JP2002095183A - Uninterruptible power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously supply the power to a load even if an overload condition is temporarily generated while the power is supplied to the load from the commercial power supply. SOLUTION: If the overload condition is generated temporarily while the power is supplied to the load 4 from the commercial power supply 5, a detected voltage of a voltage detector 16 is lowered and thereby the voltage detector 16 outputs a power failure detecting signal 17, and an inverter control circuit 9A drives an inverter 1. In this timing, a power direction judging circuit 36 outputs a power direction judging signal indicating that the power direction is not the load regenerating direction to a switching control circuit 15A based on the detected signal from a voltage detector 23 and a current detector 48. Accordingly, the switching control circuit 15A maintains a semiconductor switch 7 of a connecting condition switching means 6 to the ON state.

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 supplying power to a load when a commercial power supply fails.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional uninterruptible power supply. In this figure, an inverter 1 as a power converter
Is configured to supply power to the load 4 via the inverter transformer 3 using the battery 2 as an input power supply.
Note that the input power supply of the inverter 1 is not limited to the battery 2 and another DC voltage source such as a D / D converter may be used.

[0003] The load 4 always receives the supply of AC power from the commercial power supply 5 through the connection state switching means 6. The connection state switching means 6 is disposed in a power supply path between the commercial power supply 5 and the load 4 and includes a semiconductor switch 7 and a contactor 8 connected in parallel to the semiconductor switch 7. ing. The semiconductor element used for the semiconductor switch 7 is a thyristor in this embodiment, but another switching element such as a transistor, an IGBT, or a triac may be used. The contactor 8 protects these semiconductor elements of the semiconductor switch 7. That is, a current detector (not shown) is provided between the connection state switching means 6 and the load 4.
When the detected current value increases by a certain amount or more, the contactor control means (not shown) closes the contactor 8 and closes the semiconductor switch 7.
Are short-circuited to protect the semiconductor element from overcurrent.

The inverter 1 is controlled by an inverter control circuit 9. The inverter control circuit 9 includes a reference generation circuit 10, an output voltage control circuit 1
1, a gate control circuit 12, a power failure detection circuit 13, a PLL circuit 14, and a switching control circuit 15. A voltage detector 16 is provided between the commercial power supply 5 and the connection state switching means 6, and a voltage detection signal from the voltage detector 16 is input to the power failure detection circuit 13 and the PLL circuit 14. ing. The power failure detection circuit 13 outputs the power failure detection signal 17 to the switching control circuit 15 and the reference generation circuit 1 when the input voltage detection signal falls below a certain level.
0 is output. The switching control circuit 15
The switching control signal 18 is output to the connection state switching means 6 based on the input of the power failure detection signal 17. Also,
The PLL circuit 14 outputs an output voltage phase reference signal 20 to the output voltage control circuit 11 based on the input of the voltage detection signal from the voltage detector 16.

When the power failure detection signal 17 from the power failure detection circuit 13 is input, the reference generation circuit 10 outputs the output voltage reference signal 1
9 is output to the output voltage control circuit 11. Here, a voltage detector 23 is attached to the output side of the inverter transformer 3.
The output voltage feedback signal 24 is input to the output voltage control circuit 11. The output voltage control circuit 11 outputs the output voltage reference signal 19, the output voltage phase reference signal 20, and the output voltage feedback signal 2
4 so that the output voltage feedback signal 24 matches the output voltage reference signal 19 and the output voltage command signal 21
Is output to the gate control circuit 12. The gate control circuit 12 outputs the output voltage command signal 21
Outputs a gate signal 22 based on the input of
Supplies the AC power to the load 4 via the inverter transformer 3 based on the input of the gate signal 22.

FIG. 10 is a configuration diagram of the inverter 1 in FIG. The main circuit of the inverter 1 includes switching elements S1, S2 forming a U-phase arm, switching elements S3, S4 forming a V-phase arm, and switching elements S5, S6 forming a W-phase arm. The connection points between the switching elements forming each arm are output terminals of the U-phase, V-phase, and W-phase. One end and the other end of each arm are connected to one end and the other end of a DC capacitor 26 connected in parallel to the battery 2.

In this embodiment, IGBTs are used as switching elements, and a reverse voltage prevention diode D is connected in anti-parallel between the collector and emitter of each IGBT. A gate drive circuit 25 is provided at the gate of each IGBT.
IGBTs are inputted, and on / off control of each IGBT is performed by the gate drive signals. Then, pulse width modulation (PWM) control of the inverter 1 is performed by the on / off control of the IGBT, whereby the output voltage of the inverter 1 is controlled. Although a snubber circuit for suppressing a surge voltage at the time of switching is individually or collectively provided in each of the switching elements S1 to S6, description thereof will be omitted. Also, the gate signal 22
Are switching elements (for example, S
1, S2) is generated such that a period (dead time) for preventing the snubber circuits from being turned on at the same time can be secured to secure a charging / discharging period of each snubber circuit.

FIG. 11 shows the reference generation circuit 10 in FIG.
FIG. Voltage reference generator 2 for each phase of U, V, W
Sine-wave voltage reference signals are output from 7a to 27c, and these voltage reference signals are multiplied by a soft start signal from a soft start circuit 29 by multipliers 28a to 28c. The signals from the multipliers 28a to 28c are used as the output voltage reference signal 19 as the output voltage control circuit 1.
1 is output.

The above-mentioned soft start signal is a signal for gradually increasing the output voltage from zero when the inverter 1 is started. The soft start signal is a temporary increase function such as a ramp function during the start-up period. Is a constant value such as 1. The technique of gradually increasing the output voltage at startup without suddenly increasing the output voltage is called “soft start”. In the above example, the case where the multipliers 28a to 28c output a constant sinusoidal voltage reference signal has been described. However, for example, a voltage reference signal whose signal level changes with time, such as VVVF (variable voltage variable frequency) control. May be output.

FIG. 12 is a configuration diagram of the output voltage control circuit 11 in FIG. Subtractor 30a for each phase of U, V, W
To 30c are signals obtained by calculating the difference between the output voltage reference signal 19 and the output voltage feedback signal 24 by the PI control circuit 3.
Output to 1a to 31c. Then, the PI control circuit 31a
The signal subjected to the PI calculation by .about.31c is output to the gate control circuit 12 as the output voltage command signal 21. The output voltage feedback signal 24 is output from the output voltage reference signal 1 under the control of the PI control circuits 31a to 31c.
9 can be followed. Although PI control is used in this example, PID control, IP control, or other general control methods may be used, or a method such as modern control theory may be used. Although not described in detail, a circuit for controlling the output current can be added to the output voltage control circuit 11 at the subsequent stage, at the previous stage, or in parallel in order to increase the speed and stabilize. It is.

FIG. 13 shows the gate control circuit 1 shown in FIG.
FIG. The subtracters 33a to 33c for each phase output the output voltage command signal 21 for each phase from the output voltage control circuit 11.
And the difference between the carrier signal from the carrier signal generation circuit 32 and the carrier signal. The comparators 34a to 34c output signals based on the input of the difference to the gate signal output circuits 35a to 35c.
5c, and the gate signal output circuits 35a to 35c output the gate signal 22 to the inverter 1. In this example, a so-called triangular wave comparison method has been described, but the generation method of the gate pulse is not particularly limited.

Next, the operation of FIG. 9 will be described. Normally, the semiconductor switch 7 of the connection state switching means 6 is in the ON state, the contactor 8 is in the OFF state, and the load 4 is supplied with AC power from the commercial power supply 5. At this time, the operation of the inverter 1 is not performed. As described above, when the voltage detection signal of the voltage detector 16 falls below a certain level while the load 4 is receiving power supply from the commercial power supply 5, the power failure detection circuit 13 outputs the power failure detection signal 17. Upon receiving the power failure detection signal 17, the switching control circuit 15 outputs a switching control signal 18 to the connection state switching means 6, switches the semiconductor switch 7 to the off state, and switches from the commercial power supply 5 to the load 4
Power supply to the power supply is stopped.

The reference generation circuit 10 includes a power failure detection circuit 1
When the power failure detection signal 17 is input, the output voltage reference signal 19 is output to the output voltage control circuit 11. The output voltage control circuit 11 outputs P P
An output voltage phase reference signal 20 from the LL circuit 14 and an output voltage feedback signal 24 from the voltage detector 23 are input, and an output voltage command signal 21 is output to the gate control circuit 12 based on the input of these signals. Gate control circuit 12 outputs gate signal 22 to inverter 1 based on the input of output voltage command signal 21. Inverter 1
Outputs AC power to the load 4 via the inverter transformer 3 based on the input of the gate signal 22. At this time, as described above, since the semiconductor switch 7 is in the OFF state, the uninterruptible power supply is insulated from the commercial power supply 5 even if the power failure on the commercial power supply 5 side is caused by a short circuit accident or the like. Is in a safe condition.

[0014]

As described above, the AC power from the commercial power supply 5 is normally supplied to the load 4 as described above, and when a power failure occurs on the commercial power supply 5 side, the AC power is immediately supplied from the inverter 1. Electric power is supplied to the load 4. However, the power failure detection circuit 13 detects the power failure state of the commercial power supply 5 based on the voltage detection of the voltage detector 16, so that if a temporary overload state occurs on the load 4 side, In some cases, the power failure detection circuit 13 detects the occurrence of a power failure even though no power failure has actually occurred.

For example, when a large-capacity motor is started on the load 4 side or when a large-capacity transformer is turned on, an overload state that requires 4 to 5 times as much power as in a steady state occurs. A so-called rush current flows into the load 4,
The voltage on the commercial power supply 5 side is greatly reduced. The power failure detection circuit 13 determines that such a voltage drop has occurred as a power failure, and outputs a power failure detection signal 17. As a result, the semiconductor switch 7 is switched from the on state to the off state, the power supply from the commercial power supply 5 is stopped, and the AC power from the inverter 1 is supplied to the load 4.

However, the inverter 1 cannot supply more than the rated power to the load 4, and when the large-capacity motor is started on the load 4 side as described above, the overcurrent protection of the inverter 1 is performed. The function will work. Therefore, the operation of the inverter 1 is stopped and the load 4
Could not be supplied continuously.

The present invention has been made in view of the above circumstances, and even if a temporary overload state occurs while power is supplied from a commercial power supply to a load, the load is continuously applied to the load. It is an object to provide an uninterruptible power supply capable of supplying power.

[0018]

According to a first aspect of the present invention, there is provided a power conversion device capable of supplying power to a load which is normally supplied with power from a commercial power supply. And a power supply path between the commercial power supply and the load, and a semiconductor switch. The semiconductor switch is turned on and off by the semiconductor switch to connect the commercial power supply with the load and the power converter. A connection state switching means for switching a connection state between the power converter and the switching operation of the connection state switching means, and when detecting a voltage drop indicating that the commercial power supply is in a power failure state, the power converter supplies the load to the load. And a converter control circuit for performing power supply of the power supply, wherein the converter control circuit determines a direction of power transferred between the commercial power supply and the load. If the power direction at the time of power outage detection of the commercial power supply is not the load regeneration direction, the power converter does not require the connection state switching unit to be in the supply path cutoff state. The power supply to the load is performed.

According to the above configuration, it is possible to determine whether the voltage drop on the commercial power supply side is caused by a short circuit accident on the commercial power supply side or a temporary overload on the load side by determining the power direction. Then, in the case of a temporary overload, the power is supplied from the power converter to the load without the connection state switching unit being in the cutoff state.
Power will be supplied from both the commercial power supply and the power converter. Therefore, sufficient power supply capability can be ensured even in a temporary overload state, and stable power supply can be continuously performed.

According to a second aspect of the present invention, in the first aspect of the present invention, the power direction determining circuit is configured to detect a voltage and a current in a power supply path between the commercial power supply and the connection state switching means. The determination of the power direction is performed.

According to the above configuration, since the determination of the power direction is made based on the detection of the voltage and current near the commercial power supply, in the case where it is difficult to make the determination based on the detection of the voltage and current near the load, It will be effective.

According to a third aspect of the present invention, in the first or second aspect of the invention, the converter control circuit is configured to control the power converter when an output current detection value of the power converter becomes equal to or more than a predetermined value. And an overcurrent control circuit for reducing the output current.

According to the above configuration, even when the output current of the power converter increases, the output current can be reduced by controlling the output of the converter. Therefore, power can be continuously supplied to the load without operating the overcurrent protection function of the power converter itself.

According to a fourth aspect of the present invention, there is provided a power converter capable of constantly supplying power to a load which is supplied with power from a commercial power supply, and a power supply path between the commercial power supply and the load. Connection state switching means for switching a connection state between the commercial power supply, the load, and the power converter by on / off control of the semiconductor switch; and A converter control circuit for controlling the switching operation of the means and causing the power converter to supply power to the load when detecting a voltage drop indicating that the commercial power supply is in a power failure state. In the power failure power supply device, the converter control circuit has a manual operation circuit for manually performing control on a switching operation of the connection state switching unit. That.

According to the above configuration, if the timing of the temporary overload state can be known in advance, the connection state of the connection state switching means 6 can be manually switched in advance. Therefore, sufficient power supply capability can be ensured by a simple configuration without adding the power direction determination function.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the converter control circuit outputs the power of the power converter when an output current detection value of the power converter becomes equal to or more than a predetermined value. An overcurrent control circuit for reducing a current is provided.

According to the above configuration, power can be continuously supplied to the load without activating the overcurrent protection function of the power converter itself, similarly to the third aspect of the invention.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. However, the same components as those described with reference to FIGS. 9 to 13 are denoted by the same or similar reference numerals, and redundant description will be omitted.

FIG. 1 is a configuration diagram of a first embodiment of the present invention. FIG. 1 differs from FIG. 9 in that the inverter control circuit 9 is replaced with the inverter control circuit 9A, and a current detector 48 is added between the connection state switching means 6 and the load 4. The inverter control circuit 9A is different from the inverter control circuit 9 in that a power direction determination circuit 36 is added, and the switching control circuit 15A has a function different from that of the switching control circuit 15.

The power direction judging circuit 36 has a multiplier 37 and judging means 38. The multiplier 37 receives the current detection signal from the current detector 48 and the voltage detection signal from the voltage detector 23, and outputs a signal generated by multiplying them by the determination means 38. The judging means 38 receives the signal from the multiplier 37 and
It is determined that the direction of power transmitted and received between the load 4 and the power amount and the power amount are equal to or more than a certain value, and a power direction determination signal 39 is output to the switching control circuit 15A. The switching control circuit 15A includes a power failure detection signal 17 from the power failure detection circuit 13 and a power direction determination signal 39 from the determination means 38.
The switching control signal 18 is output to the semiconductor switch 7 of the connection state switching means 6 on the basis of the two signals, namely, the power direction determination signal 39 from the power supply control unit 6. The determination means 38
May have a software configuration or a hardware configuration such as a comparator.

FIG. 2 shows the switching control circuit 15A in FIG.
FIG. As shown in this figure, the switching control circuit 15A includes a power failure detection signal 17 and a power direction determination signal 3
9. A hold circuit 40 for outputting a switching signal based on the input of the switch 9
And switching switches 41a to 41c for each phase, the contacts of which are controlled by switching signals from the hold circuit 40. When the contacts of the changeover switches 41a to 41c are on the ON command side, the semiconductor switches 7a to 7c of each phase are in the ON state, and the commercial power supply 5 can supply power to the load 4. ing. When the contacts of the changeover switches 41a to 41c are on the off command side, the semiconductor switches 7a to 7c of each phase are in the off state, and the power supply from the commercial power supply 5 to the load 4 is cut off. It is in a state.

When the power is supplied from the commercial power supply 5 to the load 4, the hold circuit 40 receives the power failure detection signal 17 and the power direction determination signal 39 indicating the load regeneration direction (ie, short-circuit). In the case where a power failure accident occurs due to this, the hold circuit 40 switches the respective contacts of the changeover switches 41a to 41c which have been the on-command side to the off-command side. As a result, the power supply from the commercial power supply 5 to the load 4 is cut off. on the other hand,
The hold circuit 40 detects the power failure detection signal 17 and the power direction determination signal 39 indicating the direction opposite to the load regeneration direction.
Is input (that is, when the voltage on the commercial power supply 5 side decreases due to temporary overload), the hold circuit 40 keeps the contacts of the change-over switches 41a to 41c in the ON state. Therefore, power supply from the commercial power supply 5 to the load 4 is continued regardless of the input of the power failure detection signal 17.

Next, the operation of FIG. 1 will be described. Now
It is assumed that the semiconductor switch 7 is on and the load 4 is receiving power from the commercial power supply 5 (at this time, the inverter 1 is not operated). In this state, if a short circuit accident occurs on the commercial power supply 5 side,
Since the voltage detection signal from the voltage detector 16 drops below a certain level, the power failure detection circuit 13 outputs a power failure detection signal 17. At this time, the power direction determination circuit 36 determines that the direction of the power transmitted and received between the commercial power supply 5 and the load 4 is the load regeneration direction based on the input of the detection signals from the voltage detector 23 and the current detector 48. And outputs the power direction determination signal 39 to the switching control circuit 15A.

The switching control circuit 15A outputs the power failure detection signal 17
And a power direction determination signal 3 indicating a load regeneration direction
9, the semiconductor switch 7 is activated by the functions of the hold circuit 40 and the changeover switches 41a to 41c.
Is switched from the ON state to the OFF state. Thereby, the power supply from the commercial power supply 5 to the load 4 is cut off. When the power failure detection signal 17 is input from the power failure detection circuit 13, the reference generation circuit 10 outputs the output voltage reference signal 19.
Is output to the output voltage control circuit 11, and the output voltage control circuit 1
1 is an output voltage reference signal 19, an output voltage phase reference signal 2
The output voltage command signal 21 is output to the gate control circuit 12 based on 0 and the input of the output voltage feedback signal 24. The gate control circuit 12 outputs the output voltage command signal 21
, The gate signal 22 is output to the inverter 1. The inverter 1 supplies power to the load 4 via the inverter transformer 3 based on the input of the output voltage command signal 21.

On the other hand, if a temporary overload state occurs on the load 4 side while the load 4 is receiving power supply only from the commercial power supply 5, the voltage detection signal from the voltage detector 16 drops below a certain level. Therefore, the power failure detection circuit 13 outputs a power failure detection signal 17. At this time, based on the input of the detection signals from the voltage detector 23 and the current detector 48, the power direction determination circuit 36 determines that the direction of the power transmitted and received between the commercial power supply 5 and the load 4 is the load regeneration direction. It is determined that the direction is the opposite direction, and the power direction determination signal 39 is output to the switching control circuit 15A.

The switching control circuit 15A outputs the power failure detection signal 17
And the power direction determination signal 39 indicating the direction opposite to the load regeneration direction, the connection state of the semiconductor switch 7 is turned on by the functions of the hold circuit 40 and the changeover switches 41a to 41c. maintain. Therefore, power supply from the commercial power supply 5 to the load 4 is continued. Further, the inverter 1 is started under the control of the inverter control circuit 9A, and supplies power to the load 4 via the inverter transformer 3. That is, the load 4 receives power supply from both the commercial power supply 5 and the inverter 1. Therefore, the amount of power supply to the load 4 becomes sufficient, and it is possible to avoid a situation in which power supply to the load 4 cannot be continued because the overcurrent protection function of the inverter 1 works as in the related art. . Although a detailed description is omitted, it is also possible to adopt a configuration in which the operation of the inverter 1 is stopped after the temporary overload state is released, and the power supply to the load 4 is performed only by the commercial power supply 5 again.

FIG. 3 is a configuration diagram of a second embodiment of the present invention. FIG. 3 is different from FIG. 1 in that a current detector 48 is provided between the commercial power supply 5 and the connection state switching means 6, and a multiplier 37 of the power direction determination circuit 36 includes a voltage detector 16 and a current detector The point is that a detection signal from the detector 48 is input. The other points are the same as those in FIG.

The configuration of this embodiment is effective when it is difficult to determine the power amount and the power direction by detecting the voltage and the current near the load 4. For example, load 4
In such a case, the influence of the short-circuit accident occurring on the commercial power supply 5 side is buffered on the load side, so that the voltage detection value near the load 4 side and The current detection value may not be accurate. Therefore, in consideration of such a case, in the present embodiment, the determination of the power amount and the power direction is performed based on the voltage detection value and the current detection value on the commercial power supply 5 side.

FIG. 4 is a configuration diagram of a third embodiment of the present invention. FIG. 4 differs from FIG. 1 in that a current detector 42 is added between the inverter 1 and the inverter transformer 3, and the gate control circuit 12 </ b> A based on the input of a current detection signal from the current detector 42. Is that an overcurrent control circuit 43 that outputs an overcurrent control signal 44 is added to the inverter control circuit 9C. The other points are the same as those in FIG.

FIG. 5 shows the gate control circuit 12 shown in FIG.
FIG. The gate control circuit 12A of FIG.
The difference from the conventional gate control circuit 12 shown in FIG. 3 is that changeover switches 45a to 45c for performing a contact switching operation by an overcurrent control signal 44 are provided on the output side of the gate signal output circuits 35a to 35c. It is.

Next, the operation of the overcurrent control circuit 43 in the third embodiment will be described. Overcurrent control circuit 4
3 always receives a current detection signal from the current detector 42, and outputs the current detection signal at a fixed level (inverter 1).
When the level is higher than the overcurrent level set in the own overcurrent protection function) or more, an overcurrent control signal 44 is output to the gate control circuit 12A. When the overcurrent control signal 44 is input, the gate control circuit 12A receives the changeover switch 45a which has been turned on until then.
To 45c are turned off, and the gate signal output circuit 3
The output of the gate signal 22 from 5a to 35c is stopped.
Thus, the amount of current output from inverter 1 decreases quickly. When the current detection signal from the current detector 42 falls below a certain level, the output of the overcurrent control signal 44 from the overcurrent control circuit 43 to the gate control circuit 12A is stopped. Therefore, the changeover switches 45a to 45c
Returns from the off state to the on state, and the gate signal 22 is output again from the gate signal output circuits 35a to 35c.

As described above, in this embodiment, the overcurrent control circuit 43 controls the output of the inverter 1 by controlling the output of the gate signal 22 from the gate control circuit 12A, and the overcurrent control of the inverter 1 itself is performed. It prevents the protection function from working. Therefore, even if a phase difference or a voltage difference occurs suddenly while the inverter 1 is operated in cooperation with the commercial power supply 5, the operation of the inverter 1 is not stopped by its own overcurrent protection function. , The power supply to the load 4 can be continuously performed.

FIG. 6 is a configuration diagram of a fourth embodiment of the present invention. FIG. 6 is different from FIG. 4 in that a current detector 48 is provided between the commercial power supply 5 and the connection state switching means 6 as in FIG.
Is that the detection signals from the voltage detector 16 and the current detector 48 are input. Other points are the same as those in FIG.

FIG. 7 is a configuration diagram of a fifth embodiment of the present invention. FIG. 7 differs from FIG. 1 in that the current detector 48 and the power direction determination circuit 36 in FIG. 1 are deleted, and a manual operation circuit 46 is added in the inverter control circuit 9E instead. The manual operation circuit 46 outputs a manual operation signal 47 based on the operation of the operator to the switching control circuit 1.
5 so that the switching of the semiconductor switch 7 can be controlled by the operator's intention.

According to the configuration of this embodiment, when the timing of starting a large-capacity motor on the load 4 side or turning on a large-capacity transformer, that is, the timing at which a temporary overload occurs, is known. A manual operation signal 47 from the manual operation circuit 46 can be input to the switching control circuit 15 in advance. Thus, even when the switching control circuit 15 receives the power failure detection signal 17 from the power failure detection circuit 13,
The semiconductor switch 7 can be kept in the ON state as it is. Therefore, according to the present embodiment, the same effect as in the first and second embodiments can be obtained with a simple configuration in which only the manual operation circuit 46 is added.

FIG. 8 is a configuration diagram of a sixth embodiment of the present invention. FIG. 8 differs from FIG. 7 in that a current detector 42 and an overcurrent control circuit 43 are added, and the other points are the same as those in FIG. 7. For other points, see FIG.
The description is omitted because it is the same as that of FIG. According to this embodiment, the same effects as those of the third and fourth embodiments can be obtained with a simple configuration in which only the manual operation circuit 46 is added.

[0047]

As described above, according to the present invention, even if a temporary overload state occurs while power is supplied from a commercial power supply to a load, the power to the load is continuously maintained. It becomes possible to supply.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a main part of a switching control circuit 15A in FIG. 1;

FIG. 3 is a configuration diagram of a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a gate control circuit 12A in FIG. 4;

FIG. 6 is a configuration diagram of a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram of a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram of a sixth embodiment of the present invention.

FIG. 9 is a configuration diagram of a conventional device.

FIG. 10 is a configuration diagram of an inverter 1 in FIG. 9;

11 is a configuration diagram of a reference generation circuit 10 in FIG.

FIG. 12 is a configuration diagram of an output voltage control circuit 11 in FIG. 9;

FIG. 13 is a configuration diagram of a gate control circuit 12 in FIG. 9;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Inverter (power converter) 2 Battery 3 Inverter transformer 4 Load 5 Commercial power supply 6 Connection state switching means 7, 7A-7C Semiconductor switch 8 Contactor 9, 9A-9F Inverter control circuit (Converter control circuit) 10 Reference generation circuit Reference Signs List 11 output voltage control circuit 12, 12A gate control circuit 13 power failure detection circuit 14 PLL circuit 15, 15A switching control circuit 16 voltage detector 17 power failure detection signal 18 switching control signal 19 output voltage reference signal 20 output voltage phase reference signal 21 output voltage Command signal 22 Gate signal 23 Voltage detector 24 Output voltage feedback signal 25 Gate drive circuit 26 DC capacitor 27a-27c Voltage reference generator 28a-28c Multiplier 29 Soft start circuit 30a-30c Subtractor 31a-31c PI control circuit 32 Carry Signal generation circuits 33a to 33c Subtractors 34a to 34c Comparators 35a to 35c Gate signal output circuits 36 Power direction determination circuits 37 Multipliers 38 Determination means 39 Power direction determination signals 40 Hold circuits 41a to 41c Changeover switches 42 Current detectors 43 Overcurrent Control circuit 44 Overcurrent control signal 45a to 45c Changeover switch 46 Manual operation circuit 47 Manual operation signal 48 Current detector S1 to S6 Switching element D Reverse voltage prevention diode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5G003 AA01 BA01 DA07 DA18 GA01 GA02 GB06 5G015 FA16 GA06 JA10 JA11 JA32 JA34 JA35 JA52 5H007 BB05 CA01 CA03 CC01 CC32 DA06 DB01 DC02 DC05 EA13 FA02 FA03 GA02 GA09

Claims (5)

[Claims] 1. A power converter capable of constantly supplying power to a load that is supplied with power from a commercial power supply, and a power converter provided in a power supply path between the commercial power supply and the load. A connection state switching unit configured to switch a connection state between the commercial power supply, the load, and the power converter by on / off control of the semiconductor switch; and controlling a switching operation of the connection state switching unit. And a converter control circuit for causing the power converter to supply power to the load when detecting a voltage drop indicating that the commercial power supply is in a power failure state. The converter control circuit has a power direction determination circuit that determines a direction of power transmitted and received between the commercial power supply and the load, and the power direction when the power failure of the commercial power supply is detected is determined by the load direction. When the power supply is not in the regenerative direction, the power converter causes the power converter to supply power to the load without setting the connection state switching unit to a supply path cutoff state. 2. The power direction determining circuit determines the power direction based on detection of a voltage and a current in a power supply path between the commercial power supply and the connection state switching means. The uninterruptible power supply according to claim 1. 3. The converter control circuit includes an overcurrent control circuit that reduces an output current of the power converter when an output current detection value of the power converter becomes equal to or greater than a predetermined value. The uninterruptible power supply according to claim 1 or 2, wherein: 4. A power converter capable of constantly supplying power to a load which is supplied with power from a commercial power supply, wherein the power converter is provided in a power supply path between the commercial power supply and the load. A connection state switching unit configured to switch a connection state between the commercial power supply, the load, and the power converter by on / off control of the semiconductor switch; and controlling a switching operation of the connection state switching unit. And a converter control circuit for causing the power converter to supply power to the load when detecting a voltage drop indicating that the commercial power supply is in a power failure state. The converter control circuit has a manual operation circuit for manually controlling the switching operation of the connection state switching means, characterized in that: 5. The converter control circuit according to claim 1, further comprising an overcurrent control circuit configured to reduce an output current of the power converter when an output current detection value of the power converter becomes equal to or more than a predetermined value. The uninterruptible power supply according to claim 4, characterized in that: