| 摘要 |
PURPOSE: To simplify an output filter which reduces harmonic components. CONSTITUTION: In a PWM waveform generation circuit for a neutral-point clamp PWM inverter, carriers generated from two carrier-wave generators 4A, 4B and sine waves generated from a sine-wave generator 5 are level- compared by respective comparators 6A, 6B, outputs of both comparators are added by an addition circuit 6C, their phase is returned by a sign-inverting circuit 6D, and a PWM waveform which comprises a high level H, a low level L and a zero level 0 is generated. By this constitution, the carriers by both carrier-wave generators are changed into sawtooth waves. Thereby, a constitution in which the spectrum distribution of harmonic components contained in an inverter output concentrate near a frequency which is integral multiples of a carrier frequency and in which a specific frequency acts intensively on a specific frequency in an output filter to reduce the harmonic component, i.e., a filter constitution, is made simple, and the harmonic component is suppressed. |
