DC power distribution system

Abstract

To provide a DC power distribution system that facilitates control of a plurality of interconnected apparatuses in a distribution warehouse.SOLUTION: A DC power distribution system includes: first power converters 10 and 11 that supply power in one direction from power sources 20 and 21 to a DC bus 2; second power converters 13, 14, and 15 that supply power in both directions between the DC bus 2 and storage-battery-built-in loads 23, 24, and 25; a third power converter 16 that supplies power in both directions between the DC bus 2 and a motor load 26; and a control device 1 that transmits and instructs operation parameters that are a target voltage value on a DC bus side and a power conversion direction relative to the first power converters 10 and 11 and the second power converters 13, 14, and 15.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a DC power distribution system. [Background technology]

[0002] The installation of solar panels is progressing in logistics warehouses, and the introduction of loads that generate regenerative power, such as automated warehouses, is also progressing. As a conventional technology, a system has been proposed in which a logistics warehouse is equipped with solar panels and a battery-powered forklift, and in the event of a disaster, power is supplied from the battery in the forklift (see Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-4552 Summary of the Invention [Problem to be solved by the invention]

[0004] In existing logistics warehouses, the power distribution system is an AC power distribution system, and when multiple storage battery loads are connected to the system, the control becomes complicated.

[0005] The present disclosure discloses a technique for solving the above-described problems, and aims to provide a DC power distribution system that facilitates control of multiple interconnected devices in a logistics warehouse. [Means for solving the problem]

[0006] The DC power distribution system of the present disclosure comprises: A DC power distribution system that supplies power from a power source to a plurality of devices via a DC bus in a logistics warehouse, a first power converter connected between the power supply and the DC bus and supplying power unidirectionally from the power supply to the DC bus; a second power converter connected between the DC bus and the load incorporating a storage battery, and configured to supply power bidirectionally between the DC bus and the load incorporating a storage battery; a third power converter connected between the DC bus and a motor load and supplying power bidirectionally between the DC bus and the motor load; and a control device that transmits and instructs the first power converter, the second power converter, and the third power converter to operate in accordance with a target voltage value on the DC bus side and a power conversion direction. [Effects of the Invention]

[0007] According to the DC power distribution system of the present disclosure, it is possible to easily control a plurality of interconnected devices in a logistics warehouse. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a device configuration of a DC power distribution system according to a first embodiment. [Figure 2] FIG. 3 is a diagram showing initial setting values ​​of each device in the DC power distribution system according to the first embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of operation in the DC power distribution system according to the first embodiment. [Figure 4] FIG. 2 is a diagram illustrating an example of operation in the DC power distribution system according to the first embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of operation in the DC power distribution system according to the first embodiment. [Figure 6] FIG. 2 is a diagram illustrating an example of operation in the DC power distribution system according to the first embodiment. [Figure 7] FIG. 2 is a diagram illustrating an example of operation in the DC power distribution system according to the first embodiment. [Figure 8] FIG. 10 is a diagram showing initial setting values ​​of each device in the DC power distribution system according to the second embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the second embodiment. [Figure 10]FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the second embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the second embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the second embodiment. [Figure 13] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the second embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the second embodiment. [Figure 15] FIG. 11 is a diagram showing initial setting values ​​of each device in the DC power distribution system according to the third embodiment. [Figure 16] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 17] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 18] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 19] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 20] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 21] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 22] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 23] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 24] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 25] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 26] FIG. 10 is a diagram illustrating an example of operation in the DC power distribution system according to the third embodiment. [Figure 27]FIG. 10 is a diagram showing initial setting values ​​of each device in a DC power distribution system according to a fourth embodiment. [Figure 28] FIG. 10 is a characteristic diagram showing a case where a plurality of power converters have the same target voltage value and output voltage characteristics with no gradient. [Figure 29] FIG. 10 is a characteristic diagram illustrating a case where a plurality of power converters have the same target voltage value but output voltage characteristics with different slopes. [Figure 30] FIG. 10 is a diagram illustrating an example of operation in a DC power distribution system according to a fourth embodiment. [Figure 31] FIG. 10 is a diagram illustrating an example of operation in a DC power distribution system according to a fourth embodiment. [Figure 32] 2 is a diagram illustrating an example of the hardware configuration of a control device 1 according to the embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the same or corresponding parts in the text will be denoted by the same reference numerals and their description will be omitted.

[0010] Embodiment 1 (Device configuration of the first embodiment) FIG. 1 is a block diagram showing the device configuration of a DC power distribution system according to a first embodiment. As shown in FIG. 1, the DC power distribution system of the present disclosure is a DC power distribution system that supplies power from a power source to a plurality of devices via a DC bus 2 in a logistics warehouse. The power supply sources (power sources) include a commercial power supply 20, a solar panel (hereinafter referred to as PV) 21, and a system storage battery (hereinafter referred to as BAT) 22. The loads include an automatic guided vehicle (hereinafter referred to as an AGV (Automatic Guided Vehicle)) 23, a forklift 24, an electric transport vehicle (hereinafter referred to as an EV) 25, a motor 26, and a DC load 27. The power converters include an AC / DC converter 10 for commercial power, a DC / DC converter 11 for PV, a DC / DC converter 12 for BAT, a DC / DC converter 13 for AGV, a DC / DC converter 14 for forklift, a DC / DC converter 15 for EV, and a DC / AC converter 16 for motor. The system includes a control device 1 that transmits and instructs each of the power converters 10, 11, 12, 13, 14, 15, and 16 to operate parameters. The forklift 24 is battery operated. The DC load 27 is an air conditioner, a refrigeration facility, lighting, etc. that operate on DC power in the logistics warehouse. Furthermore, motor 26 is assumed to be an AC motor that operates equipment (shuttles, cranes, lifts, etc.) for an automated warehouse or the like. During powering, motor 26 is operated by AC power obtained by converting DC power from DC bus 2 using motor DC / AC converter 16. During regeneration, AC power generated by motor 26 is converted by motor DC / AC converter 16 and the converted DC power is supplied to DC bus 2. Although the AGV DC / DC converter 13, the forklift DC / DC converter 14, and the EV DC / DC converter 15 are called DC / DC converters, they are synonymous with chargers or power supply stations. However, the power conversion direction is bidirectional rather than unidirectional, and they can discharge to the DC bus 2 in an emergency.

[0011] In this disclosure, the commercial power supply AC / DC converter 10 and the PV DC / DC converter 11 are referred to as a first power converter that supplies power unidirectionally from the commercial power supply 20 and the PV 21 to the DC bus 2. In addition, the AGV 23, the forklift 24, and the EV 25 are referred to as loads with built-in batteries, and the DC / DC converter 13 for the AGV, the DC / DC converter 14 for the forklift, and the DC / DC converter 15 for the EV are referred to as second power converters that supply power in both directions between the DC bus 2 and the loads with built-in batteries. Furthermore, the motor DC / AC converter 16, which is connected between the DC bus 2 and the motor 26 and supplies power bidirectionally between the DC bus 2 and the motor 26, is referred to as a third power converter. Furthermore, the BAT DC / DC converter 12, which is connected between the DC bus 2 and the BAT 22 and supplies power bidirectionally between the DC bus 2 and the BAT 22, is referred to as a battery power converter.

[0012] 1, for simplicity, each of the loads 23, 24, 25, and 26 is depicted as one each, but there may be multiple of them. In particular, the motor 26 is assumed to be any motor load within the logistics warehouse.

[0013] The commercial power AC / DC converter 10 is connected between the commercial power supply 20 and the DC bus 2, and converts AC power supplied from the commercial power supply 20 into DC power. The control device 1 also sets a target voltage value on the DC bus 2 side and controls the output power so that the target voltage value is reached. When the upper limit power of the commercial power AC / DC converter 10 is reached, it operates at the upper limit power even if the voltage is below the target voltage value.

[0014] The PV DC / DC converter 11 is connected between the PV 21 and the DC bus 2, and maximizes the DC power supplied from the PV 21. The control device 1 also sets a target voltage value on the DC bus 2 side and controls the output power to achieve that voltage. When the upper limit power of the PV DC / DC converter 11 is reached, it operates at the upper limit power even if it is below the target voltage value. Note that when the amount of power generated by the PV 21 exceeds the demand on the DC bus 2, the output is suppressed so that the amount of power supplied from the PV 21 is equal to the demand.

[0015] The BAT DC / DC converter 12 is connected between the BAT 22 and the DC bus 2. The control device 1 sets a target voltage value on the DC bus 2 side, and if the target voltage value is higher than the bus voltage of the DC bus 2, power is converted from the BAT 22 to the DC bus 2 in the discharging direction. If the target voltage value is lower than the bus voltage of the DC bus 2, power is converted from the DC bus 2 to the BAT 22 in the charging direction. Note that in both the discharging direction and the charging direction, once the upper limit power of the BAT DC / DC converter 12 is reached, it operates at the upper limit power even if the target voltage value has not been reached.

[0016] The DC / DC converter 13 for the AGV is connected between the AGV 23 and the DC bus 2. Its operation is similar to that of the DC / DC converter 12 for the BAT.

[0017] The forklift DC / DC converter 14 is connected between the forklift 24 and the DC bus 2. Its operation is similar to that of the BAT DC / DC converter 12.

[0018] The EV DC / DC converter 15 is connected between the EV 25 and the DC bus 2. Its operation is similar to that of the BAT DC / DC converter 12.

[0019] The motor DC / AC converter 16 is connected between the motor 26 and the DC bus 2. In powering operation, the DC power supplied from the DC bus 2 is converted into AC power to drive the motor 26. In regenerative operation of the motor 26, the AC power generated by the motor 26 is converted into DC power and supplied to the DC bus 2. In powering operation, no target voltage value is set for the DC bus 2, and the required power is consumed from the DC bus 2. In regenerative operation, no target voltage value is set for the DC bus 2, and the generated regenerative power is supplied to the DC bus 2.

[0020] The DC load 27 is connected to the DC bus 2 without a power converter. In the DC power distribution system of the present disclosure, the voltage of the DC bus 2 fluctuates, but the DC load 27 is a load that can operate within that voltage fluctuation range.

[0021] The control device 1 can provide operating parameters such as a target voltage value, a power conversion direction, and a converter capacity to each of the power converters 10, 11, 12, 13, 14, 15, and 16. As explained above, in the DC power distribution system, power converters with higher target voltage values ​​are given priority for discharging, and power converters with lower target voltage values ​​are given priority for charging. In the following description, the target voltage value of each power converter is set to around 360V, but the target voltage range may be a value other than around 360V depending on the operating voltage of the power converter, the operating voltage of the load, or the standard. Furthermore, in a power distribution system, current and power can also be considered as target values, but in a DC power distribution system, by using voltage as the target value, as described above, each power converter can determine the power to be input and output by that power converter according to the difference between the target voltage value of that power converter and the actual voltage value of the DC bus 2 without the need for sequential instructions from a higher-level system, making control particularly easy. In this case, the actual voltage value of the DC bus 2 is input to each power converter, but this value does not necessarily need to be input to the control device 1.

[0022] (Initial settings of the device in the first embodiment) FIG. 2 shows initial setting values ​​(operation parameters) of each device in the DC power distribution system according to the first embodiment. In the settings in Figure 2, the target voltage value of the BAT DC / DC converter 12 is set higher than the target voltage value of the commercial power AC / DC converter 10. Therefore, the BAT 22 is not charged by power supply from the commercial power supply 20. Therefore, the basic operation of the BAT 22 is to charge when there is excess power generated by the PV 21, and to discharge when there is insufficient power generated by the PV 21. Here, the target voltage values ​​of the power converters 13, 14, and 15 are lower than the target voltage value of the commercial power AC / DC converter 10, and if the power supply from the PV 21 and BAT 22 is insufficient, they will be charged by the power supply from the commercial power source 20. In addition, the first embodiment is basically intended to be operated during time periods when PV power generation is possible.

[0023] (Operation of the first embodiment) <Operation during normal commercial power supply (1) (BAT charges surplus PV and discharges insufficient PV)> The actual operation of the DC power distribution system of the first embodiment will be described with reference to FIGS. In the figure, TV next to each of the power converters 10, 11, 12, 13, 14, 15, and 16 indicates the target voltage value, CC indicates the conversion capacity, and LC below the DC load 27 indicates the load capacity.

[0024] First, the operation of FIG. 3 will be described. In the case of Figure 3, we consider a case where there are no problems with the weather (clear weather) and the PV 21 can generate sufficient power. Here, the BAT 22 has a charge amount that allows both charging and discharging, the AGV 23, the forklift 24, and the EV 25 have charge amounts that can be charged, and for simplicity, the motor 26 is in power running mode. At this time, the PV 21 can generate sufficient power, so the PV DC / DC converter 11 can output 100 kW of power. The total of the charging power for the AGV 23, forklift 24, and EV 25, and the power consumption of the motor 26 and DC load 27 is 95 kW. Therefore, the BAT 22 charges with the surplus power of 5 kW.

[0025] Consider the situation in Figure 3 where PV21 is unable to generate sufficient power due to factors such as clouds covering the PV21. Here, the power generation capacity of PV21 is assumed to be 50 kW. The operation in this case is as shown in Figure 4. At this time, the power demand is 95 kW while the power generation amount of PV 21 is 50 kW. Therefore, BAT 22 discharges the shortfall of 45 kW.

[0026] Consider the case where the battery 22 becomes empty from the state shown in Figure 4. The operation in this case is that shown in Figure 5. At this time, since power cannot be supplied from BAT 22, the shortage of 45 kW is supplied from commercial power supply 20.

[0027] Consider a case where the motor 26 performs a regenerative operation from the state shown in Fig. 3. The operation in this case is shown in Fig. 6. At this time, the total power generated by the PV 21 and the regenerated power from the motor 26 is 110 kW, and the total power consumed by the AGV 23, the forklift 24, and the EV 25 and the DC load 27 is 85 kW. Therefore, the BAT 22 charges with the surplus power of 25 kW.

[0028] Consider the case where BAT22 and EV25 are fully charged from the state shown in Figure 3. The operation in this case is shown in Figure 7. At this time, the PV 21 can generate 100 kW of power, but the demand for power from the DC bus 2 is 45 kW. Therefore, the PV DC / DC converter 11 reduces its output and outputs only 45 kW of power.

[0029] (Effects of the First Embodiment) As described above, according to the first embodiment, by applying a DC power distribution system to a logistics warehouse, the discharge power and charge power from the power supply source can be easily controlled by setting the target voltage value of each power converter. Furthermore, when regenerative power is generated from the motor, it can be used to consume DC loads or charge the storage battery. When trying to utilize regenerative power in a conventional AC power distribution system, the following conversion is required: motor → AC / DC conversion → DC / AC conversion → AC bus, but with DC power distribution, the process is motor → AC / DC conversion → DC bus, so the DC / AC conversion can be omitted.This is expected to increase efficiency by reducing the number of conversions, and also eliminates the need for complex control such as synchronization control in DC / AC conversion. The reduction in the number of conversions applies not only to regenerative power generation from a motor, but also to all power supply sources other than commercial power sources. For example, in the case of an AC power distribution system that utilizes solar energy in a logistics warehouse, when trying to charge an EV from PV, conversions such as DC / DC conversion → DC / AC conversion → AC / DC conversion → DC / DC conversion are required, but in a DC power distribution system, DC / AC conversion → AC / DC conversion is not necessary, so the number of conversions can be reduced. This is expected to increase the efficiency and simplify the system. Furthermore, logistics warehouses have many control targets, such as PV, forklifts, AGVs, and automated warehouses, and these are interconnected in one direction or two directions to supply power, so applying a conventional AC power distribution system would make the above-mentioned control more complex. Therefore, in this embodiment, by applying a DC power distribution system to logistics warehouses and setting a target voltage value, it is expected that the system will become more efficient and simpler.

[0030] Embodiment 2 (Device Configuration of Second Embodiment) The equipment configuration of the DC power distribution system according to the second embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0031] (Initial settings of the device in the second embodiment) FIG. 8 shows initial setting values ​​(operation parameters) of each device in the DC power distribution system according to the second embodiment. 8, the target voltage value of the BAT DC / DC converter 12 is set lower than the target voltage value of the commercial power supply AC / DC converter 10. Therefore, the BAT 22 is charged by power supply from the commercial power supply 20. Here, the target voltage values ​​of power converters 13 , 14 , 15 are also lower than the target voltage value of commercial power AC / DC converter 10 , and they are charged by power supply from commercial power supply 20 . In the second embodiment, operation is basically considered at night when electricity is cheap, and power generation by the PV 21 is not considered because it is night.

[0032] (Operation of the second embodiment) <Operation during normal commercial power supply (2) (BAT is also charged from commercial power)> The actual operation of the second embodiment will be described with reference to FIGS. First, consider the case where the BAT 22, AGV 23, forklift 24, and EV 25 are charged by power supplied from commercial power source 20. Here, the BAT 22, AGV 23, forklift 24, and EV 25 are charged to a chargeable amount, and for simplicity, the motor 26 is in power running mode. Operation in this case is shown in Figure 9. In this case, the conversion capacity of commercial power AC / DC converter 10 is 100 kW, but the total of the charging power of AGV 23, forklift 24, and EV 25 and the power consumption of motor 26 and DC load 27 is 95 kW. Therefore, BAT 22 charges the surplus of 5 kW.

[0033] Consider the case where the converter capacity of commercial power AC / DC converter 10 is reduced based on the conditions in Figure 9. Here, the conversion capacity of commercial power AC / DC converter 10 is assumed to be 80 kW. Operation in this case is shown in Figure 10. The full charge capacity and charge amount at that time for BAT 22, AGV 23, forklift 24, and EV 25 are also shown to the right of each device. At this time, the power supplied from commercial power supply 20 is 80 kW, while the total power consumed by motor 26 and DC load 27 is 30 kW. Therefore, the remaining 50 kW of power supply is used for charging. If the target voltage values ​​of the power converters of the devices to be charged are arranged in ascending order, the order is EV 25, forklift 24, AGV 23, and BAT 22. Charging is prioritized in descending order of target voltage value, so EV 25 will be charged first. The conversion capacity of EV DC / DC converter 15 is 50 kW, so the remaining 50 kW of power supply is used only to charge EV 25.

[0034] Consider the case where 120 minutes have passed since the state shown in Figure 10. The operation in this case is shown in Figure 11. At this point, EV25 is fully charged and will not be charged any further. Therefore, the remaining 50 kW of power supply is used to charge other devices. Charging is prioritized in order of lowest target voltage value, so forklift 24 and AGV23 are charged with power converter capacities of 10 kW and 5 kW, respectively. The remaining 35 kW of power supply is then used to charge BAT22.

[0035] Consider the case where 60 minutes have passed since the state in Figure 11. The operation in this case is shown in Figure 12. At this point, AGV23 is fully charged and will not be charged any further. Therefore, the remaining 50 kW of power supply is used to charge other devices. Charging is prioritized in order of lowest target voltage value, so forklift24 is charged with 10 kW of power converter capacity. The remaining 40 kW of power supply is then used to charge BAT22.

[0036] Consider the case where 120 minutes have passed since the state in Figure 12. The operation in this case is shown in Figure 13. At this point, forklift 24 is fully charged and will not be charged any further. Therefore, the remaining 50 kW of power supply is diverted to other charging. At this point, only BAT22 is not fully charged, so the remaining 50 kW of power supply is diverted to charging BAT22.

[0037] Consider the case where 42 minutes have passed since the state in Figure 13. Figure 14 shows the operation in this case. At this time, the battery 22 is fully charged and no further charging is performed. Therefore, the commercial power supply 20 supplies only the power supply of 30 kW required by the motor 26 and the DC load 27.

[0038] (Effects of the second embodiment) In an AC power distribution system, under the conditions shown in Figure 10, the power demand (total charging power + power consumption) is 195kW compared to the 80kW supplied from the commercial power source, which could result in an overload. However, in a DC power distribution system, charging priority can be easily controlled by setting a target voltage value, and overload can be prevented because charging will not exceed the supplied power.

[0039] Embodiment 3 (Device Configuration of Third Embodiment) The device configuration of the DC power distribution system according to the third embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0040] (Initial settings of the device in the third embodiment) FIG. 15 shows initial setting values ​​(operation parameters) of each device in the DC power distribution system according to the third embodiment. In the initial settings of Figure 15, the basic settings are the same as those of Figure 2, but here we consider a case where commercial power supply 20 experiences a power outage and the power supply from commercial power supply 20 is cut off. In addition, as an operation during a power outage, power converters 13, 14, and 15 are switched so that they can convert not only in the charging direction but also in both charging and discharging directions.

[0041] (Operation of the third embodiment) <Operation during commercial power outage (1) (batteries have priority for charging and discharging)> The actual operation of the third embodiment will be described with reference to FIGS. First, consider a case where commercial power supply 20 is interrupted due to a disaster or the like, and the power generation of PV 21 becomes 0 kW due to bad weather, etc. Here, for simplicity, it is assumed that motor 26 is in power running operation. The full charge capacity and charge amount at that time for BAT22, AGV23, forklift24, and EV25 are shown on the right side of each. The initial conditions for charge amount are 145kWh, 0kWh, 10kWh, and 50kWh, respectively. The operation in this case is shown in Figure 16. At this time, because there is no power supply from commercial power source 20 or PV 21, the storage batteries discharge to maintain the DC power distribution system. Since power converters discharge in order of highest target voltage value and charge in order of lowest target voltage value, based on the target voltage values ​​of power converters 12, 13, 14, and 15, the discharge priority of the storage batteries is BAT22, AGV23, forklift 24, and EV25, and the charge priority is EV25, forklift 24, AGV23, and BAT22. As a result, when BAT22 discharges 100 kW and AGV23, forklift 24, and EV25 charge at their rated capacity, the supply and demand of power is balanced.

[0042] Consider the case where 60 minutes have passed since the state in Figure 16. Figure 17 shows the operation in this case. At this time, AGV23 and EV25 are fully charged and will not be charged any further. Therefore, when BAT22 discharges 45kW and forklift24 charges at its rated capacity, the power supply and demand are balanced.

[0043] Consider the case where 60 minutes have passed since the state in Figure 17. Figure 18 shows the operation in this case. At this time, the forklift 24 is fully charged and will not be charged any further. Also, the charge amount of BAT22 becomes 0kWh. Therefore, from this point on, discharge will be prioritized as follows: AGV23, forklift 24, and EV25. Now, the total power required by motor 26 and DC load 27 is 35kW, so AGV23 will discharge 5kW of its rated power, forklift 24 will discharge 10kW of its rated power, and EV25 will discharge the missing power of 20kW.

[0044] Consider the case where 60 minutes have passed since the state in Figure 18. Figure 19 shows the operation in this case. At this time, the charge amount of AGV23 is 0kWh. Therefore, from this point on, discharge will be prioritized as forklift 24 and EV25. Now, since the 5kW power supply from AGV23 has been lost, EV25 will discharge 25kW of power.

[0045] Consider the case where 120 minutes have passed since the state shown in Figure 19. The operation in this case is shown in Figure 20. At this time, the charge level of forklift 24 is 0 kWh. Therefore, from this point on, only EV 25 will discharge. Now, since the 10 kW of power supplied from forklift 24 has been lost, EV 25 will discharge 35 kW of power.

[0046] Consider the case where 52 minutes have passed since the state in Figure 20. The operation in this case is shown in Figure 21. At this time, the charge level of the EV25 becomes 0kWh, and all power supply sources are lost, causing the DC power distribution system to stop.

[0047] Consider the case where the PV 21 is restored from the state shown in Fig. 21. Here, the power generated by the PV 21 is assumed to be 100 kW. The operation in this case is shown in Fig. 22. At this time, the power consumption of the motor 26 and DC load 27 is 35 kW, so the remaining power of 65 kW is used to charge the EV 25, forklift 24, AGV 23, and BAT 22 in the order of priority. Therefore, the EV 25, forklift 24, and AGV 23 are charged to their rated capacity, and the BAT 22 is not charged because there is no surplus power.

[0048] Consider the case where 60 minutes have passed since the state in Figure 22. The operation in this case is shown in Figure 23. At this point, AGV23 is fully charged and will not charge any more, so BAT22 will charge the remaining 5kW of power.

[0049] Consider the case where 60 minutes have passed since the state in Figure 23. The operation in this case is shown in Figure 24. At this point, the EV25 is fully charged and will not charge any more, so the BAT22 will charge the remaining 55kW of power.

[0050] Consider the case where 60 minutes have passed since the state in Figure 24. Figure 25 shows the operation in this case. At this time, forklift 24 is fully charged and will not be charged any further, so BAT 22 will charge the remaining 65 kW of power.

[0051] Consider the case where 82 minutes have passed since the state in Figure 25. The operation in this case is shown in Figure 26. At this time, the battery 22 is fully charged and no further charging is performed. Therefore, the photovoltaic cell 21 supplies only the electric power of 35 kW required by the motor 26 and the DC load 27.

[0052] (Effects of the Third Embodiment) As described above, during a power outage, not only BATs but also AGVs, forklifts, and EVs can discharge power to the DC distribution system, allowing the logistics warehouse equipment to continue operating. Controlling the order of charging and discharging in an AC power distribution system requires power instructions, but in a DC power distribution system, the priority of charging and discharging can be set by setting a target voltage value for each power converter, which simplifies control. In addition, for EVs that serve as a means of transportation during disasters, it is possible to control the charging process by giving them a higher priority and discharging by giving them a lower priority, so that they remain charged until the end.

[0053] Embodiment 4 (Device Configuration of Fourth Embodiment) The equipment configuration of the DC power distribution system according to the fourth embodiment is the same as that of the first embodiment (FIG. 1), and therefore a description thereof will be omitted.

[0054] (Initial setting values ​​of the device in the fourth embodiment) FIG. 27 shows initial setting values ​​(operation parameters) of each device in the DC power distribution system according to the fourth embodiment. The basic settings in FIG. 27 (Embodiment 4) are the same as those in FIG. 15 (Embodiment 3), but here the target voltage values ​​of the power converters 12, 13, 14, and 15 are set to the same value (360 V). This allows the storage batteries to charge and discharge together. However, if the power converters 12, 13, 14, and 15 have characteristics such as those in FIG. 28, there is a risk that a slight measurement error or the like will cause each power converter to charge and discharge unstably. Therefore, in the fourth embodiment, each of the power converters 12, 13, 14, and 15 is configured to have a different slope in the output voltage characteristic with the target voltage value (DC 360 V) as the base point, as shown in Fig. 29. Note that the vertical axis in Fig. 28 and Fig. 29 represents the actual voltage of the DC bus 2, and the horizontal axis represents the charge / discharge power.

[0055] (Explanation of the operation of the fourth embodiment) <Operation during commercial power outage (2) (storage batteries are charged and discharged together)> The actual operation of the fourth embodiment will be described with reference to FIGS. First, consider a case where commercial power supply 20 is interrupted due to a disaster or the like, and the power generated by PV 21 falls to 0 kW due to bad weather. For simplicity, assume that motor 26 is in power running mode. Operation in this case is shown in FIG. 30. At this time, because there is no power supply from commercial power source 20 or PV 21, the batteries of BAT 22, AGV 23, forklift 24, and EV 25 discharge to maintain the DC power distribution system. The total power consumption of motor 26 and DC load 27 is 16.5 kW. As shown in Figure 29, regardless of the actual voltage value of DC bus 2, the output of each power converter is set to a ratio of power converter 12:power converter 13:power converter 14:power converter 15 = 100:5:10:50 based on the converter capacity. Therefore, for a power consumption of 16.5 kW, power converters 12, 13, 14, and 15 output 10 kW, 0.5 kW, 1 kW, and 5 kW, respectively, aiming for the target voltage (360 V).

[0056] Consider the case where the PV 21 is restored from the state shown in Fig. 30. Here, it is assumed that the power generated by the PV 21 is 100 kW and the load capacity of the DC load 27 has changed to 7.5 kW. The operation in this case is shown in Fig. 31. At this time, the total power consumption of the motor 26 and DC load 27 is 17.5 kW compared to the 100 kW of power supplied from the PV 21. Therefore, 82.5 kW is surplus power, which is used to charge the storage batteries BAT 22, AGV 23, forklift 24, and EV 25. As for the charging power, the ratio of power converter 12:power converter 13:power converter 14:power converter 15 is also 100:5:10:50, so power converters 12, 13, 14, and 15 charge 50 kW, 2.5 kW, 5 kW, and 25 kW, respectively.

[0057] (Effects of the Fourth Embodiment) In the above explanation of the operation, the conversion efficiency of the power converter has been omitted for simplicity, but in reality, losses occur with each conversion. Therefore, as shown in Figures 16 and 17 of the third embodiment, operations such as charging from one storage battery to another storage battery result in losses. In contrast, if the target voltage value is the same and the storage batteries are charged and discharged as a whole, as in the fourth embodiment, charging from one storage battery to another can be prevented, and higher efficiency can be expected. In addition, in an AC power distribution system, when controlling multiple storage batteries to charge and discharge in a balanced manner, it is necessary to sequentially give power instructions to each power converter. However, in a DC power distribution system, this can be easily controlled by giving each power converter the characteristics shown in Figure 29.

[0058] An example of the hardware configuration of the control device 1 in these embodiments is shown in FIG. As shown in Figure 32, the control device 1 is composed of a processor 100 and a memory device 101, and is connected to a commercial power supply AC / DC converter 10, a PV DC / DC converter 11, a BAT DC / DC converter 12, an AGV DC / DC converter 13, a forklift DC / DC converter 14, an EV DC / DC converter 15, and a motor DC / AC converter 16 via a wireless or wired network. The storage device 101 includes a volatile storage device such as a random access memory and a non-volatile auxiliary storage device such as a flash memory, both not shown. Alternatively, a hard disk auxiliary storage device may be included instead of the flash memory. The processor 100 executes a program input from the storage device 101. In this case, the program is input from the auxiliary storage device to the processor 100 via the volatile storage device. The processor 100 may also output data such as calculation results to the volatile storage device of the storage device 101, or may store the data in the auxiliary storage device via the volatile storage device. The control device 1 may be installed as a server.

[0059] Although the present disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not exemplified are conceivable within the scope of the technology disclosed in this specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment.

[0060] Various aspects of the present disclosure are summarized below as appendices.

[0061] (Appendix 1) A DC power distribution system that supplies power from a power source to a plurality of devices via a DC bus in a logistics warehouse, a first power converter connected between the power supply and the DC bus and supplying power unidirectionally from the power supply to the DC bus; a second power converter connected between the DC bus and the load incorporating a storage battery, and configured to supply power bidirectionally between the DC bus and the load incorporating a storage battery; a third power converter connected between the DC bus and a motor load and supplying power bidirectionally between the DC bus and the motor load; a control device that transmits and instructs the first power converter and the second power converter to operate parameters including a target voltage value on the DC bus side and a power conversion direction. (Appendix 2) The power source includes a commercial power source and a solar panel; the first power converter is a commercial power supply power converter connected between the commercial power supply and the DC bus and supplying power unidirectionally from the commercial power supply to the DC bus, and a solar panel power converter connected between the solar panel and the DC bus and supplying power unidirectionally from the solar panel to the DC bus, The DC power distribution system according to claim 1, wherein the control device determines an operation mode depending on whether the commercial power supply is operating normally, whether there is a power outage of the commercial power supply, whether it is daytime or nighttime, and weather conditions, and transmits instructions to the first power converter and the second power converter regarding the operating parameters corresponding to the operation mode. (Appendix 3) 3. The DC power distribution system according to claim 1, wherein a first target voltage value on a DC bus side is set as the operating parameter, and the first power converter increases the power supplied from the power source to the DC bus when the voltage of the DC bus is lower than the first target voltage value, and decreases the power supplied from the power source to the DC bus when the voltage of the DC bus is higher than the first target voltage value. (Appendix 4) 4. The DC power distribution system according to claim 1, wherein a second target voltage value on the DC bus side is set as the operating parameter, and the second power converter increases the power supplied from the load incorporating a storage battery to the DC bus when the voltage of the DC bus is lower than the second target voltage value, and increases the power supplied from the DC bus to the load incorporating a storage battery when the voltage of the DC bus is higher than the second target voltage value. (Appendix 5) A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 2, wherein, in an operation mode in which the solar panel can generate power, a target voltage value on a DC bus side of the battery power converter is made higher than a target voltage value on a DC bus side of the commercial power supply power converter, and a target voltage value on a DC bus side of the second power converter is made lower than a target voltage value on the DC bus side of the commercial power supply power converter. (Appendix 6) A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 2, wherein, in an operation mode in which the solar panel cannot generate power, the target voltage value on the DC bus side of the storage battery power converter is made lower than the target voltage value on the DC bus side of the commercial power supply power converter, and the target voltage value on the DC bus side of the second power converter is made lower than the target voltage value on the DC bus side of the commercial power supply power converter. (Appendix 7) A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 2, wherein when the commercial power source is in a power outage operation mode, the conversion direction of the second power converter of the storage battery built-in load is bidirectionally convertible between charging and discharging. (Appendix 8) A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 5. The DC power distribution system according to claim 1, wherein, when there are a plurality of the storage battery power converters and the second power converters having the same target voltage value on the DC bus side, the storage battery power converters and the second power converters have output voltage characteristics with different slopes. (Appendix 9) 9. The DC power distribution system according to any one of Supplementary note 1 to Supplementary note 8, wherein the motor load operates the motor with AC power obtained by converting DC power of the DC bus by the third power converter during power running, and supplies DC power obtained by converting AC power generated by the motor by the third power converter to the DC bus during regeneration. (Appendix 10) 10. A DC power distribution system according to any one of Supplementary Note 1 to Supplementary Note 9, comprising a DC load connected to the DC bus and operable by DC power. (Appendix 11) The power source includes a commercial power source, a solar panel, and a storage battery. The battery-integrated load includes a forklift and an electric transport vehicle, 11. The DC power distribution system according to any one of Supplementary Note 1 to Supplementary Note 10, wherein the motor load is an automated warehouse. [Explanation of symbols]

[0062] 1 control device, 2 DC bus, 10 AC / DC converter for commercial power supply, 11 DC / DC converter for PV, 12 DC / DC converter for BAT, 13 DC / DC converter for AGV, 14 DC / DC converter for forklift, 15 DC / DC converter for EV, 16 DC / AC converter for motor, 20 Commercial power supply, 21 Photovoltaic panels (PV), 22 Grid storage batteries (BAT), 23 Automated guided vehicles (AGVs), 24 Forklifts, 25 Electric vehicles (EVs) for transportation, 26 Motors, 27 DC loads.

Claims

1. A DC power distribution system that supplies power from a power source to a plurality of devices via a DC bus in a logistics warehouse, a first power converter connected between the power supply and the DC bus and supplying power in one direction from the power supply to the DC bus; a second power converter connected between the DC bus and the load incorporating a storage battery, and configured to supply power bidirectionally between the DC bus and the load incorporating a storage battery; a third power converter connected between the DC bus and a motor load and supplying power bidirectionally between the DC bus and the motor load; a control device that transmits and instructs the first power converter and the second power converter to operate parameters including a target voltage value on the DC bus side and a power conversion direction.

2. The power source includes a commercial power source and a solar panel; the first power converter is a commercial power supply power converter connected between the commercial power supply and the DC bus and configured to supply power unidirectionally from the commercial power supply to the DC bus, and a solar panel power converter connected between the solar panel and the DC bus and configured to supply power unidirectionally from the solar panel to the DC bus, 2. The DC power distribution system according to claim 1, wherein the control device determines an operation mode depending on whether the commercial power supply is operating normally, whether there is a power outage of the commercial power supply, the time of day or night, and weather conditions, and transmits and instructs the first power converter and the second power converter to use the operating parameters corresponding to the operation mode.

3. 3. The DC power distribution system according to claim 1, wherein a first target voltage value on a DC bus side is set as the operating parameter, and when the voltage of the DC bus is lower than the first target voltage value, the first power converter increases the power supplied from the power source to the DC bus, and when the voltage of the DC bus is higher than the first target voltage value, reduces the power supplied from the power source to the DC bus.

4. 3. The DC power distribution system according to claim 1, wherein a second target voltage value on the DC bus side is set as the operating parameter, and when the voltage of the DC bus is lower than the second target voltage value, the second power converter increases the power supplied from the load incorporating a storage battery to the DC bus, and when the voltage of the DC bus is higher than the second target voltage value, increases the power supplied from the DC bus to the load incorporating a storage battery.

5. A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 2, wherein, in an operation mode in which the solar panel can generate power, a target voltage value on the DC bus side of the battery power converter is made higher than a target voltage value on the DC bus side of the commercial power supply power converter, and a target voltage value on the DC bus side of the second power converter is made lower than the target voltage value on the DC bus side of the commercial power supply power converter.

6. A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 2, wherein, in an operation mode in which the solar panel cannot generate power, a target voltage value on the DC bus side of the battery power converter is made lower than a target voltage value on the DC bus side of the commercial power supply power converter, and a target voltage value on the DC bus side of the second power converter is made lower than a target voltage value on the DC bus side of the commercial power supply power converter.

7. A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 2, wherein when the commercial power source is in a power outage operation mode, the conversion direction of the second power converter of the storage battery built-in load is bidirectionally convertible between charging and discharging.

8. A storage battery is provided as the power source, a battery power converter connected between the DC bus and the battery, for supplying power bidirectionally between the DC bus and the battery; 3. The DC power distribution system according to claim 1, wherein when there are a plurality of the storage battery power converters and the second power converters having the same target voltage value on the DC bus side, the storage battery power converters and the second power converters are configured to have different slopes in the output voltage characteristics of the storage battery power converters and the second power converters.

9. 3. The DC power distribution system according to claim 1, wherein the motor load operates the motor with AC power obtained by converting DC power from the DC bus using the third power converter during power running, and supplies DC power obtained by converting AC power generated by the motor using the third power converter to the DC bus during regeneration.

10. 3. The DC power distribution system according to claim 1, further comprising a DC load connected to the DC bus and operable by DC power.

11. The power source includes a commercial power source, a solar panel, and a storage battery. The battery-integrated load includes a forklift and an electric transport vehicle, 3. The DC power distribution system according to claim 1, wherein the motor load includes an automated warehouse.

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