Three level power converting apparatus having means for balancing DC component thereof

A power converting apparatus comprising:

• a plurality of capacitors connected in series across a DC voltage source,
• converter for converting DC voltages supplied from the capacitors to an AC phase voltage having three potentials, including a positive, zero, and negative potential,
• at least one current polarity detector disposed between said converter for converting and a load, for detecting an output current polarity of a current flowing between said means for converting and said load, and
• zero-voltage adjuster for adjusting a zero-voltage duration of the AC phase voltage on a basis of said output current polarity of the power converting apparatus and a value representing a voltage difference between the voltages of the capacitors connected in series so as to balance the voltages.

A power converting apparatus comprising:

• a plurality of capacitors connected in series across a DC voltage source,
• converter for converting DC voltages supplied from the capacitors to at least two AC phase voltages having three potentials, including a positive, zero, and negative potential, and outputting each AC phase voltage of said at least two AC phase voltages on a separate output line,
• a current polarity detector disposed on each output line between said converter for converting and a load, for detecting output current polarities of phase currents flowing between said converter for converting and said load, and
• zero-voltage converter for adjusting a zero-voltage duration of the AC phase voltage on a basis of said output current polarities of the power converting apparatus and a value representing a voltage difference between the voltages of the capacitors connected in series so as to balance the voltages.

A power converting apparatus comprising:

• a plurality of capacitors connected in series across a DC voltage source,
• converter for converting DC voltages supplied from the capacitors to three AC phase voltages having three potentials, including a positive, zero, and negative potential, and outputting each AC phase voltage of said three AC phase voltages on a separate output line,
• a current polarity detector disposed on each output line between said converter for converting and a load, for detecting output current polarities of three phase currents flowing between said converter for converting and said load, and
• zero-voltage adjuster for adjusting a zero-voltage duration of the AC phase voltage on a basis of said output current polarities of the power converting apparatus and a value representing a voltage difference between the voltages of the capacitors connected in series so as to balance the voltages.