Anomaly detection device and method for power transmission systems of solar power generation systems.

Abstract

The system detects abnormalities in the AC power transmission section of the solar power generation system. [Solution] The abnormality detection device of this disclosure is for an AC power transmission unit that transmits AC power output from a solar panel 1, and comprises sensing circuits 5001 to 5003, a measuring device 3001, and an abnormality detection processing unit 3002. The sensing circuit is a two-terminal sensing circuit that includes at least one of a resistor, a capacitor, and an inductor and exhibits a predetermined impedance, and one terminal is electrically connected to at least one of the AC transmission conductors 2301 to 2303 provided in the AC power transmission unit. The measuring device measures the AC transmission unit impedance exhibited by the conductor. The abnormality detection processing unit detects an abnormality in the AC power transmission unit by comparing the AC transmission unit impedance measured by the measuring device with a judgment criterion value.

Description

Technical Field

[0001] The present disclosure relates to an abnormality detection device and an abnormality detection method for a power transmission system of a photovoltaic power generation system. More specifically, the present disclosure relates to an abnormality detection device and an abnormality detection method for an AC power transmission unit in a photovoltaic power generation system.

Background Art

[0002] A photovoltaic power generation system typically includes a solar panel including at least one photovoltaic cell, a power conditioner that converts DC power generated by the solar panel into AC power, and AC equipment such as a system connection transformer. The AC power from the power conditioner is finally connected to the power grid through the system connection transformer. For this power transmission, in addition to a three-phase AC power cable for connecting to the system connection transformer, the above photovoltaic power generation system is equipped with safety equipment such as a DC power cable and a fuse for transmitting high-current DC power. The power conditioner is classified into a configuration in which the DC power generated by all solar panels is converted into AC power by a single large power conditioner (hereinafter referred to as a "centralized photovoltaic power generation system") and a configuration in which the DC power generated by a small number of solar panels is converted into AC power by a plurality of small power conditioners (hereinafter referred to as a "distributed photovoltaic power generation system").

[0003] Figure 1 is a block diagram showing the configuration of a solar power generation system 90, which is an example of a distributed solar power generation system. In the solar power generation system 90, solar panels 1 to 4 are divided into groups of a certain number, and small power conditioners 2101 to 2104 are installed near each group of panels. The DC power generated by solar panels 1 to 4 is converted to AC power by power conditioners 2101 to 2104, then integrated by AC junction boxes 2201 and 2202, and transmitted to the AC power receiving equipment 2000 via three-phase AC power cables 2301 to 2303 and 2311 to 2313. In AC power receiving equipment 2000, the AC voltage (~500V) is stepped up by a step-up transformer 500 via circuit breaker 2001 and three-phase AC main cables 2501~2503, and then transmitted to the power grid 600, for example, to the grid power network (transmission lines, 6.6kV~150kV).

[0004] In situations where a distributed solar power generation system like solar power generation system 90 is in operation, malfunctions can occur in the components that transmit this AC power. Typical malfunctions include cable theft and blown fuses. Although solar power generation system 90, which is an example, shows two AC junction boxes, the number of AC junction boxes and solar panels in an actual solar power generation system is not particularly limited. For example, there may be around 10 AC junction boxes and correspondingly 10 or 20 solar panels.

[0005] In distributed solar power generation systems currently in use, theft of some or all of the AC power cables is a frequent occurrence. Three-phase AC power cables 2301-2303 and 2311-2313, installed between the AC junction box and the AC power receiving equipment 2000, are expensive due to their high copper wire mass per unit length, and theft often involves cutting and removing these cables. In addition to this theft, the circuit breaker 2001, which protects the system in the event of excessive current flow through the power cables, is frequently tripped and shut off due to lightning strikes or other causes. Furthermore, irregular electrical conduction with the ground, also known as ground faults or leakage current, can occur. To address these anomalies, there has been a need for highly reliable and practical methods for detecting anomalies in solar power generation systems, particularly in the AC power transmission system.

[0006] Patent documents 1 and 2 disclose a configuration for measuring the DC circuit impedance of a DC power supply system (solar panels and DC cables) as a conventional technology for sensing abnormalities in part or all of the DC power transmission system of a solar power generation system employing a centralized power conditioner. Specifically, paragraphs 0010 to 0011 of Patent Document 1 (Japanese Patent Application Publication No. 2016-131570) disclose a "system for detecting abnormalities in a solar power generation facility comprising a lower unit that aggregates DC power generated by solar cell units and an upper unit that aggregates the DC power collected by the lower unit, wherein multiple lower units are connected in parallel to the upper unit, and measuring instruments for measuring impedance are provided in each wiring cable connecting each of these lower units and the upper unit, and a determination unit is provided that detects the abnormality based on the measurement results when the solar cell units are not generating power, and the measuring instruments measure the combined impedance of the solar cell units aggregated in each of the lower units connected in parallel to the upper unit as the impedance." Patent Document 1 discloses a system for detecting abnormalities (theft) in a solar cell unit (solar panel and cable). The system consists of a lower-level unit and a higher-level unit that aggregates the lower-level units. When the solar cell unit is not generating power, it includes a measurement unit that measures the impedance of the circuit composed of the solar panel and cable, and a determination unit that compares this with a pre-registered set value to determine whether they match or not. In this system, any mismatch is detected as an abnormality.

[0007] Paragraphs 0009 to 0010 of Patent Document 2 (Japanese Unexamined Patent Publication No. 2017-169263) state: "An example of a 'method for detecting theft of a cable connected to a power conditioner' is a method for detecting theft of a cable connected to a power conditioner having a solar panel connected to the DC input side via a cable, a grid power supply connected to the AC output side, and an inverter that converts DC power input from the DC input side into AC power, comprising the steps of: measuring the capacitance between the DC input terminal and the ground terminal of the power conditioner; detecting a break in the cable by comparing the measured capacitance value with a break detection value and outputting an abnormality detection signal; and outputting an alarm output based on the abnormality detection signal." Patent Document 2 discloses a method for detecting cable theft in a solar power generation system (solar panel, cable and power conditioner) by measuring the capacitance between the DC input terminal and the ground terminal of the solar panel using a measurement circuit and determining a break in the cable from the change in the measured capacitance value. Furthermore, Patent Document 2 suggests that a break in the wire can be determined by the insulation resistance value instead of capacitance. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2016-131470 [Patent Document 2] Japanese Patent Publication No. 2017-169263 [Patent Document 3] Japanese Patent Publication No. 2019-180188 [Patent Document 4] Japanese Patent Publication No. 2013-130536 [Non-patent literature]

[0009] [Non-Patent Document 1] Kazumi Takano et al., "Degradation and Failure Evaluation of Crystalline Silicon Solar Cell Modules Based on Series Resistance (Rs) and Impedance (Z)," AIST Photovoltaic Power Generation Research Results Presentation Meeting 2016, Poster Session, URL: https: / / unit.aist.go.jp / rpd-envene / PV / ja / results / 2016 / poster / P66.pdf [Non-Patent Document 2] Tomio Yamaguchi, Kuniomi Nakamura, "1-3 Relationship between Insulation Resistance Change and Environmental Factors in Outdoor Exposure Tests of Solar Cell Modules (REAJ 10th Research Presentation Meeting)," Journal of the Reliability Engineering Society of Japan, Reliability Vol. 24 No. 4, pp 333-334 (2002), DOI: 10.11348 / reajshinrai.24.4_333 [Non-Patent Document 3] Yasuhiro Sakurai, Kosuke Kurokawa, "Simulation of Distributed-Parameter Circuits in Photovoltaic Arrays: Examination of Simulation Methods," Proceedings of the Joint Research Conference of the Japan Solar Energy Society and the Japan Wind Energy Association, No. 2000, pp. 307-310 (November 2000). [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] Patent Document 1 discloses measuring the impedance of a circuit consisting of a solar panel and cables when the solar cell unit is not generating power. Patent Document 2 discloses a conventional technology for detecting theft of a solar power generation system, which involves measuring the resistance R, capacitance C, or impedance between the DC portion of the cable and the ground terminal, comparing the measured value with a judgment value, and determining and detecting whether or not there is an abnormality. However, in relation to the technology disclosed in Patent Document 1, it has also been reported that the impedance (resistance value) increases when, for example, a crystalline silicon-based solar panel deteriorates (Non-Patent Document 1). Therefore, in order to accurately detect abnormalities with the technology disclosed in Patent Document 1, it is necessary to deal with fluctuating physical quantities.

[0011] Furthermore, it is known that the insulation resistance and capacitance between DC cables and the ground constantly fluctuate due to factors such as the large area of ​​a solar panel array and changes in weather conditions (humidity, temperature). For example, Non-Patent Literature 2 shows data on the insulation resistance of a solar cell module measured over nine years, indicating that the insulation resistance fluctuates significantly between several hundred kΩ and 1000 MΩ. Non-Patent Literature 3 also describes how the junction capacitance of a solar cell diode differs between the bright state (when sunlight is irradiated) and the dark state (at night), affecting the capacitance.

[0012] Conventional devices and methods that directly measure the impedance of a circuit consisting of solar panels and cables, or the impedance between the DC portion of the cable and the ground terminal, and compare it with a judgment value to determine abnormalities, cannot necessarily be expected to operate stably, and improvements in practicality are desired.

[0013] Furthermore, to the best of the inventor's knowledge, there are no prior art disclosures that disclose countermeasures for abnormalities in the transmission cables that constitute the AC power transmission section of a distributed solar power generation system, such as theft of transmission cables or the blown fuses connected to transmission cables.

[0014] Therefore, in distributed photovoltaic power generation systems, there is a continuing need for practical methods that can reliably detect abnormalities in the AC power transmission section, namely open circuits, ground faults, and leakage currents. The purpose of this disclosure is to provide an abnormality detection device and method that can stably and accurately detect abnormalities in the transmission cables that constitute the AC power transmission section of a distributed photovoltaic power generation system, such as theft of transmission cables, tripping of circuit breakers connected to transmission cables, or ground faults or leakage currents in the AC power transmission section. [Means for solving the problem]

[0015] The inventors have created a method for detecting abnormalities in the AC power transmission section of a solar power generation system without adding complex circuit components, thus completing the invention.

[0016] In other words, in one embodiment of the present disclosure, an abnormality detection device is provided for an AC power transmission unit that transmits AC power output from a power conditioner that converts DC power of at least one solar panel into AC power, the device comprising: at least one sensing circuit having two terminals that include at least one of a resistor, a capacitor, and an inductor and exhibit a predetermined impedance, wherein one of the two terminals is electrically connected to at least one of the conductors for AC transmission provided in the AC power transmission unit; a measuring device electrically connected to the conductor for measuring the AC transmission unit impedance shown by the conductor and the sensing circuit; and an abnormality detection processing unit that detects an abnormality in the AC power transmission unit by comparing the AC transmission unit impedance measured by the measuring device with a judgment criterion value.

[0017] Furthermore, in one embodiment of the present disclosure, there is a method for detecting an anomaly for an AC power transmission unit that transmits AC power output from a power conditioner that converts DC power of at least one solar panel into AC power, wherein the AC power transmission unit is provided with at least one two-terminal sensing circuit that includes at least one of a resistor, a capacitor, and an inductor and exhibits a predetermined impedance, such that one terminal of the two terminals is electrically connected to at least one of the conductors for AC transmission provided in the AC power transmission unit, and the method for detecting an anomaly includes the steps of: measuring the AC transmission unit impedance shown by the conductor and the sensing circuit using a measuring device electrically connected to the conductor; and comparing the AC transmission unit impedance with a judgment criterion value and generating and outputting an anomaly detection signal indicating an anomaly in the AC power transmission system using an anomaly detection processing unit.

[0018] In this disclosure, impedance is a complex impedance that can be expressed as a complex number, but the impedance value expressed as a measurement may mean the norm of the complex impedance, that is, the value obtained by squaring the real part and imaginary part of the complex impedance, adding them together, and taking the square root. [Effect of the Invention]

[0019] According to the present disclosure, an abnormality in the AC power transmission section of a photovoltaic power generation system can be detected with high reliability. [Brief Description of the Drawings]

[0020] [Figure 1] FIG. 1 is a block diagram showing the configuration of a photovoltaic power generation system, which is an example of a conventional distributed photovoltaic power generation system. [Figure 2] FIG. 2 is a block diagram showing the configuration of an example of a photovoltaic power generation system to which Example 1 of the abnormality detection device and the abnormality detection method according to the present disclosure is applied. [Figure 3] FIG. 3 is a circuit diagram of a part showing the electrical connection of the pre-stage circuit and the impedance measurement device in Example 1 of the present disclosure. [Figure 4] FIG. 4 is a circuit diagram of a part showing the electrical connection of the BRF and the sensing circuit in the photovoltaic power generation system of Example 1 of the present disclosure. [Figure 5] FIG. 5 is a circuit diagram of an RLC anti-resonance circuit, which is an example of the BRF in Example 1 of the present disclosure. [Figure 6] FIG. 6 is a graph of the frequency characteristics of the RLC anti-resonance circuit in the present disclosure. [Figure 7] FIG. 7 is a circuit diagram of an RLC series resonance circuit, which is an example of the BPF in the present disclosure. [Figure 8A-B] FIGS. 8A to 8B are graphs of the frequency characteristics of the RLC series resonance circuit in the present disclosure. FIG. 8A shows an example of the frequency characteristics applied to the sensing circuit, and FIG. 8B shows an example of the frequency characteristics applied to the pre-stage circuit. [Figure 9] FIG. 9 is a block diagram showing an example of a photovoltaic power generation system to which Example 2 of the abnormality detection device and the abnormality detection method according to the embodiment of the present disclosure is applied. [Figure 10] FIG. 10 is a block diagram showing an example of a photovoltaic power generation system to which Example 3 of the abnormality detection device and the abnormality detection method according to the embodiment of the present disclosure is applied. [Figure 11A-C]Figures 11A to 11C are circuit diagrams illustrating the impedance measuring device and sensing circuit in the photovoltaic power generation system of Embodiment 3 of this disclosure. Figure 11A shows the configuration of the impedance measuring device and sensing circuit, Figure 11B shows its equivalent circuit, and Figure 11C shows a further reconfigured version. [Figure 12] Figure 12 is a circuit diagram showing the connection configuration between the main cable and the impedance measuring device in a photovoltaic power generation system to which Embodiment 4 of the abnormality detection device and abnormality detection method of the present disclosure is applied. [Figure 13] Figure 13 is a circuit diagram showing the connection configuration to an impedance measuring device in a photovoltaic power generation system to which Embodiment 5 of the abnormality detection device and abnormality detection method of this disclosure is applied. [Figure 14] Figure 14 is a circuit diagram showing the connection configuration to an impedance measuring device in a photovoltaic power generation system to which Embodiment 6 of the anomaly detection device and anomaly detection method of this disclosure is applied. [Figure 15] Figure 15 is a block diagram showing an example of a solar power generation system to which Embodiment 7 of the anomaly detection device and anomaly detection method of the present disclosure is applied. [Figure 16] Figure 16 is a circuit diagram showing the connection configuration to an impedance measuring device in a photovoltaic power generation system to which Embodiment 8 of the abnormality detection device and abnormality detection method of this disclosure is applied. [Modes for carrying out the invention]

[0021] Embodiments of this disclosure are described below. Unless otherwise specified in the following description, common parts or elements are denoted by the same reference numerals throughout the figures. Also, in the figures, the elements of each embodiment are not necessarily shown in proportion to each other. Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

[0022] 1. Overview The anomaly detection device and anomaly detection method of the embodiments of this disclosure will be described in comparison with a conventional configuration (photovoltaic power generation system 90, Figure 1).

[0023] In short, the abnormality detection device of this embodiment has a configuration in which a circuit for sensing abnormalities (hereinafter referred to as the sensing circuit) is added to the conventional solar power generation system 90 illustrated in Figure 1, and an abnormality detection processing unit is further added, and the abnormality detection method of this embodiment can be implemented as the operation of such a solar power generation system. The sensing circuit is electrically connected, typically, between the AC input terminal and the ground terminal for the AC cable connecting the AC junction box and the AC power receiving equipment. Since the AC cable is connected to the AC input terminal, the sensing circuit can also respond to the cutting or short circuit of the AC cable, the tripping (interruption) or fault of the circuit breaker connected thereto, or the blown fuse (if present), or a ground fault. For this purpose, the sensing circuit is a two-terminal circuit block as a whole that exhibits a predetermined impedance by including at least one of a resistor, capacitor, and inductor. Typical electrically connected configurations involve high impedance connections at the transmission AC frequency, and these may include connections through conductors alone, as well as configurations involving the intermediary of transmission AC frequency band rejection filters (BRFs) or impedance measurement frequency band pass filters (BPFs).

[0024] The specific configuration and operation of the abnormality detection device and abnormality detection method of this embodiment will be described below with reference to the examples. The contents described in each example can be applied to any of the abnormality detection devices and abnormality detection methods of this embodiment, insofar as they do not contradict each other. In the following examples, the solar power generation system is described using a configuration in which each solar panel is equipped with one distributed power conditioner and four AC junction boxes are used in the solar power generation system, but the number of solar panels per AC junction box and the number of AC junction boxes per solar power generation system are not particularly limited. Furthermore, in the description of each solar power generation system, the description of solar panel 1 and the AC junction box 2201 connected to it also applies similarly to the part of solar panel 2 connected in parallel and the AC junction box 2202 connected to it.

[0025] 2. Example 1 2-1. Overall Structure Figure 2 is a block diagram showing the configuration of a photovoltaic power generation system 41 to which Embodiment 1 of the abnormality detection device and abnormality detection method of this embodiment is applied. In a distributed system, DC power is converted to AC power by small power conditioners 2101 to 2104 located near the solar panels, then integrated into AC junction boxes 2201 and 2202, and transmitted to the AC power receiving equipment 2000 by three-phase AC power cables 2301 to 2303 and 2311 to 2313.

[0026] In this disclosure, the AC power transmission section of a photovoltaic power generation system refers to the part that transmits AC power from distributed power conditioners 2101 to 2104 to the AC power receiving equipment 2000 via AC junction boxes 2201 and 2202 and the power transmission paths of three-phase AC power cables 2301 to 2303 and 2311 to 2313. This AC power transmission section is the target of abnormality detection in the abnormality detection device and abnormality detection method of this disclosure.

[0027] Using the solar power generation system 41 shown in Figure 2 as an example, the AC power transmission section mainly consists of three-phase AC power cables 2301-2303 and 2311-2313. Typical abnormalities in the AC power transmission section include the cutting of three-phase AC power cables 2301-2303 and 2311-2313 (including those caused by theft or other human error), or ground faults or short circuits.

[0028] In contrast to the solar power generation system 90, the additional components in the solar power generation system 41 (Figure 2) of Embodiment 1 of this embodiment are sensing circuits 5001-5003 and 5011-5013, which are two-terminal elements, located inside the AC junction boxes 2201 and 2202, respectively. One of the two terminals in each set is attached to the three-phase AC power cables 2301-2303 and 2311-2313, while the other terminals are interconnected in a star connection and connected to the grounding wire 2007.

[0029] The sensing circuits 5001-5003 and 5011-5013 are typically band-pass filter (BPFs). By setting the measurement frequency sufficiently far from the transmission AC frequency, the impedance of the BPF at the transmission AC frequency increases, preventing the transmission AC current from flowing into the sensing circuits and thus preventing damage to the sensing circuits. Furthermore, in Example 1, in addition to the sensing circuits 5001-5003 and 5011-5013, there is also a configuration in which BRFs 5111-5113 and 5121-5123 are added in series to the AC power transmission section. The purpose of installing BRFs 5111-5113 and 5121-5123 is to prevent the transmission AC current from flowing into the sensing circuits 5001-5003 and 5011-5013 and generating heat. If BRF5111~5113 and 5121~5123 are installed, no AC current will flow into the sensing circuits 5001~5003 and 5011~5013. Therefore, BPF characteristics are not required for the sensing circuits 5001~5003 and 5011~5013, and pure resistors or the like with no frequency dependence can be used.

[0030] In Figure 2, BRFs 5111-5113, 5121-5123, and sensing circuits 5001-5003 and 5011-5013 are installed within the AC junction box, between the connection points of each distributed power conditioner and the AC power receiving equipment 2000. However, the abnormality detection device and method of this embodiment are not limited to the connection points and can be installed at any location within the AC junction boxes 2201-2202 or near the output terminals of the distributed power conditioners 2101-2104. Furthermore, it is not necessarily required that sensing circuits be connected to all power cables.

[0031] BRF5111~5113, 5121~5123, and the sensing circuits 5001~5003, 5011~5013 connected in series with them are each two-terminal circuit elements or combinational circuit blocks, with one terminal of the two terminals connected to the three-phase AC power cables 2301~2303, 2311~2313 and the other terminal grounded. The sensing circuits 5001~5003, 5011~5013 have a configuration that enables the function of sensing abnormalities in the AC power transmission section. Specifically, they include resistors, capacitors, and inductors that exhibit a specific impedance.

[0032] The AC power receiving equipment 2000 used in the solar power generation system 41 is equipped with a monitoring and processing unit 3000 as an additional component compared to the solar power generation system 90. The monitoring and processing unit 3000 has BRF or BPF (hereinafter referred to as "BRF / BPF") installed as its pre-circuits 5101 to 5103. The pre-circuits 5101 to 5103 are installed to interrupt the AC current being transmitted. Furthermore, the monitoring and processing unit 3000 consists of an impedance measuring device 3001, an abnormality detection processing unit 3002 for cable theft, ground faults, etc., and an alarm output circuit 3003.

[0033] The input circuit to the impedance measuring device 3001 constitutes a closed circuit. Specifically, it is a closed circuit consisting of the impedance measuring device input terminal, pre-circuits 5101-5103, main cables 2501-2013, three-phase AC power cables 2301-2303, 2311-2313, BRFs 5111-5113, 5121-5123, sensing circuits 5001-5003, 5011-5013, grounding wire 2007 in the junction box, grounding wire in the power receiving equipment, and the impedance measuring device input terminal. The three-phase AC main cables 2501-2503 are cable assemblies that combine the conductors of the three-phase AC power cables 2301-2303 and the conductors of the three-phase AC power cables 2311-2313 by connecting them in parallel. The sensing circuits 5001-5003 and 5011-5013 are connected in parallel. Therefore, the impedance measuring device 3001 measures the parallel impedance Zm of the sensing circuits 5001-5003 and 5011-5013. In other words, the impedance measuring device 3001 applies an AC voltage between the terminal on the impedance measuring device 3001 side and the ground wire, measures the current, and then performs a calculation by dividing the applied voltage value by the measured current value to output Zm. The impedance Zm is expressed by the following formula. Zm = (Zp + (Zb + Ze) / n) / 3 (1) Here, n is the number of AC junction boxes, Zp is the impedance of the pre-circuits 5101-5103, Zb is the impedance of BRF 5111-5113, and Ze is the impedance of the sensing circuits 5001-5003 and 5011-5013. Note that the impedance of the AC power cable is negligible and is therefore not included in equation (1). The measured value of impedance Zm is output to the abnormality detection processing unit 3002.

[0034] The anomaly detection processing unit 3002 compares the impedance Zm output by the impedance measuring device 3001 with a separately set impedance reference value Zs and outputs an anomaly detection signal for the cable. The anomaly detection processing unit 3002 stores the pre-set impedance reference value Zs in an appropriate recording unit.

[0035] The alarm output circuit 3003 outputs an alarm output to the alarm output terminal 3004 based on the abnormality detection signal input from the abnormality detection processing unit 3002. Alarm means (not shown), such as display means or alarm means, are connected to the alarm output terminal 3004, and when an alarm output is output from the alarm output terminal 3004, an abnormality should be notified. The alarm means may also be provided within the AC power receiving equipment 2000.

[0036] 2-2. Detailed configuration of the impedance measurement circuit and the sensing circuit. Figure 3 is a circuit diagram showing the electrical connections of the pre-circuits 5101-5103 and the impedance measuring unit 3001 in the photovoltaic power generation system 41 of Embodiment 1 of this disclosure. By employing a BPF or BRF as the pre-circuit, it is possible to block the flow of the transmission AC current into the impedance measuring device 3001.

[0037] Figure 4 is a circuit diagram showing the electrical connections of BRF5111~5113 and sensing circuits 5001~5003 and 5011~5013 in the photovoltaic power generation system 41 of Example 1. The AC at the measurement frequency output from one of the measurement terminals of the impedance measuring device 3001 is input to BRF5111~5113 and sensing circuits 5001~5003 via pre-circuits 5101~5103, three-phase AC main cables 2501~2503, and power cables 2301, 2302, and 2303, and is connected to the grounding wire 2007 (Figure 2). This grounding wire 2007 is connected to the other measurement terminal of the impedance measuring device 3001. If the sensing circuits 5001-5003 and 5011-5013 themselves have a sufficiently large impedance at the transmission AC frequency (i.e., when a band-pass filter is used), then the BRFs 5111-5113 and 5121-5123 preceding the sensing circuits may be omitted.

[0038] 2-3 Operation The following provides a specific example of anomaly detection operation. The example illustrates an anomaly detection operation performed to detect cable cutting due to theft of an AC cable. Similar operation can be applied to fuse blowing, as its electrical behavior is similar to that of cable cutting.

[0039] First, we will explain how to set the impedance Ze of sensing circuits 5001-5003 and 5011-5013, which combine resistors, capacitors, inductors, diodes, and other necessary electronic components.

[0040] In a solar power generation system with a configuration similar to the solar power generation system 41 shown in Figure 2, let's assume, for example, that there are 10 AC junction boxes, and that each AC junction box is arranged in parallel with the others. In this case, 10 sets of 3 parallel circuits, each of the sensing circuits 5001-5003 and 5011-5013, which each exhibit an impedance Ze, are connected in parallel with each other. In a normal state in this configuration, the impedance Zm of this parallel circuit measured by the impedance measuring device 3001 is given by equation (1) above as follows. Zm = (Zp + (Zb + Ze) / 10) / 3 (2) Here, if we set Zp and Zb to be sufficiently small compared to Ze at the measurement frequency, equation (2) can be approximated as follows. Zm = Ze / 30 (3) In this state, if, for example, one of the three-phase AC power cables 2301-2303 or 2311-2313, such as three-phase AC power cable 2301, is cut first, the number of parallel connections changes from 30 to 29. The impedance value Zm changes to Ze / 29.

[0041] It is desirable that an alarm be triggered immediately if one of the three AC power cables (2301-2303, 2311-2313) connected to any one of the 10 AC junction boxes is cut. Therefore, the impedance reference value Zs is Ze / 30 <Zs<Ze / 29 (4) Set to a value that satisfies the condition.

[0042] In the phase where the number of three-phase AC power cables 2301-2303 and 2311-2313 that are cut increases sequentially from one to two, the impedance Zm changes as follows. Before cable cutting: Zm=Ze / 30 <zs (5) ケーブル1本切断後: zm="Ze / 29">Zs (6) After cutting two cables: Zm = Ze / 28 > Zs (7)

[0043] Therefore, by setting the impedance reference value Zs according to equation (4), the abnormality detection processing unit 3002 immediately outputs an abnormality detection signal when the first cable is cut, and subsequently the alarm output circuit 3003 outputs an alarm output to the alarm output terminal 3004 based on the abnormality detection signal input from the abnormality detection processing unit 3002. By activating some kind of suppression device in response to this alarm output, it is expected that damage can be minimized. This suppression device may include, for example, a warning sound emitter, a warning light emitter, and a remote alarm communication device. Even if a second, third, or subsequent cable is cut after the first cable, the measured impedance Zm will always be greater than the impedance reference value Zs, so the alarm will continue to be output.

[0044] In the distributed power conditioners 2101-2104 in Figure 2, and in the step-up transformer (grid-connected transformer) 500, there may be a configuration in which a specific phase of the three phases is grounded to earth. In such cases, it is useful to install BRF / BPF, BRF, and sensing circuits on all phases except that specific phase, and to exclude the AC cable of the grounded phase from the alarm system.

[0045] In the above-mentioned deterrent device, the warning sound emitter can emit sounds at an appropriate volume, such as mechanically generated sounds like sirens or voice announcements of warning messages that can be understood by the person being warned. The warning light emitter can emit any light that is useful for observing the situation or intimidating the person being warned, such as ambient lighting, flashing colored lights, or flashes of light. The remote warning communication device is a communication transmitter that can, for example, send messages or signals to a security company's monitoring center to report an anomaly. For this purpose, there are no particular restrictions on the communication network used by the remote warning communication device, and any communication network or communication path can be used, including always-on networks, closed networks, as well as any public access networks including LTE (Long Term Evolution) lines and 5G (5th generation mobile communication system) lines, and satellite lines.

[0046] 2-4. BRF, BPF, and sensing circuits The configuration of the BRF, pre-circuit, and sensing circuit in the photovoltaic power generation system 41 of Example 1 is described in detail. Figure 5 is a circuit diagram of an anti-resonant circuit consisting of a resistor R, an inductor L, and a capacitor C, which is an example of a BRF that can be used for BRFs 5111-5113, 5121-5123 and pre-circuits 5101-5103 in Example 1. Figure 6 shows the frequency characteristics of the impedance of the BRF with an anti-resonant frequency of 50Hz, R1=0.01Ω, L=600mH, and C=16.9μF. At 50Hz, which is an example of the frequency of AC transmitted by a three-phase AC power cable, the impedance is approximately 2MΩ. If the phase voltage of the transmitted AC is 400V, the leakage phase current can be blocked down to a sufficiently small value of approximately 0.2mA. If the transmission frequency of AC power is 60Hz, the anti-resonant frequency is 60Hz, R1 = 0.01Ω, L = 600mH, and C = 11.7μF. Similar settings are easily applied even if the transmission frequency is different. On the other hand, if the impedance measurement frequency is 135kHz, the impedance is small, at 0.07Ω. Thus, at the measurement frequency, the impedances Zp and Zb of the preamplifier circuits 5101-5103 and BRFs 5111-5113 and 5121-5123 become very small. In this case, by using a sensing circuit whose impedance at the measurement frequency is sufficiently larger than these (e.g., a 10Ω pure resistor), it becomes possible to measure Ze accurately. Note that the BRF and BPF configurations exemplified in Figures 4-6 are basic configurations; in reality, BRFs and BPFs can employ more complex configurations consisting of more elements (resistors, capacitors, inductors). Furthermore, the capacitance value of the capacitor and the inductance coefficient value of the inductor that achieve resonance or anti-resonance at the measurement frequency can be arbitrarily combined according to the conditions for resonance or anti-resonance.

[0047] Figure 7 is a circuit diagram of a series resonant circuit consisting of a resistor R, an inductor L, and a capacitor C, which is an example of a BPF that can be used for the sensing circuits 5001-5003 and 5011-5013 in the photovoltaic power generation system 41 of Example 1. The resonant frequency of the BPF is set to match the measurement transmission frequency of the impedance measuring device 3001. If the measurement frequency is 135 kHz, then R=100 Ω, L=1.0 mH, and C=1.4 nF. Figure 8A shows the frequency characteristics of the impedance of this BPF. At the transmission AC frequency of 50 Hz or 60 Hz, the impedance Ze of the above BPF is large, about 2.3 MΩ, so if the transmission AC phase voltage is 400 V, the leakage phase current can be cut off to a sufficiently small value of about 0.17 mA. In such cases, BRFs 5111-5113 and 5121-5123 do not necessarily need to be installed. At a measurement frequency of 135 kHz, the impedance Ze of the sensing circuit is 10 Ω. For the pre-circuits 5101-5103 in the photovoltaic power generation system 41 of Example 1, when a BRF (Figure 6) is adopted, the impedance Zp is sufficiently small at 0.07 Ω at a measurement frequency of 135 kHz. Also, when a BPF is adopted for the pre-circuits 5101-5103, and the resistance R in Figure 7 is set to 1 Ω, the frequency characteristics are as shown in Figure 8B, and the impedance Zp of the pre-circuit is 1 Ω at a measurement frequency of 135 kHz.

[0048] As described above, the impedance Zb of BRF5111~5113 and 5121~5123, and the impedance Zp of preamplifier circuits 5101~5103 can all be set to be 1 / 100 or less of the resistance value Ze of the sensing circuit. Therefore, as shown in equations (2) and (3), the relationship in equations (4) to (7) can be realized in which resistances Zp and Zb can be ignored with respect to Ze.

[0049] 3. Example 2 3-1. Overall Structure Figure 9 is a block diagram showing an example of a solar power generation system 51 to which Embodiment 2 of this embodiment is applied. To explain the solar power generation system 51 in comparison with the solar power generation system 41 in Figure 2, in the AC junction boxes 2201-2202, one of the two terminals of the sensing circuits 5001-5003 and 5011-5013 is attached to the three-phase AC power cables 2301-2303 and 2311-2313, and the other terminals are interconnected in a star connection, and this interconnection is connected to the neutral wire 2008. This neutral wire 2008 is connected to the impedance measuring device 3001. The configuration of the impedance measuring device 3001, pre-circuits 5101-5103, main cables 2501-2503, three-phase AC power cables 2301-2303, 2311-2313, BRFs 5111-5113, sensing circuits 5001-5003, and other components is the same as that of the conventional photovoltaic power generation system 41 (Figure 2).

[0050] 3-2. BRF, BPF, and sensing circuits The configuration of the sensing circuits 5001-5003 and 5011-5013 is the same as in Example 1. In Example 2, the ground wire 2007 in Figure 2 is replaced with the neutral wire 2008. The sensing circuits 5001-5003 and 5011-5013 are the same as in Example 1, including their operation and function.

[0051] 4. Example 3 4-1. Overall Structure Figure 10 is a block diagram showing the photovoltaic power generation system 61 of Embodiment 3 of this embodiment. Comparing the photovoltaic power generation system 61 to the photovoltaic power generation system 41 in Figure 2, the configuration is similar to that of the photovoltaic power generation system 41. Within the AC junction box 2201, the sensing circuits 5001-5003 and 5011-5013 are interconnected in a delta connection. The sensing circuits 5001-5003 and 5011-5013 are connected via three-phase AC power cables 2301-2303 and 2311-2313 and BRFs 5111-5113 and 5121-5123. Therefore, the configuration of Embodiment 3 is particularly effective for power plants that do not have grounding or neutral wires. Furthermore, the configuration of Embodiment 3 is also applicable to power plants that ground one of the three phases near the step-up transformer 500. Note that, as will be described later in relation to the explanation of Figures 11A-C, the delta connection can be converted to a star connection. Therefore, in the photovoltaic power generation system 61 for Example 3, the sensing circuits 5001-5003 and 5011-5013 can also be connected in a star configuration. In this case, the neutral point of the star configuration is not connected to the ground wire or neutral wire.

[0052] Within the AC power receiving equipment 3000, one terminal of each of the three-phase AC main cables 2501 to 2503 is branched off and connected to one terminal of the pre-circuits 5101 to 5103. The other terminals of any two of the pre-circuits 5101 to 5103 BRF / BPFs are interconnected and connected to one input terminal of the impedance measuring device 3001. The other terminal of the remaining BRF / BPF from the pre-circuits 5101 to 5103 is connected to the other input terminal of the impedance measuring device 3001.

[0053] 4-2.Operation This paper details the configuration of the impedance measuring device 3001 and sensing circuits 5001-5003 and 5011-5013 of the photovoltaic power generation system 61 in Example 3, as well as the method for setting the impedance of sensing circuits 5001-5003 and 5011-5013.

[0054] Figures 11A-C are circuit diagrams illustrating the impedance measuring device 3001 and sensing circuits 5001-5003 and 5011-5013 in the photovoltaic power generation system 61 of Embodiment 3 of this embodiment. They show, in order, the configuration of the impedance measuring device and sensing circuits, their equivalent circuits, and a reconfigured version. The pre-circuits 5111-5113, 5121-5123, 5101-5103, and BRFs 5111-5113 and 5121-5123 described in Figure 10 are not shown in Figures 11A-C because they are set to be small enough that the impedance value can be ignored at the impedance measurement frequency. In the following explanation, the change when parallel cables are cut will be expressed as admittance, which can be expressed as a sum.

[0055] The delta connection of the sensing circuits 5001-5003 in the photovoltaic power generation system 61 in Figure 10 (Figure 11A) can be converted (equivalent conversion) to an equivalent star connection including sensing circuits 5021, 5022, and 5023, as shown in Figure 11B. In this case, the admittance values ​​of each sensing circuit equivalent circuit 5021, 5022, and 5023 converted to a star connection take the values ​​of the following formula. Yf = 3Ye (8) Here, Ye is the admittance of the original delta-connected sensing circuit, and Yf ​​is the admittance after conversion to a star connection. Furthermore, this equivalent circuit (Figure 11B) can be reconstructed as shown in Figure 11C. The total admittance Yt of the reconstructed sensing circuit equivalent circuits 5021, 5022, and 5023 is: Yt = 2 / 3·Yf (9) This is the result.

[0056] The total admittance Ym measured by the impedance measuring device 3001 is the admittance of an n-parallel circuit, where n is the number of AC junction boxes. Ym = nYt = 2 / 3 · n · Yf (10) This is the result.

[0057] Assuming that the three-phase AC power cable 2301 of the three-phase cables is cut, in that case, one parallel circuit is removed, so the total admittance Ym measured by the impedance measuring device 3001 is Ym = 2 / 3·(n-1)·Yf (11) It decreases to [a certain value].

[0058] In contrast, if only the three-phase AC power cable 2302 is cut among the three-phase cables, the paths of the three-phase AC power cable 2303, the sensing circuit equivalent circuits 5023 and 5021, and the three-phase AC power cable 2301 remain, so the total admittance Ym measured by the impedance measuring device 3001 is Ym = 2 / 3·(n-1)·Yf + 0.5Yf =(2 / 3(n-1)+0.5)Yf (12) It decreases to [a certain value].

[0059] If the number of AC junction boxes n is, for example, 13, then equations (10), (11), and (12) are, Ym = 2 / 3·n·Yf = 8.66Yf (13) Ym = 2 / 3 * (n-1) * Yf = 8Yf Ym=(2 / 3(n-1)+0.5)Yf=8.5Yf (14) This is the result.

[0060] From the above, the admittance reference value Ys that triggers an alarm when a single AC cable is cut is 8.5Yf <Ys<8.66Yf (15) Set to a value that satisfies the condition.

[0061] In the phase where the number of three-phase AC power cables 2301-2303 and 2311-2313 that are cut increases sequentially from one to two, the admittance Ym changes as follows. Before cable cut: Ym = 8.66Ye > Ys (16) After cutting one cable: Ym = 8Ye <Ys (17) or After cutting one cable: Ym = 8.5Ye <Ys (18) After two cables were cut: Ym = 7.3Ye <Ys (19) or After two cables were cut: Ym = 7.8Ye <Ys (20) Therefore, according to equation (15), an admittance reference value Ys is set, and an abnormality detection signal is emitted when Ym becomes smaller than Ys. As a result, if the first cable is cut, the abnormality detection processing unit 3002 immediately outputs an abnormality detection signal, and subsequently the alarm output circuit 3003 operates to output an alarm to the alarm output terminal 3004 based on the abnormality detection signal input from the abnormality detection processing unit 3002.

[0062] 4-3. BRF / BPF, sensing circuit, and impedance measuring device In Example 3, the sensing circuits 5001-5003 and 5011-5013 can be configured in a delta connection as shown in Figure 11A. The BRFs 5111-5113 and 5121-5123 for interrupting the AC power transmission can be installed between the branching points from the three-phase AC power cables 2301-2303 and 2311-2313 and the junction points of the delta connection, as shown in Figure 10. In addition, a configuration (not shown) in which the BRFs are attached in series to each of the delta-connected sensing circuits can also be adopted. The operation of the impedance measuring device 3001 is the same as in Example 1 or 2.

[0063] 5. Example 4 Example 4 is an improvement that includes a circuit to prevent surge current inflow and protect the input terminals, and is implemented in a solar power generation system 71 that has an improved circuit configuration in which the connection configuration between the main cables 2501-2503 and the impedance measuring device 3001 is improved in the solar power generation system 41 of Figure 2. Figure 12 is a circuit diagram of the part showing the connection configuration between the main cables 2501-2503 and the impedance measuring device 3001 in the solar power generation system 71 to which Example 4 of the abnormality detection device and abnormality detection method of this embodiment is applied. Since solar power generation systems are installed outdoors, they are often affected by lightning strikes and induced lightning. For example, if lightning strikes a solar panel, or if induced lightning occurs due to a nearby lightning strike, a large surge voltage is induced in the three-phase AC power cables 2301-2303, 2311-2313 and the neutral wire 2008 (Figure 9) of Example 2. Because the impedance measuring device 3001 has a low input impedance, there is a concern that it could be easily destroyed by a large surge current flowing in due to an induced surge voltage.

[0064] The circuit configuration of the main cables 2501-2503 and the impedance measuring device 3001 in the photovoltaic power generation system 71 of Example 4 will be explained in comparison with the configuration of the impedance measuring device 3001 in Figure 3 of Example 1. Multiple solar panels, such as solar panels 1 and 2, may be connected to the photovoltaic power generation system 71. In the photovoltaic power generation system 71, as with the photovoltaic power generation system 41 shown in Figure 3, pre-circuits 5101-5103 are star-connected to the main cables 2501-2503, and the potential difference and current value between the neutral point of the pre-circuits 5101-5103 and the ground are measured by the impedance measuring device 3001, and the impedance or admittance is calculated by dividing each complex number (Figure 12). When lightning strikes or induced lightning occurs, the surge voltage induced between the main cables 2501-2503 and the ground may enter the neutral point, i.e., the input terminal of the impedance measuring device 3001. Therefore, in the photovoltaic power generation system 71, a gas discharge tube (GDT) 4001 is interposed between the neutral point and ground to suppress the voltage rise at the neutral point by gas discharge. In the photovoltaic power generation system 71, one end of an inductor 4002 is further connected to the neutral point, and the other end is connected to one end of another inductor (inflow prevention inductor) 4005. The other end of the inductor 4005 is coupled to the impedance measurement input of the impedance measuring device 3001. One end of either a Zener diode 4003 or a varistor 4004, or both, is connected to the connection point between inductors 4002 and 4005, and the other ends of both are grounded.

[0065] The surge voltage that needs to be prevented from entering the input terminal of the impedance measuring device 3001 has a large high-frequency component. Since the impedance of inductors 4002 and 4005 increases proportionally with frequency, inserting them in series makes it possible to prevent the high-frequency component of the surge voltage from entering the input of the impedance measuring device.

[0066] The Zener diode 4003 and varistor 4004 are installed to bypass the surge voltage current to ground when they are switched on, mitigating its intrusion into the next stage inductor 4005. For this reason, either the Zener diode 4003 or the varistor 4004 is sufficient. The junction of the Zener diode 4003 also functions as a capacitor. Therefore, the circuit consisting of inductor 4002, Zener diode 4003, varistor 4004, and inductor 4005 forms an LCL (T-type) filter, a type of high-frequency filter, and as a whole, can remove the high-frequency components of the surge voltage.

[0067] 6. Example 5 Example 5 is an improvement to prevent surge voltage intrusion in a configuration where one end of the sensing circuits 5001-5003 is not grounded. This is implemented in a photovoltaic power generation system 81 that has an improved circuit configuration in the photovoltaic power generation system 51 of Figure 9, specifically in the connection configuration between the main cables 2501-2503 and the impedance measuring device 3001, and the connection configuration between the three-phase AC power cables 2301-2303 and the impedance measuring device 3001. In the photovoltaic power generation system 51 of Figure 9, surge current intrusion and induction of surge voltage can occur in the neutral wire 2008, which is floating above the ground. Therefore, surge current may also intrude into both input terminals of the impedance measuring device 3001, which receives input from the neutral wire 2008. Figure 13 is a circuit diagram showing the connection configuration to the impedance measuring device 3001 in the photovoltaic power generation system 81 to which Example 5 of the abnormality detection device and abnormality detection method of this embodiment is applied. In the vicinity of the impedance measuring device 3001 in Example 5, a surge current protection circuit consisting of a GDT4001, inductors 4002 and 4005, similar to that in Example 4, is connected to both input terminals of the neutral wire 2008, not just one input terminal. This ensures protection of the input section of the impedance measuring device 3001 in Example 5.

[0068] 7. Example 6 Example 6 is an improvement for preventing surge voltage intrusion in a configuration where one end of the sensing circuits 5001-5003 is not connected to the ground or neutral wire. This is implemented in a photovoltaic power generation system 91 (Figure 14) which has an improved circuit configuration in the photovoltaic power generation system 61 of Figure 10, specifically in the connection configuration between the main cables 2501-2503 and the impedance measuring device 3001, and the connection configuration between the three-phase AC power cables 2301-2303 and the impedance measuring device 3001. In the photovoltaic power generation system 61 of Figure 10, if lightning strikes or induced lightning occurs, surge voltage induced between the main cables 2501-2503 and the ground may intrude. As a result, surge current may also intrude into both input terminals of the impedance measuring device 3001. Figure 14 is a circuit diagram showing the connection configuration to the impedance measuring device 3001 in the photovoltaic power generation system 91 to which Example 6 of the abnormality detection device and abnormality detection method of this embodiment is applied. In the vicinity of the impedance measuring device 3001 in Example 6, a surge current protection circuit consisting of a GDT4001, inductors 4002 and 4005, similar to that in Example 5, is connected to both input terminals. This provides protection for the input section of the impedance measuring device 3001 in Example 5.

[0069] In the configurations for preventing surge voltage inflow shown in Examples 4, 5, and 6, it is not necessary to use the GDT, inductor, Zener diode, and varistor all at the same time; any part of these components may be used.

[0070] 8. Example 7 Example 7 is an improvement for all photovoltaic power generation systems of this disclosure and is implemented by a photovoltaic power generation system 101 having a configuration that completely eliminates the influence of the transmission AC voltage. In the photovoltaic power generation systems of this disclosure, one input terminal of the impedance measuring device 3001 is connected to the main cables 2501-2503, and the other input terminal is connected to the main cables 2501-2503 in photovoltaic power generation system 61, to the ground wire 2007 in photovoltaic power generation system 41, and to the neutral wire 2008 in photovoltaic power generation system 51. Therefore, in photovoltaic power generation system 61, the transmission AC voltage is applied to both input terminals, and in photovoltaic power generation systems 41 and 51, the transmission AC voltage is applied to one of the input terminals, so it is not possible to completely eliminate the inflow of the transmission AC current into the impedance measuring device 3001 in any of the photovoltaic power generation systems. As a result, errors may occur in impedance measurement. Figure 15 is a block diagram illustrating the photovoltaic power generation system 101 of Example 7 of this embodiment. The following explanation will use a solar power generation system 101, which applies Example 7 to the solar power generation system 61 shown in Figure 10, as an example. In Example 7, an electromagnetic contactor 4000 with a timer is installed between the main cables 2501-2503 and the transformer 500. This timer is pre-set to control the opening (switch-off) operation so that the electromagnetic contactor 4000 is off (open) for at least a portion of the time when the solar power generation system is not generating power, from sunset to sunrise, and to control the closing (switch-on) operation so that the electromagnetic contactor 4000 is on (closed) for at least a portion of the time when the solar power generation system is generating power, from sunrise to sunset. When the solar power generation system is not generating power, the power conditioners 2101-2104 are stopped, and when the solar power generation system is generating power, the power conditioners 2101-2104 are operating. With this configuration, when the electromagnetic contactor 4000 is open, no AC power flows through the main cables 2501-2503, completely preventing AC power from flowing into the impedance measuring device 3001, thus eliminating errors in impedance measurement.In this configuration, when the electromagnetic contactor 4000 is open, no AC power flows through the three-phase AC power cables 2301-2303 and 2311-2313 in addition to the main cables 2501-2503. However, in order to prevent the transmission AC voltage from being applied to the impedance measuring device 3001 and the sensing circuits 5001-5003 and 5011-5013 when the electromagnetic contactor 4000 is closed, it is necessary to install pre-circuits 5101-5103 and BRFs 5111-5113 and 5121-5123 in the solar power generation system 101. However, as a variation of Example 7, it is also useful to configure the system to install timer-equipped electromagnetic contactors between the sensing circuits 5001-5003, 5011-5013 and the three-phase AC power cables 2301-2303, 2311-2313, and between the impedance measuring device 3001 and the main cables 2501-2503. In such a configuration, if the opening and closing operations of the electromagnetic contactors are controlled to turn them off only during periods when AC power is flowing, the pre-circuits 5101-5103 and BRFs 5111-5113, 5121-5123 are unnecessary. Note that some distributed power conditioners may be in standby mode during periods when the solar power generation system is stopped (i.e., when the electromagnetic contactor 4000 is open). In this case, power is not supplied from the grid side during the period when the electromagnetic contactor 4000 is open, but standby operation of the electromagnetic contactor 4000 is possible by adding an uninterruptible power supply. Example 7 describes an example of application to the photovoltaic power generation system 61 shown in Figure 10, but it is applicable to all photovoltaic power generation systems of this disclosure.

[0071] 9. Example 8 Example 8 is an improvement over Examples 1 to 7 of this disclosure and is implemented by a photovoltaic power generation system 111 having an improved circuit configuration in which the connection configuration between the main cables 2501 to 2503 and the impedance measuring device 3001, and the connection configuration between the grounding wire 2007 and the neutral wire 2008 and the impedance measuring device 3001 are improved. Below, an example of application to the photovoltaic power generation system 61 shown in Figure 10 is illustrated. In this configuration, the main cables 2501 to 2503 are connected through pre-circuits 5101 to 5103 installed at both input terminals of the impedance measuring device 3001. If the input impedance of the impedance measuring device at the transmission AC frequency is large, the ratio between that impedance and the impedance of the pre-circuit may not be small enough, and transmission AC may enter the input terminal of the impedance measuring device. Figure 16 is a circuit diagram showing the connection configuration to the impedance measuring device 3001 in a photovoltaic power generation system 111 to which Example 8 of the abnormality detection device and abnormality detection method of this embodiment is applied. In Example 8, a bandpass filter (BPF) 6000 is installed near both input terminals of the impedance measuring device 3001. As an example, if the BPF 6000 has R=1Ω, L=60mH, and C=169uF, the impedance at the transmission AC frequency of 50Hz is Zbp=1Ω. ​​On the other hand, the impedance at 50Hz of the two pre-circuits 5101~5103 installed in series with the BPF 6000 is Zp=2.3MΩ each, as described above in Section 2-4. Therefore, the transmission AC voltage applied to the BPF 6000 is the line voltage multiplied by the ratio of each impedance (Zbp / 2Zp), that is, about 1 / 4,000,000,000 of the line voltage, making it possible to suppress the transmission AC voltage input to the impedance measuring device to a value of that magnitude. Note that this Example 8 is applicable to all photovoltaic power generation systems described in this disclosure, in addition to the example photovoltaic power generation system 61.

[0072] 10. Conclusion This disclosure is not limited to the embodiments described above, but includes various modifications. For example, the embodiments described above are described in detail for illustrative purposes and are not necessarily limited to having all the configurations described. It is possible to replace some of the configurations of one embodiment with those of another embodiment, and to add configurations of other embodiments to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace some of the configurations of each embodiment with those of other embodiments. In other words, a person skilled in the art may make various changes, combinations, subcombinations, and substitutions with respect to the components of the embodiments described above, within the technical scope of this disclosure or its equivalents. Although all embodiments are described for three-phase AC circuits, they are applicable to single-phase AC circuits and two-phase three-wire AC circuits. [Explanation of Symbols]

[0073] 90, 41, 51, 61, 71, 81 Solar power generation systems 1-4 Solar panels 500 Step-up transformer (for grid connection) 600 grid power grid 2000 AC power receiving equipment 2001 Circuit breaker 2007 ground wire 2008 Neutral Line 2101~2104 Distributed Power Conditioner 2201, 2202 AC current collection box 2301-2303, 2311-2313 Three-phase AC power cables 2501~2503 Main Cable 3000 Monitoring and Processing Units 3001 Impedance measuring device 3002 Anomaly Detection Processing Unit 3003 Alarm output device 4000 Electromagnetic contactor with timer 4001 GDT (Gas Discharge Tubes) 4002 Inductor (for preventing water inflow) 4003 Zener Deed 4004 Barista 4005 Inductor (for preventing water inflow) 5001~5003, 5011~5013 Sensing circuit 5021~5023 Equivalent circuit for star connection conversion of delta connection sensing circuit 5101~5103 Front circuit 5111~5113, 5121~5123 Transmission AC frequency band rejection filter (BRF) 6000 AC Transmission Frequency Band Pass Filter< / zs>

Claims

1. An anomaly detection device for an AC power transmission unit that transmits AC power output from a power conditioner that converts DC power from at least one solar panel to AC power, A two-terminal sensing circuit having a predetermined impedance and including at least one of a resistor, a capacitor, and an inductor, wherein one of the two terminals is electrically connected to at least one of the AC transmission conductors provided in the AC power transmission unit, A measuring device electrically connected to the conductor for measuring the AC transmission impedance indicated by the conductor and the sensing circuit, An abnormality detection processing unit that detects an abnormality in the AC power transmission unit by comparing the impedance of the AC transmission unit measured by the measuring device with a judgment criterion value. An anomaly detection device equipped with the following features.

2. The AC power transmission section includes a plurality of conductors, In a plurality of sensing circuits, each of which one terminal is electrically connected to a separate conductor, the other terminal of the two terminals is electrically connected to each other in a star connection, and the neutral point of the star connection is electrically grounded. The impedance of the AC transmission section is the value that the conductor and the sensing circuit show between ground. An anomaly detection device according to claim 1.

3. The AC power transmission section includes a plurality of conductors, In a plurality of sensing circuits, each of which one terminal is electrically connected to a separate conductor, the other terminal of the two terminals is electrically connected to each other in a star connection, and the neutral point of the star connection is electrically connected to the neutral wire. The impedance of the AC transmission section is the value shown between the conductor and the sensing circuit and the neutral wire. An anomaly detection device according to claim 1.

4. The aforementioned at least one solar panel constitutes a plurality of sets, each set containing at least one solar panel. The aforementioned power conditioners are provided for each set of solar panels, and the solar panels belonging to each set are connected to the power conditioner associated with that set. The AC power transmission unit includes a cable assembly in which the conductors are connected in parallel to aggregate the AC transmission output from the power conditioner in each set. Each sensing circuit is provided with at least one corresponding to each set, and one terminal of each sensing circuit is electrically connected to a position in the cable assembly's conductor that connects to the power conditioner in the set to which the sensing circuit belongs. The other terminals of the two terminals of the multiple sensing circuits, each electrically connected to a separate power conditioner, are electrically connected to each other in a star configuration, and the neutral point of the star configuration is electrically connected to or grounded to a ground wire. An anomaly detection device according to claim 1.

5. The aforementioned at least one solar panel constitutes a plurality of sets, each set containing at least one solar panel. The aforementioned power conditioners are provided for each set of solar panels, and the solar panels belonging to each set are connected to the power conditioner associated with that set. The AC power transmission unit includes a cable assembly in which the conductors are connected in parallel to aggregate the AC transmission output from the power conditioner in each set. Each sensing circuit is provided with at least one corresponding to each set, and one terminal of each sensing circuit is electrically connected to a position in the cable assembly's conductor that connects to the power conditioner in the set to which the sensing circuit belongs. The other terminals of the two terminals of the multiple sensing circuits, each electrically connected to a separate power conditioner, are electrically connected to each other in a star configuration, and the neutral point of the star configuration is electrically connected to the neutral wire. An anomaly detection device according to claim 1.

6. It further comprises a plurality of two-terminal band-stop filters (BRFs) or band-pass filters (BPFs) provided corresponding to each conductor, each containing at least one of a resistor, capacitor, and inductor and exhibiting a predetermined impedance. One terminal of the BRF or BPF is connected to each conductor of the AC power transmission section, the other terminals of the BRF or BPF are connected to each other in a star connection, and the neutral point of the star connection is input to one of the measuring terminals of the measuring device. The other measuring terminals of the measuring device are connected to the neutral wire. An anomaly detection device according to claim 2 or 4.

7. It further comprises a plurality of two-terminal band-stop filters (BRFs) or band-pass filters (BPFs) provided corresponding to each conductor, each containing at least one of a resistor, capacitor, and inductor and exhibiting a predetermined impedance. One terminal of the BRF or BPF is connected to each conductor of the AC power transmission section, the other terminals of the BRF or BPF are connected to each other in a star connection, and the neutral point of the star connection is input to one of the measuring terminals of the measuring device. Other measuring terminals of the measuring device are connected to or grounded to the grounding wire. An anomaly detection device according to claim 3 or 5.

8. The conductor includes conductors for each phase for transmitting three-phase alternating current. The at least one sensing circuit is connected to each other by a delta connection in which one of the two terminals is connected to a conductor for a different phase and the other terminals are connected to each other by a star connection in which one of the two terminals is connected to a conductor for a different phase and the other terminals are connected together. It further comprises three two-terminal band-stopping filters (BRFs) that include at least one of a resistor, capacitor, and inductor, exhibiting a predetermined impedance, and provided corresponding to each conductor for each phase. The two BRFs, one terminal of the AC power transmission unit, are electrically connected to two conductors of the AC power transmission unit, and the other terminal is input to one measuring terminal of the measuring device. One of the remaining BRFs has one terminal electrically connected to the remaining conductor of the AC power transmission unit, and the other terminal is input to another measuring terminal of the measuring device. An anomaly detection device according to claim 1.

9. The abnormality detection processing unit detects an abnormality in the AC power transmission unit by including a value for determining the numerical range of the impedance of the AC power transmission unit when the AC power transmission unit and the sensing circuit are all functioning normally in at least part of the judgment criterion value. An anomaly detection device according to any one of claims 1 to 5 or 8.

10. The sensing circuit includes a capacitor and an inductor connected in series between the two terminals. An anomaly detection device according to any one of claims 1 to 5 or 8.

11. The sensing circuit includes a capacitor and an inductor connected in parallel between the two terminals. An anomaly detection device according to any one of claims 1 to 5 or 8.

12. The aforementioned sensing circuit is a resonant circuit. An anomaly detection device according to any one of claims 1 to 5 or 8.

13. The aforementioned conductor for AC transmission is grounded through the BRF or BPF connected in series and a gas-filled discharge tube (GDT), The interconnection between the BRF or BPF and the GDT is input to one of the measuring terminals of the measuring device via two inductors included in the T-type high-frequency filter. The other measuring terminals of the aforementioned measuring device are grounded. An anomaly detection device according to claim 7.

14. A grid-connection transformer that enables the output of the aforementioned AC power to the grid power grid, A timer-equipped electromagnetic contactor connected to the AC power transmission section between the power conditioner and the grid-connection transformer. Furthermore, The timer of the aforementioned electromagnetic contactor with a timer controls the electromagnetic contactor so that it is open for at least a portion of the time when the power conditioner is stopped and closed for at least a portion of the time when the power conditioner is operating. An anomaly detection device according to any one of claims 1 to 5 or 8.

15. A power transmission AC frequency band-pass filter, which allows a band including the power transmission AC frequency to pass between the two measurement terminals of the measuring device, is connected to both measurement terminals. An anomaly detection device according to any one of claims 1 to 5 or 8.

16. An abnormality detection method for an AC power transmission unit that transmits AC power output from a power conditioner that converts DC power from at least one solar panel to AC power, The AC power transmission unit is provided with at least one two-terminal sensing circuit that includes at least one of a resistor, a capacitor, and an inductor and exhibits a predetermined impedance, such that one of the two terminals is electrically connected to at least one of the conductors for AC transmission provided in the AC power transmission unit. The steps include measuring the AC transmission impedance indicated by the conductor and the sensing circuit using a measuring device electrically connected to the conductor, The steps include: comparing the impedance of the AC transmission unit with a judgment criterion value and generating and outputting an abnormality detection signal indicating an abnormality in the AC power transmission system using an abnormality detection processing unit; An anomaly detection method including

17. The AC power transmission section includes a plurality of conductors, In a plurality of sensing circuits, each of which one terminal is electrically connected to a separate conductor, the other terminal of the two terminals is electrically connected in a star configuration, and the neutral point of the star configuration is electrically grounded. The impedance of the AC transmission section is the value that the conductor and the sensing circuit show between ground. The abnormality detection method according to claim 16.

18. The AC power transmission section includes a plurality of conductors, In a plurality of sensing circuits, each of which one terminal is electrically connected to a separate conductor, the other terminal of the two terminals is electrically connected in a star configuration, and the neutral point of the star configuration is electrically connected to the neutral wire. The impedance of the AC transmission section is the value shown between the conductor and the sensing circuit and the neutral wire. The abnormality detection method according to claim 16.

19. Steps to output an alarm based on the abnormality detection signal. Includes An anomaly detection method according to any one of claims 16 to 18.

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