Power conversion system and power conversion method

Abstract

When supplying power to a load during a power outage using multiple batteries, the selected battery is used preferentially, while also enabling power supply to the load even when the load power increases. [Solution] The system comprises an AC port connected to a commercial power source or load, multiple DC ports connected to multiple storage batteries, and a control unit that controls the input and output of each DC port. The control unit designates a DC port with a higher priority among the multiple DC ports as the priority port. When the charge state of the storage battery connected to the priority port is higher than a first threshold, the control unit preferentially inputs power from the priority port while also inputting power from both the priority port and the other DC ports and outputting power to the AC port. Furthermore, when the charge state of the storage battery connected to the priority port is lower than the first threshold, the control unit preferentially inputs power from the other DC ports while also inputting power from both the priority port and the other DC ports and outputting power to the AC port.

Description

[[Technical Field]]

[0001] The present invention relates to a power conversion system and a power conversion method. [[Background Art]]

[0002] With the popularization of electric vehicles, power conversion systems that effectively utilize on-board drive batteries mounted in electric vehicles have been developed. In addition, storage batteries (stationary batteries) and solar cells have been installed in buildings, houses, and the like to effectively utilize electric power. Patent Document 1 describes a charging / discharging device that supplies electric power stored in a main battery of an electric vehicle to a load in a house when a commercial power supply fails. [[Prior Art Literature]] [[Patent Literature]]

[0003] [[Patent Document 1]] Japanese Patent Laid-Open No. 2018-61432 [[Summary of the Invention]] [[Problem to be Solved by the Invention]]

[0004] By installing an on-board battery mounted on an electric vehicle or a stationary battery, electric power can be supplied by connecting to loads such as houses and buildings even during a power outage. Here, for general household loads and short-time power outages, backup power supply during a power outage is often possible even with a single electric vehicle. However, when the power consumption of a load such as an office building or a commercial facility is large, or when a power outage is prolonged, a plurality of storage batteries such as on-board batteries of a plurality of electric vehicles and a plurality of stationary batteries are required.

[0005] When multiple battery storage systems are installed, it is desirable to be able to appropriately select which battery to use preferentially for backup power supply. For example, when an on-board battery and a stationary battery are connected, it is advisable to prioritize the use of the stationary battery to prevent situations where the electric vehicle becomes unusable due to the discharge of the on-board battery. Even when multiple stationary batteries are connected, it is preferable to decide in advance which battery to use preferentially, according to the capacity and usage status of each stationary battery.

[0006] However, there are also problems when a battery is designated for priority use. For example, suppose that prioritizing the use of a selected battery causes its charge level to drop, making it unable to discharge to the load. And suppose the load's power increases in this state. In such a case, if simultaneous discharge from multiple batteries is not possible, a situation will arise where sufficient power cannot be supplied to the load. If such a situation occurs, there is a concern that backup power supply may not be able to continue.

[0007] The objective of the present invention is to provide a power conversion system and a power conversion method that, when supplying power to a load during a power outage using multiple storage batteries, prioritizes the use of a selected storage battery while also enabling power supply to the load even when the load power increases. [Means for solving the problem]

[0008] To solve the above problems, for example, the configuration described in the claims is adopted. This application includes several means for solving the above problems, but to give one example, the power conversion system of the present invention is a power conversion system comprising an AC port connected to a commercial power source or load, a plurality of DC ports to which a plurality of storage batteries, each consisting of a stationary battery or an on-board battery, are individually connected, and a control unit that controls the output and input of the plurality of DC ports. The power conversion system converts the AC power input from the AC port into DC power and outputs it to multiple DC ports, and also converts the DC power input from the multiple DC ports into AC power and outputs it to the AC port. The control unit sets the DC port with the highest priority among the multiple DC ports connected to each of the multiple batteries as the priority port. Furthermore, when the charge state or remaining energy level of the battery connected to the priority port is higher than the first threshold, the control unit preferentially inputs power from the priority port over the DC ports to which other batteries are connected, while inputting power from both the priority port and the DC ports to which other batteries are connected, and outputs power to the AC port. Furthermore, if the charge state or remaining energy level of the battery connected to the priority port is lower than the first threshold, the control unit preferentially inputs power from the DC port to which the other battery is connected, while simultaneously inputting power from both the priority port and the DC port to which the other battery is connected and outputting power to the AC port. [Effects of the Invention]

[0009] According to the present invention, when supplying power to a load during a power outage using multiple storage batteries, it is possible to prioritize the use of the selected storage battery while also being able to supply power to the load even when the load power increases. Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block diagram showing an example configuration of a power conversion system according to one embodiment of the present invention. [Figure 2] This figure shows an example of a priority port setting screen for a power conversion system according to one embodiment of the present invention. [Figure 3] This flowchart shows an example of processing performed by the control unit of a power conversion system according to one embodiment of the present invention. [Figure 4]This is a characteristic diagram showing an example of the time variation of power by a power conversion system according to one embodiment of the present invention (an example in which the load consumes power with the onboard battery as the priority port). [Figure 5] This is a characteristic diagram showing an example of the time variation of power generated by a power conversion system according to one embodiment of the present invention (an example in which the load generates power with the onboard battery as the priority port). [Figure 6] This is a characteristic diagram showing an example of the time variation of power by a power conversion system according to one embodiment of the present invention (an example in which a load consumes power with a stationary battery as the priority port). [Figure 7] This is a characteristic diagram showing an example of the time variation of power generated by a power conversion system according to one embodiment of the present invention (an example in which a load generates power with a stationary battery as the priority port). [Figure 8] This is a block diagram showing an example configuration of a power conversion system according to a modified example (Example 1) of one embodiment of the present invention. [Figure 9] This is a block diagram showing an example configuration of a power conversion system according to a modified example (Example 2) of one embodiment of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, a power conversion system and power conversion method according to one embodiment of the present invention will be described with reference to the attached drawings.

[0012] [Configuration of the power conversion system] Figure 1 is a block diagram showing the configuration of the power conversion system 1. As shown in Figure 1, the power conversion system 1 comprises relays 11 and 12, AC / DC conversion units 21 to 23, DC / DC conversion units 31 to 33, a control unit 10, AC ports 61 and 62, and DC ports 71 to 73. Relays 11 and 12 switch the connection between AC ports 61 and 62 and AC / DC conversion units 21 to 23 on and off. AC / DC conversion units 21 to 23 perform conversion from AC power to DC power and from DC power to AC power.

[0013] The power conversion system 1 is connected to a commercial power source 2, a switching device 13, an on-vehicle battery 51 mounted on a vehicle 41, a stationary battery 52, and a solar cell 53. The power conversion system 1, the commercial power source 2, and a load 3 are connected to the switching device 13. The on-vehicle battery 51 is mounted on a vehicle 41 such as an electric vehicle. The solar cell 53 is installed in a building where the power conversion system 1 is installed or an adjacent site.

[0014] It should be noted that connecting one each of the on-vehicle battery 51, the stationary battery 52, and the solar cell 53 to the power conversion system 1 is merely an example. As the power conversion system 1, for example, a plurality of on-vehicle batteries or stationary batteries may be connected to the power conversion system 1. Furthermore, connecting both the on-vehicle battery and the stationary battery is also an example, and a plurality of either an on-vehicle battery or a stationary battery may be connected. Furthermore, the power conversion system 1 may be configured not to connect any solar cell.

[0015] DC / DC converters 31 to 33 are respectively connected between the DC side of AC / DC converters 21 to 23 and DC ports 71 to 73, and perform DC / DC conversion that converts voltage between the DC power handled by the AC / DC converters 21 to 23 and the DC power input / output to / from the DC ports 71 to 73. In the case of the present embodiment, the DC port 71 is connected to the on-vehicle battery 51, the DC port 72 is connected to the stationary battery 52, and the DC port 73 is connected to the solar cell 53. It should be noted that the DC / DC converters 31 to 33 also have a function of controlling the respective power (charge / discharge power) of the on-vehicle battery 51, the stationary battery 52, and the solar cell 53 based on instructions from the control unit 10. For controlling the charge / discharge power and the like of the on-vehicle battery 51 and the stationary battery 52, the control unit 10 may control the amount of power input / output in the DC / DC converters 31 to 33, or the control unit 10 may transmit commands to the on-vehicle battery 51, the stationary battery 52, and the solar cell 53 side to perform control.

[0016] The AC / DC converters 21-23 are connected in parallel to relays 11 and 12. The AC side of the AC / DC converters 21-23 is connected to AC port 61 via relay 11 and to AC port 62 via relay 12. AC port 61 is connected to commercial power supply 2, and AC port 62 is connected to switch 13. Relays 11 and 12, the changeover switch 13, AC / DC conversion units 21 to 23, and DC / DC conversion units 31 to 33 are controlled by the control unit 10. The changeover switch 13 switches the load 3 so that it is connected to either the commercial power supply 2 or the power conversion system 1.

[0017] During normal operation when the commercial power supply 2 is not experiencing a power outage, the control unit 10 turns on relay 11, turns off relay 12, and switches the changeover switch 13 to the commercial power supply 2. As a result, the power conversion system 1 converts power between the commercial power supply 2 and the on-board battery 51, stationary battery 52, or solar cell 53. Specifically, the power conversion system 1 converts the AC power of the commercial power supply 2 input from the AC port 61 into DC power using AC / DC conversion units 21-23, and outputs this DC power to DC ports 71 and 72 using DC / DC conversion units 31 and 32. As a result, the power conversion system 1 can charge the on-board battery 51 and the stationary battery 52 with the power input from the commercial power supply 2.

[0018] Furthermore, the power conversion system 1 uses DC / DC conversion units 31-33 to convert the DC power from the on-board battery 51, stationary battery 52, or solar cell 53 input from the DC ports 71-73 into AC power using AC / DC conversion units 21-23 and outputs it to the AC port 61. In this way, the power conversion system 1 can adjust the power received from the commercial power source 2 to the load 3 using the power from the on-board battery 51, stationary battery 52, or solar cell 53. Load 3 is connected to commercial power supply 2 via a switch 13, and power received from commercial power supply 2, or power output from the on-board battery 51, stationary battery 52, or solar cell 53 via the power conversion system 1, is supplied to load 3.

[0019] On the other hand, in the event of a power outage at commercial power supply 2, the control unit 10 turns off relay 11, turns on relay 12, and switches the changeover switch 13 to power conversion system 1. As a result, power conversion system 1 supplies power input from the on-board battery 51, stationary battery 52, or solar cell 53 to load 3. Specifically, power conversion system 1 uses DC / DC conversion units 31-33 to convert the DC power from the on-board battery 51, stationary battery 52, or solar cell 53 input from DC ports 71-73 to AC power using AC / DC conversion units 21-23, and outputs it to AC port 62 to supply to load 3. In this way, even if commercial power supply 2 is interrupted, power conversion system 1 can use the power from the on-board battery 51, stationary battery 52, or solar cell 53 to supply power to load 3 as a backup.

[0020] In this embodiment, it is assumed that the load 3, which is subject to backup power supply during a power outage, includes loads whose power consumption changes over time due to operation and stopping, such as elevators installed in a building. In addition, the output from the solar cell 53 can be converted to AC power and supplied to the load 3, or it can be used to charge the on-board battery 51 or the stationary battery 52.

[0021] The control unit 10 is configured as a computer that executes the control processes described above. Specifically, as shown in Figure 1, the control unit 10 has a hardware configuration in which a CPU (Central Processing Unit) 10a, memory 10b, interface (I / F) 10c, etc., are connected to each other via a bus line for communication. The CPU 10a executes a program implemented in memory 10b to configure a processing unit that executes control processes within memory 10b, and transmits the instructions generated by that processing unit to the power conversion system 1 via interface 10c.

[0022] The control unit 10 can receive measured values, such as power values ​​(described later), via the interface 10c. Furthermore, a display device (not shown) may be connected to the control unit 10 for purposes such as setting priority ports, as described below. The display device may be provided by the power conversion system 1, or by an external terminal capable of communicating with the power conversion system 1.

[0023] Furthermore, the power conversion system 1 of this embodiment can select which battery to use preferentially from among multiple storage batteries, namely the on-board battery 51 and the stationary battery 52. ​​When prioritizing the use of the on-board battery 51, the user performs an operation to select DC port 71 as the priority port. When prioritizing the use of the stationary battery 52, the user performs an operation to select DC port 72 as the priority port.

[0024] Figure 2 shows an example of the display when setting the priority port. This display is shown on the display device provided by the power conversion system 1, or on an external terminal that communicates with the power conversion system 1. Here, the three DC ports 71, 72, and 73 are referred to as port 1, port 2, and port 3, respectively. As shown in Figure 2, port 1 is labeled "EV," meaning vehicle 41; port 2 is labeled "BT," meaning stationary battery 52; and port 3 is labeled "PV," meaning solar cell 53. The display example shown in Figure 2 illustrates the case where, through user operation of the power conversion system 1, port 2 (BT) is set as the preferred port among ports 1, 2, and 3. In other words, the display area for port 2 (BT) in Figure 2 has a different display format than the other ports.

[0025] [Overview of control processing performed in power conversion systems] Figure 3 is a flowchart showing an example of the control process performed by the control unit 10 of the power conversion system 1. The control process described in Figure 3 is an overview of the control process performed by the control unit 10 in this embodiment, and the details of the first to fourth thresholds described below will be explained by the specific operation examples shown in Figures 4 to 7.

[0026] First, the control unit 10 performs a priority port setting process (step ST11) which involves having the user set a priority port and registering the information of the set priority port. Next, the control unit 10 determines whether or not the commercial power supply 2 is experiencing a power outage (step ST12). If, in step ST12, the commercial power supply 2 is not experiencing a power outage (No. in step ST12), the control unit 10 turns on relay 11 and off relay 12 to drive load 3 with commercial power supply 2 (step ST13).

[0027] At this time, power from the solar cell 53 or the like may be supplied to the load 3 via the relay 11 to reduce the amount of commercial power 2 used. Then, the control unit 10 charges the on-board battery 51 or stationary battery 52 with power from the commercial power 2 or solar cell 53, depending on the situation (step ST14). The on-board battery 51 or stationary battery 52 can also be charged when the load 3 is generating power. After processing in step ST14, the control unit 10 returns to the power outage detection process in step ST12.

[0028] Furthermore, if a power outage of the commercial power supply 2 is detected in step ST12 (Yes in step ST12), the control unit 10 turns off relay 11 and on relay 12 to make it possible to drive load 3 with power from the battery connected to the power conversion system 1 (step ST15). Then, the control unit 10 controls the discharge of the battery connected to the priority port (in this case, the stationary battery 52) using the first and second thresholds, and controls the charge using the third and fourth thresholds (step ST16). In this state, since the commercial power supply 2 is out of service, when the load 3 is consuming power, the load 3 is driven by the discharge power from each battery 51-53, while the battery connected to the priority port is used preferentially. Also, when the load 3 is generating power, the generated power is used to charge the storage batteries 51 and 52 while charging the battery connected to the priority port is prioritized. Details of this charging and discharging while prioritizing the use of the battery connected to the priority port will be explained using Figures 4 to 7 below. After processing in step ST16, the control unit 10 returns to the power outage detection process in step ST12.

[0029] [Example of operation of a power conversion system during a power outage (example when the vehicle battery is connected to the priority port)] Next, we will explain in detail the operation of power conversion system 1 during a power outage using Figures 4 to 7. In Figures 4 to 7, P0 represents the power output from AC port 62 to load 3. When commercial power supply 2 is shut off, power P0 is equal to the power of load 3. P1 represents the power input from the onboard battery 51 to the DC port 71, P2 represents the power input from the stationary battery 52 to the DC port 72, and P3 represents the power input from the solar cell 53 to the DC port 73. Furthermore, Ph1 and Ph2 represent the maximum discharge power of the onboard battery 51 and the stationary battery 52, respectively, and Pj1 and Pj2 represent the maximum charging power of the onboard battery 51 and the stationary battery 52, respectively.

[0030] Furthermore, S1 and S2 represent the charge states of the on-board battery 51 and the stationary battery 52, respectively, with 1 representing a fully charged state and 0 representing a completely discharged state. Here, Slim1 represents the lower discharge limit of the on-board battery 51, and Slim2 represents the lower discharge limit of the stationary battery 52. Furthermore, Sth11 to Sth14 represent the first to fourth thresholds of the onboard battery 51, respectively, and Sth21 to Sth24 represent the first to fourth thresholds of the stationary battery 52, respectively.

[0031] The control unit 10 of the power conversion system 1 sets and maintains the first threshold Sth11 to the fourth threshold Sth14 for the on-board battery 51 and the first threshold Sth21 to the fourth threshold Sth24 for the stationary battery 52. ​​The first and second thresholds are thresholds used to determine when to stop the discharge of each battery (on-board battery 51, stationary battery 52) by comparing them with the charge state or remaining energy of the battery. The second threshold is a value lower than the first threshold in terms of the charge state or remaining energy of the battery. These first and second thresholds are set to values ​​higher than the lower discharge limit of the battery connected to the priority port. Furthermore, the third and fourth thresholds are thresholds used to determine the switching of the charge state of each battery (vehicle battery 51, stationary battery 52) by comparing them with the battery's charge state or remaining energy. The fourth threshold is a value higher than the third threshold for the battery's charge state or remaining energy. These third and fourth thresholds are set to values ​​lower than the value corresponding to a fully charged battery connected to the priority port. In the graphs shown in Figures 4 to 7, the vertical axis represents power or charge status, and the horizontal axis represents time.

[0032] The discharge limit is the lower limit of the charge state set to prevent over-discharge of the battery, and in this embodiment, the operation is described as being such that once the battery is discharged and the charge state drops to the discharge limit, it cannot be discharged any further. As explained in Figure 2, the power conversion system 1 can set which of the DC ports 71 and 72, to which the on-board battery 51 and the stationary battery 52 are connected, has higher priority.

[0033] [Example of power consumption by the load when the vehicle battery is connected to a priority port] Figures 4 and 5 show the operation when the DC port 71 to which the vehicle battery 51 is connected is set to a higher priority and designated as a priority port. Figure 4 shows the operation when load 3 consumes power. In Figure 4, ta0 to ta8 represent time, and a0 to a8 represent duration.

[0034] • Period a0 During period a0, power P3 input from solar cell 53 and power P1 input from onboard battery 51 connected to priority port DC port 71 are supplied to load 3. Power P2 is not input from stationary battery 52 connected to non-priority port DC port 72. During this period a0, onboard battery 51 discharges, and the charge state S1 decreases.

[0035] • Period a1 When time ta1 arrives and period a1 begins, the power P0 of load 3 increases. At this time, the power P1 input from the onboard battery 51 connected to the priority port DC port 71 increases to the maximum discharge power Ph1. In this state, power P2 is also input from the stationary battery 52 connected to the non-priority port DC port 72, and the power input from the onboard battery 51, the stationary battery 52, and the solar cell 53 is supplied to load 3. Therefore, during period a1, both the onboard battery 51 and the stationary battery 52 discharge, and the charge states S1 and S2 decrease. Here, the charge state S1 is a state that has not reached the first threshold Sth11, and the control unit 10 executes control processing (first power input / output processing) using the onboard battery 51 connected to the priority port.

[0036] ·Period a2 When time ta2 arrives and period a2 begins, the power P0 of load 3 decreases, and the power P2 input from the stationary battery 52 also decreases to zero. Furthermore, during this period a2, the power P1 input from the onboard battery 51 decreases, returning to the same state as period a0. During this period a2, the onboard battery 51 discharges, and the charge state S1 decreases.

[0037] • Period a3 At time ta3, the charge state S1 of the onboard battery 51 decreases until the charge state S1 reaches the first threshold Sth11, resulting in the state of period a3. At this time, power P1 from the onboard battery 51 connected to the priority DC port 71 is no longer input, and the system switches to inputting power P2 from the stationary battery 52 connected to the non-priority DC port 72 (second power input / output process). As a result, the power conversion system 1 supplies power P2 input from the stationary battery 52 and power P3 input from the solar cell 53 to the load 3. In this state, the onboard battery 51 does not discharge, so the charge state S1 does not decrease, while the stationary battery 52 discharges, causing the charge state S2 to decrease.

[0038] • Period a4 When time ta4 and period a4 begins, the power P0 of load 3 increases, and the power P2 input to power conversion system 1 from the stationary battery 52 connected to the non-priority DC port 72 increases, reaching the maximum discharge power Ph2. At this time, power conversion system 1 also receives power P1 from the onboard battery 51 connected to the priority DC port 71, and supplies power input from the onboard battery 51, the stationary battery 52, and the solar cell 53 to load 3. In this state, the onboard battery 51 and the stationary battery 52 discharge, and the charge states S1 and S2 decrease.

[0039] • Period a5 When time ta5 arrives and period a5 begins, the power P0 of load 3 decreases, and the power P1 input from the onboard battery 51 decreases to zero. Also, the power P2 input from the stationary battery 52 decreases, resulting in the same state as in period a3. In this state, the stationary battery 52 discharges, causing the charge state S2 to decrease.

[0040] ·Period a6 When time ta6 arrives and period a6 begins, the power P0 of load 3 increases, and the power conversion system 1 enters the same state as in period a4. That is, the on-board battery 51 and the stationary battery 52 discharge, and the charge states S1 and S2 decrease. Note that the charge state S1 of the on-board battery 51 remains below the second threshold Sth12 and continues to discharge.

[0041] ·Period a7 When time ta7 arrives and period a7 begins, the power P0 of load 3 decreases, and the charge state S1 of the onboard battery 51 falls below the second threshold Sth12. At this time, power P2 continues to be input from the stationary battery 52 connected to the non-priority DC port 72, and the onboard battery 51 connected to the priority DC port 71 outputs power P1. In other words, during period a7, the power conversion system 1 supplies power input from the stationary battery 52 and the solar cell 53 to load 3 and the onboard battery 51. As the stationary battery 52 is discharged, its charge state S2 decreases, and as the onboard battery 51 is charged, its charge state S1 increases.

[0042] ·Period a8 At time ta8, when the charge state S1 of the onboard battery 51 rises and reaches the second threshold Sth12, the power conversion system 1 enters the state of period a8. During period a8, the power conversion system 1 stops outputting power P1 to the onboard battery 51 connected to the priority port DC port 71, so the power P2 input from the stationary battery 52 connected to the non-priority port DC port 72 decreases. The power conversion system 1 then supplies power P2 input from the stationary battery 52 and power P3 input from the solar cell 53 to the load 3, and is in the same state as during period a5. During period a8, the onboard battery 51 is no longer charged, so the charge state S1 does not rise. Also, during period a8, the stationary battery 52 continues to discharge, and the charge state S2 decreases.

[0043] As described above, the power conversion system 1 preferentially discharges the onboard battery 51 connected to the DC port 71 of the priority port when its charge state S1 is sufficiently high. Then, if the power of the load 3 is relatively large and the discharge power of the onboard battery 51 is insufficient, the power conversion system 1 also discharges the stationary battery 52 connected to the DC port 72, which is not a priority port, to supply power to the load 3 (period a0 to a2).

[0044] Then, by preferentially discharging the onboard battery 51 connected to the priority port DC port 71, the power conversion system 1 suppresses the decrease in the charge state S1 of the onboard battery 51 when it reaches the first threshold Sth11. In other words, when the first threshold Sth11 is reached, the power conversion system 1 switches to preferentially discharging the stationary battery 52 connected to the non-priority port DC port 72 (periods a2 to a3). Furthermore, if the power of the load 3 is relatively large and the discharge power of the stationary battery 52 is insufficient, the power conversion system 1 also discharges the onboard battery 51 to supply power to the load 3 (periods a3 to a6).

[0045] Furthermore, when the charge state S1 of the onboard battery 51 connected to the priority DC port 71 falls below the second threshold Sth12, and the power P0 of the load 3 output from the AC port 62 decreases, the power conversion system 1 changes the power P1 of the onboard battery 51 from discharge to charge. While changing the power P1 from discharge to charge, the power conversion system 1 continues to maintain the discharge of the power P2 of the stationary battery 52 connected to the non-priority DC port 72. As a result, the power conversion system 1 restores the charge state S1 of the onboard battery 51 to the second threshold Sth12 (period a6-a7).

[0046] By operating as described above, the power conversion system 1 preferentially discharges the onboard battery 51, which is a storage battery connected to the priority port, to supply power to the load 3, while ensuring that its charge state S1 does not fall to the discharge lower limit Slim1. As a result, even when the power of the load 3 becomes relatively large, the power conversion system 1 is able to discharge both the onboard battery 51 and the stationary battery 52, enabling the continuation of backup power supply.

[0047] The second threshold Sth12 should be set so that the charge state S1 of the onboard battery 51 does not fall to the discharge lower limit Slim1, taking into consideration the maximum power of load 3 and its duration. The first threshold Sth11 should be set to a value higher than the second threshold Sth12, according to the priority of the onboard battery 51 over the stationary battery 52.

[0048] In the above explanation, the operation to preferentially discharge the on-board battery 51 is such that if the power is insufficient even after discharging the on-board battery 51 to its maximum power, the remaining power will also be discharged from the stationary battery 52. ​​In contrast, the operation to preferentially discharge the on-board battery 51 may also be performed in other ways, such as discharging both the on-board battery 51 and the stationary battery 52 while making the discharge power of the on-board battery 51 greater than the discharge power of the stationary battery 52.

[0049] [Example of a load generating power when a vehicle battery is connected to a priority port] Next, we will explain the operation when load 3 generates power using Figure 5. One example of a situation where load 3 generates power is when load 3 is an elevator, and the electric motor in the elevator performs regenerative braking, thereby generating power. In Figure 5, tb0 to tb8 represent time periods, and b0 to b8 represent time periods.

[0050] • Period b0 During period b0, the power conversion system 1 outputs the power input from the solar cell 53 and the power input from the load 3 to the DC port 71 of the priority port, thereby charging the onboard battery 51. The power conversion system 1 does not output power to the DC port 72, which is not a priority port and to which the stationary battery 52 is connected. As a result, the onboard battery 51 is charged, and the charge state S1 increases.

[0051] • Period B1 When time tb1 arrives and period b1 begins, the power input from load 3 increases, and the power output to the onboard battery 51 connected to the priority port DC port 71 increases. The power conversion system 1 then reaches its maximum charging power Pj1. Also during period b1, the power conversion system 1 outputs power to the stationary battery 52 connected to the non-priority port DC port 72, supplying power input from the solar cell 53 and load 3 to the onboard battery 51 and the stationary battery 52. ​​As a result, the onboard battery 51 and the stationary battery 52 are charged, and the charging states S1 and S2 increase.

[0052] • Period b2 When time tb2 arrives and period b2 begins, the power input from load 3 decreases, the power output to stationary battery 52 decreases to zero, and the power output to onboard battery 51 also decreases, causing the power conversion system 1 to return to the same state as during period b0. As a result, the onboard battery 51 is charged, and the charge state S1 increases.

[0053] • Period b3 At time tb3, when the charge state S1 of the onboard battery 51 rises and reaches the third threshold Sth13, the power conversion system 1 enters state b3. Then, the power conversion system 1 does not output power to the onboard battery 51 connected to the priority port DC port 71, but instead outputs power to the stationary battery 52 connected to the non-priority port DC port 72. As a result, the power input from the solar cell 53 and load 3 is supplied to the stationary battery 52. ​​Then, the onboard battery 51 is no longer charged, so the charge state S1 does not rise, and the stationary battery 52 is charged, causing the charge state S2 to rise.

[0054] • Period b4 When time tb4 arrives and period b4 begins, the power input from load 3 increases, and the power output to the stationary battery 52 connected to the non-priority DC port 72 increases, reaching the maximum charging power Pj2. The power conversion system 1 then also outputs power to the on-board battery 51 connected to the priority DC port 71, supplying the power input from the solar cell 53 and load 3 to the on-board battery 51 and the stationary battery 52. ​​During this period, the on-board battery 51 and the stationary battery 52 are charged, and their respective charge states S1 and S2 increase.

[0055] • Period b5 When time tb5 arrives and period b5 begins, the power input from load 3 decreases, the power output to the onboard battery 51 decreases to zero, and the power output to the stationary battery 52 also decreases, so the power conversion system 1 returns to the same state as in period b3. During this period, the stationary battery 52 is charged, so the charge state S2 increases.

[0056] ·Period b6 When time tb6 arrives and period b6 begins, the power input from load 3 increases, and the power conversion system 1 enters the same state as in period b4. During this period, the on-board battery 51 and the stationary battery 52 are charged, and their respective charge states S1 and S2 increase. The charge state S1 of the on-board battery 51 exceeds the fourth threshold Sth14, and charging continues.

[0057] • Period b7 When time tb7 arrives and period b7 begins, the power input from load 3 decreases. At this point, the charge state S1 of the onboard battery 51 exceeds the fourth threshold Sth14, and the power conversion system 1 continues to output power to the stationary battery 52 connected to the non-priority DC port 72, and inputs power from the onboard battery 51 connected to the priority DC port 71. In other words, the power conversion system 1 supplies power input from load 3, the onboard battery 51, and the solar cell 53 to the stationary battery 52. ​​As a result, the stationary battery 52 is charged and its charge state S2 increases, while the onboard battery 51 is discharged and its charge state S1 decreases.

[0058] ·Period b8 At time tb8, when the charge state S1 of the onboard battery 51 decreases and reaches the fourth threshold Sth14, the power conversion system 1 enters the state of period b8. In the state of period b8, the power conversion system 1 does not receive power from the onboard battery 51 connected to the priority port DC port 71, and the power output to the stationary battery 52 connected to the non-priority port DC port 72 decreases. Here, power input from the solar cell 53 and load 3 is supplied to the stationary battery 52, so the power conversion system 1 enters the same state as in period b5. Also, since the onboard battery 51 is not discharged, the charge state S1 does not decrease. On the other hand, the stationary battery 52 continues to be charged, and the charge state S2 increases.

[0059] As described above, in this embodiment, the power conversion system 1 prioritizes charging the onboard battery 51 when its charge state S1 is sufficiently low. Then, if the power generated by the load 3 is relatively large and cannot be absorbed by the charging power of the onboard battery 51, the power conversion system 1 also charges the stationary battery 52 connected to the DC port 72, which is not a priority port, with the power generated by the load 3 (periods b0 to b2).

[0060] The power conversion system 1 prioritizes charging the onboard battery 51 on the priority port (DC port 72), and when the charge state S1 rises to the third threshold Sth13, it switches to prioritizing the charging of the stationary battery 52 on the non-priority DC port 72 (periods b2-b3). This is done to suppress the rise in the charge state S1 of the onboard battery 51. Furthermore, if the power generated by load 3 is relatively large and cannot be absorbed by the charging power of the stationary battery 52, the power generated by load 3 is also used to charge the onboard battery 51 (periods b3-b6).

[0061] Furthermore, when the charge state S1 of the on-board battery 51 connected to the DC port 71 of the priority port exceeds the fourth threshold Sth14, and the power of the load 3 input from the AC port 62 decreases, the power of the on-board battery 51 changes from charging to discharging. On the other hand, the power of the stationary battery 52 connected to the DC port 72, which is not a priority port, continues to be charged. As a result, the power conversion system 1 can reduce the charge state S1 of the on-board battery 51 to the fourth threshold Sth14 (periods b6 to b7).

[0062] By operating as described above, the power conversion system 1 prioritizes charging the onboard battery 51, which is a storage battery connected to the priority port, and inputs power from the load 3, while preventing its charge state S1 from rising to a fully charged state (=1). As a result, even if the power generated by the load 3 becomes relatively large, both the onboard battery 51 and the stationary battery 52 can be charged with the power generated by the load 3, thus enabling the system to continue absorbing the power generated by the load 3.

[0063] To perform this operation, the power conversion system 1 should set a fourth threshold Sth14 so that the charge state S1 of the onboard battery 51 does not rise to a fully charged state (=1), taking into consideration the maximum value of the power generated by the load 3 and its duration. In addition, the power conversion system 1 should set a third threshold Sth13 to a value lower than the fourth threshold Sth14, according to the priority of the onboard battery 51 over the stationary battery 52. Furthermore, while the examples described so far have explained the operation of absorbing the power generated by load 3, the power conversion system 1 can also be operated in the same way as in the examples in Figures 4 and 5 when absorbing the power generated by solar cell 53.

[0064] In the above explanation, "prioritizing the charging of the on-board battery 51" means that if the on-board battery 51 cannot absorb all the power even when charged at maximum power, the excess power is used to charge the stationary battery 52. ​​Alternatively, for example, both the on-board battery 51 and the stationary battery 52 may be charged, while the charging power of the on-board battery 51 is set to a higher value than that of the stationary battery 52.

[0065] [Example of connecting a stationary battery to a priority port] Figures 6 and 7 show the operation when the DC port 72 to which the stationary battery 52 is connected is set to a higher priority and designated as a priority port. Figures 6 and 7 show the operation when load 3 consumes power. In Figure 6, tc0 to tc8 represent time, and c0 to c8 represent duration. Figure 7 shows the operation when load 3 generates power. Here, td0 to td8 represent time, and d0 to d8 represent duration.

[0066] In Figures 4 and 5, the DC port 71 to which the onboard battery 51 is connected is designated as the priority port, whereas in Figures 6 and 7, the DC port 72 to which the stationary battery 52 is connected is designated as the priority port. As a result, the power P1 and charge state S1 of the onboard battery 51 in Figures 6 and 7 behave the same as the power P2 and charge state S2 of the stationary battery 52 in Figures 4 and 5. Furthermore, the power P2 and charge state S2 of the stationary battery 52 in Figures 4 and 5 behave similarly to the power P1 and charge state S1 of the on-board battery 51 in Figures 2 and 3. Thus, the operation during periods c0-c8 and d0-d8 in Figures 4 and 5 is simply a swap of charge states S1 and S2 with those of charge states S1 and S2 in periods c0-c8 and d0-d8 in Figures 2 and 3, and a detailed explanation of the transitions is omitted.

[0067] However, in the cases of Figures 6 and 7, since the DC port 72 to which the stationary battery 52 is connected is designated as the priority port, the first threshold Sth21, second threshold Sth22, third threshold Sth23, and fourth threshold Sth24 are set relative to the charge state S2 of the stationary battery 52. The threshold value set for the stationary battery 52 is determined by factors such as the charging capacity, characteristics, and usage conditions of the stationary battery 52, and is therefore likely to differ from the threshold value set for the on-board battery 51.

[0068] As explained above, according to the power conversion system 1 of this embodiment, in the event of a commercial power outage, the power of multiple storage batteries, such as stationary batteries or on-board batteries installed in vehicles such as electric vehicles, can be used to supply backup power to the load and continue operating the load. At this time, the power conversion system 1 can select which storage battery to use preferentially from among the multiple storage batteries. Furthermore, the power conversion system 1 can use the selected storage battery preferentially while ensuring that it does not reach its discharge limit. Therefore, according to the power conversion system 1 of this embodiment, even when multiple storage batteries are required to supply the peak power required by the load, it becomes possible to continue operating the load by supplying the peak power required by the load.

[0069] [Another example configuration of a power conversion system (Example 1)] Next, a modified configuration of the power conversion system of this embodiment will be described. Figure 8 shows the configuration of power conversion system 5 as a modified example (Example 1). In Figure 6, the power conversion system 5 is composed of multiple power conversion devices 101 and 102. Power conversion device 101 includes relays 111 and 112, an AC / DC conversion unit 121, DC / DC conversion units 131 and 132, and a control unit 110. Power conversion device 201 includes relays 211 and 212, an AC / DC conversion unit 221, DC / DC conversion units 231 and 232, and a control unit 210.

[0070] Power converters 101 and 201 are connected in parallel to the commercial power supply 2 and the switch 13 via AC ports 63 and 64, respectively. The switch 13 is connected to the power conversion system 5, the commercial power supply 2, and the load 3. The DC / DC converter 131 is connected to the on-board battery 51 mounted on the vehicle 41 via a DC port 74, and the DC / DC converter 132 is connected to the stationary battery 52 via a DC port 75. Furthermore, the DC / DC converter 231 is connected to the on-board battery 54 mounted on the vehicle 42 via a DC port 76, and the DC / DC converter 232 is connected to the solar cell 53 via a DC port 77.

[0071] The control unit 110 of the power converter 101 controls the relays 111 and 112, the switch 13, the AC / DC converter 121, and the DC / DC converters 131 and 132. The control unit 210 of the power converter 201 controls the relays 211 and 212, the AC / DC converter 221, and the DC / DC converters 231 and 232. Furthermore, both control units 110 and 210 are interconnected and communicate with each other. Therefore, the power converter 101 and power converter 201 are configured to work together as a single power conversion system 5. In other words, the control processing performed by the control unit 10 of the power conversion system 1 shown in Figure 1 is distributed and executed by the two control units 110 and 210. In this case, for example, one control unit 110 may set priority ports and thresholds, while the other control unit 210 processes based on instructions from control unit 110. Alternatively, both control units 110 and 210 may store the settings for priority ports and thresholds.

[0072] Under normal conditions when commercial power supply 2 is not experiencing a power outage, control units 110 and 210 turn on relays 111 and 211, turn off relays 112 and 212, and switch the changeover switch 13 to commercial power supply 2. In the event of a power outage of commercial power supply 2, control units 110 and 210 turn off relays 111 and 211, turn on relays 112 and 212, and switch the changeover switch 13 to the power conversion system 5. These switching controls are performed by setting the first, second, third, and fourth thresholds as described in the power conversion system 1 configuration of Figure 1, and are executed as described in Figures 4 to 7.

[0073] With this configuration, the power conversion system 5, which is equipped with multiple power conversion devices 101, 201, can operate in the same way as the power conversion system 1 shown in Figure 1. The power conversion system 5 shown in Figure 8 is composed of units of power converters 101 and 201, allowing it to handle larger power capacities and to be configured to connect to more vehicles and stationary batteries. Although Figure 8 shows two power converters 101 and 201, it is possible to connect to more batteries and other storage devices by increasing the number of power converters connected. Therefore, the power conversion system 5 shown in Figure 8 has the advantage of making it easier to construct a power conversion system on a wider scale compared to the power conversion system 1 shown in Figure 1.

[0074] [Another example configuration of a power conversion system (Example 2)] Figure 9 shows the configuration of power conversion system 5′ as a modified example (Example 2). The power conversion system 5′ shown in Figure 9 is the same as the power conversion system 5 in Figure 8 in that it is composed of multiple power conversion devices 101′, 102′, and the configuration of the AC ports 63, 64 and DC ports 74, 75, 76, 77 is also the same as the configuration shown in Figure 8. Furthermore, the relays 111, 112, 211, 212, AC / DC conversion units 121, 221, and DC / DC conversion units 131, 132, 231, 232 located inside each power conversion device 101′, 102′ are also the same as the configuration shown in Figure 8.

[0075] Furthermore, the power conversion system 5′ in the example of Figure 9 differs from the example of Figure 8 in that one power conversion device 101′ is equipped with a control unit 110′, while the other power conversion device 201′ is not equipped with a control unit. The control unit 110' of the power converter 101' controls all power converters 101' and 102'. Specifically, the control unit 110' controls relays 111, 112, 211, and 212, AC / DC converters 121 and 221, and DC / DC converters 131, 132, 231, and 232. The control operations performed by the control unit 110' are the same as those performed by the power conversion system 5 shown in Figure 8, which is distributed among the two control units 110 and 210. The threshold values ​​described in the power conversion system 1 configuration of Figure 1 are set, and the operations are executed as described in Figures 4 to 7.

[0076] With the configuration shown in Figure 9, even if the number of power converters 101' and 201' increases, only one control unit 110' is needed, thus simplifying the control configuration.

[0077] [Differentiation] Furthermore, the power conversion system and power conversion method of the present invention are not limited to the configurations and processes described in the above-described embodiments, and various modifications can be implemented without departing from the gist of the invention as described in the claims. In addition, the above-described embodiments are described in detail for the purpose of clearly explaining the present invention, and are not necessarily limited to those having all the configurations described.

[0078] For example, the above-described embodiment explained the operation when a solar cell, an on-board battery, and a stationary battery are all connected to the DC port. However, the present invention can be applied to any case where multiple storage batteries, such as on-board batteries and stationary batteries, are connected. Furthermore, while the above-described embodiment explained operation using the charge state of the storage battery to be used preferentially and its threshold, it is not necessarily required to use the charge state. For example, the control unit of the power conversion system may operate using the remaining energy and its threshold. Furthermore, although the above-described embodiments mainly described operations assuming a power outage, a system may also be constructed that applies the processing described in the above-described embodiments to compensate for power fluctuations of the load during normal times when there is no power outage, thereby suppressing fluctuations in power received from the commercial power source.

[0079] Furthermore, in the above-described embodiment, the power conversion system sets four thresholds to supply power to the load and charge the storage battery. In contrast, the power conversion system may omit the setting of any of the thresholds. For example, the first and second thresholds may be set to ensure that power is supplied to the load from multiple storage batteries appropriately during a power outage, and the power supply to the storage battery from the load may be controlled without setting the third and fourth thresholds. Alternatively, the power conversion system may switch when supplying power to the load based on only the first threshold, or when supplying power from the load based on only the third threshold.

[0080] Furthermore, some of the processing functions performed by the control unit within the power conversion system may be performed by a control unit configured on an external terminal connected via the internet or other means, and the control unit within the power conversion system may perform switching and other operations based on instructions from the external terminal. Furthermore, the program used by the control unit within the power conversion system to execute the processing in this embodiment may be stored on an external recording medium such as memory, an IC card, an SD card, or an optical disc, and transferred to a computer that functions as the control unit within the power conversion system. Furthermore, as shown in Figure 1, configuring the control unit as a computer equipped with a CPU and memory is just one example. For instance, some or all of the functions performed by the control unit may be implemented by hardware such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0081] Furthermore, in the configuration diagrams shown in Figures 1, 8, and 9, only control lines and information lines deemed necessary for explanation are shown, and not all control lines and information lines are necessarily shown in the actual product. In reality, it can be assumed that almost all components are interconnected. Furthermore, the flowchart shown in Figure 3 is just one example; if the processing results are the same, some processing orders may be changed, or multiple processes may be executed simultaneously. [Explanation of Symbols]

[0082] 1…Power conversion system, 2…Commercial power supply, 3…Load, 5,5′…Power conversion system, 10…Control unit, 10a…CPU, 10b…Memory, 10c…Interface, 11,12…Relays, 21,31…DC / DC converter, 41,42…Vehicle, 51…On-board battery, 52…Stationary battery, 53…Solar cell, 54…On-board battery, 61,62,63,64…AC port, 71,72,73,74,75,76,77…DC port, 101,101′…Power conversion device, 110,110′…Control unit, 111,112…Relays, 121,131,132…DC / DC converter, 201,201′…Power conversion device, 210…Control unit, 211…Relay, 221…AC / DC conversion unit, 231,232…DC / DC conversion unit

Claims

1. The system comprises an AC port connected to a commercial power source or load, multiple DC ports to which multiple storage batteries, each consisting of a stationary battery or an on-board battery, are individually connected, and a control unit that controls the output and input of the multiple DC ports, A power conversion system capable of converting AC power input from the aforementioned AC port into DC power and outputting it to a plurality of aforementioned DC ports, and capable of converting DC power input from a plurality of aforementioned DC ports into AC power and outputting it to the aforementioned AC ports, The control unit sets the DC port with the highest priority among the multiple DC ports connected to each of the multiple storage batteries as the priority port. When the charge state or remaining energy level of the battery connected to the priority port is higher than the first threshold, power is preferentially input from the priority port over the DC ports to which other batteries are connected, while power is input from both the priority port and the DC ports to which other batteries are connected, and power is output to the AC port. When the charge state or remaining energy level of the battery connected to the priority port is lower than the first threshold, power is preferentially input from the DC port to which the other battery is connected, while power is input from both the priority port and the DC port to which the other battery is connected, and power is output to the AC port. Power conversion system.

2. The control unit, If the charge state or remaining energy of the battery connected to the priority port is lower than a second threshold set lower than the first threshold, the process is executed to input power from the DC port to which another battery is connected and output power to both the priority port and the AC port. The power conversion system according to claim 1.

3. The control unit, When the charge state or remaining energy of the battery connected to the priority port is lower than a second threshold set lower than the first threshold, the power output from the AC port decreases, causing the power of the battery connected to the priority port to change from discharge to charge, while the power of the other batteries remains at discharge. The power conversion system according to claim 1.

4. The control unit, When the charge state or remaining energy level of the battery connected to the priority port is lower than a third threshold set higher than the first threshold, the process involves outputting power preferentially to the priority port over the DC ports to which other batteries are connected, while simultaneously inputting power from the AC port and outputting power to both the priority port and the DC ports to which other batteries are connected. If the charge state or remaining energy level of the battery connected to the priority port is higher than the third threshold, the process is executed to preferentially output power to the DC port to which the other battery is connected, while inputting power from the AC port and outputting power to both the priority port and the DC port to which the other battery is connected. The power conversion system according to claim 1.

5. The control unit, When the charge state or remaining energy level of the battery connected to the priority port is higher than the fourth threshold, which is set to be higher than the third threshold, the process is executed to input power from both the AC port and the priority port and output power to the DC port to which the other battery is connected. The power conversion system according to claim 4.

6. The control unit, When the charge state or remaining energy level of the battery connected to the priority port is higher than the fourth threshold, which is set higher than the third threshold, the power of the battery connected to the priority port changes from charging to discharging as the power input from the AC port decreases, while the power of the other batteries maintains its charge. The power conversion system according to claim 4.

7. A solar cell is connected to at least one of the multiple DC ports. The control unit, When the charge state or remaining energy level of the battery connected to the priority port is lower than a third threshold set higher than the first threshold, the process involves outputting power preferentially to the priority port over the DC ports to which other batteries are connected, while simultaneously inputting power from the DC port to which the solar cell is connected and outputting power to both the priority port and the DC ports to which other batteries are connected. If the charge state or remaining energy level of the battery connected to the priority port is higher than the third threshold, the process is executed to output power preferentially to the DC port to which the other battery is connected, while inputting power from the DC port to which the solar cell is connected and outputting power to both the priority port and the DC port to which the other battery is connected. The power conversion system according to claim 1.

8. The control unit, When the charge state or remaining energy level of the battery connected to the priority port is higher than the fourth threshold, which is set higher than the third threshold, the process is executed to input power from both the DC port to which the solar cell is connected and the priority port, and output power to the other DC port to which the battery is connected. The power conversion system according to claim 7.

9. The first threshold is higher than the lower discharge limit of the battery connected to the priority port. The power conversion system according to claim 1.

10. The second threshold is higher than the lower discharge limit of the battery connected to the priority port. The power conversion system according to claim 2.

11. The aforementioned AC port includes a first AC port connected to a commercial power supply and a second AC port connected to a load. The AC power of the commercial power supply input from the first AC port is converted to DC power, and the converted DC power can be output from multiple DC ports to multiple storage batteries. In the event of a power outage of the commercial power supply, the DC power from the multiple batteries input from the multiple DC ports is converted to AC power and output from the second AC port to supply power to the load, and the AC power generated from the load is input from the second AC port, converted to DC power and output from the multiple DC ports to the multiple batteries. The power conversion system according to claim 1.

12. The multiple DC ports are divided into multiple groups, The control unit is provided for each of the divided groups, and the control units of each group work together to control the output or input of the multiple DC ports. The power conversion system according to claim 1.

13. The multiple DC ports are divided into multiple groups, The control unit controls the output or input of all of the divided DC ports. The power conversion system according to claim 1.

14. A power conversion method applicable to a power conversion system comprising: an AC port connected to a commercial power source or load; a plurality of DC ports to which a plurality of storage batteries, each consisting of a stationary battery or an on-board battery, are individually connected; and a control unit that controls the output and input of the plurality of DC ports, The system can convert AC power input from the aforementioned AC port into DC power and output it to multiple DC ports, and it can also convert DC power input from multiple DC ports into AC power and output it to the AC ports. A process to set a DC port with a higher priority as a priority port among the multiple DC ports connected to each of the multiple storage batteries, A first power input / output process is performed in which, when the charge state or remaining energy of the battery connected to the priority port is higher than a first threshold, power is preferentially input from the priority port over the DC ports to which other batteries are connected, while power is input from both the priority port and the DC ports to which other batteries are connected, and power is output to the AC port. The process includes, when the charge state or remaining energy of the battery connected to the priority port is lower than the first threshold, a second power input / output process that prioritizes inputting power from the DC port to which the other battery is connected, while inputting power from both the priority port and the DC port to which the other battery is connected, and outputting power to the AC port. Power conversion method.

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