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Compute total harmonic distortion (THD) of signal

  • THD block

Simscape / Electrical / Specialized Power Systems / Sensors and Measurements


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

total harmonic distortion (THD)=IHIFIH=I22+I32++In2     In:RMS value of the harmonic nIF:RMS value of the fundamental current

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


Sample TimeSpecified in the Sample Time parameter
Continuous if Sample Time = 0
Scalar ExpansionYes, of the parameters


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.


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

Frequency, in hertz, of the fundamental signal.

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