WO2018179714A1 - Power conversion device and power conversion system - Google Patents

Power conversion device and power conversion system Download PDF

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Publication number
WO2018179714A1
WO2018179714A1 PCT/JP2018/001804 JP2018001804W WO2018179714A1 WO 2018179714 A1 WO2018179714 A1 WO 2018179714A1 JP 2018001804 W JP2018001804 W JP 2018001804W WO 2018179714 A1 WO2018179714 A1 WO 2018179714A1
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WIPO (PCT)
Prior art keywords
power
inverter
converter
bus
control circuit
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PCT/JP2018/001804
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French (fr)
Japanese (ja)
Inventor
賢治 花村
藤井　裕之
渉 堀尾
菊池　彰洋
智規 伊藤
康太 前場
Original Assignee
パナソニックＩｐマネジメント株式会社
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Publication of WO2018179714A1 publication Critical patent/WO2018179714A1/en

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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode

Definitions

  • the present invention relates to a power conversion device and a power conversion system that convert DC power into AC power.
  • a typical configuration of a distributed power supply system connected to a system is a configuration in which a single distributed power supply is used to connect the system via a DC-DC converter, a DC bus and an inverter, and a plurality of distributed power supplies. Are connected to each other via each DC-DC converter, a common DC bus and one inverter.
  • the DC-DC converter and the inverter are physically installed in a single housing, the DC-DC converter and the inverter are controlled independently by separate control devices (for example, a microcomputer). Sometimes it is done. In such a distributed power supply system in which the DC-DC converter and the inverter are physically or controlly separated, it is necessary to make adjustments between the respective power conversion units.
  • the inverter discharge power in response to events such as system voltage rise, inverter component temperature rise, remote output command reception, and reverse power flow detection
  • a control method for suppressing the above is used.
  • the voltage of the DC bus rises immediately after starting the inverter output suppression.
  • the DC-DC converter determines from the rise in the voltage of the DC bus that the inverter is suppressing the output, and suppresses the discharge power to the DC bus so that the voltage of the DC bus does not rise above a predetermined voltage.
  • the voltage of the DC bus is controlled to be maintained at the set voltage by the DC-DC converter while the output suppression function of the inverter is working.
  • the voltage of the DC bus set in this DC-DC converter is higher than the voltage of the DC bus in the steady state, which causes a reduction in the power conversion efficiency of the inverter.
  • the present invention has been made in view of such a situation, and an object thereof is to provide a power conversion device and a power conversion system that realize high-efficiency power conversion even while the output suppression function of the inverter is working.
  • a power converter includes a DC-DC converter that converts a voltage of DC power output from a DC power source and outputs the converted DC power to a DC bus, and the DC bus. And an inverter that converts the DC power of the DC bus into AC power, supplies the converted AC power to a load or a power system, and a control circuit that controls the inverter.
  • the control circuit controls the inverter to lower the output of the inverter to a first target value when the output from the inverter to the power system should be suppressed, and a second lower than the first target value.
  • the target value is notified to another control circuit that controls the DC-DC converter.
  • FIGS. 2A and 2B are diagrams schematically showing the voltage state of the DC bus (part 1).
  • FIGS. 3A and 3B are diagrams schematically showing the voltage state of the DC bus (part 2).
  • FIG. 1 is a diagram for explaining a power conversion system 1 according to an embodiment of the present invention.
  • the power conversion system 1 includes a first power conversion device 10 and a second power conversion device 20.
  • the first power conversion device 10 is a power conditioner system for the solar cell 2
  • the second power conversion device 20 is a power conditioner system for the power storage unit 3.
  • FIG. 1 the example which retrofitted the power conditioner system for the electrical storage part 3 to the power conditioner system for the solar cells 2 is shown.
  • the solar cell 2 is a power generation device that directly converts light energy into electric power using the photovoltaic effect.
  • a silicon solar cell, a solar cell made of a compound semiconductor or the like, a dye-sensitized type (organic solar cell), or the like is used as the solar cell 2.
  • the solar cell 2 is connected to the first power conversion device 10 and outputs the generated power to the first power conversion device 10.
  • the first power converter 10 includes a DC-DC converter 11, a converter control circuit 12, an inverter 13, an inverter control circuit 14, and a system control circuit 15.
  • the system control circuit 15 includes a reverse flow power measurement unit 15a, a command value generation unit 15b, and a communication control unit 15c.
  • the DC-DC converter 11 and the inverter 13 are connected by a DC bus 40.
  • the converter control circuit 12 and the system control circuit 15 are connected by a communication line 41, and communication conforming to a predetermined serial communication standard (for example, RS-485 standard, TCP-IP standard) is performed between the two.
  • a predetermined serial communication standard for example, RS-485 standard, TCP-IP standard
  • the DC-DC converter 11 converts the DC power output from the solar cell 2 into DC power having a desired voltage value, and outputs the converted DC power to the DC bus 40.
  • the DC-DC converter 11 can be constituted by a step-up chopper, for example.
  • the converter control circuit 12 controls the DC-DC converter 11. As a basic control, the converter control circuit 12 performs MPPT (Maximum Power Point Tracking) control of the DC-DC converter 11 so that the output power of the solar cell 2 is maximized. Specifically, converter control circuit 12 measures the input voltage and input current of DC-DC converter 11, which are the output voltage and output current of solar cell 2, and estimates the generated power of solar cell 2. The converter control circuit 12 generates a command value for setting the generated power of the solar battery 2 to the maximum power point (optimum operating point) based on the measured output voltage of the solar battery 2 and the estimated generated power.
  • MPPT Maximum Power Point Tracking
  • the maximum power point is searched by changing the operating point voltage with a predetermined step width according to the hill-climbing method, and the command value is generated so as to maintain the maximum power point.
  • the DC-DC converter 11 performs a switching operation according to a drive signal based on the generated command value.
  • the inverter 13 is a bidirectional inverter that converts DC power input from the DC bus 40 into AC power and outputs the converted AC power to a distribution line 50 connected to a commercial power system (hereinafter simply referred to as system 4). To do. A load 5 is connected to the distribution line 50. Further, the inverter 13 converts AC power supplied from the system 4 into DC power, and outputs the converted DC power to the DC bus 40. A smoothing electrolytic capacitor (not shown) is connected to the DC bus 40.
  • the inverter control circuit 14 controls the inverter 13. As a basic control, the inverter control circuit 14 controls the inverter 13 so that the voltage of the DC bus 40 maintains the first threshold voltage. Specifically, the inverter control circuit 14 detects the voltage of the DC bus 40 and generates a command value for making the detected bus voltage coincide with the first threshold voltage. The inverter control circuit 14 generates a command value for increasing the duty ratio of the inverter 13 when the voltage of the DC bus 40 is higher than the first threshold voltage, and the inverter control circuit 14 when the voltage of the DC bus 40 is lower than the first threshold voltage. A command value for lowering the duty ratio of 13 is generated. The inverter 13 performs a switching operation according to a drive signal based on the generated command value.
  • the power storage unit 3 can charge and discharge electric power, and includes a lithium ion storage battery, a nickel hydride storage battery, a lead storage battery, an electric double layer capacitor, a lithium ion capacitor, and the like.
  • the power storage unit 3 is connected to the second power conversion device 20.
  • the second power conversion device 20 includes a DC-DC converter 21 and a converter control circuit 22.
  • the converter control circuit 22 and the system control circuit 15 of the first power conversion device 10 are connected by a communication line 42, and communication based on a predetermined serial communication standard is performed between them.
  • the DC-DC converter 21 is a bidirectional converter that is connected between the power storage unit 3 and the DC bus 40 and charges and discharges the power storage unit 3.
  • the converter control circuit 22 controls the DC-DC converter 21.
  • the converter control circuit 22 controls the DC-DC converter 21 based on the command value transmitted from the system control circuit 15 to control the power storage unit 3 at a constant current (CC) / constant voltage (CV).
  • CC constant current
  • CV constant voltage
  • Charge / discharge For example, the converter control circuit 22 receives a power command value from the system control circuit 15 at the time of discharging, and uses a value obtained by dividing the power command value by the voltage of the power storage unit 3 as a current command value. Discharge.
  • the operation display device 30 is a user interface of the first power conversion device 10 and is installed at a predetermined position in the room.
  • the operation display device 30 can be constituted by a touch panel display, for example, and provides predetermined information to the user and accepts an operation from the user.
  • the operation display device 30 and the system control circuit 15 are connected by a communication line 43, and communication based on a predetermined serial communication standard is performed between them.
  • the operation display device 30 and the system control circuit 15 may be connected wirelessly.
  • the output power of the inverter 13 needs to be suppressed.
  • the main output suppression reasons include the occurrence of reverse power flow from the inverter 13 to the grid 4, the rise of the grid voltage exceeding the set voltage, the reception of the remote output command, the temperature rise exceeding the set temperature of the components in the inverter 13, the inverter 13 An increase in power exceeding the rated power and an increase in current exceeding the rated current of the inverter 13 can be mentioned.
  • the system control circuit 15 receives an instruction related to the output power amount and output timing to the grid 4 from a grid operating organization such as a power company via an external network (for example, the Internet or a dedicated line).
  • a grid operating organization such as a power company
  • an external network for example, the Internet or a dedicated line
  • the reverse power flow measurement unit 15 a of the first power conversion device 10 detects the occurrence of reverse power flow based on the measurement value of a CT sensor (not shown) installed on the distribution line 50. .
  • the converter control circuit 22 of the second power conversion device 20 receives reverse flow detection information from the system control circuit 15 via the communication line 42.
  • the communication line 42 is often installed over the DC bus 40 that connects the first power conversion device 10 and the second power conversion device 20, and in this configuration, the communication line 42 is affected by noise from the DC bus 40. .
  • the shorter the unit period representing one bit the weaker it becomes to noise. Basically, the bit error is more likely to occur as the communication speed is increased.
  • the first power conversion device 10 detects reverse power flow, generates communication data instructing output suppression, and transmits the communication data to the second power conversion device 20 via the communication line 42, it is defined in the grid interconnection regulations.
  • the time limit 500 ms
  • the content of communication data may change during the process due to noise.
  • the inverter control circuit 14 controls the inverter 13 so that the voltage of the DC bus 40 maintains the first threshold voltage as basic control.
  • the inverter control circuit 14 executes output suppression control as priority control. Specifically, the inverter control circuit 14 controls the inverter 13 so that the output of the inverter 13 does not exceed the command value (specifically, the upper limit current value or the upper limit power value) generated by the command value generation unit 15b.
  • the bus voltage stabilization control for controlling the voltage of the DC bus 40 to be maintained at the first threshold voltage is stopped.
  • the converter control circuit 22 receives, as basic control, the amount of discharge from the power storage unit 3 to the DC-DC converter 21 or the amount of charge from the DC-DC converter 21 to the power storage unit 3 transmitted from the system control circuit 15.
  • the DC-DC converter 21 is controlled so that the command value comes.
  • the converter control circuit 22 controls the DC-DC converter 21 as priority control so that the voltage of the DC bus 40 does not exceed the second threshold voltage. This control has priority over the control for adjusting the output to the command value transmitted from the system control circuit 15.
  • the second threshold voltage is set to a value higher than the first threshold voltage.
  • the converter control circuit 12 performs MPPT control on the DC-DC converter 11 so that the output power of the solar cell 2 is maximized as basic control. Further, the converter control circuit 12 controls the DC-DC converter 11 as priority control so that the voltage of the DC bus 40 does not exceed the third threshold voltage. This control has priority over MPPT control.
  • the third threshold voltage is set to a value higher than the second threshold voltage.
  • the first threshold voltage is set to a steady voltage of the DC bus 40.
  • the first threshold voltage is set in the range of DC 280 V to 360 V, for example.
  • the second threshold voltage is set to 390V
  • the third threshold voltage is set to 410V, for example.
  • FIGS. 2A and 2B are diagrams schematically showing the voltage state of the DC bus 40 (part 1).
  • FIG. 2A shows the voltage state of the DC bus 40 in a steady state. The constant voltage of the DC bus 40 is maintained at the first threshold voltage by the inverter 13.
  • FIG. 2B shows the voltage state of the DC bus 40 immediately after the output of the inverter 13 is suppressed. Normally, immediately after the output is suppressed, the voltage of the DC bus 40 increases, and the DC-DC converter 21 of the power storage unit 3 controls the voltage of the DC bus 40 so as not to exceed the second threshold voltage.
  • the power conversion efficiency of the inverter 13 increases as the voltage of the DC bus 40 is closer to the voltage of the system 4. Conversely, at the time of discharging, the conversion efficiency of the inverter 13 decreases as the voltage of the DC bus 40 becomes higher than the voltage of the system 4. As shown in FIG. 2B, in a state where the voltage of the DC bus 40 is higher than that in the steady state, the conversion efficiency of the inverter 13 is lower than that in the steady state.
  • FIGS. 3A and 3B are diagrams schematically showing the voltage state of the DC bus 40 (part 2).
  • a mechanism is introduced to reduce the voltage of the DC bus 40 from the second threshold voltage to the first threshold voltage during output suppression in order to avoid a decrease in the conversion efficiency of the inverter 13.
  • FIG. 4 is a diagram illustrating a first example of power control of the inverter 13 and power control of the DC-DC converter 21 of the power storage unit 3 when the output of the inverter 13 is suppressed.
  • the limit value (upper limit value) of the suppression power of the inverter 13 is set to the rated output power value of the inverter 13 in a steady state. That is, even if the voltage of the DC bus 40 increases due to a sudden event during normal operation, the output power of the inverter 13 is set to stop increasing at the rated output power value.
  • the limit value (upper limit value) of the DC-DC converter 21 of the power storage unit 3 is also set to the rated output power value of the DC-DC converter 21 in a steady state.
  • the inverter control circuit 14 decreases the output of the inverter 13 with a first slope.
  • the first slope is defined by a suppression amount [W / ms] per unit time.
  • the first slope is set so that the time from when the inverter 13 starts suppression during discharging at the rated output value to when suppression is completed is within 500 ms.
  • the power storage unit 3 discharges 2.0 kW, and the inverter 13 supplies 5.5 kW to the load 5.
  • the load 5 is disconnected from this state and the power consumption of the load 5 becomes 0.0 W, the 5.5 kW output power of the inverter 13 flows backward to the grid 4.
  • the reverse power flow is not stopped within 500 ms, the inverter 13 must be disconnected from the system 4, and the power generation of the solar cell 2 is stopped during the disconnection, resulting in an economic loss.
  • the command value generation unit 15b of the system control circuit 15 decreases the power command value of the inverter 13 from 5.5 kW to (0.0 ⁇ ) kW (first target value) according to the first inclination.
  • the command value generating unit 15b notifies the inverter control circuit 14 of the updated power command value for each first period.
  • Command value generation unit 15b reduces the power command value of DC-DC converter 21 of power storage unit 3 from 2.0 kW to (0.0 ⁇ ) kW (second target value) according to the first inclination. I will let you.
  • the command value generation unit 15b notifies the converter control circuit 22 of the updated power command value via the communication line 42 every second period.
  • the margin ⁇ is set to 0.05 kW, and the margin ⁇ is also set to 0.05 kW.
  • the second period is longer than the first period. That is, the power command value of the inverter 13 is updated more frequently. This is a limitation due to the use of the communication line 42.
  • the output suppression of the inverter 13 and the output suppression of the DC-DC converter 21 of the power storage unit 3 are started at the same timing, but actually, the DC-DC converter 21 of the power storage unit 3 is affected by the communication delay. Suppression of output starts later.
  • the first target value of the power command value of the inverter 13 is set to a negative value.
  • the first target value may be set to 0.0 kW. In this case, neither power purchase nor power sale occurs, and the most economical reverse power flow suppression control is achieved.
  • the first target value is set to a negative value, there is a slight power purchase state. In this case, the reverse power flow defined in the grid connection regulations can be more reliably prevented.
  • the first target value of the power command value of the inverter 13 is (reverse power flow ⁇ power consumption of the load ⁇ ) kW
  • the DC-DC converter of the power storage unit 3 The second target value of the power command value 21 is (reverse power flow-power consumption of the load 5- ⁇ - ⁇ ) kW.
  • the output of the inverter 13 may be suppressed by a current value or may be suppressed by a power value.
  • the current value it is possible to suppress overcurrent due to excessive output at the time of release of suppression.
  • the power value the output can be accurately suppressed even when the system voltage changes.
  • the output of the inverter 13 may be suppressed by both the current value and the power value. The same applies to the output suppression of the DC-DC converter 21 of the power storage unit 3.
  • the inverter control circuit 14 increases the output of the inverter 13 with the second slope.
  • the second slope is defined by the suppression release amount [W / ms] per unit time.
  • the second inclination is set more gently than the first inclination.
  • the second slope is determined based on the rated output value of the inverter 13 and the rated output value of the DC-DC converter 21, for example.
  • FIG. 5 is a diagram illustrating a second example of power control of the inverter 13 and power control of the DC-DC converter 21 of the power storage unit 3 when the output of the inverter 13 is suppressed.
  • the first example the example in which the first slope of the inverter 13 and the first slope of the DC-DC converter 21 of the power storage unit 3 are set to be the same has been described, but the first slope of the DC-DC converter 21 of the power storage unit 3 is described.
  • the inclination of 1 may be made gentler than the first inclination of the inverter 13. The same applies to the second inclination.
  • the first slope of the DC-DC converter 21 of the power storage unit 3 is set to be gentler than the first slope of the inverter 13 (see S1 and S1a).
  • the second slope of the DC-DC converter 21 of the power storage unit 3 is set to be gentler than the second slope of the inverter 13 (see S2 and S2a).
  • FIG. 6 is a diagram illustrating a third example of power control of the inverter 13 and power control of the DC-DC converter 21 of the power storage unit 3 when the output of the inverter 13 is suppressed.
  • the third example is an example in which the voltage of the DC bus 40 is reduced to the first threshold voltage during output suppression.
  • the voltage of the DC bus 40 decreases to the first threshold voltage, it is not necessary to increase the output suppression amount of the DC-DC converter 21 of the power storage unit 3 with respect to the output suppression amount of the inverter 13, so that both output suppression amounts Are controlled in the same way.
  • the DC-DC converter 21 of the power storage unit 3 suppresses the voltage rise of the DC bus 40 in preference to the suppression of the reverse flow power. To control. Thereby, power balance can be secured by suppressing the voltage of the DC bus 40 while eliminating the continuity of the reverse flow power. Therefore, the operation stop of the power conversion system 1 can be prevented.
  • the voltage of the DC bus 40 is increased by suppressing the output of the inverter 13. Can be prevented, and the voltage of the DC bus 40 can be lowered to a steady value. Therefore, a decrease in power conversion efficiency of the inverter 13 can be suppressed.
  • the temperature in the first power converter 10 rises, and output suppression due to the temperature rise is likely to be activated. In this case, an increase in the amount of electricity purchased and a reduction in the amount of power generated by the solar cell 2 lead to a decrease in economy.
  • the temperature rise in the 1st power converter device 10 leads to the temperature rise of the components (for example, electrolytic capacitor) in the 1st power converter device 10, and leads to shortening of a product life.
  • the temperature rise in the 1st power converter device 10 can be suppressed by suppressing the voltage rise of the DC bus 40.
  • the DC-DC converter 11 does not have to suppress the power generation of the solar cell 2.
  • the opportunity for selling the power generated by the solar cell 2 can be secured to the maximum, so that the economic merit is not impaired.
  • the inverter control circuit 14 and the system control circuit 15 are depicted separately, but each may be realized by a separate microcomputer or may be realized by a single microcomputer.
  • the example in which the first power conversion device 10 and the second power conversion device 20 are installed in different cases has been described.
  • a configuration example in which the system control circuit 15 and the converter control circuit 22 are connected by the communication line 42 while the first power conversion device 10 and the second power conversion device 20 are installed in one housing is also an example of the present invention. It is included in the embodiment.
  • the solar cell 2 is connected to the first power conversion device 10 .
  • another power generation device using renewable energy such as a wind power generation device or a micro hydraulic power generation device, may be connected.
  • a DC-DC converter (21) that converts the voltage of the DC power output from the DC power source (3) and outputs the converted DC power to the DC bus (40) is connected via the DC bus (40),
  • the control circuit (14, 15) is configured to reduce the output of the inverter (13) to a first target value when the output from the inverter (13) to the power system (4) is to be suppressed. (13) and a second target value lower than the first target value is notified to another control circuit (22) for controlling the DC-DC converter (21).
  • the DC power source (3) is the power storage unit (3), The power converter according to item 1, wherein the time when the output from the inverter (13) to the power system (4) should be suppressed is when a reverse power flow to the power system (4) occurs. (10). According to this, the voltage of the DC bus (40) can be reduced while the reverse power flow is suppressed.
  • the control circuit (14, 15) sets the first target value so that the reverse flow power to the power system (4) becomes a negative value.
  • the power conversion device (10) according to item 1 or 2, wherein the power conversion device (10) generates the second target value at a value lower than the first target value. According to this, it is possible to reduce the voltage of the DC bus (40) while more reliably suppressing the reverse power flow.
  • a DC-DC converter (21) for converting the voltage of the DC power output from the DC power supply (3) and outputting the converted DC power to the DC bus (40);
  • An inverter (13) connected via the DC bus (40), converting DC power of the DC bus (40) into AC power, and supplying the converted AC power to the load (5) or the power system (4)
  • a second control circuit (14, 15) for controlling the inverter (13) When the output from the inverter (13) to the power system (14) is to be suppressed, the second control circuit (14, 15) reduces the output of the inverter (13) to a first target value.
  • the power conversion system (1) characterized by controlling the inverter (13) and notifying the first control circuit (22) of a second target value lower than the first target value. According to this, the voltage of the DC bus (40) can be reduced during output suppression, and the reduction in conversion efficiency of the inverter (13) can be suppressed.
  • the first control circuit (22) and the second control circuit (14, 15) are connected by a communication line (42), The second control circuit (14, 15) maintains the voltage of the DC bus (40) at the first threshold voltage when it is not necessary to suppress the output from the inverter (13) to the power system (4).
  • the first control circuit (22) receives the DC-DC converter (21) based on a command value generated from the second target value received from the second control circuit (14, 15). And controlling the voltage of the DC bus (40) so as not to exceed a second threshold voltage higher than the first threshold voltage. According to this, it is possible to stabilize the voltage of the DC bus (40) during suppression and after cancellation of suppression while suppressing a voltage increase immediately after the start of suppression of the DC bus (40).
  • a DC-DC converter for the power generator (2) that converts the voltage of the DC power output from the power generator (2) that generates power based on renewable energy and outputs the converted DC power to the DC bus (40).
  • the power generator (2) is controlled so that the output power is maximized, and the voltage of the DC bus (40) is controlled so as not to exceed a third threshold voltage higher than the second threshold voltage.
  • the second control circuit (14, 15) receives the amount of power input to the inverter (13).
  • a DC-DC converter (21) for converting the voltage of the DC power output from the DC power supply (3) and outputting the converted DC power to the DC bus (40);
  • the DC-DC converter (21) converts the DC power of the DC bus (40) into AC power via the DC bus (40), and converts the converted AC power into a load (5) or a power system (4).
  • the first control circuit (22) reduces the output of the inverter (13) to a first target value.
  • control is performed so that the DC-DC converter (21) is lowered to the second target value.
  • the power converter device (20) characterized by performing. According to this, the voltage of the DC bus (40) can be reduced during output suppression, and the reduction in conversion efficiency of the inverter (13) can be suppressed.
  • the present invention can be used for a distributed power supply system in which a solar battery and a stationary storage battery are combined.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)
  • Charge And Discharge Circuits For Batteries Or The Like (AREA)

Abstract

In a power conversion device 10, an inverter 13 is connected, via a DC bus 40, to a DC-DC converter 21 that converts the voltage of DC power outputted from a DC power source and that outputs the converted DC power to the DC bus 40. The inverter 13 converts the DC power in the DC bus 40 to AC power, and supplies the AC power obtained through the conversion to a load 5 or a system 4. Control circuits 14, 15 control the inverter 13. When output of the inverter 13 to the system 4 should be suppressed, the control circuits 14, 15 control the inverter 13 such that output of the inverter 13 is lowered to a first target value, and notify, of a second target value which is lower than the first target value, a converter control circuit 22 that controls the DC-DC converter 21.

Description

電力変換装置、電力変換システムPower conversion device, power conversion system
　本発明は、直流電力を交流電力に変換する電力変換装置、電力変換システムに関する。 The present invention relates to a power conversion device and a power conversion system that convert DC power into AC power.
　現在、系統連系される分散型電源には、電源ソースとして太陽電池、燃料電池、定置型蓄電池、車載蓄電池などがある。系統に連系する分散型電源システムの代表的な構成として、単一の分散型電源を使用してＤＣ－ＤＣコンバータ、直流バス及びインバータを介して系統連系する構成と、複数の分散型電源を使用してそれぞれのＤＣ－ＤＣコンバータ、共通の直流バス及び１つのインバータを介して系統連系する構成がある。 Currently, distributed power sources that are grid-connected include solar cells, fuel cells, stationary storage batteries, and in-vehicle storage batteries as power sources. A typical configuration of a distributed power supply system connected to a system is a configuration in which a single distributed power supply is used to connect the system via a DC-DC converter, a DC bus and an inverter, and a plurality of distributed power supplies. Are connected to each other via each DC-DC converter, a common DC bus and one inverter.
　後者において、複数のＤＣ－ＤＣコンバータと１つのインバータが１つの筐体内に設置される構成と、少なくとも１つのＤＣ－ＤＣコンバータと１つのインバータが分離された筐体内に設置される構成がある（例えば、特許文献１参照）。 In the latter, there are a configuration in which a plurality of DC-DC converters and one inverter are installed in one casing, and a configuration in which at least one DC-DC converter and one inverter are installed in a separate casing ( For example, see Patent Document 1).
　また、物理的に１つの筐体内にＤＣ－ＤＣコンバータとインバータが設置される構成であっても、制御的にはＤＣ－ＤＣコンバータとインバータが別々の制御装置(例えば、マイコン)により独立に制御されることもある。このようなＤＣ－ＤＣコンバータとインバータが物理的もしくは制御的に分離された分散型電源システムでは、それぞれの電力変換部間の調整を行う必要がある。 Even if the DC-DC converter and the inverter are physically installed in a single housing, the DC-DC converter and the inverter are controlled independently by separate control devices (for example, a microcomputer). Sometimes it is done. In such a distributed power supply system in which the DC-DC converter and the inverter are physically or controlly separated, it is necessary to make adjustments between the respective power conversion units.
　例えば、太陽電池と定置型蓄電池を組み合わせた分散型電源システムにおいて、系統電圧の上昇、インバータ部品温度の上昇、遠隔出力指令の受信、逆潮流電力の検出などの事象に対して、インバータの放電電力を抑制する制御方式が用いられる場合がある。この制御方式では、インバータの出力抑制を開始した直後、直流バスの電圧が上昇する。ＤＣ－ＤＣコンバータは直流バスの電圧上昇から、インバータが出力抑制中であると判断し、直流バスの電圧が所定の電圧以上に上昇しないように、直流バスへの放電電力を抑制する。 For example, in a distributed power system that combines solar cells and stationary storage batteries, the inverter discharge power in response to events such as system voltage rise, inverter component temperature rise, remote output command reception, and reverse power flow detection In some cases, a control method for suppressing the above is used. In this control method, the voltage of the DC bus rises immediately after starting the inverter output suppression. The DC-DC converter determines from the rise in the voltage of the DC bus that the inverter is suppressing the output, and suppresses the discharge power to the DC bus so that the voltage of the DC bus does not rise above a predetermined voltage.
特開２０１５－１２２９０６号公報JP2015-122906A
　上記の制御方式では、インバータの出力抑制機能が働いている間、直流バスの電圧は、ＤＣ－ＤＣコンバータにより、設定された電圧に維持されるように制御される。このＤＣ－ＤＣコンバータに設定された直流バスの電圧は、定常時の直流バスの電圧より高い値であり、インバータの電力変換効率の低下を招く。 In the above control method, the voltage of the DC bus is controlled to be maintained at the set voltage by the DC-DC converter while the output suppression function of the inverter is working. The voltage of the DC bus set in this DC-DC converter is higher than the voltage of the DC bus in the steady state, which causes a reduction in the power conversion efficiency of the inverter.
　本発明はこうした状況に鑑みなされたものであり、その目的は、インバータの出力抑制機能が働いている間も高効率な電力変換を実現する電力変換装置、電力変換システムを提供することにある。 The present invention has been made in view of such a situation, and an object thereof is to provide a power conversion device and a power conversion system that realize high-efficiency power conversion even while the output suppression function of the inverter is working.
　上記課題を解決するために、本発明のある態様の電力変換装置は、直流電源の出力する直流電力の電圧を変換し、変換した直流電力を直流バスに出力するＤＣ－ＤＣコンバータと前記直流バスを介して接続され、前記直流バスの直流電力を交流電力に変換し、変換した交流電力を負荷または電力系統に供給するインバータと、前記インバータを制御する制御回路と、を備える。前記制御回路は、前記インバータから前記電力系統への出力を抑制すべきとき、前記インバータの出力を第１目標値に低下させるように前記インバータを制御するとともに、前記第１目標値より低い第２目標値を、前記ＤＣ－ＤＣコンバータを制御する別の制御回路に通知する。 In order to solve the above-described problems, a power converter according to an aspect of the present invention includes a DC-DC converter that converts a voltage of DC power output from a DC power source and outputs the converted DC power to a DC bus, and the DC bus. And an inverter that converts the DC power of the DC bus into AC power, supplies the converted AC power to a load or a power system, and a control circuit that controls the inverter. The control circuit controls the inverter to lower the output of the inverter to a first target value when the output from the inverter to the power system should be suppressed, and a second lower than the first target value. The target value is notified to another control circuit that controls the DC-DC converter.
　本発明によれば、インバータの出力抑制機能が働いている間も高効率な電力変換を実現することができる。 According to the present invention, highly efficient power conversion can be realized even while the output suppression function of the inverter is working.
本発明の実施の形態に係る電力変換システムを説明するための図である。It is a figure for demonstrating the power conversion system which concerns on embodiment of this invention. 図２（ａ）、（ｂ）は、直流バスの電圧の状態を模式的に描いた図である（その１）。FIGS. 2A and 2B are diagrams schematically showing the voltage state of the DC bus (part 1). 図３（ａ）、（ｂ）は、直流バスの電圧の状態を模式的に描いた図である（その２）。FIGS. 3A and 3B are diagrams schematically showing the voltage state of the DC bus (part 2). インバータの出力抑制時の、インバータの電力制御および蓄電部のＤＣ－ＤＣコンバータの電力制御の第１例を示す図である。It is a figure which shows the 1st example of the power control of an inverter and the power control of the DC-DC converter of an electrical storage part at the time of the output suppression of an inverter. インバータの出力抑制時の、インバータの電力制御および蓄電部のＤＣ－ＤＣコンバータの電力制御の第２例を示す図である。It is a figure which shows the 2nd example of the power control of an inverter and the power control of the DC-DC converter of an electrical storage part at the time of the output suppression of an inverter. インバータの出力抑制時の、インバータの電力制御および蓄電部のＤＣ－ＤＣコンバータの電力制御の第３例を示す図である。It is a figure which shows the 3rd example of the power control of an inverter and the power control of the DC-DC converter of an electrical storage part at the time of the output suppression of an inverter.
　図１は、本発明の実施の形態に係る電力変換システム１を説明するための図である。電力変換システム１は、第１電力変換装置１０及び第２電力変換装置２０を備える。第１電力変換装置１０は太陽電池２用のパワーコンディショナシステムであり、第２電力変換装置２０は蓄電部３用のパワーコンディショナシステムである。図１では、太陽電池２用のパワーコンディショナシステムに、蓄電部３用のパワーコンディショナシステムを後付けした例を示している。 FIG. 1 is a diagram for explaining a power conversion system 1 according to an embodiment of the present invention. The power conversion system 1 includes a first power conversion device 10 and a second power conversion device 20. The first power conversion device 10 is a power conditioner system for the solar cell 2, and the second power conversion device 20 is a power conditioner system for the power storage unit 3. In FIG. 1, the example which retrofitted the power conditioner system for the electrical storage part 3 to the power conditioner system for the solar cells 2 is shown.
　太陽電池２は、光起電力効果を利用し、光エネルギーを直接電力に変換する発電装置である。太陽電池２として、シリコン太陽電池、化合物半導体などを素材にした太陽電池、色素増感型（有機太陽電池）等が使用される。太陽電池２は第１電力変換装置１０と接続され、発電した電力を第１電力変換装置１０に出力する。 The solar cell 2 is a power generation device that directly converts light energy into electric power using the photovoltaic effect. As the solar cell 2, a silicon solar cell, a solar cell made of a compound semiconductor or the like, a dye-sensitized type (organic solar cell), or the like is used. The solar cell 2 is connected to the first power conversion device 10 and outputs the generated power to the first power conversion device 10.
　第１電力変換装置１０は、ＤＣ－ＤＣコンバータ１１、コンバータ制御回路１２、インバータ１３、インバータ制御回路１４、及びシステム制御回路１５を備える。システム制御回路１５は、逆潮流電力計測部１５ａ、指令値生成部１５ｂ、及び通信制御部１５ｃを含む。ＤＣ－ＤＣコンバータ１１とインバータ１３間は直流バス４０で接続される。コンバータ制御回路１２とシステム制御回路１５間は通信線４１で接続され、両者の間で所定のシリアル通信規格（例えば、例えばＲＳ－４８５規格、ＴＣＰ－ＩＰ規格）に準拠した通信が行われる。 The first power converter 10 includes a DC-DC converter 11, a converter control circuit 12, an inverter 13, an inverter control circuit 14, and a system control circuit 15. The system control circuit 15 includes a reverse flow power measurement unit 15a, a command value generation unit 15b, and a communication control unit 15c. The DC-DC converter 11 and the inverter 13 are connected by a DC bus 40. The converter control circuit 12 and the system control circuit 15 are connected by a communication line 41, and communication conforming to a predetermined serial communication standard (for example, RS-485 standard, TCP-IP standard) is performed between the two.
　ＤＣ－ＤＣコンバータ１１は、太陽電池２から出力される直流電力を、所望の電圧値の直流電力に変換し、変換した直流電力を直流バス４０に出力する。ＤＣ－ＤＣコンバータ１１は例えば、昇圧チョッパで構成することができる。 The DC-DC converter 11 converts the DC power output from the solar cell 2 into DC power having a desired voltage value, and outputs the converted DC power to the DC bus 40. The DC-DC converter 11 can be constituted by a step-up chopper, for example.
　コンバータ制御回路１２はＤＣ－ＤＣコンバータ１１を制御する。コンバータ制御回路１２は基本制御として、太陽電池２の出力電力が最大になるようＤＣ－ＤＣコンバータ１１をＭＰＰＴ(Maximum Power Point Tracking) 制御する。具体的にはコンバータ制御回路１２は、太陽電池２の出力電圧および出力電流である、ＤＣ－ＤＣコンバータ１１の入力電圧および入力電流を計測して太陽電池２の発電電力を推定する。コンバータ制御回路１２は、計測した太陽電池２の出力電圧と推定した発電電力をもとに、太陽電池２の発電電力を最大電力点（最適動作点）にするための指令値を生成する。例えば、山登り法に従い動作点電圧を所定のステップ幅で変化させて最大電力点を探索し、最大電力点を維持するように指令値を生成する。ＤＣ－ＤＣコンバータ１１は、生成された指令値に基づく駆動信号に応じてスイッチング動作する。 The converter control circuit 12 controls the DC-DC converter 11. As a basic control, the converter control circuit 12 performs MPPT (Maximum Power Point Tracking) control of the DC-DC converter 11 so that the output power of the solar cell 2 is maximized. Specifically, converter control circuit 12 measures the input voltage and input current of DC-DC converter 11, which are the output voltage and output current of solar cell 2, and estimates the generated power of solar cell 2. The converter control circuit 12 generates a command value for setting the generated power of the solar battery 2 to the maximum power point (optimum operating point) based on the measured output voltage of the solar battery 2 and the estimated generated power. For example, the maximum power point is searched by changing the operating point voltage with a predetermined step width according to the hill-climbing method, and the command value is generated so as to maintain the maximum power point. The DC-DC converter 11 performs a switching operation according to a drive signal based on the generated command value.
　インバータ１３は双方向インバータであり、直流バス４０から入力される直流電力を交流電力に変換し、変換した交流電力を商用電力系統（以下、単に系統４という）に接続された配電線５０に出力する。当該配電線５０には負荷５が接続される。またインバータ１３は、系統４から供給される交流電力を直流電力に変換し、変換した直流電力を直流バス４０に出力する。直流バス４０には、平滑用の電解コンデンサ（不図示）が接続されている。 The inverter 13 is a bidirectional inverter that converts DC power input from the DC bus 40 into AC power and outputs the converted AC power to a distribution line 50 connected to a commercial power system (hereinafter simply referred to as system 4). To do. A load 5 is connected to the distribution line 50. Further, the inverter 13 converts AC power supplied from the system 4 into DC power, and outputs the converted DC power to the DC bus 40. A smoothing electrolytic capacitor (not shown) is connected to the DC bus 40.
　インバータ制御回路１４はインバータ１３を制御する。インバータ制御回路１４は基本制御として、直流バス４０の電圧が第１閾値電圧を維持するようにインバータ１３を制御する。具体的にはインバータ制御回路１４は、直流バス４０の電圧を検出し、検出したバス電圧を第１閾値電圧に一致させるための指令値を生成する。インバータ制御回路１４は、直流バス４０の電圧が第１閾値電圧より高い場合はインバータ１３のデューティ比を上げるための指令値を生成し、直流バス４０の電圧が第１閾値電圧より低い場合はインバータ１３のデューティ比を下げるための指令値を生成する。インバータ１３は、生成された指令値に基づく駆動信号に応じてスイッチング動作する。 The inverter control circuit 14 controls the inverter 13. As a basic control, the inverter control circuit 14 controls the inverter 13 so that the voltage of the DC bus 40 maintains the first threshold voltage. Specifically, the inverter control circuit 14 detects the voltage of the DC bus 40 and generates a command value for making the detected bus voltage coincide with the first threshold voltage. The inverter control circuit 14 generates a command value for increasing the duty ratio of the inverter 13 when the voltage of the DC bus 40 is higher than the first threshold voltage, and the inverter control circuit 14 when the voltage of the DC bus 40 is lower than the first threshold voltage. A command value for lowering the duty ratio of 13 is generated. The inverter 13 performs a switching operation according to a drive signal based on the generated command value.
　蓄電部３は、電力を充放電可能であり、リチウムイオン蓄電池、ニッケル水素蓄電池、鉛蓄電池、電気二重層キャパシタ、リチウムイオンキャパシタ等を含む。蓄電部３は第２電力変換装置２０と接続される。 The power storage unit 3 can charge and discharge electric power, and includes a lithium ion storage battery, a nickel hydride storage battery, a lead storage battery, an electric double layer capacitor, a lithium ion capacitor, and the like. The power storage unit 3 is connected to the second power conversion device 20.
　第２電力変換装置２０は、ＤＣ－ＤＣコンバータ２１及びコンバータ制御回路２２を備える。コンバータ制御回路２２と、第１電力変換装置１０のシステム制御回路１５は通信線４２で接続され、両者の間で所定のシリアル通信規格に準拠した通信が行われる。 The second power conversion device 20 includes a DC-DC converter 21 and a converter control circuit 22. The converter control circuit 22 and the system control circuit 15 of the first power conversion device 10 are connected by a communication line 42, and communication based on a predetermined serial communication standard is performed between them.
　ＤＣ－ＤＣコンバータ２１は、蓄電部３と直流バス４０の間に接続され、蓄電部３を充放電する双方向コンバータである。コンバータ制御回路２２はＤＣ－ＤＣコンバータ２１を制御する。コンバータ制御回路２２は基本制御として、システム制御回路１５から送信されてくる指令値をもとにＤＣ－ＤＣコンバータ２１を制御して、蓄電部３を定電流（ＣＣ）／定電圧（ＣＶ）で充電／放電する。例えばコンバータ制御回路２２は、放電時においてシステム制御回路１５から電力指令値を受信し、当該電力指令値を蓄電部３の電圧で割った値を電流指令値として、ＤＣ－ＤＣコンバータ２１に定電流放電させる。 The DC-DC converter 21 is a bidirectional converter that is connected between the power storage unit 3 and the DC bus 40 and charges and discharges the power storage unit 3. The converter control circuit 22 controls the DC-DC converter 21. As a basic control, the converter control circuit 22 controls the DC-DC converter 21 based on the command value transmitted from the system control circuit 15 to control the power storage unit 3 at a constant current (CC) / constant voltage (CV). Charge / discharge. For example, the converter control circuit 22 receives a power command value from the system control circuit 15 at the time of discharging, and uses a value obtained by dividing the power command value by the voltage of the power storage unit 3 as a current command value. Discharge.
　操作表示装置３０は、第１電力変換装置１０のユーザインターフェイスであり、室内の所定の位置に設置される。操作表示装置３０は例えば、タッチパネルディスプレイで構成することができ、ユーザに所定の情報を提供すると共に、ユーザからの操作を受け付ける。操作表示装置３０とシステム制御回路１５は通信線４３で接続され、両者の間で所定のシリアル通信規格に準拠した通信が行われる。なお操作表示装置３０とシステム制御回路１５の間は無線で接続されてもよい。 The operation display device 30 is a user interface of the first power conversion device 10 and is installed at a predetermined position in the room. The operation display device 30 can be constituted by a touch panel display, for example, and provides predetermined information to the user and accepts an operation from the user. The operation display device 30 and the system control circuit 15 are connected by a communication line 43, and communication based on a predetermined serial communication standard is performed between them. The operation display device 30 and the system control circuit 15 may be connected wirelessly.
　以上の回路構成において、インバータ１３の出力電力を抑制する必要がある場合が発生する。主な出力抑制事由として、インバータ１３から系統４への逆潮流の発生、系統電圧の設定電圧を超える上昇、遠隔出力指令の受信、インバータ１３内の部品の設定温度を超える温度上昇、インバータ１３の定格電力を超える電力上昇、インバータ１３の定格電流を超える電流上昇が挙げられる。 In the above circuit configuration, the output power of the inverter 13 needs to be suppressed. The main output suppression reasons include the occurrence of reverse power flow from the inverter 13 to the grid 4, the rise of the grid voltage exceeding the set voltage, the reception of the remote output command, the temperature rise exceeding the set temperature of the components in the inverter 13, the inverter 13 An increase in power exceeding the rated power and an increase in current exceeding the rated current of the inverter 13 can be mentioned.
　蓄電部３からの放電中に、日射変動により太陽電池２の発電量が増加した場合、又は負荷５の消費電力が低下した場合、系統４への逆潮流電力が発生し、売電状態になることがある。日本では系統連系規程により蓄電システムから、蓄電池の定格容量の５％以上の電力を５００ｍｓを超えて系統４へ逆潮流することが禁止されている。従って、蓄電部３が接続された電力変換システム１において逆潮流が検出された場合、５００ｍｓ以内に逆潮流を抑える必要がある。 When the amount of power generated by the solar cell 2 increases due to fluctuations in solar radiation or when the power consumption of the load 5 decreases during discharge from the power storage unit 3, reverse power flow to the grid 4 is generated and the power is sold. Sometimes. In Japan, the grid connection regulations prohibit the reverse flow of power from the power storage system to the grid 4 for more than 5% of the rated capacity of the storage battery over 500 ms. Therefore, when a reverse power flow is detected in the power conversion system 1 to which the power storage unit 3 is connected, it is necessary to suppress the reverse power flow within 500 ms.
　また日本では２０１５年１月の再生可能エネルギー固定価格買取制度の改正により、新たに系統に連系する太陽光発電と風力発電の設備に遠隔出力制御システムの導入が義務付けられている。システム制御回路１５は、電力会社などの系統運用機関から外部ネットワーク（例えば、インターネット又は専用線）を介して、系統４への出力電力量と出力タイミングに関する指示を受信する。 In Japan, the revision of the renewable energy feed-in tariff system in January 2015 has made it mandatory to introduce a remote output control system for solar and wind power generation facilities that are newly connected to the grid. The system control circuit 15 receives an instruction related to the output power amount and output timing to the grid 4 from a grid operating organization such as a power company via an external network (for example, the Internet or a dedicated line).
　インバータ１３の出力電力を抑制する方法として、太陽電池２のＤＣ－ＤＣコンバータ１１の出力電力を抑制する方法、蓄電部３のＤＣ－ＤＣコンバータ２１の出力電力を抑制する方法、インバータ１３の出力電力を抑制する方法がある。太陽電池２のＤＣ－ＤＣコンバータ１１の出力電力を抑制する方法は、太陽電池２の発電量を無駄にすることに繋がる。従って太陽電池２のＤＣ－ＤＣコンバータ１１の出力抑制は最後に実行すべき制御である。 As a method of suppressing the output power of the inverter 13, a method of suppressing the output power of the DC-DC converter 11 of the solar cell 2, a method of suppressing the output power of the DC-DC converter 21 of the power storage unit 3, and the output power of the inverter 13 There is a way to suppress this. The method of suppressing the output power of the DC-DC converter 11 of the solar cell 2 leads to wasted power generation amount of the solar cell 2. Therefore, the output suppression of the DC-DC converter 11 of the solar cell 2 is the control to be executed last.
　逆潮流が検出された場合、蓄電部３からの放電を停止すればよいため、蓄電部３のＤＣ－ＤＣコンバータ２１の出力電力を抑制する方法が最も直截的な制御である。しかしながら、第２電力変換装置２０が第１電力変換装置１０から分離され、系統４から離れた位置に設置されている場合、逆潮流の検出から蓄電部３のＤＣ－ＤＣコンバータ２１の出力抑制までにタイムラグが発生しやすくなる。 When the reverse power flow is detected, it is only necessary to stop the discharge from the power storage unit 3, so the method for suppressing the output power of the DC-DC converter 21 of the power storage unit 3 is the most straightforward control. However, when the second power conversion device 20 is separated from the first power conversion device 10 and installed at a position away from the grid 4, from detection of reverse power flow to output suppression of the DC-DC converter 21 of the power storage unit 3. Time lag is likely to occur.
　図１に示した構成では、第１電力変換装置１０の逆潮流電力計測部１５ａが、配電線５０に設置されたＣＴセンサ（不図示）の計測値をもとに逆潮流の発生を検出する。第２電力変換装置２０のコンバータ制御回路２２は、システム制御回路１５から通信線４２を介して逆潮流の検出情報を受信する。通信線４２は、第１電力変換装置１０と第２電力変換装置２０を繋ぐ直流バス４０に這わせて設置されることが多く、この構成では通信線４２は直流バス４０からノイズの影響を受ける。また二値の電圧を使用したデジタル通信では、１ビットを表す単位期間を短くするほどノイズに弱くなる性質があり、基本的に通信速度を上げるほどビット誤りが発生しやすくなる。 In the configuration shown in FIG. 1, the reverse power flow measurement unit 15 a of the first power conversion device 10 detects the occurrence of reverse power flow based on the measurement value of a CT sensor (not shown) installed on the distribution line 50. . The converter control circuit 22 of the second power conversion device 20 receives reverse flow detection information from the system control circuit 15 via the communication line 42. The communication line 42 is often installed over the DC bus 40 that connects the first power conversion device 10 and the second power conversion device 20, and in this configuration, the communication line 42 is affected by noise from the DC bus 40. . In digital communication using a binary voltage, the shorter the unit period representing one bit, the weaker it becomes to noise. Basically, the bit error is more likely to occur as the communication speed is increased.
　従って第１電力変換装置１０が逆潮流を検出し、出力抑制を指示する通信データを生成し、通信線４２を介して第２電力変換装置２０に送信する方法では、系統連系規程に定められる時限（５００ｍｓ）を遵守できない可能性がある。またノイズにより通信データの内容が途中で変わってしまう可能性もある。 Therefore, in the method in which the first power conversion device 10 detects reverse power flow, generates communication data instructing output suppression, and transmits the communication data to the second power conversion device 20 via the communication line 42, it is defined in the grid interconnection regulations. There is a possibility that the time limit (500 ms) cannot be observed. In addition, the content of communication data may change during the process due to noise.
　そこで先にインバータ１３の出力電力を抑制し、後から蓄電部３のＤＣ－ＤＣコンバータ２１の出力電力を抑制する方法が考えられる。上述のようにインバータ制御回路１４は基本制御として、直流バス４０の電圧が第１閾値電圧を維持するようにインバータ１３を制御する。出力抑制をすべき場合は、インバータ制御回路１４は優先制御として、出力抑制制御を実行する。具体的にはインバータ制御回路１４は、インバータ１３の出力が指令値生成部１５ｂにより生成された指令値（具体的には上限電流値または上限電力値）を超えないようにインバータ１３を制御する。出力抑制中は、直流バス４０の電圧を第１閾値電圧に維持するように制御するバス電圧の安定化制御は停止する。 Therefore, a method is conceivable in which the output power of the inverter 13 is first suppressed and the output power of the DC-DC converter 21 of the power storage unit 3 is subsequently suppressed. As described above, the inverter control circuit 14 controls the inverter 13 so that the voltage of the DC bus 40 maintains the first threshold voltage as basic control. When output suppression is to be performed, the inverter control circuit 14 executes output suppression control as priority control. Specifically, the inverter control circuit 14 controls the inverter 13 so that the output of the inverter 13 does not exceed the command value (specifically, the upper limit current value or the upper limit power value) generated by the command value generation unit 15b. During the output suppression, the bus voltage stabilization control for controlling the voltage of the DC bus 40 to be maintained at the first threshold voltage is stopped.
　インバータ１３の出力抑制が開始した時点では、太陽電池２のＤＣ－ＤＣコンバータ１１及び／又は蓄電部３のＤＣ－ＤＣコンバータ２１の出力抑制は開始していない。従ってインバータ１３の出力電力に対してインバータ１３の入力電力が過多となり、直流バス４０の電圧が上昇する。より具体的には直流バス４０に接続された電解コンデンサに電荷が蓄積されていく。 At the time when output suppression of the inverter 13 is started, output suppression of the DC-DC converter 11 of the solar cell 2 and / or the DC-DC converter 21 of the power storage unit 3 is not started. Therefore, the input power of the inverter 13 becomes excessive with respect to the output power of the inverter 13, and the voltage of the DC bus 40 increases. More specifically, electric charges are accumulated in the electrolytic capacitor connected to the DC bus 40.
　上述のようにコンバータ制御回路２２は基本制御として、蓄電部３からＤＣ－ＤＣコンバータ２１への放電量またはＤＣ－ＤＣコンバータ２１から蓄電部３への充電量が、システム制御回路１５から送信されてくる指令値になるようにＤＣ－ＤＣコンバータ２１を制御する。さらにコンバータ制御回路２２は優先制御として、直流バス４０の電圧が第２閾値電圧を超えないようにＤＣ－ＤＣコンバータ２１を制御する。この制御は、システム制御回路１５から送信されてくる指令値に出力を合わせる制御に対して優先する。第２閾値電圧は第１閾値電圧より高い値に設定される。 As described above, the converter control circuit 22 receives, as basic control, the amount of discharge from the power storage unit 3 to the DC-DC converter 21 or the amount of charge from the DC-DC converter 21 to the power storage unit 3 transmitted from the system control circuit 15. The DC-DC converter 21 is controlled so that the command value comes. Furthermore, the converter control circuit 22 controls the DC-DC converter 21 as priority control so that the voltage of the DC bus 40 does not exceed the second threshold voltage. This control has priority over the control for adjusting the output to the command value transmitted from the system control circuit 15. The second threshold voltage is set to a value higher than the first threshold voltage.
　上述のようにコンバータ制御回路１２は基本制御として、太陽電池２の出力電力が最大になるようＤＣ－ＤＣコンバータ１１をＭＰＰＴ制御する。さらにコンバータ制御回路１２は優先制御として、直流バス４０の電圧が第３閾値電圧を超えないようにＤＣ－ＤＣコンバータ１１を制御する。この制御は、ＭＰＰＴ制御に対して優先する。第３閾値電圧は第２閾値電圧より高い値に設定される。 As described above, the converter control circuit 12 performs MPPT control on the DC-DC converter 11 so that the output power of the solar cell 2 is maximized as basic control. Further, the converter control circuit 12 controls the DC-DC converter 11 as priority control so that the voltage of the DC bus 40 does not exceed the third threshold voltage. This control has priority over MPPT control. The third threshold voltage is set to a value higher than the second threshold voltage.
　第１閾値電圧は、直流バス４０の定常時の電圧に設定される。系統電圧がＡＣ２００Ｖの場合、第１閾値電圧は例えば、ＤＣ２８０Ｖ～３６０Ｖの範囲に設定される。第２閾値電圧は例えば３９０Ｖ、第３閾値電圧は例えば４１０Ｖに設定される。インバータ１３の出力抑制により直流バス４０の電圧が上昇し、直流バス４０の電圧が第２閾値電圧に到達すると蓄電部３のＤＣ－ＤＣコンバータ２１によるバス電圧の上昇抑制制御が発動する。直流バス４０の電圧上昇のエネルギーが、蓄電部３のＤＣ－ＤＣコンバータ２１による上昇抑制エネルギーより大きい場合は、直流バス４０の電圧がさらに上昇する。直流バス４０の電圧が第３閾値電圧に到達すると太陽電池２のＤＣ－ＤＣコンバータ１１によるバス電圧の上昇抑制制御が発動する。 The first threshold voltage is set to a steady voltage of the DC bus 40. When the system voltage is 200 V AC, the first threshold voltage is set in the range of DC 280 V to 360 V, for example. For example, the second threshold voltage is set to 390V, and the third threshold voltage is set to 410V, for example. When the output of the inverter 13 is suppressed, the voltage of the DC bus 40 increases, and when the voltage of the DC bus 40 reaches the second threshold voltage, the bus voltage increase suppression control by the DC-DC converter 21 of the power storage unit 3 is activated. When the energy for increasing the voltage of the DC bus 40 is larger than the energy for suppressing the increase by the DC-DC converter 21 of the power storage unit 3, the voltage of the DC bus 40 further increases. When the voltage of the DC bus 40 reaches the third threshold voltage, the bus voltage rise suppression control by the DC-DC converter 11 of the solar cell 2 is activated.
　図２（ａ）、（ｂ）は、直流バス４０の電圧の状態を模式的に描いた図である（その１）。図２（ａ）は、定常時の直流バス４０の電圧の状態を示している。定常時の直流バス４０の電圧は、インバータ１３により第１閾値電圧に維持される。図２（ｂ）は、インバータ１３の出力抑制直後の直流バス４０の電圧の状態を示している。通常、出力抑制直後は直流バス４０の電圧が上昇し、蓄電部３のＤＣ－ＤＣコンバータ２１が直流バス４０の電圧を、第２閾値電圧を超えないように抑え込む制御となる。 FIGS. 2A and 2B are diagrams schematically showing the voltage state of the DC bus 40 (part 1). FIG. 2A shows the voltage state of the DC bus 40 in a steady state. The constant voltage of the DC bus 40 is maintained at the first threshold voltage by the inverter 13. FIG. 2B shows the voltage state of the DC bus 40 immediately after the output of the inverter 13 is suppressed. Normally, immediately after the output is suppressed, the voltage of the DC bus 40 increases, and the DC-DC converter 21 of the power storage unit 3 controls the voltage of the DC bus 40 so as not to exceed the second threshold voltage.
　直流バス４０の電圧と系統４の電圧が近いほどインバータ１３の電力変換効率が高くなる。逆に言えば放電時においては、直流バス４０の電圧が系統４の電圧に対して高くなるほど、インバータ１３の変換効率が低下する。図２（ｂ）に示すように直流バス４０の電圧が定常時より高い状態では、インバータ１３の変換効率が定常時より低下することになる。 The power conversion efficiency of the inverter 13 increases as the voltage of the DC bus 40 is closer to the voltage of the system 4. Conversely, at the time of discharging, the conversion efficiency of the inverter 13 decreases as the voltage of the DC bus 40 becomes higher than the voltage of the system 4. As shown in FIG. 2B, in a state where the voltage of the DC bus 40 is higher than that in the steady state, the conversion efficiency of the inverter 13 is lower than that in the steady state.
　図３（ａ）、（ｂ）は、直流バス４０の電圧の状態を模式的に描いた図である（その２）。本実施の形態では、インバータ１３の変換効率の低下を回避するために出力抑制中に、直流バス４０の電圧を第２閾値電圧から第１閾値電圧まで低下させる仕組みを導入する。 FIGS. 3A and 3B are diagrams schematically showing the voltage state of the DC bus 40 (part 2). In the present embodiment, a mechanism is introduced to reduce the voltage of the DC bus 40 from the second threshold voltage to the first threshold voltage during output suppression in order to avoid a decrease in the conversion efficiency of the inverter 13.
　次の説明では簡略化のため、太陽電池２のＤＣ－ＤＣコンバータ１１の出力と負荷５の消費電力を無視して考える。定常時は、（蓄電部３のＤＣ－ＤＣコンバータ２１の放電量）＝（インバータ１３の放電量）の関係になり、直流バス４０の電圧は第１閾値電圧で安定する。出力抑制開始直後は、（蓄電部３のＤＣ－ＤＣコンバータ２１の放電量）＞（インバータ１３の放電量）－（抑制量）の関係になる。この関係ではインバータ１３の入力が過多となり、直流バス４０の電圧が上昇する。 In the following description, for simplification, the output of the DC-DC converter 11 of the solar cell 2 and the power consumption of the load 5 are ignored. In the normal state, the relationship of (discharge amount of DC-DC converter 21 of power storage unit 3) = (discharge amount of inverter 13) is established, and the voltage of DC bus 40 is stabilized at the first threshold voltage. Immediately after the start of output suppression, the relationship of (discharge amount of DC-DC converter 21 of power storage unit 3)> (discharge amount of inverter 13)-(suppression amount) is satisfied. In this relationship, the input of the inverter 13 becomes excessive, and the voltage of the DC bus 40 increases.
　直流バス４０の電圧が第１閾値電圧を上回ると、蓄電部３のＤＣ－ＤＣコンバータ２１の抑制制御が開始する。これにより、（蓄電部３のＤＣ－ＤＣコンバータ２１の放電量）－（抑制量）＝（インバータ１３の放電量）－（抑制量）の関係になる。このとき、電力は平衡するため直流バス４０の電圧は第２閾値電圧で安定する。ただし、この状態ではインバータ１３の変換効率が定常時より低下している。 When the voltage of the DC bus 40 exceeds the first threshold voltage, the suppression control of the DC-DC converter 21 of the power storage unit 3 is started. As a result, a relationship of (discharge amount of DC-DC converter 21 of power storage unit 3) − (suppression amount) = (discharge amount of inverter 13) − (suppression amount) is established. At this time, since the power is balanced, the voltage of the DC bus 40 is stabilized at the second threshold voltage. However, in this state, the conversion efficiency of the inverter 13 is lower than that in the steady state.
　そこで本実施の形態では蓄電部３のＤＣ－ＤＣコンバータ２１の抑制量を増加させる。即ち、（蓄電部３のＤＣ－ＤＣコンバータ２１の放電量）－（抑制量＋α）＝（インバータ１３の放電量）－（抑制量）の関係になる。この関係ではインバータ１３の入力が不足し、直流バス４０の電圧が下降する。直流バス４０の電圧が第１閾値電圧まで低下すると、インバータ１３は直流バス４０の電圧を第１閾値電圧に維持するように動作する。以上の流れで、インバータ１３の出力抑制中の直流バス４０の電圧が、定常時と同じとなり、電力変換効率の低下を回避できる。 Therefore, in this embodiment, the suppression amount of the DC-DC converter 21 of the power storage unit 3 is increased. That is, a relationship of (discharge amount of DC-DC converter 21 of power storage unit 3) − (suppression amount + α) = (discharge amount of inverter 13) − (suppression amount) is satisfied. In this relationship, the input of the inverter 13 is insufficient, and the voltage of the DC bus 40 drops. When the voltage of the DC bus 40 decreases to the first threshold voltage, the inverter 13 operates to maintain the voltage of the DC bus 40 at the first threshold voltage. With the above flow, the voltage of the DC bus 40 during the suppression of the output of the inverter 13 becomes the same as in the steady state, and a decrease in power conversion efficiency can be avoided.
　図４は、インバータ１３の出力抑制時の、インバータ１３の電力制御および蓄電部３のＤＣ－ＤＣコンバータ２１の電力制御の第１例を示す図である。インバータ１３の抑制電力のリミット値（上限値）は定常時において、インバータ１３の定格出力電力値に設定されている。即ち、定常時に突発的な事由により直流バス４０の電圧が上昇しても、インバータ１３の出力電力は定格出力電力値で上昇が止まるように設定されている。同様に蓄電部３のＤＣ－ＤＣコンバータ２１のリミット値（上限値）も定常時において、ＤＣ－ＤＣコンバータ２１の定格出力電力値に設定されている。 FIG. 4 is a diagram illustrating a first example of power control of the inverter 13 and power control of the DC-DC converter 21 of the power storage unit 3 when the output of the inverter 13 is suppressed. The limit value (upper limit value) of the suppression power of the inverter 13 is set to the rated output power value of the inverter 13 in a steady state. That is, even if the voltage of the DC bus 40 increases due to a sudden event during normal operation, the output power of the inverter 13 is set to stop increasing at the rated output power value. Similarly, the limit value (upper limit value) of the DC-DC converter 21 of the power storage unit 3 is also set to the rated output power value of the DC-DC converter 21 in a steady state.
　系統４への逆潮流が検出されると、インバータ制御回路１４はインバータ１３の出力を第１の傾きで低下させる。第１の傾きは、単位時間あたりの抑制量［Ｗ／ｍｓ］で規定される。第１の傾きは例えば、インバータ１３が定格出力値で放電中に抑制を開始してから抑制が完了するまでの時間が５００ｍｓに収まるように設定される。 When a reverse power flow to the system 4 is detected, the inverter control circuit 14 decreases the output of the inverter 13 with a first slope. The first slope is defined by a suppression amount [W / ms] per unit time. For example, the first slope is set so that the time from when the inverter 13 starts suppression during discharging at the rated output value to when suppression is completed is within 500 ms.
　例えば、太陽電池２が３．５ｋＷを発電し、蓄電部３が２．０ｋＷを放電し、インバータ１３が５．５ｋＷを負荷５に供給している状態を考える。この状態から負荷５が解列され、負荷５の消費電力が０．０Ｗになった場合、インバータ１３の５．５ｋＷの出力電力が系統４に逆潮流される。この場合、５００ｍｓ以内に逆潮流を止めなければ、インバータ１３を系統４から解列しなければならず、解列中は太陽電池２の発電が停止するため経済的損失となる。 For example, consider a state where the solar cell 2 generates 3.5 kW, the power storage unit 3 discharges 2.0 kW, and the inverter 13 supplies 5.5 kW to the load 5. When the load 5 is disconnected from this state and the power consumption of the load 5 becomes 0.0 W, the 5.5 kW output power of the inverter 13 flows backward to the grid 4. In this case, if the reverse power flow is not stopped within 500 ms, the inverter 13 must be disconnected from the system 4, and the power generation of the solar cell 2 is stopped during the disconnection, resulting in an economic loss.
　システム制御回路１５の指令値生成部１５ｂは、第１の傾きに応じてインバータ１３の電力指令値を５．５ｋｗから（０．０－β）ｋＷ（第１目標値）まで低下させていく。指令値生成部１５ｂは第１の期間毎に、更新された電力指令値をインバータ制御回路１４に通知する。指令値生成部１５ｂは、第１の傾きに応じて蓄電部３のＤＣ－ＤＣコンバータ２１の電力指令値を２．０ｋｗから（０．０－β－α）ｋＷ（第２目標値）まで低下させていく。指令値生成部１５ｂは通信線４２を介して第２の期間毎に、更新された電力指令値をコンバータ制御回路２２に通知する。例えば、マージンβは０．０５ｋＷに設定され、マージンαも０．０５ｋＷに設定される。 The command value generation unit 15b of the system control circuit 15 decreases the power command value of the inverter 13 from 5.5 kW to (0.0−β) kW (first target value) according to the first inclination. The command value generating unit 15b notifies the inverter control circuit 14 of the updated power command value for each first period. Command value generation unit 15b reduces the power command value of DC-DC converter 21 of power storage unit 3 from 2.0 kW to (0.0−β−α) kW (second target value) according to the first inclination. I will let you. The command value generation unit 15b notifies the converter control circuit 22 of the updated power command value via the communication line 42 every second period. For example, the margin β is set to 0.05 kW, and the margin α is also set to 0.05 kW.
　なお、第２の期間は第１の期間より長くなる。即ち、インバータ１３の電力指令値の方が更新頻度が高くなる。これは通信線４２を用いることによる制約である。なお図４では、インバータ１３の出力抑制と蓄電部３のＤＣ－ＤＣコンバータ２１の出力抑制が同じタイミングで開始しているが、実際には通信遅延の影響により蓄電部３のＤＣ－ＤＣコンバータ２１の出力抑制の方が遅れて開始する。 Note that the second period is longer than the first period. That is, the power command value of the inverter 13 is updated more frequently. This is a limitation due to the use of the communication line 42. In FIG. 4, the output suppression of the inverter 13 and the output suppression of the DC-DC converter 21 of the power storage unit 3 are started at the same timing, but actually, the DC-DC converter 21 of the power storage unit 3 is affected by the communication delay. Suppression of output starts later.
　なお上記の例では、インバータ１３の電力指令値の第１目標値を負の値に設定する例を説明したが、第１目標値を０．０ｋＷに設定してもよい。この場合、買電も売電も発生しない状態であり、最も経済的な逆潮流の抑制制御となる。これに対して、第１の目標値を負の値に設定する場合、若干の買電状態になる。この場合、系統連系規程に定められる逆潮流をより確実に防止することができる。なお、負荷５が電力消費している場合、インバータ１３の電力指令値の第１目標値は、（逆潮流電力－負荷５の消費電力－β）ｋＷになり、蓄電部３のＤＣ－ＤＣコンバータ２１の電力指令値の第２目標値は、（逆潮流電力－負荷５の消費電力－β－α）ｋＷになる。 In the above example, the first target value of the power command value of the inverter 13 is set to a negative value. However, the first target value may be set to 0.0 kW. In this case, neither power purchase nor power sale occurs, and the most economical reverse power flow suppression control is achieved. On the other hand, when the first target value is set to a negative value, there is a slight power purchase state. In this case, the reverse power flow defined in the grid connection regulations can be more reliably prevented. When the load 5 is consuming power, the first target value of the power command value of the inverter 13 is (reverse power flow−power consumption of the load−β) kW, and the DC-DC converter of the power storage unit 3 The second target value of the power command value 21 is (reverse power flow-power consumption of the load 5-β-α) kW.
　なお、インバータ１３の出力は電流値で抑制してもよいし、電力値で抑制してもよい。電流値を使用する場合、抑制解除時の出力過多による過電流を抑制することができる。電力値を使用する場合、系統電圧が変化した場合でも正確に出力抑制を行うことができる。なお、インバータ１３の出力を電流値と電力値の両方で抑制してもよい。蓄電部３のＤＣ－ＤＣコンバータ２１の出力抑制も同様である。 Note that the output of the inverter 13 may be suppressed by a current value or may be suppressed by a power value. When using the current value, it is possible to suppress overcurrent due to excessive output at the time of release of suppression. When the power value is used, the output can be accurately suppressed even when the system voltage changes. Note that the output of the inverter 13 may be suppressed by both the current value and the power value. The same applies to the output suppression of the DC-DC converter 21 of the power storage unit 3.
　逆潮流が解消すると、インバータ制御回路１４はインバータ１３の出力を第２の傾きで上昇させる。第２の傾きは、単位時間あたりの抑制解除量［Ｗ／ｍｓ］で規定される。第２の傾きは、第１の傾きより緩やかに設定される。第２の傾きは例えば、インバータ１３の定格出力値及びＤＣ－ＤＣコンバータ２１の定格出力値にもとづき決定される。 When the reverse power flow is eliminated, the inverter control circuit 14 increases the output of the inverter 13 with the second slope. The second slope is defined by the suppression release amount [W / ms] per unit time. The second inclination is set more gently than the first inclination. The second slope is determined based on the rated output value of the inverter 13 and the rated output value of the DC-DC converter 21, for example.
　図５は、インバータ１３の出力抑制時の、インバータ１３の電力制御および蓄電部３のＤＣ－ＤＣコンバータ２１の電力制御の第２例を示す図である。第１例ではインバータ１３の第１の傾きと蓄電部３のＤＣ－ＤＣコンバータ２１の第１の傾きを同じに設定している例を説明したが、蓄電部３のＤＣ－ＤＣコンバータ２１の第１の傾きを、インバータ１３の第１の傾きより緩くしてもよい。第２の傾きも同様である。 FIG. 5 is a diagram illustrating a second example of power control of the inverter 13 and power control of the DC-DC converter 21 of the power storage unit 3 when the output of the inverter 13 is suppressed. In the first example, the example in which the first slope of the inverter 13 and the first slope of the DC-DC converter 21 of the power storage unit 3 are set to be the same has been described, but the first slope of the DC-DC converter 21 of the power storage unit 3 is described. The inclination of 1 may be made gentler than the first inclination of the inverter 13. The same applies to the second inclination.
　蓄電池の放電電流が急峻に変化すると蓄電池の負担が大きくなり、蓄電池の寿命短縮につながる。また高速応答を実現するにはコンバータ制御回路２２に使用されるマイクロコンピュータを高スペックにする必要があり、コスト増につながる。そこで第２例では、図５に示すように蓄電部３のＤＣ－ＤＣコンバータ２１の第１の傾きを、インバータ１３の第１の傾きより緩く設定している（Ｓ１、Ｓ１ａ参照）。同様に蓄電部３のＤＣ－ＤＣコンバータ２１の第２の傾きを、インバータ１３の第２の傾きより緩く設定している（Ｓ２、Ｓ２ａ参照）。 If the discharge current of the storage battery changes sharply, the burden on the storage battery increases, leading to a shortened life of the storage battery. In order to realize a high-speed response, it is necessary to make the microcomputer used for the converter control circuit 22 have high specifications, which leads to an increase in cost. Therefore, in the second example, as shown in FIG. 5, the first slope of the DC-DC converter 21 of the power storage unit 3 is set to be gentler than the first slope of the inverter 13 (see S1 and S1a). Similarly, the second slope of the DC-DC converter 21 of the power storage unit 3 is set to be gentler than the second slope of the inverter 13 (see S2 and S2a).
　図６は、インバータ１３の出力抑制時の、インバータ１３の電力制御および蓄電部３のＤＣ－ＤＣコンバータ２１の電力制御の第３例を示す図である。第３例は、出力抑制中に直流バス４０の電圧が第１閾値電圧まで低下した例である。直流バス４０の電圧が第１閾値電圧まで低下すると、インバータ１３の出力抑制量に対して、蓄電部３のＤＣ－ＤＣコンバータ２１の出力抑制量を大きくする必要がなくなるため、両者の出力抑制量を同じに制御する。 FIG. 6 is a diagram illustrating a third example of power control of the inverter 13 and power control of the DC-DC converter 21 of the power storage unit 3 when the output of the inverter 13 is suppressed. The third example is an example in which the voltage of the DC bus 40 is reduced to the first threshold voltage during output suppression. When the voltage of the DC bus 40 decreases to the first threshold voltage, it is not necessary to increase the output suppression amount of the DC-DC converter 21 of the power storage unit 3 with respect to the output suppression amount of the inverter 13, so that both output suppression amounts Are controlled in the same way.
　以上説明したように本実施の形態によれば、インバータ１３による逆潮流電力の抑制中、蓄電部３のＤＣ－ＤＣコンバータ２１は逆潮流電力の抑制に優先して直流バス４０の電圧上昇を抑えるように制御する。これにより逆潮流電力の継続を解消しつつ、直流バス４０の電圧を抑制することで電力平衡を担保することができる。従って電力変換システム１の運転停止を防止することができる。 As described above, according to the present embodiment, while the reverse flow power is suppressed by the inverter 13, the DC-DC converter 21 of the power storage unit 3 suppresses the voltage rise of the DC bus 40 in preference to the suppression of the reverse flow power. To control. Thereby, power balance can be secured by suppressing the voltage of the DC bus 40 while eliminating the continuity of the reverse flow power. Therefore, the operation stop of the power conversion system 1 can be prevented.
　蓄電部３のＤＣ－ＤＣコンバータ２１の電力指令値の第２目標値を、インバータ１３の電力指令値の第１目標値より低く制御することにより、インバータ１３の出力抑制により直流バス４０の電圧上昇が継続することを防止するだけでなく、直流バス４０の電圧を定常値まで低下させることができる。従って、インバータ１３の電力変換効率の低下を抑えることができる。 By controlling the second target value of the power command value of the DC-DC converter 21 of the power storage unit 3 to be lower than the first target value of the power command value of the inverter 13, the voltage of the DC bus 40 is increased by suppressing the output of the inverter 13. Can be prevented, and the voltage of the DC bus 40 can be lowered to a steady value. Therefore, a decrease in power conversion efficiency of the inverter 13 can be suppressed.
　直流バス４０の電圧が定常時より高い場合、第１電力変換装置１０内の温度が上昇し、温度上昇による出力抑制が発動しやすくなる。この場合、買電量の増加や太陽電池２の発電量の抑制につながり経済性の低下につながる。また第１電力変換装置１０内の温度上昇は、第１電力変換装置１０内の部品（例えば、電解コンデンサ）の温度上昇につながり、商品寿命の短縮につながる。これに対して本実施の形態では、直流バス４０の電圧上昇を抑えることにより、第１電力変換装置１０内の温度上昇を抑えることができる。 When the voltage of the DC bus 40 is higher than that in a steady state, the temperature in the first power converter 10 rises, and output suppression due to the temperature rise is likely to be activated. In this case, an increase in the amount of electricity purchased and a reduction in the amount of power generated by the solar cell 2 lead to a decrease in economy. Moreover, the temperature rise in the 1st power converter device 10 leads to the temperature rise of the components (for example, electrolytic capacitor) in the 1st power converter device 10, and leads to shortening of a product life. On the other hand, in this Embodiment, the temperature rise in the 1st power converter device 10 can be suppressed by suppressing the voltage rise of the DC bus 40. FIG.
　また太陽電池２のＤＣ－ＤＣコンバータ１１のバス抑制電圧である第３閾値電圧を、蓄電部３のＤＣ－ＤＣコンバータ２１のバス抑制電圧である第２閾値電圧より高く設定することにより、ＤＣ－ＤＣコンバータ２１で直流バス４０の電圧上昇を抑制できる場合は、ＤＣ－ＤＣコンバータ１１は太陽電池２の発電を抑制せずに済む。これにより、太陽電池２の発電電力の売電機会を最大限に確保できるため経済的メリットを損なわずに済む。 Further, by setting the third threshold voltage, which is the bus suppression voltage of the DC-DC converter 11 of the solar cell 2, higher than the second threshold voltage, which is the bus suppression voltage of the DC-DC converter 21 of the power storage unit 3, the DC− When the DC converter 21 can suppress the voltage increase of the DC bus 40, the DC-DC converter 11 does not have to suppress the power generation of the solar cell 2. As a result, the opportunity for selling the power generated by the solar cell 2 can be secured to the maximum, so that the economic merit is not impaired.
　以上、本発明を実施の形態をもとに説明した。実施の形態は例示であり、それらの各構成要素や各処理プロセスの組み合わせにいろいろな変形例が可能なこと、またそうした変形例も本発明の範囲にあることは当業者に理解されるところである。 The present invention has been described based on the embodiments. The embodiments are exemplifications, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. .
　図１では、インバータ制御回路１４とシステム制御回路１５を分離して描いているが、それぞれが別のマイクロコンピュータで実現されてもよいし、１つのマイクロコンピュータで実現されてもよい。また上述の実施の形態では、第１電力変換装置１０と第２電力変換装置２０が別の筐体に設置される例を説明した。この点、第１電力変換装置１０と第２電力変換装置２０が１つの筐体に設置されつつ、システム制御回路１５とコンバータ制御回路２２が通信線４２で接続される構成例も本発明の一実施の形態に含まれる。 In FIG. 1, the inverter control circuit 14 and the system control circuit 15 are depicted separately, but each may be realized by a separate microcomputer or may be realized by a single microcomputer. Moreover, in the above-described embodiment, the example in which the first power conversion device 10 and the second power conversion device 20 are installed in different cases has been described. In this regard, a configuration example in which the system control circuit 15 and the converter control circuit 22 are connected by the communication line 42 while the first power conversion device 10 and the second power conversion device 20 are installed in one housing is also an example of the present invention. It is included in the embodiment.
　また上記実施の形態では、第１電力変換装置１０に太陽電池２が接続される例を説明した。この点、太陽電池２の代わりに、風力発電装置、マイクロ水力発電装置など、再生可能エネルギーを用いた他の発電装置が接続されてもよい。 In the above embodiment, an example in which the solar cell 2 is connected to the first power conversion device 10 has been described. In this respect, instead of the solar battery 2, another power generation device using renewable energy, such as a wind power generation device or a micro hydraulic power generation device, may be connected.
　なお、実施の形態は、以下の項目によって特定されてもよい。 Note that the embodiment may be specified by the following items.
［項目１］
　直流電源（３）の出力する直流電力の電圧を変換し、変換した直流電力を直流バス（４０）に出力するＤＣ－ＤＣコンバータ（２１）と前記直流バス（４０）を介して接続され、前記直流バス（４０）の直流電力を交流電力に変換し、変換した交流電力を負荷（５）または電力系統（４）に供給するインバータ（１３）と、
　前記インバータ（１３）を制御する制御回路（１４、１５）と、を備え、
　前記制御回路（１４、１５）は、前記インバータ（１３）から前記電力系統（４）への出力を抑制すべきとき、前記インバータ（１３）の出力を第１目標値に低下させるように前記インバータ（１３）を制御するとともに、前記第１目標値より低い第２目標値を、前記ＤＣ－ＤＣコンバータ（２１）を制御する別の制御回路（２２）に通知することを特徴とする電力変換装置（１０）。
　これによれば、出力抑制中に直流バス（４０）の電圧を低下させることができ、インバータ（１３）の変換効率の低下を抑えることができる。
［項目２］
　前記直流電源（３）は、前記蓄電部（３）であり、
　前記インバータ（１３）から前記電力系統（４）への出力を抑制すべきときとは、前記電力系統（４）への逆潮流が発生したときであることを特徴とする項目１に記載の電力変換装置（１０）。
　これによれば、逆潮流の抑制中に直流バス（４０）の電圧を低下させることができる。
［項目３］
　前記制御回路（１４、１５）は、前記電力系統（４）への出力を抑制すべきとき、前記電力系統（４）への逆潮流電力が負の値になるように前記第１目標値を生成し、前記第２目標値を第１目標値より低い値で生成することを特徴とする項目１または２に記載の電力変換装置（１０）。
　これによれば、逆潮流をより確実に抑制しつつ、直流バス（４０）の電圧を低下させることができる。
［項目４］
　直流電源（３）の出力する直流電力の電圧を変換し、変換した直流電力を直流バス（４０）に出力するＤＣ－ＤＣコンバータ（２１）と、
　前記ＤＣ－ＤＣコンバータ（２１）を制御する第１制御回路（２２）と、
　前記直流バス（４０）を介して接続され、前記直流バス（４０）の直流電力を交流電力に変換し、変換した交流電力を負荷（５）または電力系統（４）に供給するインバータ（１３）と、
　前記インバータ（１３）を制御する第２制御回路（１４、１５）と、を備え、
　前記第２制御回路（１４、１５）は、前記インバータ（１３）から前記電力系統（１４）への出力を抑制すべきとき、前記インバータ（１３）の出力を第１目標値に低下させるように前記インバータ（１３）を制御するとともに、前記第１目標値より低い第２目標値を、前記第１制御回路（２２）に通知することを特徴とする電力変換システム（１）。
　これによれば、出力抑制中に直流バス（４０）の電圧を低下させることができ、インバータ（１３）の変換効率の低下を抑えることができる。
［項目５］
　前記第１制御回路（２２）と前記第２制御回路（１４、１５）は通信線（４２）で接続されており、
　前記第２制御回路（１４、１５）は、前記インバータ（１３）から前記電力系統（４）への出力を抑制する必要がないとき、前記直流バス（４０）の電圧を第１閾値電圧に維持するよう前記インバータ（１３）を制御し、
　前記第１制御回路（２２）は、前記第２制御回路（１４、１５）から受信する、前記第２目標値をもとに生成される指令値をもとに前記ＤＣ－ＤＣコンバータ（２１）を制御するとともに、前記直流バス（４０）の電圧を、第１閾値電圧より高い第２閾値電圧を超えないように制御することを特徴とする項目４に記載の電力変換システム（１）。
　これによれば、直流バス（４０）の抑制開始直後の電圧上昇を抑えつつ、抑制中および抑制解除後の直流バス（４０）の電圧を安定化させることができる。
［項目６］
　再生可能エネルギーをもとに発電する発電装置（２）の出力する直流電力の電圧を変換し、変換した直流電力を前記直流バス（４０）に出力する発電装置（２）用のＤＣ－ＤＣコンバータ（１１）と、
　前記発電装置（２）の出力電力が最大になるように制御するとともに、前記直流バス（４０）の電圧を、前記第２閾値電圧より高い第３閾値電圧を超えないように、前記発電装置（２）用のＤＣ－ＤＣコンバータ（１１）を制御する第３制御回路（１２）と、
　をさらに備えることを特徴とする項目５に記載の電力変換システム（１）。
　これによれば、出力抑制により、発電装置（２）の発電が抑制される事態を最小限に抑えることができる。
［項目７］
　前記第２制御回路（１４、１５）は、前記直流バス（４０）の電圧が前記第１閾値電圧より高い状態から前記第１閾値電圧まで低下すると、前記インバータ（１３）に入力される電力量と、前記インバータ（１３）から出力される電力量が等しくなるように、前記１目標値および／または前記第２目標値の少なくとも一方を変更することを特徴とする項目５または６に記載の電力変換システム（１）。
　これによれば、インバータ（１３）の電力が平衡するように制御することができる。
［項目８］
　直流電源（３）の出力する直流電力の電圧を変換し、変換した直流電力を直流バス（４０）に出力するＤＣ－ＤＣコンバータ（２１）と、
　前記ＤＣ－ＤＣコンバータ（２１）を制御する第１制御回路（２２）と、を備え、
　前記ＤＣ－ＤＣコンバータ（２１）は、前記直流バス（４０）を介して、前記直流バス（４０）の直流電力を交流電力に変換し、変換した交流電力を負荷（５）または電力系統（４）に供給するインバータ（１３）と接続され、
　前記第１制御回路（２２）は、前記インバータ（１３）から前記電力系統（４）への出力を抑制すべきとき、前記インバータ（１３）の出力を第１目標値に低下させるように前記インバータ（１３）を制御する第２制御回路から、前記第１目標値より低い第２目標値を含む通知を受けて、前記ＤＣ－ＤＣコンバータ（２１）を前記第２目標値に低下させるように制御することを特徴とする電力変換装置（２０）。
　これによれば、出力抑制中に直流バス（４０）の電圧を低下させることができ、インバータ（１３）の変換効率の低下を抑えることができる。 [Item 1]
A DC-DC converter (21) that converts the voltage of the DC power output from the DC power source (3) and outputs the converted DC power to the DC bus (40) is connected via the DC bus (40), An inverter (13) for converting the DC power of the DC bus (40) into AC power and supplying the converted AC power to the load (5) or the power system (4);
A control circuit (14, 15) for controlling the inverter (13),
The control circuit (14, 15) is configured to reduce the output of the inverter (13) to a first target value when the output from the inverter (13) to the power system (4) is to be suppressed. (13) and a second target value lower than the first target value is notified to another control circuit (22) for controlling the DC-DC converter (21). (10).
According to this, the voltage of the DC bus (40) can be reduced during output suppression, and the reduction in conversion efficiency of the inverter (13) can be suppressed.
[Item 2]
The DC power source (3) is the power storage unit (3),
The power converter according to item 1, wherein the time when the output from the inverter (13) to the power system (4) should be suppressed is when a reverse power flow to the power system (4) occurs. (10).
According to this, the voltage of the DC bus (40) can be reduced while the reverse power flow is suppressed.
[Item 3]
When the control circuit (14, 15) should suppress the output to the power system (4), the control circuit (14, 15) sets the first target value so that the reverse flow power to the power system (4) becomes a negative value. The power conversion device (10) according to item 1 or 2, wherein the power conversion device (10) generates the second target value at a value lower than the first target value.
According to this, it is possible to reduce the voltage of the DC bus (40) while more reliably suppressing the reverse power flow.
[Item 4]
A DC-DC converter (21) for converting the voltage of the DC power output from the DC power supply (3) and outputting the converted DC power to the DC bus (40);
A first control circuit (22) for controlling the DC-DC converter (21);
An inverter (13) connected via the DC bus (40), converting DC power of the DC bus (40) into AC power, and supplying the converted AC power to the load (5) or the power system (4) When,
A second control circuit (14, 15) for controlling the inverter (13),
When the output from the inverter (13) to the power system (14) is to be suppressed, the second control circuit (14, 15) reduces the output of the inverter (13) to a first target value. The power conversion system (1) characterized by controlling the inverter (13) and notifying the first control circuit (22) of a second target value lower than the first target value.
According to this, the voltage of the DC bus (40) can be reduced during output suppression, and the reduction in conversion efficiency of the inverter (13) can be suppressed.
[Item 5]
The first control circuit (22) and the second control circuit (14, 15) are connected by a communication line (42),
The second control circuit (14, 15) maintains the voltage of the DC bus (40) at the first threshold voltage when it is not necessary to suppress the output from the inverter (13) to the power system (4). Controlling the inverter (13) to
The first control circuit (22) receives the DC-DC converter (21) based on a command value generated from the second target value received from the second control circuit (14, 15). And controlling the voltage of the DC bus (40) so as not to exceed a second threshold voltage higher than the first threshold voltage.
According to this, it is possible to stabilize the voltage of the DC bus (40) during suppression and after cancellation of suppression while suppressing a voltage increase immediately after the start of suppression of the DC bus (40).
[Item 6]
A DC-DC converter for the power generator (2) that converts the voltage of the DC power output from the power generator (2) that generates power based on renewable energy and outputs the converted DC power to the DC bus (40). (11) and
The power generator (2) is controlled so that the output power is maximized, and the voltage of the DC bus (40) is controlled so as not to exceed a third threshold voltage higher than the second threshold voltage. 2) a third control circuit (12) for controlling the DC-DC converter (11) for
The power conversion system (1) according to item 5, further comprising:
According to this, the situation where the power generation of the power generation device (2) is suppressed can be minimized by the output suppression.
[Item 7]
When the voltage of the DC bus (40) drops from a state higher than the first threshold voltage to the first threshold voltage, the second control circuit (14, 15) receives the amount of power input to the inverter (13). And at least one of the first target value and / or the second target value so that the amount of power output from the inverter (13) becomes equal. Conversion system (1).
According to this, it can control so that the electric power of an inverter (13) may be balanced.
[Item 8]
A DC-DC converter (21) for converting the voltage of the DC power output from the DC power supply (3) and outputting the converted DC power to the DC bus (40);
A first control circuit (22) for controlling the DC-DC converter (21),
The DC-DC converter (21) converts the DC power of the DC bus (40) into AC power via the DC bus (40), and converts the converted AC power into a load (5) or a power system (4). Connected to an inverter (13) for supplying
When the output from the inverter (13) to the power system (4) is to be suppressed, the first control circuit (22) reduces the output of the inverter (13) to a first target value. In response to a notification including a second target value lower than the first target value from the second control circuit that controls (13), control is performed so that the DC-DC converter (21) is lowered to the second target value. The power converter device (20) characterized by performing.
According to this, the voltage of the DC bus (40) can be reduced during output suppression, and the reduction in conversion efficiency of the inverter (13) can be suppressed.
　１　電力変換システム、　２　太陽電池、　３　蓄電部、　４　系統、　５　負荷、　１０　第１電力変換装置、　１１　ＤＣ－ＤＣコンバータ、　１２　コンバータ制御回路、　１３　インバータ、　１４　インバータ制御回路、　１５　システム制御回路、　１５ａ　逆潮流電力計測部、　１５ｂ　指令値生成部、　１５ｃ　通信制御部、　２０　第２電力変換装置、　２１　ＤＣ－ＤＣコンバータ、　２２　コンバータ制御回路、　３０　操作表示装置、　４０　直流バス、　４１，４２，４３　通信線、　５０　配電線。 DESCRIPTION OF SYMBOLS 1 Power conversion system, 2 Solar cell, 3 Power storage part, 4 system | strain, 5 load, 10 1st power converter, 11 DC-DC converter, 12 Converter control circuit, 13 inverter, 14 inverter control circuit, 15 system control circuit, 15a Reverse power flow measurement unit, 15b Command value generation unit, 15c Communication control unit, 20 Second power conversion device, 21 DC-DC converter, 22 Converter control circuit, 30 Operation display device, 40 DC bus, 41, 42, 43 Communication line, 50 distribution lines.
　本発明は、太陽電池と定置型蓄電池を組み合わせた分散型電源システムに利用可能である。 The present invention can be used for a distributed power supply system in which a solar battery and a stationary storage battery are combined.

Claims (8)

  1. 　直流電源の出力する直流電力の電圧を変換し、変換した直流電力を直流バスに出力するＤＣ－ＤＣコンバータと前記直流バスを介して接続され、前記直流バスの直流電力を交流電力に変換し、変換した交流電力を負荷または電力系統に供給するインバータと、
    　前記インバータを制御する制御回路と、を備え、
    　前記制御回路は、前記インバータから前記電力系統への出力を抑制すべきとき、前記インバータの出力を第１目標値に低下させるように前記インバータを制御するとともに、前記第１目標値より低い第２目標値を、前記ＤＣ－ＤＣコンバータを制御する別の制御回路に通知することを特徴とする電力変換装置。     A DC-DC converter that converts the voltage of the DC power output from the DC power source and outputs the converted DC power to the DC bus is connected to the DC bus, and converts the DC power of the DC bus into AC power, An inverter that supplies the converted AC power to a load or power system;
    A control circuit for controlling the inverter,
    The control circuit controls the inverter to lower the output of the inverter to a first target value when the output from the inverter to the power system should be suppressed, and a second lower than the first target value. A power converter which notifies a target value to another control circuit which controls the DC-DC converter.
  2. 　前記直流電源は、蓄電部であり、
    　前記インバータから前記電力系統への出力を抑制すべきときとは、前記電力系統への逆潮流が発生したときであることを特徴とする請求項１に記載の電力変換装置。     The DC power supply is a power storage unit,
    The power conversion device according to claim 1, wherein the time when the output from the inverter to the power system should be suppressed is when a reverse power flow to the power system occurs.
  3. 　前記制御回路は、前記電力系統への出力を抑制すべきとき、前記電力系統への逆潮流電力が負の値になるように前記第１目標値を生成し、前記第２目標値を第１目標値より低い値で生成することを特徴とする請求項１または２に記載の電力変換装置。 When the output to the power system is to be suppressed, the control circuit generates the first target value so that the reverse power flow to the power system becomes a negative value, and sets the second target value to the first value. The power converter according to claim 1, wherein the power converter is generated with a value lower than a target value.
  4. 　直流電源の出力する直流電力の電圧を変換し、変換した直流電力を直流バスに出力するＤＣ－ＤＣコンバータと、
    　前記ＤＣ－ＤＣコンバータを制御する第１制御回路と、
    　前記直流バスを介して接続され、前記直流バスの直流電力を交流電力に変換し、変換した交流電力を負荷または電力系統に供給するインバータと、
    　前記インバータを制御する第２制御回路と、を備え、
    　前記第２制御回路は、前記インバータから前記電力系統への出力を抑制すべきとき、前記インバータの出力を第１目標値に低下させるように前記インバータを制御するとともに、前記第１目標値より低い第２目標値を、前記第１制御回路に通知することを特徴とする電力変換システム。     A DC-DC converter that converts the voltage of the DC power output from the DC power source and outputs the converted DC power to the DC bus;
    A first control circuit for controlling the DC-DC converter;
    An inverter connected via the DC bus, converting the DC power of the DC bus into AC power, and supplying the converted AC power to a load or a power system;
    A second control circuit for controlling the inverter,
    The second control circuit controls the inverter to lower the output of the inverter to a first target value when the output from the inverter to the power system is to be suppressed, and is lower than the first target value. A power conversion system, wherein a second target value is notified to the first control circuit.
  5. 　前記第１制御回路と前記第２制御回路は通信線で接続されており、
    　前記第２制御回路は、前記インバータから前記電力系統への出力を抑制する必要がないとき、前記直流バスの電圧を第１閾値電圧に維持するよう前記インバータを制御し、
    　前記第１制御回路は、前記第２制御回路から受信する、前記第２目標値をもとに生成される指令値をもとに前記ＤＣ－ＤＣコンバータを制御するとともに、前記直流バスの電圧を、第１閾値電圧より高い第２閾値電圧を超えないように制御することを特徴とする請求項４に記載の電力変換システム。     The first control circuit and the second control circuit are connected by a communication line,
    The second control circuit controls the inverter to maintain the voltage of the DC bus at the first threshold voltage when it is not necessary to suppress the output from the inverter to the power system,
    The first control circuit controls the DC-DC converter based on a command value generated based on the second target value received from the second control circuit, and controls the voltage of the DC bus. 5. The power conversion system according to claim 4, wherein control is performed so as not to exceed a second threshold voltage higher than the first threshold voltage.
  6. 　再生可能エネルギーをもとに発電する発電装置の出力する直流電力の電圧を変換し、変換した直流電力を前記直流バスに出力する発電装置用のＤＣ－ＤＣコンバータと、
    　前記発電装置の出力電力が最大になるように制御するとともに、前記直流バスの電圧を、前記第２閾値電圧より高い第３閾値電圧を超えないように、前記発電装置用のＤＣ－ＤＣコンバータを制御する第３制御回路と、
    　をさらに備えることを特徴とする請求項５に記載の電力変換システム。     A DC-DC converter for a power generator that converts the voltage of DC power output from a power generator that generates power based on renewable energy, and outputs the converted DC power to the DC bus;
    A DC-DC converter for the power generator is controlled so that the output power of the power generator is maximized and the voltage of the DC bus does not exceed a third threshold voltage higher than the second threshold voltage. A third control circuit to control;
    The power conversion system according to claim 5, further comprising:
  7. 　前記第２制御回路は、前記直流バスの電圧が前記第１閾値電圧より高い状態から前記第１閾値電圧まで低下すると、前記インバータに入力される電力量と、前記インバータから出力される電力量が等しくなるように、前記１目標値および／または前記第２目標値の少なくとも一方を変更することを特徴とする請求項５または６に記載の電力変換システム。 When the voltage of the DC bus decreases from the state where the voltage of the DC bus is higher than the first threshold voltage to the first threshold voltage, the second control circuit determines the amount of power input to the inverter and the amount of power output from the inverter. The power conversion system according to claim 5 or 6, wherein at least one of the first target value and / or the second target value is changed to be equal.
  8. 　直流電源の出力する直流電力の電圧を変換し、変換した直流電力を直流バスに出力するＤＣ－ＤＣコンバータと、
    　前記ＤＣ－ＤＣコンバータを制御する第１制御回路と、を備え、
    　前記ＤＣ－ＤＣコンバータは、前記直流バスを介して、前記直流バスの直流電力を交流電力に変換し、変換した交流電力を負荷または電力系統に供給するインバータと接続され、
    　前記第１制御回路は、前記インバータから前記電力系統への出力を抑制すべきとき、
    　前記インバータの出力を第１目標値に低下させるように前記インバータを制御する第２制御回路から、前記第１目標値より低い第２目標値を含む通知を受けて、前記ＤＣ－ＤＣコンバータを前記第２目標値に低下させるように制御することを特徴とする電力変換装置。     A DC-DC converter that converts the voltage of the DC power output from the DC power source and outputs the converted DC power to the DC bus;
    A first control circuit for controlling the DC-DC converter,
    The DC-DC converter is connected to an inverter that converts the DC power of the DC bus into AC power via the DC bus, and supplies the converted AC power to a load or a power system.
    When the first control circuit should suppress the output from the inverter to the power system,
    In response to a notification including a second target value lower than the first target value from a second control circuit that controls the inverter to reduce the output of the inverter to the first target value, the DC-DC converter is A power conversion device, characterized in that control is performed so as to reduce the second target value.
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