# Sequence Analyzer

Calculate the magnitude and phase of the positive, negative, or zero sequence of a three-phase signal

**Libraries:**

Simscape /
Electrical /
Control /
Measurements

## Description

The Sequence Analyzer block takes a three-phase signal (usually voltage) as the input and outputs the magnitude and phase of the positive, negative, or zero sequence.

The input signals are first converted to phasor representation based on the base frequency and harmonic specified in the block mask. The block then transforms the phasor into a sequence of components..

You can represent the zero, positive, and negative sequence components with
*V _{0}*,

*V*,

_{1}*V*in phasor representation;

_{2}*V*,

_{a}*V*,

_{b}*V*are the voltage of three phases. The sequence components are computed as:

_{c}$$\left[\begin{array}{c}{V}_{0}\\ {V}_{1}\\ {V}_{2}\end{array}\right]=\frac{1}{3}\left[\begin{array}{ccc}1& 1& 1\\ 1& a& {a}^{2}\\ 1& {a}^{2}& {a}^{2}\end{array}\right]\left[\begin{array}{c}{V}_{a}\\ {V}_{b}\\ {V}_{c}\end{array}\right]$$

where $$a={e}^{j\frac{2}{3}\pi}$$.

## Limitations

Because the computation of the three-phase signal requires integration over a full cycle, the output of the sequence analyzer is not accurate during the first period.

If the base frequency or the harmonic change during the simulation, the output signal is not accurate.

## Ports

### Input

### Output

## Parameters

## Extended Capabilities

## Version History

**Introduced in R2019b**