A power supply system, comprising: a first DC power source; a second DC power source; and a power converter, for executing DC voltage conversion between said first and second DC power sources and a power line electrically connected to a load so as to control an output voltage (Vo) on said power line wherein said power converter includes a plurality of switching elements (S1-S4), and is configured to be switchable, by controlling said plurality of switching elements, between a first operation mode in which said DC voltage conversion is executed with said first and second DC power sources electrically connected in parallel with said power line and a second operation mode in which the DC voltage conversion is executed with said first and second DC power sources electrically connected in series with said power line, and said plurality of switching elements (S1-S4) include a first switching element electrically connected between said power line and a first node, a second switching element electrically connected between a second node and said first node, a third switching element electrically connected between a third node electrically connected to a negative terminal of said second DC power source and said second node, and a fourth switching element electrically connected between a negative terminal of said first DC power source and said third node, characterised in that said power converter further includes a first reactor electrically connected between said second node and a positive terminal of said first DC power source, and a second reactor electrically connected between said first node and the positive terminal of said second DC power source. a first DC power source; a second DC power source; and a power converter, for executing DC voltage conversion between said first and second DC power sources and a power line electrically connected to a load so as to control an output voltage (Vo) on said power line wherein said power converter includes a plurality of switching elements (S1-S4), and is configured to be switchable, by controlling said plurality of switching elements, between a first operation mode in which said DC voltage conversion is executed with said first and second DC power sources electrically connected in parallel with said power line and a second operation mode in which the DC voltage conversion is executed with said first and second DC power sources electrically connected in series with said power line, and said plurality of switching elements (S1-S4) include a first switching element electrically connected between said power line and a first node, a second switching element electrically connected between a second node and said first node, a third switching element electrically connected between a third node electrically connected to a negative terminal of said second DC power source and said second node, and a fourth switching element electrically connected between a negative terminal of said first DC power source and said third node, characterised in that said power converter further includes a first reactor electrically connected between said second node and a positive terminal of said first DC power source, and a second reactor electrically connected between said first node and the positive terminal of said second DC power source.