Power conversion device and power conditioner

Abstract

To provide a power conversion device capable of detecting contact abnormality in a grid-connected relay without outputting an inverter output.SOLUTION: A power conversion device includes an inverter, a relay system connection end connected to a system power source side, an electric line between the inverter and the relay system connection end, a grid-connected relay interposed in the electric line, and a relay abnormality detection circuit provided per grid-connected relay. The relay abnormality detection circuit includes a detection power source that makes a detection current flow toward a detection unit, a first open / close unit between the detection power source and one end of the grid-connected relay and a second open / close unit connected to the other end of the grid-connected relay. The detection unit is connected to the second open / close unit and outputs a detection signal when the detection current is detected, and the relay abnormality detection circuit closes the first open / close unit and the second open / close unit by receiving the output stop of AC power and open of a relay portion and detects the abnormality of the grid-connected relay by the detection signal.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a power conversion device and a power conditioner that control DC power sources such as photovoltaic cells, wind power generation, and fuel cells, and to detecting abnormalities such as contact abnormalities and welding in an interconnection relay used for interconnection to a grid within the device. [Background technology]

[0002] Power conversion devices such as power conditioners can control power from DC power sources, connect to a (commercial) grid, and directly or indirectly supply power to AC loads such as residential loads. Power supply and other functions of power conversion devices are performed via relay contacts. However, in the event of an abnormality or shutdown, the power conversion device must be isolated from the grid power source and load. In such power conversion devices, the contacts of each relay must be kept closed while the device is connected to the grid power source or supplying power to the load. Meanwhile, when the device is shut down, the relay contacts must be open. Furthermore, for example, if a ground fault or short-circuit occurs in the distribution line where the power conversion device is operating in grid-connected mode, or if power transmission from the substation to the distribution line is stopped due to a planned outage or other reason (i.e., an islanding state occurs), the grid-connection relay (also called a grid-connection relay) is opened, disconnecting the power conversion device from the grid power source to prevent any impact on operation and ensure safety during maintenance work on the distribution line. However, due to contact abnormality or welding of the contact pieces of the relay unit, the relay unit may be in a closed state even though the interconnection relay should be in an open state.

[0003] Therefore, as a conventional technique, a method of providing an auxiliary contact piece to detect such contact abnormalities, welding, etc. is known (Patent Document 1). However, in this case, the power supplied to the exciting coil for operating the relay unit becomes large, and a solution to this problem has arisen. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2014 / 020671 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, another conventional method for detecting contact abnormalities, welding, etc. in a grid-connected relay involves electrically detecting the abnormality by outputting AC inverter output from an inverter in a power conversion device to the grid. However, in this method, in the event of a power outage on the grid side, a reverse current flows from the low-voltage side to the high-voltage side in a transformer (pole transformer) that converts high voltage to low voltage, resulting in excessive voltage on the high-voltage side. Therefore, there is a need for an electrical contact abnormality detection method that does not output this inverter output. However, while Patent Document 1 detects contact abnormalities, welding, etc., and discloses a technique for solving the problem of increased power supplied to the excitation coil for operating the relay unit, it does not disclose or suggest any solution to the problem of the reverse current occurring in the method of electrically detecting contact abnormalities by outputting inverter output.

[0006] Therefore, in order to solve the above-mentioned conventional problems, the present invention aims to provide a power conversion device and a power conditioner that can detect contact abnormalities in a grid interconnection relay without outputting an inverter output, and that can also contribute to energy conservation. [Means for solving the problem]

[0007] As a result of various investigations, the present inventors have found that the above object can be achieved by the present invention described below.

[0008] That is, the power conversion device according to the present invention (hereinafter also referred to as configuration IA) has: A power conversion device including an inverter that receives output power from a DC power source or power obtained by voltage-converting the output power from the DC power source and converts it into AC power, and a relay system connection terminal that is connected to a system power source side, The power supply system further includes at least one phase of an electric line between the inverter and the relay system connection end, an interconnection relay interposed in at least one of the at least one phase of the electric line, and a relay abnormality detection circuit provided in the interconnection relay, the relay abnormality detection circuit has a detection power supply that flows a detection current toward a detection unit, and at least one of a first opening / closing unit between the detection power supply and one end of the interconnection relay and a second opening / closing unit connected to the other end of the interconnection relay, the detection unit being connected to the other end of the interconnection relay or the second opening / closing unit and configured to detect the detection current in the event of an abnormality, and outputting a detection signal when the detection current is detected; the inverter stops output of the AC power in response to a command from an inverter output stop command unit, and the interconnection relay opens a relay unit in response to a command from a relay open command unit; The relay abnormality detection circuit closes at least one of the first opening / closing unit and the second opening / closing unit after the inverter output stop command unit outputs a command to stop the output of AC power and the relay open command unit outputs a command to open the relay unit, and in the event of an abnormality, causes the detection current to flow to the detection unit and detects an abnormality in the grid-connection relay based on the detection signal from the detection unit. In the above power conversion device, the relay abnormality detection circuit may be provided for each of the interconnection relays, and the relay abnormality detection circuit may have both the first opening / closing unit and the second opening / closing unit (hereinafter, these configurations will also be referred to as configuration II).

[0009] In the configuration of the power conversion device of the above-mentioned configuration IA, "the relay abnormality detection circuit has a detection power supply that flows a detection current toward a detection unit, and at least one of a first switching unit between the detection power supply and one end of the interconnection relay and a second switching unit connected to the other end of the interconnection relay, and the detection unit is connected to the other end of the interconnection relay or the second switching unit and is configured to detect the detection current in the event of an abnormality" means a configuration such as the following configuration IB (IB-1, IB-2, IB-3), A configuration including at least one phase of an electric line between the inverter and the relay system connection end, an interconnection relay interposed in at least one of the at least one phase of the electric line, and a relay abnormality detection circuit provided for each of the interconnection relays, "(Configuration IB-1) The relay abnormality detection circuit has a detection power supply that flows a detection current toward a detection unit, and a first opening / closing unit between the detection power supply and one end of the interconnection relay, and the detection unit is connected to the other end of the interconnection relay and outputs a detection signal when the detection current is detected, or (Configuration IB-2) The relay abnormality detection circuit has a detection power supply connected to one end of the interconnection relay and causing a detection current to flow toward a detection unit, and a second switching unit connected to the other end of the interconnection relay, and the detection unit is connected to the second switching unit and outputs a detection signal when the detection current is detected, or (Configuration IB-3) The relay abnormality detection circuit has a detection power supply that flows a detection current toward a detection unit, a first switching unit between the detection power supply and one end of the interconnection relay, and a second switching unit connected to the other end of the interconnection relay, and the detection unit is connected to the second switching unit and outputs a detection signal when it detects the detection current. This means that...

[0010] Furthermore, the above-mentioned configuration IA's "after a command to stop the output of the AC power is output from the inverter output stop command unit and a command to open the relay unit is output from the relay open command unit, the relay abnormality detection circuit closes at least one of the first open / close unit and the second open / close unit, and in the event of an abnormality, causes the detection current to flow to the detection unit" means that in each of the above-mentioned configurations IB (configurations IB-1, IB-2, IB-3), The relay abnormality detection circuit closes the first opening / closing unit in configuration IB-1, the second opening / closing unit in configuration IB-2, and the first opening / closing unit and the second opening / closing unit in configuration IB-3 after the inverter output stop command unit outputs a command to stop the output of AC power and the relay open command unit outputs a command to open the relay unit so that the detection current flows in the detection unit in the event of an abnormality.As a result, the detection signal is output from the detection unit in the event of an abnormality, and an abnormality in the grid-connected relay can be detected.

[0011] Here, in the case of a so-called typical configuration including the above-mentioned configuration IB-3 and configuration II, the configuration of the power conversion device of the above-mentioned configuration IA is as follows (hereinafter also referred to as configuration III). A power conversion device including an inverter that receives output power from a DC power source or power obtained by voltage-converting the output power from the DC power source and converts it into AC power, and a relay system connection terminal that is connected to a system power source side, The power supply system further includes at least one phase of an electric line between the inverter and the relay system connection end, an interconnection relay interposed in at least one of the at least one phase of the electric line, and a relay abnormality detection circuit provided for each of the interconnection relays, the relay abnormality detection circuit has a detection power supply that flows a detection current toward a detection unit, a first switching unit between the detection power supply and one end of the interconnection relay, and a second switching unit connected to the other end of the interconnection relay, the detection unit is connected to the second switching unit, and outputs a detection signal when the detection current is detected; the inverter stops output of the AC power in response to a command from an inverter output stop command unit, and the interconnection relay opens a relay unit in response to a command from a relay open command unit; The relay abnormality detection circuit closes the first opening / closing unit and the second opening / closing unit after a command to stop the output of the AC power is output from the inverter output stop command unit and a command to open the relay unit is output from the relay open command unit, and detects an abnormality in the interconnection relay based on the detection signal from the detection unit.

[0012] As described above, the above-mentioned configuration III is a typical configuration, particularly in terms of the positions and number of switching units such as the first switching unit and the second switching unit. However, this configuration naturally implicitly discloses the above-mentioned configuration IA, which is a higher-level configuration that can be divided into the above-mentioned configurations IB-1 to IB-3, and each of the above-mentioned configurations IB-1 and IB-2 other than configuration IB-3. In other words, it goes without saying that the above-mentioned configurations IA, IB-1, and IB-2 are not easily conceived from the above-mentioned configuration III. However, in the course of technological development, it is clear that the above-mentioned configuration III was devised as a more optimal configuration that is less likely to cause malfunctions, while or after the above-mentioned configurations IA, IB-1, and IB-2, which are the minimum configurations for detecting abnormalities in the interconnection relay, were devised. Therefore, there is nothing unnatural about assuming that someone who only proposed the above-mentioned configuration III also recognized the above-mentioned configurations IA, IB-1, and IB-2.

[0013] The relay abnormality detection circuit may detect a contact abnormality or welding in the interconnection relay, and the detection power supply may be an insulated power supply.

[0014] As can be seen from the above configuration, the power conversion device according to the present invention does not perform electrical detection by outputting AC inverter output from the inverter to the grid as in the conventional case, but rather closes the first and second switching units after outputting a command to open the relay unit from the relay open command unit, so that in the event of an abnormality in the grid relay such as a contact abnormality or welding, a detection current flows through the relay unit even though the relay unit is open, and the abnormality in the grid relay is detected by the detection signal from the detection unit. Thus, the power conversion device according to the present invention can detect a contact abnormality in the grid interconnection relay without outputting an inverter output as in the conventional case.

[0015] Here, the detection power supply is provided uniquely for each relay abnormality detection circuit. The detection power supply does not use the power output via the inverter, but rather uses, for example, power branched from the power directly input to the power conversion device. As described above, the detection power supply does not pass a current intended for consumption by the grid or household loads like the inverter output, but passes the detection current toward the detector, indicating that it is provided uniquely for each relay abnormality detection circuit and is dedicated to detecting abnormalities in the grid-connected relay. Therefore, the relay abnormality detection circuit should be distinguished from technologies that detect abnormalities in the grid-connected relay by, for example, comparing the voltage from the inverter with a comparator. As described above, since the detection power supply does not pass a current intended for consumption by the grid or household loads like the inverter output, it can also contribute to energy savings.

[0016] The power converter may further include a rectifying element connected between the high-voltage side electric line and the low-voltage side electric line of the insulated power supply, a rectifying element connected in parallel with the detector, or a rectifying element connected in series to the high-voltage side electric line of the insulated power supply. Such a configuration can prevent reverse voltage or a voltage exceeding the rated voltage from being applied to electronic components (components) that make up the power conversion device.

[0017] In addition, when the output voltage of the detection power supply is lower than the output voltage of the DC power supply, an abnormality in the interconnection relay may be detected. With this configuration, it is possible to avoid a voltage exceeding the rated voltage being applied to the grid side, magnetic saturation occurring in the pole transformer, and the like.

[0018] The power conversion device according to the present invention comprises: The power supply may further include two-phase electric lines between the inverter and the relay system connection end, interconnection relays interposed in all of the two-phase electric lines, and a relay abnormality detection circuit provided for each of the interconnection relays and having both the first switching unit and the second switching unit. This makes it possible to achieve the above-mentioned effects in a specific configuration in which the interconnection relays are interposed in the two-phase electric lines of so-called U-phase and W-phase.

[0019] The power conditioner according to the present invention comprises: The power converter includes: The DC power source is a solar power generation device. Therefore, the power conditioner according to the present invention can achieve the same effects as those of the above-described power conversion device. [Effects of the Invention]

[0020] The power conversion device and power conditioner according to the present invention can detect contact abnormalities in a grid interconnection relay without outputting an inverter output, and can also contribute to energy conservation. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a diagram illustrating an example of a conventional connection including a connection between an inverter and a system power supply side and an interconnection relay interposed therebetween. [Figure 2] FIG. 1 is a diagram illustrating an example of a connection configuration according to an embodiment, including a connection between an inverter and a system power supply side, an interconnection relay interposed therebetween, and a relay abnormality detection circuit provided for each of the interconnection relays. [Figure 3] FIG. 4 is a diagram illustrating an example of a detection power supply of the relay abnormality detection circuit in the connection configuration according to the present embodiment. [Figure 4] FIG. 10 is a diagram showing an example of a connection configuration according to another embodiment, including a connection between an inverter and a system power supply side, an interconnection relay interposed therebetween, and a relay abnormality detection circuit provided for each of the interconnection relays. [Figure 5]10A and 10B are diagrams illustrating an example in which a reverse voltage and a voltage exceeding a rated voltage are applied to components in a power conversion device in a connection configuration according to the present embodiment. [Figure 6] 10A and 10B are diagrams illustrating another example in which a reverse voltage and a voltage exceeding a rated voltage are applied to components in the power conversion device in the connection configuration according to the present embodiment. [Figure 7] 10A and 10B are diagrams illustrating still another example in which a reverse voltage and a voltage exceeding a rated voltage are applied to components in the power conversion device in the connection configuration according to the present embodiment. [Figure 8] 10A and 10B are diagrams illustrating still another example in which a reverse voltage and a voltage exceeding a rated voltage are applied to components in the power conversion device in the connection configuration according to the present embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example in which a DC voltage is applied to the system side in the connection configuration according to the present embodiment. [Figure 10] 10A and 10B are diagrams illustrating another example in which a DC voltage is applied to the system side in the connection configuration according to the present embodiment. [Figure 11] FIG. 1 is a diagram illustrating an example of an intrusion path of a lightning surge intruding from the system side. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same reference numerals indicate the same or corresponding parts, and unless otherwise specified, the description thereof will be omitted.

[0023] FIG. 1 shows an example of a conventional connection between a power conversion device and a grid power supply. The power conversion device 1 is, for example, a power conditioner (hereinafter simply referred to as a power conditioner) 1. A solar power generation device 200, which is a DC power source, is connected to the power conditioner 1 via a DC / DC converter 300 that converts the voltage of the output power of the DC power source. The power conversion device 1 controls the solar power generation device 200 through MPPT control (maximum power point tracking control) and other methods. The power conversion device 1 also includes an inverter 120 connected to the DC / DC converter 300. The inverter 120 outputs single-phase three-wire AC power (U-phase, O-phase, W-phase) or three-phase AC power (U-phase, V-phase, W-phase) to a switching box 400 that supplies power to a household load L such as a home appliance. In this embodiment, the inverter 120 outputs single-phase three-wire AC power (U-phase, O-phase, W-phase). The switching box 400 performs a switching operation to connect two of the inverter 120, the grid power source G, and the household load L.

[0024] In the power conditioner 1, the inverter 120 is connected to a relay system connection terminal 110, which is connected to the system power supply G side, via a grid-connection relay 130. At least one-phase electric line and a grid-connection relay 130 interposed in at least one of the at least one-phase electric lines are provided between the inverter 120 and the relay system connection terminal 110. Typically, two-phase (U-phase, W-phase) electric lines Lu, Lw and grid-connection relays 135 (130), 136 (130) interposed in all of the two-phase electric lines are provided between the inverter 120, which outputs the single-phase three-wire (U-phase, O-phase, W-phase) AC power, and the relay system connection terminal 110.

[0025] The interconnection relays 135, 136 are provided in the inverter unit 1 for protection in the event of an abnormality in the inverter 1 or an abnormality on the grid side (such as a power outage when there is no voltage on the grid power supply G side). If the inverter 1 operates with a contact abnormality, such as welding, between the contacts CPu, CPw of the relay sections (relays) Su, Sw included in the interconnection relays 135, 136 and the contacts, this could lead to a malfunction or accident, so it is necessary to detect contact abnormalities, such as welding, in the relays.

[0026] When there is no voltage on the system power supply G side, the ON (closed state of the contacts and the breaker) / OFF (open state of the contacts and the breaker) combinations of relay unit Su and relay unit Sw are set to one of three possible combinations: (Su: ON, Sw: OFF), (Su: OFF, Sw: ON), and (Su: OFF, Sw: OFF). After that, inverter output of AC power is output from inverter 120 to the system side, generating voltage Esd. At this time, inter-phase voltage Euw between the U phase and W phase on the system power supply G side is measured, and voltage |Esd-Euw| is calculated. If the calculation result is equal to or greater than a predetermined threshold, it is detected that a contact abnormality such as welding of the relay unit (hereinafter, welding is used as an example) has occurred.

[0027] If the relay unit is welded, the inverter output (AC voltage Esd) is output toward the grid, creating an unsafe state. Until now, it was believed that safety was ensured because voltage Esd is a low voltage. However, it has been discovered that in transformers (pole transformers) that convert high voltage to low voltage, reverse current flows from the low voltage side to the high voltage side, generating excessive voltage on the high voltage side. In other words, it has been discovered that voltage Esd can become high voltage through the pole transformer, creating an unsafe state on the grid side. To address this issue, a power conversion device according to one embodiment of the present invention will be described below.

[0028] FIG. 2 shows an example of a connection between a power conversion device and a grid power supply according to one embodiment of the present invention. In this embodiment, unlike FIG. 1, a relay abnormality detection circuit is provided for each grid-connected relay 130 between the inverter 120 and the relay grid connection end 110. Specifically, relay abnormality detection circuits 170 and 180 are provided for each grid-connected relay 135 and 136. In this embodiment, the relay abnormality detection circuits 170 and 180 detect contact abnormalities or welding in the grid-connected relays 135 and 136 in the corresponding phases. Note that the relay abnormality detection circuits that detect the grid-connected relay to be identified may be provided on one or both sides of the two phases, but in this embodiment, they are provided on both sides as described above.

[0029] 2 controls the DC / DC converter 300, the inverter 120, the grid-connected relays 135 and 136, the switching box 400, etc. The control circuit 500 of this embodiment includes an inverter output stop command unit 510 that outputs an inverter output command to stop (and / or start) the output of AC power from the inverter 120, and a relay open command unit 530 that outputs a relay command to open (and / or close) the relay units Su and Sw in the grid-connected relays 135 and 136.

[0030] The relay abnormality detection circuit 170 (180) includes a detection power supply V1SR (V2SR) that supplies a detection current Iu (Iw) to a detection unit 179 (189), a first switching unit 173 (183) between the detection power supply V1SR (V2SR) and one end Tu1 (Tw1) of a grid-connected relay contact, and a second switching unit 177 (187) connected to the other end Tu2 (Tw2) of the grid-connected relay contact. The detection units 179 (189) are connected to the second switching units 177 (187), respectively. In this embodiment, the detection units 179 (189) are connected between the second switching units 177 (187) and grounds V1_GND (V2_GND) corresponding to the power supply V1SR (V2SR), and output a detection signal Su_chk (Sw_chk) when the detection current Iu (Iw) is detected.

[0031] In this embodiment, the detection power supply V1SR (V2SR) is provided uniquely for each relay abnormality detection circuit and does not use power output via the inverter 120. Instead, it uses power branched from the power directly input to the power conversion device 1. As described above, the detection power supply V1SR (V2SR) flows the detection current Iu (Iw) toward the detector 179 (189). This indicates that the detection power supply V1SR (V2SR) does not flow a current intended for consumption by the grid or household loads, as in the inverter output, but is specifically provided for each relay abnormality detection circuit specifically for detecting abnormalities in the grid-connected relay. Therefore, the relay abnormality detection circuit 130 should be distinguished from technologies that detect abnormalities in the grid-connected relay by, for example, comparing the voltage from the inverter 120 with a comparator. As described above, the detection power supply V1SR (V2SR) does not flow a current intended for consumption by the grid or household loads, as in the inverter output, and therefore can contribute to energy savings. Here, the detection power supplies V1SR and V2SR serve as power supplies for driving, i.e., for opening and / or closing, the relay units Su and Sw in the grid-connection relays 135 and 136. The detection power supplies V1SR and V2SR are supplied, for example, from the output of the solar power generation device 200 or the output of the DC / DC converter 300 via an isolation transformer (not shown). Note that, if a storage battery (not shown) is provided, the detection power supplies V1SR and V2SR may be supplied from the output of the storage battery via an isolation transformer (not shown).

[0032] In this embodiment, welding detection is performed separately for the U phase and the W phase. In the prior art, when welding detection is performed, the inverter output (AC voltage Esd) is output toward the grid side as described above, and the inverter 120 is operated. However, in this embodiment, the inverter 120 is not operated. That is, the AC voltage Esd output toward the grid side is zero. Therefore, this embodiment can detect contact abnormalities in the grid interconnection relay without outputting the inverter output, and therefore can avoid the conventional problem of a reverse current flowing from the low-voltage side to the high-voltage side in a transformer (pole transformer) that converts high voltage to low voltage, causing an excessive voltage on the high-voltage side and resulting in an unsafe state on the grid side.

[0033] A method for detecting contact abnormalities (such as welding) in this embodiment will be described using as an example a method for detecting welding of the grid-connection relay 135 on the U-phase side. First, the inverter 120 stops the output of the AC power in response to an inverter output command from the inverter output stop command unit 510, and the grid-connection relay 135 opens the relay unit Su in response to a relay command from the relay open command unit 530 (relay unit Su is OFF). The relay abnormality detection circuit 170 closes the first switching unit 173 and the second switching unit 177 after the inverter output command is output from the inverter output stop command unit 510 and the relay command is output from the relay open command unit 530. The relay abnormality detection circuit 170 detects whether an abnormality has occurred in the grid-connection relay 135 based on a detection signal Su_chk from the detection unit 179. That is, in the detection unit 179, if no contact abnormality such as welding occurs in the relay unit Su, no detection current flows through the relay unit Su, but if a contact abnormality such as welding occurs in the relay unit Su, a detection current flows through the relay unit Su, and the detection current Iu (Iw) is detected.When the detection current is detected, a detection signal for a contact abnormality such as welding is output, and the relay abnormality detection circuit 170 detects that an abnormality has occurred in the interconnection relay 135 based on the output of this detection signal.

[0034] Specifically, when the first switching unit 173 and the second switching unit 177 are turned ON (relay unit Su is OFF), if relay unit Su is welded or the like, a current flows through the path of power supply V1SR(+) ⇒ first switching unit 173 ⇒ relay unit Su ⇒ second switching unit 177 ⇒ detection unit 179 ⇒ ground V1_GND, as shown in the figure. Note that if welding or the like does not occur, no current flows through the above path. Therefore, by detecting this current (which may be in the form of a voltage) with the detection unit 179, the presence or absence of a contact abnormality such as welding in the interconnection relay 135 is detected. If welding or the like occurs, the detection unit 179 outputs the detection signal Su_Chk. Note that the same method can be used to detect welding of the interconnection relay 136 on the W-phase side.

[0035] FIG. 3 shows a specific example of the detection power supply configuration of the relay abnormality detection circuit in FIG. 2, taking the U phase as an example. The detection power supply V1SR in this figure is connected to ground V1_GND and is implemented as an isolated power supply, such as a transformer-based power supply. As shown by the arrows in this figure, the relay unit Su is OFF (shown by the dashed line in this figure) but is welded (shown by the solid line in this figure). Therefore, when the first switching unit 173 and the second switching unit 177 are ON (shown by the solid line in this figure), current flows through the isolated power supply V1SR(+) ⇒ first switching unit 173 ⇒ relay unit Su ⇒ second switching unit 177 ⇒ detection unit 179 ⇒ ground V1_GND, and the detection signal Su_Chk is output from the detection unit 179. The same applies to specific examples of the detection power supply on the W phase side.

[0036] FIG. 4 shows an example of a connection between a power conversion device and a system power supply according to another embodiment of the present invention. In this figure, the DC / DC converter 300 is omitted, and the inverter 120 includes only two switching element arrays (switching element arrays 120_1 and 120_2) in parallel with the DC power supply 200, each of which has two switching elements connected in series. Note that in this embodiment, compared to FIG. 3, the detection power supplies V1SR and V2SR are each configured as isolated flyback converters (DC-DC converters) that utilize transformers for the primary-side power supply VSR, as indicated by the two dashed lines in the upper part of FIG. 4. The respective output voltages [v] are V1 and V2. Compared to FIG. 2, the differences are primarily in the positions of the second switching units 177 and 187, the detection units (detection circuits) 179 and 189, and the grounds V1_GND and V2_GND, but the circuit configuration is the same as in FIG. 2 (also shown in FIGS. 5 to 11). Here, at the locations where electrical lines intersect with each other on the entire diagram, intersections marked with a filled circle indicate that the electrical lines intersect with each other, and intersections marked with no filled circle indicate that the electrical lines do not intersect with each other.

[0037] In FIG. 4, rectifier elements D3 and D4 are connected between the high-voltage side electrical lines V1H and V2H and the low-voltage side electrical lines V1L and V2L of the isolated power supplies (detection power supplies) V1SR and V2SR, respectively. Also in the figure, protective elements ZD1 and ZD2 are connected in parallel to the detection units 179 and 189, respectively. The protective elements ZD1 and ZD2 are, for example, Zener diodes. Furthermore, in the figure, rectifier elements D1 and D2 are connected (inserted) in series on the high-voltage side electrical lines V1H and V2H of the isolated power supplies V1SR and V2SR, respectively. The rectifier elements D1, D2, D3, and D4 are, for example, diodes. Note that, although this embodiment includes all of the rectifier elements D3 and D4, the protective elements ZD1 and ZD2, and the rectifier elements D1 and D2, only some of these elements may be included.

[0038] The effect of providing the rectifier element D4 and the protective element ZD2 will be described using Fig. 5. In the state shown in Fig. 5, when the relay unit Su is welded, the first switching unit 183 and the second switching unit 187 are turned ON, and the first switching unit 173 and the second switching unit 177 are turned OFF. At this time, as indicated by the bold line and arrows in Fig. 5, a current flows through the welded relay unit Su, the high-voltage side switching element of the switching element array 120_2, the photovoltaic power generation device 200 which is a DC power supply, the low-voltage side switching element of the switching element array 120_1, the low-voltage side electric line V2L including the second switching unit 187 and the detection circuit 189, the secondary-side winding of the detection power supply V2SR and the capacitor C2 connected in parallel thereto, and the high-voltage side electric line V2H including the first switching unit 183, in this order, due to the voltage difference between the voltage Vg of the system power supply G and the voltage Vbus of the photovoltaic power generation device 200 which is a DC power supply. It is assumed that the voltage Vg shown in the figure is applied to the system power supply G.

[0039] If the output voltage V2 of the detection power supply V2SR is lost due to a component failure or other reason, the power supply to capacitor C2 will be lost. At this time, if Vg > Vbus, depending on the circuit constants and the state of the system, a reverse voltage (maximum Vg - Vbus) may be applied to capacitor C2 from the system power supply G. Because capacitor C2 is a power circuit element, it may be made of, for example, a polarized electrolytic capacitor, which may be damaged if a reverse voltage is applied. Therefore, by inserting rectifier element D4 as described above (Figure 4), the above current flows through rectifier element D4, reducing the possibility of reverse voltage being applied to capacitor C2.

[0040] Furthermore, in this state, when Vg>Vbus, there is a possibility that a voltage (maximum Vg-Vbus) will also be applied to the detection circuit 189 from the system power supply G. If Vg-Vbus becomes large, there is a possibility that a voltage exceeding the rated voltage will be applied to the detection circuit 189. Therefore, by inserting the protective element ZD2 as described above (FIG. 4), it is possible to reduce the possibility that a voltage exceeding the rated voltage will be applied to the detection circuit 189.

[0041] The effects of providing the rectifying element D3 and the protective element ZD1 can be understood in the same way from the above explanation by referring to FIG. 6 instead of FIG. 5, and therefore the explanation thereof will be omitted.

[0042] The effect of providing the rectifier element D1 will be described using FIG. 7. In the state shown in FIG. 7, when the relay unit Sw is welded, the first and second switching units 173 and 177 are turned ON, and the first and second switching units 183 and 187 are turned OFF. At this time, as indicated by the bold line and arrows in FIG. 7, a current flows due to the difference between the voltage Vg of the power grid G ​​and the voltage Vbus of the photovoltaic power generation device 200, which is a DC power supply, through the high-voltage side electric line V1H including the first switching unit 173, the capacitor C1 connected in parallel to the secondary winding of the detection power supply V1SR, the low-voltage side electric line V1L including the second switching unit 177 and the detection circuit 179, the high-voltage side switching element of the switching element array 120_2, the photovoltaic power generation device 200, which is a DC power supply, the low-voltage side switching element of the switching element array 120_1, and the welded relay unit Sw, in this order. It is assumed that the voltage Vg shown in FIG. 7 is applied to the power grid G.

[0043] Here, when Vg > Vbus, depending on the circuit constants and the state of the system, there is a possibility that a voltage (maximum Vg - Vbus) will be applied to capacitor C1 from the system power supply G. If Vg - Vbus becomes large, there is a possibility that a voltage exceeding the rated voltage will be applied to capacitor C1. Note that this figure may also include a case where the output voltage V1 of the detection power supply V1SR is not lost. There is also a possibility that a reverse voltage (maximum Vg - Vbus) will be applied to the detection circuit 179 from the system power supply G. Therefore, by inserting the rectifier element D1 as described above (FIG. 4), the rectifier element D1 inhibits the flow of the current, thereby reducing the possibility that a voltage exceeding the rated voltage will be applied to capacitor C1 and that a reverse voltage will be applied to the detection circuit 179.

[0044] The effect of providing the rectifying element D2 can be understood from the above explanation by referring to FIG. 8 instead of FIG. 7, and therefore the explanation thereof will be omitted.

[0045] 9, a description will be given of cases where the above-mentioned welding detection is performed (or not performed) in relation to the relationship between the output voltage Vbus of the DC power supply 200 and the output voltages V1 and V2 of the detection power supplies V1SR and V2SR. Note that a state such as that shown in Figure 10, which corresponds to Figure 9, is also possible, but since this can be understood in the same way from the above explanation, a description thereof will be omitted.

[0046] 9, when the relay unit Sw is welded, the first switching unit 173 and the second switching unit 177 are turned ON, and the first switching unit 183 and the second switching unit 187 are turned OFF, a state is assumed in which the voltage Vg is not applied due to a power outage or the like on the side of the system power supply G. At this time, as indicated by the bold line and arrow in the figure, a current flows due to the voltage V1 of the detection power supply V1SR through the high-voltage side electric line V1H including the first switching unit 173, the system power supply G (output voltage Vg≈0), the welded relay unit Sw, the high-voltage side switching element of the switching element array 120_1, the photovoltaic power generation device 200 which is a DC power supply, the low-voltage side switching element of the switching element array 120_2, the low-voltage side electric line V1L including the second switching unit 177 and the detection circuit 179, the secondary side winding (output voltage V1) of the detection power supply V1SR, and the capacitor C1 connected in parallel thereto, in this order.

[0047] Referring to the same figure, depending on the circuit constants and system conditions, during a power outage on the system side, if the relay unit Sw is welded and the output voltage V1 of the detection power supply V1SR is greater than the bus voltage Vbus of the DC power supply 200, the DC output voltage V1 may be applied to the system side. The moment the output voltage V1 is applied to the system side, a high voltage may be induced on the high-voltage distribution line side of the power receiving transformer (pole transformer) on the system side, and a potential may be generated on the high-voltage distribution line side despite the power outage. This may also cause DC bias magnetization of the power receiving transformer. That is, if the output voltage V1 is applied to the system side abruptly, such as when the first switching unit 173 and the second switching unit 177 are turned on, the magnetic flux on the low-voltage distribution line side of the pole transformer also changes abruptly, potentially inducing a high voltage on the high-voltage distribution line side of the pole transformer.

[0048] Therefore, in the above power conversion device, when Vbus (the output voltage of the DC power supply 200) is greater than the output voltage V1, the above-mentioned interconnection relay abnormality detection (welding detection, etc.) is performed. In this case, no current flows to the system side as shown in the figure. On the other hand, since the output voltage V1 is a relatively small value (for example, it can be set to about 5 V), the inverter 120 itself does not operate when the output voltage Vbus of the DC power supply 200 is close to V1. Therefore, under such conditions, abnormality detection (welding detection, etc.) is not performed. The upper left of the figure shows the relationship between the output voltage V1, the output voltage Vbus of the DC power supply 200 when welding detection is performed, and the output voltage Vbus when welding detection is not performed.

[0049] The present invention is not limited to the above-described embodiments, and various additions, modifications, and omissions are possible without departing from the spirit of the present invention. Therefore, such additions, modifications, and omissions are also included in the scope of the present invention.

[0050] For example, it is not necessary for a relay abnormality detection circuit to be provided for each interconnection relay. Furthermore, each relay abnormality detection circuit may naturally have either a first switching unit or a second switching unit. In other words, if a relay abnormality detection circuit is provided for only one interconnection relay, even if a contact abnormality or welding occurs in another interconnection relay, if the contact abnormality or welding of that interconnection relay can be detected, the power conversion device can be isolated from the system power supply and the load in the event of an abnormality or shutdown. Furthermore, even if the relay abnormality detection circuit includes only one of the first switching unit and the second switching unit, closing that switching unit closes the relay abnormality detection circuit, so that the contact abnormality or welding can be detected.

[0051] However, as shown in Figure 11, a capacitance component C3 is provided between the low-voltage electrical lines V1L and V2L of the isolated power supply as a countermeasure against EMI (electromagnetic interference), or the capacitance component C3 exists as stray capacitance between transformer windings. In this case, if a lightning surge enters from the power system, for example, a normal mode lightning surge that flows only within the electrical lines or a common mode lightning surge in which current flows from the electrical lines to the ground may enter via the capacitance component C3 (thick line and arrow) as shown in the figure, potentially causing malfunction or destruction of the detection circuit. However, if there are no problems with lightning surges, including either the first or second switching unit, there is little problem. To address this issue, for example, in the typical configuration described above, the relay anomaly detection circuit uses two switching units, the first and second, to completely isolate the detection circuit from the power system. [Explanation of symbols]

[0052] 1 Power conversion device, power conditioner 110 Relay system connection end 120 Inverter 135, 136 Interconnection relay 170, 180 Relay abnormality detection circuit 173, 183 First opening and closing section 177, 187 Second opening and closing section 179, 189 Detector 200 Solar power generation equipment (DC power supply) 510 Inverter output stop command unit 530 Relay Opening Command Center Lu, Lw Electrical lines V1SR, V2SR detection power supply

Claims

1. A power conversion device including an inverter that receives output power from a DC power source or power obtained by voltage-converting the output power from the DC power source and converts it into AC power, and a relay system connection terminal that is connected to a system power source side, The power supply system further includes at least one phase of an electric line between the inverter and the relay system connection end, an interconnection relay interposed in at least one of the at least one phase of the electric line, and a relay abnormality detection circuit provided in the interconnection relay, the relay abnormality detection circuit has a detection power supply that causes a detection current to flow toward a detection unit, and at least one of a first opening / closing unit between the detection power supply and one end of the interconnection relay and a second opening / closing unit connected to the other end of the interconnection relay, the detection unit being connected to the other end of the interconnection relay or the second opening / closing unit and configured to detect the detection current in the event of an abnormality, and outputting a detection signal when the detection current is detected; the inverter stops output of the AC power in response to a command from an inverter output stop command unit, and the interconnection relay opens a relay unit in response to a command from a relay open command unit; the relay abnormality detection circuit closes at least one of the first opening / closing unit and the second opening / closing unit after a command to stop the output of the AC power is output from the inverter output stop command unit and a command to open the relay unit is output from the relay open command unit, and when an abnormality occurs, causes the detection current to flow to the detection unit, and detects an abnormality in the interconnection relay based on the detection signal from the detection unit. Power conversion device.

2. The power conversion device according to claim 1, The relay abnormality detection circuit is provided for each of the interconnection relays. Power conversion device.

3. The power conversion device according to claim 1, the relay abnormality detection circuit has the first opening / closing unit and the second opening / closing unit; Power conversion device.

4. The power conversion device according to claim 1, The relay abnormality detection circuit detects a contact abnormality or welding in the interconnection relay. Power conversion device.

5. The power conversion device according to claim 1, The detection power supply is an isolated power supply. Power conversion device.

6. The power conversion device according to claim 5, a rectifying element connected between a high-voltage side electric line and a low-voltage side electric line of the isolated power supply, Power conversion device.

7. The power conversion device according to claim 6, A rectifying element is connected in parallel to the detecting unit. Power conversion device.

8. The power conversion device according to claim 5, a rectifying element connected in series on a high-voltage side electric line of the isolated power supply; Power conversion device.

9. The power conversion device according to claim 1, When the output voltage of the detection power supply is lower than the output voltage of the DC power supply, an abnormality of the interconnection relay is detected. Power conversion device.

10. The power conversion device according to claim 1, a relay abnormality detection circuit provided for each of the interconnection relays, the relay abnormality detection circuit having both the first opening / closing unit and the second opening / closing unit; and a two-phase electric line between the inverter and the relay system connection end, the interconnection relay being interposed in all of the two-phase electric lines; Power conversion device.

11. The power conversion device according to any one of claims 1 to 10 is provided, Controlling the solar power generation device that is the DC power source. Power conditioner.

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