No reactive power measured when signals are distorded

[CyGa]

Hi !

I'm using the Electrical Power Suite to calculate powers. When my signals (voltages and currents) are purely sinusoidal without any phase between V and I, reactive power is 0VAR. Which is perfectly normal.

However, when I add distorsion to V or I, I would expect to measure reactive power (which my reference Yokogawa power meter does). But with the toolkit, in that case, ractive power stays to 0 !

Why is that ? Only fundamental is taken into account ?

Signals are 60Hz voltages and currents generated by a source used to calibrate lab instruments (very accurate and often checked). Measures are done with a cRIO, signals are resampled in the FPGA.

Thanks !

[ThreeLions]

Hello,

Adding distorsion don't bring reactive power.So you cannot get reactive power in this case.

Apparent Power(S) consists of two parts, Active Power(P) and Reactive Power(Q). We can describe their relation by 2 equations:

P = S*cosθ = U*I*cosθ = U*I*F

Q = S*sinθ = U*I*sinθ

ps: F = cosθ is said Power Factor

θ means the phase difference between voltage and current in nonlinear load. If there is no phase difference between voltage and current, θ = 0. Then Q = S*0 = 0. So, if you want to get Reactive Power, you should add the phase difference between voltage and current .

Thanks!

[CyGa]

Hi! Your explanation is only true for purely sinusoïdal signals. Adding harmonic distorsion is like adding different sinusoïdal signals together to building one (Fourier). Lets say that both of your fundamental signals for voltage ans current and with a phase of 0 degrees,50hz. In that case Q =0.

Now add distorsion by adding a 57hz signal upon your current fundamental, 10% of the fundamental amplitude. What happens with Q? Is the distorsion in phase with your voltage?!

[ThreeLions]

Hello,

I create a sample to achieve your hypothesis, add distorsion by adding a 57hz signal upon your current fundamental, 10% of the fundamental amplitude. And I added brief notes in block diagram. Please see the attachment.

In this case, the reactive power is not 0. Because the phase of voltage and current are different.

Thanks!