Power (3ph, Instantaneous)

Compute three-phase instantaneous active and reactive powers

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

Description

The Power (3ph, Instantaneous) block computes the three-phase instantaneous active power P (in watts) and reactive power Q (in vars) associated with a periodic set of three-phase voltages and currents. These formulas are used to perform the calculations:

$\begin{array}{l} P = V_{a} \cdot I_{a} + V_{b} \cdot I_{b} + V_{c} \cdot I_{c} \\ Q = \frac{1}{\sqrt{3}} [(V_{b} - V_{c}) \cdot I_{a} + (V_{c} - V_{a}) \cdot I_{b} + (V_{a} - V_{b}) \cdot I_{c}] \end{array}$

With these formulas, a current flowing into an RL circuit produces a positive P and a positive Q.

The computed instantaneous reactive power is accurate only for balanced and harmonic-free three-phase voltages and currents.

Examples

The power_ThreePhasePower model compares the outputs of the block with the Power (Positive-Sequence) block and the Power (dq0, Instantaneous) block. It shows that the Power (3ph, Instantaneous) block gives accurate results when the voltages and currents are balanced and harmonic free. When the voltage supply becomes unbalanced, the P output exhibits a ripple, and an error appears on the Q output.

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 and change the Simulation type parameter of the Powergui block to Continuous to simulate the model in continuous mode.

Ports

Input

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Vabc — Three-phase voltage signal

Three-phase voltage signal.

Iabc — Three-phase current signal

Three-phase current signal.

Output

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P — Three-phase instantaneous active power

Three-phase instantaneous active power P, in watts.

Q — Three-phase instantaneous reactive power

Three-phase instantaneous reactive power Q, in vars.

Extended Capabilities

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

Version History

Introduced in R2013a