JP7607490B2 - Power System - Google Patents

Description

The present invention relates to a power supply system that includes a charge/discharge device that is connected to a power line that is connected to a power grid and that charges and discharges power between the power line and a solar power generation device that is connected to the power line, and a power load device that is connected to the power line.

The solar output power of a solar power generation device can increase or decrease rapidly in a short period of time, for example, depending on the weather. If the solar output power of a solar power generation device increases or decreases rapidly in a short period of time, there is a high possibility that the reverse flow power to the power grid or the received power from the power grid will increase or decrease rapidly in a short period of time.

However, if a charging/discharging device is also installed, it may be possible to reduce the increase or decrease in the reverse flow power to the power grid by increasing the discharge power or decreasing the charge power of the charging/discharging device in response to a decrease in the solar output power of the solar power generation device, or by decreasing the discharge power or increasing the charge power of the charging/discharging device in response to an increase in the solar output power of the solar power generation device.
Patent Document 1 (JP 2016-140182 A) describes a technique for smoothing out fluctuations in photovoltaic power generation by using discharge power from a storage battery.

JP 2016-140182 A

However, if the solar power generated by the solar power generation device cannot be obtained in real time, for example, if it can only be obtained at set intervals, the solar power generation power may already be fluctuating at the time information about the solar power generation power is obtained. Therefore, in a system in which the solar power generation power of the solar power generation device cannot be obtained in real time, the increase or decrease in the reverse flow power to the power grid may become too large. For example, if the solar power generation power of the solar power generation device is detected to be very low and the charging/discharging device subsequently discharges a large amount of power, if the solar power generation power of the solar power generation device has increased at that point, the reverse flow power, which is the sum of the solar power generation power of the solar power generation device and the discharge power of the charging/discharging device, may become very large.

The present invention was made in consideration of the above problems, and its purpose is to provide a power supply system that can prevent the increase or decrease in reverse flow power to the power grid from becoming too large.

A characteristic configuration of a power supply system according to the present invention for achieving the above object is a power supply system including a charge/discharge device connected to a power line connected to a power grid and charging/discharging power between the power line and the charge/discharge device, and a photovoltaic power generation device connected to the power line, and a power load device connected to the power line,
a control device that performs a reverse flow control process that acquires, for each first set time, information about a specific reverse flow power originating from the solar power generation device among reverse flow power that is assumed to be supplied from the power line to the power system when it is assumed that there is no charging power or discharging power of the charging/discharging device, acquires information about a remaining charge amount of the charging/discharging device for each second set period, and issues an operation command to the charging/discharging device by referring to the information about the specific reverse flow power and the information about the remaining charge amount;
In the reverse flow control process, the control device
When the most recent specific reverse flow power in the past is smaller than a representative value that is determined so as to increase as the remaining charge amount increases, an instruction is given to the charging/discharging device to operate in a discharge mode in which a power shortage corresponding to the shortage is discharged;
When the most recent specific reverse flow power in the past is larger than the representative value, an instruction is given to operate in a charging mode in which excess power equivalent to the excess is charged.

According to the above characteristic configuration, even if the specific reverse flow power originating from the solar power generation device increases or decreases, if the specific reverse flow power is smaller than the representative value, the charging/discharging device operates in the discharging mode, and if the specific reverse flow power is larger than the representative value, the charging/discharging device operates in the charging mode. As a result, the reverse flow power supplied to the power grid from the charging/discharging device and the solar power generation device becomes a value close to the representative value, and the increase or decrease is prevented from becoming too large.
Furthermore, the larger the remaining charge, the larger the representative value, and the smaller the remaining charge, the smaller the representative value, so that the larger the remaining charge, the more the charging/discharging device operates in a manner that does not increase the remaining charge, and the smaller the remaining charge, the more the charging/discharging device operates in a manner that does not decrease the remaining charge. As a result, it is possible to prevent the remaining charge of the charging/discharging device from becoming too high or too low.

Another characteristic feature of the power supply system of the present invention is that the representative value is determined as a value obtained by correcting the average value of the specific reverse flow power included in a specified calculation period in the most recent past so that the larger the remaining charge, the larger the value becomes.

According to the above characteristic configuration, the representative value is determined using the average value of the specific reverse flow power included in a specified calculation period in the most recent past, so the representative value will not deviate significantly from the actual specific reverse flow power.

A further characteristic feature of the power supply system according to the present invention is that the representative value is determined in such a manner that the greater the remaining charge is, the larger the representative value is, and the closer the time period including sunset is, the smaller the representative value is.
Here, the representative value may be determined as a value obtained by correcting the average value of the specific reverse flow power included in a specified calculation period in the most recent past so that the larger the remaining charge is, the larger the value becomes, and the smaller the value becomes as the time period including sunset approaches.

According to the above characteristic configuration, the greater the remaining charge, the greater the representative value, and the smaller the remaining charge, the smaller the representative value. Therefore, the greater the remaining charge, the greater the possibility that the specific reverse flow power will be smaller than the representative value, and therefore the charge/discharge device will be more likely to operate in discharge mode. Also, the smaller the remaining charge, the greater the possibility that the specific reverse flow power will be larger than the representative value, and therefore the charge/discharge device will be more likely to operate in charge mode. As a result, it is possible to prevent the remaining charge of the charge/discharge device from becoming too high or too low.

Furthermore, since the solar power generated by the solar power generation device becomes zero after sunset, it is preferable that the remaining charge of the charge/discharge device is large before the time period that includes sunset.
In this characteristic configuration, the representative value becomes smaller as the time period including sunset approaches, so that when the charging/discharging device operates in a discharging mode, the discharge power becomes small, and when the charging/discharging device operates in a charging mode, the charge power becomes large. In other words, the closer the time period including sunset approaches, the larger the remaining charge of the charging/discharging device becomes, and it can be expected that there will be more opportunities to utilize the remaining charge of the charging/discharging device after sunset.
Furthermore, when the representative value is determined using the average value of the specific reverse flow power included in a specified calculation period in the most recent past, the representative value will not deviate significantly from the actual specific reverse flow power.

FIG. 1 is a diagram illustrating a configuration of a power supply system. FIG. 4 is a diagram illustrating the contents of a reverse power flow control process. FIG. 4 is a diagram illustrating the contents of a reverse power flow control process. 10 is a graph showing a correction value determined according to a remaining charge amount. FIG. 4 is a diagram illustrating the contents of a reverse power flow control process. FIG. 4 is a diagram illustrating the contents of a reverse power flow control process. 11 is a graph showing a simulation result of reverse flow power supplied from a power line to a power grid. 4 is a graph showing a change in the remaining charge of a charge/discharge device. 10 is a graph showing a correction value determined according to a remaining charge amount and a time.

First Embodiment
A power supply system according to a first embodiment of the present invention will be described below with reference to the drawings.
Fig. 1 is a diagram showing the configuration of a power supply system. As shown in the figure, the power supply system includes a charge/discharge device 10, a solar power generation device 30, and a control device 7. In addition, the power supply system of this embodiment also includes a fuel cell device 20. In the example shown in Fig. 1, the charge/discharge device 10 is connected to a first connection point 4 of a power line 2 connected to a power grid 1, the solar power generation device 30 is connected to a second connection point 5 of the power line 2, and the fuel cell device 20 and a power load device 3 are connected to a third connection point 6 of the power line 2.

The charging/discharging device 10 is connected to a power line 2 that is connected to a power system 1, and charges and discharges power between the charging/discharging device 10 and the power line 2. Specifically, the charging/discharging device 10 includes a charging/discharging unit 12, a power conversion unit 11 that adjusts the charging power to the charging/discharging unit 12 and the discharging power from the charging/discharging unit 12, a charging/discharging control unit 13 that controls the operation of the power conversion unit 11, and a storage unit 14 that stores information handled by the charging/discharging device 10. The charging/discharging unit 12 includes, for example, a storage battery. The charging/discharging control unit 13 can adjust the discharging power and charging power to the power line 2 between a predetermined upper limit discharging power and an upper limit charging power.

In addition, information about the power measured by the power measurement unit 8 is transmitted to the charging/discharging device 10. The power measured by the power measurement unit 8 is the power received from the power grid 1 or the reverse flow power to the power grid 1.

The solar power generation device 30 includes a solar cell unit 32, a power conversion unit 31 that converts the power generated by the solar cell unit 32 into a predetermined voltage, frequency, and phase and supplies it to the power line 2, a solar power generation control unit 33 that controls the operation of the power conversion unit 31, and a storage unit 34 that stores information handled by the solar power generation device 30. The solar power generation control unit 33 can adjust the solar power generation power supplied to the power line 2 by controlling the operation of the power conversion unit 31. For example, the solar power generation control unit 33 can also operate the power conversion unit 31 to perform maximum power tracking control.

The fuel cell device 20 includes a fuel cell section 22, a power conversion section 21 that converts the power generated by the fuel cell section 22 into a predetermined voltage, frequency, and phase and supplies it to the power line 2, a fuel cell control section 23 that controls the operation of the fuel cell section 22 and the power conversion section 21, and a memory section 24 that stores information handled by the fuel cell device 20. The fuel cell device 20 may also include a fuel reformer that generates hydrogen, which is the fuel gas for the fuel cell section 22.

The fuel cell control unit 23 can adjust the output power from the fuel cell device 20 to the power line 2 between a predetermined upper limit output power and a predetermined lower limit output power. For example, the fuel cell control unit 23 can maintain the output power of the fuel cell device 20 at the upper limit output power to operate it continuously.

In addition, information about the power measured by the power measurement unit 9 is transmitted to the fuel cell device 20. The power measured by the power measurement unit 9 is the power obtained by subtracting the output power of the fuel cell device 20 from the load power of the power load device 3, which is, for example, a residential load such as lighting equipment and air conditioning equipment. In other words, when the load power is greater than the output power of the fuel cell device 20, the sign of the power measured by the power measurement unit 9 is positive, when the load power is smaller than the output power of the fuel cell device 20, the sign of the power measured by the power measurement unit 9 is negative, and when the load power is the same as the output power of the fuel cell device 20, the power measured by the power measurement unit 9 is zero. The fuel cell control unit 23 can also operate the fuel cell device 20 so that the output power of the fuel cell device 20 follows the load power of the power load device 3. For example, the fuel cell control unit 23 can operate the fuel cell device 20 so that the output power of the fuel cell device 20 follows the load power of the power load device 3 by adjusting the output power of the fuel cell device 20 so that the power measured by the power measurement unit 9 (i.e., the power supplied from the power grid 1) becomes zero.

The control device 7 can communicate information between the charge/discharge device 10, the solar power generation device 30, and the fuel cell device 20. In this embodiment, the control device 7 acquires information about the reverse flow power P1 measured by the power measurement unit 8 and information about the discharge power P2 output from the charge/discharge device 10 to the power line 2 from the charge/discharge device 10, acquires information about the solar power generation power P3 output from the solar power generation device 30 to the power line 2 from the solar power generation device 30, and acquires information about the supply power P4 measured by the power measurement unit 9 from the fuel cell device 20.

The reverse flow power P1 is derived by subtracting the supply power P4 from the sum of the discharge power P2 and the solar power generation power P3. In other words, P1 = P2 + P3 - P4. In this embodiment, the fuel cell device 20 is performing load following operation, that is, an operation in which the output power of the fuel cell device 20 is adjusted so that the power measured by the power measurement unit 9 (i.e., the power supplied from the power grid 1) becomes zero, so P4 = 0.

The control device 7 acquires (i.e., derives) information on the specific reverse flow power originating from the solar power generation device 30 among the reverse flow power assumed to be supplied from the power line 2 to the power system 1 if it is assumed that there is no charging power or discharging power of the charging/discharging device 10 at every first set time (e.g., every minute). In this embodiment, since the solar power generation device 30 and the fuel cell device 20 are connected to the power line 2, the reverse flow power assumed to be supplied from the power line 2 to the power system 1 if it is assumed that there is no charging power or discharging power of the charging/discharging device 10 is "P3-P4". If P4 is a positive value, that is, if there is no reverse flow power originating from the fuel cell device 20, the specific reverse flow power originating from the solar power generation device 30 is "P3-P4". On the other hand, if P4 is a negative value, that is, if there is reverse flow power originating from the fuel cell device 20, the specific reverse flow power originating from the solar power generation device 30 is "P3". The control device 7 then acquires information about the remaining charge of the charge/discharge device 10 for each second set period, and performs reverse flow control processing to issue an operation command to the charge/discharge device 10 by referring to information about the specific reverse flow power and information about the remaining charge.

Specifically, in the reverse flow control process, if the most recent specific reverse flow power in the past is smaller than a representative value that is determined so that the larger the remaining charge, the greater the power reserve, the control device 7 instructs the charging/discharging device 10 to operate in a discharge mode in which the shortage power corresponding to the shortage is discharged, and if the most recent specific reverse flow power in the past is greater than the representative value, the control device 7 instructs the charging/discharging device 10 to operate in a charge mode in which the excess power corresponding to the excess is charged.

[Discharge mode]
2 and 3 are diagrams illustrating a case where the charging/discharging device 10 operates in a discharge mode. As shown in the figures, the control device 7 determines and stores the specific reverse flow power originating from the solar power generation device 30 every minute. In the figures, the specific reverse flow power originating from the solar power generation device 30 is described as "photovoltaic power generation portion". In this embodiment, since P4=0, the specific reverse flow power originating from the solar power generation device 30 is the solar power generation power P3. Then, the control device 7 determines a representative value at the timing of the reverse flow control process for each second set period. The control device 7 determines the representative value to be a value obtained by correcting the average value of the specific reverse flow power included in a predetermined calculation period (e.g., 60 minutes) in the most recent past so that the larger the remaining charge, the larger the value becomes. In FIGS. 2 and 3, the bar graphs shown in time before the timing of the reverse flow control process are the specific reverse flow power originating from the solar power generation device 30, and the control device 7 derives the average value of the specific reverse flow power from these values.

Figure 4 is a graph showing the correction value determined according to the remaining charge. The control device 7 derives the representative value by subtracting the correction value from the average value of the specific reverse flow power, i.e., by the formula "representative value = average value of specific reverse flow power - correction value". As shown in the figure, the correction value is set to be smaller as the remaining charge: SOC (state of charge) increases. In other words, the representative value increases as the remaining charge increases. For example, the average value of the specific reverse flow power shown in Figures 2 and 3 is the same, but in the case of Figure 2, the correction value is small because the remaining charge is large, and in the case of Figure 3, the correction value is large because the remaining charge is small. Therefore, the representative value is larger in the example shown in Figure 2 (i.e., when the remaining charge is large) than in the example shown in Figure 3.

Then, because the most recent specific reverse flow power shown at time t0 is smaller than the representative value, the control device 7 instructs the charging/discharging device 10 to operate in a discharge mode to discharge the shortage power corresponding to the shortage. In the case shown in FIG. 2, the remaining charge is large, so the discharge power instructed to the charging/discharging device 10 is large. In contrast, in the case shown in FIG. 3, the remaining charge is small, so the discharge power instructed to the charging/discharging device 10 is small.

[Charging mode]
5 and 6 are schematic diagrams illustrating the case where the charging/discharging device 10 operates in the charging mode. The average values of the specific reverse flow power shown in Fig. 5 and Fig. 6 are the same, but the correction value is small in Fig. 5 because the remaining charge is large, and the correction value is large in Fig. 6 because the remaining charge is small. Therefore, the representative value is larger in the example shown in Fig. 5 (i.e., when the remaining charge is large) than in the example shown in Fig. 6.

Then, because the most recent specific reverse flow power shown at time t0 is greater than the representative value, the control device 7 instructs the charging/discharging device 10 to operate in a charging mode in which the excess power corresponding to the excess is charged. Figures 5 and 6 show a state in which a portion of the photovoltaic power generation amount (specific reverse flow power) is charged by the charging power of the charging/discharging device 10 after the reverse flow control processing timing. The portion of the photovoltaic power generation amount after the reverse flow control processing timing shown by the dashed line is the power amount charged by the charging/discharging device 10. In the case shown in Figure 5, the remaining charge amount is large, so the charging power instructed to the charging/discharging device 10 is small. In contrast, in the case shown in Figure 6, the remaining charge amount is small, so the charging power instructed to the charging/discharging device 10 is large.

7 is a graph showing a simulation result of reverse flow power supplied from the power line 2 to the power system 1. In the figure, a 5-minute moving average value is shown.
Example 1 shows the reverse flow power when the charge/discharge device 10 and the fuel cell device 20 are not installed, and only the photovoltaic power generation device 30 and the power load device 3 are installed. That is, in Example 1, when the photovoltaic power generation power of the photovoltaic power generation device 30 is larger than the load power of the power load device 3, the surplus power is reverse flowed to the power grid 1.
Example 2 shows the reverse flow power when the fuel cell device 20 is not installed, but the photovoltaic power generation device 30, the charging/discharging device 10, and the power load device 3 are installed. The charging/discharging device 10 is set so that when the photovoltaic power generated by the photovoltaic power generation device 30 is greater than the load power of the power load device 3, the charging/discharging device 10 charges the entire surplus power, and when the photovoltaic power generated by the photovoltaic power generation device 30 is less than the load power, the charging/discharging device 10 discharges the entire shortage power. When the remaining charge of the charging/discharging device 10 reaches an upper limit, the charging of the surplus power is stopped, and the surplus power is reverse flowed to the power grid 1.
Example 3 shows the reverse flow power when the controller 7 performs the above-described reverse flow control process.

As can be seen from FIG. 7, in the case of Example 1 where the charging/discharging device 10 is not installed, the reverse flow power increases and decreases abruptly. In addition, in the case of Example 2, when the remaining charge of the charging/discharging device 10 reaches the upper limit before 11:00, the charging/discharging device 10 stops charging, so the reverse flow power increases abruptly. In addition, after the remaining charge of the charging/discharging device 10 reaches the upper limit, the charging/discharging device 10 does not charge surplus power, so the reverse flow power in Examples 1 and 2 shows similar changes. Example 3 is preferable in that there is no sudden fluctuation in the reverse flow power throughout the day. In other words, it is possible to suppress a large increase or decrease in the reverse flow power to the power grid 1.

Figure 8 is a graph showing the progress of the remaining charge of the charge/discharge device 10 in Example 2 shown in Figure 7 and the progress of the remaining charge of the charge/discharge device 10 in Example 3 shown in Figure 7. As shown in the figure, in the case of Example 3, the remaining charge is also sufficiently large, and the power supply capacity from the charge/discharge device 10 is sufficiently secured.

As described above, even if the specific reverse flow power originating from the solar power generation device 30 increases or decreases, if the specific reverse flow power is smaller than the representative value, the charging/discharging device 10 operates in the discharge mode, and if the specific reverse flow power is larger than the representative value, the charging/discharging device 10 operates in the charge mode. As a result, the reverse flow power supplied to the power system 1 from the charging/discharging device 10 and the solar power generation device 30 becomes closer to the representative value, and the increase or decrease is prevented from becoming too large. Furthermore, the larger the remaining charge of the charging/discharging device 10, the larger the representative value becomes, and the smaller the remaining charge, the smaller the representative value becomes. Therefore, the larger the remaining charge, the more the charging/discharging device 10 operates without increasing the remaining charge, and the smaller the remaining charge, the more the charging/discharging device 10 operates without decreasing the remaining charge. As a result, it is possible to prevent the remaining charge of the charging/discharging device 10 from becoming too large or too small.

Second Embodiment
The power supply system of the second embodiment differs from the above-mentioned embodiment in the method of determining the representative value. The power supply system of the second embodiment will be described below, but a description of the same configuration as the above-mentioned embodiment will be omitted.

In this embodiment, in the reverse flow control process, if the most recent specific reverse flow power in the past is smaller than a representative value that is determined so that the larger the remaining charge, the greater the power reserve, the control device 7 instructs the charging/discharging device 10 to operate in a discharge mode in which the shortage power corresponding to the shortage is discharged, and if the most recent specific reverse flow power in the past is greater than the representative value, the control device 7 instructs the charging/discharging device 10 to operate in a charge mode in which the excess power corresponding to the excess is charged.

In this embodiment, the representative value is determined so that it is larger the greater the remaining charge and smaller the closer to the time period including sunset. Specifically, the control device 7 determines the representative value to be a value obtained by correcting the average value of the specific reverse flow power included in a specified calculation period in the most recent past so that it is larger the greater the remaining charge and smaller the closer to the time period including sunset. The control device 7 stores the time period including sunset in advance. In this embodiment, sunset itself is used as the "time period including sunset."

Figure 9 is a graph showing the correction value determined according to the remaining charge and time. As shown in the figure, the correction value is set to be larger as the remaining charge (SOC: state of charge) decreases and as the time approaches sunset. If the remaining charge is the same, the correction value is largest for the period from 13:00 to sunset, which is closest to sunset, and the correction value is smallest for the period from sunset to midnight, and from midnight to 10:00 the next day, which is farthest from sunset. The control device 7 then subtracts the correction value from the average value of the specific reverse flow power to derive the representative value, that is, using the formula "representative value = average value of specific reverse flow power - correction value". In other words, the larger the remaining charge, the larger the representative value, and the closer to sunset, the smaller the representative value.

In this way, the representative value becomes smaller as the time period including sunset approaches, so that when the charge/discharge device 10 operates in discharge mode, the discharge power is small, and when the charge/discharge device 10 operates in charge mode, the charge power is large. In other words, the closer the time period including sunset approaches, the larger the remaining charge of the charge/discharge device 10 becomes, and it can be expected that there will be more opportunities to utilize the remaining charge of the charge/discharge device 10 after sunset.

<Another embodiment>
＜1＞
In the above embodiment, specific examples of the configuration of the power supply system have been given and explained, but the configuration can be changed as appropriate.
For example, in the above embodiment, an example has been described in which the power supply system includes the fuel cell device 20, but the power supply system does not necessarily have to include the fuel cell device 20.

＜2＞
In the above embodiment, several examples of the correction value are shown, but they are described for illustrative purposes and can be changed as appropriate. For example, in Fig. 4 and Fig. 9, an example in which the correction value is continuously determined according to the remaining charge of the charge/discharge device 10 is described, but the correction value may be determined stepwise according to the remaining charge of the charge/discharge device 10, for example, by applying correction value A when the remaining charge is 0% or more and less than 30%, applying correction value B when the remaining charge is 30% or more and less than 60%, and applying correction value C when the remaining charge is 60% or more and less than 100%.

＜3＞
The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided that no contradiction arises. Furthermore, the embodiments disclosed in this specification are illustrative, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention.

The present invention can be used in a power supply system that can prevent excessive increases and decreases in reverse flow power to the power grid.

1 Power system 2 Power line 3 Power load device 7 Control device 10 Charging/discharging device 30 Photovoltaic power generation device

Claims (4)

A power supply system including a charge/discharge device connected to a power line connected to a power grid and charging/discharging power between the charge/discharge device and the power line, and a solar power generation device connected to the power line, the power supply system including a power load device connected to the power line,
a control device that performs a reverse flow control process that acquires, for each first set time, information about a specific reverse flow power originating from the solar power generation device among reverse flow power that is assumed to be supplied from the power line to the power system when it is assumed that there is no charging power or discharging power of the charging/discharging device, acquires information about a remaining charge amount of the charging/discharging device for each second set period, and issues an operation command to the charging/discharging device by referring to the information about the specific reverse flow power and the information about the remaining charge amount;
In the reverse flow control process, the control device
When the most recent specific reverse flow power in the past is smaller than a representative value that is determined so as to increase as the remaining charge amount increases, an instruction is given to the charging/discharging device to operate in a discharge mode in which a power shortage corresponding to the shortage is discharged;
The power supply system is configured to, when the most recent past specific reverse flow power is greater than the representative value, give an instruction to operate in a charging mode in which excess power equivalent to the excess is charged. The power supply system according to claim 1, wherein the representative value is determined as a value obtained by correcting the average value of the specific reverse flow power included in a specified calculation period in the most recent past so that the larger the remaining charge, the larger the value. The power supply system according to claim 1, wherein the representative value is determined so that it is larger as the remaining charge increases and is smaller as the time period including sunset approaches. The power supply system according to claim 3, wherein the representative value is determined as a value obtained by correcting the average value of the specific reverse flow power included in a specified calculation period in the most recent past so that the larger the remaining charge is, the larger the value becomes, and the closer the time period including the sunset is, the smaller the value becomes.

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