Controller rectifier

[julian403]

Hello I was reading the books: "power electronic" by Muhammad and Rashid and I have a question about some kind of aspect. I found this:


That's its a complete bridget rectifier with tiristor and for a one phase input voltage. What's means that it can operate in two quadrants? Because Vd will be always positive.

For example, if VA > VB then D1 and D2 will drive and if VB > VA D3 and D4. So Vd will be always positive.

regards

 

[FvM]

For example, if VA > VB then D1 and D2 will drive and if VB > VA D3 and D4. So Vd will be always positive.

No. You are apparently assuming that both paths are conducting simultaneously (as for an uncontrolled bridge rectifier). But that's not necessary.

As an example, you can analyze the case of Vemf=0, assume R = 0 for simplicity. Inductor voltage average is zero, If you ignite the SCRs at phi=90°, they will conduct till about phi=270°, vd being negative after phi = 180°.

 

[julian403]

ah thanks, but that only happends when there is a inductor? no?



that for one shooting T1 and T2

regards

 

[FvM]

You surely need a respective load to operate the two-quadrant power controller in second quadrant. Inductor is one possible case.

Please notice that second quadrant involves a reverse power flow from load to mains.

 

[julian403]

Please notice that second quadrant involves a reverse power flow from load to mains.

So, the voltage in the quadrant's graph is the input voltage?

But for example in the semi converter. So a semi convert work in two quadrants too.
Unlike what rashid says



There is a power flow for the loat to mains, too. Because the transformer's second coil changes the potential difference but for the inductor there is a still a current. So, a flow from the load to AC side it's posible for all tiristor topology rectifier?

That makes me think and ask. If instead of an inductance a solar panel is placed, even though the current is positive, is it possible to deliver power to the grid? 8-O And in that way there will be not necesary an inverter. Something like this:



Where for the inductors Id it's always positive.