JP3979278B2

JP3979278B2 - Grid-connected inverter device

Info

Publication number: JP3979278B2
Application number: JP2002349045A
Authority: JP
Inventors: 博昭小新; 潔後藤; 信一郎岡本; 晃吉武
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 2002-11-29
Filing date: 2002-11-29
Publication date: 2007-09-19
Anticipated expiration: 2022-11-29
Also published as: JP2004187362A

Description

【０００１】
【発明の属する技術分野】
本発明は、太陽電池や燃料電池などの直流電源を交流に変換して商用系統と連系する系統連系インバータ装置に関するものである。
【０００２】
【従来の技術】
従来より、太陽電池や燃料電池などの直流電源を交流に変換し、商用系統（商用交流電源）と連系して負荷に電力を供給する系統連系インバータ装置が提供されている。
【０００３】
図６はこのような系統連系インバータ装置を利用した太陽電池発電システムの一例を示す図で、この発電システムは、日射量に応じた直流電力を得る太陽電池１、この太陽電池１からの直流電力を交流電力に変換する系統連系インバータ装置２、及び商用系統３０により構成され、これら系統連系インバータ装置２と商用系統３０との間に接続された負荷（図示せず）に対して、系統連系インバータ装置２及び商用系統３０の連系運転と商用系統３０のみの単独運転とのいずれか一方に切り替えて交流電力を供給するものである（例えば特許文献１参照）。
【０００４】
系統連系インバータ装置２は、太陽電池１の出力電圧を昇圧する昇圧回路４、昇圧回路４の出力を交流電圧に変換する正弦波生成回路５、及び正弦波生成回路５の出力を平滑して出力波形を正弦波状の波形とするフィルタ回路６からなるインバータ回路部３と、インバータ回路部３と商用系統３０との間に直列に接続された解列開閉器７ａ，７ｂと、マイクロコンピュータからなりインバータ回路部３の各スイッチ素子にオン／オフ信号を与える制御回路８とで構成される。昇圧回路４では、日射量に応じて０Ｖ〜３００Ｖ程度の範囲内で絶えず変動する太陽電池１の出力電圧を３５０Ｖ程度まで昇圧しており、この昇圧された直流電圧を入力として正弦波生成回路５でＰＷＭ制御を行って交流電圧に変換した後、フィルタ回路６で正弦波生成回路５の出力に含まれるＰＷＭキャリア周波数のリップル成分を平滑することにより正弦波状の交流電圧に変換して出力するものである。
【０００５】
昇圧回路４は、太陽電池１の正極側に一端が接続されるリアクトル４１と、このリアクトル４１の他端にコレクタが接続されエミッタが太陽電池１の負極側に接続されるＩＧＢＴのようなスイッチ素子４２と、このスイッチ素子４２のコレクタにアノードが接続されるダイオード４３と、このダイオード４３のカソードとスイッチ素子４２のエミッタとの間に接続されるコンデンサ４４とで、１石式昇圧チョッパとして構成される。昇圧回路４の出力電圧は図示しない電圧検出器によって検出され、その検出信号が制御回路８に入力されており、制御回路８で演算処理を行って決定したデューティ比のパルス信号がスイッチ素子４２のゲートに与えられ、昇圧回路４の出力電圧が所定の一定電圧に制御される。
【０００６】
正弦波生成回路５は、ＩＧＢＴのようなスイッチ素子５１〜５４をフルブリッジ接続して構成され、制御回路８のＰＷＭ制御にしたがって各スイッチ素子５１〜５４をスイッチングして、昇圧回路４からの直流電力を交流電力に変換するものである。
【０００７】
フィルタ回路６は、直列接続されたスイッチ素子５１，５２の接続点に一端が接続されたリアクトル６１と、直列接続されたスイッチ素子５３，５４の接続点に一端が接続されたリアクトル６２と、これらリアクトル６１，６２の他端間に接続されたコンデンサ６３とで構成されるＬＣフィルタからなり、ＰＷＭキャリア周波数のリップル成分を平滑して、正弦波生成回路５の出力を正弦波状の電流波形に平滑し、商用系統３０に出力するものである。
【０００８】
解列開閉器７ａ，７ｂは、それぞれ制御回路８からの制御信号によってオン／オフが制御されるリレー等で構成され、インバータ回路部３と商用系統３０との間に接続されて、インバータ回路部３と商用系統３０との間を連系乃至解列するものである。
【０００９】
【特許文献１】
特開平９−２１５２０５号公報（第３頁−第４頁、及び、第１図）
【００１０】
【発明が解決しようとする課題】
上述した系統連系インバータ装置２では、制御回路８が解列開閉器７ａ，７ｂのオン／オフを制御しており、停電などによって商用系統３０側の系統電圧に異常が発生した場合や、系統連系インバータ装置２自身に故障などの異常が発生した場合や、ユーザーの操作によって運転動作が停止された場合などに解列開閉器７ａ，７ｂをオフにして、インバータ回路部３を商用系統３０から解列し、安全性を確保している。
【００１１】
しかしながら、解列開閉器７ａ，７ｂに用いるリレーで異常電流や接点寿命により接点の溶着現象が発生すると、制御回路８からの制御信号を受けてもインバータ回路部３を解列できないような状況が発生する可能性がある。このような解列開閉器７ａ，７ｂの故障による安全性の低下を回避するために、従来の系統連系インバータ装置２では、資源エネルギー庁から提示されているガイドラインに示されるように、解列開閉器７ａ，７ｂを２台直列に接続して用いる方式が広く採用されている。
【００１２】
このように従来の系統連系インバータ装置２では、解列開閉器の故障による安全性の低下を回避するために、複数台の解列開閉器を直列に接続しているので、解列開閉器の台数が増えてコスト高になるという問題があった。また、１台の解列開閉器が故障する確立よりは低いものの、２台の解列開閉器が同時に溶着する可能性もあり、そのままの状態で系統連系インバータ装置２が運転を開始してしまう虞もあった。
【００１３】
本発明は上記問題点に鑑みて為されたものであり、その目的とするところは、連系運転を開始する前に解列開閉器の異常を検知して、連系運転を中止することのできる低コストの系統連系インバータ装置を提供することにある。
【００１４】
【課題を解決するための手段】
上記目的を達成するために、請求項１の発明では、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する電圧検出部と、電圧検出部の検出結果から求めた端子間電圧の実効値が商用電源電圧の実効値と略同じであるか否かを判定する実効値判定部と、電圧検出部の検出した端子間電圧を商用系統の電源周期の自然数倍の期間積算した結果が略ゼロになるか否かを判定する積算値判定部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、電圧検出部の検出した端子間電圧をもとに解列開閉器が正常か否かを判断し、異常と判断した場合は連系運転を中止しており、制御回路部は、端子間電圧の実効値が商用電源電圧の実効値と略同じであると実効値判定部が判定し、且つ、端子間電圧を積算した結果が略ゼロであると積算値判定部が判定すると、解列開閉器が異常であると判断することを特徴とする。
【００１７】
請求項２の発明では、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する電圧検出部と、電圧検出部の検出結果から零クロス点を検出する零クロス検出部と、当該零クロス検出部が零クロス点を検出する時間間隔から求めた周波数が商用系統の電源周波数に一致しているか否かを判定する周波数判定部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、電圧検出部の検出した端子間電圧をもとに解列開閉器が正常か否かを判断し、異常と判断した場合は連系運転を中止しており、制御回路部は、零クロス点の検出間隔から求めた周波数が電源周波数に一致していると周波数判定部が判定すると、解列開閉器の異常と判断することを特徴とする。
【００１８】
請求項３の発明では、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する電圧検出部と、電圧検出部の検出結果から求めた端子間電圧の実効値が商用電源電圧の実効値と略同じであるか否かを判定する実効値判定部と、電圧検出部の検出結果から零クロス点を検出する零クロス検出部と、当該零クロス検出部が零クロス点を検出する時間間隔から求めた周波数が、電源周波数よりも低い所定の基準周波数以上であるか否かを判定する周波数判定部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、電圧検出部の検出した端子間電圧をもとに解列開閉器が正常か否かを判断し、異常と判断した場合は連系運転を中止しており、制御回路部は、端子間電圧の実効値が商用電源電圧の実効値と略同じであると実効値判定部が判定し、且つ、零クロス点の検出間隔から求めた周波数が基準周波数以上であると周波数判定部が判定すると、解列開閉器が異常であると判断することを特徴とする。
【００１９】
請求項４の発明では、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する第１の電圧検出部と、解列開閉器における商用系統側の端子間電圧を検出する第２の電圧検出部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、第１の電圧検出部の検出結果と第２の電圧検出部の検出結果との高低を比較し、第１及び第２の電圧検出部の検出結果が略同じであれば解列開閉器の異常と判断して、連系運転を中止することを特徴とする。
【００２０】
【発明の実施の形態】
本発明の実施の形態を図面に基づいて説明する。
【００２１】
（参考例）
本発明に係る系統連系インバータ装置を用いる太陽電池発電システムの参考例のブロック図を図１に示す。この発電システムは、日射量に応じた直流電力を得る太陽電池１、この太陽電池１からの直流電力を交流電力に変換する系統連系インバータ装置２、及び商用系統３０により構成され、これら系統連系インバータ装置２と商用系統３０との間に接続された負荷（図示せず）に対して、系統連系インバータ装置２及び商用系統３０の連系運転と商用系統３０のみの単独運転とのいずれか一方に切り替えて交流電力を供給するものである。尚、基本的な構成は従来の系統連系インバータ装置と同様であるので、共通する構成要素には同一の符号を付して、その説明は省略する。
【００２２】
系統連系インバータ装置２は、例えば１石式の昇圧チョッパからなり太陽電池１の出力電圧をスイッチ素子でスイッチングすることによって所定の一定電圧に昇圧する昇圧回路４、スイッチ素子をブリッジ接続して構成され昇圧回路４の出力を交流電圧に変換する正弦波生成回路５、及び正弦波生成回路５の出力を平滑して出力波形を正弦波状の波形とするＬＣフィルタのようなフィルタ回路６からなるインバータ回路部３と、インバータ回路部３と商用系統３０との間に直列に接続された解列開閉器７と、マイクロコンピュータからなりインバータ回路部３の各スイッチ素子にオン／オフ信号を与えるとともに、解列開閉器７のオン／オフを制御する制御回路８（制御回路部）とで構成される。
【００２３】
昇圧回路４は、日射量に応じて０Ｖ〜３００Ｖ程度の範囲内で絶えず変動する太陽電池１の出力電圧を３５０Ｖ程度まで昇圧しており、この昇圧された直流電圧を入力として正弦波生成回路５でＰＷＭ制御を行った後、フィルタ回路６で正弦波生成回路５の出力に含まれるＰＷＭキャリア周波数のリップル成分を平滑することにより正弦波状の交流電圧に変換して出力している。
【００２４】
解列開閉器７は、制御回路８からの制御信号によってオン／オフが制御されるリレー等で構成され、インバータ回路部３と商用系統３０との間に接続されて、インバータ回路部３（昇圧回路４、正弦波生成回路５、及びフィルタ回路６からなる）と商用系統３０との間を連系乃至解列するものである。そして、この解列開閉器７のインバータ回路部３側、及び、商用系統３０側の端子間にはそれぞれ電圧検出器９，１０が接続されている。
【００２５】
電圧検出器１０は、解列開閉器７における商用系統３０側の端子間電圧を検出するものであり、その検出信号は制御回路８に入力される。制御回路８は、電圧検出器１０の検出信号をもとに、停電等により発生する系統電圧の過電圧、電圧低下、周波数異常などの系統異常状態の有無を判断し、系統異常状態を検出すると解列開閉器７を遮断するとともに、インバータ回路部３の動作を停止させ、例えば液晶ディスプレイからなるモニタ１１に異常情報を表示させる。
【００２６】
また、電圧検出部たる電圧検出器９は、解列開閉器７におけるインバータ回路部３側の端子間電圧を検出しており、その検出信号は制御回路８に入力されている。
【００２７】
ここで、制御回路８は、インバータ回路部３の動作を停止させるとともに解列開閉器７をオフにした連系運転を開始する直前の状態において、電圧検出器９の検出結果を取り込み、電圧検出器９の検出した端子間電圧と所定のしきい値との高低を比較している。そして、解列開閉器７をオンさせる信号が入力されていないにも関わらず、電圧検出器９の端子間電圧が所定のしきい値よりも高ければ、制御回路８は、解列開閉器７に接点溶着などの異常が発生したと判断して、インバータ回路部３を停止状態にし、連系運転を中止するとともに、異常情報をモニタ１１に表示させる。
【００２８】
このように、本参考例では連系運転を開始する直前の状態で、解列開閉器７におけるインバータ回路部３側の端子間電圧を電圧検出器９で検出し、電圧検出器９で検出された端子間電圧をもとに解列開閉器７の動作が正常か否かを判断し、異常と判断した場合は連系運転を中止しているので、解列開閉器７が異常な状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように、解列開閉器７が異常な状態で連系運転が開始されるのを防止するために、複数台の解列開閉器を直列に接続する必要がなく、解列開閉器７の台数が１台で済むので、系統連系インバータ装置のコストダウンを図ることができる。また、後述する実施形態４のように、解列開閉器７のインバータ回路部３側及び商用系統３０側の端子間電圧をそれぞれ検出して、それらの検出結果を比較する場合に比べて、電圧検出器の数が１つで済むという利点もある。
【００２９】
（実施形態１）
本発明の実施形態１を図２に基づいて説明する。尚、系統連系インバータ装置の主回路の構成は上述の参考例と同様であるので、共通する構成要素には同一の符号を付して、その説明は省略する。
【００３０】
本実施形態では、参考例で説明した系統連系インバータ装置において、電圧検出器９の検出信号をもとに解列開閉器７の端子間電圧の実効値を求める実効値検出部１２と、実効値検出部１２の検出した実効値と所定の基準レベルとの高低を判定する実効値判定部１３と、電圧検出器９の検出した端子間電圧を商用系統３０の電源周期の自然数倍の期間（本実施形態では例えば一周期の間）積算する積算部１４と、積算部１４の積算結果が略ゼロになるか否かを判定する積算値判定部１５と、実効値判定部１３の判定結果と積算値判定部１５の判定結果との論理積を求めるＡＮＤゲート１６とを設けており、制御回路８はＡＮＤゲート１６の出力信号をもとに解列開閉器７の異常の有無を判別している。
【００３１】
実効値判定部１３は、実効値検出部１２の出力と所定の基準レベルＶ１との高低を比較するコンパレータＣＰ１からなり、実効値検出部１２の出力が基準レベルＶ１を上回るとコンパレータＣＰ１の出力はハイになる。ここで、基準レベルＶ１は商用系統３０の電源電圧の実効値レベルに対応した電圧値に設定されており、実効値検出部１２の出力が商用系統３０の電源電圧の実効値レベルであれば、コンパレータＣＰ１の出力はハイになる。
【００３２】
積算値判定部１５は、積算部１４の出力と所定の基準レベルＶ２との高低を比較するコンパレータＣＰ２と、積算部１４の出力と所定の基準レベルＶ３との高低を比較するコンパレータＣＰ３と、コンパレータＣＰ２，ＣＰ３の出力の論理積を出力するＡＮＤゲート１５ａとで構成される。ここで、積算部１４の出力が基準レベルＶ２よりも低ければコンパレータＣＰ２の出力はハイに、積算部１４の出力が基準レベル（−Ｖ３）よりも高ければコンパレータＣＰ３の出力はハイになる。尚、基準レベルＶ２はゼロボルト付近の正の電圧値に、（−Ｖ３）はゼロボルト付近の負の電圧値にそれぞれ設定されている。而して、積算部１４の出力が基準レベルＶ２よりも低く、且つ、基準レベル（−Ｖ３）よりも高ければ、つまり解列開閉器７におけるインバータ回路部３側の端子間電圧を電源周期の一周期に亘って積算した結果がゼロレベル付近であれば、積算値判定部１５の出力はハイになる。
【００３３】
ＡＮＤゲート１６には実効値判定部１３の判定結果と積算値判定部１５の判定結果とが入力されており、実効値判定部１３及び積算値判定部１５の出力が共にハイになると、すなわち実効値検出部１２の出力が基準レベルＶ１を上回り、且つ、積算部１４の出力がゼロ付近になると、ＡＮＤゲート１６の出力はハイになる。
【００３４】
ここで、制御回路８は、インバータ回路部３の動作を停止させるとともに解列開閉器７をオフにした連系運転を開始する直前の状態において、ＡＮＤゲート１６の出力を取り込み、この出力をもとに解列開閉器７が正常か否かを判断している。そして、解列開閉器７をオンさせる信号が入力されていないにも関わらず、ＡＮＤゲート１６の出力がハイになっていると、つまり実効値検出部１２が検出した端子間電圧の実効値が商用電源電圧の実効値に略等しくなり、且つ、端子間電圧を電源周期の自然数倍した期間積算した結果が略ゼロになると、制御回路８は、解列開閉器７に接点溶着などの異常が発生したと判断して、インバータ回路部３を停止状態にし、連系運転を中止するとともに、異常情報をモニタ１１に表示させる。
【００３５】
このように、本実施形態では連系運転を開始する直前の状態で、解列開閉器７におけるインバータ回路部３側の端子間電圧を電圧検出器９で検出し、電圧検出器９で検出された端子間電圧をもとに解列開閉器７の動作が正常か否かを判断し、異常と判断した場合は連系運転を中止しているので、解列開閉器７が異常な状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように、解列開閉器７が異常な状態で連系運転が開始されるのを防止するために、複数台の解列開閉器を直列に接続する必要がなく、解列開閉器７の台数が１台で済むので、系統連系インバータ装置のコストダウンを図ることができる。
【００３６】
（実施形態２）
本発明の実施形態２を図３に基づいて説明する。尚、系統連系インバータ装置の主回路の構成は上述の参考例と同様であるので、共通する構成要素には同一の符号を付して、その説明は省略する。
【００３７】
本実施形態では、参考例で説明した系統連系インバータ装置において、電圧検出器９の検出信号をもとに零クロス点を検出する零クロス検出部１７と、零クロス検出部１７が零クロス点を検出する時間間隔から求めた周波数が、商用系統３０の電源周波数（５０又は６０Ｈｚ）と略同じか否かを判定する周波数判定部１８とを設けている。
【００３８】
零クロス検出部１７は、電圧検出器９の検出信号の正負を判定するコンパレータＣＰ４からなり、解列開閉器７の端子間電圧の零クロス点の前後では、コンパレータＣＰ４の出力がハイからロー、或いはローからハイに反転する。而して、周波数判定部１８では、零クロス検出部１７の出力のハイ／ローをもとに零クロス点を検出する時間間隔を求めることができ、この時間間隔から求めた周波数が電源周波数に一致するか否かを判定して、その判定結果を制御回路８に出力している。
【００３９】
ここで、制御回路８は、インバータ回路部３の動作を停止させるとともに解列開閉器７をオフにした連系運転を開始する直前の状態において、周波数判定部１８の判定結果を取り込み、この判定結果をもとに解列開閉器７が正常か否かを判断しており、解列開閉器７をオンさせる信号が入力されていないにも関わらず、解列開閉器７におけるインバータ回路部３側の端子間電圧の周波数が商用系統３０の電源周波数に略一致していれば、解列開閉器７に接点溶着などの異常が発生していると判断して、インバータ回路部３を停止状態にし、連系運転を中止するとともに、異常情報をモニタ１１に表示させる。
【００４０】
このように、本実施形態では連系運転を開始する直前の状態で、解列開閉器７におけるインバータ回路部３側の端子間電圧を電圧検出器９で検出し、電圧検出器９で検出された端子間電圧をもとに解列開閉器７の動作が正常か否かを判断し、異常と判断した場合は連系運転を中止しているので、解列開閉器７が異常な状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように、解列開閉器７が異常な状態で連系運転が開始されるのを防止するために、複数台の解列開閉器を直列に接続する必要がなく、解列開閉器７の台数が１台で済むので、系統連系インバータ装置のコストダウンを図ることもできる。また、本実施形態では、実施形態１又は参考例のように電圧検出器９で検出した端子間電圧の電圧レベルや実効値レベルの判定を行っていないので、電圧レベルや実効値レベルの判定に用いる基準レベルの管理が不要になり、解列開閉器７の異常を判定する回路部分の構成を簡単にできる。
【００４１】
（実施形態３）
本発明の実施形態３を図４に基づいて説明する。尚、系統連系インバータ装置の主回路の構成は上述の参考例と同様であるので、共通する構成要素には同一の符号を付して、その説明は省略する。
【００４２】
本実施形態では、参考例で説明した系統連系インバータ装置において、電圧検出器９の検出信号をもとに零クロス点を検出する零クロス検出部１７と、零クロス検出部１７が零クロス点を検出する時間間隔から求めた周波数が所定の基準周波数（例えば３０Ｈｚ）以上であるか否かを判定する周波数判定部１９と、電圧検出器９の検出信号をもとに解列開閉器７の端子間電圧の実効値を求める実効値検出部１２と、実効値検出部１２の検出した実効値と所定の基準レベルとの高低を判定する実効値判定部１３と、周波数判定部１９の判定結果と実効値判定部１３の判定結果との論理積を求めるＡＮＤゲート２０とを設けており、制御回路８はＡＮＤゲート２０の出力信号をもとに解列開閉器７の異常の有無を判別している。
【００４３】
零クロス検出部１７は、電圧検出器９の検出信号の正負を判定するコンパレータＣＰ４からなり、解列開閉器７の端子間電圧の零クロス点の前後では、コンパレータＣＰ４の出力がハイからロー、或いはローからハイに反転する。而して、周波数判定部１９では、零クロス検出部１７の出力をもとに零クロス点を検出する時間間隔を求めることができ、この時間間隔から求めた周波数が所定の基準周波数以上であるか否かを判定して、その判定結果をＡＮＤゲート２０に出力する。尚、基準周波数としては商用周波数である５０Ｈｚ以下の値であれば、検出時限に応じた適宜の値に設定することができ、零クロス点の検出間隔から求めた周波数が基準周波数以上であれば周波数判定部１９の出力はハイに、基準周波数未満であれば周波数判定部１９の出力はローになる。
【００４４】
実効値判定部１３は、実効値検出部１２の出力と所定の基準レベルＶ１との高低を比較するコンパレータＣＰ１からなり、実効値検出部１２の出力が基準レベルＶ１を上回るとコンパレータＣＰ１の出力はハイになる。なお、基準レベルＶ１は商用系統３０の実効値レベルに対応した電圧に設定されており、実効値検出部１２の検出した端子間電圧の実効値が商用電源電圧の実効値レベルであれば、コンパレータＣＰ１の出力はハイになる。
【００４５】
ＡＮＤゲート２０には周波数判定部１９の出力と実効値判定部１３の出力とが入力されており、周波数判定部１９及び実効値判定部１３の出力が共にハイになると、すなわち零クロス点の検出間隔から求めた周波数が基準周波数以上であり、且つ、実効値検出部１２の出力が基準レベルＶ１を上回ると、ＡＮＤゲート１６の出力はハイになる。
【００４６】
ここで、制御回路８は、インバータ回路部３の動作を停止させるとともに解列開閉器７をオフにした連系運転を開始する直前の状態において、ＡＮＤゲート２０の出力を取り込み、この出力をもとに解列開閉器７が正常か否かを判断している。そして、解列開閉器７をオンさせる信号が入力されていないにも関わらず、ＡＮＤゲート２０の出力がハイになっていると、つまり零クロス点の検出間隔から求めた周波数が基準周波数以上であり、且つ、実効値検出部１２の検出した端子間電圧の実効値が商用電源電圧の実効値レベルであると、制御回路８は、解列開閉器７に接点溶着などの異常が発生して、インバータ回路部３側の端子間に商用系統３０の電源電圧が現れたものと判断し、インバータ回路部３を停止状態にして、連系運転を中止するとともに、異常情報をモニタ１１に表示させる。
【００４７】
このように、本実施形態では連系運転を開始する直前の状態で、解列開閉器７におけるインバータ回路部３側の端子間電圧を電圧検出器９で検出し、電圧検出器９で検出された端子間電圧をもとに解列開閉器７の動作が正常か否かを判断し、異常と判断した場合は連系運転を中止しているので、解列開閉器７が異常な状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように、解列開閉器７が異常な状態で連系運転が開始されるのを防止するために、複数台の解列開閉器を直列に接続する必要がなく、解列開閉器７の台数が１台で済むので、系統連系インバータ装置のコストダウンを図ることができる。また本実施形態では、実施形態２に比べて、電圧検出器９で検出した端子間電圧の実効値レベルを判定する回路が必要になるものの、実効値レベルの判定に用いる基準レベルや基準周波数の設定が大まかでよいので、設定作業を簡略化できるという効果がある。
【００４８】
（実施形態４）
本発明の実施形態４を図５に基づいて説明する。尚、系統連系インバータ装置の主回路の構成は上述した参考例と同様であるので、共通する構成要素には同一の符号を付して、その説明は省略する。
【００４９】
上述の実施形態１〜３及び参考例では、電圧検出器９を用いて解列開閉器７におけるインバータ回路部３側の端子間電圧を検出し、この検出信号のみから解列開閉器７が正常か否かを判定しているのに対して、本実施形態では、第１の電圧検出部たる電圧検出器９で解列開閉器７におけるインバータ回路部３側の端子間電圧を検出するとともに、第２の電圧検出部たる電圧検出器１０で解列開閉器７における商用系統３０側の端子間電圧を検出し、両電圧検出器９，１０の検出信号をもとに解列開閉器７が正常か否かを判定している。
【００５０】
すなわち、電圧検出器９の出力と電圧検出器１０の出力との差分を求める差動増幅器２１を設け、制御回路８が、インバータ回路部３の動作を停止させるとともに解列開閉器７をオフにした連系運転を開始する直前の状態において差動増幅器２１の出力を取り込み、この出力をもとに解列開閉器７が正常か否かを判断している。そして、解列開閉器７をオンさせる信号が入力されていないにも関わらず、差動増幅器２１の出力が略ゼロになる状態（電圧検出器９の出力と電圧検出器１０の出力とが略同じになる状態）が一定時間継続すると、制御回路８は、解列開閉器７で接点溶着などの異常が発生してインバータ回路部３側の端子間に商用系統３０の電源電圧が現れたものと判断し、インバータ回路部３を停止状態にして、連系運転を中止するとともに、異常情報をモニタ１１に表示させる。
【００５１】
上述の実施形態１〜３及び参考例のように電圧検出器９で検出したインバータ回路部３側の端子間電圧のみから、解列開閉器７が正常か否かを判定している場合には、判定以前にインバータ回路部３が動作していると、フィルタ回路６を構成するコンデンサに電圧が残っている可能性があり、解列開閉器７を遮断していてもこの残留電圧を電圧検出器９が検出することで誤検出する虞があるが、本実施形態では電圧検出器９，１０により解列開閉器７の両側の端子間電圧を検出して、両者が一致するか否かを判定しているので、残留電圧を検出することによる誤検知を防止できる。
【００５２】
尚、上述の各実施形態では直流電源として太陽電池１を用い、太陽電池１の出力を昇圧し、昇圧した電圧を交流に変換して商用系統と連系しているが、直流電源を太陽電池１に限定する趣旨のものではなく、燃料電池などの直流電源を用いても良いことは言うまでもない。
【００５３】
【発明の効果】
上述のように、請求項１の発明は、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する電圧検出部と、電圧検出部の検出結果から求めた端子間電圧の実効値が商用電源電圧の実効値と略同じであるか否かを判定する実効値判定部と、電圧検出部の検出した端子間電圧を商用系統の電源周期の自然数倍の期間積算した結果が略ゼロになるか否かを判定する積算値判定部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、電圧検出部の検出した端子間電圧をもとに解列開閉器が正常か否かを判断し、異常と判断した場合は連系運転を中止しており、制御回路部は、端子間電圧の実効値が商用電源電圧の実効値と略同じであると実効値判定部が判定し、且つ、端子間電圧を積算した結果が略ゼロであると積算値判定部が判定すると、解列開閉器が異常であると判断することを特徴とし、解列開閉器の接点が溶着した場合には、解列開閉器におけるインバータ回路部側の端子間に商用系統の電源電圧が現れるので、電圧検出部により検出されたインバータ回路部側の端子間電圧のみから、解列開閉器が正常であるか否かを判定でき、制御回路では解列開閉器が異常と判断すると連系運転を中止しているので、解列開閉器が故障している状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように安全性を確保するために２台の解列開閉器を直列に接続する必要がなく、解列開閉器の個数を減らしてコストダウンを図ることができる。また、解列開閉器のインバータ回路部側及び商用系統側の端子間電圧をそれぞれ検出して、それらの検出結果を比較する場合に比べて、電圧検出部の数が１つで済むという利点もある。
【００５５】
しかも、解列開閉器の接点が溶着した場合には、解列開閉器におけるインバータ回路部側の端子間に商用系統の電源電圧が現れるので、電圧検出部の検出した端子間電圧の実効値が商用電源電圧の実効値と略同じになり、且つ、端子間電圧を電源周期の自然数倍の期間積算した結果が略ゼロになることから、解列開閉器の異常を確実に判別することができる。
【００５６】
請求項２の発明は、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する電圧検出部と、電圧検出部の検出結果から零クロス点を検出する零クロス検出部と、当該零クロス検出部が零クロス点を検出する時間間隔から求めた周波数が商用系統の電源周波数に一致しているか否かを判定する周波数判定部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、電圧検出部の検出した端子間電圧をもとに解列開閉器が正常か否かを判断し、異常と判断した場合は連系運転を中止しており、制御回路部は、零クロス点の検出間隔から求めた周波数が電源周波数に一致していると周波数判定部が判定すると、解列開閉器の異常と判断することを特徴とし、制御回路では解列開閉器が異常と判断すると連系運転を中止しているので、解列開閉器が故障している状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように安全性を確保するために２台の解列開閉器を直列に接続する必要がなく、解列開閉器の個数を減らしてコストダウンを図ることができる。また、解列開閉器のインバータ回路部側及び商用系統側の端子間電圧をそれぞれ検出して、それらの検出結果を比較する場合に比べて、電圧検出部の数が１つで済むという利点もある。しかも解列開閉器の接点が溶着した場合には、解列開閉器におけるインバータ回路部側の端子間に商用系統の電源電圧が現れるので、端子間電圧の零クロス点の検出間隔から求めた周波数が電源周波数に一致することから、解列開閉器の異常を確実に判別することができる。しかも、請求項１の発明のように端子間電圧の電圧レベルを基準値と比較する回路がないので、基準値の設定が不要になり、判定を行う回路の構成を簡単にできる。
【００５７】
請求項３の発明は、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する電圧検出部と、電圧検出部の検出結果から求めた端子間電圧の実効値が商用電源電圧の実効値と略同じであるか否かを判定する実効値判定部と、電圧検出部の検出結果から零クロス点を検出する零クロス検出部と、当該零クロス検出部が零クロス点を検出する時間間隔から求めた周波数が、電源周波数よりも低い所定の基準周波数以上であるか否かを判定する周波数判定部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、電圧検出部の検出した端子間電圧をもとに解列開閉器が正常か否かを判断し、異常と判断した場合は連系運転を中止しており、制御回路部は、端子間電圧の実効値が商用電源電圧の実効値と略同じであると実効値判定部が判定し、且つ、零クロス点の検出間隔から求めた周波数が基準周波数以上であると周波数判定部が判定すると、解列開閉器が異常であると判断することを特徴とし、制御回路では解列開閉器が異常と判断すると連系運転を中止しているので、解列開閉器が故障している状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように安全性を確保するために２台の解列開閉器を直列に接続する必要がなく、解列開閉器の個数を減らしてコストダウンを図ることができる。また、解列開閉器のインバータ回路部側及び商用系統側の端子間電圧をそれぞれ検出して、それらの検出結果を比較する場合に比べて、電圧検出部の数が１つで済むという利点もある。しかも解列開閉器の接点が溶着した場合には、解列開閉器におけるインバータ回路部側の端子間に商用系統の電源電圧が現れるので、電圧検出部の検出した端子間電圧の実効値が商用系統の実効値と略同じになり、且つ、端子間電圧の零クロス点の検出間隔から求めた周波数が基準周波数以上になることから、解列開閉器の異常を確実に判別することができる。さらに、請求項２の発明に比べて端子間電圧の実効値を基準値と比較する部分が増えるものの、判定に用いる基準周波数の設定が大まかで良いので、基準周波数の設定作業が簡単になるという効果もある。
【００５８】
請求項４の発明は、直流電源の直流電力をスイッチ素子でスイッチングすることによって交流電力に変換して商用系統側に供給するインバータ回路部と、インバータ回路部と商用系統との間に設けられ、これらインバータ回路部と商用系統との間を連系乃至解列する解列開閉器と、スイッチ素子のオン／オフを制御してインバータ回路部の出力を制御するとともに、解列開閉器のオン／オフを制御してインバータ回路部を連系乃至解列する制御回路部と、解列開閉器におけるインバータ回路部側の端子間電圧を検出する第１の電圧検出部と、解列開閉器における商用系統側の端子間電圧を検出する第２の電圧検出部とを備え、制御回路部は、インバータ回路部を停止させるとともに解列開閉器をオフにした連系運転を開始する直前の状態において、第１の電圧検出部の検出結果と第２の電圧検出部の検出結果との高低を比較し、第１及び第２の電圧検出部の検出結果が略同じであれば解列開閉器の異常と判断して、連系運転を中止することを特徴とし、解列開閉器の接点が溶着した場合には、解列開閉器におけるインバータ回路部側の端子間に商用系統の電源電圧が現れるので、第１及び第２の電圧検出部により検出されたインバータ回路部側の端子間電圧と商用系統側の端子間電圧とをもとに、解列開閉器が正常であるか否かを判定でき、制御回路は解列開閉器が異常であると判断すると連系運転を中止しているので、解列開閉器が故障している状態で連系運転が開始されるのを防止できる。したがって、従来の系統連系インバータ装置のように安全性を確保するために２台の解列開閉器を直列に接続する必要がなく、解列開閉器の個数を減らしてコストダウンを図ることができる。また、制御回路が、解列開閉器におけるインバータ回路部側の端子間電圧のみから解列開閉器が正常か否かを判定する場合は、判定以前にインバータ回路部が動作してインバータ回路部側の端子間に電圧が残っていると、この残存電圧を誤検出する虞があるが、第１及び第２の電圧検出部により検出されたインバータ回路部側の端子間電圧と商用系統側の端子間電圧が略同じであれば、解列開閉器が異常であると判定しているので、残存電圧による誤検出を防止できる。
【図面の簡単な説明】
【図１】参考例の系統連系インバータ装置を用いた太陽電池発電システムのブロック図である。
【図２】実施形態１の系統連系インバータ装置の要部を示すブロック図である。
【図３】実施形態２の系統連系インバータ装置の要部を示すブロック図である。
【図４】実施形態３の系統連系インバータ装置の要部を示すブロック図である。
【図５】実施形態４の系統連系インバータ装置の要部を示すブロック図である。
【図６】従来の系統連系インバータ装置を用いた太陽電池発電システムのブロック回路図である。
【符号の説明】
１太陽電池
２系統連系インバータ装置
３インバータ回路部
４昇圧回路
５正弦波生成回路
６フィルタ回路
７解列開閉器
８制御回路
９電圧検出器
３０商用系統[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a grid-connected inverter device that converts a DC power source such as a solar cell or a fuel cell into AC and links it to a commercial system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there is provided a grid-connected inverter device that converts a DC power source such as a solar cell or a fuel cell into AC and links the commercial power source (commercial AC power source) to supply power to a load.
[0003]
FIG. 6 is a diagram showing an example of a solar battery power generation system using such a grid-connected inverter device. This power generation system includes a solar battery 1 that obtains direct current power corresponding to the amount of solar radiation, and a direct current from the solar battery 1. Consists of a grid-connected inverter device 2 that converts electric power into AC power and a commercial system 30, and for a load (not shown) connected between the grid-connected inverter device 2 and the commercial system 30, The AC power is supplied by switching to either one of the grid-connected inverter device 2 and the commercial system 30 and the single operation of the commercial system 30 (see, for example, Patent Document 1).
[0004]
The grid interconnection inverter device 2 smoothes the output of the booster circuit 4 that boosts the output voltage of the solar cell 1, the sine wave generation circuit 5 that converts the output of the booster circuit 4 into an alternating voltage, and the sine wave generation circuit 5. It comprises an inverter circuit unit 3 composed of a filter circuit 6 whose output waveform is a sinusoidal waveform, disconnecting switches 7a and 7b connected in series between the inverter circuit unit 3 and the commercial system 30, and a microcomputer. And a control circuit 8 for supplying an on / off signal to each switch element of the inverter circuit section 3. In the booster circuit 4, the output voltage of the solar cell 1 that constantly fluctuates in the range of about 0 V to 300 V depending on the amount of solar radiation is boosted to about 350 V, and the sine wave generating circuit 5 is input with this boosted DC voltage as an input. After the PWM control is performed and converted to an AC voltage, the filter circuit 6 smoothes the ripple component of the PWM carrier frequency included in the output of the sine wave generation circuit 5 to convert it into a sine wave AC voltage and output it. It is.
[0005]
The booster circuit 4 includes a reactor 41 having one end connected to the positive electrode side of the solar cell 1 and a switching element such as an IGBT having a collector connected to the other end of the reactor 41 and an emitter connected to the negative electrode side of the solar cell 1. 42, a diode 43 whose anode is connected to the collector of the switch element 42, and a capacitor 44 connected between the cathode of the diode 43 and the emitter of the switch element 42, constitute a one-stone boost chopper. The The output voltage of the booster circuit 4 is detected by a voltage detector (not shown), and the detection signal is input to the control circuit 8. A pulse signal having a duty ratio determined by performing arithmetic processing in the control circuit 8 is supplied to the switch element 42. Given to the gate, the output voltage of the booster circuit 4 is controlled to a predetermined constant voltage.
[0006]
The sine wave generation circuit 5 is configured by full-bridge connection of switch elements 51 to 54 such as IGBTs, and switches each of the switch elements 51 to 54 according to the PWM control of the control circuit 8 so as to generate a direct current from the booster circuit 4. It converts power into AC power.
[0007]
The filter circuit 6 includes a reactor 61 having one end connected to a connection point of the switch elements 51 and 52 connected in series, a reactor 62 having one end connected to a connection point of the switch elements 53 and 54 connected in series, It consists of an LC filter composed of a capacitor 63 connected between the other ends of the reactors 61 and 62, smoothes the ripple component of the PWM carrier frequency, and smoothes the output of the sine wave generation circuit 5 into a sinusoidal current waveform. And output to the commercial system 30.
[0008]
The disconnection switches 7a and 7b are each configured by a relay or the like whose on / off is controlled by a control signal from the control circuit 8, and is connected between the inverter circuit unit 3 and the commercial system 30 to be connected to the inverter circuit unit. 3 and commercial system 30 are connected or disconnected.
[0009]
[Patent Document 1]
JP-A-9-215205 (pages 3 to 4 and FIG. 1)
[0010]
[Problems to be solved by the invention]
In the grid-connected inverter device 2 described above, the control circuit 8 controls on / off of the disconnecting switches 7a and 7b, and when the abnormality occurs in the system voltage on the commercial system 30 side due to a power failure or the like, When an abnormality such as a failure occurs in the interconnection inverter device 2 itself, or when the operation is stopped by a user operation, the disconnect switches 7a and 7b are turned off, and the inverter circuit unit 3 is connected to the commercial system 30. To ensure safety.
[0011]
However, if contact welding occurs due to abnormal current or contact life in the relays used for the disconnect switches 7a and 7b, there is a situation in which the inverter circuit unit 3 cannot be disconnected even if a control signal is received from the control circuit 8. May occur. In order to avoid such a decrease in safety due to the failure of the disconnection switches 7a and 7b, the conventional grid-connected inverter device 2 is disconnected as shown in the guidelines presented by the Agency for Natural Resources and Energy. A system in which two switches 7a and 7b are connected in series is widely used.
[0012]
As described above, in the conventional grid-connected inverter device 2, in order to avoid a decrease in safety due to a failure of the disconnection switch, a plurality of disconnection switches are connected in series. There was a problem that the number of units increased and the cost increased. In addition, although it is lower than the probability that one disconnect switch will fail, two disconnect switches may be welded at the same time, and the grid-connected inverter device 2 starts operation in that state. There was also a risk of it.
[0013]
The present invention has been made in view of the above problems, and the object of the present invention is to detect an abnormality of the disconnection switch before starting the interconnection operation and to stop the interconnection operation. An object of the present invention is to provide a low-cost grid-connected inverter device.
[0014]
[Means for Solving the Problems]
  In order to achieve the above object, according to the first aspect of the present invention, an inverter circuit unit that converts DC power of a DC power source into AC power by switching with a switching element and supplies the AC power to the commercial system side, Controlling the output of the inverter circuit unit by controlling the on / off of the switch element and the disconnecting switch provided between the system and linking or disconnecting between the inverter circuit unit and the commercial system A control circuit unit for connecting or disconnecting the inverter circuit unit by controlling on / off of the disconnection switch; and a voltage detection unit for detecting a voltage between terminals on the inverter circuit unit side in the disconnection switch;The effective value determination unit for determining whether the effective value of the inter-terminal voltage obtained from the detection result of the voltage detection unit is substantially the same as the effective value of the commercial power supply voltage, and the inter-terminal voltage detected by the voltage detection unit An integrated value determination unit that determines whether or not the result of integration for a period that is a natural number times the power cycle of the commercial system is substantially zero;The control circuit unit is connected and disconnected based on the voltage between the terminals detected by the voltage detection unit immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If the vessel is normal or notIn the control circuit unit, the effective value determination unit determines that the effective value of the inter-terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the result of integrating the inter-terminal voltage is substantially zero. And the integrated value determination unit determines that the disconnect switch is abnormal.It is characterized by that.
[0017]
  Claim2In the invention ofAn inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. A control circuit unit that interconnects or disconnects the unit, a voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch,Whether or not the zero cross detection unit that detects the zero cross point from the detection result of the voltage detection unit and the frequency obtained from the time interval at which the zero cross detection unit detects the zero cross point matches the power supply frequency of the commercial system A frequency determination unit for determiningThe control circuit unit is connected and disconnected based on the voltage between the terminals detected by the voltage detection unit immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If it is determined that the vessel is normal or not, the grid operation is stopped.The control circuit unit determines that the disconnection switch is abnormal when the frequency determination unit determines that the frequency obtained from the zero-crossing point detection interval matches the power supply frequency.
[0018]
  Claim3In the invention ofAn inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. A control circuit unit that interconnects or disconnects the unit, a voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch,An effective value determination unit that determines whether or not the effective value of the inter-terminal voltage obtained from the detection result of the voltage detection unit is substantially the same as the effective value of the commercial power supply voltage, and a zero cross point from the detection result of the voltage detection unit A zero cross detection unit for detecting, and a frequency determination unit for determining whether or not a frequency obtained from a time interval at which the zero cross detection unit detects a zero cross point is equal to or higher than a predetermined reference frequency lower than the power supply frequency;The control circuit unit is connected and disconnected based on the voltage between the terminals detected by the voltage detection unit immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If it is determined that the vessel is normal or not, the grid operation is stopped.The control circuit unit determines that the effective value determination unit determines that the effective value of the inter-terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the frequency obtained from the detection interval of the zero cross point is equal to or higher than the reference frequency. When the frequency determination unit determines, the disconnect switch is determined to be abnormal.
[0019]
  Claim4In the invention, the inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switching element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. Disconnection switch that connects or disconnects the power supply unit and the commercial system, and controls the output of the inverter circuit by controlling the on / off of the switch element, and also controls the on / off of the disconnection switch A control circuit unit that interconnects or disconnects the inverter circuit unit, a first voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch, and a commercial system side in the disconnection switch A second voltage detection unit that detects a voltage between the terminals, the control circuit unit is in a state immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off, Compare the detection result of the first voltage detection unit with the detection result of the second voltage detection unit, and if the detection results of the first and second voltage detection units are substantially the same, Judgment is made and the interconnection operation is stopped.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
[0021]
  (Reference example)
  According to the present inventionOf solar power generation system using grid-connected inverter deviceReference exampleA block diagram is shown in FIG. This power generation system includes a solar cell 1 that obtains DC power corresponding to the amount of solar radiation, a grid-connected inverter device 2 that converts DC power from the solar battery 1 into AC power, and a commercial grid 30. For the load (not shown) connected between the system inverter device 2 and the commercial system 30, any of the grid-connected inverter device 2 and the commercial system 30 or the single operation of the commercial system 30 alone One of them is switched to supply AC power. Since the basic configuration is the same as that of a conventional grid-connected inverter device, common components are denoted by the same reference numerals, and description thereof is omitted.
[0022]
The grid-connected inverter device 2 is composed of, for example, a one-stone booster chopper, and a booster circuit 4 that boosts the output voltage of the solar cell 1 to a predetermined constant voltage by switching with the switch element, and the switch elements are bridge-connected. And an inverter composed of a sine wave generation circuit 5 that converts the output of the booster circuit 4 into an alternating voltage, and a filter circuit 6 such as an LC filter that smoothes the output of the sine wave generation circuit 5 and makes the output waveform a sine wave waveform. The circuit unit 3, the disconnection switch 7 connected in series between the inverter circuit unit 3 and the commercial system 30, and an on / off signal to each switch element of the inverter circuit unit 3 made of a microcomputer, It is comprised with the control circuit 8 (control circuit part) which controls ON / OFF of the disconnection switch 7.
[0023]
The booster circuit 4 boosts the output voltage of the solar cell 1 that constantly fluctuates within a range of about 0V to 300V according to the amount of solar radiation to about 350V, and the sine wave generation circuit 5 receives the boosted DC voltage as an input. After the PWM control, the filter circuit 6 smoothes the ripple component of the PWM carrier frequency included in the output of the sine wave generation circuit 5 to convert it into a sine wave AC voltage and output it.
[0024]
The disconnection switch 7 is configured by a relay or the like whose on / off is controlled by a control signal from the control circuit 8, and is connected between the inverter circuit unit 3 and the commercial system 30, and is connected to the inverter circuit unit 3 (boost booster). Circuit 4, sine wave generation circuit 5, and filter circuit 6) and commercial system 30 are connected or disconnected. The voltage detectors 9 and 10 are connected between terminals of the disconnecting switch 7 on the inverter circuit unit 3 side and the commercial system 30 side, respectively.
[0025]
The voltage detector 10 detects a voltage between terminals on the commercial system 30 side in the disconnecting switch 7, and the detection signal is input to the control circuit 8. Based on the detection signal of the voltage detector 10, the control circuit 8 determines the presence or absence of a system abnormal state such as an overvoltage, voltage drop, frequency abnormality, etc. caused by a power failure, etc. The column switch 7 is shut off and the operation of the inverter circuit unit 3 is stopped, and abnormality information is displayed on the monitor 11 formed of, for example, a liquid crystal display.
[0026]
The voltage detector 9 serving as a voltage detector detects a voltage between terminals on the inverter circuit unit 3 side in the disconnecting switch 7, and the detection signal is input to the control circuit 8.
[0027]
Here, the control circuit 8 captures the detection result of the voltage detector 9 in the state immediately before starting the interconnection operation in which the operation of the inverter circuit unit 3 is stopped and the disconnect switch 7 is turned off, and the voltage detection is performed. The voltage between the terminals detected by the device 9 is compared with a predetermined threshold value. If the voltage between the terminals of the voltage detector 9 is higher than a predetermined threshold value even though the signal for turning on the disconnect switch 7 is not input, the control circuit 8 causes the disconnect switch 7 It is determined that an abnormality such as contact welding has occurred, the inverter circuit unit 3 is stopped, the interconnection operation is stopped, and the abnormality information is displayed on the monitor 11.
[0028]
  in this way,Reference exampleIn the state immediately before starting the interconnection operation, the voltage between the terminals on the inverter circuit unit 3 side in the disconnecting switch 7 is detected by the voltage detector 9, and the voltage between the terminals detected by the voltage detector 9 is used as the basis. It is determined whether or not the operation of the disconnect switch 7 is normal. If it is determined that the disconnection switch 7 is abnormal, the connection operation is stopped. Therefore, the disconnect operation 7 is started in an abnormal state. Can be prevented. Therefore, like the conventional grid-connected inverter device, it is necessary to connect a plurality of disconnection switches in series in order to prevent the disconnection switch 7 from starting the connection operation in an abnormal state. Since only one disconnecting switch 7 is required, the cost of the grid-connected inverter device can be reduced. In addition, an embodiment to be described later4Thus, the number of voltage detectors is one as compared with the case where the voltage between the terminals of the inverter circuit unit 3 side and the commercial system 30 side of the disconnecting switch 7 is detected and the detection results thereof are compared. There is also an advantage that it is sufficient.
[0029]
  (Embodiment1)
  Embodiment of the present invention1Will be described with reference to FIG. The main circuit configuration of the grid-connected inverter device isReference example aboveTherefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0030]
  In this embodiment,Explained in the reference exampleIn the grid-connected inverter device, an effective value detection unit 12 that obtains an effective value of the voltage across the terminals of the disconnect switch 7 based on the detection signal of the voltage detector 9, and the effective value detected by the effective value detection unit 12 The effective value determination unit 13 that determines the level of the predetermined reference level, and the terminal voltage detected by the voltage detector 9 is a period that is a natural number times the power cycle of the commercial system 30 (in this embodiment, for example, for one cycle). ) Integration unit 14 for integration, integration value determination unit 15 for determining whether the integration result of integration unit 14 is substantially zero, determination result of effective value determination unit 13 and determination result of integration value determination unit 15 An AND gate 16 for obtaining a logical product of the AND gate 16 is provided, and the control circuit 8 determines whether or not the disconnection switch 7 is abnormal based on the output signal of the AND gate 16.
[0031]
The effective value determination unit 13 includes a comparator CP1 that compares the output of the effective value detection unit 12 with a predetermined reference level V1. When the output of the effective value detection unit 12 exceeds the reference level V1, the output of the comparator CP1 is Become high. Here, the reference level V1 is set to a voltage value corresponding to the effective value level of the power supply voltage of the commercial system 30, and if the output of the effective value detection unit 12 is the effective value level of the power supply voltage of the commercial system 30, The output of the comparator CP1 goes high.
[0032]
The integrated value determining unit 15 includes a comparator CP2 that compares the level of the output of the integrating unit 14 with a predetermined reference level V2, a comparator CP3 that compares the level of the output of the integrating unit 14 and a predetermined reference level V3, and a comparator The AND gate 15a outputs a logical product of the outputs of CP2 and CP3. Here, if the output of the integration unit 14 is lower than the reference level V2, the output of the comparator CP2 is high, and if the output of the integration unit 14 is higher than the reference level (−V3), the output of the comparator CP3 is high. The reference level V2 is set to a positive voltage value near zero volts, and (−V3) is set to a negative voltage value near zero volts. Thus, if the output of the integrating unit 14 is lower than the reference level V2 and higher than the reference level (−V3), that is, the voltage across the terminals on the inverter circuit unit 3 side of the disconnecting switch 7 is set to the power supply cycle. If the result of integration over one period is near zero level, the output of the integrated value determination unit 15 becomes high.
[0033]
The determination result of the effective value determination unit 13 and the determination result of the integrated value determination unit 15 are input to the AND gate 16, and both the effective value determination unit 13 and the integrated value determination unit 15 output high, that is, the effective value. When the output of the value detection unit 12 exceeds the reference level V1 and the output of the integration unit 14 is near zero, the output of the AND gate 16 becomes high.
[0034]
Here, the control circuit 8 captures the output of the AND gate 16 in a state immediately before starting the interconnection operation in which the operation of the inverter circuit unit 3 is stopped and the disconnection switch 7 is turned off. Whether or not the disconnect switch 7 is normal is determined. If the output of the AND gate 16 is high even though the signal for turning on the disconnect switch 7 is not input, that is, the effective value of the inter-terminal voltage detected by the effective value detector 12 is obtained. When the result obtained by integrating the terminal voltage to a value obtained by multiplying the terminal voltage by a natural number times the power supply period becomes substantially zero when the commercial power supply voltage is approximately equal to the effective value of the commercial power supply voltage, the control circuit 8 detects abnormalities such as contact welding on the disconnection switch 7. When the inverter circuit unit 3 is stopped, the interconnection operation is stopped and abnormality information is displayed on the monitor 11.
[0035]
As described above, in the present embodiment, the voltage between the terminals on the inverter circuit unit 3 side in the disconnecting switch 7 is detected by the voltage detector 9 and is detected by the voltage detector 9 immediately before the start of the interconnection operation. Based on the voltage between the terminals, it is determined whether or not the operation of the disconnecting switch 7 is normal. If the disconnecting switch 7 is determined to be abnormal, the interconnection operation is stopped, so that the disconnecting switch 7 is in an abnormal state. It is possible to prevent the interconnection operation from starting. Therefore, like the conventional grid-connected inverter device, it is necessary to connect a plurality of disconnection switches in series in order to prevent the disconnection switch 7 from starting the connection operation in an abnormal state. Since only one disconnecting switch 7 is required, the cost of the grid-connected inverter device can be reduced.
[0036]
  (Embodiment2)
  Embodiment of the present invention2Will be described with reference to FIG. The main circuit configuration of the grid-connected inverter device isReference example aboveTherefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0037]
  In this embodiment,Explained in the reference exampleIn the grid-connected inverter device, the zero cross detection unit 17 that detects the zero cross point based on the detection signal of the voltage detector 9 and the frequency obtained from the time interval at which the zero cross detection unit 17 detects the zero cross point is A frequency determination unit 18 that determines whether or not the power frequency (50 or 60 Hz) of the commercial system 30 is substantially the same is provided.
[0038]
The zero cross detector 17 includes a comparator CP4 that determines whether the detection signal of the voltage detector 9 is positive or negative. The output of the comparator CP4 is changed from high to low before and after the zero cross point of the voltage across the disconnection switch 7. Or flip from low to high. Thus, the frequency determination unit 18 can obtain the time interval for detecting the zero cross point based on the high / low of the output of the zero cross detection unit 17, and the frequency obtained from this time interval becomes the power supply frequency. It is determined whether or not they match, and the determination result is output to the control circuit 8.
[0039]
Here, the control circuit 8 captures the determination result of the frequency determination unit 18 immediately before starting the interconnection operation in which the operation of the inverter circuit unit 3 is stopped and the disconnect switch 7 is turned off. Based on the result, it is determined whether or not the disconnection switch 7 is normal, and the inverter circuit unit 3 in the disconnection switch 7 is not input although the signal for turning on the disconnection switch 7 is not input. If the frequency of the terminal-to-terminal voltage substantially matches the power frequency of the commercial system 30, it is determined that an abnormality such as contact welding has occurred in the disconnect switch 7 and the inverter circuit unit 3 is stopped. In addition, the interconnection operation is stopped and the abnormality information is displayed on the monitor 11.
[0040]
  As described above, in the present embodiment, the voltage between the terminals on the inverter circuit unit 3 side in the disconnecting switch 7 is detected by the voltage detector 9 and is detected by the voltage detector 9 immediately before the start of the interconnection operation. Based on the voltage between the terminals, it is determined whether or not the operation of the disconnecting switch 7 is normal. If the disconnecting switch 7 is determined to be abnormal, the interconnection operation is stopped, so that the disconnecting switch 7 is in an abnormal state. It is possible to prevent the interconnection operation from starting. Therefore, like the conventional grid-connected inverter device, it is necessary to connect a plurality of disconnection switches in series in order to prevent the disconnection switch 7 from starting the connection operation in an abnormal state. Since only one disconnecting switch 7 is required, the cost of the grid-connected inverter device can be reduced. In this embodiment, the first embodiment orReference exampleAs described above, the voltage level and effective value level of the voltage between terminals detected by the voltage detector 9 are not determined, so that management of the reference level used for determination of the voltage level and effective value level becomes unnecessary, and the disconnection switching is performed. The configuration of the circuit portion for determining the abnormality of the device 7 can be simplified.
[0041]
  (Embodiment3)
  Embodiment of the present invention3Will be described with reference to FIG. The configuration of the main circuit of the grid-connected inverter device isReference example aboveTherefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0042]
  In this embodiment,Explained in the reference exampleIn the grid-connected inverter device, the zero cross detection unit 17 that detects the zero cross point based on the detection signal of the voltage detector 9 and the frequency obtained from the time interval at which the zero cross detection unit 17 detects the zero cross point is An effective value for obtaining an effective value of the voltage across the terminals of the disconnecting switch 7 based on a detection signal from the voltage detector 9 and a frequency determination unit 19 that determines whether or not the frequency is a predetermined reference frequency (for example, 30 Hz) or more. The detection unit 12, the effective value determination unit 13 that determines the level of the effective value detected by the effective value detection unit 12 and a predetermined reference level, the determination result of the frequency determination unit 19, and the determination result of the effective value determination unit 13 An AND gate 20 for obtaining the logical product of the AND gate 20 is provided, and the control circuit 8 determines whether or not the disconnection switch 7 is abnormal based on the output signal of the AND gate 20.
[0043]
The zero cross detector 17 includes a comparator CP4 that determines whether the detection signal of the voltage detector 9 is positive or negative. The output of the comparator CP4 is changed from high to low before and after the zero cross point of the voltage across the disconnection switch 7. Or flip from low to high. Thus, the frequency determination unit 19 can obtain the time interval for detecting the zero cross point based on the output of the zero cross detection unit 17, and the frequency obtained from this time interval is equal to or higher than a predetermined reference frequency. And the determination result is output to the AND gate 20. In addition, if it is a value below 50 Hz which is a commercial frequency as a reference frequency, it can be set to an appropriate value according to the detection time limit, and if the frequency obtained from the detection interval of the zero cross point is equal to or higher than the reference frequency. The output of the frequency determination unit 19 is high, and if it is less than the reference frequency, the output of the frequency determination unit 19 is low.
[0044]
The effective value determination unit 13 includes a comparator CP1 that compares the output of the effective value detection unit 12 with a predetermined reference level V1. When the output of the effective value detection unit 12 exceeds the reference level V1, the output of the comparator CP1 is Become high. Note that the reference level V1 is set to a voltage corresponding to the effective value level of the commercial system 30, and if the effective value of the inter-terminal voltage detected by the effective value detecting unit 12 is the effective value level of the commercial power supply voltage, the comparator The output of CP1 goes high.
[0045]
The AND gate 20 receives the output of the frequency determination unit 19 and the output of the effective value determination unit 13, and when both the outputs of the frequency determination unit 19 and the effective value determination unit 13 become high, that is, detection of the zero cross point. When the frequency obtained from the interval is equal to or higher than the reference frequency and the output of the effective value detection unit 12 exceeds the reference level V1, the output of the AND gate 16 becomes high.
[0046]
Here, the control circuit 8 captures the output of the AND gate 20 in a state immediately before starting the interconnection operation in which the operation of the inverter circuit unit 3 is stopped and the disconnect switch 7 is turned off, and this output is also output. Whether or not the disconnect switch 7 is normal is determined. When the output of the AND gate 20 is high even though the signal for turning on the disconnect switch 7 is not input, that is, the frequency obtained from the detection interval of the zero cross point is equal to or higher than the reference frequency. If the effective value of the inter-terminal voltage detected by the effective value detection unit 12 is the effective value level of the commercial power supply voltage, the control circuit 8 causes an abnormality such as contact welding in the disconnect switch 7. Then, it is determined that the power supply voltage of the commercial system 30 has appeared between the terminals on the inverter circuit unit 3 side, the inverter circuit unit 3 is stopped, the interconnection operation is stopped, and the abnormality information is displayed on the monitor 11. .
[0047]
  As described above, in the present embodiment, the voltage between the terminals on the inverter circuit unit 3 side in the disconnecting switch 7 is detected by the voltage detector 9 and is detected by the voltage detector 9 immediately before the start of the interconnection operation. Based on the voltage between the terminals, it is determined whether or not the operation of the disconnecting switch 7 is normal. If the disconnecting switch 7 is determined to be abnormal, the interconnection operation is stopped, so that the disconnecting switch 7 is in an abnormal state. It is possible to prevent the interconnection operation from starting. Therefore, like the conventional grid-connected inverter device, it is necessary to connect a plurality of disconnection switches in series in order to prevent the disconnection switch 7 from starting the connection operation in an abnormal state. Since only one disconnecting switch 7 is required, the cost of the grid-connected inverter device can be reduced. In the present embodiment, the embodiment2Compared to the above, although a circuit for determining the effective value level of the voltage across the terminals detected by the voltage detector 9 is required, the setting of the reference level and the reference frequency used for determining the effective value level may be rough. Has the effect of simplifying.
[0048]
  (Embodiment4)
  Embodiment of the present invention4Will be described with reference to FIG. The configuration of the main circuit of the grid-connected inverter device isReference example aboveTherefore, the same components are denoted by the same reference numerals, and the description thereof is omitted.
[0049]
  Embodiments 1 to 1 above3 and reference examplesThen, the voltage detector 9 is used to detect the voltage across the terminals on the inverter circuit unit 3 side of the disconnection switch 7, and it is determined only from this detection signal whether the disconnection switch 7 is normal or not. On the other hand, in the present embodiment, the voltage detector 9 as the first voltage detector detects the voltage across the terminals on the inverter circuit unit 3 side in the disconnect switch 7 and the voltage detector as the second voltage detector. 10 detects the voltage between terminals on the commercial system 30 side of the disconnect switch 7 and determines whether the disconnect switch 7 is normal or not based on the detection signals of both voltage detectors 9 and 10.
[0050]
That is, a differential amplifier 21 for obtaining a difference between the output of the voltage detector 9 and the output of the voltage detector 10 is provided, and the control circuit 8 stops the operation of the inverter circuit unit 3 and turns off the disconnection switch 7. The output of the differential amplifier 21 is taken in immediately before starting the connected operation, and it is determined whether or not the disconnect switch 7 is normal based on this output. Then, although the signal for turning on the disconnect switch 7 is not input, the output of the differential amplifier 21 becomes substantially zero (the output of the voltage detector 9 and the output of the voltage detector 10 are substantially the same). When the same state) continues for a certain period of time, the control circuit 8 has an abnormality such as contact welding in the disconnect switch 7 and the power supply voltage of the commercial system 30 appears between the terminals on the inverter circuit unit 3 side. In other words, the inverter circuit unit 3 is brought into a stopped state, the interconnection operation is stopped, and the abnormality information is displayed on the monitor 11.
[0051]
  Embodiments 1 to 1 above3 and reference examplesWhen it is determined whether or not the disconnect switch 7 is normal only from the voltage between the terminals on the inverter circuit unit 3 side detected by the voltage detector 9 as described above, the inverter circuit unit 3 operates before the determination. If so, there is a possibility that a voltage remains in the capacitor constituting the filter circuit 6. Even if the disconnecting switch 7 is cut off, the residual voltage is detected by the voltage detector 9 and erroneously detected. Although there is a possibility, in this embodiment, the voltage detectors 9 and 10 detect the voltage between the terminals on both sides of the disconnect switch 7 and determine whether or not they match, so the residual voltage is detected. Can prevent false detection.
[0052]
In each of the above-described embodiments, the solar cell 1 is used as a DC power source, and the output of the solar cell 1 is boosted, and the boosted voltage is converted to AC to be connected to a commercial system. Needless to say, it is not limited to 1, and a DC power source such as a fuel cell may be used.
[0053]
【The invention's effect】
  As described above, the invention of claim 1 includes an inverter circuit unit that converts DC power of a DC power source into AC power by switching with a switching element and supplies the AC power to the commercial system side, and an inverter circuit unit and a commercial system. A disconnecting switch provided between and connecting or disconnecting the inverter circuit unit and the commercial system, and controlling the output of the inverter circuit unit by controlling on / off of the switch element, and disconnecting A control circuit unit for connecting or disconnecting the inverter circuit unit by controlling on / off of the switch; a voltage detection unit for detecting a voltage between terminals on the inverter circuit unit side in the disconnecting switch;The effective value determination unit for determining whether the effective value of the inter-terminal voltage obtained from the detection result of the voltage detection unit is substantially the same as the effective value of the commercial power supply voltage, and the inter-terminal voltage detected by the voltage detection unit An integrated value determination unit that determines whether or not the result of integration for a period that is a natural number times the power cycle of the commercial system is substantially zero;The control circuit unit is connected and disconnected based on the voltage between the terminals detected by the voltage detection unit immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If the vessel is normal or notIn the control circuit unit, the effective value determination unit determines that the effective value of the inter-terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the result of integrating the inter-terminal voltage is substantially zero. And the integrated value determination unit determines that the disconnect switch is abnormal.When the contacts of the disconnect switch are welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit unit side of the disconnect switch, so the inverter circuit section detected by the voltage detector Whether the disconnect switch is normal or not can be determined only from the voltage between the terminals on the side, and if the disconnect switch is determined to be abnormal in the control circuit, the interconnection operation is stopped. It is possible to prevent the interconnection operation from being started in the state of failure. Therefore, unlike the conventional grid-connected inverter device, it is not necessary to connect two disconnecting switches in series in order to ensure safety, and the cost can be reduced by reducing the number of disconnecting switches. it can. In addition, there is an advantage that only one voltage detection unit is required compared to the case where the voltage between terminals on the inverter circuit unit side and the commercial system side of the disconnection switch is detected and the detection results are compared. is there.
[0055]
  Moreover,When the contacts of the disconnect switch are welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit side of the disconnect switch, so the effective value of the voltage across the terminals detected by the voltage detector is the commercial power supply. Since the result of integrating the inter-terminal voltage for a period that is a natural number multiple of the power cycle becomes substantially zero, the abnormality of the disconnecting switch can be reliably determined.
[0056]
  Claim2The invention ofAn inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. A control circuit unit that interconnects or disconnects the unit, a voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch,Whether or not the zero cross detection unit that detects the zero cross point from the detection result of the voltage detection unit and the frequency obtained from the time interval at which the zero cross detection unit detects the zero cross point matches the power supply frequency of the commercial system A frequency determination unit for determiningThe control circuit unit is connected and disconnected based on the voltage between the terminals detected by the voltage detection unit immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If it is determined that the vessel is normal or not, the grid operation is stopped.The control circuit unit is characterized by determining that the disconnection switch is abnormal when the frequency determination unit determines that the frequency obtained from the zero-cross point detection interval matches the power supply frequency,Since the control circuit stops the interconnection operation when it is determined that the disconnect switch is abnormal, it is possible to prevent the interconnect operation from being started in a state where the disconnect switch is out of order. Therefore, unlike the conventional grid-connected inverter device, it is not necessary to connect two disconnecting switches in series in order to ensure safety, and the cost can be reduced by reducing the number of disconnecting switches. it can. In addition, there is an advantage that only one voltage detection unit is required compared to the case where the voltage between terminals on the inverter circuit unit side and the commercial system side of the disconnection switch is detected and the detection results are compared. is there. MoreoverWhen the contact of the disconnection switch is welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit side of the disconnection switch, so the frequency obtained from the detection interval of the zero cross point of the voltage between the terminals is Since it matches the power supply frequency, it is possible to reliably determine abnormality of the disconnect switch. And claims1Since there is no circuit for comparing the voltage level of the inter-terminal voltage with the reference value as in the present invention, setting of the reference value becomes unnecessary, and the configuration of the circuit for performing the determination can be simplified.
[0057]
  Claim3The invention ofAn inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. A control circuit unit that interconnects or disconnects the unit, a voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch,An effective value determination unit that determines whether or not the effective value of the inter-terminal voltage obtained from the detection result of the voltage detection unit is substantially the same as the effective value of the commercial power supply voltage, and a zero cross point from the detection result of the voltage detection unit A zero cross detection unit for detecting, and a frequency determination unit for determining whether or not a frequency obtained from a time interval at which the zero cross detection unit detects a zero cross point is equal to or higher than a predetermined reference frequency lower than the power supply frequency;The control circuit unit is connected and disconnected based on the voltage between the terminals detected by the voltage detection unit immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If it is determined that the vessel is normal or not, the grid operation is stopped.The control circuit unit determines that the effective value determination unit determines that the effective value of the inter-terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the frequency obtained from the detection interval of the zero cross point is equal to or higher than the reference frequency. And the frequency determination unit determines that the disconnect switch is abnormal,Since the control circuit stops the interconnection operation when it is determined that the disconnect switch is abnormal, it is possible to prevent the interconnect operation from being started in a state where the disconnect switch is out of order. Therefore, unlike the conventional grid-connected inverter device, it is not necessary to connect two disconnecting switches in series in order to ensure safety, and the cost can be reduced by reducing the number of disconnecting switches. it can. In addition, there is an advantage that only one voltage detection unit is required compared to the case where the voltage between terminals on the inverter circuit unit side and the commercial system side of the disconnection switch is detected and the detection results are compared. is there. MoreoverWhen the contact of the disconnect switch is welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit side of the disconnect switch, so the effective value of the voltage across the terminals detected by the voltage detector is And the frequency obtained from the detection interval of the zero cross point of the voltage between the terminals is equal to or higher than the reference frequency, so that the disconnection switch abnormality can be reliably determined. And claims2Although the portion for comparing the effective value of the inter-terminal voltage with the reference value is increased as compared with the present invention, since the setting of the reference frequency used for the determination is rough, there is an effect that the setting operation of the reference frequency is simplified.
[0058]
  Claim4The invention is provided with an inverter circuit unit that converts DC power of a DC power source into AC power by switching with a switching element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. Disconnection switch that connects or disconnects the power supply unit and the commercial system, and controls the output of the inverter circuit by controlling the on / off of the switch element, and also controls the on / off of the disconnection switch A control circuit unit that interconnects or disconnects the inverter circuit unit, a first voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch, and a commercial system side in the disconnection switch A second voltage detection unit that detects a voltage between the terminals, and the control circuit unit stops the inverter circuit unit and immediately turns off the disconnection switch, If the detection result of the first voltage detection unit is substantially the same as the detection result of the second voltage detection unit, it is determined that the disconnection switch is abnormal. When the contact of the disconnection switch is welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit side of the disconnection switch. Based on the voltage between the terminals on the inverter circuit side detected by the first and second voltage detectors and the voltage between the terminals on the commercial system side, it can be determined whether the disconnect switch is normal or not. When the circuit determines that the disconnect switch is abnormal, the circuit operation is stopped, so that it is possible to prevent the interconnect operation from being started in a state where the disconnect switch is out of order. Therefore, unlike the conventional grid-connected inverter device, it is not necessary to connect two disconnecting switches in series in order to ensure safety, and the cost can be reduced by reducing the number of disconnecting switches. it can. In addition, when the control circuit determines whether the disconnect switch is normal only from the voltage across the terminals on the inverter circuit side of the disconnect switch, the inverter circuit unit operates before the determination and the inverter circuit side If there is a voltage remaining between the terminals, the residual voltage may be erroneously detected, but the voltage between the terminals on the inverter circuit side detected by the first and second voltage detectors and the terminal on the commercial system side If the inter-voltage is substantially the same, it is determined that the disconnect switch is abnormal, so that erroneous detection due to the residual voltage can be prevented.
[Brief description of the drawings]
[Figure 1]Reference exampleIt is a block diagram of a solar cell power generation system using the grid-connected inverter device.
FIG. 21It is a block diagram which shows the principal part of the grid connection inverter apparatus of this.
FIG. 32It is a block diagram which shows the principal part of the grid connection inverter apparatus of this.
FIG. 4 Embodiment3It is a block diagram which shows the principal part of the grid connection inverter apparatus of this.
FIG. 5 is an embodiment.4It is a block diagram which shows the principal part of the grid connection inverter apparatus of this.
FIG. 6 is a block circuit diagram of a solar cell power generation system using a conventional grid-connected inverter device.
[Explanation of symbols]
  1 Solar cell
  2 grid-connected inverter device
  3 Inverter circuit
  4 Booster circuit
  5 Sine wave generator
  6 Filter circuit
  7 Disconnection switch
  8 Control circuit
  9 Voltage detector
  30 Commercial system

Claims

An inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. The effective value of the inter-terminal voltage obtained from the detection result of the control circuit unit that interconnects or disconnects the unit, the voltage detection unit that detects the inter-terminal voltage on the inverter circuit side in the disconnection switch, The effective value determination unit that determines whether or not it is substantially the same as the effective value of the commercial power supply voltage, and the result obtained by integrating the terminal voltage detected by the voltage detection unit for a period that is a natural number times the power cycle of the commercial system is approximately zero. In Luke and a whether the determined integration value determination unit, the control circuit unit, in a state immediately before the start of the interconnected operation has been off disconnecting switch stops the inverter circuit unit, the voltage detecting section the voltage between the detected terminal determines whether based on Kairetsu switch is normal, if it is determined that abnormality has discontinued interconnected operation, the control circuit section, the effective value of the voltage between terminals commercial When the effective value determination unit determines that the power supply voltage is substantially the same as the effective value of the power supply voltage, and the integrated value determination unit determines that the result of integrating the inter-terminal voltage is approximately zero, the disconnection switch is abnormal. It is judged that the system interconnection inverter device.

An inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. Control circuit unit that interconnects or disconnects the units, a voltage detection unit that detects a voltage across the terminals on the inverter circuit unit side of the disconnection switch, and a zero cross detection that detects a zero cross point from the detection result of the voltage detection unit And a frequency determination unit that determines whether or not the frequency obtained from the time interval at which the zero cross detection unit detects the zero cross point matches the power supply frequency of the commercial system, Whether the disconnection switch is normal based on the voltage between the terminals detected by the voltage detection unit in the state immediately before starting the interconnection operation with the inverter circuit unit stopped and the disconnection switch turned off. If it is determined that there is an abnormality, the grid operation is stopped, and the control circuit determines that the frequency obtained from the zero-cross point detection interval matches the power supply frequency. Then, you and determines that abnormality of the disconnecting switch system Mitsururen inverter device.

An inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. The effective value of the inter-terminal voltage obtained from the detection result of the control circuit unit that interconnects or disconnects the unit, the voltage detection unit that detects the inter-terminal voltage on the inverter circuit side in the disconnection switch, An effective value determination unit that determines whether or not the effective value of the commercial power supply voltage is substantially the same, a zero cross detection unit that detects a zero cross point from the detection result of the voltage detection unit, and the zero cross detection unit A frequency determination unit that determines whether or not the frequency obtained from the time interval for detecting the point is equal to or higher than a predetermined reference frequency lower than the power supply frequency, and the control circuit unit stops the inverter circuit unit and solves the problem. When it is determined that the disconnection switch is normal or not based on the voltage across the terminals detected by the voltage detector in the state immediately before starting the grid operation with the column switch turned off. The interconnection operation is stopped, and the control circuit unit determines that the effective value determination unit determines that the effective value of the inter-terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and from the detection interval of the zero cross point. determined frequency is greater than or equal to the reference frequency when the frequency determining section determines, disconnection switch is you characterized based Mitsururen inverter device that is judged to be abnormal.

An inverter circuit unit that converts the DC power of the DC power source into AC power by switching with a switch element and supplies the AC power to the commercial system side, and is provided between the inverter circuit unit and the commercial system. A disconnecting switch for connecting or disconnecting between the switching circuit and an inverter circuit by controlling on / off of the switching element to control the output of the inverter circuit unit and controlling the on / off of the disconnecting switch. A control circuit unit that interconnects or disconnects the first unit, a first voltage detection unit that detects a voltage between terminals on the inverter circuit unit side in the disconnection switch, and a terminal voltage on the commercial system side in the disconnection switch. A second voltage detection unit for detecting, and the control circuit unit stops the inverter circuit unit and turns off the disconnection switch and immediately before starting the grid operation, the first voltage detection unit is provided. If the detection results of the first voltage detector and the second voltage detector are substantially the same, it is determined that the disconnection switch is abnormal. A grid-connected inverter device characterized in that the grid -operated operation is stopped .