JP2013031309A - Power conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conditioner that reduces deterioration of a switch on a feed line for supplying power from an electric power system to a DC link section.SOLUTION: In a power conditioner 3 having a converter 4 and an inverter 5 connected via a DC link section 6 and having a system feed relay 13 on a feed line 10 enabling power supply from a system power supply 2 to the DC link section 6 as bypassing the inverter 5, the system feed relay 13 is configured not to be closed unless a voltage at the DC link section 6 drops to a predetermined threshold voltage Vx even when an output voltage of a solar panel 1 drops to stop a system interconnection operation, so that the number of switching cycles of the system feed relay 13 is reduced.

Description

  The present invention relates to a power conditioner, and more particularly to a power conditioner configured to be able to supply power from both a power generation unit side and a power system side to a DC link unit of an inverter.

  Conventionally, a power conditioner has been proposed as an inverter device for connecting DC power generated by a power generation unit such as a solar panel to a power system such as a commercial power source.

  FIG. 4 shows an example of such a power conditioner. The power conditioner shown in this figure is a power conditioner of a power generation system using a solar panel as a power generation unit. The converter b to which the solar panel a is connected and the DC power boosted by the converter b are used. The main part includes an inverter c that converts AC power having a frequency that can be linked to the system power supply (power system) f, and a grid interconnection switch d that links the AC power converted by the inverter c to the system power supply f. The converter b and the inverter c are connected via a DC link capacitor (DC link portion) e.

  In the power conditioner shown in FIG. 4, the power supply unit h of the control microcomputer g that controls each part of the power conditioner is configured to receive power supply from the DC link unit e. The DC link section e is configured to receive power supply from the system power supply f.

  In other words, the power conditioner shown in FIG. 4 is provided with a power supply path i that can supply power from the system power supply f to the DC link unit e without using the inverter c. By closing the system power supply relay j, power can be supplied from the system power supply f to the DC link section e.

  In the power conditioner configured as described above, when the solar panel a is generating power, the power generated by the solar panel a is boosted by the converter b and supplied to the DC link unit e, while at night. When the solar panel a is not generating power (in other words, when the output voltage of the solar panel a is equal to or lower than a predetermined voltage), the operation of the converter b and the inverter c is stopped, and the system The connection relay d is opened to release the connection between the inverter c and the system power supply f, and the system power supply relay j is closed to rectify the power (AC200V) supplied from the system power supply f by the rectifier k. And is supplied to the DC link unit e.

  That is, in the power conditioner shown in FIG. 4, not only when the solar panel a is generating power, but also when the solar panel a is not generating power, DC power is supplied to the DC link unit e, so that the DC The power is always supplied to the power supply unit h that receives power supply from the link unit e, so that the microcomputer g can always monitor each unit of the power conditioner (note that power is supplied from the DC link unit e to the power supply). For the configuration to be supplied, see, for example, Patent Document 1).

JP 2011-49053 A

  However, the power conditioner having such a configuration has the following problems, and improvement has been desired.

  That is, in the power conditioner shown in FIG. 4 described above, the system power supply relay j is closed when the output voltage of the solar panel a becomes equal to or lower than a predetermined voltage. Since the output voltage increases / decreases depending on the weather (amount of solar radiation), the output voltage of the solar panel a may frequently fluctuate up and down depending on the weather. In such a case, the solar panel a As the output voltage fluctuates, the system feed relay j frequently repeats closing and opening, and there is a problem that the system feed relay j deteriorates in a short period of time.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a power conditioner with less deterioration of a switch in a power supply path for supplying power from a power system to a DC link unit. It is to provide.

  In order to achieve the above object, a power conditioner according to claim 1 of the present invention is capable of interconnecting a converter that boosts DC power generated by a power generation unit and DC power boosted by the converter to a system power supply. And an inverter for converting the AC power into the AC power. These are connected via a DC link unit, and the converter and the inverter are operated on condition that the output voltage of the power generation unit exceeds a predetermined voltage. In a power conditioner configured to perform system operation, a power supply unit that receives power supply from the DC link unit and power supply from the system power supply to the DC link unit without passing through the inverter are enabled. A power supply path and a switch that opens and closes the power supply path. The switch is a system of the converter and the inverter. System operation is stopped and wherein the voltage of the DC link section is configured to close on the condition that has dropped to a predetermined threshold voltage.

  That is, in the power conditioner according to the first aspect, the converter and the inverter are used as a condition for closing the switch provided in the power supply path that enables power supply from the system power supply to the DC link unit without going through the inverter. For example, the output voltage of the power generation unit drops below the predetermined voltage because it is based on two conditions: the stop of the grid interconnection operation with the stop of the power supply and the voltage of the DC link unit lowering to a predetermined threshold voltage. Even if the grid interconnection operation is stopped (operation of the converter and the inverter is stopped), if the voltage of the DC link unit is maintained higher than the threshold voltage, power is supplied from the system power source to the DC link unit. The switch of the power supply path for supplying the power is not closed and is kept open. Therefore, in this state, when the output voltage of the power generation unit returns to a voltage exceeding the predetermined voltage, the switch operation is resumed without closing the switch.

  Therefore, when a solar panel is used as the power generation unit, the number of times that the voltage of the DC link unit falls below the threshold voltage during this period can be reduced even if the grid connection operation is intermittently repeated due to fluctuations in sunlight. For this reason, the number of opening / closing operations of the switch can be reduced by a corresponding amount compared to the number of grid interconnection operations, and as a result, the number of switching operations of the switch can be reduced as a whole. Can be prevented.

  A power conditioner according to a second aspect of the present invention is the power conditioner according to the first aspect, wherein the threshold voltage depends on a voltage value of power supplied to the DC link unit via the power feeding path. It is characterized by being set.

  That is, in the power conditioner according to the second aspect, the threshold voltage that is one of the conditions for closing the switch is set according to the voltage value of the electric power supplied to the DC link unit through the power feeding path. Therefore, for example, the switch is closed by setting the threshold voltage to a value (same value or a value close to it) equal to the voltage value of the power supplied to the DC link unit via the power feeding path. When the power from the system power source is supplied to the DC link unit, the voltage of the DC link unit is equivalent to the voltage of the power supplied from the system power source side. Inrush current can be prevented from flowing through. Therefore, according to the power conditioner according to the second aspect, since it is not necessary to use an expensive component having a large current capacity for the electronic component provided in the power feeding path, it is possible to suppress the manufacturing cost of the power conditioner and to reduce the cost. A power conditioner can be provided.

  The power conditioner according to claim 3 of the present invention is the power conditioner according to claim 1 or 2, wherein the power feeding path is neutral with respect to the single-phase three-wire wiring from the system power supply. It is connected to a line and one voltage line.

  That is, in the power conditioner according to the third aspect, the power feeding path is connected to the neutral line and the voltage line of 1 for the single-phase three-wire wiring from the system power supply. When the system power supply is a single-phase three-wire AC200V, the power feeding path is connected to a grounded neutral line (N phase) and one voltage line (U phase or V phase) to which voltage is applied, AC100V is supplied to the power supply path. In other words, in the power conditioner according to the third aspect, when the switch is closed, the voltage supplied to the DC link unit is half the voltage (AC100V) of the system power supply voltage (AC200V). Thus, the risk of inrush current flowing when the switch is closed by the amount of this voltage drop is reduced, and less measures against inrush current are required for the electronic components in the power supply path. Further, in the power conditioner according to the third aspect, since AC 100 V is supplied to the DC link unit, the threshold voltage, which is one of the conditions for closing the switch, can be set lower accordingly, and the switching can be further performed. The number of operations of the device can be reduced, and the effect of suppressing deterioration can be enhanced.

  According to the present invention, in a power conditioner in which a converter and an inverter are connected via a DC link unit and the grid connection operation is performed on condition that the output voltage of the power generation unit exceeds a predetermined voltage, the system is connected without an inverter. As a condition for closing the switch provided in the power supply path that enables power supply from the power source to the DC link unit, the system interconnection operation is stopped and the voltage of the DC link unit is reduced to a predetermined threshold voltage. Therefore, even if the grid interconnection operation is stopped due to a decrease in the output voltage of the power generation unit, the switch is closed if the voltage of the DC link unit is maintained higher than the threshold voltage. In this state, when the output voltage of the power generation unit returns to a voltage exceeding the predetermined voltage, the grid interconnection operation is resumed without closing the switch. Therefore, even if the grid connection operation is intermittently repeated due to fluctuations in sunshine, if the number of times the voltage of the DC link section falls below the threshold voltage during this period, the number of times of opening / closing operation of the switch is increased accordingly. And the deterioration of the switch is prevented.

  According to the second aspect of the present invention, the threshold voltage, which is a condition for closing the switch, is set according to the voltage value of the power supplied to the DC link unit via the feeding path. By setting this threshold voltage to a value equivalent to the voltage value of the electric power supplied from the system power supply to the DC link unit, an inrush current from the system power supply side that may occur when the switch is closed is prevented. In addition, the cost of electronic components provided in the power supply path can be kept low, and an inexpensive power conditioner can be provided.

  Further, according to the invention of claim 3, since the power feeding path is connected to the neutral line and the voltage line of 1 for the single-phase three-wire wiring from the system power supply, it is supplied to the DC link unit. Therefore, the inrush current can be suppressed by that amount, and inexpensive parts can be used for the electronic parts in the power feeding path. In addition, since the threshold voltage can be set low, the number of operations of the switch can be further reduced, and the effect of suppressing the deterioration of the switch can be enhanced.

It is a circuit block diagram which shows schematic structure of the electric power generation system using the power conditioner which concerns on this invention. It is explanatory drawing which showed typically the operation | movement of the system | strain power supply relay in the same power conditioner. It is a flowchart which shows an example of the procedure of the electric power supply to the DC link part of the same inverter. It is a circuit block diagram which shows schematic structure of the electric power generation system using the conventional power conditioner.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
An example of a power generation system using the power conditioner according to the present invention is shown in FIG. The power generation system shown in FIG. 1 is a power generation system including a solar panel 1 as a power generation unit, and is a power conditioner as an inverter device for connecting DC power generated by the solar panel 1 to a system power supply 2. Na 3 is provided.

  The solar panel 1 is a well-known power generation device formed by unitizing a plurality of power generation elements (solar cells) that generate power by a photoelectric phenomenon into a panel shape. Two electrical cables 20a and 20b for positive electrode and negative electrode are provided as output means, and these two electrical cables 20a and 20b are input terminals (not shown) for inputting generated power in the power conditioner 3. )It is connected to the.

  In addition, although the case where the solar panel 1 was comprised by one sheet was shown in the example of illustration, the solar panel 1 used as a power generation part is not restricted to one sheet, You may use the several solar panel 1. FIG. However, in that case, a connection box is provided between the solar panel 1 and the power conditioner 3 to collect the DC power output from the plurality of solar panels 1 into two electrical cables. Two electric cables for the positive electrode and the negative electrode arranged in the box are connected to the input terminal (not shown) of the power conditioner 3.

  The system power supply 2 is composed of an AC power supply such as a commercial power supply. In this embodiment, a single-phase three-wire AC 200 V AC power source is used as the system power source 2. The system power supply 2 is connected to a power conditioner 3 and a household power load (not shown) through a distribution board (not shown).

  As described above, the power conditioner 3 is an inverter device for connecting the DC power generated by the solar panel 1 to the system power supply 2, and the power conditioner 3 includes the solar panel 1. A converter 4 for boosting the generated DC power, an inverter 5 for converting the DC power boosted by the converter 4 into AC power that can be connected to the system power supply 2, and the converter 4 and the inverter 5 A DC link unit 6 to be connected, a system interconnection relay 7 for linking the AC power converted by the inverter 5 to the system power supply 2, a control microcomputer 8 for controlling each part of the power conditioner 3, The power supply unit 9 of the microcomputer 8 is provided as a main part, and the power conditioner 3 of the present embodiment does not include the inverter 5 in addition to these. Feeding path 10 is provided to the system power source 2 side to allow the power supply to the DC link portion 6.

  The converter 4 is constituted by a DC-DC converter. In this embodiment, a non-insulated step-up chopper type DC-DC converter is used as the converter 4. The input side of the converter 4 is connected to an input terminal (not shown) of the generated power of the solar panel 1 so that DC power generated by the solar panel 1 is input. The output side of the converter 4 is connected to the inverter 5 via the DC link unit 6. The DC link unit 6 is configured by connecting an electrolytic capacitor 21 serving as a DC link capacitor between electrical lines connecting the converter 4 and the inverter 5.

  The inverter 5 is composed of a DC-AC inverter, and the grid connection relay 7 is connected to the output side of the inverter 5, and the output side of the inverter 5 is connected to the power conditioner 3 via the grid connection relay 7. The terminal block 11 is connected. The grid connection relay 7 can be controlled to open and close by a microcomputer 8 described later.

  The terminal block 11 is a terminal block connected to the system power source 2 via a distribution board (not shown). In the present embodiment, a single-phase three-wire power source is used for the system power source 2, The terminal block 11 is provided with three terminals (not shown) for connecting the U-phase and V-phase voltage lines of the system power supply 2 and the grounded N-phase neutral line, and the inverter 5 (that is, the output of the grid interconnection relay 7) is connected to the U-phase and V-phase terminals of the terminal block 11. That is, the AC 200 V output from the inverter 5 is linked to the system power supply 2 via the terminal block 11.

  The microcomputer 8 constitutes a control means for controlling each part of the power conditioner 3. The microcomputer 8 stores a control program for performing various controls described later, control data, and the like. Yes. The microcomputer 8 is connected to various sensors (not shown). Based on information from these sensors, the microcomputer 8 determines the power generation status (output voltage) of the photovoltaic power generation panel 1 and the system power supply. 2 is configured to acquire various types of information related to the power generation system, such as power supplied from 2 (purchased power) and power consumed by an indoor power load (power consumption).

  The power supply unit 9 is a power supply device for generating power to be supplied to the microcomputer 8. The power supply unit 9 is connected to both ends of the electrolytic capacitor 21 constituting the DC link unit 6, and is configured to generate power to be supplied to the microcomputer 8 by receiving power supply from the DC link unit 6. That is, the power supply unit 9 is configured by a DC-DC converter that converts the voltage of the DC link unit 6 into a voltage that can be supplied to the microcomputer 8. In addition, the power supply part 9 is comprised with the insulation-type power supply device which connects the DC link part 6 and the microcomputer 8 in an insulated state.

  The power supply path 10 is an electric circuit for supplying power from the system power supply 2 to the DC link unit 6 without going through the inverter 5. Specifically, the terminal block 11 and the DC link unit 6 are connected to each other. It is comprised with the electrical component etc. which have the electrical equipment wire 12 and the system | strain feeding relay (switch) 13 provided in this electrical equipment wire 12, and the rectifier 14 as the principal part.

  More specifically, the electrical wiring 12 is composed of two electrical wirings 12a and 12b, and the two electrical wirings 12a and 12b are used to extract 100 VAC power from the terminal block 11. ing. That is, with respect to the system power source 2 wired to the terminal block 11 by the single-phase three-wire system from the system power source 2, one of the electrical wires 12a and 12b is a neutral line (N phase) of the system power source 2. The other is connected to one voltage line (U phase or V phase) of the system power supply 2. In this embodiment, one end of the electrical wire 12a of the electrical wire 12 is connected to the V phase of the terminal block 11, and one end of the electrical wire 12b is connected to the N phase of the terminal block 11, The AC 100 V is taken out from the AC 200 V supplied to the terminal block 11 from 2, and can be used as the power supplied to the DC link unit 6.

  The other end of the electrical wire 12 a is connected to the positive electrode of the electrolytic capacitor 21 constituting the DC link portion 6, and the other end of the electrical wire 12 b is connected to the negative electrode of the electrolytic capacitor 21.

  The system power supply relay 13 is a switch for supplying the power of the system power supply 2 to the DC link unit 6 at night when the solar panel 1 does not generate power. These contacts are arranged so that they can be opened and closed, and their contacts can be controlled by the microcomputer 8 in the same manner as the contacts of the grid interconnection relay 7.

  The rectifier 14 is a rectifier for converting AC 100V AC power supplied from the system power supply 2 via the system power supply relay 13 into DC power and supplying the DC power to the DC link unit 6. A diode bridge circuit (full-wave rectifier circuit) is used as the rectifier 14. In addition, electronic parts such as a fuse 15 and a PTC thermistor (or resistor) 16 for preventing an overcurrent are disposed on the electrical line 12.

Next, the operation of the power conditioner 3 configured as described above will be described.
The power conditioner 3 shown in the present embodiment boosts the DC power generated by the solar panel 1 by the converter 4 and supplies it to the inverter 5, which converts the DC power into AC power that can be connected to the system power supply 2. Are connected to the system power supply 2 via the system connection relay 7, but the system connection operation by the power conditioner 3 (the system connection relay is operated by operating the converter 4 and the inverter 5). 7 is a condition under which the voltage input from the solar panel 1 to the power conditioner 3 (that is, the output voltage of the solar panel 1) Vin starts the grid interconnection operation in the power conditioner 3. As described above, a predetermined interconnection allowable voltage (predetermined voltage) Von that is set in advance is exceeded (provided that Von <Vin). There.

  Here, the interconnection operation allowable voltage Von generates AC power that can be linked to the system power supply 2 by operating the converter 4 and the inverter 5 in the power conditioner 3 (AC power of AC 200 V in this embodiment). The lower limit voltage (or voltage near the lower limit voltage) of the input voltage to the power conditioner 3 that can be set is set.

  The reason why the above-mentioned lower limit voltage is adopted as the interconnection operation allowable voltage Von is that the interconnection operation allowable voltage Von functions as determining the operation start timing of the power conditioner 3 with respect to the power generation amount of the solar panel 1. It is. That is, if the interconnection operation allowable voltage Von is set higher than the lower limit voltage, the start of the grid interconnection operation is delayed by that amount, and the power generated by the solar panel 1 is wasted. Therefore, this interconnection operation allowable voltage Von is set to a value as low as possible in relation to the ability to boost the input voltage in converter 4 (boosting ability). In other words, the interconnection operation allowable voltage Von is supplied by the converter 4 with a DC voltage required for the inverter 5 to generate AC power that can be connected to the system power supply 2 based on the boosting capability of the converter 4. Set as low as possible. In the present embodiment, the interconnection operation allowable voltage Von is set to 70V.

  On the other hand, when the output voltage Vin of the solar panel 1 is equal to or lower than the interconnection operation allowable voltage Von (when Vin ≦ Von), the power conditioner 3 does not perform the above-described grid interconnection operation. In the case of the power conditioner 3, even when the grid interconnection operation is not performed as described above (that is, when the converter 4 and the inverter 5 are stopped and the grid interconnection relay 7 is opened), Assuming that the predetermined condition is satisfied, the system power supply relay 13 is closed and power is supplied from the system power supply 2 to the DC link unit 6.

  Here, even if the power conditioner 3 is not performing the grid connection operation, the power is supplied to the DC link unit 6 from the system power supply 2 side. 3 is because the power supply unit 9 of the microcomputer 8 is supplied with power from the DC link unit 6. In other words, even when the grid connection operation is not performed, power is supplied to the DC link unit 6 so that the microcomputer 8 is always supplied with power from the power supply unit 9 (even when the grid connection operation is not performed). In this way, the microcomputer 8 can constantly monitor the power generation system.

  One of the predetermined conditions in the power conditioner 3 of the present embodiment is that the voltage Vdc of the DC link unit 6 when the converter 4 is in the operation stop state is equal to or higher than a preset switching threshold voltage Vth of the power supply path. (Vth ≦ Vdc).

  That is, in this power conditioner 3, even when the output voltage Vin of the solar panel 1 is not more than the interconnection operation allowable voltage Von and the grid interconnection operation is not performed, the voltage Vdc of the DC link unit 6 is If it is above the switching threshold voltage Vth, the microcomputer 8 closes the system power supply relay 13 so that power can be supplied from the system power supply 2 to the DC link unit 6.

  By the way, as a condition for closing the power feeding relay 13 in this way, if the condition is that the voltage Vdc of the DC link unit 6 is equal to or higher than the switching threshold voltage Vth, the solar panel 1 is caused by a change in weather (amount of solar radiation). When the output voltage Vin of the power supply fluctuates, there is a possibility that the system power supply relay 13 frequently repeats closing and opening.

  Therefore, in the power conditioner 3 of the present embodiment, as a second condition for closing the grid power supply relay 13, in addition to the stop of the grid interconnection operation, the voltage Vdc of the DC link unit 6 is a predetermined threshold voltage. The power feeding relay 13 is closed when these two conditions are satisfied under the condition that the voltage drops to Vx.

  Here, the threshold voltage Vx, which is a condition for closing the system power supply relay 13, depends on the voltage value of the power supplied to the DC link unit 6 through the power supply path 10 (AC100V in this embodiment). Is set. Specifically, the threshold voltage Vx is a value equivalent to the voltage value of power supplied to the DC link unit 6 via the power supply path 10 (for example, the same value as the voltage value of supplied power or Neighbor values) are preferably employed. That is, in the present embodiment, AC 100 V is supplied from the system power supply 2 via the power supply path 10, and thus the threshold voltage Vx is set to a voltage of about 141 V that is its peak value.

  Therefore, in the power conditioner 3 of the present embodiment, even when the output voltage Vin of the solar panel 1 is equal to or lower than the above-described interconnection operation allowable voltage Von and the grid interconnection operation is stopped, the voltage Vdc of the DC link unit 6 is If the state higher than the threshold voltage Vx is maintained, the system power supply relay 13 is not closed but is kept open. Therefore, in this state, if the output voltage Vin of the solar panel 1 returns to a voltage exceeding the interconnection operation allowable voltage Von due to, for example, resumption of sunshine, the power feeding relay 13 is not closed. Grid connection operation is resumed. That is, even if the grid interconnection operation is intermittently repeated due to fluctuations in sunlight, if the number of times that the voltage Vdc of the DC link unit 6 falls below the threshold voltage Vx is small during this period, the grid feed relay 13 is correspondingly increased. The number of opening / closing operations of the power supply is reduced, and the system power supply relay 13 is prevented from deteriorating.

  FIG. 2 is an explanatory diagram schematically showing the operation of the system power supply relay 13. Therefore, when the operation of the system power supply relay 13 is organized with reference to FIG. 2, the system power supply relay 13 is in the state shown in FIG. 2 when the solar panel 1 is generating power, that is, when Von <Vin. As shown in S1, the system power supply relay 13 is in an open (OFF) state. When the output voltage Vin of the solar panel 1 decreases and Vin ≦ Von, as shown in step S2 of FIG. 2, the grid interconnection operation is stopped, but the grid feed relay 13 is maintained OFF. In this state, when the voltage Vdc of the DC link unit 6 is reduced to be equal to the threshold voltage Vx, the grid feed relay 13 is closed while the grid interconnection operation is stopped as shown in step S3 of FIG. In the (ON) state, power (AC 100 V) from the system power source 2 side is supplied to the DC link unit 6.

  FIG. 3 is a flowchart showing a series of operations (processing of the microcomputer 8) in the power conditioner 3. Hereinafter, the operation procedure of the power conditioner 3 will be described with reference to FIG.

  When the microcomputer 8 of the power conditioner 3 receives the supply of power from the power supply unit 9 and starts its operation, the microcomputer 8 first supplies power to the DC link unit 6 from the solar panel 1 side or the system power supply 2. It is determined from the side (see step S1 in FIG. 3).

  Specifically, first, the microcomputer 8 compares the voltage Vdc of the DC link unit 6 with the switching threshold voltage Vth, and the voltage Vdc of the DC link unit 6 is less than the switching threshold voltage Vth (Vdc <Vth). (See step S2 in FIG. 3).

  If this determination is affirmative, the microcomputer 8 supplies the output voltage Vin of the solar panel 1 to the DC link unit 6 as it is without operating the converter 4 (see step S3 in FIG. 3). That is, in the present embodiment, a non-insulated step-up chopper type DC-DC converter is used as the converter 4, so that the output voltage Vin of the solar panel 1 can be supplied to the DC link section without operating the converter 4. 6 is supplied. However, in the present embodiment, the switching threshold voltage Vth is set to 40 V, and when the determination in step S2 of FIG. 3 is affirmative, the solar panel 1 is in a state of hardly generating power.

  Here, when the determination in step S2 of FIG. 3 is affirmative, the output voltage Vin of the solar panel 1 is equal to or lower than the above-described interconnection operation allowable voltage Von, and thus the grid interconnection operation of the power conditioner 3 is not performed. . In this state, the microcomputer 8 maintains the system power supply relay 13 in the open state. That is, the microcomputer 8 is configured not to close the system power supply relay 13 when the voltage Vdc of the DC link unit 6 is less than the switching threshold voltage Vth.

  In the power conditioner 3 of the present embodiment, as will be described later, when the power generation output of the solar panel 1 is reduced, power is supplied from the system power supply 2 to the DC link unit 6. The case where the determination of step S2 in FIG. 3 becomes affirmative is limited, for example, when the power supply to the power conditioner 3 is started (at the time of construction) or when the solar panel 1 is not generating power such as at night The process of step S3 in FIG. 3 is performed when the power source 2 has a power failure.

  On the other hand, if the determination in step S2 of FIG. 3 is negative, the microcomputer 8 next determines whether the output voltage Vin of the solar panel 1 is equal to or lower than the interconnection operation allowable voltage Von (Vin ≦ Von). Is determined (see step S4 in FIG. 3). In other words, in step S4 in FIG. 3, the microcomputer 8 determines that the voltage Vdc of the DC link unit 6 is equal to or higher than the switching threshold voltage Vth (Vth ≦ Vdc), and the output voltage Vin of the solar panel 1 is the above-described link. It is determined whether or not the system operation allowable voltage Von or less (Vin ≦ Von).

  And if this judgment is affirmative, the microcomputer 8 will close the system | strain feeding relay 13 according to the procedure shown in FIG. 2 mentioned above. That is, on the condition that the voltage Vdc of the DC link unit 6 decreases to the threshold voltage Vx, the system power supply relay 13 is closed and power is supplied from the system power supply 2 side to the DC link unit 6 (step S5 in FIG. 3). If the voltage Vdc of the DC link unit 6 does not decrease to the threshold voltage Vx, the system power supply relay 13 is kept open as shown in step S2 of FIG. 2 described above. In this case, as the process, after the process proceeds to step S3 in FIG. 3, the process is restarted from step S1 in FIG.

  At this time as well, the output voltage Vin of the solar panel 1 is equal to or lower than the interconnection operation allowable voltage Von, and thus the grid interconnection operation of the power conditioner 3 is not performed. Therefore, converter 4 and inverter 5 of power conditioner 3 are stopped, and grid interconnection relay 7 is maintained in the open state.

  If the determination in step S4 in FIG. 3 is negative, as shown in step S6 in FIG. 3, the voltage Vdc of the DC link unit 6 is not less than the switching threshold voltage Vth (Vth ≦ Vdc) and the solar panel. The output voltage Vin of 1 is higher than the interconnection operation allowable voltage Von (Von <Vin).

  Here, as shown in step S6 of FIG. 3, the output voltage Vin of the solar panel 1 becomes higher than the interconnection operation allowable voltage Von, as described above, the power conditioner 3 performs the grid interconnection operation. In this case, the microcomputer 8 causes the power conditioner 3 to perform a grid interconnection operation. That is, the microcomputer 8 opens the system power supply relay 13 (without supplying power from the system power supply 2 side to the DC link unit 6), and puts the converter 4 and the inverter 5 into an operating state, thereby connecting the system connection relay. 7 is closed. Therefore, in this case, the DC link unit 6 is supplied with power generated by the solar panel 1 and boosted by the converter 4 (see step S7 in FIG. 3).

  When the power conditioner 3 is in the grid connection operation (see step S8 in FIG. 3), the microcomputer 8 monitors the output voltage Vin of the solar panel 1 (see step S9 in FIG. 3), and the solar panel. 1 whether the output voltage Vin of the solar panel 1 is not less than or equal to the interconnection operation allowable voltage Von (Vin ≦ Von), in other words, whether the power generation amount of the solar panel 1 is decreased due to a decrease in sunlight or the like. If the determination is made periodically (see step S9 in FIG. 3) and this determination is affirmative, the grid interconnection operation is stopped (that is, the operations of the converter 4 and the inverter 5 are stopped and the grid interconnection relay 7 is stopped). The system power supply relay 13 is closed again, and the power supply from the system power source 2 side to the DC link unit 6 is started.

  At this time, as in the case of step S5 in FIG. 3, the power feeding relay 13 is closed according to the procedure shown in FIG. That is, on the condition that the voltage Vdc of the DC link unit 6 decreases to the threshold voltage Vx, the system power supply relay 13 is closed and power is supplied from the system power supply 2 side to the DC link unit 6 (see step S5 in FIG. 3). ).

  Thus, in the power conditioner 3 according to the present invention, as a condition for starting the power supply from the system power supply 2 to the DC link unit 6 by closing the system power supply relay 13, the system interconnection operation is stopped, and the DC link Since the voltage of the unit 6 decreases to the threshold voltage Vx, even if the grid connection operation is stopped due to the decrease of the output voltage Vin of the solar panel 1, the voltage of the DC link unit 6 remains the threshold voltage Vx. If the higher state is maintained, the grid feed relay 13 is not closed, and when the output voltage Vin of the solar panel 1 returns before the interconnection operation allowable voltage Von is exceeded in this state, the grid feed relay 13 is The grid connection operation is resumed without being closed. Therefore, even if the grid interconnection operation is repeatedly performed due to fluctuations in sunshine, if the number of times that the voltage Vdc of the DC link unit 6 falls below the threshold voltage Vx is small during this period, the grid feeding relay 13 is correspondingly increased. The number of open / close operations is reduced, and deterioration of the power feeding relay 13 is prevented.

  And since the electric power supplied to the electric power feeding path | route 10 from the system power supply 2 is set to AC100V, compared with the case where AC200V is supplied, the voltage supplied to the DC link part 6 is suppressed low. Therefore, the inrush current to the DC link portion 6 is suppressed correspondingly, and an inexpensive component can be used for the electronic component of the power feeding path. That is, according to the power conditioner 3 according to the present invention, it is not necessary to use an expensive electronic component that can withstand a large inrush current as a component of the power conditioner 3. A power conditioner can be provided. Specifically, inexpensive parts having a small current capacity can be adopted as the fuse 15, the PTC thermistor 16, and the system power supply relay 13 in the power supply path 10, and these costs can be suppressed.

  The above-described embodiments show preferred embodiments of the present invention, and the present invention is not limited to these, and various design changes can be made within the scope of the invention.

  For example, in the above-described embodiment, the case where the electrical wires 12a and 12b of the system power supply means 10 are wired so as to extract AC 100V power from the terminal block 11 is shown, but this closes the system power supply relay 13. In order to reduce the inrush current to the DC link unit 6 at this time, the voltage taken out from the terminal block 11 is lowered, so that the inrush current to the DC link unit power is sufficiently set by setting the switching threshold voltage Vth and the like. If it is possible to suppress the electric power, the electric wires 12a and 12b can be connected to the U-phase and the V-phase of the terminal block 11 so as to extract AC200V power from the system power supply 2.

  In the above-described embodiment, the switching threshold voltage Vth is 40 V and the interconnection operation allowable voltage Von is 70 V. These values depend on the voltage of the system power supply 2 and the boosting capability of the converter 4. Of course, since specific values are determined, specific numerical values can be appropriately changed.

  In the above-described embodiment, the case where the microcomputer 8 receives power supply from the power supply unit 9 has been described. For example, a remote controller (not shown) of the power conditioner 3 configured separately from the power conditioner 3 is used. ) And a display device (not shown) installed in the power conditioner 3, the power supply unit 9 can be configured to supply power to parts other than the microcomputer 8. As a result, these remote controllers and display devices can be operated and displayed while the grid connection operation is stopped.

  In the above-described embodiment, the case where the voltage Vdc of the DC link unit 6 is compared with the switching threshold voltage Vth in the control of the power conditioner 3 has been described. However, in the present embodiment, the converter 4 is a non-insulated type. Since the step-up chopper method is employed, the input voltage to the power conditioner 3, that is, the output voltage Vin of the solar panel 1 can be used instead of the voltage Vdc of the DC link unit 6.

  In the above-described embodiment, a voltage comparison between a preset voltage such as the switching threshold voltage Vth, the threshold voltage Vx, and the interconnection operation allowable voltage Von and a measured voltage such as the output voltage Vin of the solar panel 1 is performed. When performing, it is desirable to take measures to prevent control hunting, such as providing a hysteresis voltage and a fixed time.

1 Solar panel (power generation unit)
2 System power supply 3 Power conditioner 4 Converter 5 Inverter 6 DC link part 7 System connection relay 8 Microcomputer 9 Power supply part 10 Power supply path 11 Terminal block 12 Electric wire 13 System power supply relay (switch)
14 Rectifier

Claims (3)

A converter that boosts the DC power generated by the power generation unit and an inverter that converts the DC power boosted by the converter into AC power that can be connected to a system power supply, which are connected via a DC link unit In the power conditioner configured to operate the converter and the inverter on the condition that the output voltage of the power generation unit exceeds a predetermined voltage, and perform the grid connection operation,
A power supply unit that receives power supply from the DC link unit, a power supply path that enables power supply from the system power supply to the DC link unit without going through the inverter, and a switch that opens and closes the electric path of the power supply path And
The switch is configured to be closed on condition that the system interconnection operation of the converter and the inverter is stopped and the voltage of the DC link unit is reduced to a predetermined threshold voltage. A power conditioner.   The power conditioner according to claim 1, wherein the threshold voltage is set according to a voltage value of electric power supplied to the DC link unit via the power supply path.   3. The power condition according to claim 1, wherein the power supply path is connected to a neutral line and a voltage line of 1 with respect to a single-phase three-wire wiring from the system power supply. 4. Na.

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