Small and community-wind farms (25 to 100 kW) are fast growing markets in North America for wind-energy applications. But this great opportunity has drawbacks. For instance, farms are mostly supplied with split single phase power. Though single phase inverters are available for small wind turbines, such products are not practically usable at such power levels. Larger wind turbines at such power levels typically work on three-phase power which is not readily available in rural areas, so products that need it go unused.
Though the available wind inverters have many useful features, they can only supply power into a grid. Power can’t be taken from the grid for critical functions such as electrical breaking of a turbine during high winds or starting a turbine and overcoming its inertia under light winds. This issue forces turbine manufactures to design around the drawback by adding larger resistor and mechanical brakes which drives costs up.
A third issue is safety. To their knowledge, says a company spokesman, there are no UL 1741 certified bi-directional single phase 25 to 100-kW systems commercially available to the small and community-wind-turbine manufactures at this time.
Smart Power Systems Inc says it has developed a solution to the problems with the introduction of a 25 kW single phase bi-directional inverter. The SPS-Pavan 25 features minimum harmonic point tracking to reduce harmonic distortion, and a unity power factor operation while drawing or supplying power to a single-phase grid.
The inverter has passed UL 1741 certification tests at Metlabs Inc and is certified for production. The 25-kW model can be paralleled to produce 50 or 100 kW systems. Three such inverters can also be used to make 3 phase, high-power systems. The SPS Pavan-25 inverter is said to be a versatile unit that with minor modifications can be used for solar farms as well. Additional inverter features include
- Single phase grid tie in for generated power
- Bi-directional power conversion
- Net metering made possible for single-phase farm lines and small businesses.
- Useful where three-phase power is unavailable or prohibitively expensive
- Helps energy production under light wind conditions by starting a wind turbine from rest
- Provides assistance in shutting down the wind turbine under high wind conditions.
- Low harmonic distortions, less than 5 %
- Possible to add power generation capacity through modular approach. (up to 100 kW)
Smart Power Systems Inc.