Power supply system

1. A power supply system comprising:

a load;

a power line connected to the load;

first and second DC power supplies capable of supplying power to the load;

a power converter connected between the power line and at least one of the first and second DC power supplies, and

a controller for controlling operation of the power converter, wherein;

the power converter comprises a plurality of switching elements, and is operated in one of a plurality of operation modes which differ from each other in a way of converting power between the power line and the first and second DC power supplies;

upon selection, from among the plurality of operation modes, of one operation mode in which the first and second DC power supplies are parallelly connected to the power line to provide an output of the first DC power supply to the power line after the output is converted into a DC voltage by the power converter, and provide an output of the second DC power supply to the power line without performing DC voltage conversion, the controller sets a maximum value of a total power output from the first and second DC power supplies to the power line to the sum of an actual power of the first DC power supply and a discharge limiting value defined for the second DC power supply, wherein the actual power is a product of a detected current value of the first direct current power supply and a detected voltage value of the first direct current power supply, and the discharge limit value is an upper limit value of electric power that can be discharged from the second direction current power supply.

2. The power supply system according to claim 1 , wherein:

upper and lower limit values are defined for the total power supplied from the first and second DC power supplies, to perform a process of correcting a power command value given to the total power when the total power exceeds the upper or lower limit value.

3. The power supply system according to claim 1 , wherein:

in the selected one operation mode, the plurality of switching elements are switched by on-off control, to thereby perform the DC voltage conversion between the first DC power supply and the power line, and to directly connect the second DC power supply to the power line.

4. The power supply system according to claim 3 , wherein:

the second DC power supply is connected to the power line via a current path including predetermined switching elements among the plurality of switching elements, and the second DC power supply is directly connected to the power line by fixing the predetermined switching elements to an ON state in the selected one operation mode.

5. The power supply system according to claim 3 , wherein:

a first power converter including a plurality of switching elements is connected between the first DC power supply and the power line,

a second power converter including other plurality of switching elements different from those in the first power converter is connected between the second DC power supply and the power line,

in the selected one operation mode, the plurality of switching elements in the first power converter are switched by on-off control, to thereby perform the DC power conversion between the first DC power supply and the power line, while at least one of the other plurality of switching elements in the second power converter is fixed to an ON state, to thereby directly connect the second DC power supply to the power line.

6. A power supply system comprising:

a load;

a power line connected to the load;

first and second DC power supplies capable of supplying power to the load;

a power converter connected between the power line and at least one of the first and second DC power supplies, and

a controller for controlling operation of the power converter, wherein;

the power converter comprises a plurality of switching elements, and is operated in one of a plurality of operation modes which differ from each other in a way of converting power between the power line and the first and second DC power supplies;

upon selection, from among the plurality of operation modes, of one operation mode in which the first and second DC power supplies are parallelly connected to the power line to provide an output of the first DC power supply to the power line after the output is converted into a DC voltage by the power converter, and provide an output of the second DC power supply to the power line without performing DC voltage conversion, the controller sets a maximum value of a total power output from the first and second DC power supplies to the power line to the sum of an actual power of the first DC power supply and a discharge limiting value defined for the second DC power supply,

wherein upper and lower limit values are defined for the total power supplied from the first and second DC power supplies, to perform a process of correcting a power command value given to the total power when the total power exceeds the upper or lower limit value.

7. A power supply system comprising:

a load;

a power line connected to the load;

first and second DC power supplies capable of supplying power to the load;

a power converter connected between the power line and at least one of the first and second DC power supplies, and

a controller for controlling operation of the power converter, wherein;

the power converter comprises a plurality of switching elements, and is operated in one of a plurality of operation modes which differ from each other in a way of converting power between the power line and the first and second DC power supplies;

upon selection, from among the plurality of operation modes, of one operation mode in which the first and second DC power supplies are parallelly connected to the power line to provide an output of the first DC power supply to the power line after the output is converted into a DC voltage by the power converter, and provide an output of the second DC power supply to the power line without performing DC voltage conversion, the controller sets a maximum value of a total power output from the first and second DC power supplies to the power line to the sum of an actual power of the first DC power supply and a discharge limiting value defined for the second DC power supply,

wherein in the selected one operation mode, the plurality of switching elements are switched by on-off control, to thereby perform the DC voltage conversion between the first DC power supply and the power line, and to directly connect the second DC power supply to the power line.

8. The power supply system according to claim 7 , wherein:

the second DC power supply is connected to the power line via a current path including predetermined switching elements among the plurality of switching elements, and the second DC power supply is directly connected to the power line by fixing the predetermined switching elements to an ON state in the selected one operation mode.

9. The power supply system according to claim 7 , wherein:

a first power converter including a plurality of switching elements is connected between the first DC power supply and the power line,

a second power converter including other plurality of switching elements different from those in the first power converter is connected between the second DC power supply and the power line,

in the selected one operation mode, the plurality of switching elements in the first power converter are switched by on-off control, to thereby perform the DC power conversion between the first DC power supply and the power line, while at least one of the other plurality of switching elements in the second power converter is fixed to an ON state, to thereby directly connect the second DC power supply to the power line.