JP2012122986A

JP2012122986A - Earth fault detection circuit of ungrounded circuit

Info

Publication number: JP2012122986A
Application number: JP2011160461A
Authority: JP
Inventors: Toshihiro Maeda; 俊博前田; Itsuki Ashida; 樹芦田
Original assignee: Fuji Electric Co Ltd
Current assignee: Fuji Electric Co Ltd
Priority date: 2010-11-19
Filing date: 2011-07-22
Publication date: 2012-06-28
Anticipated expiration: 2031-07-22
Also published as: JP5858215B2

Abstract

PROBLEM TO BE SOLVED: To simplify and downsize a circuit by reducing the number of parts, eliminate misjudgment caused by a variation in threshold of earth fault determination, and enable notification of abnormality forecast prior to a warning when detecting an earth fault.SOLUTION: An earth fault detection circuit detects an earth fault in an ungrounded DC circuit where a load 2 is connected to a DC power 1 through a positive DC bus PL and a negative DC bus NL, and comprises: a resistor 3a one end of which is connected to the positive DC bus PL; a resistor 3b one end of which is connected to the negative DC bus NL and which has a resistance value equal to that of the resistor 3a; and a photo-coupler 10A that is connected to a place between a point where the other ends of the resistors 3a and 3b are connected and a grounding point 100. The photo-coupler 10A includes: a current detection circuit 11A for outputting a driving signal when an input current exceeds a prescribed threshold; a light-emitting element 12A that is turned on by the driving signal; and a light-receiving element 13A that is turned on by the output light, and detects the earth fault by an output signal from the light-receiving element 13A.

Description

本発明は、非接地回路の地絡故障（絶縁抵抗の低下）を検出する回路に関し、詳しくは、非接地直流回路の地絡故障、または、直流電源に正側直流母線及び負側直流母線を介して接続された非接地電力変換回路の交流出力側の地絡故障を検出する回路に関するものである。 The present invention relates to a circuit for detecting a ground fault in a non-grounded circuit (decrease in insulation resistance), and more specifically, a ground fault in a non-grounded DC circuit or a positive DC bus and a negative DC bus are connected to a DC power supply. The present invention relates to a circuit for detecting a ground fault on the AC output side of a non-grounded power conversion circuit connected through the circuit.

電気自動車やハイブリッド自動車には、直流電源としての蓄電装置と、この蓄電装置から電源電圧が供給されて駆動力を発生する電力変換器及び電動機等からなる負荷と、が搭載されている。ここで、蓄電装置の正極と負荷との間の電路を正側直流母線といい、蓄電装置の負極と負荷との間の電路を負側直流母線と呼ぶことにする。また、自動車の車台（シャーシ）を接地点とみなし、この接地点の電位を接地電位とする。 An electric vehicle or a hybrid vehicle is equipped with a power storage device as a DC power source and a load made up of a power converter, an electric motor, and the like that are supplied with a power supply voltage to generate a driving force. Here, the electric circuit between the positive electrode of the power storage device and the load is referred to as a positive DC bus, and the electric circuit between the negative electrode of the power storage device and the load is referred to as a negative DC bus. Further, the vehicle chassis (chassis) is regarded as a grounding point, and the potential of this grounding point is set as the grounding potential.

仮に、正側直流母線または負側直流母線の何れか一方がシャーシに接続されていても、その直流母線とシャーシとを含む経路が閉回路を形成しない限り、電流が流れない。従って、蓄電装置を直流電源として電動機を駆動する動作に、何ら支障はない。
しかし、何らかの異常により一方の直流母線（例えば、負側直流母線）がシャーシと接続されている状態において、シャーシに接触している人が、他方の直流母線（例えば、正側直流母線）に触れた場合には、蓄電装置−人体−シャーシによる閉回路が形成される。このため、蓄電装置の数百[Ｖ]の直流電圧が人体に印加されることになり、非常に危険である。 Even if either the positive DC bus or the negative DC bus is connected to the chassis, no current flows unless the path including the DC bus and the chassis forms a closed circuit. Therefore, there is no problem in the operation of driving the electric motor using the power storage device as a DC power source.
However, when one DC bus (for example, negative DC bus) is connected to the chassis due to some abnormality, a person in contact with the chassis touches the other DC bus (for example, positive DC bus). In this case, a closed circuit is formed by the power storage device-human body-chassis. For this reason, a DC voltage of several hundreds [V] of the power storage device is applied to the human body, which is very dangerous.

従って、電気自動車やハイブリッド自動車の電気システムでは、人が一方の直流母線に接触しても感電しないように、正側直流母線及び負側直流母線をシャーシから絶縁する必要がある。すなわち、蓄電装置、正側直流母線、負側直流母線及び負荷からなる直流回路を非接地状態に保つことが必要である。 Therefore, in an electric system of an electric vehicle or a hybrid vehicle, it is necessary to insulate the positive DC bus and the negative DC bus from the chassis so that no electric shock is caused even if a person touches one of the DC buses. That is, it is necessary to keep the DC circuit including the power storage device, the positive DC bus, the negative DC bus, and the load in an ungrounded state.

そこで、従来より、非接地状態であるべき直流回路と接地点との間の絶縁抵抗を測定して地絡故障（絶縁抵抗の低下）を検出する回路が提供されている。
図１０は、この種の地絡検出回路の従来の一般的な回路を示している。図１０において、１は蓄電装置等の直流電源、２はインバータ及び電動機等からなる負荷、ＰＬは正側直流母線、ＮＬは負側直流母線である。 Therefore, conventionally, there has been provided a circuit for detecting a ground fault (decrease in insulation resistance) by measuring an insulation resistance between a DC circuit that should be in a non-grounded state and a ground point.
FIG. 10 shows a conventional general circuit of this type of ground fault detection circuit. In FIG. 10, 1 is a DC power source such as a power storage device, 2 is a load composed of an inverter and an electric motor, PL is a positive DC bus, and NL is a negative DC bus.

また、３ａは一端が正側直流母線ＰＬに接続された第1の抵抗器、３ｂは一端が負側直流母線ＮＬに接続された第２の抵抗器であり、これらの抵抗器３ａ，３ｂの抵抗値は等しい。抵抗器３ａ，３ｂの他端同士の接続点と接地点１００との間には、電流検出回路４が接続されている。ここで、接地点１００は自動車のシャーシに相当する。
更に、１０１Ｐは正側直流母線ＰＬと接地点１００との間の絶縁抵抗、１０１Ｎは負側直流母線ＮＬと接地点１００との間の絶縁抵抗である。これらの絶縁抵抗１０１Ｐ，１０１Ｎの抵抗値は、本来、無限大でなくてはならない。 3a is a first resistor having one end connected to the positive DC bus PL, and 3b is a second resistor having one end connected to the negative DC bus NL. Resistance values are equal. A current detection circuit 4 is connected between a connection point between the other ends of the resistors 3 a and 3 b and the ground point 100. Here, the grounding point 100 corresponds to the chassis of the automobile.
Further, 101P is an insulation resistance between the positive DC bus PL and the ground point 100, and 101N is an insulation resistance between the negative DC bus NL and the ground point 100. The resistance values of these insulation resistors 101P and 101N must be essentially infinite.

図１０において、前述したように抵抗器３ａ，３ｂの抵抗値が等しい状態で、絶縁抵抗１０１Ｐ，１０１Ｎの抵抗値が等しい場合には、抵抗器３ａ，３ｂ同士の接続点と接地点１００（つまり、絶縁抵抗１０１Ｐ，１０１Ｎ同士の接続点）との間に電位差は生じない。このため、電流検出回路４に電流は流れない。
仮に、絶縁抵抗１０１Ｐ，１０１Ｎの抵抗値が互いに異なると、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に電位差が生じるので、電流検出回路４に電流が流れる。しかし、正常時の絶縁抵抗１０１Ｐ，１０１Ｎは数Ｍ[Ω]程度あるため、電流検出回路４を流れる電流はごく僅かである。 In FIG. 10, as described above, when the resistance values of the resistors 3a and 3b are equal and the resistance values of the insulation resistors 101P and 101N are equal, the connection point between the resistors 3a and 3b and the ground point 100 (that is, , No potential difference occurs between the insulation resistances 101P and 101N). For this reason, no current flows through the current detection circuit 4.
If the resistance values of the insulation resistors 101P and 101N are different from each other, a potential difference is generated between the connection point between the resistors 3a and 3b and the ground point 100, so that a current flows through the current detection circuit 4. However, since the normal insulation resistances 101P and 101N are about several M [Ω], the current flowing through the current detection circuit 4 is very small.

次に、図１１に基づいて、負側直流母線ＮＬの絶縁が劣化して絶縁抵抗１０１Ｎの抵抗値が低下した場合の動作を説明する。
絶縁抵抗１０１Ｎの抵抗値が低下すると、図１１に破線で示す経路で電流が流れるため、この電流の大きさを検出すれば、絶縁抵抗１０１Ｎの抵抗値や地絡の程度を知ることができる。電流検出回路４を流れる電流値は、絶縁抵抗１０１Ｎの抵抗値、及び、抵抗器３ａ，３ｂの抵抗値に依存するため、抵抗器３ａ，３ｂの抵抗値を変更すれば、地絡を検出するための閾値（判定値）を変更することができる。
なお、正側直流母線ＰＬの絶縁抵抗１０１Ｐの抵抗値が低下した場合には、電流検出回路４に流れる電流の向きは図１１とは逆となる。従って、電流検出回路４には、双方向の電流を検出できる機能が要求される。 Next, based on FIG. 11, the operation when the insulation of the negative side DC bus NL deteriorates and the resistance value of the insulation resistance 101N decreases will be described.
When the resistance value of the insulation resistor 101N decreases, a current flows through a path indicated by a broken line in FIG. 11. Therefore, if the magnitude of this current is detected, the resistance value of the insulation resistor 101N and the degree of ground fault can be known. Since the value of the current flowing through the current detection circuit 4 depends on the resistance value of the insulation resistor 101N and the resistance values of the resistors 3a and 3b, a ground fault is detected by changing the resistance values of the resistors 3a and 3b. The threshold value (determination value) for this can be changed.
When the resistance value of the insulation resistance 101P of the positive side DC bus PL is lowered, the direction of the current flowing through the current detection circuit 4 is opposite to that in FIG. Therefore, the current detection circuit 4 is required to have a function capable of detecting bidirectional current.

次に、図１２は第１の従来技術を示す回路図である。図１２において、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間には、シャント抵抗５が接続されている。このシャント抵抗５の両端には、電圧測定回路６、地絡判定回路７が順次接続されている。
この従来技術では、絶縁抵抗１０１Ｐまたは絶縁抵抗１０１Ｎの抵抗値が低下したときに流れる電流をシャント抵抗５により検出し、この電流を電圧測定回路６により電圧に変換する。そして、地絡判定回路７では、電圧測定回路６の出力電圧が閾値を超えた場合に地絡と判定し、警報を出力する。 Next, FIG. 12 is a circuit diagram showing the first prior art. In FIG. 12, a shunt resistor 5 is connected between the connection point between the resistors 3 a and 3 b and the ground point 100. A voltage measurement circuit 6 and a ground fault determination circuit 7 are sequentially connected to both ends of the shunt resistor 5.
In this prior art, the current that flows when the resistance value of the insulation resistor 101P or the insulation resistor 101N decreases is detected by the shunt resistor 5, and this current is converted into a voltage by the voltage measurement circuit 6. And in the ground fault determination circuit 7, when the output voltage of the voltage measurement circuit 6 exceeds a threshold value, it determines with a ground fault and outputs an alarm.

図１３は、第２の従来技術を示す回路図である。この従来技術では、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に、フォトカプラ８が接続されている。なお、フォトカプラ８は、発光ダイオード（ＬＥＤ）等の発光素子８１とフォトトランジスタ等の受光素子８２とから構成されている。
この従来技術では、絶縁抵抗１０１Ｐまたは絶縁抵抗１０１Ｎの抵抗値が低下して発光素子８１に電流が流れ、光出力が生じると、受光素子８２がオンして信号が出力される。よって、この出力信号を利用して地絡の警報を出力させることが可能である。 FIG. 13 is a circuit diagram showing the second prior art. In this prior art, the photocoupler 8 is connected between the connection point between the resistors 3 a and 3 b and the ground point 100. The photocoupler 8 includes a light emitting element 81 such as a light emitting diode (LED) and a light receiving element 82 such as a phototransistor.
In this prior art, when the resistance value of the insulation resistor 101P or the insulation resistor 101N decreases and a current flows through the light emitting element 81 to generate a light output, the light receiving element 82 is turned on and a signal is output. Therefore, it is possible to output a ground fault alarm using this output signal.

図１２の第１の従来技術では、直流電源１，正側直流母線ＰＬ，負側直流母線ＮＬ及び負荷２からなる直流回路と、制御用の低圧電源により動作する電圧測定回路６や地絡判定回路７とを絶縁するために、絶縁増幅信号が必要になり、直流電源１や制御用の低圧電源とは別個に電源を準備する必要がある。また、これらの電圧測定回路６や地絡判定回路７、及びその電源等に起因して部品点数が増え、回路の実装面積が大きくなると共に、装置全体が高価格化するという問題がある。 In the first prior art of FIG. 12, a voltage measurement circuit 6 operated by a DC circuit including a DC power supply 1, a positive DC bus PL, a negative DC bus NL, and a load 2, a control low voltage power supply, and a ground fault determination. In order to insulate the circuit 7, an insulation amplification signal is required, and it is necessary to prepare a power source separately from the DC power source 1 and the low-voltage power source for control. In addition, there is a problem that the number of parts increases due to the voltage measurement circuit 6, the ground fault determination circuit 7, the power supply, and the like, the circuit mounting area is increased, and the entire apparatus is expensive.

これに対し、図１３の第２の従来技術では、第１の従来技術よりも回路構成を簡略化できる利点がある。しかし、フォトカプラ８は通常、アナログ素子により構成されているため、発光素子８１に流れる入力電流がごく少量でも受光素子８２のベースに電流が流れてしまい、フォトカプラ８がオンする場合がある。
フォトカプラ８の出力信号がオフからオン、またはオンからオフに反転する閾値は、発光素子８１と受光素子８２との間の光−電流変換効率に依存する。一般に、この光−電流変換効率はばらつきが大きく経年変化があるため、前記閾値を正確に定めることは困難である。 On the other hand, the second prior art in FIG. 13 has an advantage that the circuit configuration can be simplified as compared with the first prior art. However, since the photocoupler 8 is normally composed of an analog element, even if the input current flowing through the light emitting element 81 is very small, a current flows to the base of the light receiving element 82, and the photocoupler 8 may be turned on.
The threshold value at which the output signal of the photocoupler 8 is inverted from off to on or from on to off depends on the light-current conversion efficiency between the light emitting element 81 and the light receiving element 82. In general, since the light-current conversion efficiency varies greatly and changes with time, it is difficult to accurately determine the threshold value.

このため、絶縁抵抗１０１Ｐまたは絶縁抵抗１０１Ｎに異常がなく、直流回路が接地されていないにも関わらず、発光素子８１に流れる僅かな入力電流により受光素子８２がオンされて地絡と誤判定してしまうおそれがある。特に、実際に地絡を検出した場合に保護動作として装置の運転を停止するシステムでは、誤判定により装置の運転が停止されてしまうので、ユーザにとって大変不便である。 For this reason, although the insulation resistance 101P or the insulation resistance 101N is not abnormal and the DC circuit is not grounded, the light receiving element 82 is turned on by a slight input current flowing through the light emitting element 81, and it is erroneously determined as a ground fault. There is a risk that. In particular, in a system that stops the operation of the device as a protective operation when a ground fault is actually detected, the operation of the device is stopped due to an erroneous determination, which is very inconvenient for the user.

一方、絶縁抵抗１０１Ｐまたは絶縁抵抗１０１Ｎの抵抗値が実際に低下して地絡状態になった場合には、ユーザの感電を防止するために装置の運転を停止させる必要がある。しかし、ユーザにとって、車両等の運転が突然停止されるのは好ましくない。
この場合の対策としては、地絡検出によって装置の運転を停止する前に、絶縁抵抗の低下を異常予報としてユーザに予め通報することが望ましい。 On the other hand, when the resistance value of the insulation resistance 101P or the insulation resistance 101N is actually lowered and becomes a ground fault state, it is necessary to stop the operation of the apparatus in order to prevent a user's electric shock. However, it is not preferable for the user to suddenly stop the operation of the vehicle or the like.
As a countermeasure in this case, it is desirable to notify the user in advance of a decrease in insulation resistance as an abnormal forecast before stopping the operation of the apparatus due to ground fault detection.

図１４は、図１３の回路に上記の異常予報機能を付加した例である。
図１４において、抵抗器３ａ，３ｂ及びフォトカプラ８Ａによって警報出力回路９Ａが構成されている。この警報出力回路９Ａは、実質的に図１３の抵抗器３ａ，３ｂ及びフォトカプラ８からなる回路と同一の構成であり、地絡発生時に警報出力や装置の運転停止を行うためのものである。
また、図１４では、警報出力回路９Ａと並列に予報出力回路９Ｂが接続されている。この予報出力回路９Ｂは、抵抗器３ｃ，３ｄ及びフォトカプラ８Ｂによって構成されており、抵抗器３ｃ，３ｄの抵抗値は抵抗器３ａ，３ｂの抵抗値よりも低くなっている。 FIG. 14 is an example in which the abnormality forecast function is added to the circuit of FIG.
In FIG. 14, the alarm output circuit 9A is constituted by the resistors 3a and 3b and the photocoupler 8A. This alarm output circuit 9A has substantially the same configuration as the circuit composed of the resistors 3a and 3b and the photocoupler 8 in FIG. 13, and is used to output an alarm and stop the operation of the device when a ground fault occurs. .
In FIG. 14, a forecast output circuit 9B is connected in parallel with the alarm output circuit 9A. The forecast output circuit 9B includes resistors 3c and 3d and a photocoupler 8B. The resistance values of the resistors 3c and 3d are lower than the resistance values of the resistors 3a and 3b.

図１４の回路において、絶縁抵抗１０１Ｐまたは絶縁抵抗１０１Ｎの抵抗値が低下した場合には、警報出力回路９Ａが動作する前に、予報出力回路９Ｂの抵抗器３ｃまたは抵抗器３ｄを流れる電流によってフォトカプラ８Ｂから異常予報が出力される。すなわち、図１４の回路によれば、警報出力回路９Ａが動作して警報の出力や装置の運転停止が行われる前に、予報出力回路９Ｂから異常予報を発生させてユーザの注意を喚起することができ、図１３の回路による不便さを解消することができる。
しかし、図１４の回路は、図１３の回路に予報出力回路９Ｂを追加した構成であるため、部品点数が多くなってコスト高になり、回路の実装面積も一層大きくなるという問題がある。 In the circuit of FIG. 14, when the resistance value of the insulation resistor 101P or the insulation resistor 101N decreases, before the alarm output circuit 9A operates, the photocurrent is generated by the current flowing through the resistor 3c or the resistor 3d of the forecast output circuit 9B. An abnormality forecast is output from the coupler 8B. That is, according to the circuit of FIG. 14, before the alarm output circuit 9A operates to output an alarm or stop the operation of the apparatus, an abnormality forecast is generated from the forecast output circuit 9B to alert the user. Inconvenience due to the circuit of FIG. 13 can be eliminated.
However, since the circuit of FIG. 14 has a configuration in which the forecast output circuit 9B is added to the circuit of FIG. 13, there is a problem that the number of parts increases, the cost increases, and the circuit mounting area further increases.

なお、半導体電力変換回路の地絡検出回路として、特許文献１に記載された従来技術が知られている。
この地絡検出回路では、地絡による正側直流母線及び負側直流母線の過電流を検出する手段としての比較器の電源回路を共通にし、更に高速フォトカプラを不要にすることによって回路構成の簡略化、小型化、低コスト化を図っている。 In addition, the prior art described in patent document 1 is known as a ground fault detection circuit of a semiconductor power converter circuit.
In this ground fault detection circuit, the power supply circuit of the comparator as a means for detecting the overcurrent of the positive side DC bus line and the negative side DC bus line due to the ground fault is made common, and further, a high-speed photocoupler is not required, thereby making the circuit configuration. Simplification, miniaturization, and cost reduction are achieved.

特開２００６−１５８１５０号公報（段落[０００９]〜[００１１]）JP 2006-158150 A (paragraphs [0009] to [0011])

特許文献１に記載された従来技術では、正側直流母線の電圧変動を負側直流母線から見た電圧変動に変換するために、正負の直流母線の間にコンデンサと抵抗との直列回路が接続されている。また、地絡検出用の二つの比較器の基準電圧を得るために多数の抵抗も必要である。
このように、特許文献１の従来技術では多くの部品を必要としており、回路構成の簡略化や低コスト化の点でいまだ改善の余地がある。 In the prior art described in Patent Document 1, a series circuit of a capacitor and a resistor is connected between the positive and negative DC buses in order to convert the voltage fluctuation of the positive DC bus into voltage fluctuations seen from the negative DC bus. Has been. A large number of resistors are also required to obtain the reference voltage of the two comparators for ground fault detection.
As described above, the conventional technique of Patent Document 1 requires many components, and there is still room for improvement in terms of simplification of the circuit configuration and cost reduction.

そこで、本発明の目的は、部品数が少なく、回路構成の簡略化、小型化、低コスト化が可能な非接地回路の地絡検出回路を提供することにある。
また、本発明の他の目的は、地絡判定の閾値のばらつきが小さく、誤判定の恐れがない非接地回路の地絡検出回路を提供することにある。
更に、本発明の別の目的は、地絡検出時の警報に先立って、絶縁抵抗の低下により地絡の恐れがあることを異常予報として通報するようにした非接地回路の地絡検出回路を提供することにある。
また、本発明の他の目的は、非接地直流回路用に構成された地絡検出回路の構成を変更することなく、直流電源に正側直流母線及び負側直流母線を介して接続された非接地電力変換回路の交流出力側の地絡故障を容易かつ高精度に検出することにある。 SUMMARY OF THE INVENTION An object of the present invention is to provide a ground fault detection circuit for a non-grounded circuit that has a small number of parts and can be simplified, downsized, and reduced in cost.
Another object of the present invention is to provide a ground fault detection circuit of a non-grounded circuit that has a small variation in the ground fault determination threshold value and does not cause a false determination.
Furthermore, another object of the present invention is to provide a ground fault detection circuit for a non-grounded circuit which reports as an abnormal forecast that there is a risk of a ground fault due to a decrease in insulation resistance prior to an alarm at the time of ground fault detection. It is to provide.
Another object of the present invention is to connect a non-grounded DC circuit connected to a DC power source via a positive DC bus and a negative DC bus without changing the configuration of the ground fault detection circuit configured for a non-grounded DC circuit. The purpose is to easily and accurately detect a ground fault on the AC output side of the ground power conversion circuit.

請求項１に係る発明は、直流電源に正側直流母線及び負側直流母線を介して負荷が接続され、かつ、接地されていない直流回路の地絡を検出するための回路である。本発明は、具体的には、正側直流母線または負側直流母線の絶縁抵抗値が低下した時に前記直流母線と接地点との間に流れる電流を検出して地絡を検出するものである。
すなわち、本発明は、正側直流母線に一端が接続された第１の抵抗器と負側直流母線に一端が接続された第２の抵抗器とを備えており、これら第１，第２の抵抗器の抵抗値は等しくなっている。
また、本発明は、第１，第２の抵抗器の他端同士の接続点と接地点との間に接続されたフォトカプラを備えている。このフォトカプラは、入力電流が所定の閾値を超えると駆動信号を出力する電流検出回路と、前記駆動信号によりオンする発光ダイオード等の発光素子と、その出力光によりオンするフォトトランジスタ等の受光素子とを有する。そして、電流検出回路の入力電流が閾値を超えたときに、受光素子により警報信号を出力して地絡と判定する。 The invention according to claim 1 is a circuit for detecting a ground fault of a DC circuit that is connected to a DC power source via a positive DC bus and a negative DC bus and that is not grounded. Specifically, the present invention detects a ground fault by detecting a current flowing between the DC bus and a ground point when the insulation resistance value of the positive DC bus or the negative DC bus is lowered. .
In other words, the present invention includes a first resistor having one end connected to the positive DC bus and a second resistor having one end connected to the negative DC bus. The resistance values of the resistors are equal.
The present invention further includes a photocoupler connected between a connection point between the other ends of the first and second resistors and a ground point. The photocoupler includes a current detection circuit that outputs a driving signal when an input current exceeds a predetermined threshold, a light emitting element such as a light emitting diode that is turned on by the driving signal, and a light receiving element such as a phototransistor that is turned on by the output light. And have. Then, when the input current of the current detection circuit exceeds the threshold value, an alarm signal is output by the light receiving element to determine a ground fault.

なお、請求項２に係る発明のように、第１，第２の抵抗器同士の接続点と接地点との間に、複数のフォトカプラを直列に接続すると共に、各フォトカプラの閾値を異なる大きさに設定してもよい。この場合、閾値が小さい一つのフォトカプラによって小さい入力電流を検出することにより地絡の予報信号を出力させ、閾値が大きい他のフォトカプラによって大きい入力電流（地絡時の入力電流）を検出することにより、地絡の警報信号を出力させることができる。 As in the invention according to claim 2, a plurality of photocouplers are connected in series between the connection point between the first and second resistors and the ground point, and the threshold values of the respective photocouplers are different. You may set to a magnitude | size. In this case, a ground fault forecast signal is output by detecting a small input current with one photocoupler with a small threshold, and a large input current (input current at the time of ground fault) is detected with another photocoupler with a large threshold. Thus, a ground fault alarm signal can be output.

請求項３に係る発明は、請求項１の地絡検出回路を非接地電力変換回路に適用したものであり、請求項４に係る発明は、請求項２の地絡検出回路を非接地電力変換回路に適用したものである。これらの請求項３または請求項４の発明では、電力変換回路を構成する半導体スイッチング素子のうちの何れかをオンしたときにフォトカプラから警報信号が出力されれば、電力変換回路の交流側の地絡と判定する。
請求項３または請求項４の発明において、電力変換回路の交流出力側の特定相の地絡を検出するためには、電力変換回路を構成する半導体スイッチング素子のうち前記特定相の上アームまたは下アームの半導体スイッチング素子をオンさせる出力地絡検出パターンに従って電力変換回路をスイッチングし、そのときのフォトカプラの出力信号を観察すればよい。 The invention according to claim 3 applies the ground fault detection circuit according to claim 1 to a non-grounded power conversion circuit, and the invention according to claim 4 relates to the ground fault detection circuit according to claim 2 as a non-ground power conversion. It is applied to the circuit. In these inventions of claim 3 or claim 4, if an alarm signal is output from the photocoupler when any of the semiconductor switching elements constituting the power conversion circuit is turned on, the AC side of the power conversion circuit is Judge as a ground fault.
In the invention of claim 3 or claim 4, in order to detect the ground fault of the specific phase on the AC output side of the power conversion circuit, the upper arm or the lower side of the specific phase among the semiconductor switching elements constituting the power conversion circuit. The power conversion circuit may be switched according to the output ground fault detection pattern for turning on the arm semiconductor switching element, and the output signal of the photocoupler at that time may be observed.

なお、閾値が小さいフォトカプラでは、絶縁抵抗が大きい（入力電流が小さい）場合でも出力信号がオンしてしまう。このため、フォトカプラの閾値が小さく所望の地絡判定用の閾値が得られない場合には、そのフォトカプラの閾値と等しい閾値を有する別のフォトカプラを並列に接続し、第１，第２の抵抗器同士の接続点と接地点との間に流れる電流を、並列接続された各フォトカプラ内の電流検出回路にそれぞれ分流させてもよい。
これにより、例えば２個のフォトカプラを並列接続した場合は、第１，第２の抵抗器同士の接続点と接地点間を流れる電流が一つのフォトカプラの閾値の２倍になったときに各フォトカプラの出力がオンされるので、２倍の閾値を持つフォトカプラ１個を使用する場合と等価になる。 Note that in an optocoupler with a small threshold, the output signal is turned on even when the insulation resistance is large (the input current is small). For this reason, when the threshold of the photocoupler is small and a desired ground fault determination threshold cannot be obtained, another photocoupler having a threshold equal to the threshold of the photocoupler is connected in parallel, and the first and second The current flowing between the connection point of the resistors and the ground point may be shunted to the current detection circuit in each photocoupler connected in parallel.
Thus, for example, when two photocouplers are connected in parallel, when the current flowing between the connection point between the first and second resistors and the ground point becomes twice the threshold value of one photocoupler. Since the output of each photocoupler is turned on, this is equivalent to using one photocoupler having a double threshold.

更に、本発明においては、第１，第２の抵抗器同士の接続点と前記接地点との間に流れる両方向の電流を検出できるように、一方向の電流を検出する少なくとも二つのフォトカプラを、互いに逆方向にして並列接続してもよい。 Furthermore, in the present invention, at least two photocouplers for detecting a unidirectional current are provided so that a bidirectional current flowing between the connection point between the first and second resistors and the grounding point can be detected. These may be connected in parallel in opposite directions.

本発明によれば、正側直流母線及び負側直流母線と接地点との間に接続される第１，第２の抵抗器と、一または複数のフォトカプラのみによって地絡検出回路を構成することができ、部品数が少なく、回路構成が簡単で小型化、低コスト化が可能である。
また、本発明によれば、フォトカプラ内の発光素子の前段に設けた電流検出回路によってフォトカプラが動作する入力電流の閾値を設定しているので、フォトカプラの動作は、発光素子と受光素子との間の光−電流変換効率のばらつきに依存しない。このため、何らかの原因によって電流検出回路にわずかな入力電流が流れたとしても、フォトカプラの動作は上述した閾値により管理されているので、入力電流がこの閾値を超えない限りフォトカプラは動作せず、地絡を誤判定するおそれがない。よって、地絡の誤判定による装置の不要な運転停止を防ぐことができる。
更に、必要に応じてフォトカプラを複数、直列または並列に接続することにより、地絡検出時の警報に先立って、絶縁抵抗の低下により地絡の恐れがあることを予報信号として通報することも可能である。
また、同一構成の地絡検出回路により、非接地直流回路と非接地電力変換回路の交流出力側との地絡を検出可能であるため、汎用性、経済性に優れている。 According to the present invention, the ground fault detection circuit is configured by only the first and second resistors connected between the positive and negative DC buses and the ground point, and one or a plurality of photocouplers. The number of components is small, the circuit configuration is simple, and the size and cost can be reduced.
Further, according to the present invention, the threshold value of the input current at which the photocoupler operates is set by the current detection circuit provided in the preceding stage of the light emitting element in the photocoupler. It does not depend on the variation in the light-current conversion efficiency between the two. For this reason, even if a slight input current flows in the current detection circuit for some reason, the operation of the photocoupler is controlled by the above-described threshold value. Therefore, the photocoupler does not operate unless the input current exceeds this threshold value. There is no risk of misjudging ground faults. Therefore, it is possible to prevent an unnecessary operation stop of the apparatus due to an erroneous determination of ground fault.
In addition, by connecting multiple photocouplers in series or in parallel as necessary, it is possible to notify that there is a possibility of a ground fault due to a decrease in insulation resistance prior to an alarm at the time of ground fault detection. Is possible.
Moreover, since the ground fault between the non-grounded DC circuit and the AC output side of the non-grounded power conversion circuit can be detected by the ground fault detection circuit having the same configuration, the versatility and economy are excellent.

本発明の第１実施形態を示す回路図である。1 is a circuit diagram showing a first embodiment of the present invention. 図１における電流検出回路の特性図である。FIG. 2 is a characteristic diagram of the current detection circuit in FIG. 1. 本発明の第２実施形態を示す回路図である。It is a circuit diagram which shows 2nd Embodiment of this invention. 本発明の第３実施形態を示す回路図である。It is a circuit diagram which shows 3rd Embodiment of this invention. 本発明の第４実施形態を示す回路図である。It is a circuit diagram which shows 4th Embodiment of this invention. 図５の動作説明図である。It is operation | movement explanatory drawing of FIG. 図５の動作説明図である。It is operation | movement explanatory drawing of FIG. 本発明の第５実施形態を示す回路図である。It is a circuit diagram which shows 5th Embodiment of this invention. 本発明の第６実施形態を示す回路図である。It is a circuit diagram which shows 6th Embodiment of this invention. 従来の一般的な地絡検出回路を示す回路図である。It is a circuit diagram which shows the conventional common ground fault detection circuit. 図１０の動作を示す回路図である。It is a circuit diagram which shows the operation | movement of FIG. 第１の従来技術を示す回路図である。It is a circuit diagram which shows the 1st prior art. 第２の従来技術を示す回路図である。It is a circuit diagram which shows a 2nd prior art. 図１３の回路に異常予報機能を付加した回路を示す回路図である。It is a circuit diagram which shows the circuit which added the abnormality forecast function to the circuit of FIG.

以下、図に沿って本発明の実施形態を説明する。
まず、以下に説明する第１〜第３実施形態は、本発明を電気自動車やハイブリッド自動車等の電気システムを構成する非接地直流回路の地絡検出に適用した場合のものであるが、本発明は、上記以外の用途を持つ非接地直流回路の地絡検出にも適用可能である。 Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, the first to third embodiments described below are cases where the present invention is applied to ground fault detection of an ungrounded DC circuit constituting an electric system such as an electric vehicle or a hybrid vehicle. Can also be applied to ground fault detection of ungrounded DC circuits having applications other than those described above.

図１は、本発明の第１実施形態を示す回路図である。
図１において、１は蓄電装置等の直流電源、２はインバータ及び電動機等の負荷、ＰＬは正側直流母線、ＮＬは負側直流母線である。また、３ａは一端が正側直流母線ＰＬに接続された第１の抵抗器、３ｂは一端が負側直流母線ＮＬに接続された第２の抵抗器であり、これらの抵抗器３ａ，３ｂの抵抗値は等しい。抵抗器３ａ，３ｂの他端同士の接続点と接地点１００との間には、フォトカプラ１０Ａが接続されている。
また、１０１Ｐは正側直流母線ＰＬの絶縁抵抗、１０１Ｎは負側直流母線ＮＬの絶縁抵抗である。 FIG. 1 is a circuit diagram showing a first embodiment of the present invention.
In FIG. 1, 1 is a DC power source such as a power storage device, 2 is a load such as an inverter and an electric motor, PL is a positive DC bus, and NL is a negative DC bus. 3a is a first resistor whose one end is connected to the positive DC bus PL, and 3b is a second resistor whose one end is connected to the negative DC bus NL. The resistors 3a and 3b Resistance values are equal. A photocoupler 10A is connected between the connection point between the other ends of the resistors 3a and 3b and the ground point 100.
Further, 101P is an insulation resistance of the positive side DC bus PL, and 101N is an insulation resistance of the negative side DC bus NL.

ここで、フォトカプラ１０Ａは、抵抗器３ａ，３ｂの他端同士の接続点と接地点１００との間に接続された電流検出回路１１Ａと、その出力側に接続された発光素子１２Ａと、発光素子１２Ａの出力光によってオンする受光素子１３Ａと、を備えている。なお、従来技術と同様に、発光素子１２Ａは発光ダイオードにより、受光素子１３Ａはフォトトランジスタにより構成されている。 Here, the photocoupler 10A includes a current detection circuit 11A connected between a connection point between the other ends of the resistors 3a and 3b and the ground point 100, a light emitting element 12A connected to the output side thereof, and a light emission. And a light receiving element 13A that is turned on by the output light of the element 12A. As in the prior art, the light emitting element 12A is composed of a light emitting diode, and the light receiving element 13A is composed of a phototransistor.

次に、図２は、フォトカプラ１０Ａの特性を示している。
このフォトカプラ１０Ａは、図２に示すように、入力信号（電流検出回路１１Ａの入力電流）がある閾値ＴＨ^＋以上になったときに電流検出回路１１Ａからの駆動信号により発光素子１２Ａを点灯させ、受光素子１３Ａの出力信号を反転させる。また、電流検出回路１１Ａの入力電流がある閾値ＴＨ⁻以下になったときに発光素子１２Ａを消灯させ、受光素子１３Ａの出力信号を反転させるものである。 Next, FIG. 2 shows the characteristics of the photocoupler 10A.
As shown in FIG. 2, the photocoupler 10A turns on the light emitting element 12A with a drive signal from the current detection circuit 11A when the input signal (input current of the current detection circuit 11A) exceeds a certain threshold TH ^+. The output signal of the light receiving element 13A is inverted. The threshold TH is the input current of the current detection circuit 11A ^- to turn off the light emitting element 12A when it is below, but to invert the output signal of the light receiving element 13A.

上記のように、この実施形態では、フォトカプラ１０Ａを動作させる入力電流の閾値が、発光素子１２Ａの前段に接続した電流検出回路１１Ａによって設定されており、発光素子１２Ａと受光素子１３Ａとの間の光−電流変換効率に依存しない。このため、絶縁抵抗１０１Ｐまたは絶縁抵抗１０１Ｎに異常がなく地絡が発生していない場合に、何らかの原因によって電流検出回路１１Ａにわずかな入力電流が流れたとしても、フォトカプラ１０Ａの動作は上述した閾値ＴＨ^＋，ＴＨ⁻により管理されているので、入力電流がこれらの閾値を超えない限りフォトカプラ１０Ａは動作せず、地絡を誤判定するおそれがない。
なお、フォトカプラ１０Ａが地絡を検出した場合には、図１３等の従来技術と同様に、受光素子１３Ａの出力信号を用いて警報を出力したり、装置の運転を停止させる等の動作を行う。 As described above, in this embodiment, the threshold value of the input current for operating the photocoupler 10A is set by the current detection circuit 11A connected to the previous stage of the light emitting element 12A, and between the light emitting element 12A and the light receiving element 13A. It does not depend on the light-current conversion efficiency. Therefore, when the insulation resistance 101P or the insulation resistance 101N is normal and no ground fault has occurred, even if a slight input current flows through the current detection circuit 11A for some reason, the operation of the photocoupler 10A has been described above. Since they are managed by the thresholds TH ⁺ and TH ⁻ , the photocoupler 10A does not operate unless the input current exceeds these thresholds, and there is no possibility of erroneously determining a ground fault.
When the photocoupler 10A detects a ground fault, an operation such as outputting an alarm using the output signal of the light receiving element 13A or stopping the operation of the apparatus is performed, as in the conventional technique of FIG. Do.

また、前述したように、正側直流母線ＰＬと負側直流母線ＮＬとのどちらが地絡したかによって電流検出回路に流れる電流の方向が変わるため、電流検出回路は双方向の電流を検出する必要がある。従って、図１に示したフォトカプラ１０Ａの電流検出回路１１Ａは両方向の電流を検出できるものが望ましい。ここで、片方向の電流しか検出できないフォトカプラを使用する場合は、別のフォトカプラ(図示せず)を上記フォトカプラ１０Ａに対して逆方向に並列接続することによって双方向の電流を検出可能になり、正側直流母線ＰＬと負側直流母線ＮＬとの両方の地絡を検出することができる。 Further, as described above, since the direction of the current flowing through the current detection circuit changes depending on which of the positive side DC bus PL and the negative side DC bus NL is grounded, the current detection circuit needs to detect a bidirectional current. There is. Therefore, it is desirable that the current detection circuit 11A of the photocoupler 10A shown in FIG. 1 can detect current in both directions. Here, when using a photocoupler that can only detect current in one direction, bidirectional current can be detected by connecting another photocoupler (not shown) in parallel to the photocoupler 10A in the opposite direction. Thus, it is possible to detect the ground faults of both the positive DC bus PL and the negative DC bus NL.

次に、図３は本発明の第２実施形態を示す回路図である。図３及び図１では、同一の機能を有する部品に同一の参照符号を付してある。
図３の第２実施形態において、１０Ｂは第２のフォトカプラであり、このフォトカプラ１０Ｂは、電流検出回路１１Ｂ、発光素子１２Ｂ及び受光素子１３Ｂによって構成されている。なお、フォトカプラ１０Ａを、便宜上、第１のフォトカプラと呼ぶ。
第１のフォトカプラ１０Ａの電流検出回路１１Ａと第２のフォトカプラ１０Ｂの電流検出回路１１Ｂとは、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に直列に接続されている。言い換えれば、第１のフォトカプラ１０Ａと第２のフォトカプラ１０Ｂとは、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に直列に接続されている。 Next, FIG. 3 is a circuit diagram showing a second embodiment of the present invention. 3 and 1, parts having the same function are denoted by the same reference numerals.
In the second embodiment of FIG. 3, reference numeral 10B denotes a second photocoupler, and the photocoupler 10B includes a current detection circuit 11B, a light emitting element 12B, and a light receiving element 13B. Note that the photocoupler 10A is referred to as a first photocoupler for convenience.
The current detection circuit 11A of the first photocoupler 10A and the current detection circuit 11B of the second photocoupler 10B are connected in series between the connection point between the resistors 3a and 3b and the ground point 100. In other words, the first photocoupler 10A and the second photocoupler 10B are connected in series between the connection point between the resistors 3a and 3b and the ground point 100.

この第２実施形態では、第１のフォトカプラ１０Ａを動作させる入力電流の閾値よりも、第２のフォトカプラ１０Ｂを動作させる入力電流の閾値を低い値に設定する。これにより、例えば絶縁抵抗１０１Ｎの抵抗値が低下し、抵抗器３ａ，３ｂ同士の接続点から電流検出回路１１Ａ，１１Ｂを介して接地点１００に電流が流れた場合に、第１のフォトカプラ１０Ａが動作する以前に第２のフォトカプラ１０Ｂを動作させることができる。
従って、第１のフォトカプラ１０Ａを、実際に地絡が発生した時の警報発生や運転停止を行う警報出力回路として機能させ、第２のフォトカプラ１０Ｂを、絶縁抵抗が低下していて地絡の危険性があることをユーザに知らせる予報出力回路として機能させることが可能である。
なお、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に直列に接続されるフォトカプラの数を３以上とし、それぞれが動作する入力電流の閾値を少しずつ異ならせてもよい。 In the second embodiment, the input current threshold value for operating the second photocoupler 10B is set to a lower value than the input current threshold value for operating the first photocoupler 10A. As a result, for example, when the resistance value of the insulation resistor 101N decreases and a current flows from the connection point between the resistors 3a and 3b to the ground point 100 via the current detection circuits 11A and 11B, the first photocoupler 10A. The second photocoupler 10B can be operated before.
Therefore, the first photocoupler 10A is caused to function as an alarm output circuit for generating an alarm when the ground fault actually occurs or the operation is stopped, and the second photocoupler 10B is reduced in the insulation resistance and has a ground fault. It is possible to function as a forecast output circuit for informing the user that there is a risk of
Note that the number of photocouplers connected in series between the connection point between the resistors 3a and 3b and the grounding point 100 may be three or more, and the threshold values of the input currents at which each operates may be slightly different.

この第２実施形態においても、正側直流母線ＰＬと負側直流母線ＮＬとの両方の地絡検出を可能にするためには、電流検出回路１１Ａ，１１Ｂ（フォトカプラ１０Ａ，１０Ｂ）が両方向の電流を検出可能であることが望ましい。しかし、片方向の電流しか検出できないフォトカプラを使用する場合は、各フォトカプラ１０Ａ，１０Ｂに対して、同一構成の別のフォトカプラ(図示せず)をそれぞれ逆方向に並列接続すればよい。 Also in the second embodiment, the current detection circuits 11A and 11B (photocouplers 10A and 10B) are provided in both directions in order to enable detection of ground faults of both the positive DC bus PL and the negative DC bus NL. It is desirable that the current can be detected. However, when using a photocoupler that can detect only current in one direction, another photocoupler (not shown) having the same configuration may be connected in parallel in the opposite direction to each of the photocouplers 10A and 10B.

次いで、図４は本発明の第３実施形態を示す回路図である。この第３実施形態では、図４に示すように、フォトカプラ１０Ｃ（図３のフォトカプラ１０Ｂに相当）に、このフォトカプラ１０Ｃと同一構成の別のフォトカプラ１０Ｄが並列に接続されている。なお、１１Ｃ，１１Ｄは電流検出回路、１２Ｃ，１２Ｄは発光素子、１３Ｃ，１３Ｄは受光素子である。ここで、フォトカプラ１０Ｃ，１０Ｄが動作する入力電流の閾値は同じでよい。 FIG. 4 is a circuit diagram showing a third embodiment of the present invention. In the third embodiment, as shown in FIG. 4, another photocoupler 10D having the same configuration as the photocoupler 10C is connected in parallel to the photocoupler 10C (corresponding to the photocoupler 10B in FIG. 3). 11C and 11D are current detection circuits, 12C and 12D are light emitting elements, and 13C and 13D are light receiving elements. Here, the threshold values of the input currents at which the photocouplers 10C and 10D operate may be the same.

この第３実施形態は、例えば第２実施形態（図３）において、フォトカプラ１０Ｂを動作させる入力電流の閾値が低過ぎて所望の絶縁抵抗値での異常判定が行えない場合を考慮したものである。すなわち、図４に示すごとく２つのフォトカプラ１０Ｃ，１０Ｄを並列に接続すれば、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に流れる電流を電流検出回路１１Ｃ，１１Ｄに分流させて減少させることができる。これにより、抵抗器３ａ，３ｂの接続点と接地点との間を流れる電流が一つのフォトカプラ１０Ｃ（または１０Ｄ）の閾値の２倍になったときに各フォトカプラ１０Ｃ，１０Ｄの出力がオンするので、２倍の閾値を持つフォトカプラを一つ使用するのと同等にすることができる。
この第３実施形態において、並列接続されるフォトカプラの数は３以上でもよい。更に、図４のフォトカプラ１０Ａに対して、別のフォトカプラを並列に接続してもよい。 In the third embodiment, for example, in the second embodiment (FIG. 3), the case where the threshold value of the input current for operating the photocoupler 10B is too low to perform abnormality determination with a desired insulation resistance value is considered. is there. That is, if two photocouplers 10C and 10D are connected in parallel as shown in FIG. 4, the current flowing between the connection point between the resistors 3a and 3b and the ground point 100 is divided into the current detection circuits 11C and 11D. Can be reduced. As a result, when the current flowing between the connection point of the resistors 3a and 3b and the ground point becomes twice the threshold value of one photocoupler 10C (or 10D), the output of each photocoupler 10C and 10D is turned on. Therefore, it can be equivalent to using one photocoupler having a double threshold.
In the third embodiment, the number of photocouplers connected in parallel may be three or more. Furthermore, another photocoupler may be connected in parallel to the photocoupler 10A of FIG.

次に、本発明の第４〜第６実施形態を説明する。これらの実施形態は、本発明を電気自動車やハイブリッド自動車等の電気システムを構成する非接地電力変換回路の交流出力側の地絡検出に適用した場合のものであるが、本発明は、上記以外の用途を持つ非接地電力変換回路の地絡検出にも適用可能である。 Next, fourth to sixth embodiments of the present invention will be described. In these embodiments, the present invention is applied to ground fault detection on the AC output side of an ungrounded power conversion circuit constituting an electric system such as an electric vehicle or a hybrid vehicle. However, the present invention is not limited to the above. The present invention can also be applied to ground fault detection of a non-grounded power conversion circuit having the following uses.

まず、図５は本発明の第４実施形態を示す回路図であり、図１の第１実施形態と同一の構成要素には同一の参照符号を付して説明を省略し、以下では第１実施形態と異なる部分を中心に説明する。
図５において、正側直流母線ＰＬ及び負側直流母線ＮＬは、非接地電力変換回路としての三相電圧形インバータ２０の直流入力端子にそれぞれ接続されている。インバータ２０は、ＩＧＢＴ等の半導体スイッチング素子２１ａ〜２１ｆからなり、その交流出力端子Ｕ，Ｖ，Ｗは交流出力線２２Ｕ，２２Ｖ，２２Ｗを介して交流電動機等の負荷２Ｍに接続されている。 First, FIG. 5 is a circuit diagram showing a fourth embodiment of the present invention. The same components as those of the first embodiment of FIG. A description will be given centering on differences from the embodiment.
In FIG. 5, the positive side DC bus PL and the negative side DC bus NL are respectively connected to the DC input terminals of a three-phase voltage source inverter 20 as a non-grounded power conversion circuit. The inverter 20 includes semiconductor switching elements 21a to 21f such as IGBTs, and the AC output terminals U, V, and W are connected to a load 2M such as an AC motor via AC output lines 22U, 22V, and 22W.

インバータ２０の直流側の回路構成は図１の第１実施形態と同一であって、抵抗器３ａ，３ｂとフォトカプラ１０Ａとを備え、フォトカプラ１０Ａは、双方向の電流を検出可能な電流検出回路１１Ａ、発光素子１２Ａ及び受光素子１３Ａによって構成されている。
なお、図５において、１０１Ｕ，１０１Ｖ，１０１Ｗは交流出力線２２Ｕ，２２Ｖ，２２Ｗと接地点１００との間の絶縁抵抗である。 The circuit configuration on the DC side of the inverter 20 is the same as that of the first embodiment of FIG. 1 and includes resistors 3a and 3b and a photocoupler 10A. The photocoupler 10A is a current detector capable of detecting a bidirectional current. The circuit 11A, the light emitting element 12A, and the light receiving element 13A are configured.
In FIG. 5, 101 U, 101 V, and 101 W are insulation resistances between the AC output lines 22 U, 22 V, and 22 W and the ground point 100.

次に、この実施形態の動作を説明する。
いま、インバータ２０の通常動作時に、スイッチング素子２１ａ，２１ｂ，２１ｃ，２１ｄ，２１ｅ，２１ｆの何れかがオンした場合、オンした相の交流出力線の絶縁抵抗１０１Ｕ，１０１Ｖまたは１０１Ｗが低下していて地絡が発生すると、当該絶縁抵抗を介して、直流電源１−オン状態のスイッチング素子−当該絶縁抵抗−接地点１００−電流検出回路１１Ａ−抵抗器３ａまたは３ｂ、の経路で地絡電流が流れる。
このため、第１実施形態と同様に、地絡電流が電流検出回路１１Ａの閾値（図２参照）以上になったときに発光素子１２Ａが発光して受光素子１３Ａから信号が出力される。この出力信号を利用すれば、地絡を示す警報を出力させたり、インバータ２０の運転を停止させることができる。
すなわち、インバータ２０の通常運転時に受光素子１３Ａから信号が出力されれば、地絡している相を特定できなくても、インバータ２０の交流出力側に地絡故障が発生していることを検出可能である。 Next, the operation of this embodiment will be described.
Now, when any of the switching elements 21a, 21b, 21c, 21d, 21e, and 21f is turned on during the normal operation of the inverter 20, the insulation resistance 101U, 101V, or 101W of the turned-on AC output line is lowered. When a ground fault occurs, a ground fault current flows through the path of the DC power supply 1 -on-state switching element-the insulation resistance-the grounding point 100-the current detection circuit 11A-the resistor 3a or 3b through the insulation resistance. .
Therefore, as in the first embodiment, when the ground fault current becomes equal to or greater than the threshold value of the current detection circuit 11A (see FIG. 2), the light emitting element 12A emits light and a signal is output from the light receiving element 13A. By using this output signal, an alarm indicating a ground fault can be output or the operation of the inverter 20 can be stopped.
That is, if a signal is output from the light receiving element 13A during normal operation of the inverter 20, it is detected that a ground fault has occurred on the AC output side of the inverter 20 even if the ground fault phase cannot be specified. Is possible.

また、インバータ２０の交流出力側の特定相の地絡の有無を検出したい場合には、以下のようにすればよい。
例えば、Ｕ相を検出対象とする場合には、図６に示すようにインバータ２０のＵ相上アームのスイッチング素子２１ａ、または、図７に示すようにＵ相下アームのスイッチング素子２１ｂをオンすればよい。それぞれの場合の地絡電流の通流経路は図６，図７に破線で示すとおりであり、いずれの場合も、受光素子１３Ａの出力信号を確認すれば、Ｕ相の絶縁抵抗１０１Ｕの低下による地絡故障を検出することができる。 Further, when it is desired to detect the presence or absence of a ground fault of a specific phase on the AC output side of the inverter 20, the following may be performed.
For example, when the U phase is to be detected, the switching element 21a of the U phase upper arm of the inverter 20 as shown in FIG. 6 or the switching element 21b of the U phase lower arm as shown in FIG. That's fine. The path of ground fault current in each case is as shown by the broken lines in FIGS. 6 and 7, and in either case, if the output signal of the light receiving element 13A is confirmed, the U-phase insulation resistance 101U decreases. A ground fault can be detected.

なお、図示しないが、Ｖ相を検出対象とする場合には、インバータ２０のＶ相上アームのスイッチング素子２１ｃまたは下アームのスイッチング素子２１ｄをオンし、Ｗ相を検出対象とする場合には、インバータ２０のＷ相上アームのスイッチング素子２１ｅまたは下アームのスイッチング素子２１ｆをオンして受光素子１３Ａの出力信号を確認すればよい。この場合、インバータ２０の通常の運転モードとは別に、出力地絡検出パターンとして、上述したＵ相用、Ｖ相用、Ｗ相用のスイッチングパターンを制御装置（図示せず）に記憶させておき、検出対象である特定相の出力地絡検出パターンを用いてインバータ２０をスイッチングすればよい。 Although not shown, when the V phase is a detection target, the switching element 21c of the V-phase upper arm or the lower arm switching element 21d of the inverter 20 is turned on and the W phase is the detection target. The W-phase upper arm switching element 21e or the lower arm switching element 21f of the inverter 20 may be turned on to check the output signal of the light receiving element 13A. In this case, in addition to the normal operation mode of the inverter 20, the above-described switching patterns for U phase, V phase, and W phase are stored in a control device (not shown) as an output ground fault detection pattern. The inverter 20 may be switched using the output ground fault detection pattern of the specific phase that is the detection target.

この第４実施形態においても、フォトカプラ１０Ａの電流検出回路１１Ａは両方向の電流を検出可能であることが望ましい。しかし、片方向の電流しか検出できないフォトカプラを使用する場合は、フォトカプラ１０Ａに対して、同一構成の別のフォトカプラ(図示せず)を逆方向に並列接続すればよい。 Also in the fourth embodiment, it is desirable that the current detection circuit 11A of the photocoupler 10A can detect currents in both directions. However, when using a photocoupler that can detect only current in one direction, another photocoupler (not shown) having the same configuration may be connected in parallel in the opposite direction to the photocoupler 10A.

次に、図８は本発明の第５実施形態を示す回路図である。
この第５実施形態は、図３の第２実施形態を非接地電力変換回路に適用した場合のものであり、インバータ２０の直流側の回路構成は図３と同一である。また、第２実施形態と同様に、第２のフォトカプラ１０Ｂを動作させる入力電流の閾値は、第１のフォトカプラ１０Ａを動作させる入力電流の閾値よりも低い値に設定してある。
第５実施形態の動作は第２実施形態，第４実施形態から容易に類推できるため、以下では動作の概要を説明する。 Next, FIG. 8 is a circuit diagram showing a fifth embodiment of the present invention.
In the fifth embodiment, the second embodiment of FIG. 3 is applied to a non-grounded power conversion circuit, and the circuit configuration on the DC side of the inverter 20 is the same as that of FIG. Similarly to the second embodiment, the threshold value of the input current for operating the second photocoupler 10B is set to a value lower than the threshold value of the input current for operating the first photocoupler 10A.
Since the operation of the fifth embodiment can be easily inferred from the second embodiment and the fourth embodiment, an outline of the operation will be described below.

図８において、第１のフォトカプラ１０Ａ及び第２のフォトカプラ１０Ｂに関して入力電流の閾値を上記のように設定すると、インバータ２０の交流出力側の絶縁抵抗が低下して地絡の危険性がある場合に、直流電源１−オン状態のスイッチング素子−絶縁抵抗−接地点１００−抵抗器３ａまたは３ｂの経路で流れる電流により、第２のフォトカプラ１０Ｂを地絡の予報出力回路として機能させることができる。そして、実際に地絡が発生して第１のフォトカプラ１０Ａの閾値以上の電流が上記経路に流れた場合には、第１のフォトカプラ１０Ａにより警報発生やインバータ２０の運転停止を行わせることができる。 In FIG. 8, when the threshold value of the input current is set as described above for the first photocoupler 10A and the second photocoupler 10B, the insulation resistance on the AC output side of the inverter 20 is lowered and there is a risk of a ground fault. In this case, the second photocoupler 10B can function as a ground fault forecast output circuit by the current flowing through the path of the DC power source 1-switching element in the ON state, the insulation resistance, the grounding point 100, and the resistor 3a or 3b. it can. When a ground fault actually occurs and a current equal to or greater than the threshold value of the first photocoupler 10A flows in the path, the first photocoupler 10A causes an alarm to be generated or the inverter 20 to be stopped. Can do.

この第５実施形態においても、電流検出回路１１Ａ，１１Ｂとしては両方向の電流を検出可能であることが望ましい。しかし、片方向の電流しか検出できないフォトカプラを使用する場合は、各フォトカプラ１０Ａ，１０Ｂに対して、同一構成の別のフォトカプラ(図示せず)をそれぞれ逆方向に並列接続すればよい。 Also in the fifth embodiment, it is desirable that the current detection circuits 11A and 11B can detect currents in both directions. However, when using a photocoupler that can detect only current in one direction, another photocoupler (not shown) having the same configuration may be connected in parallel in the opposite direction to each of the photocouplers 10A and 10B.

次いで、図９は本発明の第６実施形態を示す回路図である。
この第６実施形態は、図４の第３実施形態を非接地電力変換回路に適用した場合のものであり、インバータ２０の直流側の回路構成は図４と同一である。第３実施形態と同様に、フォトカプラ１０Ｃ，１０Ｄを動作させる入力電流の閾値は等しい。また、フォトカプラ１０Ｃ，１０Ｄを予報出力回路として動作させ、フォトカプラ１０Ａを警報出力回路として動作させるためには、フォトカプラ１０Ｃ，１０Ｄをそれぞれ動作させる入力電流の閾値の２倍以上の値を、フォトカプラ１０Ａを動作させる入力電流の閾値として設定することが望ましい。
第６実施形態の動作は第３実施形態，第４実施形態等から容易に類推できるため、以下では動作の概要を説明する。 FIG. 9 is a circuit diagram showing a sixth embodiment of the present invention.
In the sixth embodiment, the third embodiment of FIG. 4 is applied to a non-grounded power conversion circuit, and the circuit configuration on the DC side of the inverter 20 is the same as that of FIG. As in the third embodiment, the input current threshold values for operating the photocouplers 10C and 10D are equal. Further, in order to operate the photocouplers 10C and 10D as the forecast output circuit and the photocoupler 10A as the alarm output circuit, a value more than twice the threshold value of the input current for operating the photocouplers 10C and 10D, respectively, It is desirable to set the threshold value of the input current for operating the photocoupler 10A.
Since the operation of the sixth embodiment can be easily inferred from the third embodiment, the fourth embodiment, etc., an outline of the operation will be described below.

第３実施形態と同様に、図９に示すようにフォトカプラ１０Ｃ，１０Ｄを並列に接続すれば、抵抗器３ａ，３ｂ同士の接続点と接地点１００との間に流れる電流を電流検出回路１１Ｃ，１１Ｄに分流させて減少させることができる。これにより、抵抗器３ａ，３ｂ同士の接続点と接地点との間を流れる電流がフォトカプラ１０Ｃ（または１０Ｄ）の閾値の２倍になったときに各フォトカプラ１０Ｃ，１０Ｄの出力がオンされるので、２倍の閾値を持つフォトカプラを一つ使用した場合と等価になる。
従って、各フォトカプラ１０Ｃ，１０Ｄの入力電流の閾値が低く、それぞれ単独では所望の絶縁抵抗値での異常判定（地絡の予報判定）が行えない場合にも、本実施形態のようにフォトカプラ１０Ｃ，１０Ｄを並列に接続することで異常判定が可能になる。
この第６実施形態においても、並列接続されるフォトカプラの数は３以上でもよい。また、図９のフォトカプラ１０Ａに別のフォトカプラを並列に接続してもよい。 Similarly to the third embodiment, if the photocouplers 10C and 10D are connected in parallel as shown in FIG. 9, a current flowing between the connection point between the resistors 3a and 3b and the ground point 100 is supplied to the current detection circuit 11C. , 11D and can be reduced. As a result, when the current flowing between the connection point between the resistors 3a and 3b and the grounding point becomes twice the threshold value of the photocoupler 10C (or 10D), the outputs of the photocouplers 10C and 10D are turned on. Therefore, this is equivalent to the case where one photocoupler having a double threshold is used.
Therefore, even when the threshold value of the input current of each of the photocouplers 10C and 10D is low and it is not possible to perform abnormality determination (ground fault forecast determination) with a desired insulation resistance value alone, the photocoupler as in this embodiment An abnormality can be determined by connecting 10C and 10D in parallel.
Also in the sixth embodiment, the number of photocouplers connected in parallel may be three or more. Further, another photocoupler may be connected in parallel to the photocoupler 10A of FIG.

本発明は、電気自動車やハイブリッド自動車等の電気システムを構成する非接地直流回路または非接地電力変換回路ばかりでなく、様々な用途の非接地回路の地絡検出に利用することができる。 INDUSTRIAL APPLICABILITY The present invention can be used not only for non-grounded DC circuits or non-grounded power conversion circuits constituting electric systems such as electric vehicles and hybrid vehicles, but also for detecting ground faults in various applications.

１：直流電源
２，２Ｍ：負荷
３ａ，３ｂ：抵抗器
１０Ａ，１０Ｂ，１０Ｃ，１０Ｄ：フォトカプラ
１１Ａ，１１Ｂ，１１Ｃ，１１Ｄ：電流検出回路
１２Ａ，１２Ｂ，１２Ｃ，１２Ｄ：発光素子
１３Ａ，１３Ｂ，１３Ｃ，１３Ｄ：受光素子
２０：インバータ
２１ａ，２１ｂ，２１ｃ，２１ｄ，２１ｅ，２１ｆ：半導体スイッチング素子
２２Ｕ，２２Ｖ，２２Ｗ：交流出力線
１００：接地点
１０１Ｐ，１０１Ｎ，１０１Ｕ，１０１Ｖ，１０１Ｗ：絶縁抵抗
ＰＬ：正側直流母線
ＮＬ：負側直流母線
Ｕ，Ｖ，Ｗ：交流出力端子 1: DC power supply 2, 2M: Load 3a, 3b: Resistors 10A, 10B, 10C, 10D: Photocouplers 11A, 11B, 11C, 11D: Current detection circuits 12A, 12B, 12C, 12D: Light emitting elements 13A, 13B, 13C, 13D: Light receiving element 20: Inverter 21a, 21b, 21c, 21d, 21e, 21f: Semiconductor switching element 22U, 22V, 22W: AC output line 100: Grounding point 101P, 101N, 101U, 101V, 101W: Insulation resistance PL : Positive DC bus NL: Negative DC bus U, V, W: AC output terminal

Claims

A load is connected between the positive DC bus connected to the positive pole of the DC power supply and the negative DC bus connected to the negative pole of the DC power supply, and a ground fault of the DC circuit as a non-grounded circuit is detected. In the circuit
A first resistor having one end connected to the positive DC bus;
A second resistor having one end connected to the negative DC bus and having the same resistance value as the first resistor;
A photocoupler connected between a connection point between the other ends of the first resistor and the second resistor and a ground point;
The photocoupler is
A current detection circuit that outputs a drive signal when a current flowing between the connection point and the ground point exceeds a predetermined threshold;
A light emitting element connected to the subsequent stage of the current detection circuit and turned on by the drive signal;
A light receiving element that is turned on by output light of the light emitting element,
A ground fault detection circuit for an ungrounded circuit, wherein an alarm signal when a ground fault occurs is output from the light receiving element.

A load is connected between the positive DC bus connected to the positive pole of the DC power supply and the negative DC bus connected to the negative pole of the DC power supply, and a ground fault of the DC circuit as a non-grounded circuit is detected. In the circuit
A first resistor having one end connected to the positive DC bus;
A second resistor having one end connected to the negative DC bus and having the same resistance value as the first resistor;
A plurality of photocouplers connected in series between a connection point between the other ends of the first resistor and the second resistor and a ground point;
The plurality of photocouplers are:
A current detection circuit that outputs a drive signal when a current flowing between the connection point and the ground point exceeds a predetermined threshold;
A light emitting element connected to the subsequent stage of the current detection circuit and turned on by the drive signal;
A light receiving element that is turned on by output light of the light emitting element, and
While setting the thresholds in the plurality of photocouplers to different sizes,
The light-receiving element in one photocoupler outputs a forecast signal that reports the risk of ground fault in advance, and the alarm signal is output by the light-receiving element in another photocoupler that has a larger threshold than the photocoupler. A ground fault detection circuit for a non-grounded circuit.

A positive DC bus connected to the positive pole of the DC power source and a negative DC bus connected to the negative pole of the DC power source are connected to the DC input terminal, a load is connected to the AC output terminal, and ungrounded In the circuit for detecting the ground fault on the AC output side of the power conversion circuit as a circuit,
A first resistor having one end connected to the positive DC bus;
A second resistor having one end connected to the negative DC bus and having the same resistance value as the first resistor;
A photocoupler connected between a connection point between the other ends of the first resistor and the second resistor and a ground point;
The photocoupler is
When a current flowing between the AC output terminal and the connection point through the grounding point exceeds a predetermined threshold when any one of the plurality of semiconductor switching elements constituting the power conversion circuit is turned on A current detection circuit for outputting a drive signal;
A light emitting element connected to the subsequent stage of the current detection circuit and turned on by the drive signal;
A light receiving element that is turned on by output light of the light emitting element,
A ground fault detection circuit for an ungrounded circuit, wherein an alarm signal when a ground fault occurs is output from the light receiving element.

A positive DC bus connected to the positive pole of the DC power supply and a negative DC bus connected to the negative pole of the DC power supply are connected to the DC input terminal, a load is connected to the AC output terminal, and ungrounded In the circuit for detecting the ground fault on the AC output side of the power conversion circuit as a circuit,
A first resistor having one end connected to the positive DC bus;
A second resistor having one end connected to the negative DC bus and having the same resistance value as the first resistor;
A plurality of photocouplers connected in series between a connection point between the other ends of the first resistor and the second resistor and a ground point;
The plurality of photocouplers are:
When a current flowing between the AC output terminal and the connection point through the grounding point exceeds a predetermined threshold when any one of the plurality of semiconductor switching elements constituting the power conversion circuit is turned on A current detection circuit for outputting a drive signal;
A light emitting element connected to the subsequent stage of the current detection circuit and turned on by the drive signal;
A light receiving element that is turned on by output light of the light emitting element, and
While setting the thresholds in the plurality of photocouplers to different sizes,
The light-receiving element in one photocoupler outputs a forecast signal that reports the risk of ground fault in advance, and the alarm signal is output by the light-receiving element in another photocoupler that has a larger threshold than the photocoupler. A ground fault detection circuit for a non-grounded circuit.

In the ground fault detection circuit of the non-ground circuit according to claim 3 or 4,
In order to detect a ground fault of a specific phase on the AC output side of the power conversion circuit, the semiconductor switching element of the upper arm or the lower arm of the specific phase among the semiconductor switching elements is turned on. Circuit ground fault detection circuit.

In the ground fault detection circuit of the non-ground circuit according to claim 5,
A ground fault detection circuit for a non-grounded circuit having a switching pattern for turning on an upper arm or a lower arm semiconductor switching element of the specific phase as an output ground fault detection pattern.

In the ground fault detection circuit of the non-grounded circuit according to claim 1 or 3,
Another photocoupler having a threshold value equal to the threshold value of the photocoupler is connected in parallel to the photocoupler, and a current flowing between the connection point and the grounding point is connected to the photocoupler in each of the photocouplers connected in parallel. A ground fault detection circuit for a non-grounded circuit, characterized in that each current detection circuit is shunted.

In the ground fault detection circuit of the non-ground circuit according to claim 2 or 4,
Another photocoupler having a threshold equal to the threshold of the photocoupler is connected in parallel to any one of the plurality of photocouplers connected in series between the connection point and the ground point, A ground fault detection circuit for a non-ground circuit, wherein a current flowing between the connection point and the ground point is shunted to the current detection circuit in each photocoupler connected in parallel.

In the ground fault detection circuit of the non-ground circuit according to any one of claims 1 to 8,
In order to detect a bidirectional current flowing between the connection point and the ground point,
A ground fault detection circuit for a non-grounded circuit, wherein at least two photocouplers for detecting a current in one direction are connected in parallel in opposite directions.

In the ground fault detection circuit of the non-grounded circuit according to any one of claims 1 to 9,
The ground fault detection circuit of the non-ground circuit, wherein the operation of the non-ground circuit is stopped by the alarm signal.

In the ground fault detection circuit of the non-grounded circuit according to any one of claims 1 to 10,
A ground fault detection circuit for a non-grounded circuit, wherein the non-grounded circuit constitutes an electrical system mounted on an automobile.