Wind Inverters

increase the power harvested from the turbine as the turbine speed increases. Usually this is calculated from voltage, but using frequency to estimate the power from RPM can be a lot more accurate. The speed to power ratio has an exponential increase – at low speeds, only a minimal amount of power is harvested.

Most wind turbines have been configured for voltage based power curves. As the turbine speeds up, voltage rises, and this is used to determine the power harvested. SMA Windy Boy and many other inverters only allowed for this type of power curve. This is because most wind inverters were initially designed as solar inverters, and subsequently modified to allow a power curve to be entered as a table in the inverter’s firmware.

Power One was the first company to mass produce inverters which could take a frequency signal to read in the RPM of the turbine. This is a much more accurate way to determine the power available from the turbine. Turbine voltage often lags behind the RPM and vice-versa. As a turbine accelerates, the voltage will rise rapidly, then inverter will respond to the rising voltage by harvesting more power, but that will cause the turbine voltage to drop, and the inverter will momentarily be over-taxing the turbine, which slows down, causing the voltage to drop again.

We would recommend using frequency to determine available power where possible. We can assist you in this work. The Aurora / Power One wind interface has a frequency output which can send an RPM signal to one or more inverters.

SMA no longer makes Windy Boy wind inverters. However, the Power One UNO is a similar replacement for the 2.5kw Windy Boy with a high frequency transformer. We can advise on replacing Windy Boy inverters with Power One and other units where needed in the event of a non-warranty failure.

Following the successful launch of the UNO range of solar inverters, we now carry the 2kw and 2.5kw versions of the new UNO wind inverter.

Unlike other Aurora wind inverters, this unit has a high frequency transformer providing galvanic isolation, but without the power consumption and weight of a conventional transformer. The inverter is 96% efficient across most of its operating range.

This inverter works with DC voltages between 90V and 470V, with an absolute maximum voltage of 500V DC. For this reason, wind interfaces for use with this inverter will have to be modified to introduce dump loads at less than the default voltage of 530V DC. We can do this modification for you on request.