Displacement Power Factor measurement block in MATLAB Simulink

More often, in power electronic converter simulation, we need to measure the phase difference between sinusoidal input AC voltage (V) and AC current (I). The cosine of the phase difference between V and I gives the displacement power factor.

Recently, while I was doing simulation for a matrix based AC-DC converter, I needed to know the displacement power factor to find out the active and reactive power. Therefore, I developed a Simulink block to measure the DPF. In this post, I will be discussing the implementation of a discreet DPF Simulink model for two sinusoidal signals of the same frequency.

The features of DPF Simulink block are following.

• If I lags V, the phase difference is negative
• If I leads V, the phase difference is positive.

With these two features in the mind, the DPF Simulink model is developed. The zero crossing of sinusoidal signals are used to find out the phase difference between V and I and subsequently, the DPF is calculated.

Fig. 1: Internal implementation of the DPF block.

A reset-able integrator is required to integrate a unity value over the time period of the sinusoidal cycle as shown in Figs. 2(b) and 2(c). The difference of the integrated values of the two signals shown in Fig. 2(d) provides the time difference which needs to be converted into the angle by using sinusoidal frequency. As we can see in Fig. 2(d), the difference in phase using this method is not same throughout the cycle. However, the DPF which is cosine of the phase difference will be constant as

cos(360 - theta) = cos (theta) 

Fig. 2: Phase difference measurement method

A MATLAB function block shown in Fig. 1 is used to convert any phase different more than 180 degrees or less than -180 degrees between the range of [-180, 180].

The DPF block can be downloaded for free from my MATLAB community profile. You can also download many other power electronic converter models from there.

Fig. 3: The developed DPF model in action. The signal 2 lags the signal 1 by 30 degrees.

Please provide your valuable feedbacks and comments.