About PV or Wind Power Converter

[blackseaman]

Hello, ?f PV panels or windmill rectified output have not constant output voltage, how can we get constant a d.c voltage, ? am confused since the input d.c is variable and cant imagine how we get it constant with a battery or something else, also can u tell me what happens if a source like these one is connected parallel by a battery , i mean the output of this combination, batteries output is inclined to be steady for a long time but if source voltage changes drastically so what happens? is there any protective measures like cut-off the connection if a margin is exceeded? pls introduce these systems briefly to me. best regards...

 

[blackseaman]

is it possible that i cant describe what i mean with the post above? if so pls tell me...

 

[alehman]

This is done with voltage converters. Many DC output wind turbines have an AC generator with a solid-state converter and voltage regulator.

For wind or PV, electronic DC-DC converters are used for battery charging, commonly known as a charge controller. They take input at range of voltage and convert it to match with the required battery voltage. It's common for PV arrays to be wired for relatively high output voltage (several hundred volts) and use a charge controller to feed a 24 or 48V battery system. Most have programmable battery charge cycles for bulking, absorption and equalization functions. They usually have numerous protection functions to handle out-of-range input or output voltages or currents. The more you want to spend, the more flexibility you will get.

Take a look at the O&M manual for a Xantrex or Outback charge controller.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[cranky108]

Or maybe the source (wind or PV) is held to the battery voltage,and the current veries.

 

[MAGTiger]

do a search on boost converter and you'll see a very common circuit used to boost dc voltage. I know that is is used on some fuel cells I have worked on and I am sure it could be used to maintain some dc voltage level. Otherwise it may simply be that the pv or wind mover shutys down when voltage is too low. Certainly the wind mills seem to have a fairly narrow operational window of wind speeds. I think they are typically rated to run about 30% of the time.

Neil

 

[blackseaman]

so what i wonder is what about if source voltage is very unstable?? SO how a dc-dc converter can convert it ? using capacitors perhaps but i dont know how to convert a continuously changing voltage to a stable one with batteries. is it something of using voltage regulators ?? but i guess they are convenient mostly for sinusoidal waves, for dc ones what can we say?

 

[xnuke]

Since the converters are switching power supplies, as the input voltage varies, the converter controller varies the duty cycle of the switching to achieve the desired constant output voltage. The converter can even be tuned to provide maximum power transfer by acting to match impedance between source and load.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[blackseaman]

Thank you.

 

[LionelHutz]

Or maybe the source (wind or PV) is held to the battery voltage,and the current veries.

This is typical for small wind systems. The unit uses a permanent magnet alternator connected to a rectifier and then a battery.

Large wind systems are typically grid tied and do not use batteries. Solar also typically does not use batteries. Both would only use batteries if there is an off-grid requirement. The controller converts the raw output voltage directly to power line voltage.