JP3599387B2 - Power storage system - Google Patents

Description

モジュールＡは、その放電深度が５０％（これが、特許請求の範囲においていうパラメータの”基準値”に相当するものである。）に達するまでは、定格電力Ｐｓ（Ｗ）で運転する。そして、それ以降の放電深度では、０．３Ｐｓ（定格電力の３０％）の出力電力で運転する。これは、放電深度が高い（ここでは、５０％以上）領域では、内部抵抗が増大するため（図３参照）、出力電力を下げることによって、電力損失を少なくするためである。既に述べたとおり、出力電力の調整は、電流値の変更により行なう。
【００６８】
一方、モジュールＢは、モジュールＡが定格電力Ｐｓで運転されている間（つまり、モジュールＡの放電深度が５０％以下の場合）は、電力を出力させない。モジュールＢは、モジュールＡの出力電力が０．３Ｐｓとされている時（すなわち、放電深度が５０％を越えた場合）に、０．７Ｐｓ（定格電力の７０％）の出力電力で運転を行う。該モジュールＢについては、モジュールＢ自身の放電深度には関係なく、常に、出力電力を０．７Ｐｓとされる。
【００６９】
このような負荷配分を行うことにより、モジュールＡの出力電力が０．３Ｐｓとされているときでも、電力貯蔵分散電源システム１９全体としては、一定電力（＝定格電力Ｐｓ）を出力しつづけることができる。
【００７０】
ここで述べた各モジュールＡ，Ｂの出力電力（モジュールＡ：Ｐｓ，０．３Ｐｓ、モジュールＢ：０．７Ｐｓ）は、当該放電深度領域における出力電力の最大値である。電力の需要が少なく、電力貯蔵分散電源システム１９として出力しなければならない出力電力がＰｓよりも小さい場合には、適宜、モジュールＡ，Ｂの出力電力を下げることは言うまでもない。
【００７１】
出力電力の切下げは、モジュールＢに対して優先的に行う。各放電深度毎の出力電力の最大値（Ｐｓ，０．３Ｐｓ）を越えない範囲内で、常に、モジュールＡを優先して放電させるようにする。例えば、モジュールＡの放電深度が８０％の領域において、電力貯蔵分散電源システム１９全体として必要な出力電力が０．９Ｐｓであった場合を考える。この場合には、モジュールＡの出力電力は０．３Ｐｓのままにして、モジュールＢの出力電力のみを０．６Ｐｓに切り下げる。
【００７２】
次に上記運転計画のもとでの動作を、図４、図５を用いて説明する。
【００７３】
運転計画に従って電力制御手段３９が電力変換器１１等を作動させることによって、モジュールＡ，Ｂの出力電力は制御される。
【００７４】
電力制御手段３９は、出力電力をＰｓとする内容の電力設定信号３９３を電力変換器１１ａに出力している。一方、電力変換器１１ｂには、出力電力を０とする内容の電力設定信号３９３を送っている。モジュールＡの電流は当初はほぼ一定にされている（図４参照）。これは、放電深度が浅い領域においては、電圧の低下、および、内部抵抗の増大がないためである。
【００７５】
運転計画上、放電深度が５０％を越える時刻になると、電力制御手段３９は、出力電力をＰｓから０．３Ｐｓに下げることを電力変換器１１ａに指示する。電力変換器１１ａは、これに対応してモジュールＡの電流を、一旦、減少させる。しかし、これ以降の放電深度領域においては、電圧の低下、内部抵抗の増大が生じてくるため、電力変換器１１ａは、これを相殺するためにモジュールＡの電流値を徐々に増大させてゆく。
【００７６】
また、モジュールＡの出力電力を０．３Ｐｓに下げさせるのと同期して、電力制御手段３９は、出力電力０．７Ｐｓで放電を開始するように電力変換器１１ｂに指示を出す。電力変換器１１ｂは、該指示に従って、モジュールＢに０．７Ｐｓでの放電を行わせる。モジュールＡの場合と同様に、電流値は、当初はほぼ一定にされているが、放電深度が高くなるにつれて徐々に増大されてゆく。なお、参考のため、図４には、モジュールＡ，Ｂそれぞれが単独で、定格出力電力Ｐｓで放電しつづけた場合（従来技術）の電流変化の様子を、定格Ｉｐとして破線で示した。
【００７７】
ここまで特に述べなかったが、該動作中、開閉器１０は、当然、閉じられている。また、交流／直流切り替え指令３９２は、直流を交流に変換させる内容となっている。
【００７８】
このような運転を行った場合の、各モジュールごとの電力損失、電力貯蔵分散電源システム１９全体での電力損失を、図５に示した。モジュールＡの放電効率ηｃは８８％であり、定格出力電力での放電効率（＝７０％）よりも高くなっている。これは、放電深度５０％以後の出力を０．３Ｐｓに低下させているからである。モジュールＢについても、同様に、放電効率ηｃが８８％と定格運転時よりも高くなっている。本システム全体での放電効率は８８％（電力量損失１２％）である。比較のため、図５には、１つの二次電池モジュールを定格電力Ｐｓで運転つづけた場合（従来技術）の電圧変化、および電力損失量も示している。この場合（従来技術）の定格放電効率ηｃは７０％である（電力量損失３０％）。つまり、本実施例では、従来のシステムと比べて効率が１８％も改善されている。
【００７９】
以上説明したとおり、本実施例では、放電深度、すなわち、内部抵抗特性に応じて各モジュール間での電力配分を最適化することにより、効率の高い運転が可能となる。
【００８０】
本実施例では、運転計画上、放電深度との関係において各モジュールの出力電力の大きさを規定していた。しかし、これに限定されるものではなく、電池の内部抵抗との関係において、出力電力を規定するような運転計画を作成するようにしてもよい。さらには、内部抵抗と一定の関係があり、かつ、検出（あるいは、算出）可能な他のなんらかの量との関係において、出力電力の大きさを規定するようにしてもよい。
【００８１】
なお、放電深度を求めることは、内部抵抗を間接的に求めることに相当する。
【００８２】
［実施例２］
実施例２は、電力需要を予測することによって系統電力のピークカット運転を可能とした点を特徴とするものである。また、異常な負荷変動への対応を可能とした点を特徴とするものである。
【００８３】
該実施例２の電力貯蔵分散電源システム２０を含んだ給電システムの概要を図６に示す。電力貯蔵分散電源システム２０と、上記実施例１の電力貯蔵分散電源システム１９との違いは、電力制御手段３０のみである。従って、ここでは電力制御システム３０のみを説明し、他の部分については説明を省略する。
【００８４】
電力制御システム３０の詳細を図７を用いて説明する。
【００８５】
電力制御システム３０は、電力需要予測手段３２、過去事例データ格納手段３３、運転計画作成手段３４、基本データ格納手段３６、入力手段３７、演算機４０、運転計画修正手段３８、電力制御手段３９などを含んで構成される。
【００８６】
電力需要予測手段３２は、負荷３における、日間あるいは昼、夜間の電力需要を所定の時間間隔で予測する機能（以下”長期予測”という）を備えている。また、現在の時刻から、１時間あるいは３０分先の電力需要を逐次予測する機能（以下”逐次予測”という）を備えている。これらの予測は、記憶手段３３に格納されている過去事例データ３３０を学習させたニューラルネットワークに、電力需要に影響を与える因子（以下”影響因子”という）３２１を入力して行っている。そのため、工業地域や住宅地域などの制御する系統特有の需要変化を高い精度で需要予測ができる。影響因子３２１としては、例えば、気温、湿度等の天候予報情報、平休日、イベント情報が挙げられる。過去事例データ３３０は、過去における、影響因子３２１の内容（３３１）と、時刻毎の電力需要値等を含んで構成される過去需要データ３５１と、を対応づけて蓄積したものである。この過去事例データ３３０は、ニューラルネットワークを学習させるのに必要な教師データの作成に用いられる。ニューラルネットワークの詳細については後ほど述べる。
【００８７】
電力需要予測手段３２は、長期予測の結果を、需要予測結果３２２として運転計画作成手段３４に出力する構成となっている。一方、逐次予測の結果は、逐次予測結果３２３として、運転計画修正手段３８に出力する構成となっている。
【００８８】
基本データ格納手段３６は、上記実施例と同様のものである。つまり、基本データ格納手段３６には、モジュールＡ，Ｂの開路電圧や内部抵抗等のデータが格納されている。
【００８９】
入力手段３７は、運転上の様々な制約条件等を入力するためのものである。制約条件としては、本実施例では、例えば、各モジュールＡ，Ｂについての、放電深度と出力電力の上限との関係が挙げられる。また、通常の運転時に使用する放電深度の範囲、あるいは、非常時のみ使用する放電深度の範囲が挙げられる（後述の例におけるＤｘｃ，Ｄｘｄがこれに相当する）。
【００９０】
運転計画作成上の制約条件としては、この他にも、充電／放電におけるモジュールＡ，Ｂ間での優先順位などが挙げられる。しかし、この優先順位は、固定的なものであり、入力手段３７からの入力によっては変更できない。該優先順位は、運転計画作成手段３４自身が予め備えている。
【００９１】
演算機４０は、電流・電圧検出器９の検出結果に所定の演算（例えば、Ａ／Ｄ変換）を行った後、各運転計画作成手段３４に出力するものである。
【００９２】
運転計画作成手段３４は、電流・電圧検出器９の検出結果に基づいて、電力量、放電深度を求め、これを電流値、電圧値とともに、運転計画修正手段３８に出力する機能を備えている。また、モジュールＡ，Ｂの運転計画を作成する機能を備えている。該運転計画は、電力需要予測結果３２２、入力手段３７から入力される電力運転規定条件３７１、基本データ格納手段３６内の各種データ、モジュールＡ，Ｂの電圧、電流の実測値等を用いて作成される。さらに、図では明らかでないが、系統の電源１の運転計画等も入力される構成となっている。なお、ピークカット運転を行っている場合には、充電終了後から放電開始前までの間に運転計画を作成する。作成された運転計画は、運転データ格納手段３５に格納される。運転データ格納手段３５には、この他に、各モジュールの電流、電圧の実測データおよび計算結果（充放電容量、放電深度、電力量、効率、損失など）が、運転計画作成手段３４によって格納される。また、運転計画修正手段３８には、電圧、電流、電力量、放電深度を示す信号４０１が出力される。
【００９３】
運転計画修正手段３８は、逐次予測結果３２３を用いて運転計画を修正する機能を備えている。修正後の運転計画は、電力制御手段３９へ制御信号３８１として送る。運転計画修正手段３８は、さらに、運転計画作成手段３４から入力された放電深度に従って、各モジュールの出力電力を変更するタイミング（注：これは、上記実施例１と同様、運転計画上、規定されているものである）の修正を行う機能を備えている。この他、運転計画修正手段３８は、実施例１におけるシステム保護判定手段と同様の機能をも備えている。つまり、系統モニタ１３の検出した系統電力や周波数測定値３８０に基づいて、異常の有無を判定し、異常があった場合には、非常時運転モードへの切り替えの指示などを電力制御手段３９に出力する。
【００９４】
電力制御手段３９は、運転計画修正手段３８によって適宜修正された運転計画（制御信号３８１）に従って、制御信号３９１〜３９４を出力し、開閉器１０、電力変換器１１等を制御するものである。
【００９５】
特許請求の範囲において言う”制御手段”とは、本実施例においては、電力制御手段３９、運転計画作成手段３４等によって構成されるものである。運転計画作成手段３４が、特許請求の範囲においていう”パラメータ手段”に相当するものである。但し、電力制御システムは、全体が密接に連携して動作するものであるため、ここで述べた特許請求の範囲との対応関係は厳密なものではない。電力制御システム全体として上記機能を実現していれば、具体的な機能の分担（あるいは、区分）は、どのようになっていても構わない。
【００９６】
電力需要予測手段３２の詳細を図８を用いて説明する。上述したとおり、本実施例では、電力需要予測手段３２をニューラルネットワークを用いて構成している。
【００９７】
需要予測手段３２は、目標データ作成手段３２０１、ニューラルネットワーク３２０５、入力データ作成手段３２０６、比較修正手段３２０３を含んで構成される。
【００９８】
ニューラルネットワーク３２０５は、既に広く知られているとおり、複数のニューロンを含んだ入力層、中間層、出力層から構成される。そして、各層間のニューロンは互いに結合されている。また、該結合には、それぞれ、重み係数がつけられている。ニューロンは、入力された信号に重み係数を乗算等した後、他のニューロンに出力する。重み係数は各結合ごとに異なっているため、該他のニューロンへの出力は、各結合毎に異なったものとなる。教師データを用いて、各結合に付与しておく重み係数を予め最適化しておく（以下”学習”という）ことにより、ある入力３２０７に対する出力２０４が、目的とするデータの予測値となる。実際に予測を行う場合の入力３２０７は、入力データ作成手段３２０６が影響因子３２１を用いて作成する。
【００９９】
教師データは、ニューラルネットワーク３２０５への入力データと、該入力データに対応した目標データとの組合せからなる。該目標データは、目標データ作成手段３２０１が、記憶手段３３に格納されている過去データ３５１を規格化等することによって作成する。該目標データに対応する入力データは、入力データ作成手段３２０６が、記憶手段３３に格納されている過去事例データ３３１を用いて規格化等することによって作成する。
【０１００】
教師データに含まれる入力データをニューラルネットワークの入力層に入力する。これに応じて出力層から出力されるデータ３２０４と、目標データとが一致（あるいは、近似）したものとなるように、適宜、各結合ごとの重み係数に修正（図中、該修正動作を矢印３２０８として示した）を加えて行くことによって学習を行うことができる。比較修正手段３２０３が、このようなデータ３２０４と目標データとの比較および重み係数の修正を行うものである。本実施例のニューラルネットワーク３２０５は、過去事例データ３３１（入力データ）と、過去データ３５１（入力データ）とからなる教師データを用いて予め学習が行われている。
【０１０１】
なお、ニューラルネットワークの学習方法および重み係数修正の具体的な計算方法の一例としては、パックプロパゲーション法がある。ニューラルネットワークおよびその学習方法の詳細は、例えば、「Ｌｅａｒｎｉｎｇ ｉｎｔｅｒｎａｌ ｒｅｐｒｅｓｅｎｔａｔｉｏｎｓ ｂｙ ｅｒｒｏｒ ｐｒｏｐａｇａｔｉｏｎ」Ｐａｒａｌｌｅｌ Ｄｉｓｔｒｉｂｕｔｅｄ Ｐｒｏｃｅｓｓｉｎｇ：Ｅｘｐｌｏｒａｔｉｏｎｓ ｉｎ ｔｈｅ Ｍｉｃｒｏｓｔｒｕｃｔｕｒｅｓ ｏｆ Ｃｏｇｎｉｔｉｏｎ，１９８６，Ｖｏｌ．１，Ｃｈａｐｔｅｒ４１，ｐｐ．６７５−６９５：ＭＡ：ＭＩＴ Ｐｒｅｓｓ，ｐｐ．３１８−３６２に記載されている。
【０１０２】
運転計画作成手段３４は、上述した各種制約条件のすべてを満たす運転計画３４１を作成するものである。本実施例では、該計画の作成においては、数理計画法を用いている。数理計画法については既に広く知られているため説明は省略する。例えば、「コージェネレーションの最適計画」伊東弘一、横山良平：産業図書株式会社発行に記載されている。但し、運転計画を作成するための具体的手法は、これに限定されるものではない。
【０１０３】
動作を説明する。
【０１０４】
ここでは、運転計画作成の前提となる制約条件が以下のように設定されているものとして説明を行う（図９参照）。
【０１０５】
モジュールＡ：
Ｄｘｃの領域は、非常時充電用として確保する。通常は、Ｄｘｃ以上の放電深度領域（これが、特許請求の範囲において言う”予め定められた範囲”に相当するものである）でのみ、充電／放電を行う。放電深度５０％までは、定格電力Ｐｓを出力電力の上限とする。放電深度５０％以上の領域では、出力電力の上限を０．５Ｐｓ、下限を０．１Ｐｓとし、この囲内において自由に出力電力を設定できるものとする。
【０１０６】
モジュールＢ：
Ｄｘｄの領域を非常時放電用として確保しておく。従って、通常は、これよりも放電深度の小さい領域（これが、特許請求の範囲において言う”予め定められた範囲”に相当するものである）でのみ、充電、放電を行う。放電深度５０％までは、定格電力Ｐｓを出力電力の上限値をとする。放電深度５０％以上の領域では、出力電力の上限値を０．５Ｐｓとする。
【０１０７】
平常時の放電は、モジュールＡを優先して行う。充電はモジュールＢを優先して行う。ＤｘｃおよびＤｘｄは、系統電力の変動性や設備の利用効率などを考慮して適切な値を設定するが、１０〜４０％程度が好ましい。参考のために、放電深度と充放電可能な定格電力量の関係を図１０に示す。図１０から明らかなとおり、放電深度を制約することにより、必要な定格電力量を確保することができる。本実施例ではＤｘｃ＝２０±５％、Ｄｘｄ＝４０±５％とすることで、非常時に充電可能な定格電力量Ｗｘｃを２３±５％、放電可能な定格電力量Ｗｘｄを３０±５％分確保できる。
【０１０８】
以上のような制約条件の下、平常時における定格充放電電力量Ｗｔは、下記数１２から求められる。
【０１０９】
【数１２】
Ｗｔ＝（Ｗａ−Ｗｘｃ）＋（Ｗｂ−Ｗｘｄ）
Ｗｔ ：平常時における定格充放電電力量
Ｗａ ：モジュールＡの全定格電力量
Ｗｘｃ：非常時に充電可能な定格電力量
Ｗｂ ：モジュールＢの全定格電力量
Ｗｘｄ：非常時に放電可能な定格電力量
電力需要予測手段３２による長期予測の結果が、図１１（ａ）のようなものであった場合、系統の電源１だけでは電力需要のピークに対応できない。また、電力需要の減少する時間帯においては、電力が余ってしまう。そのため、図１１（ｂ）に示すようなピークカット運転を行う必要がある。つまり、電力需要の減少する時刻ｔａ−時刻ｔｂ間は、余った電力をモジュールＡ，Ｂに充電する。一方、電力需要のひっ迫する時刻ｔｃ−時刻ｔｅ間は、放電を行う。充電電力量Ｗｃ，放電電力量Ｗｄは、当然ながら、数１２におけるＷｔ以下でなければならない。
【０１１０】
そこで、運転計画作成手段３４は、上述の制約条件を満たしつつピークカット運転を行うためのモジュールＡ，Ｂ間の電力配分についての運転計画を作成する。また、運転計画修正手段３８は、逐次予測の結果に従って、該運転計画を修正する。ここでは、図１１（ｂ）における時刻ｔｃから時刻ｔｅの間の放電を例にとり、該運転計画の修正動作を図１２、図１３を用いて説明する。
【０１１１】
まず、最初に立てた運転計画について説明する。
【０１１２】
モジュールＡは、時刻ｔｄ_１から放電を開始させる。時刻ｔｄ１から時刻ｔｄ２までは、需要に合わせた出力電力で放電を行う。この時はまだ放電深度が小さいため、モジュールＡからの出力電力は、最大、Ｐｓまで増やすことができる。時刻ｔｄ２から時刻ｔｄ３の期間において、出力電力が下げられているのは、需要が少ないことに対応したためである。時刻ｔｄ３からは、再び需要が増大するため、モジュールＡの出力電力もこれに合わせて増大させるはずである。しかし、計算上、時刻ｔｄ２から時刻ｔｄ４の間に、モジュールＡの放電深度は５０％に達してしまう。そのため、これ以降は、時刻ｔｄ６までモジュールＡは放電深度に応じた出力電力（最大０．５Ｐｓ、最小０．１Ｐｓ）で放電させるに留める。
【０１１３】
時刻ｔｄ４において再び需要が増大することが予測されている。上述したとおりモジュールＡの放電深度は、既に５０％を越えているため、モジュールＡだけではこれに対応できない。従って、時刻ｔｄ４においてモジュールＢを起動し、モジュールＡのみでは不足する分だけ、該モジュールＢから放電させる。
【０１１４】
この後は、徐々に、需要が減少してくることが予測されているためこれにあわせて電力貯蔵分散電源システム２０からの出力電力も低下させてゆく。ここでは、モジュールＡを優先して放電させることが制約条件において規定されている。そのため出力電力の低下は、モジュールＢについて優先して行う。需要の減少に応じて、モジュールＡの出力電力を低下させるのは、モジュールＢからの放電を完全に停止した後でも、更に、電力が需要よりも多い場合である。
【０１１５】
このような運転計画を立てていたにも関わらず、逐次予測の結果、長期予測の結果とは異なる需要が予測される場合がある。この場合には、運転計画修正手段３８が適宜運転計画を修正しつつ、電力制御手段３９へ指令を出す。ここでは図１２において、電力Ｗｅ１，Ｗｅ２として示した分だけ、需要が長期予測よりも多かった場合を例にとって考える。
【０１１６】
運転計画修正手段３８は、逐次予測の結果と、運転計画（あるいは、当該運転計画のもとになった長期予測結果）とを比較する。すると、時刻ｔｄ_３で予測外の電力需要Ｗｅ_１が新たに生じていることがわかる。そのため、運転計画修正手段３８は、モジュールＢの起動タイミング時刻を、時刻ｔｄ_４からｔｄ_３に早める。また、モジュールＡについても、放電深度５０％を越えた後の出力電力を、該電力需要Ｗｅ１を考慮して、当初予定よりも多少大きくする。
【０１１７】
また、時刻ｔｄ_５からｔｄ_６間にも予測外の電力需要Ｗｅ_２が生じている。そのため、モジュールＢの出力電力を当初予定よりも高く保って、これに対応する。
【０１１８】
次に、非常事態への対応動作について説明する。
【０１１９】
本実施例では、逆潮流などの非平常負荷変動により、系統周波数が急変するのを抑制することもできる。
【０１２０】
非常時（例えば、系統モニター１３により検知した系統の周波数変動が、ある変動巾を超えるような場合）には、電力貯蔵分散電源システム２０からの電力を融通して、系統周波数を安定化させる。
【０１２１】
系統周波数が低下する場合（すなわち、需要に対して電力供給が不足するような場合）は、放電優先条件に従ってモジュールＡ，Ｂの順に、あるいは、必要に応じてモジュールＡ，Ｂの両方から電力を供給する。本実施例では、システムの電力貯蔵量が最も少ない時間帯（図１１（ｂ）における、時刻ｔｅ−時刻ｔａ）でも、モジュールＢには、電力量Ｗｘｄが確保されている。そのため、予想外に電力需要が増大したような事態が生じても、これに対応できる。
【０１２２】
逆に、系統周波数が上昇する場合（すなわち、電力供給が需要を大幅に上回ってしまう場合）は、モジュールＢ，Ａの順に、あるいは、必要に応じてモジュールＡ，Ｂの両方に電力を充電する。従って、システムの電力貯蔵量が最も多い時間帯（図１１（ｂ）における時刻ｔｂ−時刻ｔｃ）でも、モジュールＡには、電力量Ｗｘｃを充電可能な分だけ容量が残されている。そのため、予想外に電力需要が低下したような事態が生じてもこれに対応できる。
【０１２３】
以上説明したとおり、本実施例では需要予測に基づいた運転計画の立案および修正を行うことで、実際の電力需要に負荷追従した精度の高いピークカット電力運転が可能となる。また、系統に必要な電力を供給しつつ、二次電池設備のエネルギー変換効率を向上させることができる。
【０１２４】
さらに、常に充放電可能な領域を確保しておくことで、非常事態へも十分に対応することができる。
【０１２５】
本実施例では、放電深度５０％を基準として出力電力を調整していた。しかし、該基準となる放電深度をさらに多数設定し、よりきめこまかに設定してもよいことは言うまでもない。あるいは、放電深度に従って出力電力の制限を連続的に設定するようにしてもよい。このようにすれば、より電力損失の少ない運転が可能となる。しかし、制御のし易さ、最適化するための計算手法とこれに要する時間、電力損失低減の目標、需要予測の精度、等を考慮して、適切な刻み巾を設定することが好ましい。
【０１２６】
上記説明においては、主として放電についてのみ述べたが、充電に際しても同様の観点から、放電深度に応じて充電電流を調整するようにしてもよい。但し、充電は、基本的に余剰電力を用いて行うものであるため、充電時間等に制約がある。そのため、これらの各種制約条件をより優先して充電電流を決定するようにしても構わない。
【０１２７】
［実施例３］
本実施例は、二次電池モジュール７ａ，ｂ等の二次電池設備と並列に、燃料電池発電設備を接続したハイブリッド型システムである。
【０１２８】
本実施例の電力貯蔵分散電源システム２１を備えた給電システムを図１４に示した。
【０１２９】
二次電池設備および制御関連構成部は、実施例２と同様の設備で構成されるため、ここでの説明は省略する。
【０１３０】
燃料電池モジュール８は、空気と燃料ガスを電気化学的に反応させて直流電力を得るものである。該燃料電池モジュール８は、単位電池を複数個積層して構成されている。該燃料電池モジュール８は、発電した電力を、配電系統線４、あるいは、二次電池モジュール７ａ，ｂに出力する構成となっている。なお、出力先の変更は、後述する開閉器１０ｃ，１０ｄ_１，１０ｄ_２により行われる。
【０１３１】
二次電池モジュール７ａ，７ｂは、燃料電池モジュール８の発電した電力の貯蔵、および、貯蔵した電力の配電系統線４への放出、を行うものである。上記実施例とは異なり、電源１の発電した電力を二次電池モジュール７ａ，７ｂに蓄えることはない。充電は、燃料電池モジュール８の発生する直流出力を、直接（直／交変換することなく）行うことができるため効率がよい。このような上記実施例との相違は、周辺回路（例えば、開閉器１０ａ〜１０ｄ、電力変換器１１等）によって実現されるものであって、二次電池モジュール７ａ，７ｂ自体は、上記実施例と同様のものでよい。ただし、二次電池モジュール７ａ，７ｂの最大充電電流密度は、燃料電池の出力する電流密度より大きくされている。
【０１３２】
補機設備８０は、燃料供給手段やヒータ等の燃料電池モジュール８に関連した各種機器である。
【０１３３】
電流・電圧検出器９ｃは、燃料電池モジュール８からの出力の電流値、電圧値を検出するものである。検出結果は、電力制御システム３１に出力している。
【０１３４】
開閉器１０ｃは、燃料電池モジュール８と、配電系統線４の電気回路とを接続／遮断するためのものである。開閉器１０ｄ_１，１０ｄ_２は、二次電池モジュール７ａ，７ｂと燃料電池モジュール８とを直流側で接続／遮断するためのものである。既に述べたとおり、開閉器１０ｃ，１０ｄ_１，１０ｄ_２は、燃料電池モジュール８の発電した電力の出力先（配電系統線４、二次電池モジュール７ａ，７ｂ）を変更するのに用いられる。
【０１３５】
直流電圧調整器１６は、燃料電池発電電圧を調整するものである。
【０１３６】
以上述べた各部は、電力制御システム３１からの指令信号に従って動作する構成となっている。
【０１３７】
電力制御システム３１は、基本的には上記第２の実施例と同様の機能に加えて、燃料電池モジュール８の制御、および、燃料電池８と二次電池モジュール７ａ，ｂとの連携の制御を行う機能を備えている。以下、電力制御システム３１の詳細を、図１５を用いて説明する。
【０１３８】
電力制御システム３１の基本的な構成は、実施例２の電力制御システムと同様ではあるものの、燃料電池モジュール８の制御をも行う必要から、各機能区分の有する機能が多少異なっている。従って、以下においては、実施例２における電力制御システムとの相違点を中心として述べることとする。
【０１３９】
基本データ格納手段３６に格納される基本データは、上記実施例と同様のもので構わない。
【０１４０】
入力手段３７からは、上記実施例と同様の制約条件に加え、燃料電池モジュールを保護するための各種制約条件も入力するようになっている。
【０１４１】
運転計画作成手段３４は、電力需要予測手段３２による長期予測の結果を満たすための運転計画を決定する機能を備えている。本実施例で言う”運転計画”とは、二次電池モジュール７ａ，７ｂ間における負荷配分のみならず、燃料電池モジュール８の出力電力の調整計画をも含む（注：この点において、上記第１、第２の実施例とは異なる）。該運転計画は、基本的には、燃料電池モジュール８の出力変動をできるだけ小さくするように、二次電池モジュール７ａ，ｂを用いたピークカット運転を行う、との観点から作成される。この場合、その時点での（あるいは、当該運転計画が実施される時の）二次電池モジュール７の放電深度をも考慮して計画を作成することは当然である。二次電池モジュール７ａ，７ｂ間における負荷配分の決定は、上記実施例２における運転計画の作成と同様の観点から行う。
【０１４２】
なお、運転計画を作成するには、電力貯蔵分散電源システム全体として出力しなければならない電力を知っている必要がある。そして、そのためには、電源１が予定している出力電力値を知らなければならない。そこで、本実施例の運転計画作成手段３４は、電源１の運転計画等をベース電力運転情報３１０として入力されている。
【０１４３】
運転計画修正手段３８は、需要予測手段３２による逐次予測結果に従って、運転計画を適宜修正するものである。該修正は、基本的には、二次電池モジュール７ａ，７ｂの出力電力を修正することによって行う。これは、燃料電池モジュール８の出力電力を頻繁に変更すると、発電効率の低下、寿命の低下につながるからである。但し、二次電池モジュール７ａ，７ｂのみでは対応し切れない場合には、燃料電池モジュール８の出力電力を修正することは言うまでもない。
【０１４４】
電力制御手段３９は、運転計画修正手段３８からの指示に従って、燃料電池モジュール８，二次電池モジュール７ａ，７ｂを制御すべく、各種制御信号３９１〜３９５を出力している。燃料電池出力調整信号３９５は、燃料電池モジュール８の出力電圧を調整するためのもので、直流電圧調整器１６に出力されている。開閉動作指令３９１は、開閉器１０ａ，１０ｂ，１０ｃ，１０ｄ１，１０ｄ２に出力されている。交流／直流変換切り替え指令３９２および電力設定信号３９３は、電力変換器１１ａ，１１ｂ，１１ｃに出力されている。補機設備制御信号３９４は、補機設備８ａ，８ｂに出力されている。
【０１４５】
本実施例の動作を図１６を用いて説明する。
【０１４６】
運転計画作成手段３４は、負荷３における電力需要から、電源１の供給する電力Ｐｏを差引き、残りを電力貯蔵分散電源システム２１によって供給する運転計画を作成する。なお、電力Ｐｏは、一般に一定に保たれているため、系統の電源１の動作については説明を省略する。
【０１４７】
平常時には、燃料電池モジュール８から（あるいは、燃料電池モジュール８および二次電池モジュール７の両方から）、配電系統線４の側へ電力を供給する。つまり、昼間（時刻ｔｃ−時刻ｔｅ）は、電力需要が大きく燃料電池モジュール８だけでは電力が不足するため、不足分Ｗｄを二次電池モジュール７ａ，７ｂから放電する（図１６（ａ）参照）。従って、この場合、電力制御手段３９は、開閉器１０ｄ_１，１０ｄ_２は開路とする。また、開閉器１０ａ，１０ｂ，１０ｃは閉路とする。一方、夜間（時刻ｔａ−時刻ｔｂ）は需要が減少して電力が余るため、燃料電池モジュール８の発生する電力を二次電池モジュール８に蓄える（図１６（ａ）参照）。従って、この場合、電力制御手段３９は、開閉器１０ｃ，１０ｄ_１，１０ｄ_２は閉路とする。開閉器１０ａ，１０ｂは開路とする。昼間のピークカット運転を行うのに必要な電力（電力量Ｗｃ）は、この時充電した電力によってまかなわれる。なお、二次電池モジュール７ａ，７ｂの間における負荷配分は、上記実施例２と同様の観点から行う。
【０１４８】
このように、本実施例では、系統上、上位に位置する電源１は一定出力で運転を続けることができる。また、二次電池モジュール７ａ，７ｂにおけるエネルギー変換効率を高く保つことができる。さらには、燃料電池モジュール８の出力の変動も小さくできる（図１６（ｂ）参照）。二次電池モジュール７ａ，７ｂとして十分に容量の大きなものを採用すれば、燃料電池モジュール７の出力を常に一定に保った運転を行うことも可能である。さらには、二次電池モジュール７ａ，７ｂの充電可能な電流密度が大きいほど、変動に対する融通性を大きくできる。
【０１４９】
次に系統負荷が急変した場合への対応について説明する。
【０１５０】
ここでは、図１７のごとく、配電系統線４から枝別れした複数の系統フィーダＦ_１〜Ｆ_ｎそれぞれについて、交流負荷群２３が接続されている場合を考える。また、系統フィーダＦ_１〜Ｆ_ｎには、それぞれ、遮断器５_（１）〜５_（ｎ）が取り付けられているものとする。
【０１５１】
このような構成において、例えば、系統フィーダＦ_３において異常（例えば、地落事故）が発生すると、該系統フィーダＦ_３は、遮断器５_（３）によってただちに配電系統線４から切り離される。すると、該系統フィーダＦ_３に設けられている負荷２３が脱落するため（つまり、電力需要が急減少するため）、このままでは配電系統線４における周波数が急上昇してしまう。
【０１５２】
しかし、本実施例では運転計画修正手段３８が、系統モニタ１３からの信号に基づいて異常（この場合、周波数の上昇）を検知して、その旨を電力制御部３９に知らせる。すると、電力制御部３９は、該異常状態に対応すべく、開閉器１０ａ，１０ｂを開路状態として、二次電池モジュール７から配電系統線４への出力を停止させる。また、これと同時に開閉器１０ｄ_１，１０ｄ_２を閉じて、燃料電池モジュール８の出力する電力の少なくとも一部を、二次電池モジュール７に蓄えさせる。これにより、燃料電池モジュール７の出力を低下させることなく、電力貯蔵分散電源システム２１の出力を低下させることができる。そして、配電系統線４における周波数の上昇を最小限に抑えることができる。
【０１５３】
系統負荷群３からの急激な逆潮流に対しても、同様にして対処することができる。
【０１５４】
これにより、燃料電池モジュール７は、設備稼動率の高い状態で運転を継続できる。また、上位の電源１も、平常時および非常時の負荷変動による影響が少ないため、稼動率の高い一定出力を保った運転が可能となる。燃料電池発電設備に代えて太陽電池発電設備を採用しても、同様な効果を得ることができる。
【０１５５】
次に、別の例として、図２０のごとく系統フィーダの負荷の間に電力貯蔵分散電源システム２１を設けている場合における、非常時への対応を説明する。
【０１５６】
系統フィーダＦ_ｘは、遮断器５_ｘを介して、配電系統線４に接続されている。そして、系統フィーダＦ_ｘには、交流電力負荷群２３と、開閉器１７とが多数接続されている。さらに、系統フィーダＦ_ｘの各所には、遮断器５０を介して、電力貯蔵分散電源システム２１が接続されている。
【０１５７】
系統フィーダＦ_ｘのいずれかの部分において事故が生じた場合、事故のあった区間に設けられている電力貯蔵分散電源システム２１を、遮断器５を開いて系統フィーダＦ_ｘから切り離さなければならない。そして、その場合、当該電力貯蔵分散電源システム２１の燃料電池モジュール８は、極端な低負荷の運転状態を強いられることになりかねない。燃料電池の出力は瞬時に低下させることは不可能であり、また負荷の急変動は燃料電池設備の著しい寿命低下につながる。しかし、本実施例では、燃料電池の出力を瞬時に二次電池モジュール７ａ，ｂの充電に振り向けることができるため、燃料電池モジュール８の出力を急激に低下させなくても、このような事態に対応することができる。
【０１５８】
さらに、図１８における遮断器５_ｘと開閉器１７ｂとの間で事故が発生した場合、下流側に配置されている電力貯蔵分散電源システム２１から、負荷群２３ａ，ｂに電力を供給することができる。従って、停電区間をできるだけ小さくできる。
【０１５９】
［実施例４］
本実施例は、本発明による電力貯蔵分散電源システム２１から、交流電力と直流電力の両方を供給する点を特徴とするものである。
【０１６０】
本実施例の電力貯蔵分散電源システムを備えた給電システムを図１９に示す。電力貯蔵分散電源システム２１自体は、基本的には、実施例２または実施例３と同じ構成を備えているが、本実施例ではさらに直流電力出力手段４５を備えている。
【０１６１】
直流電力出力手段４５は、直流電力系統線４６を通じて、直流電力需要家４７へ直流電力を供給するものである。該直流電力出力手段４５は、各電池モジュール（二次電池、燃料電池）と回路接続するスイッチおよび出力電圧調整器等から構成される。そして、該直流電力出力手段４５の動作は、電力制御システム３０または３１により制御される構成となっている。
【０１６２】
直流電力系統線４６は、直流電力需要家４７へ電力を導くためのケーブルである。本実施例では、落雷による停電を防ぐため地中に埋設している。
【０１６３】
直流電力需要家４７としては、例えば、電気自動車用充電スタンドやコンピュータユーザ等が考えられる。
【０１６４】
本実施例では、直流電力需要家へ、高品質で信頼性の高い直流電力を効率よく供給することができる。
【０１６５】
【発明の効果】
以上説明したとおり本発明によれば、二次電池のエネルギー変換効率を向上させることができる。また、非常時の負荷急変動に対しても供給電力の安定化を図ることができる。
【０１６６】
さらには、上位系統電源の安定性も確保できる。これは、上位系統電源の稼動率を向上につながる。
【図面の簡単な説明】
【図１】本発明の第１実施例を示す電力貯蔵分散電源システム１９およびこれを備えた給電システムを示すブロック図である。
【図２】電力制御システム２９の機能構成を示すブロック図である。
【図３】基本データとして格納されているナトリウム硫黄電池の特性データを表すグラフである。
【図４】二次電池モジュール毎の電力配分運転例を示すグラフである。
【図５】本実施例における電力損失割合を表すグラフである。
【図６】本発明の第２実施例を示す電力貯蔵分散電源システム２０およびこれを備えた給電システムを示すブロック図である。
【図７】電力制御システム３０の機能構成を示すブロック図である。
【図８】需要予測手段を構成するニューラルネットワークの概要を示すブロック図である。
【図９】制約条件の一例を示す図である。
【図１０】放電深度と定格電力量との関係を示すグラフである。
【図１１】（ａ）需要予測結果および（ｂ）当該需要予測に対して行うピークカット運転の一例を示すグラフである。
【図１２】電力配分運転計画およびその修正の一例を示す図である。
【図１３】図１２の運転計画および修正に対応したモジュール毎の負荷配分を示す図である。
【図１４】本発明の第３実施例を示す電力貯蔵分散電源システム２１およびこれを備えた給電システムを示すブロック図である。
【図１５】電力制御システム３１の機能構成を示すブロック図である。
【図１６】第３の実施例の運用例を示すグラフである。
【図１７】第３の実施例の電力貯蔵分散電源システム２１を複数の系統フィーダを有する系統母線につないだ例を示すブロック図である。
【図１８】第３の実施例の電力貯蔵分散電源システム２１を系統フィーダの負荷の間に設けて連系した例である。
【図１９】本発明にかかる電力貯蔵分散電源システムから直流電力を供給する給電システムのブロック図である。
【図２０】従来の電力貯蔵システム構成例である。
【図２１】従来技術における電力損失を示すグラフである。
【符号の説明】
１……電源 、２……配電変電所 、３……系統負荷群 、４……配電系統 、５……遮断器 、６……変圧器 、７……二次電池モジュール 、８……燃料電池モジュール 、１０……開閉器 、１１……電力変換器 、１２……電力制御部 、１４……運転計画作成支援手段 、１６……直流電圧調整器 、１９……電力貯蔵分散電源システム 、２０……電力貯蔵分散電源システム 、２１……電力貯蔵分散電源システム 、２９……電力制御システム 、３０……電力制御システム 、３１ ……電力制御システム 、３２……電力需要予測手段 、３３……記憶手段 、３４……電池運転計画作成手段 、３６……基本データ格納手段 、３７……制約条件入力手段 、３８……運転計画修正手段 、３９……電力制御手段 、４５……直流電力出力手段 、４６……直流電力系統線 、４７……直流電力需要家[0001]
[Industrial applications]
The present invention relates to a power storage system using a secondary battery.
[0002]
[Prior art]
The power storage system is used for load leveling and peak cutting of system power, and for stabilizing system frequency and system voltage.
[0003]
In recent years, the development of power storage systems using secondary battery modules has been promoted. An outline of a power storage system using a secondary battery and a usage form thereof will be described with reference to FIG.
[0004]
The power generated by a power source (for example, a nuclear power plant or a thermal power plant) 1 of a system serving as a base of the system power is subjected to voltage transformation adjustment in a distribution substation 2 and supplied to a customer of a system load group 3. The power storage distributed power supply system 20 is connected to the distribution system 4 via the circuit breaker 5 and the AC voltage transformer 6.
[0005]
The power storage / distributed power supply system 20 includes a battery module 7 configured by connecting a plurality of secondary batteries in series / parallel, a power control unit 12, and a power conversion unit 11 for performing alternating / direct reversible conversion of power. It is configured. When the power of the power distribution system 4 is insufficient, the DC power discharged from the secondary battery module 7 is converted into AC by the power conversion unit 11 and supplied to the system. Conversely, when the system power becomes excessive at night or the like, the AC power transmitted from the power distribution system 4 is converted into DC power by the power conversion unit 11, and the battery module 7 is charged.
[0006]
A hybrid power storage system that stabilizes system power in combination with a fuel cell system has also been proposed. For example, JP-A-63-45765 discloses a system in which a secondary battery and a fuel cell system are connected in parallel on the DC side. The system supplies power to a load while floating charging the secondary battery in a charged state, except when compensating for insufficient output of the fuel cell.
[0007]
Secondary batteries used in such power storage systems are required to have high energy density and low charge / discharge loss. Attention has been paid to a sodium-sulfur secondary battery that satisfies such demands, and its development is currently being vigorously continued.
[0008]
It is known that the sodium-sulfur battery has an internal resistance R at the time of discharge increasing in a region where the depth of discharge is high and has a maximum value (see FIG. 3). For such characteristics, see, for example, Electrochem Soc. , Vol. 136, No. 7, P1962, July 1989.
[0009]
In the figure, "depth of discharge" means the total amount of power (discharge capacity) that can be discharged from a battery when discharging is started from a fully charged state and the amount of power already discharged at that time. Ratio. Alternatively, it is the ratio of the time required for the battery voltage to drop to a certain voltage at which the discharge is started from the fully charged state to the certain voltage, and the time that has already passed by that time.
[0010]
[Problems to be solved by the invention]
Assuming that the battery voltage is E, the battery current is I, and the internal resistance is R, the charge / discharge power amount W and the energy conversion efficiency η are represented by the following formulas 1, 2, and 3.
[0011]
(Equation 1)
Charge power amount Wc = ∫I · E dt + ∫I²・ R dt
[0012]
(Equation 2)
Discharge power amount Wd = ∫I · E dt-∫I²・ R dt
[0013]
(Equation 3)
Energy conversion efficiency η = discharge power Wd / charge power Wc
As can be seen from Equation 3, when the charging power amount Wc is considered to be constant, the energy conversion efficiency changes according to the output of the discharge power. Here, considering the case where the charging power amount Wc = the rated power amount Ws (see Expression 4), the energy conversion efficiency ηs is expressed by Expression 5 below. Further, the power loss amount Wp1 is expressed by the following equation (6).
[0014]
(Equation 4)
Rated power amount Ws = ∫I · Eocv dt
Eocv: Open circuit voltage
[0015]
(Equation 5)
Energy conversion efficiency ηs based on rated power = discharge power Wd / rated power Ws
[0016]
(Equation 6)
Power loss Wp1 = Rated power Ws-Discharge power Wd
The power loss amount Wp1 (see Equation 6) corresponds to the second term on the right side of Equation 2. The smaller the internal resistance R, the higher the energy conversion efficiency ηs based on the rated power. In other words, the amount of energy loss increases in a discharge in a region where the internal resistance R is high. If a constant current is discharged regardless of the depth of discharge, the efficiency ηs decreases. In order to reduce the amount of energy loss and increase the energy conversion efficiency ηs, it is preferable for the sodium-sulfur battery to perform charging and discharging only in a low-resistance region having a depth of discharge of about 50% or less (see FIG. 3).
[0017]
In addition, a battery generally has a low electromotive force in a region where the depth of discharge is high. In order to constantly supply constant power to the outside (constant power operation), the output current must be increased in the region where the discharge depth is high. Therefore, such constant power operation would further increase the amount of energy loss (see FIG. 21).
[0018]
Further, there is a problem that the larger the size of the battery module, the greater the amount of energy loss due to internal resistance.
[0019]
However, in the conventional system, output control is not performed in consideration of such fluctuations of the internal resistance and the electromotive force according to the charge / discharge depth, resulting in a decrease in energy conversion efficiency.
[0020]
As another problem, the conventional system has not taken sufficient care in response to an emergency. For example, if the load fluctuates suddenly due to an accident or the like, the frequency of the AC power supplied to the system will suddenly change. In such a case, the system frequency can be stabilized by adjusting the active power charged and discharged by the secondary battery. However, in the conventional system, the charge / discharge capacity of the secondary battery is not always limited. When such a situation occurs while approaching the end-of-charge / discharge state, it cannot be dealt with.
[0021]
This problem was the same in the conventional hybrid system. Changing the operating state of the fuel cell system to cope with a sudden change in load causes a significant reduction in the life of the fuel cell equipment. For example, the pressure balance between the anode and the cathode is disturbed, and the electrolyte plate is damaged or deteriorated. Further, since an excessive amount of unreacted fuel gas is sent to the burner of the reformer, the reformer temperature is abnormally overheated, which causes deterioration of the reforming catalyst and damage to the reformer.
[0022]
As a method for dealing with a situation where the load is small, for example, Japanese Patent Application Laid-Open No. 63-276877 discloses a technique for controlling the output of a fuel cell in accordance with the charge amount of a secondary battery.
[0023]
However, when the battery is near the end of charging at the time of light load such as at night, the system may be disconnected from the system due to a system accident such as a ground fault. In such a case, charging by the secondary battery becomes impossible, so that the output of the fuel cell must be temporarily stopped. Unlike a secondary battery or the like, once the fuel cell is stopped, a startup time is required to increase the output again. In addition, there is a problem that the operating rate of the fuel cell device is reduced.
[0024]
In a conventional hybrid system, charging and discharging of a secondary battery cannot be performed individually and independently for each battery module. Therefore, it was impossible to always secure a chargeable / dischargeable area.
[0025]
An object of the present invention is to provide a power storage distributed power supply system that can sufficiently cope with both normal operation and emergency.
[0026]
SUMMARY OF THE INVENTION An object of the present invention is to provide a power storage / distributed power supply system capable of increasing the energy conversion efficiency as much as possible.
[0027]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made to achieve the above-described object, and increases the output current (output power) in a region where the internal resistance is low, and decreases the output current (output power) in a region where the internal resistance is high. This is to increase the energy conversion efficiency η (discharge energy / charge energy) of the module. The decrease in output power is compensated for by appropriately combining a plurality of battery modules.
[0028]
Hereinafter, the configuration of the present invention will be described more specifically.
[0029]
According to a first aspect of the present invention, there is provided a secondary battery module including one or more secondary batteries, and a parameter value (hereinafter, referred to as a “parameter value”) having a correlation with an internal resistance of the secondary battery. ") And control means for adjusting the discharge power from the secondary battery module according to the parameter value obtained by the parameter means. You.
[0030]
The control unit includes a reference value of the parameter determined based on a relationship with the internal resistance, and the adjustment is performed based on a magnitude relationship between the reference value and a parameter value obtained by the parameter unit. Preferably, it is
[0031]
Preferably, the adjustment is to reduce the discharge power in a region where the internal resistance is large.
[0032]
The parameter is preferably a depth of discharge of the secondary battery.
[0033]
The control means preferably causes the secondary battery module to discharge and / or charge within a range where the depth of discharge is within a predetermined range.
[0034]
Placed in parallel with each other, independent of charge and dischargeTargetA plurality of the secondary battery modules configured so as to be controllable, and the control unit controls a priority between the secondary battery modules predetermined for charging and discharging respectively.RankingWith the priorityRankingIt is preferable that the above charging and discharging be performed in accordance with the following.
[0035]
The above control means has priorityRankingIf the power discharged from the secondary battery module with highRankingIt is preferable that discharge from a secondary battery module having a low temperature is permitted.
[0036]
According to a second aspect of the present invention, in the method for operating a power storage system using a secondary battery, the internal resistance of the secondary battery is directly or indirectly determined, and the above-described method is performed according to the magnitude of the internal resistance. There is provided a method of operating a power storage system, wherein at least one of output power and input power of a secondary battery is adjusted.
[0037]
[Action]
The control means has priorityRankingCharge and discharge are performed on any of the secondary battery modules determined in accordance with the following. Also priorityRankingIf the power discharged from the secondary battery module with highRankingDischarge from the secondary battery module having a low power. In this case, the control means adjusts the output (discharge power) from the secondary battery module based on the magnitude relationship between the reference value and the value of the parameter (for example, the depth of discharge) obtained by the parameter means. For example, the discharge power is reduced in a region where the internal resistance of the secondary battery is large. Thereby, power loss can be suppressed.
[0038]
Usually, the control means causes the secondary battery module to discharge and / or charge only when the depth of discharge is within a predetermined range. As a result, usually, a certain constant capacity for charging and discharging is always secured, and it is possible to respond to an emergency.
[0039]
【Example】
Embodiments of the present invention will be described with reference to the drawings.
[0040]
[Example 1]
FIG. 1 shows an outline of a power storage distributed power supply system of this embodiment and a power supply system using the same.
[0041]
The power generated by a power source (for example, a nuclear power plant or a thermal power plant) 1 serving as a base of the grid power is transformed and regulated by a distribution substation 2 and is supplied to consumers of a grid load group 3. The power storage / distributed power supply system 19 of the present embodiment is connected to the distribution system line 4 via the circuit breaker 5 and the AC voltage transformer 6.
[0042]
The power storage distributed power supply system 19 includes secondary battery modules 7a and 7b, battery auxiliary equipment 70, current / voltage detectors 9a and 9b, switches 10a and 10b, power converters 11a and 11b, And a control system 29.
[0043]
Hereinafter, the secondary battery module 7a and the secondary battery module 7b are collectively simply referred to as “secondary battery module 7”. The same applies to the current / voltage detector 9 and the like. The secondary battery module 7a and the secondary battery module 7b may be simply referred to as "module A" and "module B", respectively.
[0044]
The secondary battery module 7 is for storing electric power, and in this embodiment, is configured by connecting sodium-sulfur secondary batteries in series and parallel. The type of secondary battery used and the number of modules are not limited to these. However, it goes without saying that it is necessary to change the contents of the operation control described later according to the type and characteristics of the battery to be used. The charging and discharging of the secondary battery modules 7a and 7b can be performed independently of each other. Therefore, for example, it is also possible to charge only the secondary battery module 7a.
[0045]
The battery auxiliary equipment 70 is for maintaining the operating temperature of the battery, such as a heat insulating container and a heater that house the secondary battery module 7. In this embodiment, the battery auxiliary equipment 70 is shared by the secondary battery module 7a and the secondary battery module 7b, but may be independently provided depending on the scale of the battery module.
[0046]
The power converter 11 is for adjusting charging / discharging power of the secondary battery module 7 and performing AC / DC conversion. The power is adjusted by changing the current value. Therefore, the reduction of the output power described later will directly lead to a decrease in the current value. When charging the secondary battery module 7, the AC power supplied from the power distribution system line 4 is converted to DC power, and conversely, when discharging, the DC power released from the secondary battery module 7 is converted to AC power. Convert to electric power. These operations are controlled according to an AC / DC switching command 392 and a power setting signal 393 input from the power control system 29. The power converter 11a and the power converter 11b can be controlled independently of each other.
[0047]
The current / voltage detector 9 is for detecting a current value and a voltage value when charging and discharging the secondary battery module 7. The current / voltage detector 9 is connected between the secondary battery module 7 and the power converter 11. The current / voltage detector 9 outputs the measurement result to the power control system 29 as a detection signal 400. These data are used for calculation of the amount of power and the like in the power control system 29 (in particular, the operation plan creation support means 14 described later).
[0048]
The switch 10 is for opening and closing an electric circuit between the two-battery module 7 and the power distribution system line 4. The switch 10 operates according to a circuit switch command signal 391 input from the power control system 29. The switch 10a and the switch 10b are configured to be independently controllable from each other.
[0049]
The power control system 29 is for monitoring and controlling the entire power storage distributed power supply system 19. The power control system 29 is connected to the current / voltage detector 9, the switch 10, the power converter 11, and the battery auxiliary equipment 70 by a communication line. In the present embodiment, the power control system 29 is configured by hardware such as a microprocessor and a memory, and software (programs and data) stored in the memory. Hereinafter, the power control system 29 will be described in detail with reference to FIG.
[0050]
The power control system 29 functionally includes a basic data storage unit 36, an input unit 37, an operation plan creation support unit 14, an operation data storage unit 35, an operation plan storage unit 15, a system protection determination unit 12, a power control unit 39. And so on.
[0051]
The basic data storage means 36 stores basic data indicating the relationship between battery characteristics (for example, internal resistance, open circuit voltage, current-voltage) of the secondary battery module 7 and the depth of discharge. However, in order to achieve the object of the present embodiment (reduction of power loss due to output regulation), at least two of the basic relationship between the depth of discharge and the internal resistance and the relationship between the depth of discharge and the circuit voltage are the basics. It only has to be included in the data. The characteristics of the sodium-sulfur battery including the basic data are shown in FIG.
[0052]
The input means 37 is used by a system administrator to input an instruction to the system when creating an operation plan. The “operation plan” here refers to the distribution of power load between the secondary battery module 7a and the secondary battery module 7b, the charge / discharge cut voltage, and the like. In this embodiment, the input means 37 includes a display device, a keyboard, a mouse, and the like. On the display device, various simulation results described later are displayed. Therefore, the system administrator is configured to make these inputs while looking at the display.
[0053]
The operation plan creation support means 14 has a function of calculating the depth of discharge and the amount of discharge power of the secondary battery module 7, the energy conversion efficiency, and the like. In addition, a function for performing various simulations is provided to assist the system administrator in creating an operation plan. Hereinafter, each function will be described in detail.
[0054]
The discharge depth and the discharge power amount are obtained by substituting the actually measured data (the detection signal 400 of the current / voltage detector 9) into the following Expressions 7 to 9. Further, the obtained depth of discharge and the like are stored in the operation data storage means 35. The operation data storage means 35 is for storing the history of use of the secondary battery module (for example, the number of cycles, the accumulated amount of electricity, etc.).
[0055]
(Equation 7)
Discharge capacity C (Ah) = {i (t) dt
[0056]
(Equation 8)
Discharge depth D (%) = C / C₀
[0057]
(Equation 9)
Discharge power Wd (Wh) = i (t) · E (t) dt− −i²(T) · R (t) dt
C₀  : Rated discharge capacity (Ah)
i (t): current value
E (t): voltage
R (t): internal resistance
The energy conversion efficiency ηc and the loss (1−ηc) are calculated based on the measured electric energy after the end of the operation. The calculation result is displayed on the operation control screen of the input unit 37.
[0058]
Simulations such as voltage characteristics and operation efficiency are performed using the constraint conditions, basic data (see FIG. 3) input from the input unit 37, and equations 4 to 11.
[0059]
(Equation 10)
P (D) = I (D) · Eocv (D) −I²(D) ・ R (D)
[0060]
[Equation 11]
E (D) = I (D) · R (D)
P (D): output power at discharge depth D
I (D): current at discharge depth D
Eocv (D): open circuit voltage at depth of discharge D
R (D): Internal resistance at discharge depth D
E (D): battery voltage at depth of discharge D
The operation plan (plan of load distribution between the modules A and B) is configured such that the system administrator creates the operation plan according to his / her own judgment while watching the results of these simulations. For example, by obtaining the discharge depth or the like of the module A at that time (or after a certain amount of power discharge) by the simulation, the output power change timing of the modules A and B (note: the module A will be described later). The discharge depth of 50% corresponds to this) can be included in the operation plan as the actual operation switching “time”. The operation plan created in this way is stored in the operation plan storage means 15 (signal 141). The operation plan (or the method of determining the plan) actually defines the content of the operation control of the secondary battery module according to the depth of discharge, which is the greatest feature of the present embodiment. Therefore, the operation plan will be described later in detail together with the operation description.
[0061]
In this embodiment, the operation plan creation support means 14 corresponds to "parameter means" in the claims. The “control means” is realized by the entire power control system 29 (among them, particularly, the power control means 39).
[0062]
The system protection judging means 12 is for monitoring the presence or absence of an abnormality in the power supply system (FIG. 1). The presence or absence of an abnormality is determined by comparing the signal 142 input from the operation plan creation support means 14 with the detection result (signal 380) of the system monitoring unit 13. Then, the presence / absence of the abnormality and, if there is an abnormality, the content of the abnormality are output to the power control means 39 as the determination signal 121. The system monitor 13 detects a current and a voltage in the power distribution system line 4. The signal 142 indicates a voltage, a current, a power amount, a depth of discharge, and the like.
[0063]
The power control means 39 controls the battery auxiliary equipment 70, the switch 10, and the power converter 11. The power control unit 39 outputs a switching operation command 391 to the switch 10. Similarly, an AC / DC switching command 392 and a power setting signal 393 are output to the power converter 11, and an auxiliary equipment control signal 394 is output to the battery auxiliary equipment 70. The switch 10 and the like are configured to operate according to these control signals 391 to 394.
[0064]
Normally, the power control unit 39 outputs control signals 391 to 394 according to the operation plan stored in the operation plan storage unit 15. However, when an abnormality is notified by the determination signal 121, a special control is performed in response to the notification. For example, when the fluctuation range of the power or frequency in the distribution system line 4 is equal to or larger than a predetermined value, the switch 10 is switched to the open state. Further, even when the voltage of the secondary battery module 7 reaches a predetermined cut voltage or a predetermined depth of discharge, a similar operation is performed to prevent overcharging and discharging. It should be noted that the information defining the content of the special control at the time of such an abnormality is provided in advance by the power control means 39 itself.
[0065]
Next, an example of an operation plan and a criterion for determining the operation plan in the power storage distributed power supply system 19 of the present embodiment will be described with reference to FIG. In addition, the power demand PL of the system load group 3 is satisfied by both the power supplied by the power storage distributed power system 19 and the power Po supplied from the system power supply 1. However, the electric power Po is not related to the electric power storage / distributed power supply system 19 of the present embodiment, and thus the description is omitted.
[0066]
Here, a case where constant power (here, Ps (W)) is always output will be described as an example. Further, the description will be made assuming that the specifications of the modules A and B are as follows.
[0067]

The module A is operated at the rated power Ps (W) until the depth of discharge reaches 50% (this corresponds to the "reference value" of the parameter in the claims). Then, at the subsequent depth of discharge, the operation is performed with the output power of 0.3 Ps (30% of the rated power). This is because, in a region where the depth of discharge is high (here, 50% or more), the internal resistance increases (see FIG. 3), and thus the power loss is reduced by lowering the output power. As described above, the output power is adjusted by changing the current value.
[0068]
On the other hand, the module B does not output power while the module A is operated at the rated power Ps (that is, when the discharge depth of the module A is 50% or less). When the output power of the module A is 0.3 Ps (that is, when the depth of discharge exceeds 50%), the module B operates at an output power of 0.7 Ps (70% of the rated power). . Regarding the module B, the output power is always set to 0.7 Ps regardless of the discharge depth of the module B itself.
[0069]
By performing such load distribution, even when the output power of the module A is set to 0.3 Ps, the power storage / distributed power system 19 as a whole can continuously output constant power (= rated power Ps). it can.
[0070]
The output power of each of the modules A and B described above (module A: Ps, 0.3 Ps, module B: 0.7 Ps) is the maximum value of the output power in the discharge depth region. When the power demand is small and the output power to be output as the power storage / distributed power supply system 19 is smaller than Ps, it goes without saying that the output power of the modules A and B is appropriately reduced.
[0071]
The reduction of the output power is performed preferentially for the module B. The module A is always preferentially discharged within a range not exceeding the maximum value (Ps, 0.3 Ps) of the output power at each discharge depth. For example, consider a case where the output power required for the entire power storage and distribution power supply system 19 is 0.9 Ps in a region where the discharge depth of the module A is 80%. In this case, the output power of module A is kept at 0.3 Ps, and only the output power of module B is reduced to 0.6 Ps.
[0072]
Next, the operation under the operation plan will be described with reference to FIGS.
[0073]
The output power of the modules A and B is controlled by the power control means 39 operating the power converter 11 and the like according to the operation plan.
[0074]
The power control unit 39 outputs a power setting signal 393 having a content of output power Ps to the power converter 11a. On the other hand, a power setting signal 393 whose content is to set the output power to 0 is sent to the power converter 11b. The current of the module A is initially substantially constant (see FIG. 4). This is because there is no decrease in voltage and no increase in internal resistance in a region where the depth of discharge is shallow.
[0075]
At the time when the depth of discharge exceeds 50% in the operation plan, the power control unit 39 instructs the power converter 11a to reduce the output power from Ps to 0.3Ps. The power converter 11a temporarily reduces the current of the module A correspondingly. However, in the depth of discharge region thereafter, a decrease in voltage and an increase in internal resistance occur. Therefore, the power converter 11a gradually increases the current value of the module A in order to offset the decrease.
[0076]
Further, in synchronization with the reduction of the output power of the module A to 0.3 Ps, the power control unit 39 instructs the power converter 11b to start discharging at the output power of 0.7 Ps. The power converter 11b causes the module B to discharge at 0.7 Ps according to the instruction. As in the case of module A, the current value is initially substantially constant, but gradually increases as the depth of discharge increases. For reference, FIG. 4 shows the state of a current change when each of the modules A and B independently discharges at the rated output power Ps (prior art) by a broken line as the rated Ip.
[0077]
Although not specifically described so far, the switch 10 is naturally closed during the operation. Further, the AC / DC switching command 392 has a content for converting DC to AC.
[0078]
FIG. 5 shows the power loss of each module and the power loss of the entire power storage / distribution power supply system 19 when such an operation is performed. The discharge efficiency ηc of the module A is 88%, which is higher than the discharge efficiency (= 70%) at the rated output power. This is because the output after the discharge depth of 50% is reduced to 0.3 Ps. Similarly, regarding the module B, the discharge efficiency ηc is 88%, which is higher than that during the rated operation. The discharge efficiency of the entire system is 88% (power loss 12%). For comparison, FIG. 5 also shows a voltage change and a power loss amount when one secondary battery module is continuously operated at the rated power Ps (prior art). In this case (prior art), the rated discharge efficiency ηc is 70% (power loss 30%). That is, in the present embodiment, the efficiency is improved by 18% as compared with the conventional system.
[0079]
As described above, in this embodiment, a highly efficient operation can be performed by optimizing the power distribution among the modules according to the depth of discharge, that is, the internal resistance characteristics.
[0080]
In the present embodiment, the magnitude of the output power of each module is defined in relation to the depth of discharge in the operation plan. However, the present invention is not limited to this, and an operation plan that defines the output power may be created in relation to the internal resistance of the battery. Furthermore, the magnitude of the output power may be defined in a relationship with the internal resistance and a relationship with some other amount that can be detected (or calculated).
[0081]
Note that obtaining the discharge depth corresponds to indirectly obtaining the internal resistance.
[0082]
[Example 2]
The second embodiment is characterized in that a peak cut operation of system power is enabled by predicting power demand. Further, the present invention is characterized in that it is possible to cope with abnormal load fluctuation.
[0083]
FIG. 6 shows an outline of a power supply system including the power storage distributed power supply system 20 of the second embodiment. The difference between the power storage distributed power system 20 and the power storage distributed power system 19 of the first embodiment is only the power control means 30. Therefore, only the power control system 30 will be described here, and description of the other parts will be omitted.
[0084]
The details of the power control system 30 will be described with reference to FIG.
[0085]
The power control system 30 includes a power demand prediction unit 32, a past case data storage unit 33, an operation plan creation unit 34, a basic data storage unit 36, an input unit 37, a calculator 40, an operation plan correction unit 38, a power control unit 39, and the like. It is comprised including.
[0086]
The power demand prediction means 32 has a function of predicting the power demand of the load 3 during the day, day, or night at predetermined time intervals (hereinafter, referred to as “long-term prediction”). In addition, a function of sequentially predicting the power demand one hour or 30 minutes ahead from the current time (hereinafter, referred to as “sequential prediction”) is provided. These predictions are performed by inputting factors (hereinafter referred to as “influencing factors”) 321 that affect power demand into a neural network that has learned the past case data 330 stored in the storage unit 33. Therefore, a demand change peculiar to a system to be controlled, such as an industrial area or a residential area, can be predicted with high accuracy. Examples of the influence factors 321 include weather forecast information such as temperature and humidity, weekdays, and event information. The past case data 330 is data in which the contents (331) of the influence factors 321 in the past and past demand data 351 including power demand values at each time are stored in association with each other. The past case data 330 is used for creating teacher data necessary for learning the neural network. Details of the neural network will be described later.
[0087]
The power demand forecasting means 32 is configured to output the result of the long-term forecast to the operation plan creating means 34 as a demand forecast result 322. On the other hand, the result of the sequential prediction is output to the operation plan correction means 38 as the sequential prediction result 323.
[0088]
The basic data storage means 36 is the same as in the above embodiment. That is, the basic data storage means 36 stores data such as the open circuit voltages and the internal resistances of the modules A and B.
[0089]
The input means 37 is for inputting various constraints on operation and the like. In the present embodiment, for example, the relation between the depth of discharge and the upper limit of the output power for each of the modules A and B is given as the constraint condition. In addition, a range of a depth of discharge used during normal operation or a range of a depth of discharge used only in an emergency (Dxc and Dxd in examples described later correspond to this).
[0090]
Other constraints on the operation plan creation include a priority between modules A and B in charge / discharge.RankingAnd the like. But this priorityRankingIs fixed and cannot be changed by the input from the input means 37. The priorityRankingAre provided in advance by the operation plan creation means 34 itself.
[0091]
The arithmetic unit 40 performs a predetermined operation (for example, A / D conversion) on the detection result of the current / voltage detector 9 and outputs the result to each operation plan creating unit 34.
[0092]
The operation plan creating means 34 has a function of obtaining the electric energy and the depth of discharge based on the detection result of the current / voltage detector 9 and outputting these to the operation plan correcting means 38 together with the current value and the voltage value. . In addition, a function for creating an operation plan for the modules A and B is provided. The operation plan is created using the power demand prediction result 322, the power operation regulation condition 371 input from the input unit 37, various data in the basic data storage unit 36, the measured values of the voltages and currents of the modules A and B, and the like. Is done. Further, although not clear in the figure, an operation plan of the power supply 1 of the system and the like are also inputted. In the case where the peak cut operation is performed, an operation plan is created from after the end of charging to before the start of discharging. The created operation plan is stored in the operation data storage unit 35. In addition to the above, in the operation data storage means 35, actual measurement data of current and voltage of each module and calculation results (charge / discharge capacity, depth of discharge, electric energy, efficiency, loss, etc.) are stored by the operation plan creation means 34. You. Further, a signal 401 indicating the voltage, current, electric energy, and depth of discharge is output to the operation plan correction means 38.
[0093]
The operation plan correction means 38 has a function of correcting the operation plan using the sequential prediction result 323. The corrected operation plan is sent to the power control unit 39 as a control signal 381. The operation plan correction unit 38 further changes the output power of each module according to the discharge depth input from the operation plan creation unit 34 (note: this is specified in the operation plan as in the first embodiment. The function to make corrections is provided. In addition, the operation plan correction unit 38 has the same function as the system protection determination unit in the first embodiment. That is, the presence or absence of an abnormality is determined based on the system power and the frequency measurement value 380 detected by the system monitor 13, and when there is an abnormality, an instruction to switch to the emergency operation mode or the like is given to the power control unit 39. Output.
[0094]
The power control unit 39 outputs control signals 391 to 394 according to the operation plan (control signal 381) appropriately corrected by the operation plan correction unit 38, and controls the switch 10, the power converter 11, and the like.
[0095]
In the present embodiment, the "control means" in the claims is constituted by the power control means 39, the operation plan creating means 34, and the like. The operation plan creating means 34 corresponds to "parameter means" in the claims. However, since the entire power control system operates in close coordination, the correspondence with the claims described herein is not strict. As long as the above functions are realized as the entire power control system, the specific functions may be assigned (or divided) in any manner.
[0096]
Details of the power demand prediction means 32 will be described with reference to FIG. As described above, in this embodiment, the power demand prediction means 32 is configured using a neural network.
[0097]
The demand forecasting unit 32 includes a target data creating unit 3201, a neural network 3205, an input data creating unit 3206, and a comparing and correcting unit 3203.
[0098]
As is widely known, the neural network 3205 includes an input layer including a plurality of neurons, an intermediate layer, and an output layer. The neurons between the layers are connected to each other. Also, a weighting factor is assigned to each of the combinations. The neuron multiplies the input signal by a weight coefficient and outputs the signal to other neurons. Since the weighting factors are different for each connection, the output to the other neurons will be different for each connection. By using the teacher data and optimizing the weighting factor assigned to each connection in advance (hereinafter referred to as “learning”), an output 204 corresponding to a certain input 3207 becomes a predicted value of target data. The input 3207 for the actual prediction is created by the input data creating means 3206 using the influence factor 321.
[0099]
The teacher data includes a combination of input data to the neural network 3205 and target data corresponding to the input data. The target data is created by the target data creating unit 3201 by normalizing the past data 351 stored in the storage unit 33 and the like. The input data corresponding to the target data is created by the input data creating unit 3206 performing normalization or the like using the past case data 331 stored in the storage unit 33.
[0100]
Input data included in the teacher data is input to the input layer of the neural network. In response to this, the data 3204 output from the output layer and the target data are corrected (or approximated) by appropriately adjusting the weighting coefficient for each connection so that the target data matches (or approximates). (Shown as 3208) can be learned. The comparing and correcting means 3203 compares the data 3204 with the target data and corrects the weight coefficient. In the neural network 3205 of this embodiment, learning is performed in advance using teacher data including past case data 331 (input data) and past data 351 (input data).
[0101]
As an example of a neural network learning method and a specific calculation method of weight coefficient correction, there is a pack propagation method. Details of the neural network and the learning method thereof are described in, for example, "Learning internal representations by error propagation", Parallel Distributed Processing: Explorations in the Microstructure of Cog. 1, Chapter 41, pp., 675-695: MA: MIT Press, pp. 318-362.
[0102]
The operation plan creation unit 34 creates an operation plan 341 that satisfies all of the above-described various constraint conditions. In the present embodiment, mathematical planning is used to create the plan. Mathematical programming is already widely known and will not be described. For example, it is described in "Optimal Cogeneration Planning" by Koichi Ito and Ryohei Yokoyama: Published by Sangyo Tosho Co., Ltd. However, a specific method for creating an operation plan is not limited to this.
[0103]
The operation will be described.
[0104]
Here, the description will be made assuming that the constraint conditions that are the premise of the operation plan creation are set as follows (see FIG. 9).
[0105]
Module A:
The area of Dxc is secured for emergency charging. Normally, charging / discharging is performed only in a discharge depth region equal to or greater than Dxc (this corresponds to a “predetermined range” in the claims). Up to the discharge depth of 50%, the rated power Ps is set as the upper limit of the output power. In the region where the discharge depth is 50% or more, the upper limit of the output power is set to 0.5 Ps and the lower limit is set to 0.1 Ps, and the output power can be set freely within this range.
[0106]
Module B:
The area of Dxd is reserved for emergency discharge. Therefore, usually, charging and discharging are performed only in a region having a smaller discharge depth (this corresponds to a "predetermined range" in the claims). Up to the discharge depth of 50%, the rated power Ps is set to the upper limit of the output power. In the region where the discharge depth is 50% or more, the upper limit value of the output power is set to 0.5 Ps.
[0107]
The normal discharge is performed with priority given to the module A. Charging is performed with priority given to the module B. Dxc and Dxd are set to appropriate values in consideration of system power variability, facility utilization efficiency, and the like, but are preferably about 10 to 40%. For reference, FIG. 10 shows the relationship between the depth of discharge and the rated power that can be charged and discharged. As is clear from FIG. 10, the required rated power amount can be secured by restricting the depth of discharge. In this embodiment, by setting Dxc = 20 ± 5% and Dxd = 40 ± 5%, the rated power amount Wxc that can be charged in an emergency is 23 ± 5% and the rated power amount Wxd that can be discharged is 30 ± 5%. Can be secured.
[0108]
Under the above-described constraints, the rated charge / discharge power amount Wt in normal times can be obtained from the following equation (12).
[0109]
(Equation 12)
Wt = (Wa-Wxc) + (Wb-Wxd)
Wt: Rated charge / discharge power during normal times
Wa: Total rated power of module A
Wxc: Rated power that can be charged in an emergency
Wb: Total rated power of module B
Wxd: Rated power that can be discharged in an emergency
When the result of the long-term prediction by the power demand prediction means 32 is as shown in FIG. 11A, the power demand 1 alone cannot cope with the peak of the power demand. Further, in a time zone in which the power demand decreases, power is left over. Therefore, it is necessary to perform a peak cut operation as shown in FIG. That is, during the time ta to the time tb when the power demand decreases, the remaining power is charged to the modules A and B. On the other hand, discharge is performed between time tc and time te when power demand is tight. Of course, the charging power amount Wc and the discharging power amount Wd must be equal to or smaller than Wt in Expression 12.
[0110]
Therefore, the operation plan creation unit 34 creates an operation plan for power distribution between the modules A and B for performing the peak cut operation while satisfying the above-described constraint conditions. Further, the operation plan correction means 38 corrects the operation plan according to the result of the sequential prediction. Here, taking the discharge from time tc to time te in FIG. 11B as an example, the operation of correcting the operation plan will be described with reference to FIGS.
[0111]
First, an operation plan that has been initially set will be described.
[0112]
Module A is at time td₁To start discharging. From time td1 to time td2, discharge is performed with output power that matches demand. At this time, since the depth of discharge is still small, the output power from the module A can be increased up to Ps. The reason why the output power is reduced in the period from the time td2 to the time td3 is to cope with a low demand. From time td3, since the demand increases again, the output power of module A should increase accordingly. However, from calculation, the discharge depth of module A reaches 50% between time td2 and time td4. Therefore, thereafter, the module A only discharges at the output power (maximum 0.5 Ps, minimum 0.1 Ps) corresponding to the depth of discharge until time td6.
[0113]
It is predicted that the demand will increase again at time td4. As described above, since the discharge depth of module A already exceeds 50%, module A alone cannot cope with this. Therefore, at time td4, the module B is activated, and the module B discharges only the shortage of the module A.
[0114]
After that, since the demand is expected to gradually decrease, the output power from the power storage / distributed power supply system 20 is also reduced accordingly. Here, it is specified in the constraint that the module A is preferentially discharged. Therefore, the reduction of the output power is preferentially performed for the module B. The reason why the output power of the module A is reduced in accordance with the decrease in the demand is that even after the discharge from the module B is completely stopped, the power is still higher than the demand.
[0115]
Despite having made such an operation plan, there is a case where a demand different from the result of the sequential prediction and the result of the long-term prediction is predicted. In this case, the operation plan correction unit 38 issues a command to the power control unit 39 while appropriately correcting the operation plan. Here, a case where the demand is larger than the long-term forecast by the amount of power We1 and We2 in FIG. 12 will be considered as an example.
[0116]
The operation plan correction means 38 compares the result of the sequential prediction with the operation plan (or the long-term prediction result based on the operation plan). Then, time td₃Unexpected power demand We₁Is newly generated. Therefore, the operation plan correction means 38 sets the start timing time of the module B to the time td.₄From td₃Hasten. Also, regarding the module A, the output power after exceeding the discharge depth of 50% is made slightly larger than originally planned in consideration of the power demand We1.
[0117]
Also, at time td₅From td₆Unexpected power demand We₂Has occurred. Therefore, the output power of the module B is kept higher than originally planned to cope with this.
[0118]
Next, an operation in response to an emergency will be described.
[0119]
In this embodiment, it is also possible to suppress a sudden change in the system frequency due to an abnormal load fluctuation such as a reverse power flow.
[0120]
In an emergency (for example, when the frequency fluctuation of the system detected by the system monitor 13 exceeds a certain fluctuation range), the power from the power storage / distributed power supply system 20 is provided to stabilize the system frequency.
[0121]
When the system frequency is lowered (that is, when the power supply is insufficient for the demand), the power is supplied from the modules A and B in order in accordance with the discharge priority condition or from both the modules A and B as necessary. Supply. In the present embodiment, the power amount Wxd is secured in the module B even during the time period when the power storage amount of the system is the smallest (time te-time ta in FIG. 11B). Therefore, even if an unexpected increase in power demand occurs, the situation can be dealt with.
[0122]
Conversely, when the system frequency increases (that is, when the power supply greatly exceeds the demand), power is charged to the modules B and A in order, or to both of the modules A and B as necessary. . Therefore, even in a time zone in which the amount of power stored in the system is the largest (time tb-time tc in FIG. 11B), the module A has a capacity that can be charged with the power amount Wxc. Therefore, it is possible to cope with a situation where the power demand unexpectedly decreases.
[0123]
As described above, in the present embodiment, by making and correcting the operation plan based on the demand forecast, it is possible to perform the peak cut power operation with high accuracy that follows the actual power demand. In addition, it is possible to improve the energy conversion efficiency of the secondary battery facility while supplying necessary power to the system.
[0124]
Further, by always securing a chargeable / dischargeable area, it is possible to sufficiently cope with an emergency.
[0125]
In this embodiment, the output power is adjusted based on the discharge depth of 50%. However, it goes without saying that a greater number of discharge depths serving as the reference may be set and more finely set. Alternatively, the output power limit may be set continuously according to the depth of discharge. In this way, operation with less power loss is possible. However, it is preferable to set an appropriate step size in consideration of ease of control, a calculation method for optimization and a time required for the optimization, a target of power loss reduction, accuracy of demand prediction, and the like.
[0126]
In the above description, only the discharging is mainly described. However, the charging current may be adjusted in accordance with the depth of discharge from the same viewpoint when charging. However, since charging is basically performed using surplus power, there are restrictions on charging time and the like. Therefore, the charging current may be determined with higher priority given to these various constraints.
[0127]
[Example 3]
The present embodiment is a hybrid system in which fuel cell power generation equipment is connected in parallel with secondary battery equipment such as secondary battery modules 7a and b.
[0128]
FIG. 14 shows a power supply system including the power storage / distributed power supply system 21 of this embodiment.
[0129]
Since the secondary battery equipment and the control-related components are configured with the same equipment as in the second embodiment, the description is omitted here.
[0130]
The fuel cell module 8 obtains DC power by electrochemically reacting air and fuel gas. The fuel cell module 8 is configured by stacking a plurality of unit cells. The fuel cell module 8 is configured to output the generated power to the power distribution system line 4 or the secondary battery modules 7a and b. The change of the output destination is performed by the switches 10c and 10d described later.₁, 10d₂It is performed by.
[0131]
The secondary battery modules 7a and 7b store the power generated by the fuel cell module 8 and release the stored power to the distribution system line 4. Unlike the above embodiment, the electric power generated by the power supply 1 is not stored in the secondary battery modules 7a and 7b. The charging can be performed efficiently because the DC output generated by the fuel cell module 8 can be performed directly (without performing direct / interchange conversion). Such a difference from the above embodiment is realized by peripheral circuits (for example, switches 10a to 10d, power converter 11 and the like), and the secondary battery modules 7a and 7b themselves are different from the above embodiment. May be the same as However, the maximum charging current densities of the secondary battery modules 7a and 7b are set higher than the current density output from the fuel cell.
[0132]
The auxiliary equipment 80 is various devices related to the fuel cell module 8 such as a fuel supply unit and a heater.
[0133]
The current / voltage detector 9c detects a current value and a voltage value of an output from the fuel cell module 8. The detection result is output to the power control system 31.
[0134]
The switch 10c is for connecting / disconnecting the fuel cell module 8 and the electric circuit of the power distribution system line 4. Switch 10d₁, 10d₂Is for connecting / disconnecting the secondary battery modules 7a, 7b and the fuel cell module 8 on the DC side. As already described, the switches 10c, 10d₁, 10d₂Is used to change the output destination (the power distribution system line 4, the secondary battery modules 7a and 7b) of the power generated by the fuel cell module 8.
[0135]
The DC voltage regulator 16 regulates the fuel cell power generation voltage.
[0136]
Each unit described above is configured to operate according to a command signal from the power control system 31.
[0137]
The power control system 31 basically controls the fuel cell module 8 and controls the cooperation between the fuel cell 8 and the secondary battery modules 7a and 7b in addition to the functions similar to those of the second embodiment. It has a function to perform. Hereinafter, the power control system 31 will be described in detail with reference to FIG.
[0138]
Although the basic configuration of the power control system 31 is the same as that of the power control system of the second embodiment, the functions of the respective functional sections are slightly different because the control of the fuel cell module 8 is also required. Therefore, the following description focuses on differences from the power control system in the second embodiment.
[0139]
The basic data stored in the basic data storage means 36 may be the same as in the above embodiment.
[0140]
From the input means 37, in addition to the same restrictions as in the above embodiment, various restrictions for protecting the fuel cell module are also input.
[0141]
The operation plan creation unit 34 has a function of determining an operation plan for satisfying the result of the long-term prediction by the power demand prediction unit 32. The “operation plan” in this embodiment includes not only the load distribution between the secondary battery modules 7a and 7b, but also the adjustment plan of the output power of the fuel cell module 8 (note: in this regard, the first , Different from the second embodiment). The operation plan is basically created from the viewpoint of performing the peak cut operation using the secondary battery modules 7a and b so as to minimize the output fluctuation of the fuel cell module 8. In this case, it is natural that the plan is created in consideration of the discharge depth of the secondary battery module 7 at that time (or when the operation plan is performed). The determination of the load distribution between the secondary battery modules 7a and 7b is performed from the same viewpoint as the creation of the operation plan in the second embodiment.
[0142]
To create an operation plan, it is necessary to know the power that must be output as the entire power storage and distributed power system. For that purpose, it is necessary to know the output power value expected by the power supply 1. Therefore, the operation plan creating unit 34 of the present embodiment inputs the operation plan of the power supply 1 and the like as the base power operation information 310.
[0143]
The operation plan correction means 38 appropriately corrects the operation plan according to the result of the sequential prediction by the demand prediction means 32. The correction is basically performed by correcting the output power of the secondary battery modules 7a and 7b. This is because, if the output power of the fuel cell module 8 is frequently changed, the power generation efficiency is reduced and the life is reduced. However, it is needless to say that the output power of the fuel cell module 8 is corrected when the rechargeable battery modules 7a and 7b alone cannot cope.
[0144]
The power control unit 39 outputs various control signals 391 to 395 to control the fuel cell module 8 and the secondary battery modules 7a and 7b in accordance with an instruction from the operation plan correction unit 38. The fuel cell output adjustment signal 395 is for adjusting the output voltage of the fuel cell module 8, and is output to the DC voltage regulator 16. The switching operation command 391 is output to the switches 10a, 10b, 10c, 10d1, and 10d2. The AC / DC conversion switching command 392 and the power setting signal 393 are output to the power converters 11a, 11b, 11c. The auxiliary equipment control signal 394 is output to the auxiliary equipments 8a and 8b.
[0145]
The operation of this embodiment will be described with reference to FIG.
[0146]
The operation plan creating means 34 creates an operation plan in which the power Po supplied by the power supply 1 is subtracted from the power demand in the load 3 and the remainder is supplied by the power storage / distributed power supply system 21. Since the power Po is generally kept constant, the description of the operation of the power supply 1 of the system is omitted.
[0147]
In normal times, power is supplied from the fuel cell module 8 (or from both the fuel cell module 8 and the secondary battery module 7) to the power distribution system line 4 side. That is, during the daytime (time tc-time te), the power demand is large and the power is insufficient only with the fuel cell module 8, so the shortage Wd is discharged from the secondary battery modules 7a and 7b (see FIG. 16A). . Therefore, in this case, the power control means 39₁, 10d₂Is an open circuit. The switches 10a, 10b, 10c are closed. On the other hand, during the nighttime (time ta-time tb), the demand decreases and the power remains, so the power generated by the fuel cell module 8 is stored in the secondary battery module 8 (see FIG. 16A). Therefore, in this case, the power control means 39 includes the switches 10c and 10d.₁, 10d₂Is closed. The switches 10a and 10b are open circuits. The electric power (electric energy Wc) required to perform the peak cut operation in the daytime is covered by the electric power charged at this time. The load distribution between the secondary battery modules 7a and 7b is performed from the same viewpoint as in the second embodiment.
[0148]
As described above, in the present embodiment, the power supply 1 located at a higher position in the system can continue to operate at a constant output. In addition, the energy conversion efficiency of the secondary battery modules 7a and 7b can be kept high. Further, the fluctuation of the output of the fuel cell module 8 can be reduced (see FIG. 16B). If the secondary battery modules 7a and 7b have sufficiently large capacities, it is possible to operate the fuel cell module 7 while keeping the output constant. Furthermore, the higher the chargeable current density of the secondary battery modules 7a and 7b, the greater the flexibility with respect to fluctuations.
[0149]
Next, a description will be given of how to deal with a sudden change in the system load.
[0150]
Here, as shown in FIG. 17, a plurality of system feeders F branched from the power distribution system line 4 are provided.₁~ F_nConsider a case where the AC load group 23 is connected to each of them. Also, the system feeder F₁~ F_nHas a circuit breaker 5₍₁₎~ 5_(N)Shall be attached.
[0151]
In such a configuration, for example, the system feeder F₃(For example, a ground accident), the system feeder F₃Is a circuit breaker 5₍₃₎Is immediately disconnected from the distribution system line 4. Then, the system feeder F₃In this case, the frequency of the power distribution system line 4 rises sharply because the load 23 provided in the power supply system falls off (that is, the power demand sharply decreases).
[0152]
However, in the present embodiment, the operation plan correction means 38 detects an abnormality (in this case, an increase in frequency) based on a signal from the system monitor 13 and notifies the power control unit 39 of that. Then, the power control unit 39 stops the output from the secondary battery module 7 to the power distribution system line 4 by opening the switches 10a and 10b to respond to the abnormal state. At the same time, the switch 10d₁, 10d₂Is closed, and at least a part of the electric power output from the fuel cell module 8 is stored in the secondary cell module 7. Thus, the output of the power storage / distributed power supply system 21 can be reduced without lowering the output of the fuel cell module 7. And the rise of the frequency in the distribution system line 4 can be suppressed to the minimum.
[0153]
A sudden reverse power flow from the system load group 3 can be dealt with in the same manner.
[0154]
Thereby, the fuel cell module 7 can continue to operate in a state where the facility operation rate is high. The upper power supply 1 is also less affected by load fluctuations in normal times and in emergency, so that it can be operated while maintaining a constant output with a high operation rate. The same effect can be obtained by employing a solar cell power generation facility instead of the fuel cell power generation facility.
[0155]
Next, as another example, a description will be given of an emergency response in a case where the power storage distributed power supply system 21 is provided between the loads of the system feeder as shown in FIG.
[0156]
System feeder F_xIs a circuit breaker 5_xIs connected to the power distribution system line 4 via the. And the system feeder F_x, An AC power load group 23 and a large number of switches 17 are connected. Further, the system feeder F_xAre connected to the power storage / distributed power supply system 21 via a circuit breaker 50.
[0157]
System feeder F_xIf an accident occurs in any part of the above, the power storage / distributed power supply system 21 provided in the section where the accident occurred is opened by opening the circuit breaker 5 and the system feeder F_xMust be disconnected from In this case, the fuel cell module 8 of the power storage / distributed power supply system 21 may be forced to operate at an extremely low load. The output of the fuel cell cannot be reduced instantaneously, and a sudden change in load leads to a significant reduction in the life of the fuel cell equipment. However, in this embodiment, since the output of the fuel cell can be instantaneously redirected to the charging of the secondary battery modules 7a and 7b, such a situation can be obtained even if the output of the fuel cell module 8 is not suddenly reduced. Can be handled.
[0158]
Further, the circuit breaker 5 in FIG._xWhen an accident occurs between the switch and the switch 17b, power can be supplied to the load groups 23a and 23b from the power storage / distributed power supply system 21 disposed on the downstream side. Therefore, the power failure section can be made as small as possible.
[0159]
[Example 4]
This embodiment is characterized in that both the AC power and the DC power are supplied from the distributed power storage system 21 according to the present invention.
[0160]
FIG. 19 shows a power supply system including the power storage distributed power supply system according to the present embodiment. The power storage / distributed power system 21 itself basically has the same configuration as that of the second or third embodiment, but further includes a DC power output unit 45 in this embodiment.
[0161]
The DC power output means 45 supplies DC power to the DC power consumer 47 through the DC power system line 46. The DC power output means 45 includes a switch connected to each battery module (secondary battery, fuel cell) and an output voltage regulator, and the like. The operation of the DC power output unit 45 is controlled by the power control system 30 or 31.
[0162]
The DC power system line 46 is a cable for guiding power to a DC power customer 47. In the present embodiment, it is buried underground to prevent a power failure due to a lightning strike.
[0163]
As the DC power consumer 47, for example, a charging station for an electric vehicle, a computer user, and the like are considered.
[0164]
In this embodiment, high-quality and highly reliable DC power can be efficiently supplied to DC power consumers.
[0165]
【The invention's effect】
As described above, according to the present invention, the energy conversion efficiency of a secondary battery can be improved. Further, it is possible to stabilize the supplied power even in the event of a sudden load change in an emergency.
[0166]
Further, the stability of the upper system power supply can be secured. This leads to an improvement in the operation rate of the upper system power supply.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a power storage / distributed power system 19 and a power supply system including the same according to a first embodiment of the present invention.
FIG. 2 is a block diagram showing a functional configuration of a power control system 29.
FIG. 3 is a graph showing characteristic data of a sodium-sulfur battery stored as basic data.
FIG. 4 is a graph showing an example of power distribution operation for each secondary battery module.
FIG. 5 is a graph showing a power loss ratio in the present embodiment.
FIG. 6 is a block diagram illustrating a power storage / distributed power system 20 and a power supply system including the same according to a second embodiment of the present invention.
FIG. 7 is a block diagram showing a functional configuration of a power control system 30.
FIG. 8 is a block diagram showing an outline of a neural network constituting the demand forecasting means.
FIG. 9 is a diagram illustrating an example of a constraint condition.
FIG. 10 is a graph showing a relationship between a depth of discharge and a rated power amount.
FIG. 11 is a graph showing an example of (a) a demand forecast result and (b) a peak cut operation performed on the demand forecast.
FIG. 12 is a diagram showing an example of a power distribution operation plan and its correction.
13 is a diagram showing load distribution for each module corresponding to the operation plan and correction of FIG.
FIG. 14 is a block diagram illustrating a power storage / distributed power system 21 and a power supply system including the same according to a third embodiment of the present invention.
FIG. 15 is a block diagram showing a functional configuration of a power control system 31.
FIG. 16 is a graph showing an operation example of the third embodiment.
FIG. 17 is a block diagram showing an example in which the distributed power storage system 21 according to the third embodiment is connected to a system bus having a plurality of system feeders.
FIG. 18 is an example in which the power storage distributed power supply system 21 of the third embodiment is provided between the loads of a system feeder and interconnected.
FIG. 19 is a block diagram of a power supply system that supplies DC power from the distributed power storage system according to the present invention.
FIG. 20 is a configuration example of a conventional power storage system.
FIG. 21 is a graph showing power loss in the related art.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Power supply 2 ... Distribution substation 3 ... System load group 4 ... Distribution system 5 ... Circuit breaker 6 ... Transformer 7 ... Secondary battery module 8 ... Fuel cell Module 10 Switchgear 11 Power converter 12 Power control unit 14 Operation plan creation support means 16 DC voltage regulator 19 Power storage distributed power supply system 20 ... power storage distributed power supply system, 21 ... power storage distributed power supply system, 29 ... power control system, 30 ... power control system, 31 ... power control system, 32 ... power demand prediction means, 33 ... storage means , 34: battery operation plan creation means 36: basic data storage means 37: constraint condition input means 38: operation plan correction means 39: power control means 45: DC power output Stage, 46 ...... DC power system line, 47 ...... DC power consumers

Claims (2)

A plurality of secondary battery modules configured to include one or more secondary batteries,
Parameter means for obtaining a value of a certain parameter having a correlation with the internal resistance of the secondary battery (hereinafter referred to as “parameter value”);
Control means for adjusting the discharge power from the secondary battery module according to the parameter value obtained by the parameter means,
The plurality of secondary battery modules are arranged in parallel with each other, and configured to be able to control charging and discharging independently of each other,
The control means, a reference value of the parameter determined based on the relationship with the internal resistance,
And a priority order between the secondary battery modules predetermined for charging and discharging, respectively,
The adjustment is performed based on the magnitude relationship between the reference value and the parameter value obtained by the parameter means. In the region where the internal resistance is large, the discharge power is reduced, and That the above charging and discharging are performed according to the order,
A power storage system characterized by the above-mentioned. The control means, when the power is insufficient only with the power discharged from the high-priority secondary battery module, is to permit discharge from the low-priority secondary battery module;
The power storage system according to claim 1, wherein:

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