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Sequence Analyzer

Compute positive-, negative-, and zero-sequence components of three-phase signal

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  • Sequence Analyzer block

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:

V1=13(Va+a⋅Vb+a2⋅Vc)V2=13(Va+a2⋅Vb+a⋅Vc)V0=13(Va+Vb+Vc)Va,Vb,Vc=three voltage phasors at the specified frequencya=ej2π/3=1∠120∘ complex operator

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.

Examples

The power_SequenceAnalyzer model shows the use of the Sequence Analyzer block to compute the three sequence components of a three-phase sinusoidal voltage.

The model sample time 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.

Characteristics

Sample TimeSpecified in the Sample Time parameter
Continuous if Sample Time = 0
Scalar ExpansionNo
DimensionalizedNo

Ports

Input

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

Output

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

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

Parameters

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

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.

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

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

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