sinewave inverters reactive power handling
sinewave inverters reactive power handling
(OP)
How do designs that transform dc-ac sinewave handle the return energy of a reactive load. I know the basic building block of an inverter is an H bridge with a filter after, using PWM to implement a sine wave wave output. But if you connect a large reactive load the power flow must be bi-directional. So energy must be transferred from a lower voltage to the dc bus voltage.
How is this done???
thanks
How is this done???
thanks






RE: sinewave inverters reactive power handling
RE: sinewave inverters reactive power handling
RE: sinewave inverters reactive power handling
RE: sinewave inverters reactive power handling
Driving a reactive load entails energy transferred to the
reactive device during part of the cycle and then energy returned to the source during the other part of the cycle.
In a sine wave inverter fed from a DC bus power must be withdrawn from the load and returned to the bus despite various voltage levels.
In short 4 quadrant operation.
But how to do this is my question
CJCPE
In order for current to flow back to the antiparallel diodes the load voltage must have risen to the dc bus value.
RE: sinewave inverters reactive power handling
BBL
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: sinewave inverters reactive power handling
H-Bridge-Inv-1.jpg
H-Bridge-Inv-2.jpg
H-Bridge-Inv-3.jpg
RE: sinewave inverters reactive power handling
That is close to the output stage i envision, except the
thyristors are FET or IGBT and they are driven with a PWM wave to get a clean sine wave. Your drawing appears to me to be a square wave inverter.
The reason for wanting a sine wave is that it causes no problems with any load designed for the grid as that is what the grid is (sine wave). This type of inverter is gaining usefullness in alternative power applications and anywhere sensitive equipment is being driven by back up.
I have heard that an additional full stage is often added in parallel in a flyback arrangement to achieve power return. I hope for something better though
RE: sinewave inverters reactive power handling
The addition of a filter may make it desireable to change the configuration, but filters are available as an add-on accessory, so a different inverter configuration can't be essential.
There are a lot of multilevel inverter configurations. It may be that some of them require a different return energy handling method.
It may be that inverters that are designed for an output voltage that is always much below the input voltage may gain some advantage from a different return energy configuration. The fact that motor drive inverters have an output voltage operation range that is very wide demonstrates that the inverse parallel diode configuration is suitable for high input V / low output V operation.
RE: sinewave inverters reactive power handling
would create square pulses at the Bus voltage until the inductive stored energy was absorbed then abruptly the voltage would fall to the level dictated by the PWM switching now occuring in the opposite legs. Some waveforms with sin output would help me understand.
Thanks for all the help so far
RE: sinewave inverters reactive power handling
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: sinewave inverters reactive power handling
I hope this sheds some light on the subject.