DC-DC converter comprising DC power sources to be connected in parallel or in series

A power supply system for use as a step-up chopper circuit, the power supply system comprising:

• a first DC power source;
• a second DC power source;
• and
• a power converter that converts DC voltage between the first and second DC power sources and a power line electrically connected to a load so as to control an output voltage on the power line, the power converter including a plurality of switching elements, the power converter being configured to be switchable, by controlling the plurality of switching elements, between a first operation mode and a second operation mode, in the first operation mode, the DC voltage conversion is executed with the first and second DC power sources electrically connected in parallel with the power line, and in the second operation mode, the DC voltage conversion is executed with the first and second DC power sources electrically connected in series with the power line, wherein
• the plurality of switching elements include:
• a first switching element electrically connected between the power line and a first node;
• a second switching element electrically connected between a second node and the first node;
• a third switching element electrically connected between a third node electrically connected to a negative terminal of the second DC power source and the second node;
• and
• a fourth switching element electrically connected between a negative terminal of the first DC power source and the third node;
• the power converter further includes:
• a first reactor electrically connected between the second node and a positive terminal of the first DC power source;
• and
• a second reactor electrically connected between the first node and the positive terminal of the second DC power source;
• and
• in the first operation mode, one of the first and second DC power sources is a voltage source and another one of the first and second DC power sources is a current source, the power converter controls the DC voltage conversion between the one of the first and second DC power sources and the power line such that the one of the first and second DC power sources operating as the voltage source controls the output voltage to be equal to a command voltage, which is different than the output voltage, and the power convertor controls the DC voltage conversion between the other one of the first and second DC power sources and the power line such that the other one of the first and second DC power sources operating as a current source controls a current of the other one of the DC power sources to be equal to a command current, which is different than the current.