White Papers

Reactive Power Compensation

Reactive power compensation: Using a Northern Power Systems NPS 100 or NPS 60 to manage power factor

Electrical systems using alternating current are subject to situations where voltage and current get out of step with each other… they get “out of phase.” When voltage and current are out of phase, the power produced – the product of voltage times current – is affected. Apparent power, what is metered and what we typically pay for, is composed of real power, that provides useful work, and reactive power, that only exists to balance out the misalignment between voltage and current. That misalignment is referred to as power factor (PF). Among other things, low PF results in consumers paying for more power, the apparent power, than actually does useful work, the real power.

The power triangle

The relationship between real power, reactive power, and apparent power is described by the power triangle – a right triangle whose perpendicular legs represent the real and reactive components and whose hypotenuse represents the apparent power. Apparent power is traditionally described in units of VA (volt-amp). Reactive power is traditionally described in units of VAR (volt-amp-reactive). Real power is traditionally described in units of W (watt).

Reactive power and the Northern Power Systems wind turbine

By virtue of its full power converter, the NPS 60 and NPS 100 wind turbines can be configured to provide reactive power compensation regardless of how much, if any, real power it produces. This reactive power compensation capability can be useful in a number of situations. The Engineering White Paper discusses two: a site with low PF and a site where turbines are connected at the far end of a long distribution run on a weak diesel grid.

For more information on the power triangle, reactive power and the two types of sites, please download the Engineering Bulletin:

NPS Engineering Bulletin – Reactive power compensation

–Alan Axworthy, Director, Application Engineering

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