JP2001008464A - System linkage inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate distortion of an output voltage in a self-contained operation state and prevent overcurrent from being applied to a self-contained operation load at operation changeover to secure safety. SOLUTION: If a power supply interruption detection unit 47 detects interruption of a commercial power system 3, a linkage self-contained changeover control unit 48 stops the operation of an inverter main circuit 20, and after the parallel-off of a linkage relay 11, a linkage self-contained changeover switch 16 is opened to change the main circuit structure of the inverter main circuit 20 to a transformerless type from a high-frequency transformer insulation type. Then a self-contained relay 13 is closed, and a high-frequency inverter bridge 5 is operated to supply power to a self-contained operation load 14. If recovery from the interruption is detected, the operation of the inverter main circuit 20 is stopped, and after the self-contained relay 13 is paralleled off, the linkage self-contained changeover switch 16 is closed to restore the high-frequency transformer insulation type main circuit structure, the linkage relay 11 is closed, the high-frequency inverter bridge 5 and a low-frequency inverter bridge 9 are operated, and power is supplied to a commercial power system.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter main circuit for converting DC power generated by an independent DC power source such as a solar cell into AC power and connecting the AC power to a system (commercial power system);
The present invention relates to a system interconnection inverter device having a control circuit for controlling the inverter main circuit by inputting the state of the DC power supply and the state of the system, and particularly to a self-sustained operation control technique.

[0002]

2. Description of the Related Art A solar cell, which is a DC power supply, outputs DC power when the solar irradiance is higher than a certain level.
This means that DC power can be output only from solar cells without intervening other energy sources such as secondary batteries.Since it does not emit harmful substances as in the case of thermal power generation, it is simple and clean energy. Effective as a source.

In a grid-connected inverter that converts DC power generated by a solar cell into AC power and supplies the AC power to a commercial power system, control is performed so that the solar cell is used as effectively as possible. In the daytime when the solar irradiance is above a certain level, the inverter main circuit converts the DC power generated by the solar cell into AC power and supplies it to the general AC load, supplies the surplus power to the commercial power system, and supplies it to the general AC load. When the power supply from the solar cell alone is insufficient, the commercial power grid is used to operate the grid.However, if the commercial power grid fails due to an accident or disaster, the inverter main circuit is stopped and the power is cut off. Do not perform conversion. However, despite the fact that the solar radiation intensity is above a certain level,
Not performing power conversion means that power generation by the solar cell is not being used effectively. Therefore, at the time of a power failure, it is required that the inverter main circuit be disconnected from the commercial power system to perform an independent operation. Especially in the event of a disaster, such independent driving becomes important.

[0004] When a power failure occurs in the commercial power system due to an accident or the like, the control circuit detects the power failure and stops the inverter main circuit. If there is insolation intensity, the inverter main circuit is disconnected from the commercial power system. Independent operation is performed in which DC power from a solar cell is converted into AC power and supplied to an independent operation load.

A conventional example of a system interconnection inverter device having a function of switching between interconnection operation and independent operation will be described below with reference to FIG.

First, the grid interconnection inverter device 101 converts the DC power output from the solar cell 102 into the commercial power system 1.
03 and the same frequency (50 / 60H
A description will be given of interconnection operation control in which the power is converted into AC power having z) and supplied to the commercial power system 103. The grid-connected inverter device 101 is roughly divided into an inverter main circuit 120 that converts DC power of the solar cell 102 into AC power and connects the AC power to the commercial power system 103, a state of the solar cell 102, and a state of the commercial power system 103. , And a control circuit 115 for controlling the inverter main circuit 120.

[0007] DC power input from the solar cell 102 to the inverter main circuit 120 in the grid-connected inverter device 101 is converted into high-frequency AC (several tens to several hundred kHz) in the high-frequency inverter bridge 104, and the primary side of the high-frequency transformer 105 Supplied to High frequency transformer 10
5 is a solar cell 102 side (primary side) and a commercial power system 103
It has the role of insulating the side (secondary side). The high-frequency alternating current (corresponding to FIG. 3A) induced on the secondary side while being insulated by the high-frequency transformer 105 is applied to the diode bridge 10 provided on the secondary side of the high-frequency transformer 105.
6 is rectified. The rectified component (corresponding to FIG. 3B) rectified by the diode bridge 106 is subjected to removal and smoothing of a high-frequency component by a filter circuit 107 including a DC reactor 107a and a capacitor 107b (corresponding to FIG. 3C). ). Then, the direct current formed into a full-wave rectified wave shape by the filter circuit 107 is looped back and controlled at a low frequency (50/60 Hz to several hundred Hz) in the low frequency inverter bridge 108, so that the low frequency (50/60 H
A sine wave AC of z) is obtained (corresponding to FIG. 3D). This return control is performed by the commercial power system voltage signal V _EUL in the commercial power system 103 obtained from the subsequent stage of the interconnection relay 112.
It is performed based on.

Further, a DC capacitor 109 for suppressing a change in input power to the inverter main circuit 120 is provided at a stage preceding the high-frequency inverter bridge 104. At the subsequent stage of the low-frequency inverter bridge 108, there are provided an inverter output current detector 110, an AC filter 111 for absorbing harmonic components, and a connection relay 112 for connection and disconnection with the commercial power system 103 side. . Further, the AC filter 1 is provided at a stage subsequent to the low-frequency inverter bridge 108.
In the next stage of the load 11, the load 114 for the independent operation is connected to the independent relay 1.
13 are connected.

The control circuit 115 includes an inverter main circuit 1
20 and control of high-frequency inverter bridge 104 and low-frequency inverter bridge 108 and interconnection relay 11
There is provided an interconnection control unit 116 for performing on / off control of the second. In addition, the interconnection relay 112 and the independent relay 11
An independent control unit 117 for controlling the high-frequency inverter bridge 104 and the low-frequency inverter bridge 108 together with the on / off control of No. 3 is provided.

[0010] The system interconnection inverter device 101 is connected to the interconnection control unit 116 of the control circuit 115 during the interconnection operation.
The voltage and frequency of the commercial power system 103 are monitored based on the commercial power system voltage signal V _EUL detected from the subsequent stage of the interconnection relay 112. When the commercial power system 103 has a power failure due to an accident or the like, the interconnection control unit 116 detects the power failure based on a change in the monitored system voltage / system frequency, and issues a disconnection command signal to the interconnection relay 112. GR is output to disconnect the interconnection relay 112 and stop the operation of the inverter main circuit 120. In this power failure, if the solar cell 102 has a sufficient solar radiation intensity, the autonomous control unit 117 in the control circuit 115 transmits the connection command signal IR to the autonomous relay 113 in a state where the commercial power system 103 is disconnected from the inverter main circuit 120. Output, self-supporting relay 113
To close the self-sustained operation load 114 to the inverter main circuit 1
20. Next, the inverter main circuit 120 is operated to convert DC power from the solar cell 102 into AC power and supply the AC power to the load 114 for the self-sustaining operation, thereby performing an independent operation.

As described above, the system interconnection inverter device 1
In 01, the DC power from the solar cell 102 is converted to AC power to perform the interconnection operation control to supply the AC power to the commercial power system 103. On the other hand, when the commercial power system 103 is out of service due to an accident or the like, the power outage is detected. With the inverter main circuit 120 disconnected from the commercial power system 103, the DC power from the solar cell 102 is converted into AC power to
4 to perform self-sustaining operation control.

[0012]

However, in the prior art described above, the low-frequency inverter bridge 10
8, the direct current (corresponding to FIG. 3C) of the full-wave rectified wave shape by the filter circuit 107 at the preceding stage is connected to the interconnection relay 1.
12 based on the commercial power system voltage signal V _EUL in the commercial power system 103 obtained from the subsequent stage of FIG.
(D), the phase of the output voltage waveform and the phase of the output current waveform in the low-frequency inverter bridge 108 must coincide with each other, and the delay angle φ is 0 and the power factor cos φ = 1. Only rate 1 control can be performed. That is, the configuration is such that reactive power control for generating reactive power by shifting the phases of the output voltage waveform and the output current waveform cannot be performed.

In the event of a power failure, the self-contained relay 113
The low-frequency inverter bridge 1 is also connected to the independent operation load 114 connected to the inverter main circuit 120 via the
In this case, the power factor 1 control in the return control by the control unit 08 has an effect. That is, the reactive power control cannot be performed even during the self-sustained operation control. As a result, the output voltage waveform from the inverter main circuit 120 is distorted, and if the output voltage waveform is distorted, the inverter main circuit 120 is distorted. In the stand-alone operation load 114 connected to the power supply 120, there is a possibility that an inductive load such as a motor load may cause troubles such as overheating, overcurrent, abnormal sound, and malfunction. Further, when these failures occur, the life of the self-sustaining operation load 114 may be adversely affected.

Further, when the inverter main circuit 120 switches from the interconnection operation control to the self-sustained operation control, the interconnection operation of the inverter main circuit 120 is stopped and the interconnection relay 112 is disconnected to disconnect from the commercial power system 103. Although the inverter main circuit 120 is disconnected, the interconnection control unit 116 only outputs the disconnection command signal GR to the interconnection relay 112, and the interconnection relay 112 receives the disconnection instruction signal GR and There is no means for confirming whether or not the disconnection operation has been performed, and it is not known whether the interconnection relay 112 is in the disconnection state. Therefore, if the interconnection relay 112 is not disconnected, the inverter main circuit 120
Is connected to the commercial power system 103, the self-standing relay 113 is turned on, and the inverter main circuit 12
When the operation is performed at 0, an overvoltage is applied to the self-sustained operation load 114, which may lead to failure or destruction of components.

On the other hand, when the inverter main circuit 120 is switched from the independent operation control to the interconnection operation control, the independent operation of the inverter main circuit 120 is stopped, and the independent relay 1 is turned off.
13 is disconnected to disconnect the independent operation load 114 from the inverter main circuit 120. The independent control unit 117 only outputs a disconnection command signal IR to the independent relay 113, and the independent relay 113 There is no means for receiving the command signal IR and confirming whether or not the disconnection operation has actually been performed, and it is not known whether or not the independent relay 113 is in the disconnected state. Therefore, if the self-supporting relay 113 is not disconnected, the inverter main circuit 120
When the interconnection relay 112 is turned on and the inverter main circuit 120 is operated in a state where is connected to the independent operation load 114, the independent operation load 11
There was a possibility that an overvoltage would be applied to No. 4, resulting in failure or destruction of components.

The present invention has been made in order to solve the above-mentioned problems, and aims to make effective use of a DC power supply such as a solar cell even when a commercial power system is out of power, and to operate the inverter main circuit independently. It is an object of the present invention to provide a grid-connected inverter device that sometimes enables reactive power control, eliminates distortion of the output voltage at that time, and does not cause a failure in the operation of the load for independent operation. It is another object of the present invention to provide a safe grid-connected inverter device in which an overvoltage is not applied to a load for independent operation when switching between interconnected operation control and independent operation control.

[0017]

A system interconnection inverter device according to a first aspect of the present invention for solving the above-mentioned problems of the prior art converts a DC power of a DC power source such as a solar cell into an AC power and converts the DC power into AC power. The inverter main circuit is connected to the system assuming a configuration including an inverter main circuit connected to the power supply and a control circuit that inputs the state of the DC power supply and the state of the system to control the inverter main circuit. A main circuit equivalent to an interconnection self-contained changeover switch that switches between a main circuit configuration for interconnected operation and a main circuit configuration for self-contained operation that is disconnected from the system and connected to an independent operation load to operate. It is characterized by having circuit configuration switching means. According to this configuration, the following operation is provided. In other words, when switching from the interconnection operation control to the independent operation control due to a power failure, even if the system interconnection disconnection means corresponding to the interconnection relay is not disconnected for some reason, the independent operation may be performed unexpectedly. The main circuit configuration switching means separates the independent operation load from the grid interconnection disconnection means, and the main circuit configuration switches from the grid to the independent operation load regardless of the state of the system interconnection disconnection means. Since the load for independent operation is not directly connected to the grid, there is no overvoltage applied to the load for independent operation, and safety is improved. In addition, when the power failure is canceled and the operation is switched from the independent operation control to the interconnection operation control, unexpected connection to the system is performed in a state where the independent load connection disconnecting means corresponding to the independent relay is not disconnected for some reason. Due to the main circuit configuration, there is no effect on the independent operation load between the system and the independent operation load, regardless of the state of the independent load connection / disconnection means. Since the load for operation is not directly connected to the system, overvoltage is not applied to the load for independent operation, and safety is improved.

According to a second aspect of the present invention, there is provided a grid-connected inverter device.
In the first invention, the main circuit configuration during the interconnection operation is a high-frequency transformer insulation system, and the main circuit configuration during the self-sustaining operation is a transformerless system. According to this configuration, the following operation is provided. In other words, during the interconnection operation of the inverter main circuit, the main circuit configuration is a high-frequency transformer insulation system, and the high-frequency transformer insulates the DC power supply side such as solar cells from the system side. The main circuit configuration is a transformerless system that does not pass through a high-frequency transformer when the inverter main circuit operates independently, and a low-frequency inverter bridge that is limited to power factor 1 control is used. Since the turning control of the inverter becomes irrelevant, the inverter main circuit can perform the reactive power control. As described above, when the reactive power control is performed, no distortion occurs in the output voltage waveform of the inverter main circuit, and overheating and overheating of the connected independent operation load, particularly an inductive load such as a motor load. There is no danger of causing obstacles such as current, abnormal noise, and malfunction.

According to a third aspect of the present invention, there is provided a grid-connected inverter device.
In the first and second inventions, the main circuit configuration switching means is provided on a primary side of a high-frequency transformer. According to this configuration, the following operation is provided.
That is, by providing the main circuit configuration switching means corresponding to the interconnection independent switch on the primary side of the high-frequency transformer, it becomes possible to supply AC power to the independent operation load without passing through the high-frequency transformer, Since the return control in the low frequency inverter bridge limited to the power factor 1 control becomes irrelevant, the inverter main circuit can perform the reactive power control. Thus, when the reactive power control is performed,
There is no distortion in the output voltage waveform of the inverter main circuit, and it causes troubles such as overheating, overcurrent, abnormal sound, and malfunction to the connected independent operation load, especially the inductive load such as the motor load. There is no danger. In addition, parts can be shared. This means the following. Another configuration is conceivable for performing the reactive power control of the output with respect to the independent operation load. In other words, an inverter bridge operated during self-sustaining operation, a DC capacitor, an inverter bridge operated during interconnection operation, and a separate DC capacitor provided exclusively for autonomous operation, and two DC capacitors connected to a DC power source such as a solar cell. It is conceivable to adopt a configuration in which switching is performed by a main circuit configuration switching unit equivalent to an independent switch. However, in this case, another pair of the DC capacitor and the inverter bridge is required, which leads to an increase in cost. In the third aspect of the present invention, since the main circuit configuration switching means is provided on the primary side of the high-frequency transformer, there is no need to provide a DC capacitor and an inverter bridge dedicated to independent operation control. Among the main circuit components in the main circuit, the DC capacitor and the inverter bridge can be shared, and the cost of the components can be reduced.

According to a fourth aspect of the present invention, there is provided a grid-connected inverter device.
In the first to third inventions, in the high-frequency transformer insulation system, which is the main circuit configuration during the interconnection operation, the inverter main circuit is controlled so that there is no error between the waveforms of the inverter output current signal and the current reference signal. However, in the transformerless system, which is the main circuit configuration during the self-sustaining operation, the inverter main circuit is controlled so that there is no error between the waveforms of the inverter output voltage signal and the voltage reference signal and the output voltage is constant. Features. According to this configuration,
It has the following effects. That is, in the main circuit configuration of the high-frequency transformer isolation system during the interconnection operation, the inverter main circuit is controlled so that the error between the waveforms of the inverter output current signal and the current reference signal is eliminated, so that the inverter output current It is possible to supply high-quality power with little distortion in the waveform. On the other hand, in the transformerless main circuit configuration during the self-sustained operation, the self-sustained operation is controlled by controlling the inverter main circuit so that the error between the waveforms of the inverter output voltage signal and the voltage reference signal is eliminated and the output voltage is constant. It is possible to supply high-quality power with a constant output voltage to the load for use and low distortion in the inverter output voltage waveform.

According to a fifth aspect of the present invention, there is provided a grid-connected inverter device.
In the first to fourth inventions, the output in the main circuit configuration of the high-frequency transformer isolation system is set to 200 V AC, and the output in the main circuit configuration of the transformerless system is set to 100 V AC.
It is characterized by having. According to this configuration,
It has the following effects. That is, during the interconnection operation, the output voltage is AC2 because the inverter main circuit outputs to the grid.
However, during self-sustained operation, in which the inverter main circuit is operated in the event of a power outage due to an accident or disaster, it is not necessary to supply the output of the inverter main circuit to the system. As a result, a household electric load using AC100V as a power source can be used as a self-sustaining operation load. Further, since an AC100V output is used in the inverter control, AC200V to AC10V can be used in the inverter main circuit.
Since there is no need to convert the voltage to 0V, components such as a transformer for voltage transformation are not required.

A system interconnection inverter device according to a sixth aspect of the present invention
An inverter main circuit that converts DC power of a DC power supply such as a solar cell into AC power and connects the AC power to a system, and a control circuit that inputs the state of the DC power supply and the state of the system and controls the inverter main circuit. A system interconnection inverter device comprising: a power failure detection unit that detects a power failure of the system; and a system interconnection disconnection unit equivalent to a interconnection relay that interconnects and disconnects the inverter main circuit and the system. A self-sustained load connection / disconnection means corresponding to a self-contained relay for connecting and disconnecting the inverter main circuit and the self-sustained operation load, and a main unit for an interconnected operation in which the inverter main circuit is operated in connection with the system. Main circuit configuration switching means equivalent to an interconnection self-contained changeover switch for switching between a circuit configuration and a main circuit configuration during self-sustained operation that is disconnected from the system and connected to an independent operation load, and the system interconnection solution Means, is characterized in that it comprises a said self load connection disconnection means and interconnection self switching control unit equivalent interconnection autonomous switching control means for controlling the main circuit configuration switching means. According to this configuration, the following operation is provided. That is, during the daytime when the solar irradiance is more than a certain level, if the system is not out of power, the inverter main circuit and the system are interconnected to operate the inverter main circuit, and obtained from a DC power source such as a solar cell. DC power can be converted to AC power and output to the grid, while if the grid fails, the power failure is detected, the inverter main circuit is stopped, and the inverter main circuit and the grid are disconnected, A self-sustained operation load is connected to the inverter main circuit to perform self-sustained operation, and DC power from a DC power supply such as a solar cell is converted into AC power and output to the self-sustained operation load. Effective utilization can be achieved.

According to a seventh aspect of the present invention, there is provided a grid-connected inverter device.
In the sixth aspect, the system interconnection disconnecting means corresponding to the interconnection relay outputs a disconnection confirmation signal in a disconnection state between the inverter main circuit and the system, and outputs the interconnection confirmation signal in a connection state. It is characterized by outputting. According to this configuration, the following operation is provided. In other words, the system interconnection disconnecting means equivalent to the interconnection relay outputs a disconnection confirmation signal to the control circuit when the inverter main circuit is disconnected from the system, and the control circuit is disconnected from the inverter main circuit. Therefore, there is no danger that the inverter main circuit will operate in a self-sustaining manner in an interconnected state with the system, and furthermore, no overvoltage will be applied to the self-sustaining operation load, so that safety can be improved.

According to an eighth aspect of the present invention, there is provided a system interconnection inverter device comprising:
In the sixth and seventh inventions, the independent load connection disconnecting means corresponding to the independent relay outputs a disconnection confirmation signal in a disconnected state between the inverter main circuit and the independent operation load, and connects in a connected state. It is characterized by outputting a confirmation signal. According to this configuration, the following operation is provided. That is, the independent load connection disconnecting means corresponding to the independent relay outputs a disconnection confirmation signal to the control circuit when the inverter main circuit and the independent operation load are disconnected, and the control circuit connects the inverter main circuit and the independent operation load. Since the inverter main circuit can be reliably identified as being disconnected, there is no danger of performing interconnected operation in the state of connection with the self-sustaining operation load. Can be improved.

According to a ninth invention, there is provided a grid-connected inverter device comprising:
In the sixth to eighth inventions, the interconnection independent switching control means monitors a signal output from the interconnection disconnection means corresponding to the interconnection relay, and confirms disconnection from the interconnection disconnection means. Upon detecting the signal, the main circuit configuration switching means equivalent to the interconnection independent switch allows the switching operation from the main circuit configuration during interconnection operation to the main circuit configuration during independent operation, while the system equivalent to the interconnection relay When the disconnection confirmation signal from the interconnection disconnection means is not detected, the switching operation is not permitted and the signal is continuously monitored. According to this configuration, the following operation is provided. That is, the interconnection independent switching control means monitors the disconnection confirmation signal output by the interconnection disconnection means equivalent to the interconnection relay, and after confirming that the inverter main circuit and the system are disconnected, Since the main circuit configuration at the time of interconnection operation can be switched to the main circuit configuration at the time of self-sustaining operation, the main circuit configuration switching means equivalent to the interconnection self-contained changeover switch can be switched without applying a large voltage from the system. , Safety can be improved. Further, since a type having a small withstand voltage can be used as the main circuit configuration switching means, the cost of parts can be reduced.

In a tenth aspect of the present invention, in the sixth to ninth aspects, the interconnection independent switching control means monitors a signal output from the independent load connection disconnecting means corresponding to the independent relay. When the disconnection confirmation signal from the independent load connection disconnecting means equivalent to the independent relay is detected, the main circuit configuration switching means equivalent to the interconnection independent switch is switched from the main circuit configuration during the independent operation to the main circuit configuration during the interconnection operation. While permitting the switching operation to the circuit configuration, when the disconnection confirmation signal from the independent load connection disconnecting means corresponding to the independent relay is not detected, the switching operation is not permitted and the signal is continuously monitored. And According to this configuration, the following operation is provided. That is, the interconnection independent switching control means monitors the disconnection confirmation signal output by the independent load connection disconnecting means corresponding to the independent relay, and confirms that the inverter main circuit and the independent operation load are disconnected. Since the main circuit configuration during self-sustained operation can be switched to the main circuit configuration during interconnected operation, there is no danger of performing interconnected operation with the load connected to the self-sustaining operation. Since no overvoltage is applied to the utility load, safety can be improved.

The above components of the present invention can be interpreted as follows. The term “system” generally refers to a commercial system, but is not limited to a commercial system, and is thus expressed as such. "Solar cell status"
Is a power or voltage or current generated in the solar cell or other electric quantity or a physical quantity related thereto in general. The same applies to “system status”. Furthermore, the meaning of “characterized” in the claims is merely for the convenience of explanation, and the actual configuration of the grid-connected inverter device to which the present invention is applied has a special configuration. Should not be interpreted merely as meaning that it is prominently expressed. It should be noted that the wording is used for convenience of explanation in comparison with the related art.

[0028]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of a system interconnection inverter device according to the present invention.

FIG. 1 is a circuit diagram showing a circuit configuration of a system interconnection inverter device. The grid interconnection inverter device 1 converts DC power output from the solar cell 2 into AC power having the same phase and the same frequency (50/60 Hz) as the commercial power system 3 and supplies the AC power to the commercial power system 3. . Also,
In the event of a power outage of the commercial power system 3, for example,
Supply AC power to

The grid-connected inverter device 1 is roughly divided into an inverter main circuit 20 for converting the DC power of the solar cell 2 into AC power and connecting the AC power to the commercial power system 3, a state of the solar cell 2 and a commercial power system. 3 and a control circuit 30 for controlling the inverter main circuit 20 by inputting the state of FIG.

The inverter main circuit 20 includes input terminals 17a and 17b for connecting the solar cell 2 and input terminals 17a and 1b.
7b, and four switching elements Q1-Q connected in parallel with the DC capacitor 4.
High-frequency inverter bridge 5 consisting of 4 bridges
A high-frequency transformer 6 having a primary winding connected between both ends of the interconnection self-contained switch 16 connected between output terminals of the high-frequency inverter bridge 5; A diode bridge 7 having a bridge configuration of four diodes connected in parallel between both ends of the winding, a DC reactor 8a and a capacitor 8b connected between output terminals of the diode bridge 7
A low frequency inverter bridge 9 having a bridge configuration of four switching elements S1 to S4 connected in parallel between both ends of a capacitor 8b in the filter circuit 8, and an output terminal of the low frequency inverter bridge 9 An AC filter 10 composed of a connected AC reactor 10a and a capacitor 10b;
0, the interconnection relay 11 connected between both ends of the capacitor 10b, the inverter output current detector 12 interposed at the AC filter 10, and the output to the commercial power system 3 connected to the interconnection relay 11. Terminals 18a, 18b,
A self-contained relay 13 connected between the output terminals of the high-frequency inverter bridge 5, a self-contained filter circuit 15 including an AC reactor 15a and a capacitor 15b connected to the self-contained relay 13, and both ends of the capacitor 15b in the self-contained filter circuit 15 Independent operation load 14 connected to
, And load connection terminals 19a and 19b. In this circuit configuration, the interconnection independent switch 16 is inserted between the output terminal of the high-frequency inverter bridge 5 and the primary winding of the high-frequency transformer 6, and the interconnection independent switch 16 is connected to the high-frequency inverter bridge. The embodiment of the present invention has devised that an independent load output system composed of an independent relay 13, an independent filter circuit 15, and load connection terminals 19a and 19b is connected to a connection point with the output terminal No. 5. Is a point.

The DC capacitor 4 is composed of an electrolytic capacitor and suppresses fluctuations in DC power input from the solar cell 2. The high-frequency inverter bridge 5 converts DC power input to the inverter main circuit 20 into high-frequency AC (several tens to several hundred kHz). The high-frequency transformer 6 is connected between the solar cell 2 (primary side) and the commercial power system 3.
It plays the role of insulating the side (secondary side). The diode bridge 7 rectifies the high-frequency alternating current obtained on the secondary side of the high-frequency transformer 6 as shown in FIG. 3A, and the voltage thus rectified is as shown in FIG. become. The filter circuit 8 composed of the DC reactor 8a and the capacitor 8b removes and smoothes high-frequency components contained in the rectified waveform, and the voltage of the smoothed full-wave rectified waveform shown in FIG. ). The low-frequency inverter bridge 9 converts the direct current of the full-wave rectified wave shape by the filter circuit 8 into a low-frequency (50 / 60H
3 to several hundred Hz) to generate a low frequency (50/60 Hz) sine wave alternating current as shown in FIG. AC reactor 10a and capacitor 10
The AC filter 10 constituted by b absorbs a harmonic component.

The interconnection relay 11 includes an inverter main circuit 20
Are connected to and disconnected from the commercial power system 3. The interconnection relay 11 corresponds to a “system interconnection / disconnection unit” described in the claims.

The inverter output current detector 12 detects an inverter output current signal Iout at a stage subsequent to the low frequency inverter bridge 9 and outputs the signal to the PWM modulation control unit 43 in the control circuit 30.

The interconnection independent switch 16 is closed during the interconnection operation so that the main circuit configuration of the inverter main circuit 20 is of a high-frequency transformer insulation type. This is for switching the main circuit configuration of the inverter main circuit 20 such that the main circuit configuration of the circuit 20 is a transformerless system. This interconnection independent switch 16 is
It corresponds to "main circuit configuration switching means" in the claims.
The independent relay 13 connects and disconnects with the independent operation load 14. The self-supporting relay 13 corresponds to “self-supporting load connection / disconnection means” described in the claims.

The control circuit 30 controls the high-frequency inverter bridge 5, the low-frequency inverter bridge 9, the interconnection relay 11, the independent relay 13, and the interconnection independent switch 16, and the control circuit 30 It comprises a bridge control unit 31, a low-frequency inverter bridge control unit 32, and an interconnection independent control unit 33.

The high-frequency inverter bridge control unit 31
Maximum power point tracking control unit 41, control amount calculation unit 42, and PWM
A modulation control unit 43 and a gate drive signal generation unit 44 are provided.

The maximum power point follow-up controller 41 monitors the rate of change of the solar cell operating point voltage obtained from the DC input voltage Vin detected from both ends of the DC capacitor 4 during the interconnection operation, and monitors the monitoring result. The output is output to the control amount calculation unit 42. The control amount calculation unit 42 generates a current reference signal Iref as a reference for comparison with the inverter output current signal Iout from the inverter output current detector 12 during the interconnection operation, and the high frequency inverter bridge 5 , And generates a voltage reference signal Vref as a reference for comparison with the inverter output voltage signal Vout from the output terminal of the PWM control unit 43. During the interconnection operation, the PWM modulation control unit 43 integrates an error between the inverter output current signal Iout and the current reference signal Iref in a predetermined cycle unit,
The obtained integrated waveform data is subjected to PWM modulation control to generate a pulse train signal PL, which is output to the gate drive signal generator 44. Also,
The PWM modulation control unit 43 operates during the self-sustaining operation.
An error amplification signal obtained by amplifying an error between the inverter output voltage signal Vout and the voltage reference signal Vref is generated,
This error amplified signal is a sine wave signal having the same frequency (50/60 Hz) as the voltage waveform of the commercial power system 3 as shown in FIG. 4A, and a high-frequency carrier synchronized with such an error amplified signal. A pulse train signal PL as shown in FIG. 4B is generated by performing PWM modulation control by comparing a signal (several tens of kHz) with an error amplified signal, and is output to the gate drive signal generation unit 44. Have been.
The gate drive signal generation unit 44 includes the PWM modulation control unit 4
The on / off control of the four switching elements Q1 to Q4 of the high-frequency inverter bridge 5 is performed based on the pulse train signal PL generated by the switching element 3.

The low frequency inverter bridge control unit 32
It comprises a turn-back controller 45 and a gate drive signal generator 46. The return control unit 45 converts the full-wave rectified wave-shaped DC as shown in FIG. 3C to a low-frequency (based on the commercial power system voltage signal _VEUL detected from the subsequent stage of the interconnection relay 11 during the interconnection operation. The return control is performed at 50/60 Hz to several hundred Hz). The gate drive signal generation unit 46 controls the four switching elements S1 of the low-frequency inverter bridge 9 based on the control of the return control unit 45.
To S4 are turned on / off.

The interconnection independent control section 33 is composed of a power failure detection section 47, an interconnection independent switching control section 48, and an independent synchronization signal generation section 49. The power failure detection unit 47 is connected to the interconnection relay 1
1 to detect a power failure by monitoring a commercial power system voltage signal _VEUL detected from the subsequent stage. This power failure detection unit 4
Reference numeral 7 corresponds to "power failure detection means" in the claims.
Based on the power failure detection signal BO ₁ or the power failure cancellation detection signal BO ₂ from the power failure detection part 47, the interconnection self-sustained switching control part 48 controls the interconnection / disconnection of the interconnection relay 11 and the self-sustained relay 1
3 is configured to control the connection / disconnection of the switch 3, and to control the interconnection independent switch 16 and the two gate drive signal generators 44 and 46. This interconnection independent switching control unit 48 corresponds to “interconnection independent switching control means” described in the claims.

The self-sustained synchronizing signal generation section 49 performs timing for comparing the inverter output voltage signal Vout with the voltage reference signal Vref in the PWM modulation control section 43 because the commercial power system 3 is out of power during the self-sustaining operation. A synchronization signal V _SCR for use as a reference is generated.

Next, the operation of the system interconnection inverter device 1 according to the embodiment configured as described above will be described with reference to the flow chart showing the sequence processing of FIG.

During the interconnection operation in which the inverter main circuit 20 and the commercial power system 3 are connected to operate the inverter main circuit 20, first, both the interconnection relay 11 and the self-supporting relay 13 are turned off. In the state (T1), in order to set the main circuit configuration of the inverter main circuit 20 to the high-frequency transformer insulation system at the time of the interconnection operation, the interconnection independent switching control unit 48 of the interconnection independent control unit 33 includes the interconnection independent switching switch 16. and it outputs a closing command signal CS ₁ against (T2).
Then, the interconnection independent changeover switch 16 outputs the closing command signal CS.
_{When 1} is received, the switch is closed and the main circuit configuration is set to the high-frequency transformer insulation type (T3). When the main circuit configuration is switched, the interconnection independent switch 16 outputs a closing confirmation signal CK ₁ to the interconnection independent switching control unit 48. When interconnection autonomous switching controller 48 detects that it has received the closing confirmation signal CK _1, confirms that the main circuit configuration is high-frequency transformer insulating system (T4), the closure against connector relay 11 and it outputs the interconnection command signal GR ₁ instructing (T
5). The connector relay 11 receives the interconnection command signal GR _1, to interconnection of the inverter main circuit 20 and the commercial power system 3 performs closed (T6). When interconnection is performed,
Connector relay 11 outputs the interconnection confirmation signal GK ₁ to the interconnection autonomous switching controller 48. Interconnection autonomous switching controller 48 detects that it has received the communication system confirmation signal GK _1, in terms of the inverter main circuit 20 and the commercial power system 3, it was confirmed that the interconnection (T7), the inverter main circuit 20 To supply AC power to the commercial power system 3 (T8).

The operation mode at this time is the interconnection operation mode. That is, the interconnection independent switching control unit 48 transmits the interconnection operation command signal SS ₁ to the gate drive signal generation unit 44 in the high frequency inverter bridge control unit 31 and the gate drive signal generation unit 46 in the low frequency inverter bridge control unit 32, respectively. The DC power input from the solar cell 2 is converted into AC power based on switching control between the high-frequency inverter bridge 5 and the low-frequency inverter bridge 9 by the respective gate drive signal generators 44 and 46, and commercial power is output. Supply to system 3. At this time, since the high-frequency transformer insulation system using the high-frequency transformer 6 functions, a ground fault accident of the solar cell 2 to the commercial power system 3 is prevented.

Inverter main circuit 20 during interconnection operation
In the switching control, basically, an error between the inverter output current signal Iout detected and fed back by the inverter output current detector 12 and the current reference signal Iref determined by the control amount calculation unit 42 is eliminated. The switching elements Q1-Q of the high-frequency inverter bridge 5
4 is turned on / off. As a result, the primary side of the high-frequency transformer 6 is excited by the high-frequency AC, and FIG.
As shown in (a), a high-frequency AC similar to that of the primary side is output to the secondary side of the high-frequency transformer 6. Then, the high-frequency alternating current is rectified by the diode bridge 7 provided on the secondary side of the high-frequency transformer 6, and has a voltage waveform as shown in FIG. The rectified component rectified by the diode bridge 7 is subjected to removal and smoothing of the high-frequency component by the filter circuit 8 to form a full-wave rectified voltage waveform as shown in FIG. The voltage waveform that has been full-wave rectified by the filter circuit 8 is turned back at a low frequency (50/60 Hz to several hundred Hz) by a low-frequency inverter bridge 9, as shown in FIG. (50 /
(60 Hz). This is A
C200V. Then, after the harmonic component is absorbed by the AC filter 10, AC power is supplied to the commercial power system 3 via the interconnection relay 11.

As described above, the inverter output current signal Iout
The high-frequency inverter bridge 5 is controlled so that there is no error between the waveforms of the current reference signal Iref and the current reference signal Iref. it can.

During this interconnection operation, the interconnection relay 1
1, the return control in the low-frequency inverter bridge 9 is performed based on the commercial power system voltage signal V _EUL in the commercial power system 3 obtained from the subsequent stage, so that the phase of the output voltage waveform and the output current waveform in the low-frequency inverter bridge 9 Are power factor 1 controls that match each other, and no reactive power is generated.

The switching elements Q1 to Q4 of the high-frequency inverter bridge 5 and the switching elements S1 to S4 of the low-frequency inverter bridge 9 are, for example, I
GBT (insulated gate bipolar transistor) or the like can be used.

Next, the operation of the inverter main circuit 20 during the self-sustaining operation will be described.

During the interconnection operation, the interconnection independent control unit 33
The power failure detection unit 47 monitors the voltage and frequency of the commercial power system 3 based on the commercial power system voltage signal _VEUL detected from the subsequent stage of the interconnection relay 11 to check whether a power failure occurs. (T9). When the commercial power system 3 has a power failure due to an accident, disaster, or the like, the power failure detection unit 47 detects a power failure based on a change in monitored system voltage / system frequency. and outputs a power failure detection signal BO _1. The interconnection independent switching control unit 48 having received the power failure detection signal BO ₁ is connected to the gate drive signal generation unit 46 in the low frequency inverter bridge control unit 32 and the gate drive signal generation unit 44 in the high frequency inverter bridge control unit 31. Operation stop signal SS ₂
To turn off the four switching elements S1 to S4 of the low-frequency inverter bridge 9, and to control the four switching elements Q1 to Q4 of the high-frequency inverter bridge 5.
Q4 is turned off to stop the operation of the inverter main circuit 20 (T10). Next, the interconnection independent switching control unit 48 disconnects the disconnection command signal G for instructing the interconnection relay 11 to disconnect.
And outputs the R ₂ (T11). When connector relay 11 receives a disconnection instruction signal GR _2, performs disconnection and Kairetsu the inverter main circuit 20 and the commercial power system 3 (T12). Doing disconnection, connector relay 11 outputs a disconnection confirmation signal GK ₂ in interconnection autonomous switching controller 48. Interconnection autonomous switching controller 48 detects that it has received the disconnection confirmation signal GK _2,
After confirming that the inverter main circuit 20 has been disconnected from the commercial power system 3 (T13), the inverter main circuit 2
0 to switch from the high-frequency transformer insulation system during the interconnected operation to the transformerless system during the independent operation, the open command signal C
And it outputs the S ₂ (U2). When the interconnection freestanding selector switch 16 receives an opening command signal CS _2, and opens the switch, switches the main circuit configuration transformerless system not through the high-frequency transformer 6 (U3). When the main circuit configuration is switched to the transformerless mode, the interconnection independent switching switch 16 outputs the opening confirmation signal CK ₂ to the interconnection independent switching control unit 4.
8 is output. Interconnection autonomous switching controller 48 detects that it has received the open check signal CK _2, the main circuit structure is confirmed that trans-less system (U4), and instructs the closed against self relay 13 outputs a connection command signal IR ₁ (U5). When the self relay 13 receives a connection command signal IR _1, the inverter main circuit 2 performs closed
0 and the independent operation load 14 are connected (U6). When the connection is made, self relay 13 outputs a connection confirmation signal IK ₁ to interconnection autonomous switching controller 48. Interconnection autonomous switching controller 48 detects that it has received a connection confirmation signal IK _1,
After confirming that the inverter main circuit 20 and the independent operation load 14 are connected (U7), the inverter main circuit 2
0 to supply AC power to the self-sustained operation load 14 (U8).

The operation mode at this time is an independent operation mode. The interconnection self-contained switching control unit 48 controls the gate drive signal generation unit 4 in the high-frequency inverter bridge control unit 31.
4 to output the self-sustained operation command signal SS ₃ , and convert the DC power input from the solar cell 2 into AC power based on the switching control of the high-frequency inverter bridge 5 by the gate drive signal generation unit 44, and perform the self-sustained operation load. 14.

Inverter main circuit 20 during autonomous operation
Is basically controlled so that an error between the inverter output voltage signal Vout detected from the subsequent stage of the high-frequency inverter bridge 5 and the voltage reference signal Vref determined by the control amount calculation unit 42 is eliminated. The on / off control of the switching elements Q1 to Q4 of the inverter bridge 5 is performed. Since the high-frequency inverter bridge 5 is controlled so that there is no error between the waveforms of the inverter output voltage signal Vout and the voltage reference signal Vref, the inverter output voltage waveform has less distortion with respect to the self-sustaining operation load 14. High quality power can be supplied.

The operation of the high-frequency inverter bridge 5 during the self-sustaining operation will be described. Since the main circuit configuration of the inverter main circuit 20 is a transformerless system that does not pass through the high-frequency transformer 6, the high-frequency inverter bridge 5
Then, the commercial frequency PWM modulation control for outputting the commercial frequency alternating current of 50/60 Hz is performed. That is, load 1 for independent operation
4 determines a new control amount of the inverter main circuit 20 so as to obtain a solar cell output corresponding to the power required by the control unit 4, generates a voltage reference signal Vref, and generates a PWM signal.
In the modulation control unit 43, the high-frequency inverter bridge 5
An amplified error signal obtained by amplifying an error between the inverter output voltage signal Vout and the voltage reference signal Vref detected from the subsequent stage is generated. This error amplified signal is supplied to the commercial power system 3
Is a sine wave signal having the same frequency (50/60 Hz) as the voltage waveform. FIG. 4A shows the waveform of the sine wave signal.
Then, it performs a PWM modulation control by comparing a high-frequency carrier signal (several tens of kHz) synchronized with the error amplification signal and the error amplification signal, generates a pulse train signal PL, and outputs the pulse train signal PL to the gate drive signal generation section 44. FIG. 4B shows a waveform of such a pulse train signal PL. Each of the four switching elements Q1 in the high-frequency inverter bridge 5
To Q4. Regarding the output timing, since the commercial power system 3 is out of power, the synchronizing signal V output from the autonomous synchronizing signal generator 49 is output.
_{Based on SCR} . The gate drive signal generation unit 44 controls on / off of each of the switching elements Q1 to Q4 of the high-frequency inverter bridge 5 based on the input pulse train signal PL. As a result, the high-frequency inverter bridge 5 outputs a pulse train-shaped output voltage Ei as shown in FIG. Then, the self-supporting filter circuit 15
Removal and smoothing the high-frequency component is performed, the load AC voltage V _AC is autonomous operation of the 50 / 60Hz as shown in FIG. 4 (c) 1
4 is supplied. This is AC100V.

In this self-sustaining operation mode, the inverter main circuit 2 is opened by opening the interconnection self-sustaining changeover switch 16.
Since the main circuit configuration of 0 is a transformerless system, and the return control in the low-frequency inverter bridge 9 limited to the power factor 1 control becomes irrelevant, the inverter main circuit 20 can perform the reactive power control. . In other words, the inverter main circuit 20 in which the high-frequency AC of the high-frequency inverter bridge 5 shown in FIG.
4 (d) is shifted from the phase of the output current waveform (not shown) to generate reactive power. As described above, when the reactive power control is performed, the load 14 for the independent operation from the inverter main circuit 20 is controlled.
The output voltage waveform to the inverter does not generate distortion, and may cause a failure such as overheating, overcurrent, abnormal sound, or malfunction to the connected self-sustaining operation load 14, particularly an inductive load such as a motor load. There is no sex. In the independent operation mode, the low-frequency inverter bridge control unit 32 is stopped, and accordingly, the low-frequency inverter bridge 9 is also stopped.

[0055] As shown in the above steps T9~T13 and step U2～U8, at the beginning of a power failure, connector relay 11 is adapted to output a disconnection confirmation signal GK ₂ to perform the disconnection, communication system self switching controller 48 until receiving the disconnection confirmation signal GK ₂ without closing independence relay 13, the inverter main circuit 20 is disconnected from the commercial power system 3 by receiving disconnection confirmation signal GK ₂ Is confirmed, the independent relay 13 is closed, and then the high-frequency inverter bridge 5 is operated to supply the AC power to the independent operation load 14.
There is no danger that the inverter main circuit 20 performs the self-sustaining operation in a state where the inverter main circuit 20 is connected to the commercial power system 3.
Thus, the safety can be improved without applying an overvoltage.

Further, the interconnection independent switching switch 16 outputs an opening confirmation signal CK _{2 when} it is opened, and the interconnection independent switching control unit 48 outputs the opening confirmation signal CK.
Until receiving the ₂ without closing independence relay 13, interconnection self changeover switch 1 by receiving opening confirmation signal CK ₂
6 is opened, and then the self-supporting relay 13
Is closed, and then the high-frequency inverter bridge 5 is operated to supply AC power to the self-sustaining operation load 14, so that safety is further ensured.

When a power failure occurs in the commercial power system 3 during the daytime when the solar radiation intensity is a certain level or more,
The power generated by the solar cell 2 by the independent operation as described above can be effectively used.

In performing the reactive power control of the output to the self-sustaining operation load 14, another configuration is conceivable. That is, the self-supporting filter circuit 15, the self-supporting relay 13, the inverter bridge, and the DC capacitor, which are to be connected to the self-sustaining operation load 14, are provided with an inverter bridge and a DC capacitor separately from those shown in the figure. It is conceivable to configure the switch 2 by using an interconnection independent switch corresponding to the interconnection independent switch 16. However, in this case, another pair of the DC capacitor and the inverter bridge is required, which leads to an increase in cost. In view of such a concept, in the present embodiment, since the interconnection independent switch 16 is interposed on the primary side of the high-frequency transformer 6, there is no need to provide a DC capacitor and an inverter bridge dedicated to independent operation control. , The DC capacitor 4 and the high-frequency inverter bridge 5 shown in FIG.
Parts cost can be reduced.

In the above-described independent operation mode,
The power failure detection unit 47 in the interconnection independent control unit 33 constantly monitors whether or not the power failure of the commercial power system 3 has been canceled based on the commercial power system voltage signal _VEUL at the _subsequent stage of the interconnection relay 11. (U9). When that led to the power failure is released, the power failure detecting section 47 outputs a power failure release detection signal BO ₂ against interconnection autonomous switching controller 48. The interconnection independent switching control unit 48 that has received the power failure release detection signal BO ₂ outputs the independent operation stop signal SS ₄ to the gate drive signal generation unit 44 in the high frequency inverter bridge control unit 31, and outputs the signal from the high frequency inverter bridge 5. The two switching elements Q1 to Q4 are turned off, and the inverter main circuit 20 is turned off.
Is stopped (U10). Then, interconnection autonomous switching controller 48 outputs a disconnecting command signal IR ₂ for instructing disconnection against self relay 13 (U11). Independent relay 1
3 Upon receiving the disconnection instruction signal IR _2, performs disconnection and Kairetsu the inverter main circuit 20 and the isolated operation for a load 14 (U12). Doing disconnection, self relay 13 outputs a disconnection confirmation signal IK ₂ to interconnection autonomous switching controller 48. Interconnection autonomous switching controller 48 detects that it has received the disconnection confirmation signal IK _2, in the inverter main circuit 20 after confirming that disconnecting the isolated operation for a load 14 (U1
3) In order to switch the main circuit configuration of the inverter main circuit 20 from the transformerless system during the independent operation to the high-frequency transformer insulation system during the interconnected operation, the interconnection independent switch 16
And it outputs a closing command signal CS ₁ against (T2). When the interconnection freestanding changeover switch 16 receives a closing command signal CS _1, close the switch, it switches the main circuit configuration in a high-frequency transformer insulating system through the high-frequency transformer 6 (T3). When the main circuit configuration is switched to the high-frequency transformer insulation type, the interconnection independent switch 16 outputs a closing confirmation signal CK ₁ to the interconnection independent switching control unit 48. Interconnection autonomous switching controller 48 detects that it has received the closing confirmation signal CK _1, make sure that the main circuit configuration is high-frequency transformer insulating system (T4), interconnection respect connector relay 11 and it outputs the interconnection command signal GR ₁ instructing (T5).
The connector relay 11 receives the interconnection command signal GR _1, to interconnection of the inverter main circuit 20 and the commercial power system 3 performs closed (T6). When the interconnection is performed, the interconnection relay 11 outputs the interconnection confirmation signal GK ₁ to the interconnection independent switching control unit 4.
8 is output. Interconnection autonomous switching controller 48 detects that it has received the communication system confirmation signal GK _1, the inverter main circuit 2
After confirming that 0 and the commercial power system 3 are interconnected (T7), the inverter main circuit 20 is operated to supply AC power to the commercial power system 3 (T8). The operation mode at this time is the interconnection operation mode, and the low-frequency inverter bridge 9 is driven together with the high-frequency inverter bridge 5 again.

As shown in steps U9 to U13 and steps T2 to T8, at the beginning of the power failure cancellation,
Closing of the self relay 13 solution to perform the disconnecting column check signal IK ₂ is adapted to output, interconnection autonomous switching controller 48 that disconnection confirmation signal IK ₂ until receiving the connector relay 11 the without performs closing of disconnection confirmation signal IK ₂ inverter main circuit 20 connector relay 11 after confirming that it is disconnected from the isolated operation for the load 14 by receiving, then the high frequency inverter bridge 5 And the low-frequency inverter bridge 9 is operated to supply the AC power to the commercial power system 3, so that the inverter main circuit 20 may perform the independent operation while being connected to the independent operation load 14. Therefore, the safety can be improved without applying an overvoltage to the self-sustaining operation load 14.

Further, when the interconnection independent switch 16 is closed, it outputs a closing confirmation signal CK ₁ , and the interconnection independent switching control unit 48 outputs the closing confirmation signal CK.
₁ without closure of connector relay 11 until it receives, interconnection self changeover switch 1 by receiving closing confirmation signal CK ₁
After confirming that the relay 6 is closed, the interconnection relay 11
Is closed, and then the high-frequency inverter bridge 5 and the low-frequency inverter bridge 9 are operated to supply AC power to the self-sustaining operation load 14, so that safety is further ensured.

Next, a description will be given of a control in which the commercial frequency alternating current supplied to the self-sustaining operation load 14 is set to 100 VAC. First, the relationship between the solar cell output voltage and the AC voltage will be described. As described above, during the self-sustaining operation, the high-frequency inverter bridge 5 outputs the pulse train-shaped output voltage Ei shown in FIG. This height V _Ei output voltage Ei is determined by the solar cell output voltage detected from both ends of the DC capacitor 4. Further, FIG. 4 by autonomous filter circuit 15 shown in (d) of the AC voltage V _AC after the removal of high frequency components and smoothing is performed for the amplitude V _AC is half the period of the ON signal of the pulse train shaped output voltage Ei Determined by the total area. From these facts, in order for the _AC voltage VAC output to the self-sustaining operation load 14 to be constant at 100 V _AC , the total area of the ON signal for a half cycle of the pulse train output voltage Ei at the time of 100 V AC output (the value Sa) is calculated in advance and prepared in the PWM modulation control unit 43, and when the PWM modulation control is actually performed, the total area of the ON signal for a half cycle of the pulse train output voltage Ei is a predetermined value. May be adjusted so as to be Sa. Here, if the height V _Ei (solar cell output voltage) of the pulse train output voltage Ei is constant, the total area of the ON signal for a half cycle of the pulse train output voltage Ei changes depending on the pulse width. It is only necessary to adjust the pulse width. On the other hand, when the solar cell output voltage (V _Ei ) is not constant but fluctuates, as described above, the total area of the ON signal for a half cycle of the pulse train output voltage Ei is set to a predetermined value Sa. Will be adjusted. In this way, by setting the electric power supplied to the independent operation load 14 to 100 V AC, a household electric load using 100 V AC as a power source can be used as the independent operation load 14. In addition, since the inverter control uses the AC100V output, there is no need to specially equip a transformer for voltage conversion from AC200V to AC100V in the inverter main circuit, and it is possible to reduce parts costs.

When the transformer ratio of the high-frequency transformer 6 is, for example, 1: 2, in order to supply a constant AC of 200 V to the commercial power system 3 during the interconnection operation, the output voltage of the solar cell 2 must be about 140 V or more. I just need. In the independent operation, the high frequency transformer 6 is not included in the main circuit configuration, but the alternating current supplied to the independent operation load 14 may be constant at 100 V AC, so that the output voltage of the solar cell 2 may be 140 V or more.

By performing the above-described processing, the commercial power system 3 loses power due to an accident or the like, and the inverter main circuit 20 is disconnected from the commercial power system 3 while the inverter main circuit 20 is disconnected.
By switching the main circuit configuration from high-frequency transformer insulation type to transformerless type and performing independent operation control,
Since the reactive power can be controlled at that time, the DC power from the solar cell 2 can be converted into AC 100 V constant AC power having no waveform distortion and supplied to the independent operation load 14.

Although one embodiment has been described in detail above, the present invention can include the following configuration.

(1) In the above embodiment, only the solar cell 2 is shown as the DC power supply connected to the input terminals 17a and 17b of the grid interconnection inverter device 1, but it is not always necessary to do so. A storage battery may be used as the DC power supply, or a combination of a solar battery and a storage battery may be used.

(2) In the above embodiment, the maximum power point follow-up control unit 41, the control amount calculation unit 42, the PWM modulation control unit 43, the turnback control unit 45, the power failure detection unit 47, the interconnection independent switching control unit 48 Although the self-sustained synchronizing signal generator 49 is shown in a block diagram, each of them may be configured by hardware or software.

(3) In the above embodiment, the control circuit 3
Although the switching operation of the interconnection independent switch 16 is automatically performed by the interconnection independent switching control unit 48 within 0, the switching operation of the interconnection independent switching switch 16 may be performed manually.

(4) As for any other items which are not directly related to the gist of the present invention, any known ones can be applied. It is needless to say that the present invention can be applied within a range not to be applied.

The above items (1) to (4) are independent from each other, and any of these items may be combined in an appropriate number.

Finally, notes on the description of the specification relating to the present case will be described. In the specification (especially, the detailed description of the invention and the claims) or the drawings relating to the present case, regarding any given matter (including any element or a connection relation / combination relation of any element), Reserve the possibility of omission. Furthermore, the possibility of adding any matter not described in the claims but described in the detailed description of the invention or in the drawings to the claims and the possibility of changing the description accompanying the additions is described. Reserve

[0072]

EFFECT OF THE INVENTION First of the grid-connected inverter devices
According to the invention of the above, when switching from the interconnection operation control to the independent operation control due to a power failure, the independent operation is unexpectedly performed in a state where the interconnection interconnection means corresponding to the interconnection relay is not disconnected for some reason. In the main circuit configuration, regardless of the state of the grid connection / disconnection means, there is no effect on the load for independent operation from the system, so overvoltage is not applied to the load for independent operation and safety is improved. can do. Also, when the power outage is canceled and the operation is switched from independent operation control to interconnected operation control,
Even if the autonomous load connection / disconnection means corresponding to the autonomous relay is not disconnected for any reason and the operation is unexpectedly linked to the grid, the main circuit configuration may cause a gap between the grid and the autonomous operation load. In this case, regardless of the state of the independent load connection / disconnection means, there is no influence from the system to the independent operation load, so that an overvoltage is not applied to the independent operation load and safety can be improved.

According to the second aspect of the present invention, when the inverter main circuit operates in a self-sustaining manner, the main circuit configuration is of a transformerless type that does not involve a high-frequency transformer, and is implemented by a low-frequency inverter bridge limited to power factor 1 control. Since the loop-back control becomes irrelevant, the inverter main circuit can perform the reactive power control, and the output voltage waveform of the inverter main circuit does not generate distortion.
In particular, it is possible to avoid a risk of causing an obstacle such as overheating, overcurrent, abnormal sound, or malfunction to an inductive load such as a motor load.

According to the third aspect of the present invention, the main circuit configuration switching means corresponding to the interconnection self-contained changeover switch is provided on the primary side of the high frequency transformer. Realizes control and does not cause distortion in the output voltage waveform of the inverter main circuit, and overheating, overcurrent, abnormal sound, malfunction, etc. to the connected independent operation load, especially to inductive loads such as motor loads The risk of causing a failure can be avoided. Moreover,
The DC capacitor and the high-frequency inverter bridge can be shared, and the cost of parts can be reduced.

According to the fourth invention, during the interconnection operation, the inverter main circuit is controlled so that there is no error between the waveforms of the inverter output current signal and the current reference signal. High-quality power with little distortion. On the other hand, during the self-sustaining operation, the inverter main circuit is controlled so that there is no error between the waveforms of the inverter output voltage signal and the voltage reference signal and the output voltage is constant. As a result, it is possible to supply high-quality power with little distortion to the inverter output voltage waveform.

According to the fifth aspect of the present invention, in the case of a self-sustained operation in which the inverter main circuit is operated in the event of a power failure due to an accident or disaster, it is not necessary to supply the output of the inverter main circuit to the system. You do n’t have to
By using AC100V, a household electric load using AC100V as a power source can be used as a self-sustaining operation load.
Since the output is 0 V, the AC200
Since there is no need to convert the voltage from V to 100 V AC, components such as a transformer for voltage transformation are not required, and cost can be reduced.

According to the sixth aspect of the present invention, when a power outage occurs during the daytime when the solar radiation intensity is a certain level or more, the power outage is detected, the inverter main circuit is stopped, and the inverter main circuit and the system are disconnected. In addition, a self-sustaining operation load is connected to the inverter main circuit to perform self-sustaining operation, and DC power from a DC power source such as a solar cell is converted into AC power and output to the self-sustaining operation load. Effective use of the DC power supply can be achieved.

According to the seventh invention, there is no danger that the inverter main circuit will operate in a self-sustaining manner in a state of interconnection with the system, and no overvoltage will be applied to the self-sustaining operation load. it can.

According to the eighth aspect of the invention, the inverter main circuit has no danger of performing the interconnection operation in a state of connection with the independent operation load, and there is no overvoltage applied to the independent operation load, thereby improving safety. can do.

According to the ninth aspect, the main circuit configuration switching means equivalent to the interconnection independent switch can be switched in a state where no large voltage is applied from the system, and safety can be improved. Further, since a type having a small withstand voltage can be used as the main circuit configuration switching means, the cost of parts can be reduced.

According to the tenth aspect, after confirming that the inverter main circuit and the load for independent operation are disconnected, switching from the main circuit configuration during independent operation to the main circuit configuration during interconnected operation is performed. Therefore, there is no danger of performing the interconnected operation in the state of connection with the independent operation load, and no overvoltage is applied to the independent operation load, so that safety can be improved.

[Brief description of the drawings]

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

FIG. 2 is a flowchart showing a sequence for switching between interconnected operation control and independent operation control of the system interconnection inverter device according to the embodiment;

FIG. 3 is a waveform diagram of a main part of an inverter main circuit during interconnection operation in the system interconnection inverter device according to the embodiment;

FIG. 4 is a waveform diagram of a main part of an inverter main circuit at the time of a self-sustaining operation in the grid-connected inverter device according to the embodiment;

FIG. 5 is a block circuit diagram showing a circuit configuration of a conventional system interconnection inverter device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 grid-connected inverter device 2 solar cell 3 commercial power system 4 DC capacitor 5 high-frequency inverter bridge 6 high-frequency transformer 7 diode bridge 8 filter circuit 9 low-frequency inverter Bridge, 10 AC filter, 11 interconnection relay, 12 inverter output current detector, 13 independent relay, 14 independent operation load, 15 independent filter circuit, 16 interconnection independent switch, 17a, 17b ... input terminal, 18
a, 18b: output terminal, 19a, 19b: load connection terminal, 20: inverter main circuit, 30: control circuit, 31 ...
High frequency inverter bridge control unit, 32: low frequency inverter bridge control unit, 33: interconnection independent control unit, 41: maximum power point tracking control unit, 42: control amount calculation unit, 43: PW
M modulation controller, 44... Gate drive signal generator, 45
... Foldback controller, 46 ... Gate drive signal generator, 4
7: power failure detection unit, 48: interconnection self-contained switching control unit, 49: self-contained synchronization signal generation unit, Q1 to Q4: switching elements,
S1 to S4: switching element, V _EUL ... commercial power system voltage signal, Iout ... inverter output current signal, Vout ...
Inverter output voltage signal, Iref ... current reference signal, Vre
f ... voltage reference signal, V _SCR ... synchronization signal, PL ... pulse train signal, Ei ... pulse train output voltage, BO ₁ ... power failure detection signal, BO ₂ ... power failure release detection signal, CS ₁ ... closing command signal, CK ₁ ... Close confirmation signal, CS ₂ ... Open command signal, C
K ₂ ... opening confirmation signal, GR ₁ ... interconnection command signal, GK ₁ ...
Interconnection confirmation signal, GR ₂ ... disconnection command signal, GK ₂ ... disconnection confirmation signals, IR ₁ ... connection command signal, IK ₁ ... connection confirmation signal, IR ₂ ... disconnection command signal, IK ₂ ... disconnection confirmation signal , S
S ₁ : interconnection operation command signal, SS ₂ : interconnection operation stop signal,
SS ₃ ... self-sustained operation command signal, SS ₄ ... self-sustaining operation stop signal

Continued on the front page (72) Inventor Masaki Eguchi 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside (72) Inventor Tsukasa Takebayashi 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Inside Sharp Corporation F term (reference) 5H007 AA04 BB07 CA01 CB04 CB05 CC03 CC32 DA03 DA04 DB01 DC05 EA02 GA01

Claims (10)

[Claims] 1. An inverter main circuit that converts DC power of a DC power supply such as a solar cell into AC power and connects the AC power to a system, and controls the inverter main circuit by inputting a state of the DC power supply and a state of the system. A system interconnection inverter device comprising: a main circuit configuration at the time of interconnection operation in which the inverter main circuit is operated in interconnection with the system; A system interconnection inverter device comprising: a main circuit configuration switching unit that switches between a main circuit configuration at the time of a self-sustained operation that is operated by being connected to a load. 2. The system interconnection inverter device according to claim 1, wherein the main circuit configuration during the interconnection operation is a high-frequency transformer insulation system, and the main circuit configuration during the self-sustaining operation is a transformerless system. A system interconnection inverter device characterized by the above-mentioned. 3. The grid-connected inverter device according to claim 1, wherein the main circuit configuration switching means is provided on a primary side of a high-frequency transformer. apparatus. 4. The system interconnection inverter device according to claim 1, wherein an inverter output current signal and a current are output in a high-frequency transformer insulation system, which is a main circuit configuration during the interconnection operation. The inverter main circuit is controlled so that the error between the waveforms of the reference signal and the reference signal is eliminated, and the error between the waveforms of the inverter output voltage signal and the voltage reference signal is eliminated in the transformerless system which is the main circuit configuration during the self-sustaining operation. A system interconnection inverter device, wherein the inverter main circuit is controlled so that an output voltage is constant. 5. The grid-connected inverter device according to claim 1, wherein an output of the main circuit configuration of the high-frequency transformer isolation system is 200 V AC, and the main unit of the transformerless system is AC output in circuit configuration
A system interconnection inverter device which is set to 100V. 6. An inverter main circuit for converting DC power of a DC power supply such as a solar battery into AC power and connecting the AC power to a system, and controlling the inverter main circuit by inputting a state of the DC power supply and a state of the system. Grid-connected inverter device comprising: a power failure detection means for detecting a power failure of the system, and a system interconnection / disconnection means for interconnecting and disconnecting the inverter main circuit and the system. A self-contained load connection / disconnection means for connecting and disconnecting the inverter main circuit and the self-sustained operation load, a main circuit configuration at the time of interconnection operation in which the inverter main circuit is operated in interconnection with the system, and Main circuit configuration switching means for switching between a main circuit configuration at the time of self-sustained operation which is disconnected from the system and connected to the self-sustaining operation load and operated, and the system interconnection / separation means, the self-sustaining load connection / separation means and The main round A system interconnection inverter device comprising: interconnection independent switching control means for controlling road configuration switching means. 7. The system interconnection inverter device according to claim 6, wherein the system interconnection disconnection unit outputs a disconnection confirmation signal when the inverter main circuit and the system are disconnected. A system interconnection inverter device that outputs an interconnection confirmation signal in a system state. 8. The grid-connected inverter device according to claim 6, wherein the independent load connection disconnecting means is disconnected when the inverter main circuit and the independent operation load are disconnected. A system interconnection inverter device that outputs a confirmation signal and outputs a connection confirmation signal in a connected state. 9. The system interconnection inverter device according to claim 6, wherein the interconnection independent switching control unit monitors a signal output from the system interconnection disconnection unit. Upon detecting a disconnection confirmation signal from the system interconnection disconnection means, the main circuit configuration switching means allows a switching operation from a main circuit configuration during interconnection operation to a main circuit configuration during autonomous operation, A system interconnection inverter device characterized in that when a disconnection confirmation signal from the system interconnection disconnection means is not detected, a signal is continuously monitored without permitting the switching operation. 10. The system interconnection inverter device according to claim 6, wherein the interconnection independent switching control unit monitors a signal output from the independent load connection disconnecting unit. When detecting the disconnection confirmation signal from the independent load connection disconnecting means, the main circuit configuration switching means allows the switching operation from the main circuit configuration during the independent operation to the main circuit configuration during the interconnection operation, When the disconnection confirmation signal from the independent load connection disconnecting means is not detected, the switching operation is not permitted and the signal is continuously monitored without allowing the switching operation.