JPH07213072A - Grounding protective device for single-phase three-wire inverter - Google Patents

Abstract

PURPOSE:To provide a grounding protective device, of an inverter, which can prevent a fire due to leakage electricity. CONSTITUTION:The grounding protective device is provided with a separation means made of an electromagnetic actuator 47, with a second current detection means of a fuse 34, with a means which is constituted of a fusing detection contact 34a, of a fault detection circuit 38 and of a trip circuit 39 and which gives a separation instruction to the separation means, with a first current detection means constituted of current detectors 13, 14 and with a control means which is constituted of voltage detectors 7, 8, of a transformer 22, of a voltage- reference generator 23, of a low-voltage selection circuit 24, of an amplifier 25, of a multiplier 25 and of amplifiers 27, 28.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-phase three-wire inverter in the case where an alternating current is obtained from a direct current power source such as a solar cell or a fuel cell and is directly connected to the single-phase three-wire system power source without a transformer. Ground protection device.

[0002]

2. Description of the Related Art FIG. 10 shows a typical example of a solar photovoltaic inverter connected to a conventional single-phase three-wire distribution system, which is a schematic main circuit, a control circuit for the inverter, and a protection circuit for the main circuit. It consists of The main circuit includes solar cells 1 and 2 that form a DC power source, an inverter that converts the DC output of the solar cells 1 and 2 into an AC, and is composed of, for example, IGBTs (insulated gate bipolar transistors) 9a, 9b, 10a, 10b, System power supply 20, which constitutes a three-phase three-wire system power supply,
21, the reactors 11 and 12, and the filter capacitors 15 and 16.

The protection circuit comprises fuses 17 and 18 and an earth leakage breaker (ELCB) 19.

The control circuit of the inverter includes a voltage detector 7,
8, a transformer 22, a voltage reference signal generator 23, a low voltage selection circuit 24, an amplifier 25, a multiplier 26, amplifiers 27 and 28, PWM signal circuits 29 and 31, and a triangular wave generator 30. And drive circuits 32 and 33.

Specifically, the solar cells 1 and 2 are connected in series, and the middle point (connection point) of the solar cells 1 and 2 is connected via the earth leakage breaker 19 to the second line of the system power supplies 20 and 21 (middle point or ground point).
Connect to.

The positive electrode of the solar cell 1 is connected to the positive electrode of the electrolytic capacitor 5 through the backflow prevention diode 3, and the negative electrode of the solar cell 2 is connected to the negative electrode of the electrolytic capacitor 6 through the backflow prevention diode 4 to connect the electrolytic capacitor 5 The point where the negative electrode of 1 and the positive electrode of the electrolytic capacitor 6 are connected is connected to the midpoint of the solar cells 1 and 2.

The voltages of the electrolytic capacitors 5 and 6 are detected by the voltage detectors 7 and 8 and input to the low voltage selection circuit 24. The voltage between the positive electrode of the electrolytic capacitor 5 and the negative electrode of the electrolytic capacitor 6 is PWM-controlled for the half bridge composed of the IGBT 9a and the IGBT 9b, the output is smoothed through the reactor 11, the current is detected by the current detector 13, and the fuse 17 is connected. System power supply 2 via earth leakage breaker 19
0 to the first line.

The voltage between the positive electrode of the electrolytic capacitor 5 and the negative electrode of the electrolytic capacitor 6 is PWM-controlled by the half bridge composed of the IGBT 10a and the IGBT 10b, and the output is connected to the system through the reactor 12, the current detector 14, the fuse 18, and the earth leakage breaker 19. Connect to the third line of the power supply 21.

The filter capacitor 15 is connected between the connection point of the current detector 13 and the fuse 17 and the midpoint of the solar cells 1 and 2, and the filter capacitor 16 is connected to the connection point of the current detector 14 and the fuse 18 and the solar cell. Connect between the midpoints of batteries 1 and 2.

In order to control the maximum output power of the solar cells 1 and 2, that is, the battery output voltage constant, the voltage reference generator 23
And the lower voltage detected by the low voltage selection circuit 24 are compared, the output v25 amplified by the amplifier 25 and the voltage of the system power supply 21 are detected by the transformer 22 and multiplied by the multiplier 26, and are in phase with the system power supply 21. The current reference v26 is output. The current reference v26 and the value I1 detected by the current detector 13 are compared, and the amplifier 2
The value amplified by 7 and the output of the triangular wave generator 30 are compared with each other to generate a PWM signal by the PWM signal circuit 29 and the drive circuit 3
1 to drive the IGBTs 9a and 9b via the reactor 2.
The current flowing through 1 is controlled to match the current reference v26.

Similarly, v26 and the current I3 are compared and the amplifier 2
The output amplified by 8 and the output of the triangular wave generator 30 are compared, a PWM signal is obtained by the PWM signal circuit 31, and the drive circuit 3
The IGBTs 10a and 10b are PWM-controlled via 3 to form a current control loop in which the current of the reactor 12 matches the current reference v26.

FIG. 11 shows a detailed structure of the earth leakage breaker 19, in which the first, second and third wires of the system power supplies 20 and 21 are passed through the iron core 191 of the zero-phase current transformer.
A secondary winding 192 is wound around the output and its output is detected by a detection circuit 193.
The trip coil (TC) 194 is excited and the main contact 195 of the earth leakage breaker 19 is opened when the level is detected at.

[0013]

In the structure as described above, the earth leakage breaker 19 has the following features:
The leakage current component flows to the ground point, the sum of the penetrating currents of the iron core 191 of the zero-phase current transformer is not zero, and the leakage current component flows, which can be detected by the secondary winding 192.

However, considering the case where the point A of the solar cell 1 in FIG. 10 is grounded, the earth leakage is cut off from the positive electrode of the solar cell 1 through the point A and through the grounding portion of the second line of the system power sources 20 and 21. A DC leakage current flows through the second line of the container 19 in the route of the negative electrode of the solar cell 1.

However, the AC current from the system power supply 20 is connected to the first line of the earth leakage breaker 19, the fuse 17, the current detector 1.
3, a path passing through the reactor 11, the diode portion of the IGBT 9a, and the diode 3 is conceivable, but since it is blocked by the diode 3, the current does not flow backward except when the diode 3 is conducting.

On the other hand, from the system power supply 20 through the ground point of the second line, point A, diode 3, IGBT 9a, reactor 1
1, the current detector 13, the fuse 17, the route of the first line of the ELCB19 is also considered, but this current is IGBT9a
It is controlled by turning on and off and does not appear as a leakage current.

Therefore, the AC component on the primary side of the current transformer of the earth leakage breaker 19 is zero, so that the earth leakage cannot be detected.
Further, when a direct current component flows through the primary side of the zero-phase current transformer, it is saturated and cannot be detected as an output.

Therefore, when the solar cells 1 and 2 are mainly installed on the roof of a private house, for example, the leakage current of the solar cells 1 and 2 may increase, which may cause a fire. The nature becomes great.

In view of the above, an object of the present invention is to provide a grounding protection device for an inverter which can prevent the risk of fire due to electric leakage.

[0020]

In order to achieve the above object, the invention corresponding to claim 1 is to convert DC power of a DC power supply into AC power by an inverter and directly connect to a single-phase three-wire AC power supply. In a single-phase three-wire inverter, a separating means provided between the inverter and the AC power supply, for separating the inverter and the AC power supply, and between a neutral point of the inverter and a neutral point of the AC power supply. A grounding protection device for a single-phase three-wire inverter, comprising: a means for separating the separating means based on a flowing current.

In order to achieve the above-mentioned object, the invention according to claim 2 is a single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting it to a single-phase three-wire alternating-current power supply. In, a detection means is provided between the inverter and the AC power supply, for separating the inverter and the AC power supply, and a current flowing through each of the first line and the third line connected to the inverter and the AC power supply is detected. A first current detection means, a control means for controlling the detection values detected by the first current detection means to be substantially equal to each other, a neutral point of the inverter and a neutral point of the AC power supply. Second current detecting means for detecting a current flowing in the second line between the two, and when the detected value detected by the second current detecting means exceeds a set value, a separation command is issued to the separating means. Means for obtaining a grounding protective device of the single-phase three-wire inverter provided with the.

To achieve the above object, the invention according to claim 3 is a single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting it to a single-phase three-wire alternating-current power supply. In the above, a separating means provided between the inverter and the AC power supply for separating the inverter and the AC power supply, and DC current components respectively flowing in the first line and the third line to which the inverter and the AC power supply are connected, First current detecting means for detecting, control means for controlling the detection value detected by the first current detecting means to be substantially zero, neutral point of the inverter and neutrality of AC power source Second current detection means for detecting a direct current component flowing in the second line connected to the point, and when the detection value detected by the second current detection means exceeds a set value, the separation means is Means for providing a separation instruction, the ground protection device of the single-phase three-wire inverter provided with the.

In order to achieve the above object, the invention according to claim 4 is a single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting it to a single-phase three-wire alternating-current power supply. In, a separation means provided between the inverter and the AC power supply, for separating the inverter and the AC power supply, and a current detection means for detecting the total sum of the DC current of each line to which the inverter and the AC power supply are connected, A grounding protection device for a single-phase three-wire inverter, comprising: a means for giving a separation command to the separation means when the detection value detected by the current detection means exceeds a set value.

In order to achieve the above object, the invention according to claim 5 is a single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting it to a single-phase three-wire alternating-current power supply. In, the separation means provided between the inverter and the AC power supply, for separating the inverter and the AC power supply, current detection means for detecting the sum of the current of each line connected to the output side of the DC power supply, A ground protection device for a single-phase three-wire inverter, comprising: a means for giving a separation command to the separation means when the detection value detected by the current detection means exceeds a set value.

In order to achieve the above-mentioned object, the invention according to claim 6 is a single-phase 3 connecting a single-phase three-wire type AC power supply by converting DC power of a DC power supply into AC power by an inverter.
In a line type inverter, a separating means that is provided between the inverter and the AC power supply and separates the inverter and the AC power supply, and a DC that respectively flows through a first line and a third line to which the inverter and the AC power supply are connected. First current detection means for detecting a current component, control means for controlling the detection value detected by the first current detection means to be substantially zero, and the second line of the inverter and the AC power supply. Voltage drop detection means for detecting the DC voltage drop of
A ground protection device for a single-phase three-wire inverter, comprising: a means for giving a separation command to the separation means when the detection value detected by the voltage drop detection means exceeds a set value.

To achieve the above object, the invention according to claim 7 is a single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting it to a single-phase three-wire alternating-current power supply. In the above, a separating means provided between the inverter and the AC power supply for separating the inverter and the AC power supply, and DC current components respectively flowing in the first line and the third line to which the inverter and the AC power supply are connected, A first current detecting means for detecting, a control means for controlling the detected value detected by the first current detecting means to be substantially zero in accordance with the relationship with each independent current reference, Second current detecting means for detecting a DC current component flowing in a second line between the neutral point of the inverter and the neutral point of the AC power supply, and the detecting current detected by the second current detecting means. When the value exceeds the set value, a grounding protective device of the single-phase three-wire inverter anda means for providing a separation command to the separating means.

In order to achieve the above-mentioned object, the invention corresponding to claim 8 is the ground protection device for a single-phase three-wire inverter according to any one of claims 1 to 7, in which the DC voltage is higher than that of the separating means. This is a grounding protection device for a single-phase three-wire inverter in which a non-linear resistance is connected between the midpoint of the power supply side and ground.

[0028]

According to the invention corresponding to claim 1, as a ground protection device having high sensitivity, the separating means is separated based on the current flowing between the neutral point of the inverter and the neutral point of the AC power source. It is possible to prevent fires caused by electric leakage.

According to the invention corresponding to claim 2, the single phase 3
The output current of the linear inverter is controlled so that the detected currents of the first and third lines are substantially equal, and it is detected that a current has flowed in the second line of the output of the inverter, and the inverter and the AC power supply are separated. By doing so, it is possible to prevent a fire or the like due to electric leakage as a grounding protection device with high sensitivity. According to the invention corresponding to claim 3, the direct current component flowing through the first line and the third line of the output of the single-phase three-wire inverter is controlled so as to be substantially zero, and the single-phase three-wire inverter is controlled. By disconnecting the inverter and the AC power supply from the system when the DC current flowing in the second line of the output of 1 exceeds the set value, it is possible to prevent a fire or the like due to electric leakage as a ground protection device with high sensitivity.

According to the invention corresponding to claim 4, the single phase 3
Detects the sum of the DC current of each line of the output of the wire type inverter, and when this detected value exceeds the set value, the AC power source is separated from the inverter to provide a highly sensitive ground protection device. Can be prevented.

According to the invention corresponding to claim 5, the single phase 3
Detects the sum of the DC current of each line of the input of the wire type inverter, and when the detected value exceeds the set value, the AC power source is separated from the inverter to provide a highly sensitive ground protection device. Can be prevented.

According to the invention corresponding to claim 6, the single phase 3
The direct current components of the first and third lines of the output of the linear inverter are controlled to be substantially zero, and the direct current voltage drop of the second line of the output of the single-phase three-wire inverter is detected, When the detected value exceeds the set value, by disconnecting the AC power source from the inverter, it is possible to prevent a fire due to electric leakage as a grounding protection device with high sensitivity.

According to the invention corresponding to claim 7, the single phase 3
The direct current components flowing in the first line and the third line of the output of the linear inverter are controlled so as to be substantially zero due to the relationship with the respective independent current references, and the neutral point of the inverter and the AC power supply are controlled. By disconnecting the AC power source from the inverter when the detected value of the DC current flowing between the neutral points exceeds the set value, it is possible to prevent fires due to electric leakage as a grounding protection device with good sensitivity.

According to the invention of claim 8, in addition to the operation of the invention of claims 1 to 7, after detecting a ground fault,
It is possible to prevent the neutral point potential from rising too high.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Here, the same parts as those of the conventional example of FIG.

[First Embodiment] FIG. 1 is a circuit diagram showing a first embodiment (embodiment of the invention corresponding to claims 1 and 2) of the present invention. A DC power source including a capacitor 6 is connected in series, and a fuse 3 is provided between the midpoint and the neutral point (second line) of the system power sources 20 and 21.
Insert 4. The fuse 34 has a current rating smaller than that of the fuses 17 and 18.

Further, an electromagnetic contactor 47 is provided in this portion without providing the earth leakage breaker 19 provided in FIG. Further, a fusing detection contact 34a for detecting fusing of the fuse 34, and a failure detection circuit 38 in series with the contact 34a.
The trip circuit 39 is connected via the, and when the output of the trip circuit 39 is generated, the electromagnetic contactor 47 is opened.

Specifically, when the fuse 34 is blown,
The fusing detection contact 34a is closed, the failure detection circuit 38 and the trip circuit 39 are operated, and the electromagnetic contactor 47 is opened.

When the output of the failure detection circuit 38, that is, when the fuse 34 is blown, it is input to the drive circuits 32 and 33 of the inverter bridge to stop the operation of the inverter bridge.

In the embodiment of FIG. 1, the electromagnetic contactor 47 constitutes the separating means, the fuse 34 constitutes the second current detecting means, and the fusing detection contact 34a, the failure detecting circuit 38 and the trip circuit 39 are the separating means. The current detectors 13 and 14 constitute the first current detection means, and the voltage detectors 7 and 8, the transformer 22, the voltage reference generator 23, and the low voltage selection circuit. 24, the amplifier 25, the multiplier 26, and the amplifiers 27 and 28 constitute a control means.

According to the first embodiment constructed as described above, the following operational effects can be obtained. That is, the current I1 detected by the current detector 13 and the current detector 1
The current I3 detected at 4 is controlled so that the current reference v26 obtained from the multiplier 26 matches. Therefore, I
1 and I3 are substantially equal (substantially equal), and the current flowing through the fuse 34 at normal times is about 0.1% or less of the rated current, which is the current control error component including the direct current component. Therefore, the fuses 17 and 18 need a capacity to carry the rated current, but the fuse 34 can be reduced to several percent or less of the rated current.

Now, if a leakage accident occurs at point A, a current flows from the (+) pole of the solar cell 1 → A → the ground point B of the system power source → fuse 34 → the (−) pole of the solar cell 1, The fuse 34 is blown even if the leakage current is several percent of the rated current.
Then, the fusing detection contact 34a is closed, whereby the failure detection circuit 38 operates to turn off the drive circuits 32 and 33 to stop the inverter, and at the same time, opens the electromagnetic contactor 47 via the trip circuit 39. Because of this, the leakage current is turned off, so that a fire due to the leakage current can be prevented.

In the embodiment of FIG. 1, the fusing detection contact 34
The same operation can be carried out by using a means for detecting the voltage across the fuse 34 instead of a. Further, in the embodiment of FIG. 1, instead of the fuse 34, a re-circuit breaker which opens a circuit when a predetermined current is exceeded like the fuse may be used.

According to the first embodiment described above, the currents of the first line and the third line of the output of the single-phase three-wire inverter are controlled to be substantially equal, and the second line (ground potential) has a small value. By providing a fuse 34 having a capacity to detect that a direct current flows slightly and disconnecting the inverter from the system, a ground protection device with high sensitivity can prevent a fire due to electric leakage.

[Second Embodiment] FIG. 2 is a circuit diagram showing a second embodiment (embodiment of the invention corresponding to claim 3) of the present invention, in which a DC power source including a capacitor 5 and a DC voltage including a capacitor 6 are provided. Power sources are connected in series, and the midpoint and system power source 2
Between the neutral point of 0,21 (the second line), the current detector 35
Connect. Only the direct current component of the current I2 detected by the current detector 35 is detected by the filter 36, and when the level detector 37 exceeds the set level, the operation of the inverter bridge is stopped via the failure detection circuit 38. At the same time, via the trip circuit 39, the electromagnetic contactor 4
7 is configured to be opened.

The inverter of FIG. 2 controls the DC component of the current I1 detected by the current detector 13 to zero,
A direct current component of the current I1 is detected by the filter 51, and the current I1 is input to the subtractor 55 via the amplifier 53. Here, the current reference v26 from the multiplier 26 is corrected by the output of the filter 51, and this is corrected to a new current reference I1b. And the current I1 detected by the current detector 13 is differentially input to the amplifier 27. Further, in order to control the direct current component of the current I3 detected by the current detector 14 to zero, the current I3 is filtered by the filter 52.
DC component is detected by the subtractor 56 via the amplifier 54.
To the output of the filter 52 from the current reference v26 from the multiplier 26, and a new current reference I3b
And the current I3 detected by this and the current detector 14.
Are differentially input to the amplifier 28.

As the current detectors 13, 14, and 35 shown in FIG. 2, generally, a Hall CT type current detector capable of detecting a direct current component is used. The configuration other than the points described above is the same as in FIG.

Next, the function and effect of the second embodiment constructed as described above will be described. Since the direct current component of the detection currents I1 and I3 is controlled to be zero, the direct current component of the detection current I2 is usually almost zero. Now, if a leakage accident occurs at point A, the (+) pole of the solar cell 1 → A → grid power supply 2
Since a DC current flows from the ground point B of 0, 21 to the current detector 35 to the (-) pole of the solar cell 1, I2 is filtered by the filter 36.
Only the direct current component is detected via the level detector 37, and when this value exceeds the set value by the level detector 37, the inverter is disconnected from the system power supplies 20 and 21 via the failure detection circuit 38,
The leakage circuit on the side of the solar cells 1 and 2 is opened.

In FIG. 2, the electromagnetic contactor 47 constitutes a separating means, the current detector 35 and the filter 36 constitute a second current detecting means, and the level detector 37 and the failure detecting circuit 3 are included.
8 and the trip circuit 39 constitute means for giving a separation command to the separation means, and the current detectors 13 and 14 and the filter 5
1, 52 and amplifiers 53, 54 constitute a first current detecting means, and include voltage detectors 7, 8, a transformer 22, a voltage reference generator 23, a low voltage selecting circuit 24, an amplifier 25, a multiplier 26 and an amplifier. 27 and 28 and subtractors 55 and 56 constitute a control means.

According to the second embodiment described above, the DC components of the currents of the first line and the third line of the output of the single-phase three-wire inverter are controlled to be substantially equal to each other, and the second line (ground potential) is controlled. )
Is provided with a current detector 35, and the detected current is filtered by a filter 36.
DC level is taken out by the level detector 37
By detecting that the set value of is exceeded and disconnecting the inverter from the system, as a sensitive ground protection device,
It is possible to prevent fires due to electric leakage.

[Third Embodiment] FIG. 3 is a circuit diagram showing only the essential parts of a third embodiment of the present invention (an embodiment of the invention corresponding to claim 4), omitting an inverter control circuit. However, it may be either the control circuit of the inverter shown in FIG. 1 or FIG. A current detector 41 is provided between the output side of the inverter and the electromagnetic contactor 47 to detect the current sum of the three lines of the output of the inverter. As this current detector 41, for example, a current detector capable of detecting a direct current component of the Hall CT method is used, and three wires of the inverter output are penetrated through this iron core at the same number of times in the same direction to generate a magnetic flux of the iron core. It is detected and designated as I2, which is input to the filter 36, where only the DC component is detected. Only the direct current component detected by the filter 36 is input to the level detector 37, and the output generated when the set value is exceeded is opened through the failure detection circuit 38 and the trip circuit 39 to open the electromagnetic contactor 47. This is different from the embodiment shown in FIG. 1 or 2.

The third embodiment thus constructed has the following effects and advantages. That is, in a normal state, the current sum of the three lines of the output of the inverter is zero, so that I2 is zero. However, for example, when the point A is grounded, the ground current flows only in the second line. Then, the current detector 41 detects this ground current as I2, the detected current I2 is input to the filter 37 and only the DC component is detected, and when only this DC component exceeds the set level of the level detector 37. , The failure detection circuit 38 operates to stop the operation of the inverter bridge, and at the same time, the electromagnetic contactor 4 is operated via the trip circuit 39.
Open seven.

In the inverter shown in FIG. 3, it is not necessary to control the direct current components of the currents I1 and I3 of the current detectors 13 and 14 to substantially zero.

In FIG. 3, the electromagnetic contactor 47 constitutes a separating means, the current detector 41 and the filter 36 constitute a current detecting means, and the level detector 37, the failure detecting circuit 38 and the trip circuit 39 constitute a separating means. It also constitutes means for giving a separation command.

As described above, according to the third embodiment, the current detector 41 for detecting the current sum of the three lines of the output of the single-phase three-wire type inverter is provided, and the filter 36 of the current flowing in the second line is provided. When it is detected that the DC component detected by the level detector 37 exceeds the level set by the level detector 37, the inverter is disconnected from the system power supplies 20 and 21 to provide a highly sensitive ground protection device to prevent a fire due to electric leakage. Can be prevented.

[Fourth Embodiment] FIG. 4 is a circuit diagram showing only a main portion of a fourth embodiment of the present invention (an embodiment of the invention corresponding to claim 5), omitting an inverter control circuit. However, it may be either the control circuit of the inverter shown in FIG. 1 or FIG.

Between the output sides of the solar cells 1 and 2 and the input side of the inverter, a current detector 40 for detecting the sum of currents of the three lines of the input of the inverter is provided. As the current detector 40, for example, a Hall CT type detector capable of detecting a direct current component is used, and the input wire of the inverter is penetrated through this iron core at the same number of times in the same direction, and the magnetic flux of the iron core is detected to obtain I2. The configuration is such that this is input to the level detector 37, and the output generated when the set value is exceeded here is configured to open the electromagnetic contactor 47 via the failure detection circuit 38 and the trip circuit 39. 1 or the embodiment of FIG.

In the inverter shown in FIG. 4, it is not necessary to control the direct current components of the currents I1 and I3 of the current detectors 13 and 14 to substantially zero.

In FIG. 4, the electromagnetic contactor 47 constitutes a separating means, the current detector 40 constitutes a current detecting means, and the level detector 37, the failure detecting circuit 38, and the trip circuit 39.
Constitutes means for giving a separation command to the separation means.

As described above, according to the fourth embodiment, the current detector 40 for detecting the current sum of the three wires of the input of the single-phase three-wire inverter is provided, and this current is set to the level set by the level detector 37. When it is detected that the voltage exceeds the limit, by disconnecting the inverter from the system power supplies 20 and 21, it is possible to prevent a fire or the like due to electric leakage as a ground protection device with high sensitivity.

[Fifth Embodiment] FIG. 5 is a circuit diagram showing a fifth embodiment of the present invention (an embodiment of the invention corresponding to claim 6). The current detector 35 of the embodiment of FIG. 2 is different from the embodiment of FIG. 2 only in that a resistor 42 is provided in the second line, the voltage across the resistor 42 is detected, and the voltage is input to the filter 36 as I2 instead of being not provided. .

In such a structure, the current flowing through the second line appears as a voltage drop I2 across the resistor 42.
In this case, since the direct current component of the output currents of the first and third lines of the inverter is controlled to be zero, the direct current component of I2 is usually almost zero.

Now, if a leakage accident occurs at point A, the ground current flows only through the second line. In this case, the voltage drop I2 of the resistor 42 detects only the direct current component by the filter 36,
When this DC component exceeds the level set by the level setter 37, the failure detection circuit 38 operates to stop the operation of the inverter bridge, and at the same time, the electromagnetic contactor 47 is opened via the trip circuit 39.

In FIG. 5, the electromagnetic contactor 47 constitutes a separating means, the resistor 42 and the filter 36 constitute a voltage drop detecting means, and the level detector 37, the failure detecting circuit 38 and the trip circuit 39 correspond to the separating means. Means for giving a separation command by the current detectors 13 and 14 and the filters 51 and 52.
And the amplifiers 53 and 54 constitute first current detecting means, and the voltage detectors 7 and 8, the transformer 22, the voltage reference generator 23, the low voltage selection circuit 24, the amplifier 25, the multiplier 26 and the amplifier 2 are included.
7, 28 and subtractors 55, 56 constitute a control means.

According to the fifth embodiment described above, the direct current component of the currents of the first and third lines of the output of the single-phase three-wire type inverter is controlled to be zero and inserted into the second line. Resistance 42
The DC component of the voltage drop that occurs in the power supply is detected by the filter 36, and when it is detected that the detected DC current exceeds the level set by the level detector 37, the sensitivity is set by disconnecting the inverter from the system power supplies 20 and 21. As a good grounding protection device, it is possible to prevent fires due to electric leakage.

[Sixth Embodiment] FIG. 6 is a circuit diagram showing only a main portion of a sixth embodiment of the present invention (an embodiment of the invention corresponding to claim 8), omitting an inverter control circuit. However, it may be either the control circuit of the inverter shown in FIG. 1 or FIG.

The only difference is that a non-linear resistor 46, for example, a bidirectional Zener diode of several tens of volts is provided between the neutral point of the inverter and the grounded portion.

With such a configuration, after the ground fault is detected, the electromagnetic contactor 47 is opened, and if the neutral point potential rises too much, a current flows through the non-linear resistor 46 and the neutral point potential rises. Suppressed.

According to the sixth embodiment described above, inconveniences in terms of insulation and safety can be avoided. [Seventh Embodiment] FIG. 7 is a circuit diagram showing a seventh embodiment of the present invention. Differences from the embodiment of FIG. 3 are as follows. That is, in the embodiment shown in FIG.
Whereas the total sum of the currents of the books is detected all at once,
In FIG. 7, the direct current detector 41 is not provided and the current detector 35
Is provided on the second line, the current detector 13 is provided on the first line, and the current detector 14 is provided on the third line.
The currents I1, I2 ', and I3 detected by 14, 35 are input to the adder 57, and the sum of the respective currents is set as I2. This is input to the filter 36, and only the point for detecting the DC current is detected. different.

In FIG. 7, the electromagnetic contactor 47 constitutes the separating means, the current detector 35 and the filter 36 constitute the second current detecting means, and the adder 57, the filter 36, the level detector 37 and the failure detection. The circuit 38 and the trip circuit 39 constitute means for giving a separation command to the separation means, and the current detectors 13 and 14, the filters 51 and 52, and the amplifiers 53 and 5
Reference numeral 4 constitutes a first current detecting means, which includes voltage detectors 7 and 8, a transformer 22, a voltage reference generator 23, and a low voltage selection circuit 24.
The amplifier 25, the multiplier 26, the amplifiers 27 and 28, and the subtracters 55 and 56 constitute control means.

With this structure, not only the same operational effects as the embodiment of FIG. 3 but also the following operational effects can be obtained. That is, in the case of the embodiment shown in FIG. 3, a Hall CT is generally used as the DC current detector 41, but in order to increase the detection sensitivity, the number of times the three wires to be detected are collectively passed through the iron core can be increased. Good. However, since the iron core size is limited, the detection sensitivity is limited to the iron core size. On the other hand, in the embodiment of FIG. 7, since the current of each line is detected individually, each current detector 13, 35, 14 can be penetrated by one line several times. The detection sensitivity of Example 7 can be increased.

[Eighth Embodiment] FIG. 8 is a circuit diagram showing only an essential part of the eighth embodiment of the present invention, and the other inverter control circuits are the same as those of the embodiments shown in FIGS. Is composed of. In each of the examples shown in FIGS. 1 to 6, two sets of solar cells 1 and 2 were connected in series, and there were three DC input lines of the inverter, but in the example of FIG. DC output side of the solar cell 2 and the IGBTs 9a, 9b, 10a, 1
Between the input side of the inverter consisting of 0b, the reactor 4
3, a chopper circuit composed of the diode 44 and the IGBT 45 is connected, and two sets of DC power supplies are equivalently produced by this chopper circuit. Then, between the output side of the solar cell 2 and the input side of the chopper circuit, as in the embodiment of FIG. 4, a DC current detector 4 such as a Hall CT is provided.
0 is provided, where the ground line current I of the two wires of the output of the solar cell 2
It is configured to detect 2.

In such a structure, the IGBT
When 45 is turned on, a circuit from the (+) pole of the solar cell 2 to the (-) pole of the solar cell 2 through the reactor 43, the IGBT 45, and the diode 4 is formed, and current energy is accumulated in the reactor 43. . IGBT in this state
When 45 is turned off, the current of the reactor 43 flows through the circuit passing through the diode 44, the capacitor 5, and the reactor 43, and charges the capacitor 5. On the other hand, capacitor 6
Will be charged directly from the solar cell 2 to generate a total of two sets of DC power supplies. Other functions and effects are the same as those of the embodiment shown in FIG.

[Ninth Embodiment] FIG. 9 is a circuit diagram showing a ninth embodiment of the present invention (an embodiment of the invention corresponding to claim 7). The embodiment shown in FIGS. This is a modified example. For example, the first output of the inverter of the embodiment of FIG.
In controlling the detection currents I1 and I3 of the third and third lines, a common current reference v26 is given from the multiplier 26. In the embodiment of FIG. 9, the current reference v2 of I1 and I3 is given.
6 and v60 are separately created by the multipliers 26 and 60.

In FIG. 9, the electromagnetic contactor 47 constitutes a separating means, the current detector 35 and the filter 36 constitute a second current detecting means, and the level detector 37 and the failure detecting circuit 3 are included.
8 and the trip circuit 39 constitute means for giving a separation command to the separation means, and the current detectors 13 and 14 and the filter 5
1, 52 and the amplifiers 53, 54 constitute a first current detecting means, and the voltage detectors 7, 8, the transformer 22, the voltage reference generator 23, the low voltage selecting circuit 24, the amplifiers 25, 59 and the multiplier 26. , 60, the amplifiers 27 and 28, and the subtracters 55 and 56 constitute a control means.

With this configuration, I1, I
If 3 is different, the second line will see the current difference between I1 and I3. In the case of the embodiment of FIG. 2 or the embodiment of FIG. 5 in which the DC component of I1 and I3 is controlled to zero, if there is no ground fault on the DC side, the difference between I1 and I3 is on the second line. Only the exchange part of appears. When a ground fault on the DC side occurs, a DC component flows through the second line, and this can be detected. Therefore, the same protection operation as in the embodiment of FIG. 3 or 4 is performed.

On the other hand, the embodiment of FIG. 3 or FIG.
Both are methods for detecting the sum of the currents of the first line to the third line. For example, even when a direct current component is superimposed on I1 and I3,
If there is no ground fault on the DC side, the total current becomes zero,
When a ground fault on the DC side occurs, a DC component appears in the total current, and the protection operation is performed by detecting this.

[0078]

According to the present invention, it is possible to provide a grounding protection device for an inverter which can prevent the risk of fire due to electric leakage.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of a ground protection device for a single-phase three-wire inverter according to the present invention.

FIG. 5 is a circuit diagram showing a fifth embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 6 is a circuit diagram showing a sixth embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 7 is a circuit diagram showing a seventh embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 8 is a circuit diagram showing an eighth embodiment of a grounding protection device for a single-phase three-wire inverter according to the present invention.

FIG. 9 is a circuit diagram showing a ninth embodiment of the ground protection device for a single-phase three-wire inverter according to the present invention.

FIG. 10 is a circuit diagram showing an example of a photovoltaic power generation inverter that is connected to a conventional single-phase three-wire power distribution system.

11 is a diagram for explaining the configuration of the earth leakage breaker of FIG.

[Explanation of symbols]

1, 2 ... Solar cell, 3, 4 ... Diode, 5, 6 ... Electrolytic capacitor, 7, 8 ... Voltage detector, 9a, 9b, 10
a, 10b ... IGBT, 11, 12, ... Reactor, 1
3, 14 ... Current detector, 15, 16 ... Capacitor, 1
7, 18 ... Fuse, 19 ... Earth leakage breaker, 20, 21
... System power supply, 27, 28 ... Amplifier, 29, 31 ... PWM
Signal circuit, 30 ... Triangle wave generator, 32, 33 ... Driving circuit, 34 ... Fuse, 35 ... Current detector, 36 ... Filter, 37 ... Level detector, 38 ... Failure detection circuit, 39 ...
Trip circuit, 40, 41 ... Current detector, 42 ... Resistance,
46 ... Non-linear resistance.

Front Page Continuation (72) Kenichi Kimoto, 1st Toshiba Town, Fuchu, Tokyo, Fuchu factory, Tokyo (72) Takuo Itami, 1st Toshiba, Fuchu city, Tokyo, Fuchu factory, Toshiba

Claims (8)

[Claims] 1. A single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting to a single-phase three-wire alternating-current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating-current power supply. A single-phase 3 comprising: a separating unit that separates the inverter and the AC power supply; and a unit that separates the separating unit based on a current flowing between a neutral point of the inverter and a neutral point of the AC power supply. Grounding protection device for wire inverter. 2. A single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting to a single-phase three-wire alternating-current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating-current power supply. Separation means for separating the inverter from the AC power supply, first current detection means for detecting currents respectively flowing in the first line and the third line connected to the inverter and the AC power supply, and the first current detection Control means for controlling the detection values detected by the means to be substantially equal to each other; and a second means for detecting a current flowing in a second line between the neutral point of the inverter and the neutral point of the AC power supply. A single-phase three-wire inverter comprising: a current detection means; and a means for giving a separation command to the separation means when the detection value detected by the second current detection means exceeds a set value. Ground protection device. 3. A single-phase three-wire inverter, which converts direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connects to a single-phase three-wire alternating-current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating-current power supply. Separation means for separating the inverter and the AC power supply, and a first detection unit for detecting DC currents respectively flowing in the first line and the third line to which the inverter and the AC power supply are connected.
Current detecting means, control means for controlling the detection value detected by the first current detecting means to be substantially zero, the neutral point of the inverter and the neutral point of the AC power source are connected. And a second current detecting means for detecting a direct current component flowing through the second line, and when the detected value detected by the second current detecting means exceeds a set value, a separation command is issued to the separating means. A grounding protection device for a single-phase three-wire inverter, which is provided with: 4. A single-phase three-wire inverter that converts direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connects the single-phase three-wire alternating-current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating-current power supply. Separation means for separating the inverter and the AC power supply, current detection means for detecting the sum of the DC current components of the lines to which the inverter and the AC power supply are connected, and the detection value detected by the current detection means is a set value. And a means for giving a separation command to the separation means when the voltage exceeds the ground level, and a ground protection device for a single-phase three-wire inverter. 5. A single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and directly connecting to a single-phase three-wire alternating-current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating-current power supply. Separation means for separating the inverter and the AC power supply, current detection means for detecting the sum of the currents of the respective lines connected to the output side of the DC power supply, and the detection value detected by the current detection means is a set value. A grounding protection device for a single-phase three-wire inverter, comprising means for giving a separation command to the separation means when the voltage exceeds. 6. A single-phase three-wire inverter for converting direct-current power of a direct-current power supply into alternating-current power by an inverter and connecting the alternating-current power to a single-phase three-wire alternating current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating current power supply. Separation means for separating the inverter from the AC power supply, and a first means for detecting DC current components respectively flowing in the first line and the third line to which the inverter and the AC power supply are connected.
Current detecting means, control means for controlling the detection value detected by the first current detecting means to be substantially zero, and detecting a DC voltage drop in the second line of the inverter and the AC power supply. Grounding protection of a single-phase three-wire inverter comprising voltage drop detection means and means for giving a separation command to the separation means when the detection value detected by the voltage drop detection means exceeds a set value. apparatus. 7. A single-phase three-wire inverter, which converts direct-current power of a direct-current power supply into alternating-current power by an inverter and is directly connected to a single-phase three-wire alternating-current power supply, wherein the single-phase three-wire inverter is provided between the inverter and the alternating-current power supply. Separation means for separating the inverter and the AC power supply, and a first detection unit for detecting DC currents respectively flowing in the first line and the third line to which the inverter and the AC power supply are connected.
Current detecting means, control means for controlling the detected values detected by the first current detecting means to be substantially zero according to the relationship with each independent current reference, and the inverter neutral Point and the second current detecting means for detecting a direct current component flowing in the second line between the neutral point of the AC power source, and the detection value detected by the second current detecting means exceeds a set value. At this time, a means for giving a separation command to the separation means, and a grounding protection device for a single-phase three-wire inverter. 8. The grounding protection device for a single-phase three-wire inverter according to claim 1, wherein a non-linear resistance is provided between the midpoint of the DC power source side of the separating means and the ground. Ground protection device for connected single-phase 3-wire inverter.