JPH06197541A - Inverter device - Google Patents

Abstract

PURPOSE:To highly efficiently operate an inverter by stabilizing the voltage of an AC power source and improving the power factor of the power source. CONSTITUTION:In this device in which two sets of DC power sources 1a and 1b are connected in series and the centerpoint of the power sources 1a and 1b is connected to the centerpoint of a single-phase three-wire AC power source, and then, the input terminal of an inverter 2 is connected to one ends of the power sources 1a and 1b connected in series and the output terminal of the inverter 2 is connected to the other ends of the power sources 1a and 1b, the electric currents flowing to the AC power sources are individually controlled by controlling the inverter 2 based on the deviation of the detecting values of the currents flowing to the AC power sources from the values of reference currents. In addition, by detecting whether or not the voltage of each AC power source is higher than a reference voltage and, at the same time, whether or not the current flowing to each AC power source from the inverter 2 reaches a preset limit value, the power factor of the current of the inverter device is changed by controlling each reference current and current phase based on the voltage detecting information and limit detecting information of the AC power sources.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device which is connected to a commercial power source from a solar cell or a fuel cell via an inverter.

[0002]

2. Description of the Related Art Conventionally, as an inverter device using, for example, a solar cell as a power source, a structure as shown in FIG. 7 has been adopted.

That is, as shown in FIG. 7, a solar cell 1A
From the reverse voltage blocking diode 1B to the capacitor 1
A DC power source 1 configured to charge C is converted into an AC voltage through an inverter 2 configured in a bridge circuit, and a reactor 3 and a capacitor 4 remove harmonic components associated with pulse width modulation (PWM), and a switch 5 The main circuit is connected to the AC power supply 6 via the.

In this case, the inverter 2 is the IGPT 2a,
2b, 2c, 2d are bridge-connected to form a current control type inverter whose output current is controlled. A MOSFET may be used instead of this IGPT.

On the other hand, in the control system of the inverter 2, the voltage reference 8 and the voltage of the DC power supply 1 are compared and amplified by the amplifier 9 so that the voltage of the DC power supply becomes constant.
Is applied to the multiplier 11 via the switch 10, and the multiplier 11 multiplies the value of the voltage of the AC power supply 6 detected by the transformer 14 by the output I of the amplifier 9 to obtain the AC current reference I.
_R , and this AC current reference I _R and the main circuit inverter 2
The output I _AC of the current detector 7 provided in the output circuit is compared and amplified by the amplifier 12, and the inverter 2 is PWM-controlled via the PWM circuit 13 to control the inverter output current to the power factor 1. Has become.

In this case, the output of the transformer 14 is applied to the undervoltage detector 15 and the overvoltage detector 16, and when the AC power source becomes abnormal, the switch 10 is opened so that the inverter current becomes zero. .

By the way, the allowable range of the voltage fluctuation of the AC power source in Japan is extremely narrow as compared with the overseas, and the range is 101V ± 6V for 100V system and 202V ± 12 for 200V system.
The inverter can be operated in the V range.

However, at the present time when the solar cell inverter is put into practical use, there are many chances of exceeding 107 V, and when the inverter is stopped or the voltage rises,
It has become clear that when the inverter output current is limited, the output power of the solar cell cannot be effectively used frequently.

Therefore, when the voltage exceeds 107 V, control is also under consideration to allow the current to flow out from the inverter and reduce the voltage. In this case, since a leading current is supplied from the inverter as the load, a lagging current is taken from the AC power source.

[0010]

However, if the delay current is taken from the AC power source as described above, the loss of the transmission line is increased and the efficiency is lowered, which is not preferable.

Further, recently, as shown in FIG. 8, single-phase three-wire type wiring has been mainly used. In this case, the current control inverter 21 generally outputs a current to the 200V line. The loads 19 and 20 are 10
Many are connected to the 0V line, and in most cases the load is unbalanced at the ends. Therefore, the voltage drop due to the wiring inductances 17 and 18 is different,
The current situation is that the 100V system voltage is in an unbalanced state. In FIG. 8, the voltage of the 100V system is checked, and if some phase voltage exceeds 107V, the probability of performing the phase lead control of the inverter becomes high.

Further, since the voltage of the DC power supply 1 must be limited to 300V DC or less due to the extension regulation, a transformerless inverter cannot be used to satisfy this, and therefore a transformer is added to excite the transformer. This is a drawback that efficiency is reduced due to loss or the like.

The present invention eliminates the above-mentioned drawbacks and provides a power factor of approximately 1.
It is an object of the present invention to provide an inverter device capable of reducing the number of times the power factor advance control is performed by supplying the above electric power for efficient operation.

[0014]

In order to achieve the above object, the present invention constitutes an inverter device by the following means.

In the invention corresponding to claim 1, two sets of DC power supplies are connected in series, and the middle point is connected to the middle point of the single-phase three-wire type AC power supply, and the series connected DC power supplies are connected. In an inverter device in which an input end of an inverter is connected to both ends and an output end of this inverter is connected to the other end of each AC power supply through a reactor, a detected current value and a current reference value flowing from the inverter to each AC power supply. And first voltage control means for individually controlling the currents flowing in the respective AC power supplies on the basis of the deviation between the AC power supply and voltage detection means for detecting whether or not the voltage of each AC power supply is equal to or higher than a voltage reference. A limit detecting means for detecting whether or not the current flowing from the inverter to each AC power source has reached a preset limit value, and the AC power source voltage obtained by the voltage detecting means. And a second control means for changing the current power factor by controlling the respective current reference and the current phase on the basis of information obtained from the information and the limit detection means.

In the invention corresponding to claim 3, two sets of DC power supplies are connected in series, and the middle point is connected to the middle point of the single-phase three-wire type AC power supply, and the DC power supplies each have a step-down chopper circuit. In an inverter device in which the output end of the step-down chopper circuit is connected to the DC side of a bridge circuit in which a pair of electric valves are bridge-connected, and the AC side of this bridge circuit is connected to each AC power source. A voltage detecting means for detecting whether or not the voltage of each AC power supply is equal to or higher than a voltage reference, and a limit detecting means for detecting whether or not a current flowing from the inverter to each AC power supply has reached a preset limit value. And controlling the output current of each DC power source input to each of the step-down chopper circuits into a double-wave rectified wave shape, and the double-wave rectified wave shape current is supplied from the voltage detection means. Current control means for controlling based on voltage information of the AC power supply and information obtained from the limit detection means, and each electric valve of the bridge circuit is turned on in accordance with a positive or negative cycle of the respective AC power supply, And an electric valve control means for supplying the chopper output, which is turned off and controlled by the waveform control means, to the AC power supply.

[0017]

In the inverter device of the invention according to claim 1, when the voltage detecting means detects that the voltage of one of the alternating-current power supplies is equal to or higher than the voltage reference, the second control means detects the voltage based on the voltage information. While the power factor is 1 and the current flowing through one of the AC power supplies is reduced, the current reference is changed so that more current flowing toward the lower voltage of the other AC power supply flows, and the current is changed by the limit detecting means. Is detected to reach the limit value, it is controlled so that the phase of the current reference for the current flowing through one of the AC power supplies is advanced to lower the voltage of the AC power supply, so that the voltage is stabilized and the power factor is improved. It is possible to improve the driving efficiency.

Further, in the inverter device of the invention according to claim 3, when the voltage detecting means detects that the voltage of one of the AC power supplies is equal to or higher than the voltage reference, the current controlling means detects the voltage based on the voltage information. The output current of the chopper circuit is controlled so that the double-sided rectified wave shape remains at the power factor of 1 and the current flowing to one of the AC power supplies is reduced, while the current flowing to the lower voltage of the other AC power supply flows more. When the limit detection means detects that the current has reached the limit value, it is controlled so that the phase of the current flowing in one of the AC power supplies is advanced and the voltage of the AC power supply is lowered, so that the voltage is stabilized. It is possible to improve the operating efficiency by increasing the efficiency and power factor.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration example of an inverter device according to the present invention.

In FIG. 1, 1a and 1b are DC power supplies,
These DC power supplies 1a and 1b are connected in series, and the midpoint thereof is grounded. The DC side input terminals of an inverter 2 in which IGBTs 2a, 2b, 2c, 2d are bridge-connected are connected to both ends of the series circuit of the DC power sources 1a and 1b, and the AC side output terminals of the inverters 2 are connected to the reactor 3 respectively.
It is connected to AC power supplies (single-phase three-wire system) 6a, 6b via a, 3b and current detectors 7a, 7b. In this case, the midpoint of connection between the AC power supplies 6a and 6b is grounded. In addition, PWM is provided in parallel with the AC power supplies 6a and 6b on the output side of the inverter 2.
Capacitors 4a, 4 for absorbing harmonic currents associated with
b is connected. These DC power supplies 1a and 1b, inverter 2, reactors 3a and 3b, capacitors 4a and 4
b and the AC power supplies 6a and 6b form a main circuit.

On the other hand, the control system has a voltage reference 8 and a DC power supply 1
An amplifier 9 that compares the voltages of a and 1b and amplifies the voltage deviation to obtain a current reference I such that the DC power supply becomes constant, and the current reference I output from this amplifier 9 is input and two sets of AC Sharing of current flowing out to the power supplies 6a, 6b _Ia , _Ib
Current sharing / distributing device 30 and phase circuits 32a and 32b
Transformer 14a which is inputted via the AC power supply 6a detected by 14b, sharing is determined by the voltage and current sharing distributor 30 of 6b I _a, the current reference by multiplying the I _b I
Multipliers 11a and 11b for obtaining _Ra and I _Rb , and this multiplier 11
Amplifiers 12a and 12b for comparing the current references I _Ra and I _Rb output from a and 11b with the outputs I _7a and I _{7b of the} current detectors 7a and 7b and amplifying the current deviation, and this amplifier 12
The current deviation amplified by a and 12b is input, pulse width modulated, and IGBTs 2a, 2b, 2c and 2 of the inverter 2 are input.
PWM circuits 13a and 13b are provided for controlling d to drive the current reference I _Ra and the output I _{7a so} that the current reference I _Rb and the output I _7b match.

[0022] In this case, the limit detectors 31a, 31b is connected to the output side of the current sharing distributor 30, current sharing I _a, the magnitude of I _b detects if reached the maximum limit value, the output V _31a and V _31b are obtained.

Further, the reference values V _Ra and V _{Rb of} the AC voltage are compared with the outputs of the transformers 14a and 14b, and the amplifiers 33a and 33b for amplifying the deviation, and the outputs amplified by the amplifiers 33a and 33b are switched. Phase advance circuits 36a and 36b input via 35a and 35b are provided, and outputs A and B of the phase advance circuits 36a and 36b are the phase circuit 32 described above.
a, 32b. In this case, the amplifiers 33a, 3
Polarity detectors 34a and 34b are connected to the output side of 3b to obtain outputs _V37a and _V37b .

Further, the limit detectors 31a, 31
The outputs V _31a and V _{31b of b} and the outputs V _37a and V _{37b of the} polarity detectors 34a and 34b are respectively inputted, and the output V _37c is given to the current sharing / distributing device 30 and the switches 35a,
A logic circuit 37 for outputting the opening signals V _37a and V _37b of 35b is provided. Next, the operation of the inverter device configured as described above will be described.

The recent domestic electric power system in Japan is single-phase 3
The line type, that is, 100 V between the earth and 200 V between the lines is generally used. Moreover, in the house, a part of 200V is mainly used and 100V is mainly used. This one
Since the 00V power distribution system is performed by dividing the system into each room, the power used for housework and heating and cooling mainly plays a role in the unbalanced load of the 100V line, especially during the time when the solar cells are generating power. Grows larger. At such a time, the voltage of the line with a light load rises, and a state occurs in which power cannot be injected from the inverter beyond 101 + 6V. Therefore, first, the function of preventing such a state will be described.

Now, the voltage reference V _Ra (V _Rb ) is (101+
6) When set to V, the AC power supply 6a turns to (101
When +6) V or more, the amplifier 33a amplifies the difference voltage, and the output V34a of the polarity detector _34a has a voltage of (10
1 + 6) V is detected and it outputs "1".

On the other hand, at this time, the AC power source 6b is (101+
6) If it is less than V, similarly output V of the polarity detector 34b
_34b becomes "0" (the inverted output of _V34b is "1").

The output V _34a of the polarity detector _34a and the output V _34b of the polarity detector _34b are input to a logic circuit 37, and the logic circuit 37 operates according to the logic condition shown in FIG. Multiplier 11a
Current input shared I _a, is I _b increases and decreases. That is, the AC power supply 6a is equal to or greater than the set voltage, the AC power supply 6b current is input to the multiplier 11a than current sharing distributor 30 by the output of the AND circuit of Figure 2 (a) when less than the set voltage distribution I _a And the current sharing I input to the multiplier 11b is reduced.
Increase _b . Therefore, the inverter 2 reduces the output current to the AC power supply 6a and controls the current with the power factor of 1 so that the output current to the AC power supply 6b increases.

Similarly, when the voltage of the AC power supply 6b is higher than the set value and the voltage of the AC power supply 6a is lower than the set value, the inverted output of the output V _34a of the polarity detector _34a and the polarity detector 3 are detected.
The output V _{34b of} 4b is input to the logic circuit 37,
Increasing the current sharing I _a which is input to the multiplier 11a than current sharing distributor 30 by the output of the AND circuit (b), lowering the current sharing I _b input to the multiplier 11b. Therefore, the inverter 2 reduces the output current to the AC power supply 6b,
It is controlled to increase the output current to the AC power supply 6a.

Next, when the voltages of the AC power supplies 6a and 6b both exceed the set value, the output V _34a (logic value "1") of the polarity detector 34a and the output V _34b (logic value "1") of the polarity detector 34b. ) Is input to the logic circuit 37, and the switches 35a and 35b are both turned "on" by the output of the AND circuit shown in FIG. Therefore, when the switch 35a is turned "on", the output of the amplifier 33a is input to the phase advance circuit 36a and the phase of the phase circuit 32a is advanced from the voltage of the AC power supply 6a to advance the phase of the current reference I _Ra by the multiplier 11a. By advancing the output current of the inverter 2, the voltage of the AC power supply 6a is decreased as described above, and the control loop automatically controls the voltage to reach the set value V _Ra . Also for the AC power supply 6b, the switch 35b is "on".
By doing so, the operation is exactly the same as described above.

Further, the output V _34a of the polarity detector _34a is "1", the inverted output of the output V _34b of the polarity detector 34b is "1", and the output of the AND circuit of FIG. Current sharing I input to multiplier 11a from 30
lowering _a, the control to increase the current sharing I _b inputted conducted to a multiplier 11b, the current sharing I _b by the limit detector 31b is detected to have reached the Rimmitto value of the inverter output current, logic applied to the aND circuit shown in the output V _34a Togazu 2 (d) of the output V _31b and the polarity detector 34a of the limit detector 31b is inputted to the circuit 37, and "on" the switch 35a by its output, the phase The output of the advance circuit 36a is given to the multiplier 11a through the phase circuit 32a. Therefore, since the phase of the output I _Ra of the multiplier 11a is advanced, the inverter 2 is controlled to lower the voltage of the AC power supply 6a.

Similarly, the inverted output V _34a of the polarity detector _34a
Is "1", the output of the polarity detector 34b V _34b is "1", and the current share I input from the current share distributor 30 to the multiplier 11b by the output of the AND circuit of FIG.
Lower the _b, the multiplier 11a is controlled to increase the current sharing I _a input performed in, the current sharing I _a reaches the Rimmitto value of the inverter output current by the limit detector 31a, is inputted to the logic circuit 37 The output V 31a of the limit detector _31a and the output V _34a of the polarity detector 34b are shown in FIG.
In addition to the AND circuit shown in (e), the switch 35b is turned "on", and the output of the phase advance circuit 36b is multiplied by the multiplier 11b.
To the phase circuit 32b. Therefore, since the phase of the output I _Pb of the multiplier 11b is advanced, the inverter 2 is controlled to reduce the voltage of the AC power supply 6b.

As described above, in this embodiment, when a current is supplied from the inverter 2 to the single-phase, three-wire type AC power supplies 6a and 6b, if the voltage of any one of the AC power supplies 6a and 6b exceeds the set value. By controlling the inverter 2 so that a large amount of current with a power factor of 1 is output to the line with low voltage,
This enables efficient control of power factor (efficiency) and is effective for stabilizing the voltage of the AC power supply. Also, only when all the line voltages exceed the set value or when the inverter current reaches the limit value, the inverter 2 advances to the AC power source to supply the current and stabilize the voltage, thereby avoiding the decrease of the power factor as much as possible. be able to.

That is, by supplying more electric power from the inverter 2 to a line with a large load, it is extremely effective in stabilizing the voltage, and highly efficient operation is achieved by controlling the power factor of 1 to the limit. It can be performed.
Next, another embodiment of the present invention will be described.

In the embodiment shown in FIG. 1, the current reference I output from the amplifier 9 is given to the current sharing distributor 30 and the current sharing to be supplied to the AC power supplies 6a and 6b is determined according to the output from the logic circuit 37. However, as shown in FIG. 3, by comparing and amplifying the output voltage of the transformer 14a and the output voltage of the transformer 14b by the amplifier 42 and operating the current sharing / distributing device 30, the current reference _Ia , I. change the share of _b ,
A function of controlling so as to balance the voltages between the phases of the single-phase three-wire system may be added. Such a configuration can be easily realized by incorporating the voltages of the transformers 14a and 14b into the logic circuit 37 in FIG. Needless to say, these controls can be easily realized recently by using a microcomputer.

Further, in the embodiment shown in FIG. 1, two DC power supplies 1a and 1b were required, but in the case of one DC power supply as shown in FIG. can do. That is, as shown in FIG.
By configuring a polarity reversal chopper circuit including the GPT 38, the reactor 39, the diode 40, and the capacitor 41, and controlling the voltage across the capacitor 41 with the IGPT 38, the DC power supply 1 can be used as two DC power supplies 1a and 1b. it can. Further, the current sharing control described above can be applied not only to the main circuit of the inverter shown in FIG. 1 but also to the main inverter circuit system shown in FIG.

That is, as shown in FIG. 5, the DC power supply 1a to the IGPT 22a, the diode 23a, the reactor 3a,
A step-down chopper circuit composed of the current detector 7a and the filter capacitor 4a is configured, and its output current is represented by V in FIG.
Control to the double wave rectified wave shape shown in _7a .

Next, the step-down chopper output current turns on the electric valve 24 by the electric valves 24 and 26 while the AC power source 6a is positive with respect to the ground. In addition, AC power supply 6
While b is positive with respect to earth, the electric valve 26
Turn on.

Similarly, the DC power supply 1b to the IGPT 22b,
Diode 23b, reactor 3b, current detector 7b,
A step-down chopper composed of the capacitor 4b is configured, and the chopper output current is controlled to have a waveform like V _7b in FIG. Next, the AC power source 6a has a negative period with respect to qe ground,
The electric valve 27 is turned on, and the electric power source 6b turns on the electric valve 27 for a negative period with respect to the ground. By this operation, the inverter currents I _6a , I ₆ flowing into the AC power supplies 6a, 6b
_6b has a current waveform with a power factor of 1 as shown by I _6a and I _6b in FIG.

In such a circuit, the current sharing control by the AC voltage described in FIG. 1, that is, by changing the current value shared by the current sharing distributor 30 by the output of the logic circuit 37, V _{7a in} FIG. , V _7b by controlling the waveform
The current sharing control shown by I _6a and I _6b is performed.

On the other hand, when the voltage of the AC power supply 6a becomes high, the waveforms of V _7a and V _7b shown in FIG. 7C are controlled so that I _6b becomes I _6a and I _6b. The control becomes larger. Although this circuit can also perform power factor control, if the control range is enlarged, the waveform factor deteriorates.

Further, although the inverter is constructed as a current control system in the embodiment shown in FIG. 1, such an inverter cannot be controlled when the AC power supplies 6a and 6b fail.

Therefore, as shown in FIG. 6, the AC power source 6a,
If 6b fails, open the switches 5a and 5b,
The voltages of the capacitors 4a and 4b are detected by the transformers 14a and 14b, the AC voltage reference 39 is compared with the output voltage of the transformer 14a, and the amplified voltage is amplified by the amplifier 12a.
The voltage of the capacitor 4a is controlled via a similarly to FIG.

The output of the AC voltage reference 43 is supplied to the inverting amplifier 44.
The reference voltage whose phase has been inverted by the output voltage of the transformer 14b is compared with the output voltage of the transformer 14b, and the amplified voltage is amplified by the amplifier 12b.
The voltage of the capacitor 4b is controlled via 3b. By switching the control as described above, it is possible to obtain an independent power source which can take out the load from the capacitors 4a and 4b.

[0045]

As described above, according to the present invention, in an inverter device connected to a single-phase three-wire power supply, a large amount of electric power with a power factor of 1 is supplied to a heavy load (low voltage) phase. The distributed control enables highly efficient operation by stabilizing the voltage and improving the power factor.Moreover, when the control reaches the limit or the voltage of all phases rises too much, the power factor advance control is performed. By inserting the inverter device, it is possible to provide an inverter device that can control the voltage in a direction to stabilize the voltage rather than efficiency.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of an inverter device according to the present invention.

FIG. 2 is a diagram for explaining an operation based on a logic condition of a logic circuit in the embodiment.

FIG. 3 is a circuit diagram for explaining a sharing function for a current sharing distributor according to another embodiment of the present invention.

FIG. 4 is a power supply circuit diagram showing a configuration example when the present invention is applied to an inverter using one DC power supply.

5 is a diagram showing a configuration example of a main circuit and its control waveform when the present invention is applied to an inverter of a method different from that of FIG.

FIG. 6 is a diagram showing a configuration example when the present invention is applied to an inverter in consideration of a power failure of an AC power source.

FIG. 7 is a circuit diagram showing a configuration example of a conventional inverter device.

FIG. 8 is a circuit diagram showing a single-phase three-wire type power distribution system as an AC power supply to which the inverter device is connected.

[Explanation of symbols]

1 ... DC power supply, 2 ... Inverter, 3a, 3b ... Reactor, 4a, 4b ... Capacitor, 5a, 5b ...
Switch, 6a, 6b ... AC power supply, 7a, 7b ... Current detector, 8 ... Voltage reference, 9 ... Amplifier, 11a, 11
b ... Multiplier, 12a, 12b ... Amplifier, 13a, 1
3b ... PWM circuit, 14a, 14b ... Transformer, 1
9, 20 ... Load, 21 ... Current control inverter, 22
... IGBT, 23a, 23b ... diode, 24 to
27 ... Electric valve, 30 ... Current sharing distributor, 31a, 3
1b ... Limit detector, 32a, 32b ... Phase circuit, 33a, 33b ... Amplifier, 34a, 34b ... Polarity detector, 35a, 35b ... Switch, 36a, 36
b ... Phase lead circuit, 37 ... Logic circuit, 38 ... IG
BT, 39 ... Reactor, 40 ... Diode, 41
...... Capacitor, 43 …… AC voltage reference, 44 …… Inversion amplifier.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tatsuaki Anbo No. 1 Toshiba-cho, Fuchu-shi, Tokyo Toshiba Corporation Fuchu factory

Claims (4)

[Claims] 1. Two sets of DC power supplies are connected in series, the middle point of which is connected to the middle point of a single-phase three-wire type AC power supply, and the input ends of the inverters are connected to both ends of the DC power supplies connected in series. In an inverter device in which the output end of this inverter is connected to the other end of each AC power supply via a reactor, the connection is based on the deviation between the detected value of the current flowing from the inverter to each AC power supply and the current reference. First control means for controlling an inverter to individually control currents flowing in the respective AC power supplies, voltage detection means for detecting whether or not the voltage of each of the AC power supplies is equal to or higher than a voltage reference, and each AC from the inverter Limit detection means for detecting whether or not the current flowing through the power supply has reached a preset limit value,
Second control means for changing the current power factor by controlling the respective current reference and current phase based on the voltage information of the AC power source obtained by the voltage detecting means and the information obtained by the limit detecting means. An inverter device characterized by being provided. 2. The inverter device according to claim 1, wherein voltage control means is provided, and when the AC power supply fails, the AC power supply is disconnected and the inverter is controlled from the current control by the first control means by the voltage control means. An inverter device characterized by switching to voltage control. 3. Two sets of DC power supplies are connected in series, the middle point of which is connected to the middle point of a single-phase three-wire AC power supply, and each of the DC power supplies is provided with a step-down chopper circuit. In an inverter device in which the output ends of the circuit are connected to the DC side of a bridge circuit in which a pair of electric valves are bridge-connected, and the AC side of this bridge circuit is connected to each AC power supply, the voltage of each AC power supply Is a voltage reference or more, a voltage detection unit for detecting whether the current flowing from the inverter to each AC power source has reached a preset limit value, and each step-down chopper circuit. The output current of each DC power supply is controlled in a double-wave rectified wave shape by means of, and the current of the double-wave rectified wave shape is obtained by the voltage detection means. And current control means for controlling based on information obtained from the limit detection means, and each electric valve of the bridge circuit is turned on / off in accordance with the positive / negative cycle of the respective AC power source, and the waveform control means is provided. And an electric valve control means for supplying the chopper output controlled by the above to the AC power supply. 4. The inverter device according to claim 1, wherein two sets of direct current power supplies are controlled by one direct current power supply and an output of the direct current power supplies is controlled by a polarity reversal type chopper circuit. An inverter device characterized in that a circuit for obtaining a current is configured to be another DC power supply.