Total Harmonic Distortion

Purpose

Calculate total harmonic distortion of periodic signal

Control / Measurements

This block calculates the total harmonic distortion of a periodic input signal. The sample time and the fundamental frequency can be specified.

The THD is defined as:

\[\text{THD} = \sqrt{\frac{\sum_{\nu\ge2} U_\nu^2}{U_1^2}} = \sqrt{\frac{U_{\text{rms}}^2 - U_0^2 - U_1^2}{U_1^2}}\]

where \(U_\nu\) is the RMS value of the \(\nu\)-th harmonic of the input signal and \(U_{\text{rms}}\) is its overall RMS value.

Example Model

See the example model “Total Harmonic Distortion”.
Find it in PLECS under Help > PLECS Documentation > List of Example Models.

Sample time: A scalar specifying the sampling period or a two-element vector specifying the sampling period and offset, in seconds \((\mathrm{s})\). See also the Discrete-Periodic sample time type in section Sample Times. If a sample time of 0 is specified, a continuous implementation based on the Moving Average block is active. The Discrete-Periodic implementation can potentially force a variable-step solver to take small integration steps. This may slow down the simulation. The default value of this parameter is 0.
Fundamental frequency: The fundamental frequency of the periodic input signal in hertz \((\mathrm{Hz})\).