Power conversion device
Provided is a power conversion device that can be realized with a small circuit and is capable of stably converting AC power inputted from a three-phase power source system into DC power. In a power conversion device: an output terminal of a common converter cell in a J-numbered stage is connected, together with output terminals of common converter cells of the other two phases, to common lines; an output terminal of an independent converter cell in a K-numbered stage is connected to independent lines independently of converter cells of the other two phases; and a plurality of switches comprise a common switch for switching the connection relationship between the common lines and DC buses, and an independent switch for switching the connection relationship between the independent lines and DC buses.
1. A power conversion device comprising:
three input lines to which a three-phase voltage is inputted;
3×N converter cells having their respective input terminals connected in series or in parallel between each of the input lines and a neutral line;
M lines of DC bus; and
a plurality of switches that set a state of connection between each of output terminals of the 3×N converter cells and each of the M lines of DC buses, wherein
the output terminals of common converter cells that are the converter cells of a number of stages J (where N>J and J≥1) connected between each of the input lines and the neutral line are connected to a common line as the output terminals of the other common converter cells of two phases are connected to the common line as well,
the output terminals of independent converter cells that are the converter cells of a number of stages K (where K=N−J and K≥1) connected between each of the input lines and the neutral line are connected to an independent line independent of the other independent converter cells of two-phase, and
the plurality of switches includes a common switch that switches a connection relationship between each of the common lines and each of the DC buses, and an independent switch that switches a connection relationship between each of the independent lines and each of the DC buses.
2. The power conversion device according to claim 1 , wherein
the 3×N converter cells have the input terminals connected in series as input terminals of a number of stages N between each of the input lines and the neutral line.
3. The power conversion device according to claim 2 , further comprising a switch control unit that acquires electric device information on an electric device connected to some or all of the M lines of DC buses and that sets connection states of the switches, based on the acquired electric device information.
4. The power conversion device according to claim 3 , wherein
the switch control unit further includes a number-of-allocated-cells calculating unit that calculates a number of the converter cells to be connected to each of the DC buses, based on the electric device information.
5. The power conversion device according to claim 4 , wherein
the number-of-allocated-cells calculating unit includes
a function of determining a number of common cells used which is a number of the common converter cells that supply power to any one of the DC buses, from a number equal to or smaller than 3×J, and
a function of determining a number of independent cells used which is a number of the independent converter cells that supply power to any one of the DC buses, from a number equal to or smaller than 3×K.
6. The power conversion device according to claim 1 , wherein
the converter cell includes
a high-frequency transformer,
a first power converter connected to a primary side of the high-frequency transformer, and
a second power converter connected to a secondary side of the high-frequency transformer.
7. The power conversion device according to claim 6 , wherein
the converter cell further includes a first capacitor connected in series between the first power converter and the high-frequency transformer.
8. The power conversion device according to claim 7 , wherein
the converter cell further includes a second capacitor connected in series between the second power converter and the high-frequency transformer.