| 摘要 |
<p>Prior types of neutral point clamped PWM inverters pulses in a PWM waveform having reference points which are evenly spaced. Such a control technique, however, accomplishes a significant reduction in output harmonics only for relatively low inverter output magnitudes. In order to overcome this problem, a control for a PWM inverter defines a series of reference points (alpha) spaced in time in accordance with an inverse trigonometric function of the number of pulses (9) to be produced in a portion (180°) of the inverter output wherein each reference point is associated with a pulse to be produced in the PWM waveform and determines rising (R1, R2...) and falling (F1, F2...) edges of each pulse of the AC output relative to the reference point associated with such pulse in dependence upon an output parameter of the inverter. Switch control signals are developed for each switch from the defined rising and falling edges. The control of the present invention accomplishes a significant reduction in the harmonics produced by the inverter at higher inverter output magnitudes.</p> |
