AC-DC power converting apparatus having sub-converters connected in series between main converter and AC power supply

A power converting apparatus comprising:

• a power converter for performing power conversion between AC and DC including a main converter and sub-converters which deliver outputs to respective power storage devices provided individually at a DC side wherein a DC voltage of said main converter is higher than DC voltages of said sub-converters, said sub-converters being connected between said main converter and an AC power supply in series therewith;
• and
• a control device which controls said main converter by a first control signal generated based on a phase of said AC power supply, calculates an AC current command for an AC current input into said power converter and controls said sub-converters by a second control signal generated in such a fashion that the instantaneous value of the AC current follows the AC current command;
• said control device including:
• a current command calculator which adjusts a DC voltage command given to said main converter such that the DC voltages of said sub-converters follow a specific voltage command and generates the AC current command such that the DC voltage of said main converter follows the DC voltage command;
• a first control section which generates the first control signal to be delivered to said main converter;
• and
• a second control section which generates the second control signal for switching output voltage levels of said sub-converters at an AC side thereof such that a deviation of the instantaneous AC current value from the AC current command becomes smaller.