JP2022061672A - Controller - Google Patents

Abstract

To implement a storage battery controller capable of establishing both of management of DC bus bar voltage and management of a charging rate of a storage battery in a DC power distribution system.SOLUTION: A controller (30) comprises: an SOC acquisition unit (31) for acquiring a charging rate of a storage battery; a DC bus bar voltage acquisition unit (32) for acquiring DC bus bar voltage; a charge/discharge power determination unit (33) for determining charge power or discharge power for the storage battery depending on the charging rate and the DC bus bar voltage; and a charge/discharge control unit (34) for controlling the storage battery according to the charge power or discharge power determined by the charge/discharge power determination unit.SELECTED DRAWING: Figure 2

Description

The present invention relates to a control device for controlling charging / discharging of a storage battery included in a DC power distribution system.

Patent Document 1 discloses a control device for a storage battery attached to a DC transmission system including a DC transmission line and a plurality of AC / DC converters connected to the DC transmission line. The control device includes a comparison determination unit, a control unit, and an SOC management unit (first and second). The comparison determination unit compares the DC voltage of the DC transmission line with the preset dead zone. The control unit generates a command to the storage battery when the DC voltage of the DC transmission line deviates from the dead zone. The SOC management unit controls the charge / discharge of the storage battery by changing the DC voltage command value of the AC / DC converter or the upper limit or the lower limit of the dead zone according to the charge rate of the storage battery.

Japanese Unexamined Patent Publication No. 2017-11855

However, the control device disclosed in Patent Document 1 has a problem that it cannot be applied to a DC power transmission system in which a device capable of voltage control does not exist other than a storage battery.

One aspect of the present invention is to realize a storage battery control device capable of achieving both management of a DC bus voltage using a storage battery and appropriate management of the charge rate of the storage battery in a DC power distribution system. And.

In order to solve the above problems, the control device according to one aspect of the present invention has a charge rate acquisition unit that acquires the charge rate of the storage battery interconnected to the DC distribution system, and a DC bus voltage of the DC distribution system. The DC bus voltage acquisition unit to be acquired, the charge / discharge power determination unit that determines the charge power or discharge power of the storage battery according to the charge rate and the DC bus voltage, and the charge determined by the charge / discharge power determination unit. A charge / discharge control unit that controls charging or discharging of the storage battery according to electric power or discharging power is provided.

The control device according to each aspect of the present invention may be realized by a computer, and in this case, the control device is realized by the computer by operating the computer as each part (software element) included in the control device. The control program of the control device and the computer-readable recording medium on which it is recorded also fall within the scope of the present invention.

According to one aspect of the present invention, in a DC power distribution system, it is possible to realize a storage battery control device capable of achieving both management of a DC bus voltage using a storage battery and appropriate management of the charge rate of the storage battery. Can be done.

It is a figure which shows the structure of the DC power distribution system to which the control device which concerns on embodiment is applied. It is a figure which shows the structure of the control device which concerns on embodiment. It is a figure which shows the example which the charge / discharge power determination part determines whether the charge power or the discharge power is determined according to the SOC of a storage battery. It is a graph which shows the specific example of the charge power and the discharge power which a charge / discharge power determination part determines when a DC bus voltage is more than a voltage lower limit value and is not more than a voltage upper limit value. It is a flowchart which shows an example of the process in the control apparatus which concerns on embodiment. It is a flowchart which shows the specific example of the 1st charge / discharge voltage determination process and the 2nd charge / discharge voltage determination process shown in FIG. It is a flowchart which shows the specific example of the 3rd charge / discharge voltage determination process shown in FIG. It is a figure which shows the operation of each part of the DC distribution system which concerns on this embodiment, and the DC distribution system of a comparative example when the SOC is larger than 90%. It is a figure which shows the operation of each part of the DC distribution system which concerns on this embodiment, and the DC distribution system of a comparative example in the case where SOC is 40% or more and 60% or less. It is a figure which shows the operation of each part of the DC distribution system which concerns on this embodiment, and the DC distribution system of a comparative example when the SOC is less than 10%. It is a figure which shows the operation of each part of the DC distribution system which concerns on this embodiment, and the DC distribution system of a comparative example, when SOC is 10% or more and less than 40%. It is a figure which shows the operation of each part of the DC distribution system which concerns on this embodiment, and the DC distribution system of a comparative example in the case where the SOC is larger than 60% and is 90% or less.

Hereinafter, one embodiment of the present invention will be described in detail.

(Configuration of DC power distribution system 1)
FIG. 1 is a diagram showing a configuration of a DC power distribution system 1 to which the control device 30 according to the present embodiment is applied. As shown in FIG. 1, the DC power distribution system 1 includes a commercial power supply 10, a storage battery 20, a control device 30, a solar cell panel 40, a DC bus 50, and a DC load 60.

The commercial power source 10 supplies electric power to the direct current bus 50 by AC (Alternating Current). The commercial power supply 10 is connected to the direct current bus 50 via a transformer 11, an AC-DC (Direct Current) converter 12, and a breaker 13. The transformer 11 transforms the AC voltage input from the commercial power source 10. The AC-DC converter 12 converts the AC input from the transformer 11 into DC and outputs it. Further, the DC power distribution system 1 may include a rectifier circuit instead of the AC-DC converter 12. The breaker 13 cuts off between the AC-DC converter 12 and the DC bus 50 when the DC current input from the AC-DC converter 12 becomes excessive.

The DC bus 50 is a power line that supplies power supplied from the commercial power source 10, the storage battery 20, and the solar cell panel 40 to the DC load 60. In the example shown in FIG. 1, two loads 61 and 62 are shown as the DC load 60. However, the number of DC loads 60 in the DC distribution system 1 may be 1 or 3 or more.

The storage battery 20 holds electric power as energy inside, and supplies the held energy to the DC bus 50 by DC as needed. The storage battery 20 may be connected to the DC bus 50 via the breaker 21 and the DC-DC converter 22. The breaker 21 cuts off between the storage battery 20 and the DC bus 50 when the DC current input from the storage battery 20 becomes excessive. The DC-DC converter 22 converts the voltage of DC input from the storage battery 20 and outputs it to the DC bus 50 based on the command value input from the control device 30, or DC input from the DC bus 50. Is converted and output to the storage battery 20.

The storage battery 20 may be a device including a secondary battery such as a lithium ion battery, a NaS (sodium-sulfur) battery, a redox flow battery, and a lead storage battery. However, the storage battery 20 is not limited to the device including the secondary battery. As the storage battery 20, any unit having a function of storing electric energy, such as a capacitor, a superconducting power storage unit, a flywheel type power storage unit, and a compressed air type power storage unit, can be used.

The control device 30 controls the charging / discharging of the storage battery 20. The specific configuration of the control device 30 will be described later.

The solar cell panel 40 supplies the electric power generated according to the amount of solar radiation to the DC bus 50 by DC. The solar cell panel 40 is connected to the DC bus 50 via the DC-DC converter 41. The DC-DC converter 41 converts and outputs the DC voltage input from the solar cell panel 40.

(Configuration of control device 30)
FIG. 2 is a diagram showing a configuration of a control device 30 according to the present embodiment. As shown in FIG. 2, the control device 30 includes an SOC (State Of Charge) acquisition unit (charge rate acquisition unit) 31, a direct current bus voltage acquisition unit 32, a charge / discharge power determination unit 33, and a charge / discharge control unit 34. And prepare.

The SOC acquisition unit 31 acquires the SOC (charge rate) of the storage battery 20 connected to the DC power distribution system 1. The SOC is the ratio of the amount of electric power charged in the storage battery 20 to the maximum value of the amount of electric power that can be charged in the storage battery 20. The SOC acquisition unit 31 outputs a signal indicating SOC to the charge / discharge power determination unit 33. The DC bus voltage acquisition unit 32 acquires the DC bus voltage. The DC bus voltage is the voltage at the DC bus 50. The DC bus voltage acquisition unit 32 is connected to the DC bus 50 via a DC bus voltage detection transformer 51 for detecting the DC bus voltage. The DC bus voltage acquisition unit 32 outputs a signal indicating the DC bus voltage to the charge / discharge power determination unit 33.

The charge / discharge power determination unit 33 determines the charge power or the discharge power of the storage battery 20 according to the SOC of the storage battery 20 and the DC bus voltage in the DC bus 50. The charge / discharge power determination unit 33 outputs the determined charge power or discharge power to the charge / discharge control unit 34.

Note that FIG. 2 shows a specific example of the circuit constituting the charge / discharge power determination unit 33. In the example shown in FIG. 2, the charge / discharge power determination unit 33 includes a power determination unit 331 and a fluctuation suppression unit 332. The power determination unit 331 determines the charge power or the discharge power based on the SOC. The fluctuation suppression unit 332 suppresses the charge power or the discharge power determined by the power determination unit 331 according to the DC bus voltage. However, the configuration of the charge / discharge power determination unit 33 is not limited to the example shown in FIG.

The charge / discharge control unit 34 controls charging or discharging of the storage battery 20 according to the charging power or discharging power determined by the charging / discharging power determining unit 33. Specifically, the charge / discharge control unit 34 generates a command value for controlling the DC-DC converter 22 so that charging or discharging is performed according to the charging power or discharging power determined by the charging / discharging power determining unit 33. And output to the DC-DC converter 22.

The permissible fluctuation range of the DC bus 50 in the DC distribution system 1 from the rated DC bus voltage is determined. The permissible fluctuation range is, for example, ± 10%. The lower limit of the allowable DC bus voltage is referred to as the lower voltage limit. Further, the upper limit value of the allowable DC bus voltage is referred to as a voltage upper limit value. The value between the lower limit voltage value and the upper limit voltage value is the rated DC bus voltage, which is called the voltage target value. In the present embodiment, the voltage target value is a value at the center of the voltage lower limit value and the voltage upper limit value. When the DC bus voltage is equal to or greater than the lower limit of the voltage and equal to or less than the upper limit of the voltage, the charge / discharge power determination unit 33 determines the charge power or the discharge power according to the SOC. However, the charge / discharge power determination unit 33 suppresses the charging power according to the SOC of the storage battery 20 when the DC bus voltage is equal to or higher than the lower limit of the voltage and less than the voltage target value, as compared with the case where the DC bus voltage is the voltage target value. The value is set. As a result, it is possible to suppress a decrease in the DC bus voltage due to charging and increase the SOC. Further, the charge / discharge power determination unit 33 suppresses the discharge power according to the SOC of the storage battery 20 when the DC bus voltage exceeds the voltage target value and is equal to or lower than the voltage upper limit value than when the DC bus voltage is the voltage target value. The value is set. As a result, it is possible to suppress an increase in the DC bus voltage due to discharge and reduce the SOC. Therefore, it is possible to achieve both the DC bus voltage and the appropriate management of the SOC.

Further, the charge / discharge power determination unit 33 sets the charging power to 0 when the DC bus voltage is equal to or higher than the voltage lower limit value and equal to or lower than the voltage upper limit value, and the SOC is equal to or higher than the preset first threshold value. Further, the charge / discharge power determination unit 33 sets the discharge power to 0 when the SOC is equal to or less than the second threshold value larger than the first threshold value. That is, when the SOC is equal to or greater than the first threshold value and equal to or less than the second threshold value, the charge / discharge power determination unit 33 determines that both the charge power and the discharge power are 0. The first threshold and the second threshold are the lower and upper limits of the appropriate range of SOC in the storage battery 20. The first threshold and the second threshold are appropriately determined in consideration of the range of SOC that requires charging or discharging. Therefore, if both the DC bus voltage and the SOC are in the proper range, that state can be maintained.

Further, the charge / discharge power determination unit 33 sets the charge power to a value other than 0 when the DC bus voltage exceeds the voltage upper limit value and the SOC is equal to or less than the SOC upper limit value (charge rate upper limit value). The SOC upper limit value is an SOC upper limit value that allows the storage battery 20 to be charged. As a result, the control device 30 can reduce the DC bus voltage. However, when the SOC exceeds the SOC upper limit value, the charge / discharge power determination unit 33 gives priority to the SOC control and sets the charging power to 0 even when the DC bus voltage exceeds the voltage upper limit value.

Further, the charge / discharge power determination unit 33 sets the discharge power to a value other than 0 when the DC bus voltage is less than the voltage lower limit value and the SOC is equal to or higher than the SOC lower limit value (charge rate lower limit value). The SOC lower limit value is an SOC upper limit value that allows discharge from the storage battery 20. As a result, the control device 30 can increase the DC bus voltage. However, when the SOC is less than the SOC lower limit value, the charge / discharge power determination unit 33 gives priority to the SOC control and sets the discharge power to 0 even when the DC bus voltage is less than the voltage lower limit value. ..

(SOC classification)
FIG. 3 is a diagram showing an example of whether the charge / discharge power determination unit 33 determines whether the charge power or the discharge power is determined according to the SOC of the storage battery 20. In the example shown in FIG. 3, the first threshold value is 40% and the second threshold value is 60%. The SOC lower limit is 10%, and the SOC upper limit is 90%. In the example shown in FIG. 3, the SOC is divided into five regions 101 to 105 with these values as boundaries.

The region 101, that is, the region where the SOC exceeds 90% will be described below. When the DC bus voltage is equal to or lower than the voltage upper limit value, the charge / discharge power determination unit 33 determines the discharge power to a value corresponding to the DC bus voltage. At this time, when the DC bus voltage exceeds the voltage target value, the charge / discharge power determination unit 33 sets the value to suppress the discharge power as compared with the case where the DC bus voltage is the voltage target value. As a result, it is possible to avoid a situation in which the DC bus voltage rises beyond the voltage upper limit value. Further, when the DC bus voltage exceeds the voltage upper limit value, the charge / discharge power determination unit 33 only sets the discharge power to 0, does not charge for lowering the DC bus voltage, and discharges the DC bus. not. That is, in the region 101, the charge / discharge power determination unit 33 prioritizes the management of the SOC over the management of the DC bus voltage because the SOC is higher than the SOC upper limit value.

The region 102, that is, the region where the SOC is more than 60% and 90% or less will be described below. The charge / discharge power determination unit 33 determines the discharge power to a value according to the SOC when the DC bus voltage is equal to or lower than the voltage upper limit value. However, the charge / discharge power determination unit 33 sets the discharge power to a value suppressed when the DC bus voltage exceeds the voltage target value and is equal to or less than the voltage upper limit value, as compared with the case where the DC bus voltage is the voltage target value. do. As a result, it is possible to avoid a situation in which the DC bus voltage rises beyond the voltage upper limit value. On the other hand, the charge / discharge power determination unit 33 determines the charge power to a value other than 0 when the DC bus voltage exceeds the voltage upper limit value. That is, in the region 102, the charge / discharge power determination unit 33 determines or suppresses the suppressed discharge power by giving priority to the control of the DC bus voltage over the SOC when the DC bus voltage exceeds the voltage target value. Determine the charging power that is not available.

Region 103, that is, a region having an SOC of 40% or more and 60% or less will be described below. When the DC bus voltage is equal to or greater than the lower limit value and equal to or less than the upper limit value, the charge / discharge power determination unit 33 sets both the charge power and the discharge power to 0. Further, when the DC bus voltage exceeds the voltage upper limit value, the charge / discharge power determination unit 33 sets the charge power to a value other than 0. Further, the charge / discharge power determination unit 33 sets the discharge power to a value other than 0 when the DC bus voltage is less than the voltage lower limit value. That is, in the region 103, the charge / discharge power determination unit 33 puts the storage battery 20 on standby when the DC bus voltage is equal to or greater than the lower limit value and equal to or less than the upper limit value. Further, the charge / discharge power determination unit 33 determines the charge power or the discharge power by giving priority to the control of the DC bus voltage over the SOC when the DC bus voltage exceeds the voltage upper limit value or is less than the voltage lower limit value. ..

Region 104, i.e., a region having an SOC of 10% or more and less than 40% will be described below. The charge / discharge power determination unit 33 determines the charge power to a value according to the SOC when the DC bus voltage is equal to or higher than the lower voltage limit value. However, the charge / discharge power determination unit 33 sets the charging power to a value suppressed when the DC bus voltage is equal to or higher than the voltage lower limit value and less than the voltage target value, as compared with the case where the DC bus voltage is the voltage target value. This makes it possible to avoid a situation in which the DC bus voltage drops below the lower limit of the voltage. On the other hand, the charge / discharge power determination unit 33 determines the discharge power to a value other than 0 when the DC bus voltage is less than the lower limit of the voltage. That is, in the region 104, when the DC bus voltage is less than the voltage target value, the charge / discharge power determination unit 33 gives priority to the control of the DC bus voltage over the SOC and determines the suppressed charge power or discharge power. decide.

The region 105, that is, the region where the SOC is less than 10%, will be described below. When the DC bus voltage is equal to or higher than the lower voltage limit value, the charge / discharge power determination unit 33 determines the charging power to a value corresponding to the DC bus voltage. At this time, when the DC bus voltage is less than the voltage target value, the charge / discharge power determination unit 33 sets the value to suppress the charging power as compared with the case where the DC bus voltage is the voltage target value. This makes it possible to avoid a situation in which the DC bus voltage drops below the lower limit of the voltage. Further, when the DC bus voltage is less than the lower limit of the voltage, the charge / discharge power determination unit 33 only sets the charging power to 0, does not discharge to raise the DC bus voltage, and charges the DC bus. not. That is, in the region 105, the charge / discharge power determination unit 33 prioritizes the management of the SOC over the management of the DC bus voltage because the SOC is lower than the lower limit of the SOC.

(Specific examples of charge power and discharge power)
FIG. 4 is a graph showing specific examples of charge power and discharge power determined by the charge / discharge power determination unit 33 when the DC bus voltage is equal to or higher than the voltage lower limit value and equal to or lower than the voltage upper limit value. In FIG. 4, the horizontal axis shows the SOC of the storage battery 20. Further, the vertical axis shows the charging / discharging power of the storage battery 20, the charged power as a positive value, and the discharging power as a negative value. FIG. 4 shows the relationship between the SOC of the storage battery 20 and the charge / discharge power for each of the cases where the bus voltage is 540V, 570V, 600V, 630V, and 660V. In the example shown in FIG. 4, the lower limit value of the DC bus voltage is 540V, the target voltage value is 600V, and the upper limit voltage value is 660V.

Reference numeral 201 is a graph showing the charging power according to the SOC of the storage battery 20 when the DC bus voltage is 600 V. In this case, the charge / discharge power determination unit 33 linearly increases the charging power according to the decrease in the SOC when the SOC of the storage battery 20 is 10% or more and 40% or less. When the SOC of the storage battery 20 is less than 10%, the charge / discharge power determination unit 33 sets the charging power to be the same as that when the SOC of the storage battery 20 is 10%. When the SOC of the storage battery 20 is 40% or more and 60% or less, the charge / discharge power determination unit 33 sets the charge power and the discharge power to 0. The charge / discharge power determination unit 33 linearly increases the discharge power as the SOC increases when the SOC of the storage battery 20 is 60% or more and 90% or less. When the SOC of the storage battery 20 is 90% or more, the charge / discharge power determination unit 33 sets the discharge power to be the same as when the SOC of the storage battery 20 is 90%.

Reference numeral 202 is a graph showing the charging power according to the SOC of the storage battery 20 when the DC bus voltage is 570V. The voltage of 570V is a specific example of the DC bus voltage which is equal to or more than the lower limit of the voltage and less than the voltage target value. In this case, the charge / discharge power determination unit 33 determines the charging power according to the SOC, when the SOC of the storage battery 20 is 10% or more and less than 40%, and when the SOC is less than 10%, the DC bus voltage is When the voltage is 600 V, the value is suppressed as compared with the case where the SOC is the same. When the SOC of the storage battery 20 is 40% or more, the charge / discharge power determination unit 33 determines the charge power or the discharge power as in the case where the DC bus voltage is 600 V.

Reference numeral 203 is a graph showing the charging power when the DC bus voltage is 540V. The voltage of 540V is a specific example of the lower limit of the voltage. In this case, the charge / discharge power determination unit 33 sets the charge power to 0 when the SOC of the storage battery 20 is less than 40%. When the SOC of the storage battery 20 is 40% or more, the charge / discharge power determination unit 33 determines the discharge power as in the case where the DC bus voltage is 600 V.

Reference numeral 204 is a graph showing the discharge power according to the SOC of the storage battery 20 when the DC bus voltage is 630V. The voltage of 630V is a specific example of the DC bus voltage that exceeds the voltage target value and is equal to or less than the voltage upper limit value. In this case, the charge / discharge power determination unit 33 determines the discharge power according to the SOC when (i) the SOC of the storage battery 20 exceeds 60% and is 90% or less, and (ii) exceeds 90%. In each case, when the DC bus voltage is 600 V, the value is suppressed as compared with the case where the SOC is the same. When the SOC of the storage battery 20 is 60% or less, the charge / discharge power determination unit 33 determines the charge power or the discharge power as in the case where the DC bus voltage is 600 V.

Reference numeral 205 is a graph showing the discharge power when the DC bus voltage is 660 V. The voltage of 660V is a specific example of the upper limit of the voltage. In this case, the charge / discharge power determination unit 33 sets the discharge power to 0 when the SOC of the storage battery 20 exceeds 60%. When the SOC of the storage battery 20 is 60% or less, the charge / discharge power determination unit 33 determines the charging power as in the case where the DC bus voltage is 600 V.

(Processing in the control device 30)
FIG. 5 is a flowchart showing an example of processing in the control device 30. In the flowchart shown in FIG. 5, the voltage target value, the voltage lower limit value, and the voltage upper limit value for the DC bus voltage, and the first threshold value, the second threshold value, the SOC lower limit value, and the SOC upper limit value for the SOC are shown in FIGS. It is the same as the value in the example shown in FIG. In the control device 30, the SOC acquisition unit 31 first acquires the SOC of the storage battery 20 (S1), and the DC bus voltage acquisition unit 32 acquires the DC bus voltage of the DC bus 50 (S2). Steps S1 and S2 may be executed in the reverse order or may be executed at the same time.

The charge / discharge power determination unit 33 determines whether the DC bus voltage is 540 V or more and 660 V or less (S3). When the DC bus voltage is 540 V or more and 660 V or less (YES in S3), the charge / discharge power determination unit 33 determines whether the DC bus voltage is less than 600 V (S4). When the DC bus voltage is less than 600 V (YES in S4), the charge / discharge power determination unit 33 executes the first charge / discharge voltage determination process described later (S5). When the DC bus voltage is not less than 600 V (NO in S4), the charge / discharge power determination unit 33 executes a second charge / discharge voltage determination process described later (S6). When the DC bus voltage is not 540 V or more and 660 V or less (NO in S3), the charge / discharge power determination unit 33 executes a third charge / discharge voltage determination process described later (S7). The charge / discharge control unit 34 controls charging or discharging of the storage battery 20 according to the charging power or discharging power determined by the charging / discharging power determining unit 33 in steps S5, S6 or S7 (S8).

FIG. 6 is a flowchart showing a specific example of the first charge / discharge voltage determination process and the second charge / discharge voltage determination process shown in FIG. In FIG. 5, an example of the first charge / discharge voltage determination process is indicated by reference numeral 6001, and an example of the second charge / discharge voltage determination process is indicated by reference numeral 6002.

In the first charge / discharge voltage determination process, the charge / discharge power determination unit 33 first determines the SOC (S51). When the SOC is less than 40% (SOC <40 in S51), the charge / discharge power determination unit 33 determines the charging power according to the SOC (S52). The charging power determined in step S52 is a suppressed charging power as shown by reference numeral 202 or 203 in FIG. When the SOC is 40% or more and 60% or less (40 ≦ SOC ≦ 60 in S51), the charge / discharge power determination unit 33 puts the storage battery 20 in a standby state (S53). That is, the charge / discharge power determination unit 33 sets both the charge power and the discharge power to 0. When the SOC exceeds 60% (SOC> 60 in S51), the charge / discharge power determination unit 33 determines the discharge power according to the SOC (S54). The discharge power determined in step S54 is an unsuppressed discharge power as shown by reference numeral 204 in FIG.

In the second charge / discharge voltage determination process, the charge / discharge power determination unit 33 executes steps S61 to 64 which are substantially the same as steps S51 to S54 in the first charge / discharge voltage determination process. However, the charging power determined by the charge / discharge power determination unit 33 in step S62 is suppressed as shown by reference numeral 201 in FIG. 4, unlike the charge power determined by the charge / discharge power determination unit 33 in step S52. There is no charging power. Further, the discharge power determined by the charge / discharge power determination unit 33 in step S64 is different from the discharge power determined by the charge / discharge power determination unit 33 in step S54, and is suppressed as shown by reference numeral 205 or 206 in FIG. It is the discharged power.

FIG. 7 is a flowchart showing a specific example of the third charge / discharge voltage determination process shown in FIG. As shown in FIG. 5, the third charge / discharge voltage determination process is started when it is determined in step S3 that the DC bus voltage is not 540 V or more and 660 V or less. Therefore, when the third charge / discharge voltage determination process is started, the DC bus voltage is a value of less than 540 V or more than 660 V.

In the third charge / discharge voltage determination process, the charge / discharge power determination unit 33 determines whether the DC bus voltage is less than 540 V (S71). When the DC bus voltage is less than 540 V (YES in S71), the charge / discharge power determination unit 33 determines whether the SOC is 10% or more (S72). When the SOC is 10% or more (YES in S72), the charge / discharge power determination unit 33 determines the discharge power to a value other than 0 (S73). The discharge power determined in step S73 is different from that determined in steps S54 and S64. The discharge power determined in step S73 is determined to maintain the DC bus voltage at 540V, for example using proportional integral control according to the DC bus voltage.

When the DC bus voltage is not less than 540V (NO in S71), that is, when the DC bus voltage exceeds 660V, the charge / discharge power determination unit 33 determines whether the SOC is 90% or less (S75). When the SOC is 90% or less (YES in S75), the charge / discharge power determination unit 33 determines the charge power to a value other than 0 (S76). The charging power determined in step S76 is different from that determined in steps S52 and S62. The charging power determined in step S76 is determined to maintain the DC bus voltage at 660V, for example using proportional integral control according to the DC bus voltage.

When the SOC is not 10% or more (NO in S72), or when the SOC is not 90% or less (NO in S75), the charge / discharge power determination unit 33 puts the storage battery 20 on standby (S74). That is, the charge / discharge power determination unit 33 sets both the charge power and the discharge power to 0.
Specific examples of the processing in the charge / discharge power determination unit 33 for determining the charge power or the discharge power in steps S52 to S54, S62 to S64, S73, and S76 are as follows. In this specific example, the discharge power is a positive value and the charge power is a negative value. The power determination unit 331 determines the charge power or the discharge power P when the DC bus voltage is not taken into consideration by the following equation (1).
P = ((SOCU-60) / (90-60)) x rated discharge current + ((SOCL-40) / (40-10)) x rated charge current (1)
In the formula (1), the value of SOCU is (i) 60 when the value of SOC is less than 60, and (ii) the value of SOC when the value of SOC is 60 or more and 90 or less. Equal values, 90 if the (iii) SOC value exceeds 90. Further, in the formula (1), the value of SOCL is (i) 10 when the value of SOC is less than 10, and (ii) the value of SOC when the value of SOC is 10 or more and 40 or less. It is a value equal to the value, and is 40 when the (iii) SOC value exceeds 40. Further, the values of the rated discharge current and the rated charge current are values that serve as a reference for the charge current or the discharge current to the storage battery 20. The fluctuation suppression unit 332 divides the DC bus voltage acquired by the DC bus voltage acquisition unit 32 by the voltage target value described later, and normalizes the value to 0 or more and 1 or less. When the normalized DC bus voltage is (i) 1 or more and 1.1 or less, or (ii) 0.9 or more and less than 1, the fluctuation suppression unit 332 actually determines the DC bus voltage based on the SOC. Determines charge or discharge power. The above (i) and (ii) correspond to the case of NO in step S4 and the case of YES in step S4, respectively. When the normalized DC bus voltage is less than 0.9 (YES in S71) and the SOC is 10% or more (YES in S72), the fluctuation suppression unit 332 maintains the DC bus voltage at 540V. The discharge power is determined so as to be (S73). When the normalized DC bus voltage exceeds 0.9 (NO in S71) and the SOC is 90% or less (YES in S75), the fluctuation suppression unit 332 maintains the DC bus voltage at 660V. The charging power is determined so as to be (S76).

As described above, the control device 30 determines the charging power or the discharging power of the storage battery 20 according to the SOC of the storage battery 20 and the DC bus voltage in the DC bus 50, and charges the storage battery 20 according to the charging power or the discharging power. Or control the discharge. Therefore, according to the control device 30, in the DC power distribution system 1, it is possible to achieve both the management of the DC bus voltage using the storage battery 20 and the appropriate management of the charge rate of the storage battery 20. In particular, the control device 30 suppresses the discharge power from the storage battery 20 when the SOC and the DC bus voltage are high, and suppresses the charging power when the SOC and the DC bus voltage are low. Therefore, fluctuations in the DC voltage in these cases can be suppressed. In addition, by controlling the SOC while suppressing fluctuations in the DC bus voltage, the DC distribution system 1 can be stabilized for a long period of time even when the DC bus voltage of the DC distribution system 1 fluctuates sensitively to load fluctuations. Can be operated as a system.

Further, the DC distribution system 1 may further include a control device that suppresses the output current from the solar cell panel 40 so as to suppress fluctuations in the DC bus voltage. Further, the DC distribution system 1 may further include a control device that controls the power supplied to the DC load 60 so as to suppress fluctuations in the DC bus voltage. When these control devices are provided, the DC distribution system 1 can be operated with a more stable DC bus voltage.

(Operation verification result)
The operation of the DC distribution system 1 and the DC distribution system of the comparative example were verified. The operation here means the operation of the current, voltage, or SOC in each part. The DC power distribution system of the comparative example differs from the DC power distribution system 1 in that it includes a control device for determining charge power or discharge power based only on the SOC instead of the control device 30. The processing in the control device provided in the DC distribution system of the comparative example is the same as the processing in the control device 30 when the DC bus voltage is always the voltage target value. Further, in the verification of this operation, not only the charging / discharging of the storage battery but also the current from the solar cell panel 40 is controlled. Further, the voltage target value, the voltage lower limit value, and the voltage upper limit value for the DC bus voltage, and the first threshold value, the second threshold value, the SOC lower limit value, and the SOC upper limit value for the SOC are shown in FIGS. 3 and 4. It is the same as in the specific example.

FIG. 8 is a diagram showing the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example when the SOC is larger than 90%. In FIG. 8, the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example is shown by reference numerals 8001 and 8002, respectively.

FIG. 9 is a diagram showing the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example when the SOC is 40% or more and 60% or less. In FIG. 9, the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example is shown by reference numerals 9001 and 9002, respectively.

FIG. 10 is a diagram showing the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example when the SOC is less than 10%. In FIG. 10, the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example is shown by reference numerals 10001 and 10002, respectively.

FIG. 11 is a diagram showing the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example when the SOC is 10% or more and less than 40%. In FIG. 11, the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example is shown by reference numerals 11001 and 11002, respectively.

FIG. 12 is a diagram showing the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example when the SOC is larger than 60% and 90% or less. In FIG. 12, the operation of each part of the DC distribution system 1 and the DC distribution system of the comparative example is shown by reference numerals 12001 and 12002, respectively.

In FIGS. 8 to 12, the horizontal axis is time. Further, in FIGS. 8 to 12, the “load current” indicates the current flowing from the DC bus 50 to the DC load 60. Further, in FIGS. 8 to 12, "DC voltage" indicates a DC bus voltage. Further, the "storage battery current" indicates the charging current from the DC bus 50 to the storage battery 20. When the storage battery current is negative, the discharge current from the storage battery 20 is shown. Further, in FIGS. 8 to 12, the “PV current” indicates the current flowing from the solar cell panel 40 to the DC bus 50. As for "PV current", the current flowing from the solar cell panel 40 to the DC bus 50 is shown as a negative value.

As shown by reference numeral 8001 in FIG. 8, in the DC power distribution system 1, even when the SOC is larger than 90%, the DC bus voltage rises to the vicinity of 660 V as surrounded by the broken line 501 (two places). At that time, the control device 30 kept the storage battery 20 on standby as surrounded by broken lines 502 (two places). Further, the PV current was also suppressed as surrounded by the broken line 503 (two places) when the DC bus voltage rose to the vicinity of 660V. Therefore, the DC bus voltage was maintained at 660 V or less.

As shown by reference numeral 8002 in FIG. 8, in the DC power distribution system of the comparative example, when the SOC is larger than 90%, the control device according to the comparative example is used even when the DC bus voltage rises to the vicinity of 660V. , As surrounded by a broken line 504, was discharged from the storage battery 20. Therefore, in the DC power distribution system of the comparative example, the DC bus voltage increased beyond 660 V as surrounded by the broken line 505. The DC distribution system used for the verification was equipped with a protective device that cuts off the current from the storage battery 20 and the solar cell panel 40 in order to protect the system when the DC bus voltage reaches 720V. In the DC power distribution system of the comparative example, the protective device was activated and the storage battery current and the PV current became 0 as surrounded by the broken lines 505 and 506.

As shown by reference numeral 9001 in FIG. 9, in the DC power distribution system 1, when the SOC is 40% or more and 60% or less, the control device 30 adjusts the SOC of the storage battery 20 in charge current and discharge current. Was set to 0. However, in the DC distribution system used for verification, when the DC bus voltage was the upper limit value or the lower limit value, the control to keep the DC bus voltage constant at the upper limit value or the lower limit value was operated. Therefore, in reference numeral 9001 of FIG. 9, the storage battery current also shows a slight fluctuation according to the fluctuation of the DC bus voltage. As shown by reference numeral 9002 in FIG. 9, the operation when the SOC is 40% or more and 60% or less is the same in the DC power distribution system of the comparative example.

As shown by reference numeral 10001 in FIG. 10, in the DC power distribution system 1, even when the SOC is less than 10%, when the DC bus voltage is low, the control device 30 charges the storage battery 20. The current was suppressed. Therefore, in the DC power distribution system 1, the DC bus voltage is maintained at 540 V or higher.

As shown by reference numeral 10002 in FIG. 10, in the DC power distribution system of the comparative example, when the SOC is less than 10%, the control device according to the comparative example charges the storage battery 20 without suppressing the charging current. Therefore, in the DC power distribution system of the comparative example, the DC bus voltage dropped to less than 540 V as surrounded by the broken line 511 (two places).

As shown by reference numeral 11001 in FIG. 11, in the DC power distribution system 1, when the SOC is 10% or more and less than 40%, the control device 30 charges the storage battery 20. In this case, since the SOC is large as compared with the case where the SOC is less than 10%, the control device 30 further suppresses the charging current. Specifically, the charging current was about 50 A.

As shown by reference numeral 11002 in FIG. 11, in the DC power distribution system of the comparative example, when the SOC is 10% or more and less than 40%, the control device according to the comparative example does not suppress the charging current and the storage battery 20. Was charged. In this case, the charging current decreased because the SOC was large as compared with the case where the SOC was less than 10%. However, the specific charging current is about 100 A, which is about twice the charging current determined by the control device 30. Therefore, the DC bus voltage did not decrease to less than 540 V as surrounded by the broken line 521 (two places), but decreased to the vicinity thereof.

As shown by reference numeral 12001 in FIG. 12, in the DC power distribution system 1, when the SOC is larger than 60% and 90% or less, the control device 30 determines that the increase width of the DC bus voltage is large. The storage battery 20 was charged as surrounded by the broken line 531 (two places). Further, when the increase width of the DC bus voltage is small, the control device 30 suppresses the discharge current and discharges from the storage battery 20 as surrounded by the broken line 532. As a result, fluctuations in the DC bus voltage were suppressed, so that the PV current was constant in the DC distribution system 1.

As shown by reference numeral 12002 in FIG. 12, in the DC power distribution system of the comparative example, when the SOC is larger than 60% and 90% or less, the control device according to the comparative example does not suppress the discharge current. Was discharged from the storage battery 20. Therefore, in the DC distribution system of the comparative example, in order to suppress the fluctuation of the DC bus voltage, the control of suppressing the PV current was executed twice as surrounded by the broken line 533 (two places).

〔summary〕
The control device according to the first aspect of the present invention includes a charge rate acquisition unit that acquires the charge rate of the storage battery connected to the DC distribution system, a DC bus voltage acquisition unit that acquires the DC bus voltage of the DC distribution system, and a DC bus voltage acquisition unit. According to the charge / discharge power determination unit that determines the charge power or discharge power of the storage battery according to the charge rate and the DC bus voltage, and the charge power or discharge power determined by the charge / discharge power determination unit, the storage battery A charge / discharge control unit for controlling charging or discharging is provided.

According to the above configuration, the charge / discharge power determination unit determines the charge power or the discharge power of the storage battery according to the charge rate acquired by the charge rate acquisition unit and the DC bus voltage acquired by the DC bus voltage acquisition unit. do. The charge / discharge control unit controls charging or discharging of the storage battery according to the charging power or discharging power determined by the charging / discharging power determining unit. Therefore, in the DC power distribution system, it is possible to achieve both the management of the DC bus voltage using the storage battery and the appropriate management of the charge rate of the storage battery.

In the control device according to the second aspect of the present invention, the charge / discharge power determination unit uses the charge power according to the charge rate when the DC bus voltage is equal to or higher than the lower limit of the voltage and less than the voltage target value. The voltage is set to a value suppressed more than when the voltage is the voltage target value, and when the DC bus voltage exceeds the voltage target value and is equal to or less than the voltage upper limit value, the DC bus voltage corresponds to the charge rate. It is preferable to set the value to be more suppressed than when it is the voltage target value.

According to the above configuration, the charge / discharge power determination unit suppresses the charge power or the discharge power according to the DC bus voltage. Therefore, it is possible to bring the charge rate of the storage battery closer to an appropriate range while suppressing fluctuations in the DC bus voltage.

In the control device according to the third aspect of the present invention, the charge / discharge power determination unit is used when the DC bus voltage is equal to or higher than the voltage lower limit value and equal to or lower than the voltage upper limit value, and when the charge rate is equal to or higher than the first threshold value. It is preferable that the charging power is 0 and the discharging power is 0 when the charging rate is equal to or less than the second threshold value larger than the first threshold value.

According to the above configuration, the charge / discharge power determination unit sets the charge power and the discharge power to 0 when the DC bus voltage is within the normal range and the charge rate is equal to or greater than the first threshold and equal to or less than the second threshold. do. Therefore, when the DC bus voltage and the charge rate are in appropriate states, those states can be maintained.

In the control device according to the fourth aspect of the present invention, the charge / discharge power determination unit sets the charge power to 0 when the DC bus voltage exceeds the voltage upper limit value and the charge rate is equal to or less than the charge rate upper limit value. It is preferable to set a value other than.

According to the above configuration, the charge / discharge power determination unit sets the charge power to a value other than 0 when the DC bus voltage exceeds the voltage upper limit value when the charge rate is equal to or less than the charge rate upper limit value. Therefore, when the DC bus voltage exceeds the voltage upper limit value and the charge rate is not more than the charge rate upper limit value, the DC bus voltage can be lowered by charging the storage battery.

In the control device according to the fifth aspect of the present invention, the charge / discharge power determination unit reduces the discharge power to 0 when the DC bus voltage is less than the voltage lower limit value and the charge rate is equal to or higher than the charge rate lower limit value. It is preferable to set a value other than.

According to the above configuration, the charge / discharge power determination unit sets the discharge power to a value other than 0 when the charge rate is equal to or higher than the lower limit of the charge rate and the DC bus voltage is less than the lower limit of the voltage. Therefore, when the DC bus voltage is less than the lower limit of the voltage and the charge rate is not more than the lower limit of the charge rate, the DC bus voltage can be increased by discharging from the storage battery.

[Example of implementation by software]
The control block of the control device 30 (particularly the SOC acquisition unit 31, the DC bus voltage acquisition unit 32, the charge / discharge power determination unit 33, and the charge / discharge control unit 34) is a logic circuit (especially an integrated circuit (IC chip)) formed in a logic circuit (IC chip) or the like. It may be realized by hardware) or by software.

In the latter case, the control device 30 includes a computer that executes instructions of a program that is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes the program, thereby achieving the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, a "non-temporary tangible medium", for example, a ROM (Read Only Memory) or the like, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like can be used. Further, a RAM (Random Access Memory) for expanding the above program may be further provided. Further, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. It should be noted that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

1 DC power distribution system 20 Storage battery 30 Control device 31 SOC acquisition unit (charge rate acquisition unit)
32 DC bus voltage acquisition unit 33 Charge / discharge power determination unit 34 Charge / discharge control unit

Claims (5)

A charge rate acquisition unit that acquires the charge rate of the storage battery connected to the DC power distribution system,
A DC bus voltage acquisition unit that acquires the DC bus voltage of the DC distribution system,
A charge / discharge power determination unit that determines the charge power or discharge power of the storage battery according to the charge rate and the DC bus voltage.
A control device including a charge / discharge control unit that controls charging or discharging of the storage battery according to the charging power or discharging power determined by the charging / discharging power determining unit. The charge / discharge power determination unit is
The charging power according to the charging rate is set to a value suppressed more than when the DC bus voltage is the voltage target value when the DC bus voltage is equal to or higher than the voltage lower limit value and less than the voltage target value.
When the DC bus voltage exceeds the voltage target value and is equal to or less than the voltage upper limit value, the discharge power according to the charge rate is set to a value suppressed more than when the DC bus voltage is the voltage target value. The control device according to claim 1, wherein the control device is characterized. The charge / discharge power determination unit is
When the DC bus voltage is equal to or greater than the voltage lower limit value and equal to or lower than the voltage upper limit value,
When the charge rate is equal to or higher than the first threshold value, the charge power is set to 0.
The control device according to claim 2, wherein the discharge power is set to 0 when the charge rate is equal to or less than the second threshold value larger than the first threshold value. The charge / discharge power determination unit is
When the DC bus voltage exceeds the voltage upper limit value,
The control device according to claim 2 or 3, wherein the charging power is set to a value other than 0 when the charging rate is equal to or less than the upper limit value of the charging rate. The charge / discharge power determination unit is
When the DC bus voltage is less than the lower voltage limit,
The control device according to any one of claims 2 to 4, wherein the discharge power is set to a value other than 0 when the charge rate is equal to or higher than the lower limit value of the charge rate.

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