DC power distribution system

Abstract

This DC power distribution system supplies power from power supplies (20, 21) through a DC bus (2) to a plurality of devices (23, 24, 25, 26) in a logistics warehouse, and comprises: first power converters (10, 11) that supply power unidirectionally from the power supplies (20, 21) toward the DC bus (2); second power converters (13, 14, 15) that supply power bidirectionally between the DC bus (2) and built-in storage battery loads (23, 24, 25); a third power converter (16) that supplies power bidirectionally between the DC bus (2) and a motor load (26); and a control device (1) that instructs the first power converters (10, 11) and the second power converters (13, 14, 15) to transmit a target voltage value on the DC bus side and operation parameters being the power conversion directions.

Description

DC power distribution system

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

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

[0003] Japanese Patent Application Publication No. 11-4552

[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.

[0006] The DC power distribution system disclosed herein is a DC power distribution system that supplies power from a power source to a plurality of devices in a logistics warehouse via a DC bus, and includes: a first power converter connected between the power source and the DC bus and supplying power unidirectionally from the power source to the DC bus; a second power converter connected between the DC bus and a load incorporating a storage battery and supplying 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 based on a target voltage value on the DC bus side and a power conversion direction.

[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.

[0008] FIG. 1 is a block diagram showing a device configuration of a DC power distribution system according to embodiment 1. FIG. 2 is a diagram showing initial setting values ​​of each device of the DC power distribution system according to embodiment 1. FIG. 3 is a diagram showing an operation example in the DC power distribution system according to embodiment 1. FIG. 4 is a diagram showing an operation example in the DC power distribution system according to embodiment 1. FIG. 5 is a diagram showing an operation example in the DC power distribution system according to embodiment 1. FIG. 6 is a diagram showing an operation example in the DC power distribution system according to embodiment 1. FIG. 7 is a diagram showing an operation example in the DC power distribution system according to embodiment 1. FIG. 8 is a diagram showing an operation example in the DC power distribution system according to embodiment 1. FIG. 9 is a diagram showing an operation example in the DC power distribution system according to embodiment 2. FIG. 10 is a diagram showing an operation example in the DC power distribution system according to embodiment 2. FIG. 11 is a diagram showing an operation example in the DC power distribution system according to embodiment 2. FIG. 12 is a diagram showing an operation example in the DC power distribution system according to embodiment 2. FIG. 13 is a diagram showing an operation example in the DC power distribution system according to embodiment 2. FIG. 10 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 11 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 12 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 13 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 14 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 15 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 16 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 17 is a diagram showing an example of operation in a DC power distribution system according to embodiment 3. FIG. 18 is a diagram showing an example of operation in a DC power distribution system according to embodiment 4. FIG. 19 is a characteristic diagram when a plurality of power converters have the same target voltage value and no gradient in the output voltage characteristics. FIG. 19 is a characteristic diagram when a plurality of power converters have the same target voltage value and have different gradients in the output voltage characteristics.Fig. 10 is a diagram showing an example of operation in a DC power distribution system according to embodiment 4. Fig. 11 is a diagram showing an example of operation in a DC power distribution system according to embodiment 4. Fig. 12 is a diagram showing an example of the hardware configuration of a control device 1 in an embodiment.

[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 Embodiment 1) Fig. 1 is a block diagram showing the device configuration of a DC power distribution system according to embodiment 1. 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 in a logistics warehouse via a DC bus 2. The system includes, as power supply sources (power sources), a commercial power source 20, solar panels (hereinafter referred to as PV) 21, and a system storage battery (hereinafter referred to as BAT) 22. The system includes, as loads, an automated guided vehicle (hereinafter referred to as AGV (Automatic Guided Vehicle)) 23, a forklift 24, a transport electric vehicle (hereinafter referred to as EV) 25, a motor 26, and a DC load 27. The system includes power converters: a commercial power 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. The system also includes a control device 1 that transmits operating parameters to each of the power converters 10, 11, 12, 13, 14, 15, and 16. The forklift 24 is battery-powered. The DC load 27 is an air conditioner, refrigeration equipment, lighting, and the like that operate on DC power in a logistics warehouse. The motor 26 is an AC motor that operates equipment (such as a shuttle, a crane, and a lift) in an automated warehouse. During powering, the motor 26 is operated by AC power converted from DC power from the DC bus 2 by the motor DC / AC converter 16. During regeneration, AC power generated by the motor 26 is converted by the motor DC / AC converter 16, and the converted DC power is supplied to the DC bus 2. The AGV DC / DC converter 13, the forklift DC / DC converter 14, and the EV DC / DC converter 15 are called DC / DC converters, but 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 first power converters that supply power unidirectionally from the commercial power supply 20 and the PV 21 to the DC bus 2. The AGV 23, the forklift 24, and the EV 25 are referred to as loads incorporating a storage battery, and the AGV DC / DC converter 13, the forklift DC / DC converter 14, and the EV DC / DC converter 15 are referred to as second power converters that supply power bidirectionally between the DC bus 2 and the loads incorporating a storage battery. 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. 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 power converter for the storage battery.

[0012] 1, for simplicity, each of the loads 23, 24, 25, and 26 is depicted as one each, but there may be multiple loads. 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 sets a target voltage value on the DC bus 2 side and controls the output power to reach that target voltage value. 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. 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 AGV DC / DC converter 13 is connected between the AGV 23 and the DC bus 2. Its operation is similar to that of the BAT DC / DC converter 12.

[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 each power converter 10, 11, 12, 13, 14, 15, and 16 with operating parameters such as a target voltage value, a power conversion direction, and a converter capacity. As explained above, in a DC power distribution system, power converters with higher target voltage values ​​are preferentially discharged and power converters with lower target voltage values ​​are preferentially charged. In the following explanation, the target voltage value of each power converter is set to around 360 V. However, the target voltage range may be a value other than around 360 V depending on the operating voltage of the power converter, the operating voltage of the load, or specifications. While current and power can be considered as target values ​​in a power distribution system, using voltage as the target value in a DC power distribution system allows each power converter to determine the power to be input or output based on the difference between the target voltage value of the power converter and the actual voltage value of the DC bus 2 without the need for sequential instructions from a higher-level system, thereby making control particularly easy. At this time, the actual voltage value of the DC bus 2 is input to each power converter, but this value does not necessarily have to be input to the control device 1 .

[0022] (Initialized Settings of Devices in First Embodiment) FIG. 2 shows initial settings (operating parameters) of each device in the DC distribution system according to the first embodiment. In the settings shown in FIG. 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 supplied from the commercial power source 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. Therefore, when the power supply from the PV 21 and the BAT 22 is insufficient, the BAT 22 is charged by power supplied from the commercial power source 20. Note that the first embodiment is basically intended for operation during time periods when PV power generation is possible.

[0023] (Operation of Embodiment 1) <Operation under normal commercial power supply conditions (1) (BAT charges PV surplus and discharges PV shortage)> The actual operation of the DC power distribution system of Embodiment 1 will be described with reference to Figures 3 to 7. Note that TV drawn next to each power converter 10, 11, 12, 13, 14, 15, and 16 in the figures indicates the target voltage value, and CC indicates the conversion capacity. Furthermore, LC drawn below the DC load 27 indicates the load capacity.

[0024] First, the operation of FIG. 3 will be described. In the case of FIG. 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 is charged to a level that allows both charging and discharging, the AGV 23, the forklift 24, and the EV 25 are charged to a level that allows charging, and for simplicity, the motor 26 is in power running mode. In this case, since the PV 21 can generate sufficient power, the PV DC / DC converter 11 can output 100 kW of power. Furthermore, the total of the charging power of the AGV 23, the forklift 24, and the EV 25, and the power consumption of the motor 26 and the DC load 27, is 95 kW. Therefore, the BAT 22 charges the surplus power of 5 kW.

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

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

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

[0028] Consider the case where the BAT 22 and EV 25 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 power demand from the DC bus 2 is 45 kW. Therefore, the PV DC / DC converter 11 suppresses its output and outputs only 45 kW of power.

[0029] (Effects of 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 a motor, it can be used to consume DC loads or charge a storage battery. In a conventional AC power distribution system, attempting to utilize regenerative power requires conversion from motor → AC / DC conversion → DC / AC conversion → AC bus. However, with DC power distribution, the process is motor → AC / DC conversion → DC bus, eliminating the need for DC / AC conversion. This can be expected to improve efficiency by reducing the number of conversions, and also eliminates the need for complex control, such as synchronization control, during DC / AC conversion. The reduction in the number of conversions applies not only to regenerative power generated by 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 utilizing solar energy in a logistics warehouse, charging an EV from PV requires conversions such as DC / DC → DC / AC → AC / DC → DC / DC. However, a DC power distribution system does not require DC / AC → AC / DC conversion, reducing the number of conversions. This is expected to improve system efficiency and simplify the system. Furthermore, a logistics warehouse contains many control targets, such as PV, forklifts, AGVs, and automated warehouses, which are interconnected unidirectionally or bidirectionally to supply power. Therefore, applying a conventional AC power distribution system would significantly increase the complexity of the control. Therefore, in this embodiment, by applying a DC power distribution system to a logistics warehouse and setting a target voltage value, it is expected to improve system efficiency and simplify the system.

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

[0031] (Initial Setting Values ​​of Devices in Second Embodiment) Fig. 8 shows initial setting values ​​(operating parameters) of each device of a DC power distribution system according to the second embodiment. In the settings in Fig. 8, the target voltage value of the BAT DC / DC converter 12 is set lower than the target voltage value of the commercial power 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 the power converters 13, 14, and 15 are also lower than the target voltage value of the commercial power AC / DC converter 10, and the BAT 22 is charged by power supply from the commercial power supply 20. Note that the second embodiment is basically intended for operation at night when electricity rates are low. Furthermore, because it is nighttime, power generation by the PV 21 is not considered.

[0032] (Operation of Embodiment 2) <Operation When Commercial Power Supply is Normal (2) (BAT is Also Charged from Commercial Power Supply)> Actual operation of Embodiment 2 will be described with reference to FIGS. 9 to 14 . First, consider the case where BAT 22, AGV 23, forklift 24, and EV 25 are charged with power supplied from commercial power supply 20. Here, BAT 22, AGV 23, forklift 24, and EV 25 are charged to a chargeable amount, and for simplicity, motor 26 is in power running operation. Operation in this case is shown in FIG. 9 . In this case, while the conversion capacity of commercial power supply AC / DC converter 10 is 100 kW, 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 5 kW.

[0033] Consider the case where the converter capacity of the commercial power AC / DC converter 10 is reduced based on the conditions in FIG. 9 . Here, the conversion capacity of the commercial power AC / DC converter 10 is assumed to be 80 kW. The operation in this case is shown in FIG. 10 . The full charge capacity and charge amount at that time for the BAT 22, AGV 23, forklift 24, and EV 25 are shown to the right of each device. In this case, the power supplied from the commercial power source 20 is 80 kW, while the total power consumed by the motor 26 and DC load 27 is 30 kW. Therefore, the remaining 50 kW of power supply is used for charging. The target voltage values ​​of the power converters of the devices to be charged are arranged in ascending order: EV 25, forklift 24, AGV 23, and BAT 22. Since charging is prioritized in descending order of target voltage value, EV 25 is charged first. Since the conversion capacity of the EV DC / DC converter 15 is 50 kW, the surplus supply power of 50 kW is used only for charging the 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, EV 25 is fully charged and no further charging is performed. Therefore, the remaining supply power of 50 kW is diverted to charging other devices. Charging is prioritized in order of lowest target voltage value, so forklift 24 and AGV 23 are charged with power converter capacities of 10 kW and 5 kW, respectively. The remaining supply power of 35 kW is then diverted to charging BAT 22.

[0035] Consider the case where 60 minutes have passed since the state in Figure 11. The operation in this case is the state in Figure 12. At this point, the AGV 23 is fully charged and no further charging will occur. Therefore, the remaining supply power of 50 kW will be diverted to charging other devices. Since charging is prioritized in order of lowest target voltage value, the forklift 24 is charged with 10 kW of the power converter capacity. Then, the remaining supply power of 40 kW is diverted to charging the BAT 22.

[0036] Consider the case where 120 minutes have passed since the state shown in Figure 12. The operation in this case is shown in Figure 13. At this point, the forklift 24 is fully charged and no further charging is required. Therefore, the remaining 50 kW of supply power is diverted to other charging. At this point, only the BAT 22 is not fully charged, so the 50 kW of supply power is diverted to charging the BAT 22.

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

[0038] 10 in an AC power distribution system, the demand power (total charging power + power consumption) is 195 kW compared to the supply power of 80 kW from the commercial power source, which may result in an overload. However, in a DC power distribution system, the charging priority can be easily controlled by setting a target voltage value, and charging will not exceed the supply power, so overload can be prevented.

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

[0040] (Initialized Values ​​of Devices in Embodiment 3) Figure 15 shows initial set values ​​(operating parameters) of each device in a DC power distribution system according to embodiment 3. In the initial set values ​​in Figure 15, the basic settings are the same as those in 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. Furthermore, 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 Embodiment 3) <Operation during commercial power outage (1) (Storage batteries have priority in charging and discharging)> Actual operation of Embodiment 3 will be described with reference to Figs. 16 to 26. First, consider a case where commercial power supply 20 experiences a power outage due to a disaster or the like, and power generation by PV 21 falls to 0 kW due to bad weather or the like. For simplicity, assume that motor 26 is in power running mode. The full charge capacities and charge amounts at that time of BAT 22, AGV 23, forklift 24, and EV 25 are shown on the right side of each. The initial conditions for charge amounts are 145 kWh, 0 kWh, 10 kWh, and 50 kWh, respectively. Operation in this case is shown in Fig. 16. At this time, there is no power supply from commercial power supply 20 or PV 21, so the storage batteries are discharged to maintain the DC power distribution system. Because the 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 order of discharge priority for the storage batteries is BAT 22, AGV 23, forklift 24, and EV 25, and the order of charge priority is EV 25, forklift 24, AGV 23, and BAT 22. As a result, when BAT 22 discharges 100 kW and AGV 23, forklift 24, and EV 25 charge at rated capacity, the supply and demand of power are balanced.

[0042] Consider the case where 60 minutes have passed since the state shown in Figure 16. The operation in this case is shown in Figure 17. At this point, the AGV 23 and EV 25 are fully charged and no further charging will be performed. Therefore, when the BAT 22 discharges 45 kW and the forklift 24 is charged at its rated capacity, the supply and demand of power 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 point, the forklift 24 is fully charged and will not be charged any further. Also, the charge amount of the BAT 22 is 0 kWh. Therefore, from this point on, discharge will occur in the order of priority: AGV 23, forklift 24, and EV 25. Currently, the total power required by the motor 26 and DC load 27 is 35 kW, so the AGV 23 will discharge 5 kW of its rated power, the forklift 24 will discharge 10 kW of its rated power, and the EV 25 will discharge the missing power of 20 kW.

[0044] Consider the case where 60 minutes have passed since the state in Figure 18. The operation in this case is shown in Figure 19. At this time, the charge amount of the AGV 23 becomes 0 kWh. Therefore, from this point on, discharge is prioritized as follows: forklift 24, EV 25. Now, since 5 kW of power supply from the AGV 23 has been lost, EV 25 will discharge 25 kW 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 amount of the forklift 24 becomes 0 kWh. Therefore, from this point on, only the EV 25 discharges. Now, since the supply of 10 kW of power from the forklift 24 has been lost, the EV 25 discharges 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 amount of EV 25 becomes 0 kWh. As a result, all power supply sources are lost and the DC power distribution system stops.

[0047] Consider the case where the PV 21 is restored from the state shown in Figure 21. Here, the power generated by the PV 21 is assumed to be 100 kW. The operation in this case is shown in Figure 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 charged in the order of priority: EV 25, forklift 24, AGV 23, and BAT 22. Therefore, the EV 25, forklift 24, and AGV 23 are charged to their rated voltages, 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 shown in Figure 22. The operation in this case is shown in Figure 23. At this point, the AGV 23 is fully charged and will not be charged any further. Therefore, the BAT 22 will charge the remaining power of 5 kW.

[0049] Consider the case where 60 minutes have passed since the state shown in Figure 23. The operation in this case is shown in Figure 24. At this point, EV 25 is fully charged and no further charging will be performed. Therefore, BAT 22 charges the remaining power of 55 kW.

[0050] Consider the case where 60 minutes have passed since the state shown in Figure 24. The operation in this case is shown in Figure 25. At this point, the forklift 24 is fully charged and no further charging is required. Therefore, the BAT 22 charges the remaining power of 65 kW.

[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 point, the BAT 22 is fully charged and no further charging will be performed. Therefore, the PV 21 supplies only the power of 35 kW required by the motor 26 and the DC load 27.

[0052] (Effects of Embodiment 3) As described above, during a power outage, not only BATs but also AGVs, forklifts, and EVs can discharge power to the DC power 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, simplifying control. Furthermore, for EVs, which serve as a means of transportation in the event of a disaster, control can be performed such that charging is given a higher priority and discharging is given a lower priority, allowing EVs to remain charged until the end.

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

[0054] (Initialized Values ​​of Devices in Fourth Embodiment) Figure 27 shows the initial settings (operating parameters) of each device in a DC distribution system according to the fourth embodiment. The basic settings in Figure 27 (fourth embodiment) are the same as those in Figure 15 (third embodiment), except that 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 the characteristics shown in Figure 28, a slight measurement error or the like could cause each power converter to charge and discharge unstably. Therefore, in the fourth embodiment, the power converters 12, 13, 14, and 15 are each configured to have an output voltage characteristic with a different slope, with the target voltage value (DC 360 V) as the base point, as shown in Figure 29. Note that the vertical axis in Figures 28 and 29 represents the actual voltage of the DC bus 2, and the horizontal axis represents the charge and discharge power.

[0055] (Explanation of Operation of Embodiment 4) <Operation during commercial power outage (2) (storage batteries are charged and discharged as a unit)> Actual operation of embodiment 4 will be described with reference to Figs. 30 and 31. First, consider a case where commercial power supply 20 experiences a power outage due to a disaster or the like, and the power generated by PV 21 falls to 0 kW due to bad weather. For simplicity, motor 26 is assumed to be in power running operation. Operation in this case is shown in Fig. 30. At this time, since there is no power supply from commercial power supply 20 or PV 21, the storage batteries of BAT 22, AGV 23, forklift 24, and EV 25 are discharged to maintain the DC power distribution system. Here, the total power consumption of motor 26 and DC load 27 is 16.5 kW. As can be seen from FIG. 29 , regardless of the value of the actual voltage of DC bus 2, the slope of the output voltage characteristics is set so that the output of each power converter is in the ratio of power converter 12:power converter 13:power converter 14:power converter 15 = 100:5:10:50 based on the converter capacity, and 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 PV 21 is restored from the state shown in Figure 30. Here, assume that the power generated by PV 21 is 100 kW and the load capacity of DC load 27 has changed to 7.5 kW. The operation in this case is shown in Figure 31. At this time, the power supplied from PV 21 is 100 kW, while the total power consumed by motor 26 and DC load 27 is 17.5 kW. 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 = 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 Fourth Embodiment) In the above description of the operation, the conversion efficiency of the power converters has been omitted for simplicity. However, in reality, losses occur with each conversion. Therefore, as shown in FIGS. 16 and 17 of the third embodiment, operations such as charging from one storage battery to another result in losses. In contrast, by setting the same target voltage value and charging and discharging the storage batteries as a whole, as in the fourth embodiment, charging from one storage battery to another can be prevented, and high efficiency can be expected. Furthermore, in an AC power distribution system, when controlling the charging and discharging of multiple storage batteries in a balanced manner, it is necessary to sequentially issue power instructions to each power converter. However, in a DC power distribution system, by giving each power converter the characteristics shown in FIG. 29, control can be easily performed.

[0058] FIG. 32 shows an example of the hardware configuration of the control device 1 in these embodiments. As shown in FIG. 32 , the control device 1 includes a processor 100 and a storage device 101, and is connected to a commercial power 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 of which are not shown. Alternatively, a hard disk auxiliary storage device may be provided instead of the flash memory. The processor 100 executes a program input from the storage device 101. In this case, the program is input to the processor 100 from the auxiliary storage device via the volatile storage device. The processor 100 may 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 various exemplary embodiments and examples are described in this disclosure, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are anticipated within the scope of the technology disclosed in this specification. For example, this includes cases where at least one component is modified, added, or omitted, or 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] (Supplementary Note 1) A DC power distribution system that supplies power from a power source to a plurality of devices in a logistics warehouse via a DC bus, comprising: a first power converter connected between the power source and the DC bus and supplying power unidirectionally from the power source to the DC bus; a second power converter connected between the DC bus and a load incorporating a storage battery and supplying 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 and the second power converter to transmit operating parameters including a target voltage value on the DC bus side and a power conversion direction. (Supplementary Note 2) The DC power distribution system according to Supplementary Note 1, wherein the power source includes a commercial power source and a solar panel, the first power converter is a commercial power source power converter connected between the commercial power source and the DC bus and supplying power unidirectionally from the commercial power source 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, and the control device determines an operation mode depending on whether the commercial power source is normal, whether there is a power outage of the commercial power source, 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. (Supplementary Note 3) The DC power distribution system according to Supplementary Note 1 or Supplementary Note 2, wherein the first power converter sets a first target voltage value on a DC bus side as the operating parameter, and 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. (Supplementary Note 4) The DC power distribution system according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the second power converter sets a second target voltage value on a DC bus side as the operating parameter, and 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.(Supplementary Note 5) The DC power distribution system according to Supplementary Note 2, further comprising: a storage battery as the power source; and a storage battery power converter connected between the DC bus and the storage battery and supplying power in both directions between the DC bus and the storage battery, wherein, in an operation mode in which the solar panel can generate power, a target voltage value on the DC bus side of the storage 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. (Supplementary Note 6) The DC power distribution system according to Supplementary Note 2, comprising: a storage battery as the power source; and a storage battery power converter connected between the DC bus and the storage battery and supplying power bidirectionally between the DC bus and the storage battery, wherein in an operation mode in which the solar panel cannot generate power, a target voltage value on the DC bus side of the storage 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. (Supplementary Note 7) The DC power distribution system according to Supplementary Note 2, comprising: a storage battery as the power source; and a storage battery power converter connected between the DC bus and the storage battery and supplying power bidirectionally between the DC bus and the storage battery, wherein in an operation mode in which the commercial power supply is in a power outage, the conversion direction of the second power converter of the storage battery built-in load is bidirectionally convertible between charging and discharging. (Supplementary Note 8) The DC power distribution system according to any one of Supplementary Note 1 to Supplementary Note 4, further comprising: a storage battery as the power source; and a storage battery power converter connected between the DC bus and the storage battery and supplying power in both directions between the DC bus and the storage battery; and 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.(Supplementary Note 9) The DC power distribution system according to any one of Supplementary Notes 1 to 8, wherein the motor load operates a motor with AC power obtained by converting DC power of the DC bus by the third power converter during powering, and supplies DC power obtained by converting AC power generated by the motor by the third power converter to the DC bus during regeneration. (Supplementary Note 10) The DC power distribution system according to any one of Supplementary Notes 1 to 9, comprising a DC load connected to the DC bus and operable with DC power. (Supplementary Note 11) The DC power distribution system according to any one of Supplementary Notes 1 to 10, wherein the power source includes a commercial power source, a solar panel, and a storage battery, the storage battery-integrated load includes a forklift and an electric transport vehicle, and the motor load includes an automated warehouse.

[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 solar panel (PV), 22 system storage battery (BAT), 23 automated guided vehicle (AGV), 24 forklift, 25 electric vehicle for transport (EV), 26 motor, 27 DC load.

Claims

1. A DC power distribution system that supplies power from a power source to a plurality of devices in a logistics warehouse via a DC bus, comprising: a first power converter connected between the power source and the DC bus and supplying power unidirectionally from the power source to the DC bus; a second power converter connected between the DC bus and a load incorporating a storage battery and supplying 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 and the second power converter to operate according to operating parameters including a target voltage value on the DC bus side and a direction of power conversion.

2. The DC power distribution system according to claim 1, wherein the power source includes a commercial power source and a solar panel, the first power converter is a commercial power converter connected between the commercial power source and the DC bus and supplying power unidirectionally from the commercial power source 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, and the control device determines an operation mode depending on whether the commercial power source is normal, whether there is a power outage of the commercial power source, 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. A DC power distribution system as described in claim 1 or claim 2, wherein the first power converter has a first target voltage value on the DC bus side set as the operating parameter, and when the voltage of the DC bus is lower than the first target voltage value, 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, decreases the power supplied from the power source to the DC bus.

4. A DC distribution system as claimed in any one of claims 1 to 3, wherein the second power converter has a second target voltage value on the DC bus side set as the operating parameter, and when the voltage of the DC bus is lower than the second target voltage value, 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 DC power distribution system as claimed in claim 2, comprising a storage battery as the power source, and a storage battery power converter connected between the DC bus and the storage battery and supplying power in both directions between the DC bus and the storage battery, wherein, in an operation mode in which the solar panel can generate power, the target voltage value on the DC bus side of the storage battery power converter is made higher 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.

6. A DC power distribution system as described in claim 2, comprising a storage battery as the power source, and a storage battery power converter connected between the DC bus and the storage battery and supplying power in both directions between the DC bus and the storage battery, wherein, in an operating 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.

7. A DC power distribution system according to claim 2, comprising a storage battery as the power source, a storage battery power converter connected between the DC bus and the storage battery and supplying power in both directions between the DC bus and the storage battery, and 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 DC power distribution system according to any one of claims 1 to 4, comprising a storage battery as the power source, and a storage battery power converter connected between the DC bus and the storage battery and supplying power in both directions between the DC bus and the storage battery, wherein when there are a plurality of storage battery power converters and a plurality of second power converters having the same target voltage value on the DC bus side, the storage battery power converter and the second power converter are configured to give different slopes to the output voltage characteristics of the storage battery power converters and the second power converters.

9. A DC power distribution system as claimed in any one of claims 1 to 8, 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. A DC power distribution system according to any one of claims 1 to 9, further comprising a DC load connected to the DC bus and operable by DC power.

11. The DC power distribution system according to any one of claims 1 to 10, wherein the power source includes a commercial power source, a solar panel, and a storage battery; the storage battery-integrated load includes a forklift and an electric transport vehicle; and the motor load includes an automated warehouse.

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