THD

Compute total harmonic distortion (THD) of signal

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Libraries:
Simscape / Electrical / Specialized Power Systems / Sensors and Measurements

Description

The THD block computes the total harmonic distortion (THD) of a periodic distorted signal. The signal can be a measured voltage or current.

The THD is defined as the root mean square (RMS) value of the total harmonics of the signal, divided by the RMS value of its fundamental signal. For example, for currents, the THD is defined as

$$\begin{array}{l}\text{total harmonic distortion (THD)}=\frac{I_H}{I_F}\\ I_H=\sqrt{I_2^2+I_3^2+\dots +I_n^2}{I}_n:\text{RMS value of the harmonic n}\\ \\ I_F:\text{RMS value of the fundamental current}\end{array}$$

The THD has a null value for a pure sinusoidal voltage or current.

Characteristics

Sample Time	Specified in the Sample Time parameter Continuous if Sample Time = 0
Scalar Expansion	Yes, of the parameters
Dimensionalized	Yes

Examples

The power_RMS_THD model uses a THD block to compute the THD of a 60 Hz signal with second harmonic and a DC bias.

The model sample time is parameterized by the Ts variable set to a default value of 50e-6 s. Set Ts to 0 in the command window to simulate the model in continuous mode.

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Fundamental frequency of input signal (Hz) — Frequency of fundamental signal

60 (default) | scalar

Frequency, in hertz, of the fundamental signal.

Sample time — Block sample time

0 (default) | nonnegative scalar

Sample time of the block, in seconds. Set to 0 to implement a continuous block.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced in R2013a