Three phase sinewave using SPWM output voltage difference and harmonic distortion

Thread Starter


Joined Feb 17, 2018
Hello everyone. I'm designing a 3 phase sinewave inverter. I have used three IGBT modules and three step up transformers and six 12 V batteries. Input of the each transformer is connected to IGBT modules in delta form. And the output in star form- common neutral.

Now the s/w part. I am using the method of look up table and have taken 27 values. Each value is accessed 6 times. 1st phase starts from the 1st value, second from 9th value and third from 18th value. The carrier frequency is 16 KHz.

Problem is voltage across RN and BN is same like 150 V but the voltage across YN is 170 at no load. Also when I add a load and increase the duty ratio there is difference between all the three phases.

I read some paper and articles that tell about harmonic distortion. But not about how to reduce it. Also the topologies used in the articles and papers were different than mine. I know very less about the harmonic distortion.

What I might be missing? It it the harmonic distortion that is causing the waveforms to be different? Or else?