Power conditioner system

Abstract

In the present invention, an arc detection device comprises a current sensor, an arc determination unit, an energy calculation unit, a recording unit, a cutoff control unit, and a communication unit. The arc determination unit determines the occurrence of an arc on the basis of detection results from the current sensor. The recording unit records data related to arc energy calculated by the energy calculation unit. The cutoff control unit outputs a first control signal when an arc generation unit determines that an arc has occurred and the arc energy calculated by the energy calculation unit is greater than or equal to a prescribed threshold. The communication unit transmits, to a user interface, at least one of a warning signal and data related to the arc energy when the arc determination unit determines that an arc has occurred and the arc energy is less than the prescribed threshold.

Description

Power conditioner system

[0001] The present invention relates to a power conditioner system.

[0002] Conventionally, a power conditioner system provided with an arc detection device is known. When the arc detection device determines that an arc is occurring, it operates the breaker via the breaker control unit. As a result, the electric circuit connecting the solar cell module and the power conditioner is interrupted.

[0003] Japanese Patent Application Laid-Open No. 2020-516106

[0004] In a conventional power conditioner system, when an arc is detected by the arc detection device and the electric circuit connecting the solar cell module and the power conditioner is interrupted, it is necessary to identify the cause at the site where the arc detection device is installed, and the administrator of the power conditioner system cannot verify the details of the event in which the arc was detected at a location away from the site where the arc detection device is installed. That is, it is difficult for the administrator of the power conditioner system to grasp in advance the urgency and risk level of what happened at the site where the arc detection device is installed.

[0005] An object of the present invention is to provide a power conditioner system capable of verifying the details of an event in which an arc is detected by an arc detection device at a location away from the site where the arc detection device is installed.

[0006] A power conditioner system according to one aspect of the present invention is a power conditioner system for outputting power from at least one string containing a plurality of solar cell modules to a load or power grid. The power conditioner system comprises a power conditioner, an arc detection device, and a switchgear. The power conditioner converts DC power output from at least one string to AC power. The arc detection device detects the occurrence of an arc in the circuit connecting at least one string and the power conditioner. The switchgear includes a switching unit and opens and closes the circuit. At least one arc detection device includes a current sensor, an arc determination unit, an energy calculation unit, a recording unit, an interruption control unit, and a communication unit. The current sensor detects the current flowing through the circuit. The arc determination unit determines the occurrence of an arc based on the detection result of the current sensor. The energy calculation unit calculates the energy of the arc. The recording unit records the data regarding the arc energy calculated by the energy calculation unit. The shut-off control unit outputs a first control signal to switch the switching unit from the closed state to the open state when the arc generation unit determines that an arc has occurred and the arc energy calculated by the energy calculation unit is equal to or greater than a predetermined threshold. The communication unit transmits data regarding the arc energy and at least one of a warning signal to the user interface when the arc detection unit determines that an arc has occurred and the arc energy is less than a predetermined threshold.

[0007] In this power conditioner system, if the arc detection unit determines that an arc has occurred, and the arc energy calculated by the energy calculation unit is above a predetermined threshold, the circuit is shut off. This suppresses false detections of arc occurrences, such as misidentifying noise as an arc. As a result, it is possible to prevent the power conditioner system from shutting down. On the other hand, if the arc energy calculated by the energy calculation unit is below a predetermined threshold, the communication unit transmits at least one of the arc energy data and a warning signal to the user interface. This allows, for example, the administrator of the power conditioner system to obtain the arc energy data recorded in the recording unit via the communication unit, enabling verification of the event in which the arc detection device detected an arc, even from a location away from the site where the arc detection device is installed.

[0008] At least one arc detection device may further include a threshold suggestion unit that performs a suggestion process to propose changes to a predetermined threshold based on data relating to the arc energy. In this case, the predetermined threshold can be optimized.

[0009] The threshold proposal unit may periodically perform a proposal process to suggest changes to a predetermined threshold. In this case, further optimization of the predetermined threshold can be achieved.

[0010] At least one arc detection device may further include a machine learning unit that performs a suggestion process to propose an update to the arc detection algorithm performed by the arc determination unit. In this case, the detection algorithm can be optimized.

[0011] The machine learning unit may periodically perform a suggestion process to propose updates to the detection algorithm. In this case, further optimization of the detection algorithm can be achieved.

[0012] The switchgear may further include a control unit that controls the switchgear. The control unit may be capable of receiving a second control signal output from the user interface to switch the switchgear from an open state to a closed state. In this case, for example, if the administrator determines, after verifying the details of an event in which an arc was detected by the arc detection device, that the arc detection device has malfunctioned, the administrator can reset the switchgear by operating an external device to send a second control signal to the control unit.

[0013] The switching device may include a holding circuit for maintaining the open state of the switching part. In this case, when the switching part switches from the closed state to the open state based on the determination of the arc detection unit, the open state of the switching part can be maintained by the holding circuit.

[0014] The power conditioner may convert DC power output from multiple strings, including a first string and a second string, into AC power. At least one arc detection device may include a first arc detection device that detects the occurrence of an arc in the circuit connecting the first string and the power conditioner, and a second arc detection device that detects the occurrence of an arc in the second circuit connecting the second string and the power conditioner. In this case, it becomes possible to shut off only the strings in which an arc is detected, thereby reducing the downtime of the power conditioner.

[0015] The data regarding the arc energy stored in the recording unit of the second arc detection device may be output via the communication unit of the first arc detection device. In this case, the communication line with the user interface can be unified using the communication unit of the first arc detection device.

[0016] At least one current sensor in the arc detection device may also serve as a current sensor for detecting the output current of the power conditioner. In this case, the cost of the power conditioner system can be reduced.

[0017] According to the present invention, it is possible to provide a power conditioner system that allows verification of the content of an event in which an arc was detected by an arc detection device, even at a location away from the site where the arc detection device is installed.

[0018] This is a schematic block diagram showing the configuration of the power conditioner system. This is a schematic block diagram showing the configuration of the first arc detection device. This is a schematic block diagram showing the configuration of the first switchgear. This is a schematic block diagram showing the configuration of the power conditioner system according to another embodiment.

[0019] The power conditioner system 1 according to the embodiment will be described below with reference to the drawings. Figure 1 is a schematic block diagram showing the configuration of the power conditioner system 1. The power conditioner system 1 is a system for outputting power from at least one string containing multiple solar cell modules to a load or power grid.

[0020] The power conditioner system 1 comprises a plurality of strings 2, a power conditioner 3, an arc detection device 4, and a switchgear 5.

[0021] Each of the multiple strings 2 consists of multiple solar cell modules connected in series. Each solar cell module contains multiple solar cells (not shown) connected in series. The multiple strings 2 constitute a solar cell array 10. The multiple strings 2 are connected to a power conditioner 3 via a junction box 9. In this embodiment, the multiple strings 2 include four strings 2a to 2d, numbered from the first to the fourth.

[0022] The power conditioner 3 converts the DC power output from multiple strings 2 into AC power and outputs it. The power conditioner 3 is connected to a load and power system 8 (not shown).

[0023] The power conditioner 3 has the same configuration as conventional power conditioners and includes circuits not shown, such as a converter circuit, an inverter circuit, and a charge / discharge circuit. The power conditioner 3 also includes a linked operation circuit that controls the connection with the power grid 8, and an independent operation circuit that supplies the AC voltage generated by the inverter circuit to the load when, for example, the power grid 8 is experiencing a power outage.

[0024] The arc detection device 4 detects the occurrence of arcs in the circuit connecting the multiple strings 2 and the power conditioner 3. In this embodiment, the arc detection device 4 is located in each output path of strings 2a to 2d. That is, in this embodiment, the arc detection device 4 includes four arc detection devices 4a to 4d, numbered from the first to the fourth. The arc detection device 4 is located in the junction box 9.

[0025] Figure 2 is a schematic block diagram showing the configuration of the first arc detection device 4a. The first arc detection device 4a detects the occurrence of an arc in the first circuit 30a connecting the first string 2a and the power conditioner 3.

[0026] The first arc detection device 4a includes a current sensor 11, a voltage sensor 12, a power sensor 13, an amplifier 14, a filter 15, an A / D converter 16, an arc determination unit 17, an energy calculation unit 18, a recording unit 19, an interruption control unit 20, and a communication unit 21. The A / D converter 16, the arc determination unit 17, the energy calculation unit 18, and the interruption control unit 20 are implemented by processing using a microcomputer.

[0027] The current sensor 11 detects the current flowing through the first circuit 30a connecting the first string 2a and the power conditioner 3 and outputs a detection signal. The current sensor 11 detects current waveform data showing the waveform of the current flowing through the first circuit 30a. The voltage sensor 12 detects the voltage difference between the positive and negative sides of the first circuit 30a. The power sensor 13 detects the power output from the string 2.

[0028] The amplifier 14 amplifies the current detected by the current sensor 11. The filter 15 is a bandpass filter (BPF) that allows only currents within a predetermined frequency range to pass through the current output from the amplifier 14. For example, the frequency range through which the filter 15 passes is 40 kHz to 100 kHz. The A / D conversion unit 16 converts the analog current signal that has passed through the filter 15 into a digital signal and outputs it to the arc detection unit 17.

[0029] The arc detection unit 17 determines the occurrence of an arc in the first circuit 30a based on the detection result of the current sensor 11. The arc detection unit 17 determines the occurrence of an arc using a predetermined detection algorithm. The arc detection unit 17 performs an FFT on the digital signal output from the A / D conversion unit 16 to generate a power spectrum of the current, and uses the generated power spectrum to determine the occurrence of an arc. For example, the arc detection unit 17 determines that an arc has occurred if the power spectrum of the current is greater than or equal to a predetermined first threshold. The arc detection unit 17 may also use the frequency spectrum of the current signal obtained by performing a Fourier transform on the time waveform of the current signal output from the current sensor 11 to determine the occurrence of an arc.

[0030] The energy calculation unit 18 calculates the energy of the arc. The energy calculation unit 18 calculates the energy of the arc according to the determination result of the arc determination unit 17. For example, the energy calculation unit 18 calculates the energy of the arc based on the current detected by the current sensor 11 and the voltage detected by the voltage sensor 12. The arc determination unit 17 calculates the decrease in voltage from the time of arc generation and calculates the arc energy as the product of the decrease in voltage from the time of arc generation onward and the current at the time of arc generation. Alternatively, the energy calculation unit 18 may calculate the arc voltage from the data used by the arc determination unit 17 to generate the arc, and calculate the arc energy by multiplying the current by the arc generation time.

[0031] The recording unit 19 is a non-volatile memory, such as an EEPROM. The recording unit 19 records judgment data related to the judgment result of the arc determination unit 17. The judgment data is the data used by the arc determination unit 17 to determine the occurrence of an arc. The judgment data includes data related to the current signal output from the current sensor 11 and data generated based on the current signal. The judgment data includes, for example, the arc current value during the period in which it was determined that an arc occurred, the FFT calculation value, the power spectrum analysis result, and data related to the number of times the occurrence of an arc was detected. The recording unit 19 records data acquired from the voltage sensor 12 and the power sensor 13. The recording unit 19 records data related to the arc energy calculated by the energy calculation unit 18.

[0032] The disconnection control unit 20 determines whether or not to disconnect the connection between the first string 2a and the power conditioner 3 based on the determination result of the arc determination unit 17 and the calculation result of the energy calculation unit 18. If the arc determination unit 17 determines that an arc has occurred and the arc energy calculated by the energy calculation unit 18 is equal to or greater than a predetermined second threshold, the disconnection control unit 20 outputs a first control signal S1 to switch the opening / closing unit 51 (described later) from a closed state to an open state. If the arc determination unit 17 determines that an arc has occurred and the arc energy calculated by the energy calculation unit 18 is less than a predetermined second threshold, the disconnection control unit 20 does not output the first control signal S1.

[0033] The communication unit 21 transmits at least one of the data relating to the arc energy and a warning signal to the user interface 40 when the arc determination unit 17 determines that an arc has occurred and the arc energy is less than a predetermined second threshold. In this embodiment, the communication unit 21 transmits the data relating to the arc energy and a warning signal to the user interface 40. The user interface 40 is, for example, a management terminal for managing the power conditioner system 1. The communication unit 21 is connected to the user interface 40 via wired communication using a serial communication method or wireless communication. The data relating to the arc energy and the warning signal may also be transmitted from the communication unit 21 to the user interface 40 via the power conditioner 3. The communication unit 21 may also transmit the data relating to the arc energy and the warning signal to a communication terminal used by a user of the power conditioner system 1.

[0034] The first arc detection device 4a further includes a threshold proposal unit 22 and a machine learning unit 23. The threshold proposal unit 22 and the machine learning unit 23 are implemented by processing using a microcomputer. The threshold proposal unit 22 performs a proposal process that proposes a change to a predetermined second threshold based on data relating to the arc energy. For example, the threshold proposal unit 22 calculates the mean and standard deviation of a certain interval or number of samples from the data relating to the arc energy, and calculates the variability from the mean. This is repeated n or more times to calculate the variability from the mean. Then, the difference between the previous (n-1) variability value and the current (n) variability value is calculated from the mean. If the rate of change between the previous variability value and the current variability value is k, the predetermined second threshold value proposed by the threshold proposal unit 22 is calculated by the following formula: Proposed predetermined second threshold = (1 - k) × current predetermined second threshold

[0035] The threshold proposal unit 22 periodically performs a proposal process to update the proposed predetermined second threshold. The threshold proposal unit 22 is programmed to perform a proposal process, for example, every month. The threshold proposal unit 22 proposes a change to the predetermined second threshold to the user via the communication unit 21 and the user interface 40 only when the difference between the proposed predetermined second threshold and the current predetermined second threshold is large (for example, 10% or more). In other words, the threshold proposal unit 22 does not propose an update to the predetermined second threshold to the user if the difference between the proposed predetermined second threshold and the current predetermined second threshold is small. If the threshold proposal unit 22 determines that the user has approved the proposed predetermined second threshold, it updates the current predetermined second threshold to the predetermined second threshold proposed by the threshold proposal unit 22. The predetermined second threshold can be set to any value by the user via the user interface 40.

[0036] The machine learning unit 23 generates a detection algorithm for the arc detection unit 17 using machine learning and performs a suggestion process to propose an update to the predetermined detection algorithm of the arc detection unit 17. The machine learning unit 23 uses various data recorded in the recording unit 19 and environmental data including data on the installation environment of the power conditioner system 1 to generate a detection algorithm suitable for the actual environment of the power conditioner system 1 and proposes an update to the detection algorithm to the user via the communication unit 21 and the user interface 40. The various data recorded in the recording unit 19 include, for example, data acquired from the current sensor 11, voltage sensor 12, and power sensor 13, determination data, and data on arc energy. The data on the installation environment includes location information including weather, temperature, humidity, atmospheric pressure, and altitude. The machine learning performed by the machine learning unit 23 is, for example, deep learning.

[0037] The machine learning unit 23 periodically performs machine learning to update the proposed detection algorithm. If the machine learning unit 23 determines that the user has approved the proposed detection algorithm, it updates the current predetermined detection algorithm. Updating the detection algorithm includes, for example, correction of the first threshold. The data used for machine learning may be provided to the user, for example, via the communication unit 21 and the user interface 40. In this case, for example, by analyzing the data in the user's environment, it becomes possible to utilize the data used for machine learning when the user builds a new environment.

[0038] The second arc detection device 4b detects the occurrence of an arc in the second circuit 30b connecting the second string 2b and the power conditioner 3. The third arc detection device 4c detects the occurrence of an arc in the third circuit 30c connecting the third string 2c and the power conditioner 3. The fourth arc detection device 4d detects the occurrence of an arc in the fourth circuit 30d connecting the fourth string 2d and the power conditioner 3.

[0039] The first to fourth arc detection devices 4a to 4d have similar functional configurations, except that the strings used to detect arcs differ from one another. Therefore, a detailed explanation of the second to fourth arc detection devices 4b to 4d is omitted.

[0040] The switching devices 5 are located in each of the first to fourth circuits 30a to 30d. The switching devices 5 are relays or contactors. The switching devices 5 may also be switches, circuit breakers, or protectors. The switching devices 5 include the first to fourth switching devices 5a to 5d.

[0041] Figure 3 is a block diagram illustrating the configuration of the first switchgear 5a. The first switchgear 5a opens and closes the first circuit 30a. The first switchgear 5a includes an opening / closing unit 51 and a control unit 52. The opening / closing unit 51 can take on a closed state that connects the first string 2a and the power conditioner 3, and an open state that disconnects the connection between the first string 2a and the power conditioner 3.

[0042] The control unit 6 controls the opening / closing unit 51. The control unit 52 is supplied with power from the control power source 42. The control power source 42 may be generated from the power generated by the solar cell, or may be shared with the control power source of the power conditioner 3. The control power source of the power conditioner 3 may be supplied from the power grid 8, or may be generated from the power generated by the plurality of strings 2. In this embodiment, the arc detection device 4 is supplied with power from the control power source 42

[0043] The control unit 52 switches the opening / closing unit 51 from the closed state to the open state according to the first control signal S1 output from the cutoff control unit 20. The control unit 6 can receive a second control signal S2 for switching the opening / closing unit 51 from the open state to the closed state output from the user interface 40. The control unit 52 switches the opening / closing unit 51 from the open state to the open state according to the second control signal S2.

[0044] The first opening / closing device 5a includes a holding circuit 53 for holding the open state of the opening / closing unit 51. The holding circuit 53 includes a latch relay. The opening / closing unit 51 operates in conjunction with the latch relay. The control unit 52 outputs a signal for switching the latch relay from the on state to the off state according to the first control signal S1 output from the arc determination unit 17. As a result, when the latch relay is in the off state, the opening / closing unit 51 switches from the closed state to the open state, and the open state of the opening / closing unit 51 is held by the holding circuit 53. The control unit 52 outputs a signal for switching the latch relay from the off state to the on state according to the second control signal S2. As a result, when the latch relay is in the on state, the opening / closing unit 51 switches from the open state to the closed state.

[0045] The second opening / closing device 5b opens and closes the second circuit 30b. The third opening / closing device 5c opens and closes the third circuit 30c. The fourth opening / closing device 5d opens and closes the fourth circuit 30d. The first to fourth opening / closing devices 5a to 5d have the same functions as each other except that the circuits to be opened and closed are different from each other. Therefore, detailed descriptions of the second to fourth opening / closing devices 5b to 5d are omitted.

[0046] In the above-described power conditioner system 1, when the arc determination unit 17 determines that an arc has occurred, if the energy of the arc calculated by the energy calculation unit 18 is greater than or equal to a predetermined second threshold value, the circuit connecting the string 2 and the power conditioner 3 is interrupted. Thereby, for example, it is possible to suppress false detection of arc generation that determines noise as an arc. As a result, it is possible to suppress the power conditioner system 1 from stopping. On the other hand, if the energy of the arc calculated by the energy calculation unit 18 is less than the predetermined second threshold value, at least one of the data regarding the energy of the arc and the warning signal is transmitted to the user interface 40 by the communication unit 21. Thereby, for example, by the administrator of the power conditioner system 1 acquiring the data regarding the energy of the arc recorded in the recording unit 19 via the communication unit 21, at a location away from the site where the arc detection device 4 is installed, it becomes possible to verify the content of the event in which the arc was detected by the arc detection device 4a.

[0047] As described above, one embodiment of the present invention has been described. However, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the invention.

[0048] The number of strings of the power conditioner system 1 may be one or more. The connection box 9 may be omitted. In this case, the arc detection device 4 and the switching device 5 may be arranged in the power conditioner 3. Also, the control power supply 42 and the user interface 40 may be arranged in the power conditioner 3.

[0049] The arc detection device 4 may be configured to detect the occurrence of arcs in a plurality of strings 2 collectively, for example. The switching device 5 may be configured by, for example, one switching device including four switching units 51.

[0050] The current sensor 11 may also serve as a current sensor that detects the output current of the power conditioner 3.

[0051] As shown in Figure 4, the second arc detection device 4b may be connected to the first arc detection device 4a via wired communication using a serial communication method or wireless communication. That is, the communication unit 21 of the second arc detection device 4b may be configured to communicate with the first arc detection device 4a. In this case, the determination result of the arc determination unit 17 of the second arc detection device 4b and the determination data recorded by the recording unit 26 of the second arc detection device 4b may be output via the communication unit 21 of the first arc detection device 4a. The third arc detection device 4c and the fourth arc detection device 4d may also be connected to the first arc detection device 4a in a communicative manner. The first arc detection device 4a functions as a master for the second to fourth arc detection devices 4b to 4d, and the second to fourth arc detection devices 4b to 4d function as slaves to the first arc detection device 4a. That is, the arc detection device 4a may be configured to monitor the second to fourth arc detection devices 4b to 4d.

[0052] 1: Power conditioner system, 2: String, 3: Power conditioner, 4: Arc detection device, 5: Switching device, 11: Current sensor, 17: Arc determination unit, 18: Energy calculation unit, 19: Recording unit, 20: Interruption control unit, 21: Communication unit, 22: Threshold suggestion unit, 23: Machine learning unit, 51: Switching unit, 52: Control unit, 53: Holding circuit

Claims

1. A power conditioner system for outputting power from at least one string containing multiple solar cell modules to a load or power grid, comprising: a power conditioner that converts DC power output from the at least one string to AC power; at least one arc detection device that detects the occurrence of an arc in a circuit connecting the at least one string and the power conditioner; and a switchgear that includes a switch for opening and closing the circuit, wherein the at least one arc detection device comprises: a current sensor that detects the current flowing through the circuit; an arc determination unit that determines the occurrence of the arc based on the detection result of the current sensor; an energy calculation unit that calculates the energy of the arc; a recording unit that records data relating to the energy of the arc calculated by the energy calculation unit; and a cutoff control unit that outputs a first control signal for switching the switchgear from a closed state to an open state when the arc determination unit determines that an arc has occurred and the energy of the arc calculated by the energy calculation unit is equal to or greater than a predetermined threshold, A power conditioner system comprising: a communication unit that, when the arc determination unit determines that the arc has occurred and the energy of the arc is less than the predetermined threshold, transmits at least one of data relating to the energy of the arc and a warning signal to the user interface.

2. The power conditioner system according to claim 1, wherein the at least one arc detection device further includes a threshold suggestion unit that performs a suggestion process that proposes a change to the predetermined threshold based on data relating to the energy of the arc.

3. The power conditioner system according to claim 2, wherein the threshold proposal unit periodically performs a proposal process to propose a change to the predetermined threshold.

4. The power conditioner system according to claim 1 or 2, wherein the at least one arc detection device further includes a machine learning unit that performs a suggestion process to suggest an update to the arc detection algorithm performed by the arc determination unit.

5. The power conditioner system according to claim 4, wherein the machine learning unit periodically performs a suggestion process to suggest an update to the detection algorithm.

6. The power conditioner system according to claim 1 or 2, wherein the switching device further includes a control unit for controlling the switching unit, and the control unit is capable of receiving a second control signal for switching the switching unit, output from the user interface, from the open state to the closed state.

7. The power conditioner system according to claim 1 or 2, wherein the switching device includes a holding circuit for maintaining the open state of the switching part.

8. The power conditioner system according to claim 1 or 2, wherein the power conditioner converts DC power output from a plurality of strings, including a first string and a second string, into AC power, and the at least one arc detection device includes a first arc detection device for detecting the occurrence of an arc in a circuit connecting the first string and the power conditioner, and a second arc detection device for detecting the occurrence of an arc in a second circuit connecting the second string and the power conditioner.

9. The power conditioner system according to claim 8, wherein the data relating to the energy of the arc stored in the recording unit of the second arc detection device is output via the communication unit of the first arc detection device.

10. The power conditioner system according to claim 1 or 2, wherein the current sensor of at least one arc detection device also serves as a current sensor for detecting the output current of the power conditioner.

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