JP5742357B2 - Monitoring system for photovoltaic power generation - Google Patents

Description

  The present invention relates to a monitoring system used for solar power generation.

  Photovoltaic power generation has a configuration in which a plurality of solar battery panels each composed of an aggregate of cells as a minimum unit are prepared, and these outputs are aggregated (in parallel connection) and then sent to a power converter (for example, , See Patent Document 1). The power converter is equipped with an inverter, and converts DC power output from the solar cell panel into AC power and outputs the AC power. Each solar cell panel incorporates a diode for preventing backflow, so that no current flows from the outside.

  In the state where a plurality of solar cell panels are connected in parallel to each other, even if any one of the solar cell panels breaks down, power generation is continued without any problem as long as other solar cell panels are normal. In addition, since the amount of power generation changes from time to time, weather, atmospheric conditions, and the like, the amount of power generation is unlikely to be found.

  On the other hand, in a large-scale solar power plant with MW power generation, a system with built-in micro inverters (small capacity inverters) in each solar cell panel has been proposed to distribute the inverter function. It has also been proposed to measure the amount of power generated for each solar cell panel (see, for example, Patent Document 2). According to such a system, it is also possible to find a failure of a specific solar cell panel based on the measurement result.

Japanese Unexamined Patent Publication No. 2000-112545 (FIG. 5) JP 2010-279234 A

However, in order to employ the micro inverter as described above in an existing solar cell panel, it is necessary to cut a cable for taking out a direct current output from the solar cell panel and attach the micro inverter. Such work is actually difficult. Further, in a general household solar power generation system, a micro inverter is not necessary.
In view of such conventional problems, the present invention can detect a failure of a solar cell panel and can be easily applied to various photovoltaic power generation systems from general households to large-scale power plants. It aims at providing the monitoring system for photovoltaic power generation.

(1) The present invention relates to a photovoltaic power generation system that has a power transmission path from aggregating outputs from a plurality of solar cell panels and sending them to a power converter, for monitoring the power generation status of the solar cell panel A monitoring system for measuring and storing a power generation amount for each of the plurality of solar battery panels, and connected to the measurement device and transmitting measurement data of the power generation amount by the measurement device by power line communication The measurement data transmitted from the lower-level communication device via the power transmission path is received by power line communication by electrically inductively coupling with the lower-level communication device having a function of And a management device having a function of collecting the measurement data via the higher-level communication device. Any of the device, the lower-level communication device, and the higher-level communication device waits for the time when the total power generation amount of the plurality of solar cell panels is relatively lowered, and transmits the measurement data Is executed or executed. Here, “waiting for the time when the total amount of power generation is relatively decreased and executing or executing the transmission of the measurement data” specifically means that “the total amount of power generation is a predetermined lower limit. The transmission of the measurement data is executed or executed at a time when the value is less than or equal to the value ”.

  In the monitoring system for photovoltaic power generation configured as described above, the power generation amount of each solar battery panel is measured by the measurement device, and the measurement data is transmitted from the lower-level communication device to the higher-level communication device via the power transmission path, Furthermore, it is collected by the management device. Here, the higher-level communication device can receive measurement data from the power transmission path without being obstructed by the presence of the smoothing capacitor in the power conversion device by using inductive coupling instead of capacitive coupling.

On the other hand, it is necessary to devise so that magnetic saturation does not occur in inductive coupling, but magnetic saturation is achieved by transmitting measurement data when the total power generation amount of a plurality of solar battery panels is relatively low. Can be prevented.
By monitoring the power generation amount of each solar cell panel in this way, it is possible to quickly find a failure and take appropriate measures such as replacement. Moreover, since power line communication is performed using the power transmission path of the solar power generation system, the monitoring system can be easily applied to various solar power generation systems.

(2) Moreover, in the monitoring system for photovoltaic power generation of the above (1), it is preferable that the measuring device and the lower-level communication device are provided in a junction box that aggregates outputs from a plurality of solar battery panels.
In this case, since the output electric circuit (cable) is gathered from the plurality of solar battery panels in the connection box, it is an optimal place for providing the measuring device and the lower-level communication device.

(3) Further, in the solar power generation monitoring system according to (1) or (2), a smoothing capacitor of the power conversion device is provided in a closed loop of power line communication between the lower-level communication device and the higher-level communication device. It can be configured to be included.
That is, in this case, the smoothing capacitor can be used as an electric circuit for power line communication.

(4) Moreover, in the monitoring system for solar power generation in any one of said (1)-(3), it is preferable that the said time exists in the time zone when the light quantity of sunlight is relatively low within one day. . Here, specific candidates of “a time zone in which the amount of sunlight is relatively low in one day” include a time zone immediately before sunset and a time zone immediately after sunrise.
In this case, measurement data is transmitted in a state where the direct current flowing through the power transmission path is relatively small, so that magnetic saturation of inductive coupling can be easily and reliably prevented.

Also, in the photovoltaic power generation monitoring system of the above (1), a time when the total power generation amount is equal to or less than a predetermined lower limit value, by or executed perform the transmission of the measurement data, through the transmission path Since measurement data is transmitted in a state where the direct current is relatively small, magnetic saturation of inductive coupling can be easily and reliably prevented. Further, when the control power supply voltage of the lower-level communication device is obtained from the output of the photovoltaic power generation panel, measurement data can be transmitted before the control power supply voltage is lost.

  According to the monitoring system for photovoltaic power generation of the present invention, it is possible to detect a failure of the solar battery panel, and the monitoring system can be easily applied to various photovoltaic power generation systems from general households to large-scale power plants. Can be applied to.

1 is a connection diagram showing a main part of a monitoring system for photovoltaic power generation according to a first embodiment of the present invention incorporated in a photovoltaic power generation system. FIG. 1 is a circuit diagram showing a blocking filter not shown in FIG. It is a connection diagram which shows an example of a connection aspect at the time of using many solar cell panels. It is a connection diagram which shows the principal part of the monitoring system for solar power generation concerning 2nd Embodiment of this invention integrated in the solar power generation system.

  FIG. 1 is a connection diagram showing a main part of a monitoring system for photovoltaic power generation according to a first embodiment of the present invention incorporated in a photovoltaic power generation system. In the figure, output electric circuits (cables) from a plurality (only three are shown here, the same applies hereinafter) of solar cell panels 1, 2, and 3 are collected in a junction box 4 and connected in parallel to each other. . That is, for example, the positive electric circuits 1p, 2p, 3p and the negative electric circuits 1n, 2n, 3n are connected to each other inside the connection box 4, and a DC voltage is output to the electric circuits P, N. Note that the connection box 4 is mainly provided outdoors, and is generally not supplied with commercial AC power or the like. In the case of a general household solar power generation system, the connection box is often provided under the eaves or the like.

  Further, inside the connection box 4, a plurality of measuring devices 5, 6, 7 and a plurality of PLC (Power Line Communication) modems 8, 9, 10 are provided. Since the output electric circuit gathers from the plurality of solar battery panels 1 to 3 in the connection box 4, it is an optimal place for providing the measuring devices 5 to 7 and the PLC modems 8 to 10. In addition, it is easy to replace the existing connection box (which realizes only parallel connection of the output electric circuit) with such a connection box 4.

  The measuring device 5 includes a current sensor 51, a voltage sensor 52, and a measuring unit 53. The current sensor 51 uses, for example, a Hall element or a shunt resistor, and detects an output current from the solar cell panel 1. The voltage sensor 52 detects the output voltage (voltage between the electric circuits 1p-1n) of the solar cell panel 1. The measuring unit 53 reads and stores the current value (instantaneous value) output from the current sensor 51 and the voltage value (instantaneous value) output from the voltage sensor 52. The measurement unit 53 outputs the stored measurement data to the PLC modem 8 at a predetermined time (details will be described later). Note that the measuring unit 53 can also store and output a power value obtained by the product of the current value and the voltage value, if necessary.

  The measuring device 6 includes a current sensor 61, a voltage sensor 62, and a measuring unit 63. The current sensor 61 detects the output current from the solar cell panel 2. The voltage sensor 62 detects the output voltage (voltage between the electric circuits 2p-2n) of the solar cell panel 2. The measurement unit 63 reads and stores the current value (instantaneous value) output from the current sensor 61 and the voltage value (instantaneous value) output from the voltage sensor 62. The measurement unit 63 outputs the stored measurement data to the PLC modem 9 at a predetermined time (details will be described later). Note that the measuring unit 63 can also store and output the power value by the product of the current value and the voltage value.

  Furthermore, the measuring device 7 includes a current sensor 71, a voltage sensor 72, and a measuring unit 73. The current sensor 71 detects an output current from the solar cell panel 3. The voltage sensor 72 detects the output voltage of the solar cell panel 3 (voltage between the electric circuits 3p-3n). The measurement unit 73 reads and stores the current value (instantaneous value) output from the current sensor 71 and the voltage value (instantaneous value) output from the voltage sensor 72. The measurement unit 73 outputs the stored measurement data to the PLC modem 10 at a predetermined time (details will be described later). The measuring unit 73 can also store and output the power value by the product of the current value and the voltage value.

  The PLC modems 8 to 10 are modems of slave units (lower side communication devices) that perform power line communication using a PLC modem 15 described later as a parent unit (upper side communication device). For example, OFDM (Orthogonal Frequency Division Multiplexing) can be used as a modem modulation method. As a use band, for example, 2 to 30 MHz can be used, but a band of 10 to 450 kHz or 10 kHz or less can also be used. The PLC modems 8 to 10 obtain their own power supply voltages from the output electric circuits P and N of the connection box 4 and also use these electric circuits P and N as communication lines.

  In addition, the power supply voltage required for the measuring devices 5 to 7 may be taken from the electric circuits P and N, or may be supplied from the PLC modems 8 to 10. Also, the functions of the measuring units 53, 63, 73 can be incorporated in the PLC modems 8, 9, 10 respectively. In short, the functions of the measuring devices 5 to 8 and the PLC modems 8 to 10 may be realized as a whole regardless of the belonging entity.

  Next, the power conversion device 11 includes an inverter 12 and a smoothing capacitor 13 having a large capacity (for example, several thousand μF) in the preceding stage, which are connected as illustrated. The voltage output between the electric circuits P and N is smoothed (stabilized) by the smoothing capacitor 13 and supplied to the inverter 12. The inverter 12 converts DC power into AC power and outputs it by, for example, a PWM-controlled switching operation.

  In the present embodiment, a CT (current transformer) 14, a PLC modem 15 as a parent device, and a measuring device 19 are mounted in the power conversion device 11. The PLC modem 15 is electrically inductively coupled to the electric circuit N via the CT 14, and thus, communication signals can be extracted and injected. For example, the power line communication between the PLC modem 8 of the slave unit and the PLC modem 15 of the master unit is performed by the PLC modem 15 inductively coupled from the PLC modem 8 via the electric circuit P, the smoothing capacitor 13, and the CT 14, and the electric circuit N. This is realized by using a closed loop which returns to the PLC modem 8 via the above. That is, the large-capacity smoothing capacitor 13 has a low impedance with respect to a high-frequency signal for power line communication. Therefore, a bypass line of the inverter 12 is formed, thereby forming the above closed loop. The same applies to the other PLC modems 9 and 10.

  In this way, the power transmission path from the connection box 4 to the power converter 11 can be used for transmission of measurement data, and the PLC modem 15 is easily installed in the housing accompanying the power converter 11. be able to. However, the PLC modem 15 is not necessarily provided in the casing of the power converter 11. For example, it can be provided near the outside of the housing.

  The measuring device 19 includes a current sensor 191 using, for example, a Hall element or a shunt resistor, and a measuring unit 192 connected thereto. The current sensor 191 detects an input current to the inverter 12. The measurement unit 192 compares the current value output from the current sensor 191 with a predetermined lower limit value, and when the value decreases from a value larger than the lower limit value to a lower limit value, the PLC modem 15 is notified of the arrival of measurement data. Send a signal to inform. Note that the function of the measuring unit 192 can be incorporated in the PLC modem 15.

The PLC modem 15 is connected to a management device 16 provided separately from the power conversion device 11 by, for example, Ethernet (registered trademark). The management device 16 is a terminal having information processing and display functions, for example, a personal computer. In the case of a general household solar power generation system, it is possible to use the management device 16 by using a monitor device that displays the amount of power generation.
Normally, the power conversion device 11 and the management device 16 are provided indoors, and necessary power is supplied to the inverter 12 (including a drive control circuit), the PLC modem 15, the management device 16, and the measurement device 19. Is done.

  In the monitoring system for photovoltaic power generation configured as described above, when sunlight hits the solar cell panels 1 to 3 by sunrise, between the electric circuits 1p-1n, 2p-2n, 3p-3n, and those A direct-current voltage is generated between the electric circuits PN connected in parallel, and photovoltaic power generation is started. This voltage is not limited to the amount of light but is almost constant. However, the current varies greatly depending on the amount of light. Further, when a DC voltage is generated between the electric circuits PN, the measuring devices 5 to 7 and the PLC modems 8 to 10 are activated. Thereby, the electric power generation amount of each solar cell panel 1-3 is measured by the measuring apparatuses 5-7, and measurement data are memorize | stored in the measurement parts 53,63,73.

Next, the timing of measurement data transmission will be described.
When the input current to the inverter 12 decreases and a signal is sent from the measuring unit 192 to the PLC modem 15 informing the arrival of the timing of measurement data acquisition, the master PLC modem 15 is connected to the slave PLC modems 8 to 8. A signal for requesting transmission of measurement data is sent to 10. In response, the slave PLC modems 8 to 10 transmit the measurement data stored in the measurement units 53, 63 and 73 to the PLC modem 15 by power line communication. The measurement data that reaches the PLC modem 15 is collected by the management device 16. In this manner, measurement data can be transmitted using the power transmission path from the connection box 4 to the power converter 11 in the photovoltaic power generation system.

The measurement data to be transmitted is basically the instantaneous value of each current value and voltage value described above. In addition to this, or instead of this, the maximum value or integrated value of the power generation amount (current or power) within the measurement duration time may be transmitted. The maximum value or integrated value can be calculated and acquired by the measurement units 53, 63, 73.
Note that the PLC modems 8 to 10 may transmit only the instantaneous value and the management device 16 may obtain the maximum value or the integrated value.

  As described above, in the monitoring system for photovoltaic power generation of the present embodiment, the power generation amount of each of the solar battery panels 1 to 3 is measured by the measuring devices 5 to 7, and the measurement data is transmitted from the PLC modems 8 to 10 of the slave units. It is transmitted to the PLC modem 15 of the parent machine via the electric circuit, and further collected by the management device 16. Here, the PLC modem 15 can receive measurement data from the transmission line without being obstructed by the presence of the smoothing capacitor 13 in the power converter 12 by using inductive coupling instead of capacitive coupling.

  In addition, it is necessary to devise so that magnetic saturation does not occur in inductive coupling, but by transmitting measurement data as described above, the total power generation amount of the plurality of solar battery panels 1 to 3 is relatively reduced. Since the measurement data is transmitted at a certain time, magnetic saturation of the core of the CT 14 can be prevented. Therefore, it is not necessary to provide an air gap for preventing magnetic saturation in the core of CT14. The air gap has a weak point that the signal coupling degree of the inductive coupling is lowered. However, if the air gap is not provided, a good signal coupling degree can be obtained.

  By monitoring the power generation amount of each solar cell panel in this way, it is possible to quickly find a failure and take appropriate measures such as replacement. Moreover, since power line communication is performed using the power transmission path of the solar power generation system, the monitoring system can be easily applied to various solar power generation systems.

Note that the measurement data transmission timing is specifically a time zone in which the amount of sunlight is relatively low within one day, for example, just before sunset. Therefore, the measurement data includes almost all necessary data for one day. Moreover, measurement data can be transmitted before the control power supply voltages of the measuring devices 5 to 7 and the PLC modems 8 to 10 are lost due to sunset. Note that the power consumption of the measuring devices 5 to 7 and the PLC modems 8 to 10 is very small compared to the amount of power generated by the solar cell panels 1 to 3, and therefore the measuring device 5 even when the sunshine conditions just before sunset are bad. It is possible to supply the required power for turning on the -7 and the PLC modems 8-10.
In addition to just before sunset, for example, immediately after sunrise, since the amount of sunlight is relatively low during the day, it is also possible to transmit at this time.

Next, abnormality determination in the management device 16 will be described.
The management device 16 has a function of collecting measurement data for each of the solar battery panels 1 to 3 via the PLC modem 15. And the management apparatus 16 can determine the presence or absence of abnormality based on the difference in the electric power generation amount in the same time about each solar cell panel based on the measurement data for every solar cell panel 1-3. For example, an average value of the power generation amount of all the solar battery panels is obtained, and it is determined that it is normal if the difference from the average value is equal to or less than a predetermined threshold value, and abnormal if it is a low power generation amount that exceeds the threshold value. be able to.

  This determination is based on the fact that there is no significant difference in the amount of power generated between each solar panel when multiple solar panels are arranged in the same orientation and in the same orientation as in a large-scale photovoltaic power generation system. ing. Further, even in a general household solar power generation system, such a determination can be applied when the difference in power generation between panels is relatively small depending on installation conditions. For example, in the case of a general household solar power generation system, if there is a relatively large disparity in the amount of power generation between panels as a whole, an average value of the amount of power generation is calculated for each area that approximates sunshine conditions. When the amount of power generation is low, which is a difference exceeding the threshold, it can be regarded as abnormal.

  On the other hand, as a determination from another viewpoint, for example, the management device 16 determines whether there is an abnormality based on the maximum value or integrated value of the power generation amount for a predetermined period (for example, one day) from the measurement data for each of the solar battery panels 1 to 3. May be determined. For example, when the average value of the maximum value or integrated value of all the solar battery panels is obtained and the difference from the average value is not more than a predetermined threshold value, it is normal, and when it is a low maximum value or integrated value that is a difference exceeding the threshold value Can be determined to be abnormal.

  Also in this determination, when a plurality of solar cell panels are arranged in the same orientation and in the same orientation as in a large-scale photovoltaic power generation system, the maximum value or integration of the power generation amount in a predetermined period is obtained for each solar cell panel. Based on the fact that there is no big difference in value. Further, even in a general household solar power generation system, such a determination can be applied when the difference between the maximum value or the integrated value of each solar cell panel is relatively small depending on the installation conditions. For example, in a general household solar power generation system, when the maximum value or integrated value between panels is relatively large as a whole, the average value of the maximum value or integrated value is obtained in area units that approximate the sunshine conditions. In addition, when the value is a low maximum value or an integrated value that is a difference exceeding the threshold in comparison with this, it can be determined as abnormal.

By monitoring the power generation amount of each solar cell panel as described above, it is possible to quickly find a failure of a specific solar cell panel and take appropriate measures such as replacement. The monitoring system is extremely useful particularly for a large-scale photovoltaic power generation system.
Note that the comparison based on the average value as described above is merely an example, and the presence or absence of abnormality may be determined by comparing each other without obtaining the average value.

  FIG. 2 is a circuit diagram showing the blocking filter 20 not shown in FIG. In FIG. 2, only the solar cell panel 1 is shown, but the other solar cell panels 2 and 3 are similarly provided with blocking filters. The blocking filter 20 is an LC filter composed of an inductor 21 and a capacitor 22, and prevents the high frequency signal of power line communication from reaching the solar cell panel 1 here. By providing such a blocking filter 20, it is possible to prevent a high-frequency signal for power line communication from being radiated as electromagnetic waves from the solar cell panel 1 into the air. When a high frequency signal is radiated, there is a risk of interference with communication of other wireless devices. However, such regulations regarding the emission of high-frequency signals are different depending on the laws of each country, and a blocking filter is not always necessary.

  FIG. 3 is a connection diagram illustrating an example of a connection mode when a large number of solar cell panels are used. In the figure, the outputs of the solar cell panels 1A, 2A, 3A are connected in parallel in the junction box 4A. In the connection box 4B, the outputs of the solar cell panels 1B, 2B, 3B are connected in parallel. Furthermore, in the junction box 4C, the outputs of the solar cell panels 1C, 2C, 3C are connected in parallel. And in the connection box 4D, the outputs of the connection boxes 4A, 4B, 4C are connected in parallel. Thus, many solar cell panels can be connected in parallel by providing connection boxes in a plurality of stages. In this case, it is possible to perform power line communication in the same manner by providing a measuring device similar to that shown in FIG. It can be carried out.

  FIG. 4 is a connection diagram showing a main part of the monitoring system for photovoltaic power generation according to the second embodiment of the present invention incorporated in the photovoltaic power generation system. The difference from FIG. 1 lies in the configuration in the junction box 4 and the configuration in the power converter 11, and the others are the same as those in FIG. 1. That is, one measuring device 17 and one PLC modem 18 are provided inside the connection box 4. A plurality of sets of the current sensor 171 and the voltage sensor 172 are provided corresponding to the solar cell panels 1, 2, and 3, respectively. The measurement unit 173 can simultaneously capture all these sensor inputs, and sequentially outputs measurement data to the PLC modem 18. The PLC modem 18 transmits all measurement data to the PLC modem 15 on the upper side in order.

On the other hand, a measuring device that measures the input current to the inverter 12 is not provided in the power converter 11.
That is, in the second embodiment, measurement data is not transmitted from the PLC modem 15 of the parent device, but is transmitted based on the determination on the child device side. For example, the measuring unit 173 compares the sum of the currents output from the solar cell panels 1 to 3 with a predetermined lower limit value, and when the value decreases from a value greater than the lower limit value to a lower limit value or less, the PLC modem 18 On the other hand, a signal notifying that the time for transmitting measurement data has arrived is sent. In response to this, the slave PLC modem 18 transmits the measurement data stored in the measurement unit 173 to the PLC modem 15 by power line communication. The measurement data that reaches the PLC modem 15 is collected by the management device 16. Information processing in the management device 16 is the same as in the first embodiment.

  In the case of the second embodiment (FIG. 4), it is not necessary to monitor the timing of measurement data transmission on the base unit side, and the configuration for that can be omitted. Further, such a configuration in the connection box 4 is simplified in that the number of the slave PLC modem 18 is one and the number of the measuring unit 173 is one. However, the functional burden of the measurement unit 173 and the PLC modem 18 becomes relatively heavy accordingly.

  Even in the case of the first embodiment (FIG. 1), it is possible to transmit measurement data spontaneously from the slave unit side without depending on an instruction from the master unit side. For example, even if the total power generation amount is not monitored, if the power generation amount of any one of the solar cell panels is equal to or lower than a predetermined lower limit value, it is estimated that the power generation amount of the other solar cell panels is similarly reduced. If it uses, the system configuration | structure of transmitting measurement data with the event that the electric power generation amount of any one solar cell panel became below the predetermined | prescribed lower limit is also possible.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1-3: Solar cell panel 4: Junction box 5-7: Measuring device 8-10: PLC modem (lower side communication device)
11: Power conversion device 13: Smoothing capacitor 15: PLC modem (upper communication device)
16: Management device 17: Measuring device 18: PLC modem (lower-level communication device)

Claims (4)

A photovoltaic power generation monitoring system that monitors the power generation status of the solar cell panel for a solar power generation system having a power transmission path for collecting outputs from a plurality of solar cell panels and feeding them to a power converter,
For each of the plurality of solar cell panels, a measuring device that measures and stores the amount of power generation,
A lower-level communication device connected to the measurement device and having a function of transmitting power generation amount measurement data by the measurement device by power line communication;
An upper-level communication device having a function of receiving, through power line communication, the measurement data transmitted from the lower-level communication device via the power transmission path by electrically inductively coupling at an upper-side predetermined portion of the power transmission path;
A management device having a function of collecting the measurement data via the higher-level communication device,
The measuring device, the lower-side communication device, and, one of the upper-side communication apparatus, a time when the total amount of power generated by the plurality of solar cell panels is equal to or less than a predetermined lower limit value, the transmission of the measurement data The monitoring system for photovoltaic power generation characterized by performing or performing.   The monitoring system for photovoltaic power generation according to claim 1, wherein the measurement device and the lower-level communication device are provided in a junction box that aggregates outputs from the plurality of solar battery panels.   The monitoring system for photovoltaic power generation according to claim 1 or 2, wherein a smoothing capacitor of the power conversion device is included in a closed loop of power line communication between the lower-order communication device and the higher-order communication device. The monitoring system for photovoltaic power generation according to any one of claims 1 to 3, wherein the time candidates include a time zone immediately before sunset and a time zone immediately after sunrise .

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