JP2013055819A - Power generation control system and power conditioner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent destabilization of a system due to excess power generated by a power generation system in the case a power generation device such as a photovoltaic power generation system will become dramatically and widely used.SOLUTION: For example, in the case a power generation device is a solar cell panel, a power generation control system comprises: the solar cell panel 1; a power conditioner 2 for converting output of the panel into voltage able to execute system interconnection to a commercial alternative current power line; a communication slave unit 23 provided in the power conditioner 2 and able to extract a signal for power line communication from the power line; and a communication master unit 52 able to pour a signal for power line communication into a trunk power line of a transformer station 5. The power conditioner 2 has a function to avoid system interconnection on the basis of a control signal regarding permission or non-permission of system interconnection transmitted by the communication master unit 52 to the communication slave unit 23, and can restrain supply to the system of the power generated by photovoltaic generation.

Description

  The present invention relates to an operation technique for a small-scale power generation system such as a solar power generation system and a power conditioner used in the system.

  In recent years, photovoltaic power generation has attracted attention as one of the new energies, and the introduction of photovoltaic power generation systems to ordinary households is gradually increasing. In such a solar power generation system, the generated power can be used in the house, and surplus power can be sold to an electric power company (for example, refer to Patent Document 1).

JP 2003-298075 A (paragraph [0002])

  The amount of power generation in a conventional solar power generation system is determined by solar radiation and is not adjusted according to the power demand. At present, the spread of solar power generation to ordinary households is still small, and the ratio of the total amount of generated (sold) power to the power supply capacity of electric power companies is extremely small. However, in the near future, the solar power generation system is expected to spread dramatically to small consumers such as ordinary households. In that case, for example, if a large amount of generated power is provided to the power system from a large number of solar panels on a holiday or the like when the power demand is low, the system is expected to become unstable. If the system continues to be unstable, the switch may operate and cause a large-scale power outage.

  In view of such problems, an object of the present invention is to prevent system instability due to excessive generated power of a power generation system when a small-scale power generation system such as a solar power generation system has been widely spread. .

  (1) The power generation control system of the present invention includes a communication master unit capable of injecting a signal for power line communication with respect to a main power line that distributes power to a plurality of power lines, a power generation apparatus installed at a consumer, and the power generation A power conditioner that converts the output of the device into a voltage that can be connected to the power line to be connected to the power line, and a power line communication signal extraction from the consumer power line. The power conditioner has a function of avoiding grid connection based on a control signal relating to permission / inhibition of grid connection transmitted from the communication master unit to the communication slave unit. It is characterized by being.

  In the power generation control system configured as described above, the power system may become unstable due to excessive generated power supplied from a large number of power generation devices (for example, solar battery panels) during the daytime such as holidays when power demand is low. When expected (or when it starts to become unstable), based on the control signal, the power conditioner avoids grid connection. Thereby, system instability due to excessive generated power of the power generation system can be prevented.

(2) In the power generation control system of (1), it is preferable that the control signal is transmitted from the communication parent device to the plurality of communication child devices by a broadcast method.
In this case, for example, if a communication master unit is installed in a higher-level substation and a control signal is injected into the power line by a broadcast method, all the communication slave units in the lower level of the substation receive the control signal all at once. By avoiding such grid interconnections for a large number of power conditioners, a great effect can be obtained in suppressing excessive generated power by the power generation system.

(3) In the power generation control system according to (1) or (2) above, the communication master unit selectively and continuously selects one of the control signal for performing grid connection and the control signal for interrupting. You may transmit to.
In this case, since the signal is continuously transmitted, the communication slave unit can reliably receive the control signal. Moreover, the continuous transmission can be performed finely and flexibly in response to the grid connection.

(4) Also, in the power generation control system of (1) or (2) above, the communication master unit temporarily transmits a control signal for performing grid connection, and when the communication slave unit receives the control signal, The power conditioner may execute grid connection for a predetermined time.
In this case, since the time during which the control signal is transmitted is short, mutual interference between the control signal and other communication signals can be suppressed.

(5) In addition, in the power generation control system according to any one of (1) to (4) above, when there is a possibility that power line communication for another purpose may be performed, communication is performed at a time when the signal for the target is not transmitted The master unit preferably transmits a control signal.
In this case, it is possible to control the grid connection to the power conditioner while reliably preventing mutual interference with other power line communication signals.

(6) In addition, in the power generation control system according to any one of (1) to (5), when an accident in the connected power system is detected, the grid connection and power line communication are interrupted for a predetermined time. Is preferred.
In this case, in order to recover from an accident, for example, even when a signal for performing opening / closing control is transmitted by power line communication, the signal and the control signal related to the power conditioner do not interfere with each other. The predetermined time can be determined based on, for example, empirical / statistical time required to recover from an accident.

(7) In addition, in the power generation control system of (6) above, when an accident is detected in the connected power system and recovery from the accident is detected, the grid connection is May be started.
In this case, grid connection is started after a certain period of time has elapsed since restoration, so that grid connection control related to the power conditioner can be more reliably performed while avoiding mutual interference with other power line communication signals. it can. Moreover, if this fixed time is randomly set for each power conditioner, it is possible to mitigate the influence on the system due to the simultaneous resumption of system interconnection.

  (8) On the other hand, the present invention is a power conditioner that converts the output of the power generator into a voltage that can be grid-connected to a commercial AC power line, for power line communication injected into the power line from a communication master unit. A communication slave unit that extracts a signal is provided, and has a function of avoiding grid interconnection based on a control signal relating to permission / prohibition of grid interconnection transmitted from the communication master unit to the communication slave unit. It is what.

  In the power conditioner configured as described above, the system may become unstable due to excessive generated power supplied from a large number of power generation systems (for example, solar power generation systems) during the daytime such as holidays when power demand is low. When expected (or when it starts to become unstable), based on the control signal, the power conditioner avoids grid connection. Thereby, system instability due to excessive generated power of the power generation system can be prevented.

  According to the power generation control system and the power conditioner of the present invention, system instability due to excessive generated power in the power generation system can be prevented.

It is a block circuit diagram which shows the solar power generation control system which concerns on one Embodiment of this invention, and the power conditioner which comprises this. It is a flowchart which shows an example of the control of the grid connection in the power conditioner of FIG. 6 is a flowchart showing another example of grid interconnection control in the power conditioner of FIG. 1. It is a figure which shows the example of the timing which transmits the control signal with respect to a power conditioner. It is a block circuit diagram which shows the electric power generation control system which concerns on other embodiment of this invention, and the power conditioner which comprises this.

<< First example of system configuration >>
FIG. 1 is a block circuit diagram showing a photovoltaic power generation control system as a power generation control system according to an embodiment of the present invention and a power conditioner constituting the photovoltaic power generation control system. This solar power generation control system is not a large-scale system with full-scale power generation control capability like a so-called mega solar power plant, but is installed for consumers such as ordinary households, stores, buildings, and public facilities. This is a relatively small system. Here, it is typically described as a system used in a general household.

  In FIG. 1, the solar cell panel 1 is normally installed on the roof of a house. The power conditioner 2 connected to the solar cell 1 is installed indoors or under the eaves. The watt-hour meter 3 is installed under the eaves or on a pole in the house site. Here, only the circuit portion focusing on the power conditioner 2 is shown, but in reality, there is a distribution board below the watt hour meter 3, and many indoor wirings are connected. Actually, the watt-hour meter 3 is also divided into for power purchase and for power sale, but details are omitted here.

  The power conditioner 2 includes an inverter device 21 that converts a DC voltage output from the solar battery panel 1 into an AC voltage that can be linked to a commercial AC power system, an open / close control device 22, and a communication slave device 23. I have. The switching control device 22 has a function as a switch that opens and closes an electric circuit connected from the inverter device 21 to the commercial AC power system, and a control function that performs a certain determination for switching.

  The communication slave unit 23 is a PLC modem that performs power line communication with a communication master unit 52 described later. As a signal superposition method for power line communication, for example, TWACS (Two-Way Automatic Communications System) that superimposes a digital signal of 1 or 0 near the zero cross of a commercial AC waveform can be employed. The communication slave unit 23 obtains its own power supply voltage from the secondary side electric circuit of the watt-hour meter 3, that is, the power line of the indoor wiring, and also uses the power line as a communication line.

  It is assumed that the solar power generation control system including the solar battery panel 1 and the power conditioner 2 as described above is installed in a large number of households (only two are illustrated). A general household is supplied with 200V / 100V as a commercial AC voltage via a single-phase three-wire low piezoelectric path L2 (only two wires are shown for simplicity). In the case of a detached house, this voltage is generally supplied from a pole transformer 4 that transforms a high voltage of 6.6 kV to a low voltage of 200/100 V. A plurality of pole transformers 4 are installed in each district (only two are shown), and each has a large number of photovoltaic power generation control systems.

  There is a substation 5 above the pole transformer 4. In the substation 5, for example, a distribution transformer 51 for transforming a special high voltage of 77 kV to a high voltage of 6.6 kV is installed. A voltage is applied from the distribution transformer 51 to the pole transformer 4 through a high piezoelectric path L1 (usually three-phase three-wire or four-wire but two wires are shown for simplification). That is, the high piezoelectric path L1 is a main power line that distributes power to a plurality of low-voltage power lines via the pole transformer 4. In the substation 5, a communication master device 52, which is a PLC modem, is installed. The communication master unit 52 performs power line communication with the communication slave unit 23 of each door through the low piezoelectric path L2 from the pole transformer 4 by injecting a power line communication signal to the high piezoelectric path L1 by the signal superposition method described above. Can do.

  The communication master unit 52 is connected to the monitoring control device 6 that monitors and controls power supply and demand through a communication cable. Such a monitoring control device 6 is typically installed in a central command room of an electric power company or the like. For example, when there is less power demand on weekdays than on weekdays, and when there is a large amount of power generation (power sales) from a large number of photovoltaic power generation control systems on a clear day during the day, the power supply becomes excessive and the power system Can become unstable. When such a situation is expected (or may start to become unstable), the monitoring control device 6 sends a control signal for interrupting the grid interconnection by the generated power of the photovoltaic power generation to the communication master unit. 52 can be given. Moreover, the monitoring control apparatus 6 can give the control signal which performs grid connection with respect to the communication main | base station 52, when there is no necessity of interruption or it loses.

  The communication master device 52 transmits a control signal instructed from the host to the communication slave device 23. Based on this control signal, the power conditioner 2 can perform control for performing or interrupting grid interconnection. That is, the three persons who added the communication master unit 52 to the solar cell panel 1 and the power conditioner 2 constitute not only a mere photovoltaic power generation system but also a photovoltaic power generation control system that controls the photovoltaic power generation itself.

<< System connection control example 1 >>
Next, system interconnection control related to the above-described photovoltaic power generation control system will be described. FIG. 2 is a flowchart showing an example of such grid interconnection control. The control subject of this flowchart is the power conditioner 2 (mainly the opening / closing control device 22).
The power conditioner 2 is automatically activated from a standby state at night when a minimum amount of light is obtained by sunrise. On the other hand, when the minimum amount of light cannot be obtained due to sunset, the power conditioner 2 automatically stops driving and enters a standby state. In this case, the process of the flowchart is reset and returns to the initial state. It remains in this standby state at night.

  The automatically activated power conditioner 2 first determines whether or not the communication slave unit 23 has received a control signal for executing grid interconnection from the communication master unit 52 (step S1). If the signal is not received, it waits until it is received (repeating step S1). When the signal is received, the power conditioner 2 executes grid connection (step S2), and supplies power to a commercial AC power system if power can be sold.

  The power conditioner 2 that has started the grid connection determines whether or not the communication slave unit 23 has received a control signal for interrupting the grid connection from the communication master unit 52 (step S3), and further performs the link. It is determined whether an accident (power failure or the like) has occurred in the power system (step S4). Normally, the determinations in steps S3 and S4 are all “No”, and the processes in steps S2 to S4 are repeated.

  And when it is anticipated that more electric power than necessary for the electric power demand is supplied by solar power generation (or when such a situation starts to occur), the monitoring control device 6 communicates with the communication master unit 52. A control signal for interrupting grid connection is given. In response to this, the communication master unit 52 injects a control signal for interrupting the grid connection into the power line (high piezoelectric path L1) by the broadcast method. The injected control signal is transmitted to all the communication slave units 23 through all the power lines under the substation 5. When the communication slave unit 23 receives this control signal (Yes in step S3), the power conditioner 2 interrupts the grid connection (step S7). Due to the interruption of grid connection, power line communication is also interrupted.

Thereafter, the power conditioner 2 waits for the communication slave unit 23 to receive a control signal for executing grid connection again (repeat of step S1).
When the communication slave unit 23 receives the control signal for executing grid connection again (“Yes” in step S1), the power conditioner 2 executes steps S2 to S4 as described above.

  Even if the control signal for interrupting the grid connection is not received, when the power conditioner 2 itself detects that an accident has occurred in the grid ("Yes" in step S4), the power conditioner The na 2 interrupts the grid connection (step S5). Thereafter, the power conditioner 2 waits for the state of the system to recover from the accident and for a certain period of time to elapse (repetition of steps S5 and S6), and then returns to step S1 with the progress, and so on. Is performed.

  As described above, in the solar power generation control system including the communication master unit 52, the power system becomes unstable due to excessive generated power supplied from a large number of solar battery panels during the daytime such as a holiday when power demand is low. If it is expected (or starts to become unstable), the power conditioner 2 avoids grid connection based on the control signal. Therefore, system instability due to excessive generated power of solar power generation can be prevented.

  Further, the control signal is transmitted from the communication master unit 52 to a large number of communication slave units 23 by the broadcast method. That is, if the communication master unit 52 is installed in the upper substation 5 and a control signal is injected into the power line by the broadcast method, the control signal is sent to all the communication slave units 23 in the lower order of the substation 5 at the same time. It is possible to obtain a great effect on suppression of excessive generated power by solar power generation by receiving and causing a large number of power conditioners 2 to avoid such grid interconnection.

  Moreover, the communication main | base station 52 alternatively and continuously transmits either one of the control signal which performs grid connection, and the control signal which interrupts. Therefore, the communication slave device 23 can reliably receive the control signal without failing in reception. If no other communication signal is superimposed on the power line, a control signal indicating permission / inhibition of grid connection is continuously sent from the communication master unit 52 to the communication slave unit 23, for example, by the above-described TWACS. Can be offered. Moreover, the continuous transmission can be performed finely and flexibly in response to the grid connection.

<< Example 2 of grid interconnection control >>
FIG. 3 is a flowchart illustrating another example of grid interconnection control. In the figure, the automatically activated power conditioner 2 first determines whether or not the communication slave unit 23 has received from the communication master unit 52 a control signal for starting (executing) grid interconnection (step S11). ). If the signal is not received, it waits until it is received (repeating step S11). When the signal is received, the power conditioner 2 executes grid interconnection (step S12), and supplies power to the commercial AC power system if power can be sold.

  The power conditioner 2 that has started the grid connection determines whether or not a predetermined time has elapsed (step S13), and further determines whether or not an accident (such as a power failure) has occurred in the grid to be connected. (Step S15). If there is no grid fault within the predetermined time range, the power conditioner 2 ends the grid connection as the predetermined time elapses (step S14). Thereafter, the power conditioner 2 waits for the communication slave unit 23 to receive a control signal for executing grid connection again (repeat of step S1).

  On the other hand, when the power conditioner 2 itself detects that an accident has occurred in the system before the predetermined time has elapsed (“Yes” in step S15), the power conditioner 2 Is interrupted (step S16). Thereafter, the power conditioner 2 waits for the state of the system to recover from the accident and for a fixed time to elapse (repetition of steps S17, S13, S15, and S16). When the predetermined time in Step S17 has elapsed after the recovery from the accident before the predetermined time in Step S13 has elapsed, the power conditioner 2 executes (restarts) the grid interconnection (Step S12), The grid connection is terminated after the passage. Also, the grid interconnection is terminated when the predetermined time in step S13 elapses before the fixed time in step S17 elapses after recovery from the accident (step S14). Thereafter, the same processing is performed.

  According to the photovoltaic power generation control system that performs the processing of the flowchart of FIG. 3, the power conditioner 2 that receives a signal for starting grid connection from the communication master device 52 at a certain time and is received by the communication slave device 23 is transmitted to the power conditioner 2. The operation of supplying the generated power of the photovoltaic power generation to the system for a predetermined time becomes possible. More specifically, for example, if it is a sunny day in summer, it is possible to connect to the grid for 12 hours from 6 am to 6 pm, or to connect to the grid for a certain time in the afternoon when power supply and demand is tight. Can be used.

  Of course, grid connection is not performed unless there is a control signal for starting grid connection. Therefore, when it is expected that the system will become unstable due to excessive generated power supplied from a large number of solar cell panels during the daytime such as holidays when power demand is low, a control signal for executing grid connection is sent to the communication device. By not giving to the machine 23, the power conditioner 2 does not perform grid connection. Therefore, system instability due to excessive generated power of solar power generation can be prevented.

  Further, the control signal is transmitted from the communication master unit 52 to a large number of communication slave units 23 by the broadcast method. That is, if the communication master unit 52 is installed in the upper substation 5 and a control signal is injected into the power line by the broadcast method, the control signal is sent to all the communication slave units 23 in the lower order of the substation 5 at the same time. It can be received. As a result, the large number of power conditioners 2 that have received the control signal limit the grid connection time, and therefore, a great effect can be obtained in suppressing excessive power generated by solar power generation.

  Also, according to the control signal transmission method shown in the flowchart of FIG. 3, the control signal indicating whether or not to perform grid connection is not continuously transmitted. There is little load. Therefore, mutual interference between the control signal and other power line communication signals can be suppressed. Other power line communication signals are, for example, an open / close signal for opening and closing the switch by remote control, a voltage check signal for monitoring the system voltage, and the like. These are superimposed on the commercial alternating current as, for example, a sine wave signal having a minute amplitude with a frequency higher than that of the commercial power supply.

  FIG. 4 is a diagram illustrating an example of timing for transmitting the control signal Sp to the power conditioner 2. When there is a signal that is periodically transmitted, such as the voltage check signal Sx (t1 to t2, t3 to t4) shown in FIG. 4 (a), it is between the times t2 and t3 in the interval. The communication master device 52 transmits a control signal Sp. The communication base unit 52 constantly monitors the signal of the power line communication, and when there is a possibility that the other power line communication is performed, the signal is transmitted in the broadcast method at the time when the target signal is not transmitted. Send. Thereby, the grid connection control with respect to the power conditioner 2 can be performed while reliably preventing mutual interference with other power line communication signals.

  FIG. 4 (b) shows that when a power system accident (for example, ground fault) occurs at time t11, the associated switch is once opened and sequentially reapplied. If the location of the cause of the accident can be identified in the process of recharging, control such as energizing the system that can be energized by another route while avoiding energization to that location is performed. The time zone Δt (t11 to t12) in which such a switching control signal Sy may be transmitted as power line communication is empirically and statistically known.

  On the other hand, the power conditioner 2 connected to the system affected by the accident can detect the accident due to the voltage drop, and automatically interrupts the grid connection. The inverter 2 continues this interruption for a predetermined time. The predetermined time is at least Δt (t11 to t12). Even when the opening / closing control signal Sy is transmitted by power line communication due to such interruption of the predetermined time, the signal Sy and the control signal related to the power conditioner 2 do not interfere with each other.

  For example, when the recovery from the accident is detected at time t12, the communication master device 52 transmits a control signal Sp at a time t13 after a certain time has elapsed since the recovery to start grid interconnection. As a result, grid connection is started after a certain period of time has elapsed since the restoration, and thus the grid connection with respect to the power conditioner 2 is more reliably avoided while avoiding mutual interference with other power line communication signals (Sy). The system can be controlled. Moreover, if this fixed time is set at random for each power conditioner 2, it is possible to mitigate the influence on the system due to the simultaneous resumption of system interconnection.

  As described above, other power line communication signals (Sx, Sy) and the grid-connected control signal Sp for the power conditioner 2 have different signal superposition methods. Only the control signal Sp can be received effectively.

  In addition, the above-mentioned measures for avoiding interference with other power line communication are not only for the control signal of the power generation equipment such as the power conditioner 2 but also for the power information from the watt hour meter 3. It can be applied to an automatic meter reading system that transmits to the upper level by power line communication. The watt-hour meter 3 in this case has the same power line communication function as that of the communication slave unit 23, and transmits a meter reading result signal to the communication master unit 52 based on the meter reading command signal from the communication master unit 52.

<< Second example of system configuration >>
FIG. 5 is a block circuit diagram showing a power generation control system and a power conditioner constituting the power generation control system according to another embodiment of the present invention. This power generation system includes, for example, a fuel cell 7 and a wind power generator 8 in addition to the solar cell panel 1 as a power generation device. Each output of the solar cell panel 1, the fuel cell 7, and the wind power generator 8 is converted into an AC voltage suitable for grid connection by the power conversion device 21A in the power conditioner 2A.

  With respect to such a configuration, the grid interconnection control can be performed as in FIGS. 5 shows an example in which three types of power generators are used in combination, but the fuel cell 7 can be used alone or the wind power generator 8 can be used alone. It is also possible to combine any two types of power generation devices. Note that the power generation device is not limited to these, and for example, surplus power can be supplied to the system from the battery of the electric vehicle.

<Others>
In addition, in each said embodiment, although the communication subunit | mobile_unit 23 is provided in the inside of the power conditioner 2, it can also be provided in the external vicinity. In short, the communication slave unit 23 only needs to be provided corresponding to the power conditioner 2, and the installation location is not limited. However, from a functional point of view, the communication slave unit 23 that receives a control signal regarding permission / inhibition of grid interconnection is a component of the power conditioner 2 having a function of avoiding grid interconnection regardless of the installation location. To get.
The communication base unit 52 is preferably installed in the substation 5 in that a signal for power line communication is injected into a main power line that distributes power to a plurality of power lines. It is not done.

  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 Solar panel (power generation device)
2,2A Power conditioner 7 Fuel cell (power generation device)
8 Wind power generator (power generator)
22 Opening / closing control device 23 Communication slave unit 52 Communication master unit

Claims (8)

A communication master unit capable of injecting signals for power line communication with respect to a main power line that distributes power to a plurality of power lines,
A power generator installed in a consumer;
A power conditioner that converts the output of the power generator into a voltage that can be connected to the power line to be connected;
A communication slave unit provided corresponding to the power conditioner and capable of extracting a signal for power line communication from the power line of the consumer,
The power conditioner has a function of avoiding grid interconnection based on a control signal relating to permission / inhibition of grid interconnection transmitted from the communication master unit to the communication slave unit. .   The power generation control system according to claim 1, wherein the control signal is transmitted from the communication parent device to the plurality of communication child devices by a broadcast method.   The power generation control system according to claim 1, wherein the communication base unit alternatively and continuously transmits one of a control signal for performing grid connection and a control signal for interrupting.   The communication master unit temporarily transmits a control signal for grid connection, and when the communication slave unit receives the control signal, the power conditioner executes grid connection for a predetermined time. The power generation control system according to 1 or 2.   5. The communication base unit according to claim 1, wherein when there is a possibility that power line communication for another purpose is performed, the communication base unit transmits the control signal at a time when the target signal is not transmitted. The power generation control system described.   The power generation control system according to any one of claims 1 to 5, wherein when an accident in the connected power system is detected, the grid connection and power line communication are interrupted for a predetermined time.   The power generation control system according to claim 6, wherein when an accident in the connected power system is detected and recovery from the accident is detected, the grid interconnection is started after a lapse of a certain time from the recovery. A power conditioner that converts the output of the power generator into a voltage that can be connected to a commercial AC power line,
A communication slave unit that extracts a signal for power line communication injected into the power line from a communication master unit,
A power conditioner having a function of avoiding grid interconnection based on a control signal relating to permission / prohibition of grid interconnection transmitted from the communication master unit to the communication slave unit.

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