A UPS configured to provide AC output power, the UPS comprising: an input including a plurality of input lines (1503, 1505, 1508) each configured to be coupled to a phase of a multiphase AC power source having a sinusoidal waveform; a plurality of DC buses including a first positive DC bus having a first nominal DC voltage, a second positive DC bus having a second nominal DC voltage, a first negative DC bus having a third nominal DC voltage and a second negative DC bus having a fourth nominal DC voltage; a first power converter coupled to the input and configured to supply power from the multiphase AC power source to the plurality of DC buses during a first positive region of the sinusoidal waveform and a first negative region of the sinusoidal waveform; and a second power converter coupled to the input and configured to supply power from the multiphase AC power source to at least some of the plurality of DC buses during a second positive region of the sinusoidal waveform and a second negative region of the sinusoidal waveform; wherein the first power converter includes a positive boost circuit and a negative boost circuit, wherein the positive boost circuit is coupled to each of the input lines and is configured to draw current during the first positive region of the sinusoidal waveform for each phase of the multiphase AC power signal, wherein the negative boost circuit is coupled to each of the input lines and is configured to draw current during the first negative region of the sinusoidal waveform for each phase of the multiphase AC power signal; wherein the first positive region includes phase angles of the sinusoidal waveform in a region about a phase angle of a peak positive amplitude of the sinusoidal waveform, wherein the first negative region includes phase angles of the sinusoidal waveform in a region about a phase angle of a peak negative amplitude of the sinusoidal waveform, and wherein the second positive region and the second negative region include phase angles of the sinusoidal waveform in a region about a zero crossing of the sinusoidal waveform. an input including a plurality of input lines (1503, 1505, 1508) each configured to be coupled to a phase of a multiphase AC power source having a sinusoidal waveform; a plurality of DC buses including a first positive DC bus having a first nominal DC voltage, a second positive DC bus having a second nominal DC voltage, a first negative DC bus having a third nominal DC voltage and a second negative DC bus having a fourth nominal DC voltage; a first power converter coupled to the input and configured to supply power from the multiphase AC power source to the plurality of DC buses during a first positive region of the sinusoidal waveform and a first negative region of the sinusoidal waveform; and a second power converter coupled to the input and configured to supply power from the multiphase AC power source to at least some of the plurality of DC buses during a second positive region of the sinusoidal waveform and a second negative region of the sinusoidal waveform; wherein the first power converter includes a positive boost circuit and a negative boost circuit, wherein the positive boost circuit is coupled to each of the input lines and is configured to draw current during the first positive region of the sinusoidal waveform for each phase of the multiphase AC power signal, wherein the negative boost circuit is coupled to each of the input lines and is configured to draw current during the first negative region of the sinusoidal waveform for each phase of the multiphase AC power signal; wherein the first positive region includes phase angles of the sinusoidal waveform in a region about a phase angle of a peak positive amplitude of the sinusoidal waveform, wherein the first negative region includes phase angles of the sinusoidal waveform in a region about a phase angle of a peak negative amplitude of the sinusoidal waveform, and wherein the second positive region and the second negative region include phase angles of the sinusoidal waveform in a region about a zero crossing of the sinusoidal waveform.