Sequence Analyzer

(To be removed) Compute positive-, negative-, and zero-sequence components of three-phase signal

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.

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

Description

The Sequence Analyzer block outputs the magnitude and phase of the positive-, negative-, and zero-sequence components of a set of three balanced or unbalanced signals. Index 1 denotes the positive sequence, index 2 denotes the negative sequence, and index 0 denotes the zero sequence. The signals can optionally contain harmonics. The three sequence components of a three-phase signal (voltages V₁ V₂ V₀ or currents I₁ I₂ I₀) are computed as follows:

$$\begin{array}{l}{V}_1=\frac{1}{3}\left(V_a+a\cdot V_b+a^2\cdot Vc\right)\\ V_2=\frac{1}{3}\left(V_a+a^2\cdot V_b+a\cdot Vc\right)\\ V_0=\frac{1}{3}\left(V_a+V_b+Vc\right)\\ V_a,V_b,V_c=\text{three voltage phasors at the specified frequency}\\ a=e^{j2\pi /3}=1\angle {120}^{\circ }\text{ complex operator}\end{array}$$

A Fourier analysis over a sliding window of one cycle of the specified frequency is first applied to the three input signals. It evaluates the phasor values Va, Vb, and Vc at the specified fundamental or harmonic frequency. Then the transformation is applied to obtain the positive sequence, negative sequence, and zero sequence.

As the block uses a running average window to perform the Fourier analysis, one cycle of simulation must complete before the outputs give the correct magnitude and angle. For example, the block response to a step change of V1 is a one-cycle ramp. For the first cycle of simulation, the output is held constant using the values specified by the initial input parameters.

Characteristics

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

Ports

Input

abc — Three-phase current signal

vector

Three-phase current signal. Index 1 denotes the positive sequence, index 2 denotes the negative sequence, and index 0 denotes the zero sequence.

Output

|u| — Magnitude

scalar

Outputs the magnitude (peak value) of the specified sequence component(s), in the same units as the abc input signal.

∠u — Phase

scalar

Outputs the phase, in degrees, of the specified components.

Parameters

Fundamental frequency (Hz) — Fundamental frequency of input signal

60 (default) | scalar

Specify the fundamental frequency, in hertz, of the three-phase input signal.

Harmonic n (1=fundamental) — Harmonic component to evaluate sequences

1 (default) | scalar

Specify the harmonic component to evaluate the sequences. Set to 1 to compute the sequences at the fundamental frequency or to the number corresponding to the desired harmonic.

Sequence — Specify sequence component

Positive Negative Zero (default) | Positive | Negative | Zero

Specify the sequence component the block outputs. Select Positive Negative Zero to calculate all the sequences.

Initial input [ Mag, Phase (degrees) ] — Initial magnitude and phase of input signal

[1, 0] (default) | vector

Specify the initial magnitude and phase, in degrees, of the positive-sequence component of the input signal.

Sample time — Block sample time

0 (default) | positive scalar

Specify the sample time of the block, in seconds

Extended Capabilities

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

Version History

Introduced in R2013a