Uninterruptible power supply system and uninterruptible power supply apparatus

1. An uninterruptible power supply system for supplying DC power to a DC load, the uninterruptible power supply system comprising:

an uninterruptible power supply apparatus connected between a commercial AC power supply and the DC load;

a solar battery configured to convert sunlight energy into DC power; and

a power storage apparatus configured to store DC power, wherein

the uninterruptible power supply apparatus includes

an output terminal connected to the DC load,

a first DC/DC converter configured to perform DC voltage conversion between the solar battery and the output terminal,

a second DC/DC converter configured to perform DC voltage conversion between the power storage apparatus and the output terminal,

a converter connected between the commercial AC power supply and the output terminal and configured to convert AC power supplied from the commercial AC power supply into DC power,

a first controller configured to control the first DC/DC converter to flow a current according to a first current command value from the solar battery to the output terminal,

a second controller configured to control the second DC/DC converter to flow a current according to a second current command value between the power storage apparatus and the output terminal, and

a third controller configured to control the converter such that a voltage of the output terminal is equal to a reference voltage during normal operation in which the commercial AC power supply supplies AC power,

the first controller is configured to generate the first current command value based on a smallest value of

an output current when an output voltage of the solar battery is equal to an optimum operating voltage in maximum power point tracking control, and

an output current for outputting a consumption current between the solar battery and the DC load and a charging current of the power storage apparatus, and

the second controller is configured to generate the second current command value such that a voltage of the output terminal is equal to the reference voltage.

2. The uninterruptible power supply system according to claim 1 , wherein the first controller is configured to reduce the first current command value when the voltage of the output terminal exceeds a first upper limit voltage higher than the reference voltage.

3. The uninterruptible power supply system according to claim 1 , wherein the second controller is configured to reduce the second current command value when the voltage of the output terminal exceeds a first upper limit voltage higher than the reference voltage.

4. The uninterruptible power supply system according to claim 1 , wherein

the second DC/DC converter is configured to charge the power storage apparatus with surplus power of the DC power generated in the solar battery, and

the second controller is configured to reduce the second current command value when a voltage between terminals of the power storage apparatus exceeds a second upper limit voltage lower than the reference voltage during charging of the power storage apparatus.

5. The uninterruptible power supply system according to claim 1 , wherein

the second controller is configured to generate the second current command value such that the voltage of the output terminal is equal to the reference voltage, and to stop discharging of the power storage apparatus when a remaining capacity of the power storage apparatus is not greater than a lower limit capacity while power generation of the solar battery is stopped, and

the third controller is configured to control the converter while power generation of the solar battery is stopped such that the voltage of the output terminal is equal to the reference voltage after discharging of the power storage apparatus is stopped.

6. An uninterruptible power supply apparatus for supplying DC power to a DC load, the uninterruptible power supply apparatus comprising:

an output terminal connected to the DC load;

a first DC/DC converter configured to perform DC voltage conversion between the output terminal and a solar battery that converts sunlight energy into DC power;

a second DC/DC converter configured to perform DC voltage conversion between the output terminal and a power storage apparatus that stores DC power;

a converter connected between a commercial AC power supply and the output terminal and configured to convert AC power supplied from the commercial AC power supply into DC power;

a first controller configured to control the first DC/DC converter to flow a current according to a first current command value from the solar battery to the output terminal;

a second controller configured to control the second DC/DC converter to flow a current according to a second current command value between the power storage apparatus and the output terminal; and

a third controller configured to control the converter such that a voltage of the output terminal is equal to a reference voltage during normal operation in which the commercial AC power supply supplies AC power, wherein

the first controller is configured to generate the first current command value based on a smallest value of

an output current when an output voltage of the solar battery is equal to an optimum operating voltage in maximum power point tracking control, and

an output current for outputting a consumption current between the DC load and the solar battery and a charging current of the power storage apparatus, and

the second controller is configured to generate the second current command value such that the voltage of the output terminal is equal to the reference voltage.