JP2024089188A - Charging/discharging system and charging/discharging method - Google Patents

Abstract

A charging/discharging system and a charging/discharging method that reduce space constraints are provided.
[Solution] The charging/discharging system 1 comprises an AC/DC conversion equipment 2, a first current path 11 that supplies current from the AC/DC conversion equipment 2 to a load 92, a silicon dropper 3, a bypass current path 13 that bypasses the silicon dropper 3 and supplies current, a switch 33 arranged on the bypass current path 13, a lithium ion battery 5 that is charged by receiving current supplied from the AC/DC conversion equipment 2 and supplies power to the load 92 by discharging, and a switching means 6 that switches the charging method depending on the charging state of the lithium ion battery 5 so as to prevent an overcurrent from flowing from the AC/DC conversion equipment 2 to the lithium ion battery 5 when the lithium ion battery 5 is charged.
[Selected figure] Figure 2

Description

Embodiments of the present invention relate to a charging/discharging system and a charging/discharging method.

A system is known that supplies power to a load from a storage battery via a silicon dropper.

As a related technique, FIG. 13 of Patent Document 1 discloses a system including an AC power distribution panel (1), a transformer (4), a rectifier circuit section (5), a storage battery (7) such as a lead-acid battery, a silicon dropper circuit (8), and a load side distribution circuit section (9).

JP 2000-14038 A

When configuring a charging and discharging system using lead-acid batteries, which are vented secondary batteries, there can be significant space constraints due to the need to secure a battery room, etc.

The present invention aims to provide a charging/discharging system and a charging/discharging method that reduce space constraints by using lithium-ion batteries instead of lead-acid batteries.

In order to solve the above problems, the charging and discharging system in an embodiment of the present invention is characterized by comprising: an AC/DC converter that converts AC power to DC power; a first current path that supplies current from the AC/DC converter to a load; a silicon dropper that is disposed on the first current path and that reduces the voltage; a bypass current path that supplies current from the AC/DC converter to the load, bypassing the silicon dropper; a switch disposed on the bypass current path; a lithium-ion battery that is charged by receiving the current supplied from the AC/DC converter and supplies power to the load by discharging; and a switching means that switches the charging method according to the charging state of the lithium-ion battery so as to prevent an overcurrent from flowing from the AC/DC converter to the lithium-ion battery when the lithium-ion battery is being charged.

In addition, the charging/discharging method in an embodiment of the present invention is a charging/discharging method executed using a charging/discharging system, the charging/discharging system including an AC/DC converter that converts AC power to DC power, a first current path that supplies a current from the AC/DC converter to a load, a silicon dropper that is disposed on the first current path and that reduces a voltage, a bypass current path that bypasses the silicon dropper and supplies a current from the AC/DC converter to the load, a switch disposed on the bypass current path, and a lithium ion battery that is charged by receiving a current supplied from the AC/DC converter and supplies power to the load by discharging, and the charging/discharging method includes a first charging method that charges the lithium ion battery via the silicon dropper when the charging state of the lithium ion battery is a first state in which the charge amount is relatively small, and a constant current method that charges the lithium ion battery. The lithium ion battery is charged by at least one of a second charging method, a third charging method, and a fourth charging method, which charges the lithium ion battery by a constant voltage method, when the charging state of the lithium ion battery is a second state in which the charge amount is relatively large compared to the first state, the lithium ion battery is charged by at least one of a second charging method, which bypasses the silicon dropper and charges the lithium ion battery, and a fourth charging method, which charges the lithium ion battery by a constant voltage method; when the charging state of the lithium ion battery is a third state in which the charge amount is relatively large, the lithium ion battery supplies power to the load through the silicon dropper; and when the charging state of the lithium ion battery is a fourth state in which the charge amount is relatively small compared to the third state, the lithium ion battery supplies power to the load by bypassing the silicon dropper.

The present invention provides a charging/discharging system and a charging/discharging method that reduce space constraints.

FIG. 1 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to a first embodiment. FIG. 2 is a diagram illustrating an example of a circuit configuration of the charge/discharge system according to the first embodiment. FIG. 3 is a diagram illustrating an example of a circuit configuration of the charge/discharge system according to the first embodiment. FIG. 4 is a diagram illustrating an example of a circuit configuration of the charge/discharge system according to the first embodiment. FIG. 5 is a diagram illustrating an example of a circuit configuration of the charge/discharge system according to the first embodiment. FIG. 6 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to the second embodiment. FIG. 7 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to the second embodiment. FIG. 8 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to the second embodiment. FIG. 9 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to the second embodiment. FIG. 10 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to the second embodiment. FIG. 11 is a graph showing an example of changes in charging voltage and charging current during the charging process. FIG. 12 is a diagram illustrating an example of a circuit configuration of a charge/discharge system according to a first modified example of the embodiment. FIG. 13 is a diagram illustrating an example of a circuit configuration of a charge/discharge system in a second modified example of the embodiment.

The charging/discharging system 1 and the charging/discharging method according to the embodiment will be described below with reference to the attached drawings. In the following description, the same reference numerals are used for components and parts having the same functions, and repeated description of components and parts with the same reference numerals will be omitted. In addition, it goes without saying that the numerical values used in the following description of the embodiment are merely examples (in other words, it goes without saying that the scope of the claims is not limited by the numerical values used in the embodiment).

First Embodiment
A charge/discharge system 1A according to the first embodiment will be described with reference to Fig. 1 to Fig. 5. Fig. 1 to Fig. 5 are diagrams that show an example of a circuit configuration of the charge/discharge system 1A according to the first embodiment. Fig. 2 and Fig. 3 show a state in which the lithium ion battery 5 is being charged, and Fig. 4 and Fig. 5 show a state in which power is being supplied from the lithium ion battery 5 to a load 92.

(Composition and Function)
In the example shown in FIG. 1 , the charge/discharge system 1A includes an AC/DC converter 2, a first current path 11, a silicon dropper 3, a bypass current path 13, a switch 33, a lithium ion battery 5, and a switching means 6.

The AC/DC converter 2 converts AC power into DC power. The first current path 11 supplies power from the AC/DC converter 2 to the load 92.

The silicon dropper 3 is disposed in the first current path 11 and drops the voltage. In the example shown in FIG. 1, the silicon dropper 3 includes at least one silicon diode 31. In the example shown in FIG. 1, the silicon dropper 3 includes a plurality of silicon diodes 31 connected in series. In the example shown in FIG. 1, the number of silicon diodes 31 included in the silicon dropper 3 is three, but the number of silicon diodes 31 included in the silicon dropper 3 may be one, two, or four or more.

Each silicon diode 31 drops the voltage so that the voltage downstream of the silicon diode 31 in the current flow direction is a predetermined voltage lower than the voltage upstream of the silicon diode 31 in the current flow direction. The voltage drop amount by each silicon diode is, for example, 0.6 V or more and 1 V or less.

The bypass current path 13 supplies current from the AC/DC converter 2 to the load 92, bypassing the silicon dropper 3.

The switch 33 is disposed in the bypass current path 13. When the switch 33 is in a closed state, power can be supplied from the AC/DC converter 2 to the load 92 via the bypass current path 13. On the other hand, when the switch 33 is in an open state, power can be supplied from the AC/DC converter 2 to the load 92 via the silicon dropper 3 without passing through the bypass current path 13.

The lithium ion battery 5 is charged by receiving a current supplied from the AC/DC converter 2. The lithium ion battery 5 also supplies power to the load 92 by discharging.

The switching means 6 switches the charging method according to the charging state of the lithium-ion battery 5 (more specifically, the terminal voltage of the lithium-ion battery 5 or the charging rate of the lithium-ion battery 5 (in other words, the amount of charge relative to the charging capacity)) so as to prevent an overcurrent from flowing from the AC/DC converter 2 to the lithium-ion battery 5 when the lithium-ion battery 5 is being charged.

In the example shown in Figures 2 and 3, the switching means 6 switches the charging method between a first charging method M1 (see Figure 2) in which the lithium ion battery 5 is charged via the silicon dropper 3, and a second charging method M2 (see Figure 3) in which the lithium ion battery 5 is charged by bypassing the silicon dropper 3.

2, it is assumed that there is a large potential difference between the output voltage of the AC/DC converter 2 and the terminal voltage of the lithium-ion battery 5. In this case, the first charging method M1 is executed to charge the lithium-ion battery 5 via the silicon dropper 3 using the switching means 6, thereby preventing an overcurrent from flowing from the AC/DC converter 2 to the lithium-ion battery 5. More specifically, since the potential difference between the voltage downstream of the silicon dropper 3 in the current flow direction and the terminal voltage of the lithium-ion battery 5 is relatively small, no overcurrent flows to the lithium-ion battery 5.

In the example shown in FIG. 3, it is assumed that the potential difference between the output voltage of the AC/DC converter 2 and the terminal voltage of the lithium-ion battery 5 is small. In this case, the second charging method M2 is executed using the switching means 6 to charge the lithium-ion battery 5 by bypassing the silicon dropper 3 (more specifically, the second charging method M2 to charge the lithium-ion battery 5 without passing through the silicon dropper 3). In this way, the lithium-ion battery 5 can be charged so that the terminal voltage of the lithium-ion battery 5 is sufficient (in other words, so that a sufficient charge amount is ensured).

(effect)
In the first embodiment, the lithium ion battery 5 is used instead of the lead storage battery, thereby reducing the space constraints associated with the use of the lead storage battery. The charge/discharge system 1A in the first embodiment includes a switching means 6 that switches the charging method according to the charging state of the lithium ion battery 5 (more specifically, the terminal voltage of the lithium ion battery 5 or the charging rate of the lithium ion battery 5). By using the switching means 6, even if the terminal voltage of the lithium ion battery 5 is low (or the charging rate of the lithium ion battery 5 is low) when the lithium ion battery 5 is being charged, an overcurrent is prevented from flowing from the AC/DC converter 2 to the lithium ion battery 5.

In addition, in the first embodiment, the charging method of the lithium ion battery 5 is switched by utilizing the characteristics of the silicon dropper 3 that reduces the output voltage of the AC/DC converter 2 to match the load 92. More specifically, the switching means 6 switches the charging method between a charging method via the silicon dropper 3 and a charging method that bypasses the silicon dropper 3. Thus, the charging method can be switched with a simple configuration.

(Optional additional configuration)
Optional additional configurations that can be adopted in the charge/discharge system 1A in the first embodiment will be described with reference to FIGS. 1 to 5. FIG.

(Charging and discharging systems for ships)
The charge/discharge system 1A in the first embodiment may be a charge/discharge system in a ship. More specifically, the charge/discharge system 1A may have an inboard AC busbar 10. A high-voltage AC current (e.g., 440V AC current) flows through the inboard AC busbar 10. The inboard AC busbar 10 supplies power to various locations in the ship via a power distribution line. The inboard AC busbar 10 may supply power to a propeller of the ship (e.g., a motor that drives a screw).

In the example shown in FIG. 2, the AC/DC converter 2 receives AC power from the onboard AC busbar 10 and supplies DC power to the first current path 11. The AC/DC converter 2 may receive AC power from the onboard AC busbar 10 via a transformer 81. The transformer 81 steps down the voltage of the onboard AC busbar 10, and the stepped-down voltage is supplied to the AC/DC converter 2. The transformer 81 steps down the voltage of the onboard AC busbar 10, for example, from 440 V to 220 V. A circuit breaker 82 may be arranged between the onboard AC busbar 10 and the transformer 81.

In ships, lead-acid batteries need to be installed in a dedicated compartment. In other words, ships need a battery room to install lead-acid batteries. By replacing at least some of the lead-acid batteries (preferably all of the lead-acid batteries) with lithium-ion batteries 5, the battery room can be omitted or made smaller. In this way, restrictions on the layout of space within the ship can be eliminated or reduced. For example, it is possible to place the lithium-ion batteries 5 in the same panel as the charging and discharging panel. In addition, the general replacement cycle for lead-acid batteries is about 3 to 5 years, but if lithium-ion batteries 5 are used, the replacement cycle can be made longer.

(AC/DC converter 2)
In the example shown in Fig. 2, the AC/DC converter 2 is a rectifier 21, such as a diode rectifier. Alternatively, as illustrated in Fig. 6, the AC/DC converter 2 may include at least one AC/DC converter 23 controllable by the controller 7.

The DC output voltage of the AC/DC converter 2 is, for example, about 26.8 V (for example, 25 V or more and 30 V or less).

(First current path 11)
2, the first current path 11 includes a first portion 111 connecting the AC/DC converter 2 and the upstream end of the silicon dropper 3, and a second portion 112 connecting the downstream end of the silicon dropper 3 and the load 92 or the load side distribution circuit 91. The first portion 111 is a portion of the first current path 11 that is upstream of the silicon dropper 3 in the current flow direction, and the second portion 112 is a portion of the first current path 11 that is downstream of the silicon dropper 3 in the current flow direction.

(Bypass current path 13)
In the example shown in FIG. 2 , one end 13 a of the bypass current path 13 is connected to a first portion 111 of the first current path 11 , and the other end 13 b of the bypass current path 13 is connected to a second portion 112 of the first current path 11 .

In the example shown in FIG. 2, the switch 33 includes a first switch 33a arranged in the bypass current path 13. The first switch 33a is, for example, a first contactor (in other words, a first contactor).

(Second current path 15)
In the example shown in Fig. 2, the charging/discharging system 1A has a second current path 15. The second current path 15 connects a portion of the first current path 11 between the silicon dropper 3 and the load 92 (in other words, a second portion 112 of the first current path 11) and the lithium ion battery 5. In the example shown in Fig. 2, a portion of the second current path 15 and a portion of the bypass current path 13 are shared. In other words, a portion of the second current path 15 functions as a portion of the bypass current path 13. In this specification, a portion of the second current path 15 that constitutes a portion of the bypass current path 13 is referred to as a shared current path 15b.

In the example shown in FIG. 2, the second switch 35 is disposed in the second current path 15. More specifically, the second switch 35 is disposed in the shared current path 15b. In other words, the second switch 35 is disposed in the second current path 15 and also in the bypass current path 13. The second switch 35 is, for example, a second contactor (in other words, a second contactor).

A circuit breaker 88 may be disposed in the second current path 15. The charging/discharging system 1A may also include a third switch 89 that electrically disconnects the lithium ion battery 5 from the second current path 15 based on a command received from the control device 7 or the battery management unit (hereinafter referred to as "BMU 14").

(Switching Means 6)
In the example shown in Figures 2 and 3, the switching means 6 includes a switch 33 (more specifically, a first switch 33a) arranged in the bypass current path 13 and a second switch 35 arranged in the second current path 15.

2 (see arrow AR1), when power is supplied from the AC/DC converter 2 to the load 92 (more specifically, when power is supplied from the onboard AC bus 10 via the AC/DC converter 2 to the load 92), the first switch 33a is maintained in an open state and the second switch 35 is maintained in a closed state, so that the AC/DC converter 2 can charge the lithium-ion battery 5 via the silicon dropper 3 (see arrow AR2). This charging method is performed via the silicon dropper 3, and therefore corresponds to the first charging method M1 described above.

As illustrated in FIG. 3 (see arrow AR3), when power is supplied from the AC/DC converter 2 to the load 92 (more specifically, when power is supplied from the onboard AC bus 10 via the AC/DC converter 2 to the load 92), the first switch 33a is maintained in a closed state and the second switch 35 is maintained in an open state, so that the AC/DC converter 2 can bypass the silicon dropper 3 and charge the lithium-ion battery 5 (see arrow AR4). This charging method is performed by bypassing the silicon dropper 3, and therefore corresponds to the second charging method M2 described above.

4, when the power supply from the AC/DC converter 2 to the load 92 is interrupted (more specifically, when power is not being supplied from the onboard AC bus 10 to the load 92 via the AC/DC converter 2), the first switch 33a is maintained in a closed state and the second switch 35 is maintained in an open state, so that the lithium ion battery 5 can supply power to the load 92 via the silicon dropper 3 (see arrow AR5). In this way, the lithium ion battery 5 functions as a backup power source (more specifically, a backup power source in the event of a power outage of the onboard AC bus 10).

5, when the power supply from the AC/DC converter 2 to the load 92 is interrupted (more specifically, when power is not being supplied from the onboard AC bus 10 to the load 92 via the AC/DC converter 2), the first switch 33a is maintained in an open state and the second switch 35 is maintained in a closed state, so that the lithium ion battery 5 can supply power to the load 92, bypassing the silicon dropper 3 (see arrow AR6). In this way, the lithium ion battery 5 functions as a backup power source (more specifically, a backup power source in the event of a power outage of the onboard AC bus 10).

(Control device 7)
In the example shown in Fig. 2, the charge/discharge system 1A includes a control device 7. The control device 7 controls the switch 33 (more specifically, the first switch 33a) and the second switch 35 arranged on the second current path 15. The control device 7 may include one computer or may include multiple computers.

The control device 7 may be configured to switch the state of the switch 33 (more specifically, the first switch 33a) from an open state to a closed state by transmitting a first close command to the switch 33 (more specifically, the first switch 33a). Also, the control device 7 may be configured to switch the state of the switch 33 (more specifically, the first switch 33a) from a closed state to an open state by transmitting a first open command to the switch 33 (more specifically, the first switch 33a).

The control device 7 may be configured to switch the state of the second switch 35 from an open state to a closed state by transmitting a second close command to the second switch 35. The control device 7 may also be configured to switch the state of the second switch 35 from a closed state to an open state by transmitting a second open command to the second switch 35.

(Charge State Detector 83)
The charging/discharging system 1A may include a charging state detector 83 that detects the charging state of the lithium-ion battery 5. The control device 7 receives a signal indicating the charging state of the lithium-ion battery 5 from the charging state detector 83, and controls the switch 33 (more specifically, the first switch 33a) and the second switch 35 based on the signal.

(Determinator 85)
The charging/discharging system 1A may include a determiner 85 that determines whether or not power is being supplied from the AC/DC converter 2 to the load 92 (more specifically, whether or not power is being supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2). The determiner 85 may be configured by the control device 7, or may be configured by a device separate from the control device 7. The determiner 85 may determine whether or not power is being supplied from the AC/DC converter 2 to the load 92 based on the voltage and/or current of the inboard AC bus 10, or may determine whether or not power is being supplied from the AC/DC converter 2 to the load 92 by monitoring the AC/DC converter 23, as illustrated in FIG. 7.

(Charging the lithium ion battery 5)
2 or 3 , a state in which power is supplied from the AC/DC converter 2 to the load 92 (more specifically, a state in which power is supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2) is assumed. More specifically, a case in which the determiner 85 determines that power is being supplied from the AC/DC converter 2 to the load 92 is assumed.

2 and 3, the control device 7 judges whether the charging state of the lithium ion battery 5 is a first state in which the charge amount is relatively low, or a second state in which the charge amount is relatively high, based on a signal indicating the charging state of the lithium ion battery 5 received from the charging state detector 83. When the charging state of the lithium ion battery 5 is judged to be the first state in which the charge amount is relatively low, the control device 7 controls the first switch 33a and the second switch 35 so that the first switch 33a is in the open state and the second switch 35 is in the closed state (see FIG. 2). When the charging state of the lithium ion battery 5 is judged to be the second state in which the charge amount is relatively high, the control device 7 controls the first switch 33a and the second switch 35 so that the first switch 33a is in the closed state and the second switch 35 is in the open state (see FIG. 3).

The charge state detector 83 may include a voltage detector 84a that detects the terminal voltage of the lithium ion battery 5. In this case, when the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is equal to or lower than the first threshold TH1, the control device 7 may determine that the charge state of the lithium ion battery 5 is a first state in which the charge amount is relatively small. Also, when the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is greater than the first threshold TH1, the control device 7 may determine that the charge state of the lithium ion battery 5 is a second state in which the charge amount is relatively large. The voltage detector 84a may be included in the BMU 14.

Alternatively, or additionally, the charge state detector 83 may include a charge rate detection device 84b that detects the state of charge of the lithium ion battery 5. In this case, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is equal to or lower than the second threshold TH2, the control device 7 may determine that the charge state of the lithium ion battery 5 is a first state in which the charge amount is relatively small. Also, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is greater than the second threshold TH2, the control device 7 may determine that the charge state of the lithium ion battery 5 is a second state in which the charge amount is relatively large. The charge rate detection device 84b may be included in the BMU 14.

(Discharging of lithium ion battery 5)
4 or 5, a state in which the supply of power from the AC/DC converter 2 to the load 92 is interrupted (more specifically, a state in which power is not supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2) is assumed. More specifically, a case in which the determiner 85 determines that power is not being supplied from the AC/DC converter 2 to the load 92 is assumed.

4 and 5, the control device 7 judges whether the state of charge of the lithium ion battery 5 is the third state in which the charge amount is relatively large, or the fourth state in which the charge amount is relatively small, based on the signal indicating the state of charge of the lithium ion battery 5 received from the charge state detector 83. When the state of charge of the lithium ion battery 5 is judged to be the third state in which the charge amount is relatively large, the control device 7 controls the first switch 33a and the second switch 35 so that the first switch 33a is closed and the second switch 35 is open (see FIG. 4). When the state of charge of the lithium ion battery 5 is judged to be the fourth state in which the charge amount is relatively small, the control device 7 controls the first switch 33a and the second switch 35 so that the first switch 33a is open and the second switch 35 is closed (see FIG. 5).

The charge state detector 83 may include a voltage detector 84a that detects the terminal voltage of the lithium ion battery 5. In this case, when the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is greater than the third threshold TH3, the control device 7 may determine that the charge state of the lithium ion battery 5 is a third state in which the charge amount is relatively large. When the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is equal to or less than the third threshold TH3, the control device 7 may determine that the charge state of the lithium ion battery 5 is a fourth state in which the charge amount is relatively small. The value of the third threshold TH3 may be the same as the value of the first threshold TH1 described above, or may be different from the value of the first threshold TH1 described above.

Alternatively, or additionally, the charge state detector 83 may include a charge rate detection device 84b that detects the state of charge of the lithium ion battery 5. In this case, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is greater than the fourth threshold TH4, the control device 7 may determine that the charge state of the lithium ion battery 5 is a third state in which the charge amount is relatively large. Also, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is equal to or less than the fourth threshold TH4, the control device 7 may determine that the charge state of the lithium ion battery 5 is a fourth state in which the charge amount is relatively small. The value of the fourth threshold TH4 may be the same as the value of the second threshold TH2 described above, or may be different from the value of the second threshold TH2 described above.

(Lithium-ion battery 5)
The lithium ion battery 5 may be configured with one battery unit U, or may be configured with a plurality of battery units U. When the lithium ion battery 5 is configured with a plurality of battery units U, some of the plurality of battery units U may be electrically connected in parallel. Alternatively, or additionally, when the lithium ion battery 5 is configured with a plurality of battery units U, some of the plurality of battery units U may be electrically connected in series.

(BMU14)
The charge/discharge system 1A may include a BMU 14. The BMU 14 monitors the lithium ion battery 5 and protects the lithium ion battery 5. The BMU 14 has, for example, a function of preventing overdischarge of the lithium ion battery 5. The BMU 14 monitors the temperature, voltage, current, etc. of the lithium ion battery 5, and may stop charging the lithium ion battery 5 when the temperature, voltage, current, etc. indicate abnormal values. Each BMU 14 may monitor and protect a corresponding battery unit U, or one BMU 14 may monitor and protect multiple battery units U.

(Load side power distribution circuit 91, load 92)
The charging/discharging system 1A may include a load-side distribution circuit 91 that connects the load 92 and the first current path 11. The load-side distribution circuit 91 may have a plurality of connection switches 912. When the connection switch 912 is ON, power is supplied from the first current path 11 to the load 92 via the connection switch 912.

Second Embodiment
A charging/discharging system 1B according to the second embodiment will be described with reference to Fig. 6 to Fig. 10. Fig. 6 to Fig. 10 are diagrams that show an example of a circuit configuration of the charging/discharging system 1B according to the second embodiment. Fig. 7 and Fig. 8 show a state in which the lithium ion battery 5 is being charged, and Fig. 9 and Fig. 10 show a state in which power is being supplied from the lithium ion battery 5 to a load 92.

(Composition and Function)
In the second embodiment, the switching means 6 is configured to be able to switch the charging method between a third charging method M3 in which the lithium ion battery 5 is charged by a constant current method and a fourth charging method M4 in which the lithium ion battery 5 is charged by a constant voltage method.

In the second embodiment, the differences from the first embodiment will be mainly described. On the other hand, in the second embodiment, repeated explanations of matters already described in the first embodiment will be omitted. Therefore, it goes without saying that matters already described in the first embodiment can be applied to the second embodiment even if they are not explicitly described in the second embodiment.

As illustrated in FIG. 6, the charging/discharging system 1B in the second embodiment includes: (1) an AC/DC converter 2 that converts AC power into DC power; (2) a first current path 11 that supplies current from the AC/DC converter 2 to a load 92; (3) a silicon dropper 3 that is disposed on the first current path 11 and that reduces the voltage; (4) a bypass current path 13 that supplies current from the AC/DC converter 2 to the load 92, bypassing the silicon dropper 3; (5) a switch 33 that is disposed on the bypass current path 13; (6) a lithium-ion battery 5 that is charged by receiving a current supplied from the AC/DC converter 2 and that supplies power to the load 92 by discharging; and (7) a switching means 6 that switches the charging method depending on the charging state of the lithium-ion battery 5 so as to prevent an overcurrent from flowing from the AC/DC converter 2 to the lithium-ion battery 5 when the lithium-ion battery 5 is being charged. The first current path 11, silicon dropper 3, bypass current path 13, switch 33, and lithium ion battery 5 have already been described in the first embodiment, so repeated descriptions of these components will be omitted in the second embodiment.

The switching means 6 switches the charging method according to the charging state of the lithium-ion battery 5 (more specifically, the terminal voltage of the lithium-ion battery 5 or the charging rate of the lithium-ion battery 5 (in other words, the amount of charge relative to the charging capacity)) so as to prevent an overcurrent from flowing from the AC/DC converter 2 to the lithium-ion battery 5 when the lithium-ion battery 5 is being charged.

In the example shown in Figures 7 and 8, the switching means 6 switches the charging method between a third charging method M3 (see Figure 7) in which the lithium ion battery 5 is charged by a constant current method, and a fourth charging method M4 (see Figure 8) in which the lithium ion battery 5 is charged by a constant voltage method.

In the examples shown in Figures 7 and 8, the switching means 6 includes an AC/DC converter 2 that can be controlled by the control device 7 (more specifically, at least one AC/DC converter 23 that can be controlled by the control device 7).

In the example shown in FIG. 7, the control device 7 controls the AC/DC converter 2 so that the charging current for charging the lithium ion battery 5 is substantially constant, thereby charging the lithium ion battery 5 using the third charging method M3. In the example shown in FIG. 8, the control device 7 controls the AC/DC converter 2 so that the charging voltage for charging the lithium ion battery 5 is substantially constant, thereby charging the lithium ion battery 5 using the fourth charging method M4.

(effect)
In the second embodiment, the lithium ion battery 5 is used instead of the lead storage battery, thereby reducing the space constraints associated with the use of the lead storage battery. The charging/discharging system 1B in the second embodiment includes a switching means 6 that switches the charging method according to the charging state of the lithium ion battery 5 (more specifically, the terminal voltage of the lithium ion battery 5 or the charging rate of the lithium ion battery 5). By using the switching means 6, even if the terminal voltage of the lithium ion battery 5 is low (or the charging rate of the lithium ion battery 5 is low) when the lithium ion battery 5 is being charged, an overcurrent is prevented from flowing from the AC/DC converter 2 to the lithium ion battery 5.

More specifically, by charging the lithium-ion battery 5 using a constant current method, even if the terminal voltage of the lithium-ion battery 5 is low (or even if the charging rate of the lithium-ion battery 5 is low), an overcurrent is prevented from flowing from the AC/DC converter 2 to the lithium-ion battery 5.

In the example shown in Figures 7 and 8, the AC/DC converter 2 is controlled by the control device 7, and the charging method of the lithium-ion battery 5 is switched between the constant current method and the constant voltage method. Therefore, the charging method can be switched with a simple configuration.

(Optional additional configuration)
Optional additional configurations that can be adopted in the charge/discharge system 1B in the second embodiment will be described with reference to FIGS.

(Charging and discharging systems for ships)
The charge/discharge system 1B in the second embodiment may be a charge/discharge system in a ship. More specifically, the charge/discharge system 1B may have an inboard AC busbar 10. A high-voltage AC current (e.g., 440 V AC current) flows through the inboard AC busbar 10. The inboard AC busbar 10 supplies power to various locations in the ship via a power distribution line. The inboard AC busbar 10 may supply power to a propeller of the ship (e.g., a motor that drives a screw).

In the example shown in FIG. 7, the AC/DC converter 2 receives AC power from the onboard AC busbar 10 and supplies DC power to the first current path 11. The AC/DC converter 2 may receive AC power from the onboard AC busbar 10 via a transformer 81. The transformer 81 steps down the voltage of the onboard AC busbar 10, and the stepped-down voltage is supplied to the AC/DC converter 2. The transformer 81 steps down the voltage of the onboard AC busbar 10, for example, from 440 V to 220 V. A circuit breaker 82 may be arranged between the onboard AC busbar 10 and the transformer 81.

In ships, lead-acid batteries need to be installed in a dedicated compartment. In other words, ships need a battery room to install lead-acid batteries. By replacing at least some of the lead-acid batteries (preferably all of the lead-acid batteries) with lithium-ion batteries 5, the battery room can be omitted or made smaller. In this way, restrictions on the layout of space within the ship can be eliminated or reduced. For example, it is possible to place the lithium-ion batteries 5 in the same panel as the charging and discharging panel. In addition, the general replacement cycle for lead-acid batteries is about 3 to 5 years, but if lithium-ion batteries 5 are used, the replacement cycle can be made longer.

(AC/DC converter 2)
7, the AC/DC converter 2 includes at least one AC/DC converter 23 that is controllable by the control device 7. The AC/DC converter 23 converts AC power into DC power.

In the example shown in FIG. 7, the AC/DC conversion device 2 includes multiple AC/DC converters 23, which are electrically connected in parallel. When multiple AC/DC converters 23 are provided, even if the capacity of one AC/DC converter 23 is small, the multiple AC/DC converters 23 as a whole can convert a large AC power into DC power. Note that when a sufficient capacity is ensured with one AC/DC converter 23, the AC/DC conversion device 2 may have only one AC/DC converter 23.

The charging/discharging system 1B may be equipped with a voltage detector 86a that detects the charging voltage of the lithium ion battery 5 and/or a current detector 86b that detects the charging current of the lithium ion battery 5.

When the lithium ion battery 5 is charged by the constant current method (in other words, the third charging method M3), the control device 7 may receive a signal indicating the charging current for charging the lithium ion battery 5 from the current detector 86b, and based on the signal, control the AC/DC converter 2 (more specifically, each AC/DC converter 23) so that the charging current is substantially constant. For example, the control device 7 may control the AC/DC converter 2 (more specifically, each AC/DC converter 23) so that the charging current of the lithium ion battery 5 is constant at about 60 A (e.g., 55 A or more and 65 A or less).

When the lithium-ion battery 5 is charged by the constant voltage method (in other words, the fourth charging method M4), the control device 7 may receive a signal indicating the charging voltage at which the lithium-ion battery 5 is charged from the voltage detector 86a, and based on the signal, control the AC/DC converter 2 (more specifically, each AC/DC converter 23) so that the charging voltage is substantially constant. For example, the control device 7 may control the AC/DC converter 2 (more specifically, each AC/DC converter 23) so that the charging voltage of the lithium-ion battery 5 is constant at about 29.6 V (e.g., 27 V or more and 33 V or less). In the example shown in FIG. 8, the charging voltage at which the lithium-ion battery 5 is charged is substantially equal to the output voltage of the AC/DC converter 2.

If there is variation in the output voltages of the multiple AC/DC converters 23, cross currents will occur between the multiple AC/DC converters 23. Therefore, when the lithium-ion battery 5 is charged using the constant voltage method (in other words, the fourth charging method M4), it is preferable that the control device 7 controls the multiple AC/DC converters 23 so that variation in the output voltages of the multiple AC/DC converters 23 is prevented and each of the output voltages of the multiple AC/DC converters 23 becomes a preset voltage.

7 and 8, the AC input voltage to the AC/DC converter 2 is, for example, about 220 V (200 V or more and 240 V or less). Also, in the example shown in FIG. 8, the DC output voltage of the AC/DC converter 2 is constant, for example, about 29.6 V (for example, 27 V or more and 33 V or less).

(First current path 11, bypass current path 13)
The first current path 11 and the bypass current path 13 have already been described in the first embodiment, so a repeated description of these configurations will be omitted.

(Switch 33)
The switch 33 is disposed in the bypass current path 13. The switch 33 is controlled by the control device 7. As illustrated in FIG. 7, when the lithium ion battery 5 is charged by the constant current method (in other words, the third charging method M3), if the charging voltage for charging the lithium ion battery 5 is relatively low (for example, if the charging voltage is equal to or lower than the fifth threshold value TH5), the switch 33 is preferably closed. In this case, the lithium ion battery 5 is charged by the constant current method, and power is supplied from the AC/DC converter 2 to the load 92, bypassing the silicon dropper 3. On the other hand, when the lithium ion battery 5 is charged by the constant current method (in other words, the third charging method M3), if the charging voltage for charging the lithium ion battery 5 is relatively high (for example, if the charging voltage is higher than the fifth threshold value TH5), the switch 33 is preferably opened. In this case, the lithium ion battery 5 is charged by the constant current method, and power is supplied from the AC/DC converter 2 to the load 92 via the silicon dropper 3 .

(Second current path 15)
7, the charge/discharge system 1B has a second current path 15. The second current path 15 connects a portion of the first current path 11 between the AC/DC converter 2 and the silicon dropper 3 (in other words, a first portion 111 of the first current path 11) and the lithium ion battery 5.

(Switching Means 6)
7 and 8, the switching means 6 includes an AC/DC converter 2. In the example shown in Fig. 7, in a state where power is supplied from the AC/DC converter 2 to the load 92 (more specifically, in a state where power is supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2), the control device 7 controls the AC/DC converter 2 so that the charging current for charging the lithium-ion battery 5 is substantially constant, whereby the switching means 6 (more specifically, the AC/DC converter 2) charges the lithium-ion battery 5 in a constant current manner (see arrows AR7 and AR8).

In the example shown in FIG. 8, when power is being supplied from the AC/DC converter 2 to the load 92 (more specifically, when power is being supplied from the onboard AC bus 10 via the AC/DC converter 2 to the load 92), the control device 7 controls the AC/DC converter 2 so that the charging voltage for charging the lithium-ion battery 5 is substantially constant, and the switching means 6 (more specifically, the AC/DC converter 2) charges the lithium-ion battery 5 in a constant voltage manner (see arrows AR9 and AR10).

9, when the power supply from the AC/DC converter 2 to the load 92 is interrupted (more specifically, when power is not being supplied from the onboard AC bus 10 to the load 92 via the AC/DC converter 2), the switch 33 is maintained in the open state, allowing the lithium-ion battery 5 to supply power to the load 92 via the silicon dropper 3 (see arrow AR11). In this way, the lithium-ion battery 5 functions as a backup power source (more specifically, a backup power source in the event of a power outage on the onboard AC bus 10).

10, when the power supply from the AC/DC converter 2 to the load 92 is interrupted (more specifically, when power is not being supplied from the onboard AC bus 10 to the load 92 via the AC/DC converter 2), the switch 33 is maintained in a closed state, so that the lithium-ion battery 5 can supply power to the load 92, bypassing the silicon dropper 3 (see arrow AR12). In this way, the lithium-ion battery 5 functions as a backup power source (more specifically, a backup power source in the event of a power outage on the onboard AC bus 10).

(Control device 7)
7, the charge/discharge system 1B includes a control device 7. The control device 7 controls the switch 33 and the AC/DC converter 2 (more specifically, the multiple AC/DC converters 23). The control device 7 may include one computer or multiple computers.

The control device 7 may be configured to switch the state of the switch 33 from an open state to a closed state by transmitting a close command to the switch 33. The control device 7 may also be configured to switch the state of the switch 33 from a closed state to an open state by transmitting an open command to the switch 33.

(Charge State Detector 83)
The charging/discharging system 1B may include a charging state detector 83 that detects the charging state of the lithium-ion battery 5. The control device 7 receives a signal indicating the charging state of the lithium-ion battery 5 from the charging state detector 83, and controls the switch 33 and the AC/DC converter 2 (more specifically, the multiple AC/DC converters 23) based on the signal.

(Determinator 85)
The charging/discharging system 1B may include a determiner 85 that determines whether or not power is being supplied from the AC/DC converter 2 to the load 92 (more specifically, whether or not power is being supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2). The determiner 85 may be configured by the control device 7, or may be configured by a device separate from the control device 7. The determiner 85 may determine whether or not power is being supplied from the AC/DC converter 2 to the load 92 based on the voltage and/or current of the inboard AC bus 10, or may determine whether or not power is being supplied from the AC/DC converter 2 to the load 92 by monitoring the AC/DC converter 23.

(Charging the lithium ion battery 5)
7 or 8 , a state in which power is supplied from the AC/DC converter 2 to the load 92 (more specifically, a state in which power is supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2) is assumed. More specifically, a case in which the determiner 85 determines that power is being supplied from the AC/DC converter 2 to the load 92 is assumed.

In the examples shown in Figures 7 and 8, the control device 7 determines whether the charging state of the lithium ion battery 5 is in a first state in which the charge amount is relatively low, or in a second state in which the charge amount is relatively high, based on a signal indicating the charging state of the lithium ion battery 5 received from the charging state detector 83.

When the charging state of the lithium ion battery 5 is determined to be in the first state in which the charge amount is relatively small, the control device 7 controls the AC/DC converter 2 (more specifically, the multiple AC/DC converters 23) so that the charging current for charging the lithium ion battery 5 is substantially constant (see FIG. 7). Additionally, when the charging state is determined to be in the first state in which the charge amount is relatively small, the control device 7 may control the switch 33 so that the switch 33 is in the closed state.

When the charging state of the lithium ion battery 5 is determined to be in the second state in which the amount of charge is relatively large, the control device 7 controls the AC/DC converter 2 (more specifically, the multiple AC/DC converters 23) so that the charging voltage for charging the lithium ion battery 5 is substantially constant (see FIG. 8). Additionally, when the charging state is determined to be in the second state in which the amount of charge is relatively large, the control device 7 may control the switch 33 so that the switch 33 is in the open state.

The charge state detector 83 may include a voltage detector 84a that detects the terminal voltage of the lithium ion battery 5. In this case, when the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is equal to or lower than the first threshold TH1, the control device 7 may determine that the charge state of the lithium ion battery 5 is a first state in which the charge amount is relatively small. Also, when the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is greater than the first threshold TH1, the control device 7 may determine that the charge state of the lithium ion battery 5 is a second state in which the charge amount is relatively large. The voltage detector 84a may be included in the BMU 14.

Alternatively, or additionally, the charge state detector 83 may include a charge rate detection device 84b that detects the state of charge of the lithium ion battery 5. In this case, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is equal to or lower than the second threshold TH2, the control device 7 may determine that the charge state of the lithium ion battery 5 is a first state in which the charge amount is relatively small. Also, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is greater than the second threshold TH2, the control device 7 may determine that the charge state of the lithium ion battery 5 is a second state in which the charge amount is relatively large. The charge rate detection device 84b may be included in the BMU 14.

(Discharging of lithium ion battery 5)
9 or 10 , a state is assumed in which the supply of power from the AC/DC converter 2 to the load 92 is interrupted (more specifically, a state in which power is not supplied from the inboard AC bus 10 to the load 92 via the AC/DC converter 2). More specifically, a case is assumed in which the determiner 85 determines that power is not being supplied from the AC/DC converter 2 to the load 92.

In the example shown in Figures 9 and 10, the control device 7 determines whether the charging state of the lithium ion battery 5 is in the third state, in which the charge amount is relatively high, or in the fourth state, in which the charge amount is relatively low, based on the signal indicating the charging state of the lithium ion battery 5 received from the charging state detector 83.

When the charging state of the lithium ion battery 5 is determined to be in the third state, in which the amount of charge is relatively large, the control device 7 controls the switch 33 so that the switch 33 is in the open state (see FIG. 9). On the other hand, when the charging state of the lithium ion battery 5 is determined to be in the fourth state, in which the amount of charge is relatively small, the control device 7 controls the switch 33 so that the switch 33 is in the closed state (see FIG. 10).

The charge state detector 83 may include a voltage detector 84a that detects the terminal voltage of the lithium ion battery 5. In this case, when the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is greater than the third threshold TH3, the control device 7 may determine that the charge state of the lithium ion battery 5 is a third state in which the charge amount is relatively large. When the terminal voltage of the lithium ion battery 5 detected by the voltage detector 84a is equal to or less than the third threshold TH3, the control device 7 may determine that the charge state of the lithium ion battery 5 is a fourth state in which the charge amount is relatively small. The value of the third threshold TH3 may be the same as the value of the first threshold TH1 described above, or may be different from the value of the first threshold TH1 described above.

Alternatively, or additionally, the charge state detector 83 may include a charge rate detection device 84b that detects the state of charge of the lithium ion battery 5. In this case, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is greater than the fourth threshold TH4, the control device 7 may determine that the charge state of the lithium ion battery 5 is a third state in which the charge amount is relatively large. Also, when the charge rate of the lithium ion battery 5 detected by the charge rate detection device 84b is equal to or less than the fourth threshold TH4, the control device 7 may determine that the charge state of the lithium ion battery 5 is a fourth state in which the charge amount is relatively small. The value of the fourth threshold TH4 may be the same as the value of the second threshold TH2 described above, or may be different from the value of the second threshold TH2 described above.

(5 lithium-ion batteries, 14 BMU)
The lithium ion battery 5 and the BUM 14 have already been described in the first embodiment, so a repeated description of their configuration will be omitted.

(Charging and discharging method)
A charge/discharge method according to an embodiment will be described with reference to Figures 1 to 11. Figure 11 is a graph showing an example of changes in charging voltage and charging current during a charging process.

The charging/discharging method in the embodiment may be performed using the charging/discharging system 1A in the first embodiment, the charging/discharging system 1B in the second embodiment, or another charging/discharging system. The charging/discharging system 1A in the first embodiment and the charging/discharging system 1B in the second embodiment have already been described, so repeated descriptions of these systems will be omitted.

As illustrated in FIG. 1 or FIG. 6, the charging/discharging system 1 used in the charging/discharging method in the embodiment includes: (1) an AC/DC converter 2 that converts AC power into DC power; (2) a first current path 11 that supplies current from the AC/DC converter 2 to a load 92; (3) a silicon dropper 3 that is disposed on the first current path 11 and that reduces the voltage; (4) a bypass current path 13 that supplies current from the AC/DC converter 2 to the load 92, bypassing the silicon dropper 3; (5) a switch 33 that is disposed on the bypass current path 13; and (6) a lithium ion battery 5 that is charged by receiving the current supplied from the AC/DC converter 2 and that supplies power to the load 92 by discharging.

As illustrated in FIG. 2 or FIG. 7, the charging/discharging method in the embodiment includes charging the lithium ion battery 5 by at least one of the above-mentioned first charging method M1 (in other words, a method of charging via a silicon dropper 3) and the above-mentioned third charging method M3 (in other words, a constant current charging method) (hereinafter referred to as the "first charging step").

The first charging step is performed when the charging state of the lithium ion battery 5 is in a first state in which the charge amount is relatively small. The first charging step is preferably performed in a state in which power is being supplied from the AC/DC converter 2 to the load 92 (more specifically, it is preferably performed in a state in which power is being supplied from the onboard AC bus 10 to the load 92 via the AC/DC converter 2).

Whether the state of charge of the lithium-ion battery 5 is a first state in which the charge amount is relatively low is determined by the control device 7. For example, when the terminal voltage of the lithium-ion battery 5 detected by the voltage detector 84a is equal to or lower than a first threshold value TH1, the control device 7 determines that the state of charge of the lithium-ion battery 5 is a first state in which the charge amount is relatively low. Alternatively, or additionally, when the charge rate of the lithium-ion battery 5 detected by the charge rate detection device 84b is equal to or lower than a second threshold value TH2, the control device 7 may determine that the state of charge of the lithium-ion battery 5 is a first state in which the charge amount is relatively low.

In the example shown in FIG. 2, the first charging step includes charging the lithium ion battery 5 using a first charging method M1 that charges the lithium ion battery 5 through a silicon dropper 3 when the charging state of the lithium ion battery 5 is a first state in which the charged amount is relatively low.

More specifically, in the example shown in FIG. 2, the first charging step includes charging the lithium ion battery 5 through the silicon dropper 3 by maintaining the switch 33 in an open state and the second switch 35 in a closed state when the lithium ion battery 5 is in a first state in which the charge amount is relatively small. The first charging step may be performed in a state in which power is supplied from the AC/DC converter 2 to the load 92 through the silicon dropper 3.

In the example shown in FIG. 2, charging is performed through the silicon dropper 3, which reduces the potential difference between the terminal voltage of the lithium ion battery 5 and the charging voltage of the lithium ion battery 5, thereby preventing an overcurrent from flowing through the lithium ion battery 5.

In the example shown in FIG. 7, the first charging step includes charging the lithium ion battery 5 using a third charging method M3 that charges the lithium ion battery 5 using a constant current method when the charging state of the lithium ion battery 5 is a first state in which the charged amount is relatively small.

7, the first charging step includes the control device 7 controlling the AC/DC converter 2 (more specifically, each AC/DC converter 23) so that the charging current for charging the lithium ion battery 5 is substantially constant (see region RG1 in FIG. 11). As illustrated in FIG. 7, the first charging step may be performed in a state in which power is supplied from the AC/DC converter 2 to the load 92, bypassing the silicon dropper 3.

In the example shown in FIG. 7, charging is performed using a constant current method, which prevents an overcurrent from flowing through the lithium ion battery 5.

As illustrated in FIG. 3 or FIG. 8, the charging/discharging method in the embodiment includes charging the lithium ion battery 5 by at least one of the above-mentioned second charging method M2 (in other words, a method of charging by bypassing the silicon dropper 3) and the above-mentioned fourth charging method M4 (in other words, a constant voltage charging method) (hereinafter referred to as the "second charging step").

The second charging process is executed when the charging state of the lithium ion battery 5 is in the second state in which the charge amount is relatively high. The second charging process is preferably executed in a state in which power is being supplied from the AC/DC converter 2 to the load 92 (more specifically, it is preferably executed in a state in which power is being supplied from the onboard AC bus 10 to the load 92 via the AC/DC converter 2).

Whether the state of charge of the lithium-ion battery 5 is the second state in which the charge amount is relatively high is determined by the control device 7. For example, when the terminal voltage of the lithium-ion battery 5 detected by the voltage detector 84a is greater than a first threshold value TH1, the control device 7 determines that the state of charge of the lithium-ion battery 5 is the second state in which the charge amount is relatively high. Alternatively, or additionally, when the charge rate of the lithium-ion battery 5 detected by the charge rate detection device 84b is greater than a second threshold value TH2, the control device 7 may determine that the state of charge of the lithium-ion battery 5 is the second state in which the charge amount is relatively high.

In the example shown in FIG. 3, the second charging step includes charging the lithium ion battery 5 by a second charging method M2 that bypasses the silicon dropper 3 and charges the lithium ion battery 5 when the charging state of the lithium ion battery 5 is in a second state in which the charge amount is relatively high.

More specifically, in the example shown in FIG. 3, the second charging step includes, when the charging state of the lithium ion battery 5 is the second state in which the charge amount is relatively high, maintaining the switch 33 in a closed state and the second switch 35 in an open state, thereby bypassing the silicon dropper 3 and charging the lithium ion battery 5. The second charging step may be performed in a state in which power is supplied from the AC/DC converter 2 to the load 92 via the silicon dropper 3.

In the example shown in FIG. 3, charging is performed by bypassing the silicon dropper 3, so that the lithium ion battery 5 can be charged so that the terminal voltage of the lithium ion battery 5 is sufficient (in other words, so that a sufficient charge amount is ensured).

In the example shown in FIG. 8, the second charging step includes charging the lithium ion battery 5 using a fourth charging method M4 that charges the lithium ion battery 5 using a constant voltage method when the charging state of the lithium ion battery 5 is a second state in which the charged amount is relatively high.

More specifically, in the example shown in FIG. 8, the second charging step includes the control device 7 controlling the AC/DC converter 2 (more specifically, each AC/DC converter 23) so that the charging voltage for charging the lithium ion battery 5 is substantially constant (see region RG2 in FIG. 11). As illustrated in FIG. 8, the second charging step may be performed in a state in which power is supplied from the AC/DC converter 2 to the load 92 via the silicon dropper 3.

In the example shown in FIG. 8, charging is performed using a constant voltage method, so that the terminal voltage of the lithium ion battery 5 is sufficient (in other words, a sufficient charge amount is ensured), and the lithium ion battery 5 can be charged.

As illustrated in FIG. 4 or FIG. 9, the charging/discharging method in the embodiment includes the lithium ion battery 5 supplying power to the load 92 via the silicon dropper 3 (hereinafter referred to as the "first discharging step").

The first discharge process is executed when the charge state of the lithium ion battery 5 is in the third state, in which the charge amount is relatively high. The first discharge process is executed, for example, in a state in which no power is supplied from the AC/DC converter 2 to the load 92 (more specifically, in a state in which the supply of power from the onboard AC bus 10 to the AC/DC converter 2 is interrupted).

Whether the state of charge of the lithium-ion battery 5 is the third state in which the charge amount is relatively high is determined by the control device 7. For example, when the terminal voltage of the lithium-ion battery 5 detected by the voltage detector 84a is greater than a third threshold value TH3, the control device 7 determines that the state of charge of the lithium-ion battery 5 is the third state in which the charge amount is relatively high. Alternatively, or additionally, when the charge rate of the lithium-ion battery 5 detected by the charge rate detection device 84b is greater than a fourth threshold value TH4, the control device 7 may determine that the state of charge of the lithium-ion battery 5 is the third state in which the charge amount is relatively high.

In the example shown in FIG. 4, the first discharge process includes supplying power from the lithium ion battery 5 to the load 92 via the silicon dropper 3 by maintaining the switch 33 in a closed state and the second switch 35 in an open state when the charge state of the lithium ion battery 5 is the third state in which the charge amount is relatively high.

In the example shown in FIG. 4, when the supply of power from the in-ship AC bus 10 to the AC/DC converter 2 is resumed from the state in which the lithium-ion battery 5 is supplied to the load 92 via the silicon dropper 3, the switch 33 is maintained in the closed state and the second switch 35 is maintained in the open state. On the other hand, in the example shown in FIG. 4, when the charge state of the lithium-ion battery 5 changes from the third state in which the charge amount is relatively high to the fourth state in which the charge amount is relatively low due to discharge from the lithium-ion battery 5 (for example, when the terminal voltage of the lithium-ion battery 5 becomes equal to or lower than the third threshold value TH3), the switch 33 is switched from the closed state to the open state and the second switch 35 is switched from the open state to the closed state (see FIG. 5). As an example, assume that the allowable voltage range on the load side is 21V to 26V and the voltage drop amount by the silicon dropper 3 is 2V. In this case, if the terminal voltage of the lithium ion battery 5 is 24V to 28V, a voltage of 22V to 26V is applied to the load 92 from the lithium ion battery 5 via the silicon dropper 3, as shown in FIG. 4. On the other hand, if the terminal voltage of the lithium ion battery 5 is 21V to 24V, a voltage of 21V to 24V is applied directly to the load 92 from the lithium ion battery 5 without passing through the silicon dropper 3, as shown in FIG. 5.

In the example shown in FIG. 9, the first discharge process includes supplying power from the lithium ion battery 5 to the load 92 via the silicon dropper 3 by maintaining the switch 33 in an open state when the charge state of the lithium ion battery 5 is the third state in which the charge amount is relatively high.

In the examples shown in Figures 4 and 9, power is supplied from the lithium ion battery 5 to the load 92 via the silicon dropper 3, so that power can be suitably supplied to the load 92 even when there is a large potential difference between the terminal voltage of the lithium ion battery 5, which is relatively highly charged, and the specification voltage of the load 92.

As illustrated in FIG. 5 or FIG. 10, the charging/discharging method in the embodiment includes the lithium ion battery 5 bypassing the silicon dropper 3 and supplying power to the load 92 (hereinafter referred to as the "second discharging step").

The second discharge process is executed when the charge state of the lithium ion battery 5 is in the fourth state, in which the charge amount is relatively small. The second discharge process is executed, for example, when no power is supplied from the AC/DC converter 2 to the load 92 (more specifically, when the supply of power from the onboard AC bus 10 to the AC/DC converter 2 is interrupted).

Whether the state of charge of the lithium-ion battery 5 is in the fourth state, in which the amount of charge is relatively low, is determined by the control device 7. For example, when the terminal voltage of the lithium-ion battery 5 detected by the voltage detector 84a is equal to or lower than the third threshold value TH3, the control device 7 determines that the state of charge of the lithium-ion battery 5 is in the fourth state, in which the amount of charge is relatively low. Alternatively, or additionally, when the charge rate of the lithium-ion battery 5 detected by the charge rate detection device 84b is equal to or lower than the fourth threshold value TH4, the control device 7 may determine that the state of charge of the lithium-ion battery 5 is in the fourth state, in which the amount of charge is relatively low.

In the example shown in FIG. 5, the second discharge process includes, when the charge state of the lithium ion battery 5 is the fourth state in which the charge amount is relatively low, maintaining the switch 33 in an open state and the second switch 35 in a closed state, thereby supplying power from the lithium ion battery 5 to the load 92, bypassing the silicon dropper 3.

In the example shown in FIG. 5, when the supply of power from the inboard AC bus 10 to the AC/DC converter 2 is resumed from a state in which the lithium-ion battery 5 is supplying power to the load 92 by bypassing the silicon dropper 3, the switch 33 is maintained in the open state and the second switch 35 is maintained in the closed state. After that, when the charge amount of the lithium-ion battery 5 increases due to the power supply from the AC/DC converter 2, the switch 33 is switched from the open state to the closed state, and the second switch 35 is switched from the closed state to the open state (see the change from the state shown in FIG. 2 to the state shown in FIG. 3).

In the example shown in FIG. 10, the second discharge process includes supplying power from the lithium ion battery 5 to the load 92, bypassing the silicon dropper 3, by keeping the switch 33 in a closed state when the charge state of the lithium ion battery 5 is a fourth state in which the charge amount is relatively low.

10, when the supply of power from the onboard AC bus 10 to the AC/DC converter 2 is resumed, if the output voltage of the AC/DC converter 2 (in other words, the charging voltage for charging the lithium-ion battery 5) is relatively low, it is preferable that the switch 33 be maintained in the closed state. Thereafter, when the charge amount of the lithium-ion battery 5 increases and the output voltage of the AC/DC converter 2 (in other words, the charging voltage for charging the lithium-ion battery 5) becomes relatively high (for example, when the charging voltage of the lithium-ion battery 5 becomes higher than the fifth threshold value TH5), it is preferable that the switch 33 be switched from the closed state to the open state.

In the examples shown in Figures 5 and 10, power is supplied from the lithium ion battery 5 to the load 92 bypassing the silicon dropper 3, so that power can be suitably supplied to the load 92 when the potential difference between the terminal voltage of the lithium ion battery 5, which is relatively lightly charged, and the specification voltage of the load 92 is small.

The present invention is not limited to the above-described embodiments or modifications, and it is clear that each embodiment or modification may be modified or changed as appropriate within the scope of the technical concept of the present invention. Furthermore, the various techniques used in each embodiment or modification may be applied to other embodiments or modifications as long as no technical contradiction arises. Furthermore, any additional configurations in each embodiment or modification may be omitted as appropriate.

5 and 10 show an example in which power is supplied from the lithium ion battery 5 to the load 92 by bypassing the entire silicon dropper 3. Alternatively, in the charge/discharge system 1A in the first embodiment, the charge/discharge system 1B in the second embodiment, or the charge/discharge method in the above-mentioned embodiment, power may be supplied from the lithium ion battery 5 to the load 92 by bypassing a part (3) of the multiple silicon droppers (3, 3') (see FIG. 12). Also, in the charge/discharge system 1A in the first embodiment, the charge/discharge system 1B in the second embodiment, or the charge/discharge method in the above-mentioned embodiment, the silicon droppers (3, 3') may be configured to be bypassed in a multi-stage manner (see FIG. 13).

1, 1A, 1B...charging and discharging system, 2...AC/DC converter, 3, 3'...silicon dropper, 5...lithium ion battery, 6...switching means, 7...control device, 10...inboard AC busbar, 11...first current path, 13...bypass current path, 13a...one end of the bypass current path, 13b...other end of the bypass current path, 15...second current path, 15b...shared current path, 21...rectifier, 23...AC/DC converter, 31...silicon diode, 33...switch, 33a...first switch, 35...second switch Switch, 81... transformer, 82... circuit breaker, 83... charging state detector, 84a... voltage detector, 84b... charging rate detection device, 85... determiner, 86a... voltage detector, 86b... current detector, 88... circuit breaker, 89... third switch, 91... load side distribution circuit, 92... load, 111... first part of first current path, 112... second part of first current path, 912... connection switch, M1... first charging method, M2... second charging method, M3... third charging method, M4... fourth charging method, U... battery unit

Claims (8)

an AC/DC converter for converting AC power into DC power;
A first current path for supplying a current from the AC/DC converter to a load;
a silicon dropper disposed in the first current path for dropping a voltage;
a bypass current path that supplies a current from the AC/DC converter to the load, bypassing the silicon dropper;
A switch disposed in the bypass current path;
a lithium ion battery that is charged by receiving a current supplied from the AC/DC converter and supplies power to the load by discharging;
a switching means for switching a charging method according to a charging state of the lithium ion battery so as to prevent an overcurrent from flowing from the AC/DC converter to the lithium ion battery when the lithium ion battery is being charged. Further comprising an inboard AC busbar;
The charging and discharging system according to claim 1 , wherein the AC/DC converter receives the AC power from the onboard AC bus and supplies the DC power to the first current path. 3. The charging and discharging system according to claim 1, wherein the switching means switches the charging method between a first charging method in which the lithium ion battery is charged through the silicon dropper and a second charging method in which the lithium ion battery is charged by bypassing the silicon dropper. a second current path connecting a portion of the first current path between the silicon dropper and the load and the lithium ion battery;
The charging/discharging system according to claim 3 , further comprising: a second switch disposed in the second current path. 3. The charging and discharging system according to claim 1, wherein the switching means switches the charging method between a third charging method in which the lithium ion battery is charged by a constant current method and a fourth charging method in which the lithium ion battery is charged by a constant voltage method. Further comprising a control device for controlling the AC/DC converter;
The switching means includes the AC/DC converter controlled by the control device,
the control device is configured to control the AC/DC converter so that a charging current for charging the lithium ion battery is substantially constant, thereby charging the lithium ion battery by the third charging method;
The charging and discharging system according to claim 5, wherein the control device is configured to control the AC/DC converter so that a charging voltage for charging the lithium ion battery is substantially constant, thereby charging the lithium ion battery using the fourth charging method. 6. The charging and discharging system according to claim 5, wherein when the lithium ion battery is charged using the constant current method, if a charging voltage for charging the lithium ion battery is relatively low, the switch is closed, and if a charging voltage for charging the lithium ion battery is relatively high, the switch is opened. A charging/discharging method performed using a charging/discharging system, comprising:
The charging and discharging system includes:
an AC/DC converter for converting AC power into DC power;
A first current path for supplying a current from the AC/DC converter to a load;
a silicon dropper disposed in the first current path for dropping a voltage;
a bypass current path that supplies a current from the AC/DC converter to the load, bypassing the silicon dropper;
A switch disposed in the bypass current path;
a lithium ion battery that is charged by receiving a current supplied from the AC/DC converter and supplies power to the load by discharging;
The charging and discharging method includes:
When the charging state of the lithium ion battery is a first state in which the charged amount is relatively small, charging the lithium ion battery by at least one of a first charging method in which the lithium ion battery is charged through the silicon dropper and a third charging method in which the lithium ion battery is charged by a constant current method;
When the charging state of the lithium ion battery is a second state in which the charging amount is relatively larger than that of the first state, charging the lithium ion battery by at least one of a second charging method in which the lithium ion battery is charged by bypassing the silicon dropper and a fourth charging method in which the lithium ion battery is charged by a constant voltage method;
When the charge state of the lithium ion battery is a third state in which the charge amount is relatively high, the lithium ion battery supplies power to the load through the silicon dropper;
When the charge state of the lithium ion battery is a fourth state in which the charge amount is relatively small compared to the third state, the lithium ion battery bypasses the silicon dropper and supplies power to the load.

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