JP3817921B2

JP3817921B2 - Grid interconnection device

Info

Publication number: JP3817921B2
Application number: JP24750398A
Authority: JP
Inventors: 友紀井村
Original assignee: Nissin Electric Co Ltd
Current assignee: Nissin Electric Co Ltd
Priority date: 1998-09-01
Filing date: 1998-09-01
Publication date: 2006-09-06
Anticipated expiration: 2018-09-01
Also published as: JP2000078755A

Description

【０００１】
【発明の属する技術分野】
本発明は、電力系統に連系される自家用発電設備の母線を、電力系統の電圧低下，停電等の故障が発生したときに電力系統に接続された受電母線から切離し、前記故障が復旧したときに受電母線に再び接続し、自家用発電設備の母線の負荷給電を確保する系統連系装置に関する。
【０００２】
【従来の技術】
従来、工場，ビル等の高圧又は特高の受電設備にあっては商用の電力系統にコージェネレーション設備等の自家用発電設備を連系し、この発電設備の母線（自家発系母線）に接続されたいわゆる重要負荷の給電の２重化が行われている。
【０００３】
この場合の系統連系は、従来、図５の単線系統図に示す系統連系装置を用いて行われる。
【０００４】
そして、商用の系統電源１に遮断器２，トランス３を介して受電母線４が接続され、受電母線４から遮断器５ａ，…，５ｎを介して各フィーダ６ａ，…，６ｎの一般負荷７ａ，…，７ｎに系統電源１が給電される。
【０００５】
また、自家用発電設備としての発電機（コジェネ発電機）８に遮断器９を介して自家用発電設備の母線（自家発系母線）１０が接続され、この母線１０が遮断器等の機械式の母線連絡用の開閉器１１を介して受電母線４に接続される。
【０００６】
そして、図示省略された制御部のシーケンス制御等により、常時は開閉器１１が系統電源１に同期投入されて閉成され、発電機８が電力系統に連系運転される。
【０００７】
さらに、自家発系母線１０に遮断器１２ａ，…，１２ｎを介して各フィーダ１３ａ，…，１３ｎの重要負荷１４ａ，…，１４ｎが接続され、これらの負荷１４ａ，…，１４ｎに系統電源１及び発電機８の交流出力が給電され、各重要負荷１４ａ，…，１４ｎの給電が２重化される。
【０００８】
この２重化に基づき、発電機８の出力低下等が発生すると、各重要負荷１４ａ，…，１４ｎに系統電源１から給電され、各重要負荷１４ａ，…，１４ｎの安定給電が確保される。
【０００９】
【発明が解決しようとする課題】
前記図５の従来装置の場合、電力系統や受電母線４に雷害による瞬時電圧低下等の電圧低下や地絡，短絡の停電等の故障が発生したときに、その検出に基づいて開閉器１１を開放（解列）し、自家発系母線１０を受電母線４から切離して重要負荷１４ａ，…，１４ｎの給電を確保しようとしても、機械式の開閉器１１の解列に時間を要し、瞬時に切離すことができない。
【００１０】
そして、その間に発電機８から開閉器１１を介して故障点に過電流が流れるため、発電機８が停止しなかったとしても自家発系母線１０の電圧が低下し、重要負荷１４ａ，…，１４ｎの誤動作やデータ消去等の事故を引起こす。
【００１１】
また、前記の過電流が極めて大きく、発電機８の容量を大幅に上回るようなときは、発電機８が過負荷によって停止し、重要負荷１４ａ，…，１４ｎまでもが停電する事態を招来する。
【００１２】
そこで、図６に示すように母線４，１０の連絡路に、開閉器１１と過電流制限機能付きの高速遮断用の整流器型ブリッジ回路１５との直列回路を設け、前記故障が発生したときに、ブリッジ回路１５の電流制限と高速遮断とにより自家発系母線１０の電圧低下，停電を防止して重要負荷１４ａ，…，１４ｎの給電を確保することが考えられる。
【００１３】
そして、ブリッジ回路１５は制御整流素子としての２アームのサイリスタ１６ａ，１６ｂと２アームのダイオード１７ａ，１７ｂとをブリッジ接続して形成され、開閉器１１を介して受電母線４に接続された一方の交流端子ＡＣ1 と自家発系母線１０に接続された他方の交流端子ＡＣ_２との間に、サイリスタ１６ａのアノード，カソード，一方の直流端子ＤＣ_１，ダイオード１７ａのカソード，アノードの直列回路と、サイリスタ１６ｂのカソード，アノード，他方の直流端子ＤＣ_２，ダイオード１７ｂのアノード，カソードの直列回路とを並列に設けて形成される。
さらに、直流端子ＤＣ_１，ＤＣ_２間には限流用のリアクトル１８が設けられる。
そして、連系運転中はサイリスタ１６ａ，１６ｂがオンする。
【００１４】
このとき、ブリッジ回路１５を図７の実線▲１▼，破線▲２▼の交流の電流が通流し、この交流の電流が直流端子ＤＣ_１から直流端子ＤＣ_２に一方向に流れ、リアクトル１８を通流する電流は直流になる。
【００１５】
さらに、リアクトル１８は放電時定数が十分に大きくなるように容量設定され、その放電に時間がかかるため、連系運転中（定常時）は、リアクトル１８に図７の実線▲３▼に示すサイリスタ１６ａ，リアクトル１８，サイリスタ１６ｂのループの環流電流と，同図の実線▲４▼に示すダイオード１７ａ，リアクトル１８，ダイオード１７ｂのループの環流電流との和の直流電流が流れる。
【００１６】
そして、リアクトル１８に直流が流れるため、そのインピーダンスはほぼ零になり、挿入損失もほぼ零になる。
【００１７】
また、サイリスタ１６ａ，１６ｂ及びダイオード１７ａ，１７ｂを流れる電流は、前記実線▲１▼又は破線▲２▼の交流の電流と前記実線▲３▼又は実線▲４▼の直流の環流電流との和の電流になり、例えばサイリスタ１６ａには実線▲１▼の交流の電流と実線▲３▼の直流の還流電流が流れる。
【００１８】
つぎに、電力系統側に電圧低下，停電等の故障が発生し、発電機８からブリッジ回路１５，開閉器１１を介して故障点に短絡電流等の過電流が流れようとすると、ブリッジ回路１５のサイリスタ１６ａ，ダイオード１７ｂ又はサイリスタ１６ｂ，ダイオード１７ａを前記の環流電流と逆向きの電流が流れ、環流電流が消失して交流端子ＡＣ_１，ＡＣ_２間の交流の電流がリアクトル１８を流れるようになる。
【００１９】
この場合、リアクトル１８を開閉器１１に直列に接続した状態と等価になり、交流端子ＡＣ_１，ＡＣ_２間からみたブリッジ回路１５のインピーダンスが増大し、リアクトル１８の限流作用により交流端子ＡＣ_１，ＡＣ_２間の過電流の通流が抑制されて短絡電流が制限される。
【００２０】
ここで、リアクトル１８に流れる直流電流と基準値との比較による系統異常のリアルタイム監視検出により、電力系統の電圧低下，停電等の故障の発生から限流機能を保ちつつ瞬時に系統電圧の低下，消失が検出され、この検出に基づき次の半サイクルの零クロス点でサイリスタ１６ａ，１６ｂの消弧制御により直ちにサイリスタ１６ａ，１６ｂがオフし、自家発系母線１０が高速遮断動作で受電母線４から切離される。
【００２１】
そのため、電力系統側に電圧低下，停電等の故障が発生したときに、ブリッジ回路１５の限流作用と高速遮断とにより、自家発系母線１０の電圧低下や停電が防止されて重要負荷１４ａ，…，１４ｎの安定な給電が継続される。
【００２２】
つぎに、系統連系状態に復帰するときは、ブリッジ回路１５の交流端子ＡＣ_１，ＡＣ_２間のバイパス路１９に設けたバイパス路開閉用の開閉器２０を閉成した後、開閉器１１を同期投入し、自家発系母線１０をバイパス路１９，開閉器１１を介して受電母線４に接続して過渡的な系統連系状態にする。
【００２３】
さらに、サイリスタ１６ａ，１６ｂを点弧制御してブリッジ回路１５をオンし、その後、開閉器２０を開放して自家発系母線１０をブリッジ回路１５，開閉器１１を介して受電母線４に接続し、正常な系統連系状態に復帰する。
【００２４】
しかし、図６の構成においては、開閉器１１の同期投入からブリッジ回路１５がオンするまでの過渡期間に電力系統側に瞬時電圧低下等の電圧低下や停電等の故障が発生した場合、自家発系母線１０からバイパス路１９，開閉器１１を介して受電母線４に短絡電流等の過電流が流れる。
【００２５】
そこで、図８に示すようにバイパス路１９の開閉器２０に直列にヒューズ２１を設けることが考えられる。
【００２６】
この場合、ヒューズ２１が溶断して前記過渡期間の過電流が防止され、自家発系母線１０の各重要負荷１４ａ〜１４ｎの安定給電が確保される。
【００２７】
しかし、図８の構成の場合、溶断したヒューズ２１を取換えるまで系統連系状態に復帰することができず、ヒューズ２１の溶断後系統電圧が回復しても直ちに系統連系状態に復帰することができない問題点がある。
【００２８】
本発明は、系統連系状態に復帰する際に、前記過渡期間に電圧低下，停電等の故障が発生しても、その復旧後に迅速に系統連系に復帰し得るようにすることを課題とする。
【００２９】
【課題を解決するための手段】
前記の課題を解決するために、本発明の系統連系装置は、電力系統に接続された受電母線と，電力系統に連系運転される自家用発電設備の母線（自家発系母線）との間に設けられ，電力系統の電圧低下，停電等の故障の発生により開放され，故障の復旧後に再投入される母線連絡用の開閉器と、
半導体制御整流素子のフルブリッジ接続又は半導体制御整流素子とダイオードとの混合ブリッジ接続からなるブリッジ接続回路と，この回路の１対の直流端子間に設けられ連系運転中の前記両母線間の過電流を阻止する限流用の第１のリアクトルにより形成され，ブリッジ接続回路の１対の交流端子が母線連絡用の開閉器を介して前記両母線に接続され，半導体制御整流素子の点消弧制御に基づき前記故障が発生したときに母線連絡用の開閉器の開放に先立ってオフしこの開閉器の再投入後にオンする高速遮断用の整流器型ブリッジ回路と、
前記１対の交流端子間のバイパス路に設けられ，故障の復旧後母線連絡用の開閉器の再投入から整流器型ブリッジ回路がオンして連系運転に移行するまでの短時間だけ閉成されるバイパス路開閉用の開閉器と、
この開閉器に直列に接続されてバイパス路に設けられ，バイパス路の過電流を阻止する短時間定格の限流用の第２のリアクトルとを備える。
【００３０】
したがって、整流器型ブリッジ回路の１対の交流端子間のバイパス路に、バイパス路開閉用の開閉器と短時間定格の限流用の第２のリアクトルとの直列回路が設けられる。
【００３１】
そして、電力系統側の故障が復旧して系統連系に復帰する際に、バイパス路開閉用の開閉器を閉成した後母線連絡用の開閉器を投入すると、自家発系母線がバイパス路の第２のリアクトル，バイパス路開閉用の開閉器及び母線連絡用の開閉器を介して受電母線に接続され、過渡的な系統連系状態になる。
【００３２】
つぎに、整流器型ブリッジ回路がオンすると、バイパス路開閉用の開閉器が開放され、両母線の連絡路が前記バイパス路から整流器型ブリッジ回路に切換わる。
【００３３】
そして、前記整流器型ブリッジ回路がオンするまでの過渡期間に、受電母線を含む電力系統側に電圧低下，停電等の故障が生じると、第２のリアクトルにより短絡電流等の過電流が制限され、自家発系母線の電圧低下や停電が防止される。
【００３４】
この場合、ヒューズの溶断等でなく、第２のリアクトルの限流作用により自家発系母線の電圧低下や停電が防止されるため、ヒューズの取換等を必要とせず、故障の復旧により直ちに系統連系に復帰することが可能になる。
【００３５】
【発明の実施の形態】
本発明の実施の１形態につき、図１ないし図４を参照して説明する。
いわゆる主回路部の全体構成を示した図１において、図８と異なる点は、ブリッジ回路１５のリアクトル１８を限流用の第１のリアクトルとし、バイパス路１９の図８のヒューズ２１の位置に限流用の第２のリアクトル２２を設け、ヒューズ２１を省いた点である。
【００３６】
そして、開閉器１１，２０の開閉，ブリッジ回路１５のサイリスタ１６ａ，１６ｂの点消弧制御等は、図示省略された制御部により、例えば、設定されたシーケンス制御等にしたがって行われる。
【００３７】
そして、受電母線４を含む電力系統側が正常な常時は、開閉器１１が閉成されるとともにサイリスタ１６ａ，１６ｂが点弧制御されてブリッジ回路１５がオンし、受電母線４と自家発系母線１０とが開閉器１１，ブリッジ回路１５を介して接続され、発電機８が連系運転されて図２の（ａ）の系統連系中の状態になる。
【００３８】
なお、図２の〈オン〉は閉成，オン（導通）の状態を示し、〈オフ〉は開放，オフ（非導通）の状態を示す。
このとき、開閉器２０は開放され、バイパス路１９は開放状態に保たれる。
【００３９】
そして、母線４，１０の電圧関係等に基づき、例えば、図３の実線▲５▼に示すように発電機８の一部の出力がブリッジ回路１５を介して受電母線４に補給される。
【００４０】
つぎに、この状態で電力系統側に例えば図２の（ｂ）に示す雷害による瞬時電圧低下の故障が発生すると、ブリッジ回路５のリアクトル１８の限流作用によって母線４，１０間の過電流が制限され、同時に、系統異常のリアルタイムの監視に基づくサイリスタ１６ａ，１６ｂの消弧制御により、ブリッジ回路１５が系統電源１の１周期以内にオフし、母線４，１０間が高速遮断動作で開放される。
【００４１】
そのため、自家発系母線１０の電圧変動が防止され、発電機８の出力に基づき、各重要負荷１４ａ〜１４ｎに瞬時電圧低下等のない安定な電力供給が続けられる。
【００４２】
その後、故障の継続又はブリッジ回路１５のオフに連動し、図２の（ｃ）に示すように開閉器１１がバックアップ開放される。
【００４３】
つぎに、シーケンス制御等により図２の（ｄ）の併入待機に移行し、開閉器２０が投入されてバイパス路１９が導通状態になる。
【００４４】
さらに、例えば系統電圧の正常復帰の検出に基づいて図２の（ｅ）の併入に移行し、系統電源１に同期して開閉器１１が投入され、自家発系母線１０がバイパス路１９，開閉器１１を介して受電母線４に接続され、過渡的な系統連系状態になる。
【００４５】
そして、母線４，１０の電圧差等に基づき、例えば図４の実線▲６▼に示すように、発電機１６の出力の一部が自家発系母線１０からバイパス路１９，開閉器１１を介して受電母線４に流れる。
【００４６】
ところで、この過渡的な系統連系状態のときに、電力系統側に雷害による瞬時電圧低下等の電圧低下又は地絡、短絡の停電等の故障が発生すると、自家発系母線１０からバイパス路１９，開閉器１１を介して受電母線４に短絡電流等の過電流が流れようとするが、この過電流はリアクトル２２の限流作用により制限されて阻止される。
【００４７】
そして、例えば前記の系統異常のリアルタイムの監視により開閉器２０が開放され、その後、開閉器１１も開放されて同図の（ｃ）の状態に戻り、この状態から動作がくり返される。
【００４８】
一方、図２の（ｅ）の併入により開閉器１１が同期投入されたときに、電力系統側の故障等が発生せず、母線４，１０間が正常に接続されると、図２の（ｆ）の系統連系復帰に移行し、サイリスタ１６ａ，１６ｂの点弧制御が開始されてブリッジ回路１５がオンし、その後、開閉器２０が開放され、母線４，１０が再び開閉器１１，ブリッジ回路１５を介して接続され、正常な系統連系状態に戻る。
【００４９】
そして、バイパス路１９に図８のヒューズ２１でなく限流用のリアクトル２２を設け、母線４，１０がバイパス路１９を介して接続される過渡的な系統連系状態での短絡電流等の過電流をリアクトル２２の限流作用で制限して阻止する構成であるため、ヒューズ２１の取換え等の作業が不要であり、その後の電力系統側の復旧により直ちに系統連系に復帰することができる。
【００５０】
しかも、系統連系に復帰する一連の制御処理に基づき、図２の（ｅ）の併入により開閉器１１が投入されてからブリッジ回路１５がオンして同図の（ｆ）の正常な系統連系に復帰するまでの時間，前記併入により開閉器１１が投入されたときに系統側に故障が発生して開閉器１１が開放されるまでの時間は、いずれも１秒内外の短時間であり、リアクトル２２はこの短時間の過電流を限流する短時間定格の小型のものでよい。
【００５１】
ところで、実際の電力系統に適用する場合は、この系統連系装置が相毎に設けられる。
【００５２】
具体的には、母線４，１０の相毎に、開閉器１１，２０，ブリッジ回路１５，リアクトル２２の主回路部及びこれらの制御部が設けられる。
【００５３】
そして、ブリッジ回路１５の半導体制御直流素子は、例えば電力用のスイッチングトランジスタ等であってもよい。
【００５４】
また、ブリッジ回路１５の半導体制御整流素子，ダイオードの数及びそれらの接続組合せ等は実施の形態のものに限られるものではない。
【００５５】
そして、前記実施の形態においては、ブリッジ回路１５のブリッジ接続回路をサイリスタ１６ａ，１６ｂとダイオード１７ａ，１７ｂとの混合ブリッジ接続により形成し、小型化を図るようにしたが、前記ブリッジ接続回路はサイリスタのフルブリッジ接続により形成してもよい。
【００５６】
さらに、リアクトル１８，２２の容量等は母線４，１０の負荷７ａ〜７ｎ，１４ａ〜１４ｎ等を考慮して設定すればよい。
【００５７】
そして、本発明は自家用発電設備として種々のコージェネレーション設備等を有する工場，ビル等の高圧又は特高の受電設備に適用することができる。
【００５８】
【発明の効果】
本発明は、以下に説明する効果を奏する。
整流器型ブリッジ回路１５の交流端子ＡＣ1 ，ＡＣ2 間のバイパス路１９に、バイパス路開閉用の開閉器２０と短時間定格の限流用の第２のリアクトル２２との直列回路が設けられ、電力系統側の故障が復旧して系統連系運転に復帰するときに、開閉器２０を閉成した後母線連絡用の開閉器１１を投入すると、母線（自家発系母線）１０がリアクトル２２，開閉器２０及び開閉器１１を介して受電母線４に接続され、過渡的な系統連系状態になる。
【００５９】
このとき、受電母線４を含む系統側に電圧低下，停電等の故障が生じると、リアクトル２２の限流作用により短絡電流等の過電流が制限されて母線１０の電圧低下や停電が防止される。
【００６０】
そして、ヒューズの溶断等でなく、リアクトル２２の限流作用により母線１０の電圧低下や停電が防止されるため、ヒューズの取換等を必要とせず、故障の復旧により直ちに系統連系に復帰することができる。
【図面の簡単な説明】
【図１】本発明の実施の１形態の単線系統図である。
【図２】（ａ）〜（ｆ）はそれぞれ図１の動作説明用の単線系統図である。
【図３】図１の系統連系中の電流路の説明図である。
【図４】図１の連系過渡期の電流路の説明図である
【図５】従来装置の単線系統図である。
【図６】図５の装置に高速遮断用の整流器型ブリッジ回路及びバイパス路を付加した場合の一部の結線図である。
【図７】図６のブリッジ回路の動作説明図である。
【図８】図６のバイパス路にヒューズを付加した場合の単線系統図である。
【符号の説明】
１系統電源
４受電母線
８発電機
１０自家用発電設備の母線（自家発系母線）
１１母線連絡用の開閉器
１５整流器型ブリッジ回路
１６ａ，１６ｂサイリスタ
１７ａ，１７ｂダイオード
１８第１のリアクトル
１９バイパス路
２０バイパス路開閉用の開閉器
２２第２のリアクトル[0001]
BACKGROUND OF THE INVENTION
The present invention disconnects the bus of the private power generation facility linked to the power system from the power receiving bus connected to the power system when a failure such as a voltage drop or power failure of the power system occurs, and the failure is restored The present invention relates to a grid interconnection device that is reconnected to a power receiving bus and secures load feeding of the bus of a private power generation facility.
[0002]
[Prior art]
Conventionally, for high-voltage or extra-high-voltage power receiving facilities such as factories and buildings, a private power generation facility such as a cogeneration facility is connected to a commercial power system and connected to the bus of this power generation facility (self-generated bus). The so-called important load power supply is duplicated.
[0003]
The grid interconnection in this case is conventionally performed using a grid interconnection apparatus shown in the single-line system diagram of FIG.
[0004]
Then, the power receiving bus 4 is connected to the commercial system power supply 1 via the circuit breaker 2 and the transformer 3, and the general loads 7a of the feeders 6a,..., 6n are connected from the power receiving bus 4 to the circuit breakers 5a,. .., 7n are fed with the system power supply 1.
[0005]
Also, a generator (cogeneration generator) 8 serving as a private power generation facility is connected to a bus (self-generated bus) 10 of the private power generation facility via a circuit breaker 9, and this bus 10 is a mechanical bus such as a circuit breaker. It is connected to the power receiving bus 4 via a contact switch 11.
[0006]
Then, by means of sequence control of a control unit (not shown), the switch 11 is normally turned on and closed in synchronization with the system power supply 1, and the generator 8 is connected to the power system.
[0007]
Furthermore, important loads 14a,..., 14n of feeders 13a,..., 13n are connected to the self-generated bus 10 via circuit breakers 12a,..., 12n, and the system power supply 1 and the load 14a,. The AC output of the generator 8 is fed, and the feeding of each important load 14a, ..., 14n is duplicated.
[0008]
When the output of the generator 8 is reduced due to the duplexing, the important loads 14a,..., 14n are supplied with power from the system power supply 1, and stable supply of the important loads 14a,.
[0009]
[Problems to be solved by the invention]
In the case of the conventional apparatus shown in FIG. 5, when a voltage drop such as an instantaneous voltage drop due to lightning damage or a fault such as a ground fault or a short-circuit power failure occurs in the power system or the power receiving bus 4, the switch 11 is detected based on the detection. Even if an attempt is made to secure power supply for the important loads 14a,..., 14n by disconnecting the self-generated bus 10 from the power receiving bus 4 and disconnecting the self-generated bus 10 from the power receiving bus 4, it takes time to disconnect the mechanical switch 11; It cannot be disconnected instantly.
[0010]
And since overcurrent flows from the generator 8 through the switch 11 to the failure point during that time, even if the generator 8 does not stop, the voltage of the self-generated bus 10 decreases, and the important loads 14a,. It causes accidents such as 14n malfunction and data erasure.
[0011]
Further, when the overcurrent is extremely large and greatly exceeds the capacity of the generator 8, the generator 8 stops due to the overload, leading to a situation where the critical loads 14a,. .
[0012]
Therefore, as shown in FIG. 6, a series circuit of a switch 11 and a rectifier bridge circuit 15 for high-speed interruption with an overcurrent limiting function is provided in the connection path of the buses 4 and 10, and when the failure occurs It is conceivable to secure the power supply of the important loads 14a,..., 14n by preventing the voltage drop and power failure of the private bus 10 by limiting the current of the bridge circuit 15 and cutting off at high speed.
[0013]
The bridge circuit 15 is formed by bridge-connecting two-arm thyristors 16 a and 16 b as control rectifier elements and two-arm diodes 17 a and 17 b, and is connected to the power receiving bus 4 via the switch 11. between the AC terminals AC1 and the other AC terminal AC ₂ connected to the private power-generating system bus 10, the anode of the thyristor 16a, cathode, one of the DC terminals DC _1, the cathode of the diode 17a, the anode of the series circuit, a thyristor the cathode of 16b, the anode, the other DC terminal DC _2, the anode of the diode 17b, the cathode of the series circuit provided in parallel is formed.
Furthermore, a current limiting reactor 18 is provided between the DC terminals DC ₁ and DC ₂ .
The thyristors 16a and 16b are turned on during the interconnection operation.
[0014]
At this time, an alternating current indicated by a solid line (1) and a broken line (2) in FIG. 7 flows through the bridge circuit 15, and this alternating current flows in one direction from the direct current terminal DC ₁ to the direct current terminal DC _2. The current that flows is a direct current.
[0015]
Further, since the capacity of the reactor 18 is set so that the discharge time constant becomes sufficiently large and the discharge takes time, the thyristor indicated by the solid line (3) in FIG. A direct current of the sum of the circulating current of the loop of 16a, the reactor 18, and the thyristor 16b and the circulating current of the loop of the diode 17a, the reactor 18, and the diode 17b shown by the solid line (4) in FIG.
[0016]
Since a direct current flows through the reactor 18, the impedance becomes almost zero and the insertion loss becomes almost zero.
[0017]
The current flowing through the thyristors 16a and 16b and the diodes 17a and 17b is the sum of the alternating current of the solid line (1) or the broken line (2) and the direct current of the solid line (3) or the solid line (4). For example, an alternating current indicated by a solid line (1) and a direct current return current indicated by a solid line (3) flow through the thyristor 16a.
[0018]
Next, when a failure such as a voltage drop or a power failure occurs on the power system side and an overcurrent such as a short-circuit current flows from the generator 8 via the bridge circuit 15 and the switch 11 to the failure point, the bridge circuit 15 In the thyristor 16a and diode 17b or thyristor 16b and diode 17a, a current in the direction opposite to the circulating current flows, the circulating current disappears, and the AC terminals AC ₁ and AC ₂ The alternating current flows between the reactors 18.
[0019]
In this case, it becomes equivalent to a state in which the reactor 18 is connected in series with the switch 11, the impedance of the bridge circuit 15 viewed from between the AC terminals AC ₁ and AC ₂ increases, and the AC terminal AC _{1 is} caused by the current limiting action of the reactor 18. , The overcurrent flow between AC ₂ is suppressed and the short circuit current is limited.
[0020]
Here, the real-time monitoring and detection of the system abnormality by comparing the direct current flowing through the reactor 18 and the reference value allows the system voltage to be instantaneously reduced while maintaining the current-limiting function from the occurrence of a failure such as a power supply voltage drop or power failure. The disappearance is detected. Based on this detection, the thyristors 16a and 16b are immediately turned off by the extinction control of the thyristors 16a and 16b at the zero-cross point of the next half cycle, and the self-generated bus 10 is disconnected from the power receiving bus 4 by the high-speed shutoff operation. Disconnected.
[0021]
For this reason, when a failure such as a voltage drop or a power failure occurs on the power system side, the voltage drop or power failure of the self-system bus 10 is prevented by the current limiting action and the high-speed interruption of the bridge circuit 15, and the important load 14a, ..., 14n stable power feeding is continued.
[0022]
Next, when returning to the grid connection state, the AC terminals AC ₁ and AC _{2 of the} bridge circuit 15 are used. After closing the switch 20 for opening and closing the bypass path provided in the bypass path 19 between them, the switch 11 is synchronized and the self-generated bus 10 is connected to the power receiving bus 4 via the bypass 19 and the switch 11. Connect to a transient grid connection.
[0023]
Further, the thyristors 16 a and 16 b are controlled to be turned on to turn on the bridge circuit 15, and then the switch 20 is opened to connect the self-generated bus 10 to the power receiving bus 4 via the bridge circuit 15 and switch 11. Return to normal grid connection.
[0024]
However, in the configuration of FIG. 6, if a failure such as a voltage drop such as an instantaneous voltage drop or a power failure occurs on the power system side during a transitional period from the synchronous turning on of the switch 11 to the turning on of the bridge circuit 15, An overcurrent such as a short-circuit current flows from the system bus 10 to the power receiving bus 4 through the bypass 19 and the switch 11.
[0025]
Therefore, it is conceivable to provide a fuse 21 in series with the switch 20 of the bypass 19 as shown in FIG.
[0026]
In this case, the fuse 21 is blown to prevent the overcurrent during the transient period, and stable power feeding of the important loads 14a to 14n of the self-generated bus 10 is ensured.
[0027]
However, in the case of the configuration of FIG. 8, the grid connection state cannot be restored until the blown fuse 21 is replaced, and even if the system voltage is restored after the fuse 21 is blown, the grid connection state is restored immediately. There is a problem that can not be.
[0028]
It is an object of the present invention to enable quick return to the grid connection after recovery even if a failure such as a voltage drop or a power failure occurs during the transition period when returning to the grid connection state. To do.
[0029]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the grid interconnection device of the present invention is provided between a power receiving bus connected to the power system and a bus (self-generated bus) of a private power generation facility connected to the power system. A bus contact switch that is opened in the event of a failure such as a voltage drop in the power system or a power failure, and is re-entered after the failure is restored;
A bridge connection circuit consisting of a full bridge connection of a semiconductor controlled rectifier element or a mixed bridge connection of a semiconductor controlled rectifier element and a diode, and an excess between the two buses that are provided between a pair of DC terminals of the circuit and are connected to each other during operation. Formed by a first current-limiting reactor for blocking current, a pair of AC terminals of a bridge connection circuit are connected to both buses via a bus-connecting switch, and point extinction control of a semiconductor control rectifier A rectifier type bridge circuit for high-speed shut-off that is turned off prior to opening of the switch for connecting the bus when the failure occurs based on
It is provided in the bypass path between the pair of AC terminals, and is closed only for a short time after the failure is restored until the rectifier-type bridge circuit turns on and shifts to grid operation after reconnecting the bus contactor switch. A bypass for opening and closing the bypass path;
A short-current rated current-reducing second reactor that is connected to the switch in series and is provided in the bypass path and prevents overcurrent in the bypass path.
[0030]
Therefore, the bypass circuit between the pair of AC terminals of the rectifier type bridge circuit is provided with a series circuit of a switch for opening / closing the bypass path and a second reactor for current limiting with a short-time rating.
[0031]
Then, when the failure on the power system side is recovered and the system is returned to the grid connection, after closing the bypass path opening / closing switch and turning on the bus connection switch, the self-generated bus is connected to the bypass path. It is connected to the power receiving bus line via the second reactor, the bypass path opening / closing switch, and the bus line connecting switch, so that a transient grid connection state is established.
[0032]
Next, when the rectifier type bridge circuit is turned on, the switch for opening and closing the bypass path is opened, and the connecting path of both buses is switched from the bypass path to the rectifier type bridge circuit.
[0033]
And, in the transition period until the rectifier bridge circuit is turned on, when a failure such as voltage drop or power failure occurs on the power system side including the power receiving bus, overcurrent such as short circuit current is limited by the second reactor, The voltage drop and power outage of the self-generated bus are prevented.
[0034]
In this case, a voltage drop or power failure of the self-generated bus is prevented by the current limiting action of the second reactor, not by fusing the fuse, etc., so it is not necessary to replace the fuse, etc. It becomes possible to return to the interconnection.
[0035]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
In FIG. 1 showing the entire configuration of the so-called main circuit section, the difference from FIG. 8 is that the reactor 18 of the bridge circuit 15 is the first reactor for current limiting and is limited to the position of the fuse 21 in FIG. The diverted second reactor 22 is provided and the fuse 21 is omitted.
[0036]
The switching of the switches 11 and 20 and the point-extinguishing control of the thyristors 16a and 16b of the bridge circuit 15 are performed by a control unit (not shown) according to, for example, set sequence control.
[0037]
When the power system side including the power receiving bus 4 is normal, the switch 11 is closed, the thyristors 16a and 16b are controlled to be turned on, the bridge circuit 15 is turned on, and the power receiving bus 4 and the self-generated bus 10 Are connected via the switch 11 and the bridge circuit 15, and the generator 8 is operated in an interconnected state to enter the state of the interconnected system shown in FIG.
[0038]
In addition, <ON> of FIG. 2 shows a closed state and an ON (conduction) state, and <OFF> shows an open state and an OFF (non-conduction) state.
At this time, the switch 20 is opened and the bypass path 19 is kept open.
[0039]
Then, based on the voltage relationship between the buses 4 and 10, for example, a part of the output of the generator 8 is supplied to the power receiving bus 4 via the bridge circuit 15 as indicated by a solid line (5) in FIG.
[0040]
Next, in this state, for example, when a failure of an instantaneous voltage drop due to lightning damage shown in FIG. 2B occurs on the power system side, an overcurrent between the buses 4 and 10 is generated by the current limiting action of the reactor 18 of the bridge circuit 5. At the same time, by the arc extinguishing control of the thyristors 16a and 16b based on the real-time monitoring of the system abnormality, the bridge circuit 15 is turned off within one cycle of the system power supply 1, and the buses 4 and 10 are opened by the high-speed disconnection operation. Is done.
[0041]
Therefore, voltage fluctuation of the self-generated bus 10 is prevented, and stable power supply without any instantaneous voltage drop or the like is continued to each of the important loads 14a to 14n based on the output of the generator 8.
[0042]
After that, the switch 11 is backed up as shown in FIG. 2C in conjunction with the continuation of the failure or the bridge circuit 15 being turned off.
[0043]
Next, the sequence control or the like shifts to the waiting state shown in FIG. 2D, the switch 20 is turned on, and the bypass 19 is turned on.
[0044]
Further, for example, based on the detection of normal return of the system voltage, the process shifts to FIG. 2 (e), the switch 11 is turned on in synchronization with the system power supply 1, and the self-generated bus 10 is connected to the bypass path 19, It is connected to the power receiving bus 4 via the switch 11 and enters a transient grid connection state.
[0045]
Then, based on the voltage difference between the buses 4 and 10, for example, as indicated by a solid line (6) in FIG. 4, a part of the output of the generator 16 is routed from the self-generated bus 10 via the bypass 19 and the switch 11. To the power receiving bus 4.
[0046]
By the way, when a voltage drop such as an instantaneous voltage drop due to lightning damage or a fault such as a ground fault or a short-circuit power failure occurs on the power system side in this transitional grid connection state, a bypass path from the self-generated bus 10 19, Overcurrent such as short-circuit current tends to flow through the power receiving bus 4 via the switch 11, but this overcurrent is limited and prevented by the current limiting action of the reactor 22.
[0047]
Then, for example, the switch 20 is opened by real-time monitoring of the above-described system abnormality, and then the switch 11 is also opened to return to the state of (c) in the figure, and the operation is repeated from this state.
[0048]
On the other hand, when the switch 11 is turned on synchronously due to the insertion of FIG. 2 (e), no fault or the like on the power system side occurs and the buses 4 and 10 are normally connected. Shifting to the grid connection return of (f), the ignition control of the thyristors 16a, 16b is started, the bridge circuit 15 is turned on, the switch 20 is then opened, and the buses 4, 10 are again connected to the switches 11, It is connected via the bridge circuit 15 and returns to a normal grid connection state.
[0049]
8 is provided in the bypass path 19 instead of the fuse 21 of FIG. 8, and an overcurrent such as a short-circuit current in a transient grid connection state in which the buses 4 and 10 are connected via the bypass path 19 is provided. Therefore, the work such as replacement of the fuse 21 is not necessary and can be immediately restored to the grid connection by the subsequent restoration on the power system side.
[0050]
In addition, based on a series of control processes for returning to the grid connection, the bridge circuit 15 is turned on after the switch 11 is turned on by the insertion of FIG. 2E, and the normal system of FIG. The time required for returning to the grid connection, and the time required for opening the switch 11 when the switch 11 is turned on due to the above-mentioned insertion, are both a short time within 1 second. The reactor 22 may be a short-time rated small-sized one that limits this short-time overcurrent.
[0051]
By the way, when applying to an actual electric power system, this grid connection apparatus is provided for every phase.
[0052]
Specifically, the switches 11 and 20, the bridge circuit 15, the main circuit unit of the reactor 22, and these control units are provided for each phase of the bus bars 4 and 10.
[0053]
The semiconductor control DC element of the bridge circuit 15 may be, for example, a power switching transistor.
[0054]
Further, the semiconductor control rectifying element, the number of diodes, the connection combination thereof, and the like of the bridge circuit 15 are not limited to those in the embodiment.
[0055]
In the above embodiment, the bridge connection circuit of the bridge circuit 15 is formed by the mixed bridge connection of the thyristors 16a and 16b and the diodes 17a and 17b so as to reduce the size. However, the bridge connection circuit is a thyristor. It may be formed by full bridge connection.
[0056]
Further, the capacity of the reactors 18 and 22 may be set in consideration of the loads 7a to 7n and 14a to 14n of the buses 4 and 10.
[0057]
The present invention can be applied to high-voltage or extra-high power receiving facilities such as factories and buildings having various cogeneration facilities as private power generation facilities.
[0058]
【The invention's effect】
The present invention has the effects described below.
A bypass circuit 19 between the AC terminals AC1 and AC2 of the rectifier type bridge circuit 15 is provided with a series circuit of a switch 20 for opening and closing the bypass path and a second reactor 22 for current limiting with a short-time rating. When the failure of the system is restored and the system interconnection operation is resumed, when the switch 11 for connecting the bus is turned on after the switch 20 is closed, the bus (in-house system bus) 10 is connected to the reactor 22 and the switch 20 And it is connected to the power receiving bus 4 via the switch 11 and enters a transient grid connection state.
[0059]
At this time, when a failure such as a voltage drop or a power failure occurs on the system side including the power receiving bus 4, an overcurrent such as a short-circuit current is limited by the current limiting action of the reactor 22, thereby preventing a voltage drop or a power failure of the bus 10. .
[0060]
And since the voltage drop and power failure of the bus line 10 are prevented by the current limiting action of the reactor 22 rather than the fusing of the fuse or the like, it is not necessary to replace the fuse, and the system is immediately restored to the grid connection after the failure is restored. be able to.
[Brief description of the drawings]
FIG. 1 is a single-line system diagram of a first embodiment of the present invention.
2A to 2F are single line diagrams for explaining the operation of FIG.
3 is an explanatory diagram of a current path in the grid interconnection of FIG. 1. FIG.
4 is an explanatory diagram of a current path in an interconnection transition period of FIG. 1. FIG. 5 is a single-line system diagram of a conventional device.
6 is a partial connection diagram in the case where a rectifier bridge circuit and a bypass path for high-speed shutoff are added to the apparatus of FIG. 5;
7 is an operation explanatory diagram of the bridge circuit of FIG. 6;
8 is a single-line system diagram when a fuse is added to the bypass path of FIG. 6;
[Explanation of symbols]
1 System power supply 4 Receiving bus 8 Generator 10 Bus for private power generation facilities (in-house bus)
11 Bus Switch 15 Rectifier Bridge Circuits 16a, 16b Thyristors 17a, 17b Diode 18 First Reactor 19 Bypass Path 20 Bypass Path Opening Switch 22 Second Reactor

Claims

It is provided between the power receiving bus connected to the power grid and the bus of the private power generation facility linked to the power grid, and is opened when a fault such as a voltage drop or power failure occurs in the power grid. A switch for connecting the bus that will be re-entered later,
A bridge connection circuit comprising a full bridge connection of a semiconductor control rectifier element or a mixed bridge connection of the semiconductor control rectifier element and a diode, and between the two buses that are provided between a pair of DC terminals of the circuit and are connected to each other. A first current-limiting reactor for preventing overcurrent, and a pair of AC terminals of the bridge connection circuit are connected to the both buses via the bus-connecting switch; A rectifier type bridge circuit for high-speed shut-off that is turned off prior to opening of the bus contact switch when the failure occurs based on the point arc extinction control, and turned on after the switch is turned on again;
Bypass provided in a bypass path between the pair of AC terminals and closed only for a short time from when the bus-connecting switch is turned on again until the rectifier bridge circuit is turned on and the grid connection is restored A switch for opening and closing the road;
And a second reactor for short-time rating current limiting, which is connected to the bypass path switching switch in series and provided in the bypass path to prevent an overcurrent of the bypass path. Grid interconnection device.