JP3697285B2

JP3697285B2 - Water supply pump controller

Info

Publication number: JP3697285B2
Application number: JP03771795A
Authority: JP
Inventors: 信之高橋; 岳司宇久
Original assignee: Toshiba Corp; Toshiba System Technology Corp
Current assignee: Toshiba Corp; Toshiba System Technology Corp
Priority date: 1995-02-03
Filing date: 1995-02-03
Publication date: 2005-09-21
Anticipated expiration: 2020-09-21
Also published as: JPH08210605A

Description

【０００１】
【産業上の利用分野】
本発明は、発電プラントの給水ポンプ流量制御装置に関する。
【０００２】
【従来の技術】
発電プラントにおける給水ポンプは、発電量の増加に伴ってボイラの要求する給水流量をボイラへ供給するために、給水ポンプの回転数を増加させる構成となっている。一方、給水ポンプは、ポンプの加熱を防止するために最小吸込流量以上の吸込流量を流すことが必要である。この最小吸込流量は、給水ポンプの回転数に応じて変わる値である。
【０００３】
仮に、給水ポンプの吸込流量が最小吸込流量以下になった場合は、警報を出力したり、給水ポンプを強制停止させなければならない。そこで、ボイラへの給水流量が減少し、吸込流量が減少した場合には、再循環弁の開度を調節して脱気器へ戻す再循環流量を増加することにより、給水ポンプの吸込流量を最小吸込流量以上としている。
【０００４】
図６は、この種の給水ポンプの系統図である。
【０００５】
図において、給水ポンプ１は、図示省略する脱気器からボイラへの給水配管２に配置されており、給水ポンプ１の出口側には、脱気器へ再循環する再循環配管３が分岐している。再循環配管３には、再循環弁４が配置されている。また、給水配管２には、給水流量検出器５が設けられ、さらに、吸込流量検出器６が設けられている。給水ポンプ１は、蒸気タービン７と回転軸によって連結しており、蒸気タービン７には、蒸気加減弁９から蒸気が供給され、蒸気タービン７には、回転数検出器８が設置されている。
【０００６】
給水ポンプ制御装置２０は、給水配管２に設置されている給水流量検出器５により得られる給水流量信号ＱＦを入力し、図示しないボイラ制御装置から入力する給水流量指令信号ＱＣに基づき回転数指令信号を算出する。給水ポンプ１の回転数検出器８から回転数検出信号Ｎを入力し、回転数指令信号とに基づき蒸気加減弁開度指令信号Ｚを算出し蒸気加減弁９へ出力する。
【０００７】
また、給水ポンプ制御装置２０は、給水配管２に設置される吸込流量検出器６から吸込流量検出信号ＱＲを入力し、給水ポンプ１に設置された回転数検出器８により得られる回転数検出信号Ｎとに基づき再循環弁開度指令信号Ｖを算出して再循環弁４へ出力する。
【０００８】
このようにして、ボイラへの給水流量が減少し、給水流量が減少した場合には、再循環弁４の開度を調節して脱気器へ戻す再循環流量を増加することにより、給水ポンプの吸込流量を最小吸込流量以上としている。
【０００９】
給水ポンプ制御装置２０は、図７に示す如く、給水流量制御部２１と再循環弁開度制御部２２とからなり、給水流量検出器５により得られる給水流量信号ＱＦと給水流量指令信号ＱＣとを偏差演算手段２３へ入力し、得られる演算出力を比例積分演算手段２４へ入力し、回転数指令信号ＮＳを出力する。
【００１０】
また、回転数検出器８により得られる回転数検出信号Ｎが偏差演算手段２５に入力され、その出力が比例演算手段２６に入力される。蒸気加減弁開度指令信号Ｚを蒸気加減弁９へ出力する。
【００１１】
一方、給水ポンプ制御装置２０の再循環弁開度制御部２２は、図７に示す如く、吸込流量設定関数発生手段２７と偏差演算手段２８と比例演算手段２９と変化率制限手段３０とから構成されている。
【００１２】
吸込流量設定関数発生手段２７は、回転数検出信号Ｎに応じて予め設定された関数によって吸込流量設定信号ＱＴを出力する。この吸込流量設定信号ＱＴと吸込流量検出信号ＱＲは、偏差演算手段２８により偏差が演算され、比例演算手段２９に入力される。比例演算手段２９では、偏差に応じて比例演算され、変化率制限手段３０に入力される。この変化率制限手段３０は、再循環弁４を閉方向とする入力信号のとき入力信号に制限した出力信号とする一方、入力信号が開方向のとき制限をかけない出力信号とする。
【００１３】
ここで、図７の示す吸込流量設定関数発生手段２７に設定される吸込流量設定信号ＱＴと回転数検出信号Ｎとの関係について図８を参照して説明する。
【００１４】
まず、吸込流量設定信号ＱＴは、予め回転数検出信号Ｎに応じて設定され、回転数検出信号ＮがＮ１〜Ｎ２の範囲において回転数検出信号Ｎに応じて増加するようになっている。また、回転数検出信号ＮがＮ２以上のとき一定値を保持し、回転数検出信号ＮがＮ１以下でも一定値を保持するようになっている。この図８における最小吸込流量設定信号ＱＳ（図示鎖線）は、再循環弁４を全開とする吸込流量設定値を示し、また、吸込流量設定信号ＱＴは、最小吸込流量設定信号ＱＳよりαだけ上側に設定されている。
【００１５】
次に、図７に示す比例演算手段２９では、吸込流量検出信号ＱＲの変化αに対して、再循環弁開度指令信号Ｖを全閉−全開に変化させるようにしている。すなわち、吸込流量検出信号ＱＲが最小吸込流量設定信号ＱＳと一致するとき、比例演算手段２９の出力が１００％｛＝Ｋ×（ＱＴ−ＱＳ）｝により再循環弁開度指令信号Ｖを全開とする。また、吸込流量検出信号ＱＲが吸込流量設定信号ＱＴと一致したとき、比例演算手段２９の出力が、０％｛＝Ｋ×（ＱＴ−ＱＴ）｝により再循環弁開度指令信号Ｖを全閉とする。
【００１６】
ここで、発電プラントの高負荷時および低負荷時の吸込流量検出信号ＱＲ（二点鎖線）とボイラへの給水流量信号ＱＦ（一点鎖線）とを図８を参照して説明すると、発電プラントが高負荷にあるとき、給水ポンプ１の回転数検出信号ＮはＮ２にある。このとき、吸込流量検出信号ＱＲは吸込流量設定信号ＱＴより大きく、再循環弁開度指令信号Ｖは全閉となり、吸込流量検出信号ＱＲと給水流量信号ＱＦとは一致する。
【００１７】
この状態から、発電プラントの負荷を徐々に下げると、給水流量信号ＱＦが減少し、回転数検出信号Ｎも降下すると共に、吸込流量検出信号ＱＲも減少する。
【００１８】
発電プラントが低負荷にあるとき、図８に示すように給水流量信号ＱＦが吸込流量設定信号ＱＴより下回る。このような場合、吸込流量検出信号ＱＲが最小吸込流量設定信号ＱＳより下回らないようにする必要がある。そこで、回転数検出信号ＮがＮ１になると、給水ポンプ１が供給する給水が全て再循環弁４へ流すようにして吸込流量検出信号ＱＲを確保する。
【００１９】
変化率制限手段３０は、再循環弁４の開方向の信号に対して再循環弁４を変化速度に制限なく開き、給水ポンプ１の加熱を防止する。また、変化率制限手段３０は閉方向の動作に対して再循環弁４を低速で閉じて、ボイラの給水流量制御への外乱を小さくする。
【００２０】
【発明が解決しようとする課題】
しかしながら、上記した図７に示した従来の給水ポンプ制御装置２０では、次のような問題がある。
【００２１】
まず、一例として、図９を参照して発電プラントの低負荷時にボイラへ供給する給水量を徐々に減少させていく場合の問題点を説明する。ここで、図中の上段は、吸込流量検出信号ＱＲとボイラへの給水流量信号ＱＦと吸込流量設定信号ＱＴの関係を示し、図中の下段は再循環弁開度指令信号Ｖの変化を示している。
【００２２】
図において、発電プラントの発電量が時刻ｔ１から低下すると、給水ポンプ制御装置２０は、給水流量指令信号ＱＣの減少に伴って、図７の給水流量制御部２１からの蒸気加減弁開度指令信号Ｚが減少され、給水ポンプ１の回転数の減少によりボイラへの給水流量信号ＱＦが徐々に減少される。このとき、吸込流量設定信号ＱＴと吸込流量検出信号ＱＲとの偏差はα以上ある。従って、給水ポンプ制御装置２０は、再循環弁開度指令信号Ｖを全閉とする出力をする。このため再循環弁４へ給水が流れず、吸込流量検出信号ＱＲは給水流量信号ＱＦと同じ値となって徐々に減少する。
【００２３】
その後、時刻ｔ２になると、給水流量信号ＱＦが急減され、さらに、時刻ｔ３に吸込流量検出信号ＱＲが吸込流量設定信号ＱＴ以下になる。この状態では、図７に示す給水ポンプ制御装置２０の再循環弁開度制御部２２が再循環弁開度指令信号Ｖを全閉から急開させる。これによって、再循環弁４に流れる流量が増加し、吸込流量検出信号ＱＲが増加するが、ボイラへの給水流量信号ＱＦがさらに急減する。
【００２４】
すなわち、給水ポンプ１の加熱防止のために再循環弁開度指令信号Ｖが高速に増加させ、しかも、ボイラ系統より再循環系統の方が給水流量の吸込力が大きいために再循環系統へ流量が増加し、これに対応してボイラへの給水流量信号ＱＦは、時刻ｔ３から時刻ｔ４にわたって必要以上に急減する。
【００２５】
一方、図７に示す給水ポンプ制御装置２０の給水流量制御部２１では、給水ポンプ１の給水流量信号ＱＦの急減に伴って、必要流量が送れるように制御する。
これにより、給水流量信号ＱＦは、時刻ｔ４から時刻ｔ５に増加する。その後、吸込流量検出信号ＱＲは、吸込流量設定信号ＱＴより大きく増加した後に降下して、時刻ｔ６に吸込流量検出信号ＱＲが吸込流量設定信号ＱＴとほぼ一致し、吸込流量検出信号ＱＲは吸込流量設定信号ＱＴより減少する。
【００２６】
このため、時刻ｔ７になると、再循環弁開度指令信号Ｖが増加方向となる。これに伴って、再び吸込流量検出信号ＱＲが増加するが、時刻ｔ３から時刻ｔ４と同様に給水流量信号ＱＦが再び急減する。これにより、前述したように給水ポンプ制御装置２０の給水流量制御部２１によって時刻ｔ８に再び給水流量信号ＱＦが増加して復帰する。このような給水流量信号ＱＦの急減と復帰との変動の繰り返しがされ、給水流量の制御が不安定となり、ボイラへ外乱を与えるという問題がある。
【００２７】
そこで、本発明は給水流量を安定に制御してボイラへ外乱を与えることを回避する給水ポンプ制御装置を提供することを目的とする。
【００２８】
【課題を解決するための手段】
請求項１の発明は、蒸気タービンの回転を駆動源とする給水ポンプにより脱気器からボイラへ給水を供給する給水系統と、給水を再循環弁を介して脱気器へ再循環させる再循環系統とを有し、給水系統の給水流量検出信号が給水流量指令信号となるように蒸気加減弁開度指令信号により蒸気タービンへ供給する蒸気を制御すると共に、再循環弁を再循環弁開度指令信号により開閉して循環系統の再循環流量を制御する給水ポンプ制御装置において、給水ポンプの回転数検出信号に応じて予め設定された関数に基づいて吸込流量設定信号を出力する関数発生手段と、吸込流量設定信号と給水ポンプの吸込流量検出信号との偏差に応じて制御演算をして得られる第１の再循環弁開度指令信号を出力する制御手段と、発電プラントの発電量信号に応じて予め設定した関数に基づいて第２の再循環弁開度指令信号を出力する手段と、第１の再循環弁開度指令信号と第２の再循環弁開度指令信号とを入力して、いずれかの高値信号を再循環弁開度指令信号として再循環弁へ出力する高値選択手段とを具備する再循環弁開度制御部を設けるようにしたものである。
【００２９】
請求項２の発明は、蒸気タービンの回転を駆動源とする給水ポンプにより脱気器からボイラへ給水を供給する給水系統と、給水を再循環弁を介して脱気器へ再循環させる再循環系統とを有し、給水系統の給水流量検出信号が給水流量指令信号となるように蒸気加減弁開度指令信号により蒸気タービンへ供給する蒸気を制御をすると共に、再循環弁を再循環弁開度指令信号により開閉して循環系統の再循環流量を制御する給水ポンプ制御装置において、給水ポンプの回転数によって予め定められる吸込流量設定信号と給水流量指令信号とを比較して両信号の偏差が所定値以下のとき検出信号を出力する検出手段と、給水流量指令信号を入力してそのまま変化率制限信号として出力する一方、検出信号が入力したときのみ給水流量指令信号の減少を制限する変化率制限信号を出力する変化率制限手段と、給水流量検出信号と変化率制限信号との偏差信号を制御演算して得られる制御信号を蒸気加減弁開度指令信号とする制御手段とを具備する給水流量制御部を設けるようにしたものである。
【００３０】
【作用】
請求項１の給水ポンプ制御装置によれば、給水ポンプの回転数検出信号により設定される吸込流量設定信号と吸込流量検出信号との偏差に応じて制御演算された第１の再循環弁開度指令信号と低負荷のとき第１の再循環弁開度指令信号より高値となるように発電量検出信号に応じて設定される第２の再循環弁開度指令信号とが高値選択手段へ入力される。そして、低負荷でないとき、第１の再循環弁開度指令信号が選択され再循環弁を開閉し、低負荷のとき第２の再循環弁開度指令信号が選択され再循環弁を開閉させる。さらに、低負荷のとき、発電量信号に応じた急変のない穏やかに徐々に変化する第２の再循環弁開度指令信号によって最小吸込流量を確保するように再循環弁の開度を変化させる。これにより、従来のように低負荷のとき必要以上に再循環弁を急開や急閉させて、給水流量の急減と復帰の繰り返しを回避し、安定した給水流量制御をすることができ、ボイラへの外乱を与えることを防止できる。
【００３１】
請求項２の給水ポンプ制御装置によれば、給水流量指令信号と吸込流量設定信号との偏差が所定値以下となると、検出手段により検出信号が変化率制限手段へ出力される。変化率制限手段では、検出信号が入力されているときのみ給水流量指令信号の減少が所定値に抑制される。これにより、給水流量指令信号の急減がなくなるから、給水流量が急減なく穏やかに推移する。従って、再循環弁が必要に応じて穏やかにゆっくり開き、従来のように、給水流量の急減と復帰の繰り返しがなく、安定した給水流量制御ができ、ボイラへ外乱を与えることを回避することができる。
【００３２】
【実施例】
以下、本発明の実施例について図面を参照して説明する。
【００３３】
図１は、本発明の第１実施例を示す給水ポンプ制御装置の構成図である。図中、図１が従来例を示す図７と同一符号は同一部分または相当部分を示し、図１が図７と異なる主な点は、再循環弁開度制御部２２の構成を異にし、再循環弁開度制御部２２Ａとし、再循環弁開度制御部２２Ａは、図７の再循環弁開度制御部２２に再循環弁開度指令関数発生手段３１と高値選択手段３２とを追設して、低負荷時の給水流量制御を安定させるようにしたことである。
【００３４】
ここで、再循環弁開度制御部２２Ａに設ける再循環弁開度指令関数発生手段３１は、図２の上段に示されるような関数が設定されており、発電プラントの低負荷時、再循環弁４を所定開度に開けさせる値を設定している。高値選択手段３２は、変化率制限手段３０の出力信号と再循環弁開度指令関数発生手段３１の出力信号を入力し、いずれか高値の入力を選択して再循環弁開度指令信号Ｖを出力するようにしている。
【００３５】
次に、本発明の第１実施例の作用を図３を参照して説明する。
【００３６】
この一例は、発電プラントの低負荷時においてボイラへ供給する給水流量を徐々に減少させていく場合の作用を説明し、図３において、下段の再循環弁開度指令信号Ｖの内で、ＶＡは図１に示す変化率制限手段３０の出力であり、ＶＢは図１に示す再循環弁開度指令関数発生手段３１の出力とする。
【００３７】
ここで、発電プラントが通常の運転をしている時刻ｔ１まで、図２の上段に示す発電量信号Ｌ１に対する関数設定から再循環弁開度指令関数発生手段３１の出力ＶＢはほぼ零である。これに対して、変化率制限手段３０の出力ＶＡもほぼ零であり、高値選択手段３２の出力が全閉の信号を出力している。
【００３８】
すなわち、図２の上段は、再循環弁開度指令関数発生手段３１に設定される関数の一実施例を示す特性図であり、図２の下段は、従来技術による発電量信号Ｌと給水流量信号ＱＦ，吸込流量検出信号ＱＲの関係を示す一例である。このように発電量信号Ｌと給水流量信号ＱＦとは比例関係にあり（発電量信号Ｌ１以上のとき）、給水流量信号ＱＦが減少すると、吸込流量検出信号ＱＲが給水ポンプ１の最小吸込流量設定信号以下にならないように再循環弁４が開かれるようになっている。そこで、再循環弁開度指令関数発生手段３１の設定関数は、再循環弁４が開き始める発電量信号Ｌ１から、発電量信号Ｌの減少に伴って、再循環弁４を開いて吸込流量検出信号ＱＲが確保されるように関数を設定する。
【００３９】
次に、図３において時刻ｔ１に、発電プラントが低負荷への移行を始めると、給水流量指令信号ＱＣが減少し、給水流量信号ＱＦが減少され、これに応じて吸込流量検出信号ＱＲが徐々に減少される。このとき、再循環弁開度指令関数発生手段３１の出力ＶＢは、発電量信号Ｌの減少により全閉から開方向に徐々に増加する。これにより、高値選択手段３２が再循環弁開度指令関数発生手段３１の出力信号ＶＢを選択して再循環弁開度指令信号Ｖとする。このとき、発電量信号Ｌの減少速度が遅く徐々に減少し、再循環弁開度指令信号Ｖの増加速度も遅く、給水流量信号ＱＦの外乱にならないように推移する。
【００４０】
ここで、時刻ｔ２に給水流量信号ＱＦが急減されるが、再循環弁４が開いている。従って、吸込流量検出信号ＱＲが吸込流量設定信号ＱＴ以下になることはなく、高値選択手段３２では、そのまま出力ＶＢが選択され、再循環弁開度指令信号Ｖが急増することなく推移する。このように、発電量信号Ｌの減少に対して再循環弁開度指令信号Ｖの増加を適宜定めると、給水流量信号ＱＦの急減があっても、吸込流量検出信号ＱＲが吸込流量設定信号ＱＴ以下となることがなく、再循環弁４の急閉に伴う給水流量信号ＱＦの急増が生じることが防止される。
【００４１】
また、吸込流量検出信号ＱＲが吸込流量設定信号ＱＴから大きく離れることがなく、再循環弁開度指令信号ＶＡが急上昇することがないから、再循環弁４が急開することによる給水流量の急減する状態が生じることが防止される。
【００４２】
その後、図３のように、低負荷となり、時刻ｔ３に、給水流量信号ＱＦが急減され、吸込流量検出信号ＱＲが吸込流量設定信号ＱＴ以下となった場合について説明する。
【００４３】
この場合、変化率制限手段３０の出力ＶＡが急増指令を出力し、時刻ｔ４に変化率制限手段３０の出力ＶＡが再循環弁開度指令関数発生手段３１の出力ＶＢより大きくなり、高値選択手段３２が変化率制限手段３０の出力ＶＡを選択して再循環弁開度指令信号Ｖを出力する。これによって、吸込流量検出信号ＱＲが上昇し、ピークに達した後に徐々に降下する。吸込流量検出信号ＱＲが降下すると、これに応じて変化率制限手段３０の出力ＶＡも減少して時刻ｔ５に、再循環弁開度指令関数発生手段３１の出力ＶＢの方が高値となる。このため、高値選択手段３２では、再循環弁開度指令関数発生手段３１の出力ＶＢが選択され再循環弁開度指令信号Ｖとして再循環弁４へ出力する。
【００４４】
この結果、給水流量制御部２１の制御により給水流量信号ＱＦが急減され、図３の時刻ｔ３以降のように吸込流量検出信号ＱＲが吸込流量設定信号ＱＴ以下に割り込んだ場合でも、吸込流量検出信号ＱＲの減少に相当する再循環弁開度指令信号ＶＡが急増し、高値選択手段３２で再循環弁開度指令信号ＶＡが選択されて再循環弁開度指令信号Ｖとして、吸込流量検出信号ＱＲが最小吸込流量設定信号ＱＳ以下となることを防止する。
【００４５】
このように、給水ポンプの吸込流量急減による過熱防止を図ると共に、発電プラントの低負荷時に再循環弁が急開や急閉することによるボイラへ供給する給水流量の急減や急増の繰り返しを防止し、給水流量を安定して制御することができ、ボイラへ外乱を与えることを防止することができる。
【００４６】
なお、第１実施例では、再循環弁開度指令関数発生手段３１による再循環弁開度指令信号ＶＢを発生させる信号に発電量信号Ｌを用いたが、発電プラントの運転において再循環弁４の開度と相関関係がある信号として、発電量指令信号またはボイラの出力要求指令信号を用いてもよい。
【００４７】
図４は、本発明の第２実施例を示す給水ポンプ制御装置の構成図である。
【００４８】
図４が従来例を示す図７と同一符号は、同一部分または相当部分を示し、図４が図７と異なる主な点は、給水流量制御部２１の構成を異にし、給水流量制御部２１Ｂとし、給水流量制御部２１Ｂは、検出手段３３と変化率制限手段３４とを追設し、再循環弁４の急開を防止して給水流量を安定に制御するようにしている。
【００４９】
ここで、検出手段３３は、給水流量指令信号ＱＣと吸込流量設定信号ＱＴとを比較して、その偏差が所定値以下のとき検出信号を出力する。変化率制限手段３４は、検出信号の入力があるときのみ、給水流量指令信号ＱＣの減少方向の信号を所定の変化率で制限して出力する。
【００５０】
次に、発電プラントの低負荷時にボイラへ供給する給水流量を徐々に減少させる場合の作用を図５を参照して説明する。なお、図５に示す、ＱＤは変化率制限手段３４の出力とする。
【００５１】
ここで、給水流量指令信号ＱＣが吸込流量設定信号ＱＴより大きい時刻ｔ１までは、検出手段３３から検出信号が変化率制限手段３４へ出力されていない。このため変化率制限手段３４によって給水流量指令信号ＱＣの変化率を制限する動作が行われない。従って、給水流量指令信号ＱＣと変化率制限手段３４の出力ＱＤは常にほぼ同じ値となっている。
【００５２】
その後の時刻ｔ１以降に、検出手段３３が給水流量指令信号ＱＣが吸込流量設定信号ＱＴに近づいたことを検出すると、検出信号が変化率制限手段３４へ入力される。これに伴い、変化率制限手段３４の出力ＱＤの減少方向への変化に制限をかける動作を始める。これに応じて、給水流量信号ＱＦの減少に制限がかかり、吸込流量検出信号ＱＲの急減がなくなり、横ばいとなる。さらに、時刻ｔ２に吸込流量検出信号ＱＲが吸込流量設定信号ＱＴを下回ると、再循環弁４が開き始めるが、給水流量信号ＱＦが穏やかに減少し、吸込流量検出信号ＱＲも穏やかに減少する。従って、変化率制限手段３０からの再循環弁開度指令信号Ｖも時刻ｔ２から徐々に上昇し、再循環弁４の急開が防止される。
【００５３】
このように、給水流量指令信号ＱＣの減少を制限することによって、再循環弁４の急開や急閉を防止しボイラへ供給する給水流量の急減急増を防止し、給水流量を安定に制御することができ、ボイラへ外乱を与えることを防止することができる。
【００５４】
また、給水ポンプ１の吸込流量設定信号ＱＴに基づいて制限を行っているため、発電プラントの任意の負荷帯および給水ポンプの任意の運転点において、再循環弁４の急開を防止できる。
【００５５】
なお、給水流量指令信号ＱＣの増加方向は、給水ポンプ１の過熱にならないので、制限をかけない。
【００５６】
【発明の効果】
以上説明したように請求項１の給水ポンプ制御装置によれば、低負荷のとき発電量信号に応じた急変のない穏やかに徐々に変化する第２の再循環弁開度指令信号によって最小吸込流量を確保するように再循環弁の開度を変化させるようにしたために従来のように低負荷のとき必要以上に再循環弁を急開や急閉させて、給水流量の急減と復帰の繰り返すという状態を回避し、安定した給水流量制御ができ、ボイラ−へ外乱を与えることを防止することができる。
【００５７】
請求項２の給水ポンプ制御装置によれば、給水流量指令信号と吸込流量設定信号との偏差が所定値以下となると、給水流量指令信号の減少を抑制して給水流量が急減なく穏やかに推移する。従って、再循環弁が必要に応じて穏やかにゆっくり開き、従来のように、給水流量の急減と復帰の繰り返しがなく、安定した給水流量制御ができ、ボイラ−へ外乱を与えることを防止することができる。
【図面の簡単な説明】
【図１】本発明の第１実施例を示す給水ポンプ制御装置の構成図である。
【図２】図１の給水ポンプ制御装置に備える再循環弁開度指令関数発生手段の特性を示す説明図である。
【図３】図１の給水ポンプ制御装置の作用を示す説明図である。
【図４】本発明の第２実施例を示す給水ポンプ制御装置の構成図である。
【図５】図４の給水ポンプ制御装置の作用を示す説明図である。
【図６】給水ポンプの系統図である。
【図７】従来例を示す給水ポンプ制御装置の図１または図４に対応する構成図である。
【図８】図７の給水ポンプ制御装置に備える吸込流量設定関数発生手段の特性を示す説明図である。
【図９】図７の給水ポンプ制御装置の作用を示す図３または図５に対応する説明図である。
【符号の説明】
２０給水ポンプ制御装置
２１給水流量制御部
２２再循環弁開度制御部
２３偏差演算手段
２４比例積分演算手段
２５偏差演算手段
２６比例演算手段
２７吸込流量設定関数発生手段
２８偏差演算手段
２９比例演算手段
３０変化率制限手段
３１再循環弁開度指令関数発生手段
３２高値選択手段
３３検出手段
３４変化率制限手段[0001]
[Industrial application fields]
The present invention relates to a feed water pump flow control device for a power plant.
[0002]
[Prior art]
The feed water pump in the power plant is configured to increase the rotation speed of the feed water pump in order to supply the boiler with a feed water flow rate required by the boiler as the amount of power generation increases. On the other hand, in order to prevent the pump from being heated, the feed water pump needs to flow a suction flow rate that is equal to or greater than the minimum suction flow rate. This minimum suction flow rate is a value that varies depending on the rotation speed of the feed water pump.
[0003]
If the suction flow rate of the water supply pump falls below the minimum suction flow rate, an alarm must be output or the water supply pump must be forcibly stopped. Therefore, when the feed water flow rate to the boiler decreases and the suction flow rate decreases, the suction flow rate of the feed water pump is increased by adjusting the opening of the recirculation valve and increasing the recirculation flow rate returned to the deaerator. The minimum suction flow rate is exceeded.
[0004]
FIG. 6 is a system diagram of this type of water supply pump.
[0005]
In the figure, a feed water pump 1 is arranged in a feed water pipe 2 from a deaerator (not shown) to a boiler, and a recirculation pipe 3 for recirculation to the deaerator branches off on the outlet side of the feed water pump 1. ing. A recirculation valve 4 is disposed in the recirculation pipe 3. Further, the water supply pipe 2 is provided with a water supply flow rate detector 5 and further with a suction flow rate detector 6. The feed water pump 1 is connected to a steam turbine 7 by a rotating shaft, steam is supplied from the steam control valve 9 to the steam turbine 7, and a rotation speed detector 8 is installed in the steam turbine 7.
[0006]
The feed water pump control device 20 inputs a feed water flow rate signal QF obtained by a feed water flow rate detector 5 installed in the feed water pipe 2, and a rotation speed command signal based on a feed water flow rate command signal QC input from a boiler control device (not shown). Is calculated. A rotation speed detection signal N is input from the rotation speed detector 8 of the feed water pump 1, and a steam control valve opening command signal Z is calculated based on the rotation speed command signal and output to the steam control valve 9.
[0007]
In addition, the feed water pump control device 20 inputs the suction flow rate detection signal QR from the suction flow rate detector 6 installed in the feed water pipe 2, and the rotation speed detection signal obtained by the rotation speed detector 8 installed in the feed water pump 1. Based on N, a recirculation valve opening command signal V is calculated and output to the recirculation valve 4.
[0008]
In this way, when the feed water flow rate to the boiler decreases and the feed water flow rate decreases, the feed water pump is adjusted by increasing the recirculation flow rate that is returned to the deaerator by adjusting the opening of the recirculation valve 4. The suction flow rate is set to be greater than the minimum suction flow rate.
[0009]
As shown in FIG. 7, the feed water pump control device 20 includes a feed water flow rate control unit 21 and a recirculation valve opening degree control unit 22, and a feed water flow rate signal QF and a feed water flow rate command signal QC obtained by the feed water flow rate detector 5. Is input to the deviation calculating means 23, and the obtained calculation output is input to the proportional-integral calculating means 24, and the rotation speed command signal NS is output.
[0010]
Further, the rotation speed detection signal N obtained by the rotation speed detector 8 is input to the deviation calculation means 25, and the output thereof is input to the proportional calculation means 26. A steam control valve opening command signal Z is output to the steam control valve 9.
[0011]
On the other hand, the recirculation valve opening degree control unit 22 of the feed water pump control device 20 includes a suction flow rate setting function generating means 27, a deviation calculating means 28, a proportional calculating means 29, and a change rate limiting means 30, as shown in FIG. Has been.
[0012]
The suction flow rate setting function generating means 27 outputs a suction flow rate setting signal QT by a function set in advance according to the rotation speed detection signal N. Deviations of the suction flow rate setting signal QT and the suction flow rate detection signal QR are calculated by the deviation calculation unit 28 and input to the proportional calculation unit 29. In the proportional calculation means 29, proportional calculation is performed in accordance with the deviation and the change rate restriction means 30 inputs the proportional calculation. This rate-of-change limiting means 30 is an output signal that is limited to the input signal when the input signal is for the recirculation valve 4 in the closing direction, and an output signal that is not limited when the input signal is in the opening direction.
[0013]
Here, the relationship between the suction flow rate setting signal QT set in the suction flow rate setting function generating means 27 shown in FIG. 7 and the rotation speed detection signal N will be described with reference to FIG.
[0014]
First, the suction flow rate setting signal QT is set in advance according to the rotational speed detection signal N, and the rotational speed detection signal N increases in accordance with the rotational speed detection signal N in the range of N1 to N2. Further, a constant value is held when the rotation speed detection signal N is N2 or more, and a constant value is held even when the rotation speed detection signal N is N1 or less. In FIG. 8, the minimum suction flow rate setting signal QS (shown chain line) indicates a suction flow rate setting value for fully opening the recirculation valve 4, and the suction flow rate setting signal QT is higher by α than the minimum suction flow rate setting signal QS. Is set to
[0015]
Next, in the proportional calculation means 29 shown in FIG. 7, the recirculation valve opening command signal V is changed from fully closed to fully open with respect to the change α of the suction flow rate detection signal QR. That is, when the suction flow rate detection signal QR matches the minimum suction flow rate setting signal QS, the output of the proportional calculation means 29 is 100% {= K × (QT−QS)} and the recirculation valve opening command signal V is fully opened. To do. Further, when the suction flow rate detection signal QR coincides with the suction flow rate setting signal QT, the output of the proportional calculation means 29 is fully closed by 0% {= K × (QT−QT)}. And
[0016]
Here, the suction flow rate detection signal QR (two-dot chain line) and the boiler feed water flow signal QF (one-dot chain line) at the time of high load and low load of the power plant will be described with reference to FIG. When the load is high, the rotation speed detection signal N of the feed water pump 1 is at N2. At this time, the suction flow rate detection signal QR is larger than the suction flow rate setting signal QT, the recirculation valve opening command signal V is fully closed, and the suction flow rate detection signal QR and the feed water flow rate signal QF coincide.
[0017]
When the load of the power plant is gradually reduced from this state, the feed water flow rate signal QF decreases, the rotation speed detection signal N also decreases, and the suction flow rate detection signal QR also decreases.
[0018]
When the power plant is at a low load, the feed water flow rate signal QF is lower than the suction flow rate setting signal QT as shown in FIG. In such a case, it is necessary to prevent the suction flow rate detection signal QR from being lower than the minimum suction flow rate setting signal QS. Therefore, when the rotational speed detection signal N becomes N1, the suction flow rate detection signal QR is secured by allowing all the water supplied by the water supply pump 1 to flow to the recirculation valve 4.
[0019]
The rate-of-change limiting means 30 opens the recirculation valve 4 without limitation to the change speed with respect to the signal in the opening direction of the recirculation valve 4, and prevents the feed water pump 1 from being heated. Further, the change rate limiting means 30 closes the recirculation valve 4 at a low speed with respect to the operation in the closing direction, thereby reducing disturbance to the feed water flow rate control of the boiler.
[0020]
[Problems to be solved by the invention]
However, the conventional feed pump control device 20 shown in FIG. 7 has the following problems.
[0021]
First, as an example, a problem in the case where the amount of water supplied to the boiler is gradually reduced when the power plant is under low load will be described with reference to FIG. Here, the upper part of the figure shows the relationship between the suction flow rate detection signal QR, the feed water flow rate signal QF to the boiler, and the suction flow rate setting signal QT, and the lower part of the figure shows the change of the recirculation valve opening command signal V. ing.
[0022]
In the figure, when the power generation amount of the power plant decreases from time t1, the feed water pump control device 20 causes the steam control valve opening command signal from the feed water flow rate control unit 21 in FIG. 7 as the feed water flow rate command signal QC decreases. Z is decreased, and the feed water flow rate signal QF to the boiler is gradually reduced due to the decrease in the rotation speed of the feed water pump 1. At this time, the deviation between the suction flow rate setting signal QT and the suction flow rate detection signal QR is greater than or equal to α. Therefore, the feed water pump control apparatus 20 outputs the recirculation valve opening command signal V that is fully closed. For this reason, feed water does not flow to the recirculation valve 4, and the suction flow rate detection signal QR becomes the same value as the feed water flow rate signal QF and gradually decreases.
[0023]
Thereafter, at time t2, the feed water flow rate signal QF is suddenly reduced, and further, the suction flow rate detection signal QR becomes equal to or lower than the suction flow rate setting signal QT at time t3. In this state, the recirculation valve opening degree control unit 22 of the feed water pump control device 20 shown in FIG. 7 rapidly opens the recirculation valve opening degree command signal V from the fully closed state. As a result, the flow rate flowing through the recirculation valve 4 increases and the suction flow rate detection signal QR increases, but the feed water flow rate signal QF to the boiler further decreases rapidly.
[0024]
That is, the recirculation valve opening command signal V is increased at a high speed in order to prevent heating of the feed water pump 1, and the recirculation system has a larger suction capacity of the feed water flow rate than the boiler system, so the flow rate to the recirculation system In response to this, the feed water flow rate signal QF to the boiler suddenly decreases more than necessary from time t3 to time t4.
[0025]
On the other hand, the feed water flow rate control unit 21 of the feed water pump control device 20 shown in FIG. 7 performs control so that the necessary flow rate can be sent as the feed water flow rate signal QF of the feed water pump 1 rapidly decreases.
Thereby, the feed water flow signal QF increases from time t4 to time t5. Thereafter, the suction flow rate detection signal QR increases after the suction flow rate setting signal QT is greatly increased and then drops, and at time t6, the suction flow rate detection signal QR substantially coincides with the suction flow rate setting signal QT, and the suction flow rate detection signal QR is the suction flow rate. Decreases from the setting signal QT.
[0026]
For this reason, at time t7, the recirculation valve opening command signal V increases. Along with this, the suction flow rate detection signal QR increases again, but the feed water flow rate signal QF decreases rapidly again from time t3 to time t4. Thereby, as described above, the feed water flow rate signal QF is increased again at time t8 by the feed water flow rate control unit 21 of the feed water pump control device 20 and returned. Such a sudden decrease and return of the feed water flow rate signal QF are repeated, and the control of the feed water flow rate becomes unstable, and there is a problem that disturbance is given to the boiler.
[0027]
Then, an object of this invention is to provide the feed water pump control apparatus which controls a feed water flow stably and avoids giving a disturbance to a boiler.
[0028]
[Means for Solving the Problems]
The invention of claim 1 is a water supply system that supplies water from a deaerator to a boiler by a water supply pump driven by the rotation of a steam turbine, and recirculation that recirculates the water to the deaerator through a recirculation valve. and a system, water system of the water supply flow rate detection signal is feed water flow rate command signal to become as by steam control valve opening command signal Gyosu control the steam supplied to the steam turbine Rutotomoni, the recirculation valve recirculation valve Function generation that outputs a suction flow rate setting signal based on a function preset according to the rotation speed detection signal of the feed water pump in the feed water pump control device that controls the recirculation flow rate of the circulation system by opening and closing by the opening command signal Means, a control means for outputting a first recirculation valve opening command signal obtained by performing a control calculation in accordance with a deviation between the suction flow rate setting signal and the suction flow rate detection signal of the feed water pump, and the power generation amount of the power plant Depending on the signal And inputting a second recirculation valve opening command signal, a first recirculation valve opening command signal, and a second recirculation valve opening command signal based on a preset function. A recirculation valve opening degree control unit comprising high value selection means for outputting any high value signal as a recirculation valve opening degree command signal to the recirculation valve is provided.
[0029]
The invention of claim 2 is a water supply system for supplying water from the deaerator to the boiler by a water supply pump driven by the rotation of the steam turbine, and recirculation for recirculating the water supply to the deaerator through a recirculation valve. The steam supplied to the steam turbine is controlled by the steam control valve opening command signal so that the feed water flow detection signal of the feed water system becomes the feed water flow command signal, and the recirculation valve is opened. In the feed water pump control device that controls the recirculation flow rate of the circulation system by opening and closing with the degree command signal, the suction flow setting signal predetermined by the rotation speed of the feed water pump is compared with the feed water flow command signal, and the deviation between both signals is Detection means that outputs a detection signal when the value is below a predetermined value, and a feed water flow command signal is input and output as it is as a change rate limiting signal, while the feed water flow command signal is decreased only when the detection signal is input And change rate limiting means for outputting the change rate limit signal limiting to, and control means for the control signal obtained deviation signal between the feed water flow detection signal and the change rate limiting signal control operation to the steam control valve opening command signal A water supply flow rate control unit is provided.
[0030]
[Action]
According to the water supply pump control device of the first aspect, the first recirculation valve opening degree that is calculated by control according to the deviation between the suction flow rate setting signal and the suction flow rate detection signal set by the rotation speed detection signal of the feed water pump. The command signal and a second recirculation valve opening command signal set in accordance with the power generation amount detection signal so as to be higher than the first recirculation valve opening command signal at low load are input to the high value selection means. Is done. When the load is not low, the first recirculation valve opening command signal is selected to open and close the recirculation valve. When the load is low, the second recirculation valve opening command signal is selected to open and close the recirculation valve. . Further, when the load is low, the opening degree of the recirculation valve is changed so as to ensure the minimum suction flow rate by the second recirculation valve opening degree command signal that changes gradually and gradually without the sudden change according to the power generation amount signal. . As a result, the recirculation valve is suddenly opened and closed more than necessary when the load is low as in the conventional case, and it is possible to avoid the sudden decrease and return of the feed water flow, and to control the feed water flow stably. Can be prevented from being disturbed.
[0031]
According to the feed water pump control device of the second aspect, when the deviation between the feed water flow rate command signal and the suction flow rate setting signal becomes a predetermined value or less, the detection means outputs the detection signal to the change rate limiting means. In the change rate limiting means, the decrease in the feed water flow rate command signal is suppressed to a predetermined value only when the detection signal is input. As a result, the sudden decrease in the feed water flow rate command signal is eliminated, and the feed water flow rate changes gently without sudden decrease. Therefore, the recirculation valve opens gently and slowly as necessary, and there is no repeated reduction and return of the feed water flow rate as in the conventional case, stable feed water flow rate control can be performed, and disturbance to the boiler can be avoided. it can.
[0032]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
[0033]
FIG. 1 is a configuration diagram of a feed water pump control device showing a first embodiment of the present invention. In FIG. 1, the same reference numerals as those in FIG. 1 showing the conventional example in FIG. 1 denote the same or corresponding parts, and the main point that FIG. 1 differs from FIG. The recirculation valve opening degree control unit 22A is added, and the recirculation valve opening degree control unit 22A adds the recirculation valve opening degree command function generation means 31 and the high value selection means 32 to the recirculation valve opening degree control part 22 in FIG. This is to stabilize the feed water flow control at low load.
[0034]
Here, the recirculation valve opening command function generating means 31 provided in the recirculation valve opening control unit 22A is set with a function as shown in the upper part of FIG. A value for opening the valve 4 to a predetermined opening is set. The high value selection means 32 receives the output signal of the change rate limiting means 30 and the output signal of the recirculation valve opening command function generation means 31, selects either high value input, and outputs the recirculation valve opening command signal V. I am trying to output.
[0035]
Next, the operation of the first embodiment of the present invention will be described with reference to FIG.
[0036]
This example explains the operation in the case where the feed water flow rate supplied to the boiler is gradually reduced at the time of low load of the power plant. In FIG. Is the output of the change rate limiting means 30 shown in FIG. 1, and VB is the output of the recirculation valve opening command function generating means 31 shown in FIG.
[0037]
Here, until the time t1 when the power plant is operating normally, the output VB of the recirculation valve opening command function generating means 31 is almost zero from the function setting for the power generation amount signal L1 shown in the upper part of FIG. On the other hand, the output VA of the change rate limiting means 30 is also almost zero, and the output of the high value selecting means 32 outputs a fully closed signal.
[0038]
That is, the upper part of FIG. 2 is a characteristic diagram showing an example of the function set in the recirculation valve opening command function generating means 31, and the lower part of FIG. 2 is the power generation amount signal L and the feed water flow rate according to the prior art. It is an example which shows the relationship between the signal QF and the suction flow rate detection signal QR. Thus, the power generation amount signal L and the feed water flow rate signal QF are in a proportional relationship (when the power generation amount signal L1 or more), and when the feed water flow rate signal QF decreases, the suction flow rate detection signal QR is set to the minimum suction flow rate of the feed water pump 1. The recirculation valve 4 is opened so that it does not fall below the signal. Therefore, the setting function of the recirculation valve opening command function generation means 31 is that the recirculation valve 4 is opened and the suction flow rate detection is performed as the power generation amount signal L decreases from the power generation amount signal L1 at which the recirculation valve 4 starts to open. A function is set so that the signal QR is secured.
[0039]
Next, when the power plant starts shifting to a low load at time t1 in FIG. 3, the feed water flow rate command signal QC decreases, the feed water flow rate signal QF decreases, and the suction flow rate detection signal QR gradually increases accordingly. Reduced to At this time, the output VB of the recirculation valve opening command function generating means 31 gradually increases in the opening direction from the fully closed state due to the decrease in the power generation amount signal L. As a result, the high value selection means 32 selects the output signal VB of the recirculation valve opening command function generation means 31 to obtain the recirculation valve opening command signal V. At this time, the decrease rate of the power generation amount signal L gradually decreases and gradually decreases, and the increase rate of the recirculation valve opening command signal V also decreases, so that it does not become a disturbance of the feed water flow rate signal QF.
[0040]
Here, the feed water flow rate signal QF is suddenly reduced at time t2, but the recirculation valve 4 is open. Accordingly, the suction flow rate detection signal QR does not become equal to or lower than the suction flow rate setting signal QT, and the high value selection means 32 selects the output VB as it is and changes without the recirculation valve opening command signal V increasing rapidly. Thus, if the increase of the recirculation valve opening command signal V is appropriately determined with respect to the decrease of the power generation amount signal L, the suction flow rate detection signal QR is changed to the suction flow rate setting signal QT even if there is a sudden decrease in the feed water flow rate signal QF. Thus, the sudden increase in the feed water flow rate signal QF accompanying the sudden closing of the recirculation valve 4 is prevented.
[0041]
Further, since the suction flow rate detection signal QR does not greatly deviate from the suction flow rate setting signal QT, and the recirculation valve opening command signal VA does not rise rapidly, a sudden decrease in the feed water flow rate due to the sudden opening of the recirculation valve 4 It is prevented that the state which carries out is produced.
[0042]
After that, as shown in FIG. 3, the case where the load becomes low, the water supply flow rate signal QF is rapidly reduced at time t3, and the suction flow rate detection signal QR becomes equal to or lower than the suction flow rate setting signal QT will be described.
[0043]
In this case, the output VA of the change rate limiting means 30 outputs a rapid increase command, and the output VA of the change rate limiting means 30 becomes larger than the output VB of the recirculation valve opening command function generating means 31 at time t4, and the high value selection means 32 selects the output VA of the change rate limiting means 30 and outputs the recirculation valve opening command signal V. As a result, the suction flow rate detection signal QR rises and gradually falls after reaching the peak. When the suction flow rate detection signal QR falls, the output VA of the change rate limiting means 30 correspondingly decreases accordingly, and the output VB of the recirculation valve opening command function generating means 31 becomes higher at time t5. Therefore, the high value selection means 32 selects the output VB of the recirculation valve opening command function generation means 31 and outputs it to the recirculation valve 4 as the recirculation valve opening command signal V.
[0044]
As a result, the feed water flow rate signal QF is suddenly decreased by the control of the feed water flow rate control unit 21, and even when the suction flow rate detection signal QR is interrupted below the suction flow rate setting signal QT as at time t3 in FIG. The recirculation valve opening command signal VA corresponding to a decrease in QR increases rapidly, the recirculation valve opening command signal VA is selected by the high value selection means 32, and the suction flow rate detection signal QR is used as the recirculation valve opening command signal V. Is less than the minimum suction flow rate setting signal QS.
[0045]
In this way, while preventing overheating due to a sudden decrease in the suction flow rate of the feed water pump, it prevents the sudden decrease or rapid increase in the feed water flow rate supplied to the boiler due to sudden opening and closing of the recirculation valve when the power plant is under low load. The feed water flow rate can be controlled stably, and disturbance to the boiler can be prevented.
[0046]
In the first embodiment, the power generation amount signal L is used as a signal for generating the recirculation valve opening command signal VB by the recirculation valve opening command function generating means 31, but the recirculation valve 4 is used in the operation of the power plant. A power generation amount command signal or a boiler output request command signal may be used as a signal having a correlation with the opening degree.
[0047]
FIG. 4 is a configuration diagram of a feed water pump control device showing a second embodiment of the present invention.
[0048]
The same reference numerals as those in FIG. 7 showing the conventional example in FIG. 4 indicate the same or corresponding parts, and the main difference in FIG. 4 from FIG. 7 is that the configuration of the water supply flow rate control unit 21 is different, and the water supply flow rate control unit 21B. The feed water flow rate control unit 21B is additionally provided with a detection means 33 and a change rate limiting means 34 to prevent sudden opening of the recirculation valve 4 and to stably control the feed water flow rate.
[0049]
Here, the detection means 33 compares the feed water flow rate command signal QC and the suction flow rate setting signal QT, and outputs a detection signal when the deviation is equal to or less than a predetermined value. The change rate limiting means 34 limits and outputs a signal in the decreasing direction of the feed water flow rate command signal QC at a predetermined change rate only when a detection signal is input.
[0050]
Next, an operation when the flow rate of water supplied to the boiler is gradually reduced when the power plant is under low load will be described with reference to FIG. Note that QD shown in FIG. 5 is an output of the change rate limiting means 34.
[0051]
Here, until the time t1 when the feed water flow rate command signal QC is greater than the suction flow rate setting signal QT, the detection signal is not output from the detection unit 33 to the change rate limiting unit 34. Therefore, the operation for limiting the rate of change of the feed water flow rate command signal QC is not performed by the rate of change limiting means 34. Accordingly, the feed water flow rate command signal QC and the output QD of the change rate limiting means 34 are always substantially the same value.
[0052]
Thereafter, when the detection means 33 detects that the water supply flow rate command signal QC has approached the suction flow rate setting signal QT after time t1, the detection signal is input to the change rate limiting means 34. Along with this, an operation to limit the change in the decreasing direction of the output QD of the change rate limiting means 34 is started. Accordingly, the reduction of the feed water flow rate signal QF is limited, the sudden decrease of the suction flow rate detection signal QR is eliminated, and it is leveled out. Further, when the suction flow rate detection signal QR falls below the suction flow rate setting signal QT at time t2, the recirculation valve 4 starts to open, but the feed water flow rate signal QF gently decreases and the suction flow rate detection signal QR also decreases gently. Therefore, the recirculation valve opening command signal V from the change rate limiting means 30 also gradually increases from time t2, and the recirculation valve 4 is prevented from opening rapidly.
[0053]
In this way, by limiting the decrease in the feed water flow rate command signal QC, the recirculation valve 4 is prevented from suddenly opening and closing, the sudden decrease or sudden increase in the feed water flow rate supplied to the boiler is prevented, and the feed water flow rate is stably controlled. It is possible to prevent disturbance to the boiler.
[0054]
In addition, since the restriction is performed based on the suction flow rate setting signal QT of the feed water pump 1, the recirculation valve 4 can be prevented from being suddenly opened at any load zone of the power plant and any operation point of the feed water pump.
[0055]
The increasing direction of the feed water flow command signal QC is not limited because the feed water pump 1 does not overheat.
[0056]
【The invention's effect】
As described above, according to the water supply pump control device of the first aspect, the minimum suction flow rate is determined by the second recirculation valve opening command signal that changes gradually and gradually without the sudden change according to the power generation amount signal at low load. Since the opening of the recirculation valve is changed so as to ensure that the recirculation valve is suddenly opened and closed more rapidly than necessary when the load is low as in the past, the rapid decrease and return of the water supply flow rate are repeated. The state can be avoided, stable feed water flow rate control can be performed, and disturbance to the boiler can be prevented.
[0057]
According to the feed water pump control device of claim 2, when the deviation between the feed water flow rate command signal and the suction flow rate setting signal is equal to or less than a predetermined value, the feed water flow rate command changes gently without suppressing a decrease in the feed water flow rate command signal. . Therefore, the recirculation valve opens gently and slowly as necessary, and there is no repeated reduction and return of the feed water flow as in the past, stable feed water flow control can be performed, and disturbance to the boiler can be prevented. Can do.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a feed water pump control device showing a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing characteristics of a recirculation valve opening command function generating means provided in the feed water pump control device of FIG. 1;
FIG. 3 is an explanatory diagram showing an operation of the feed water pump control device of FIG. 1;
FIG. 4 is a configuration diagram of a feed water pump control device showing a second embodiment of the present invention.
FIG. 5 is an explanatory diagram showing an operation of the feed water pump control device of FIG. 4;
FIG. 6 is a system diagram of a water supply pump.
FIG. 7 is a configuration diagram corresponding to FIG. 1 or FIG. 4 of a feed water pump control device showing a conventional example.
FIG. 8 is an explanatory diagram showing characteristics of a suction flow rate setting function generating means provided in the feed water pump control device of FIG.
9 is an explanatory view corresponding to FIG. 3 or FIG. 5 showing the operation of the feed water pump control device of FIG. 7;
[Explanation of symbols]
20 Water supply pump control device 21 Water supply flow rate control unit 22 Recirculation valve opening degree control unit 23 Deviation calculating means 24 Proportional integral calculating means 25 Deviation calculating means 26 Proportional calculating means 27 Suction flow rate setting function generating means 28 Deviation calculating means 29 Proportional calculating means 30 Change rate limiting means 31 Recirculation valve opening command function generating means 32 High value selecting means 33 Detection means 34 Change rate limiting means

Claims

A feed water system that feeds water from the deaerator to the boiler by a feed water pump driven by the rotation of the steam turbine, and a recirculation system that recirculates the feed water to the deaerator through a recirculation valve; the water system of the water supply flow rate detection signal is feed water flow rate command signal to become as by steam control valve opening command signal Gyosu control the steam supplied to the steam turbine Rutotomoni, recirculation valve opening command the recirculation valve A function generating means for outputting a suction flow rate setting signal based on a function preset according to a rotation speed detection signal of the feed water pump in a feed water pump control device that controls the recirculation flow rate of the circulation system by opening and closing by a signal And a control means for outputting a first recirculation valve opening command signal obtained by performing a control calculation according to a deviation between the suction flow rate setting signal and the suction flow rate detection signal of the feed water pump, Means for outputting a second recirculation valve opening command signal based on a function set in advance according to the electric energy signal, the first recirculation valve opening command signal and the second recirculation valve opening command; A recirculation valve opening degree control unit comprising high value selection means for inputting a signal and outputting any high value signal as the recirculation valve opening degree instruction signal to the recirculation valve. Water supply pump control device.

A feed water system that feeds water from the deaerator to the boiler by a feed water pump driven by the rotation of the steam turbine, and a recirculation system that recirculates the feed water to the deaerator through a recirculation valve; The steam supplied to the steam turbine is controlled by a steam control valve opening command signal so that the feed water flow detection signal of the water supply system becomes a feed water flow command signal, and the recirculation valve is operated by a recirculation valve opening command signal. In the feed water pump control device that controls the recirculation flow rate of the circulation system by opening and closing by the suction flow, the suction flow setting signal predetermined by the rotation speed of the feed water pump and the feed water flow command signal are compared, and the deviation of both signals is A detecting means for outputting a detection signal when the value is equal to or less than a predetermined value, and the water supply flow rate command signal is inputted and outputted as it is as a change rate limiting signal, while only when the detection signal is inputted And change rate limiting means for outputting the change rate limit signal for limiting the decrease in the water flow command signal, feed water flow detection signal and the change rate limit signal and said steam control valve a control signal obtained deviation signal control operation on the A feed water pump control device comprising: a feed water flow rate control unit comprising a control means for making an opening degree command signal.