JP3563865B2

JP3563865B2 - Solar cell power controller

Info

Publication number: JP3563865B2
Application number: JP06514396A
Authority: JP
Inventors: 誠路黒神; 信善竹原; 公俊深江
Original assignee: Canon Inc
Current assignee: Canon Inc
Priority date: 1996-02-28
Filing date: 1996-02-28
Publication date: 2004-09-08
Anticipated expiration: 2016-02-28
Also published as: JPH09230952A

Description

【０００１】
【産業上の利用分野】
本発明は電力変換装置を有する太陽光発電システムの電力制御装置に関する。
【０００２】
【従来の技術】
今日、地球環境に対する意識の高まりから、クリーンエネルギーを提供する太陽光発電、風力発電等の電池電源システムに大きな期待が寄せられている。例えば、太陽電池を電池電源として、既存の商用交流系統と接続した場合には、家庭内負荷に給電するとともに商用交流系統を無限大の負荷とみなして余剰電力を売電することができることから、その太陽電池やその出力を交流電力に変換する電力変換装置および家庭内負荷を含む電源システムは、全体として最も効率よく稼働することが求められている。
【０００３】
光電変換素子を用いた太陽電池では、その出力は、日射量、温度、動作点電圧などによりかなり変動するために、太陽電池から見た負荷を調整して、常に最大の電力を取り出すことが要望される。このため、複数の太陽電池から構成される太陽電池アレイの動作点の電圧や電流を変動させて、その時の電力変動を調べて太陽電池アレイの最大電力または最大電力近傍の動作点を追尾する最大電力点追尾制御、いわゆるＭＰＰＴ制御が提案されている。例えば、特公昭６３−５７８０７号公報に記載される電力の電圧微分値を利用するものや、特開昭６２−８５３１２号公報に記載されている電力変化量が正の方向に探索する、いわゆる山登り法などがある。
【０００４】
また、特開平７−２２５６２４号公報に記載されるものにおいては、太陽電池の開放電圧から最低電圧までの間で極大点を検出し、極大点の中で最大電力となる極大点の電圧を設定している。
【０００５】
従来は、このような方法を利用して、太陽電池から最大電力を取り出すように電力変換装置などを制御していた。
【０００６】
【発明が解決しようとする課題】
しかし、上記の方法には以下の問題点がある。
通常、太陽電池アレイの電圧−電力特性は、図８（ａ）に示したような形状（横軸は電圧、縦軸は電力）であるが、太陽電池アレイの一部に雪や建物の影が落ちる場合には、図８（ｂ）に示すような電圧−電力特性となる場合がある。図８（ｂ）中の動作点▲１▼は太陽電池アレイから最大電力を取り出すことができるが、動作点▲２▼は極大点ではあるが最大電力点ではない。
【０００７】
従来の山登り法では、動作点を変化させたことによる電力変化量の正負により、電圧−電力特性曲線の「山」の頂上のある方向を見いだすものであるので、動作点が▲１▼または▲１▼近傍にある場合には、動作点は▲１▼の「山」の頂上を追いかけて、太陽電池アレイからは最大電力を取り出すことができる。しかし、動作点が▲２▼または▲２▼近傍にある場合には、動作点は▲２▼の「山」の頂上を最大電力点と誤認して追従し、太陽電池アレイからは最大電力を取り出すことができない。
【０００８】
このように、いわゆる「２山問題」が生じる場合がある。
【０００９】
以上、山登り法での動作について説明したが、電力の電圧微分値を利用する制御方法でも同様の結果となる。
【００１０】
これに対して、特開平７−２２５６２４号公報記載の方法では、２つの「山」のどちらかの電力の大きいほうの頂上を取ることができる。しかし、太陽電池に接続される電力変換装置の動作可能範囲は図８（ｃ）のように限定されるので、動作可能範囲内での最大電力動作点▲３▼は極大点にはなく、前記方法では最大電力を取り出せない。また、前記方法は太陽電池の開放電圧から最低電圧までという極めて広い範囲をスキャンするので、スキャン時の電力損失が懸念される。このため長いインターバルで上記方法を行うと、最適動作点は常時変動するので最適動作点からずれて精密に追尾はできず、最大電力を取り出すことができない。また、広範囲を探索する最中に日射変動が生じると、異なった電圧−電力特性での動作点をサンプリングして、それに基づいて動作点を設定するので、誤動作して出力が低下する恐れがある。
【００１１】
本発明の目的は、従来の太陽電池の電力制御方法の欠点を補完し、太陽電池から最大出力を取り出す電力制御装置を提供することである。
【００１２】
【課題を解決するための手段】
上記の目的を達成するため、本発明では、常時は、通常のＭＰＰＴ制御を行うとともに、前記ＭＰＰＴ制御より長い周期にて広い探索範囲で太陽電池の動作点を変動させてその動作点の電圧および電流を取り込んで電力を算出し、電圧ー電力特性が２山であるときは元の動作点が最大電力が得られる山にいるか否かを判定し、最大電力が得られる山にいるなら元の動作点を選択し、最大電力が得られる動作点が他の山にあるならその山にある動作点を選択し、前記選択動作点の電圧を前記ＭＰＰＴ制御する際の設定値とすることを特徴とする。
【００１３】
【発明の実施の形態】
より具体的には、上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期においては、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するものであることを特徴とする電力制御装置により達成される。
【００１４】
また上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期においては、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて第２変動範囲内の電圧−電力特性が２山以上あるかを判断し、２山以上なら前記電圧値および電流値に基づき最大電力が得られる動作点が存在する山の中の動作点の電圧に前記設定値を設定するものであることを特徴とする電力制御装置により達成される。
【００１５】
また上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期にて、現在の動作点を基準動作点として電圧値および電流値をサンプリングして記憶し、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値から各動作点での電力値を算出し、前記電池電源の出力電力の極大点および第２変動範囲端での動作点を記憶し、前記極大点が１つのみの場合には、前記極大点を前記基準動作点として設定した後、前記第２変動範囲端の動作点と前記基準動作点の電力値を比較して前記第２変動範囲端の動作点の電力値のほうが大きい時は、前記第２変動範囲端の動作点を前記基準動作点に設定する第１比較設定を行い、前記極大点が２つ以上ある場合には、前記第１比較設定とともに、複数の前記極大点の中から電力が最大となる極大点を選び、前記選んだ極大点と前記基準動作点の電力値を比較して前記極大点のほうが大きい時は、前記極大点を前記基準動作点に設定する第２比較設定を行い、前記基準動作点の電圧を前記設定値に設定するものであることを特徴とする電力制御装置により達成される。
【００１６】
また上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期にて、現在の動作点を基準動作点として電圧値および電流値をサンプリングして記憶し、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値から各動作点での電力値を算出し、前記電池電源の出力電力の極小点を検出し、前記極小点が検出された場合には、前記極小点より前記第２変動範囲の端側にある極大点および前記第２変動範囲端の動作点を検出、記憶し、前記第２変動範囲端の動作点と前記基準動作点の電力値を比較して前記第２変動範囲端の動作点の電力値のほうが大きい時は、前記第２変動範囲端の動作点を前記基準動作点に設定する第１比較設定を行い、前記極大点がある場合には、前記第１比較設定とともに、複数の前記極大点の中から電力が最大となる極大点を選び、前記選んだ極大点と前記基準動作点の電力値を比較して前記極大点のほうが大きい時は、前記極大点を前記基準動作点に設定する第２比較設定を行い、前記基準動作点の電圧を前記設定値に設定するものであることを特徴とする電力制御装置により達成される。
【００１７】
また上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期にて、現在の動作点を基準動作点として電圧値および電流値をサンプリングして記憶し、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値から各動作点での電力値を算出し、前記電池電源の出力電力の極小点を検出し、極小点が検出された場合には、前記極小点より前記第２変動範囲の端側にある最大電力の動作点を検出、記憶し、前記最大電力動作点と前記基準動作点の電力値を比較して前記最大電力動作点の電力値のほうが大きい時は、前記最大電力動作点を前記基準動作点に設定し、前記基準動作点の電圧を前記設定値に設定するものであることを特徴とする電力制御装置により達成される。
【００１８】
また上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期にて、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値から各動作点での電力値を算出し、サンプリングされたうちの３点以上の動作点を検出値を用いてその電圧対電力曲線を有極関数により近似し、前記有極関数の極大値となる点の電圧を前記設定値に設定するものであることを特徴とする電力制御装置により達成される。
【００１９】
また上記目的は、電池電源と、前記電池電源からの電力を変換して負荷に供給する電力変換手段と、前記電池電源の電圧値を検出する電圧検出手段と、前記電池電源の電流値を検出する電流検出手段と、前記電圧検出手段と前記電流検出手段の検出値に基づいて前記電池電源の出力値を設定するための出力値設定手段と、前記電池電源の出力値が前記出力値設定手段の設定値に一致するように前記電力変換手段を制御する制御手段とを備え、前記出力値設定手段は、第１周期にて前記電池電源の動作点を第１変動範囲で変動させて電圧値および電流値をサンプリングし、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するとともに、前記第１周期より長い周期である第２周期においては、前記第１変動範囲より広い第２変動範囲にて動作点を変動させて電圧値および電流値をサンプリングし、同一電圧の複数の動作点の電流値、または電圧値と電流値の乗算により算出される電力値の差が所定値以上なら所定回数まで前記サンプリングをやり直すか、または、設定動作を取り消して元の動作点を設定し、前記電力値の差が所定値未満であれば、前記電圧値と前記電流値に基づいて前記電池電源からの電力が最大となるように前記設定値を設定するものであることを特徴とする電力制御装置により達成される。
【００２０】
【作用】
本発明の電力制御装置では、第１周期の短い周期にて第１変動範囲の狭い動作点変動範囲にてＭＰＰＴ制御を行うことで、常時は精密に太陽電池の最適動作点を追尾する。
【００２１】
また、第１周期と比較して長い周期の第２周期にて、第１変動範囲より広い第２変動範囲の動作点変動範囲を探索し、電力の極大点の数により「２山」になってるかを判断し、極大点および探索範囲端動作点を元にして、「２山」の場合には電力が大きいほうの「山」の動作点を設定することで、２山問題を解決して、太陽電池から最大電力と取り出すことができる。
【００２２】
また、第１周期と比較して長い周期の第２周期にて、第１変動範囲より広い第２変動範囲の動作点変動範囲を探索し、電力の極小点が有るか否かにより「２山」になっているかを判断し、極大点および探索範囲端動作点を元にして、「２山」の場合には電力が大きいほうの「山」の動作点を設定することで、２山問題を解決して、太陽電池から最大電力と取り出すことができる。
【００２３】
また、第１周期と比較して長い周期の第２周期にて、第１変動範囲より広い第２変動範囲の動作点変動範囲を探索し、探索範囲の一部または全部の電圧ー電力特性曲線の有極な近似曲線の極大点の電圧に動作点を設定することにより、２山問題を解決して、太陽電池から最大電力と取り出すことができる。
【００２４】
また、同じ電圧の複数の動作点の電流値または電力値の差に基づき日射変動の有無を判定することにより誤動作を抑制し、出力低下を抑制できる。
【００２５】
【実施例１】
以下、図面を参照して本発明の実施例を説明する。
【００２６】
図１に本発明の一実施例に係る電力制御装置を用いた太陽光発電システムの構成を示す。図中、電池電源１の直流電力は、電力変換手段２にて電力変換され、負荷３に供給される。
【００２７】
電池電源１としては、アモルファスシリコン、微結晶シリコン、多結晶シリコン、単結晶シリコンあるいは化合物半導体などを用いた太陽電池がある。通常は、複数の太陽電池モジュールを直並列に組み合わせて、所望の電圧および電流が得られるようにアレイを構成する。
【００２８】
電力変換手段２としては、パワートランジスタ、パワーＭＯＳＦＥＴ、ＩＧＢＴ、ＧＴＯなどの自己消孤型スイッチングデバイスを用いたＤＣ／ＤＣコンバータ、自動式電圧型ＤＣ／ＡＣインバータなどがある。この電力変換手段２は、ゲートパルスのオン／オフデューティ比を変えることで電力潮流、入出力電圧、出力周波数などを制御できる。
【００２９】
負荷３としては、電熱負荷や電動機負荷あるいは商用交流系統およびそれらの組み合わせなどがある。負荷３が商用交流系統の場合は、系統連系太陽光発電システムと呼ばれており、系統に投入され得る電力は制限されないので、電池電源１からより多くの電力を取出す本実施例が適用される対象として非常に好ましい。
【００３０】
電池電源１の出力電圧および出力電流は、通常用いられる電圧検出手段４および電流検出手段５により検出され、電圧検出信号は出力電圧設定手段６および制御手段７に入力され、電流検出信号は出力電圧設定手段６に入力される。出力電圧設定手段６はこれらの電圧検出信号および電流検出信号を記憶する。
【００３１】
出力電圧設定手段６は、記憶された電圧検出信号、電流検出信号をもとに、電圧設定値を決定する。出力電圧設定手段６は、制御用マイクロコンピュータであり、ＣＰＵ、ＲＡＭ、ＲＯＭ、Ｉ／Ｏなどで構成される。
【００３２】
制御手段７は、電力変換手段２の出力制御回路とゲート駆動回路である。例えば、出力電圧設定手段６からの電圧設定値と電圧検出手段４からの電圧検出信号との偏差である電圧誤差信号が入力され、これが零となるように制御するＰＩ制御回路と、ＰＩ制御回路からの出力に応じて三角波比較方式や瞬時電流追従制御などによりゲート駆動用のＰＷＭパルスを生成するＰＷＭ回路などからなる。これにより、電力変換手段２のスイッチングデバイスのオン／オフデューティ比を制御して、太陽電池の出力電圧を制御する。
【００３３】
次に、図２、図３を用いて、本実施例の電力制御装置において最大電力が得られる動作点の探索について説明する。図２は、横軸が電圧、縦軸が電力を示しており、電圧ー電力出力特性曲線を示している。また、図３に本実施例に係るフローチャートが示されている。
本実施例においては、まず、初期動作電圧Ｖ０、ステップ変動幅ｄＶ、探索方向、変動範囲下限電圧ＶＬ、変動範囲上限電圧ＶＨ、広範囲探索による電力制御の周期（以下、ＷＡＳ周期という）を予め決めておき、ＲＯＭに記憶させておくとよい。初期動作電圧Ｖ０は太陽電池アレイの構成によって決められる。ステップ変動幅ｄＶは電力変換手段２の動作可能電圧範囲の１〜３％程度にしておく。探索方向は増加方向、減少方向のどちらでもよい。変動範囲下限電圧ＶＬおよび変動範囲上限電圧ＶＨは電力変換手段２の動作可能電圧範囲内で設定する。ＷＡＳ周期は、通常のＭＰＰＴ制御よりも長い周期で行う広範囲探索の電力制御（ここではＷＡＳ制御と呼ぶ）の周期であり、例えば、数十分程度となるように設定する。
【００３４】
電力変換開始時には、動作電圧Ｖを初期動作電圧Ｖ０に設定した後、常時は山登り法によるＭＰＰＴ制御を行い、時々ＷＡＳ周期に応じてＷＡＳ制御を行う。
実際の動作は、以下のようになる。
ＭＰＰＴ制御を開始すると、まず始めに、ＷＡＳ周期をカウントするタイマーをリセットする（ＳｔｅｐＭ０１）。
次に、設定されている動作点での電圧、電流をサンプリングし、電力値Ｐ０を算出・記憶する（ＳｔｅｐＭ０２）。
次に、タイマーをみてＷＡＳ周期になったか否かを判定する（ＳｔｅｐＭ０３）。ＷＡＳ周期になっていないのであれば通常のＭＰＰＴ制御を行うものとしてＳｔｅｐＭ０４へ移り、ＷＡＳ周期であるならＷＡＳ制御を行うものとしてＳｔｅｐＷ００へ移動する。ＷＡＳ周期は長くとってあるので、多くの場合は通常ＭＰＰＴ制御のＳｔｅｐＭ０４へ行く。
【００３５】
ＳｔｅｐＭ０４では、探索方向に応じて分岐し、探索方向が「増加」ならＳｔｅｐＭ０５へ進んで動作点電圧を現在の電圧よりステップ変動幅ｄＶほど高い電圧に設定し、探索方向が「減少」ならＳｔｅｐＭ０６へ進んで動作点電圧をステップ変動幅ｄＶほど低い電圧に設定する。そして、ＳｔｅｐＭ０７に進む。
【００３６】
次に、設定されている動作点での電圧および電流をサンプリングし、電力値Ｐ１を算出・記憶する（ＳｔｅｐＭ０７）。
ＳｔｅｐＭ０８では現在の動作点の電力値Ｐ１と以前の動作点の電力値Ｐ０を比較する。もし、電力値Ｐ１が電力値Ｐ０以下であれば、最適動作点を通りすぎたと判断し、ＳｔｅｐＭ０９にて探索方向を反転させる。電力値Ｐ１が電力値Ｐ０より大きいのであれば、最適動作点はまだ先にあるので、探索方向はそのままとして、ＳｔｅｐＭ０９はバイパスとする。
そして、電力値Ｐ１を電力値Ｐ０として記憶してから（ＳｔｅｐＭ１０）、ＳｔｅｐＭ０３に戻り、上記動作を繰り返す。
【００３７】
ＳｔｅｐＭ０３において、ＷＡＳ周期になったと判断するとＳｔｅｐＭ００のＷＡＳルーチンに飛ぶ。
ＷＡＳルーチンでは、まず始めに、現在の動作点の電圧および電流値をサンプリングして電力値を計算し、その電圧値および電力値を基準動作点電圧ＶＲおよび基準動作点電力ＰＲとして記憶する（ＳｔｅｐＷ０１）。
次に、変動範囲下限電圧ＶＬから変動範囲上限電圧ＶＨの間の変動範囲で動作点を変動させて、電圧および電流をサンプリングして電力値を計算する。そして、電力値の極大点を検出し、極大点の電圧および電力を記憶する。また、変動範囲下限電圧ＶＬおよび変動範囲上限電圧ＶＨでの動作点の電力値ＰＶＬおよびＰＶＨを記憶する（ＳｔｅｐＷ０２）。
【００３８】
次に、極大点の有無を判定し、極大点が無い場合は探索範囲内には２山は無いと判断してＳｔｅｐＷ１３へ処理を飛ばし、極大点がある場合には次のＳｔｅｐＷ０３に進む。
そして、極大点がある場合は、極大点の数が１つだけか２つ以上あるかに応じて分岐する（ＳｔｅｐＷ０４）。
【００３９】
極大点の数が１つだけの場合は、前記極大点を前記基準動作点として前記極大点の電圧Ｖ極大点１および電力Ｐ極大点１を前記基準動作点電圧ＶＲおよび電力ＰＲに設定し（ＳｔｅｐＷ０８）、次のＳｔｅｐＷ０９へ進む。
【００４０】
極大点の数が２つ以上の場合は、前記極大点の中から電力が最大となる極大点（電圧Ｖ極大点ｘ、電力Ｐ極大点ｘ）を抽出し（ＳｔｅｐＭ０５）、前記電力最大極大点の電力値Ｐ極大点ｘと前記基準動作点の電力ＰＲを比較し（ＳｔｅｐＷ０６）、前記基準動作点電力ＰＲのほうが小さい時には、前記極大点を前記基準動作点となるよう設定して（ＳｔｅｐＷ０７）、次のＳｔｅｐＷ０９へ進む。
【００４１】
ＳｔｅｐＷ０９では、前記基準動作点の電力ＰＲと前記探索範囲下限電圧ＶＬでの電力ＰＶＬの大小関係を比較し、前記基準動作点電力ＰＲのほうが小さい時には、前記探索範囲下限電圧ＶＬでの動作点を基準動作点として前記動作点の電圧ＶＬおよび電力ＰＶＬを前記基準動作点の電圧ＶＲおよび電力ＰＲに設定して（ＳｔｅｐＷ１０）、次のＳｔｅｐＷ１１へ進む。
ＳｔｅｐＷ１１では、前記基準動作点の電力ＰＲと前記探索範囲上限電圧ＶＨでの電力ＰＶＨの大小関係を比較し、前記基準動作点電力ＰＲのほうが小さい時には、前記探索範囲上限電圧ＶＨでの動作点を基準動作点として前記動作点の電圧ＶＨおよび電力ＰＶＨを前記基準動作点の電圧ＶＲおよび電力ＰＲに設定して（ＳｔｅｐＷ１２）、次のＳｔｅｐＷ１３へ進む。
そして、ＳｔｅｐＷ１３で前記基準動作点電圧ＶＲを動作電圧Ｖに設定して、ＷＡＳルーチンの処理は終了する。
【００４２】
ＳｔｅｐＷ００にてＷＡＳ制御を行った後は、ＳｔｅｐＭ０１に戻りＷＡＳ周期をカウントするタイマーをリセットし、前述の動作を繰り返す。
【００４３】
このように、常時は通常のＭＰＰＴ制御を行うことにより、現在の「山」における最大電力点を精密に追従し、長い周期にて広範囲探索し電圧ー電力特性の電力カーブの極大点の数から「山」に応じた動作点を設定するＷＡＳ制御により、「２山」があった場合でも時々は極大点および探索範囲端動作点に基づき最大電力が得られる「山」に移動を行う。これにより、動作中の大部分の時間において電池電源から最大電力を取り出すことが出来る。
【００４４】
なお、常時行う通常のＭＰＰＴ制御は、前記山登り法だけに限定するものではなく、他の方法でもよい。
【００４５】
【実施例２】
次に、本発明の他の実施例について説明する。
本発明の電力制御方法を用いた太陽光発電システムは、実施例１と同様に図１のような構成をとる。以下、図４および図５により実施例１とは違った電力制御方法について説明する。図４は、横軸が電圧、縦軸が電力を示しており、電圧ー電力出力特性曲線を示している。また、図５に本実施例に係るフローチャートが示されている。
図５において、ＳｔｅｐＭ０１からＳｔｅｐＭ１０までの常時行われるＭＰＰＴ制御は実施例１と同様の山登り法であり、以下においては、実施例１と異なるＷＡＳ制御（ＳｔｅｐＷ２０）について説明する。
【００４６】
ＳｔｅｐＷ２０のＷＡＳルーチンでは、まず初めに、現在の動作点の電圧および電流をサンプリングして電力値を計算し、その電圧値および電力値を基準動作点電圧ＶＲおよび基準動作点電力ＰＲとして記憶する（ＳｔｅｐＷ２１）。
次に、変動範囲下限電圧ＶＬから変動範囲上限電圧ＶＨの間の変動範囲で動作点を変動させて、電圧および電流をサンプリングして電力値を計算する。変動範囲下限電圧ＶＬおよび変動範囲上限電圧ＶＨでの動作点の電力値ＰＶＬおよびＰＶＨを記憶するとともに、もし電力値の極小点が検出されたなら、前記変動範囲内で前記極小点より外側における極大点の動作点を検出して記憶する（ＳｔｅｐＷ２２）。
【００４７】
次のＳｔｅｐＷ２３にて極小点の有無を判断して分岐する。
もし極小点があるのなら、探索した変動範囲内に２つ以上の山が存在しており他の山に最大電力点がある可能性があることを意味しており、以下のように極大点および探索範囲端の動作点について吟味する。
まず、前記極大点の中から電力が最大となる極大点（電圧Ｖ極大点ｘ、電力Ｐ極大点ｘ）を抽出し（ＳｔｅｐＷ２４）、前記最大電力極大点の電力Ｐ極大点ｘと前記基準動作点の電力ＰＲを比較し（ＳｔｅｐＷ２５）、基準動作点電力ＰＲのほうが小さいなら、前記極大点を前記基準動作点となるよう設定して（ＳｔｅｐＷ２６）、次のＳｔｅｐＷ２７へ進む。
【００４８】
ＳｔｅｐＷ２７では、前記基準動作点の電力ＰＲと前記探索範囲下限電圧ＶＬでの電力ＰＶＬの大小関係を比較し、前記基準動作点電力ＰＲのほうが小さい時には、前記探索範囲上限電圧ＶＬでの動作点を基準動作点として前記動作点の電圧ＶＬおよび電力ＰＶＬを前記基準動作点の電圧ＶＲおよび電力ＰＲに設定して（ＳｔｅｐＷ２８）、次のＳｔｅｐＷ２９へ進む。
【００４９】
ＳｔｅｐＷ２９では、前記基準動作点の電力ＰＲと前記探索範囲上限電圧ＶＨでの電力ＰＶＨの大小関係を比較し、前記基準動作点電力ＰＲのほうが小さい時には、前記探索範囲上限電圧ＶＨでの動作点を基準動作点として前記動作点の電圧ＶＨおよび電力ＰＶＨを前記基準動作点の電圧ＶＲおよび電力ＰＲに設定して（ＳｔｅｐＷ３０）、次のＳｔｅｐＷ３１へ進む。
【００５０】
もし極小点がないのであれば、探索範囲内には１山しか存在しないので、通常のＭＰＰＴ制御により最大電力を取り出すことができ、ＳｔｅｐＷ３１へ飛ぶ。そして、ＳｔｅｐＷ３１で前記基準動作点電圧ＶＲを動作電圧Ｖに設定して、ＷＡＳルーチンの処理は終了する。
【００５１】
ＳｔｅｐＷ２０にてＷＡＳ制御を行った後は、ＳｔｅｐＭ０１に戻りＷＡＳ周期をカウントするタイマーをリセットし、前述の動作を繰り返す。
【００５２】
このように、常時は通常のＭＰＰＴ制御を行うことにより、現在の「山」における最大電力点を精密に追従し、長い周期にて広範囲探索し電圧ー電力特性の電力カーブの極小点の有無を判断し、極小点が有れば「２山」であるとして極大点および探索範囲端動作点を吟味し、「山」に応じた動作点を設定するＷＡＳ制御を行うことにより、「２山」があった場合でも時々は最大電力が得られる「山」に移動を行うことにより、電池電源から最大電力を取り出すことが出来る。
【００５３】
【実施例３】
次に、さらに他の実施例について説明する。
【００５４】
本発明の電力制御方法を用いた太陽光発電システムは、実施例１および２と同様に図１のような構成をとる。以下、図６および図７により実施例１および２とは違った電力制御方法について説明する。図６は、横軸が電圧、縦軸が電力を示しており、電圧ー電力出力特性曲線を示している。また、図７に本実施例に係るフローチャートが示されている。
【００５５】
ＳｔｅｐＭ０１からＳｔｅｐＭ１０までの常時行われるＭＰＰＴ制御は実施例１および２と同様の山登り法であり、以下、実施例１および２と異なるＷＡＳ制御（ＳｔｅｐＷ４０）について説明する。
【００５６】
ＳｔｅｐＷ４０のＷＡＳルーチンでは、まず初めに、変動範囲下限電圧ＶＬから変動範囲上限電圧ＶＨの間の変動範囲で動作点を変動させて、電圧および電流をサンプリングして電力値を計算する（ＳｔｅｐＷ４１）。
次に、サンプリングされた動作点の中から電力が最大となる動作点を検出し（ＳｔｅｐＷ４２）、前記検出電力最大動作点および前記検出電力最大動作点のすぐ近傍の２つの動作点を抽出し、各々（Ｖ１、Ｐ１）（Ｖ２、Ｐ２）（Ｖ３、Ｐ３）に設定する（ＳｔｅｐＷ４３）。
上記（Ｖ１、Ｐ１）（Ｖ２、Ｐ２）（Ｖ３、Ｐ３）の３つの動作点をもとに電圧ー電力特性曲線を二次曲線により近似し、前記近似二次曲線の電力が最大となる電圧Ｖｐｍａｘを算出する（ＳｔｅｐＷ４４、ＳｔｅｐＷ４５）。
そして、ＳｔｅｐＷ４６で前記Ｖｐｍａｘを動作電圧Ｖに設定して、ＷＡＳルーチンの処理は終了する。
【００５７】
ＳｔｅｐＷ４０にてＷＡＳ制御を行った後は、ＳｔｅｐＭ０１に戻りタイマーをリセットし、前述の動作を繰り返す。
【００５８】
このように、常時は通常のＭＰＰＴ制御を行うことにより、現在の「山」における最大電力点を精密に追従し、長い周期にて広範囲探索し電圧ー電力特性の電力カーブを有極関数により特性を近似して近似曲線が最大となる電圧を動作点として設定するＷＡＳ制御を行うことにより、「２山」があった場合でも時々は最大電力が得られる「山」に移動を行い、電池電源から最大電力を取り出すことができる。
【００５９】
【実施例の変形例】
なお、ＷＡＳ制御における曲線近似を用いる手法に、特開平６ー３４８３５２号公報などに開示されている方法を適用してもよい。
【００６０】
また、ＷＡＳ制御においては、「山」の数が２つ以上あるか否かを判定し、「山」の数が２つ以上なら最大電力が得られる「山」に移動する（「山」と「山」の間の「谷」を越える）ものであればよい。また、必ずしも最大電力が得られる「山」の中の最大電力が得られる動作点を設定する必要はない。これらは、本発明の主旨に反しない。
【００６１】
さらに、ＷＡＳ制御において、同じ電圧で電流値を２回以上、所定回数以下で毎回の電流値または電力値の差が所定値以下になるまでサンプリングを行うようにしてもよい。この場合、日射変動の影響を取り除いたより確実なＷＡＳ制御を行うことができる。この複数回のサンプリングは、同一電圧を持続した状態で連続して行ってもよく、電圧を繰り返しスキャンする等して電圧を変化させながら行ってもよい。
【００６２】
【発明の効果】
以上述べてきたように、本発明の電力制御装置では、以下の効果を有する。
（１）電圧ー電力特性曲線で２山が生じる場合でも、電力が大きいほうの山へ移動でき、最大電力を取り出すことができる。
（２）常時は通常のＭＰＰＴ制御を行っているので、最適動作点を精密に追尾出来る。
（３）長いインターバルにてＷＡＳ制御を行うので、広範囲探索によるロスを極力抑えられる。
（４）動作可能な範囲の中で電力が最大となる動作点が極大点でない場合でも追従できる。
（５）ＷＡＳ制御にてサンプリング動作点の間の動作点を精密に設定できる。
（６）日射変動の有無を検出することによりＷＡＳ制御の誤動作による出力低下を抑制出来る。
【図面の簡単な説明】
【図１】本発明の一実施例に係る電力制御装置を備えた太陽光発電システムの一構成例を示すブロック図である。
【図２】図１のシステムにおける最適動作点探索の説明図である。
【図３】図１のシステムにおける最適動作点探索動作を説明するフローチャートである。
【図４】本発明の他の実施例に係る最適動作点探索の説明図である。
【図５】本発明の他の実施例に係る最適動作点探索動作を説明するフローチャートである。
【図６】本発明のさらに他の実施例に係る最適動作点探索の説明図である。
【図７】本発明のさらに他の実施例に係る最適動作点探索動作を説明するフローチャートである。
【図８】太陽電池の電圧ー電力特性の例を示すグラフである。
【符号の説明】１：電池電源、２：電力変換手段、３：負荷、４：電圧検出手段、５：電流検出手段、６：出力電圧設定手段、７：制御手段。[0001]
[Industrial applications]
The present invention relates to a power control device of a photovoltaic power generation system having a power conversion device.
[0002]
[Prior art]
Today, with increasing awareness of the global environment, great expectations are placed on battery power systems such as solar power generation and wind power generation that provide clean energy. For example, when a solar battery is used as a battery power source and connected to an existing commercial AC system, it is possible to supply surplus electric power to the domestic load while considering the commercial AC system as an infinite load. A power supply system including the solar cell, a power conversion device that converts the output into AC power, and a domestic load is required to operate most efficiently as a whole.
[0003]
Since the output of a solar cell using a photoelectric conversion element fluctuates considerably depending on the amount of solar radiation, temperature, operating point voltage, etc., it is necessary to adjust the load seen from the solar cell and always extract the maximum power. Is done. For this reason, the voltage or current at the operating point of a solar cell array composed of a plurality of solar cells is varied, the power fluctuation at that time is examined, and the maximum power of the solar cell array or the operating point near the maximum power is tracked. Power point tracking control, so-called MPPT control, has been proposed. For example, a method using a voltage differential value of power described in JP-B-63-57807 or a so-called hill-climbing method in which the amount of power change described in JP-A-62-25312 is searched in a positive direction. There is a law.
[0004]
Further, in Japanese Patent Application Laid-Open No. 7-225624, a local maximum point is detected between the open voltage of the solar cell and the minimum voltage, and a local maximum voltage at which the maximum electric power is set among the local maximum points is set. are doing.
[0005]
Conventionally, such a method has been used to control a power converter or the like so as to extract the maximum power from the solar cell.
[0006]
[Problems to be solved by the invention]
However, the above method has the following problems.
Normally, the voltage-power characteristic of the solar cell array has a shape (horizontal axis is voltage and vertical axis is power) as shown in FIG. Falls, a voltage-power characteristic as shown in FIG. 8B may be obtained. The operating point (1) in FIG. 8B can extract the maximum power from the solar cell array, but the operating point (2) is the maximum point but not the maximum power point.
[0007]
In the conventional hill-climbing method, since a certain direction at the top of the “mountain” of the voltage-power characteristic curve is found by the sign of the amount of power change caused by changing the operating point, the operating point is (1) or (1). If it is near 1), the operating point can follow the top of the "mountain" of 1) and extract the maximum power from the solar cell array. However, when the operating point is located at or near (2), the operating point mistakenly follows the peak of the "mountain" of (2) as the maximum power point, and follows the peak power from the solar cell array. I can't take it out.
[0008]
Thus, a so-called “two-mountain problem” may occur.
[0009]
Although the operation in the hill-climbing method has been described above, the same result is obtained in the control method using the voltage differential value of the electric power.
[0010]
On the other hand, in the method described in Japanese Patent Application Laid-Open No. Hei 7-225624, it is possible to take the peak of one of the two “mountains” with the larger power. However, since the operable range of the power converter connected to the solar cell is limited as shown in FIG. 8C, the maximum power operating point {circle around (3)} within the operable range is not the maximum point. The method cannot extract the maximum power. In addition, since the above method scans a very wide range from the open voltage of the solar cell to the minimum voltage, there is a concern about power loss during scanning. Therefore, if the above method is performed at a long interval, the optimum operating point constantly fluctuates, so that the tracking cannot be performed precisely because the optimum operating point deviates from the optimum operating point, and the maximum power cannot be extracted. In addition, when solar radiation fluctuations occur while searching for a wide range, operating points with different voltage-power characteristics are sampled, and the operating points are set based on the sampling points. .
[0011]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a power control device that supplements the drawbacks of the conventional solar cell power control method and extracts the maximum output from the solar cell.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, the normal MPPT control is always performed, and the operating point of the solar cell is varied over a wide search range in a longer cycle than the MPPT control to change the operating point voltage and The power is calculated by taking in the current, and when the voltage-power characteristic is two peaks, it is determined whether or not the original operating point is on the peak where the maximum power can be obtained. An operating point is selected, and if the operating point at which the maximum power is obtained is on another peak, an operating point on that peak is selected, and the voltage of the selected operating point is set as a set value for the MPPT control. And
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
More specifically, the object is to provide a battery power supply, power conversion means for converting power from the battery power supply to supply the load to a load, voltage detection means for detecting a voltage value of the battery power supply, Current detection means for detecting the current value of the power supply, output value setting means for setting the output value of the battery power supply based on the detection value of the voltage detection means and the current detection means, the output value of the battery power supply Control means for controlling the power conversion means so as to match a set value of the output value setting means, wherein the output value setting means sets an operating point of the battery power supply in a first variation range in a first cycle. The voltage value and the current value are sampled by fluctuating, and the set value is set so that the power from the battery power supply is maximized based on the voltage value and the current value, and at a period longer than the first period. In a certain second cycle That is, a voltage value and a current value are sampled by varying an operating point in a second variation range wider than the first variation range, and the power from the battery power source is determined to be maximum based on the voltage value and the current value. The power control device is characterized in that the set value is set so as to be as follows.
[0014]
The above object is also achieved by a battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and detecting a current value of the battery power supply. Current detection means, output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means, and the output value of the battery power supply being the output value setting means Control means for controlling the power conversion means so as to match the set value of the power supply means, wherein the output value setting means changes the operating point of the battery power supply in a first fluctuation range in a first cycle to obtain a voltage value. And the current value is sampled, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle. Is before A voltage value and a current value are sampled by varying an operating point in a second variation range wider than the first variation range, and a voltage-power characteristic in the second variation range is two peaks based on the voltage value and the current value. It is determined whether or not there is more than two peaks, and if the number is two or more, the set value is set to the voltage of the operating point in the mountain where the operating point at which the maximum power is obtained is based on the voltage value and the current value. This is achieved by a power control device.
[0015]
The above object is also achieved by a battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and detecting a current value of the battery power supply. Current detection means, output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means, and the output value of the battery power supply being the output value setting means Control means for controlling the power conversion means so as to match the set value of the power supply means, wherein the output value setting means changes the operating point of the battery power supply in a first fluctuation range in a first cycle to obtain a voltage value. And the current value is sampled, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle. The current movement The voltage value and the current value are sampled and stored using the point as a reference operating point, and the voltage value and the current value are sampled by changing the operating point in a second variation range wider than the first variation range. Calculate the power value at each operating point from the current value, store the local maximum point of the output power of the battery power source and the operating point at the end of the second fluctuation range, and when there is only one local maximum point, After setting the maximum point as the reference operating point, comparing the power value of the operating point at the end of the second variation range with the power value of the reference operating point, the power value of the operating point at the end of the second variation range is larger. Performs a first comparison setting for setting the operating point at the end of the second variation range to the reference operating point, and when there are two or more local maximum points, a plurality of the local maximum points together with the first comparative setting Of the maximum power from the When the local maximum point is compared with the power value of the reference operating point and the local maximum point is larger, a second comparison setting for setting the local maximum point to the reference operating point is performed, and the voltage of the standard operating point is set to the voltage. This is achieved by a power control device characterized by setting to a set value.
[0016]
The above object is also achieved by a battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and detecting a current value of the battery power supply. Current detection means, output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means, and the output value of the battery power supply being the output value setting means Control means for controlling the power conversion means so as to match the set value of the power supply means, wherein the output value setting means changes the operating point of the battery power supply in a first fluctuation range in a first cycle to obtain a voltage value. And the current value is sampled, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle. The current movement The voltage value and the current value are sampled and stored using the point as a reference operating point, and the voltage value and the current value are sampled by changing the operating point in a second variation range wider than the first variation range. An electric power value at each operating point is calculated from the current value, a minimum point of the output power of the battery power supply is detected, and when the minimum point is detected, an end of the second fluctuation range is calculated from the minimum point. The maximum value on the side and the operating point at the end of the second variable range are detected and stored, and the operating point at the end of the second variable range is compared with the power value at the reference operating point to operate at the end of the second variable range. When the power value of the point is larger, a first comparison setting for setting the operating point at the end of the second fluctuation range to the reference operating point is performed, and when there is the maximum point, together with the first comparison setting, The maximum point where the electric power is maximum from among the plurality of maximum points The power value of the selected maximum point and the reference operation point are compared, and when the maximum point is larger, a second comparison setting for setting the maximum point to the reference operation point is performed, and the reference operation point is set. Is set to the set value by the power control apparatus.
[0017]
The above object is also achieved by a battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and detecting a current value of the battery power supply. Current detection means, output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means, and the output value of the battery power supply being the output value setting means Control means for controlling the power conversion means so as to match the set value of the power supply means, wherein the output value setting means changes the operating point of the battery power supply in a first fluctuation range in a first cycle to obtain a voltage value. And the current value is sampled, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle. The current movement The voltage value and the current value are sampled and stored using the point as a reference operating point, and the voltage value and the current value are sampled by changing the operating point in a second variation range wider than the first variation range. Calculating the power value at each operating point from the current value, detecting the minimum point of the output power of the battery power supply, and detecting the minimum point, the end point of the second fluctuation range from the minimum point. The maximum power operating point is detected and stored, and the maximum power operating point is compared with the power value of the reference operating point, and when the power value of the maximum power operating point is larger, the maximum power operating point is determined. The power control device is set at the reference operating point, and the voltage at the reference operating point is set at the set value.
[0018]
The above object is also achieved by a battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and detecting a current value of the battery power supply. Current detection means, output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means, and the output value of the battery power supply being the output value setting means Control means for controlling the power conversion means so as to match the set value of the power supply means, wherein the output value setting means changes the operating point of the battery power supply in a first fluctuation range in a first cycle to obtain a voltage value. And the current value is sampled, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle. And the first The operating point is varied in a second variation range wider than the dynamic range, and the voltage value and the current value are sampled. The power value at each operating point is calculated from the voltage value and the current value. The operating point above the point is approximated by a polar function with respect to a voltage-power curve using a detected value, and a voltage at a point at which the local maximum of the polar function is set to the set value. This is achieved by a power control device.
[0019]
The above object is also achieved by a battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and detecting a current value of the battery power supply. Current detection means, output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means, and the output value of the battery power supply being the output value setting means Control means for controlling the power conversion means so as to match the set value of the power supply means, wherein the output value setting means changes the operating point of the battery power supply in a first fluctuation range in a first cycle to obtain a voltage value. And the current value is sampled, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle. Is before A voltage value and a current value are sampled by varying the operating point in a second variation range wider than the first variation range, and the current value is calculated by multiplying the current value or the voltage value and the current value at a plurality of operating points of the same voltage. If the difference between the power values is equal to or more than a predetermined value, the sampling is repeated up to a predetermined number of times, or the original operation point is set by canceling the setting operation, and if the difference between the power values is less than a predetermined value, the voltage value and the The power control apparatus is characterized in that the set value is set so that the power from the battery power supply is maximized based on the current value.
[0020]
[Action]
In the power control apparatus of the present invention, the optimal operating point of the solar cell is always accurately tracked by performing the MPPT control in the short operating range of the first variable range in the short cycle of the first cycle.
[0021]
Also, in the second cycle longer than the first cycle, the operating point variation range of the second variation range that is wider than the first variation range is searched, and the number of peaks of the power becomes “two peaks”. Judgment is made based on the maximum point and the operating point at the end of the search range, and in the case of “two peaks”, the operating point of the “mountain” with the larger power is set to solve the two-peak problem. Thus, the maximum power can be extracted from the solar cell.
[0022]
Also, in the second cycle longer than the first cycle, the operating point variation range of the second variation range wider than the first variation range is searched, and “two peaks” is determined based on whether or not there is a minimum point of power. Is determined, and based on the local maximum point and the operating point at the end of the search range, in the case of “two peaks”, the operating point of the “mountain” with the larger power is set, thereby solving the two-peak problem. And the maximum power can be extracted from the solar cell.
[0023]
Further, in a second cycle longer than the first cycle, an operating point variation range of a second variation range wider than the first variation range is searched, and a voltage-power characteristic curve of part or all of the search range is searched. By setting the operating point to the voltage at the maximum point of the polar approximation curve, the two-mountain problem can be solved and the maximum power can be extracted from the solar cell.
[0024]
Further, by determining the presence or absence of the fluctuation of the solar radiation based on the difference between the current values or the electric power values of a plurality of operating points of the same voltage, it is possible to suppress the malfunction and to suppress the output reduction.
[0025]
Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0026]
FIG. 1 shows a configuration of a photovoltaic power generation system using a power control device according to one embodiment of the present invention. In the figure, DC power of a battery power supply 1 is converted into power by a power conversion means 2 and supplied to a load 3.
[0027]
As the battery power supply 1, there is a solar battery using amorphous silicon, microcrystalline silicon, polycrystalline silicon, single crystal silicon, a compound semiconductor, or the like. Usually, a plurality of solar cell modules are combined in series and parallel to form an array so as to obtain a desired voltage and current.
[0028]
Examples of the power conversion means 2 include a DC / DC converter using a self-extinguishing switching device such as a power transistor, a power MOSFET, an IGBT, and a GTO, and an automatic voltage-type DC / AC inverter. The power converter 2 can control the power flow, input / output voltage, output frequency, and the like by changing the on / off duty ratio of the gate pulse.
[0029]
The load 3 includes an electric heat load, a motor load, a commercial AC system, and a combination thereof. When the load 3 is a commercial AC system, it is called a grid-connected solar power generation system, and the power that can be supplied to the system is not limited. It is very preferable as a target.
[0030]
The output voltage and output current of the battery power supply 1 are detected by voltage detection means 4 and current detection means 5 which are usually used, a voltage detection signal is input to output voltage setting means 6 and control means 7, and a current detection signal is output voltage It is input to the setting means 6. The output voltage setting means 6 stores these voltage detection signal and current detection signal.
[0031]
The output voltage setting means 6 determines a voltage set value based on the stored voltage detection signal and current detection signal. The output voltage setting means 6 is a control microcomputer and includes a CPU, a RAM, a ROM, an I / O, and the like.
[0032]
The control means 7 is an output control circuit and a gate drive circuit of the power conversion means 2. For example, a PI control circuit which receives a voltage error signal which is a deviation between a voltage setting value from the output voltage setting means 6 and a voltage detection signal from the voltage detecting means 4 and controls the voltage error signal to be zero, And a PWM circuit that generates a PWM pulse for gate drive by a triangular wave comparison method, instantaneous current tracking control, or the like in accordance with the output from the controller. This controls the on / off duty ratio of the switching device of the power conversion means 2 to control the output voltage of the solar cell.
[0033]
Next, a search for an operating point at which the maximum power is obtained in the power control device of the present embodiment will be described with reference to FIGS. FIG. 2 shows a voltage-power output characteristic curve, with the horizontal axis representing voltage and the vertical axis representing power. FIG. 3 shows a flowchart according to the present embodiment.
In the present embodiment, first, an initial operation voltage V0, a step variation width dV, a search direction, a variation range lower limit voltage VL, a variation range upper limit voltage VH, and a cycle of power control by a wide range search (hereinafter, referred to as a WAS cycle) are predetermined. It is better to store it in a ROM. The initial operation voltage V0 is determined by the configuration of the solar cell array. The step fluctuation width dV is set to be about 1 to 3% of the operable voltage range of the power conversion means 2. The search direction may be either the increasing direction or the decreasing direction. The fluctuation range lower limit voltage VL and the fluctuation range upper limit voltage VH are set within the operable voltage range of the power conversion means 2. The WAS cycle is a cycle of power control (herein referred to as WAS control) for a wide range search performed in a longer cycle than normal MPPT control, and is set to be, for example, about several tens of minutes.
[0034]
At the start of power conversion, after setting the operating voltage V to the initial operating voltage V0, the MPPT control is always performed by the hill-climbing method, and the WAS control is sometimes performed according to the WAS cycle.
The actual operation is as follows.
When the MPPT control is started, first, a timer for counting the WAS cycle is reset (Step M01).
Next, the voltage and current at the set operating point are sampled, and the power value P0 is calculated and stored (Step M02).
Next, it is determined whether the WAS cycle has been reached by looking at the timer (Step M03). If it is not the WAS cycle, the process proceeds to Step M04 as to perform the normal MPPT control, and if it is the WAS cycle, the process proceeds to Step W00 as to perform the WAS control. Since the WAS cycle is set to be long, in most cases, the process goes to Step M04 of the normal MPPT control.
[0035]
In Step M04, the process branches in accordance with the search direction. If the search direction is "increase", the process proceeds to Step M05, and the operating point voltage is set to a voltage higher than the current voltage by the step variation width dV, and if the search direction is "decrease", the process proceeds to Step M06. Then, the operating point voltage is set to a voltage lower by the step variation width dV. Then, the process proceeds to Step M07.
[0036]
Next, the voltage and current at the set operating point are sampled, and the power value P1 is calculated and stored (Step M07).
In Step M08, the power value P1 at the current operating point is compared with the power value P0 at the previous operating point. If the power value P1 is equal to or less than the power value P0, it is determined that the vehicle has passed the optimum operating point, and the search direction is reversed in Step M09. If the power value P1 is larger than the power value P0, the optimum operating point is still ahead, so that the search direction is left as it is, and Step M09 is bypassed.
Then, after storing the power value P1 as the power value P0 (Step M10), the process returns to Step M03, and the above operation is repeated.
[0037]
If it is determined in Step M03 that the WAS cycle has been reached, the process jumps to the WAS routine of Step M00.
In the WAS routine, first, a voltage and a current value of a current operating point are sampled to calculate a power value, and the voltage value and the power value are stored as a reference operating point voltage VR and a reference operating point power PR (Step W01). ).
Next, the operating point is varied in the fluctuation range between the fluctuation range lower limit voltage VL and the fluctuation range upper limit voltage VH, and the voltage and current are sampled to calculate the power value. Then, the maximum point of the power value is detected, and the voltage and the power at the maximum point are stored. Also, the power values PVL and PVH at the operating point at the fluctuation range lower limit voltage VL and the fluctuation range upper limit voltage VH are stored (Step W02).
[0038]
Next, it is determined whether or not there is a local maximum point. If there is no local maximum point, it is determined that there are no two peaks in the search range, and the process is skipped to Step W13. If there is a local maximum point, the process proceeds to the next Step W03.
If there is a local maximum point, the process branches depending on whether the number of local maximum points is one or two or more (Step W04).
[0039]
When the number of the local maximum points is only one, the local maximum point is set as the reference operating point, and the voltage V local maximum point 1 and the power P local maximum point 1 of the local maximum point are set as the reference operating point voltage VR and the power PR ( (StepW08), and proceed to the next StepW09.
[0040]
When the number of local maximum points is two or more, local maximum points (voltage V local maximum x, power P local maximum x) at which the power becomes maximum are extracted from the local maximum points (Step M05), and the power maximum local point is obtained. Is compared with the power PR of the reference operating point (Step W06), and when the reference operating point power PR is smaller, the maximum point is set to be the reference operating point (Step W07). Then, the process proceeds to the next Step W09.
[0041]
In Step W09, the magnitude relationship between the power PR at the reference operating point and the power PVL at the search range lower limit voltage VL is compared. When the reference operating point power PR is smaller, the operating point at the search range lower limit voltage VL is determined. The voltage VL and the power PVL of the operating point are set as the reference operating point as the voltage VR and the power PR of the reference operating point (Step W10), and the process proceeds to the next Step W11.
In Step W11, the magnitude relation between the power PR at the reference operating point and the power PVH at the search range upper limit voltage VH is compared. When the reference operating point power PR is smaller, the operating point at the search range upper limit voltage VH is determined. The voltage VH and the power PVH at the operating point are set as the reference operating point as the voltage VR and the power PR at the reference operating point (Step W12), and the process proceeds to the next Step W13.
Then, in step W13, the reference operating point voltage VR is set to the operating voltage V, and the processing of the WAS routine ends.
[0042]
After performing the WAS control in Step W00, the process returns to Step M01, resets the timer for counting the WAS cycle, and repeats the above operation.
[0043]
As described above, by always performing the normal MPPT control, the current maximum power point in the “mountain” is accurately followed, and a wide range search is performed in a long cycle, and the number of the maximum points in the power curve of the voltage-power characteristic is calculated. By the WAS control for setting the operating point according to the "mountain", even when there is "two peaks", the vehicle sometimes moves to the "mountain" where the maximum power can be obtained based on the local maximum point and the search range end operating point. As a result, the maximum power can be extracted from the battery power supply during most of the operation.
[0044]
The normal MPPT control that is always performed is not limited to the hill-climbing method, but may be another method.
[0045]
Embodiment 2
Next, another embodiment of the present invention will be described.
A solar power generation system using the power control method of the present invention has a configuration as shown in FIG. Hereinafter, a power control method different from that of the first embodiment will be described with reference to FIGS. 4 and 5. FIG. 4 shows a voltage-power output characteristic curve, with the horizontal axis representing voltage and the vertical axis representing power. FIG. 5 shows a flowchart according to the present embodiment.
In FIG. 5, the MPPT control that is always performed from Step M01 to Step M10 is a hill-climbing method similar to that of the first embodiment. Hereinafter, a WAS control (Step W20) different from that of the first embodiment will be described.
[0046]
In the WAS routine of Step W20, first, the voltage and current at the current operating point are sampled to calculate a power value, and the voltage value and the power value are stored as the reference operating point voltage VR and the reference operating point power PR ( StepW21).
Next, the operating point is varied in the fluctuation range between the fluctuation range lower limit voltage VL and the fluctuation range upper limit voltage VH, and the voltage and current are sampled to calculate the power value. The power values PVL and PVH at the operating point at the fluctuation range lower limit voltage VL and the fluctuation range upper limit voltage VH are stored, and if the minimum point of the power value is detected, the maximum outside the minimum point within the fluctuation range is detected. The operating point is detected and stored (Step W22).
[0047]
In the next Step W23, it is determined whether or not there is a minimum point, and the process branches.
If there is a minimum point, it means that there are two or more peaks in the searched fluctuation range, and there is a possibility that the maximum power point exists in other peaks. And the operating point at the end of the search range.
First, a maximum point (voltage V maximum point x, power P maximum point x) at which the power is maximum is extracted from the maximum points (Step W24), and the power P maximum point x of the maximum power maximum point and the reference operation are extracted. The power PR at the points is compared (Step W25). If the reference operating point power PR is smaller, the maximum point is set to be the reference operating point (Step W26), and the process proceeds to the next Step W27.
[0048]
In Step W27, the magnitude relationship between the power PR at the reference operating point and the power PVL at the search range lower limit voltage VL is compared. When the reference operating point power PR is smaller, the operating point at the search range upper limit voltage VL is determined. The voltage VL and the power PVL at the operating point are set as the reference operating point as the voltage VR and the power PR at the reference operating point (Step W28), and the process proceeds to the next Step W29.
[0049]
In Step W29, the magnitude relation between the power PR at the reference operating point and the power PVH at the search range upper limit voltage VH is compared. The voltage VH and the power PVH at the operating point are set as the reference operating point as the voltage VR and the power PR at the reference operating point (Step W30), and the process proceeds to the next Step W31.
[0050]
If there is no minimum point, since only one peak exists in the search range, the maximum power can be extracted by ordinary MPPT control, and the process jumps to Step W31. Then, in Step W31, the reference operating point voltage VR is set to the operating voltage V, and the processing of the WAS routine ends.
[0051]
After performing the WAS control in Step W20, the process returns to Step M01, resets the timer for counting the WAS cycle, and repeats the above operation.
[0052]
As described above, by always performing the normal MPPT control, the current maximum power point in the “mountain” is accurately tracked, and a wide range is searched in a long cycle to determine whether or not there is a minimum point in the power curve of the voltage-power characteristic. Judgment is made, and if there is a minimum point, the maximum point and the operating point at the end of the search range are determined as "two peaks", and the WAS control for setting an operating point according to "mountain" is performed, thereby "two peaks". Even if there is, sometimes the maximum power can be obtained from the battery power source by moving to the “mountain” where the maximum power can be obtained.
[0053]
Embodiment 3
Next, still another embodiment will be described.
[0054]
A solar power generation system using the power control method of the present invention has a configuration as shown in FIG. 1 as in the first and second embodiments. Hereinafter, a power control method different from the first and second embodiments will be described with reference to FIGS. 6 and 7. FIG. 6 shows a voltage-power output characteristic curve in which the horizontal axis represents voltage and the vertical axis represents power. FIG. 7 shows a flowchart according to the present embodiment.
[0055]
The MPPT control that is constantly performed from Step M01 to Step M10 is a hill-climbing method similar to the first and second embodiments. Hereinafter, a WAS control (Step W40) different from the first and second embodiments will be described.
[0056]
In the WAS routine of Step W40, first, the operating point is changed in the fluctuation range between the fluctuation range lower limit voltage VL and the fluctuation range upper limit voltage VH, and the voltage and current are sampled to calculate the power value (Step W41).
Next, from the sampled operating points, an operating point at which the power becomes the maximum is detected (Step W42), and two operating points immediately adjacent to the detected power maximum operating point and the detected power maximum operating point are extracted, Each is set to (V1, P1) (V2, P2) (V3, P3) (Step W43).
A voltage-power characteristic curve is approximated by a quadratic curve based on the three operating points (V1, P1) (V2, P2) (V3, P3), and a voltage at which the power of the approximate quadratic curve is maximized. Vpmax is calculated (StepW44, StepW45).
Then, in step W46, the Vpmax is set to the operating voltage V, and the processing of the WAS routine ends.
[0057]
After performing the WAS control in Step W40, the process returns to Step M01, resets the timer, and repeats the above-described operation.
[0058]
As described above, by always performing the normal MPPT control, the maximum power point in the current “mountain” is accurately tracked, a wide range search is performed in a long cycle, and the power curve of the voltage-power characteristic is characterized by a polar function. By performing the WAS control that sets the voltage at which the approximation curve becomes the maximum as the operating point by approximating the equation (2), even if there are "two peaks", the peak power is sometimes moved to the "mountain" where the maximum power can be obtained. From the maximum power.
[0059]
[Modification of Embodiment]
It should be noted that a method disclosed in Japanese Patent Application Laid-Open No. 6-348352 may be applied to a method using curve approximation in WAS control.
[0060]
Also, in the WAS control, it is determined whether or not the number of “mountains” is two or more, and if the number of “mountains” is two or more, it moves to the “mountain” where the maximum power can be obtained (the “mountain”). Anything that crosses the "valley" between "mountains" may be used. In addition, it is not always necessary to set the operating point at which the maximum power is obtained in the “mountain” where the maximum power is obtained. These do not contradict the gist of the present invention.
[0061]
Further, in the WAS control, the current value may be sampled at the same voltage twice or more, a predetermined number of times or less, and the difference between the current value or the power value at each time becomes a predetermined value or less. In this case, it is possible to perform more reliable WAS control by removing the influence of the solar radiation fluctuation. The plurality of samplings may be performed continuously while maintaining the same voltage, or may be performed while changing the voltage by repeatedly scanning the voltage.
[0062]
【The invention's effect】
As described above, the power control device of the present invention has the following effects.
(1) Even when two peaks occur in the voltage-power characteristic curve, it is possible to move to the peak with the larger power and to extract the maximum power.
(2) Since normal MPPT control is always performed, the optimum operating point can be accurately tracked.
(3) Since the WAS control is performed at a long interval, loss due to a wide range search can be minimized.
(4) Even if the operating point where the electric power becomes maximum in the operable range is not the maximum point, it can be followed.
(5) The operating point between the sampling operating points can be set precisely by WAS control.
(6) By detecting the presence or absence of solar radiation fluctuation, it is possible to suppress a decrease in output due to a malfunction of the WAS control.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a photovoltaic power generation system including a power control device according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of an optimum operating point search in the system of FIG. 1;
FIG. 3 is a flowchart illustrating an optimum operation point search operation in the system of FIG. 1;
FIG. 4 is an explanatory diagram of an optimum operating point search according to another embodiment of the present invention.
FIG. 5 is a flowchart illustrating an optimal operation point search operation according to another embodiment of the present invention.
FIG. 6 is an explanatory diagram of an optimum operating point search according to still another embodiment of the present invention.
FIG. 7 is a flowchart illustrating an optimal operation point search operation according to still another embodiment of the present invention.
FIG. 8 is a graph showing an example of voltage-power characteristics of a solar cell.
[Description of Signs] 1: battery power source, 2: power conversion means, 3: load, 4: voltage detection means, 5: current detection means, 6: output voltage setting means, 7: control means.

Claims

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; An output value setting unit that sets an output value of the battery power supply based on the detection values of the voltage detection unit and the current detection unit; and an output value of the battery power supply matches the set value of the output value setting unit. Control means for controlling the power conversion means, and the output value setting means samples a voltage value and a current value by changing an operating point of the battery power supply in a first change range in a first cycle, The set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle, the first variation range is set. Wider The operating point is varied in two variation ranges to sample a voltage value and a current value, and the set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized. A power control device, comprising:

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; An output value setting unit that sets an output value of the battery power supply based on the detection values of the voltage detection unit and the current detection unit; and an output value of the battery power supply matches the set value of the output value setting unit. Control means for controlling the power conversion means, and the output value setting means samples a voltage value and a current value by changing an operating point of the battery power supply in a first change range in a first cycle, The set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in a second cycle that is longer than the first cycle, the first variation range is set. Wider A voltage value and a current value are sampled by changing an operating point in two fluctuation ranges, and it is determined whether there are two or more voltage-power characteristics in a second fluctuation range based on the voltage value and the current value, A power control device, wherein the set value is set to a voltage at an operating point in a mountain where an operating point at which the maximum power is obtained exists based on the voltage value and the current value if there are two or more peaks.

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; An output value setting unit that sets an output value of the battery power supply based on the detection values of the voltage detection unit and the current detection unit; and an output value of the battery power supply matches the set value of the output value setting unit. Control means for controlling the power conversion means, and the output value setting means samples a voltage value and a current value by changing an operating point of the battery power supply in a first change range in a first cycle, The set value is set so that the power from the battery power supply is maximized based on the voltage value and the current value, and the current operating point is set in a second cycle that is longer than the first cycle. As a reference operating point The voltage value and the current value are sampled and stored, and the voltage value and the current value are sampled by changing the operating point in a second fluctuation range wider than the first fluctuation range, and each operation is performed based on the voltage value and the current value. Calculating the power value at the point, storing the maximum point of the output power of the battery power source and the operating point at the end of the second fluctuation range, and when there is only one maximum point, sets the maximum point to the reference point. When the power value at the operating point at the end of the second fluctuation range is greater than the power value at the operation point at the end of the second fluctuation range and the power value at the reference operating point, A first comparison setting for setting the operating point at the end of the range to the reference operating point is performed. If there are two or more local maximum points, the power is maximized from among the plurality of local maximum points together with the first comparative setting. Is selected, and the selected maximum point and the When the power value at the quasi-operation point is compared and the maximum point is larger, a second comparison setting for setting the maximum point to the reference operation point is performed, and the voltage at the reference operation point is set to the set value. A power control device, characterized in that:

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; Output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means; and the output value of the battery power supply matches the set value of the output value setting means. Control means for controlling the power conversion means so that the operation value of the battery power source is varied in a first variation range in a first cycle to sample a voltage value and a current value. The set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and the current operation is performed in a second cycle that is longer than the first cycle. Point as reference operating point Sample and store the voltage value and the current value, and sample the voltage value and the current value by changing the operating point in the second fluctuation range wider than the first fluctuation range. A power value at each operating point is calculated, a minimum point of the output power of the battery power supply is detected, and when the minimum point is detected, the maximum value located on the end side of the second fluctuation range from the minimum point is detected. And the operating point at the end of the second variable range is detected and stored, and the operating value at the end of the second variable range is compared with the power value at the reference operating point to determine the power value at the operating point at the second variable range end. Is larger, the first comparison setting for setting the operating point at the end of the second variation range to the reference operating point is performed. If there is the maximum point, the plurality of local maximums are set together with the first comparison setting. From the points, select the maximum point where the power is the maximum, When the local maximum point is compared with the power value of the reference operating point and the local maximum point is larger, a second comparison setting for setting the local maximum point to the reference operating point is performed, and the voltage of the standard operating point is set. A power control device characterized in that it is set to a value.

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; Output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means; and the output value of the battery power supply matches the set value of the output value setting means. Control means for controlling the power conversion means so that the operation value of the battery power source is varied in a first variation range in a first cycle to sample a voltage value and a current value. The set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and the current operation is performed in a second cycle that is longer than the first cycle. Point as reference operating point Sample and store the voltage value and the current value, and sample the voltage value and the current value by changing the operating point in the second fluctuation range wider than the first fluctuation range. Calculate the power value at each operating point, detect the minimum point of the output power of the battery power supply, and if the minimum point is detected, the maximum power on the end side of the second fluctuation range from the minimum point. The operating point is detected and stored, and when the power value of the maximum power operating point is larger by comparing the power value of the maximum power operating point and the power value of the reference operating point, the maximum power operating point is set to the reference operating point. And the voltage at the reference operating point is set to the set value.

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; Output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means; and the output value of the battery power supply matches the set value of the output value setting means. Control means for controlling the power conversion means so that the operation value of the battery power source is varied in a first variation range in a first cycle to sample a voltage value and a current value. The set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and the first value is set in a second cycle that is longer than the first cycle. Wider than fluctuation range (2) The operating point is varied in the variation range, the voltage value and the current value are sampled, the power value at each operating point is calculated from the voltage value and the current value, and three or more operating points are sampled. The power control device is characterized in that the voltage vs. power curve is approximated by a polar function using the detected values of the above, and a voltage at a point where the polar function has a local maximum value is set to the set value.

A battery power supply, power conversion means for converting power from the battery power supply and supplying the load to a load, voltage detection means for detecting a voltage value of the battery power supply, and current detection means for detecting a current value of the battery power supply; Output value setting means for setting the output value of the battery power supply based on the detection values of the voltage detection means and the current detection means; and the output value of the battery power supply matches the set value of the output value setting means. Control means for controlling the power conversion means so that the operation value of the battery power source is varied in a first variation range in a first cycle to sample a voltage value and a current value. The set value is set based on the voltage value and the current value so that the power from the battery power supply is maximized, and in the second cycle that is longer than the first cycle, the first The fluctuation range A voltage value and a current value are sampled by varying an operating point in a wide second variation range, and a current value of a plurality of operating points of the same voltage or a difference between power values calculated by multiplying the voltage value and the current value is determined. If the value is equal to or greater than a predetermined value, the sampling is repeated up to a predetermined number of times, or the setting operation is canceled and the original operating point is set. And setting the set value such that the power from the battery power supply is maximized.