Power (PLL-Driven, Positive-Sequence)

(To be removed) Compute positive-sequence active and reactive powers

The Specialized Power Systems library will be removed in R2026a. Use the Simscape™ Electrical™ blocks and functions instead. For more information on updating your models, see Upgrade Specialized Power System Models to use Simscape Electrical Blocks.

Library

Simscape / Electrical / Specialized Power Systems / Sensors and Measurements

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Description

The Power (PLL-Driven, Positive-Sequence) block computes the positive-sequence active power P (in watts) and reactive power Q (in vars) of a periodic set of three-phase voltages and currents. To perform this computation, the block first computes the positive sequence of the input voltages and currents with a running window over one cycle of the fundamental frequency given by input 1. The reference frame required for the computation is given by the input 2. The first two inputs are normally connected to the outputs of a PLL block.

These formulas are then evaluated:

$$\begin{array}{c}P=3\times \frac{\left|V_1\right|}{\sqrt{2}}\times \frac{\left|I_1\right|}{\sqrt{2}}\times \cos (\phi )\\ Q=3\times \frac{\left|V_1\right|}{\sqrt{2}}\times \frac{\left|I_1\right|}{\sqrt{2}}\times \sin (\phi )\\ \phi =\angle V_1-\angle I_1\end{array}$$

V₁ is the positive-sequence component of input Vabc. I₁ is the positive-sequence component of input Iabc.

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

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 output is held constant using the values specified by the Voltage initial input and Current initial input parameters.

Parameters

Initial frequency (Hz)

Specify the frequency of the first cycle of simulation. Default is 60.

Minimum frequency (Hz)

Specify the minimum frequency value to determine the buffer size of the Variable Time Delay block used by the block to compute the phasors. Default is 45.

Voltage initial input [ Mag, Phase (degrees) ]

Specify the initial positive-sequence magnitude and phase (relative to the PLL phase), in degrees, of the voltage signals. Default is [1, 0].

Current initial input [ Mag, Phase (degrees) ]

Specify the initial positive-sequence magnitude and phase (relative to the PLL phase), in degrees, of the current signals. Default is [1, 0].

Sample time

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

Inputs and Outputs

Freq

Fundamental frequency (Hz) required by the computation. This input is normally connected to the output Freq of a PLL block.

wt

Angle of the reference frame (rad/s) required for the computation. This input is normally connected to the output wt of a PLL block.

Vabc

The vectorized signal of the three [a b c ] voltage sinusoidal signals. Typical input signals are voltages measured by the Three-Phase V-I Measurement block.

Iabc

The vectorized signal of the three [a b c ] current sinusoidal signals. Typical input signals are currents measured by the Three-Phase V-I Measurement block.

P

Positive-sequence active power (watts)

Q

Positive-sequence reactive power (vars)

Characteristics

Sample Time	Specified in the Sample Time parameter Continuous if Sample Time = 0
Scalar Expansion	No
Dimensionalized	No

Version History

Introduced in R2013a