Control device and control method

Abstract

To provide a control device capable of keeping a voltage at a load within an allowable range.SOLUTION: A control device (30) includes a lower limit determination unit (34) that determines whether a bus voltage is less than a lower limit value and a charging / discharging control unit (36) that controls charging / discharging current or charging / discharging power of a power storage device so that the bus voltage becomes equal to or higher than the lower limit value when the bus voltage is lower than the lower limit value and the lower limit value is the largest value among the lower limit voltages determined for each load connected to a DC bus.SELECTED DRAWING: Figure 2

Description

Technical Field

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[0001] The present invention relates to a control device and a control method for controlling charging and discharging of a power storage device included in a DC power distribution system.

Background Art

[0002] Patent Document 1 discloses a power sharing system including a plurality of input sources, a power bus that receives inputs from these plurality of input sources and outputs them, and a plurality of output sources that receive power from the input sources output from the power bus. In this power sharing system, for input control between a plurality of input sources, priority is given in descending order of set voltage for input control to the power bus. Also, for output to a plurality of output sources, priority is given in ascending order of set voltage for output control.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the power sharing system disclosed in Patent Document 1, when the wiring distance between the power bus and the input source or output source becomes long, the voltage fluctuation between the power bus and the input source or output source becomes large. Therefore, even if the voltage in the power bus is controlled to be within the allowable range, there is a problem that the voltage at the input source or output source may deviate from the allowable range.

[0005] One aspect of the present invention aims to realize a control device capable of keeping the voltage at a load within the allowable range in the power distribution system regardless of the wiring distance.

Means for Solving the Problems

[0006] To solve the above problems, a control device according to one aspect of the present invention is a control device for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power supply and distribution system, comprising: a lower limit determination unit that determines whether the bus voltage at the connection point of the energy storage device to the DC bus is less than a lower limit value; and a charge / discharge control unit that controls the charging / discharging current or charging / discharging power of the energy storage device so that the bus voltage at the connection point is greater than or equal to the lower limit value when the bus voltage at the connection point is less than the lower limit value, wherein the lower limit value is the largest of the lower limit voltages at the connection point that ensure the minimum operating voltage at each of the one or more loads connected to the DC bus, which are determined by reflecting the impedance between the load and the connection point.

[0007] Furthermore, a control device according to one aspect of the present invention is a control device for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power supply and distribution system, comprising: an upper limit determination unit that determines whether the bus voltage at the connection point of the energy storage device exceeds an upper limit; and a charge / discharge control unit that controls the charging / discharging current or charging / discharging power of the energy storage device so that the bus voltage at the connection point is less than or equal to the upper limit, wherein the upper limit is the smallest value among the upper limit voltages at the connection point when the output power of the power generation device is at its maximum, which are determined for each of the one or more power generation devices connected to the DC bus, reflecting the impedance between the power generation device and the connection point.

[0008] Furthermore, a control method according to one aspect of the present invention is a control method for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power supply and distribution system, comprising: a lower limit determination step of determining whether the bus voltage at the connection point of the energy storage device is less than a lower limit; and a charge / discharge control step of controlling the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point is greater than or equal to the lower limit, wherein the lower limit is the largest of the lower limit voltages at the connection point that ensure the minimum operating voltage at each of the one or more loads connected to the DC bus, which are determined by reflecting the impedance between the load and the connection point.

[0009] Furthermore, a control method according to one aspect of the present invention is a control method for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power distribution system, comprising: an upper limit determination step of determining whether the bus voltage at the connection point of the energy storage device exceeds an upper limit; and a charge / discharge control step of controlling the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point exceeds the upper limit, wherein the upper limit is the smallest value among the upper limit voltages at the connection point when the output power of the power generation device is at its maximum, which are determined for each of the one or more power generation devices connected to the DC bus, reflecting the impedance between the power generation device and the connection point.

[0010] Each aspect of the present invention may be implemented by a computer, in which case a control program for the control device that enables the computer to implement the control device by operating the computer as each part (software element) of the control device, and a computer-readable recording medium on which the program is recorded, also fall within the scope of the present invention. [Effects of the Invention]

[0011] According to one aspect of the present invention, the voltage at the load can be kept within the permissible range in the power distribution system, regardless of the wiring distance. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example of the configuration of a DC power supply and distribution system according to Embodiment 1. [Figure 2] This diagram shows the configuration of the control device according to Embodiment 1. [Figure 3] This figure shows the values ​​related to the control according to Embodiment 1 for each of the load and power generation equipment. [Figure 4] This diagram shows the relationship between the bus voltage and the control by the charge / discharge control unit in Embodiment 1. [Figure 5] This flowchart shows an example of a control method by the control device according to Embodiment 1. [Figure 6] This flowchart shows an example of the process by which the lower limit determination unit determines the lower limit of the bus voltage. [Figure 7] This flowchart shows an example of the process by which the upper limit determination unit determines the upper limit of the bus voltage. [Figure 8] This figure shows the relationship between the bus voltage and the voltage in the battery in Embodiment 2. [Figure 9] This figure shows the values ​​related to the control according to Embodiment 2 for each of the load and power generation equipment. [Figure 10] This figure shows an example of the configuration of a DC power supply and distribution system according to Embodiment 3. [Figure 11] This diagram shows the configuration of the control device according to Embodiment 3. [Figure 12] This graph illustrates the lower limit of the bus voltage in Embodiment 3. [Figure 13] This graph illustrates the upper limit of the bus voltage in Embodiment 3. [Modes for carrying out the invention]

[0013] [Embodiment 1] Hereinafter, an embodiment of the present invention will be described in detail.

[0014] (Configuration of DC power supply and distribution system 1) FIG. 1 is a diagram showing an example of the configuration of a DC power supply and distribution system 1 according to Embodiment 1. As shown in FIG. 1, the DC power supply and distribution system 1 includes a commercial power supply 10, a storage battery 20 (energy storage device), a control device 30, and a DC bus 40. In the DC power supply and distribution system 1, a first solar panel 50a, a second solar panel 50b, a third solar panel 50c, a first DC load 60a, a second DC load 60b, and a third DC load 60c are connected to the DC bus 40.

[0015] The commercial power supply 10 supplies power to the DC bus 40 by AC (Alternating Current). The commercial power supply 10 is connected to the DC bus 40 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 supply 10. The AC-DC converter 12 converts the form of the power input from the transformer 11 from AC to DC and outputs it. Also, the DC power supply and distribution system 1 may include a rectifier circuit instead of the AC-DC converter 12. The breaker 13 disconnects the AC-DC converter 12 from the DC bus 40 as needed.

[0016] The storage battery 20 holds power as energy internally and supplies the held energy to the DC bus 40 by DC as needed. The storage battery 20 may be connected to the DC bus 40 via a DC-DC converter 21 and a breaker 22. The DC-DC converter 21 converts the power input from the storage battery 20 based on a command value input from the control device 30, converts the DC voltage thereof, and outputs it to the DC bus 40, or converts the power input from the DC bus 40, converts the DC voltage thereof, and outputs it to the storage battery 20. The breaker 22 disconnects the storage battery 20 from the DC bus 40 as needed.

[0017] The storage battery 20 may be a device equipped with a secondary battery such as a lithium-ion battery, a NaS (sodium-sulfur) battery, a redox flow battery, or a lead-acid battery. However, the storage battery 20 is not limited to a device equipped with a secondary battery. Any unit with the function of storing electrical energy can be used as the storage battery 20, such as a capacitor, a superconducting power storage unit, a flywheel type power storage unit, or a compressed air type power storage unit.

[0018] The control device 30 controls the charging and discharging current or charging and discharging power of the storage battery 20 by controlling the DC-DC converter 21. The specific configuration of the control device 30 will be described later.

[0019] The first solar panel 50a, the second solar panel 50b, and the third solar panel 50c supply power generated according to the amount of solar irradiance to the DC bus 40 via DC. The first solar panel 50a is connected to the DC bus 40 via a DC-DC converter 51a and a circuit breaker 52a. The DC-DC converter 51a converts the power input from the first solar panel 50a into a DC voltage and outputs it. The circuit breaker 52a disconnects the first solar panel 50a from the DC bus 40 as needed.

[0020] The second solar panel 50b is connected to the DC bus 40 via a DC-DC converter 51b and a circuit breaker 52b. The third solar panel 50c is connected to the DC bus 40 via a DC-DC converter 51c and a circuit breaker 52c. The functions of the DC-DC converters 51b and 51c are the same as those of the DC-DC converter 51a. The functions of the circuit breakers 52b and 52c are the same as those of the circuit breaker 52a.

[0021] The first DC load 60a, the second DC load 60b, and the third DC load 60c are supplied with DC power from the DC bus 40. The first DC load 60a is connected to the DC bus 40 via a DC-DC converter 61a and a circuit breaker 62a. The DC-DC converter 61a converts the power input from the DC bus 40 into a DC voltage output. The circuit breaker 62a disconnects the first DC load 60a from the DC bus 40 as needed.

[0022] The second DC load 60b is connected to the DC bus 40 via a DC-DC converter 61b and a circuit breaker 62b. The third DC load 60c is connected to the DC bus 40 via a DC-DC converter 61c and a circuit breaker 62c. The functions of the DC-DC converters 61b and 61c are the same as those of the DC-DC converter 61a. The functions of the circuit breakers 62b and 62c are the same as those of the circuit breaker 62a.

[0023] The DC bus 40 supplies power from the commercial power supply 10, the first solar panel 50a, the second solar panel 50b, and the third solar panel 50c to the first DC load 60a, the second DC load 60b, and the third DC load 60c. In addition, the DC bus 40 is either supplied with power from the battery 20 or supplies power to the battery 20, depending on the bus voltage.

[0024] A DC capacitor 41 is provided on the DC bus 40. The bus voltage is assumed to be constant regardless of the position on the DC bus 40. However, in Embodiment 1, it is assumed that no voltage drop occurs in the wiring between the DC-DC converter 21 and the DC bus 40. Therefore, in Embodiment 1, the bus voltage can be detected from the DC-DC converter 21.

[0025] In the following explanation, the first solar panel 50a, the second solar panel 50b, and the third solar panel 50c may be collectively referred to as the "power generation device." Similarly, the first DC load 60a, the second DC load 60b, and the third DC load 60c may be collectively referred to as the "load." In the DC power supply and distribution system 1, the number of loads connected to the DC busbar 40 and the number of power generation devices are not limited to three. Furthermore, the number of loads and the number of power generation devices may differ from each other.

[0026] (Configuration of the control device 30) Figure 2 is a diagram showing the configuration of the control device 30 according to Embodiment 1. As shown in Figure 2, the control device 30 includes a de-coupling information acquisition unit 31, a lower limit determination unit 32, an upper limit determination unit 33, a lower limit determination unit 34, an upper limit determination unit 35, and a charge / discharge control unit 36.

[0027] The disconnection information acquisition unit 31 acquires disconnection information from the breakers 52a, 52b, 52c, 62a, 62b, and 62c. The disconnection information may include information indicating whether each load is disconnected from the DC bus 40. The disconnection information may also include information indicating whether each power generation device is disconnected from the DC bus 40.

[0028] The lower limit determination unit 32 determines the lower limit of the bus voltage. The lower limit of the bus voltage is the largest of the lower limit voltages for each load connected to the DC bus 40. The lower limit voltage is the lower limit voltage at the connection point to ensure the minimum operating voltage for the load, and is determined by reflecting the impedance between the load and the connection point to which the load is connected to the DC bus 40. By determining the lower limit of the bus voltage in this way, the minimum operating voltage can be ensured for all loads.

[0029] As described above, in the control device 30, the disconnection information acquisition unit 31 acquires disconnection information from the breakers 62a, 62b, and 62c. The lower limit value determined by the lower limit value determination unit 32 in the control device 30 is the largest value among the lower limit voltages for loads that have not been disconnected from the DC bus 40 by the breakers 62a, 62b, and 62c. Therefore, the lower limit value of the bus voltage can be set to a more appropriate value that reflects only the lower limit voltage for each load actually connected to the DC bus 40.

[0030] The upper limit determination unit 33 determines the upper limit of the bus voltage. The upper limit of the bus voltage is the smallest of the upper limit voltages for each of the power generators connected to the DC bus 40. The upper limit voltage is the upper limit voltage at the connection point when the output power of the power generator is at its maximum, i.e., when the rated power is being output, and is determined by reflecting the impedance between the power generator and the connection point to which the power generator is connected to the DC bus 40. By determining the upper limit of the bus voltage in this way, the voltage for all power generators can be kept below the upper limit voltage.

[0031] As described above, in the control device 30, the disconnection information acquisition unit 31 acquires disconnection information from the breakers 52a, 52b, and 52c. The upper limit value determined by the upper limit value determination unit 33 in the control device 30 is the smallest upper limit voltage among the power generation devices that have not been disconnected from the DC bus 40 by the breakers 52a, 52b, and 52c. Therefore, the upper limit value of the bus voltage can be set to a more appropriate value that reflects only the upper limit voltage for each power generation device actually connected to the DC bus 40.

[0032] The method for calculating the lower voltage limit for each load and the upper voltage limit for each power generation device is described below. In Embodiment 1, these lower and upper voltage limits are not values ​​that fluctuate according to the operation of the DC power supply and distribution system 1, but rather are constant values ​​corresponding to the specifications of the loads and power generation devices, as well as the wiring distance. Therefore, the control device 30 does not need to calculate these lower and upper voltage limits during the control process. Furthermore, when adding loads or power generation devices, the lower and upper voltage limits for those loads or power generation devices can be calculated in advance.

[0033] If VbusL is the lower limit voltage for each load, the value of VbusL is calculated by the following equation (1). VbusL = VL + PL / VL × R × DL × 2 (1) In equation (1), VL is the lower limit of the appropriate voltage at the load when the voltage of the DC bus 40 drops, PL is the absolute value of the power consumption at the load, and DL is the wiring distance from the DC bus 40 to the load. In Embodiment 1, VL is the lower limit voltage in the DC power supply and distribution system 1. In Embodiment 1, PL is the rated power at the load. R is the cable impedance per unit distance in the wiring from the DC bus 40 to the load.

[0034] As shown in equation (1), the value of VbusL is PL / VL × R × DL × 2 higher than the lower limit VL of the appropriate voltage at the load. PL / VL × R × DL × 2 is the voltage drop in the wiring from the DC bus 40 to the load. Therefore, by controlling the battery 20 so that the bus voltage at the DC bus 40 is greater than or equal to VbusL, the actual voltage at the load becomes greater than or equal to VL.

[0035] If VbusG is the upper limit voltage for each power generation device, the value of VbusG is calculated by the following equation (2). VbusG = VG - PG / VG × R × DG × 2 (2) In equation (2), VG is the upper limit of the appropriate voltage in the power generator when the voltage of the DC bus 40 rises, PG is the absolute value of the power generated by the power generator, and DG is the wiring distance from the DC bus 40 to the power generator. In Embodiment 1, VG is the upper limit voltage in the DC power supply and distribution system 1. In Embodiment 1, PG is the rated power of the power generator.

[0036] As shown in equation (2), the value of VbusG is PG / VG × R × DG × 2 lower than the upper limit of the appropriate voltage VG in the power generation device. PG / VG × R × DG × 2 is the voltage drop in the wiring from the power generation device to the DC bus 40. Therefore, by controlling the battery 20 so that the bus voltage at the DC bus 40 is less than or equal to VbusG, the actual voltage in the power generation device becomes less than or equal to VG.

[0037] Figure 3 shows the values ​​related to control according to Embodiment 1 for each of the loads and power generation devices in the DC power supply and distribution system 1. Figure 3 shows the rated power, wiring distance, and lower voltage limit for each of the first DC load 60a, second DC load 60b, and third DC load 60c. The lower voltage limit is the value calculated by equation (1) above. Figure 3 also shows the rated power, wiring distance, and upper voltage limit for each of the first solar panel 50a, second solar panel 50b, and third solar panel 50c. The upper voltage limit is the value calculated by equation (2) above. In calculating the lower and upper voltage limits, VL = 540V, VG = 660V, and R = 0.53mΩ / m were used.

[0038] The lower limit determination unit 34 determines whether the bus voltage is below the lower limit. The upper limit determination unit 35 determines whether the bus voltage exceeds the upper limit. The lower limit determination unit 34 and the upper limit determination unit 35 acquire a signal indicating the bus voltage from the DC-DC converter 21.

[0039] The charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 by controlling the DC-DC converter 21. If the bus voltage is below the lower limit, the charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 so that the bus voltage becomes equal to or above the lower limit. If the bus voltage exceeds the upper limit, the charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 so that the bus voltage becomes equal to or below the upper limit. If the bus voltage is above the lower limit and below the upper limit, the charge / discharge control unit 36 ​​does not control the charge / discharge current or charge / discharge power of the battery 20.

[0040] Figure 4 shows the relationship between the bus voltage and the control by the charge / discharge control unit 36 ​​in Embodiment 1. In Figure 4, reference numeral 401 indicates the case where the wiring distance from the DC bus 40 to the load or power generator is short, i.e., the voltage drop in the wiring can be ignored. In Figure 4, reference numeral 402 indicates the case where the wiring distance from the DC bus 40 to the load or power generator is long, i.e., the voltage drop in the wiring cannot be ignored.

[0041] Figure 4 shows three ranges for the bus voltage: ranges R1, R2, and R0. Range R1 is the range where the bus voltage is less than VbusL. When the bus voltage is within range R1, the charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 so that the bus voltage is greater than or equal to VbusL. Range R2 is the range where the bus voltage is greater than VbusG. When the bus voltage is within range R2, the charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 so that the bus voltage is less than or equal to VbusG.

[0042] Range R0 is the range in which the bus voltage is greater than or equal to VbusL and less than or equal to VbusG. When the bus voltage is within range R0, the charge / discharge control unit 36 ​​does not control the charge / discharge current or charge / discharge power of the battery 20. In other words, range R0 is a dead zone in the control by the charge / discharge control unit 36.

[0043] When the wiring distance from the DC bus 40 to the load or the power generation device is short, both DL in Equation (1) and DG in Equation (2) become 0. Therefore, VbusL = VL and VbusG = VG. On the other hand, when the wiring distance from the DC bus 40 to the load or the power generation device is long, both DL in Equation (1) and DG in Equation (2) become values greater than 0. Therefore, VbusL > VL and VbusG < VG. Thus, when the wiring distance from the DC bus 40 to the load or the power generation device is long, the dead band in the control by the control device 30 becomes narrower compared to the case where the wiring distance is short.

[0044] The control device 30 is communicably connected to the storage device 70. The storage device 70 is a storage device that stores information necessary for the control by the control device 30. For example, the storage device 70 stores the table of values shown in FIG. 3. The storage device 70 may be included in the DC power distribution system 1 or may be outside the DC power distribution system 1.

[0045] (Voltage drop and rise between the DC-DC converter 21 and the DC bus 40) The voltage actually controlled by the control device 30 is the voltage at the end on the DC-DC converter 21 side in the wiring from the DC bus 40 to the DC-DC converter 21 (hereinafter sometimes referred to as "the voltage in the DC-DC converter 21"). As described above, in Embodiment 1, it is assumed that no voltage drop occurs in the wiring between the DC-DC converter 21 and the DC bus 40. Therefore, for each load, by setting the lower limit voltage in the DC-DC converter 21 as VbusL, the lower limit voltage at the connection point between the load and the DC bus 40 also becomes VbusL. Also, for each power generation device, by setting the upper limit voltage in the DC-DC converter 21 as VbusG, the upper limit voltage at the connection point between the power generation device and the DC bus 40 also becomes VbusG.

[0046] When a voltage drop occurs in the wiring between the DC-DC converter 21 and the DC bus 40, an example of a method for calculating the lower limit voltage in the battery 20 for each load is to use the wiring distance between the DC-DC converter 21 and the load as the value of DL in equation (1). In this case, an example of a method for calculating the upper limit voltage in the battery 20 for each power generation device is to use the wiring distance between the DC-DC converter 21 and the power generation device as the value of DG in equation (2). That is, a method is to include the wiring distance between the DC-DC converter 21 and the DC bus 40 in DL in equation (1) and DG in equation (2). The VbusL and VbusG calculated in this way will reflect the voltage drop in the wiring between the DC-DC converter 21 and the DC bus 40.

[0047] (Control method by control device 30) Figure 5 is a flowchart showing an example of a control method by the control device 30. First, the disconnection information acquisition unit 31 acquires disconnection information from the breakers 52a, 52b, 52c, 62a, 62b, and 62c (S1).

[0048] The lower limit determination unit 32 determines the lower limit of the bus voltage based on the disconnection information (S2). The upper limit determination unit 33 determines the lower limit of the bus voltage based on the disconnection information (S3). The specific details of the processing in steps S2 and S3 will be described later. Steps S2 and S3 may be executed in reverse order or in parallel.

[0049] The lower limit determination unit 34 determines whether the bus voltage is below the lower limit (S4, lower limit determination step). If the bus voltage is below the lower limit (YES in S4), the charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 so that the bus voltage is equal to or greater than the lower limit (S5, charge / discharge control step). If the bus voltage is not below the lower limit (NO in S4), the upper limit determination unit 35 determines whether the bus voltage exceeds the upper limit (S6, upper limit determination step). If the bus voltage exceeds the upper limit (YES in S6), the charge / discharge control unit 36 ​​controls the charge / discharge current or charge / discharge power of the battery 20 so that the bus voltage is equal to or less than the upper limit (S7, charge / discharge control step). If the bus voltage does not exceed the upper limit (NO in S6), the charge / discharge control unit 36 ​​does not control the charge / discharge current or charge / discharge power of the battery 20.

[0050] Figure 6 is a flowchart showing an example of the process by which the lower limit determination unit 32 determines the lower limit of the bus voltage. First, the lower limit determination unit 32 sorts the first DC load 60a, the second DC load 60b, and the third DC load 60c in descending order of their lower limit voltages (S21). In the table shown in Figure 3, the order of lower limit voltages is second DC load 60b (598.9V) > first DC load 60a (589.1V) > third DC load 60c (579.3V). In the following processes, the lower limit determination unit 32 determines whether each load has been disconnected from the DC bus 40, in the order they were sorted.

[0051] The lower limit determination unit 32 determines whether the second DC load 60b is disconnected from the DC bus 40 (S22). If the second DC load 60b is not disconnected from the DC bus 40 (NO in S22), the lower limit determination unit 32 determines the lower limit voltage of the second DC load 60b as the lower limit of the bus voltage (S23).

[0052] If the second DC load 60b is disconnected from the DC bus 40 (YES in S22), the lower limit determination unit 32 determines whether the first DC load 60a is disconnected from the DC bus 40 (S24). If the first DC load 60a is not disconnected from the DC bus 40 (NO in S24), the lower limit determination unit 32 determines the lower limit voltage of the first DC load 60a as the lower limit of the bus voltage (S25).

[0053] If the first DC load 60a is disconnected from the DC bus 40 (YES in S24), the lower limit determination unit 32 determines whether the third DC load 60c is disconnected from the DC bus 40 (S26). If the third DC load 60c is not disconnected from the DC bus 40 (NO in S26), the lower limit determination unit 32 determines the lower limit voltage of the third DC load 60c as the lower limit of the bus voltage (S27).

[0054] If the third DC load 60c is disconnected from the DC bus 40 (YES in S26), the lower limit determination unit 32 determines the lower limit voltage in the DC power supply and distribution system 1 as the lower limit of the bus voltage (S28). For example, if the rated voltage of the DC power supply and distribution system 1 is 600V and it operates within the range of -10% to +10%, the lower limit voltage in the DC power supply and distribution system 1 is 540V.

[0055] Figure 7 is a flowchart showing an example of the process by which the upper limit determination unit 33 determines the upper limit of the bus voltage. First, the upper limit determination unit 33 sorts the first solar panel 50a, the second solar panel 50b, and the third solar panel 50c in order from the lowest upper limit voltage (S31). In the table shown in Figure 3, the relationship between the upper limits of the voltages is second solar panel 50b (611.8V) < first solar panel 50a (619.8V) < third solar panel 50c (627.9V). In the following processes, the upper limit determination unit 33 determines whether each of the power generation devices is disconnected from the DC bus 40, in the sorted order.

[0056] The upper limit determination unit 33 determines whether the second solar cell panel 50b is disconnected from the DC bus 40 (S32). If the second solar cell panel 50b is not disconnected from the DC bus 40 (NO in S32), the upper limit determination unit 33 determines the upper limit voltage of the second solar cell panel 50b as the upper limit of the bus voltage (S33).

[0057] If the second solar cell panel 50b is disconnected from the DC bus 40 (YES in S32), the upper limit determination unit 33 determines whether the first solar cell panel 50a is disconnected from the DC bus 40 (S34). If the first solar cell panel 50a is not disconnected from the DC bus 40 (NO in S34), the upper limit determination unit 33 determines the upper limit voltage of the first solar cell panel 50a as the upper limit of the bus voltage (S35).

[0058] If the first solar cell panel 50a is disconnected from the DC bus 40 (YES in S34), the upper limit determination unit 33 determines whether the third solar cell panel 50c is disconnected from the DC bus 40 (S36). If the third solar cell panel 50c is not disconnected from the DC bus 40 (NO in S36), the upper limit determination unit 33 determines the upper limit voltage of the third solar cell panel 50c as the upper limit of the bus voltage (S37).

[0059] If the third solar cell panel 50c is disconnected from the DC bus 40 (YES in S36), the upper limit determination unit 33 determines the upper limit voltage in the DC power supply and distribution system 1 as the upper limit of the bus voltage (S38). For example, if the rated voltage of the DC power supply and distribution system 1 is 600V and it operates within a range of -10% to +10%, the upper limit voltage in the DC power supply and distribution system 1 is 660V.

[0060] With the above control method, the control device 30 can set the voltage at each load to be above the lower limit voltage of the DC power supply and distribution system 1, regardless of the wiring distance from the DC bus 40 to the load. Furthermore, with the above control method, the control device 30 does not need to monitor the voltage at each load; it only needs to obtain disconnection information from the breakers 52a, 52b, and 52c. Therefore, the control device 30 can set the voltage at each load to be above the lower limit voltage of the DC power supply and distribution system 1 without requiring high-speed communication.

[0061] Furthermore, generally, the storage battery 20 deteriorates with repeated charging and discharging. According to the control method described above, the control device 30 does not control the bus voltage using the storage battery 20 when the bus voltage is within the dead zone. Therefore, the frequency of charging and discharging of the storage battery 20 can be reduced, and the lifespan of the storage battery 20 can be extended.

[0062] Furthermore, through the above process, the control device 30 can set the voltage at each power generation device to be below the upper limit voltage of the DC power supply and distribution system 1, regardless of the wiring distance from the DC bus 40 to the power generation device. Also, in the above process, the control device 30 does not need to monitor the voltage at each load and power generation device, but only needs to obtain disconnection information from the breakers 52a, 52b, 52c, 62a, 62b, and 62c. Therefore, the control device 30 can set the voltage at each power generation device to be below the upper limit voltage of the DC power supply and distribution system 1 without requiring high-speed communication.

[0063] (modified version) In the DC power supply and distribution system 1, the control device 30 does not necessarily have to include a disconnection information acquisition unit 31, a lower limit determination unit 32, and an upper limit determination unit 33. In this case, the control device 30 sets the lower limit of the bus voltage of the DC bus 40 to the largest of the lower limit voltages for each load connected to the DC bus 40, regardless of whether each load is disconnected or not. Also, the control device 30 sets the upper limit of the bus voltage of the DC bus 40 to the smallest of the upper limit voltages for each generator connected to the DC bus 40, regardless of whether each generator is disconnected or not. With such control, the process of keeping the voltages at the loads and generators within an acceptable range regardless of the wiring distance can be simplified.

[0064] Furthermore, the control device 30 does not necessarily need to include both the lower limit determination unit 32 and the lower limit determination unit 34, and the upper limit determination unit 33 and the upper limit determination unit 35. For example, the control device 30 may include only the lower limit determination unit 32 and the lower limit determination unit 34, and may not include the upper limit determination unit 33 and the upper limit determination unit 35. Even in this case, the control device 30 can ensure that the voltage at each load is equal to or greater than the lower limit voltage in the DC power supply and distribution system 1, regardless of the wiring distance from the DC bus 40 to the load.

[0065] [Embodiment 2] Other embodiments of the present invention are described below. For the sake of clarity, components having the same function as those described in the above embodiments will be denoted by the same reference numerals, and their descriptions will not be repeated. The same applies to Embodiment 3, which will be described later.

[0066] As described above, the voltage controlled by the control device 30 is the voltage at the end of the wiring from the DC bus 40 to the DC-DC converter 21 on the DC-DC converter 21 side. In Embodiment 1, a method was described in which the wiring distance between the DC-DC converter 21 and the DC bus 40 is included in DL in equation (1) and DG in equation (2) as a method for calculating the lower limit voltage and upper limit voltage of the DC-DC converter 21 when a voltage drop or rise occurs in the wiring between the DC-DC converter 21 and the DC bus 40. In Embodiment 2, a different method from Embodiment 1 is described for calculating the lower limit voltage for the load and the upper limit voltage for the power generation device when a voltage drop or rise occurs in the wiring between the DC-DC converter 21 and the DC bus 40.

[0067] For example, consider the case where the power supplied from each power generation device to the DC bus 40, and the power supplied from the DC bus 40 to each load, are as follows. • Power supplied from the first solar panel 50a to the DC bus 40: 30kW • Power supplied from the second solar panel 50b to the DC bus 40: 30kW • Power supplied from the third solar panel 50c to the DC bus 40: 10kW Power supplied from DC bus 40 to the first DC load 60a: 20kW Power supplied from DC bus 40 to the second DC load 60b: 30kW Power supplied from DC bus 40 to the third DC load 60c: 10kW In this case, the power supplied from the DC bus 40 to the battery 20 will be 10kW.

[0068] In the method of Embodiment 1, the wiring distance DC between the DC-DC converter 21 and the DC bus 40 is added to DL in equation (1) and DG in equation (2). Furthermore, the voltage fluctuation in the wiring between the DC-DC converter 21 and the DC bus 40 is calculated using the absolute value of the power consumption at the load or the absolute value of the power generated at the power generator. In other words, the current or power charged or discharged by the battery 20 is not used to calculate the voltage fluctuation occurring in the wiring between the DC-DC converter 21 and the DC bus 40. Therefore, it may not be possible to calculate an appropriate value.

[0069] In Embodiment 2, the control device 30 sets the lower and upper voltage limits of the battery 20 to values ​​that are shifted from the lower and upper voltage limits for the load and the power generation device, respectively, by the amount of the voltage drop in the wiring from the DC bus 40 to the DC-DC converter 21.

[0070] If VcL is the lower limit voltage in the battery 20 for each load, and VcG is the upper limit voltage in the battery 20 for each power generation device, then the values ​​of VcL and VcG are calculated by the following equations (3) and (4). VcL = VbusL + IC × R × DC × 2 (3) VcG = VbusG + IC × R × DC × 2 (4) In equation (3), VbusL is the value obtained when DL in equation (1) is the wiring distance between the DC bus 40 and the load, similar to the case where no voltage drop occurs in the wiring between the DC-DC converter 21 and the DC bus 40. In equation (4), VbusG is the value obtained when DG in equation (2) is the wiring distance between the DC bus 40 and the power generator, similar to the case where no voltage drop occurs in the wiring between the DC-DC converter 21 and the DC bus 40. In equations (3) and (4), IC is the current charged and discharged to the battery 20, and DC is the wiring distance between the DC-DC converter 21 and the DC bus 40. The value of IC is the value of the current in the DC-DC converter 21. Therefore, the control device 30 does not need to provide a separate communication device or the like to obtain the value of IC. The value of IC is positive when the battery 20 is discharged to the DC bus 40, and negative when the DC bus 40 is charged to the battery 20.

[0071] As shown in equations (3) and (4), when the battery 20 is discharged to the DC bus 40, the values ​​of VcL and VcG are higher than VbusL and VbusG by IC × R × DC × 2, respectively. Also, when the DC bus 40 is charged to the battery 20, the values ​​of VcL and VcG are lower than VbusL and VbusG by IC × R × DC × 2, respectively.

[0072] IC × R × DC × 2 is the voltage drop in the wiring between the DC-DC converter 21 and the DC bus 40. Therefore, in the DC power supply and distribution system 1, when the voltage at the battery 20 is VcL, the bus voltage is VbusL. Also, when the voltage at the battery 20 is VcG, the bus voltage is VbusG. The control device 30 performs the control described with reference to Figures 5 to 7, with the lower voltage limit set to VcL and the upper voltage limit set to VcG.

[0073] Figure 8 shows the relationship between the bus voltage and the voltage in the battery 20 in Embodiment 2. In Figure 8, reference numeral 801 denotes the above relationship when the battery 20 is discharged to the DC bus 40. In Figure 8, reference numeral 802 denotes the above relationship when the DC bus 40 is charged to the battery 20.

[0074] As shown by reference numeral 801 in Figure 8, when the battery 20 is discharged to the DC bus 40, VcL is higher than VbusL. Similarly, VcG is higher than VbusG. On the other hand, as shown by reference numeral 802 in Figure 8, when the DC bus 40 is charged to the battery 20, VcL is lower than VbusL. Similarly, VcG is lower than VbusG.

[0075] In Embodiment 2, the range in which the bus voltage is above VcL and below VcG becomes the dead zone in the control by the charge / discharge control unit 36. Therefore, as shown in Figure 8, in Embodiment 2, when discharging from the battery 20 to the DC bus 40, the dead zone shifts to the higher voltage side compared to Embodiment 1. Also, when charging from the DC bus 40 to the battery 20, the dead zone shifts to the lower voltage side compared to Embodiment 1.

[0076] However, discharge from the battery 20 to the DC bus 40 basically occurs when the bus voltage is low. Therefore, when discharging from the battery 20 to the DC bus 40, VcG becomes higher than VbusG as the discharge current increases. On the other hand, charging from the DC bus 40 to the battery 20 basically occurs when the bus voltage is high. Therefore, when charging from the DC bus 40 to the battery 20, VcG becomes lower than VbusL as the charging current increases.

[0077] Figure 9 shows the values ​​related to control according to Embodiment 2 for each of the loads and power generators in the DC power supply and distribution system 1. Figure 9 shows the rated power, wiring distance, and VbusL for each of the loads. Figure 9 also shows the rated power, wiring distance, and VbusG for each of the power generators. The rated power and wiring distance shown in Figure 9 are different from the rated power and wiring distance for each of the loads and power generators with the same names shown in Figure 3. Therefore, VbusL for each of the loads and VbusG for each of the power generators are also different from VbusL and VbusG shown in Figure 3.

[0078] Furthermore, Figure 9 shows the following (A) to (F).

[0079] (A) VbusL calculated for each load using the calculation method described in Embodiment 1 (B) VbusG calculated for each power generation device using the calculation method described in Embodiment 1 (C) VcL for each load calculated by the calculation method described in Embodiment 2 (D) VcG calculated for each power generation device using the calculation method described in Embodiment 2 (E) Lower and upper voltage limits in the battery 20 based on VbusL and VbusG calculated by the calculation method described in Embodiment 1. (F) Lower and upper voltage limits in the battery 20, based on VcL and VcG calculated by the calculation method described in Embodiment 2. For the calculation of each value, the following assumptions were made: VL = 540V, VG = 660V, R = 0.53mΩ / m, and DC = 500m.

[0080] Regarding (A) and (B), the calculation method described in Embodiment 1 is a method that includes the wiring distance between the DC-DC converter 21 and the DC bus 40 in DL in equation (1) and DG in equation (2). In Figure 9, the lower limit values ​​calculated by this calculation method are also referred to as VbusL and VbusG, following the notation in equations (1) and (2). Furthermore, (E) and (F) are the values ​​when neither the load nor the power generator is disconnected from the DC bus 40.

[0081] As shown in Figure 9, the lower limit of the voltage in the battery 20 based on VcL is lower than the lower limit of the voltage in the battery 20 based on VbusL. Also, the upper limit of the voltage in the battery 20 based on VcG is higher than the upper limit of the voltage in the battery 20 based on VbusG. In other words, when the lower and upper limits are determined based on the calculation method according to Embodiment 2, the dead zone of the bus voltage in the control by the control device 30 becomes wider than when the lower and upper limits are determined based on the calculation method described in Embodiment 1.

[0082] As described above, the battery 20 deteriorates with repeated charging and discharging. Therefore, according to the control according to Embodiment 2, the dead zone of the bus voltage is widened, which reduces the frequency of charging and discharging of the battery and extends the lifespan of the battery 20.

[0083] [Embodiment 3] Further embodiments of the present invention are described below.

[0084] Figure 10 shows an example of the configuration of a DC power supply and distribution system 3 according to Embodiment 3. In addition to the configuration of DC power supply and distribution system 1, DC power supply and distribution system 3 includes power meters 53a, 53b, 53c, 63a, 63b, and 63c. Furthermore, DC power supply and distribution system 3 includes a control device 30A instead of the control device 30.

[0085] Power meters 53a, 53b, and 53c are power meters that measure the power generated by the first solar panel 50a, the second solar panel 50b, and the third solar panel 50c, respectively. Power meters 63a, 63b, and 63c are power meters that measure the power consumed by the first DC load 60a, the second DC load 60b, and the third DC load 60c, respectively.

[0086] Figure 11 shows the configuration of the control device 30A. In addition to the configuration of the control device 30, the control device 30A includes an upper and lower voltage calculation unit 37. The upper and lower voltage calculation unit 37 calculates the lower voltage for each load and the upper voltage for each power generation device.

[0087] Specifically, in equation (1) described above, the upper and lower voltage limit calculation unit 37 calculates VbusL as the measured power consumption PL for each load, measured by power meters 63a, 63b, and 63c. In addition, in equation (2) described above, the upper and lower voltage limit calculation unit 37 calculates VbusG as the measured power generation PG for each power generation device, measured by power meters 53a, 53b, and 53c.

[0088] Depending on the type of load, the power consumption may fluctuate from the rated power depending on the operation of the load. Also, the power generated by a power generation device may fluctuate from the rated power depending on factors such as sunlight on the solar panels. The upper and lower voltage limit calculation unit 37 calculates the lower voltage for each load using the measured power consumption of each load. The upper and lower voltage limit calculation unit 37 also calculates the upper voltage for each power generation device using the measured power generation of each power generation device. Therefore, the upper and lower voltage limit calculation unit 37 can calculate more appropriate lower and upper voltage limits based on the measured power consumption of the loads and the measured power generation of the power generation devices.

[0089] (Example of operation) Figure 12 is a graph illustrating the lower limit of the bus voltage in Embodiment 3. In Figure 12, reference numeral 1201 denotes a graph showing examples of measured power consumption values ​​for each load. Reference numeral 1201 denotes graphs G11, G12, and G13 respectively. G11: Measured power consumption under a first DC load of 60A G12: Measured power consumption under the second DC load 60b G13: Measured power consumption under a third DC load of 60c In Figure 12, reference numeral 1202 denotes a graph showing the lower limit voltage based on the measured power consumption for each load, the lower limit of the bus voltage based on said lower limit voltage, and the lower limit of the bus voltage based on the rated power for each load. Reference numeral 1202 denotes graphs G21, G22, G23, G24, and G25 respectively. G21: Lower limit voltage based on measured power consumption for the first DC load of 60A G22: Lower limit voltage based on measured power consumption for the second DC load 60b G23: Lower limit voltage based on measured power consumption for the third DC load 60c G24: Lower limit of bus voltage based on the lower limit voltage shown in graphs G21-G23 G25: Lower limit of bus voltage based on rated power for each load. As explained in Embodiment 1, the lower limit of the bus voltage is the largest value among the lower voltage limits for each load. Therefore, graph G24 fluctuates in accordance with the fluctuations in graphs G21 to G23. On the other hand, since the rated power is constant, graph G25 remains constant regardless of the fluctuations in graphs G21 to G23.

[0090] Figure 13 is a graph illustrating the upper limit of the bus voltage in Embodiment 3. In Figure 13, reference numeral 1301 denotes a graph showing an example of the measured power output in each of the power generation devices. Reference numeral 1301 denotes graphs G31, G32, and G33 respectively. G31: Measured power generation value of the first solar panel 50a G32: Measured power generation value of the second solar panel 50b G33: Measured power generation value of the third solar panel 50c In Figure 13, reference numeral 1302 denotes a graph showing the upper limit voltage based on the measured value of the generated power for each power generation device, the upper limit of the bus voltage based on said upper limit voltage, and the upper limit of the bus voltage based on the rated power for each power generation device. Reference numeral 1202 denotes graphs G41, G42, G43, G44, and G45, respectively. G41: Upper limit voltage based on measured power generation values ​​for the first solar panel 50a G42: Upper limit voltage based on measured power generation values ​​for the second solar panel 50b. G43: Upper voltage limit based on measured power generation values ​​for the third solar panel 50c. G44: Upper limit of bus voltage based on the upper limit voltage shown in graphs G41-G43 G45: Upper limit of bus voltage based on the rated power of each power generation device As explained in Embodiment 1, the upper limit of the bus voltage is the smallest of the upper limits of the voltages for each of the power generation devices. Therefore, graph G44 fluctuates in accordance with the fluctuations in graphs G41 to G43. On the other hand, since the rated power is constant, graph G45 remains constant regardless of the fluctuations in graphs G41 to G43.

[0091] As described above, the control device 30A can appropriately determine the lower limit of the bus voltage based on the measured power consumption of each load. Furthermore, the control device 30A can appropriately determine the upper limit of the bus voltage based on the measured power generation of each power generation device.

[0092] 〔summary〕 A control device according to Embodiment 1 of the present invention is a control device for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power supply and distribution system, comprising: a lower limit determination unit that determines whether the bus voltage at the connection point of the energy storage device to the DC bus is less than a lower limit value; and a charge / discharge control unit that controls the charging / discharging current or charging / discharging power of the energy storage device so that the bus voltage at the connection point is greater than or equal to the lower limit value when the bus voltage at the connection point is less than the lower limit value, wherein the lower limit value is the largest of the lower limit voltages at the connection point that ensure the minimum operating voltage at each of the one or more loads connected to the DC bus, which are determined by reflecting the impedance between the load and the connection point.

[0093] With the above configuration, the lower limit of the busbar voltage is set to a value that ensures the minimum operating voltage for all loads. Therefore, the control device can keep the voltage at the load within the permissible range of the power distribution system, regardless of the wiring distance.

[0094] In a control device according to embodiment 2 of the present invention, the one or more loads are connected to the DC bus via a circuit breaker, and the control device further comprises a disconnection information acquisition unit that acquires disconnection information indicating whether or not the loads have been disconnected from the DC bus by the circuit breaker, and the lower limit value is the largest of the lower limit voltages for the loads that have not been disconnected from the DC bus by the circuit breaker.

[0095] With the above configuration, the control device can obtain disconnection information from each circuit breaker, thereby setting a more appropriate lower limit for the bus voltage.

[0096] In a control device according to embodiment 3 of the present invention, for each of the one or more loads, when the voltage of the DC bus drops, VL is the lower limit of the appropriate voltage at the load, PL is the power consumption at the load, DL is the wiring distance from the DC bus to the load, and R is the cable impedance per unit distance in the wiring from the DC bus to the load, the lower limit voltage at the connection point for the load is VbusL, which is calculated by the following formula (1). VbusL = VL + PL / VL × R × DL × 2 (1) With the above configuration, the control device can appropriately calculate the lower limit of the voltage at the connection point with the DC bus for each load.

[0097] In the control device according to aspect 4 of the present invention, when the current charged and discharged to the energy storage device is IC and the wiring distance between the energy storage device and the DC busbar is DC, the lower limit voltage of the energy storage device for the load is VcL, which is calculated by the following formula (3). VcL = VbusL + IC × R × DC × 2 (3) With the above configuration, the control device can appropriately calculate the lower limit voltage in the energy storage device so that the voltage at the connection point with the DC bus is equal to or greater than the lower limit voltage for each load.

[0098] In the control device according to aspect 5 of the present invention, PL in formula (1) is the measured value of the power consumption at the load.

[0099] With the above configuration, the control device can calculate a more appropriate lower voltage limit based on the measured value of power consumption.

[0100] A control device according to aspect 6 of the present invention is a control device for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power supply and distribution system, comprising: an upper limit determination unit that determines whether the bus voltage at the connection point of the energy storage device exceeds an upper limit; and a charge / discharge control unit that controls the charging / discharging current or charging / discharging power of the energy storage device so that the bus voltage at the connection point is less than or equal to the upper limit, wherein the upper limit is the smallest value among the upper limit voltages at the connection point when the output power of the power generation device is at its maximum, which are determined for each of the one or more power generation devices connected to the DC bus, reflecting the impedance between the power generation device and the connection point.

[0101] With the above configuration, the upper limit of the busbar voltage can be kept below the upper limit voltage for all power generators. Therefore, the control device can keep the voltage at the power generators within the permissible range of the power distribution system, regardless of the wiring distance.

[0102] In a control device according to embodiment 7 of the present invention, the one or more power generation devices are connected to the DC bus via a circuit breaker, and the control device further comprises a disconnection information acquisition unit that acquires disconnection information indicating whether or not the power generation device is disconnected from the DC bus by the circuit breaker, and the upper limit value is the smallest of the upper limit voltages for the power generation devices that are not disconnected from the DC bus by the circuit breaker.

[0103] With the above configuration, the control device can obtain disconnection information from each circuit breaker, thereby setting a more appropriate upper limit for the bus voltage.

[0104] In a control device according to embodiment 8 of the present invention, in each of the one or more power generation devices, when the voltage of the DC bus rises, the upper limit of the appropriate voltage in the power generation device is VG, the power generated by the power generation device is PG, the wiring distance from the DC bus to the power generation device is DG, and the cable impedance per unit distance in the wiring from the DC bus to the power generation device is R, then the upper limit voltage at the connection point for the power generation device is VbusG, which is calculated by the following formula (2). VbusG = VG - PG / VG × R × DG × 2 (2) With the above configuration, the control device can appropriately calculate the upper limit of the voltage at the connection point with the DC bus for each power generation device.

[0105] In the control device according to aspect 9 of the present invention, when the current charged and discharged to the energy storage device is IC and the wiring distance between the energy storage device and the DC busbar is DC, the lower limit voltage in the energy storage device for the power generation device is VcG, which is calculated by the following formula (4). VcG = VbusG + IC × R × DC × 2 (4) With the above configuration, the control device can appropriately calculate the upper limit voltage in the energy storage device for each power generation device, so that the voltage at the connection point with the DC busbar is equal to or greater than the upper limit voltage.

[0106] In the control device according to embodiment 10 of the present invention, PG in formula (2) is the measured value of the power generated by the power generation device.

[0107] With the above configuration, the control device can calculate a more appropriate upper voltage limit based on the measured value of the generated power.

[0108] A control method according to aspect 11 of the present invention is a control method for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power distribution system, comprising: a lower limit determination step of determining whether the bus voltage at the connection point of the energy storage device is less than a lower limit; and a charge / discharge control step of controlling the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point is greater than or equal to the lower limit, wherein the lower limit is the largest of the lower limit voltages at the connection point that ensure the minimum operating voltage at each of the one or more loads connected to the DC bus, which are determined by reflecting the impedance between the load and the connection point.

[0109] The above configuration produces the same effects as in the first embodiment.

[0110] A control method according to aspect 12 of the present invention is a control method for controlling the charging and discharging of an energy storage device connected to a DC bus of a DC power supply and distribution system, comprising: an upper limit determination step of determining whether the bus voltage at the connection point of the energy storage device exceeds an upper limit; and a charge / discharge control step of controlling the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point exceeds the upper limit, wherein the upper limit is the smallest value among the upper limit voltages at the connection point when the output power of the power generation device is at its maximum, which are determined for each of the one or more power generation devices connected to the DC bus, reflecting the impedance between the power generation device and the connection point.

[0111] The above configuration produces the same effects as in the 6th embodiment.

[0112] [Examples of implementation using software] The functions of the control devices 30 and 30A (hereinafter referred to as "devices") are programs that cause the devices to function as computers, and these can be realized by programs that cause the devices to function as computers as each control block.

[0113] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., memory) as hardware for executing the program. By executing the program using this control device and storage device, the functions described in each of the embodiments are realized.

[0114] The above program may be recorded on one or more computer-readable recording media, not temporary ones. These recording media may or may not be provided by the above device. In the latter case, the program may be supplied to the above device via any wired or wireless transmission medium.

[0115] Furthermore, some or all of the functions of each of the above control blocks can also be realized by logic circuits. For example, an integrated circuit in which logic circuits functioning as each of the above control blocks are formed is also included in the scope of the present invention. In addition, it is also possible to realize the functions of each of the above control blocks by, for example, a quantum computer.

[0116] Furthermore, each process described in the above embodiments may be performed by AI (Artificial Intelligence). In this case, the AI ​​may operate on the control device described above, or it may operate on other devices (for example, an edge computer or a cloud server).

[0117] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of Symbols]

[0118] 1.3 DC power supply and distribution system 20. Storage batteries (energy storage devices) 30, 30A control device 34 Lower limit determination unit 35 Upper limit determination unit 36 Charge / Discharge Control Unit 40 DC bus 52a, 52b, 52c, 62a, 62b, 62c circuit breakers (circuit breakers)

Claims

1. A control device for controlling the charging and discharging of an energy storage device connected to a DC busbar in a DC power distribution system, A lower limit determination unit that determines whether the bus voltage at the connection point of the energy storage device to the DC bus is below a lower limit, The system includes a charge / discharge control unit that controls the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point of the energy storage device to the DC bus is equal to or greater than the lower limit, when the bus voltage at the connection point of the energy storage device is less than the lower limit. The aforementioned lower limit is the largest of the lower limit voltages at the connection point where the load is connected to the DC bus, which are determined for each of the one or more loads connected to the DC bus, reflecting the impedance between the load and the connection point where the load is connected to the DC bus, in order to ensure the minimum operating voltage at the load. In each of the one or more loads, When the voltage of the DC bus drops, the lower limit of the appropriate voltage at the load is VL. The power consumption under the load is PL, The wiring distance from the DC busbar to the load is DL. Let R be the cable impedance per unit distance in the wiring from the DC bus to the load. In that case, A control device in which the lower limit voltage at the connection point where the load is connected to the DC bus is VbusL calculated by the following formula (1). VbusL=VL+PL / VL×R×DL×2 (1)

2. The one or more loads are connected to the DC bus via a circuit breaker. The control device further includes a disconnection information acquisition unit that acquires disconnection information indicating whether or not the load has been disconnected from the DC bus by the circuit breaker, The control device according to claim 1, wherein the lower limit value is the largest of the lower limit voltages for the load that has not been disconnected from the DC bus by the circuit breaker.

3. The current charged and discharged to the aforementioned energy storage device is IC, The wiring distance between the energy storage device and the DC busbar is DC, In that case, The control device according to claim 1, wherein the lower limit voltage in the energy storage device for the load is VcL calculated by the following formula (3). VcL=VbusL+IC×R×DC×2 (3)

4. The control device according to any one of claims 1 to 3, wherein PL in formula (1) is the measured value of the power consumption at the load.

5. A control device for controlling the charging and discharging of an energy storage device connected to a DC busbar in a DC power distribution system, An upper limit determination unit that determines whether the bus voltage at the connection point of the energy storage device exceeds an upper limit, The system includes a charge / discharge control unit that controls the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point of the energy storage device to the DC bus exceeds the upper limit, so that the bus voltage becomes less than or equal to the upper limit. A control device in which the upper limit value is the smallest of the upper limit voltages at the connection point where a power generator is connected to the DC bus, when the output power of the power generator is at its maximum, determined for each of the one or more power generators connected to the DC bus, reflecting the impedance between the power generator and the connection point where the power generator is connected to the DC bus.

6. The one or more power generation devices are connected to the DC bus via a circuit breaker. The control device further includes a disconnection information acquisition unit that acquires disconnection information indicating whether or not the power generation device has been disconnected from the DC bus by the circuit breaker, The control device according to claim 5, wherein the upper limit value is the smallest of the upper limit voltages for the power generation device that has not been disconnected from the DC bus by the circuit breaker.

7. In each of the one or more power generation devices, When the voltage of the DC bus rises, the appropriate upper limit of the voltage in the power generation device is VG. The power generated by the power generation device is called PG. The wiring distance from the DC bus to the power generation device is DG, Let R be the cable impedance per unit distance in the wiring from the DC bus to the power generation device. In that case, The control device according to claim 5 or 6, wherein the upper limit voltage at the connection point where the power generation device is connected to the DC bus is VbusG calculated by the following formula (2). VbusG=VG-PG / VG×R×DG×2 (2)

8. The current charged and discharged to the aforementioned energy storage device is called IC, The wiring distance between the energy storage device and the DC busbar is DC, In that case, The control device according to claim 7, wherein the lower limit voltage in the energy storage device for the power generation device is VcG calculated by the following formula (4). VcG=VbusG+IC×R×DC×2 (4)

9. The control device according to claim 7 or 8, wherein PG in formula (2) is the measured value of the power generated in the power generation device.

10. A control method for controlling the charging and discharging of an energy storage device connected to a DC busbar in a DC power distribution system, A lower limit determination step of determining whether the bus voltage at the connection point of the energy storage device is below a lower limit, The system includes a charge / discharge control step that controls the charge / discharge current or charge / discharge power of the energy storage device so that, when the bus voltage at the connection point of the energy storage device to the DC bus is less than the lower limit, the bus voltage at the connection point of the energy storage device is greater than or equal to the lower limit, The aforementioned lower limit is the largest of the lower limit voltages at the connection point where the load is connected to the DC bus, which are determined for each of the one or more loads connected to the DC bus, reflecting the impedance between the load and the connection point where the load is connected to the DC bus, in order to ensure the minimum operating voltage at the load. In each of the one or more loads, When the voltage of the DC bus drops, the lower limit of the appropriate voltage at the load is VL. The power consumption under the load is PL, The wiring distance from the DC busbar to the load is DL. Let R be the cable impedance per unit distance in the wiring from the DC bus to the load. In that case, A control method in which the lower limit voltage at the connection point where the load is connected to the DC bus is VbusL calculated by the following formula (1). VbusL=VL+PL / VL×R×DL×2 (1)

11. A control method for controlling the charging and discharging of an energy storage device connected to a DC busbar in a DC power distribution system, An upper limit determination step of determining whether the bus voltage at the connection point of the energy storage device exceeds an upper limit, The system includes a charge / discharge control step that controls the charge / discharge current or charge / discharge power of the energy storage device so that the bus voltage at the connection point of the energy storage device to the DC bus exceeds the upper limit, so that the bus voltage becomes less than or equal to the upper limit. A control method in which the upper limit value is determined for each of the one or more power generators connected to the DC bus, reflecting the impedance between the power generator and the connection point to which the power generator is connected to the DC bus, and is the smallest of the upper limit voltages at the connection point to which the power generator is connected when the output power of the power generator is at its maximum.

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