Compute active and reactive powers of voltage-current pair at fundamental frequency

Control and Measurements/Measurements

The Power block computes the active power (P), in watts, and the reactive power (Q), in vars, of a voltage-current pair at fundamental frequency. To perform this computation, the block first determines the fundamental values (magnitude and phase) of the two input signals V & I. The following P and Q are then calculated:

$$\begin{array}{l}P=\frac{\left|V\right|}{\sqrt{2}}\times \frac{\left|I\right|}{\sqrt{2}}\times \mathrm{cos}(\phi )\\ Q=\frac{\left|V\right|}{\sqrt{2}}\times \frac{\left|I\right|}{\sqrt{2}}\times \mathrm{sin}(\phi )\\ \phi =\angle V-\angle I\end{array}$$

As this block uses a running average window, one cycle of simulation
must complete before the outputs give the correct value. For the first
cycle of simulation, the outputs are held constant using the values
specified by the **Voltage initial input** and **Current
initial input** parameters.

**Fundamental frequency (Hz)**Specify the fundamental frequency, in hertz, of the input signals.

**Voltage initial input [ Mag, Phase (degrees) ]**Specify the voltage initial magnitude and phase to set a constant output for the first cycle of simulation.

**Current initial input [ Mag, Phase (degrees) ]**Specify the current initial magnitude and phase to set a constant output for the first cycle of simulation.

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

`V`

The voltage signal.

`I`

The current signal.

`P`

The active power of voltage-current pair signal, in watts.

`Q`

The reactive power of voltage-current pair signal, in vars.

Sample Time | Specified in the Sample Time parameterContinuous if Sample Time = 0 |

Scalar Expansion | Yes, of the parameters |

Dimensionalized | Yes |

The `power_Power`

model
shows the accuracy of the Power block in evaluating the active and
reactive powers of a voltage-current set.

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.

Was this topic helpful?