JP3839643B2

JP3839643B2 - Uninterrupted self-sustained power generation system

Info

Publication number: JP3839643B2
Application number: JP2000208620A
Authority: JP
Inventors: 典彦高松; 淳武田
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2000-07-10
Filing date: 2000-07-10
Publication date: 2006-11-01
Anticipated expiration: 2020-07-10
Also published as: JP2002027670A

Description

【０００１】
【発明が属する技術分野】
本発明は、燃料電池等の系統連係運転において系統異常が発生した場合、無瞬断で系統電源を切り替える無瞬断自立移行発電システムに関するものである。
【０００２】
【従来の技術】
図９は、例えば、特開平１０−１８９０２０号公報に記載されている無瞬断自立移行発電システムの一例としての燃料電池発電システムの構成図である。
図４において、２は燃料電池本体、３は逆変換装置、４は逆変換装置３を介して燃料電池本体２の出力側へ接続する負荷装置、１０は交流系統、１５は電流検出手段である。３１は供給物生成調整設備、３８は単独負荷への供電力供給源を交流系統から逆変換装置発電出力側へ切り替える切替スイッチ、４０は制卸装置、４１は設定関数、４２は調節制御系、４３は信号切替スイッチ、４４は電流設定器である。
【０００３】
次に、この従来例の動作について説明する。都市ガスや天然ガス等からなる原燃料は、供給物生成調整設備３１によって水素に変化させられ、空気と共に燃料電池本体２に供給される。燃料電池本体２は直流電力を発電し、直流発電電力は逆変換装置３によって交流電力に変換される。単独負荷４には、切替スイッチ３８により交流系統１０又は逆変換装置３の交流出力から電力が供給される。
【０００４】
制御装置４０は、電流検出手段１５による検出電流値を電流設定器４４による設定電流値に保持するため、設定関数４１によって調節制御系４２の調節値を指定し、供給物生成調整設備３１の原燃料を制御する。
【０００５】
供給物生成調整設備３１に原燃料ガス及び空気を供給し、燃料電池本体２から直流発電出力を逆変換装置３へ入力して得られた交流出力が、切替スイッチ３８を通して単独負荷４に電力供給される。このような運転時に、供給物生成調整設備３１、燃料電池本体２、直流検出手段１５、逆変換装置３、及び制御装置４０に異常が発生し、且つ交流系統１０が正常な場合には、負荷４への電力供給は、切替スイッチ３８によって、逆変換装置３の出力から交流系統１０に切り替えられる。
【０００６】
交流系統１０から切替スイッチ３８を通して単独負荷４へ電力供給している時に、供給物生成調整設備３１、燃料電池本体２、直流検出手段１５、逆変換装置３、及び制御装置４０がいずれも正常であり、且つ交流系統１０に異常が発生した場合には、単独負荷４への電力供給は、切替スイッチ３８によって、交流系統１０から逆変換装置３の出力に切り替えられる。
【０００７】
単独負荷４への電力供給を無瞬断で上記交流系統１０から逆変換装置３の出力へ切り替えるためには、非常に高速に燃料電池本体２が発電開始可能となる状態を保持する必要があるので、常時、燃料電池発電を行い、燃料電池出力を切替スイッチバイパス回路１７のスイッチ１８を常時閉路しておくことで、交流系統１０へ逆潮流しておき、上記異常発生時にスイッチ１８を高速で解列し、切替スイッチ３８を交流系統１０から逆変換装置３の出力に切り替える。
【０００８】
【発明が解決しようとする課題】
従来の制御方法では、非常に高速に燃料電池本体２が発電開始可能となる状態を保持する必要があるため、ツインインバータと呼ばれる従来例を示す図１４のように、常時は燃料電池の出力を切替スイッチバイパス回路１７を通して交流系統１０へ逆潮流する系統連係運転専用の逆変換装置３Ａと、燃料電池の出力を切替スイッチ３８を通して単独負荷４へ電力供給する単独運転専用の逆変換装置３Ｂとの２台の逆変換装置が必要となる上、切替スイッチ３及び切替スイッチバイパス回路１７用のスイッチ１８の２個のスイッチが必要となっていた。
【０００９】
２個のスイッチ共、遮断及び切替の高速性を実現するためサイリスタスイッチなどを用いるが、サイリスタスイッチは高価な上、スイッチ部の電流通電ロスが真空遮断器などと比べて大きいため、高速切替システム全体としてコストアップとなっていた。
【００１０】
また、サイリスタスイッチの動作上、半サイクル程度の遮断時間が必要なため、従来の高速切替システムでは、瞬停時間が半サイクル以上であり、小容量電磁リレー等は従来システムの瞬停時間に耐えられずダウンする等、一部制御機器に対する完全な瞬停補償は不可能であった。半サイクル以上の瞬停に耐えられない一部の制御機器に対しても瞬停補償する為には、系統瞬停時に切替を伴わない常時バックアップ型の無停電電源装置（ＵＰＳ）などを導入する必要があった。しかし、無停電電源装置は一般的に装置に搭載するバッテリー容量の都合により、数分から数時間程度の短時間補償手段であり、長時間の系統停電及び需要家構内工事などの長期間停電に対応するためには、膨大なバッテリーが必要となるので、非常に高コストとなっている。
【００１１】
長期間停電に対応するために、ガスタービン発電機、ディーゼル発電機などの電源を交流系統から切り離して常時単独運転を行い、発電機異常時も想定してバックアップ用発電機を並列運転すれば、単独負荷への安定した電力供給が行えるが、初期コストアップとなる。
【００１２】
本発明は、上述したような問題点を解決するためになされたもので、切替及び遮断スイッチ部における交流電流通電ロスを減少させ、連係運転と単独運転の切替遮断時間を短縮して瞬停に対して完全補償できる安価で信頼性が高く、長時間の停電が発生した場合でも重要負荷を運転継続可能とすることができる無瞬断自立移行システムを提供することを目的とする。
【００１３】
【課題を解決するための手段】
この発明に係る無瞬断自立移行システムは、直流発電機へのガス供給設備と、前記供給ガスによって直流電力を発電する燃料電池本体と、前記直流電力を交流電力に変換する逆変換装置と、前記交流発電電流を測定する交流発電電流測定手段と、前記交流電流に相当する供給ガス流量を調整する供給ガス流量制御手段と、前記交流出力電力を消費する負荷装置と、前記交流出力電力のうち前記負荷装置消費電力を除いた余剰分を交流系統へ送電する送電点と、前記送電点と前記系統を無瞬断解列可能な高速遮断手段と、前記高速遮断手段の操作電源として前記交流出力電力を利用する手段と、系統の異常を瞬時に検出する系統異常瞬時検出手段と、前記系統異常瞬時検出手段の検出信号を受けて前記高速遮断手段へ解列指令を出して前記逆変換装置の運転モードを定電力制御から定電圧制御へ切り替える発電制御モード切替手段とを備え、前記系統異常瞬時検出手段は、系統過電圧及び系統不足電圧の系統異常を検出する際に、系統電圧レベルがゼロ電圧付近は無視することを特徴とするものである。
また、本発明の無瞬断自立移行システムは、前記逆変換装置の異常を検出する逆変換装置異常検出手段と、前記逆変換装置異常検出手段からの検出信号により負荷装置への電力供給源を前記系統側に切り替える制御手段とを更に備え、前記発電制御モード切替手段は前記送電点及び前記系統からの解列動作を必要最小限に抑制可能であることを特徴とするものである。
さらに、本発明の無瞬断自立移行システムは、発電制御モード切替後の発電機過負荷状態を防止する過負荷抑制制御手段を更に備え、前記高速遮断手段は、前記負荷装置を複数単位に分割して構成された各分割負荷装置と系統とを無瞬断解列可能であることを特徴とするものである。
さらにまた、本発明の無瞬断自立移行システムは、前記高速遮断手段の操作電源として、前記直流出力電力及び前記交流系統を併用する手段を更に備えることを特徴とするものである。
【００１４】
【発明の実施の形態】
以下、この発明の実施の形態を添付図面について説明する。尚、以下の説明では、本発明による無瞬断自立移行システムを燃料電池発電プラントに適用した場合について記載する。
実施の形態１．
図１は、この発明の実施の形態１に係る燃料電池発電プラントのフロー図である。図１において、この燃料電池発電プラントは、ガス供給設備１、燃料電池本体２、逆変換装置３、負荷装置４、高速遮断スイッチ５等から構成されている。燃料電池発電プラントは更に、逆変換装置制御回路６、系統異常検出回路６ａ、発電出力電力制御回路６ｂ、高速遮断スイッチ操作電源８、ガス供給量制御回路９、交流系統１０、保護遮断器１１、系統電圧計測器１２、発電電圧計測器１３、発電電流測定器１５を備えている。
【００１５】
次に、本実施の形態１の動作について図１及び図２に基づいて説明する。
図１において、ガス供給設備１から供給される水素ガス及び酸素ガスによって燃料電池２は直流電力を発電し、逆変換装置３によって直流電力は交流電力に変換される。逆変換装置３の発電出力は保護遮断器１１を通して負荷装置４へ電力供給され、発電出力のうち負荷装置４で消費される電力を引いた余剰発電出力分は、高速遮断スイッチ５及び保護遮断器１１を通して系統１０へ出力される。すなわち、燃料電池発電システムは系統１０が正常な場合、系統連係運転の状態にある。
【００１６】
系統連係運転では、逆変換装置制御回路６は系統電圧計測器１２及び発電電圧計測器１３の電圧を同期させた連係同期運転を行っており、発電電圧計測器１３及び発電電流測定器１５により逆変換装置３の発電電力を制御し、発電電流測定器１５で計測した発電電流値に必要なガス量をガス供給量制御回路９で演算し、ガス供給設備１から燃料電池２本体へ供給するガス量を調整する。
【００１７】
図２は、系統異常検出回路６ａ内での系統瞬停検出方法及び逆変換装置３の運転制御モード切替タイミングを示している。例えば、各相電圧に対してそれぞれ系統電圧異常レベルを系統電圧±２５％に設定した場合、系統電圧計測器１２で測定した系統電圧値が予め設定した系統電圧不足レベル（系統正常電圧×７５％）を下回ったとき、系統異常検出回路６ａは発電出力電力制御回路６ｂへ系統異常信号を送出し、発電出力電力制御回路６ｂは高速遮断スイッチ５へ遮断信号を送出し、高速遮断スイッチ解列のタイミングに合わせて電力変換装置出力を定電力制御から定電圧制御に切り替え、負荷装置４へは無瞬断で電力を供給し続ける。すなわち、系統１０が正常な状態である系統連係運転から、燃料電池出力を系統４から解列した単独運転状態に無瞬断で切り替わる。また、発電電圧計測器１３で計測した系統電圧測定値が予め設定した系統電圧過剰レベル（系統正常電圧×１２５％）より上回ったとき、系統異常検出回路６ａは発電出力電力制御回路６ｂへ系統異常信号を送出し、前記系統瞬停の場合と同様の動作で、無瞬断自立移行する。単独運転検出、不足周波数、過周波数、過電流など他系統異常検出の場合も、前記系統瞬停の場合と同様の動作で無瞬断自立移行する。
【００１８】
一般的な電動遮断器と同様、高速遮断スイッチ５を操作するための電源が必要であり、逆変換装置３の発電電力の一部を供給している。具体的には、特開平１１−１１１１２３号公報に記載されているような高速遮断スイッチを使用するため、充電装置として直流電源８への交流電源が必要となる。
【００１９】
実施の形態２．
図３は、この発明の実施の形態２に係る系統異常検出回路の動作、すなわち系統異常検出回路６ａ内での系統瞬停検出方法及び逆変換装置３の運転制御モード切替タイミングを示している。尚、本実施の形態２の構成は図１に示した上記実施の形態１と同様である。
次に、本実施の形態２の動作について図３に基づいて説明する。
図３では、各相電圧の実効値にほとんど影響しない電圧ゼロ付近レベル、例えば、検出レベル電圧がピーク電圧×２０％以下の電圧範囲は系統異常検出対象外としている。前記検出対象外となる間の負荷設備への電力供給実効値は非常に小さいため、負荷設備の消費パワーへ与える影響はほとんどない。
【００２０】
実施の形態３．
図４はこの発明の実施の形態３に係る燃料電池発電プラントのフロー図であり、図５はその系統異常監視モードの制御ブロック図である。図４において、１〜１２は図１と同様であり、６ｃは逆変換装置異常検出回路、５ａ及び５ｂは高速スイッチである。
【００２１】
次に、本実施の形態３の動作について図４及び図５に基づいて説明する。
図４において、系統連係運転及び単独運転におけるガス供給動作及び発電動作は図１の上記実施の形態１と同様である。図５は、系統異常監視モードでの逆変換装置の運転制御モード切替タイミングを示している。
系統連係運転状態において、系統瞬停（正常電圧×７５％）、系統過電流（正常電流×１２５％）、単独運転状態受動方式検出などの系統異常が発生した事を系統異常検出回路６ａが検出した時、むやみに系統１０から燃料電池発電設備を解列し自立運転へ移行する事を防ぐため、一旦高速スイッチ５ｂへ遮断信号を送出し、逆変換装置３をゲートブロックし、暫く（約０．５秒程度）系統異常を監視した後、系統異常が継続していれば高速スイッチ５ｂを再投入し、高速スイッチ５ａを解列し、電力変換装置出力を定電力制御から定電圧制御に切り替え、負荷装置４へは無瞬断で電力を供給し続ける。また、暫く（約０．５秒程度）系統異常を監視した後、系統１０が正常化していれば高速スイッチ５ｂを再投入し、電力変換装置出力の定電力制御を継続する。系統瞬停を暫く監視している間に、系統瞬停（正常×７０％）、系統過電流（正常×１３０％）が発生した場合、即時に（約０．５秒程度待たずに）高速スイッチ５ｂを再投入し、高速スイッチ５ａを解列し、電力変換装置出力を定電力制御から定電圧制御に切り替え、負荷装置４へは無瞬断で電力を供給し続ける。
【００２２】
一方、単独運転中に、逆変換装置異常検出回路６ｃにより逆変換装置３の異常を検出した場合、系統異常検出回路６ａで系統１０が正常と判断すれば、高速スイッチ５ｂを解列して逆変換装置３を非常停止させ、高速スイッチ５ａを再投入して負荷装置４への電力供給を逆変換装置出力から系統電力に無瞬断で切り替える。
【００２３】
実施の形態４．
図６はこの発明の実施の形態４に係る燃料電池発電プラントのフロー図、図７は逆変換装置の過負荷防止制御（制御モード切替）のタイムチャートである。図６において、１〜１５は図１と同様であり、６ｄは過負荷抑制制御回路、１６ａ、１６ｂ、１６ｃは高速遮断スイッチである。
【００２４】
次に、上記実施の形態４の動作について図６及び図７に基づいて説明する。
図６において系統連係運転及び単独運転におけるガス供給動作及び発電動作は図１と同様である。図７は、自立運転移行後の過負荷抑制制御モードにおける高速遮断スイッチ１６ａ，１６ｂ，１６ｃの動作シーケンスを示している。
【００２５】
系統連係運転状態において、燃料電池発電出力より大きな負荷装置が接続されている場合、例えば燃料電池発電出力が２００ｋＷで、負荷装置（ａ）４ａがｌ００ｋＷ、負荷装置（ｂ）４ｂが８０ｋＷ、負荷装置（ｃ）４ｃが５０ｋＷである場合、予め負荷グループに優先順位を定めておき、例えば、優先度の高い順に負荷装置（ａ）、（ｂ）、（ｃ）としておく。この場合、系統異常が発生した時、系統異常検出回路６ａにより系統瞬停を検出し、発電出力電力制御回路６ｂは高速遮断スイッチ５ａへ遮断信号を送出し、高速遮断スイッチ解列のタイミングに合わせて電力変換装置出力を定電力制御から定電圧制御に切り替えつつ、発電電圧計測器１３で測定する電圧を定格定電圧に保つように逆変換装置３が制御する。このため、燃料電池発電出力２００ｋＷに対して負荷装置による消費電力が合計２３０ｋＷであり、発電電流測定器１５により測定した負荷電力供給電流は燃料電池出力過電流値をオーバーしてしまい、発電過電流で逆変換装置３及び燃料電池が非常停止してしまう。
【００２６】
そこで、図７に示す手順で、高速遮断スイッチ１６ａ，１６ｂ，１６ｃを優先度の低い順に解列していき、燃料電池発電出力内で最大出力となるように、接続している負荷量を調節する。具体的には、系統異常発生後、高速遮断スイッチ５ａが解列されるので、系統受電電力が５０ｋＷから０ｋＷとなり、負荷装置４全体へ流れる電流が減少し、逆変換装置出力電流のみが前記負荷４へ供給されるため合計負荷消費電力が下がる。さらに、逆変換装置３は定電圧制御を開始し、発電電圧を一定に保ちながら合計負荷（２３０ｋＷ）に合わせようと逆変換装置出力電流を増加させていく。逆変換装置発電電流が逆変換装置過電流トリップ値に到達する前に、負荷装置グループ中で重要度が最低の負荷装置（ｃ）４ｃへの電力供給回路に設置している高速遮断スイッチ１６ｃを解列し、逆変換装置出力が定格以下となるまで重要度の低い回路順に高速遮断スイッチ４を解列していく。上記実施の形態３では、高速遮断スイッチ１６ｃを解列した段階で、逆変換装置出力が１８０ｋＷとなり定格出力以内となるので、自立運転移行後は１８０ｋＷで運転を行う。
一連の動作時間は約４ｍｓｅｃ以内であり、図７において、ｔ２−ｔ１＝４ｍｓｅｃ程度である。
また、上記実施の形態１と同様、逆変換装置制御回路６及びガス供給量制御回路９は負荷電流測定器８で測定した負荷電流値をもとに、電力出力及びガス供給量を制御する。
【００２７】
実施の形態５．
図８はこの発明の実施の形態５に係る燃料電池発電プラントのフロー図である。図８において、１〜１５は図１と同様であり、燃料電池２の直流出力を高速遮断スイッチ５へ供給する回路を有する。
【００２８】
次に、本実施の形態５の動作について図８に基づいて説明する。
図８において、系統連係運転及び単独運転におけるガス供給動作及び発電動作は図１の上記実施の形態１と同様である。通常は、高速遮断スイッチ５の操作電源として系統１０の電力を使用しており、高速遮断スイッチ５内で直流電力を蓄積するコンデンサの充電電圧が不十分となる現象が発生した場合、高速遮断スイッチ５は確実に解列できなくなるが、本実施の形態５では、上記実施の形態１のように系統電力のみでなく、燃料電池本体２の直流電力も併用するので、系統１０の電力低下が継続して、高速遮断スイッチ動作電力が不足ぎみとなった場合でも、確実に高速遮断スイッチ５の解列及び投入操作が可能となる。
【００２９】
【発明の効果】
以上のように、この発明によれば、以下に記載するような効果を奏する。
この発明によれば、逆変換装置容量を定格発電出力一台分とすることが可能となり、逆変換装置部の初期コストを抑制できると共に、逆変換装置部の構成単純化により、逆変換装置の高信頼化を実現できる。
また、通電ロスが極めてゼロに近い真空バルブ構造をもつ高速遮断スイッチを採用することで、ランニングコストを抑制することが可能となる。瞬停発生時に負荷供電力供給力の停電時間が約２ｍｓｅｃ程度であり、従来システムより短時間化しているので、制御リレー等の最も瞬停耐量が低い機器の瞬停補償も可能となる。
さらに、正常電圧波形の電圧レベルが低い範囲では、系統異常検出を行わないので、誤検出による不要な自立移行動作を防止することが可能となる。
また、この発明によれば、負荷設備の瞬停耐量に合わせた系統異常判断を行えるので、系統異常時に、むやみに直流発電機を自立移行させることなく、できる限り系統連係運転を継続することができる。
また、単独運転中に系統が正常化していて逆変換装置が異常となった場合にも、無瞬断で負荷装置への電力供給を逆変換装置出力から系統へ切り替えることが可能となり、負荷設備の運転継続性を向上できる。
さらに、この発明によれば、系統連係運転時の総負荷設備容量が直流発電機総出力より大きく、系統より一部受電している状況において系統異常が発生し自立移行する場合に、過負荷状態で自立運転継続すると逆変換装置出力過電流レベルに到達するので、逆変換装置が非常停止して全負荷とも一斉にダウンしてしまうが、本発明では、優先度の低い負荷グループへの電力供給回路に設置した高速遮断スイッチを順に解列することで、発電設備容量に対して最大限の負荷装置に対して無瞬断で電力供給を継続できる。
さらにまた、この発明によれば、高速遮断スイッチ操作電源に系統電力のみでなく、燃料電池の直流電力も併用するので、高速遮断スイッチ単体の動作信頼性を向上でき、無瞬断自立移行システムとしての信頼性を向上することが可能となる。
【図面の簡単な説明】
【図１】この発明の実施の形態１に係る燃料電池発電プラントのフロー図である。
【図２】実施の形態１の系統異常検出方法を示す図である。
【図３】この発明の実施の形態２の系統異常検出方法を示す図である。
【図４】この発明の実施の形態３に係る燃料電池発電プラントのフロー図である。
【図５】実施の形態３の系統異常監視モード制御ブロック図である。
【図６】この発明の実施の形態４に係る燃料電池発電プラントのフロー図である。
【図７】実施の形態４の過負荷防止制御タイムチャート図である。
【図８】この発明の実施の形態５に係る燃料電池発電プラントのフロー図である。
【図９】従来の燃料電池発電プラントを示すフロー図である。
【符号の説明】
１ガス供給設備、２燃料電池本体、３逆変換装置、４負荷装置、５高速遮断スイッチ、６逆変換装置制御回路、６ａ系統異常検出回路、６ｂ発電出力電力制御回路、６ｃ逆変換装置異常検出回路、６ｄ過負荷抑制制御回路、６ｅ過渡電圧上昇抑制回路、６ｆ直流発電機異常検出回路、６ｚ系統瞬停検出器、８高速遮断スイッチ操作用直流電源、９ガス供給量制御回路、１０系統、１１保護遮断器、１２送電電圧検出器、１３発電電圧検出器、１４開閉器、１５発電電流検出器、１６負荷用高速遮断スイッチ、１７バイパス回路、１８スイッチ、１９開閉器、２１直流発電機、３１供給物生成調整設備、３８切替スイッチ、４０制御装置、４１設定関数、４２調節制御系、４３信号切替スイッチ、４４電流設定器。[0001]
[Technical field to which the invention belongs]
The present invention relates to an uninterruptible self-sustained power generation system that switches an uninterrupted system power supply when a system abnormality occurs in an interconnected operation of a fuel cell or the like.
[0002]
[Prior art]
FIG. 9 is a configuration diagram of a fuel cell power generation system as an example of an uninterruptible self-sustaining transition power generation system described in, for example, Japanese Patent Laid-Open No. 10-189020.
In FIG. 4, 2 is a fuel cell body, 3 is an inverse conversion device, 4 is a load device connected to the output side of the fuel cell body 2 via the inverse conversion device 3, 10 is an AC system, and 15 is a current detection means. . 31 is a supply generation adjustment facility, 38 is a changeover switch for switching a power supply source for a single load from the AC system to the reverse converter power generation output side, 40 is a wholesale control device, 41 is a setting function, 42 is an adjustment control system, 43 is a signal selector switch, and 44 is a current setting device.
[0003]
Next, the operation of this conventional example will be described. The raw fuel made of city gas, natural gas, or the like is converted into hydrogen by the supply generation adjustment facility 31 and supplied to the fuel cell main body 2 together with air. The fuel cell main body 2 generates direct-current power, and the direct-current generated power is converted into alternating-current power by the inverse conversion device 3. The single load 4 is supplied with electric power from the AC system 10 or the AC output of the inverse conversion device 3 by the changeover switch 38.
[0004]
The control device 40 specifies the adjustment value of the adjustment control system 42 by the setting function 41 in order to hold the detected current value by the current detection means 15 at the set current value by the current setting unit 44, and the raw material of the supply generation adjustment equipment 31. Control the fuel.
[0005]
An AC output obtained by supplying raw fuel gas and air to the supply generation adjustment facility 31 and inputting a DC power generation output from the fuel cell body 2 to the reverse conversion device 3 is supplied to the single load 4 through the changeover switch 38. Is done. During such operation, if an abnormality occurs in the supply generation adjustment facility 31, the fuel cell main body 2, the DC detection means 15, the reverse conversion device 3, and the control device 40, and the AC system 10 is normal, the load The power supply to 4 is switched from the output of the reverse conversion device 3 to the AC system 10 by the changeover switch 38.
[0006]
When power is supplied from the AC system 10 to the single load 4 through the changeover switch 38, the supply generation adjustment equipment 31, the fuel cell main body 2, the DC detection means 15, the reverse conversion device 3, and the control device 40 are all normal. If there is an abnormality in the AC system 10, the power supply to the single load 4 is switched from the AC system 10 to the output of the inverter 3 by the changeover switch 38.
[0007]
In order to switch the power supply to the single load 4 from the AC system 10 to the output of the reverse conversion device 3 without interruption, it is necessary to maintain a state in which the fuel cell main body 2 can start power generation at a very high speed. Therefore, the fuel cell power generation is always performed, and the fuel cell output is always closed by switching the switch 18 of the changeover switch bypass circuit 17, so that the reverse flow flows to the AC system 10, and the switch 18 is operated at a high speed when the abnormality occurs. Disconnect and switch the changeover switch 38 from the AC system 10 to the output of the inverse conversion device 3.
[0008]
[Problems to be solved by the invention]
In the conventional control method, since it is necessary to maintain a state in which the fuel cell main body 2 can start power generation at a very high speed, the output of the fuel cell is always output as shown in FIG. 14 showing a conventional example called a twin inverter. A reverse conversion device 3A dedicated to grid-linked operation that reversely flows to the AC system 10 through the changeover switch bypass circuit 17 and a reverse conversion device 3B dedicated to single operation that supplies power from the fuel cell to the single load 4 through the changeover switch 38. In addition to the need for two reverse conversion devices, two switches of the changeover switch 3 and the switch 18 for the changeover switch bypass circuit 17 are required.
[0009]
Both switches use a thyristor switch to realize high speed of switching and switching, but the thyristor switch is expensive and the current conduction loss of the switch part is larger than the vacuum circuit breaker, etc., so the high speed switching system Overall, the cost was increased.
[0010]
In addition, since a thyristor switch operation requires a cut-off time of about half a cycle, the conventional fast switching system has a momentary power failure time of more than half a cycle, and small-capacity electromagnetic relays can withstand the momentary power failure time of the conventional system. It was impossible to completely compensate for instantaneous power failure for some control devices, such as going down. In order to compensate for momentary power outage even for some control equipment that cannot withstand momentary power outages of more than half a cycle, an always-on backup uninterruptible power supply (UPS) that does not involve switching during system power outage is introduced. There was a need. However, the uninterruptible power supply is generally a short-term compensation means of several minutes to several hours due to the capacity of the battery installed in the device, and it can handle long-term power outages and long-term power outages such as customer premises construction. In order to do so, a huge battery is required, which is very expensive.
[0011]
In order to cope with power outages for a long period of time, disconnect the power source of the gas turbine generator, diesel generator, etc. from the AC system, always operate alone, and if the backup generator is operated in parallel, assuming that the generator is abnormal, Although stable power supply to a single load can be performed, the initial cost increases.
[0012]
The present invention has been made to solve the above-described problems, and reduces the alternating current energization loss in the switching and shut-off switch section, shortens the switching cut-off time between linked operation and isolated operation, and makes instantaneous power failure. An object of the present invention is to provide an uninterruptible self-sustained transition system that is capable of complete compensation, is inexpensive and highly reliable, and can continue operation of an important load even when a long-time power failure occurs.
[0013]
[Means for Solving the Problems]
A non-instantaneous self-sustained transition system according to the present invention includes a gas supply facility to a DC generator, a fuel cell main body that generates DC power with the supply gas, an inverse converter that converts the DC power into AC power, Among the AC power generation current measuring means for measuring the AC power generation current, the supply gas flow rate control means for adjusting the flow rate of the supply gas corresponding to the AC current, the load device that consumes the AC output power, and the AC output power A power transmission point for transmitting the surplus power consumption excluding the load device power consumption to an AC system, a high-speed disconnection means capable of instantaneously disconnecting the power transmission point and the system, and the AC output as an operation power source for the high-speed disconnection means Means for utilizing electric power, system abnormality instantaneous detection means for instantaneously detecting system abnormality, and receiving a detection signal from the system abnormality instantaneous detection means to issue a disconnection command to the high speed shut-off means to perform the reverse change And a power generation control mode switching means for switching the operation mode of the apparatus from the constant power control to constant voltage control, the system abnormality instantaneous detection means, when detecting the system abnormality of the system over-voltage and the system undervoltage, the system voltage level It is characterized in that the vicinity of zero voltage is ignored .
Further , the uninterruptible self-sustained transition system of the present invention includes an inverse converter abnormality detecting means for detecting an abnormality of the inverse converter, and a power supply source to the load device by a detection signal from the inverse converter abnormality detecting means. Control means for switching to the system side, and the power generation control mode switching means can suppress the disconnection operation from the power transmission point and the system to the minimum necessary.
Furthermore , the uninterruptible self-sustained transition system of the present invention further includes an overload suppression control means for preventing a generator overload state after switching the power generation control mode, and the high speed shutoff means divides the load device into a plurality of units. Each divided load device and system configured as described above can be disconnected instantaneously.
Furthermore , the uninterruptible self-sustained transition system of the present invention is characterized by further comprising means for using the DC output power and the AC system together as an operation power source for the high-speed shut-off means.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. In the following description, a case where the uninterruptible self-sustained transition system according to the present invention is applied to a fuel cell power plant will be described.
Embodiment 1 FIG.
FIG. 1 is a flowchart of the fuel cell power plant according to Embodiment 1 of the present invention. In FIG. 1, this fuel cell power plant is composed of a gas supply facility 1, a fuel cell main body 2, an inverse conversion device 3, a load device 4, a high-speed cutoff switch 5, and the like. The fuel cell power plant further includes an inverse converter control circuit 6, a system abnormality detection circuit 6a, a power generation output power control circuit 6b, a high-speed cutoff switch operating power supply 8, a gas supply amount control circuit 9, an AC system 10, a protective circuit breaker 11, A system voltage measuring instrument 12, a generated voltage measuring instrument 13, and a generated current measuring instrument 15 are provided.
[0015]
Next, the operation of the first embodiment will be described with reference to FIGS.
In FIG. 1, the fuel cell 2 generates DC power with hydrogen gas and oxygen gas supplied from the gas supply facility 1, and the DC power is converted into AC power by the inverse conversion device 3. The power generation output of the reverse conversion device 3 is supplied to the load device 4 through the protective circuit breaker 11, and the surplus power generation output obtained by subtracting the power consumed by the load device 4 from the power generation output is the high-speed cutoff switch 5 and the protection circuit breaker. 11 to the system 10. That is, the fuel cell power generation system is in a system linkage operation state when the system 10 is normal.
[0016]
In the grid linkage operation, the inverse conversion device control circuit 6 performs linked synchronization operation in which the voltages of the grid voltage measuring instrument 12 and the generated voltage measuring instrument 13 are synchronized, and the generated voltage measuring instrument 13 and the generated current measuring instrument 15 perform the reverse operation. Gas supplied to the fuel cell 2 main body from the gas supply facility 1 by controlling the generated power of the converter 3, calculating the gas amount necessary for the generated current value measured by the generated current measuring instrument 15 by the gas supply amount control circuit 9. Adjust the amount.
[0017]
FIG. 2 shows a system instantaneous power failure detection method in the system abnormality detection circuit 6 a and the operation control mode switching timing of the inverse conversion device 3. For example, when the system voltage abnormality level is set to the system voltage ± 25% for each phase voltage, the system voltage value measured by the system voltage measuring instrument 12 is set to the system voltage undervoltage level (system normal voltage × 75%). ), The system abnormality detection circuit 6a sends a system abnormality signal to the power generation output power control circuit 6b, and the power generation output power control circuit 6b sends a cutoff signal to the high speed cutoff switch 5, The power converter output is switched from constant power control to constant voltage control in accordance with the timing, and power is continuously supplied to the load device 4 without interruption. That is, the grid-linked operation in which the system 10 is in a normal state is switched to the single operation state in which the fuel cell output is disconnected from the system 4 without interruption. Further, when the system voltage measurement value measured by the power generation voltage measuring instrument 13 exceeds a preset system voltage excess level (system normal voltage × 125%), the system abnormality detection circuit 6a supplies the system abnormality to the power generation output power control circuit 6b. A signal is sent out, and the transition is made without any interruption in the same manner as in the case of the system instantaneous power failure. In the case of other system abnormality detection such as isolated operation detection, insufficient frequency, overfrequency, overcurrent, etc., the transition is made without instantaneous interruption by the same operation as in the case of instantaneous power failure.
[0018]
Like a general electric circuit breaker, a power source for operating the high-speed cutoff switch 5 is necessary, and a part of the generated power of the reverse conversion device 3 is supplied. Specifically, since a high-speed cutoff switch as described in JP-A-11-111123 is used, an AC power source to the DC power source 8 is required as a charging device.
[0019]
Embodiment 2. FIG.
FIG. 3 shows the operation of the system abnormality detection circuit according to Embodiment 2 of the present invention, that is, the system instantaneous power failure detection method in the system abnormality detection circuit 6a and the operation control mode switching timing of the inverse conversion device 3. The configuration of the second embodiment is the same as that of the first embodiment shown in FIG.
Next, the operation of the second embodiment will be described with reference to FIG.
In FIG. 3, a voltage near zero level that hardly affects the effective value of each phase voltage, for example, a voltage range in which the detection level voltage is a peak voltage × 20% or less is excluded from the system abnormality detection target. Since the power supply effective value to the load facility during the period outside the detection target is very small, there is almost no influence on the power consumption of the load facility.
[0020]
Embodiment 3 FIG.
FIG. 4 is a flowchart of the fuel cell power plant according to Embodiment 3 of the present invention, and FIG. 5 is a control block diagram of the system abnormality monitoring mode. In FIG. 4, 1 to 12 are the same as those in FIG. 1, 6c is an inverse converter abnormality detection circuit, and 5a and 5b are high-speed switches.
[0021]
Next, the operation of the third embodiment will be described with reference to FIGS.
In FIG. 4, the gas supply operation and the power generation operation in the grid linkage operation and the single operation are the same as those in the first embodiment shown in FIG. FIG. 5 shows the operation control mode switching timing of the inverse conversion device in the system abnormality monitoring mode.
The system abnormality detection circuit 6a detects that a system abnormality has occurred such as system instantaneous power failure (normal voltage x 75%), system overcurrent (normal current x 125%), and independent operation state passive method detection in the system linkage operation state. In order to prevent unnecessarily disconnecting the fuel cell power generation facility from the grid 10 and shifting to a self-sustaining operation, a cutoff signal is once sent to the high-speed switch 5b, and the reverse conversion device 3 is gate-blocked for a while (about 0). After monitoring the system abnormality, if the system abnormality continues, restart the high-speed switch 5b, disconnect the high-speed switch 5a, and switch the power converter output from constant power control to constant voltage control The power is continuously supplied to the load device 4 without interruption. Further, after monitoring the system abnormality for a while (about 0.5 seconds), if the system 10 is normalized, the high-speed switch 5b is turned on again, and constant power control of the power converter output is continued. If system instantaneous power outage (normal x 70%) or system overcurrent (normal x 130%) occurs while monitoring system power outage for a while, high-speed immediately (without waiting for about 0.5 seconds) The switch 5b is turned on again, the high-speed switch 5a is disconnected, the power converter output is switched from constant power control to constant voltage control, and power is continuously supplied to the load device 4 without interruption.
[0022]
On the other hand, when an abnormality of the reverse conversion device 3 is detected by the reverse conversion device abnormality detection circuit 6c during the independent operation, if the system abnormality 10 is determined to be normal by the system abnormality detection circuit 6a, the high speed switch 5b is disconnected and reversed. The converter 3 is brought to an emergency stop, the high-speed switch 5a is turned on again, and the power supply to the load device 4 is switched from the inverse converter output to the system power without interruption.
[0023]
Embodiment 4 FIG.
FIG. 6 is a flowchart of the fuel cell power plant according to Embodiment 4 of the present invention, and FIG. 7 is a time chart of the overload prevention control (control mode switching) of the reverse conversion device. 6, 1 to 15 are the same as those in FIG. 1, 6d is an overload suppression control circuit, and 16a, 16b and 16c are high-speed cutoff switches.
[0024]
Next, the operation of the fourth embodiment will be described with reference to FIGS.
In FIG. 6, the gas supply operation and the power generation operation in the grid linkage operation and the single operation are the same as those in FIG. FIG. 7 shows an operation sequence of the high-speed cutoff switches 16a, 16b, and 16c in the overload suppression control mode after the transition to the independent operation.
[0025]
When a load device larger than the fuel cell power generation output is connected in the grid-linked operation state, for example, the fuel cell power generation output is 200 kW, the load device (a) 4a is 100 kW, the load device (b) 4b is 80 kW, and the load device (C) When 4c is 50 kW, priorities are set in advance for the load groups, for example, load devices (a), (b), and (c) in descending order of priority. In this case, when a system abnormality occurs, the system abnormality detection circuit 6a detects an instantaneous power interruption, and the generated output power control circuit 6b sends a cutoff signal to the high-speed cutoff switch 5a to match the timing of the high-speed cutoff switch disconnection. The inverter 3 controls the voltage measured by the generated voltage measuring instrument 13 so as to keep the rated constant voltage while switching the power converter output from constant power control to constant voltage control. For this reason, the total power consumed by the load device is 230 kW with respect to the fuel cell power generation output 200 kW, and the load power supply current measured by the power generation current measuring device 15 exceeds the fuel cell output overcurrent value. As a result, the reverse conversion device 3 and the fuel cell are brought to an emergency stop.
[0026]
Therefore, according to the procedure shown in FIG. 7, the high-speed cutoff switches 16a, 16b, and 16c are disconnected in order from the lowest priority, and the connected load amount is adjusted so that the maximum output is obtained within the fuel cell power generation output. To do. Specifically, since the high-speed cutoff switch 5a is disconnected after the occurrence of the system abnormality, the system received power is reduced from 50 kW to 0 kW, the current flowing to the entire load device 4 is reduced, and only the output power of the reverse conversion device is the load. 4, the total load power consumption is reduced. Furthermore, the inverter 3 starts constant voltage control, and increases the inverter output current to match the total load (230 kW) while keeping the generated voltage constant. Before the reverse converter power generation current reaches the reverse converter overcurrent trip value, the high speed cutoff switch 16c installed in the power supply circuit to the load apparatus (c) 4c having the lowest importance in the load apparatus group is provided. The high-speed cutoff switch 4 is disconnected in the order of circuits of low importance until the output of the inverse conversion device is below the rating. In Embodiment 3 described above, when the high-speed cutoff switch 16c is disconnected, the output of the reverse conversion device is 180 kW, which is within the rated output, and thus the operation is performed at 180 kW after the transition to the independent operation.
A series of operation time is within about 4 msec, and in FIG. 7, t2−t1 = about 4 msec.
As in the first embodiment, the inverse conversion device control circuit 6 and the gas supply amount control circuit 9 control the power output and the gas supply amount based on the load current value measured by the load current measuring device 8.
[0027]
Embodiment 5 FIG.
FIG. 8 is a flowchart of the fuel cell power plant according to Embodiment 5 of the present invention. In FIG. 8, reference numerals 1 to 15 are the same as those in FIG. 1, and have a circuit for supplying the DC output of the fuel cell 2 to the high-speed cutoff switch 5.
[0028]
Next, the operation of the fifth embodiment will be described with reference to FIG.
In FIG. 8, the gas supply operation and the power generation operation in the grid linkage operation and the single operation are the same as those in the first embodiment shown in FIG. Normally, the power of the system 10 is used as an operation power source for the high-speed cutoff switch 5, and when a phenomenon occurs in which the charging voltage of the capacitor for storing DC power becomes insufficient in the high-speed cutoff switch 5, the high-speed cutoff switch However, in the fifth embodiment, not only the system power as in the first embodiment but also the DC power of the fuel cell main body 2 is used together, so the power reduction of the system 10 continues. Thus, even when the operating power of the high-speed cutoff switch becomes insufficient, the high-speed cutoff switch 5 can be reliably disconnected and turned on.
[0029]
【The invention's effect】
As described above, according to the present invention, the following effects can be obtained.
According to the present invention, the capacity of the reverse conversion device can be set to one rated power generation output, the initial cost of the reverse conversion device unit can be suppressed, and the structure of the reverse conversion device unit can be simplified by simplifying the configuration of the reverse conversion device unit. High reliability can be realized.
In addition, the running cost can be reduced by adopting a high-speed cutoff switch having a vacuum valve structure in which the energization loss is very close to zero. When a power outage occurs, the power outage time of the load power supply is about 2 msec, which is shorter than that of the conventional system. Therefore, it is possible to compensate for a power outage of a device having the lowest power supply tolerance such as a control relay.
Furthermore , since the system abnormality detection is not performed in the range where the voltage level of the normal voltage waveform is low, it is possible to prevent unnecessary self-sustained operation due to erroneous detection.
Further , according to the present invention, it is possible to determine the system abnormality in accordance with the momentary power failure tolerance of the load facility, so that the system linkage operation can be continued as much as possible without causing the DC generator to move on its own when the system abnormality occurs. it can.
In addition, even when the grid is normalizing and the reverse converter becomes abnormal during independent operation, it is possible to switch the power supply to the load device from the reverse converter output to the grid without interruption, The continuity of driving can be improved.
Furthermore, according to the present invention, when the system load operation is greater than the total output capacity of the DC generator and part of the power is received from the system, a system abnormality occurs and the power supply shifts independently. If the inverter operates continuously, the reverse converter output overcurrent level is reached, so the reverse converter stops in an emergency and all the loads go down at the same time.In the present invention, however, power is supplied to the load group with low priority. By disconnecting the high-speed cutoff switch installed in the circuit in order, it is possible to continue supplying power to the maximum load device with respect to the power generation equipment capacity without interruption.
Furthermore , according to the present invention, not only the system power but also the DC power of the fuel cell is used in combination with the high-speed cutoff switch operating power source, so that the operational reliability of the high-speed cutoff switch alone can be improved, and as an uninterruptible independent transition system It becomes possible to improve the reliability.
[Brief description of the drawings]
FIG. 1 is a flowchart of a fuel cell power plant according to Embodiment 1 of the present invention.
FIG. 2 is a diagram illustrating a system abnormality detection method according to the first embodiment.
FIG. 3 is a diagram showing a system abnormality detection method according to a second embodiment of the present invention.
FIG. 4 is a flowchart of a fuel cell power plant according to Embodiment 3 of the present invention.
FIG. 5 is a system abnormality monitoring mode control block diagram of a third embodiment.
FIG. 6 is a flowchart of a fuel cell power plant according to Embodiment 4 of the present invention.
7 is an overload prevention control time chart according to Embodiment 4. FIG.
FIG. 8 is a flowchart of a fuel cell power plant according to Embodiment 5 of the present invention.
FIG. 9 is a flowchart showing a conventional fuel cell power plant.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gas supply equipment, 2 Fuel cell main body, 3 Reverse conversion apparatus, 4 Load apparatus, 5 High speed cutoff switch, 6 Reverse conversion apparatus control circuit, 6a System abnormality detection circuit, 6b Power generation output power control circuit, 6c Reverse conversion apparatus abnormality detection Circuit, 6d overload suppression control circuit, 6e transient voltage rise suppression circuit, 6f DC generator abnormality detection circuit, 6z system instantaneous power failure detector, 8 DC power supply for high speed cutoff switch operation, 9 gas supply amount control circuit, 10 system, DESCRIPTION OF SYMBOLS 11 Protection circuit breaker, 12 Power transmission voltage detector, 13 Power generation voltage detector, 14 Switch, 15 Power generation current detector, 16 High-speed switch for load, 17 Bypass circuit, 18 switch, 19 Switch, 21 DC generator, 31 supply production adjustment equipment, 38 changeover switch, 40 control device, 41 setting function, 42 adjustment control system, 43 signal changeover switch, 44 current setting device.

Claims

A gas supply facility for the DC generator;
A fuel cell main body for generating DC power by the supply gas;
An inverse converter for converting the DC power into AC power;
AC power generation current measuring means for measuring the AC power generation current,
Supply gas flow rate control means for adjusting a supply gas flow rate corresponding to the alternating current;
A load device that consumes the AC output power;
A transmission point that transmits the surplus of the AC output power excluding the load device power consumption to the AC system, and
High-speed shut-off means capable of uninterrupted disconnection between the power transmission point and the system;
Means for using the AC output power as an operation power source of the high-speed shut-off means;
System abnormality instantaneous detection means for instantaneously detecting system abnormality,
Power generation control mode switching means for receiving a detection signal of the system abnormality instantaneous detection means and issuing a disconnection command to the high-speed shut-off means to switch the operation mode of the reverse conversion device from constant power control to constant voltage control;
Equipped with a,
The non-instantaneous uninterrupted transition system characterized in that the system abnormality instantaneous detection means ignores a system voltage level near zero voltage when detecting system abnormality of system overvoltage and system undervoltage .

In the uninterruptible self-sustaining transition system according to claim 1 ,
An inverse converter abnormality detecting means for detecting an abnormality of the inverse converter;
Control means for switching the power supply source to the load device to the system side by a detection signal from the reverse conversion device abnormality detection means;
Further comprising
The power generation control mode switching means is capable of suppressing disconnection operation from the power transmission point and the system to a minimum necessary level.

In the uninterruptible self-sustaining transition system according to claim 1 ,
It further comprises overload suppression control means for preventing a generator overload state after the power generation control mode switching,
The non-instantaneous uninterruptible transition system characterized in that the high-speed shut-off means is capable of uninterrupted disconnection of each of the divided load devices and systems configured by dividing the load device into a plurality of units.

In the uninterruptible self-sustaining transition system according to claim 1 ,
An uninterruptible self-sustained transition system further comprising means for using the DC output power and the AC system as an operation power source for the high-speed shut-off means.