JP7334760B2 - power conditioner - Google Patents

Description

The present disclosure relates to power conditioners.

Patent Literature 1 discloses an anomaly detection device that detects an anomaly of a connected photovoltaic panel in a photovoltaic power generation system. This photovoltaic panel abnormality detection device compares the output value of any photovoltaic panel among a plurality of connected photovoltaic panels with the output value of the other photovoltaic panels to determine whether there is an abnormality. judge. Also, the photovoltaic panel abnormality detection device compares the output values of the photovoltaic panel at different times to determine whether there is an abnormality.

JP 2014-93368 A

By the way, some photovoltaic power generation systems have a function of interconnected operation with a commercial grid and a function of self-sustained operation when power is not supplied from the commercial grid. Such a photovoltaic power generation system converts the DC voltage generated by the photovoltaic power generation panel into an AC voltage in self-sustained operation, and supplies the AC voltage to a load for self-sustained operation.

In such a photovoltaic power generation system, erroneous determination may easily occur in a specific situation. As a specific situation, for example, during self-sustained operation, the amount of power generated by the photovoltaic power generation panel is adjusted according to the power consumption of the load supplying the AC voltage. In this case, since the output value of the photovoltaic power generation panel becomes low, it may be detected as an abnormality. If the presence or absence of an abnormality is determined including a specific situation in this way, there is a risk that an erroneous determination will occur.

A power conditioner, which is one aspect of the present disclosure, includes a converter that converts a voltage supplied from a power source that uses natural energy, an inverter that converts a DC voltage output from the converter into an AC voltage, and a commercial power system. a first output terminal connected; a second output terminal; a first switch connected between the inverter and the first output terminal; and a switch connected between the inverter and the second output terminal. The second switch, the first switch, the second switch, the converter, and the inverter are controlled to close the first switch and to close the second switch in a first operation mode. outputting the AC voltage to the first output terminal in an open state, and in a second operation mode, opening the first switch and closing the second switch to output the AC voltage to the second output terminal; and a first sensor connected to the converter and capable of detecting electric power, wherein the first electric power value detected by the first sensor is a predetermined threshold value When it is lower than , abnormality monitoring is performed, and when specific conditions including being in the second operation mode are met, the state of performing the abnormality monitoring is switched to the state of not performing the abnormality monitoring.

A power conditioner, which is another aspect of the present disclosure, includes a converter that converts a voltage supplied from a power source that uses natural energy, an inverter that converts a DC voltage output from the converter into an AC voltage, and a first an output terminal and a second output terminal, a first switch connected between the inverter and the first output terminal, and a second switch connected between the inverter and the second output terminal; , a control unit for controlling the first switch, the second switch, the converter, and the inverter; a first sensor connected to the converter and capable of detecting electric power; and AC power output from the inverter. and a second sensor capable of detecting the above, wherein the control unit performs abnormality monitoring for determining an abnormality when the first power value detected by the first sensor is lower than a predetermined threshold value, When a specific condition including a state in which the first power value is greater than the second power value is met, the state of performing the abnormality monitoring is switched to the state of not performing the abnormality monitoring.

According to one aspect of the present disclosure, it is possible to provide a power conditioner that suppresses erroneous determination of abnormality.

FIG. 1 is a block circuit diagram of a power conditioner of one embodiment. FIG. 2 is a block diagram showing a connection state in the self-sustained operation mode for the power conditioner of one embodiment. FIG. 3 is an explanatory diagram of strings. FIG. 4 is an explanatory diagram showing states of the control unit. FIG. 5 is an explanatory diagram showing the operation of the control unit. FIG. 6 is a flow chart showing the operation of the control unit. FIG. 7 is a block circuit diagram showing a modified power conditioner. FIG. 8 is a block circuit diagram showing a modified power conditioner. FIG. 9 is a block diagram showing a connection state in the self-sustained operation mode for the power conditioner of the modification.

An embodiment will be described below.
As shown in FIG. 1 , a power conditioner 11 of this embodiment is connected to a solar cell 12 to form a photovoltaic power generation system 13 . The solar cell 12 is an example of a power supply using natural energy. As a power source, the photovoltaic power generation system 13 is installed, for example, in a general household. Note that the photovoltaic power generation system 13 may be installed in a commercial facility, a factory, or the like.

Power conditioner 11 converts the DC power generated by solar cell 12 into AC power and outputs the AC power to commercial power system 15 . The solar cell 12 of this embodiment includes four solar cell strings (hereinafter simply referred to as strings) 12a, 12b, 12c and 12d.

As shown in FIG. 3, each string 12a-12d includes a plurality of cells SE connected in series and bypass diodes BD connecting arbitrary cells. The cell SE is the minimum unit of the solar cell 12 and has a flat plate shape of about 10 cm square, for example. If any of the cells SE fails, the strings 12a to 12d continue to generate power due to the current flowing through the bypass diodes BD. Further, when the output current is reduced by a shadow in any cell SE, current flows through the bypass diode BD, thereby suppressing the reduction in generated power.

The power conditioner 11 has a grid connection terminal 21 connected to the commercial power grid 15 . The system interconnection terminal 21 is an example of a first output terminal. The grid connection terminal 21 is connected to the grid power line 14 of a general household via a distribution board or the like (not shown). The grid power line 14 is connected to a commercial power grid 15 . The commercial power system 15 is a distribution system through which electric power companies transmit electric power. Loads 16 and 17 are connected to the system power line 14 . The loads 16 and 17 are electric devices connected to power lines installed indoors or outlets installed indoors via distribution boards. Electrical equipment includes, for example, lighting fixtures, televisions, refrigerators, washing machines, air conditioners, microwave ovens, and other electrical equipment.

Power conditioner 11 has a plurality of operation modes. In this embodiment, the operation mode includes a grid-connected operation mode and an isolated operation mode. The grid-connected operation mode is an example of the first operation mode. The independent operation mode is an example of a second operation mode.

The grid-connected operation mode is an operation mode in which the power conditioner 11 is connected in parallel with the commercial power system 15 and interconnected with the commercial power system 15 . The power conditioner 11 outputs AC power to the grid connection terminal 21 in the grid connection operation mode. Loads 16 and 17 connected to system power line 14 are operated by commercial AC power supplied from commercial power system 15 and AC power supplied from power conditioner 11 .

The self-sustained operation mode is an operation mode in which the power conditioner 11 is disconnected from the commercial power system 15 and AC voltage is supplied from the power conditioner 11 to the load 17 . The power conditioner 11 changes the operation mode from the grid-connected operation mode to the isolated operation mode when commercial AC power is not supplied from the commercial power system 15 due to a power failure or the like. The power conditioner 11 has a self-sustaining operation output terminal 22 that outputs AC power in the self-sustaining operation mode. The independent operation output terminal 22 is an example of a second output terminal. The power conditioner 11 supplies AC voltage to the load 17 connected to the self-supporting output terminal 22 . That is, the output terminal 22 for self-sustaining operation is an output terminal for self-sustaining operation through which the power conditioner 11 operating in the self-sustaining operation mode outputs AC power.

In this embodiment, the self-supporting output terminal 22 is a self-supporting outlet to which the load 17 is connected. The load 17 can be directly connected to the independent operation output terminal 22, or indirectly via an extension cord, table tap, home wiring, or the like. The user reconnects the load 17 connected to the system power line 14 of the commercial power system 15 to the self-sustained operation output terminal 22 to cause the power conditioner 11 to operate in a self-sustained manner. This allows the load 17 to be used.

[Configuration of power conditioner]
The power conditioner 11 of this embodiment has four PV converters (PVC: photovoltaic converter) 31a, 31b, 31c, and 31d. The power conditioner 11 also has an inverter 32 , a filter 33 , a system interconnection relay (simply referred to as “relay”) 34 a , an independent operation relay (simply referred to as “relay”) 34 b , and a control unit 35 . The PV converters 31 a - 31 d and inverter 32 are connected to each other via a DC voltage bus 41 . The inverter 32 is connected to the grid connection terminal 21 via the filter 33 and the grid connection relay 34a. In addition, the inverter 32 is connected to the self-sustaining operation output terminal 22 via the filter 33 and the self-sustaining operation relay 34b.

The grid connection relay 34 a is an example of a first switch (switch) that connects and disconnects the inverter 32 and the grid connection terminal 21 . For example, a semiconductor switch, a mechanical relay switch, or the like can be used as the grid connection relay 34a. The self-sustained operation relay 34b is an example of a second switch (switch) that connects and disconnects between the inverter 32 and the self-sustained operation output terminal 22 . For example, a semiconductor switch, a mechanical relay switch, or the like can be used for the independent operation relay 34b.

The control unit 35 controls the PV converters 31a to 31d, the inverter 32, the grid connection relay 34a, and the isolated operation relay 34b. The power conditioner 11 has a power supply circuit 45 that generates control power for the control section 35 . The power supply circuit 45 generates control power for the controller 35 from the DC power of the DC voltage bus 41 or the AC power of the commercial power system 15 .

Each of the PV converters 31a to 31d is a booster circuit controlled by the controller . Each PV converter 31a to 31d is configured to be connectable to a string. In other words, the power conditioner 11 is configured to be able to connect an arbitrary number of strings from 1 to 4.

Each of the PV converters 31 a - 31 d has a function of converting the electric power generated by the strings 12 a - 12 d into DC power and outputting it to the DC voltage bus 41 . Each PV converter 31a to 31d has a function of smoothing the generated DC voltage. Sensors 51a, 51b, 51c and 51d are connected to the PV converters 31a, 31b, 31c and 31d, respectively, for detecting the generated power (DC power) of the connected strings.

Each PV converter 31a-31d includes a switching element. The control unit 35 adjusts the pulse width of the control signal for turning on/off the switching elements of the PV converters 31a to 31d by, for example, a pulse width modulation (PWM) method. Then, the control unit 35 controls each of the PV converters 31a to 31d so that desired output power is output from each of the PV converters 31a to 31d to the DC voltage bus 41 according to the control signal. Note that FIG. 1 shows a state in which the strings 12a to 12c are connected to the PV converters 31a to 31c, and the string 12d is not connected to the PV converter 31d. In this embodiment, the controller 35 controls three PV converters 31a to 31c.

The inverter 32 is a DC/AC conversion circuit operated by a control signal from the control section 35 . The inverter 32 operates according to a control signal from the control section 35 and converts the DC power of the DC voltage bus 41 into AC power.

In the grid-connected operation mode, the controller 35 controls the inverter 32 to convert the DC power into AC power that can be interconnected with the commercial power system 15 . Also, in the self-supporting operation mode, the control unit 35 controls the inverter 32 so as to supply AC power to the load 17 connected to the self-supporting output terminal 22 .

The AC power output from the inverter 32 is output to the grid connection terminal 21 via the filter 33 and the grid connection relay 34 a in the closed state, and is output from the grid connection terminal 21 to the grid power line 14 . Filter 33 reduces high frequency components of the AC power output from inverter 32 . Also, the AC power output from the inverter 32 is output to the self-sustained operation output terminal 22 via the self-sustained operation relay 34b in the closed state.

Inverter 32 also converts AC power of commercial power system 15 into DC power and outputs the DC power to DC voltage bus 41 . As with AC power, the control unit 35 controls on/off of a plurality of switching elements included in the inverter 32 by a control signal to output desired DC power from the inverter 32 to the DC voltage bus 41 .

The control unit 35 has a memory 36 . The memory 36 includes ROM and RAM. The memory 36 stores a processing program executed by the control unit 35 and various data stored by executing the processing program. The memory 36 also stores various data such as threshold values necessary for processing. Further, the control unit 35 includes a peripheral circuit (not shown). Peripheral circuits include clock signal generation circuits, clock circuits, interface circuits, communication circuits, and the like. The control unit 35 directly reads information (data) necessary for executing the processing program from the peripheral circuit, or reads information (data) stored in the memory 36 from the peripheral circuit. The information (data) stored in the memory 36 includes information stored in the memory 36 from the outside via peripheral circuits.

FIG. 6 is a flowchart showing an outline of the operation of the control section 35. As shown in FIG.
The control unit 35 executes the processes of steps S21 to S27 shown in FIG.
When the control power supply is turned on, the control unit 35 performs initial setting in step S21. The initial setting includes various controls for operating the power conditioner 11 . For example, the control unit 35 turns off the system interconnection relay 34a and the self-sustaining operation relay 34b shown in FIGS. The control unit 35 also performs string setting, that is, processing for detecting and storing the connection state of the strings with respect to the PV converters 31a to 31d shown in FIGS. After finishing the initial setting, the control unit 35 waits. When the control unit 35 is instructed to start operation by an operation start/stop signal, for example, from a controller (not shown), the process proceeds to step S22.

In step S22, the controller 35 performs various controls. Various controls include control in the grid-connected operation mode and control in the isolated operation mode. For example, in the grid-connected operation mode, the control unit 35 controls the grid-connected relay 34a to the closed state (on state) and controls the self-sustained operation relay 34b to the open state (off state). Then, the control unit 35 operates the PV converters 31a to 31c and the inverter 32 . As a result, an AC voltage based on the voltage generated by the strings 12a to 12c is output from the grid connection terminal 21. FIG. In the self-sustained operation mode, the control unit 35 controls the system interconnection relay 34a to open and the self-sustained operation relay 34b to open. Then, the control unit 35 operates the PV converters 31a to 31c and the inverter 32 . As a result, an AC voltage based on the voltage generated by the strings 12a to 12c is output from the output terminal 22 for self-sustained operation.

In step S23, the control unit 35 determines whether or not control is to be stopped. Control stop is instructed by an operation start/stop signal from a controller (not shown), for example. When it is determined that the control is not stopped (determination: NO), the control unit 35 proceeds to step S24. On the other hand, when it is determined that the control should be stopped (determination: YES), the control unit 35 proceeds to step S21.

In step S24, the control unit 35 determines whether or not a specific condition is satisfied. The specific condition includes a condition indicating a state in which an erroneous determination may occur in abnormality determination.
If it is determined that the specific condition is not satisfied (determination: NO), the controller 35 proceeds to step S25. On the other hand, if it is determined that the specific condition is satisfied (determination: YES), the control section 35 proceeds to step S22.

In step S25, the control unit 35 determines whether or not there is an abnormality. For example, the anomaly determination includes anomalies of strings 12a-12c. The control unit 35 detects the states of the strings 12a-12c. The control unit 35 determines whether the states of the strings 12a to 12c are abnormal. If it is determined that there is an abnormality, that is, if an abnormality is detected (determination: YES), the controller 35 proceeds to step S26. On the other hand, if it is determined that the state is not abnormal (determination: NO), the control unit 35 proceeds to step S22.

In step S26, the control unit 35 determines whether or not it has continued for a predetermined time. More specifically, the control unit 35 determines whether or not the abnormal state detected in step S25 has continued for a predetermined period of time. When it is determined that the predetermined time has continued (determination: YES), the control unit 35 proceeds to step S27. On the other hand, if it is determined that it has not continued for the predetermined time (determination: NO), the controller 35 proceeds to step S22.

In step S27, the control unit 35 notifies the abnormality. For example, the control unit 35 waits after announcing the abnormality. Then, when a predetermined operation or the like is performed, the control section 35 proceeds to step S21.

When it is determined in step S24 that the specific condition is not satisfied, the control unit 35 executes steps S25 and S26. That is, the control unit 35 performs abnormality detection and determines whether or not the abnormal state continues. In other words, the control unit 35 enters a state of performing abnormality monitoring when the specific condition is not satisfied. On the other hand, if it is determined in step S24 that the specific condition is satisfied, the control section 35 proceeds to step S22. Therefore, when the specific condition is satisfied, the control section 35 does not execute steps S25 and S26. In other words, the control unit 35 does not perform abnormality detection and does not determine whether the abnormal state continues. In other words, the control unit 35 is in a state of not performing abnormality monitoring when the specific condition is satisfied. Therefore, when the specific condition is met, the control unit 35 switches from the state in which abnormality monitoring is performed to the state in which abnormality monitoring is not performed. Further, when the specific condition is not met, the control unit 35 switches from the state of not performing the abnormality monitoring to the state of performing the abnormality monitoring.

(action)
Next, the operation of the power conditioner 11 will be described.
[String error monitoring]
The control unit 35 has a function of monitoring an abnormality of a string as a DC power supply connected to the power conditioner 11 . In this embodiment, the power conditioner 11 is connected to three strings 12a to 12c. Here, abnormality monitoring for the three strings 12a to 12c will be described. Although the string 12d is not connected in FIG. 1, if the string 12d is connected, the control unit 35 performs abnormality monitoring in the same manner as the other strings 12a to 12c. In the following description, processing will be described in the state shown in FIG. 1, that is, in the state in which the strings 12a to 12c are connected. In addition, when common to all the strings 12a to 12d, all the strings 12a to 12d will be shown and explained.

The control unit 35 stores in the memory 36 the result of detecting the abnormality of the strings 12a to 12c for the PV converters 31a to 31c. Abnormalities in the strings 12a-12c can be detected from the generated power (DC power) of the strings 12a-12c. The abnormality of each string 12a-12c can also be detected by the DC voltage or DC current output from each string 12a-12c.

The information (data) stored in the memory 36 includes the connection status (connected, disconnected) of the strings to the PV converters 31a-31d. In the power conditioner 11 of this embodiment, the strings 12a-12c are connected to the PV converters 31a-31c, and the string 12d is not connected to the PV converter 31d. The control unit 35 detects an abnormality in the strings 12a-12c connected to the PV converters 31a-31c.

Specifically, the power conditioner 11 of this embodiment has connection terminals 23a, 23b, 23c, and 23d that are connected to the PV converters 31a, 31b, 31c, and 31d. Each connection terminal 23a to 23d is, for example, a connection connector or a terminal block provided in the power conditioner 11. FIG. Note that the connection terminals 23a to 23d may be omitted. Sensors 51a, 51b, 51c and 51d are connected to the PV converters 31a, 31b, 31c and 31d, respectively, for detecting the generated power (DC power) of the connected strings. The sensors 51a to 51d are examples of first sensors, and the values detected by the sensors 51a to 51d correspond to the first power values. Each sensor 51a-51d is provided on the input side of the corresponding PV converter 31a-31d. Therefore, each of the sensors 51a-51d can also be said to be a sensor for detecting DC power (voltage, current) on the input side of the PV converters 31a-31d.

The sensors 51a-51d are composed of voltage sensors and current sensors. Based on the voltage value detected by the voltage sensor and the current value detected by the current sensor, the amount of electric power input from the connection terminals 23a to 23d can be calculated. Whether strings are connected to the connection terminals 23a to 23d can be determined based on at least one of the voltage value and the current value. Moreover, the power generation state of the strings connected to the connection terminals 23a to 23d can be determined by at least one of the voltage value and the current value.

The memory 36 stores settings (data) for detecting abnormalities in the strings 12a to 12d. This data includes thresholds, durations. The threshold is, for example, the power (threshold power) for judging the power generated by the strings 12a-12d. Abnormality of each string 12a to 12d can also be detected by detecting voltage or current. In this case, the memory 36 stores the threshold voltage or threshold current corresponding to the voltage or current to be detected.

The controller 35 reads the threshold value stored in the memory 36 and compares the threshold value with the electric power value of the string 12a detected by the sensor 51a. The control unit 35 stores the comparison result in the memory 36 . If the power value of the string 12a is equal to or greater than the threshold value, the control unit 35 determines that the string 12a is "abnormal". Further, when the power value of the string 12a is lower than the threshold value, the control unit 35 determines that the string 12a is “abnormal”. A comparison between the threshold value and the generated power detects whether there is a possibility that an abnormality has occurred in the string 12a. Then, when the string 12a continues to state that "abnormal" exists for a predetermined period of time, the control unit 35 determines that the string 12a is abnormal, and notifies the string 12a of the abnormality.

The threshold value is set according to the generated electric power of the string 12a, for example, the rated value. The threshold value is set to a low power value that is normally difficult to occur, for example, when the string 12a is in use. The string 12a generates electricity with sunlight. For example, when sunlight is blocked by clouds or the like, the output power (output voltage) of the string 12a is reduced. In this way, the threshold is set to a lower value than the output power that drops in normal power generation conditions. For example, if the output power of the string 12a is 1.5 kW, the threshold is set to 100W.

The control unit 35 executes determination processing for comparing the power generated by the string 12a with a threshold value. Similarly, the control unit 35 executes determination processing for the strings 12b and 12c. The control unit 35 performs determination processing on each of the strings 12a to 12c at predetermined intervals. The predetermined interval is set to, for example, one hour, several hours, several tens of hours, one day, several days, one week, or the like.

The control unit 35 stores in the memory 36 the result of the judgment processing for each of the strings 12a to 12c. For example, if the control unit 35 determines that the string 12a is "abnormal", it stores data indicating that fact in the memory 36, and if it determines that the string 12a is "abnormal", it clears the data in the memory 36. This data is, for example, a count value indicating the number of times an abnormality has been determined. The control unit 35 counts up (+1) the count value when determining that there is an abnormality. On the other hand, when determining that there is no abnormality, the control unit 35 resets the count value (sets 0) and erases the comparison result.

Then, when the count value becomes equal to the predetermined value, the control unit 35 determines that the string 12a is abnormal, and notifies the string 12a of the abnormality. The predetermined value is set based on the above-described predetermined period and the feeling of performing the determination process. The predetermined period is set to, for example, one week (168 hours). Assuming that the predetermined sensation is one hour, the predetermined value is set to "168".

Note that the control unit 35 may sequentially store the results of the determination processing in the memory 36 . In this case, the number of determination results stored in the memory 36 is the above count value. Then, when the determination result of the predetermined value is stored, the control section 35 notifies the abnormality of the strings 12a to 12c. Then, when determining that there is no abnormality, the control unit 35 resets the count value, that is, clears (deletes) the determination result in the memory 36 .

[Stop monitoring]
The control unit 35 has a function of stopping (interrupting) the string abnormality monitoring. When a specific condition is satisfied, the control unit 35 enters a non-monitoring state in which abnormality monitoring for each of the strings 12a to 12c is stopped. The specific condition includes being in the self-sustaining mode. Self-sustained operation in the self-sustained operation mode is a power failure state in which commercial AC power is not supplied from the commercial power system 15 . In this self-sustained operation mode, the power conditioner 11 converts the DC power generated by the solar cells 12 (strings 12 a to 12 c ) into AC power and supplies the AC power to the load 17 . The required power varies depending on the state of the load 17 (operation state, number of connections). Therefore, the electric power generated by each string 12a-12c changes. Then, when the generated power of each string 12a to 12c becomes lower than the threshold value, the control unit 35 determines that the string is abnormal, that is, an erroneous determination occurs. The control unit 35 includes the self-sustained operation mode as a specific condition. Then, when this specific condition is satisfied, that is, when the grid-connected operation mode is changed to the isolated operation mode, the control unit 35 stops (interrupts) abnormality monitoring for each of the strings 12a to 12c. This reduces false detection of anomalies for the strings 12a-12c.

When the commercial power system 15 recovers (restores power) from the power failure state, the control unit 35 changes from the isolated operation mode to the grid connection operation mode. Then, the control unit 35 determines that the specific condition is no longer satisfied, and restarts abnormality monitoring for each of the strings 12a to 12c. While stopping the abnormality monitoring, the control unit 35 maintains the state before stopping the abnormality monitoring. In other words, the count value is stored in the memory 36 when the strings 12a to 12c are monitored for anomalies. The control unit 35 does not clear (reset) the count value of the memory 36 . Then, when the abnormality monitoring is resumed, the control unit 35 resumes counting by the electric power generated by each of the strings 12a to 12c. This makes it possible to detect an abnormality in each string 12a-12c.

Further, the specific condition includes being in an overloaded state. The overloaded state is a state in which the power that can be generated by the solar cell 12 is greater than the amount of power that the power conditioner 11 can output. The amount of power that the power conditioner 11 can output is, for example, 4 kW, and is determined by the maximum rated power of circuits such as the PV converters 31a to 31d and the inverter 32. For example, an overloaded state indicates a state in which the power that can be generated by the solar cell 12 (the power that can be generated by the connected strings 12a to 12c) is greater than the rated output of the power conditioner 11. FIG. The overloaded state is also a state in which the power conditioner 11 cannot output power lower than the rated output due to factors such as temperature. The power output by power conditioner 11 can be detected by sensor 52 provided on the output side of inverter 32, for example. The sensor 52 is an example of a second sensor, and the value detected by the sensor 52 corresponds to the second power value. The sensor 52 is composed of a current sensor or a current sensor and a voltage sensor. In such an overloaded state, the control unit 35 controls the PV converters 31a to 31c to suppress the power generation of the strings 12a to 12c to the amount of power that the power conditioner 11 can output. Therefore, the generated electric power of each string 12a to 12c may become lower than the threshold value, and the control unit 35 determines that the string is abnormal, that is, an erroneous determination occurs. The control unit 35 includes the overloaded state in the specific condition. Then, when the specific condition is satisfied, the control unit 35 stops (interrupts) abnormality monitoring for each of the strings 12a to 12c. This reduces false detection of anomalies for the strings 12a-12c.

When the overloaded state ceases, for example, when the power conditioner 11 becomes capable of outputting the rated output due to the temperature, the control unit 35 determines that the specific condition is no longer satisfied, and monitors the strings 12a to 12c for abnormalities. resume. This makes it possible to detect an abnormality in each string 12a-12c.

[String settings]
The information (data) stored in the memory 36 includes the connection status (connected, disconnected) of the strings to the PV converters 31a-31d. The control unit 35 determines the connection state of the strings with respect to the PV converters 31a to 31d, and stores the determination result in the memory 36. FIG.

The control unit 35 detects the connection state of the strings to the PV converters 31a to 31d based on the detection results of the sensors 51a to 51d. As described above, the sensors 51a-51d are provided on the input side of the PV converters 31a-31d. The sensors 51a-51d of this embodiment include voltage sensors. As shown in FIG. 1, when the strings 12a to 12c are connected, the electric power (DC power) generated by the strings 12a to 12c is applied to the sensors 51a to 51c in a power-generating state during the daytime. The controller 35 can detect the generated power (DC power) of the strings 12a to 12c using the sensors 51a to 51c. The controller 35 compares a predetermined threshold voltage with the voltage values detected by the sensors 51a-51d. The threshold voltage is set to a voltage value lower than the output voltage of each string 12a-12d depending on the configuration of each string 12a-12d. An example threshold voltage is 60V, for example. When the voltage values detected by the sensors 51a to 51d are higher than the threshold voltage (≧60V), the controller 35 determines that the strings are connected to the PV converters 31a to 31d. That is, the control unit 35 detects the connection state (connected, disconnected) of each string 12a to 12d.

Then, the control unit 35 causes the memory 36 to store data of the detected connection state. For example, the connected state is "1" and the non-connected state is "0". Thereby, the connection state of the string to the power conditioner 11 can be automatically determined. FIG. 1 shows a state in which strings 12a-12c are connected to connection terminals 23a-23c and string 12d is not connected to connection terminal 23d. In this case, the control unit 35 determines that the strings 12a to 12c are connected to the connection terminals 23a to 23c, and causes the memory 36 to store data indicating their connection state (connection). Further, the control unit 35 determines that the string is not connected to the connection terminal 23d, and causes the memory 36 to store data indicating the connection state (disconnection).

For example, the connection state of each string 12 a to 12 d can be set by an operator who installs the solar cell 12 and the power conditioner 11 . However, manual setting by an operator may cause a setting error. For example, in the state shown in FIG. 1, it is set that the string 12d is connected to the connection terminal 23d. In this case, since the string 12d is not actually connected, the power generation amount detected by the sensor 51d is "0". As a result, the controller 35 erroneously determines that the string 12d is abnormal. Also, in the state shown in FIG. 1, for example, it is set that the string 12a is not connected to the connection terminal 23a. In this case, the control unit 35 does not control the PV converter 31a that is set to be disconnected, so the power generated by the string 12a is not used.

As described above, the control unit 35 detects the power value of the DC power on the input side of each PV converter 31a-31d using the sensors 51a-51d corresponding to each PV converter 31a-31d. Based on these power values, it can be determined whether or not the strings 12a to 12d, which are DC power sources, are connected to the PV converters 31a to 31d. The control unit 35 stores the determination result in the memory 36 . That is, the connection states of the strings 12a to 12d with respect to the power conditioner 11 are automatically set. As a result, it is possible to prevent setting errors during installation and setting change errors when string connections are changed.

FIG. 4 shows the operating state of the control unit 35 in the power conditioner 11. As shown in FIG. The control unit 35 can take "standby state", "operating state", "abnormality notification", and "non-monitoring state" shown in FIG. It should be noted that the state that the control unit 35 can take may include states other than those described above.

The control unit 35 of the power conditioner 11 controls the power conditioner 11 by transitioning between states S11 to S14 according to various conditions.
[Waiting state]
The control unit 35 is in a state where it has started operating with control power supplied from the power supply circuit 45 . For example, when a controller (not shown) issues an operation start/stop signal to stop the operation, the control unit 35 enters the standby state S11. The operation start/stop signal is an example of a signal for controlling the operation and stop of the power conditioner 11 to the control unit 35, that is, for controlling the start and stop of power generation.

In this state, the control section 35 detects the connection state of the strings to the PV converters 31a to 31d. As described above, the controller 35 compares the voltage values detected by the sensors 51a-51d on the input side of the PV converters 31a-31d with the threshold voltage. Then, the control unit 35 determines that the PV converters 31a to 31d to which the sensors 51a to 51d whose detected voltage values are equal to or higher than the threshold voltage are connected are string-connected. Then, the control unit 35 causes the memory 36 to store the connection information of the strings 12a to 12d. When the operation start/stop signal instructs the control unit 35 to start operation, the control unit 35 transitions to the operation state S12.

[Operating state]
In the operation state S12, the control unit 35 sets the grid-connected operation mode or the independent operation mode based on the detection result of the sensor 53, and performs control in each operation mode. Sensor 53 is, for example, a power meter. The control unit 35 changes from the grid-connected operation mode to the isolated operation mode, and from the grid-connected operation mode to the grid-connected operation mode, depending on the presence or absence of commercial AC power from the commercial power system 15 . The control unit 35 sets the grid-connected operation mode when the commercial AC power is supplied from the commercial power system 15, and sets the isolated operation mode when the commercial AC power is not supplied from the commercial power system 15 due to a power failure or the like. Note that if the power line connected to the commercial power system 15 is a single-phase three-wire system, it is also possible to determine whether commercial AC power is supplied from the commercial power system 15 based on the voltage between the W phase and the U phase. can.

[Not monitored]
For example, when commercial AC power is not supplied from the commercial power system 15 due to a power outage, the control unit 35 changes to the self-sustained operation mode. At this time, the control unit 35 transitions to the non-monitoring state S13 in order to have the specific condition. Accordingly, the control unit 35 does not determine whether or not the strings 12a to 12c in the self-sustained operation mode are abnormal. Therefore, erroneous detection due to self-sustained operation can be suppressed. That is, it is possible to improve the accuracy of abnormality detection for each of the strings 12a to 12c.

When commercial AC power is supplied from the commercial power system 15, the control unit 35 changes from the isolated operation mode to the grid connection operation mode. Then, the control unit 35 transitions from the non-monitoring state S13 to the operating state S12.

[Continuation and Stop of Abnormality Monitoring in Operating State and Non-Monitoring State]
In the non-monitoring state S13, the control unit 35 stops (suspends) counting of abnormality monitoring. For example, assume that the string 12a shown in FIG. 1 is being monitored for anomalies in the operating state S12. When the controller 35 detects that the generated electric power of the string 12a has become lower than the threshold electric power in the operating state S12, as shown in FIG. Then, the control unit 35 performs the determination process on the string 12a at predetermined intervals. In the determination process, if the generated power of the string 12a is lower than the threshold power, the number of times of abnormality determination is counted up. That is, the control unit 35 continues counting.

When the grid-connected operation mode is changed to the isolated operation mode and the isolated operation is started, the control unit 35 stops counting the strings 12a. After that, when the self-sustained operation mode is changed to the grid-connected operation mode and the self-sustained operation ends, the control unit 35 restarts counting the strings 12a. Note that the control unit 35 may restart counting after a certain period of time has elapsed after the self-sustained operation ends. Then, the control unit 35 performs determination processing on the string 12a, and continues counting when the generated power of the string 12a is lower than the threshold power. Then, when the string 12a remains in the "abnormal" state for a predetermined period of time except for the period of self-sustained operation, the control unit 35 determines that the string 12a is abnormal, and shifts to abnormality notification S14.

[Error notification]
In the abnormality notification S14, the control unit 35 notifies the abnormality of the string 12a. In this way, the controller 35 can reliably detect an abnormality in the string 12a. Although the string 12a has been described, the other strings 12b and 12c can also be prevented from being erroneously detected as well as being reliably detected. Also, when the string 12d is connected, erroneous detection of anomaly can be suppressed and the anomaly can be reliably detected in the same manner as the string 12a.

In the abnormality notification S14, when the power conditioner 11 is reset by, for example, maintenance by the operator, the control unit 35 transitions to the standby state S11. The control unit 35 clears the data for abnormality determination stored in the memory 36, for example, the count value, when the abnormality notification S14 transitions to the standby state S11. In the operation state S12, when a power generation stop signal is input from a controller (not shown), the control unit 35 transitions to the standby state S11. In addition, when the control unit 35 transitions to the standby state S11 due to the supply of control power, the power generation start signal, or the power generation stop signal, the control unit 35 clears ( to erase.

For example, a power generation stop signal and a power generation start signal from a controller (not shown) are input upon completion of construction, maintenance, or the like. In these cases, if data remains in the memory 36, it becomes a factor of erroneous determination. For example, due to maintenance on the PV converter 31a shown in FIG. 1, the connection is changed from the string 12a to the string 12d. In this case, a different string 12d is connected to the PV converter 31a. If the counting of the string 12d is continued while the string 12a is being counted due to the abnormality detection, the abnormality of the string 12d may be erroneously detected. Therefore, erroneous detection can be suppressed by clearing (resetting) the data (comparison result, count value, etc.) in the memory 36 .

(effect)
As described above, according to this embodiment, the following effects are obtained.
(1) The power conditioner 11 includes an inverter 32 that converts DC power from the solar cell 12 into AC power. The power conditioner 11 includes a system interconnection relay 34a connected between the inverter 32 and the system interconnection terminal 21, and a self-sustained operation relay 34b connected between the inverter 32 and the self-sustained operation output terminal 22. have. The power conditioner 11 includes sensors 51a-51d for detecting power input to the PV converters 31a-31d.

In the grid-connected operation mode, the control unit 35 closes the grid-connected relay 34 a and opens the self-sustained operation relay 34 b to output the AC power of the inverter 32 to the grid-connected terminal 21 . In the self-sustained operation mode, the control unit 35 opens the system interconnection relay 34 a and closes the self-sustained operation relay 34 b to output the AC power of the inverter 32 to the self-sustained operation output terminal 22 . The control unit 35 performs anomaly monitoring to determine an anomaly when the power values detected by the sensors 51a to 51d are lower than the threshold values. Then, the control unit 35 switches from a state in which abnormality monitoring is performed to a state in which abnormality monitoring is not performed when specific conditions including being in the self-sustained operation mode are met.

In the self-sustained operation mode included in the specific conditions, the power generation of the strings 12a to 12c is suppressed so as to obtain AC power according to the state of the load 17. FIG. Therefore, the generated electric power of each string 12a to 12c may become lower than the threshold value, which may result in erroneous detection. Therefore, erroneous detection is suppressed by not performing abnormality monitoring in the self-sustained operation mode. As a result, the accuracy of abnormality detection for the strings 12a to 12c can be improved.

(3) The power conditioner 11 includes a sensor 52 capable of detecting AC power output from the inverter 32 . The control unit 35 performs anomaly monitoring to determine an anomaly when the power values detected by the sensors 51a to 51d are smaller than the power values detected by the sensor 52. FIG. Then, when the power value detected by the sensors 51a to 51d is larger than the power value detected by the sensor 52 (a so-called overloaded state), the control unit 35 changes from the state in which the abnormality monitoring is performed to the state in which the abnormality monitoring is performed. switch to a state in which no

The overloaded state included in the specific condition is a state in which the power that can be generated by the solar cell 12 is greater than the amount of power that the power conditioner 11 can output. In such an overloaded state, the control unit 35 controls the PV converters 31a to 31c to suppress the power generation of the strings 12a to 12c to the amount of power that the power conditioner 11 can output. For this reason, the generated power of each string 12a to 12c may become lower than the threshold value, which may result in erroneous detection. Therefore, abnormality monitoring for each of the strings 12a to 12c is stopped (interrupted) when the string is overloaded. This suppresses erroneous detection of anomalies in the strings 12a to 12c, thereby improving the accuracy of anomaly detection for each of the strings 12a to 12c.

(3) The control unit 35 starts abnormality monitoring when the specific condition is no longer met. For example, when the commercial power system 15 recovers (recovers power) from a power failure state, the mode is changed from the isolated operation mode to the grid connection operation mode. Then, the control unit 35 resumes abnormality monitoring for each of the strings 12a to 12c. This makes it possible to detect an abnormality in each string 12a-12c.

(4) The control unit 35 starts abnormality monitoring when the specific condition is no longer met. For example, when the overloaded state disappears, the control unit 35 resumes abnormality monitoring for each of the strings 12a to 12c. This makes it possible to detect an abnormality in each string 12a-12c.

(5) The control unit 35 detects the connection state of the strings to the PV converters 31a to 31d based on the detection results of the sensors 51a to 51d. Then, the control unit 35 causes the memory 36 to store data of the detected connection state. In this way, the connection states of the strings 12a to 12d to the power conditioner 11 are automatically set. As a result, it is possible to prevent setting errors during installation and setting change errors when string connections are changed.

(6) The control unit 35 clears the data for abnormality determination stored in the memory 36, such as the comparison result and the count value, when transitioning to the standby state S11. As a result, erroneous detection of abnormality can be suppressed.

(Change example)
For example, the above embodiment can be modified as follows. The above-described embodiment and each modification below can be combined with each other as long as there is no technical contradiction. In addition, in the following modified examples, the same reference numerals as in the above embodiment are given to the parts that are common to the above embodiment, and the explanation thereof is omitted.

- You may change the structure of a power conditioner suitably with respect to the said embodiment.
FIG. 7 shows a modified power conditioner 101 . This power conditioner 101 has a bypass relay 34c added to the configuration of the above embodiment.

The bypass relay 34c is connected between the system interconnection terminal 21 and the output terminal 22 for self-sustained operation. The control unit 35 of this modification closes (turns on) the bypass relay 34c in the grid-connected operation mode, and turns the bypass relay 34c into an open state (off) in the isolated operation mode. The bypass relay 34c is an example of a switch (switch) that connects and disconnects between the system interconnection terminal 21 and the output terminal 22 for self-sustained operation. A semiconductor switch, a mechanical relay switch, or the like can be used for the bypass relay 34c, for example.

The grid connection terminal 21 is connected to the commercial power grid 15 . Therefore, in the grid-connected operation mode, commercial AC power supplied from the commercial power grid 15 is supplied from the grid-connected terminal 21 to the self-sustained operation output terminal 22 via the bypass relay 34c. This output terminal 22 for self-sustaining operation is a terminal through which the power conditioner 101 outputs AC power in the self-sustaining operation mode. Therefore, by connecting the load 17 used in the isolated operation mode to the output terminal 22 for isolated operation, commercial AC power is supplied to the load 17 also in the grid-connected operation mode. In other words, there is no need to replace the load 17 to be used in the self-sustained operation mode.

8 and 9 show a modified power conditioner 201. FIG. FIG. 9 shows the connection state of the power conditioner 201 of the modified example in the self-sustained operation mode. This power conditioner 201 has a bidirectional DC-DC converter (BDD) 37 and a storage battery 38 added to the configuration of the above embodiment.

Bi-directional DC-DC converter 37 is connected to DC voltage bus 41 . A storage battery 38 is connected to a bidirectional DC-DC converter 37 . That is, the storage battery 38 is connected to the DC voltage bus 41 via the bi-directional DC-DC converter 37 .

The storage battery 38 is a rechargeable battery (secondary battery). Storage battery 38 is, for example, a lithium ion battery.
The bidirectional DC-DC converter 37 is, for example, a step-up/step-down circuit, and converts the DC power of the DC voltage bus 41 into DC power for charging the storage battery 38 . Also, the bidirectional DC-DC converter 37 converts the DC power discharged from the storage battery 38 into power with a voltage that corresponds to the DC voltage bus 41 . The bidirectional DC-DC converter 37 includes switching elements. The control unit 35 outputs a control signal for turning on and off the switching element, and adjusts the pulse width of the control signal by, for example, a PWM method. By turning on and off the switching element according to the control signal, the bidirectional DC-DC converter 37 converts the DC power of the DC voltage bus 41 into charging power of the storage battery 38, or discharges power from the storage battery 38 to correspond to the DC voltage bus 41. converts to DC power.

The storage battery 38 has a battery management unit (BMU: battery management unit). The battery management unit calculates the amount of power stored in the storage battery 38 . The amount of electricity stored in the storage battery 38 is indicated by the SOC (State of Charge) of the storage battery 38 . The amount of electricity stored in the storage battery 38 may be indicated by, for example, a voltage value between terminals of the storage battery 38 . The battery management unit outputs a detection signal including the amount of stored electricity.

Power conditioner 201 converts the DC power generated by solar cell 12 into AC power by inverter 32 and outputs the AC power to commercial power system 15 . The power conditioner 11 also includes a storage battery 38 . The power conditioner 11 charges the storage battery 38 with DC power. The power conditioner 11 converts the DC power output from the storage battery 38 into AC power by the inverter 32 and outputs the AC power to the commercial power system 15 .

The control unit 35 controls the bidirectional DC-DC converter 37 so that the storage battery 38 is charged with the surplus power, which is the difference between the power generated by the solar cell 12 and the power consumed by the loads 16 and 17 connected to the system power line 14. , PV converters 31 a to 31 c and inverter 32 . Further, the bidirectional DC-DC converter 37 and the inverter 32 are configured to output AC power based on the discharged power of the storage battery 38 to the system power line 14 when the power consumption of the loads 16 and 17 exceeds the power generated by the solar battery 12. Control.

The power conditioner 201 charges the storage battery 38 when the power generated by the solar cell 12 is greater than the power consumed by the loads 16 and 17, thereby reducing the overloaded period. In addition, by charging the storage battery 38 with the solar battery 12, the power stored in the storage battery 38 is converted into AC power and output while the solar battery 12 cannot generate power, so that the loads 16 and 17 can be used. can be done.

- In the above embodiment, as shown in FIG. 1, one string 12a (12b, 12c) is connected to one PV converter 31a. On the other hand, a plurality of strings, such as the strings 12a and 12d shown in FIG. 1, may be connected to one PV converter 31a. In this case, each string 12a, 12d is connected to one PV converter 31a via a blocking diode. The blocking diodes prevent the strings 12a, 12d from being stressed by reverse voltages. A semiconductor switch or the like can also be used as the blocking diode. Also, three or more strings may be connected to one PV converter 31a. Although the connection to the PV converter 31a shown in FIG. 1 has been described, a plurality of strings may be connected to other PV converters 31b to 31d.

- The number of PV converters mounted on the power conditioner may be changed to an appropriate number such as 1 to 3, or 5 or more.
- The number of strings included in the solar cell 12 connected to the power conditioner 11 of the above embodiment may be changed to an appropriate number of 1 to 3, or 5 or more.

- Although control part 35 which detected a power failure was made to automatically change from grid-connected operation mode to independent operation mode in the above-mentioned embodiment, it does not restrict to this. For example, when the user instructs to change the operation mode through various interfaces, the control unit 35 may change the operation mode. As various interfaces, for example, a switch provided in the power conditioner 11, a switch provided in a controller connected to the power conditioner 11, a mobile terminal, and the like can be used.

- In the above embodiments and modifications, the power conditioners 11, 101, and 201 connected to the solar cell 12 as a power source using natural energy have been described. As a power source using natural energy, a power generator such as a solar power generator, a solar thermal power generator, a wind power generator, a gas power generator, a geothermal power generator, or a combination thereof can be used.

The above description is merely exemplary. Those skilled in the art can recognize that many more possible combinations and permutations are possible in addition to the components and methods (manufacturing processes) listed for the purpose of describing the technology of this disclosure. This disclosure is intended to cover all alternatives, variations and modifications that fall within the scope of this disclosure, including the claims.

11, 101, 201 power conditioner 12 solar cell 12a-12d solar cell string (string)
13 Photovoltaic power generation system 14 System power line 15 Commercial power system 16, 17 Load 21 System interconnection terminal 22 Isolated operation output terminal 23a to 23d Connection terminal 31a to 31d PV converter 32 Inverter 33 Filter 34a System interconnection relay 34b Isolated operation relay 34c bypass relay 35 control unit 36 memory 37 bidirectional DC-DC converter 38 storage battery 41 DC voltage bus 45 power supply circuit 51a to 51d sensor 52 sensor 53 sensor S11 standby state S12 operating state S13 non-monitoring state S14 abnormality notification

Claims (9)

a converter that converts the voltage supplied from a power source that uses natural energy;
an inverter that converts a DC voltage output from the converter into an AC voltage;
a first output terminal connected to a commercial power system;
a second output terminal;
a first switch connected between the inverter and the first output terminal;
a second switch connected between the inverter and the second output terminal;
controlling the first switch, the second switch, the converter, and the inverter, and closing the first switch and opening the second switch in a first operation mode to generate the AC voltage; is output to the first output terminal, and in the second operation mode, the first switch is opened and the second switch is closed to output the AC voltage to the second output terminal; ,
a first sensor connected to the converter and capable of detecting power;
with
The control unit performs abnormality monitoring to determine an abnormality when the first electric power value detected by the first sensor is lower than a predetermined threshold value, and performs specific conditions including being in the second operation mode. Switching from the state in which the abnormality monitoring is performed to the state in which the abnormality monitoring is not performed when
power conditioner. 2. The power conditioner according to claim 1, wherein said control unit determines that there is an abnormality when said first power value continues to be lower than said threshold value for a certain period of time. 3. The control unit according to claim 1, wherein the control unit has a memory, sequentially stores comparison results of comparing the first power value and the threshold value in the memory, and determines whether or not there is an abnormality. of inverters. 4. The power conditioner according to claim 3, wherein said control unit erases said comparison result stored in said memory when said specific condition is met. The control unit erases the comparison result stored in the memory when starting control of the inverter or when stopping the inverter.
The power conditioner according to claim 3 or 4. 6. The control unit according to any one of claims 3 to 5, wherein the control unit erases the comparison result stored in the memory when changing from the second operation mode to the first operation mode. power conditioner. A plurality of the first sensors and the converters,
The control unit determines that there is an abnormality when the detection result of each of the plurality of first sensors is lower than the threshold value.
The power conditioner according to any one of claims 1 to 6. a converter that converts the voltage supplied from a power source that uses natural energy;
an inverter that converts a DC voltage output from the converter into an AC voltage;
a first output terminal and a second output terminal;
a first switch connected between the inverter and the first output terminal;
a second switch connected between the inverter and the second output terminal;
a control unit that controls the first switch, the second switch, the converter, and the inverter;
a first sensor connected to the converter and capable of detecting power;
a second sensor capable of detecting AC power output from the inverter;
with
The control unit performs abnormality monitoring to determine an abnormality when the first power value detected by the first sensor is smaller than the second power value detected by the second sensor, and detects the second power value. switching from the state in which the abnormality monitoring is performed to the state in which the abnormality monitoring is not performed when a specific condition including a state in which the first power value is greater than the
power conditioner. The power conditioner according to any one of claims 1 to 8, wherein said control unit starts said abnormality monitoring when said specific condition is no longer met.