Boost auxiliary converter for small wind ?

Sheldon
Sheldon Solar Expert Posts: 51 ✭✭✭✭
I'm running a Whisper 200, set to 48V, feeding a small battery bank and a grid tied Xantrex XW 4548.

As far as I can tell from idiot lights and meters, the standard whisper charge controller does not feed notable energy to the battery side, until the rectified voltage is greater than the bank.

This would correspond to a pure "buck" mode power supply.

I'm wondering if I can add a "boost" mode auxiliary supply that would take the 3 phase voltage rectified when below the battery bank, and up-convert it. When the turbine voltage exceeds the output voltage and the standard charge controller cuts ins the auxiliary would drop off.

Ideally, as the voltage from the turbine fluctuates, the boost converter scavenges what ever energy is available, some low frequency (1- 0.1hz) tuning of the feedback to avoid overloading on increasing wind speed might be in order.

Comments

  • keyturbocars
    keyturbocars Solar Expert Posts: 375 ✭✭
    Re: Boost auxiliary converter for small wind ?

    Your idea sounds interesting. Have you seen the Midnite Classic?

    http://www.midnitesolar.com/products.php?menuItem=products&productCat_ID=21&productCatName=Charge Controllers

    It can be run in buck mode, but it can not do both buck and boost simultaneously. However, it appears that you are trying to maximize the power harvest from your Whisper 200, and the Classic's MPPT mode for wind will do that.

    I have been using a Classic with my HY-2000 2kW wind turbine for a while now and I really like it. More power and my turbine is more reliable/safer (better control).

    Edward
  • Sheldon
    Sheldon Solar Expert Posts: 51 ✭✭✭✭
    Re: Boost auxiliary converter for small wind ?

    I had a discussion with Ryan on this, and perhaps I misunderstood.

    What I thought I understood, is that the Classic is a two port controller, High and low. So it can run either buck (high to low) or boost (low to high), by being reversed but not switch between them with out re-wiring. I'll probably buy one to replace the whisper controller for better efficiency in normal mode when the wind learning mode is released, and will certainly buy one when I add 3.5 KW of PV to supplement the turbine after re-roofing the work shop. .

    My question was with respect to scavenging the lower power when the turbine is not making enough volts to run any controller in buck (high to low) mode. I note that my installation has quite a bit of time where the blades are spinning "fast", just not fast enough to "turn on the green led" of the whisper's controller.

    Measuring the AC phase to phase, its coming in below 35V, before the whisper kicks in. By quick calculation assuming the 3 wires are in delta, (54/sqrt(3) ~31V) there's room to skim power albeit not much before the cut in. If I have 20V phase to phase typically in these moments, then that's 35VRMS and even if I can get a few amps, i'd rather have it than not over the long run.
  • boB
    boB Solar Expert Posts: 1,030 ✭✭✭✭
    Re: Boost auxiliary converter for small wind ?
    Sheldon wrote: »

    My question was with respect to scavenging the lower power when the turbine is not making enough volts to run any controller in buck (high to low) mode. I note that my installation has quite a bit of time where the blades are spinning "fast", just not fast enough to "turn on the green led" of the whisper's controller.

    Problem is that at low wind speeds when the voltage is low, so is that available power. Even if the turbine is wound for higher output voltage, there just won't be much power available to scavenge. You are right about the wiring method... Low to high or high to low, except that the software doesn't yet support any low to high voltage (negative current) modes. You would still need a battery on the low voltage side, at least when things are starting up.

    Unless a non-inverting Buck-and-Boost converter was used, a simple boost converter would not be able to bring the turbine voltage DOWN to the battery voltage when the wind was high... A boost converter can only bring a lower voltage UP. The best compromise is therefore a buck and to wire the turbine for a slightly higher output voltage. This especially helps when you have a longer wire run from turbine to controller and battery where the voltage drop is more significant. If one were boosting, then you'd have the higher current on the turbine side which is definitely the longer wire length and typically is more wasteful.

    boB