JP2004215439A - System cooperation inverter arrangement - Google Patents

System cooperation inverter arrangement Download PDF

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Publication number
JP2004215439A
JP2004215439A JP2003001257A JP2003001257A JP2004215439A JP 2004215439 A JP2004215439 A JP 2004215439A JP 2003001257 A JP2003001257 A JP 2003001257A JP 2003001257 A JP2003001257 A JP 2003001257A JP 2004215439 A JP2004215439 A JP 2004215439A
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power supply
negative
ground fault
voltage
switch
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JP3884386B2 (en
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Shunsuke Nishi
俊輔 西
Masaki Eguchi
政樹 江口
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Sharp Corp
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Sharp Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B10/00—Integration of renewable energy sources in buildings
    • Y02B10/10—Photovoltaic [PV]

Abstract

<P>PROBLEM TO BE SOLVED: To detect a ground fault in solar batteries with use of inexpensive components. <P>SOLUTION: When a first converter 14a is started, a first switch 23a is closed and further second and third switches 23b and 23c are opened by control through first to third converter control portions 19a to 19c. If the positive pole of a first solar battery 12a is electrically connected to the ground, the following takes place: when the first switch 23a is closed, the positive pole and the negative pole of the first solar battery 12a are short-circuited to each other, and the direct-current voltage Vin of the first solar battery 12a drops. If the positive pole of the first solar battery 12a is not electrically connected to the ground, the following takes place: when the first switch 23a is closed, the direct-current voltage Vin of the first solar battery 12a does not drop. Therefore, the first converter control portion 19a monitors the direct-current voltage Vin of the first solar battery 12a. If the direct-current voltage Vin of the first solar battery 12a drops when the first switch 23a is closed, the first converter control portion 19a judges that the positive pole of the first solar battery 12a is electrically connected to the ground. <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、蓄電池、発電機等の直流電源の直流出力を交流に変換して商用電力系統に供給する系統連系インバータ装置に関する。
【０００２】
【従来の技術】
例えば、住宅用太陽光発電システムは、太陽電池の直流出力を交流に変換して商用電力系統に供給する系統連系インバータ装置を備えており、太陽電池の直流出力を商用周波数の交流電力に変換し、この交流電力を家庭内の各電化製品に供給したり、家庭内で消費し切れなかった余剰の交流電力を電力会社の電力線に供給し売っている。
【０００３】
従来の系統連系インバータ装置は、例えば図７に示す様なものである。この装置では、太陽電池１０１の直流電圧出力を昇圧コンバータ１０２により昇圧し、この昇圧した直流電圧をインバータ１０３により交流電圧に変換して、この交流電圧のノイズ成分を低域通過フィルター１０４により除去してから、この交流電圧を連系リレー１０５及び漏電ブレーカー１０６を介して商用電力系統１０７に供給している。
【０００４】
昇圧コンバータ１０２は、リアクトルＬａ、ダイオードＤａ、コンデンサＣａ、及びスイッチング素子Ｓａを備える昇圧チョッパーであり、スイッチング素子Ｓａをオンオフして、太陽電池１０１の直流電圧を３５０Ｖ程度の一定電圧に昇圧する。インバータ１０３は、各スイッチング素子Ｓｂ，Ｓｅと各スイッチング素子Ｓｃ，Ｓｄを備えるＰＷＭ（パルス幅変調）インバータであり、各スイッチング素子をオンオフして、直流電圧から商用周波数の交流電圧を形成する。ＰＷＭ周波数は、一般に、２０ｋＨｚ程度に設定される。商用電力系統１０７は、単相３線式系統の柱上変圧器１０７ａを含んでおり、柱上変圧器１０７ａの中点１０８を接地している。制御回路１０９は、昇圧コンバータ１０２、インバータ１０３、及び連系リレー１０５等を制御している。
【０００５】
また、この系統連系インバータ装置には、太陽電池１０１からの電力供給ラインが地絡したときに該地絡を判定して、該装置を保護する保護回路を設けている。この保護回路は、太陽電池１０１と昇圧コンバータ１０２間の電力供給ラインの電流を検出する地絡検出用コア２０１、地絡検出用コア２０１の検出出力に基づいて地絡発生の有無を判定する判定回路２０２、連系リレー１０５、及び制御回路１０９等を含む。判定回路２０２により地絡が発生したと判定されると、これに応答して制御回路１０９は、インバータ１０３を停止させたり、連系リレー１０５を開放する。これにより、この系統連系インバータ装置が保護される。
【０００６】
図８は、従来の他の系統連系インバータ装置を示している。この装置では、地絡検出用コア２０１を連系リレー１０５と漏電ブレーカー１０６間の電力供給ラインの周囲に設けて、該電力供給ラインの電流を検出し、地絡検出用コア２０１の検出出力を判定回路２０２に供給している。制御回路１０９は、判定回路２０２の判定結果に応じて、インバータ１０３を停止させたり、連系リレー１０５を開放する。
【０００７】
また、特許文献１には、インバータの入力側で、太陽電池の正極と負極に流れるそれぞれの直流電流の差を検出し、この差に基づいて太陽電池の地絡を判定するという技術が開示されている。
【０００８】
【特許文献１】
特開平９−２８５０１５号公報
【０００９】
【発明が解決しようとする課題】
しかしながら、図７に示す従来の装置において、複数の太陽電池１０１及び複数の昇圧コンバータ１０２を並列に設ける場合は、各太陽電池１０１と各昇圧コンバータ１０２間に複数の地絡検出用コア２０１を設ける必要があり、高価な部品の使用個数が増加して、コストが増大した。
【００１０】
また、図８に示す従来の装置において、該装置内の電力供給ラインにトランスを介在させて、直流的な絶縁を施す場合は、該トランスの２次側、つまり地絡検出用コア２０１の部位に太陽電池１０１の地絡による零相電流が流れなくなるため、直流の地絡電流を検出することができなかった。
【００１１】
更に、図７及び図８の装置のいずれにおいても、太陽電池の正極及び負極のいずれが地絡しているかを特定することができなかった。
【００１２】
特許文献１の装置においても、複数の太陽電池を並列に設ける場合は、高価な部品の使用個数が増加して、コストが増大し、また太陽電池の正極及び負極のいずれが地絡しているかを特定するまでには至っていない。
【００１３】
そこで、本発明は、安価な部品を使用して、直流電源の正極及び負極のいずれが地絡しているかを特定することができ、装置内の電力供給ラインにトランスを介在させても、直流の地絡電流を検出することが可能な系統連系インバータ装置を提供することを目的とする。
【００１４】
【課題を解決するための手段】
上記課題を解決するために、本発明は、直流電源の直流出力を電圧変換する電圧変換手段、電圧変換手段の直流出力を交流に変換する直流交流変換手段、及び直流交流変換手段の交流出力側と商用電力系統間に挿入された交流出力側スイッチ手段を備える系統連系インバータ装置において、直流電源の負極側ラインとアース間に挿入された負極側スイッチ手段と、交流出力側スイッチ手段をオフにして、直流交流変換手段の交流出力側と商用電力系統間を切り離した状態で、負極側スイッチ手段を切り換えたときの直流電源の電流変化もしくは電圧変化に基づいて、直流電源の地絡を判定する地絡判定手段とを備えている。
【００１５】
この様な構成の本発明によれば、負極側スイッチ手段を直流電源の負極側ラインとアース間に挿入しているので、負極側スイッチ手段を切り換えれば、直流電源の負極がアースに接続されたり切り離される。そして、直流電源の負極がアースに接続されたり切り離されたときには、直流電源が地絡しているか否かにより直流電源の電流変化もしくは電圧変化が異なる。このため、負極側スイッチ手段を切り換えたときの直流電源の電流変化もしくは電圧変化に基づいて、直流電源の地絡を判定することができる。また、該装置内の電力供給ラインにトランスを介在させても、直流電源が地絡しているか否かにより直流電源の電流変化もしくは電圧変化が異なるので、直流電源の地絡電流を検出することができる。
【００１６】
また、本発明においては、地絡判定手段は、負極側スイッチ手段をオンにして、直流電源の負極側ラインをアースに接続したときの直流電源の電流変化もしくは電圧変化に基づいて、直流電源の正極の地絡を判定している。
【００１７】
この様に負極側スイッチ手段を切り換えて、直流電源の負極をアースに接続したり切り離せば、直流電源の正極が地絡しているか否かにより直流電源の電流変化もしくは電圧変化が異なるので、直流電源の正極の地絡を判定することができる。
【００１８】
次に、本発明は、複数の直流電源の直流出力を電圧変換するそれぞれの電圧変換手段、各電圧変換手段の直流出力を交流に変換する直流交流変換手段、及び直流交流変換手段の交流出力側と商用電力系統間に挿入された交流出力側スイッチ手段を備える系統連系インバータ装置において、各直流電源の負極側ラインとアース間に挿入されたそれぞれの負極側スイッチ手段と、各直流電力源の負極側ラインを共通接続する共通接続線と、交流出力側スイッチ手段をオフにして、直流交流変換手段の交流出力側と商用電力系統間を切り離した状態で、各負極側スイッチ手段を選択的に切り換えたときの各直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、各直流電源の地絡を判定する地絡判定手段とを備えている。
【００１９】
この様な構成の本発明によれば、複数の直流電源、複数の電圧変換手段、及び直流交流変換手段を備えることを前提とし、複数の負極側スイッチ手段を各直流電源の負極側ラインとアース間に挿入し、各直流電力源の負極側ラインを共通接続線により共通接続している。ここでも、各負極側スイッチ手段を切り換えれば、各直流電源の負極がアースに接続されたり切り離され、このときには各直流電源が地絡しているか否かにより各直流電源の負極側ラインの電流変化もしくは電圧変化が異なる。このため、各負極側スイッチ手段を切り換えたときの各直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、各直流電源の地絡を判定することができる。また、該装置内の電力供給ラインにトランスを介在させても、各直流電源が地絡しているか否かにより直流電源の負極側ラインの電流変化もしくは電圧変化が異なるので、各直流電源の地絡電流を検出することができる。更に、各直流電源の負極側ラインに接続される各負極側スイッチ手段として、安価な部品を適用することができるので、コストの増大を抑えることができる。
【００２０】
また、本発明においては、地絡判定手段は、各直流電源のいずれかを選択して、該選択した直流電源に対応する電圧変換手段を起動した上で、各負極側スイッチ手段を選択的に切り換えたときの各直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、各直流電源の負極の地絡を判定している。
【００２１】
この様に各直流電源のいずれかに対応する電圧変換手段を起動した上で、各負極側スイッチ手段を選択的に切り換えて、各直流電源の負極をアースに選択的に接続したり切り離せば、任意の直流電源の負極が地絡しているか否かにより他の直流電源の負極側ラインの電流変化もしくは電圧変化が異なるので、該任意の直流電源の負極の地絡を判定することができる。
【００２２】
更に、本発明においては、地絡判定手段は、各直流電源のいずれかを選択して、該選択した直流電源に対応する電圧変換手段を起動すると共に、該選択した直流電源に対応する負極側スイッチをオフにし、選択しなかった他の直流電源に対応する負極側スイッチをオンにしたときの該選択しなかった他の直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、該選択した直流電源の負極の地絡を判定している。また、各直流電源を順次選択することにより、該各直流電源の負極の地絡を順次判定している。
【００２３】
この様な手順に従って、選択した直流電源の負極の地絡を判定することができ、延いては各直流電源の負極の地絡を順次速やかに判定することができる。
【００２４】
また、本発明においては、地絡判定手段は、各直流電源のいずれかを選択して、該選択した直流電源に対応する電圧変換手段を起動すると共に、該選択した直流電源に対応する負極側スイッチをオンにし、選択しなかった他の直流電源に対応する負極側スイッチをオフにしたときの該選択しなかった他の直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、該選択しなかった直流電源の負極の地絡を判定している。更に、各直流電源を順次選択することにより、該各直流電源の負極の地絡を順次判定している。
【００２５】
この様な手順に従って、選択しなかった直流電源の負極の地絡を判定することができ、延いては各直流電源の負極の地絡を順次速やかに判定することができる。
【００２６】
【発明の実施の形態】
以下、本発明の実施形態を添付図面を参照して詳細に説明する。
【００２７】
図１は、本発明の系統連系インバータ装置の一実施形態を示すブロック図である。本実施形態の系統連系インバータ装置１１は、第１、第２、及び第３太陽電池１２ａ，１２ｂ，１２ｃの直流出力を入力し、この直流出力を交流に変換して、交流出力を商用電力系統１３に供給するものである。
【００２８】
この系統連系インバータ装置１１では、第１乃至第３太陽電池１２ａ〜１２ｃの直流電圧出力を第１乃至第３コンバータ１４ａ〜１４ｃによりそれぞれ昇圧し、第１乃至第３コンバータ１４ａ〜１４ｃの直流電圧出力をインバータ１５により交流電圧に変換して、この交流電圧のノイズ成分を低域通過フィルター１６により除去してから、この交流電圧を連系リレー１７及び漏電ブレーカー１８を介して商用電力系統１３に供給している。
【００２９】
第１乃至第３コンバータ１４ａ〜１４ｃは、スイッチング素子、高周波トランス、及び整流ダイオード等からなるＤＣ−ＤＣコンバータであり、スイッチング素子を第１乃至第３コンバータ制御部１９ａ〜１９ｃからのＰＦＭ（パルス周波数変調）制御信号によりオンオフされ、第１乃至第３太陽電池１２ａ〜１２ｃからの１５０Ｖ〜２５０Ｖ程度の直流電圧を３５０Ｖ程度まで昇圧して出力する。ＰＦＭ制御信号の周波数は、１５ｋＨｚ〜７０ｋＨｚ程度である。
【００３０】
インバータ１５は、４つのスイッチング素子等からなるＰＷＭ（パルス幅変調）インバータであり、各スイッチング素子をインバータ制御部２５からのＰＷＭ制御信号によりオンオフされ、第１乃至第３コンバータ１４ａ〜１４ｃの直流電圧出力を商用周波数の交流電圧に変換する。また、インバータ１５は、第１乃至第３コンバータ１４ａ〜１４ｃの直流電圧出力が３５０Ｖ程度に上昇するまでは起動されず、この直流電圧出力が３５０Ｖ程度に上昇してから起動される。各スイッチング素子は、例えばＩＧＢＴ（Ｉｎｓｕｌａｔｅｄ Ｇａｔｅ Ｂｉｐｏｌａｒ Ｔｒａｎｓｉｓｔｏｒ）である。ＰＷＭ制御信号の周波数は、１９ｋＨｚ程度である。
【００３１】
低域通過フィルター１６は、インバータ１５からの交流電圧のノイズ成分を除去して、この交流電圧の波形を正弦波に成形する。電源２０は、系統連系インバータ装置１１の各部に電力を供給する。
【００３２】
また、商用電力系統１３は、単相３線式系統の柱上変圧器１３ａを含んでおり、柱上変圧器１３ａの中点を接地している。
【００３３】
一方、第１乃至第３太陽電池１２ａ〜１２ｃの第１乃至第３負極側ライン２１ａ〜２１ｃには、第１乃至第３電流検出器（直流抵抗）２２ａ〜２２ｃを挿入している。また、第１乃至第３電流検出器２２ａ〜２２ｃよりも第１乃至第３太陽電池１２ａ〜１２ｃ側で、第１乃至第３負極側ライン２１ａ〜２１ｃとアース間に第１乃至第３スイッチ２３ａ〜２３ｃを挿入している。更に、第１乃至第３負極側ライン２１ａ〜２１ｃを共通接続線２４により共通接続している。
【００３４】
第１乃至第３コンバータ制御部１９ａ〜１９ｃは、第１乃至第３スイッチ２３ａ〜２３ｃを選択的に切り換えつつ、第１乃至第３太陽電池１２ａ〜１２ｃの直流電圧出力を検出したり、第１乃至第３負極側ライン２１ａ〜２１ｃに流れる電流を第１乃至第３電流検出器２２ａ〜２２ｃを通じて検出し、その結果として第１乃至第３太陽電池１２ａ〜１２ｃの地絡を判定する。
【００３５】
さて、この様な構成の系統連系インバータ装置１１において、初期状態のときには、インバータ１５が停止され、連系リレー１７が開成されて、系統連系インバータ装置１１から商用電力系統１３への電力供給が停止される。そして、系統連系インバータ装置１１の作動開始時には、第１乃至第３コンバータ１４ａ〜１４ｃが順次起動され、第１乃至第３コンバータ１４ａ〜１４ｃの直流電圧出力が３５０Ｖ程度に上昇すると、インバータ１５の作動が開始され、連系リレー１７が閉成されて、系統連系インバータ装置１１から商用電力系統１３への電力供給が開始される。
【００３６】
また、第１乃至第３コンバータ１４ａ〜１４ｃが順次起動され、第１乃至第３コンバータ１４ａ〜１４ｃの直流電圧出力が３５０Ｖ程度に上昇するまでの間に、第１乃至第３コンバータ制御部１９ａ〜１９ｃによる第１乃至第３太陽電池１２ａ〜１２ｃの地絡の判定が行われる。
【００３７】
次に、第１乃至第３太陽電池１２ａ〜１２ｃの地絡の判定手順を図２（ａ）のタイミングチャート、及び図３乃至図６のブロック図を参照して説明する。
【００３８】
まず、図２（ａ）の時点Ｔ０で第１コンバータ１４ａが起動されると、この起動直後の時点Ｔ０〜Ｔ１の間、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第１スイッチ２３ａを閉成すると共に、第２及び第３スイッチ２３ｂ，２３ｃを開成する。仮に、図３に示す様に第１太陽電池１２ａの正極が地絡していたならば、第１スイッチ２３ａの閉成により第１太陽電池１２ａの正極及び負極が短絡し、第１太陽電池１２ａの直流電圧Ｖｉｎが低下する。また、第１太陽電池１２ａの正極が地絡していなければ、第１スイッチ２３ａの閉成により第１太陽電池１２ａの直流電圧Ｖｉｎが低下することはない。そこで、第１コンバータ制御部１９ａは、第１太陽電池１２ａの直流電圧Ｖｉｎを監視し、第１スイッチ２３ａの閉成に伴い、第１太陽電池１２ａの直流電圧Ｖｉｎが低下すると、第１太陽電池１２ａの正極が地絡しているものとみなして、この旨をブザー音やＬＥＤの点灯により報知する。
【００３９】
また、第２コンバータ１４ｂの起動直後（図２（ａ）に示さず）には、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第２スイッチ２３ｂを閉成すると共に、第１及び第３スイッチ２３ａ，２３ｃを開成する。そして、第２コンバータ制御部１９ｂは、第２スイッチ２３ｂの閉成に伴い、第２太陽電池１２ｂの直流電圧Ｖｉｎが低下すると、第２太陽電池１２ｂの正極が地絡しているものとみなして、この旨をブザー音やＬＥＤの点灯により報知する。
【００４０】
同様に、第３コンバータ１４ｃの起動直後（図２（ａ）に示さず）には、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第３スイッチ２３ｃを閉成すると共に、第１及び第２スイッチ２３ａ，２３ｂを開成する。そして、第３コンバータ制御部１９ｃは、第３スイッチ２３ｃの閉成に伴い、第３太陽電池１２ｃの直流電圧Ｖｉｎが低下すると、第３太陽電池１２ｃの正極が地絡しているものとみなして、この旨をブザー音やＬＥＤの点灯により報知する。
【００４１】
次に、図２（ａ）の時点Ｔ１〜Ｔ２の間、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第２スイッチ２３ｂを閉成すると共に、第１及び第３スイッチ２３ａ，２３ｃを開成する。仮に、図４に示す様に第１太陽電池１２ａの負極が地絡していたならば、第２スイッチ２３ｂの閉成に伴い、第１太陽電池１２ａの第１負極側ライン２１ａ→共通接続線２４→第２負極側ライン２１ｂ→第２スイッチ２３ｂ→アースという経路で地絡電流が流れる。また、第１太陽電池１２ａの負極が地絡していなければ、第２スイッチ２３を閉成しても、第１太陽電池１２ａの第１負極側ライン２１ａから共通接続線２４を通じて第２負極側ライン２１ｂへと電流が流れることはない。そこで、第２コンバータ制御部１９ｂは、第２負極側ライン２１ｂに流れる電流を第２電流検出器２２ｂを通じて監視し、第２スイッチ２３ｂの閉成に伴い、第２負極側ライン２１ｂに流れる電流を検出すると、第１太陽電池１２ａの負極が地絡しているものとみなして、この旨をブザー音やＬＥＤの点灯により報知する。
【００４２】
尚、ここでは、第２スイッチ２３ｂを閉成しているが、この代わりに第３スイッチ２３ｃを閉成して、第３負極側ライン２１ｃに流れる電流を第３電流検出器２２ｃを通じて検出したり、第２及び第３スイッチ２３ｂ，２３ｃを閉成して、第２及び第３負極側ライン２１ｂ，２１ｃに流れる電流を検出して、第１太陽電池１２ａの負極の地絡を判定しても構わない。
【００４３】
次に、図２（ａ）の時点Ｔ２〜Ｔ３の間、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第１スイッチ２３ａを閉成すると共に、第２及び第３スイッチ２３ｂ，２３ｃを開成する。仮に、図５に示す様に第２太陽電池１２ｂの負極が地絡していたならば、第１スイッチ２３ａの閉成に伴い、第１太陽電池１２ａの第１負極側ライン２１ａ→共通接続線２４→第２負極側ライン２１ｂ→アースという経路で地絡電流が流れる。また仮に、図６に示す様に第３太陽電池１２ｃの負極が地絡していたならば、第１スイッチ２３ａの閉成に伴い、第１太陽電池１２ａの第１負極側ライン２１ａ→共通接続線２４→第３負極側ライン２１ｃ→アースという経路で電流が流れる。更に、第２及び第３太陽電池１２ｂ，１２ｃの負極のいずれも地絡していなければ、第１スイッチ２３ａを閉成しても、第２負極側ライン２１ｂもしくは第３負極側ライン２１ｃに電流が流れることはない。そこで、第２コンバータ制御部１９ｂは、第２負極側ライン２１ｂに流れる電流を第２電流検出器２２ｂを通じて監視し、第１スイッチ２３ａの閉成に伴い、第２負極側ライン２１ｂに流れる電流を検出すると、第２太陽電池１２ｂの負極が地絡しているものとみなして、この旨をブザー音やＬＥＤの点灯により報知する。同様に、第３コンバータ制御部１９ｃは、第３負極側ライン２１ｃに流れる電流を第３電流検出器２２ｃを通じて監視し、第１スイッチ２３ａの閉成に伴い、第３負極側ライン２１ｃに流れる電流を検出すると、第３太陽電池１２ｃの負極が地絡しているものとみなして、この旨をブザー音やＬＥＤの点灯により報知する。
【００４４】
こうして第１乃至第３太陽電池１２ａ〜１２ｃの地絡の判定が終了し、第１乃至第３太陽電池１２ａ〜１２ｃのいずれも地絡していなければ、第１乃至第３コンバータ１４ａ〜１４ｃが作動され、第１乃至第３コンバータ１４ａ〜１４ｃの直流電圧出力が３５０Ｖ程度に上昇すると、インバータ１５の作動が開始され、連系リレー１７が閉成されて、系統連系インバータ装置１１から商用電力系統１３へと電力供給が開始される。
【００４５】
この様に本実施形態の系統連系インバータ装置１１では、第１乃至第３スイッチ２３ａ〜２３ｃを選択的に切り換えつつ、第１乃至第３太陽電池１２ａ〜１２ｃの地絡を判定することができる。また、第１乃至第３電流検出器（直流抵抗）２２ａ〜２２ｃ及び第１乃至第３スイッチ２３ａ〜２３ｃという様な安価な部品を用いているので、コストの増大を抑えることができる。更に、第１乃至第３太陽電池１２ａ〜１２ｃと商用電力系統１３間に、第１乃至第３コンバータ１４ａ〜１４ｃの高周波トランスが介在するものの、各高周波トランスの１次側に第１乃至第３電流検出器２２ａ〜２２ｃを設けているため、第１乃至第３太陽電池１２ａ〜１２ｃの地絡電流を検出することができ、第１乃至第３太陽電池１２ａ〜１２ｃの地絡を判定することができる。
【００４６】
ところで、図２（ａ）のタイミングチャートの代わりに、図２（ｂ）のタイミングチャートに従って第１乃至第３コンバータ１４ａ〜１４ｃ及び第１乃至第３スイッチ２３ａ〜２３ｃを制御することによっても、第１乃至第３太陽電池１２ａ〜１２ｃの地絡を判定することができる。
【００４７】
図２（ｂ）のタイミングチャートによれば、まず時点Ｔ０〜Ｔ１の間、第１コンバータ１４ａを作動させ、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第１スイッチ２３ａを閉成すると共に、第２及び第３スイッチ２３ｂ，２３ｃを開成する。この状態では、図３に示す様に第１太陽電池１２ａの正極の地絡を第１コンバータ制御部１９ａにより判定し、図５に示す様に第２太陽電池１２ｂの負極の地絡を第２コンバータ制御部１９ｂにより判定し、図６に示す様に第３太陽電池１２ｃの負極の地絡を第３コンバータ制御部１９ｃにより判定することができる。
【００４８】
次に、時点Ｔ１〜Ｔ２の間、第２コンバータ１４ｂを作動させ、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第２スイッチ２３ｂを閉成すると共に、第１及び第３スイッチ２３ａ，２３ｃを開成する。この状態では、第２太陽電池１２ｂの正極の地絡を第２コンバータ制御部１９ｂにより判定し、第１太陽電池１２ａの負極の地絡を第１コンバータ制御部１９ａにより判定し、第３太陽電池１２ｃの負極の地絡を第３コンバータ制御部１９ｃにより判定することができる。
【００４９】
更に、時点Ｔ２〜Ｔ３の間、第３コンバータ１４ｃを作動させ、第１乃至第３コンバータ制御部１９ａ〜１９ｃの制御により第３スイッチ２３ｃを閉成すると共に、第１及び第２スイッチ２３ａ，２３ｂを開成する。この状態では、第３太陽電池１２ｃの正極の地絡を第３コンバータ制御部１９ｃにより判定し、第１太陽電池１２ａの負極の地絡を第１コンバータ制御部１９ａにより判定し、第２太陽電池１２ｂの負極の地絡を第２コンバータ制御部１９ｂにより判定することができる。
【００５０】
尚、本発明は、上記実施形態に限定されるものではなく、多様に変形することができる。例えば、コンバータやインバータの回路構成を変更しても構わない。また、太陽電池やコンバータの個数を増減しても良い。更に、コンバータやスイッチのオンオフのタイミングを多様に変更しても構わない。また、太陽電池の代わりに、他の種類の直流電源を適用しても良い。
【００５１】
【発明の効果】
以上説明した様に本発明によれば、負極側スイッチ手段を直流電源の負極側ラインとアース間に挿入しているので、負極側スイッチ手段を切り換えたときの直流電源の電流変化もしくは電圧変化に基づいて、直流電源の地絡を判定することができる。
【００５２】
また、複数の直流電源、複数の電圧変換手段、及び直流交流変換手段を備えることを前提とする場合は、複数の負極側スイッチ手段を各直流電源の負極側ラインとアース間に挿入し、各直流電力源の負極側ラインを共通接続線により共通接続しているので、各負極側スイッチ手段を切り換えたときの各直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、各直流電源の地絡を判定することができる。
【００５３】
更に、各直流電源の負極側ラインに接続される各負極側スイッチ手段として、安価な部品を適用することができるので、コストの増大を抑えることができる。また、該装置内の電力供給ラインにトランスを介在させても、直流電源が地絡しているか否かにより直流電源の電流変化もしくは電圧変化が異なるので、直流電源の地絡電流を検出することができる。
【図面の簡単な説明】
【図１】本発明の系統連系インバータ装置の一実施形態を示すブロック図である。
【図２】（ａ）及び（ｂ）は、図１の装置における第１乃至第３コンバータ及び第１乃至第３スイッチのオンオフを示すタイミングチャートである。
【図３】図１の装置における第１太陽電池の正極が地絡したときの地絡電流経路を示す図である。
【図４】図１の装置における第１太陽電池の負極が地絡したときの地絡電流経路を示す図である。
【図５】図１の装置における第２太陽電池の負極が地絡したときの地絡電流経路を示す図である。
【図６】図１の装置における第３太陽電池の負極が地絡したときの地絡電流経路を示す図である。
【図７】従来の系統連系インバータ装置を示すブロック図である。
【図８】従来の他の系統連系インバータ装置を示すブロック図である。
【符号の説明】
１１ 系統連系インバータ装置
１２ａ，１２ｂ，１２ｃ 第１、第２、及び第３太陽電池
１３ 商用電力系統
１４ａ，１４ｂ，１４ｃ 第１、第２、及び第３コンバータ
１５ インバータ
１６ 低域通過フィルター
１７ 連系リレー
１８ 漏電ブレーカー
１９ａ，１９ｂ，１９ｃ 第１、第２、及び第３コンバータ制御部
２０ 電源
２１ａ，２１ｂ，２１ｃ 第１、第２、及び第３負極側ライン
２２ａ，２２ｂ，２２ｃ 第１、第２、及び第３電流検出器
２３ａ，２３ｂ，２３ｃ 第１、第２、及び第３スイッチ
２４ 共通接続線
２５ インバータ制御部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a grid-connected inverter device that converts a DC output of a DC power supply such as a solar cell, a storage battery, and a generator into AC and supplies the AC to a commercial power system.
[0002]
[Prior art]
For example, a residential photovoltaic power generation system includes a grid-connected inverter that converts the DC output of a solar cell into AC and supplies it to a commercial power system, and converts the DC output of the solar cell into AC power at a commercial frequency. In addition, this AC power is supplied to home appliances, and surplus AC power that cannot be consumed in the home is supplied to power lines of power companies for sale.
[0003]
A conventional system interconnection inverter device is, for example, as shown in FIG. In this device, the DC voltage output of the solar cell 101 is boosted by a boost converter 102, the boosted DC voltage is converted into an AC voltage by an inverter 103, and a noise component of the AC voltage is removed by a low-pass filter 104. After that, the AC voltage is supplied to the commercial power system 107 via the interconnection relay 105 and the earth leakage breaker 106.
[0004]
The boost converter 102 is a boost chopper including a reactor La, a diode Da, a capacitor Ca, and a switching element Sa, and turns on and off the switching element Sa to boost the DC voltage of the solar cell 101 to a constant voltage of about 350V. The inverter 103 is a PWM (pulse width modulation) inverter including each of the switching elements Sb and Se and each of the switching elements Sc and Sd, and turns on and off each switching element to form an AC voltage having a commercial frequency from a DC voltage. The PWM frequency is generally set to about 20 kHz. The commercial power system 107 includes a pole transformer 107a of a single-phase three-wire system, and a midpoint 108 of the pole transformer 107a is grounded. The control circuit 109 controls the boost converter 102, the inverter 103, the interconnection relay 105, and the like.
[0005]
Further, this grid-connected inverter device is provided with a protection circuit that determines the ground fault when the power supply line from the solar cell 101 is grounded and protects the device. The protection circuit detects a ground fault detection core 201 that detects a current of a power supply line between the solar cell 101 and the boost converter 102, and determines whether a ground fault has occurred based on a detection output of the ground fault detection core 201. The circuit 202, the interconnection relay 105, and the control circuit 109 are included. When the determination circuit 202 determines that a ground fault has occurred, the control circuit 109 stops the inverter 103 or opens the interconnection relay 105 in response to the determination. This protects the grid-connected inverter device.
[0006]
FIG. 8 shows another conventional system interconnection inverter device. In this device, a ground fault detection core 201 is provided around a power supply line between the interconnection relay 105 and the earth leakage breaker 106 to detect a current of the power supply line, and output a detection output of the ground fault detection core 201. It is supplied to the judgment circuit 202. The control circuit 109 stops the inverter 103 or opens the interconnection relay 105 according to the determination result of the determination circuit 202.
[0007]
Further, Patent Literature 1 discloses a technology in which a difference between respective DC currents flowing through a positive electrode and a negative electrode of a solar cell is detected on an input side of an inverter, and a ground fault of the solar cell is determined based on the difference. ing.
[0008]
[Patent Document 1]
JP-A-9-285015
[0009]
[Problems to be solved by the invention]
However, in the conventional apparatus shown in FIG. 7, when a plurality of solar cells 101 and a plurality of boost converters 102 are provided in parallel, a plurality of ground fault detecting cores 201 are provided between each solar cell 101 and each boost converter 102. The number of expensive parts that need to be used increases, and the cost increases.
[0010]
In the conventional device shown in FIG. 8, when a transformer is interposed in a power supply line in the device to provide DC isolation, the secondary side of the transformer, that is, the portion of the ground fault detecting core 201 is used. In this case, the zero-phase current caused by the ground fault of the solar cell 101 no longer flows, so that the DC ground fault current cannot be detected.
[0011]
Further, neither of the devices of FIGS. 7 and 8 could identify which of the positive electrode and the negative electrode of the solar cell was grounded.
[0012]
Also in the apparatus of Patent Document 1, when a plurality of solar cells are provided in parallel, the number of expensive components increases, the cost increases, and which of the positive electrode and the negative electrode of the solar cell is grounded Has not yet been identified.
[0013]
Therefore, the present invention can identify which of the positive electrode and the negative electrode of the DC power supply is grounded by using inexpensive components, and even if a transformer is interposed in the power supply line in the device, the DC power supply can be specified. It is an object of the present invention to provide a grid-connected inverter device capable of detecting a ground fault current.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a voltage conversion unit for converting a DC output of a DC power supply into a voltage, a DC / AC conversion unit for converting a DC output of the voltage conversion unit into an AC, and an AC output side of the DC / AC conversion unit. In the system interconnection inverter device having AC output side switch means inserted between the power supply system and the commercial power system, the negative side switch means inserted between the negative line of the DC power supply and the ground, and the AC output side switch means are turned off. The ground fault of the DC power supply is determined based on a current change or a voltage change of the DC power supply when the negative switch is switched in a state where the AC output side of the DC / AC conversion means is disconnected from the commercial power system. Ground fault determining means.
[0015]
According to the present invention having such a configuration, since the negative switch is inserted between the negative line of the DC power supply and the ground, the negative switch of the DC power supply is connected to the ground by switching the negative switch. Or separated. Then, when the negative electrode of the DC power supply is connected to ground or disconnected, the current change or voltage change of the DC power supply differs depending on whether the DC power supply is grounded or not. Therefore, a ground fault of the DC power supply can be determined based on a current change or a voltage change of the DC power supply when the negative switch is switched. Further, even if a transformer is interposed in the power supply line in the device, the current change or voltage change of the DC power supply differs depending on whether or not the DC power supply is grounded. Can be.
[0016]
Further, in the present invention, the ground fault determining means turns on the negative side switch means and, based on a current change or a voltage change of the DC power supply when the negative side line of the DC power supply is connected to the ground, based on the DC power supply. The ground fault of the positive electrode is determined.
[0017]
If the negative switch of the DC power supply is connected to the ground or disconnected by switching the negative switch means in this manner, the current change or voltage change of the DC power supply differs depending on whether or not the positive pole of the DC power supply is grounded. The ground fault of the positive electrode of the power supply can be determined.
[0018]
Next, the present invention provides a voltage conversion means for converting the DC outputs of a plurality of DC power supplies into a voltage, a DC / AC conversion means for converting the DC output of each voltage conversion means into an AC, and an AC output side of the DC / AC conversion means. And a grid-connected inverter device having AC output-side switch means inserted between the commercial power system, and a negative-side switch means inserted between the negative-side line of each DC power supply and the ground; With the common connection line for commonly connecting the negative side lines and the AC output side switch means turned off, and the AC output side of the DC / AC converter and the commercial power system are disconnected, each negative side switch means is selectively selected. Ground fault determining means for determining a ground fault of each DC power supply based on a current change or a voltage change of the negative line of each DC power supply at the time of switching.
[0019]
According to the present invention having such a configuration, it is assumed that a plurality of DC power supplies, a plurality of voltage conversion means, and a DC / AC conversion means are provided, and the plurality of negative switch means are connected to the negative line of each DC power supply and the ground. The negative side lines of the respective DC power sources are commonly connected by a common connection line. Again, if each negative switch is switched, the negative electrode of each DC power supply is connected or disconnected from the ground. At this time, the current on the negative line of each DC power supply depends on whether each DC power supply is grounded or not. Change or voltage change. For this reason, the ground fault of each DC power supply can be determined based on the current change or the voltage change of the negative line of each DC power supply when each negative switch means is switched. Also, even if a transformer is interposed in the power supply line in the device, the current change or voltage change in the negative line of the DC power supply differs depending on whether or not each DC power supply is grounded. A short circuit current can be detected. Further, since inexpensive components can be applied as the respective negative switch units connected to the negative lines of the respective DC power supplies, an increase in cost can be suppressed.
[0020]
Further, in the present invention, the ground fault determining means selects any one of the DC power supplies, activates the voltage conversion means corresponding to the selected DC power supply, and then selectively switches each negative switch means. The ground fault of the negative electrode of each DC power supply is determined based on the current change or voltage change of the negative line of each DC power supply at the time of switching.
[0021]
In this way, after activating the voltage conversion means corresponding to any of the DC power supplies, by selectively switching the respective negative-side switch means, and selectively connecting or disconnecting the negative electrode of each DC power supply to the ground, Since the current change or the voltage change of the negative line of another DC power supply differs depending on whether or not the negative electrode of any DC power supply is grounded, the ground fault of the negative electrode of the arbitrary DC power supply can be determined.
[0022]
Further, in the present invention, the ground fault determining means selects any one of the DC power supplies, activates the voltage conversion means corresponding to the selected DC power supply, and sets the negative side corresponding to the selected DC power supply. When the switch is turned off and the negative switch corresponding to the other unselected DC power supply is turned on, the selection is performed based on a current change or a voltage change in the negative line of the other unselected DC power supply. The ground fault of the negative electrode of the DC power supply is determined. In addition, by sequentially selecting each DC power supply, the ground fault of the negative electrode of each DC power supply is sequentially determined.
[0023]
According to such a procedure, the ground fault of the negative electrode of the selected DC power supply can be determined, and thus the ground fault of the negative electrode of each DC power supply can be sequentially and promptly determined.
[0024]
Further, in the present invention, the ground fault determining means selects any one of the DC power supplies, activates the voltage converting means corresponding to the selected DC power supply, and sets the negative side corresponding to the selected DC power supply. When the switch is turned on and the negative switch corresponding to the other unselected DC power supply is turned off, the selection is performed based on a current change or a voltage change of the negative line of the other unselected DC power supply. The negative ground fault of the DC power supply that has not been performed is determined. Further, by sequentially selecting each DC power supply, the ground fault of the negative electrode of each DC power supply is sequentially determined.
[0025]
According to such a procedure, it is possible to determine the ground fault of the negative electrode of the DC power supply that is not selected, and thus it is possible to sequentially and quickly determine the ground fault of the negative electrode of each DC power supply.
[0026]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0027]
FIG. 1 is a block diagram showing an embodiment of a system interconnection inverter device of the present invention. The grid-connected inverter device 11 of the present embodiment receives the DC outputs of the first, second, and third solar cells 12a, 12b, and 12c, converts the DC output to AC, and converts the AC output to commercial power. This is supplied to the system 13.
[0028]
In the system interconnection inverter device 11, the DC voltage outputs of the first to third solar cells 12a to 12c are boosted by the first to third converters 14a to 14c, respectively, and the DC voltage of the first to third converters 14a to 14c is increased. The output is converted into an AC voltage by an inverter 15, and a noise component of the AC voltage is removed by a low-pass filter 16, and the AC voltage is transmitted to a commercial power system 13 via an interconnection relay 17 and an earth leakage breaker 18. Supplying.
[0029]
Each of the first to third converters 14a to 14c is a DC-DC converter including a switching element, a high-frequency transformer, a rectifier diode, and the like. The first to third converters 14a to 14c use a PFM (pulse frequency) from the first to third converter control units 19a to 19c. The DC voltage of about 150 V to 250 V from the first to third solar cells 12 a to 12 c is boosted to about 350 V and output. The frequency of the PFM control signal is about 15 kHz to 70 kHz.
[0030]
The inverter 15 is a PWM (pulse width modulation) inverter including four switching elements and the like. Each of the switching elements is turned on / off by a PWM control signal from the inverter control unit 25, and the DC voltage of the first to third converters 14a to 14c. Converts output to AC voltage at commercial frequency. Further, the inverter 15 is not started until the DC voltage output of the first to third converters 14a to 14c rises to about 350V, and is started after the DC voltage output rises to about 350V. Each switching element is, for example, an IGBT (Insulated Gate Bipolar Transistor). The frequency of the PWM control signal is about 19 kHz.
[0031]
The low-pass filter 16 removes a noise component of the AC voltage from the inverter 15 and shapes the waveform of the AC voltage into a sine wave. The power supply 20 supplies power to each unit of the grid-connected inverter device 11.
[0032]
The commercial power system 13 includes a pole transformer 13a of a single-phase three-wire system, and a midpoint of the pole transformer 13a is grounded.
[0033]
On the other hand, first to third current detectors (DC resistances) 22a to 22c are inserted into the first to third negative electrode lines 21a to 21c of the first to third solar cells 12a to 12c. Further, on the first to third solar cells 12a to 12c side of the first to third current detectors 22a to 22c, the first to third switches 23a are connected between the first to third negative electrode side lines 21a to 21c and the ground. To 23c. Further, the first to third negative electrode side lines 21 a to 21 c are commonly connected by a common connection line 24.
[0034]
The first to third converter control units 19a to 19c detect the DC voltage output of the first to third solar cells 12a to 12c while selectively switching the first to third switches 23a to 23c, and The current flowing to the third to third negative electrode side lines 21a to 21c is detected through the first to third current detectors 22a to 22c, and as a result, the ground fault of the first to third solar cells 12a to 12c is determined.
[0035]
Now, in the system interconnection inverter device 11 having such a configuration, in the initial state, the inverter 15 is stopped, the interconnection relay 17 is opened, and power is supplied from the system interconnection inverter device 11 to the commercial power system 13. Is stopped. Then, at the start of the operation of the system interconnection inverter device 11, the first to third converters 14a to 14c are sequentially activated, and when the DC voltage output of the first to third converters 14a to 14c rises to about 350V, the inverter 15 starts operating. The operation is started, the interconnection relay 17 is closed, and power supply from the system interconnection inverter device 11 to the commercial power system 13 is started.
[0036]
In addition, the first to third converters 14a to 14c are sequentially activated, and the first to third converter controllers 19a to 19c are connected until the DC voltage output of the first to third converters 14a to 14c rises to about 350V. The determination of the ground fault of the first to third solar cells 12a to 12c by 19c is performed.
[0037]
Next, a procedure for determining a ground fault of the first to third solar cells 12a to 12c will be described with reference to the timing chart of FIG. 2A and the block diagrams of FIGS.
[0038]
First, when the first converter 14a is started at the time T0 in FIG. 2A, the first switch 23a is controlled by the first to third converter controllers 19a to 19c during the time T0 to T1 immediately after the start. And the second and third switches 23b and 23c are opened. If the positive electrode of the first solar cell 12a is grounded as shown in FIG. 3, the positive and negative electrodes of the first solar cell 12a are short-circuited by closing the first switch 23a. DC voltage Vin decreases. If the positive electrode of the first solar cell 12a is not grounded, the DC voltage Vin of the first solar cell 12a does not decrease by closing the first switch 23a. Therefore, the first converter control unit 19a monitors the DC voltage Vin of the first solar cell 12a, and when the DC voltage Vin of the first solar cell 12a decreases with the closing of the first switch 23a, the first solar cell It is considered that the positive electrode 12a is grounded, and this is notified by a buzzer sound or LED lighting.
[0039]
Immediately after the start of the second converter 14b (not shown in FIG. 2A), the second switch 23b is closed by the control of the first to third converter control units 19a to 19c, and the first and second converters are closed. The three switches 23a and 23c are opened. When the DC voltage Vin of the second solar cell 12b decreases with the closing of the second switch 23b, the second converter control unit 19b regards the positive electrode of the second solar cell 12b as having a ground fault. This is notified by a buzzer sound or LED lighting.
[0040]
Similarly, immediately after the start of the third converter 14c (not shown in FIG. 2A), the third switch 23c is closed under the control of the first to third converter control units 19a to 19c, and the first and third converters are closed. The second switches 23a and 23b are opened. When the DC voltage Vin of the third solar cell 12c decreases with the closing of the third switch 23c, the third converter control unit 19c considers that the positive electrode of the third solar cell 12c is grounded. This is notified by a buzzer sound or LED lighting.
[0041]
Next, during the time T1 to T2 in FIG. 2A, the second switch 23b is closed by the control of the first to third converter control units 19a to 19c, and the first and third switches 23a and 23c are turned off. Open. If the negative electrode of the first solar cell 12a is grounded as shown in FIG. 4, the first switch 21b is closed and the first negative electrode side line 21a of the first solar cell 12a is connected to the common connection line. A ground fault current flows in a route of 24 → second negative electrode side line 21b → second switch 23b → ground. In addition, if the negative electrode of the first solar cell 12a is not grounded, the second switch 23 is closed and the second negative electrode side through the common connection line 24 from the first negative line 21a of the first solar cell 12a. No current flows to the line 21b. Therefore, the second converter control unit 19b monitors the current flowing in the second negative line 21b through the second current detector 22b, and detects the current flowing in the second negative line 21b with the closing of the second switch 23b. Upon detection, it is considered that the negative electrode of the first solar cell 12a is grounded, and this is notified by a buzzer sound or LED lighting.
[0042]
Although the second switch 23b is closed here, the third switch 23c is closed instead, and the current flowing through the third negative line 21c is detected through the third current detector 22c. , The second and third switches 23b and 23c are closed to detect the current flowing through the second and third negative electrode side lines 21b and 21c to determine the ground fault of the negative electrode of the first solar cell 12a. I do not care.
[0043]
Next, during the time T2 to T3 in FIG. 2A, the first switch 23a is closed by the control of the first to third converter controllers 19a to 19c, and the second and third switches 23b and 23c are turned off. Open. If the negative electrode of the second solar cell 12b is grounded as shown in FIG. 5, the first switch 23a is closed and the first negative electrode side line 21a of the first solar cell 12a → common connection line A ground fault current flows in a route of 24 → second negative electrode side line 21b → earth. If the negative electrode of the third solar cell 12c is grounded as shown in FIG. 6, the first switch 23a is closed and the first negative electrode side line 21a of the first solar cell 12a → common connection A current flows in a route of line 24 → third negative electrode side line 21c → earth. Further, if neither of the negative electrodes of the second and third solar cells 12b and 12c is grounded, even if the first switch 23a is closed, the current flows to the second negative electrode side line 21b or the third negative electrode side line 21c. Does not flow. Therefore, the second converter control unit 19b monitors the current flowing through the second negative line 21b through the second current detector 22b, and detects the current flowing through the second negative line 21b with the closing of the first switch 23a. Upon detection, it is considered that the negative electrode of the second solar cell 12b is grounded, and this is notified by a buzzer sound or LED lighting. Similarly, the third converter control unit 19c monitors the current flowing in the third negative line 21c through the third current detector 22c, and detects the current flowing in the third negative line 21c with the closing of the first switch 23a. Is detected, it is considered that the negative electrode of the third solar cell 12c is grounded, and this is notified by a buzzer sound or LED lighting.
[0044]
Thus, the determination of the ground fault of the first to third solar cells 12a to 12c is completed, and if none of the first to third solar cells 12a to 12c is grounded, the first to third converters 14a to 14c are turned off. When the DC voltage output of the first to third converters 14a to 14c rises to about 350 V, the operation of the inverter 15 is started, the interconnection relay 17 is closed, and the commercial power Power supply to the system 13 is started.
[0045]
As described above, in the grid interconnection inverter device 11 of the present embodiment, the ground fault of the first to third solar cells 12a to 12c can be determined while selectively switching the first to third switches 23a to 23c. . Further, since inexpensive components such as the first to third current detectors (DC resistances) 22a to 22c and the first to third switches 23a to 23c are used, an increase in cost can be suppressed. Further, although high-frequency transformers of the first to third converters 14a to 14c are interposed between the first to third solar cells 12a to 12c and the commercial power system 13, the first to third converters are provided on the primary side of each high-frequency transformer. Since the current detectors 22a to 22c are provided, the ground fault current of the first to third solar cells 12a to 12c can be detected, and the ground fault of the first to third solar cells 12a to 12c can be determined. Can be.
[0046]
By the way, instead of the timing chart of FIG. 2A, the first to third converters 14a to 14c and the first to third switches 23a to 23c are controlled according to the timing chart of FIG. Ground faults of the first to third solar cells 12a to 12c can be determined.
[0047]
According to the timing chart of FIG. 2B, first, the first converter 14a is operated during the time T0 to T1, and the first switch 23a is closed under the control of the first to third converter controllers 19a to 19c. At the same time, the second and third switches 23b and 23c are opened. In this state, the ground fault of the positive electrode of the first solar cell 12a is determined by the first converter control unit 19a as shown in FIG. 3, and the ground fault of the negative electrode of the second solar cell 12b is The determination is performed by the converter control unit 19b, and the ground fault of the negative electrode of the third solar cell 12c can be determined by the third converter control unit 19c as shown in FIG.
[0048]
Next, during the time T1 to T2, the second converter 14b is operated, the second switch 23b is closed by the control of the first to third converter control units 19a to 19c, and the first and third switches 23a, 23c is opened. In this state, the ground fault of the positive electrode of the second solar cell 12b is determined by the second converter control unit 19b, and the ground fault of the negative electrode of the first solar cell 12a is determined by the first converter control unit 19a. The third converter control unit 19c can determine the ground fault of the negative electrode 12c by the third converter control unit 19c.
[0049]
Further, during the time T2 to T3, the third converter 14c is operated, the third switch 23c is closed by the control of the first to third converter control units 19a to 19c, and the first and second switches 23a and 23b are closed. To open. In this state, the ground fault of the positive electrode of the third solar cell 12c is determined by the third converter control unit 19c, and the ground fault of the negative electrode of the first solar cell 12a is determined by the first converter control unit 19a. The ground fault of the negative electrode 12b can be determined by the second converter control unit 19b.
[0050]
Note that the present invention is not limited to the above-described embodiment, and can be variously modified. For example, the circuit configuration of the converter or the inverter may be changed. Further, the number of solar cells and converters may be increased or decreased. Further, the ON / OFF timing of the converter and the switch may be variously changed. Further, instead of the solar cell, another type of DC power supply may be applied.
[0051]
【The invention's effect】
As described above, according to the present invention, the negative switch means is inserted between the negative line of the DC power supply and the ground, so that the current change or voltage change of the DC power supply when the negative switch means is switched. Based on this, the ground fault of the DC power supply can be determined.
[0052]
Further, when it is assumed that a plurality of DC power supplies, a plurality of voltage conversion means, and a DC-AC conversion means are provided, a plurality of negative-side switch means are inserted between a negative-side line of each DC power supply and a ground, and Since the negative line of the DC power source is commonly connected by the common connection line, each DC power supply is connected based on the current change or voltage change of the negative line of each DC power supply when each negative switch is switched. A ground fault can be determined.
[0053]
Further, since inexpensive components can be applied as the respective negative switch units connected to the negative lines of the respective DC power supplies, an increase in cost can be suppressed. Further, even if a transformer is interposed in the power supply line in the device, the current change or voltage change of the DC power supply differs depending on whether or not the DC power supply is grounded. Can be.
[Brief description of the drawings]
FIG. 1 is a block diagram showing one embodiment of a system interconnection inverter device of the present invention.
FIGS. 2A and 2B are timing charts showing ON / OFF of first to third converters and first to third switches in the apparatus of FIG. 1;
FIG. 3 is a diagram showing a ground fault current path when the positive electrode of the first solar cell in the device of FIG. 1 is grounded.
FIG. 4 is a diagram showing a ground fault current path when the negative electrode of the first solar cell in the device of FIG. 1 is grounded.
FIG. 5 is a diagram showing a ground fault current path when the negative electrode of the second solar cell in the device of FIG. 1 is grounded.
FIG. 6 is a diagram showing a ground fault current path when the negative electrode of the third solar cell in the device of FIG. 1 is grounded.
FIG. 7 is a block diagram showing a conventional system interconnection inverter device.
FIG. 8 is a block diagram showing another conventional system interconnection inverter device.
[Explanation of symbols]
11 Grid-connected inverter device
12a, 12b, 12c First, second, and third solar cells
13 Commercial power system
14a, 14b, 14c first, second, and third converters
15 Inverter
16 Low-pass filter
17 interconnection relay
18 earth leakage breaker
19a, 19b, 19c First, second, and third converter control units
20 Power supply
21a, 21b, 21c First, second, and third negative electrode side lines
22a, 22b, 22c First, second, and third current detectors
23a, 23b, 23c First, second, and third switches
24 common connection lines
25 Inverter control unit

Claims (7)

直流電源の直流出力を電圧変換する電圧変換手段、電圧変換手段の直流出力を交流に変換する直流交流変換手段、及び直流交流変換手段の交流出力側と商用電力系統間に挿入された交流出力側スイッチ手段を備える系統連系インバータ装置において、
直流電源の負極側ラインとアース間に挿入された負極側スイッチ手段と、
交流出力側スイッチ手段をオフにして、直流交流変換手段の交流出力側と商用電力系統間を切り離した状態で、負極側スイッチ手段を切り換えたときの直流電源の電流変化もしくは電圧変化に基づいて、直流電源の地絡を判定する地絡判定手段と
を備えることを特徴とする系統連系インバータ装置。Voltage conversion means for converting the DC output of the DC power supply to voltage, DC / AC conversion means for converting the DC output of the voltage conversion means into AC, and AC output side inserted between the AC output side of the DC / AC conversion means and the commercial power system In a system interconnection inverter device having switch means,
A negative switch means inserted between the negative line of the DC power supply and the ground,
With the AC output side switch means turned off and the AC output side of the DC / AC converter and the commercial power system disconnected, based on the current change or voltage change of the DC power supply when the negative side switch means is switched, A system interconnection inverter device comprising: a ground fault determining unit that determines a ground fault of a DC power supply. 地絡判定手段は、負極側スイッチ手段をオンにして、直流電源の負極側ラインをアースに接続したときの直流電源の電流変化もしくは電圧変化に基づいて、直流電源の正極の地絡を判定することを特徴とする請求項２に記載の系統連系インバータ装置。    The ground fault determining means determines a ground fault of the positive electrode of the DC power supply based on a current change or a voltage change of the DC power supply when the negative switch is turned on and the negative line of the DC power supply is connected to the ground. 3. The system interconnection inverter device according to claim 2, wherein: 複数の直流電源の直流出力を電圧変換するそれぞれの電圧変換手段、各電圧変換手段の直流出力を交流に変換する直流交流変換手段、及び直流交流変換手段の交流出力側と商用電力系統間に挿入された交流出力側スイッチ手段を備える系統連系インバータ装置において、
各直流電源の負極側ラインとアース間に挿入されたそれぞれの負極側スイッチ手段と、
各直流電力源の負極側ラインを共通接続する共通接続線と、
交流出力側スイッチ手段をオフにして、直流交流変換手段の交流出力側と商用電力系統間を切り離した状態で、各負極側スイッチ手段を選択的に切り換えたときの各直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、各直流電源の地絡を判定する地絡判定手段と
を備えることを特徴とする系統連系インバータ装置。Voltage conversion means for converting the DC outputs of the plurality of DC power supplies into voltages, DC / AC conversion means for converting the DC outputs of the voltage conversion means into AC, and inserted between the AC output side of the DC / AC conversion means and the commercial power system. In the system interconnection inverter device provided with the AC output side switch means,
A respective negative-side switch means inserted between the negative-side line of each DC power supply and ground,
A common connection line for commonly connecting the negative line of each DC power source,
With the AC output side switch means turned off and the AC output side of the DC / AC converter and the commercial power system disconnected, the negative side line of each DC power supply when each negative side switch means is selectively switched. A system interconnection inverter device comprising: a ground fault determining unit that determines a ground fault of each DC power supply based on a current change or a voltage change. 地絡判定手段は、各直流電源のいずれかを選択して、該選択した直流電源に対応する電圧変換手段を起動した上で、各負極側スイッチ手段を選択的に切り換えたときの各直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、各直流電源の負極の地絡を判定することを特徴とする請求項３に記載の系統連系インバータ装置。    The ground fault determining means selects any one of the DC power supplies, activates the voltage conversion means corresponding to the selected DC power supply, and sets each DC power supply when the respective negative switch means is selectively switched. 4. The system interconnection inverter device according to claim 3, wherein a ground fault of the negative electrode of each DC power supply is determined based on a current change or a voltage change of the negative line. 地絡判定手段は、各直流電源のいずれかを選択して、該選択した直流電源に対応する電圧変換手段を起動すると共に、該選択した直流電源に対応する負極側スイッチをオフにし、選択しなかった他の直流電源に対応する負極側スイッチをオンにしたときの該選択しなかった他の直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、該選択した直流電源の負極の地絡を判定することを特徴とする請求項３に記載の系統連系インバータ装置。    The ground fault determination means selects one of the DC power supplies, activates the voltage conversion means corresponding to the selected DC power supply, and turns off and selects the negative switch corresponding to the selected DC power supply. Based on a current change or a voltage change of the negative line of the unselected DC power supply when the negative switch corresponding to the other DC power supply is turned on, the negative ground of the selected DC power supply is determined. The system interconnection inverter device according to claim 3, wherein a fault is determined. 地絡判定手段は、各直流電源のいずれかを選択して、該選択した直流電源に対応する電圧変換手段を起動すると共に、該選択した直流電源に対応する負極側スイッチをオンにし、選択しなかった他の直流電源に対応する負極側スイッチをオフにしたときの該選択しなかった他の直流電源の負極側ラインの電流変化もしくは電圧変化に基づいて、該選択しなかった直流電源の負極の地絡を判定することを特徴とする請求項３に記載の系統連系インバータ装置。    The ground fault determining means selects one of the DC power supplies, activates the voltage conversion means corresponding to the selected DC power supply, and turns on and selects the negative switch corresponding to the selected DC power supply. Based on a current change or a voltage change in the negative line of the other unselected DC power supply when the negative switch corresponding to the other DC power supply is turned off, based on the negative change of the unselected DC power supply. The grid-connected inverter device according to claim 3, wherein a ground fault is determined. 各直流電源を順次選択することにより、該各直流電源の負極の地絡を順次判定することを特徴とする請求項５又は６に記載の系統連系インバータ装置。    7. The system interconnection inverter device according to claim 5, wherein a ground fault of a negative electrode of each DC power supply is sequentially determined by sequentially selecting each DC power supply.
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