JP3122265B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for connecting a solar cell or a fuel cell to a commercial power supply via an inverter.

[0002]

2. Description of the Related Art Conventionally, for example, an inverter having a configuration as shown in FIG.

[0003] That is, as shown in FIG.
From the capacitor 1 via the reverse voltage blocking diode 1B
C is converted from a DC power supply 1 configured to charge C to an AC through an inverter 2 configured as a bridge circuit, and a harmonic component accompanying pulse width modulation (PWM) is removed by a reactor 3 and a capacitor 4. Constitutes a main circuit connected to the AC power supply 6 via the.

In this case, the inverter 2 has an IGPT 2a,
2b, 2c and 2d are bridge-connected to constitute a current control type inverter whose output current is controlled. Note that a MOSFET may be used instead of the IGPT.

On the other hand, the control system of the inverter 2 compares the voltage reference 8 with the voltage of the DC power supply 1 and amplifies the voltage of the DC power supply so that the voltage of the DC power supply becomes constant.
Is supplied to a multiplier 11 via a switch 10, and the multiplier 11 multiplies the voltage of the AC power supply 6 by a value detected by the transformer 14 and the output I of the amplifier 9 to obtain an AC current reference I
Give the _R, inverter 2 of the alternating current reference I _R and the main circuit
A configuration in which the output I _AC of the current detector 7 provided in the output circuit 7 is compared and amplified by the amplifier 12, and the inverter 2 is subjected to PWM control via the PWM circuit 13 so that the inverter output current is controlled to the power factor 1. It has become.

In this case, the output of the transformer 14 is applied to an under-voltage detector 15 and an over-voltage detector 16, and when the AC power supply becomes abnormal, the switch 10 is opened to operate so that the inverter current becomes zero. .

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

However, when the practical use of a solar battery inverter has started, there are extremely many chances of exceeding 107 V, and if the inverter is stopped or the voltage rises,
It has been found that when the inverter output current is limited, the output power of the solar cell cannot be used effectively at high frequency.

In view of this, a control for lowering the voltage by flowing the current from the inverter when the voltage exceeds 107 V has been studied. In this case, since a leading current is supplied from the inverter as a load, a lag current is taken from the AC power supply.

[0010]

However, taking the delay current from the AC power supply as described above is not preferable because it increases the loss of the transmission line and lowers the efficiency.

Further, recently, as shown in FIG. 8, single-phase three-wire wiring has been mainly used. In this case, current is generally output from the current control inverter 21 to a 200 V 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 end. Therefore, the voltage drop due to the wiring inductances 17 and 18 differs,
At present, the voltage of the 100 V system is in an unbalanced state. In FIG. 8, the voltage of the 100V system is checked, and if any of the phase voltages exceeds 107V, the probability of performing the phase advance control of the inverter increases.

Further, since the voltage of the DC power supply 1 must be limited to 300 V DC or less by extension rules, a transformerless inverter cannot be used to satisfy this requirement. The disadvantage is that the efficiency is reduced due to loss and the like.

The present invention eliminates the above-mentioned disadvantages and has a power factor of about 1.
It is an object of the present invention to provide an inverter device capable of performing efficient operation by supplying the above-described power and reducing the number of times of controlling the advancement of the power factor.

[0014]

According to the present invention, in order to achieve the above object, an inverter device is constituted by the following means.

According to a first aspect of the present invention, two sets of DC power supplies are connected in series, and a midpoint thereof is connected to a midpoint of a single-phase three-wire AC power supply. In an inverter device in which the input terminal of the inverter is connected to both ends and the output terminal of the inverter is connected to the other end of each AC power supply via a reactor, a current detection value flowing from the inverter to each AC power supply and a current reference First control means for controlling the inverter based on the deviation of the AC power and individually controlling the current flowing to each of the AC power supplies, and voltage detecting means for detecting whether or not the voltage of each of the AC power supplies is equal to or higher than a voltage reference Limit detection means for detecting whether the current flowing from the inverter to each AC power supply has reached a preset limit value, and the power supply of the AC power supply obtained from the voltage detection 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.

According to a third aspect of the present invention, two sets of DC power supplies are connected in series, and the midpoint thereof is connected to the midpoint of a single-phase three-wire AC power supply, and each of the DC power supplies has a step-down chopper circuit. And an output end of the step-down chopper circuit is connected to a DC side of a bridge circuit in which a pair of electric valves are connected in a bridge, and an AC side of the bridge circuit is connected to respective AC power supplies. Voltage detecting means for detecting whether the voltage of each AC power supply is equal to or higher than a voltage reference, and limit detecting means for detecting whether the current flowing from the inverter to each AC power supply has reached a preset limit value Controlling the output current of each DC power supply input to each of the step-down chopper circuits into a dual-wave rectified waveform, and converting the current in the dual-wave rectified waveform from the voltage detection means. Current control means for controlling based on the voltage information of the AC power supply and information obtained from the limit detection means, and turns on each electric valve of the bridge circuit in accordance with the positive and negative cycles of the respective AC power supply, An electric valve control means for turning off the chopper output controlled by the waveform control means to the AC power supply.

[0017]

In the inverter device according to the present invention, 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 second control means detects the voltage based on the voltage information. The current flowing through one AC power supply is reduced while the power factor remains at 1, and the current reference is changed so that the current flowing to the lower side of the voltage of the other AC power supply flows more. Is detected to reach the limit value, the phase of the current reference to the current flowing to one AC power supply is advanced to control the voltage of the AC power supply to decrease, so that the voltage is stabilized and the power factor is improved. , It is possible to increase the operation efficiency.

In the inverter device according to the present invention, 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. And control so that the current flowing to one AC power supply is reduced while the double-wave rectified wave shape of the output current of the chopper circuit remains at the power factor of 1 and more current flows to the lower voltage side of the other AC power supply. When the limit detection means detects that the current has reached the limit value, the phase of the current flowing through one AC power supply is advanced to control the voltage of the AC power supply to decrease, so that the voltage is stabilized. It is possible to improve the operation efficiency by improving the power factor.

[0019]

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 the inverter device according to the present invention.

In FIG. 1, reference numerals 1a and 1b denote DC power supplies.
These DC power supplies 1a and 1b are connected in series, and the midpoint thereof is grounded. Both ends of a series circuit of the DC power supplies 1a and 1b are connected to a DC input terminal of an inverter 2 formed by bridging IGBTs 2a, 2b, 2c and 2d.
a, 3b, and are connected to AC power supplies (single-phase, three-wire) 6a, 6b via current detectors 7a, 7b. In this case, the connection midpoint between the AC power supplies 6a and 6b is grounded. In addition, a PWM is connected to the output side of the inverter 2 in parallel with the AC power supplies 6a and 6b.
4a, 4 for absorbing harmonic currents associated with
b is connected. These DC power supplies 1a, 1b, inverter 2, reactors 3a, 3b, capacitors 4a, 4
and AC power supplies 6a and 6b constitute a main circuit.

On the other hand, the control system includes a voltage reference 8 and a DC power supply 1.
a, 1b are compared, and the voltage deviation is amplified to obtain a current reference I such that the DC power supply is constant. The current reference I output from the amplifier 9 is input, and two sets of AC Sharing of the current flowing out to the power supplies 6a, 6b _Ia , _Ib
Current sharing distributor 30, 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 ,
amplifiers 12a and 12b that compare current references I _Ra and I _Rb output from a and 11b with outputs I _7a and I _{7b of} current detectors 7a and 7b and amplify the current deviation.
a, 12b, the current deviation amplified is input and pulse width modulated to perform IGBT 2a, 2b, 2c, 2
PWM circuits 13a and 13b that drive d to control the current reference I _Ra and the output I _{7a so} that the current reference I _Rb and the output I _7b coincide with each other.

[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.

The reference values V _Ra and V _{Rb of} the AC voltage are compared with the outputs of the transformers 14a and 14b, and amplifiers 33a and 33b amplify the deviation. The outputs amplified by the amplifiers 33a and 33b are switched. Phase lead circuits 36a and 36b input through the phase circuits 35a and 35b, and outputs A and B of the phase lead circuits 36a and 36b
a, 32b. In this case, the amplifiers 33a, 3
Polarity detectors 34a and 34b are connected to the output side of 3b so as to obtain outputs _V37a and _V37b .

Further, the limit detectors 31a, 31
The outputs V _31a and V _{31b of the b} and the outputs V _37a and V _{37b of the} polarity detectors 34a and 34b are input, respectively, and the output V _37c is given to the current sharing distributor 30 and the switches 35a and
A logic circuit 37 for outputting the release 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 power system in Japan is a single-phase 3
The line type, that is, 100 V between the ground and 200 V between the lines is common. In addition, in the house, use of 200 V is mainly used in one part, and use of 100 V is mainly performed. This one
Since the power distribution system of 00V is performed by dividing the system for each room, especially during the time when the solar cell is generating power, mainly the power used for housework and cooling and heating is used, and the load imbalance of the 100V line is unbalanced. Becomes larger. In such a case, the voltage of the line with a light load rises, and a state occurs where power exceeds 101 + 6V and power cannot be injected from the inverter. Therefore, the operation of preventing such a state will be described first.

Now, the voltage reference V _Ra (V _Rb ) is (101+
6) When set to V, the AC power supply 6a
+6) V, the amplifier 33a amplifies the difference voltage, and the output V _34a of the polarity detector _34a has a voltage of (10
1 + 6) It detects that the voltage has become equal to or higher than V and outputs "1".

On the other hand, at this time, the AC power
6) If it is less than V, the output V of the polarity detector 34b is similarly determined.
_34b is "0" (the inverted output of V _34b 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. The logic circuit 37 operates according to the logic conditions 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
Increase _b . Therefore, the inverter 2 is current-controlled with the power factor 1 so that the output current to the AC power supply 6a is reduced and the output current to the AC power supply 6b is increased.

[0029] Similarly voltage of the AC power supply 6b becomes higher than the set value, when the voltage of the AC power supply 6a is less than the set value, the polarity detector 34a outputs V _34a inverted output and the polarity detector 3 of the
Output V _34b and 4b are input to the logic circuit 37, FIG. 2
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,
Control is performed so as 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 (logical value “1”) of the polarity detector 34a and the output V _34b (logical 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, so that the phase of the current reference I _Ra is advanced by the multiplier 11a. By increasing the output current of the inverter 2, the voltage of the AC power supply 6a is reduced as described above, and the control loop automatically controls the voltage to reach the set value _VRa . The switch 35b is also "ON" for the AC power supply 6b.
By doing so, the operation is exactly the same as described above.

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 shown in FIG. 30, the current sharing I input to the multiplier 11a
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 provided 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 output V _34b of the polarity detector 34b is "1", and the current sharing I input from the current sharing 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.
(E), the switch 35b is turned on, and the output of the phase lead circuit 36b is applied to the multiplier 11b.
Through the phase circuit 32b. Accordingly, since the phase of the output I _Pb of the multiplier 11b is advanced, the inverter 2 is controlled to lower 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 AC power supplies 6a and 6b, if any one of the voltages of the AC power supplies 6a and 6b exceeds a set value. By controlling the inverter 2 so that a large amount of current having a power factor of 1 is output to a low voltage line,
This enables effective (efficient) control of the power factor and is effective for stabilizing the voltage of the AC power supply. In addition, only when all the line voltages have exceeded the set value or the inverter current has reached the limit value, the inverter 2 proceeds to the AC power supply to supply the current and stabilize the voltage, thereby avoiding a decrease in the power factor as much as possible. be able to.

That is, by supplying more power from the inverter 2 to a line with a large load, it is extremely effective in stabilizing the voltage, and by controlling the power factor 1 to the limit, highly efficient operation is achieved. 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, the output voltage of the transformer 14a and the output voltage of the transformer 14b are compared and amplified by the amplifier 42 and the current sharing distributor 30 is operated, so that the current references _Ia and Ia are obtained. change the share of _b ,
A function of controlling so as to balance the voltage 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 are required. However, as shown in FIG. can do. That is, as shown in FIG.
The DC power supply 1 can be used as two DC power supplies 1a and 1b by configuring a polarity inversion 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. it can. Further, the above-described current sharing control can be applied not only to the main circuit of the inverter shown in FIG. 1 but also to the inverter main circuit shown in FIG.

That is, as shown in FIG. 5, the DC power supply 1a switches the IGPT 22a, the diode 23a, the reactor 3a,
A step-down chopper circuit comprising a current detector 7a and a filter capacitor 4a is formed, and the output current is expressed by V in FIG.
_The shape is controlled 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 supply 6a is positive with respect to the ground. AC power supply 6
While b is positive with respect to earth, the electric valve 26
Turn on.

Similarly, DC power supply 1b to IGPT 22b,
A diode 23b, a reactor 3b, a current detector 7b,
Configure the step-down chopper composed of a capacitor 4b, and controls the chopper output current waveform shown in V _7b in FIG (A). Next, the AC power supply 6a is connected to the qe ground for a negative period,
The electric valve 27 is turned on, and the electric power supply 6b turns on the electric valve 27 for a negative period with respect to the ground. Due to this operation, the inverter currents I _6a , I ₆ flowing into the AC power supplies 6a, 6b
_6b becomes I _6a, unity power factor of the current waveform as shown in I _6b in FIG (A).

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 indicated by I _6a and I _6b is performed.

On the other hand, when the voltage of the AC power supply 6a is increased, the waveforms of V _7a and V _7b shown in FIG. 9C are controlled so that I _6b becomes as shown by I _6a and I _6b. The control becomes larger. Although the power factor control can be performed by this circuit, the waveform ratio is deteriorated when the control range is increased.

Further, in the embodiment shown in FIG. 1, the inverter is configured as a current control system. However, such an inverter cannot be controlled when the AC power supplies 6a and 6b are out of power.

Therefore, as shown in FIG.
In the event of a power failure at 6b, switches 5a and 5b are opened,
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 voltage is amplified by the amplifier 12a.
The voltage of the capacitor 4a is controlled in the same manner as in FIG.

The output of the AC voltage reference 43 is supplied to an inverting amplifier 44.
Is compared with the output voltage of the transformer 14b, and after being amplified by the amplifier 12b, the PWM circuit 1
The voltage of the capacitor 4b is controlled via 3b. By performing such control switching, it is possible to obtain an independent power supply capable of taking out loads from the capacitors 4a and 4b.

[0045]

As described above, according to the present invention, in an inverter apparatus linked to a single-phase three-wire power supply, more power with a power factor of 1 is supplied to a phase with a heavy load (low voltage). By performing the distribution control, highly efficient operation can be achieved by stabilizing the voltage and improving the power factor.Moreover, when the control reaches the limit or the voltage of all phases rises excessively, the power factor advance control is performed. With this configuration, it is possible to provide an inverter device capable of controlling the voltage in a direction to stabilize the voltage rather than the efficiency.

[Brief description of the drawings]

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

FIG. 2 is an exemplary view for explaining an operation based on a logical condition of a logical circuit in the embodiment.

FIG. 3 is a circuit diagram illustrating 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.

FIG. 5 is a diagram showing a configuration example of a main circuit and a control waveform thereof when the present invention is applied to an inverter of a system different from that of the inverter of FIG. 1;

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

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 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-
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
... Capacitors 43, AC voltage reference, 44 inverting amplifiers.

Continuation of the front page (72) Inventor Tatsuaki Security Inc. 1 Toshiba-cho, Fuchu-shi, Tokyo In the Toshiba Fuchu factory (58) Fields investigated (Int. Cl. ⁷ , DB name) H02M 7/48 H02J 3/50 H02J 3/26

Claims (4)

(57) [Claims] 1. A set of DC power supplies is connected in series, a midpoint thereof is connected to a midpoint of a single-phase three-wire AC power supply, and an input terminal of an inverter is connected to both ends of the series-connected DC power supplies. Connected together, the output terminal of the inverter is connected to the other end of each AC power supply via a reactor, the inverter based on a deviation between a current reference value and a current reference value flowing from the inverter to each AC power supply. First control means for controlling an inverter to individually control the current flowing through each of the 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; Limit detection means for detecting whether the current flowing to the power supply has reached a preset limit value,
A second control unit that controls the current reference and the current phase based on the voltage information of the AC power supply obtained from the voltage detection unit and the information obtained from the limit detection unit to change the current power factor. An inverter device comprising: 2. The inverter device according to claim 1, further comprising a voltage control means, wherein when the AC power supply is cut off, the AC power supply is cut off and the inverter is controlled by the voltage control means from current control by the first control means. An inverter device characterized by switching to voltage control. 3. A set of DC power supplies connected in series, a midpoint of which is connected to a midpoint of a single-phase three-wire AC power supply, and a step-down chopper circuit is provided for each of the DC power supplies. In an inverter device in which the output terminals 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 the bridge circuit is connected to each AC power supply, the voltage of each AC power supply is Voltage detection means for detecting whether or not a voltage reference or more; limit detection means for detecting whether a current flowing from the inverter to each AC power supply has reached a preset limit value; and each of the step-down chopper circuits. Controls the output current of each DC power supply into a double-wave rectified waveform, and converts the current in the double-wave rectified waveform into voltage information and voltage information of the AC power obtained by the voltage detecting means. And current control means for controlling based on information obtained from the limit detection means, and the waveform control means for turning on and off each electric valve of the bridge circuit in accordance with positive and negative cycles of the respective AC power supply. And an electric valve control means for supplying the chopper output controlled by (1) to the AC power supply. 4. The inverter device according to claim 1, wherein two sets of DC power supplies are controlled by one DC power supply and the output of the DC power supply is controlled by a polarity inversion type chopper circuit to form another DC power supply. An inverter device comprising a circuit for obtaining a current and another DC power supply.