JPH10229679A - Inverter device linked to system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device linked to a system, which supplies a voltage synchronized with the AC voltage of a commercial power system, according to the quantity of sunlight. SOLUTION: A switch controller 18 subtracts a voltage value between the voltage line of a commercial power system 15 and that of the neutral line from the DC voltage value of a solar battery 11, at the start of an operation. When its subtraction value is not less than the specified value, it turns on a first switch 13, and then it subtracts the voltage value between the lines of the commercial power system 15 from the DC voltage value. When the subtracted value is less than a specified value, it keeps the on condition for the first switch 13, and when the subtraction value is not less than a specified value, it turns off the first switch 13 and also turns on a second switch 14. When an on condition of the first switch 13 is kept, it subtracts the voltage value between the voltage line of the commercial power system 15 and the neutral line, and when the subtracted value is under a specified value, it turns off the first switch 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic power generation system, and more particularly, to a grid-connected inverter in which a solar cell is connected to a single-phase three-wire commercial power system via an inverter main circuit. It concerns the device.

[0002]

2. Description of the Related Art FIG. 6 is a block diagram showing a configuration of a conventional grid-connected inverter disclosed in, for example, Japanese Patent Application Laid-Open No. 7-298626. The solar cell 1 is connected to the commercial power system 4 via the inverter main circuit 2, and a relay 3 turned on / off by a relay drive circuit 5 is interposed between the inverter main circuit 2 and the commercial power system 4. doing. The inverter main circuit 2 includes an inverter control circuit 6
The DC voltage generated by the solar cell 1 is converted into an AC voltage synchronized with the commercial power system 4 and supplied to the commercial power system.

[0003]

By the way, when this conventional grid-connected inverter device is connected to, for example, each single-phase three-wire voltage line of the commercial power system 4, that is, AC 200V,
The output voltage of the solar cell 1 is required to be at least 282 V which is 1.41 times 200 V, but when the amount of solar radiation decreases, the characteristics of the solar cell output voltage-solar cell output current / output power shown in FIG. As is clear from Japanese Patent Application Laid-Open No. 8-72077, the output voltage of the solar cell 1 decreases, so that when the voltage of 282 V cannot be secured, the inverter device cannot operate.

As a method for securing a voltage of 282 V or more even when the amount of solar radiation is small, there is a method of increasing the number of solar cells 1 in series. However, when the amount of solar radiation increases, the output voltage of the solar cell 1 increases. High breakdown voltage components must be used for the components such as the switching elements that constitute the inverter main circuit 2, which increases the size of the device.
Costs are also high.

When one of the single-phase three-wire lines of the commercial power system 4 is connected to the neutral line, that is, connected to AC 100 V, the output voltage of the solar cell 1 is 141 V, which is 1.41 times 100 V. The inverter device can be operated even when the amount of solar radiation is small, but for example, when supplying 3 kW of electric power, the output current of 15 A is sufficient for 200 V AC interconnection.
Since an output current of 30 A is obtained in an AC 100 V connection, parts having a large current capacity must be used as in the above case, and the size of the apparatus increases and the cost increases.

There is also a method in which a DC / DC converter circuit is provided between the solar cell 1 and the inverter main circuit 2 and the voltage of the converter circuit is increased to 282 V or more when the amount of solar radiation is small. Become larger, D
Loss of the C / DC converter results in poor efficiency and high cost.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and does not use a component having a high withstand voltage or a component having a large current capacity.
An object of the present invention is to provide a system interconnection inverter device capable of supplying a voltage synchronized with an AC voltage of a commercial power system without using a C / DC converter circuit.

[0008]

SUMMARY OF THE INVENTION A grid-connected inverter device according to the present invention includes a solar cell, first and second switches, an input side connected to the solar cell, and one output terminal on an output side. Is connected to one voltage line among the single-phase three-wires of the commercial power system, and the other output terminal is connected to the neutral wire of the single-phase three-wire via the first switch. An inverter main circuit connected to the other voltage line via a second switch, and a switch control unit that turns on the first switch or the second switch according to the DC voltage of the solar cell. It is provided with.

Further, in the system interconnection inverter device of the present invention, a solar cell, a first switch and a second switch, an input side is connected to the solar cell, and one output terminal on the output side is a commercial terminal. The power line is connected to one voltage line among the single-phase three wires, the other output terminal is connected to the single-phase three-wire neutral wire via the first switch, and the second output terminal is connected to the second power line. An inverter main circuit connected to the other voltage line via a switch of the above, a solar cell voltage detection circuit for detecting a DC voltage value of the solar cell, and a single-phase three-line voltage line of a commercial power system-neutral A system voltage detection circuit that detects a line voltage value and a line voltage value, and a voltage line detected by the system voltage detection circuit from a DC voltage value detected by the solar cell voltage detection circuit at the start of operation. Minus the voltage value between the neutral conductors,
When the subtraction value is equal to or more than a predetermined value, the first switch is turned on, and thereafter, the line voltage value detected by the system voltage detection circuit is subtracted from the DC voltage value, and the subtraction value is a predetermined value. When the value is less than the value, the first switch is kept on, and when the subtraction value is not less than a predetermined value, the first switch is turned off and the second switch is turned on. Device control unit, when holding the ON state of the first switch, subtracts the voltage value between the voltage line and the neutral line detected by the system voltage detection circuit from the DC voltage value, A second switch control unit that turns off the first switch when the subtraction value is less than a predetermined value.

[0010] Further, a system voltage detection circuit for detecting a maximum value of the AC voltage is provided.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing the configuration of a grid interconnection device according to the present invention. In FIG. 1, reference numeral 11 denotes a solar cell, and 12 denotes an inverter main circuit comprising a plurality of switching elements. And the input side is solar cell 1
1, one output terminal on the output side is connected to one voltage line A of the single-phase three wires of the commercial power system 15, and the other output terminal is connected to the single-phase It is connected to the three neutral wires B and to the other voltage wire C via the second switch 14. As the first and second switches 13 and 14, for example, an electromagnetic contactor, a bidirectional semiconductor switch, or the like is used.

Reference numeral 16 denotes a solar cell voltage / current detecting circuit for detecting the DC voltage value Vs of the solar cell 11, and 17 denotes a voltage value V AB between a single-phase three-wire voltage line A and a neutral line B of the commercial power system 15.
A system voltage detection circuit 18 for detecting the (maximum value) and the line voltage value VAC, respectively, is a switch control unit 18 including first and second switch control units, including, for example, an inverter control unit 20 described later. It consists of a microcomputer, and when starting operation,
The voltage value VAB detected by the system voltage detection circuit 17 is subtracted from the DC voltage value Vs detected by the solar cell voltage / current detection circuit 16, and when the subtraction value dV is a predetermined value α, for example, 15V or more, A signal for turning on the first switch 13 is output to the switch drive circuit 20, and then, for example, a system link start flag is set to notify the inverter control unit 20 of the start of driving of the inverter main circuit 12.

Thereafter, the line voltage value VAC detected by the system voltage detection circuit 17 is subtracted from the DC voltage value Vs, and when the subtracted value dV is less than a predetermined value β, for example, 15 V, the first switching operation is performed. When the subtraction value dV is equal to or more than the predetermined value β, the signal for turning off the first switch 13 and turning on the second switch 14 is output to the switch drive circuit 20. .

When the subtraction value dV becomes smaller than the predetermined value α while the first switch 13 is on, a signal for turning off the first switch 13 is transmitted to the switch driving circuit 2.
In addition to outputting to 0, the set system interconnection start flag is cleared and the inverter control unit 20 is notified that the drive of the inverter main circuit 12 is stopped. Then, as described above, the DC voltage value Vs and the voltage value VAB on the commercial power system side are input, and the calculation of the subtraction value dV is started.

The inverter control unit 20 determines whether or not the system interconnection start flag is set at every time T as shown in FIG. 5, and when confirming the setting of the system interconnection start flag, first, The operating point voltage of the solar cell 11 at which the output power of the solar cell 11 becomes maximum with respect to the amount of solar radiation is determined. This is because in the characteristics of the solar cell output voltage-solar cell output current / output power shown in FIG. 7, the point M1 when the amount of solar radiation is small, and the point M2 when the amount of solar radiation is large, the operation of the solar cell 11 relative to the amount of solar radiation It is determined as a point voltage. Note that a detailed method of determining the operating point voltage of the solar cell 11 is described in Japanese Patent Application No. 8-72077, and a description thereof will be omitted.

Thereafter, the output current IOBJ of the grid-connected inverter device is determined so that the determined operating point voltage is obtained, and then the output current IOBJ is synchronized with the AC voltage of the commercial power system 15, that is, the first switch 13 is turned on. The switching circuit 21 is controlled so that the current IOBJ synchronized with the voltage value VAB between the voltage line A and the neutral line B due to the above or the line voltage value VAC due to the turning on of the second switch 14 flows, and the inverter main circuit 12 Drive.
The switch drive circuit 19 turns on and off the first and second switches 13 and 14 based on the input of a signal from the switch control unit 18.

The operation of the above-configured system interconnection device will be described. FIG. 2 is a flowchart showing the operation of the system interconnection inverting device according to the present invention at the start of operation, and FIGS. 3 to 5 are flowcharts showing the operation of the system interconnection inverting device during operation.

First, at the start of operation, the switch control unit 18 switches between the single-phase three-wire AB of the commercial power system 15,
The voltage value V AB between the voltage line A and the neutral line B to which the switch 14 is not connected is measured by the system voltage detection circuit 17, and the DC voltage value VS of the solar cell 11 is Measured by the detection circuit 16 (S21, S2
2) The system-side voltage value VAB is subtracted from the DC voltage value VS to calculate a subtraction value dV (S23). And
It is determined whether the subtraction value dV is equal to or greater than a predetermined value α (15 V) (S24). If the subtraction value dV is less than the predetermined value α, it is determined that the operation of the grid-connected inverter device cannot be started, and the step is repeated. It returns to the process of 21. This step 21-
In the process of step 24, the calculated subtraction value dV is set to a predetermined value α.
The process is repeatedly executed until the amount of solar radiation described above is obtained.

If the subtraction value dV calculated in step 23 is equal to or greater than the predetermined value α, it is determined that the operation of the grid-connected inverter device can be started, and the switch drive circuit 19 sends the first switch 13
A signal for turning on only the power supply is output (S25), and then a system interconnection start flag is set (S26). At this time,
The switch drive circuit 19 receives the first signal based on the signal input.
Switch 13 is turned on to connect with AC 100V.

On the other hand, the inverter control unit 20 determines whether or not the grid connection start flag has been set at each time T (S51). The operating point voltage of the solar cell 11 at which the output power of the solar cell 11 becomes maximum with respect to the amount is determined (S52). Thereafter, the output current IOBJ of the grid-connected inverter device is determined so as to have the determined operating point voltage (S
53) Then, the switching circuit 21 is controlled so that the current IOBJ synchronized with the voltage value VAB between the voltage line A and the neutral line B when the first switch 13 is turned on flows (S54). At this time, the switching circuit 21 drives the inverter main circuit 12 based on the control.

When the interconnection operation of the present apparatus is started, the switch control unit 18 measures the line voltage VAC between the single-phase three-line AC of the commercial power system 15 by the system voltage detection circuit 17 (S3).
1) The DC voltage value VS of the solar cell 11 is measured by the solar cell voltage / current detection circuit 16 (S32), and the line voltage value VAC on the system side is subtracted from the DC voltage value VS to calculate a subtraction value dV. (S33). Then, it is determined whether or not the subtraction value dV is equal to or greater than a predetermined value β (15 V) (S34). It is determined that a solar cell voltage sufficient to interconnect with the second switch 14 has not been obtained.
Of the first switch 13 and the on state of the first switch 13 are held through the switch drive circuit 19 (S38, S39).
The 0V interconnection mode is set (S40).

When the subtraction value dV is equal to or more than the predetermined value β, it is determined that the solar radiation is large and a solar cell voltage sufficient for interconnection with the single-phase three-line voltage VAC is obtained. , First
A signal for turning off the switch 13 and turning on the second switch 14 is output to the switch drive circuit 19, and the AC 200 V interconnection mode is set (S35, S36, S37). At this time, the switch drive circuit 19 switches the first switch 13 from on to off based on the input of the signal, and at the same time, turns on the second switch 14 to link with 200 VAC.
In addition, the inverter control unit 20 executes the process shown in FIG. 5 every time T (S51 to S54). In this case, the current synchronized with the line voltage value VAC due to the turning on of the second switch 14 is performed. The switching circuit 21 is controlled so that IOBJ flows.

After the connection mode is set, the current connection mode is checked in step 41, and the mode is set to 200 V AC.
In the case of the interconnection mode, the process starts from step 31. However, in the case where the mode is the AC 100 V interconnection mode, the voltage value between the single-phase three-line voltage line A and the neutral line B of the commercial power system 15 is again obtained. VAB is measured by the system voltage detection circuit 17 (S4
2) The DC voltage value VS of the solar cell 11 is measured by the solar cell voltage / current detection circuit 16 (S43), and the system-side voltage value VAB is subtracted from the DC voltage value VS to obtain a subtraction value d.
V is calculated (S44). Then, it is determined whether or not the subtraction value dV is less than a predetermined value α (15V) (S45). If the subtraction value dV is equal to or more than the predetermined value α, it is determined that the operation can be continued, and step 31 is performed as described above. Start with the process. Further, when the subtraction value dV is less than the predetermined value α, it is determined that the amount of solar radiation is small and that the solar cell voltage sufficient to interconnect with the voltage value VAB of the single-phase three-wire is not obtained, and the first The switch 13 is turned off to shut off the output of the inverter main circuit 12 (S46, S47), and the set system interconnection start flag is cleared (S48). And step 2
It returns to 1 and starts the measurement of the voltage value VAB on the system side. After a lapse of time T, the inverter control unit 20 stops the control of the switching circuit 21 based on the operating point voltage of the solar cell 11, and stops the output of the inverter main circuit 12.

As described above, in the present embodiment, when the present apparatus is operated, the voltage value V AB between the voltage line A and the neutral line B of the commercial power system 15 is subtracted from the DC voltage value VS of the solar cell 11, When the subtraction value dV is equal to or more than the predetermined value α, the first switch 13 is turned on so that 100 V AC can be supplied. Thereafter, the line voltage value VAC of the commercial power system 15 is converted from the DC voltage value VS. When the subtraction value dV is equal to or greater than a predetermined value β, the second switch 14 is turned on and the first switch 13 is turned off at the same time to supply 200 V AC. And components with large current capacity,
There is an effect that the operation range of the present apparatus can be widened and efficient operation can be performed without using a DC / DC converter circuit.

Further, since the system voltage detecting circuit 17 for detecting the maximum value of the voltage is used for detecting the voltage of the commercial power system 15, the comparison with the DC voltage VS of the solar cell 11 can be easily performed. Since the configuration is simplified, there is an effect that a low-cost device can be provided.

[0026]

As described above, according to the present invention, the first switch is turned on in accordance with the DC voltage of the solar cell. In this case, one of the single-phase three-wires on the commercial power system side is connected to the middle. And a second switch is turned on in accordance with the DC voltage. In this case, the second switch is turned on in synchronization with the line voltage of the single-phase three-wire line on the commercial power system side. Power can be supplied, so that components with high withstand voltage, components with large current capacity, and DC / DC converter circuits are not used.
There is an effect that the operation range of the present device can be widened and efficient operation can be performed.

When the present apparatus is operated, the voltage value between the voltage line of the commercial power system and the neutral line is subtracted from the DC voltage value of the solar cell. The switch is turned on so that a voltage synchronized with the AC 100 V can be supplied, and thereafter, the line voltage value of the commercial power system is subtracted from the DC voltage value. Since the first switch is turned off at the same time when the switch is turned on, a voltage synchronized with AC 200 V can be supplied.
Parts with high breakdown voltage, parts with large current capacity, and DC / D
There is an effect that the operation range of the present device can be widened and efficient operation can be performed without using a C converter circuit.

Further, since the system voltage detecting circuit for detecting the maximum value of the voltage is used for detecting the voltage on the commercial power system side, comparison with the DC voltage of the solar cell can be easily performed, and the circuit configuration is simplified. Therefore, there is also an effect that a low-cost device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a system interconnection device according to the present invention.

FIG. 2 is a flowchart illustrating an operation of the system interconnection inverting device according to the present invention when the operation is started.

FIG. 3 is a flowchart showing an operation during operation of the system interconnection inverting device according to the present invention.

FIG. 4 is a flowchart showing an operation during operation of the system interconnection device according to the present invention.

FIG. 5 is a flowchart showing an operation during operation of the system interconnection inverting device according to the present invention.

FIG. 6 is a block diagram showing a configuration of a conventional system interconnection inverter device.

FIG. 7 is a diagram showing characteristics of solar cell output voltage-solar cell output current / output power.

[Explanation of symbols]

11 Solar cell, 12 Inverter main circuit, 13 First
Switch, 14 second switch, 16 solar cell voltage / current detection circuit, 17 system voltage detection circuit, 18 switch control section, 19 switch drive circuit, 20 inverter control section, 21 switching circuit.

Claims (3)

[Claims] 1. A solar cell, a first switch and a second switch, and an input side is connected to the solar cell, and one output terminal on an output side is one of a single-phase three-wire of a commercial power system. And the other output terminal is connected to the neutral wire of the single-phase three-wire via the first switch and the second output terminal is connected to the neutral wire of the single-phase three-wire.
An inverter main circuit connected to the other voltage line via the switch of the above, and a switch control unit for turning on the first switch or the second switch according to the DC voltage of the solar cell. A system interconnection inverter device characterized by the above-mentioned. 2. A solar cell, a first switch and a second switch, and an input side is connected to the solar cell, and one output terminal on the output side is one of a single-phase three-wire of a commercial power system. And the other output terminal is connected to the neutral wire of the single-phase three-wire via the first switch and the second output terminal is connected to the neutral wire of the single-phase three-wire.
An inverter main circuit connected to the other voltage line via the switch of the above, a solar cell voltage detection circuit for detecting a DC voltage value of the solar cell, a single-phase three-wire voltage line of a commercial power system-neutral A system voltage detection circuit for detecting a line voltage value and a line voltage value, and a voltage line detected by the system voltage detection circuit from a DC voltage value detected by the solar cell voltage detection circuit at the start of operation. Subtracting the voltage value between the neutral wires, turning on the first switch when the subtracted value is equal to or greater than a predetermined value, and thereafter,
The line voltage value detected by the system voltage detection circuit is subtracted from the DC voltage value. When the subtracted value is less than a predetermined value, the ON state of the first switch is held, and the subtracted value is a predetermined value. A first switch control unit that turns off the first switch and turns on the second switch when the value is equal to or more than the value; and when the on state of the first switch is held, A second switch for turning off the first switch when the voltage value between the voltage line and the neutral line detected by the system voltage detection circuit is subtracted from the DC voltage value and the subtraction value is less than a predetermined value. A system interconnection inverter device comprising: a power controller. 3. The system interconnection inverter device according to claim 2, wherein the system voltage detection circuit detects a maximum value of the AC voltage.