how to keep input power constant for bi-directional buck-boost converter using cosine pwm?

Thread Starter

kittoo

Joined Jul 11, 2016
27
hello sir/mdm,

I am designing a bi-directional buck-boost converter for battery charger,to keep the power factor unity. I need a constant input power (i.e, if current is minimum the voltage will max & vice versa) . you can see in fig2 the current is max when voltage is max,how to keep input power constant for bi-directional buck-boost converter using cosine pwm?






Screen Shot 2016-08-22 at 14.55.17.png Screen Shot 2016-08-22 at 14.55.17.png Screen Shot 2016-08-22 at 14.56.42.png Screen Shot 2016-08-22 at 14.56.42.png
 

tcmtech

Joined Nov 4, 2013
2,867
Okay? why do you think you need to keep the PF at unity while charging a battery? o_O

Is this a commercial application where the battery holds hundreds to thousands of kilowatts?
 

Thread Starter

kittoo

Joined Jul 11, 2016
27
Okay? why do you think you need to keep the PF at unity while charging a battery? o_O

Is this a commercial application where the battery holds hundreds to thousands of kilowatts?
if PF is unity then the efficiency of the circuit is good.
no,it is not a commercial application
 

crutschow

Joined Mar 14, 2008
25,656
The efficiency of the converter circuit has little to do with the power factor.
All a poor power factor does is increase the losses some in the main's power line.
 

tcmtech

Joined Nov 4, 2013
2,867
if PF is unity then the efficiency of the circuit is good.
No it's not. Power Factor of a circuit has very little effect on overall system efficiency. Typically fractions of a percent at best in an application like yours.

Especially so when compared to the unavoidable losses that are present in charging a battery which are measured in multiple 10's of percents.
 

Thread Starter

kittoo

Joined Jul 11, 2016
27
No it's not. Power Factor of a circuit has very little effect on overall system efficiency. Typically fractions of a percent at best in an application like yours.

Especially so when compared to the unavoidable losses that are present in charging a battery which are measured in multiple 10's of percents.
I am building this charging circuit for 72v ,10amps battery ,
when i simulate this circuit in matlab, the 2nd harmonics content is very high in source current.
is there any method to eliminate 2nd harmonics ?
 

Papabravo

Joined Feb 24, 2006
14,679
The harmonic content arises from the use of waveforms with sharp edges and corners. There is presumably a reason for doing this; but where do you want to eliminate this harmonic content? I suggest you try a different method.
 
Top