MATLAB Examples

Three-Phase Programmable Source, V-I Measurement and Sequence Analyzer

This example shows the use of the 3-Phase Programmable Voltage Source, 3-Phase V-I Measurement, and Sequence Analyzer blocks.

G. Sybille (Hydro-Quebec)

Contents

Description

A 25kV, 100 MVA short-circuit level, equivalent network feeds a 5MW, 2 Mvar capacitive load.

The internal voltage of the source is controlled by the Discrete 3-phase Programmable Voltage Source block.

Open the source dialog box and look at the parameters controlling the voltage. A positive-sequence of 1.0 pu, 0 degrees is specified. At t = 0.05 s a step of 0.5 pu is applied on positive-sequence voltage magnitude, then, at t = 0.1 s, 0.08 pu of 5th harmonic in negative sequence is added on the 1.5 pu voltage.

In order to start simulation in steady state, the three voltage sources are initialized with a positive-sequence voltage of 25 kV, 0 degree, 60 Hz.

The Three-Phase V-I Measurement block allows to monitor the three load voltages and currents. Open its dialog box and see how this block allows to output the voltages and currents in pu.

Two Discrete 3-phase Sequence Analyzer blocks are used to monitor the positive-sequence of the three fundamental voltages Va, Vb, Vc and the negative-sequence component of the 5th harmonic.

The whole system, (power network, programmable source, and sequence analyzers) is discretized at a 50 us sample time.

Simulation

Choose Simulation/Start and observe the voltage and current waveforms.

The simulation starts in steady state with 1 pu voltage. At t = 0.05 sec, the internal voltage is increased to 1.5 pu. At t = 0.10 sec. 0.08 pu of 5th harmonic internal voltage is added.

Observe the fundamental component (pos. seq.) and the 5th harmonic component (neg. seq.) measured by the two sequence analyzers. The 0.08 pu 5th harmonic internal voltage is amplified at 0.14 pu at the load terminals. As the sequence analyzers use Fourier analysis, their response time is one cycle.