Power supply system and vehicle with the system
A vehicle includes a charging unit receiving electric power from an external power source and externally charging a power storage unit. When a connector unit is coupled to the vehicle and a state ready for charging by the external power source is attained, a controller predicts degradation ratio of the power storage unit at the time point of completion of external charging based on degradation characteristic of the power storage unit in connection with SOC and battery temperature obtained in advance, and sets target state of charge of each power storage unit based on the battery temperatures so that the predicted degradation ratio does not exceed tolerable degradation ratio at the time point of completion of external charging. Then, the controller controls corresponding converters such that SOCs of power storage units attain the target states of charge.
1. A power supply system supplying electric power to a load device mounted on a vehicle, comprising:
a rechargeable power storage device;
a temperature detecting unit that detects a temperature of said power storage device;
a state estimating unit that estimates a state of charge of said power storage device;
a charging unit that externally charges said power storage device by receiving electric power from an external power source; and
a control unit that controls charging/discharging of said power storage device;
wherein said control unit includes:
a target value setting unit that sets, when said power storage device attains to a state ready for charging by the external power source, a target state of charge of said power storage device in accordance with the temperature of said power storage device, and
a charge control unit that controls charging power to said power storage device such that state of charge of said power storage device attains to said target state of charge, and
said target value setting unit sets said target state of charge to be smaller as the temperature of said power storage device becomes higher, and
said target value setting unit predicts degradation ratio of said power storage device at a time point of completion of external charging, based on degradation characteristic of said power storage device in connection with the state of charge and the temperature of said power storage device obtained in advance, and sets said target state of charge in accordance with the temperature of said power storage device such that predicted degradation ratio does not exceed tolerable degradation ratio at the time point of completion of external charging.
2. The power supply system according to claim 1 , wherein
said control unit further includes
a estimating unit that obtains a required time period necessary from a starting time point of external charging until the external charging is completed and said power storage device is used, and estimating temporal change of temperature and state of charge of said power storage device in said required time period, and
a degradation amount predicting unit that predicts an amount of degradation of said power storage device in said required time period, based on the temporal change of temperature and state of charge of said power storage device estimated by said estimating unit,
said target value setting unit includes
a determining unit that determines whether the amount of degradation of said power storage device predicted by said degradation amount predicting unit exceeds a preset tolerable amount of degradation or not, and
a target value correcting unit that corrects said target state of charge in accordance with a result of determination of said determination unit.
3. The power supply system according to claim 2 , wherein
said target value correcting unit decreases said target state of charge, if the amount of degradation of said power storage device in said required time period is determined to exceed said tolerable amount of degradation by said determining unit.
4. The power supply system according to claim 1 , further comprising
a cooling mechanism that cools said power storage device using a cooling medium; wherein
said control unit further includes a second estimating unit that obtains a required time period necessary from a starting time point of external charging until the external charging is completed and said power storage device is used, and estimating temporal change of temperature and state of charge of said power storage device in said required time period,
a degradation amount predicting unit that predicts an amount of degradation of said power storage device in said required time period, based on the temporal change of temperature and state of charge of said power storage device estimated by said second estimating unit,
a determining unit that determines whether the amount of degradation of said power storage device predicted by said degradation amount predicting unit exceeds a preset tolerable amount of degradation or not, and
a temperature control unit that controls cooling performance of said cooling mechanism during execution of external charging, in accordance with a result of determination of said determining unit.
5. The power supply system according to claim 4 , wherein
said temperature control unit raises cooling performance of said cooling mechanism during execution of external charging, if the amount of degradation of said power storage device in said required time period is determined to exceed said tolerable amount of degradation by said determining unit.
6. The power supply system according to claim 2 , wherein
said control unit further includes a storage unit that learns a pattern of use of said power supply system and stores a learned value based on the learning; and
said estimating unit that obtains said required time period based on the learned value stored in said storage unit.
7. The power supply system according to claim 1 , wherein
said control unit further includes a power storage device control unit that predicts an amount of degradation of said power storage device in an unused time period from the completion of external charging until said power storage device is used, based on degradation characteristic of said power storage device in connection with the state of charge and the temperature of said power storage device obtained in advance, and controls at least one of the temperature and the state of charge of said power storage device in said unused time period such that the amount of degradation of said power storage device in a required time period necessary from a starting time point of external charging until the external charging is completed and said power storage device is used, does not exceed a preset tolerable amount of degradation.
8. The power supply system according to claim 1 , wherein
said power storage device includes a plurality of power storage units each formed to be rechargeable;
said power supply system further comprising:
a plurality of voltage converting units provided corresponding to said plurality of power storage units, respectively; and
a pair of power lines to which said plurality of voltage converting units are connected in parallel with each other; wherein
said state estimating unit estimates state of charge of each of said plurality of power storage units in an unused time period of said power storage device from a time point of completion of external charging until said power storage device is used; and
said control unit further includes a voltage conversion control unit that controls said plurality of voltage converting units such that electric power is exchanged between a first power storage unit having relatively high state of charge and a second power storage unit having relatively low state of charge, if difference in state of charge between each of said plurality of power storage units exceeds a prescribed threshold value in said unused time period.
9. A vehicle, comprising:
a power supply system; and
a driving force generating unit receiving electric power supplied from said power supply system and generating driving force; wherein
said power supply system includes
a rechargeable power storage device;
a temperature detecting unit that detects a temperature of said power storage device;
a state estimating unit that estimates a state of charge of said power storage device;
a charging unit that externally charges said power storage device by receiving electric power from an external power source; and
a control unit that controls charging/discharging of said power storage device;
wherein said control unit includes:
a target value setting unit that sets, when said power storage device attains to a state ready for charging by the external power source, a target state of charge of said power storage device in accordance with the temperature of said power storage device, and
a charge control unit that controls charging power to said power storage device such that state of charge of said power storage device attains to said target state of charge, and
said target value setting unit sets said target state of charge to be smaller as the temperature of said power storage device becomes higher,
said target value setting unit predicts degradation ratio of said power storage device at a time point of completion of external charging, based on degradation characteristic of said power storage device in connection with the state of charge and the temperature of said power storage device obtained in advance, and sets said target state of charge in accordance with the temperature of said power storage device such that predicted degradation ratio does not exceed tolerable degradation ratio at the time point of completion of external charging.
10. The power supply system according to claim 1 , further comprising:
a temperature predicting unit that predicts the temperature of said power storage device at the time point of completion of external charging, by estimating degree of temperature increase of said power storage device during execution of external charging, and
said target value setting unit sets said target state of charge in accordance with the predicted temperature of said power storage device at the time point of completion of external charging.