Patent ID: 8547718

Claim:
A power converter apparatus configured for an ordinary operation and an initial charging operation, which occurs prior to starting of the ordinary operation, comprising: a plurality of unit cells, each of which includes terminals, a capacitor and semiconductor switching elements connected in series, the capacitor and the semiconductor switching elements being connected in parallel, and a voltage at the capacitor being output at the terminals by operation of the semiconductor switching elements; a variable voltage source for outputting a variable electric power; and wherein the terminals of adjacent ones of the unit cells are connected so that the plurality of unit cells are connected together in cascade and configure an arm of the power converter, wherein at a time of the initial charging operation, a capacitor of a selected unit cell is charged to a certain voltage to be available for the succeeding ordinary operation, wherein in the initial charging operation, the capacitor of at least a selected one of the unit cells of the arm is charged at the terminals of that unit cell to the certain voltage with the output of the variable voltage source applied to the arm via non-selected unit cells of the arm, and the capacitors of the non-selected unit cells are not charged due to shunting of the terminals of the non-selected unit cells by turning off or on of the semiconductor switching elements thereof, wherein a time period of charging the capacitor of an individual unit cell in the initial charging operation is longer than a time period of turning on/off of the semiconductor switching elements of the unit cell in the ordinary operation, and wherein in the ordinary operation of the power converter, the capacitor in each unit cell of the arm is charged from a predetermined portion of the arm via the adjacent unit cells, and an output of the power converter is a combined voltage of the output voltages of the unit cells of the arm.