The ComplexNumber class implements complex numbers into the NPSS Power System Library. These are numbers which can be expressed in the form a+bi where i²=-1 and a and b are real numbers. Complex numbers are used in the Power System Library to represent phasors (phase vectors) which the ElectricPort and many other classes uses to correctly perform their engineering calculations when alternating current (AC1) and three-phase (AC3) electric power is being modeled.

The complex number class is used by many of the NPSS Power System Library (though most importantly ElectricPort) components to represent their current, voltage, and electric power values. Components which perturb an electrical variable such as voltage or current do not utilize ComplexNumber for those variables because the NPSS solver requires these variables to be of built-in type real.

The ComplexNumber class is currently implemented in the ComplexNumber.int file.