inverter current modification of single phase inverter

[danilorj]

Hey guys

do you know anyway of modifying the current output waveform of a single phase inverter? Like, for example, adding a zero crossing in this sinewaveform.

 

[FvM]

adding a zero crossing in this sinewaveform

?? I believe a sine waveform has exactly two zero crossings per cycle. How do you add zero crossing (and maintain the sine waveform)?

 

[danilorj]

This way.



The waveform in blue.

 

[FvM]

O.K., i won't call this modification zero-crossing. Usually inverters are voltage conztrolled in a first order. So you might insert a delay between output voltage halfcycles. In case of resistive load, the current would follow the voltage waveform.

What do you want to achieve, what kind of load to you expect?

 

[danilorj]

It is a RLC load with quality factor of 2.5. But what do you mean by inserting a delay between output voltage halfcycles?

 

[FvM]

But what do you mean by inserting a delay between output voltage halfcycles?

That's how the waveform seems to be generated, isn't it?

It is a RLC load with quality factor of 2.5.

And the blue waveform shows the intended current? Did you already sketch the related voltage waveform?

If the question is somehow related to reliable operation of a solid-state relay with zero-crossing detector, a suitable snubber is the usual solution.

 

[danilorj]

The blue waveform is generated with the purpose of triggering the anti-islanding protection of the inverter by using the overfrequency/underfrequency relay.
This delay you are saying I already tried. And it seems not to work, unless I use a different current controller from the ones I tested (PR and deadbeat controller) before.
About this waveform I sent previously, the blue is with this delay and the green is the one generated by the current controller using PR controller, note that this dead-zone is untrackable using this resonant controller. Anyway, I even don't know whether it can be done this way.