JPH11299129A - Uninterruptible power supply system connected in parallel with power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to significantly reduce the capacitance of a reactor placed between a commercial power supply and a load, by installing a switching means which allows a switching element for a voltage increasing/ decreasing chopper of half-bridge configuration and a switching element for an inverter to be connected in parallel. SOLUTION: When the input voltage effective value is under a rated voltage, a changer 12 is connected to 'A'. At this time, a switching element 13b operates as a step-down chopper circuit, and a storage battery 9 is charged from a voltage source formed in capacitors 14a, 14b. When the input voltage effective value is between quasi-overvoltage and overvoltage and between quasi-low voltage and low voltage, the changer 12 is connected to 'B', and switching elements 13a and 13c, 13b and 13d are parallel-connected to perform voltage compensation. When the input voltage effective value exceeds the overvoltage or falls below the low voltage, a relay 2 on the input side is turned off to fix the changer at 'A' and the switching element 13a is caused to perform chopping operation to discharge the storage battery 9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an uninterruptible power supply.

[0002]

2. Description of the Related Art There are two types of uninterruptible power supply systems: a system in which power is supplied from an inverter to a load when the power system is normal, and a system in which power is supplied from a commercial AC when the power system is normal.
In addition, among the latter, there is a device of a type in which an inverter is operated even during commercial power supply to have functions such as voltage compensation and an active filter. Such devices generally include the Institute of Electrical Engineers of Japan, the Society of Semiconductor Power Conversion, SPC-88-8.
A configuration such as that found in “power supply parallel connection type UPS using multifunctional inverters” can be given. In this UPS (uninterruptible power supply), a single-phase AC power supply and a load are connected via a reactor, and a bridge type inverter is connected to the load side of the reactor. That is, a commercial power supply and an inverter are connected in parallel as viewed from the load. Such a power supply parallel connection type uninterruptible power supply has a constant voltage control function by reactive power control, an active filter function for load harmonics, a DC voltage control function as a charger, and a sine wave inverter control function during a power failure. It is known to have four functions.

[0003]

First, problems in the uninterruptible power supply of the power supply parallel connection type will be described with reference to FIGS. FIG. 2 shows a conventional parallel-connected uninterruptible power supply of a power supply. In this configuration, 1 is a commercial AC power supply, 2
Is an input side relay, 3a and 3b are reactors, 4 is an uninterruptible power supply, 5 is a load, 6 is a ground point, 9 is a storage battery, 10 is a capacitor, and 17 is an inverter.

When the commercial AC power supply 1 is supplying the rated voltage, the uninterruptible power supply closes the input side relay 2 and supplies the power of the commercial AC power supply 1 to the load 5 via the reactor 3a. At this time, the inverter 17 charges the storage battery 9 and operates as an AC voltage source that outputs the same effective voltage value as the commercial AC power supply 1. In addition, commercial AC power supply 1
When the power failure occurs, the power failure is detected and the input side relay 2 is opened, so that the inverter 7 transfers the power of the storage battery 9 to the load 5.
Operates as a sine wave inverter supplied to further,
When the voltage of the commercial AC power supply 1 fluctuates, it is possible to keep the voltage of the load 5 constant by flowing a reactive current from the inverter 17.

When compensating the output voltage, the reactor 3b
Has a characteristic as shown in FIG. FIG. 3A shows that the effective voltage value of the commercial AC power supply 1 is 90 V.
This is a characteristic in the case where the effective voltage value of the load 5 is compensated to the rated voltage of 100 V. The load 5 has a rated capacity, leading the power factor to 0.9, 1.0, and lagging 0.9, 0.8, 0.8.
7 was described. When the inductance value of the reactor 3a is expressed in% impedance and taken on the horizontal axis,
As the% impedance becomes smaller and the power factor of the load 5 becomes a delayed power factor, the inverter current effective value tends to increase. When a load with a delay power factor of 0.7 is used, the reactor 3a needs an inductance value of 30% or more to suppress the inverter current to 100% or less, which is the rated current. On the other hand, FIG. 3B shows a case where the effective voltage value of the commercial AC power supply 1 is 110 V and the effective voltage value of the load 5 is compensated to 100 V. In this case, the inverter current flows more in the case of a power factor of 1.0 and in the case of a leading load than in the case of a delayed load. However, the effective value of the inverter current is small as compared with the condition of the impedance of the same reactor in FIG.

As described above, in the conventional uninterruptible power supply of the power supply parallel connection type, the reactive current flowing through the inverter 17 when performing voltage compensation is large, and a large reactor must be provided in order to suppress the reactive current below the rated current. There is a problem that.

[0007]

As means for solving the above-mentioned problems, the present invention comprises an inverter having a half-bridge configuration and a step-up / step-down chopper circuit having the same configuration as a half-bridge configuration. Further, a switching means is provided which can connect the switching element for the step-up / step-down chopper in parallel with the switching element for the inverter. Other configurations are the same as those of the conventional power supply parallel connection type uninterruptible power supply.

[0008] Normally, it operates as a step-up / step-down chopper circuit to realize a storage battery charging function, an active filter function, and a power failure compensation function. In the case of compensating the inverter current to be equal to or more than the rated voltage, the switching means is switched to connect the switching element of the step-up / step-down chopper circuit in parallel with the switching element of the inverter to perform the inverter operation.

This operation makes it possible to reduce the current sharing of the switching element of the inverter. Also,
As a result, the inverter current at the time of voltage compensation can be allowed up to about twice the rating, so that the reactor capacity inserted between the commercial AC power supply and the load can be made smaller than before. For example, in FIG. 3, it can be seen that the reactor connected between the commercial AC power supply and the load needs a capacity of 25% or more in the case of the conventional method, but the reactor of about 10% is adopted according to the configuration of the present invention. However, it is possible to realize a power supply parallel connection type uninterruptible power supply having a voltage compensation function.

[0010] Even during the voltage compensation period, the charging operation of the storage battery can be continued by switching the switching means in a time-division manner. Thus, for example,
While observing the temperature of the switching element, if this temperature exceeds the specified value, increase the ratio of the time connected in parallel to the inverter and reduce the current flowing per switching element to reduce the temperature of the switching element. Can be reduced.

Further, during a period in which the step-up / step-down chopper switching element is operated in parallel with the inverter switching element, the step-up / step-down chopper reactor is connected in series with the reactor inserted between the commercial AC power supply and the load. A configuration is also possible. In this case, the reactor capacity is increased only during this period, the inverter current is suppressed, and the loss of the switching element can be reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. First, in FIG. 1, 1 is a commercial AC power supply, 2 is an input side relay, 3a, 3
Reference numerals b and 3c denote reactors, 4 denotes a power supply parallel-connected uninterruptible power supply, 5 denotes a load, 6 denotes a ground point, 7 denotes a control circuit, 8 denotes a commercial input voltage detector, 9 denotes a storage battery, 10 denotes a capacitor, 11
a to 11d are diodes, 12 is a switch, 13a to 13d
Is a switching element, 14a and 14b are DC smoothing capacitors, and 17 is an inverter.

In FIG. 1, one end of a commercial AC power supply 1 is input to an uninterruptible power supply 4 connected in parallel to a power supply, and is connected to one end of a reactor 3 a via an input side relay 2. The other end of the reactor 3a is connected to one of the external loads 5 of the power supply parallel-connected uninterruptible power supply 4. The other end of the commercial AC power supply 1 is grounded at a grounding point 6, and is connected to the other end of the load 5 through the inside of the power supply parallel connection type uninterruptible power supply 4. Further, the load side of reactor 3a is connected to one end of reactor 3b. One end of the capacitor 10 is connected to this connection point. The other end of the capacitor 10 is connected to the ground point 6.

In the inverter 17, the switching element 1
3a and 13b are connected in series such that the switching element 13b is on the high potential side. Switching element 13
c and 13d are connected in series such that the switching element 13d is on the high potential side. Switching elements 13a-1
Diodes 11a to 11d are connected in anti-parallel to 3d, respectively. The high potential sides of the switching elements 13b and 13d are connected, and the switching elements 13a and 13c
Are connected to form a bridge. A series pair of capacitors 14a and 14b is connected between the high potential side of the switching element 13b and the low potential side of the switching element 13a such that the capacitor 14b is on the high potential side.

The middle point between the switching elements 13c and 13d is connected to the other end of the reactor 3b,
The midpoint between a and 14b is connected to a terminal on the ground point side of the capacitor 10. The midpoint between the switching elements 13 a and 13 b is connected to one end of the switch 12. The other end of the switch 12 is provided with A and B terminals, and A has a reactor 3c.
Are connected at one end. The other end of reactor 3c is connected to the high potential side of storage battery 9. The low potential side of the storage battery 9 is connected to the low potential side of the switching element 13a. The B terminal of the switch 12 is connected to the midpoint between the switching elements 13c and 13d. The commercial input voltage detector 8 is located inside the uninterruptible power supply unit 4 connected in parallel to the power supply, and is connected to both ends of the commercial AC power supply 1. The output of the commercial input voltage detector 8 is input to the control circuit 7. The output of the control circuit 7 is connected to the control terminal of the input side relay 2 and the control terminal of the switch 12. Further, the control circuit 7 includes the switching elements 13a to 13a.
Connected to 3d control terminal.

Next, the operation of FIGS. 1 and 4 will be described. The voltage of the commercial AC power supply 1 is detected by a commercial input voltage detector 8 and input to a control circuit 7 to calculate an effective voltage value. First, in FIG. 4, the switch 12 is connected to A when the effective value of the input voltage is within the rated voltage between the quasi-low voltage and the quasi-overvoltage. At this time, the switching elements 13c and 13d
Operates as a PWM inverter, and outputs a sine wave voltage whose input voltage has a peak value to both ends of the capacitor 10 via a filter constituted by the reactor 3b and the capacitor 10. At the same time, the DC smoothing capacitors 14a, 14b
To form a DC voltage source on the capacitors 14a and 14b. To the load 5, a voltage formed from a voltage output from the commercial AC power supply 1 via the reactor 3a and a voltage output from the inverter 17 is output. On the other hand, at this time, switching element 13b operates as a step-down chopper circuit, and charges storage battery 9 from the voltage source formed in capacitors 14a and 14b. That is, when the switching element 13b is turned on, a current flows through a closed circuit on the high potential side of the capacitor 14b, the switching element 13b, the switch 12, the reactor 3c, the storage battery 9, and the low potential side of the capacitor 14a to charge the storage battery. When the switching element 13b is turned off, the current flowing through the reactor 3c circulates in a closed circuit including the reactor 3c, the storage battery 9, the diode 11a, and the switch 12. This switching element 1
By controlling the duty ratio, which is the ratio between the ON period and the OFF period of 3b, the storage battery 9 is stably charged.

Next, when the input voltage increases in FIG. 4 and falls between a predetermined quasi-overvoltage and an overvoltage, voltage compensation is performed. In this operation, first, a voltage change is detected by the commercial input voltage detector 8, input to the control circuit 7, and it is determined that the control circuit 7 has entered the voltage compensation region. Then, the switch 12 is switched from A to B.
At this time, the switching elements 13a and 13c and 13b and 13d are connected in parallel. The control circuit 7 stops outputting the step-down chopper signal to the switching element 13b and outputs the same signal as the switching element 13d to the switching element 13b. Further, the same signal as that of the switching element 13c is output to the switching element 13a which has been stopped. In this way, the switching elements 13a, 13c and 13b, 13d are completely operated in parallel. At the time of this voltage compensation, the peak value of the output voltage of the inverter is set equal to the quasi-overvoltage, and the load 5
To a voltage lower than the voltage of the commercial AC power supply 1.

Further, in this region, after the switching elements are operated in parallel for a certain period, the switch 12 is switched to the A side to perform the step-down chopper, that is, the charging operation. At this time, the switching element control signals output from the control circuit 7 to the switching elements 13c and 13d are simultaneously changed.
, An inverter operation signal is continuously supplied as it is, and a step-down chopper signal is output to the switching element 13b. This switching operation is periodically performed every period that satisfies both the effect of reducing the loss of the switching element and the effect of suppressing heat generation by the parallel operation with the charging of the storage battery.

Next, when the voltage of the commercial AC power supply 1 further increases and becomes higher than the overvoltage, first, the input side relay 2 is turned off. In addition, the switch 12 is fixed to A, and the switching element 13a is caused to perform a chopping operation to perform a discharging operation of the storage battery 9. This is a circuit operation generally called a boost chopper. That is, when the switching element 13a is turned on, the storage battery 9 to the reactor 3c
A current flows through a path from the switch 12 to the switching element 13a. Next, when the switching element 13a is turned off,
The current flowing through the reactor 3c flows through the path from the switch 12 to the diode 11b to the DC smoothing capacitor 14b to the DC smoothing capacitor 14a to the storage battery 9, and charges the DC smoothing capacitors 14a and 14b. Therefore, the switching element 13a is periodically turned on and off, and by controlling the duty ratio, the DC smoothing capacitors 14a and 14b are controlled.
Can be kept constant. At this time, the half-bridge inverter including the switching elements 13c and 13d uses the DC smoothing capacitors 14a and 14b as a DC power supply, outputs a sine wave having a rated voltage to both ends of the capacitor 10, and a constant frequency. Since this voltage is supplied to the load 5, a voltage higher than a certain level is not applied to the load 5.

In FIG. 4, when the voltage of the commercial AC power supply 1 drops below the rated voltage and drops to a predetermined level between the sub-low voltage and the low voltage, the voltage compensation range on the high voltage side is reversed. Operate in the same way as That is, the switch 12 is switched to the B side at regular intervals, and the switching elements 13a and 13b are respectively connected to the switching elements 13a and 13b.
The same control signals as in c and 13d are given to operate in parallel. Further, the switching unit 12 is switched to the A side at regular intervals, and an operation of charging the storage battery 9 is performed.

In FIG. 4, when the voltage of the commercial AC power supply 1 drops below a predetermined low voltage,
The same operation is performed as when an overvoltage occurs. That is, the input side relay 2 is turned off, the switch 12 is fixed to the A side,
Switching element 13a performs a step-up chopper operation to charge the power of storage battery 9 to a series pair of DC smoothing capacitors 14a and 14b. Switching elements 13c and 13
d performs an inverter operation and outputs a rated sine wave voltage across the capacitor 10.

As described above, the operation is performed by appropriately switching the charging / discharging of the storage battery and the parallel connection of the inverter.

In the present embodiment, an IGBT is used as a switching element, but the operation is the same for a switching element such as a MOSFET or a bipolar transistor. Next, a second embodiment of the present invention will be described with reference to FIGS. 5, 6, and 7. FIG. In FIG. 5, reference numeral 18 denotes current detection means, and 19 denotes temperature detection means. The other configuration is the same as that of FIG. 1, and the same symbols are given to portions representing the same functions. Current detecting means 18 detects the inverter current flowing through reactor 3b and transmits this current value to control circuit 7. The temperature detecting means 19 is installed near the switching elements 13c and 13d, measures the element temperatures of the switching elements 13c and 13d, and transmits the measured temperature to the control circuit 7. The other configuration of FIG. 5 is the same as that of FIG. 1, and the operation will be described with reference to FIG. In the present embodiment, as shown in FIG. 6, when the effective value of the input voltage is between the low voltage and the overvoltage level, the voltage compensation is always performed, and the control is performed so that the output voltage becomes a constant value of the rated voltage. I do. At this time, the effective value of the inverter current increases as the input voltage increases from the rating. In the control circuit 7, the current is constantly monitored by the current detecting means 18. If the inverter current effective value exceeds a predetermined current level 2, the control circuit 7 regards the current as an overcurrent, and The state 12 is switched from A to B, and the switching elements 13a and 13b are connected in parallel with the switching elements 13c and 13d, respectively, and the inverters operate by sharing the inverter current by two switching elements. When the input voltage becomes equal to or higher than the overvoltage level, the power failure mode is set as in the above-described embodiment, and the switch 12 switches to A to operate the boost chopper circuit. on the other hand,
When the input voltage returns to or below the overvoltage, voltage compensation is performed. However, when the inverter effective value drops to level 1 lower than level 2, the parallel operation is canceled, and the storage battery charging operation by the normal inverter and the step-down chopper is performed. I do. By separately providing a current level for shifting to the parallel operation and a current level for canceling the parallel operation in this way, it is possible to prevent an easy transition between the parallel operation and the normal operation.

It is to be noted that the switching operation is periodically switched to A during the parallel operation to perform the charging operation in the same manner as in the above-described embodiment. However, the switching ratio is as shown in FIG. Is controlled by The temperature of the switching element is detected by a temperature detector 19 shown in FIG. FIG. 7 shows an operation state in which voltage compensation is performed. When the temperature of the switching element is equal to or lower than the set level, the state of the switch 12 is switched to B at a constant cycle. However, when the switching element temperature becomes higher than the set level, one of the states of the switch 12
Since the ratio of the time during which the parallel operation is performed becomes longer, the temperature rise of the switching element is suppressed. By performing this control continuously, the switching element can be held near the set level, and the switching element can be prevented from overheating.

Next, another embodiment of the present invention will be described with reference to FIGS. 8, 3 and 9. In FIG. 8, 15 and 16 are switches. The other components in FIG. 8 are the same as those in FIG. 1 or FIG. In FIG. 8, switch 15 is connected to the input side of reactor 3a, terminal A of switch 15 is connected to input side relay 2, and terminal B is connected to the connection point between terminal A of switch 12 and reactor 3c. Is done. One end of switch 16 is connected to the storage battery side of reactor 3c, and terminal A of switch 16 is connected to the high potential side of storage battery 9. The terminal B of the switch 16 is connected to the connection point between the input side relay and the terminal A of the switch 15.

Next, the operation of FIG. 8 will be described. As shown in FIG. 9, switch 12 and switches 15 and 16 are simultaneously switched. When these switches are connected to the A side, the input side relay 2 is directly connected to the reactor 3a. Further, storage battery 9 is connected to reactor 3c via terminal A of switch 16. This connection is shown in FIGS.
Has the same configuration as that in which the switch 12 is connected to the terminal A side. On the other hand, when the switch 12 is switched to the terminal B, the switches 15 and 16 are simultaneously switched to the terminal B. At this time, the input side relay 2 is connected to the reactor 3
c, and the reactor 3c is connected in series to the reactor 3a. Further, the storage battery 9 is cut off. The switching elements 13a and 13b are respectively the switching element 1
3c and 13d are connected in parallel.

When the input voltage is between the low voltage and the overvoltage and when the effective value of the inverter current is relatively small, the switches 12, 15, and 16 are connected to the terminal A to perform the inverter operation and the charging operation. . If the inverter current effective value reaches level 2 or more in this state, the switches 12, 1
5 and 16 are switched to terminal B, and the inverter is operated with the switching elements connected in parallel. At this time, the reactor on the commercial power supply side has the inductance value larger than usual because the reactor 3a and the reactor 3c are connected in series. This corresponds to the reactor 3 on the horizontal axis in FIG.
Since this is the same as increasing the capacity of a, the inverter current can be kept low. Of course, if the parallel operation continues for a long time, the switch 1
It is necessary to switch 2, 15, and 16 to the A side to perform the charging operation of the storage battery. In this period, the inverter current increases because the value of the reactor temporarily decreases, and the waveform shown in FIG. Become. On the other hand, when the input voltage approaches the rated value, when all of the switches 12, 15, and 16 are connected to the B side, and when the inverter current is reduced to level 1 lower than level 2, the switching is performed. Bowl 12,1
5 and 16 are switched to the A side, the parallel operation is stopped, and the normal inverter and storage battery charging operation is performed. At this time, the relationship between the level 1 and the level 2 of the inverter current effective value is such that when the inverter current reaches the level 2, the switches 12, 1
It is necessary to set the current value of level 1 to be smaller than the inverter current value that is reduced by switching between 5 and 16.

In the present embodiment, operations other than the simultaneous operation of the switches 12, 15, and 16 can be performed as described above. The operation is as follows.
This is a method in which the switches 15 and 16 are switched only when the inverter current further increases to a predetermined level in a state where the switching elements are switched in parallel to B and the switching elements are operated in parallel.

As described above, in the present embodiment, by connecting the reactor for charging the storage battery in series to the reactor inserted between the commercial power supply and the load, the inverter current at the time of voltage compensation is reduced, and Loss, in other words, heat generation can be suppressed. As a result, the heat radiating means inside the uninterruptible power supply can be smaller than before, and the device can be reduced in size and weight.

[0030]

According to the present invention, the capacity of the reactor inserted between the commercial power supply and the load can be greatly reduced by using the switching element for the inverter and the switching element for charging the storage battery in parallel. It is. It is also important that only a simple switching means is added to the conventional basic circuit, and that the circuit scale hardly changes. As a result, the present invention can supply a stable electric power to the load with a simpler circuit system and a smaller volume and weight than the conventional system, which contributes to the spread of inexpensive uninterruptible power supply devices.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a power supply parallel-connected uninterruptible power supply according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of a conventional power supply parallel connection type uninterruptible power supply.

FIG. 3 shows a relationship between a reactor capacity and an inverter current of a conventional parallel-connected power supply type uninterruptible power supply.

FIG. 4 is a diagram illustrating a relationship between an input voltage and an operation of the uninterruptible power supply unit of the power supply parallel connection type according to the first embodiment of this invention.

FIG. 5 is a circuit configuration diagram of a power supply parallel-connected uninterruptible power supply according to a second embodiment of the present invention.

FIG. 6 is a diagram illustrating a relationship between an input voltage and an inverter current and an operation of a power supply parallel-connected uninterruptible power supply according to a second embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the switching element temperature and the operation of a power supply parallel-connected uninterruptible power supply according to a second embodiment of the present invention.

FIG. 8 is a circuit configuration diagram of a power supply parallel connection type uninterruptible power supply according to a third embodiment of the present invention.

FIG. 9 is a diagram illustrating a relationship between an input voltage, an inverter current, and an operation of a power supply parallel-connected uninterruptible power supply according to a third embodiment of the present invention.

[Explanation of symbols]

1: Commercial AC power supply, 2: Input side relay, 3a, 3b, 3
c: reactor, 4: parallel power supply type uninterruptible power supply,
5 ... Load, 6 ... Grounding point, 7 ... Control circuit, 8 ... Commercial input voltage detector, 9 ... Storage battery, 10 ... Capacitor, 11a-1
1d: diode, 12, 15, 16 ... switch, 13a
13d: switching element, 14a, 14b: DC smoothing capacitor, 17: inverter, 18: current detecting means, 19: temperature detecting means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideyasu Umezu 3-1-1, Sachimachi, Hitachi-City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Works (72) Inventor Hideaki Kunisada 3-Chome, Sachimachi, Hitachi-City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd. Hitachi Plant (72) Inventor Yoshihiro Taniguchi 3-1-1, Sachimachi, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Plant

Claims (8)

[Claims] A first reactor inserted into a power supply line between a commercial power supply and a load, an inverter connected in parallel between the first reactor and the load, and a storage battery charging / discharging circuit. A state 1 in which the storage battery charge / discharge circuit is formed in the power supply parallel-connected uninterruptible power supply having:
A power supply parallel connection type uninterruptible power supply having a state 2 in which the switching element of the storage battery charge / discharge circuit is connected in parallel with the switching element of the inverter, and switching between the state 1 and the state 2 during operation. Power supply. 2. The uninterruptible power supply apparatus of claim 1, further comprising a second reactor, wherein the second reactor is used for the storage battery charging / discharging circuit.
An uninterruptible power supply unit connected in parallel with a power supply, comprising a state 4 in which the second reactor is connected in series to the first reactor, and switching between state 3 and state 4 during operation. 3. A first reactor inserted into a power supply line between a commercial power supply and a load, an inverter connected in parallel between the first reactor and the load, and a storage battery charging / discharging circuit. A power supply parallel-connected uninterruptible power supply having means for detecting an effective value of an input voltage input from the commercial power supply, a quasi-overvoltage level higher than a rated voltage, and an overvoltage higher than the quasi-overvoltage level. Level, a sub-low voltage level lower than the rated voltage, and a low voltage level lower than the sub-low voltage level are set, and an effective value of the input voltage is compared with each of the levels, and When the effective value of the voltage is between the quasi-overvoltage level and the overvoltage level, the voltage is compensated so that the effective value of the output voltage supplied to the load is equal to or less than the quasi-overvoltage. When the effective value of the input voltage is between the sub-low voltage level and the low voltage level, voltage compensation is performed so that the effective value of the output voltage supplied to the load is equal to or higher than the sub-low voltage. Characteristic uninterruptible power supply with parallel power supply. 4. The uninterruptible power supply of the power supply parallel connection type according to claim 3, wherein the storage battery charging / discharging circuit is in a state 1 and a switching element of the storage battery charging / discharging circuit is connected in parallel with a switching element of the inverter. State 2
Wherein the power supply parallel connection type uninterruptible power supply device is characterized in that part or all of the voltage compensation periods are set to the state 2. 5. An uninterruptible power supply unit connected in parallel according to claim 4, further comprising a second reactor, wherein the second reactor is used in the storage battery charging / discharging circuit.
A state 4 in which the second reactor is connected in series to the first reactor, and a part or all of the period for performing the voltage compensation is set to the state 4 Parallel connection type uninterruptible power supply. 6. The uninterruptible power supply unit of claim 2 or 5, wherein switching between the state 1 and the state 2 and switching between the state 3 and the state 4 are simultaneously performed. Power supply parallel connection type uninterruptible power supply. 7. The uninterruptible power supply according to any one of claims 1, 2, 4, 5, and 6, wherein
Means for detecting the effective value of the output current of the inverter,
When a current level 1 and a current level 2 that is larger than the current level 1 are set, and when the output current of the inverter rises above the current level 2, a part or all of the inverter is set to the state 2, When the output current of the inverter is lower than the current level 1, the state 1 is set. 8. The uninterruptible power supply apparatus of claim 1, further comprising: means for measuring a temperature of the switching element, wherein at least one of the plurality of power supplies is connected to each other. During a part of the period, the operation of alternately switching between the state 2 and the state 1 is performed. When the temperature of the switching element exceeds a predetermined level, the time ratio of the state 2 to the state 1 in the alternately switching operation is determined. An uninterruptible power supply unit connected in parallel to a power supply, characterized in that the power supply unit is longer than an initial set value.