Modified Sine-Wave Inverter Enhanced

Focus:

Inverters with modified sine-wave outputs, which might be better described as modified square waves, are a lower cost alternative to sine-wave output inverters. Unlike PWM-based sine wave inverters, these inverters switch at line frequency rather than at high frequency, reducing design complexity but still permitting efficient operation. However, the ac waveform produced by modified sine-wave inverters contains significant distortion. This article proposes an enhancement of the modified sine-wave inverter that produces an output which more closely approximates a sine wave and therefore exhibits less distortion. The enhancement, which adds another voltage level to the output waveform, has only minor impact on the inverter's manufacturing costs. The proposed inverter design promises lower switching losses than PWM-controlled inverters and higher efficiency at any output power level. Implementation of the proposed design is described at a high level.

What you’ll learn:

• How to design a modified sine-wave inverter with reduced distortion
• How to calculate the total harmonic distortion (THD) of modified sine-wave inverters

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Author & Publication:

James H. Hahn, Associate Professor Emeritus, University of Missouri-Rolla Engineering Education Center, St. Louis, Power Electronics Technology, Aug 01 2006

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