Bidirectional charger

Abstract

To provide a technique by which a bidirectional charger capable of executing V2G can be used for a target lifetime period.SOLUTION: A bidirectional charger capable of executing V2G comprises a heat-generating component that generates heat according to power fed to a power system from an electric vehicle, and a processor for managing deterioration of the heat-generating component. According to the processor, there are executed processing of calculating a cumulative stress based on a cumulative value of a temperature change generated in the heat-generating component; processing of calculating an upper limit amount of the V2G in a predetermined unit period, based on an upper limit value of the cumulative stress based on a target lifetime period of the heat-generating component, the calculated cumulative stress, a life expectancy period at present with respect to the target lifetime period, and a unit stress generated by the V2G of a predetermined unit amount; and processing of determining whether or not an executing amount of the V2G in the predetermined unit period reaches the calculated upper limit amount during execution of the V2G.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a bidirectional charger capable of implementing V2G. [Background technology]

[0002] Patent Document 1 discloses a management device that manages the exchange of power between a power grid and a battery installed in an electric vehicle. This management device stores the upper limit rotation speed of a rotating machine equipped in the electric vehicle and acquires the cumulative number of rotations of the rotating machine measured from the start of the warranty period of the electric vehicle. Then, when the cumulative rotation speed is equal to or greater than the upper limit rotation speed, the management device restricts the exchange of power between the power grid and the battery.

[0003] Furthermore, Patent Document 2 discloses a vehicle control device that controls multiple converters. This vehicle control device sets the priority of multiple converters for the current trip based on the ratio of the thermal strength of each converter and the priorities of the converters in the previous trip. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2020-195202 [Patent Document 2] Japanese Patent Publication No. 2023-016581 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Documents 1 and 2 do not consider the target lifespan of a bidirectional charger capable of V2G. This specification provides a technology that enables a bidirectional charger capable of V2G to be used for a target lifespan. [Means for solving the problem]

[0006] This specification discloses a bidirectional charger that is mounted on an electric vehicle and performs V2G from the electric vehicle to a power grid. The bidirectional charger includes a heat-generating component that generates heat as the electric vehicle supplies power to the power grid, and a processing device that manages deterioration of the heat-generating component. The processing device performs the following operations: calculating a cumulative stress based on a cumulative value of temperature changes in the heat-generating component; calculating an upper limit of the cumulative stress based on a target life span of the heat-generating component, the calculated cumulative stress, a current remaining life span relative to the target life span, and a unit stress generated by a predetermined unit amount of V2G; and determining whether the amount of V2G performed in the predetermined unit period has reached the calculated upper limit during V2G execution.

[0007] In the above configuration, the processing device of the bidirectional charger monitors the accumulated stress of the heat-generating components based on the accumulated value of the temperature change that occurs in the heat-generating components. The processing device can then calculate the upper limit of V2G for a predetermined unit period (e.g., one day) by using the calculated current accumulated stress, the design upper limit of the accumulated stress, the current remaining life span relative to the target life span, and the unit stress generated by a predetermined unit amount of V2G. The processing device can then determine whether the amount of V2G performed in the predetermined unit period has reached the upper limit for that unit period. As a result, the processing device can, for example, stop or limit V2G execution depending on the determination result. The upper limit is the upper limit of the amount of V2G execution allowed in the predetermined unit period to achieve use of the bidirectional charger over the target life span. Therefore, if the amount of V2G execution in the predetermined unit period is maintained within the upper limit for that unit period, the V2G-capable bidirectional charger can continue to be used over the target life span. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of a power system. [Figure 2]4 is a flowchart of a process executed by the control device. DETAILED DESCRIPTION OF THE INVENTION

[0009] A bidirectional charger 20 according to an embodiment will be described with reference to the drawings. The bidirectional charger 20 is mounted on an electric vehicle 10. The electric vehicle 10 is not particularly limited, but may be, for example, a battery EV or a plug-in hybrid vehicle, and is equipped with a battery 12 for driving. The electric vehicle 10 is electrically connected to an electric power grid via an external power supply device 30. Although not particularly limited, the electric power grid referred to here is a so-called general electric power grid, which is a public electric power grid provided by a general electric power transmission and distribution utility.

[0010] The external power supply device 30 is also referred to as a charging stand. The external power supply device 30 is installed in a facility where the electric vehicle 10 is parked for a relatively long period of time, such as a home or a commercial facility. The external power supply device 30 can supply electric power supplied from a power grid to the electric vehicle 10 as charging power for charging the battery 12. The external power supply device 30 can also supply electric power charged in the battery 12 of the electric vehicle 10 to the power grid. In other words, the electric vehicle 10 and the external power supply device 30 constitute a power system 2 that can supply electric power from the electric vehicle 10 to the power grid as so-called V2G (Vehicle to Grid). For this reason, the external power supply device 30 is also referred to as a V2G stand.

[0011] The bidirectional charger 20 includes an inverter 22 and a control device 24. The inverter 22 is electrically connected to the battery 12. The inverter 22 is also connected to an inlet 14 provided on the electric vehicle 10. The inlet 14 is a port for connecting the electric vehicle 10 to an external power supply device 30, and is configured so that a charging cable 32 of the external power supply device 30 can be attached and detached.

[0012] When the charging cable 32 is connected to the inlet 14, the battery 12 and the external power supply device 30 are connected to each other via the bidirectional charger 20 and the charging cable 32. When charging the battery 12, the power (three-phase AC power) supplied from the external power supply device 30 is converted by the inverter 22 into charging power (DC power) for the battery 12. On the other hand, when V2G is being performed, the power (DC power) discharged from the battery 12 is converted by the inverter 22 into power (three-phase AC power) to be supplied to the power grid. The control device 24 controls the inverter 22 during charging of the battery 12 and V2G.

[0013] In V2G using the electric vehicle 10, the bidirectional charger 20 is used without the electric vehicle 10 being driven. Therefore, if V2G is performed indefinitely, the bidirectional charger 20 alone among the components of the electric vehicle 10 will be overworked, and there is a risk that the bidirectional charger 20 will reach the end of its life earlier than expected. Therefore, the control device 24 calculates an upper limit amount of V2G for a predetermined unit period (e.g., one day) and executes a process to determine whether the amount of V2G performed for the predetermined unit period has reached the upper limit amount. In order to execute this process, the control device 24 is configured to be able to calculate a cumulative stress Lt based on the cumulative value of temperature changes that have occurred in the inverter 22 up to the present time. In order to execute this process, the control device 24 also includes a memory that stores information for calculating the cumulative stress Lt, a target life period Dl of the bidirectional charger 20, an upper limit value Lp of the cumulative stress based on the target life period Dl, the number of days Dn that the bidirectional charger 20 has been used up to the present time, and a unit stress Tv. The target lifespan Dl is a target value for the period of use of the bidirectional charger 20, calculated from the start of use of a brand new bidirectional charger 20, and is a predetermined value (for example, 15 years). The upper limit value Lp of the cumulative stress is a design upper limit value of the cumulative stress, and is a value based on the target lifespan Dl. The number of days of use Dn is the number of days from the start of use of the brand new bidirectional charger 20 to the present. The unit stress Tv is the stress (i.e., temperature change) caused by the execution of V2G at a predetermined unit amount (for example, 1 kW / h).

[0014] Next, a V2G control process executed by the control device 24 will be described with reference to Fig. 2. The process in Fig. 2 is executed when the charging cable 32 is connected to the inlet 14 and V2G is started.

[0015] In S10, the control device 24 calculates the cumulative stress Lt of the inverter 22 up to the present time point using information for calculating the cumulative stress Lt stored in the memory. Specifically, the information includes the previous cumulative stress calculated at the start of the previous V2G and time-series data of temperature changes of the inverter 22 since the previous V2G. This time-series data of temperature changes includes not only temperature changes due to V2G execution but also temperature changes due to, for example, charging of the battery 12. The control device 24 calculates the cumulative stress Lt by adding the previous cumulative stress calculated at the start of the previous V2G to the cumulative value of temperature changes based on the time-series data. Here, in this embodiment, the time-series data of temperature changes includes a combination of the temperature of the inverter 22 (more specifically, the temperature of the switching elements constituting the inverter 22) and the temperature of the coolant for cooling the inverter 22. The control device 24 then calculates the difference between the temperature of the inverter 22 and the temperature of the coolant at each time point in the time-series data and adds them together to calculate the cumulative value.

[0016] In S12, the control device 24 specifies the target life period Dl, the upper limit value Lp of the accumulated stress, the number of days of use Dn, and the unit stress Tv in the memory.

[0017] In S14, the control device 24 calculates the upper limit amount U. The upper limit amount U is calculated as U={(Lp-Lt) / (Dl-Dn)} / Tv. Here, Lp-Lt in the formula means the remaining cumulative stress that the bidirectional charger 20 can tolerate, and Dl-Dn means the remaining number of usable days of the bidirectional charger 20. That is, (Lp-Lt) / (Dl-Dn) means the cumulative stress that the bidirectional charger 20 can tolerate per day out of the remaining number of usable days. The upper limit amount U, which is obtained by dividing this by the unit stress Tv, is the allowable amount of V2G output per day. That is, the upper limit amount U means the upper limit of the amount of V2G execution that is allowable per day in order to achieve use of the bidirectional charger 20 over the target life period Dl. Note that in a modified example, a safety margin may be used in calculating the upper limit amount U. That is, in a modified example, the upper limit amount U may be calculated by subtracting a certain value from the value calculated by the above formula.

[0018] In S16, the control device 24 starts V2G output. That is, the supply of power from the battery 12 to the external power supply device 30 starts. At this time, the control device 24 accumulates and stores the V2G output power for one day.

[0019] In S18, the control device 24 monitors whether the cumulative value of the V2G output power for one day reaches the upper limit amount U calculated in S14. When the cumulative value of the V2G output power for one day reaches the upper limit amount U (YES in S18), the control device 24 proceeds to S20. The control device 24 continues to execute V2G output while the cumulative value of the V2G output power for one day has not reached the upper limit amount U (NO in S18).

[0020] In S20, the control device 24 stops the V2G output. When the process of S20 ends, the process of FIG.

[0021] In the above configuration, the control device 24 of the bidirectional charger 20 monitors the cumulative stress Lt of the inverter 22 based on the cumulative value of the temperature change that has occurred in the inverter 22. The control device 24 can calculate the upper limit amount U of V2G per day by using the calculated current cumulative stress Lt, the design upper limit value Lp of the cumulative stress, the current remaining life period (Dl-Dn) relative to the target life period Dl, and the unit stress Tv generated by a predetermined unit amount of V2G (S14 in FIG. 2). The control device 24 can then determine whether the amount of V2G performed in one day has reached the upper limit amount U for that day (S18). As a result, the control device 24 can, for example, stop or limit the execution of V2G in accordance with the determination result (S20). The upper limit amount U is the upper limit of the amount of V2G performed per day that is allowed in order to achieve use of the bidirectional charger 20 over the target life period Dl. Therefore, if the amount of V2G performed in a day is maintained within the upper limit amount U for that day, the bidirectional charger 20 capable of performing V2G can be used continuously over the target life period Dl.

[0022] In particular, the inverter 22 generates heat (i.e., stress occurs) both when charging the battery 12 and when V2G is performed. Generally, in an electric vehicle 10, when comparing charging the battery 12 with performing V2G, charging the battery 12 has a higher priority because charging is necessary for the electric vehicle 10 to run. With the above configuration, by limiting the amount of V2G performed per day, stress on the bidirectional charger 20 can be suppressed without limiting the charging of the battery 12, which has a higher priority. Therefore, the bidirectional charger 20 capable of performing V2G can be used continuously over the target life period Dl.

[0023] The following points should be noted regarding the above-described embodiment. The inverter 22 and the control device 24 are examples of the "heat-generating component" and the "processing device" of the present technology, respectively. (Dl-Dn) is an example of the "remaining life span."

[0024] When the output power by V2G is a fixed amount, the stress caused by executing V2G for a predetermined time (for example, one hour) can be used as the unit stress Tv. In this modification, the predetermined time is an example of a "predetermined unit amount." [Explanation of symbols]

[0025] 2: Power system, 10: Electric vehicle, 12: Battery, 14: Inlet, 20: Bidirectional charger, 22: Inverter, 24: Control device, 30: External power supply device, 32: Charging cable

Claims

[Claim 1] A bidirectional charger mounted on an electric vehicle and performing V2G from the electric vehicle to a power grid, a heat-generating component that generates heat in association with the supply of power from the electric vehicle to the power grid; a processing device that manages deterioration of the heat-generating component, The processing device includes: A process of calculating a cumulative stress based on a cumulative value of temperature changes occurring in the heat-generating component; A process of calculating an upper limit amount of the V2G in a predetermined unit period based on an upper limit value of the cumulative stress based on a target life period of the heat-generating component, the calculated cumulative stress, a current remaining life period with respect to the target life period, and a unit stress generated by a predetermined unit amount of the V2G; and executing a process of determining whether or not the execution amount of the V2G in the predetermined unit period has reached the calculated upper limit amount during the execution of the V2G. Two-way charger.

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