Multiple Pulse Modulation in Static Inverters Reduces Selected Output Harmonics and Provides Smooth Adjustment of Fundamentals

It is the problem of the inverter designer to design a unit whose cost is low and whose reliability is high, consistent with all other application requirements. This suggests that a minimum of major switching elements be used, that conservatively rated components be employed, and that circuit redundancy be incorporated in the design. Another major problem facing the inverter designer is that of maintaining the output voltage of the inverter within an allowable band of values. This problem arises due to the normal voltage drops within the inverter. It also is aggravated by the voltage drops in the rectifier supplying power to the inverter or by the battery voltage variation. Multiple pulse modulation provides more than one polarity reversal per half-cycle. The amplitude of the input voltage to the inverter is equal to that of the source and is essentially fixed for small intervals of time. The freedom to reverse polarity is the freedom to change the harmonic structure of the output. By selecting the number and location of the reversals in polarity, the fundamental amplitude may be varied while eliminating low-order harmonics. This technique offers a unique utilization of power handling components.