One Phase Pwm Rectifier Working Principle

[ElektrikAkar]

Hello,

I was working on some rectifier circuits and I saw this circuit on a board. It is a part of a complex power supply circuit. As my experiments, it works very well and can generate 380V mean voltage (per capacitor) on capacitors. The IGBTs use 15kHz gate signal, and duty cycle is various because of the feedback. However I did not see any similiar rectifier before and I cannot understand how this circuit works. If you know the name of this circuit or have any ideas about working principle of this circuit, please tell me. It has a very well design and can hold mean voltage at 380V up to certain load, then the voltage declines a little bit if you overload.

 

[KlausST]

Hi,

The circuit shows rather a DC to AC converter than a rectifier. (I´ve not check if it could work as a rectifier)


Klaus

 

[FvM]

The function depends of course on the implemented modulation, but a half-bridge inverter can be operated as "active front end" (AFE), a bidirectional AC/DC converter with high power factor.

You surely have noticed that the capacitors are already charged to input voltage peak-to-peak of about 620 V if the IGitBTs are permanently off, by modulating it with a sine PWM you get boost PFC operation.

 

[schmitt trigger]

If one removes both IGBTs, the circuit is essentially a full wave doubler rectifier. Please Google full wave doubler circuit.

By now adding the IGBT's PWM capabilities and the series inductor, one can control the voltages to which the output capacitors will be charged.

 

[ElektrikAkar]

Thank you for all answers guys you are great.

@KlausST

Yes it looks like but I am pretty sure it is a rectifier. Because in the circuit, these are the center capacitors. Circuit has 3 sides;

One for AC to DC
One for DC to DC
One for DC to AC

So if you give DC battery input, a DC-DC converter increases the voltage and charges the capacitors.
if you give AC input, the rectifier circuit goes active and charges these capacitors again.

And at the end, you can AC or DC output which depends your desire.
You can use mains to charge your batteries by using AC-DC and DC-DC,
You can use batteries to get a sinusoidal output in case of any blackout by using DC-DC and DC-AC parts of the circuit.

I put here only the AC-DC part, to make circuit more clear, because I could understand other parts very well. However the rectifier part is very hard for me to understand.
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@FvM

Thank you for making it more clear for me. I searched for AFE and found some similiar circuits and my circuit has ability to correct power factor with full load operation. Then with your suggestion I tried giving pwm signal to IGBTs however could not get a stable output. Do you have any sources, suggestions for me to learn this type of circuits deeply?

@schmitt trigger

Yes exactly but I do not know how can I control the output voltage as I wish.

 

[FvM]

I tried giving pwm signal to IGBTs however could not get a stable output. Do you have any sources, suggestions for me to learn this type of circuits deeply?

Assuming ideal PWM inverter operation, the output DC voltage is given by input voltage peak/pwm modulation index.

Controlling the AFE operation dynamically is a different matter. The AFE controller designs I know have an inner current control loop with sinusoidal model current, input and inductor voltage feed forward and an outer voltage control loop.