WO2018159383A1 - Power conversion control device, power generation system, and power conversion control method - Google Patents

Power conversion control device, power generation system, and power conversion control method Download PDF

Info

Publication number
WO2018159383A1
WO2018159383A1 PCT/JP2018/005974 JP2018005974W WO2018159383A1 WO 2018159383 A1 WO2018159383 A1 WO 2018159383A1 JP 2018005974 W JP2018005974 W JP 2018005974W WO 2018159383 A1 WO2018159383 A1 WO 2018159383A1
Authority
WO
WIPO (PCT)
Prior art keywords
power
voltage
power conversion
output
converter
Prior art date
Application number
PCT/JP2018/005974
Other languages
French (fr)
Japanese (ja)
Inventor
公久 古川
尊衛 嶋田
充弘 門田
泰明 乗松
輝 米川
叶田　玲彦
馬淵　雄一
宮田　博昭
治郎 根本
Original Assignee
株式会社日立製作所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社日立製作所 filed Critical 株式会社日立製作所
Publication of WO2018159383A1 publication Critical patent/WO2018159383A1/en

Links

Images

Classifications

    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05F—SYSTEMS FOR REGULATING ELECTRIC OR MAGNETIC VARIABLES
    • G05F1/00—Automatic systems in which deviations of an electric quantity from one or more predetermined values are detected at the output of the system and fed back to a device within the system to restore the detected quantity to its predetermined value or values, i.e. retroactive systems
    • G05F1/66—Regulating electric power
    • G05F1/67—Regulating electric power to the maximum power available from a generator, e.g. from solar cell
    • 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 control device, a power generation system, and a power conversion control method.
  • a photovoltaic power generation system (1) includes a plurality of solar cell groups (2a, 2b to 2n) and each of these solar cell groups. And a plurality of chopper units (3a, 3b to 3n) for boosting a DC voltage obtained from each of the solar cell groups, and controlling the output currents of these chopper units, respectively.
  • the operating point control means (6a, 6b to 6n) for optimizing the operating point of the group and obtaining the maximum output from the solar cell group and the DC voltage obtained from the plurality of chopper units are input, And an inverter (4) that converts and outputs the AC power.
  • the direct-current power obtained from a solar cell fluctuates with changes in the amount of sunlight and temperature. For this reason, when the direct-current power generated in the solar cell decreases and the output voltage decreases, the operation of the inverter may become unstable. For this reason, generally, when the output voltage of the solar cell reaches the lower limit value of the preset input voltage of the inverter, the inverter is controlled so that the input voltage to the inverter becomes constant. However, if the input voltage to the inverter is controlled to be constant, the power conversion device may become unstable, and there is a problem that the energy generated in the solar cell cannot be used efficiently as power. It was.
  • the present invention has been made in view of the above-described circumstances, and an object thereof is to provide a power conversion control device, a power generation system, and a power conversion control method for operating a power conversion device stably with high efficiency.
  • the power conversion control device of the present invention provides output power to a power conversion device that converts the DC voltage to an AC voltage when the DC voltage output from the DC power source exceeds a predetermined threshold voltage.
  • the input current to the power converter has a monotonically increasing relationship with the DC voltage.
  • a monotonic increase control unit for controlling the power converter.
  • the power conversion device can be stably operated with high efficiency.
  • 1 is a block diagram of a photovoltaic power generation system according to a first embodiment of the present invention. It is a circuit diagram of the inverter in a 1st embodiment. It is a flowchart of the control program in 1st Embodiment. It is an operation characteristic figure of a power converter when a solar cell characteristic is constant in a 1st embodiment. It is an operation characteristic figure of a power converter when a solar cell characteristic changes in a 1st embodiment. It is a flowchart of the control program in a comparative example. It is an operation characteristic figure of a power converter when a solar cell characteristic changes in a comparative example. It is a block diagram of the solar energy power generation system by 2nd Embodiment of this invention. It is a circuit diagram of the converter in a 2nd embodiment. It is a block diagram of the solar energy power generation system by 3rd Embodiment of this invention.
  • FIG. 1 is a block diagram of a photovoltaic power generation system S1 according to the first embodiment of the present invention.
  • the solar power generation system S ⁇ b> 1 includes a solar battery 10 (DC power supply), a power conversion device 20, a sensor unit 30, and a power conversion control device 40, and is connected to a system voltage source 60.
  • the power conversion device 20 is generally called a PCS (Power Conditioning System), and includes a smoothing capacitor 21 and an inverter 22.
  • PCS Power Conditioning System
  • the power conversion device 20 converts the DC power output from the solar cell 10 into AC power and supplies it to the system voltage source 60.
  • the input terminals of the power converter 20 and the point A, the voltage is referred to as the input voltage V DC (direct current voltage) of the point A, referred to as an input current I DC current.
  • the input terminal of the inverter 22 is a point B, and the current at the point B is called an input current I INV .
  • FIG. 2 is a circuit diagram of the inverter 22. As shown, a full bridge circuit is generally used as the inverter 22.
  • the sensor unit 30 measures the output current I AC of the inverter 22.
  • the output voltage V AC may be calculated or estimated from the control information of the inverter 22.
  • the sensor unit 30 may measure the output voltage V AC in addition to the output current I AC of the inverter 22.
  • the power conversion control device 40 controls the power conversion device 20.
  • the power conversion control device 40 includes hardware as a general computer such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory).
  • the ROM is executed by the CPU. Control program and various data are stored.
  • the function of the power conversion control device 40 realized by a control program or the like is shown as a block. That is, the power conversion control device 40 includes an input current calculation unit 41 (monotonic increase control unit), an active power calculation unit 42 (monotonic increase control unit), an MPPT calculation unit 44 (constant power control unit), and a switching unit 45. And an active power control unit 46.
  • the MPPT calculation unit 44 provides a command value (effective output power P AC (output power, not shown)) of the inverter 22 ( P AC1 *) is calculated.
  • the constant K is determined in advance according to the target power to be output by the power conversion device 20, the characteristics of the solar cell 10, and the like.
  • the switching unit 45 selects one of the command values P AC1 * and P AC2 * output from the MPPT calculation unit 44 and the active power calculation unit 42 and outputs the selected value as the output power command value P AC *.
  • the active power control unit 46 receives the output voltage V AC and the output current I AC of the power converter 20 from the sensor unit 30, and the effective output power P AC of the inverter 22 approaches the output power command value P AC *.
  • the inverter 22 is feedback controlled.
  • the sensor unit 30 may measure only the output current I AC of the inverter 22 and calculate or estimate the output voltage V AC from the control information of the inverter 22.
  • FIG. 3 is a flowchart of a control program executed in the power conversion control device 40.
  • the power conversion control device 40 determines whether or not the input voltage V DC is equal to or lower than a predetermined threshold voltage V TH .
  • step S110 the operation mode of the power conversion control device 40 is set to the normal control mode in step S120.
  • the “normal control mode” refers to an operation mode in which the command value P AC1 * calculated by the MPPT calculation unit 44 in the switching unit 45 is selected as the output power command value P AC *.
  • step S110 the process proceeds to step S140, and the operation mode of the power conversion control device 40 is set to the monotonically increasing mode.
  • the “monotonically increasing mode” refers to an operation mode in which the command value P AC2 * calculated by the active power calculation unit 42 in the switching unit 45 is selected as the output power command value P AC *. That is, as monotonically increasing with respect to the input current I DC (i.e., as the input current I DC is proportional to the input voltage V DC), refers to a control of setting the input voltage V DC.
  • step S120 or step S140 ends, the process returns to step S110, and the processes after step S110 are repeated. Therefore, if the input voltage V DC is less than or equal to the threshold voltage V TH , the monotonically increasing mode is maintained, and if the input voltage V DC exceeds the threshold voltage V TH , the normal control mode is maintained.
  • the MPPT calculation unit 44 continues to output a constant command value P AC1 *.
  • FIG. 4 is an operation characteristic diagram of the power conversion device 20 when the solar cell characteristics are constant.
  • V DC and I DC are the input voltage and input current to the power conversion device 20
  • I INV is the input current to the inverter 22.
  • the solar cell characteristic L 1 is a characteristic realized by the solar cell 10, and as the input current I DC (output current from the solar cell 10 to the power converter 20) of the power converter 20 increases, the power The input voltage VDC of the converter 20 tends to decrease.
  • the constant power characteristic L 2 is a characteristic that the active power control unit 46 intends to realize based on the command value P AC1 * output from the MPPT calculation unit 44. As described above, assuming the operation of a short time, MPPT computing unit 44 is selected as to continue to output a constant command value P AC1 *, finger command value P AC1 * output power command value P AC * When active power control unit 46 in accordance with the constant-power characteristic L 2, controls the inverter 22.
  • the operating point at the point A shown in FIG. 1 is the operating point A 1 on the solar cell characteristic L 1
  • the input voltage V DC becomes the voltage V b shown in FIG. 4 at a certain moment.
  • the operating point at the point A becomes the operating point A 3 on the solar cell characteristic L 1
  • the input voltage V DC becomes the voltage V c shown in FIG. 1 at a certain moment.
  • the operating point at point A is the operating point A 4 on the solar cell characteristic L 1
  • the operating point at point B is the operating point B 4 on the constant power characteristic L 2 . That is, the input current I INV to the inverter 22 becomes larger than the input current I DC to the power converter 20. Then, the electric charge corresponding to the difference between the two currents is discharged from the smoothing capacitor 21, and the input voltage VDC decreases. As a result, the input voltage V DC goes to zero voltage as time passes.
  • the intersection of the characteristics L 1 and L 2 at the voltage V LIM is not an operating point where the operation is stable, but an unstable operating point. Therefore, this voltage V LIM is referred to as “stable operation limit voltage”.
  • the threshold voltage V TH described in step S110 in FIG. 3 is set to a value that is slightly higher (with a slight margin) than the stable operation limit voltage V LIM . Therefore, actually, before the input voltage V DC reaches the stable operation limit voltage V LIM , the operation mode transits to the monotonically increasing mode (S140).
  • FIG. 5 is an operation characteristic diagram of the power conversion device when the solar cell characteristics change.
  • characteristics L 11 to L 14 are solar cell characteristics when the amount of sunshine decreases sequentially and the power generation capacity decreases.
  • the characteristic L 3 is a characteristic to be realized by the active power control unit 46.
  • the operation mode In the range where the input voltage V DC exceeds the threshold voltage V TH , the operation mode is the normal control mode. Therefore, the characteristic L 3 is the same as the constant power characteristic L 2 (see FIG. 4) in the range.
  • the operation mode is a monotonically increasing mode when the input voltage V DC is equal to or lower than the threshold voltage V TH
  • the characteristic L 3 is a characteristic in which the input current I DC is proportional to the input voltage V DC .
  • the stable operating point is Q 1 .
  • the stable operating point becomes Q 2 .
  • the input voltage V DC at the operating point Q 2 matches the threshold voltage V TH . Therefore, when the input voltage V DC further decreases, the operation mode becomes a monotonically increasing mode.
  • the stable operating point becomes Q 3
  • the stable operating point becomes Q 4. become.
  • the characteristic L 3 is a combination of the constant power characteristic and the proportional characteristic. Therefore, there are stable operating points Q 1 to Q 4 in various solar cell characteristics L 11 to L 14 .
  • a comparative example will be described.
  • the configuration of the comparative example is the same as that of the first embodiment (see FIG. 1), but a constant voltage calculation unit (not shown) is provided instead of the input current calculation unit 41 and the active power calculation unit 42. The point is different.
  • the constant voltage calculation unit (not shown) calculates a command value P AC2 * such that the input voltage V DC matches the threshold voltage V TH and outputs the command value P AC2 * to the switching unit 45.
  • FIG. 6 is a flowchart of a control program executed by the power conversion control device 40 in this comparative example.
  • step S130 is executed in this comparative example instead of step S140 in the first embodiment. That is, when the input voltage V DC becomes equal to or lower than the threshold voltage V TH , the process proceeds to step S130, and the operation mode is set to the constant voltage mode.
  • the “constant voltage mode” refers to an operation mode in which a command value P AC2 * output by a constant voltage calculation unit (not shown) is selected as the output power command value P AC *.
  • FIG. 7 is an operation characteristic diagram of the power conversion device 20 when the solar cell characteristics change in this comparative example.
  • the characteristic L 4 is a characteristic to be realized by the active power control unit 46 (see FIG. 1) of this comparative example.
  • the operation mode In the range where the input voltage V DC exceeds the threshold voltage V TH , the operation mode is the normal control mode. Therefore, the characteristic L 4 is the same as the constant power characteristic L 2 (see FIG. 4) in the range.
  • the operation mode becomes the constant voltage mode, and therefore the input voltage VDC becomes a constant value (threshold voltage V TH ) in the characteristic L 4 .
  • the stable operating points are Q 1 and Q 2 as in the case of FIG. Since the input voltage V DC at the operating point Q 2 matches the threshold voltage V TH, when the power generation capability of the solar cell 10 further decreases, the operation mode becomes the constant voltage mode.
  • the solar cell characteristic becomes L 13
  • the stable operating point becomes Q 13
  • the solar cell characteristic becomes L 14
  • the power conversion control device 40 stops the power conversion device 20 and restarts the power conversion device 20.
  • FIG. 8 is a block diagram of a photovoltaic power generation system S2 according to the second embodiment of the present invention.
  • parts corresponding to those in FIGS. 1 to 7 are denoted by the same reference numerals, and description thereof may be omitted.
  • the photovoltaic power generation system S2 is applied with a power conversion device 20A instead of the power conversion device 20.
  • the other configuration of the solar power generation system S2 is the same as that of the first embodiment.
  • a smoothing capacitor 24 and a converter 23 are inserted between the input terminal (point A) and the smoothing capacitor 21.
  • FIG. 9 is a circuit diagram of the converter 23.
  • the DC voltage input to the converter 23 is converted into an AC voltage in the full bridge circuit 23a.
  • the AC voltage is stepped up or stepped down through the resonant capacitor 23d and the insulating transformer 23c and supplied to the diode bridge 23b.
  • the diode bridge 23b the boosted or stepped down AC voltage is rectified and output.
  • the converter 23 boosts or steps down the input DC voltage and outputs it.
  • the converter 23 boosts or steps down the DC voltage input to the power conversion device 20 ⁇ / b> A and supplies it to the inverter 22.
  • the efficiency of the inverter 22 can be increased.
  • FIG. 10 is a block diagram of a photovoltaic power generation system S3 according to the third embodiment of the present invention.
  • parts corresponding to those in FIGS. 1 to 9 are denoted by the same reference numerals, and description thereof may be omitted.
  • the photovoltaic power generation system S3 is applied with a power conversion device 20B instead of the power conversion device 20A.
  • power converter 20B a plurality of systems of smoothing capacitor 24, converter 23, smoothing capacitor 21, and inverter 22 are provided.
  • the configuration of these individual components 21 to 24 is the same as that of the second embodiment.
  • the plurality of inverters 22 are connected in series.
  • the configuration of the photovoltaic power generation system S3 other than the above is the same as that of the second embodiment. According to this embodiment, since the some inverter 22 is connected in series, the power converter device 20B can output a higher alternating voltage.
  • the present invention is not limited to the above-described embodiments, and various modifications can be made.
  • the above-described embodiments are illustrated for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.
  • a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment.
  • the control lines and information lines shown in the figure are those that are considered necessary for the explanation, and not all the control lines and information lines that are necessary on the product are shown. Actually, it may be considered that almost all the components are connected to each other. Examples of possible modifications to the above embodiment are as follows.
  • the DC power source is not limited to the solar battery 10, and various DC power sources such as a primary battery, a secondary battery, a wind power generator, and a thrust power generator can be applied.
  • the example in which the input voltage V DC and the input current I DC are proportional to each other has been described as the “monotonically increasing mode (S140)”.
  • the input voltage V DC and the input current I DC do not necessarily have a proportional relationship.
  • an operating point at which the maximum output can be extracted from the solar cell 10 is obtained, and the characteristics connecting these operating points are used as the characteristics in the monotonically increasing mode. You may apply.
  • FIG. 3 has been described as software processing using a program in each of the above-described embodiments, but part or all of the processing is ASIC (Application Specific Integrated Circuit). Alternatively, it may be replaced with hardware processing using FPGA (field-programmable gate array) or the like.
  • ASIC Application Specific Integrated Circuit
  • FPGA field-programmable gate array

Abstract

Provided is a power conversion control device capable of stably operating a power conversion device with high efficiency. Therefore, provided are: a constant power control unit (44) that, when a DC voltage (VDC) outputted from a DC power supply (10) exceeds a prescribed threshold voltage (VTH), controls a power conversion device (20) for converting the DC voltage (VDC) to an AC voltage such that an output power (PAC) is substantially constant; and monotonic increase control units (41, 42) that, when the DC voltage (VDC) is equal to or less than the threshold voltage (VTH), control the power conversion device (20) such that an input current (IDC) to the power conversion device (20) has a relationship of a monotonic increase with respect to the DC voltage (VDC).

Description

電力変換制御装置、発電システムおよび電力変換制御方法Power conversion control device, power generation system, and power conversion control method
　本発明は、電力変換制御装置、発電システムおよび電力変換制御方法に関する。 The present invention relates to a power conversion control device, a power generation system, and a power conversion control method.
　本技術分野の背景技術として、下記特許文献１の要約書には、「太陽光発電システム(１)は、複数の太陽電池群(２ａ,２ｂ～２ｎ)と、これらの各太陽電池群のそれぞれに対応して設けられて前記各太陽電池群からそれぞれ得られる直流電圧を昇圧する複数のチョッパユニット(３ａ,３ｂ～３ｎ)と、これらのチョッパユニットの出力電流をそれぞれ制御して前記各太陽電池群の動作点を最適化し、該太陽電池群から最大出力を得る動作点制御手段(６ａ,６ｂ～６ｎ)と、前記複数のチョッパユニットから得られる直流電圧を入力し、該直流電圧を所定電圧の交流電力に変換して出力するインバータ(４)とを備える。」と記載されている。 As background art of this technical field, the abstract of the following Patent Document 1 states that “a photovoltaic power generation system (1) includes a plurality of solar cell groups (2a, 2b to 2n) and each of these solar cell groups. And a plurality of chopper units (3a, 3b to 3n) for boosting a DC voltage obtained from each of the solar cell groups, and controlling the output currents of these chopper units, respectively. The operating point control means (6a, 6b to 6n) for optimizing the operating point of the group and obtaining the maximum output from the solar cell group and the DC voltage obtained from the plurality of chopper units are input, And an inverter (4) that converts and outputs the AC power.
国際公開第２０１４／１４７７７１号International Publication No. 2014/1477771
　ところで、太陽電池から得られる直流電力は、日照量や温度の変化に伴って変動する。このため、太陽電池に生起される直流電力が減少し、その出力電圧が低下した場合には、インバータの動作が不安定になる場合がある。このため、一般的には、太陽電池の出力電圧がインバータのあらかじめ設定した入力電圧の下限値に到達したときには、インバータへの入力電圧が一定になるように、該インバータが制御される。
　しかし、インバータへの入力電圧を一定にする制御を行うと、電力変換装置が不安定になることがあり、太陽電池にて生じるエネルギーを効率的に電力として活用することができなくなるという問題もあった。
　この発明は上述した事情に鑑みてなされたものであり、電力変換装置を高効率で安定して動作させる電力変換制御装置、発電システムおよび電力変換制御方法を提供することを目的とする。 By the way, the direct-current power obtained from a solar cell fluctuates with changes in the amount of sunlight and temperature. For this reason, when the direct-current power generated in the solar cell decreases and the output voltage decreases, the operation of the inverter may become unstable. For this reason, generally, when the output voltage of the solar cell reaches the lower limit value of the preset input voltage of the inverter, the inverter is controlled so that the input voltage to the inverter becomes constant.
However, if the input voltage to the inverter is controlled to be constant, the power conversion device may become unstable, and there is a problem that the energy generated in the solar cell cannot be used efficiently as power. It was.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a power conversion control device, a power generation system, and a power conversion control method for operating a power conversion device stably with high efficiency.
　上記課題を解決するため本発明の電力変換制御装置は、直流電源から出力された直流電圧が所定の閾値電圧を超えるとき、前記直流電圧を交流電圧に変換する電力変換装置に対して、出力電力が略一定になるように制御する定電力制御部と、前記直流電圧が前記閾値電圧以下であるとき、前記電力変換装置への入力電流が、前記直流電圧に対して単調増加の関係を有するように前記電力変換装置を制御する単調増加制御部と、を有することを特徴とする。 In order to solve the above problems, the power conversion control device of the present invention provides output power to a power conversion device that converts the DC voltage to an AC voltage when the DC voltage output from the DC power source exceeds a predetermined threshold voltage. When the DC voltage is equal to or lower than the threshold voltage, the input current to the power converter has a monotonically increasing relationship with the DC voltage. And a monotonic increase control unit for controlling the power converter.
　本発明によれば、電力変換装置を高効率で安定して動作させることができる。 According to the present invention, the power conversion device can be stably operated with high efficiency.
本発明の第１実施形態による太陽光発電システムのブロック図である。1 is a block diagram of a photovoltaic power generation system according to a first embodiment of the present invention. 第１実施形態におけるインバータの回路図である。It is a circuit diagram of the inverter in a 1st embodiment. 第１実施形態における制御プログラムのフローチャートである。It is a flowchart of the control program in 1st Embodiment. 第１実施形態において太陽電池特性が一定である場合の電力変換装置の動作特性図である。It is an operation characteristic figure of a power converter when a solar cell characteristic is constant in a 1st embodiment. 第１実施形態において太陽電池特性が変化する場合の電力変換装置の動作特性図である。It is an operation characteristic figure of a power converter when a solar cell characteristic changes in a 1st embodiment. 比較例における制御プログラムのフローチャートである。It is a flowchart of the control program in a comparative example. 比較例において太陽電池特性が変化する場合の電力変換装置の動作特性図である。It is an operation characteristic figure of a power converter when a solar cell characteristic changes in a comparative example. 本発明の第２実施形態による太陽光発電システムのブロック図である。It is a block diagram of the solar energy power generation system by 2nd Embodiment of this invention. 第２実施形態におけるコンバータの回路図である。It is a circuit diagram of the converter in a 2nd embodiment. 本発明の第３実施形態による太陽光発電システムのブロック図である。It is a block diagram of the solar energy power generation system by 3rd Embodiment of this invention.
［第１実施形態］
〈第１実施形態の構成〉
（全体構成）
　図１は、本発明の第１実施形態による太陽光発電システムＳ１のブロック図である。
　太陽光発電システムＳ１は、太陽電池１０（直流電源）と、電力変換装置２０と、センサ部３０と、電力変換制御装置４０とを有し、系統電圧源６０に接続されている。電力変換装置２０は、一般にＰＣＳ（Power Conditioning System）と呼ばれるものであり、平滑コンデンサ２１とインバータ２２とを有している。 [First Embodiment]
<Configuration of First Embodiment>
(overall structure)
FIG. 1 is a block diagram of a photovoltaic power generation system S1 according to the first embodiment of the present invention.
The solar power generation system S <b> 1 includes a solar battery 10 (DC power supply), a power conversion device 20, a sensor unit 30, and a power conversion control device 40, and is connected to a system voltage source 60. The power conversion device 20 is generally called a PCS (Power Conditioning System), and includes a smoothing capacitor 21 and an inverter 22.
　電力変換装置２０は、太陽電池１０から出力された直流電力を交流電力に変換し、系統電圧源６０に供給する。電力変換装置２０の入力端子をＡ点とし、Ａ点における電圧を入力電圧ＶDC（直流電圧）と呼び、電流を入力電流ＩDCと呼ぶ。また、インバータ２２の入力端子をＢ点とし、Ｂ点における電流を入力電流ＩINVと呼ぶ。
　図２は、インバータ２２の回路図である。図示のように、インバータ２２としては、フルブリッジ回路が一般に用いられる。 The power conversion device 20 converts the DC power output from the solar cell 10 into AC power and supplies it to the system voltage source 60. The input terminals of the power converter 20 and the point A, the voltage is referred to as the input voltage V DC (direct current voltage) of the point A, referred to as an input current I DC current. The input terminal of the inverter 22 is a point B, and the current at the point B is called an input current I INV .
FIG. 2 is a circuit diagram of the inverter 22. As shown, a full bridge circuit is generally used as the inverter 22.
　図１に戻り、センサ部３０は、インバータ２２の出力電流ＩACを測定する。出力電圧ＶACはインバータ２２の制御情報から演算または推定してもよい。或は、センサ部３０は、インバータ２２の出力電流ＩACに加えて出力電圧ＶACを測定してもよい。電力変換制御装置４０は、電力変換装置２０を制御する。電力変換制御装置４０は、ＣＰＵ（Central Processing Unit）、ＲＡＭ（Random Access Memory）、ＲＯＭ（Read Only Memory）等、一般的なコンピュータとしてのハードウエアを備えており、ＲＯＭには、ＣＰＵによって実行される制御プログラムや、各種データ等が格納されている。 Returning to FIG. 1, the sensor unit 30 measures the output current I AC of the inverter 22. The output voltage V AC may be calculated or estimated from the control information of the inverter 22. Alternatively, the sensor unit 30 may measure the output voltage V AC in addition to the output current I AC of the inverter 22. The power conversion control device 40 controls the power conversion device 20. The power conversion control device 40 includes hardware as a general computer such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The ROM is executed by the CPU. Control program and various data are stored.
　図１において、電力変換制御装置４０の内部は、制御プログラム等によって実現される機能を、ブロックとして示している。すなわち、電力変換制御装置４０は、入力電流演算部４１（単調増加制御部）と、有効電力演算部４２（単調増加制御部）と、ＭＰＰＴ演算部４４（定電力制御部）と、切替部４５と、有効電力制御部４６と、を有している。ここで、ＭＰＰＴ演算部４４は、太陽電池１０の発電能力が比較的高い時（例えば日照量が多いとき）に、インバータ２２の有効出力電力ＰAC（出力電力，図示せず）の指令値（ＰAC1*）を演算する。 In FIG. 1, the function of the power conversion control device 40 realized by a control program or the like is shown as a block. That is, the power conversion control device 40 includes an input current calculation unit 41 (monotonic increase control unit), an active power calculation unit 42 (monotonic increase control unit), an MPPT calculation unit 44 (constant power control unit), and a switching unit 45. And an active power control unit 46. Here, when the power generation capability of the solar cell 10 is relatively high (for example, when the amount of sunshine is large), the MPPT calculation unit 44 provides a command value (effective output power P AC (output power, not shown)) of the inverter 22 ( P AC1 *) is calculated.
　また、入力電流演算部４１は、太陽電池１０の発電能力が比較的低い時における電力変換装置２０の入力電流ＩDCの指令値（ＩDC*）を演算する。より具体的には、入力電流演算部４１は、電力変換装置２０の入力電圧ＶDCに対して所定の定数Ｋを乗算し、入力電流指令値ＩDC*（＝Ｋ・ＶDC）を出力する。なお、定数Ｋは、電力変換装置２０が出力しようとする目標電力や、太陽電池１０の特性等に応じて予め決定されている。 The input current calculating unit 41 calculates the command value of the input current I DC of the power converter 20 at the time is relatively low power generation capacity of the solar cell 10 (I DC *). More specifically, the input current calculation unit 41 multiplies the input voltage V DC of the power converter 20 by a predetermined constant K, and outputs an input current command value I DC * (= K · V DC ). . The constant K is determined in advance according to the target power to be output by the power conversion device 20, the characteristics of the solar cell 10, and the like.
　有効電力演算部４２は、入力電流指令値ＩDC*と、入力電圧ＶDCとを乗算し、低出力時における指令値ＰAC2*（＝ＩDC*・ＶDC）を演算する。切替部４５は、ＭＰＰＴ演算部４４および有効電力演算部４２から出力された指令値ＰAC1*，ＰAC2*のうち一方を選択し、選択したものを出力電力指令値ＰAC*として出力する。 The active power calculator 42 multiplies the input current command value I DC * and the input voltage V DC to calculate a command value P AC2 * (= I DC * · V DC ) at the time of low output. The switching unit 45 selects one of the command values P AC1 * and P AC2 * output from the MPPT calculation unit 44 and the active power calculation unit 42 and outputs the selected value as the output power command value P AC *.
　有効電力制御部４６は、電力変換装置２０の出力電圧ＶACおよび出力電流ＩACをセンサ部３０から受信し、インバータ２２の有効出力電力ＰACが出力電力指令値ＰAC*に近づくように、インバータ２２をフィードバック制御する。なお、センサ部３０はインバータ２２の出力電流ＩACのみを測定して、インバータ２２の制御情報から出力電圧ＶACを演算または推定してもよい。 The active power control unit 46 receives the output voltage V AC and the output current I AC of the power converter 20 from the sensor unit 30, and the effective output power P AC of the inverter 22 approaches the output power command value P AC *. The inverter 22 is feedback controlled. The sensor unit 30 may measure only the output current I AC of the inverter 22 and calculate or estimate the output voltage V AC from the control information of the inverter 22.
〈第１実施形態の動作〉
（全体動作）
　次に、図３を参照し、本実施形態の動作を説明する。なお、図３は、電力変換制御装置４０において実行される制御プログラムのフローチャートである。
　図３のステップＳ１００において処理が開始されると、ステップＳ１１０にて、電力変換制御装置４０は、入力電圧ＶDCが所定の閾値電圧ＶTH以下であるか否かを判定する。 <Operation of First Embodiment>
(Overall operation)
Next, the operation of this embodiment will be described with reference to FIG. FIG. 3 is a flowchart of a control program executed in the power conversion control device 40.
When the process is started in step S100 of FIG. 3, in step S110, the power conversion control device 40 determines whether or not the input voltage V DC is equal to or lower than a predetermined threshold voltage V TH .
　ステップＳ１１０において「Ｎｏ」と判定されると、ステップＳ１２０にて、電力変換制御装置４０の動作モードが通常制御モードに設定される。ここで、「通常制御モード」とは、切替部４５にてＭＰＰＴ演算部４４が演算した指令値ＰAC1*を出力電力指令値ＰAC*として選択する動作モードを指す。 If “No” is determined in step S110, the operation mode of the power conversion control device 40 is set to the normal control mode in step S120. Here, the “normal control mode” refers to an operation mode in which the command value P AC1 * calculated by the MPPT calculation unit 44 in the switching unit 45 is selected as the output power command value P AC *.
　一方、ステップＳ１１０において「Ｙｅｓ」と判定されると、処理はステップＳ１４０に進み、電力変換制御装置４０の動作モードが単調増加モードに設定される。ここで、「単調増加モード」とは、切替部４５にて有効電力演算部４２が演算した指令値ＰAC2*を出力電力指令値ＰAC*として選択する動作モードを指す。すなわち、この入力電流ＩDCに対して単調増加するように（すなわち、入力電流ＩDCが入力電圧ＶDCに比例するように）、入力電圧ＶDCを設定する制御を指す。 On the other hand, if “Yes” is determined in step S110, the process proceeds to step S140, and the operation mode of the power conversion control device 40 is set to the monotonically increasing mode. Here, the “monotonically increasing mode” refers to an operation mode in which the command value P AC2 * calculated by the active power calculation unit 42 in the switching unit 45 is selected as the output power command value P AC *. That is, as monotonically increasing with respect to the input current I DC (i.e., as the input current I DC is proportional to the input voltage V DC), refers to a control of setting the input voltage V DC.
　ステップＳ１２０またはステップＳ１４０の処理が終了すると、処理はステップＳ１１０に戻り、ステップＳ１１０以降の処理が繰り返される。従って、入力電圧ＶDCが閾値電圧ＶTH以下であれば、単調増加モードが維持され、入力電圧ＶDCが閾値電圧ＶTHを超えていれば、通常制御モードが維持される。 When the process of step S120 or step S140 ends, the process returns to step S110, and the processes after step S110 are repeated. Therefore, if the input voltage V DC is less than or equal to the threshold voltage V TH , the monotonically increasing mode is maintained, and if the input voltage V DC exceeds the threshold voltage V TH , the normal control mode is maintained.
（通常制御モードの詳細）
　次に、上述した通常制御モード（Ｓ１２０）の詳細を説明する。
　電力変換装置２０への入力電流ＩDCおよび入力電圧ＶDCの動作点には、両者の積すなわち入力電力ＰDCが最大になる最大電力点が存在する。そこで、この最大電力点を追跡して入力電力ＰDCを最大化しようとする技術が知られており、この技術はＭＰＰＴ（Maximum power Point Tracking；最大電力点追従）と称される。本実施形態の通常制御モード（Ｓ１２０）も、このＭＰＰＴを実行するものである。 (Details of normal control mode)
Next, details of the above-described normal control mode (S120) will be described.
At the operating point of the input current I DC and the input voltage V DC to the power converter 20, there is a maximum power point at which the product of both, that is, the input power P DC becomes maximum. Therefore, it is known art to attempt to maximize the input power P DC tracking this maximum power point, this technique MPPT; called (Maximum power Point Tracking maximum power point tracking). The normal control mode (S120) of this embodiment also executes this MPPT.
　但し、最大電力点は、太陽電池１０の経年変化や太陽電池１０の汚れ具合によっても変化するため、日照量等に基づいて一意に決定することは容易ではない。従って、実際に入力電圧ＶDC等の条件を変化させながら入力電力ＰDCを計測し、最大電力点を求めてゆくことが一般的である。このため、ＭＰＰＴによる指令値ＰAC1*の更新頻度は低く、例えば数秒に１回、あるいは数十秒に１回程度の頻度になる。従って、短い時間（例えば数百ｍｓ程度）の動作を想定すると、ＭＰＰＴ演算部４４は、一定の指令値ＰAC1*を出力し続けるものである。 However, since the maximum power point changes depending on the secular change of the solar cell 10 and the degree of contamination of the solar cell 10, it is not easy to determine it uniquely based on the amount of sunlight. Therefore, it is general to measure the input power P DC while actually changing the conditions such as the input voltage V DC to find the maximum power point. For this reason, the update frequency of the command value P AC1 * by the MPPT is low, for example, once every few seconds or once every several tens of seconds. Therefore, assuming an operation for a short time (for example, about several hundred ms), the MPPT calculation unit 44 continues to output a constant command value P AC1 *.
　図４は、太陽電池特性が一定である場合の電力変換装置２０の動作特性図である。上述したように、ＶDCおよびＩDCは、電力変換装置２０への入力電圧および入力電流であり、ＩINVは、インバータ２２への入力電流である。
　図４において、太陽電池特性Ｌ1は、太陽電池１０によって実現される特性であり、電力変換装置２０の入力電流ＩDC（太陽電池１０から電力変換装置２０への出力電流）が大きくなるほど、電力変換装置２０の入力電圧ＶDCが低下する傾向がある。 FIG. 4 is an operation characteristic diagram of the power conversion device 20 when the solar cell characteristics are constant. As described above, V DC and I DC are the input voltage and input current to the power conversion device 20, and I INV is the input current to the inverter 22.
In FIG. 4, the solar cell characteristic L 1 is a characteristic realized by the solar cell 10, and as the input current I DC (output current from the solar cell 10 to the power converter 20) of the power converter 20 increases, the power The input voltage VDC of the converter 20 tends to decrease.
　また、定電力特性Ｌ2は、ＭＰＰＴ演算部４４が出力する指令値ＰAC1*に基づいて、有効電力制御部４６が実現しようとする特性である。上述したように、短い時間の動作を想定すると、ＭＰＰＴ演算部４４は、一定の指令値ＰAC1*を出力し続けるため、該指令値ＰAC1*が出力電力指令値ＰAC*として選択されると、有効電力制御部４６は、定電力特性Ｌ2に従って、インバータ２２を制御する。 The constant power characteristic L 2 is a characteristic that the active power control unit 46 intends to realize based on the command value P AC1 * output from the MPPT calculation unit 44. As described above, assuming the operation of a short time, MPPT computing unit 44 is selected as to continue to output a constant command value P AC1 *, finger command value P AC1 * output power command value P AC * When active power control unit 46 in accordance with the constant-power characteristic L 2, controls the inverter 22.
　図４において、ある瞬間に、電力変換装置２０への入力電圧ＶDCが図４に示す電圧Ｖaになったとする。すると、図１に示したＡ点における動作点は、太陽電池特性Ｌ1上の動作点Ａ1になり、Ｂ点における動作点は、定電力特性Ｌ2上の動作点Ｂ1になる。すなわち、電力変換装置２０への入力電流ＩDCよりもインバータ２２への入力電流ＩINVが大きくなる。すると、両電流の差に相当する電荷が平滑コンデンサ２１から放電され、平滑コンデンサ２１の端子電圧すなわち入力電圧ＶDCが低下してゆく。これにより、Ａ点，Ｂ点の動作点は、動作点Ａ2＝Ｂ2に向かって移動する。 4, at a certain moment, and the input voltage V DC to the power converter 20 becomes the voltage V a shown in FIG. Then, the operating point at the point A shown in FIG. 1 is the operating point A 1 on the solar cell characteristic L 1 , and the operating point at the point B is the operating point B 1 on the constant power characteristic L 2 . That is, the input current I INV to the inverter 22 becomes larger than the input current I DC to the power converter 20. Then, the electric charge corresponding to the difference between the two currents is discharged from the smoothing capacitor 21, and the terminal voltage of the smoothing capacitor 21, that is, the input voltage VDC decreases. As a result, the operating points A and B move toward the operating point A 2 = B 2 .
　また、ある瞬間に入力電圧ＶDCが図４に示す電圧Ｖbになったとする。すると、Ａ点における動作点は、太陽電池特性Ｌ1上の動作点Ａ3になり、Ｂ点における動作点は、定電力特性Ｌ2上の動作点Ｂ3になる。すなわち、インバータ２２への入力電流ＩINVよりも電力変換装置２０への入力電流ＩDCが大きくなる。すると、両電流の差に相当する電荷が平滑コンデンサ２１に充電され、平滑コンデンサ２１の端子電圧すなわち入力電圧ＶDCが上昇してゆく。これにより、Ａ点，Ｂ点の動作点は、やはり動作点Ａ2＝Ｂ2に向かって移動する。従って、動作点Ａ2＝Ｂ2は、安定な動作点になる。 Further, assume that the input voltage V DC becomes the voltage V b shown in FIG. 4 at a certain moment. Then, the operating point at the point A becomes the operating point A 3 on the solar cell characteristic L 1 , and the operating point at the point B becomes the operating point B 3 on the constant power characteristic L 2 . That is, the input current I DC to the power conversion apparatus 20 than the input current I INV to the inverter 22 increases. Then, the electric charge corresponding to the difference between the two currents is charged in the smoothing capacitor 21, and the terminal voltage of the smoothing capacitor 21, that is, the input voltage V DC increases. As a result, the operating points at points A and B are also moved toward the operating point A 2 = B 2 . Therefore, the operating point A 2 = B 2 is a stable operating point.
　また、ある瞬間に入力電圧ＶDCが図１に示す電圧Ｖcになったとする。Ａ点における動作点は、太陽電池特性Ｌ1上の動作点Ａ4になり、Ｂ点における動作点は、定電力特性Ｌ2上の動作点Ｂ4になる。すなわち、電力変換装置２０への入力電流ＩDCよりもインバータ２２への入力電流ＩINVが大きくなる。すると、両電流の差に相当する電荷が平滑コンデンサ２１から放電され、入力電圧ＶDCが低下してゆく。その結果、時間の経過とともに、入力電圧ＶDCは零電圧に向かう。 Also, assume that the input voltage V DC becomes the voltage V c shown in FIG. 1 at a certain moment. The operating point at point A is the operating point A 4 on the solar cell characteristic L 1 , and the operating point at point B is the operating point B 4 on the constant power characteristic L 2 . That is, the input current I INV to the inverter 22 becomes larger than the input current I DC to the power converter 20. Then, the electric charge corresponding to the difference between the two currents is discharged from the smoothing capacitor 21, and the input voltage VDC decreases. As a result, the input voltage V DC goes to zero voltage as time passes.
　従って、電圧ＶLIMにおける特性Ｌ1，Ｌ2の交点は、動作が安定する動作点ではなく、不安定な動作点である。そこで、この電圧ＶLIMを「安定動作限界電圧」と呼ぶ。図３のステップＳ１１０において述べた閾値電圧ＶTHは、図４に示すように、安定動作限界電圧ＶLIMよりも若干高い（若干の余裕がある）値に設定されている。従って、実際には、入力電圧ＶDCが安定動作限界電圧ＶLIMに至る前に、動作モードは単調増加モード（Ｓ１４０）に遷移する。 Therefore, the intersection of the characteristics L 1 and L 2 at the voltage V LIM is not an operating point where the operation is stable, but an unstable operating point. Therefore, this voltage V LIM is referred to as “stable operation limit voltage”. As shown in FIG. 4, the threshold voltage V TH described in step S110 in FIG. 3 is set to a value that is slightly higher (with a slight margin) than the stable operation limit voltage V LIM . Therefore, actually, before the input voltage V DC reaches the stable operation limit voltage V LIM , the operation mode transits to the monotonically increasing mode (S140).
（単調増加モードの詳細）
　次に、上述した単調増加モード（Ｓ１４０）の詳細を説明する。
　図５は、太陽電池特性が変化する場合の電力変換装置の動作特性図である。
　図５において、特性Ｌ11～Ｌ14は、順次日照量が低下し、発電能力が低下した場合における太陽電池特性である。また、特性Ｌ3は、有効電力制御部４６によって実現しようとする特性である。入力電圧ＶDCが閾値電圧ＶTHを超える範囲においては、動作モードは通常制御モードになるため、特性Ｌ3は、当該範囲においては、定電力特性Ｌ2（図４参照）と同様である。但し、入力電圧ＶDCが閾値電圧ＶTH以下の範囲では、動作モードが単調増加モードになるため、特性Ｌ3は、入力電流ＩDCが入力電圧ＶDCに比例する特性になっている。 (Details of monotonic increase mode)
Next, details of the above-described monotonic increase mode (S140) will be described.
FIG. 5 is an operation characteristic diagram of the power conversion device when the solar cell characteristics change.
In FIG. 5, characteristics L 11 to L 14 are solar cell characteristics when the amount of sunshine decreases sequentially and the power generation capacity decreases. The characteristic L 3 is a characteristic to be realized by the active power control unit 46. In the range where the input voltage V DC exceeds the threshold voltage V TH , the operation mode is the normal control mode. Therefore, the characteristic L 3 is the same as the constant power characteristic L 2 (see FIG. 4) in the range. However, since the operation mode is a monotonically increasing mode when the input voltage V DC is equal to or lower than the threshold voltage V TH , the characteristic L 3 is a characteristic in which the input current I DC is proportional to the input voltage V DC .
　図５において、太陽電池特性がＬ11であるとき、安定な動作点はＱ1になる。太陽電池１０の発電能力が低下し、太陽電池特性がＬ12になると、安定な動作点はＱ2になる。ここで、動作点Ｑ2における入力電圧ＶDCは、閾値電圧ＶTHに一致している。従って、入力電圧ＶDCがさらに低下すると、動作モードは単調増加モードになる。 In FIG. 5, when the solar cell characteristic is L 11 , the stable operating point is Q 1 . When the power generation capacity of the solar cell 10 is reduced and the solar cell characteristic becomes L 12 , the stable operating point becomes Q 2 . Here, the input voltage V DC at the operating point Q 2 matches the threshold voltage V TH . Therefore, when the input voltage V DC further decreases, the operation mode becomes a monotonically increasing mode.
　単調増加モードにおいて太陽電池１０の発電能力がさらに低下し、太陽電池特性がＬ13になると、安定な動作点はＱ3になり、太陽電池特性がＬ14になると、安定な動作点はＱ4になる。このように、特性Ｌ3は、定電力特性と、比例特性とを組み合わせたものであるため、様々な太陽電池特性Ｌ11～Ｌ14において、安定な動作点Ｑ1～Ｑ4が存在する。 When the power generation capability of the solar cell 10 further decreases in the monotonically increasing mode and the solar cell characteristic becomes L 13 , the stable operating point becomes Q 3 , and when the solar cell characteristic becomes L 14 , the stable operating point becomes Q 4. become. As described above, the characteristic L 3 is a combination of the constant power characteristic and the proportional characteristic. Therefore, there are stable operating points Q 1 to Q 4 in various solar cell characteristics L 11 to L 14 .
〈比較例〉
　次に、本実施形態の効果を明らかにするため、比較例について説明する。
　比較例の構成は、第１実施形態のもの（図１参照）と同様であるが、入力電流演算部４１および有効電力演算部４２に代えて、定電圧演算部（図示せず）が設けられる点が異なる。この図示せぬ定電圧演算部は、入力電圧ＶDCが閾値電圧ＶTHと一致するような指令値ＰAC2*を演算し、切替部４５に出力する。 <Comparative example>
Next, in order to clarify the effect of the present embodiment, a comparative example will be described.
The configuration of the comparative example is the same as that of the first embodiment (see FIG. 1), but a constant voltage calculation unit (not shown) is provided instead of the input current calculation unit 41 and the active power calculation unit 42. The point is different. The constant voltage calculation unit (not shown) calculates a command value P AC2 * such that the input voltage V DC matches the threshold voltage V TH and outputs the command value P AC2 * to the switching unit 45.
　図６は、本比較例において電力変換制御装置４０にて実行される制御プログラムのフローチャートである。第１実施形態のフローチャート（図３参照）と比較すると、第１実施形態におけるステップＳ１４０に代えて、本比較例では、ステップＳ１３０が実行される。すなわち、入力電圧ＶDCが閾値電圧ＶTH以下になると、処理はステップＳ１３０に進み、動作モードが定電圧モードに設定される。ここで「定電圧モード」とは、図示せぬ定電圧演算部が出力する指令値ＰAC2*を出力電力指令値ＰAC*として選択する動作モードを指す。 FIG. 6 is a flowchart of a control program executed by the power conversion control device 40 in this comparative example. Compared to the flowchart of the first embodiment (see FIG. 3), step S130 is executed in this comparative example instead of step S140 in the first embodiment. That is, when the input voltage V DC becomes equal to or lower than the threshold voltage V TH , the process proceeds to step S130, and the operation mode is set to the constant voltage mode. Here, the “constant voltage mode” refers to an operation mode in which a command value P AC2 * output by a constant voltage calculation unit (not shown) is selected as the output power command value P AC *.
　図７は、本比較例にて太陽電池特性が変化する場合の電力変換装置２０の動作特性図である。
　図７において、特性Ｌ11～Ｌ14は、図５に示したものと同様である。また、特性Ｌ4は、本比較例の有効電力制御部４６（図１参照）によって実現しようとする特性である。入力電圧ＶDCが閾値電圧ＶTHを超える範囲においては、動作モードは通常制御モードになるため、特性Ｌ4は、当該範囲においては、定電力特性Ｌ2（図４参照）と同様である。但し、太陽電池１０の発電能力がさらに低下すると、動作モードが定電圧モードになるため、特性Ｌ4では、入力電圧ＶDCが一定値（閾値電圧ＶTH）になる。 FIG. 7 is an operation characteristic diagram of the power conversion device 20 when the solar cell characteristics change in this comparative example.
In FIG. 7, the characteristics L 11 to L 14 are the same as those shown in FIG. The characteristic L 4 is a characteristic to be realized by the active power control unit 46 (see FIG. 1) of this comparative example. In the range where the input voltage V DC exceeds the threshold voltage V TH , the operation mode is the normal control mode. Therefore, the characteristic L 4 is the same as the constant power characteristic L 2 (see FIG. 4) in the range. However, when the power generation capacity of the solar cell 10 further decreases, the operation mode becomes the constant voltage mode, and therefore the input voltage VDC becomes a constant value (threshold voltage V TH ) in the characteristic L 4 .
　図７において、太陽電池特性がＬ11，Ｌ12であるとき、図５の場合と同様に、安定な動作点はＱ1，Ｑ2になる。動作点Ｑ2における入力電圧ＶDCは、閾値電圧ＶTHに一致しているため、太陽電池１０の発電能力がさらに低下すると、動作モードは定電圧モードになる。そして、太陽電池特性がＬ13になると、安定な動作点はＱ13になり、太陽電池特性がＬ14になると、安定な動作点は存在しなくなる。安定な動作点が存在しない場合、電力変換制御装置４０は、電力変換装置２０を停止させ、電力変換装置２０を再起動させる。 In FIG. 7, when the solar cell characteristics are L 11 and L 12 , the stable operating points are Q 1 and Q 2 as in the case of FIG. Since the input voltage V DC at the operating point Q 2 matches the threshold voltage V TH, when the power generation capability of the solar cell 10 further decreases, the operation mode becomes the constant voltage mode. When the solar cell characteristic becomes L 13 , the stable operating point becomes Q 13 , and when the solar cell characteristic becomes L 14 , there is no stable operating point. When there is no stable operating point, the power conversion control device 40 stops the power conversion device 20 and restarts the power conversion device 20.
　このように、比較例（図７）によれば、太陽電池１０の発電能力が大きく低下すると（太陽電池特性がＬ14になると）、安定な動作点が存在しなくなり、電力変換装置２０が動作を継続できなくなる。また、太陽電池特性Ｌ13に対しては、安定な動作点Ｑ13は存在するが、動作点Ｑ13における入力電流ＩDCが低いため、太陽電池１０から効率的に電力を取り出せないという問題がある。 Thus, according to the comparative example (FIG. 7), when the power generation capability of the solar cell 10 is greatly reduced (when the solar cell characteristic is L 14 ), there is no stable operating point, and the power conversion device 20 operates. Can not continue. Further, for the solar cell characteristics L 13, although a stable operating point Q 13 is present, since the input current I DC at the operating point Q 13 is low, a problem that can not be extracted efficiently power from the solar cell 10 is there.
〈実施形態の効果〉
　上述したように、本実施形態（図５）によれば、太陽電池１０の発電能力が低下した場合においても（何れの太陽電池特性Ｌ11～Ｌ14においても）、安定な動作点Ｑ1～Ｑ4が存在する。これにより、太陽電池１０の発電能力が急に低下した場合においても、電力変換装置２０を継続的に動作させることができる。さらに、本実施形態（図５）によれば、発電能力が低い太陽電池特性Ｌ13，Ｌ14においても、動作点Ｑ3，Ｑ4における入力電流ＩDCは比較的大きな値にすることができ、太陽電池１０から効率的に電力を取り出せるという効果を奏する。 <Effect of the embodiment>
As described above, according to the present embodiment (FIG. 5), even when the power generation capacity of the solar cell 10 is reduced (in any of the solar cell characteristics L 11 to L 14 ), the stable operating point Q 1 to Q 4 is present. Thereby, even when the power generation capability of the solar cell 10 suddenly decreases, the power conversion device 20 can be continuously operated. Furthermore, according to the present embodiment (FIG. 5), even in the power generation capacity is low solar cell characteristics L 13, L 14, the input current I DC at the operating point Q 3, Q 4 may be a relatively large value The effect is that power can be efficiently extracted from the solar cell 10.
［第２実施形態］
　図８は、本発明の第２実施形態による太陽光発電システムＳ２のブロック図である。なお、図８において、図１～図７の各部に対応する部分には同一の符号を付し、その説明を省略する場合がある。
　太陽光発電システムＳ２は、第１実施形態の太陽光発電システムＳ１（図１参照）と比較すると、電力変換装置２０に代えて電力変換装置２０Ａが適用されている。それ以外の太陽光発電システムＳ２の構成は、第１実施形態のものと同様である。電力変換装置２０Ａにおいては、入力端子（Ａ点）と、平滑コンデンサ２１との間に、平滑コンデンサ２４と、コンバータ２３とが挿入されている。 [Second Embodiment]
FIG. 8 is a block diagram of a photovoltaic power generation system S2 according to the second embodiment of the present invention. In FIG. 8, parts corresponding to those in FIGS. 1 to 7 are denoted by the same reference numerals, and description thereof may be omitted.
When compared with the photovoltaic power generation system S1 (see FIG. 1) of the first embodiment, the photovoltaic power generation system S2 is applied with a power conversion device 20A instead of the power conversion device 20. The other configuration of the solar power generation system S2 is the same as that of the first embodiment. In the power conversion device 20 </ b> A, a smoothing capacitor 24 and a converter 23 are inserted between the input terminal (point A) and the smoothing capacitor 21.
　図９は、コンバータ２３の回路図である。コンバータ２３に入力された直流電圧は、フルブリッジ回路２３ａにおいて交流電圧に変換される。該交流電圧は、共振コンデンサ２３ｄおよび絶縁トランス２３ｃを介して昇圧または降圧され、ダイオードブリッジ２３ｂに供給される。ダイオードブリッジ２３ｂでは、昇圧または降圧された交流電圧が整流され、出力される。このように、コンバータ２３は、入力された直流電圧を昇圧または降圧して出力する。 FIG. 9 is a circuit diagram of the converter 23. The DC voltage input to the converter 23 is converted into an AC voltage in the full bridge circuit 23a. The AC voltage is stepped up or stepped down through the resonant capacitor 23d and the insulating transformer 23c and supplied to the diode bridge 23b. In the diode bridge 23b, the boosted or stepped down AC voltage is rectified and output. Thus, the converter 23 boosts or steps down the input DC voltage and outputs it.
　本実施形態の動作は、第１実施形態のものと同様である。但し、本実施形態においては、コンバータ２３は、電力変換装置２０Ａに入力された直流電圧を昇圧または降圧してインバータ２２に供給する。特に、直流電圧を昇圧してインバータ２２に供給する場合、インバータ２２の効率を高めることができる。 The operation of this embodiment is the same as that of the first embodiment. However, in the present embodiment, the converter 23 boosts or steps down the DC voltage input to the power conversion device 20 </ b> A and supplies it to the inverter 22. In particular, when the DC voltage is boosted and supplied to the inverter 22, the efficiency of the inverter 22 can be increased.
［第３実施形態］
　次に、図１０は、本発明の第３実施形態による太陽光発電システムＳ３のブロック図である。なお、図１０において、図１～図９の各部に対応する部分には同一の符号を付し、その説明を省略する場合がある。
　太陽光発電システムＳ３は、第２実施形態の太陽光発電システムＳ２（図８参照）と比較すると、電力変換装置２０Ａに代えて電力変換装置２０Ｂが適用されている。電力変換装置２０Ｂにおいては、複数系統の平滑コンデンサ２４、コンバータ２３、平滑コンデンサ２１およびインバータ２２が設けられている。 [Third Embodiment]
Next, FIG. 10 is a block diagram of a photovoltaic power generation system S3 according to the third embodiment of the present invention. In FIG. 10, parts corresponding to those in FIGS. 1 to 9 are denoted by the same reference numerals, and description thereof may be omitted.
When compared with the photovoltaic power generation system S2 (see FIG. 8) of the second embodiment, the photovoltaic power generation system S3 is applied with a power conversion device 20B instead of the power conversion device 20A. In power converter 20B, a plurality of systems of smoothing capacitor 24, converter 23, smoothing capacitor 21, and inverter 22 are provided.
　ここで、これら個々の構成要素２１～２４の構成は、第２実施形態のものと同様である。本実施形態において、複数のインバータ２２は、直列に接続されている。上記以外の太陽光発電システムＳ３の構成は、第２実施形態のものと同様である。本実施形態によれば、複数のインバータ２２が直列接続されるため、電力変換装置２０Ｂは、より高い交流電圧を出力できる。 Here, the configuration of these individual components 21 to 24 is the same as that of the second embodiment. In the present embodiment, the plurality of inverters 22 are connected in series. The configuration of the photovoltaic power generation system S3 other than the above is the same as that of the second embodiment. According to this embodiment, since the some inverter 22 is connected in series, the power converter device 20B can output a higher alternating voltage.
［変形例］
　本発明は上述した実施形態に限定されるものではなく、種々の変形が可能である。上述した実施形態は本発明を理解しやすく説明するために例示したものであり、必ずしも説明した全ての構成を備えるものに限定されるものではない。また、ある実施形態の構成の一部を他の実施形態の構成に置き換えることが可能であり、また、ある実施形態の構成に他の実施形態の構成を加えることも可能である。また、各実施形態の構成の一部について削除し、若しくは他の構成の追加・置換をすることが可能である。また、図中に示した制御線や情報線は説明上必要と考えられるものを示しており、製品上で必要な全ての制御線や情報線を示しているとは限らない。実際には殆ど全ての構成が相互に接続されていると考えてもよい。上記実施形態に対して可能な変形は、例えば以下のようなものである。 [Modification]
The present invention is not limited to the above-described embodiments, and various modifications can be made. The above-described embodiments are illustrated for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. Further, it is possible to delete a part of the configuration of each embodiment, or to add or replace another configuration. In addition, the control lines and information lines shown in the figure are those that are considered necessary for the explanation, and not all the control lines and information lines that are necessary on the product are shown. Actually, it may be considered that almost all the components are connected to each other. Examples of possible modifications to the above embodiment are as follows.
（１）上記各実施形態においては、直流電源の例として太陽電池１０を適用した例を説明した。しかし、直流電源は、太陽電池１０に限定されるわけではなく、一次電池、二次電池、風力発電装置、推力発電装置等、種々の直流電源を適用することができる。 (1) In each of the above embodiments, an example in which the solar cell 10 is applied as an example of a DC power source has been described. However, the DC power source is not limited to the solar battery 10, and various DC power sources such as a primary battery, a secondary battery, a wind power generator, and a thrust power generator can be applied.
（２）上記各実施形態においては、「単調増加モード（Ｓ１４０）」として、入力電圧ＶDCと入力電流ＩDCとに比例関係を付与した例を説明した。しかし、単調増加モードにおいて、入力電圧ＶDCと入力電流ＩDCとは、必ずしも比例関係を有しなくてもよい。例えば、様々な太陽電池特性（図５のＬ12，Ｌ13，Ｌ14等）において、太陽電池１０から最大出力が取り出せる動作点を求め、これら動作点を結んだ特性を単調増加モードにおける特性として適用してもよい。 (2) In each of the above-described embodiments, the example in which the input voltage V DC and the input current I DC are proportional to each other has been described as the “monotonically increasing mode (S140)”. However, in the monotonically increasing mode, the input voltage V DC and the input current I DC do not necessarily have a proportional relationship. For example, in various solar cell characteristics (L 12 , L 13 , L 14, etc. in FIG. 5), an operating point at which the maximum output can be extracted from the solar cell 10 is obtained, and the characteristics connecting these operating points are used as the characteristics in the monotonically increasing mode. You may apply.
（３）上記各実施形態における電力変換制御装置４０のハードウエアは一般的なコンピュータによって実現できるため、図３に示したフローチャートに係るプログラム等を記憶媒体に格納し、または伝送路を介して頒布してもよい。 (3) Since the hardware of the power conversion control device 40 in each of the above embodiments can be realized by a general computer, the program or the like according to the flowchart shown in FIG. 3 is stored in a storage medium or distributed via a transmission line May be.
（４）また、図３に示した処理は、上記各実施形態ではプログラムを用いたソフトウエア的な処理として説明したが、その一部または全部をＡＳＩＣ(Application Specific Integrated Circuit；特定用途向けＩＣ)、あるいはＦＰＧＡ(field-programmable gate array)等を用いたハードウエア的な処理に置き換えてもよい。 (4) In addition, the processing shown in FIG. 3 has been described as software processing using a program in each of the above-described embodiments, but part or all of the processing is ASIC (Application Specific Integrated Circuit). Alternatively, it may be replaced with hardware processing using FPGA (field-programmable gate array) or the like.
（５）図２に示したインバータ２２の回路図や、図９に示したコンバータ２３の回路図は、何れも一例であり、その他種々の回路構成を有するインバータまたはコンバータを適用してもよい。 (5) The circuit diagram of the inverter 22 shown in FIG. 2 and the circuit diagram of the converter 23 shown in FIG. 9 are only examples, and other inverters or converters having various circuit configurations may be applied.
１０　太陽電池（直流電源）
２０，２０Ａ，２０Ｂ　電力変換装置
２２　インバータ
２３　コンバータ
４０　電力変換制御装置
４１　入力電流演算部（単調増加制御部）
４２　有効電力演算部（単調増加制御部）
４４　ＭＰＰＴ演算部（定電力制御部）
４５　切替部
４６　有効電力制御部
Ｓ１～Ｓ３　太陽光発電システム（発電システム）
ＩDC　入力電流
ＰAC　有効出力電力（出力電力）
ＶDC　入力電圧（直流電圧）
ＶTH　閾値電圧 10 Solar cell (DC power supply)
20, 20A, 20B Power conversion device 22 Inverter 23 Converter 40 Power conversion control device 41 Input current calculation unit (monotonic increase control unit)
42 Active power calculation unit (monotonic increase control unit)
44 MPPT calculation unit (constant power control unit)
45 Switching unit 46 Active power control unit S1 to S3 Solar power generation system (power generation system)
I DC input current P AC effective output power (output power)
V DC input voltage (DC voltage)
V TH threshold voltage

Claims (7)

  1. 　直流電源から出力された直流電圧が所定の閾値電圧を超えるとき、前記直流電圧を交流電圧に変換する電力変換装置に対して、出力電力が略一定になるように制御する定電力制御部と、
    　前記直流電圧が前記閾値電圧以下であるとき、前記電力変換装置への入力電流が、前記直流電圧に対して単調増加の関係を有するように前記電力変換装置を制御する単調増加制御部と、
    　を有することを特徴とする電力変換制御装置。     A constant power control unit that controls the output power to be substantially constant with respect to the power conversion device that converts the DC voltage into an AC voltage when the DC voltage output from the DC power source exceeds a predetermined threshold voltage;
    When the DC voltage is equal to or lower than the threshold voltage, a monotonic increase control unit that controls the power converter such that an input current to the power converter has a monotonically increasing relationship with the DC voltage;
    A power conversion control device comprising:
  2. 　前記直流電源は太陽電池である
    　ことを特徴とする請求項１に記載の電力変換制御装置。     The power conversion control device according to claim 1, wherein the DC power supply is a solar battery.
  3. 　前記単調増加制御部は、前記直流電圧と前記入力電流とが比例関係を有するように、前記電力変換装置を制御する
    　ことを特徴とする請求項１に記載の電力変換制御装置。     The power conversion control device according to claim 1, wherein the monotonous increase control unit controls the power conversion device so that the DC voltage and the input current have a proportional relationship.
  4. 　前記電力変換装置は、前記直流電圧を昇圧または降圧するコンバータと、
    　前記コンバータの出力電圧を前記交流電圧に変換するインバータと、
    　を有することを特徴とする請求項１に記載の電力変換制御装置。     The power converter includes a converter that boosts or steps down the DC voltage;
    An inverter that converts the output voltage of the converter into the AC voltage;
    The power conversion control device according to claim 1, comprising:
  5. 　前記電力変換装置は、前記コンバータを複数有するとともに前記インバータを複数有し、
    　複数の前記インバータは直列に接続されている
    　ことを特徴とする請求項４に記載の電力変換制御装置。     The power converter has a plurality of the converters and a plurality of the inverters,
    The power inverter control device according to claim 4, wherein the plurality of inverters are connected in series.
  6. 　発電によって直流電圧を出力する直流電源と、
    　前記直流電圧を交流電圧に変換する電力変換装置と、
    　前記直流電源から出力された前記直流電圧が所定の閾値電圧を超えるとき、前記電力変換装置に対して、出力電力が略一定になるように制御する定電力制御部と、
    　前記直流電圧が前記閾値電圧以下であるとき、前記電力変換装置への入力電流が、前記直流電圧に対して単調増加の関係を有するように前記電力変換装置を制御する単調増加制御部と、
    　を有することを特徴とする発電システム。     A DC power supply that outputs a DC voltage by power generation;
    A power converter for converting the DC voltage into an AC voltage;
    A constant power control unit that controls the power converter so that output power is substantially constant when the DC voltage output from the DC power source exceeds a predetermined threshold voltage;
    When the DC voltage is equal to or lower than the threshold voltage, a monotonic increase control unit that controls the power converter such that an input current to the power converter has a monotonically increasing relationship with the DC voltage;
    A power generation system comprising:
  7. 　直流電源から出力された直流電圧を交流電圧に変換する電力変換装置を制御する電力変換制御方法であって、
    　前記直流電源から出力された前記直流電圧が所定の閾値電圧を超えるとき、前記電力変換装置に対して、出力電力が略一定になるように制御し、
    　前記直流電圧が前記閾値電圧以下であるとき、前記電力変換装置への入力電流が、前記直流電圧に対して単調増加の関係を有するように前記電力変換装置を制御する
    　ことを特徴とする電力変換制御方法。     A power conversion control method for controlling a power converter that converts a DC voltage output from a DC power source into an AC voltage,
    When the DC voltage output from the DC power source exceeds a predetermined threshold voltage, the power converter is controlled so that the output power is substantially constant,
    When the DC voltage is equal to or lower than the threshold voltage, the power converter is controlled so that an input current to the power converter has a monotonically increasing relationship with the DC voltage. Control method.
PCT/JP2018/005974 2017-03-01 2018-02-20 Power conversion control device, power generation system, and power conversion control method WO2018159383A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2017-037964 2017-03-01
JP2017037964 2017-03-01

Publications (1)

Publication Number Publication Date
WO2018159383A1 true WO2018159383A1 (en) 2018-09-07

Family

ID=63371067

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2018/005974 WO2018159383A1 (en) 2017-03-01 2018-02-20 Power conversion control device, power generation system, and power conversion control method

Country Status (1)

Country Link
WO (1) WO2018159383A1 (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63133214A (en) * 1986-11-26 1988-06-06 Nissin Electric Co Ltd Inverter control system for system linking photovoltaic power generating device
WO1988004801A1 (en) * 1986-12-19 1988-06-30 Stuart Maxwell Watkinson Electrical power transfer apparatus
WO2005020420A1 (en) * 2003-08-22 2005-03-03 The Circle For The Promotion Of Science And Engineering Power converter, motor drive, btb system and system linking inverter system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63133214A (en) * 1986-11-26 1988-06-06 Nissin Electric Co Ltd Inverter control system for system linking photovoltaic power generating device
WO1988004801A1 (en) * 1986-12-19 1988-06-30 Stuart Maxwell Watkinson Electrical power transfer apparatus
WO2005020420A1 (en) * 2003-08-22 2005-03-03 The Circle For The Promotion Of Science And Engineering Power converter, motor drive, btb system and system linking inverter system

Similar Documents

Publication Publication Date Title
JP4457692B2 (en) Maximum power tracking control method and power conversion device
JP5320144B2 (en) Solar cell maximum output power tracking control device
JP5773368B2 (en) Method and apparatus for improving burst mode during power conversion
AU2020353609B2 (en) Optimizer, photovoltaic power generation system, and iv curve scanning method for photovoltaic module
US10447070B2 (en) Solar energy system with built-in battery charger and its method
KR102308628B1 (en) Hybrid Power Conversion System and Method for Determining Maximum Efficiency Using the Same
WO2022087955A1 (en) Bus voltage control method and apparatus for photovoltaic system
US20130030587A1 (en) System and method for power curtailment in a power network
JP6539172B2 (en) Power supply
US11437823B2 (en) Power systems with inverter input voltage control
JPWO2016157632A1 (en) Solar cell-storage battery cooperation system and power conversion control device
US8942017B2 (en) Energy storage system and method thereof
WO2015059516A1 (en) Double-stage inverter apparatus for energy conversion systems and control method thereof
JP2000341959A (en) Power generating system
WO2015145971A1 (en) Power conversion device and power conversion method
JP6106568B2 (en) Power converter
KR20190101672A (en) Solar generating system of maximum powr tracking control
AU2023200028B2 (en) Alternating current electrolysis system, and method and device for controlling the same
WO2018159383A1 (en) Power conversion control device, power generation system, and power conversion control method
WO2022107583A1 (en) Power system and method for controlling power system
JP2007317072A (en) Photovoltaic power generation system
EP4266542A1 (en) Power converter, power system, and control method for power converter
US20240014658A1 (en) Direct current/direct current converter and control method thereof
JP7051156B2 (en) Power control system
US11979021B2 (en) Electric power system and power conversion device connected to a DC bus

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 18760887

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 18760887

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP