JP2002165369A - Power system interconnection inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enlarge power generation time by stably controlling output power of an inverter to a degree of a few percent of the rated output. SOLUTION: This power system interconnection inverter has a first inverter 102 which injects current of a DC power supply 101 and a DC power into the commercial power system and a second inverter 103 which has a 1-10% rated capacity of the first inverter. The first inverter 102 and the second inverter 103 are disposed in parallel between the DC power supply 101 and the commercial system, and the second inverter 103 is operated when the output of the DC power supply is as small as a few percent of the rated output.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a system interconnection inverter for converting DC power into AC having a commercial frequency and interconnecting the AC with a power system.

[0002]

2. Description of the Related Art An example of a conventional grid-connected inverter will be described with reference to FIG.

FIG. 20 is a block diagram showing a conventional configuration. An inverter 2 is connected to an output of the DC power supply 1, and an output of the inverter 2 is connected to a system 4 and power is injected. Here, the rating of the inverter 2 is the DC power supply 1
It is configured to have a rating equal to or higher than that of the output power. The inverter 2 usually has a switching element inside, and obtains an AC output by controlling the conduction time of the switching element. When the DC power is near the rated value, the conduction time of the switching element is increased, and when the DC power is small, the conduction time of the switching element is reduced to maintain the sine wave output of the inverter 2. Further, the control power for controlling the inverter 2 is substantially constant irrespective of the magnitude of the power converted by the inverter.

[0004]

However, in the conventional configuration, when the output range of the DC power supply is large and changes to about several percent of the maximum, the rating is designed for the maximum power. Although it is necessary to reduce the conduction time of the switching element, there is a limit on the minimum conduction time, and the control power is substantially constant regardless of the rating. Therefore, there is a problem that it is difficult to stably control the output power of the inverter to about several percent of the rated power.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and has a DC power supply and an inverter for injecting DC power into a commercial power system. % Inverters (sub inverters) are added, and the two inverters are arranged and connected in parallel between the DC power supply and the commercial power system. Since the sub-inverter has low conversion power, it can be designed with a circuit constant that outputs 1% to 10% of the rated power at the maximum conduction time of the switching element, and can also reduce the control power. Only when the power is a few percent of the main inverter rating, the inverter can operate the sub-inverter to stably control the power injected into the system.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 comprises a DC power supply, a first inverter for injecting DC power into a commercial power system, and a second inverter having a rating of 1% to 10% of the first inverter. The first inverter and the second inverter are arranged and connected in parallel between the DC power supply and the commercial system, so that the second inverter operates even when the DC power output is as small as about several percent of the rating. Thus, stable power conversion can be performed and power can be injected into the system.

According to a second aspect of the present invention, the DC power supply is a solar cell, and the second inverter operates even when the output power is low in low sunshine, particularly in the morning, dusk, or rainy weather. , Stable electric power can be injected into the system.

According to a third aspect of the present invention, the output of the solar cell is provided by having a low solar intensity detecting means in the solar cell, detecting the low sunshine level by the output thereof and switching the first and second inverter operations. It is possible to reliably extract the maximum amount of power without losing the power and to prolong the power generation operation time of the inverter.

According to a fourth aspect of the present invention, there is provided a time measuring means for measuring an output time from the low sunlight intensity detecting means provided in the solar cell, and the second inverter is activated when the output continues for a predetermined time or more. By operating the inverter, it is possible to prevent frequent switching of the operation of the inverter due to a short-time output decrease such as when a cloud is applied to the solar cell.

The invention according to claim 5 has input power detection means, and operates the second inverter at a specific input power or less, so that the switching timing of the inverter can be set without attaching illuminance detection means to the solar cell. It can be detected. According to the invention described in claim 6, since the solar cell voltage is constantly boosted to a voltage higher than the maximum value of the system voltage, each of the first and second inverters is individually turned on without having a separate boosting means. Since the time can be controlled, it is possible to simplify the entire device,
It is possible to realize small size and light weight.

According to the present invention, since the step-up means is connected only to the first inverter, the operation of the second inverter does not involve the step-up operation, so that the occurrence of loss is suppressed and the output of the second inverter is suppressed. It is possible to realize an inverter that can extend the time and generate power even in low sunshine.

According to the present invention, the boosting means performs the boosting operation only when the first inverter operates.
When the output power from the solar cell that requires the operation of the second inverter is small, no loss occurs during the boosting operation, so that the output generation time of the second inverter can be extended, and the operation time of the device can be reduced. It can be expanded.

According to a ninth aspect of the present invention, the switching element forming the first inverter is an IGBT, and the switching element forming the second inverter is a MOSFET. In the rating, since the switching loss of the second inverter can be reduced, the operation time of the device can be extended.

According to the tenth aspect of the present invention, since the output of the solar cell is boosted by the commercial transformer and connected to the system, it is possible to realize a second inverter having a simple configuration in which the loss by the boosting means can be reduced. is there.

According to the present invention, the first inverter has information detecting means for detecting the voltage, frequency and phase of the system, and separates the system information detected by the first inverter stored in the housing. By sending the data to the second inverter stored in the case using the communication means, the system information detection means required inside the second inverter can be omitted.

According to a twelfth aspect of the present invention, the first inverter has an input power detecting means inside, and the current and voltage information obtained from the solar cell is stored in a housing separate from the first inverter. By sending the signal to the two inverters, the arrangement of the input power detection means to the second inverter can be omitted, and a simple second inverter can be realized.

According to a thirteenth aspect of the present invention, an interconnection protection device having an interconnection relay inside each of the first and second inverters and the system is provided, and when the second inverter operates, power consumption is reduced. By linking with a small rated system protection relay, the solar cell output can be injected into the system without waste.

According to a fourteenth aspect of the present invention, a current having a phase opposite to a reactive current component included in the output current of the first inverter is generated at the output of the second inverter, so that the combined output current of the two inverters is reduced to the system voltage. Is what can be matched.

According to a fifteenth aspect of the present invention, the direct current component included in the output current of the first inverter is canceled by the second inverter with the direct current component in the opposite direction, whereby the combined output of the direct current component as the combined output of the two inverters is obtained. No current can be obtained.

According to the present invention, the output of the second inverter is output as an AC voltage of 100 VAC independently of the commercial system which is normally 200 VAC, so that it is necessary to boost the output when the output of the solar cell becomes small. As a result, there is no loss in the booster, and the generated power can be effectively used.

According to a seventeenth aspect of the present invention, the output of the second inverter is output as a sine wave voltage of AC100V independently of a commercial system which is normally AC200V,
It can also be used in home electric appliances that perform control based on a zero voltage reference that is difficult to use with a rectangular wave.

According to the invention described in claim 18, the second inverter has an output current detecting means, and when the output current exceeds the rating of the second inverter, the operation of the second inverter is stopped, whereby the second inverter is stopped. The inverter can be safely stopped even when a device that requires an output higher than the rated current of the inverter is connected.

According to the nineteenth aspect of the present invention, when the DC power supply is a fuel cell, the power consumption can be reduced by operating the second inverter when the fuel supply is small, so that a long operation time is obtained. It is something that can be done.

[0024]

(Embodiment 1) Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of this embodiment. The input of the grid interconnection inverter is supplied with power from a DC power supply 101 that generates DC power such as a solar cell, for example.
The output of the first inverter 102 and the second inverter 10
3 are connected at the same time, and the outputs of the respective inverters are combined inside the grid-connected inverter and connected to the grid 104 as a single output. The second inverter 103 has a rating of 1% to 10% or less of the first inverter 102.

The operation of the system interconnection inverter configured as described above will be described. Normally, since the grid-connected inverter generates AC / DC by performing pulse width modulation (PWM) on the DC input voltage at a high frequency, the on-time of the PWM under the condition that the output of the DC power supply 101 becomes smaller than the rated value. To reduce the output current.
Therefore, when the output power of the DC power supply falls below a few percent of the rating, the rating of the first inverter 102 is reduced from 1% to 10%.
% Is converted by the second inverter 103 having a rating of%.

As described above, according to this embodiment, when the output of the DC power supply is small, the second inverter 103 is operated to cover a small output current which is difficult to output with the first inverter 102 in practice. Therefore, it is possible to provide a grid-connected inverter capable of obtaining a wide power generation possible range.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing the configuration of the present embodiment. 2 differs from the circuit configuration of FIG. 1 in that a DC power supply is configured by a solar cell 201. Components other than those described above are the same as in the first embodiment, and a description thereof will not be repeated.

The operation of the grid-connected inverter configured as described above will be described. The output of the solar cell 201 is obtained in proportion to the sunshine.
Inverter 102 converts DC power to AC power. When the sunshine intensity is weak such as in the early morning or evening, the power that can be output is usually reduced to several percent of the rated power. At such a small output power, the second inverter 103 having a small loss is operated.

As described above, according to this embodiment, when a solar cell is used as a DC power supply, the second inverter 103
By operating the first inverter 10
Since the generated power can be taken out even when the sunlight intensity is low, such as in the morning or in the evening, in which the operation 2 is difficult, it is possible to provide a grid-connected inverter that can extend the power generation time.

Embodiment 3 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a block diagram showing the configuration of the present embodiment. 3 is different from the circuit configuration of FIG.
5 in that the output is input to the operation switching means 306 of the system interconnection inverter. The components other than the above are the second
And the description is omitted.

The operation of the grid-connected inverter configured as described above will be described. The sunshine intensity detecting means 305 obtains an output proportional to the sunshine intensity and inputs the output to the grid interconnection inverter. Normally, when the sunshine intensity output is above a certain value,
The output of the operation switching means 306 causes the first inverter 102 to operate. Conversely, if the output of the sunshine intensity means is equal to or less than a certain value, the second inverter 103 is operated.

As described above, according to this embodiment, by arranging the sunshine intensity detecting means 305 directly on the solar cell 201, it is possible to know the optimum timing of the inverter switching due to the sunshine change with high accuracy and to miss the power generation. It is possible to provide a grid-connected inverter that can generate power for a long time without generating power.

Embodiment 4 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a block diagram showing the configuration of this embodiment. 4 is different from the circuit configuration of FIG. 3 in that an output time measuring unit 407 is provided in the grid interconnection inverter, and an output of the output time measuring unit 407 is input to the operation switching unit 306. The other components are the same as those of the third embodiment, and the description is omitted.

The operation of the grid-connected inverter configured as described above will be described. When the sunshine intensity detecting means 305 detects a value equal to or less than a predetermined value, the duration is counted by the output time measuring means 407. Switch to 103. If it is within the predetermined time, the first inverter 102 continues the operation without switching the inverter operation, judging that the shade is caused by the cloud.

As described above, according to the present embodiment, there is provided a grid-connected inverter capable of performing a stable operation without frequently switching the inverter operation in response to a short-time decrease in sunshine due to a cloud or the like. be able to.

(Embodiment 5) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a block diagram showing the configuration of the present embodiment. 5 is different from the circuit configuration of FIG. 3 in that the sunlight intensity detecting means 305 arranged in the solar cell 201 is eliminated, the input power detecting means 508 is provided in the grid interconnection inverter, and the operation switching means 30
6 is driven. The other components are the same as those of the third embodiment, and the description is omitted.

The operation of the system interconnection inverter configured as described above will be described. The input power detection means 508 detects power from the current and voltage output from the solar cell 201, and when the obtained output power is determined to be, for example, 10% or less of the rating of the first inverter 102, the operation switching means 306 From the first inverter 102 to the second inverter 1
The power conversion operation is switched to 03.

As described above, in the present embodiment, by arranging the input power detecting means 508 in the system interconnection inverter, it becomes possible to eliminate the sunshine detecting means near the solar cell which requires heat resistance and weather resistance. In addition, it is possible to provide a grid-connected inverter that is inexpensive and can ensure operation in low sunshine.

Embodiment 6 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 6 is a block diagram showing the configuration of the present embodiment. 6 differs from the circuit configuration of FIG. 3 in that the solar cell 201, the first inverter 102, and the second
3 in that a booster 609 is provided. The other components are the same as those of the third embodiment, and the description is omitted.

The operation of the above-configured system interconnection inverter will be described. The output voltage of the solar cell is boosted by the boosting means 609 to the maximum value of the system voltage (about 282 V in the case of 200 V AC). The solar cell voltage constantly raised to a constant value regardless of the sunlight intensity is converted into a system alternating current by the first inverter 102 or the second inverter 103 and injected into the system 104.

As described above, in the present embodiment, the boosting means of the first inverter and the second inverter can be shared by boosting the solar cell voltage which greatly changes with the sunlight intensity to a voltage higher than the maximum value of the system voltage. Therefore, it is possible to simplify the entire device and to provide a grid-connected inverter capable of realizing a small size and light weight (Embodiment 7). Hereinafter, embodiments of the present invention will be described with reference to the drawings. I will explain it. FIG. 7 is a block diagram showing the configuration of the present embodiment. 7 is different from the circuit configuration of FIG. 6 in that the booster 609 is connected in series with the first inverter 102 only between the solar cell 201 and the first inverter 102 in the system interconnection inverter. is there. The other components are the same as those of the sixth embodiment, and the description is omitted.

The operation of the system-interconnected inverter configured as described above will be described. The boosting means 609 converts the unstable solar cell voltage into stable direct current due to sunlight and boosts the current to the system voltage or higher in order to allow the current to flow through the system 104. Therefore, when the first inverter 102 operates, a loss due to power conversion at the time of boosting occurs inside the system interconnection inverter. Here, at the power of several percent of the first inverter 102, which is the rating at which the second inverter 103 operates, the second inverter 103 boosts the solar cell power because the second inverter 103 has no boosting means. Without injecting into system 104.

As described above, according to the present embodiment, since the boosting means 609 is connected only to the first inverter 102, the operation of the second inverter 103 having a small rating does not involve the boosting operation. Occasionally, the occurrence of loss is suppressed, and the operation time of the second inverter 103 can be extended, so that it is possible to provide a grid-connected inverter that can increase the power generation time.

Embodiment 8 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a block diagram showing the configuration of this embodiment. 8 differs from the circuit configuration of FIG. 6 in that the boosting unit 609 is configured by a reactor, a switching element, and a diode, and that the output of the operation switching unit 306 is instructed to the boosting unit 609. . The other components are the same as those of the sixth embodiment, and the description is omitted.

The operation of the system-interconnected inverter configured as described above will be described. When the sunshine is strong, the operation switching unit 306 activates the boosting unit 609. At this time, the switching element in the booster 609 alternately turns on and off, so that the solar cell output voltage is boosted. Booster 6
09 is converted to AC by the first inverter 102, and power is injected into the system 104. When the output power of the solar cell 201 becomes about several% of the first inverter rating 102 in low sunshine, the operation switching means 306 turns on the boosting means 6.
09 is stopped. At this time, since the switching element stops, the boosting operation is not performed. However, when the system voltage is low, the solar cell output is connected to the system 104 via the reactor and the diode.
Will be injected.

As described above, according to the present embodiment, the boosting means 306 performs the boosting operation only when the first inverter 102 operates, so that the output power from the solar cell 201 requiring the operation of the second inverter 103 is required. When the value is small, there is no loss of the switching element at the time of the boosting operation, so that the output generation time of the second inverter 103 can be extended and the power generation time of the device can be extended. be able to.

(Embodiment 9) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a block diagram showing the configuration of this embodiment. 8 is different from the circuit configuration of FIG. 1 in that an IGBT is used as a switching element of the first inverter 902 and that the second inverter 90
3 is that a MOSFET is used as a switching element. Components other than those described above are the same as in the first embodiment, and a description thereof will not be repeated.

The operation of the system interconnection inverter configured as described above will be described. By using a MOSFET having a high switching speed for the second inverter 902, the frequency of the operation is approximately 10 times higher than the operating frequency of the first inverter 902. As a result, the size of the coil and capacitor, which are internal components of the second inverter 903, is greatly reduced.

As described above, according to the present embodiment, the switching elements constituting the first inverter 902 are IGBTs,
In particular, the switching element constituting the second inverter 903 having a small rating of about 1% to 10% of the rating is made of a MOSFET, so that the components can be downsized by increasing the frequency and the switching loss of the inverter can be reduced, thereby increasing the power generation time of the equipment. It is possible to provide a system interconnection inverter that performs the following.

Embodiment 10 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a block diagram showing the configuration of this embodiment. 10 differs from the circuit configuration of FIG. 1 in that a commercial frequency step-up transformer 1010 is arranged at the output of the second inverter 103. Components other than those described above are the same as in the first embodiment, and a description thereof will not be repeated.

The operation of the grid-connected inverter configured as described above will be described. The second inverter 103 applies alternating current to the primary side of the step-up transformer 1010 by switching direct current at the commercial frequency. Step-up transformer 101
On the secondary side of 01, a pseudo sine wave is generated. At this time
The switching loss of the inverter 103 becomes almost zero.

As described above, according to the present embodiment, since the output of the solar cell is boosted by the commercial transformer 10101 and connected to the system 104, the second inverter 103 having a simple configuration in which the loss by the boosting means can be reduced. Can be provided.

Embodiment 11 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 11 is a block diagram showing the configuration of this embodiment. 11 differs from the circuit configuration of FIG. 1 in that the first inverter 102 and the second inverter 103 are stored in different housings, respectively, and each inverter is internally provided with the first communication unit 101.
2 and the second communication means 1013, and the system information detection means is arranged in the first inverter 102. Components other than those described above are the same as in the first embodiment, and a description thereof will not be repeated.

The operation of the above-configured grid-connected inverter will be described. System information detecting means 1111
Detects the amplitude, phase, and frequency of the system voltage, and based on the detected values, the first inverter 102 outputs a sine wave current with a power factor of 1. Low sunshine, DC power supply 10
When the output of the first inverter 102 decreases to reach several percent of the rating of the first inverter 102, which is the operating condition of the second inverter 103, the second
The inverter 103 operates, but at the same time, information obtained by the system information detecting unit 1111 is transmitted from the first communication unit 1112 to the second communication unit 1113 via a casing.

As described above, according to this embodiment, the first inverter 102 has the system information detecting means 1111 for detecting the system voltage, frequency and phase, and the first inverter 102 stored in the housing has To provide a system interconnection inverter that eliminates system information detection means required inside the second inverter 103 by sending the detected system information to the second inverter 103 stored in another housing using a communication means. Can be.

Embodiment 12 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 12 is a block diagram showing the configuration of the present embodiment. 12 differs from the circuit configuration of FIG. 11 in that input power detection means 1214 is arranged in the first inverter, and power information such as input voltage and current is transmitted to the second inverter 1 via the first communication means 1112.
03. Components other than those described above are the same as in the first embodiment, and a description thereof will not be repeated.

The operation of the above-configured system interconnection inverter will be described. Input power detection means 1214
Detects the voltage and current of the solar cell output, and based on the detected values, the first inverter 102 performs the power conversion operation at the maximum power point of the solar cell having the characteristic that the internal impedance is large. As a result, the output of the DC power supply 101 decreases, and the first condition, which is the operable condition of the second inverter 103, is set.
When the rating of the inverter 102 has reached several percent, the information obtained by the input power detecting means 1214 is transmitted to the first communication means 11.
The second inverter 103 operates by being transmitted from 12 to the second communication means 1113 via the housing.

As described above, according to the present embodiment, the first inverter 102 has the input power detecting means 1214 inside, and the current and voltage information obtained from the solar cell is separated from the first inverter 102 by a separate casing. , The input power detecting means to the second inverter 103 can be omitted, and a grid-connected inverter capable of realizing a simple second inverter is provided. be able to.

Embodiment 13 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 13 is a block diagram showing the configuration of this embodiment. 13 differs from the circuit configuration of FIG. 1 in that a system interconnection protection device is arranged between the first inverter 102 and the second inverter 103 and the system 104, respectively.

The operation of the system-interconnected inverter configured as described above will be described. When the sunshine intensity is strong as in the daytime, the interconnection relay in the first interconnection protection device 1315 connected to the first inverter 102 conducts, and the electric power is injected into the system. Here, the interconnection relay is the first inverter 1
Since it has a current rating equivalent to 02, the contact is a large type that can withstand a large current. At low illuminance such as morning or evening, the current is small and the second inverter 103
Since the interconnection relay in the second interconnection protection device 1316 connected to the second interconnection protection device 1316 has a current rating equivalent to that of the second inverter 103, the contacts are small. Since the driving power of the relay is almost proportional to the size of the contact, the power consumption of the interconnection protection device when the second inverter 103 is operated is significantly reduced as compared to when the first inverter 102 is operated.

As described above, according to the present embodiment, the interconnection protection devices 1315, 131 having interconnection relays inside between the first and second inverters 102, 103 and the system, respectively.
6, when the second inverter 103 is operated, the grid-connected inverter capable of injecting the solar cell output into the grid without waste by linking with a low-rated grid protection relay that consumes less power. Can be provided.

Embodiment 14 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 14 is a waveform chart showing the operation of this embodiment. The configuration of this embodiment is shown in FIG.
Is the same as

The first inverter 102 needs to operate at a power factor of 1 with respect to the system voltage, but a plurality of filter capacitors for removing high-frequency components in normal mode are usually inserted between the inverter and the system. I have. Therefore, in order to make the current to be injected into the system 104 to have a power factor of 1, it is necessary to compensate for the reactive current of the filter capacitor. However, since the configuration of the control circuit is complicated, the first
The current of the inverter 102 is in a lag phase when viewed from the inverter. Here, regardless of the magnitude of the current of the first inverter 102, the second inverter 103 supplies a current for compensating the reactive current of the filter capacitor, so that the power factor 1 operation is always performed while the first inverter 102 operates. Is performed.

As described above, according to the present embodiment, a current having a phase opposite to that of the reactive current component included in the output current of the first inverter 102 is generated at the output of the second inverter 103, so that the combined output of the two inverters is generated. It is possible to provide a grid-connected inverter capable of making the current equal to the grid voltage.

Embodiment 15 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 15 is a waveform chart showing the operation of this embodiment. The configuration of this embodiment is shown in FIG.
Is the same as

First inverter 102, second inverter 1
In the full bridge configuration of the three ACs, the AC positive and negative outputs have the same absolute value of the output current theoretically if the conduction ratio of the switching element is constant, but pulse width modulation control at high frequency In practical use, the output current contains a DC component of several percent or less of the rated current of the first inverter at the maximum without becoming a positive / negative target waveform due to a variation element of the gate capacitance of the switching element. Therefore, the second inverter 103 having a small rating corrects the DC component generated from the first inverter 102 and performs an operation of removing the DC component from the combined current.

As described above, according to the present embodiment, the DC current component included in the output current of the first
By canceling with a DC component in the opposite direction by the inverter 103, it is possible to provide a grid-connected inverter capable of obtaining a current without a DC component as a combined output of the two inverters.

Embodiment 16 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 16 is a block diagram showing the configuration of this embodiment. 16 is different from the circuit configuration of FIG. 1 in that a booster 609 is arranged between the first inverter 102 and the DC power supply 201.
The point is that the output of the second inverter 103 is output to the AC independent output terminal 1617 independently of the system 104.

The operation of the grid-connected inverter configured as described above will be described with reference to FIG. The output of the solar cell is boosted by the booster to a voltage equal to or higher than the absolute value of the system voltage, and the first inverter 102 outputs a current at a power factor of 1 in synchronization with the system voltage of usually 200 V AC. The second inverter 103 performs switching at a commercial frequency so as to have an AC output irrespective of the system voltage without boosting the solar cell voltage, and generates a 50 Hz or 60 Hz AC 100 V.

As described above, according to the present embodiment, the output of the second inverter 103 is output as an AC voltage of 100 V independently of the commercial system of 200 V AC, so that the output of the solar cell is reduced. Therefore, it is possible to provide a system interconnection inverter that eliminates the occurrence of a loss in the boosting section and thus makes it possible to effectively use the generated power.

Embodiment 17 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 18 is a waveform chart showing the operation of this embodiment. The circuit configuration is the same as in FIG.

The operation of the above-configured system interconnection inverter will be described. Means for boosting solar cell output 6
At 09, the voltage is increased to a voltage equal to or higher than the absolute value of the system voltage, and the first inverter 102 outputs a current at a power factor of 1 in synchronization with the system voltage of usually 200V AC. The second inverter 103 performs high-frequency pulse width modulation (PW) so that the AC voltage is output regardless of the system voltage phase without boosting the solar cell voltage.
M) By controlling, AC1 of the commercial frequency with little distortion
Generate a 00V sine wave.

As described above, according to the present embodiment, the output of the second inverter 103 is supplied to the system 1 which is normally AC 200V.
It provides a grid-connected inverter that can be used in home appliances that perform control based on a zero-voltage reference, which is difficult to use with a square wave, by outputting a sine wave voltage of AC100V independently of the AC 04 can do.

Embodiment 18 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 19 is a block diagram showing the configuration of this embodiment. 19 is different from the circuit configuration of FIG.
4 is that an output current detecting means 1918 is arranged between the output current detecting means 1918 and the output current detecting means 1918.

The operation of the grid-connected inverter configured as described above will be described with reference to FIG. When a home electric appliance of AC100V is connected to the second inverter output and the device requiring power consumption equal to or higher than the second inverter rating is connected to the second inverter 103, the output current detecting means determines that the current is overcurrent. And the second inverter 10
Stop 3.

According to the present embodiment as described above, the second inverter 103 has the output current detecting means, and stops the operation of the second inverter 103 when the output current exceeds the rating of the second inverter 103. As a result, the second inverter 103
It is possible to safely stop the inverter even when a device that requires an output higher than the rated current is connected.

(Embodiment 19) The circuit configuration is the same as that of FIG. 1 except that a fuel cell is used as the DC power supply 101. A fuel cell capable of co-generation of electricity generates electricity and hot water simultaneously. For example, when hot water is not needed, the fuel supply is throttled to lower the power generation level. At this time, the second inverter 103
Works.

When the DC power supply 101 is a fuel cell and the fuel supply is small, the second inverter 103 is operated to reduce power consumption, so that a long operation time can be obtained.

[0079]

As is apparent from the above, according to the present invention, even when the DC power supply output is as small as several percent of the rated value,
It is capable of performing stable power conversion and injecting power into the system.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a grid-connected inverter according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a grid-connected inverter according to a second embodiment of the present invention.

FIG. 3 is a configuration diagram of a system interconnection inverter according to a third embodiment of the present invention.

FIG. 4 is a configuration diagram of a grid-connected inverter according to a fourth embodiment of the present invention.

FIG. 5 is a configuration diagram of a grid-connected inverter according to a fifth embodiment of the present invention.

FIG. 6 is a configuration diagram of a system interconnection inverter according to a sixth embodiment of the present invention.

FIG. 7 is a configuration diagram of a system interconnection inverter according to a seventh embodiment of the present invention.

FIG. 8 is a configuration diagram of a system interconnection inverter according to an eighth embodiment of the present invention.

FIG. 9 is a configuration diagram of a grid-connected inverter according to a ninth embodiment of the present invention.

FIG. 10 is a configuration diagram of a grid-connected inverter according to a tenth embodiment of the present invention.

FIG. 11 is a configuration diagram of a grid-connected inverter according to an eleventh embodiment of the present invention.

FIG. 12 is a configuration diagram of a grid-connected inverter according to a twelfth embodiment of the present invention.

FIG. 13 is a configuration diagram of a grid-connected inverter according to Embodiment 13 of the present invention.

FIG. 14 is a diagram showing operation waveforms of a grid-connected inverter according to Embodiment 14 of the present invention;

FIG. 15 is a diagram showing operation waveforms of a grid-connected inverter according to Embodiment 15 of the present invention.

FIG. 16 is a configuration diagram of a grid interconnection inverter according to Embodiment 16 of the present invention.

FIG. 17 is a diagram showing operation waveforms of a grid-connected inverter according to Embodiment 16 of the present invention.

FIG. 18 is a diagram showing operation waveforms of a grid-connected inverter according to Embodiment 17 of the present invention.

FIG. 19 is a configuration diagram of a system interconnection inverter according to Embodiment 18 of the present invention;

FIG. 20 is a configuration diagram of a conventional grid-connected inverter

[Explanation of symbols]

 Reference Signs List 101 DC power supply 102 first inverter 103 second inverter 104 system 201 solar cell 305 sunlight intensity detecting means 306 operation switching means 407 output time measuring means 508 input power detecting means 609 boosting means 902 first inverter (IGBT)) 903 second inverter (MOSFET) 1010 Commercial transformer 1111 System information detection means 1112 First communication means 1113 Second communication means 1214 Input power detection means 1315 First interconnection protection device 1316 Second interconnection protection device 1617 AC independent output terminal 1918 Output current detection means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takahiro Miyauchi 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Inventor Hideki Omori 1006 Odaka Kadoma Kadoma, Osaka Pref. Terms (reference) 5G066 HA06 HB03 HB06 5H007 BB07 CA02 CC05 CC12 DA04 DC03 GA09 5H420 BB03 BB12 BB14 CC03 DD03 EA10 EA48 EB04 EB39 FF03 FF22

Claims (19)

[Claims] 1. A first inverter having a DC power supply, a first inverter for injecting DC power into a commercial system, and a second inverter having a rating of 1% to 10% of the first inverter. Is a grid-connected inverter that is arranged and connected in parallel between a DC power supply and a commercial grid. 2. The system interconnection inverter according to claim 1, wherein the DC power supply is a solar cell. 3. The system according to claim 1, wherein the solar cell has low sunshine intensity detecting means, and the first and second inverter operations are switched by an output of the low sunshine intensity detecting means. Interconnected inverter. 4. The power converter according to claim 1, further comprising a time measuring unit, wherein the power conversion operation by the second inverter is performed when the output of the low sunlight intensity detecting unit is output for a predetermined time or more. 2. The system interconnection inverter according to claim 1. 5. The system interconnection inverter according to claim 1, further comprising input power detection means, wherein the second inverter operates at a specific input power or less. 6. The solar cell output is first, via a booster means,
6. The system interconnection inverter according to claim 1, wherein the system interconnection inverter is connected to an input of the second inverter. 7. The method according to claim 1, wherein the step-up means is connected only to the first inverter.
The system interconnection inverter described in the paragraph. 8. The system interconnection inverter according to claim 1, wherein the step-up means performs a step-up operation only when the first inverter operates. 9. The switching element forming the first inverter is an IGBT, and the switching element forming the second inverter is a MOSFET.
9. The system interconnection inverter according to any one of claims 1 to 8. 10. The system interconnection inverter according to claim 1, wherein the second inverter is insulated from a system and a commercial transformer. 11. A configuration in which a first inverter has system information detecting means therein, the first inverter and the second inverter are stored in separate housings, and each of the inverters has communication means. The system interconnection inverter according to any one of claims 1 to 10, wherein system information is communicated between the inverters. 12. The first inverter has an input power detecting means therein, and the first inverter and the second inverter are stored in separate housings, and when the inverters are operated in parallel, the first inverter and the second inverter can detect the input power. The system interconnection inverter according to any one of claims 1 to 11, wherein communication is performed between the two. 13. The system interconnection inverter according to claim 1, further comprising an interconnection protection device between the first and second inverters and the system. 14. The system of claim 1, wherein the second inverter compensates for reactive power generated by the first inverter.
14. The system interconnection inverter according to any one of items 1 to 13. 15. The power supply according to claim 1, wherein the second inverter corrects the DC power generated from the first inverter.
15. The system interconnection inverter according to any one of items 1 to 14. 16. The system according to claim 1, wherein the output of the second inverter outputs an AC voltage independently of the commercial system.
13. The system interconnection inverter according to any one of items 1 to 12. 17. The system interconnection inverter according to claim 1, wherein the output of the second inverter outputs a sine wave voltage independently of the commercial system. . 18. The second inverter according to claim 1, further comprising an output current detecting means, wherein the operation of the second inverter is stopped when the output current exceeds the rating of the second inverter. 2. The system interconnection inverter according to claim 1. 19. The system interconnection inverter according to claim 1, wherein the DC power supply is a fuel cell.