JP5511350B2 - Grid connection power conditioner - Google Patents

Grid connection power conditioner Download PDF

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JP5511350B2
JP5511350B2 JP2009282855A JP2009282855A JP5511350B2 JP 5511350 B2 JP5511350 B2 JP 5511350B2 JP 2009282855 A JP2009282855 A JP 2009282855A JP 2009282855 A JP2009282855 A JP 2009282855A JP 5511350 B2 JP5511350 B2 JP 5511350B2
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JP2011125190A (en
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誠 春日井
明彦 岩田
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Mitsubishi Electric Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B10/00—Integration of renewable energy sources in buildings
    • Y02B10/10—Photovoltaic [PV]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P80/00—Climate change mitigation technologies for sector-wide applications
    • Y02P80/20—Climate change mitigation technologies for sector-wide applications using renewable energy

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  • Photovoltaic Devices (AREA)

Description

この発明は、太陽電池で発電した電力を商用系統に連系させる系統連系パワーコンディショナに関するものである。   The present invention relates to a grid-connected power conditioner that links power generated by a solar cell to a commercial grid.

系統連系パワーコンディショナ（以下、単にパワーコンディショナという）は、太陽電池で発電された直流電力を、インバータを用いて電力会社による単相３線式または三相３線式などの商用系統の周波数及び電圧に応じた交流電力に変換し、その商用系統に接続される家庭や工場などでの交流電気機器に使用できるようにすると共に、余剰交流電力を商用系統側へ逆潮流できるようにする装置であり、日の出の時間帯とともに太陽の日射が太陽電池に照射され、太陽電池が発電したことをパワーコンディショナが検知して太陽電池の電力を出力し、夕方、日の入りの時間帯に、太陽電池が発電できないことをパワーコンディショナが検知して翌日の日の出の時間帯まで機器を停止する自動運転を行うものであった。   A grid-connected power conditioner (hereinafter simply referred to as a power conditioner) uses direct current power generated by a solar cell for a commercial system such as a single-phase three-wire type or a three-phase three-wire type by an electric power company using an inverter. Convert to AC power according to frequency and voltage so that it can be used for AC electrical equipment in homes and factories connected to the commercial system, and allow surplus AC power to flow backward to the commercial system side It is a device, and solar solar radiation is applied to the solar cell with the sunrise time zone, the power conditioner detects that the solar cell has generated power, outputs the solar cell power, and in the evening, sunset time, the solar The inverter detected that the battery could not generate electricity, and performed automatic operation to stop the equipment until the next sunrise time.

上述のパワーコンディショナの一例として、特許文献１に示されたものは、パワーコンディショナが起動条件を満足できる電力が太陽電池から発電されているかどうかを、パワーコンディショナの内部に設けた放電回路のスイッチ素子をオンオフ制御して抵抗に電力を消費させることにより起動が可能かどうかを判断していた。   As an example of the above-described power conditioner, the one disclosed in Patent Document 1 is a discharge circuit provided inside the power conditioner to determine whether or not power that can satisfy the start condition is generated from the solar cell. It is determined whether or not the switch element can be activated by controlling on / off of the switch element to cause the resistor to consume power.

特開平１０−２８９０２６号公報（図４）Japanese Patent Laid-Open No. 10-289026 (FIG. 4)

特許文献１に示されたものは、パワーコンディショナを起動する前に、放電回路内の抵抗に太陽電池の電力を一旦消費させて起動可能な電力を太陽電池から出力できるかどうかを判断しているため、放電回路という余分な設備が必要となり、パワーコンディショナの体積が大きくなると共にコストも高くなるという問題点があった。また、太陽電池の発電電力を抵抗に無駄に消費させ、運転可能最小電力が出力できないと判断されたときは、運転可能最小電力が太陽電池から出力される日射量に到達するまで、運転を開始せずに待機するため、低日射時には太陽電池から発電する電力を出力することができず、エネルギーを有効に活用できないという問題点もあった。   Before starting a power conditioner, the thing shown by patent document 1 judges whether the electric power of a solar cell can be output from the solar cell by once consuming the electric power of a solar cell to the resistance in a discharge circuit. Therefore, an extra facility called a discharge circuit is required, and there is a problem that the volume of the power conditioner is increased and the cost is increased. Also, when it is determined that the power generated by the solar cell is consumed wastefully and the minimum operable power cannot be output, the operation is started until the minimum operable power reaches the solar radiation output from the solar cell. Therefore, there is a problem that the power generated from the solar cell cannot be output during low solar radiation, and the energy cannot be used effectively.

この発明は、上記のような問題点を解消するためになされたもので、朝夕の低日射時にもパワーコンディショナから電力を出力し、日射量の少ない朝、夕方でも、太陽電池が発電する電力を捨てることなく、有効に利用することができるパワーコンディショナを得ることを目的とする。   The present invention has been made to solve the above problems, and outputs power from the power conditioner even in the morning and evening low solar radiation, and the power generated by the solar cell even in the morning and evening when the amount of solar radiation is small. An object is to obtain a power conditioner that can be used effectively without throwing away the power.

この発明に係るパワーコンディショナは、太陽電池が発電する直流電力を交流電力に変換して商用系統に出力するパワーコンディショナであって、朝夕などの日射量が少ない時間帯に、制御可能な最小電流指令値で出力して一定期間での太陽電池電圧の変化量を監視し、上記変化量が所定値を越えなければ電流指令値を増加し、上記変化量が所定値を越えたら電流指令値を減少させる制御手段を設け、上記制御手段は、最小電流指令値で出力している時に、上記変化量が所定値を超えた場合は出力を一定期間休止し、休止期間経過後
、再度最小電流指令値で運転して上記変化量が所定値を超えなければ一定休止期間内で電流指令値を出力する期間を増やすようにし、この出力動作を繰り返すことにより、日射量が少ないときでも、日射が安定するまで待つことなく、常に電力を出力するようにしたものである。 The power conditioner according to the present invention is a power conditioner that converts DC power generated by a solar cell into AC power and outputs the AC power to a commercial system, and is a minimum controllable in a time zone where the amount of solar radiation is small such as morning and evening. Outputs the current command value and monitors the amount of change in the solar cell voltage over a certain period of time. If the change does not exceed the predetermined value, the current command value is increased. If the change exceeds the predetermined value, the current command value When the output exceeds the predetermined value when outputting at the minimum current command value, the control means pauses the output for a certain period, and after the pause period has elapsed, the minimum current is again output. If the amount of change does not exceed the predetermined value when operating with the command value, the period for outputting the current command value is increased within a fixed pause period, and by repeating this output operation, even if the amount of solar radiation is small Stable Without waiting until the, at all times that to output power.

この発明によれば、朝夕の日射量が少ないときのパワーコンディショナの目標出力電流を制御可能な最小電流指令値から増加し、太陽電池電圧の変化量を監視しながら、出力する電流を増減させて出力し続けるようにしているため、従来のように、日射量が安定するまでパワーコンディショナからの出力を停止したり、パワーコンディショナが起動できるだけの日射量があるかどうかを、パワーコンディショナに搭載した専用の抵抗負荷に電力を供給して確認したりすることなく、太陽電池から電力を出力し、太陽電池が発電するわずかな電力も無駄にすることなく、電力を有効に利用することができるものである。   According to the present invention, the target output current of the inverter is increased from the controllable minimum current command value when the amount of solar radiation in the morning and evening is small, and the output current is increased or decreased while monitoring the change amount of the solar cell voltage. Since the output from the inverter is stopped until the amount of solar radiation stabilizes, and whether the solar inverter has enough solar radiation to start, Without using power to check the dedicated resistive load mounted on the solar cell, the power is output from the solar cell, and the small amount of power generated by the solar cell is not wasted. It is something that can be done.

この発明の実施の形態１によるパワーコンディショナの構成を示すブロック図である。It is a block diagram which shows the structure of the power conditioner by Embodiment 1 of this invention. 太陽電池の出力特性を示す図である。It is a figure which shows the output characteristic of a solar cell. 日射量が少ないがある程度安定している状態におけるパワーコンディショナの制御の状況を示す図である。It is a figure which shows the condition of the control of a power conditioner in the state where the amount of solar radiation is small, but is stabilized to some extent. 日射量が少ない状態におけるパワーコンディショナの制御の状況を示す図である。It is a figure which shows the condition of control of the power conditioner in a state with little solar radiation amount. 日射量が極端に少ない状態におけるパワーコンディショナの制御の状況を示す図である。It is a figure which shows the condition of the control of a power conditioner in the state where the amount of solar radiation is extremely small. 太陽電池の電圧−電流特性を示す図である。It is a figure which shows the voltage-current characteristic of a solar cell. 太陽光発電による一日の発電量を示した図で、この発明によって朝夕の電力が出力できる時間帯を斜線部分で示している。In the figure which showed the electric power generation amount of the day by photovoltaic power generation, the time zone which can output the morning and evening electric power by this invention is shown by the shaded part.

実施の形態１．
以下、この発明の実施の形態１を図にもとづいて説明する。図１は、実施の形態１によるパワーコンディショナの構成を示すブロック図である。 Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram illustrating a configuration of a power conditioner according to the first embodiment.

図１に示すように、実施の形態１によるパワーコンディショナ１は、直流電力を発電する太陽電池２と、５０Ｈｚ或いは６０Ｈｚの商用系統電源３との間に接続される。商用系統電源３は、単相３線式または三相３線式の配電系統である。パワーコンディショナ１は、太陽電池２の電圧を昇圧するための昇圧部４と、太陽電池２が発電する直流電力を図示しないパワー素子のオンオフによって交流電力に変換するインバータ部５と、インバータ部５の出力側に接続され、インバータ部５の出力電流波形を滑らかにして商用系統電源３へ出力するフィルタ部６と、太陽電池の電圧Vsと、カレントトランス８ａの検出電流Isとを入力側の電力情報とし、商用系統電源３の電圧Voとカレントトランス８ｂの検出電流Iioとを出力側の電力情報として太陽電池の電力の変化を監視し、インバータ部５に制御信号として電流指令値I*を与える制御回路部７とを有している。インバータ部５は電流指令値I*に応じてパワー素子のオンオフ幅を調整しながら制御回路部７からの電流指令値と実際に出力している電流との誤差が少なくなるように周知のフィードバック制御を行って商用系統電源３に電力を出力している。   As shown in FIG. 1, the power conditioner 1 according to Embodiment 1 is connected between a solar cell 2 that generates DC power and a commercial power source 3 of 50 Hz or 60 Hz. The commercial system power supply 3 is a single-phase three-wire system or a three-phase three-wire power distribution system. The power conditioner 1 includes a boosting unit 4 for boosting the voltage of the solar cell 2, an inverter unit 5 that converts DC power generated by the solar cell 2 into AC power by turning on and off a power element (not shown), and an inverter unit 5 Is connected to the output side of the inverter, and the output current waveform of the inverter unit 5 is smoothed and output to the commercial power supply 3. The voltage Vs of the solar cell and the detected current Is of the current transformer 8a are input power. Information, monitoring the change in the power of the solar cell using the voltage Vo of the commercial power supply 3 and the detected current Iio of the current transformer 8b as power information on the output side, and giving the inverter 5 the current command value I * as a control signal And a control circuit unit 7. The inverter unit 5 is known feedback control so that the error between the current command value from the control circuit unit 7 and the actually output current is reduced while adjusting the on / off width of the power element according to the current command value I *. To output power to the commercial power supply 3.

図２は太陽電池の出力特性を示す図で、横軸は太陽電池電圧、縦軸は太陽電池の電力を示す。図中、Ａは日射量が多い場合の特性を示し、Ｂは日射量が少ない場合の特性を示している。太陽電池から電力を取り出していない時、すなわち電流を出力していないときの太陽電池電圧は、図中のVocで、この電圧は一般的に開放電圧と呼ばれている。また、太
陽電池から最大の電力を出力する時の電圧は、図中のVpmで、この電圧は一般的に最大出
力動作電圧と呼ばれている。この開放電圧と最大出力動作電圧は、日の出の直後など、極端に日射量が少ない時間を除いて、日射量が少ない時でもＡ、Ｂの各特性においてほぼ同じ値を示すことが確認されている。 FIG. 2 is a diagram showing the output characteristics of the solar cell, where the horizontal axis indicates the solar cell voltage and the vertical axis indicates the power of the solar cell. In the figure, A indicates a characteristic when the amount of solar radiation is large, and B indicates a characteristic when the amount of solar radiation is small. The solar cell voltage when power is not extracted from the solar cell, that is, when no current is output, is Voc in the figure, and this voltage is generally called an open circuit voltage. The voltage when the maximum electric power is output from the solar cell is Vpm in the figure, and this voltage is generally called the maximum output operating voltage. It has been confirmed that the open circuit voltage and the maximum output operating voltage show substantially the same values in the characteristics of A and B even when the amount of solar radiation is small, except for the time when the amount of solar radiation is extremely small, such as immediately after sunrise. .

朝方、太陽電池に日射が当たると、日射量が少ないながらも太陽電池には電圧が発生し、日の出直後のわずかな時間を除けば、図２にＢで示す特性を示し、太陽電池の電圧は日射量が多いときの特性Ａとほぼ同じ開放電圧Vocを出力する。従来のパワーコンディショナは、この時、日射量が増えるまで一定時間出力をせずに待機状態を維持したり、特許文献１に示されているようにパワーコンディショナに設けてある放電回路に電力を消費させるなどして太陽電池の発電電力を無駄に消費していた。   In the morning, when solar cells are exposed to solar radiation, a voltage is generated in the solar cells even though the amount of solar radiation is small. Except for a short time immediately after sunrise, the characteristics shown by B in FIG. An open circuit voltage Voc that is substantially the same as the characteristic A when the amount of solar radiation is large is output. At this time, the conventional power conditioner maintains a standby state without outputting for a certain period of time until the amount of solar radiation increases, or power is supplied to a discharge circuit provided in the power conditioner as disclosed in Patent Document 1. The power generated by the solar cell was consumed in vain.

この発明のパワーコンディショナは図２に示すように、最小出力電流指令値で太陽電池から一定期間、電力を出力し、その間の太陽電池の電圧変化△Ｖを監視し、同じ電流指令値で一定期間電力を出力したとき、太陽電池の電圧変化△Ｖが所定値を超えるか超えないかを検出する。具体的には、最小出力電流指令値で一定期間（例えば系統サイクル数で１０サイクル）電力を出力しても太陽電池の電圧変化△Ｖが所定値を超えない場合は、出力電流指令値すなわち最小出力電流指令値を増加させて、更に一定期間（系統サイクル数で１０サイクル）電力を出力する。これを繰り返し、所定の電流指令値増加回数（例えば１０回）まで連続して出力を増加しても太陽電池の電圧変化△Ｖが所定値を超えなければ、ある程度日射量が安定していると判断できるため、次回の電流指令値は増加分を増やして出力する。   As shown in FIG. 2, the power conditioner of the present invention outputs power from the solar cell for a certain period at the minimum output current command value, monitors the voltage change ΔV of the solar cell during that period, and is constant at the same current command value. When the period power is output, it is detected whether the voltage change ΔV of the solar cell exceeds or does not exceed a predetermined value. Specifically, if the voltage change ΔV of the solar cell does not exceed a predetermined value even when power is output at a minimum output current command value for a certain period (for example, 10 cycles), the output current command value, that is, the minimum The output current command value is increased and power is output for a certain period (10 cycles in terms of the number of system cycles). If this is repeated and the output voltage is continuously increased up to a predetermined current command value increase count (for example, 10 times), the solar radiation amount is stabilized to some extent if the voltage change ΔV of the solar cell does not exceed the predetermined value. Since it can be determined, the next current command value is increased and output.

図３は、上述の制御の状況を図示したものである。図３では、一例として最小出力電流指令値を0.1Aとし、T1からT2まで１０サイクル0.1Aを連続出力しても太陽電池の電圧変化△Ｖが所定値を超えない場合、T2から出力電流指令値を0.2Aにして１０サイクル出力する。これを１０回繰り返し、出力電流指令値が1.0Aまで増加したT3においても電圧変化△Ｖが所定値を超えない場合は、T3において電流指令値を2.0Aに増やして１０サイクル出力する。この状態でも太陽電池の電圧変化△Ｖが所定値を超えなければ、最小出力電流指令値0.1Aに対して２０倍の電流指令値としても太陽電池の電圧変化△Ｖが少ないことから日射量がある程度安定していると判断できるため、通常のＭＰＰＴ制御（Maximum Power Point Tracking 最大電力点追従制御）で出力電流を増やし、太陽電池の電圧は最大電力点で動作する電圧値に落ち着く。ＭＰＰＴ制御は周知の技術であるため詳細な説明を省略する。 FIG. 3 illustrates the above-described control situation. In Figure 3, the minimum output current command value and 0.1A, when the voltage variation of the solar cell be consecutive outputs 10 cycles 0.1A from T 1 to T 2 △ V does not exceed a predetermined value as an example, the T 2 The output current command value is set to 0.2A, and 10 cycles are output. This was repeated 10 times, even the voltage change △ V is does not exceed a predetermined value, for 10 cycles output by increasing the current command value to 2.0A at T 3 in T 3 the output current command value increases to 1.0A. Even in this state, if the solar battery voltage change ΔV does not exceed the predetermined value, the solar battery voltage change ΔV is small even if the current command value is 20 times the minimum output current command value 0.1 A, and therefore the amount of solar radiation is small. Since it can be determined to be stable to some extent, the output current is increased by normal MPPT control (Maximum Power Point Tracking control), and the voltage of the solar cell settles to a voltage value that operates at the maximum power point. Since MPPT control is a well-known technique, detailed description thereof is omitted.

なお、日射量が安定していない状態で上述した最小出力電流指令値から電流指令値を増加中に、太陽電池の電圧変化△Ｖが所定値を超えた場合は、次のサイクルから現在の電流指令値に対して1つ前の電流指令値に減らして出力する。その後、一定期間（例えば系統
サイクル数で１０サイクル）出力した後でも電圧変化△Ｖが所定値を越えなければ、電流指令値を増やし、電圧変化△Ｖが所定値を超える場合は電流指令値を減らす操作を実施することで電流を流し続ける動作を繰り返す。 When the solar battery voltage change ΔV exceeds a predetermined value while increasing the current command value from the minimum output current command value described above in a state where the amount of solar radiation is not stable, the current current is started from the next cycle. Reduces to the current command value before the command value and outputs it. Thereafter, if the voltage change ΔV does not exceed the predetermined value even after output for a certain period (eg, 10 cycles), the current command value is increased. If the voltage change ΔV exceeds the predetermined value, the current command value is increased. Repeat the operation to keep the current flowing by performing the operation to reduce.

図４は、上述の制御の状態を示したものである。図４では、出力電流指令値が0.5Aの時、５サイクル目で電圧変化△Ｖが所定値を超えたため、T4で電流指令値を１つ前の電流指令値である0.4Aに下げて出力する。この状態で一定期間（例えば系統サイクル数で１０サイクル）を経過しても、電圧変化△Ｖが所定値を超えなければ、T5で電流指令値を再び0.5Aに増やして出力することを示している。 FIG. 4 shows the above-described control state. In FIG. 4, when the output current command value is 0.5 A, the voltage change ΔV exceeded the predetermined value in the fifth cycle. Therefore, at T 4 , the current command value is lowered to the previous current command value of 0.4 A. Output. Even after the lapse of a period of time (e.g., the number of strains cycles 10 cycles) in this state, if the voltage change △ V not exceed a predetermined value, indicates that the output by increasing the current command value again 0.5A at T 5 ing.

また、日射量が極端に少ない場合などで、最小出力電流指令値で出力しているときに電圧変化△Ｖが所定値を超えた場合は、出力電流指令値を０Ａとし、一定の休止時間（例えば系統サイクル数で１０サイクル）を設け、休止時間経過後、再度最小出力電流指令値で出力する。電圧変化△Ｖが所定値を超えなければ、今回出力したサイクル数から目標出力サイクル数を１サイクルだけ増やし、一定の休止時間の残りのサイクル期間は電流を出力しないようにする。電圧変化△Ｖが所定値を超えた場合は今回出力したサイクル数から目標出力サイクル数を１サイクルだけ減らし、一定の休止時間の残りのサイクル期間は電流を出力しないようにする。   In addition, when the amount of solar radiation is extremely small, etc., and the voltage change ΔV exceeds a predetermined value when outputting at the minimum output current command value, the output current command value is set to 0 A, and a certain pause time ( For example, 10 cycles are provided as the number of system cycles), and after the quiescent time has elapsed, the output is performed again with the minimum output current command value. If the voltage change ΔV does not exceed a predetermined value, the target output cycle number is increased by one cycle from the cycle number output this time, and no current is output during the remaining cycle period of a certain pause time. When the voltage change ΔV exceeds a predetermined value, the target output cycle number is reduced by one cycle from the number of cycles output this time, and no current is output during the remaining cycle period of a fixed pause time.

これらの電流出力制御を繰り返すことで日射量が特に少ない場合でも、日射が安定するまでわずかながら電流を流すことで長時間出力を止めることはせず、太陽電池の発電電力を有効に活用する。この電流制御の期間中、最小出力電流指令値で休止時間がなくなる（例えば１０サイクル連続）まで出力しても電圧変化△Ｖが所定値を超えない場合は、上述した電流指令値を増加して連続して電流を出力する制御に切替える。   By repeating these current output controls, even if the amount of solar radiation is particularly small, the output is not stopped for a long time by passing a small amount of current until the solar radiation stabilizes, and the generated power of the solar cell is effectively utilized. During this current control period, if the voltage change ΔV does not exceed the predetermined value even if output is performed until the minimum output current command value stops the pause time (for example, 10 consecutive cycles), the current command value described above is increased. Switch to control that outputs current continuously.

図５は、上述の制御の状況を図示したものである。図５では、最小出力電流指令値Im1
（例えば0.1A）で出力中、１サイクル目で電圧変化△Ｖが所定値を超えた場合は、T6で一定期間（例えば１０サイクル）出力電流指令値を０Ａとする。一定期間経過後、T7においてIm2で示すように、最小出力電流指令値で１サイクル出力し、この期間に電圧変化△Ｖ
が所定値を超えなければ、一定期間の残りの９サイクルを０Ａ出力とし、その９サイクルの経過後、T8においてIm3で示すように、最小出力電流指令値の出力サイクル数を１つ増
やして２サイクルとし、一定期間の残りの８サイクルを０Ａ出力とする。同様に、最小出力電流指令値での出力サイクル数を徐々に増やしていく。そして例えばT9においてIm4で
示すように、最小出力電流指令値での出力サイクルが５サイクルとなり、その５サイクル目で電圧変化△Ｖが所定値を超えた場合は、一定期間の残りの５サイクルを０Ａ出力とし、T10においてIm5で示すように、最小出力電流の目標サイクル数を１サイクル減らして４サイクルとし、一定期間の残りの６サイクルを０Ａ出力とする出力電流制御を行うものである。 FIG. 5 illustrates the above-described control situation. In FIG. 5, the minimum output current command value Im 1
If the voltage change ΔV exceeds a predetermined value in the first cycle during output (for example, 0.1 A), the output current command value is set to 0 A for a certain period (for example, 10 cycles) at T 6 . After a certain period of time, as indicated by Im 2 at T 7 , one cycle is output at the minimum output current command value, and the voltage change ΔV during this period
If There not exceed a predetermined value, the remaining 9 cycles of a predetermined period and 0A output, after the ninth cycle, as indicated by Im 3 in T 8, increasing the one of the output cycle minimum output current command value 2 cycles, and the remaining 8 cycles in a certain period are set to 0A output. Similarly, the number of output cycles at the minimum output current command value is gradually increased. For example, as indicated by Im 4 at T 9 , the output cycle at the minimum output current command value is 5 cycles, and when the voltage change ΔV exceeds a predetermined value at the 5th cycle, the remaining 5 of the fixed period the cycle as 0A output, as indicated by Im 5 in T 10, which the target cycle number of minimum output current reduce cycle and 4-cycle, performs output current control to 0A outputs the remaining 6 cycles of a predetermined period It is.

実施の形態２．
次に、この発明の実施の形態２について説明する。実施の形態１では朝方など日射量の少ない時に、最小出力電流指令値で出力している時の指令電流を増やすか減らすかの判断は、太陽電池の電圧変化△Ｖを検出して行っているが、実施の形態２では、この電圧変化量で定まる基準電圧Ｖrefを、出力電流指令値を２倍にしてもそれに対応する電流出力が
可能となる電圧値に設定するものである。 Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described. In the first embodiment, when the amount of solar radiation is small, such as in the morning, whether to increase or decrease the command current when outputting with the minimum output current command value is determined by detecting the voltage change ΔV of the solar cell. However, in the second embodiment, the reference voltage Vref determined by the amount of voltage change is set to a voltage value at which a corresponding current output is possible even if the output current command value is doubled.

以下、その詳細について説明する。図６は太陽電池の電圧−電流特性を示す図である。図中、Ｃは日射量が多い場合の特性を示し、Ｄは日射量が少ない場合の特性を示している。太陽電池が出力する電力が最大となる最大出力動作電圧Vpmは、開放電圧Vocの約８０％近辺となる。太陽電池の出力電流は開放電圧から最大出力動作電圧までは電圧が減少するのに対して電流は増加する。最大出力動作電圧より更に電圧が下がると、出力電流はほぼ一定な定電流特性を示す。   The details will be described below. FIG. 6 is a diagram showing voltage-current characteristics of the solar cell. In the figure, C indicates a characteristic when the amount of solar radiation is large, and D indicates a characteristic when the amount of solar radiation is small. The maximum output operating voltage Vpm at which the power output from the solar cell is maximized is about 80% of the open circuit voltage Voc. The output current of the solar cell decreases from the open voltage to the maximum output operating voltage, while the current increases. When the voltage is further lowered from the maximum output operating voltage, the output current exhibits a substantially constant constant current characteristic.

朝方などの日射量が少なくて不安定なときは、太陽電池から電力を出力すると、日射量が安定しているときに比べて太陽電池の動作電圧の変化量が大きくなりやすい。日射量が少ないときの出力電流指令値の増減を判断する太陽電池の基準電圧をVref2で示すように、
最大出力動作電圧Vpm近辺に設定すると、出力電流指令値を２倍に増やした場合でも、日
射量が増えない限り２倍に増やした電流指令値に対応した電流を出力する電圧が得られないため、インバータ部は、不足する電力をインバータ入力部の図示しないコンデンサから出力すると共に、太陽電池からも電力が出力されるため、太陽電池の電圧が大きく下がり、場合によってはこの電圧がパワーコンディショナの最低動作電圧を下回り、パワーコンディショナの運転が一時停止する可能性もある。 When the amount of solar radiation is small and unstable, such as in the morning, if the solar cell outputs power, the amount of change in the operating voltage of the solar cell tends to be larger than when the amount of solar radiation is stable. As shown by Vref 2 , the reference voltage of the solar cell that judges the increase or decrease of the output current command value when the amount of solar radiation is small,
If set near the maximum output operating voltage Vpm, even if the output current command value is doubled, a voltage that outputs a current corresponding to the current command value that has been doubled will not be obtained unless the amount of solar radiation increases. In addition, the inverter unit outputs insufficient power from a capacitor (not shown) of the inverter input unit and power is also output from the solar cell, so that the voltage of the solar cell is greatly reduced. There is also a possibility that operation of the inverter will be temporarily stopped because the voltage is lower than the minimum operating voltage.

そこで、日射量が少ないときの電流制御として、電流指令値を増減させる太陽電池電圧の変化量で定まる基準電圧を、電流指令値が２倍になってもそれに対応する電流を出力することができる電圧値に設定しようとするものである。この電圧は、図６の特性図において開放電圧Vocと最大出力動作電圧Vpmとの電圧差の約１／３の電圧を開放電圧Vocに対し
て保持した電圧値であるVref1に設定する。このように設定すれば、出力電流の指令値を
２倍にしても、それに対応した電流を流す電力は出力されるため、日射量が増えなくても２倍に増やした目標電流を太陽電池から出力することができ、太陽電池電圧が急激に下がって、パワーコンディショナの最低動作電圧を下回り、パワーコンディショナの運転を一時停止してしまうような事態を防ぐことができる。 Therefore, as the current control when the amount of solar radiation is small, the reference voltage determined by the amount of change in the solar cell voltage that increases or decreases the current command value can be output even if the current command value is doubled. It is intended to set the voltage value. This voltage is set to Vref 1 , which is a voltage value that holds about 1/3 of the voltage difference between the open circuit voltage Voc and the maximum output operating voltage Vpm in the characteristic diagram of FIG. If set in this way, even if the command value of the output current is doubled, the electric power that flows the corresponding current is output. Therefore, even if the amount of solar radiation does not increase, the target current increased by a factor of two from the solar cell. Thus, it is possible to prevent a situation in which the solar cell voltage drops rapidly, falls below the minimum operating voltage of the power conditioner, and temporarily stops the operation of the power conditioner.

実施の形態２によれば、朝方など日射量の少ないときの出力電流制御に対して、パワーコンディショナが停止してしまうようなことが起こらないため、低日射時の電力出力を継続して行うことができ、従来、日射量が少ないときに太陽電池から出力を取り過ぎてパワーコンディショナの入力電圧下限値を下回り、一時パワーコンディショナが停止して待機状態に陥ったりすることがなく、安定して、日射量が少ないときの太陽電池の発電電力を維持することができるという効果がある。   According to the second embodiment, since the power conditioner does not stop for output current control when the amount of solar radiation is small, such as in the morning, power output is continuously performed during low solar radiation. In the past, when the amount of solar radiation was low, the output from the solar cell was excessive and the input voltage was lower than the lower limit of the input voltage of the inverter. Thus, there is an effect that the generated power of the solar cell when the amount of solar radiation is small can be maintained.

以上のように、この発明にかかるパワーコンディショナは、朝夕の日射量が少ないときでも、パワーコンディショナから電流を出力することができるため、日射量が少なく太陽高度が低いため、朝方、日射量が安定するまでに時間がかかる冬季の朝などには特に有効であり、今まで日射量が安定するまで待機していたり、パワーコンディショナの内部の抵抗に太陽電池の発電電力を無駄に放電していた時間帯にも電力を出力することができるので、図７に示すように、１日の発電の中で、ａ，ｂで示す朝夕の日射量の少ない時間帯の発電電力を増やすことができる。また、十年以上稼動しているような太陽光発電システムにおいても、日射量の少ない時間帯に電力を出力することができて太陽電池の発電する積算電力量を増加することができるので、太陽電池の発電する電力を無駄なく、有用に活用することができる。   As described above, the power conditioner according to the present invention can output current from the power conditioner even when the amount of solar radiation in the morning and evening is small, so the amount of solar radiation is low and the solar altitude is low. This is especially effective in winter mornings, where it takes time to stabilize, and until now the solar radiation has been stabilized until it stabilizes, or the power generated by the solar cell is discharged to the internal resistance of the inverter. Since the power can be output even during the time period, the power generation power during the time period when the amount of solar radiation in the morning and evening indicated by a and b is small can be increased as shown in FIG. it can. Moreover, even in a solar power generation system that has been operating for more than 10 years, it is possible to output electric power in a time zone where the amount of solar radiation is small and to increase the integrated electric energy generated by the solar cell. The power generated by the battery can be used effectively without waste.

なお、上述した一連の制御は、朝方に限らず、日射量の少ない夕方や、雨の日の日中にも適用できることは言うまでもない。   Needless to say, the series of controls described above can be applied not only in the morning, but also in the evening when the amount of solar radiation is small or during rainy days.

１ パワーコンディショナ、
２ 太陽電池、
３ 商用系統電源、
４ 昇圧部、
５ インバータ部、
６ フィルタ部、
７ 制御回路部、
８ａ，８ｂ カレントトランス。 1 Inverter,
2 solar cells,
3 Commercial power supply,
4 Booster,
5 Inverter part,
6 Filter section,
7 Control circuit section,
8a, 8b Current transformer.

Claims (1)

太陽電池が発電する直流電力を交流電力に変換して商用系統に出力する系統連系パワーコンディショナであって、朝夕などの日射量が少ない時間帯に、制御可能な最小電流指令値で出力して一定期間での太陽電池電圧の変化量を監視し、上記変化量が所定値を越えなければ電流指令値を増加し、上記変化量が所定値を越えたら電流指令値を減少させる制御手段を設け、上記制御手段は、最小電流指令値で出力している時に、上記変化量が所定値を超えた場合は出力を一定期間休止し、休止期間経過後、再度最小電流指令値で運転して上記変化量が所定値を超えなければ一定休止期間内で電流指令値を出力する期間を増やすようにしたことを特徴とする系統連系パワーコンディショナ。   A grid-connected power conditioner that converts the DC power generated by solar cells into AC power and outputs it to the commercial system, and outputs it at a controllable minimum current command value during periods of low solar radiation, such as morning and evening. Control means for monitoring the amount of change in the solar cell voltage over a certain period, increasing the current command value if the change does not exceed a predetermined value, and decreasing the current command value if the change exceeds the predetermined value. The control means, when outputting at the minimum current command value, when the amount of change exceeds a predetermined value, pauses the output for a certain period, and after the pause period has elapsed, operates again at the minimum current command value. A grid-connected power conditioner characterized in that the period during which the current command value is output within a fixed pause period is increased if the amount of change does not exceed a predetermined value.
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