Power supply system and control method thereof

1. A power supply system including a power storage device; a positive electrode-side relay; a negative electrode-side relay; and a power control unit that includes a capacitor configured to be pre-charged in response to a system start request and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay, the power supply system comprising:

a control device programmed to close the positive electrode-side relay and the negative electrode-side relay at different timings always or under a predetermined condition in response to the system start request, the control device programmed to change a sequence of closing the positive electrode-side relay and the negative electrode-side relay in accordance with a predetermined restriction,

wherein the control device calculates a stress index of each of the positive electrode-side relay and the negative electrode-side relay, which indicates stresses accumulated into each of the positive electrode-side relay and the negative electrode-side relay accompanied with at least closing of the positive electrode-side relay or the negative electrode-side relay, and closes one of the positive electrode-side relay and the negative electrode-side relay that has a larger stress index, prior to the other.

2. The power supply system according to claim 1 ,

wherein the control device calculates the stress index of each of the positive electrode-side relay and the negative electrode-side relay by taking into account stresses accumulated into each of the positive electrode-side relay and the negative electrode-side relay accompanied with opening of the positive electrode-side relay or the negative electrode-side relay, and opens one of the positive electrode-side relay and the negative electrode-side relay that has a smaller stress index, prior to the other, in response to a system stop request.

3. The power supply system according to claim 1 ,

wherein when the positive electrode-side relay and the negative electrode-side relay are to be closed in an event of an abnormality in precharge of the capacitor, the control device closes one of the positive electrode-side relay and the negative electrode-side relay that has a larger stress index, prior to the other.

4. The power supply system according to claim 3 ,

wherein after the positive electrode-side relay and the negative electrode-side relay are closed in the event of the abnormality in precharge of the capacitor, the control device opens one of the positive electrode-side relay and the negative electrode-side relay that has a smaller stress index, prior to the other, in response to a system stop request.

5. A power supply system including a power storage device; a positive electrode-side relay; a negative electrode-side relay; and a power control unit that includes a capacitor configured to be pre-charged in response to a system start request and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay, the power supply system comprising:

a control device programmed to close the positive electrode-side relay and the negative electrode-side relay at different timings always or under a predetermined condition in response to the system start request, the control device programmed to change a sequence of closing the positive electrode-side relay and the negative electrode-side relay in accordance with a predetermined restriction,

wherein when the positive electrode-side relay and the negative electrode-side relay are to be closed in an event of an abnormality in precharge of the capacitor, the control device closes one of the positive electrode-side relay and the negative electrode-side relay that was not closed prior to the other at a previous system start in an event of an abnormality in precharge, prior to the other.

6. A power supply system including a power storage device; a positive electrode-side relay; a negative electrode-side relay; and a power control unit that includes a capacitor configured to be pre-charged in response to a system start request and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay, the power supply system comprising:

a control device programmed to close the positive electrode-side relay and the negative electrode-side relay at different timings always or under a predetermined condition in response to the system start request, the control device programmed to change a sequence of closing the positive electrode-side relay and the negative electrode-side relay in accordance with a predetermined restriction,

wherein in a case of no abnormality in precharge of the capacitor, the control device closes one of the positive electrode-side relay and the negative electrode-side relay, prior to the other, in response to the system start request, and

when the positive electrode-side relay and the negative electrode-side relay are to be closed in an event of an abnormality in precharge of the capacitor, the control device closes the other of the positive electrode-side relay and the negative electrode-side relay, prior to the one.

7. The power supply system according to claim 6 ,

wherein in the case of no abnormality in precharge of the capacitor, the control device opens one of the positive electrode-side relay and the negative electrode-side relay, prior to the other, in response to a system stop request, and

after the positive electrode-side relay and the negative electrode-side relay are closed in the event of the abnormality in precharge of the capacitor, the control device opens the other of the positive electrode-side relay and the negative electrode-side relay, prior to the one, in response to the system stop request.

8. A power supply system including a power storage device; a positive electrode-side relay; a negative electrode-side relay; and a power control unit that includes a capacitor configured to be pre-charged in response to a system start request and that is connected with the power storage device via the positive electrode-side relay and the negative electrode-side relay, the power supply system comprising:

a control device programmed to close the positive electrode-side relay and the negative electrode-side relay at different timings always or under a predetermined condition in response to the system start request, the control device programmed to change a sequence of closing the positive electrode-side relay and the negative electrode-side relay in accordance with a predetermined restriction,

wherein the control device closes one of the positive electrode-side relay and the negative electrode-side relay that was not closed prior to the other at a previous system start, prior to the other, in response to the system start request.

9. The power supply system according to claim 8 ,

wherein the control device opens one of the positive electrode-side relay and the negative electrode-side relay that was closed prior to the other in response to a last system start request, prior to the other, in response to a system stop request.

10. The power supply system according to claim 9 ,

wherein after one of the positive electrode-side relay and the negative electrode-side relay is closed prior to precharge of the capacitor in response to the system start request, the control device determines welding or no welding of the other of the positive electrode-side relay and the negative electrode-side relay, based on a voltage of the capacitor, and

after one of the positive electrode-side relay and the negative electrode-side relay is opened in response to the system stop request, the control device causes the capacitor to be discharged and determines welding or no welding of one of the positive electrode-side relay and the negative electrode-side relay.