltage on the load side cannot be stably maintained. The voltage fluctuation on the load side is generated by the load current even during bypass power feeding, and the voltage supplied to the load cannot be stably maintained.

JP-A-08-126228 JP 2009-296830 A

  In an uninterruptible power supply device including a plurality of inverters having a parallel control function and a bypass circuit, an object is to switch the inverter and the bypass circuit asynchronously and without interruption.

  The uninterruptible power supply of the present invention includes an inverter device in which a plurality of inverters are connected in parallel, a bypass circuit that supplies power from a bypass power source, and a load device that switches between an output of the inverter device and an output from the bypass power source. A power supply switching unit for supplying power to the battery is provided. The power supply switching unit includes a first switch circuit that connects or disconnects the inverter device and the load device, a second switch circuit that connects or disconnects the bypass circuit and the load device, and ON / OFF of the first switch circuit. And a switch control circuit for controlling on / off of the second switch circuit, and an inverter output power calculation unit for calculating the suppliable power of the inverter device according to the operating state of the plurality of inverters. When the inverter device can supply the power consumed by the load device, the first switch circuit is turned on, the second switch circuit is turned off, and all the inverters are instructed to operate. Furthermore, when the inverter device cannot supply the power consumed by the load device, the first switch circuit is turned off, the second switch circuit is turned on, and all the inverters are stopped.

  The uninterruptible power supply device of the present invention can easily switch the output of the inverter device and the output of the bypass power supply asynchronously and without interruption.

FIG. 1 is a circuit configuration diagram showing an uninterruptible power supply of the present invention. Example 1 FIG. 2 is a circuit configuration diagram illustrating a switch control circuit used in the uninterruptible power supply according to the first embodiment. FIG. 3 is a waveform diagram showing an example of an actual output waveform in the uninterruptible power supply of the present invention. FIG. 4 shows a modification of the switch circuit used in the uninterruptible power supply device of the present invention. FIG. 5 shows another modification of the switch circuit used in the uninterruptible power supply of the present invention. FIG. 6 is a circuit configuration diagram showing a conventional uninterruptible power supply.

FIG. 1 is a circuit configuration diagram showing an uninterruptible power supply 1 according to Embodiment 1 of the present invention.
The AC power supply 3 is connected to the battery 5 and the inverter unit 6 via the AC-DC converter 4. The output of the inverter unit 6 is connected to one of the switch circuits 10 of the power supply switching unit 8. The other side of the switch circuit 10 is connected to the load device 17. The bypass power supply 2 is connected to the load device 17 via the bypass circuit 7 and the switch circuit 9 of the power supply switching unit 8. The inverter unit 6 is configured by connecting the input IN of five DC-AC inverters 6-1, 6-2, 6-3, 6-4, 6-5 in parallel and connecting the output OUT in parallel. Do the driving. The switch circuit 9 is configured by connecting a triac 9-1 and an electromagnetic contactor 9-2 in parallel. The switch circuit 10 is configured by connecting a triac 10-1 and an electromagnetic contactor 10-2 in parallel. Furthermore, the power supply switching unit 8 includes a switch control circuit 15 that drives each triac and each electromagnetic contactor of the switch circuit 9 and the switch circuit 10. The switch control circuit 15 includes a current detector 16 that detects a current supplied to the load device 17, receives an abnormal signal output from each ALM terminal of each of the five DC-AC inverters that are operated in parallel, Drive signals are sent to the triac 9-1 and the magnetic contactor 9-2 of the circuit 9, the drive signals are sent to the triac 10-1 and the magnetic contactor 10-2 of the switch circuit 10, and five units that operate in parallel are sent. An on / off signal is sent to the ON / OFF terminal of the DC-AC inverter.

  FIG. 2 is a specific circuit configuration diagram of the switch control circuit 15. The output signal of the current detector 16 is received at the Is terminal, and the load power calculation unit 201 calculates and outputs the power amount Po of the load device 17. The inverter output power calculation unit receives an abnormal signal output from each of the ALM terminals of the five DC-AC inverters operated in parallel at the five input terminals ALM1 to ALM5, and operates normally. The maximum power Pinv that can be output by the inverter unit 6 is calculated and output from the number of units. At this time, at least one of the five DC-AC inverters operated in parallel may be used for redundant operation. In Embodiment 1 of the present invention, it is assumed that one unit is operated redundantly and each DC-AC inverter can output 10 kVA power. Therefore, when five DC-AC inverters operating in parallel are normal, a signal corresponding to 40 kVA for four units is output from the inverter output power calculation unit 203 except for one unit for redundant operation. The power comparison unit 202 compares the power amount Po and the power amount Pinv, and outputs a signal Inv / B to the SW-Drive 205 when Pinv ≧ Po. If Pinv <Po, the Inv / B signal to the SW-Drive 205 is stopped. In response to the signal Inv / B, the SW-Drive 205 outputs a drive signal DriveA for turning the switch circuit 9 on and off, and outputs a drive signal DriveB for turning the switch circuit 10 on and off, and the ON / OFF control circuit includes the inverter 6. A signal Cont for controlling operation stop is output. The drive signal DriveA is composed of signals A-1 and A-2. The signal A-1 turns on and off the triac 9-1 of the switch circuit 9, and the signal A-2 turns on and off the electromagnetic contactor 9-2. Similarly, the drive signal DriveB is composed of signals B-1 and B-2. The signal B-1 turns on / off the triac 10-1 of the switch circuit 10, and the signal B-2 turns on / off the electromagnetic contactor 10-2. The ON / OFF control 204 simultaneously activates the five DC-AC inverters operated in parallel when the signal Cont is output, and simultaneously stops the five DC-AC inverters operated in parallel when the signal Cont is not output.

The operation of the first embodiment configured as described above will be described with reference to FIGS.
In normal times, the AC-DC converter 4 converts the electric power supplied from the AC power source 3 into DC. The direct current charges the battery 5 and is supplied to the inverter unit 6. The inverter unit 6 converts direct current into alternating current, and supplies stable alternating current power to the load device 17 through the switch circuit 10 of the power supply switching unit 8. At this time, the switch control circuit 15 turns off the triac 9-1 and the magnetic contactor 9-2 of the switch circuit 9 via the SW-Drive 205, and turns on the triac 10-1 and the magnetic contactor 10-2 of the switch circuit 10. Let Further, the signal Cont is output to the ON / OFF control 204, and the ON / OFF control 204 operates five DC-AC inverters operated in parallel.

  Next, when the AC power source 3 fails, the inverter unit 6 converts the charging energy of the battery 5 into AC and supplies stable AC power to the load device 17 via the switch circuit 10 of the power source switching unit 8. These operations are general operations called a constant inverter feeding method.

[When one of the inverters fails and stops]
When any inverter fails, the first embodiment of the present invention operates as follows.
If any one of the five DC-AC inverters operated in parallel fails and stops abnormally, the following operations are performed. For example, when the DC-AC inverter 6-1 abnormally stops, the DC-AC inverter 6-1 outputs an abnormal signal to the terminal ALM1. When the switch control circuit 15 receives an abnormal signal from the DC-AC inverter 6-1, the inverter output power calculation unit 203 cancels one redundant operation and the inverter unit 6 can output the maximum power of 40 kVA. The corresponding signal is output as Pinv. The signal corresponding to 30 kVA may be output as Pinv by continuing the redundant operation and subtracting the output power for one vehicle.
Further, when another unit, for example, the DC-AC inverter 6-2 is abnormally stopped, the output voltage of one unit which has been abnormally stopped is subtracted and a signal corresponding to 30 kVA is output as Pinv. In addition, when any one of the five DC-AC inverters operated in parallel fails simultaneously and stops abnormally, the inverter output power calculation unit 203 calculates the power for the number of faults from the maximum power that the inverter unit 6 can output. Subtract and output the signal Pinv. That is, if two of the five units fail simultaneously, a signal Pinv corresponding to 30 kVA is output.

As for the power consumed by the load device 17, a signal Po is output from the load power calculation unit 201, and the power comparison unit 202 compares Pinv and Po. In the case of Pinv ≧ Po, the signal Inv / B from the power comparison unit 202 does not change and the power supply from the inverter unit 6 is continued. When Pinv <Po, the signal Inv / B from the power comparison unit 202 is stopped. Then, the SW-Drive 205 turns on the signals A-1 and A-2 of the drive signal DriveA and turns off the signals B-1 and B-2 of the drive signal DriveB. For this reason, the triac 9-1 and the electromagnetic contactor 9-2 of the switch circuit 9 are turned on, and at the same time, the triac 10-1 and the electromagnetic contactor 10-2 of the switch circuit 10 are turned off. The supply is switched from the inverter unit 6 to the bypass circuit 7.
At this time, the triac 9-1 of the switch circuit 9 is turned on instantaneously, but the contact of the electromagnetic contactor 10-2 of the switch circuit 10 cannot be immediately turned off due to a delay in mechanical operation, and the on state is maintained. In the asynchronous state, the voltage of the bypass power supply 2 and the output voltage of the inverter unit 6 are turned on at the same time, so there is an abnormality such as a short circuit current or an inrush current between the bypass power supply 2 and the inverter unit 6. There is a possibility that the inverter of a sound machine that has not stopped abnormally may be damaged or stopped due to current flowing. In the first embodiment of the present invention, in order to prevent this, the SW-Drive 205 of the switch control circuit 15 turns on the triac 9-1 and the electromagnetic contactor 9-2 of the switch circuit 9 and simultaneously turns on / off control 204. And the ON / OFF control 204 sends off signals to the ON / OFF terminals of the five DC-AC inverters connected in parallel in the inverter unit 6 to stop all inverters. Since the switching element of each inverter is turned off, an abnormal current does not flow between the output of the bypass circuit 7 and the inverter unit 6. Thus, even if any one of the inverter units 6 is abnormally stopped, the inverter of the sound machine that has not stopped abnormally can be switched to the bypass circuit 7 without instantaneous interruption without being damaged or failed.

As described above, when one or more of the DC-AC inverters connected in parallel in the inverter unit 6 are abnormally stopped, and it becomes difficult for the inverter unit 6 to supply power to the load device 17, Then, switching to the bypass circuit 7 is performed.
FIG. 2 shows an example of the voltage waveform of the load device 17 when switching is actually performed. When supplying 50 Hz alternating current with five DC-AC inverters connected in parallel, one of the five DC-AC inverters connected in parallel at time t is abnormally stopped. Although the output of the inverter unit 6 and the bypass power supply 2 have a phase difference of about 5 milliseconds, the output of the inverter unit 6 is switched from the output of the inverter unit 6 to the bypass power supply 2 at time t, and power is supplied to the load device 17 without interruption. Yes.

Furthermore, in the first embodiment of the present invention, when five DC-AC inverters connected in parallel fail and power is supplied from the bypass circuit 7 to the load device 17, the failed DC-AC inverter is repaired or replaced. When the power is restored, the power supply to the load device 17 is switched from the bypass circuit 7 to the inverter unit 6. When the failed DC-AC inverter is restored, the ALM signal is reset. Then, the inverter output power calculation unit 203 outputs a signal Pinv added by the number of DC-AC inverters whose maximum power that can be output by the inverter unit 6 is restored. The power comparison unit 202 compares the signal Pinv and the signal Po and continues bypass power supply if Pinv <Po, but outputs Pin Inb / B and instructs inverter power supply when Pinv ≧ Po. At this time, the SW-Drive 205 first outputs the signal Cont to the ON / OFF control 204, and the ON / OFF control 204 turns on all the DC-AC inverters. When all the DC-AC inverters are in the parallel operation state, the power supply to the load device 17 is switched from the bypass circuit 7 to the inverter unit 6. At this time, the triac 9-1 of the switch circuit 9 is turned off, and the contact of the electromagnetic contactor 9-2 is turned off. At the same time, the triac 10-1 of the switch circuit 10 is turned on. When the switching is completed, the electromagnetic contactor 10-2 of the switch circuit 10 is turned on to return to the normal operation state. As a result, the power supply of the load device 17 can be switched from the bypass circuit 7 to the inverter unit 6 without any abnormal current flowing. The bypass voltage and the inverter output voltage may be switched at a timing when there is a phase so that an abnormal current does not flow between the output of the bypass circuit 7 and the inverter unit 6.
[When the inverter is overloaded]

  The uninterruptible power supply 1 of the first embodiment of the present invention shown in FIG. 1 can be switched to the bypass circuit 7 even when the load device 17 is overloaded. When the overload detection unit 206 of the switch control circuit 15 detects that the current supplied to the load device 17 exceeds a predetermined value, the overload signal OC is output to the SW-Drive 205. The SW-Drive 205 turns on the triac 9-1 and the electromagnetic contactor 9-2 of the switch circuit 9 and simultaneously turns off the triac 10-1 and the electromagnetic contactor 10-2 of the switch circuit 10. Further, the SW-Drive 205 sends a signal Cont to the on / off control 204, and the on / off control 204 stops all the inverters of the inverter unit 6. As a result, no abnormal current flows between the output of the bypass circuit 7 and the inverter unit 6, and it is possible to safely switch to the power supply from the bypass circuit 7 without instantaneous interruption.

  Further, when switching to the power supply from the bypass circuit 7, the SW-Drive 205 stops sending the signal Cont to the on / off control 204 and automatically operates all the inverters of the inverter unit 6. At this time, since the triac 10-1 and the magnetic contactor 10-2 of the switch circuit 10 are off, the inverter unit 6 stands by with no load. Thereafter, when the overload of the load device 17 is resolved, the overload detection unit 206 stops sending the signal OC and switches the power supply to the load device 17 from the bypass circuit 7 to the inverter unit 6. At this time, the triac 9-1 of the switch circuit 9 is turned off, and the contact of the electromagnetic contactor 9-2 is turned off. At the same time, the triac 10-1 of the switch circuit 10 is turned on. When the switching is completed, the electromagnetic contactor 10-2 of the switch circuit 10 is turned on to return to the normal operation state. Abnormal current does not flow, and the power supply of the load device 17 can be switched from the bypass circuit 7 to the inverter unit 6. The bypass voltage and the inverter output voltage may be switched at a timing when there is a phase so that an abnormal current does not flow between the output of the bypass circuit 7 and the inverter unit 6. Also in this case, an abnormal current does not flow, and the power supply of the load device 17 can be switched from the bypass circuit 7 to the inverter unit 6. As described above, in the first embodiment of the present invention, when the load device 17 becomes overloaded, the power supply is switched from the bypass power supply, and when the load device 17 returns from the overload state to the normal load, the uninterruptible power supply device 1 automatically returns to the normal state. Can do. Note that switching to bypass power supply due to overload is also possible with the signal Inv / B from the power comparison unit 202, but the signal from the power comparison unit 202 has a slow response, which may reduce the output voltage. Since the signal OC from the overload detection unit 206 is output instantaneously when an overload occurs, the output voltage does not decrease.

  The switch circuit of the present invention is not limited to a semiconductor switch and a mechanical switch connected in parallel. Only the semiconductor switches 10 and 13 may be used as shown in FIG. In the first embodiment, a triac is used as a semiconductor switch, but a semiconductor switch in which thyristors are connected in antiparallel as shown in FIG. 4B may be used. Further, as shown in FIG. 5, one switch circuit 53 may be connected to the semiconductor switch 53-1 and the mechanical switch 53-2 in parallel, and the other switch circuit 54 may be the mechanical switch 54-2 alone. Both have the same effect.

  In the first embodiment, five DC-AC inverters are used. However, the present invention is not limited to this, and the inverter unit 6 may connect any plurality of DC-AC inverters in parallel. In the first embodiment, the bypass circuit 7 is supplied from a bypass power supply, but may be an AC power supply 3. A DC power supply may be directly input to the input of the inverter unit 6.

  It is optimal for power supply of load devices that require high reliability for power supply.

DESCRIPTION OF SYMBOLS 1 Uninterruptible power supply 2 Bypass power supply 3 AC power supply 4 AC-DC converter 5 Battery 6 Inverter part 6-1, 6-2, 6-3, 6-4, 6-5 DC-AC inverter 7 Bypass circuit 8 Power supply switching Unit 9, 10, 51, 52, 53, 54 Switch circuit 9-1, 10-1, 51-1, 52-1, 53-1 Triac 9-2, 10-2, 53-2, 54-2 Electromagnetic Contactor 15 Switch control circuit 16 Current detection means 17 Load device 51-3, 51-4, 52-3, 52-4 Thyristor 201 Load power calculation unit 202 Power comparison unit 203 Inverter output power calculation unit 204 ON / OFF control 205 SW-Drive
206 Overload detector

Claims (6)

An inverter device in which a plurality of inverters are connected in parallel;
A bypass circuit for supplying power from the bypass power supply;
An uninterruptible power supply comprising a power supply switching unit for switching the output of the inverter device and the output from the bypass power supply to supply power to the load device,
The power supply switching unit is
A first switch circuit for connecting or releasing the inverter device and the load device;
A second switch circuit for connecting or releasing the bypass circuit and the load device;
A switch control circuit for controlling on / off of the first switch circuit and for controlling on / off of the second switch circuit;
An inverter output power calculation unit that calculates the suppliable power of the inverter device according to the operating state of the plurality of inverters;
When the inverter device can supply the power consumed by the load device, the first switch circuit is turned on, the second switch circuit is turned off, and further all the inverters are instructed to operate,
When the inverter device cannot supply power consumed by the load device, the first switch circuit is turned off, the second switch circuit is turned on, and all the inverters are stopped. Uninterruptible power system. The power supply switching unit is
The current of the load device is monitored, and when the load device becomes overloaded, the first switch circuit is turned off, the second switch circuit is turned on, all the inverters are stopped, and the load device is started from the bypass circuit. The uninterruptible power supply according to claim 1, wherein power is supplied to the power supply. When switching to power supply from the bypass circuit, the inverter device automatically operates,
The uninterruptible power supply according to claim 3, wherein when the overload state of the load device is resolved, the power supply is switched to power supply from the inverter device.   The uninterruptible power supply according to any one of claims 1 to 4, wherein the first switch circuit and the second switch circuit are configured only by semiconductor switches.   5. The uninterruptible power supply according to claim 1, wherein one of the first switch circuit and the second switch circuit is configured by only a mechanical switch. The inverter device inputs DC power obtained by converting power from a commercial power source with an AC-DC converter,
The uninterruptible power supply according to claim 1, wherein the bypass power supply is the commercial power supply.

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