JP2004187362A

JP2004187362A - Grid-connected inverter arrangement

Info

Publication number: JP2004187362A
Application number: JP2002349045A
Authority: JP
Inventors: Hiroaki Koshin; 博昭小新; Kiyoshi Goto; 潔後藤; Shinichiro Okamoto; 信一郎岡本; Akira Yoshitake; 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: 2004-07-02
Anticipated expiration: 2022-11-29
Also published as: JP3979278B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost grid-connected inverter arrangement capable of stopping a grid-connected operation by detecting an abnormality of a parallel-off switch before the grid-connected operation is started. <P>SOLUTION: A grid-connected inverter arrangement 2 comprises an inverter circuit 3 composed of a step-up circuit 4 for stepping up the output of a solar cell 1, a sine wave generating circuit 5 for converting the output of the step-up circuit 4 to an AC voltage, and a filter circuit 6 that smoothes the output of the sine wave generating circuit 5; a parallel-off switch 7 connected between the inverter circuit 3 and a commercial grid 30, a control circuit 8 to control the output of the inverter circuit 3; and a voltage detector 9 for detecting an inter-terminal voltage on the inverter circuit 3 side of the parallel-off switch 7. The control circuit 8 stops an inverter operation and determines whether the parallel-off switch 7 is normal or not based on the inter-terminal voltage detected by the voltage detector 9 immediately before the starting of the grid-connected operation in which the parallel-off switch 7 is turned off. If it is decided to be abnormal, the grid-connected operation is suspended. <P>COPYRIGHT: (C)2004,JPO&NCIPI

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することを特徴とする。
【００１５】
請求項２の発明では、請求項１の発明において、制御回路部は、電圧検出部の検出した端子間電圧が所定のしきい値よりも高ければ、解列開閉器が異常であると判断することを特徴とする。
【００１６】
請求項３の発明では、請求項１の発明において、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設け、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４の発明では、請求項１の発明において、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設け、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５の発明では、請求項１の発明において、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設け、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６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】
（実施形態１）
本実施形態の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、後述する実施形態５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２）
本発明の実施形態２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実施形態１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、実施形態１の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３）
本発明の実施形態３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実施形態１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、実施形態１の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２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４）
本発明の実施形態４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実施形態１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、実施形態１の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３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５）
本発明の実施形態５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実施形態１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１〜４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】
上述した実施形態１〜４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。
【００５４】
請求項２の発明は、請求項１の発明において、制御回路部は、電圧検出部の検出した端子間電圧が所定のしきい値よりも高ければ、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、電圧検出部の検出した端子間電圧が所定のしきい値よりも高くなることから、解列開閉器の異常を判別することができる。
【００５５】
請求項３の発明は、請求項１の発明において、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設け、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４の発明は、請求項１の発明において、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設け、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、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２、３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５の発明は、請求項１の発明において、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設け、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、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４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６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】実施形態１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３】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４】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５】実施形態５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]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a system interconnection inverter device that converts a DC power supply such as a solar cell or a fuel cell into an AC and connects the AC power to a commercial system.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, there has been provided a grid-connected inverter device that converts a DC power supply such as a solar cell or a fuel cell into an AC, and supplies power to a load in connection with a commercial system (commercial AC power supply).
[0003]
FIG. 6 is a diagram illustrating an example of a solar cell power generation system using such a system interconnection inverter device. The power generation system includes a solar cell 1 for obtaining DC power according to the amount of solar radiation, and a DC from the solar cell 1. The system is configured by a grid-connected inverter device 2 that converts electric power into AC power, and a commercial system 30. With respect to 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 the interconnected operation of the system interconnection inverter device 2 and the commercial system 30 or the single operation of the commercial system 30 alone (for example, see Patent Document 1).
[0004]
The grid interconnection inverter device 2 boosts the output voltage of the solar cell 1, a sine wave generation circuit 5 that converts the output of the boost circuit 4 into an AC voltage, and smoothes the output of the sine wave generation circuit 5. An inverter circuit unit 3 including a filter circuit 6 having an output waveform of a sine wave shape, disconnection 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 that supplies an on / off signal to each switch element of the inverter circuit section 3. The booster circuit 4 boosts the output voltage of the solar cell 1 that constantly varies within a range of about 0 V to 300 V according to the amount of solar radiation to about 350 V. The sine wave generation circuit 5 receives the boosted DC voltage as an input. After converting the voltage into an AC voltage by performing PWM control, the filter circuit 6 converts the ripple component of the PWM carrier frequency included in the output of the sine wave generation circuit 5 into a sine wave AC voltage, and outputs the converted voltage. 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 switch 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 having an anode connected to the collector of the switching element 42, and a capacitor 44 connected between the cathode of the diode 43 and the emitter of the switching element 42, are configured as a one-step boost chopper. You. 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. The pulse signal of the duty ratio determined by performing arithmetic processing in the control circuit 8 is output from the switch element 42. 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 connecting switching elements 51 to 54 such as IGBTs in a full-bridge manner, and switches each of the switching elements 51 to 54 according to the PWM control of the control circuit 8 so that the DC voltage from the boosting 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 between the switch elements 51 and 52 connected in series, a reactor 62 having one end connected to a connection point between the switch elements 53 and 54 connected in series, and It comprises 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 to a sine wave current waveform. Then, it is output to the commercial system 30.
[0008]
Each of the parallel-off switches 7a and 7b 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 and the commercial system 30 are interconnected or disconnected.
[0009]
[Patent Document 1]
JP-A-9-215205 (pages 3-4 and FIG. 1)
[0010]
[Problems to be solved by the invention]
In the above-described system interconnection inverter device 2, the control circuit 8 controls on / off of the parallel-off switches 7 a and 7 b, and when an 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 parallel-off switches 7a and 7b are turned off, and the inverter circuit unit 3 is connected to the commercial system 30. To secure safety.
[0011]
However, if a contact welding phenomenon occurs due to an abnormal current or contact life in the relays used for the disconnecting switches 7a and 7b, the inverter circuit unit 3 cannot be disconnected even if a control signal from the control circuit 8 is received. Can occur. In order to avoid a decrease in safety due to such a failure of the disconnection switches 7a and 7b, the conventional grid-connected inverter device 2 is switched off according to the guidelines presented by the Agency for Natural Resources and Energy. A system in which two switches 7a and 7b are connected in series and used is widely adopted.
[0012]
As described above, in the conventional system interconnection inverter device 2, in order to avoid a decrease in safety due to the failure of the disconnection switch, a plurality of disconnection switches are connected in series. However, there is a problem that the cost increases due to an increase in the number of the devices. Further, although it is lower than the probability that one disconnecting switch will fail, there is a possibility that two disconnecting switches will be welded at the same time, and the grid-connected inverter device 2 starts operating in the same state. There was also a risk.
[0013]
The present invention has been made in view of the above-described problems, and an object of the present invention is to detect an abnormality in a parallel-off switch before starting interconnection operation and stop the interconnection operation. An object of the present invention is to provide a low-cost system interconnection inverter device that can be used.
[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 supply into AC power by switching with a switch element and supplies the AC power to a commercial system side, A disconnecting switch provided between the power supply system and the power supply system for connecting or disconnecting between the inverter circuit unit and the commercial power system, and controlling the on / off of the switch element to control the output of the inverter circuit unit. A control circuit unit that controls the on / off of the disconnecting switch to interconnect or disconnect the inverter circuit unit, and a voltage detecting unit that detects a voltage between terminals of the inverter circuit unit side in the disconnecting switch. In the state immediately before starting the interconnection operation in which the inverter circuit section is stopped and the disconnection switch is turned off, the control circuit section is disconnected based on the terminal voltage detected by the voltage detection section.閉器 it is determined whether normal or not, if it is determined that an abnormality, characterized in that to stop the interconnected operation.
[0015]
According to a second aspect of the present invention, in the first aspect of the present invention, the control circuit determines that the disconnecting switch is abnormal if the voltage between the terminals detected by the voltage detector is higher than a predetermined threshold. It is characterized by the following.
[0016]
According to a third aspect of the present invention, in the first aspect of the present invention, an effective value determination is performed to determine 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. Unit, and an integrated value determination unit that determines whether the result of integrating the voltage between terminals detected by the voltage detection unit for a period that is a natural number multiple of the power supply cycle of the commercial system becomes substantially zero, and the control circuit unit includes: When the effective value determining unit determines that the effective value of the terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the integrated value determining unit determines that the result of integrating the terminal voltage is substantially zero. , Characterized in that the disconnecting switch is determined to be abnormal.
[0017]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the zero cross point is detected from a detection result of the voltage detecting section and a time interval at which the zero cross point detects the zero cross point. A frequency determination unit that determines whether the frequency matches the power supply frequency of the commercial system, and the control circuit unit determines that the frequency obtained from the zero-cross point detection interval matches the power supply frequency. When the unit determines, it is determined that the disconnection switch is abnormal.
[0018]
According to a fifth aspect of the present invention, in the first aspect of the present invention, an effective value determination is performed to determine whether or not the effective value of the inter-terminal voltage obtained from the detection result of the voltage detector is substantially the same as the effective value of the commercial power supply voltage. Unit, a zero-crossing detecting unit that detects a zero-crossing point from the detection result of the voltage detecting unit, and a predetermined reference whose frequency obtained from a time interval at which the zero-crossing detecting unit detects the zero-crossing point is lower than the power supply frequency. A frequency determination unit that determines whether the frequency is equal to or higher than the frequency, 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 When the frequency determination unit determines that the frequency obtained from the detection interval of the zero cross point is equal to or higher than the reference frequency, the disconnection switch is determined to be abnormal.
[0019]
In the invention of claim 6, an inverter circuit unit that converts the DC power of the DC power supply 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 interconnecting or disconnecting the inverter circuit and the commercial system, an on / off control of a switch element to control an output of the inverter circuit, and an on / off of the disconnecting switch. A control circuit unit that controls off and 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; A second voltage detection unit for detecting a voltage between terminals on the system side, wherein the control circuit unit stops the inverter circuit unit and turns off the parallel-off switch to a state immediately before starting the interconnection operation. And comparing 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, the disconnection switch It is characterized in that it is determined that there is an abnormality and the interconnection operation is stopped.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described with reference to the drawings.
[0021]
(Embodiment 1)
FIG. 1 shows a block diagram of a solar cell power generation system using the grid-connected inverter device of the present embodiment. The power generation system includes a solar cell 1 that obtains DC power according to the amount of solar radiation, a grid-connected inverter device 2 that converts DC power from the solar cell 1 into AC power, and a commercial grid 30. For a load (not shown) connected between the system inverter device 2 and the commercial system 30, any one of the interconnected operation of the system interconnected inverter device 2 and the commercial system 30 or the isolated operation of only the commercial system 30 is performed. It switches to either one and supplies AC power. Since the basic configuration is the same as that of the conventional system interconnection inverter device, the same components are denoted by the same reference numerals, and description thereof will be omitted.
[0022]
The grid interconnection inverter device 2 is composed of, for example, a one-step booster chopper, and is configured such that a booster circuit 4 that boosts the output voltage of the solar cell 1 to a predetermined constant voltage by switching the output voltage with the switch element, and a bridge connection of the switch element. An inverter including a sine wave generation circuit 5 for converting the output of the booster circuit 4 into an AC voltage, and a filter circuit 6 such as an LC filter for smoothing the output of the sine wave generation circuit 5 to make the output waveform a sine wave. A circuit section 3, a parallel-off switch 7 connected in series between the inverter circuit section 3 and the commercial system 30, and a microcomputer, which provide an on / off signal to each switch element of the inverter circuit section 3, It comprises a control circuit 8 (control circuit section) for controlling on / off of the parallel-off switch 7.
[0023]
The booster circuit 4 boosts the output voltage of the solar cell 1 constantly fluctuating within a range of about 0 V to 300 V according to the amount of solar radiation to about 350 V. The sine wave generation circuit 5 receives the boosted DC voltage as an input. After performing the PWM control, the filter circuit 6 converts the ripple component of the PWM carrier frequency included in the output of the sine wave generation circuit 5 into a sine wave AC voltage by smoothing and outputs the sine wave AC voltage.
[0024]
The disconnecting switch 7 is configured by a relay or the like whose on / off is controlled by a control signal from the control circuit 8, is connected between the inverter circuit unit 3 and the commercial system 30, and is connected to the inverter circuit unit 3 (step-up circuit). (Composed of a circuit 4, a sine wave generation circuit 5, and a filter circuit 6) and the commercial system 30. Further, voltage detectors 9 and 10 are connected between terminals of the disconnecting switch 7 on the side of the inverter circuit section 3 and on the side of the commercial system 30, respectively.
[0025]
The voltage detector 10 detects a voltage between terminals of the disconnection switch 7 on the commercial system 30 side, and a detection signal is input to the control circuit 8. Based on the detection signal of the voltage detector 10, the control circuit 8 determines whether there is a system abnormal state such as an overvoltage, a voltage drop, or a frequency abnormality of the system voltage generated due to a power failure or the like, and determines that the system abnormal state is detected. The row switch 7 is shut off, the operation of the inverter circuit unit 3 is stopped, and abnormal information is displayed on a monitor 11 composed of, for example, a liquid crystal display.
[0026]
A voltage detector 9 serving as a voltage detector detects a voltage between terminals on the side of the inverter circuit unit 3 in the parallel-off switch 7, and a detection signal thereof is input to the control circuit 8.
[0027]
Here, the control circuit 8 takes in the detection result of the voltage detector 9 in a state immediately before starting the interconnection operation in which the operation of the inverter circuit section 3 is stopped and the parallel-off switch 7 is turned off, and the voltage detection is performed. Of the terminal voltage detected by the detector 9 and 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 disconnection switch 7 is not input, the control circuit 8 sets the disconnection 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 abnormality information is displayed on the monitor 11.
[0028]
As described above, in the present embodiment, the voltage between the terminals of the disconnection switch 7 on the inverter circuit unit 3 side is detected by the voltage detector 9 immediately before the interconnection operation is started, and is detected by the voltage detector 9. It is determined whether or not the operation of the disconnecting switch 7 is normal based on the inter-terminal voltage, and if it is determined that the operation is abnormal, the interconnection operation is stopped. The start of the interconnection operation can be prevented. Therefore, in order to prevent the disconnection switch 7 from starting the interconnection operation when the disconnection switch 7 is in an abnormal state as in the conventional system interconnection inverter device, it is necessary to connect a plurality of disconnection switches in series. Since the number of the disconnecting switches 7 is one, the cost of the grid-connected inverter can be reduced. Further, as compared with a case where the inter-terminal voltages of the inverter circuit unit 3 side and the commercial system 30 side of the parallel-off switch 7 are detected and the detection results are compared, as in a fifth embodiment described later. Another advantage is that only one detector is required.
[0029]
(Embodiment 2)
Embodiment 2 of the present invention will be described with reference to FIG. The configuration of the main circuit of the system interconnection inverter device is the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components, and the description thereof will be omitted.
[0030]
In the present embodiment, in the grid-connected inverter device of the first embodiment, an effective value detection unit 12 that obtains an effective value of a voltage between terminals of the parallel-off switch 7 based on a detection signal of the voltage detector 9, An effective value judging unit 13 for judging a level between an effective value detected by the detecting unit 12 and a predetermined reference level; and a terminal-to-terminal voltage detected by the voltage detector 9 for a period (natural number times) of a power supply cycle of the commercial system 30 ( In the present embodiment, for example, for one period) the integrating unit 14 that integrates, the integrated value determining unit 15 that determines whether the integration result of the integrating unit 14 becomes substantially zero, and the determination result of the effective value determining unit 13 An AND gate 16 for obtaining a logical product of the determination result of the integrated value determination unit 15 and an AND gate 16 is provided. The control circuit 8 determines whether there is an abnormality in the disconnecting switch 7 based on the output signal of the AND gate 16. I have.
[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 becomes Go 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. 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 becomes high.
[0032]
The integrated value determination unit 15 includes a comparator CP2 for comparing the level of the output of the integrating unit 14 with a predetermined reference level V2, a comparator CP3 for comparing the level of the output of the integrating unit 14 with a predetermined reference level V3, And an AND gate 15a for outputting the logical product of the outputs of CP2 and CP3. Here, if the output of the integrating unit 14 is lower than the reference level V2, the output of the comparator CP2 is high, and if the output of the integrating 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 volt, and (-V3) is set to a negative voltage value near zero volt. Therefore, if the output of the integrating section 14 is lower than the reference level V2 and higher than the reference level (-V3), that is, the voltage between the terminals of the disconnection switch 7 on the inverter circuit section 3 side is set to the power supply cycle. If the result of integration over one cycle is near the zero level, the output of the integrated value determination unit 15 will be 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 when both the outputs of the effective value determination unit 13 and the integrated value determination unit 15 become high, When the output of the value detector 12 exceeds the reference level V1 and the output of the accumulator 14 is near zero, the output of the AND gate 16 goes 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 section 3 is stopped and the parallel-off switch 7 is turned off. Then, it is determined whether or not the disconnecting switch 7 is normal. When the output of the AND gate 16 is high even though the signal for turning on the parallel-off switch 7 is not input, that is, the effective value of the inter-terminal voltage detected by the effective value detecting unit 12 is When the effective value of the commercial power supply voltage becomes substantially equal to the value obtained by integrating the voltage between the terminals and multiplying the power supply cycle by a natural number, the result becomes substantially zero. Is determined to have occurred, 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 of the disconnection switch 7 on the inverter circuit unit 3 side is detected by the voltage detector 9 immediately before the interconnection operation is started, and is detected by the voltage detector 9. It is determined whether or not the operation of the disconnecting switch 7 is normal based on the inter-terminal voltage, and if it is determined that the operation is abnormal, the interconnection operation is stopped. The start of the interconnection operation can be prevented. Therefore, in order to prevent the disconnection switch 7 from starting the interconnection operation when the disconnection switch 7 is in an abnormal state as in the conventional system interconnection inverter device, it is necessary to connect a plurality of disconnection switches in series. Since the number of the disconnecting switches 7 is one, the cost of the grid-connected inverter can be reduced.
[0036]
(Embodiment 3)
Embodiment 3 of the present invention will be described with reference to FIG. The configuration of the main circuit of the system interconnection inverter device is the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components, and the description thereof will be omitted.
[0037]
In the present embodiment, in the system interconnection inverter device of the first embodiment, a zero-crossing detecting unit 17 that detects a zero-crossing point based on a detection signal of the voltage detector 9, and the zero-crossing detecting unit 17 detects the zero-crossing point. A frequency determination unit 18 is provided for determining whether the frequency obtained from the detected time interval is substantially the same as the power frequency (50 or 60 Hz) of the commercial system 30.
[0038]
The zero-crossing 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 changes from high to low before and after the zero crossing point of the voltage between the terminals of the parallel-off switch 7. Alternatively, it is inverted from low to high. Thus, the frequency determination unit 18 can determine 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 determined from this time interval is used as the power supply frequency. It is determined whether or not they match, and the result of the determination is output to the control circuit 8.
[0039]
Here, the control circuit 8 stops the operation of the inverter circuit unit 3 and fetches the determination result of the frequency determination unit 18 immediately before starting the interconnection operation in which the parallel-off switch 7 is turned off. Based on the result, it is determined whether or not the disconnecting switch 7 is normal, and although the signal for turning on the disconnecting switch 7 is not input, the inverter circuit unit 3 in the disconnecting switch 7 If the frequency of the terminal-to-terminal voltage substantially coincides with the power supply frequency of the commercial system 30, it is determined that an abnormality such as contact welding has occurred in the disconnecting switch 7, and the inverter circuit unit 3 is stopped. Then, 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 of the disconnection switch 7 on the inverter circuit unit 3 side is detected by the voltage detector 9 immediately before the interconnection operation is started, and is detected by the voltage detector 9. It is determined whether or not the operation of the disconnecting switch 7 is normal based on the inter-terminal voltage, and if it is determined that the operation is abnormal, the interconnection operation is stopped. The start of the interconnection operation can be prevented. Therefore, in order to prevent the disconnection switch 7 from starting the interconnection operation when the disconnection switch 7 is in an abnormal state as in the conventional system interconnection inverter device, it is necessary to connect a plurality of disconnection switches in series. Since the number of the disconnecting switches 7 is one, the cost of the system interconnection inverter device can be reduced. Further, in the present embodiment, since the determination of the voltage level and the effective value level of the inter-terminal voltage detected by the voltage detector 9 is not performed as in the first and second embodiments, it is used for determining the voltage level and the effective value level. The management of the reference level becomes unnecessary, and the configuration of the circuit for determining the abnormality of the parallel-off switch 7 can be simplified.
[0041]
(Embodiment 4)
Embodiment 4 of the present invention will be described with reference to FIG. The configuration of the main circuit of the system interconnection inverter device is the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components, and the description thereof will be omitted.
[0042]
In the present embodiment, in the system interconnection inverter device of the first embodiment, a zero-crossing detecting unit 17 that detects a zero-crossing point based on a detection signal of the voltage detector 9, and the zero-crossing detecting unit 17 detects the zero-crossing point. A frequency determining unit 19 for determining whether or not the frequency obtained from the detected time interval is equal to or higher than a predetermined reference frequency (for example, 30 Hz); and a terminal of the disconnecting switch 7 based on a detection signal of the voltage detector 9. An effective value detector 12 for obtaining an effective value of the inter-voltage, an effective value determiner 13 for determining the level of the effective value detected by the effective value detector 12 and a predetermined reference level, and a determination result of the frequency determiner 19. An AND gate 20 for obtaining a logical product with the determination result of the effective value determination unit 13 is provided, and the control circuit 8 determines whether there is an abnormality in the disconnection switch 7 based on the output signal of the AND gate 20. I have.
[0043]
The zero-crossing 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 changes from high to low before and after the zero crossing point of the voltage between the terminals of the parallel-off switch 7. Alternatively, it is inverted from low to high. Thus, the frequency determination unit 19 can determine a time interval for detecting the zero cross point based on the output of the zero cross detection unit 17, and the frequency determined from this time interval is equal to or higher than a predetermined reference frequency. And outputs the result of the determination to the AND gate 20. Note that the reference frequency can be set to an appropriate value according to the detection time period if the frequency is 50 Hz or less, which is a commercial frequency, and if the frequency obtained from the zero-cross point detection interval is equal to or higher than the reference frequency. The output of the frequency determination unit 19 is high, and if it is lower 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 becomes Go high. The reference level V1 is set to a voltage corresponding to the effective value level of the commercial power system 30. 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 comparator The output of CP1 goes high.
[0045]
The output of the frequency determination unit 19 and the output of the effective value determination unit 13 are input to the AND gate 20, and when both the outputs of the frequency determination unit 19 and the effective value determination unit 13 become high, that is, the detection of the zero cross point is performed. 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 parallel-off switch 7 is turned off, and this output is also used. Then, it is determined whether or not the disconnecting switch 7 is normal. If the output of the AND gate 20 is high even though the signal for turning on the paralleling switch 7 is not input, that is, if the frequency obtained from the zero-crossing point detection interval 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 the disconnection switch 7 to have an abnormality such as contact welding. 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 of the disconnection switch 7 on the inverter circuit unit 3 side is detected by the voltage detector 9 immediately before the interconnection operation is started, and is detected by the voltage detector 9. It is determined whether or not the operation of the disconnecting switch 7 is normal based on the inter-terminal voltage, and if it is determined that the operation is abnormal, the interconnection operation is stopped. The start of the interconnection operation can be prevented. Therefore, in order to prevent the disconnection switch 7 from starting the interconnection operation when the disconnection switch 7 is in an abnormal state as in the conventional system interconnection inverter device, it is necessary to connect a plurality of disconnection switches in series. Since the number of the disconnecting switches 7 is one, the cost of the grid-connected inverter can be reduced. In this embodiment, a circuit for determining the effective value level of the inter-terminal voltage detected by the voltage detector 9 is required as compared with the third embodiment, but the reference level and the reference frequency used for the determination of the effective value level are required. Since the setting can be roughly, there is an effect that the setting operation can be simplified.
[0048]
(Embodiment 5)
Embodiment 5 of the present invention will be described with reference to FIG. The configuration of the main circuit of the system interconnection inverter device is the same as that of the first embodiment. Therefore, the same reference numerals are given to the same components, and the description thereof will be omitted.
[0049]
In the above-described first to fourth embodiments, the voltage between the terminals of the disconnection switch 7 on the inverter circuit unit 3 side is detected by using the voltage detector 9 and whether or not the disconnection switch 7 is normal is determined based on the detection signal alone. In the present embodiment, the voltage detector 9 serving as the first voltage detector detects the voltage between the terminals of the disconnection switch 7 on the side of the inverter circuit unit 3 and the second voltage detector. A voltage detector 10 serving as a voltage detector detects a voltage between terminals of the disconnection switch 7 on the commercial system 30 side, and determines whether the disconnection switch 7 is normal based on detection signals of the two voltage detectors 9 and 10. Has been determined.
[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 parallel-off switch 7. Immediately before the start of the interconnection operation, the output of the differential amplifier 21 is fetched, and based on this output, it is determined whether or not the parallel-off switch 7 is normal. Then, 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) even though the signal for turning on the parallel-off switch 7 is not input. If the power supply voltage of the commercial system 30 appears between the terminals on the inverter circuit unit 3 side due to the occurrence of an abnormality such as contact welding at the disconnecting switch 7 when the same state continues for a certain period of time. Then, the inverter circuit unit 3 is stopped, the interconnection operation is stopped, and the abnormality information is displayed on the monitor 11.
[0051]
In the case where 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 in the above-described first to fourth embodiments, When the inverter circuit section 3 is operating, there is a possibility that a voltage remains in the capacitor constituting the filter circuit 6 and the voltage detector 9 detects this residual voltage even when the disconnecting switch 7 is shut off. Although there is a risk of erroneous detection due to the detection, in the present embodiment, the voltage detectors 9 and 10 detect the voltage between the terminals on both sides of the parallel-off switch 7 and determine whether or not they match. Therefore, it is possible to prevent erroneous detection due to detection of the residual voltage.
[0052]
In each of the above-described embodiments, the solar cell 1 is used as a DC power supply, the output of the solar cell 1 is boosted, and the boosted voltage is converted to an alternating current to be connected to a commercial system. It is needless to say that a DC power source such as a fuel cell may be used instead of the purpose of limiting to one.
[0053]
【The invention's effect】
As described above, the invention of claim 1 is an inverter circuit unit that converts DC power of a DC power supply into AC power by switching with a switch element and supplies the AC power to a commercial system side, A disconnecting switch provided between the inverter circuit unit and the commercial system for interconnecting or disconnecting the inverter circuit unit, and controlling the on / off of a switch element to control the output of the inverter circuit unit and disconnecting the inverter circuit unit. A control circuit for controlling on / off of the switch to interconnect or disconnect the inverter circuit, and a voltage detector for detecting a voltage between terminals on the inverter circuit side of the disconnector; The unit determines whether the disconnection switch is normal based on the voltage between 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. It is characterized by stopping the interconnection operation when it is judged abnormal, and when the contacts of the disconnecting switch are welded, the commercial system is connected between the terminals on the inverter circuit side of the disconnecting switch. Since the power supply voltage appears, it can be determined from the voltage between the terminals on the inverter circuit side detected by the voltage detector only whether the disconnection switch is normal, and the control circuit determines that the disconnection switch is abnormal. When the judgment is made, the interconnection operation is stopped, so that it is possible to prevent the interconnection operation from being started in a state where the parallel-off switch is out of order. Therefore, it is not necessary to connect two disconnecting switches in series in order to ensure safety as in the conventional grid-connected inverter device, and it is possible to reduce the number of disconnecting switches and reduce costs. it can. Another advantage is that only one voltage detection unit is required as compared with a case where the voltage between terminals on the inverter circuit unit side and the commercial system side of the parallel-off switch is respectively detected and the detection results are compared. is there.
[0054]
According to a second aspect of the present invention, in the first aspect, the control circuit unit determines that the disconnecting switch is abnormal if the inter-terminal voltage detected by the voltage detection unit is higher than a predetermined threshold value. When the contacts of the disconnecting switch are welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit unit side in the disconnecting switch. Since it becomes higher than the predetermined threshold value, it is possible to determine the abnormality of the parallel-off switch.
[0055]
According to a third aspect of the present invention, in the first aspect of the present invention, an effective value determination is performed to determine 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. Unit, and an integrated value determination unit that determines whether the result of integrating the voltage between terminals detected by the voltage detection unit for a period that is a natural number multiple of the power supply cycle of the commercial system becomes substantially zero, and the control circuit unit includes: When the effective value determining unit determines that the effective value of the terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the integrated value determining unit determines that the result of integrating the terminal voltage is substantially zero. It is characterized by judging that the disconnecting switch is abnormal, and when the contacts of the disconnecting switch are welded, the power supply voltage of the commercial system appears between the terminals on the inverter circuit section side in the disconnecting switch. Therefore, the effective value of the terminal voltage detected by the voltage It becomes substantially the same as the effective value, and, since the natural number times the period integration result of the voltage power supply cycle between the terminals becomes substantially zero, it is possible to reliably determine the abnormality of the disconnecting switch.
[0056]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the zero cross point is detected from a detection result of the voltage detection section and a time interval at which the zero cross point detects the zero cross point. A frequency determination unit that determines whether the frequency matches the power supply frequency of the commercial system, and the control circuit unit determines that the frequency obtained from the zero-cross point detection interval matches the power supply frequency. When the disconnection switch is determined to be abnormal, it is determined that the disconnection switch is abnormal.If the contacts of the disconnection switch are welded, the power supply voltage of the commercial system is connected between the terminals on the inverter circuit section side of the disconnection switch. Since the frequency obtained from the detection interval of the zero-cross point of the terminal voltage coincides with the power supply frequency, it is possible to reliably determine the abnormality of the disconnection switch. Moreover, since there is no circuit for comparing the voltage level of the voltage between terminals with the reference value as in the second and third aspects of the present invention, the setting of the reference value becomes unnecessary, and the configuration of the circuit for making the determination can be simplified.
[0057]
According to a fifth aspect of the present invention, in the first aspect, an effective value determination is performed to determine whether or not the effective value of the inter-terminal voltage obtained from the detection result of the voltage detector is substantially the same as the effective value of the commercial power supply voltage. Unit, a zero-crossing detecting unit that detects a zero-crossing point from the detection result of the voltage detecting unit, and a predetermined reference whose frequency obtained from a time interval at which the zero-crossing detecting unit detects the zero-crossing point is lower than the power supply frequency. A frequency determination unit that determines whether the frequency is equal to or higher than the frequency, 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 When the frequency determination unit determines that the frequency obtained from the detection interval of the zero crossing point is equal to or higher than the reference frequency, the disconnecting switch is determined to be abnormal, and the contacts of the disconnecting switch are welded. In the case of inversion in the disconnecting switch Since the power supply voltage of the commercial system appears between the terminals on the circuit side, the effective value of the voltage between the terminals detected by the voltage detection unit becomes substantially the same as the effective value of the commercial system, and the zero cross point of the terminal voltage Since the frequency obtained from the detection interval is equal to or higher than the reference frequency, it is possible to reliably determine the abnormality of the parallel-off switch. Further, although the number of steps for comparing the effective value of the inter-terminal voltage with the reference value is increased as compared with the invention of claim 4, the setting of the reference frequency used for the determination can be roughly, so that the setting operation of the reference frequency is simplified. There is also an effect.
[0058]
The invention according to claim 6 is provided between the inverter circuit unit and the commercial system, an inverter circuit unit that converts the DC power of the DC power supply into AC power by switching with a switch element and supplies the AC power to the commercial system side, A disconnecting switch for interconnecting or disconnecting the inverter circuit and the commercial system, an on / off control of a switch element to control an output of the inverter circuit, and an on / off of the disconnecting switch. A control circuit unit that controls off and 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; A second voltage detection unit for detecting a voltage between terminals on the system side, wherein the control circuit unit stops the inverter circuit unit and starts the interconnection operation with the disconnection switch turned off. The detection result of the first voltage detection unit and the detection result of the second voltage detection unit are compared, and if the detection results of the first and second voltage detection units are substantially the same, the disconnection switch When the contacts of the disconnecting switch are welded, the commercial system power supply voltage is applied between the terminals on the inverter circuit side of the disconnecting switch. Therefore, based on the voltage between the terminals on the inverter circuit unit side and the voltage between the terminals on the commercial system side detected by the first and second voltage detection units, it is determined whether or not the disconnection switch is normal. When the control circuit determines that the disconnection switch is abnormal, the control circuit stops the interconnection operation, so that it is possible to prevent the interconnection operation from being started in a state where the disconnection switch is broken. Therefore, it is not necessary to connect two disconnecting switches in series in order to ensure safety as in the conventional grid-connected inverter device, and it is possible to reduce the number of disconnecting switches and reduce costs. it can. When the control circuit determines whether or not the disconnecting switch is normal only from the voltage between the terminals of the disconnecting switch on the side of the inverter circuit section, the inverter circuit section operates before the determination and the inverter circuit section side operates. If there is a voltage remaining between the terminals, there is a risk of erroneously detecting the remaining voltage. However, the terminal-to-terminal voltage on the inverter circuit unit side detected by the first and second voltage detectors and the terminal on the commercial system side If the inter-voltages are substantially the same, it is determined that the disconnecting switch is abnormal, so that erroneous detection due to the residual voltage can be prevented.
[Brief description of the drawings]
FIG. 1 is a block diagram of a solar cell power generation system using a grid-connected inverter device according to a first embodiment.
FIG. 2 is a block diagram illustrating a main part of a system interconnection inverter device according to a second embodiment.
FIG. 3 is a block diagram illustrating a main part of a system interconnection inverter device according to a third embodiment.
FIG. 4 is a block diagram illustrating a main part of a system interconnection inverter device according to a fourth embodiment.
FIG. 5 is a block diagram illustrating a main part of a system interconnection inverter device according to a fifth embodiment.
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 Step-up circuit
5 Sine wave generation circuit
6. Filter circuit
7 Disconnection switch
8 Control circuit
9 Voltage detector
30 Commercial system

Claims

An inverter circuit section that converts the DC power of the DC power supply 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 section and the commercial system. A disconnecting switch for interconnecting or disconnecting the switch, and controlling the on / off of the switch element to control the output of the inverter circuit unit, and controlling the on / off of the disconnecting switch to control the inverter circuit A control circuit unit for interconnecting or disconnecting the unit, and a voltage detection unit for detecting a voltage between terminals on the inverter circuit unit side in the disconnection switch, the control circuit unit stops the inverter circuit unit and disconnects In the state immediately before starting the interconnection operation with the switch turned off, if it is determined whether the disconnecting switch is normal based on the voltage between terminals detected by the voltage detection unit and it is determined to be abnormal System interconnection inverter apparatus characterized by cancel the interconnected operation.

The system interconnection inverter according to claim 1, wherein the control circuit unit determines that the disconnecting switch is abnormal if the voltage between the terminals detected by the voltage detection unit is higher than a predetermined threshold value. apparatus.

An effective value determination unit that determines whether the effective value of the 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 converts the terminal voltage detected by the voltage detection unit to a commercial value. An integrated value determining unit for determining whether or not the result of integration for a natural number multiple of the power supply cycle of the system becomes substantially zero; and the control circuit unit determines that the effective value of the terminal voltage is the effective value of the commercial power supply voltage. When the effective value determining unit determines that the values are substantially the same as each other, and when the integrated value determining unit determines that the result of integrating the terminal voltages is substantially zero, it is determined that the disconnection switch is abnormal. The system interconnection inverter device according to claim 1, wherein:

A zero-crossing detector that detects a zero-crossing point from the detection result of the voltage detector, and whether or not the frequency obtained from the time interval at which the zero-crossing detector detects the zero-crossing point matches the power frequency of the commercial system The control circuit unit determines 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. The system interconnection inverter device according to claim 1, wherein:

An effective value determining unit that determines 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 a zero cross point based on the detection result of the voltage detection unit. A zero-crossing detecting unit for detecting, and a frequency determining unit for determining whether the frequency obtained from the time interval at which the zero-crossing detecting unit detects the zero-crossing point is equal to or higher than a predetermined reference frequency lower than the power supply frequency. The control circuit unit determines that the effective value of the terminal-to-terminal voltage is substantially the same as the effective value of the commercial power supply voltage, and the effective value determination unit determines that the frequency obtained from the zero-cross point detection interval is the reference frequency. 2. The system interconnection inverter device according to claim 1, wherein when the frequency determination unit determines that the above is the case, the disconnection switch is determined to be abnormal.

An inverter circuit section that converts the DC power of the DC power supply 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 section and the commercial system. A disconnecting switch for interconnecting or disconnecting the switch, and controlling the on / off of the switch element to control the output of the inverter circuit unit, and controlling the on / off of the disconnecting switch to control the inverter circuit A control circuit unit for interconnecting or disconnecting the unit, a first voltage detection unit for detecting a terminal voltage 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 section for detecting the voltage, wherein the control circuit section stops the inverter circuit section and starts the first voltage detection in a state immediately before starting the interconnection operation in which the disconnection switch is turned off. The level of the detection result of the unit and the detection result of the second voltage detection unit are compared, and if the detection results of the first and second voltage detection units are substantially the same, it is determined that the disconnection switch is abnormal, A system interconnection inverter device, wherein the interconnection operation is stopped.